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The Role of Communication in Computer Science

THE ROLE OF COMMUNICATION IN COMPUTER SCIENCE

Jocelyn O. Padallan

ARCLER

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The Role of Communication in Computer Science Jocelyn O. Padallan

Arcler Press 224 Shoreacres Road Burlington, ON L7L 2H2 Canada www.arclerpress.com Email: [email protected]

e-book Edition 2023 ISBN: 978-1-77469-689-7 (e-book)

This book contains information obtained from highly regarded resources. Reprinted material sources are indicated and copyright remains with the original owners. Copyright for images and other graphics remains with the original owners as indicated. A Wide variety of references are listed. Reasonable efforts have been made to publish reliable data. Authors or Editors or Publishers are not responsible for the accuracy of the information in the published chapters or consequences of their use. The publisher assumes no responsibility for any damage or grievance to the persons or property arising out of the use of any materials, instructions, methods or thoughts in the book. The authors or editors and the publisher have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission has not been obtained. If any copyright holder has not been acknowledged, please write to us so we may rectify.

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ABOUT THE AUTHOR

Ms. Jocelyn O. Padallan is a graduate of the Bachelor of Science in Computer Science and finished her Certificate of Teaching Proficiency Program at Laguna State Polytechnic University - Los Banos Laguna. She also completed her Master in Educational Management. Currently, Ms. Jocelyn O. Padallan is an IT Professor at the Laguna State Polytechnic University - Los Banos Campus under the College of Computer Studies (CCS) where she holds different professional courses such as Effective n Business Communication and Programming Languages. She is actively involved in the college extension services programs including Life Project 4 Youth and ITeach 4 Heroes.

TABLE OF CONTENTS

List of Figures ........................................................................................................xi List of Tables ...................................................................................................... xvii List of Abbreviations ........................................................................................... xix Preface........................................................................ ................................. ....xxiii Chapter 1

Fundamentals of Computer Communications ........................................... 1 1.1. Introduction ........................................................................................ 2 1.2. Uses of Computer Communications.................................................... 4 1.3. Physical Links ................................................................................... 14 1.4. Physical Media and Their Properties.................................................. 15 1.5. Physical Communication Services..................................................... 23 References ............................................................................................... 30

Chapter 2

Types of Information Systems.................................................................. 41 2.1. Introduction ...................................................................................... 42 2.2. Categories of Information Systems .................................................... 43 2.3. Management Information Systems (MIS) ........................................... 47 2.4. Other Categorizations of Information Systems................................... 49 2.5. Modules of an Information System .................................................... 52 2.6. Resources of Information System ...................................................... 53 2.7. Information System Activities ............................................................ 56 2.8. Computer Based Information System (CBIS) ...................................... 57 2.9. Data Storage in MIS .......................................................................... 61 References ............................................................................................... 64

Chapter 3

Fundamentals of Computer Networks ..................................................... 71 3.1. Introduction ...................................................................................... 72 3.2. Models of Computer Networks ......................................................... 74 3.3. Types of Computer Network.............................................................. 75

3.4. Data Communication Media Technology .......................................... 77 3.5. Network Topology ............................................................................ 85 3.6. Network Connectivity and Procedures .............................................. 90 3.7. Network Services .............................................................................. 96 3.8. Devices for Network Connecting .................................................... 100 References ............................................................................................. 115 Chapter 4

Communication in Computer Memory Systems .................................... 129 4.1. Introduction .................................................................................... 130 4.2. Memory Hierarchy .......................................................................... 133 4.3. Handling the Memory Hierarchy .................................................... 136 4.4. Caches............................................................................................ 141 4.5. Main Memory ................................................................................. 148 4.6. Future and Current Research Problems ........................................... 154 References ............................................................................................. 159

Chapter 5

Interconnection Networks .................................................................... 169 5.1. Introduction .................................................................................... 170 5.2. Questions About Interconnection Networks .................................... 171 5.3. Uses of Interconnection Networks .................................................. 173 5.4. Network Basics ............................................................................... 183 References ............................................................................................. 192

Chapter 6

Mobile Communication Networks ........................................................ 199 6.1. Introduction .................................................................................... 200 6.2. Historical Background .................................................................... 201 6.3. Foundation ..................................................................................... 204 6.4. MCN Architecture........................................................................... 204 6.5. MCN Platforms ............................................................................... 207 6.6. Information Diffusion In MCN ........................................................ 208 6.7. Key Applications ............................................................................. 210 6.8. Future Directions ............................................................................ 212 References ............................................................................................. 214

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Chapter 7

Security for Communication Systems .................................................... 219 7.1. Introduction .................................................................................... 220 7.2. Security Objectives ......................................................................... 222 7.3. Types of Attacks .............................................................................. 225 7.4. Security in Communication Protocols and Networks ...................... 227 References ............................................................................................. 236

Chapter 8

Future Directions in the Design of Dependable Communication Systems ....................................................................... 241 8.1. Introduction .................................................................................... 242 8.2. Research Directions in Software Failure Mitigation ......................... 246 8.3. Reliability of Wireless Communications .......................................... 249 8.4. Failure Models and Measures of Fault Tolerance ............................. 250 8.5. Resilience Considerations of an IP Backbone Network in the Interplay With an Agile Optical Layer ................................. 252 References ............................................................................................. 254 Index ..................................................................................................... 259

ix

LIST OF FIGURES Figure 1.1. Communication using computer applications Figure 1.2. Various forms and modes of communication networks Figure 1.3. Communication network applications Figure 1.4. Computer-assisted communication has progressed Figure 1.5. Diagrams of telecommunication networks Figure 1.6. Network operations in telecommunications Figure 1.7. Radio broadcasting types Figure 1.8. The architecture of the interactive television (ITV) system Figure 1.9. Signals that are used in transmission Figure 1.10. Network of radio transmissions Figure 1.11. Infrared point-to-point system Figure 1.12. Microwave transmission from point to point Figure 1.13. Optical fiber characteristics Figure 1.14. Vehicular social networks’ physical communication architecture (VSNs) Figure 1.15. A telecommunications system Figure 1.16. The integrated services digital network (ISDN) is in operation (ISDN) Figure 2.1. An information system’s functions Figure 2.2. Various kinds of information systems Figure 2.3. Management and operations categorizations of information systems Figure 2.4. General model of transaction processing system (TPS) Figure 2.5. Representation of IS control Figure 2.6. Enterprise collaboration systems Figure 2.7. Management information systems (MIS) Figure 2.8. KMS Figure 2.9. The organizational framework of strategic information systems Figure 2.10. Progressive business information systems-ERP II Figure 2.11. Assimilated information system assisting operations in the industryuniversity association business process Figure 2.12. Modules of an information system

Figure 2.13. Categories of computer-based information systems (CBIS) Figure 2.14. Office automation systems Figure 3.1. Networking of computers Figure 3.2. A centralized network structure Figure 3.3. A framework for dispersed networks Figure 3.4. A LAN is a local area network Figure 3.5. A wide-area network (WAN) Figure 3.6. Non-return to zero level code NRZ-L N Figure 3.7. On one’s presentation code, NRZ-I stands for non-return to zero inverts Figure 3.8. A twisted couple Figure 3.9. Cable with coaxial connectors Figure 3.10. Fiber optics Figure 3.11. A network of meshes Figure 3.12. The structure of a tree Figure 3.13. Topology of the bus Figure 3.14. Topology of stars Figure 3.15. Topology of rings Figure 3.16. Hub of the token ring Figure 3.17. Framework for logical peer communication defined by ISO Figure 3.18. Application layers’ data frame Figure 3.19. Data frames sent via TCP Figure 3.20. Data frames sent via UDP Figure 3.21. An IP datagram’s structure Figure 3.22. Packet switching network Figure 3.23. A straightforward hub Figure 3.24. Hubs with many ports Figure 3.25. In an OSI structure, a repeater Figure 3.26. A straightforward bridge Figure 3.27. Multiple ports on a bridge Figure 3.28. A bridge’s position in an OSI process stack Figure 3.29. A router’s role in the OSI protocol stack Figure 3.30. A useful router Figure 3.31. A gateway’s operation Figure 3.32. A framework for the internet xii

Figure 3.33. A token data frame Figure 4.1. Computing system Figure 4.2. Computer memory systems are arranged in a hierarchy Figure 4.3. Main memory system and cache Figure 4.4. A memory hierarchy having three levels of caches is an instance Figure 4.5. Hierarchy representation of computer memory Figure 4.6. Virtual memory may work in tandem with the actual memory of a computer to offer quicker, more fluid processes Figure 4.7. Virtual memory system Figure 4.8. The virtual memory’s overall scheme Figure 4.9. Virtual memory enhancement Figure 4.10. Memory caches (CPU caches) employ high-speed static RAM (SRAM) chips, while disk caches have been often a portion of main memory consisting of standard dynamic RAM (DRAM) chips Figure 4.11. Cache data Figure 4.12. Logical organization Figure 4.13. A distributed cache combines the RAM of numerous computers into a single in-memory data store that serves as a data cache Figure 4.14. Single vs multi-level caches Figure 4.15. Kinds of DRAM Figure 4.16. Kinds of DRAMs Figure 4.17. DRAM organization Figure 4.18. Bank organization Figure 4.19. Management of cache Figure 4.20. Transferring a cache block Figure 4.21. DRAM scaling challenges Figure 4.22. The architecture of a three-dimensional stacked DRAM Figure 5.1. A useful representation of a connection network Figure 5.2. An interconnectivity link is used to link the CPU and memory Figure 5.3. The two message forms needed for the processor-memory link are shown Figure 5.4. A typical I/O network links a few host adapters to a greater number of I/O equipment, such as a disk drive Figure 5.5. Interconnection networks are used as a switching fabric by certain network routers, moving messages across line devices that receive and send packets through cable networks

xiii

Figure 5.6. The configurations of nodes, marked by rings labeled 00 to 33, and the routes linking the endpoints make up a network topology Figure 5.7. Packaging of a 16-node torus topology Figure 5.8. A 16-node network device has shorter latency than that of the 16-node, 2-D torus of Figure 5.6 for the limitations of our scenario. This delay comes at the cost of reduced capacity Figure 5.9. Two routes from 01 to 22 on the 2-D torus are seen in Figure 5.6 Figure 5.10. A time-space diagram illustrating two ways of flow control. The vertical axis represents space (channels), whereas the horizontal axis represents time (cycles) Figure 5.11. A simplification of a router’s block diagram Figure 5.12. Architecture of a router Figure 6.1. Structure of the mobile cell communication system Figure 6.2. Demonstrates two-way radio systems Figure 6.3. The MCN architecture’s key entities Figure 6.4. A mobile station is shown schematically Figure 6.5. Base station subsystem architecture Figure 6.6. Systems for integrated mobile networks Figure 6.7. The design of a complicated wireless communication network in the twentyfirst century, including linkages to wired backhauls Figure 6.8. People-focused mobile communication apps Figure 7.1. The network information infrastructure and the command, reconnaissance, and battle control system Figure 7.2. Framework for cyber-security Figure 7.3. Types of cyber-attacks Figure 7.4. Communication networks secure routing protocol Figure 7.5. Module for link-layer security Figure 7.6. Protocol for network layer security Figure 7.7. TLS stands for transport layer security Figure 7.8. Protocols for application-level security Figure 7.9. A simple example of firewall security Figure 7.10. Local area networks and intrusion detection systems Figure 8.1. Principal elements of the D2R2 + DR approach Figure 8.2. Illustrations of the active and backups pathways Figure 8.3. Classification tree for software fault/failure mitigation Figure 8.4. A strategy based on an environmental variety

xiv

Figure 8.5. An example of a failing in an area. A sphere of provided radial distance, positioned at the failing epicenter, represents the region of likely network breakdowns Figure 8.6. Probabilities of area collapse as an example Figure 8.7. An IP-over-optics network with A-/B-Plane architecture and how optical restoration is integrated into an ML resilience scheme are shown in this diagram Figure 8.8. A major paradigm shift is underway, moving away from fixed grid networking and toward a flexible modular optical transport network with adjustable reach and rate capabilities

xv

LIST OF TABLES Table 2.1. Types of distinct information systems Table 3.1. ISO Protocols layers with their accompanying Table 3.2. OSI datagrams include a header for each tier Table 3.3. TCP/IP protocols have many layers Table 3.4. ARP table is a kind of table that is used to Table 3.5. Interface 1 routing table Table 3.6. A routing table for gateways Table 5.1. Parameters of processor-memory interconnection networks Table 5.2. Parameters of I/O interconnection networks Table 5.3. Parameters of a packet switching fabric Table 6.1. Summary of the development of technologies

LIST OF ABBREVIATIONS 2G

second-generation

3D

three-dimensional

3G

third-generation

AH

authenticating header

AMPS

advanced mobile phone system

AP

active paths

ARBs

aging-related bugs

ARP

address resolution protocol

BP

backup paths

BSC

base station controller

BTS

base transceiver stations

CBCS

computer-based communications system

CBIS

computer based information system

CC

common criteria

CDMA

code division multiple access

CHAP

challenging handshake authentication protocol

CPU

central processing unit

CRC

cyclic redundancy check

DA

digest authentication

DARPA

Defense Advanced Research Projects Agency

DDoS

distributed DoS

DNS

domain name system

DoS

denial-of-service

DSS

decision support system

EAP

expandable authentication protocol

EDGE

enhanced data rates for GSM evolution

ESP

encapsulated security payload

FDM

frequency-division multiplexing

FIS

financial information systems

FTP

file transfer protocol

GPRS

general packet radio service

HIDS

host-based intrusion detection system

HRM

human resource management

HSDPA

high-speed downlink packet access

ICMP

internet control message protocol

IGMP

internet group management protocol

IGP

interior gateway protocol

IKE

IPSec key exchanges

ILD

injector laser diode

IP

internet protocol

IPS

information reporting systems

IPSec

internet protocol security

IPv4

internet protocol version 4

IS

information system

ISDN

integrated services digital network

ISDN

international standard digital network

ISM

industrial scientific and medical

ISO

International Organization for Standardization

ITU

International Telecommunications Union

LAN

local part networks

LED

light-emitting diode

LTE

long-term evolution

MAC

media access control

MANs

metropolitan area networks

MCN

mobile communication networks

MIS

management information systems

ML

multi-layer

MSC

mobile switching center

MSN

mobile social networks

NAMs

non-aging-related mandelbugs

NAT

network address translation

NFS

network file system xx

NIC

network interface card

NIDS

network-based IDS

N-ISDN

narrowband ISDN

NMT

Nordic mobile telephone

NRZ-L

non-return to zero level

NSP

name server protocol

OS

operating system

OSI

open system interconnection

PAP

password-based authentication protocol

PIN

personalized identifying number

PNO

public network operator

POTS

plain old telephone system

PPP

point-to-point protocol

PTT

post, telegraph, and telephone administration

QoS

quality of service

RAM

random access memory

SIM

subscriber identity module

SMTP

simple mail transfer protocol

SNMP

simple network management protocol

SSL

secure sockets layer

STP

shielded twisted pair

TACS

total access communication systems

TCP

transmission control protocol

TCP

transport control protocol

TCP/IP

transport control protocol/internet protocol

TELCO

telecommunications corporation

TLS

transport layer security

TMD

time-division multiplexing

TPS

transaction processing systems

UDP

user datagram protocol

UMTS

universal mobile telecommunications system

VPNs

virtual private network

WAN

wide-area networks

WEP

wireless equivalent privacy xxi

WIMP

window, icon, menu, and pointer

WLANs

wireless local area networks

WMNs

wireless mesh networks

WPA

wireless protected access

WWWW

world wide web

XML

eXtensible markup language

xxii

PREFACE The building of “information superhighways,” typified in the first instance by the tremendous expansion of the Internet, has introduced the general population to computers as a means of communication. The ultimate result is the ability to share computer-based resources that are geographically distributed around the globe. The techniques by which computers interact are best kept concealed from most users’ perspectives. However, no resource sharing would be possible without these systems. This book tries to reveal the fundamental concepts of computer communications and demonstrate how they support the actual communication systems. It is aimed at readers who will be involved in getting computers to interact as well as those who are simply curious about what goes on beneath the asphalt of the information highway. The work is purposefully narrowed in scope to issues of communication. It stays away from disciplines of computer science including computer programming, modeling, and simulation, as well as electronics, photonics, and mathematics. Other specialist literature deal with such topics. The reader needs no prior knowledge of computer communications and only a rudimentary understanding of computers in general. A basic familiarity of computer programming is not necessary; however, it would be helpful in a few areas. This, however, is unimportant to the primary narrative. Alternatively, the author thinks that the book can provide value to readers who have prior experience with computer communications by placing that experience in context and offering other options. This book varies from previous mainstream textbooks on computer communications in various ways. Although a beginner is unlikely to be bothered by this, a reader who is not familiar with the subject area may benefit from a brief explanation. First, uncover the fundamental principles of computer communication (which are heavily influenced by how humans communicate), and then apply these concepts in increasingly realistic scenarios. This is in contrast to a more traditional technique, which catalogs real instances of computer communication systems while underlining principles (often many times) as the cataloging progresses. One of the most essential advantages of this book’s approach is that it provides material that will stand the test of time. The book’s essential ideas have stood the test of time, even while major changes and improvements in actual computer communications have occurred. The book is divided into eight chapters. First chapter introduces the readers with fundamentals of computer communications. Chapter 2 deals with the types of information systems in detail. Chapter 3 thoroughly discusses the fundamentals of computer networks and relates it with communication. Chapter 4 introduces the readers with communication in computer memory systems. Chapter 5 focusses on the interconnection networks in detail. Chapter 6 illustrates the

phenomena mobile communication networks (MCN). Chapter 7 describes the security in communication systems. Finally, Chapter 8 focuses on the future directions in the design of dependable communication systems. The book provides an excellent overview of the many facets of the computer communication. The text succeeds in presenting the information in a manner that familiarizes the inexperienced reader with the important concepts of computer communication.

xxiv

CHAPTER

1

FUNDAMENTALS OF COMPUTER COMMUNICATIONS

CONTENTS 1.1. Introduction ........................................................................................ 2 1.2. Uses of Computer Communications.................................................... 4 1.3. Physical Links ................................................................................... 14 1.4. Physical Media and Their Properties.................................................. 15 1.5. Physical Communication Services..................................................... 23 References ............................................................................................... 30

2

The Role of Communication in Computer Science

1.1. INTRODUCTION The human race stands to benefit from improved communication. Sharing knowledge with others, whether it be historical anecdotes, current events, or forecasts for the next, is made possible via communication. This information may come from anywhere and at any time. In addition, by engaging with the appropriate individuals, resources, and specialist knowledge may be shared. Hermits will be the only people who are known for their capacity to live a contented life without any kind of interaction with other individuals (Wilson et al., 2009). If such a computer gets able to connect with other computers, three primary areas would likely benefit from this capability. It can obtain information that is saved on some other computers, it can instruct other computers to carry out specialized tasks, and it can connect with people who are using other computers (Hayes, 2013). The advantages don’t need to flow in just one way; this computer may also transfer its knowledge, as well as its specialized talents and access to the people who utilize it. The result is a product distribution of the available resources (Li et al., 2008). It is now the norm rather than the exception for computers included inside personal objects such as wristwatches or within household appliances such as microwave ovens to be unable to connect. This state of affairs is, therefore, on the verge of changing, because the connection between the most well-known categories of computers has shown to be of great benefit, and that proper communication technology is becoming more readily accessible (Bertoline et al., 2002). It is possible to get the impression that a typical home computer or a solitary computer hidden away in a stuffy office is just an island unto itself, shut off from the larger community of computers across the globe. This, however, is a fallacy because such computers often have an accommodating communication system, which consists of human people transferring the most recent products of the computing industry onto a memory stick or cd room (Santa et al., 2008). The topic of discussion in this article is computer interactions where no humans were acting as intermediaries; instead, machines can have a conversation with others directly. It is important to remember that computers only interact because humans had also instructed those to do so, and this is just feasible because humans had also directed the computers well on how to interact. This is true and although human involvement in the position of a middleman is gradually being phased out (Möller, 2016).

Fundamentals of Computer Communications

3

The covered methods are those that come from communication between different kinds of conventional computers. However, these are equally relevant to the future world, when there would be something like intelligent homes with interaction not just between household appliances but also of the fabric of the structure itself (Hacklin, 2008). Humans have a difficult time expressing themselves verbally at times. For instance, each person on earth can’t communicate properly with every individual whenever they so desire. This is because of the sheer number of people in the world. Civilization, accessibility, and physical address are three factors that contribute to problem-causing differences. When one expands communication to include the type of plant or animal, things get even more difficult, and that’s before we even consider the possibility of alien life forms visiting or being visited (Jiang et al., 2010) (Figure 1.1).

Figure 1.1. Communication using computer applications. Source: https://www.electronicsandcommunications.com/2020/08/role-of-computers-in-communication.html.

Computers can’t communicate with one another due to issues of a similar kind. For this, the solution that is employed is very like to those that have been established by humanity for millennia. As a result, the novice will typically recognize them from their regular human experiences. This is a positive development since it indicates that the explanation of procedures used may be adequately inspired by suitable examples drawn from human conversations (Fan, 2002). In addition to settling the disagreements that exist between the persons involved in the communication, another difficulty is in the manner in which communication is carried out. Movement and various forms of media are

4

The Role of Communication in Computer Science

both aspects of human life. People travel for a variety of reasons, including making communication simpler or even feasible. One could go up a mountain to confer with a mentor, travel with one’s place of employment, or go to a performance (Domingo & Prior, 2008; Sun, 1999). Once the individuals involved in the communication are all in a situation where they can do so effectively, communication may take place via the use of visual gestures, sound sent over the air, telephones, tv, or the mailing of products through the postal system. Communication between computers often does not entail any kind of movement since robotics is currently at a very infant stage of development. As a result of this, computers interact with one another via the use of media that can physically contact the computers and that is also capable of delivering computer talk fact, doesn’t rule out the idea that people may move computers to locations from where they could be accessed by various forms of media (Aspin, 1984) (Figure 1.2).

Figure 1.2. Various forms and modes of communication networks. Source: https://www.educba.com/types-of-communication-network/.

1.2. USES OF COMPUTER COMMUNICATIONS The current applications of computer communications are the result of a meeting of two worlds. One is a computer-centered world, in which computers already existed before it became practical to link them. Another is a humancentered environment in which confidential communications already existed before it became practical to computerize them. Telecommunications facilities primarily used mostly for inter-personal communications, like the telephone, and broadcast facilities primarily used for entertaining, such as televisions, converged in the later world (Salomon, 2006).

Fundamentals of Computer Communications

5

The global community is a concept that is frequently used to characterize the results of this universal convergence. It’s worth noting that when Marshall McLuhan originated this expression in 1964, he did so by relying on an alternative to current human-oriented capabilities, without anticipating the future participation of computer networks (Jackson & Stubbs, 1969). It’s also, however, as likely to accept computer-based capabilities. Another, more recent phrase for the technological revolution is the data super highway. This involves the collection of communication and information technology that will be used to support the future global community. The communication network will support the transportation of information in the same manner as highways support the mobility of persons and commerce (Kobayashi & Konheim, 1977) (Figure 1.3).

Figure 1.3. Communication network applications. Source: https://www.dtsecurity.net/enterprise-communications.html.

It is necessary to do a short historical study of how distinct communication networks arose and ultimately converged to better understand the present usage of computer communications and to look forward to future advancements. This is followed by the following three sub-sections, which discuss advancements in computer science, telecommunication, and broadcasting, correspondingly (Busse et al., 1996). The requirements that these various sorts of systems make if they are to be fulfilled by utilizing computer communication capabilities are a major problem. Time may be quantified in seconds, decimals, or multiples of seconds to measure these needs. Bits (short for ‘binary digits’) are used to quantify information (Knight et al., 1993). The amount of data accessible in a single bit is enough to discriminate between two potential values. To discriminate between ‘off’

6

The Role of Communication in Computer Science

and ‘on,’ ‘white’ and ‘black,’ or ‘no’ and ‘yes,’ one piece of information is sufficient. Because the bit is similar to any other unit, the kilobit (kbit), which is 1000 bits, and the megabit (Mbit), which is 1,000,000 bits, are useful terms. It’s worth noting that these are a power of ten, not the power of two (which are occasionally used in computer circles) (Kahn, 1972).

1.2.1. Computer-Oriented Communication The room full of boxes carrying the computer’s main components was the focus of interest in the early days of computing. Persons who’ve been physically available inside the computer lab contributed data to a computer and got data to a computer. Figure 1.4 shows a graphic representation of data communication (a). If there’s any connection among computers at all, it was done via transporting paper cassettes or magnetic media made by one computer to also be read by another. As a result, humans are just as many servants of computers as computers have been of people (Ziouva & Antonakopoulos, 2002).

Figure 1.4. Computer-assisted communication has progressed. Source: https://www.e-booksdirectory.com/details.php?ebook=3252.

Fundamentals of Computer Communications

7

People’s lives were made simpler by the early breakthroughs in communications, which eliminated being physically near a computer while engaging with it. One of them was the development of the remote terminal, which was a computer keyboard device with a keyboard for entry and a teleprinter for output that was linked to the computer through a wire. Figure 1.4(b) shows how this work. In effect, terminals were essentially additional computer peripherals, and therefore they were located a greater distance away. Since of this, and also because terminals were electromechanical devices, they functioned at extremely sluggish computer velocity: some few words per second input and roughly 30 letters per sec output (Ren & Wu, 2010). This fundamental skill developed into a form of computer communication that has lasted until the current day. There are two significant enhancements. One will be in terminal technology, where video displays have replaced printing and resulted in a significant boost in operating speed, as well as terminals with computers as their controllers (or, indeed, computers just emulating the behavior of terminals). If the computer is smart enough just to interact through a complete Window, Icon, Menu, and Pointer (WIMP) interface, it may be utilized instead of terminals (Wang et al., 1998). The other enhancement concerns computer communications. This means that any channel of communication capable of transmitting data between a computer and a terminal may replace the direct cord between them. Links via the traditional phone system or advanced computing networks are examples of usable communication routes. Figure 1.4 illustrates this in part (c). The Web became the most well-known specialized method for establishing connections between systems in all countries. In 1997, it was projected that the Web could be used by roughly 20,000,000 computers. The overall impression to a human user is that of a direct physical connection between terminals and computers, but it’s an illusion (Chiang et al., 1996). The increasing distance between the terminal and the computer creates two agreement issues that must be resolved for communications to be possible. First is that several terminals (or computers dressed up as terminals) may be utilized, and each terminal’s behavior must be harmonized with the computer’s expectations (Manvi & Venkataram, 2004). The person utilizing the terminal is the second issue. Through the keyboard, this individual provides orders to a computer or enters data into the computer. Because the terminal behaves as if it were a genuine computer

8

The Role of Communication in Computer Science

distributed system, the customer must understand how to interface with that specific sort of computer. This is okay if just a single computer is used through the terminal, however, the problem is that developments in communications now enable all types of computers to be used from anywhere around the globe. No one individual can be supposed to understand how to use all of the numerous computers available (Frost et al., 1988). To solve this difficulty, a user may simply communicate to his or her personal familiar computer, and also that computer will then engage with another computer of importance on the patient’s behalf. This automates a few of the tasks that human terminal users must do. The user’s computer claimed to be a human client of the remote computers in earlier iterations of such services (Grześkowiak et al., 2014). That is, it sent data from such a terminal keyboard (although with a quicker typist than usual) and subsequently received data from terminal printers or screens by posing as a terminal printer and monitor. Files could be transmitted to or recovered from remote computers, e-mail address is sent or received, and processing jobs could be assigned to distant computer systems and the results obtained. The human operator was in charge of these procedures (Jin & Bestavros, 2001). Such processes were modified throughout time to remove the need for superfluous humanization of computer discourse. That is, new deals defining suitable direct contact between computers have supplanted humans’ more verbose methods. The new deals encompassed file transfers, electronic communications, and job submissions, among other things (Thompson et al., 2008). Users eventually become more isolated from the whims of certain computer kinds as a result of such advancements. For example, irrespective of the sort of computers engaged in the email transfer, the very same user interface might be utilized for e-mail. Further developments in the insulating process resulted in distributed systems, in which a user is fully unaware of the presence of a cluster of computers. As a result, it looks like a single universal computer system is providing a service (Gerla, 1973). It’s quite typical in distributed applications for the machines involved to play both servers and consumer roles. Servers have unique capabilities, such as storing specific information, conducting certain data processing, or having specific input and output devices connected. Clients may interact with servers by sending requests and receiving answers (Brooks & Corey, 1966). Generally, this is comparable to how people engage with computers immediately. These computer client-server relationships, on the other hand, are concealed from humans in a distributed network. The World Wide Web

Fundamentals of Computer Communications

9

(WWW) is a well-known example of a user being provided with the illusion of a world of information. In actuality, the user’s computer serves as a user, and computers all over the globe that store certain WWW sites operate as hosts for this customer (Lim & Kim, 2001).

1.2.2. Telecommunications Human interaction via media has a long history. In the mid-nineteenth century, the telegram became a cost-effective means of transmitting information across large distances using Morse code or something similar. Morse code is similar to the bit-focused access to information utilized by computers in terms of esthetics. The distinction is that instead of two factors, information is represented in a three-valued form (dot, pause, and dash) (Juang et al., 1999). The requirement for a pricey physical wire between both communicating entities was the telegraph’s fundamental flaw. Telegraph networks were often developed in tandem with railroads, with telegraph lines running alongside railway lines. Because the pace of transmission was restricted to a speed at which individuals can press Morse keys to convey information and the rate at which others could hear the broadcast to decode the information, the channel was utilized inefficiently. As a result, the limitation was caused by human weakness rather than by any inherent physical constraint of the cabling (Lacan & Fimes, 2004) (Figure 1.5).

Figure 1.5. Diagrams of telecommunication networks. Source: https://www.pinterest.com/pin/832532681104272311/.

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The telephone was invented at the turn of the 20th century. A substantial investment in cables, similar to the telegraph, was required. The telephones, however, had been an analog instrument, in that the human voice was immediately translated to electromagnetic waveforms for communication, unlike the telegraph. The major difficulty with the analog transmission is that questionable impacts on the electric signals are reproduced on reception as audible crackles, whines, and other noises (Santa et al., 2008; Gallant et al., 2006). Most telephone networks nowadays use digital transmission methods, with voice encoded as a sequence of bits. That is because reconstructing a sequence of bits from a broken electric signal is far simpler than directly encoding speech. A sophisticated network of computerized nationally and internationally telephone exchanges offer a near-global telephonic communication system, putting us closer to our objective of enabling everyone on the planet to communicate with everyone else. Mobile phones are increasingly using radio transmission rather than wiring to transmit information (Layuan et al., 2007). The telephone network may be used to carry out computer-assisted communication, such as linking terminals to a computer. It does not include computers conversing with each other over the phone in a human manner. Rather, electrical waveforms like those used to encode voice are sent, but they encode a sequence of bits of computer-style data (Boukerche & Ren, 2008) (Figure 1.6).

Figure 1.6. Network operations in telecommunications. Source: https://favpng.com/png_view/telecommunications-network-telecommunications-network-other-telecommunications-computer-network-information-png/BgKZgLyD.

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The current phone network has progressed to the point that it resembles a networked computer system. The digital exchanges are nothing more than particularly unique computers with linkages between them that are analogous to computer links. Users of a phone system may get a completely digital service via the Integrated Services Digital Network (ISDN) service and other options. The usual subscriber, however, is still provided with classic analog-style service. The relation to data facilities is used to do this. As a result, if a subscriber utilizes the services for computer communication, the data is then passed through with an analog form before ever being delivered digitally, which is unnecessary (Isaac et al., 2008). Making a traditional telephone into a videophone, which transmits an image of the speaker and the user’s voice, is one option. A videophone service can be provided via a standard telephone line; however, the visual quality is poor. Another snag is that only a small percentage of individuals have video phone technology. However, the fundamental issue is that to encode images, significantly more data must be conveyed, necessitating the use of improved communication infrastructure (Wang et al., 1998). It is sufficient to send roughly 10 bits of data per second for voice alone. However, for video, a minimum of 60 bits per second is required, with a minimum of 1500 bits per second required for good quality. In contrast to a telephone, several telecommunication systems have been established that are aimed at sending textual data instead of direct human talks. One of them is fax (facsimile), which allows a phone user to send a picture of a textual page to the other (Christensen et al., 2004). This entails sending a digital representation of a page in form of bits of data across two fax machines, coded as a telephonestyle electrical current. Fax machines are essentially particularly unique computers that conduct conversations via analog telephone lines. Most computers now can mimic fax machine functionality, allowing them to send page pictures to certain other computers or fax machines. The amount of bits of data required to represent a faxed page varies depending just on the page’s portion. However, for a single page, roughly 200 bits is plenty (Chang et al., 2009). Telex-based information transfer services are another kind of service. Textual data is relayed across computers and terminals or between computers in such near cousins of computer-oriented communication. Telex is a lengthy telegraph service that enables customers to send textual messages to one other. Around the globe, there are over 1.2 million users, and the majority of them are enterprises (Balasubramaniam & Indulska, 2004). Upper case characters, arithmetic digits, and punctuation signs may

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all be used in the messages. These are transferred in digital format, albeit at a rate of just 50 bits per second, or 10 digits per second. Teletex would be a more current option that allows for a considerably broader character set, containing various icons and word processing page composition. It has a far quicker transmission speed of 2400 bit/sec, although, in current computer communications norms, this is still sluggish (Yi et al., 2007). Teletex and telex both are basic methods of sending digital data between the two specialized computers. Videotex is a networked computer system version that is similar to the customer concept. It’s connected to a regular phone line. A videotex user has a customized video terminal connected to a phone line that serves as that of the client. It can reach computer databases all across the globe and then perform research online. The server is the data. Videotex often is found at travel agencies, wherein video terminals have been used to query vacation and ticket booking systems so over the phone. Videotex is an instance of a telecommunication supplier’s value-added service. Additional services are given on top of the basic communication capability. This service exemplifies the merging of telecommunication and computer-based communications (Deak et al., 2012).

1.2.3. Radio and Television Broadcasting A free international communication channel, the electrical spectrum, was exploited all around the turn of the 20th century, at the same time that telephones were becoming accessible. This enabled physical processes including radio waves to be used for communication instead of costly wiring. The initial use was a wireless telegraph system. The apparent purpose of such a medium—transmitting—was not understood till after First World War, which seems bizarre in retrospect. This was partly owing to the perception that telecommunications were only useful for closed business and military uses, instead of for the public at large. To converse immediately, the typical individual was still required to travel. Another issue was the high expense of sending or receiving equipment, notwithstanding the absence of wire fees. Public radio and tv broadcasting services have grown dramatically since those early days (Kassar et al., 2008). The sound and visual data of television and radio were delivered as an analog transmission until the late 20th century. Aerials are used to capture these signals, which are subsequently decoded. In 1997, digital transmission, in which sound and images are transmitted using a sequence of bits, was still in its infancy. This is, without a doubt, the broadcast method of the future,

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combining television and radio with computer-based communications (Marco et al., 2008). Television and radio broadcast needs are substantially greater than the videophone and telephone. That is because, unlike speech production, the whole spectrum of audible sound must be transferable in the instance of radio. Furthermore, amenities such as stereo speakers are desired. The transmission rate required for high-fidelity audio transmission is around 100 kilobits per second, which is ten times that required for the telephone (Maddikunta et al., 2020). Television images are bigger, have more information, and entail more movement across time. The data rate required for television-quality video transmission is around 15 Mbits per second, which is 10 times the rate required for high-quality video communication. Notice that these rates are really for digital transmission, which means that the information may be compressed to suit these rates by considerable computer processing. The needed rate for video footage transmission is substantially greater without any such processing (Nasser & Chen, 2007) (Figure 1.7).

Figure 1.7. Radio broadcasting types. Source: https://www.agilebroadcast.com.au/types-of-radio-broadcasting/.

Teletext is a comparable feature connected with television, much as videotex permits the retrieving of digital information through the telephone system. Take note of the small name distinction between Teletext in the world of television and teletex in the telecommunications sector. In comparison to teletex, videotext allows for significantly less interactivity (Shomron & Schejter, 2020). The television receivers must then filter out the data it is of

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no use from the continuous transmission of all accessible information. As opposed to videotex, in which a user actively begins searching for relevant information, in videotex, a particular user begins searches seeking relevant data. Teletext, similar to videotex, shows a confluence with computerassisted communications (Sun & Zhang, 2020) (Figure 1.8).

Figure 1.8. The architecture of the interactive television (ITV) system. Source: https://www.researchgate.net/figure/nteractive-television-ITV-systemarchitecture-Digital-video-broadcasting-is-an_fig2_26449598.

1.3. PHYSICAL LINKS Computer communications, like human communication technologies such as the television and telephone, are supported by physical media such as electrical wires and transmissions in electromagnetic radiation. This book isn’t concerned with the physical specifics of how these media are used, but instead with their actual behavior: in other words, how effective they are still in transmitting knowledge. This includes factors such as transfer rate, dependability, and, obviously, cost (Coase, 1979). Lastly, physical media should serve as routes for information conveyed among computers from a spatial standpoint. The amount of range that a certain medium may cover is a basic feature. As the distance grows, most mediums

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degrade the quality of communication until practical bit communication is no longer practicable. This impact is often linked to the rate of transmission; in general, the quicker the rate, the smaller the range that most mediums can cover (Burch et al., 2006). Apart from space and distance, the basic features of media may be divided into two categories. The contrast between connectionless and broadcast media is such an example. The former enables a computer to communicate with another computer (Perretti et al., 2008). This is the kind of communication that you’re used to it from the telephone network. The latter allows a single computer to transmit data to a large number of many other computers, some of which could choose to accept the data while others may not. This is a style that you may have heard on the radio or seen on television. This difference should not be mixed up with another distinction (Slotten, 2000). There is a distinction to be made between unguided and guided media. The former entails the use of a few types of power cables to physically mentor transmitted bits around on their channel. The latter entails transmission ‘through the air,’ with impacts trying to spread over a larger area, including the channel’s destination(s) (Umeh, 1989; Clark et al., 2007). Radio telephones for connectionless, unguided transmission and cable television for the telecast, guided transmitting are two less obvious ones. The term “wireless” is also applied to unguided media, indicating that there are no cables involved. This group includes radio, which has long been associated with the term “wireless” (Meadows & Foxwell, 2011).

1.4. PHYSICAL MEDIA AND THEIR PROPERTIES Effective physical media have the fundamental property of including the continuous transfer of information from one place to another while in operation. This signal is being used to encode one or even more bit sequences that make up the data to be conveyed. There is a contrast between analog and digital signals. A digital signal may take on a limited number of distinct values, such as intermediate values for a digital binary signal. The signal’s value varies in discrete stages throughout time. An analog signal contains values derived from a considerable range, and the signal’s value fluctuates over time within that range (Orlandini & Micheletti, 2021) (Figure 1.9).

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Figure 1.9. Signals that are used in transmission. Source: https://www.amazon.co.uk/Computers-Communication-Gordon-Brebner/dp/0077091981.

Figure 1.6 depicts instances of such two signal kinds as they evolve. While the phrases analog” and “digital” are well-known in the computing world, the terms “baseband” and “broadband” are frequently used interchangeably in the computer communications world (Caraglio et al., 2017). The ambiguity stems from the fact that these phrases have specific connotations in the telecommunication sector, related to how frequency bands are employed.

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However, this isn’t a pressing worry in this case. Another caution is that the phrase ‘broadband’ is already it is used as an adjective to refer to ‘high speed,’ as opposed to some other technical term, ‘narrowband,’ that is now commonly used to refer to ‘poor speed’ (Groß et al., 2006). Below, the most widely used computer communication mediums are studied in order if possible (rather than usual) transmission rate. As a result, unguided media is shown first, followed by directed media. The most significant advantage of unguided media versus directed media is mobility. The necessity for computers to be close to interconnecting cables is no longer a constraint. Mobility becomes real portability when the equipment required for sending and receiving across an unguided channel is tiny and light (Mangano et al., 2006). There are very few surprises in store for the reader below, as all of the media ought to be recognizable from regular human communication networks. Two further special-case proposals from the Online community are left out of the presentation. One seems to be Weitzman’s ‘avian carrier’ method, which includes bits being transported on a roll of paper linked with one leg of an avian carrier and was suggested on April 1, 1990. Another is Eriksson’s ‘acoustical communication medium’ method, which includes bits being transferred using Morse code on sound waves created by a personal computer’s beeper, and was suggested on April 1, 1996 (Main & Burton, 1984).

1.4.1. Radio Radio signals are an analog, unguided, broadcast medium. Distinct radio wave waveforms indicate the two separate bit values. Radio has long been seen as the Cinderella of a digital communications industry, with amateur radio enthusiasts using it mostly for leisure purposes (Haynes & Goh, 1978). One significant exception is pioneering the use of radio to connect computers spread across many Hawaiian Islands, which has influenced numerous areas of computer communications in general. With the introduction of personal computers and cell phone connectivity, radio now is ‘coming to the ball.’ Radio is a cost-free media with a variety of computer connection options (Lu et al., 2013) (Figure 1.10).

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Figure 1.10. Network of radio transmissions.

Across relatively short distances, such as inside a city or town, or over a tiny rural region, radio broadcasting is employed. Transmission rates are modest across such distances, as low as 50 kbit/sec (Wallach, 2019). However, speeds of 10 Mbits/sec are possible across considerably shorter distances, such as 100 meters. This provides some flexibility while maintaining decent (i.e., computer-like) speeds. Each sent bit travels at the light speed along a straight route, resulting in the least feasible delay. Disturbance from a geological location such as mountains and lakes, to not mention amateur radio enthusiasts, is an issue with radio across long distances, and this may result in a high probability of bits getting to a reception damaged. In adverse air circumstances, the whole sequence of bits may be lost. Indoors, this is much less of an issue across short ranges (Bilderback & Fonteno 1987).

1.4.2. Infra-Red Infrared communication uses a high-frequency waveform than radio and is excellent for short-range communication. It is a common medium in the house for stuff like wireless television controls. Because infrared radiation cannot penetrate through solid things like radio waves, its employment is limited to interior rooms. Because the sun’s rays interact with infrared, it is usually not used outside. Infrared transmissions are not controlled, unlike radio, which requires the central allotment of radio frequencies to users. This is one benefit of in-room usage (Fonteno & Nelson, 1990) (Figure 1.11).

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Figure 1.11. Infrared point-to-point system. Source: https://www.geeksforgeeks.org/infrared-light-for-transmission/.

Infrared is just an unguided, natively single-hop medium that may be utilized in both unicast and broadcast modes. An infrared ray is simply aimed towards a recipient for unicasts. A diffuser is being used to scatter out infrared transmissions so that they may be received across a room during broadcasts (Schwarz & Bischofs, 2005). Slower infrared transfers, up to around 2 Mbits/sec, are carried out via digital transmission. This entails turning on or off the infrared beam to indicate the two distinct bit values. Analog transmission, similar to radio, is required for higher transmission rates of roughly 10 Mbits/sec. The various bit values are indicated by distinct waveforms. The key difficulty with infrared transmission dependability is guaranteeing that the beams are not disrupted by a person or item along the route. For the length of the blockage, this results in the entire loss of such a bit stream (Raviv et al., 2001).

1.4.3. Microwave Microwaves are in the electromagnetic radiation between infrared and radio. Microwaves are often employed over vast distances, but infrared is an interesting alternative to radios over extremely short distances. Microwaves with in Industrial Scientific and Medical (ISM) waveband are, nevertheless,

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used across short distances. ISM is given one waveband globally, thus broadcasts may be done locally with no additional restrictions (Belyaeva & Zaitsev, 1997) (Figure 1.12).

Figure 1.12. Microwave transmission from point to point. Source: https://ecomputernotes.com/computernetworkingnotes/communication-networks/microwave-transmission.

Microwaves, like an unguided unicast medium, move in a fixed direction and are tightly focused. The transmission method is analog. Microwaves, which operate in the direct connection between two sites, may be utilized for terrestrial communications across lengths of up to 50 kilometers. Microwave transmission served as the backbone of the lengthy telephone system for many decades until the introduction of fiber-optic cables (described below) (Awang et al., 2009). The earth and geosynchronous orbit satellites communicate through microwaves as well. Global distances may be bridged by using satellites to bounce communications. Because of the curving of the planet, transmission occurs is not feasible. The microwave travels outside of the atmosphere for the majority of its journey when utilizing such a satellite, reducing interference and improving dependability. Microwaves are susceptible to interruption inside the atmosphere, such as when traveling through the rain. Geostationary satellites orbit 36,000 kilometers just above the equator and circle at the very same rate as the planet, giving them the appearance of being stationary from Earth. The satellite location is strictly controlled (Noguera et al., 1996). The initial suggestions for limited satellite collecting were proposed in the 1990s. These orbits will not be geostationary since they are just 750

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kilometers in height. Instead, a significant number of satellites are all in orbit to ensure at least one is always over every given region. Motorola proposed the Iridium low-orbit satellite project, which includes 66 satellites and is aimed toward mobile phones (and six spares). The very first three satellites were launched in early 1997, with the system expected to be operational in 1998. The Teledesic project, planned by Microsoft and McCaw Cellular Communications and aimed at high-speed computer networks, consists of 840 satellites (plus 84 spares) and is expected to be operational by 2001 (Yu et al., 2009). Microwaves can transmit data at speeds of up to 50 megabits per second across vast distances. However, owing to the 72,000 km round-trip distance to and from the satellite, the delay in receiving each sent bit is roughly 250 milliseconds when a geostationary satellite is used as an intermediate. In computer terminology, this delay is quite high. When a low-orbit satellite is employed instead, the round-trip duration is decreased by a ratio of 50 (Heiskanen, 1995).

1.4.4. Copper Cable Copper cable has been the most common and conventional directed transmission system, in comparison to the aforementioned unguided media. Electrical impulses that indicate bits are sent using this method. The phrases ‘baseband’ and ‘broadband’ are often used to describe this medium, which may be analog or digital transmission. Digital transmission is utilized across short ranges, such as up to 1 kilometer, where interference effects influence dependability. Because analog communication is more resistant to interference, it may be utilized over longer distances, up to 100 kilometers (Goh & Haynes, 1977). Copper cables come in two different types of packaging, both of which are used in most homes. One is twisting pair, which is used to link telephones to the exchanges by twisting two wires together in a helical resembling a DNA structure. Coaxial cable, on either hand, is made up of a woven cylindrical wire that surrounds a rigid core wire and is used to link television to antenna arrays (Handreck, 1983). Twisted-pair cable has been the most common form of twisted pair cable (UTP). The two most prevalent quality classes for this cable are Grading 3 and Grading 5, which define the transmission speeds and distances that may be achieved. Four twisted pair wires are often packaged together, a technique

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that dates back to telephone cabling (Fouda-Onana et al., 2009). This is used in various computer wire setups; for example, three parallel Grade 3 UTP cables may provide a 100 Mbits/sec rate of transmission across 100 meters. A solitary Grade 5 UTP cable may be used to accomplish the same results. Shielded twisted pair (STP), contrary to UTP, has the twisted pairs wrapped inside a defensive cover to decrease interference. STP cable offers superior transmission properties than UTP cable, however, it requires much more attention during installation (Michel, 2007). Twisted pair cable is less expensive than coaxial cable. Although both forms of cable provide 100 Mbit/sec transfer speeds across small distances, the cable allows for better transmission rates across greater distances than twisted pairs. Twisted pairs, for example, can only transmit roughly 4 Mbits/ sec over a distance of at least a kilometer, but the coaxial cable can transmit 100 Mbits per second over the same distance. Because electrical signals move at around two-thirds the velocity of light, the latency for every bit is not as low as it might be, and while it is adequate. As provided as the signals are not susceptible to any outside electrical interference, performance is much greater than for the different unguided media listed above (Kordonsky et al., 1990).

1.4.5. Fiber Optic Cable The guiding technology that becomes the standard for computer communications is optical fiber cable, which transports light pulses that are used to encode bits. The cable is made up of glass fibers that are shielded from outside light sources by a plastic covering. Bits are communicated digitally, with such a flash of light representing pieces of info in the lack or absence of a flash of light. Fiber optic cable has mostly replaced microwave transmission over vast distances in the lengthy telephone system (Carlile et al., 2015). As cable television providers go on about their work, it is also working its way into several streets, although stopping just short of individual homes. Fiber optic cable is extremely inexpensive to produce and has several benefits over the electrical wire. It has a range of up to 100 kilometers and is virtually completely dependable because the transmitted rays are not impacted by extraneous electrical or magnetic disturbances (Dai et al., 2013) (Figure 1.13).

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Figure 1.13. Optical fiber characteristics. Source: https://www.unitekfiber.com/what-is-optical-fiber-what-is-the-difference-betwe.html.

In 1997, transmission speeds of roughly 100 Mbits/sec were normal, with transmission rates of 1000 Mbits/sec also being utilized in practice. The rate of millions of Mbits/sec is theoretically possible. Each bit travels at around two-thirds the light speed, which is comparable to the delay of electrical connection (Brückner, 1996). Because the conversion between the electrical signals in use by computers as well as the light signals needed for transmission slows transmission, the achievable transmission rates pose an issue for traditional computers. Optical computing, in which photonics instead of electronics is employed as the internal foundation of computers, is one approach under consideration (Gaver, 1992).

1.5. PHYSICAL COMMUNICATION SERVICES Physical linkages supplied by a global telecom carrier (also called a ‘carrier,’ a ‘public carrier,’ or a ‘common carrier’) are usually required for communications beyond a privately held territory. TELCO (short for ‘telecommunications corporation,’ PNO (short for ‘public network operator,’ and PTT (short for ‘post, telegraph, and telephone administration) are examples of companies that function as carriers. Till the mid-1980s, each nation had a single carrier that controlled the market. This was AT&T in the United States (operators of the Bell telephone system). In other nations, this was frequently a government department that dealt with all forms of communication (as the PTT name suggests) (Brady et al., 2016). When AT&T was broken up into several lesser component firms in 1984, the telecommunications industry in the United States was altered, allowing serious rivals to emerge. MCI and SPRINT are two instances of companies that have evolved into thorough assessment carriers in the United

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States. Originally, MCI stood for ‘Microwave Communications Inc,’ which reflected the company’s usage of microwave transmission, but it has now transitioned to fiber optic cable. The ‘SPR’ in SPRINT stands for ‘Southern Pacific Railway,’ referring to the company’s utilization of cables that run alongside current rail rails on railway territory. Private enterprise and regulation have also resulted in the emergence of a competitive market in other nations. This covers telecommunications services provided by firms that provide cable television (Toutain et al., 2011). The usual amenities provided by public transportation are listed below. These vary from traditional telephones to advanced telephone services such as Integrated Services Digital Network (ISDN) to specialized digital transmission lines rented from carriers. From the standpoint of computer communications, all of them are guided by unicast media. Analog transmission is used on the phone, whereas digital transmission is used on the others. It’s worth noting that this section solely covers public carriers’ raw transmission capability (Jazdi, 2014) (Figure 1.14).

Figure 1.14. Vehicular social networks’ physical communication architecture (VSNs). Source: https://www.researchgate.net/figure/Physical-Communication-Architecture-of-VSNs_fig1_321891283.

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1.5.1. Telephone System The global telephone system, often known as Plain Old Telephone System (POTS), was created to transmit the human voice. It enables a mobile user to make the call to any of the millions of other phones across the globe. This comprises mobile phones that use radio transmissions to connect to the POTS’ main wire backbone (Rana & Bo, 2020). The POTS sends out analog electric waveforms that resemble speech, having wave frequencies ranging from 400 to 3400 hertz permitted to pass through. Long-distance lines, and several localized parts of the system, now employ digital transmission, despite the analog interface. This feature of the mobile system is described below (Manzalini & Zambonelli, 2006) (Figure 1.15).

Figure 1.15. A telecommunications system. Source: https://www.geeksforgeeks.org/introduction-to-telephone-network/.

The focus here is on how to leverage the analog user experience to enable computer communications. In truth, it’s not much different from utilizing radios or broadband coaxial cable straight. The two input values are represented by different signal waveforms. The conversion is carried out by a device known as a modem (short for modulator-demodulator). A waveform indicating a series of bits just on phone should always have a frequency within the permitted 3000 hertz range, otherwise, it wouldn’t travel through POTS intact. The pace at which information may be sent is severely limited as a result of this phenomenon (Ferrari, 1990). According to information theory, the maximum speed for normal telephone system settings is roughly 35,000 bits per second. Some modems

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can function at a rate of 33,600 bits per second. This is effectively a realistic upper bound for modem technology over analog telephone links, and the like modems may be required to function at reduced rates (e.g., 28,800 bits per second) over conventional telephone circuits. Modems capable of 56,000 bits per second started arriving towards the end of 1996, but they need an all-digital telephone connection, which has a theoretical top limit of 64,000 bits per second. Other modems offer greater speeds than information theory permits, however, this is accomplished by compression of the stream of bits before it has been sent over the POTS (Gebhardt et al., 2003). Another disadvantage of POTS as just a computer communication channel is its high error rate. This is because people do not need perfection to understand speech sent over the telephone. People may overlook hisses, crackles, and the odd loss of word fragments. In terms of bits, a telephone connection could have an error rate of 1 in 10,000 bits conveyed being corrupted, however, current digital lines are far better. In contrast, most direct media, including such coaxial or fiber optic cable, have a figure of 1 in. As a result, while utilizing a telephone connection, computers should take many more measures in terms of mistake detection and repair (Sunny et al., 2018).

1.5.2. Integrated Services Digital Network (ISDN) As previously stated, the telephone system’s interior workings are now mostly digital. The resultant service is known as the Integrated Services Digital Network when it is expanded to give a digital interface to the enduser (ISDN). The term alludes to the fact that the service may carry not just voice but also other sorts of data. ISDN allows you to send anything that could be represented in digital bits. Calls may be placed to any ISDN subscriber, just as they could with the telephone system. Another advantage of all-digital transmission is that bit transfer reliability is substantially improved (McKinley et al., 2006) (Figure 1.16).

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Figure 1.16. The integrated services digital network (ISDN) is in operation (ISDN). Source: https://www.nextiva.com/blog/what-is-isdn.html.

The initial ISDN service was designed in 1984 to build a global system by the turn of the century. This occurred before it was evident that high-speed computer communications and real-time video communications would be in significant growth in the future (Rak et al., 2016). As a result, the service’s bit transfer rate was relatively low. To reflect its humility, it is currently called Narrowband ISDN (N-ISDN). The N-ISDN basic service, which is intended to replace a traditional telephone line, has two 64-kbps digital channels for speech or data transmission and a 16-kbps control channel. Because each 64 Kbit/second channel can carry digital voice, N-ISDN effectively provides the average of two phone lines instead of just one (Avagnina et al., 2002).

1.6. HOW COMPUTERS COMMUNICATE It may appear from the preceding sections that there is little to say about the gap that exists between user needs as well as the physical transmission services that are offered. That’s not the case, and it is the topic of the remainder of this book. If computers are not used, it is possible to provide user services via physical media, as the conventional phone system and television and radio systems demonstrate. When computers are incorporated into the picture, though, there is a lot more room for bringing nuance into the communications network, as well as what could be done with it. As a consequence, the provision becomes a distributed data processing system (Vaelcker, 1986).

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This section contains a brief explanation of the key principles that support the remainder of the book’s content. The substance is not structured in the traditional way that most computer communications books are organized: starting with the functionality of the physical data transmission, and then displaying how to add layers of richness until you can build a service that can directly support the needs of a distributed information system (IS). Two practical concerns underpin such a method. One of these is communication and computer system practical engineering. The other one is a conceptual framework that is often utilized by individuals when they are trying to agree on how computer communications must function (Maggiani, 2009).

1.6.1. Information, Time, and Space The discovery of three different aspects of computer communication: information, place, and time, is a primary strand of a book. These have previously been mentioned in this chapter and relate to the communication’s ‘what, where, and when’ (Repenning et al., 1998). The term “time” relates to how communication unfolds more than any amount of time. This involves questions such as when a communication timeframe starts and closes, whether the communication is constant during the time frame, the time it takes for data to move among computers, and the pace at which data is sent (McMahan, 2004). The computers participating in the communication, as well as the route that connects them, are referred to as space. This necessitates the creation of a system for identifying computers and networks. There’s also a natural measurement for time—seconds, for example—but a natural measurement for space, such as physical location, is insufficient since computers are likely to shift about. The function of the route in any communication is to provide a method for data to flow among computers in the manner dictated by the communication’s patterns of information exchange. For example, within the simplest instance, where just two computers are exchanging information, a channel must enable data to flow in both directions between the machines (Bell, 1974). It’s useful to envision a conversation being observed from the outside. After that the communication has occurred, the viewer will be aware of both dynamic and static elements of the communication—the information transmitted and the area across which it was sent—as well as the time of the process of communication. This specific point of reference is critical. First, because many communication is evolving in character, the precise nature

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of the communication may not be understood either during its execution. Secondly, because many communications are dispersed in nature, the actual nature of communication may not be understood by some of the computers engaged at any point (Sheldon, 2008).

1.6.2. Agreement and Implementation Two concerns are crucial to every one of the three factors of communications (Game, 1996): • agreement; and • implementation. The term “agreement” refers to the process of resolving disagreements among computers over the elements of communications. This is the distinguishing characteristic of computer communications, which distinguishes this from the analysis of individual computer networks. Relative and absolute agreement is the two most common types of agreement. When communicative parties reach an absolute agreement, they function inside a pre-determined environment. When communicative parties establish relative agreement, they come to an agreement whenever a speech act occurs. When a conversation starts, for example, one side may simply agree to deal with the style of communication utilized by the other party. It’s worth noting, however, that all comparative agreement configurations have a surrounding absolute agreement. This explains how the proportional arrangements will function (Clark, 1999). Application is focused on what a communication’s intended informational, duration, and space qualities may be achieved using a different sort of communication, generally anything simpler and much more physically realistic. This isn’t just about how well the communication could be done at all; it’s about the reliability of the application as well. latency, speed, dependability, security, and price are all factors to consider. Implementation issues are, obviously, well-known in the field of computer science. A person user is presented with a fairly appealing interface. However, in the end, this will have to be done using the computer’s extremely basic electrical circuit boards. A similar system exists in computer networks, in which a user-friendly communication service should be established in terms of the basic capacity to transmit bits of information among computers (Freiermuth & Jarrell, 2006).

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CHAPTER

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TYPES OF INFORMATION SYSTEMS

CONTENTS 2.1. Introduction ...................................................................................... 42 2.2. Categories of Information Systems .................................................... 43 2.3. Management Information Systems (MIS) ........................................... 47 2.4. Other Categorizations of Information Systems................................... 49 2.5. Modules of an Information System .................................................... 52 2.6. Resources of Information System ...................................................... 53 2.7. Information System Activities ............................................................ 56 2.8. Computer Based Information System (CBIS) ...................................... 57 2.9. Data Storage in MIS .......................................................................... 61 References ............................................................................................... 64

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2.1. INTRODUCTION The definition of an information system (IS) is based on two viewpoints: one on its function and the other on its structure. The IS, from a functional viewpoint, is a technologically advanced platform for recording, saving, and transmitting expressions of language, along with aiding inference making. An IS, from a structural viewpoint, is made up of a group of people, procedures, information, models, technologies, and partially codified language that form a cohesive structure that fulfills some organizational objectives or function (Al-Mamary et al., 2014). The functional definition is advantageous since it emphasizes on what consumers do with the medium of IS from a conceptual viewpoint when using it. They communicate with specialists to tackle a specific issue. ISs are sociotechnical systems—for example, systems composed of persons, behavior norms, and conceptual and practical artifacts, as indicated by the structural definition (Menon et al., 2009). Technically, an IS is a collection of interconnected modules that gather, process, save, and distribute data to aid decision-making and management in an organization. ISs can aid managers and employees in analyzing problems, visualizing difficult subjects, and developing novel products, in addition to assisting in decision making, synchronization, and control (Stine et al., 2008). Three processes within an IS generate the data necessary for enterprises to make choices, monitor operations, evaluate problems, and develop novel products. These three processes are (Gregor, 2006): • input; • processing; and • output. Input collects or gathers raw data from the internal or external environment of the company. This input is transformed by processing into a more useful format. The output transmits the processed data to the individuals or activities that will use it. IS also need review, which is generally an output that is sent to the relevant organization members to assist them in evaluating or correcting the input phase (Bhatt & Grover, 2005) (Figure 2.1).

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Figure 2.1. An information system’s functions.

ISs in the actual world can be categorized in numerous ways theoretically. Various kinds of ISs, for instance, can be theoretically classed as management or operations ISs (Bradley et al., 2006).

2.2. CATEGORIES OF INFORMATION SYSTEMS Different kinds of ISs are demonstrated in Figure 2.2 (Edalat & Smyth, 1991).

Figure 2.2. Various kinds of information systems. Source: https://www.managementstudyhq.com/six-major-types-of-informationsystems.html.

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2.2.1. Operations Support Systems ISs have often been required to process data produced and utilized by company activities. These operations support structures generate a number of internal and external information products. Nevertheless, they don’t prioritize the production of specialized information products that managers may most effectively utilize. Typically, additional processing of information by management information systems (MIS) is necessary. The purpose of a company’s operations support systems is to effectively manage commercial transactions, regulate industrial procedures, facilitate enterprise interactions and cooperation, and upgrade corporate databases (Rashid et al., 2021) (Figure 2.3).

Figure 2.3. Management and operations categorizations of information systems. Source: https://slidetodoc.com/chapter-2-2-fundamentals-of-information-systems-2/.

2.2.2. Transaction Processing Systems The principal group of transaction processing systems (TPS) is included in operations support systems. Data from commercial transactions is recorded and processed by TPS. ISs that manage sales, purchases, and stock changes are common examples. Customer, stock, and other organizational records are updated as an outcome of this procedure. These systems then give information sources for management IS, decision support networks, and executive IS to process and use (Star & Bowker, 2007) (Figure 2.4).

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Figure 2.4. General model of transaction processing system (TPS). Source: https://www.researchgate.net/figure/Basic-Model-of-Transaction-Processing-System_fig3_290676562.

There are two fundamental ways through which TPS process transactions. In batch processing, information of transaction is collected over time and periodically processed. Data is processed instantly after a transaction takes place in real-time processing. POS systems in retail outlets, for instance, might utilize electronic money register devices to gather and transfer sales data across telecommunication links to regional data centers for immediate or nightly processing (Narayana Samy et al., 2010).

2.2.3. Process Control Systems Additionally, operational support systems make regular choices that regulate operational procedures. Examples include automatic reordering of goods and production control choices. This covers the category of IS known as process control systems, in which computers autonomously alter a physical production procedure. A petroleum refinery, for instance, uses electrical sensors connected to computers to continuously observe chemical processes. The computers observe the chemical process, collect, and analyze data gathered by sensors, and make immediate modifications to the necessary refinery procedures (DeLone & McLean, 1992) (Figure 2.5).

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Figure 2.5. Representation of IS control. Source: https://www.semanticscholar.org/paper/Information-SystemsControl%3A-A-Review-and-Framework-Cram-Brohman/51cbc6f6b3ed2b68b7 ecd9b1bf97c31b8abc70e5.

2.2.4. Enterprise Collaboration Systems These are ISs that help people collaborate by utilizing a number of information techniques. As members of the various informal and formal business and project groups and some other teams that are a critical element of today’s enterprises, enterprise collaboration platforms enable us to cooperate to communicate ideas, exchange resources, and manage the cooperative work endeavors. As a result, the purpose of workplace association systems is to employ information technology to boost the productivity and creative thinking of teams and task forces in today’s industry (Mu’awanah & Airlangga, 2021) (Figure 2.6).

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Figure 2.6. Enterprise collaboration systems. Source: https://www.researchgate.net/figure/Enterprise-collaboration-process_fig1_264336298.

2.2.5. Management Support Systems When ISs are designed to provide managers with information and assistance for efficient decision-making, they are referred to as management support systems (Laurini & Thompson, 1992).

2.3. MANAGEMENT INFORMATION SYSTEMS (MIS) The most frequent type of management support system is MIS. They supply digital products to managerial consumers that help them with a lot of their daily decision-making. MIS provide management with a number of statistics and displays. Managers specify the content of these digital products in advance to ensure that they consist of information that supervisors require. Information regarding internal operations is retrieved by MISs from databases that have been upgraded by TPS. They also get data on the corporate environment from a third-party source (Majchrzak & Markus, 2012). The information products supplied to managers comprise displays and statistics that can be sent (a) on demand and (b) on a predefined timetable (Yew, 2008) (Figure 2.7).

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Figure 2.7. Management information systems (MIS). Source: https://www.toppr.com/guides/accountancy/application-of-computersin-accounting/management-information-systems-and-accounting-informationsystem/.

2.3.1. Decision Support Systems (DSS) These systems are an advancement from Information reporting systems (IPS) and TPS. These systems are dynamic, computer-based IS that utilize decision models and particular databases to aid management consumers in making decisions (Shah, 2014).

2.3.2. Executive Information Systems These are MIS that are customized to the strategic data requirements of the executive level. Executives obtain the information they require from a variety of sources, comprising manual and computer-generated letters, memos, journals, and assessments (Davis, 2003). Other information sources for executives include meetings, phone conversations, and social events. Consequently, the majority of a chief executive’s information originates from non-computer services. Many senior executives’ information requirements haven’t been primarily met by computer-originated information (Ehie, 2002; Mason & Mitroff, 1973).

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2.4. OTHER CATEGORIZATIONS OF INFORMATION SYSTEMS 2.4.1. Expert Systems It is a knowledge-based IS that acts as an external expert to clients by using its expertise of a specific subject. The knowledge base and software components that conduct deductions on the knowledge and provide replies to a user’s questions are the parts of this system (Apté et al., 1994). These systems are employed in a variety of sectors, such as health, engineering, and business. Expert systems, for instance, currently assist in the diagnosis of illnesses, the exploration for minerals, the analysis of compounds, the recommendation of repairs, and financial management. Expert systems can help operations and management (Wade & Hulland, 2004).

2.4.2. Knowledge Management Systems (KMS) This system enable employees to develop, organize, and exchange crucial business information whenever and wherever it is required. As fundamental technology for obtaining, collecting, and distributing company knowledge, Intranet, and internet websites, information sources, and forums are utilized by numerous KMSs. Thus, KMS support organization learning and the generation and diffusion of knowledge inside an organization (Clarke, 1986) (Figure 2.8).

Figure 2.8. KMS. Source: https://www.kpsol.com/glossary/what-is-a-knowledge-managementsystem-2/.

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2.4.3. Strategic Information Systems ISs play a critical part in the global economy by allowing companies to produce products, solutions, and competencies that provide them a strategic edge over their competitors. This results in strategic ISs, which are ISs that assist or shape an enterprise’s competitive position and objectives. As a result, this system could be any type of IS (TPS, MIS, and DSS) that aids an organization in gaining a competitive benefit, reducing a competitive deficit, or achieving other strategic organizational goals (Sharp et al., 2020; Kankanhalli et al., 2013) (Figure 2.9).

Figure 2.9. The organizational framework of strategic information systems. Source: https://www.researchgate.net/figure/The-structure-of-strategic-information-systems-planning-in-organizations_fig2_2676043.

2.4.4. Business Information Systems As a prospective managerial end customer, one must recognize that ISs directly assist operations and management operations within the company areas of accounting, economics, human resource management (HRM), marketing, and business management. All business functions require such business ISs (Johnston & Vitale, 1988). Marketing managers, for instance, require information from MIS regarding sales performance and tendencies. Financial managers want data from financial information systems (FIS) on financing expenses and investment gains (Poeppelbuss et al., 2011) (Figure 2.10).

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Figure 2.10. Progressive business information systems-ERP II. Source: https://www.researchgate.net/figure/Advanced-business-informationsystems-ERP-II_fig1_260007866.

2.4.5. Integrated Information Systems In addition, it is essential to recognize that ISs in the actual world are generally composed of multiple kinds of ISs described above. This is due to the fact that conceptual classifications of ISs are intended to highlight the many responsibilities of ISs. In reality, these responsibilities are incorporated into composite or cross-functional ISs that serve many purposes. Consequently, the majority of ISs are intended to provide data and assist decision-making for several levels of business and management processes, in addition to maintaining records and processing transactions (Cohen & Singer, 1999) (Figure 2.11).

Figure 2.11. Assimilated information system assisting operations in the industry-university association business process.

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Source: https://www.researchgate.net/figure/Integrated-Information-SystemSupporting-Functions-in-the-Industry-University_fig3_230820863.

2.5. MODULES OF AN INFORMATION SYSTEM A system is a collection of modules that work together to accomplish a common objective. The outputs of the system accomplish the system’s goals. The IS takes information sources as input and analyzes them to produce digital products as output (Kossek et al., 1994). An IS requires people (consumers and experts of IS), hardware (media and computers), software (processes and programs), data (information and knowledge grounds), and networks (communications and network support) to exercise input, processing, output, stockpiling, and control functions that convert information sources into digital products (Yousefi et al., 2019) (Figure 2.12).

Figure 2.12. Modules of an information system. Source: https://www.geeksforgeeks.org/components-of-information-system/.

The links between the modules and activities of IS are highlighted in this model of IS. It suggests a model that focuses on 4 key elements that may be used to any sort of IS (López-Ortega & Moramay, 2005): • •

People, software, hardware, networks, and data are the five fundamental components of ISs. Consumers and IS experts are examples of people resources; hardware components are media and computers; software modules are processes and programs; data modules are knowledge bases and information; and network modules are communications

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• •

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medium and networks. Information processing activities translate data resources into a range of data products for final consumer. Information processing comprises of input, processing, output, storing, and control functions.

2.6. RESOURCES OF INFORMATION SYSTEM 2.6.1. People Resources The functioning of all IS necessitates the existence of people. Consumers and IT experts are among the people resources available (Henry et al., 1994). i.

ii.

End users/Clients are individuals who utilize IS or the data it generates. Customers may be accountants, salespeople, engineers, clerks, supervisors, or customers. Many of us are consumers of ISs. ISs experts design and manage ISs. Programmers, systems analysts, hardware operators, and administrative, clerical, and technical IS workers make up this group. In a nutshell, systems analysts create ISs centered on client information requirements, programmers create computer programs centered on system analyst requirements, and computer workers manage massive computer systems.

2.6.2. Hardware Resources Hardware resources encompass all physical components and materials employed in information processing. It encompasses not only machines, like computers and other devices, but also all of the data media, or all tangible items on which information is collected, from paper to magnetic disks. Hardware examples in ISs based on computers include (Hartwick & Barki, 1994): •

•

Computer systems, which are made up of microprocessorbased CPUs and a range of associated peripheral devices. Microcomputers, midsize computers, and big mainframe computers are only a few examples. Computer peripherals, like a mouse or keyboard for command and data input, a printer or screen for information output, and optical disks for data storage.

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2.6.3. Software Resources All kinds of information processing guidelines are included in the notion of Software Resources. This broad definition of software encompasses not only the groups of operating guidelines known as programs that directly manage computer hardware, but also the groups of data processing guidelines known as processes that people require (Vinogradova et al., 2017). It is essential to realize that even non-computer-based ISs contain a module of software resource. This is valid even for antique ISs and the manually and machine-assisted ISs now in utilization in the modern world. To correctly gather, process, and spread data to their users, organizations need software resources in terms of information processing processes and guidelines (Wennberg & Gittelsohn, 1973). Given below are the instances of software resources (Eash, 1994): • •

•

System Software, like a program of operating system (OS), which governs and assists the functions of the computer system. Application Software’s are programs that control computer processing for a specific purpose. A sales evaluation program, payroll program, and the job processing software are all examples. Procedures are step-by-step instructions for persons who will be using an IS. Guidelines for filling a paper form or utilizing a software product are two examples.

2.6.4. Data Resources Data is much more than just building blocks of ISs. Executives and ISs experts have widened the definition of data resources. They understand that data is a vital resource for their company. As an outcome, one should think of data as a resource that needs to be handled well in order to benefit all of an organization’s consumers (McKinney et al., 1993). Standard alphanumeric data, comprising of numbers and alphabetic and other symbols that describe commercial transactions and events and entities, can take on a variety of forms. Text data, which consists of phrases and sections used in written correspondence; picture data, which contains graphic figures and shapes; and audio data, which includes the human voice and some other kinds of sounds, are additional essential types of data (Kumar et al., 2008).

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The data resources of IS are normally organized into: • •

Database that comprises of processed and structured data. Knowledge bases, which store information in a number of formats, including facts, and case studies regarding effective business processes. Data from sales transactions, for instance, might be gathered and saved in the database of sales for further processing, resulting in monthly, weekly, and daily sales analysis summaries for management. KMS and expert systems engage knowledge bases to share information and provide expert opinions on particular subjects (Gilliland & Baxter‐Potter, 1987).

2.6.5. Network Resources Telecommunications networks such as the Internet, and extranets have now become indispensable to the effective functioning of computer-based IS in all sorts of companies. Computers, communications processors, and some other devices are associated by communication channels and operated by communications software to form telecommunications networks. The idea of Network resources highlights the importance of communications networks as core IS resources. Network resources are discussed in the subsections (Cella et al., 2007).

2.6.5.1. Communication Media Instances comprise twisted pair wire, fiber-optic cable, coaxial cable, and communication satellite systems (Shrestha et al., 2015).

2.6.5.2. Network Support Most of the people, software, hardware, and resources of data that substantially assist the operation and utilization of the communications network fall into this broad category. Communications control software, like Internet packages and network OSs, are examples. These five components form the five component paradigm, which consists of the five core elements of IS. In order to initiate your system, you will need hardware initially. Then, you must utilize the program in order for your hardware to function. After installing your equipment and software to operate it, you will require to feed information into the hardware. Once the data is prepared, you’ll need to establish methods for storing it inside the system, and then you’ll need employees to enter the data and maintain the

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system’s functionality at all times. Clearly, you will need each module to make sure that your IS functions properly (Greene & Cruise, 1995).

2.7. INFORMATION SYSTEM ACTIVITIES The main events of an information system are discussed in the following subsections (Kossek et al., 1994).

2.7.1. Input of Data Resource The input activity must acquire and arrange data regarding commercial transactions and events for processing. Data entry tasks like editing and creating are common forms of input. End users usually record transaction information onto a physical medium, including a paper form, or input it straight into the computer. This normally entails a range of editing tasks to make sure that they have appropriately recorded data. Data can be entered and stored on a machine-readable media, like a magnetic disk, till it is required for processing (Yousefi et al., 2019). For instance, sales transaction information can be captured on source documents like paper sales forms. Alternately, salespeople can gather sales information with the help of keyboard or laser scanning devices, with video displays prompting them to input information accurately. This offers them with a much more effective and easy interface, – i.e., input, and output techniques with the computer system for consumers. Methods like as optical scanning and displaying of menus, and fill in the blank forms make it simpler for users to accurately enter data into IS (Henry & Stone, 1994).

2.7.2. Processing of Data into Information Calculating, evaluating, sorting, categorizing, and summarizing data are common data processing operations. These tasks collect, evaluate, and alter data in order to turn it into information for consumers. A continuous process of rectifying and updating activities is needed to preserve the integrity of any data recorded in IS (McKinney et al., 1993). For instance, purchase data can be (a) added to the total count of sales figures, (b) compared to a benchmark to decide eligibility for a sales voucher, (c) arranged in numerical order depending on product reference numbers, (d) designated into product categories (like food and non-food items), (e) summed up to give information to sales manager about several product categories, and (f) often used refresh sales numbers (Eash, 1994).

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2.7.3. Output of Information Products In an output action, information in multiple formats is conveyed to consumers and made accessible to them. The provision of relevant information products for consumers is the purpose of IS. Messages, documents, forms, and visual pictures are typical information products that can be delivered via video displays, audio answers, paper goods, and multimedia. A sales manager, for instance, might observe a salesperson’s performance on a television display, accept a computer-generated voice message over the phone, and obtain a hardcopy of monthly sales figures (Gilliland & Baxter‐Potter, 1987).

2.7.4. Storage of Data Resource Storage is a fundamental module in IS architecture. Storage is the activity of IS in which information and data are kept and arranged for future use. Similarly to how written text is structured into words, phrases, paragraphs, and reports, data is typically classified into fields, records, and databases. This simplifies its subsequent usage in processing or recovery by system users when required (O’brien, & Marakas, 2006).

2.7.5. Control of System Performance Controlling the performance of IS is a vital activity. IS must provide insight on its input, processing, and output, as well as if the system is fulfilling performance goals. The suitable system operations must then be changed in order to provide suitable information products for consumers (Gakibayo et al., 2013). A manager might notice, for instance, that the subtotals of sales figures in a report don’t equal the total sales. This may necessitate the correction of entering data or processing operations. Then, modifications might be required to make sure that all of the sales transactions are collected and processed correctly by a sales IS (Heineke et al., 1998).

2.8. COMPUTER BASED INFORMATION SYSTEM (CBIS) It is a type of IS in which computers have a significant part. The following components make up such a system (Leifer, 1988) (Figure 2.13): •

Hardware: Hardware is a term that relates to machinery. This category comprises the computer itself, sometimes known as

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•

•

•

•

central processing unit (CPU), as well as all of its supporting hardware. Output and input devices, storage systems, and communications equipment are all examples of support equipment. Software: This term refers to computer algorithms as well as any accompanying manuals. Computer algorithms are machinereadable commands that tell the circuitry in the hardware elements of CBIS how to work so that data can be turned into meaningful information. In most cases, programs are saved on an output/ input medium, like a tape or disk. Data: These are informations that programs employ to generate meaningful information. Data, particularly programs, is often kept on tape or disk in a machine-readable format till the computer requires it. Procedures: These are the rules that control how a computer system works. A popular metaphor used to highlight the function of procedures in a CBIS is “processes are to persons what software is to hardware.” People: If a CBIS is about being beneficial, it should have people. People are always the most overlooked aspect of the CBIS: they are most likely the modules that have the greatest impact on the success or collapse of the IS.

Figure 2.13. Categories of computer-based information systems (CBIS). Source: https://indiafreenotes.com/types-of-computer-based-information-system/.

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Kinds of CBIS are demonstrated in the following subsections.

2.8.1. Transaction Processing Systems The processing of commercial transactions constitutes the most basic CBIS in an organization. This system is a CBIS that captures, sorts, saves, preserves, updates, and recovers transaction information for keeping records and input to other CBIS. The objective of this system is to enhance the normal business operations upon which all businesses rely. A transaction is an event or action that has repercussions for the entire organization. Common transactions comprise placing orders, charging clients, employing personnel, and depositing checks. The kinds of transactions conducted differ from business to business (Mentzas, 1994). However, it is undeniable that all businesses handle transactions as routine of their day-to-day operations. The most profitable companies carry out processing of transaction in a very organized manner. These systems are fast and accurate, and they might be configured to stick to routines with no deviations (Mansour & Watson, 1980).

2.8.2. Management Information System Numerous factors have contributed to the efficiency of computerized data processing. The primary reason is that vast amounts of financial and transaction-related data can be processed rapidly. Historically, the majority of computer programs focused on archiving and the automation of daily clerical tasks. In current years, however, more emphasis has been placed on computer programs that offer information for legislation, effective management, and control. MIS focus more on management functions. This system can be defined as IM that provides all management levels with crucial business-related information. This information should be as pertinent, timely, precise, exhaustive, and brief as is economically practical (Vlahos et al., 2000).

2.8.3. Decision Support Systems It’s a data system that offers information that isn’t always anticipated, but that business experts might only need once. These systems don’t generate management reports on daily basis. Alternatively, they’re made to handle a wide variety of requirements. Indeed, not all choices in an organization are made on a regular basis. Managers who should make less-structured decisions, generally known as unstructured or semi-structured decisions,

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can benefit from DSSs. If there aren’t any defined processes for taking the decision and not all of the aspects to be evaluated in the decision could be specified in advance, this decision is deemed unstructured. When the situation isn’t structured, the manager’s judgment is crucial in making decisions. The DSS assists, but doesn’t eliminate, the manager’s judgment (Bada, 2017).

2.8.4. Office Automation Systems These systems are one of the most recent and quickly developing CBIS. It is hoped and expected that they will boost the performance and effectiveness of office workers such as stenographers, administrative assistants, staff experts, and supervisors. Numerous organizations have taken the initial step towards office automation. This step generally includes the utilization of word processing technologies to ease typing, storing, amending, and printing text materials. A further innovation is a computer-based communications system (CBCS), like electronic mail, that enables electronic communication via computer terminals. The office automation system is a multifunctional, interconnected computer-based system that enables the computerized performance of numerous office tasks (Necco et al., 1987) (Figure 2.14).

Figure 2.14. Office automation systems. Source: https://www.sketchbubble.com/en/presentation-office-automation-system.html.

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In Table 2.1, different types of ISs have been classified and their properties briefly discussed (Vijayaraman & Ramakrishna, 1993). Table 2.1. Types of Distinct Information Systems Type of Information System

Features

Transaction Processing System

Replaces manual processing with computer processing. Includes applications for keeping records.

Decision Support System

Gives information to supervisors who make decisions regarding certain scenarios. Facilitates decision making in ill-structured settings.

Management Information System

Provides information for managerial decision-making. Supports well-structured decision-making circumstances. It is possible to anticipate typical information requirements.

Office Automation System

It is a multi-functional, interconnected system based on computer system that enables various office tasks to be completed electronically.

2.9. DATA STORAGE IN MIS Storage of data is a technique of using a computer system with memory to store and retrieve information on a subject that includes the following (Chung et al., 1999). •

•

•

•

storing relevant data on the plurality of subjects in the computer memory, where said data contains descriptive phrases about numerous things with which said subjects are engaged, as well as identifying details for identifying the subjects linked with said descriptive tags; allocating specified designation numbers to said descriptive tags and recording said specified designation numbers in conjunction with the associated descriptive phrases and with the identifiable details, wherein said designation numbers relate to a corresponding plurality of subjects; recording a plurality of topic heads in the computer memory, each of which is specified to comprise a particular range of identification numbers; in a computer system, for every designation number allocated to the descriptive phrase, identifying which subject heading

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•

•

range comprises said identification number and recording said identification number and descriptive phrase in relation with the corresponding topic heading; searching the computer memory for a phrase descriptive of a particular point of curiosity, a variety of identification numbers, and a designation number, and identifying the designation number if the descriptive phrase is found retrieving the related subject’s identifying information from the computer memory using one of range and designation numbers obtained in step (e).

2.9.1. Primary Storage This refers to semiconductor microchips that are utilized to store current data and programs. All of the commands and data are stored in this storage in some data processing, after which the computer finalizes its processing and presents the findings. Every memory storage component is readily accessible, allowing for examination and modification without affecting adjacent cells. As an outcome, primary memory is also known as Random Access Memory (RAM). The primary storage capabilities of some computers are insufficient to manage the commands and data required for processing in specific applications. The outcomes of processing should be saved in primary storage because it contains volatile memory (Ifinedo, 2015).

2.9.2. Secondary Storage External non-volatile memory is the secondary storage of a computer. Magnetic tapes, disks, and optical techniques are the secondary storage media utilized by computers of all sizes. Large volumes of information could be easily saved for future recovery using secondary storage. There are two types of secondary memory: RAM and serial access memory. It is beneficial to think of a cassette tape as providing RAM and an L.P. recording as providing serial access memory (Gupta, 2013).

2.9.3. Data Warehouse for Storage It is a computer system that evaluates an organization’s historical data, like sales, salaries, or even other data from daily activities. An organization’s operational systems are typically précised and copied to the data warehouse on a daily basis, like every night as well as every weekend, so that

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management may run complex data and analyzes on the data without impacting the operational systems (Walls & Turban, 1992). Typically, the data warehouse maintains information with a finer granularity as compared to the operational systems: for instance, if the operational systems retain a log for each sale, the data warehouse may just keep the total amount of sales for every product at every store (Njoroge et al., 2015). The data warehouse should not be a relational database, but it must be structured to facilitate not only enquiry and analysis, but also enhanced evaluation techniques such as data mining. Dependent on the business data retention need, the majority of data warehouses store data for one year at minimum and occasionally up to a half century. Consequently, these databases might grow very vast (Vlahos et al., 1996).

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46. Shrestha, M. S., Grabs, W. E., & Khadgi, V. R., (2015). Establishment of a regional flood information system in the Hindu Kush Himalayas: Challenges and opportunities. International Journal of Water Resources Development, 31(2), 238–252. 47. Star, S. L., & Bowker, G. C., (2007). Enacting silence: Residual categories as a challenge for ethics, information systems, and communication. Ethics and Information Technology, 9(4), 273–280. 48. Stine, K., Kissel, R., Barker, W., Lee, A., & Fahlsing, J., (2008). Guide for Mapping Types of Information and Information Systems to Security Categories: Appendices (Vol. 2, pp. 1–9, Rev. 1)). No. NIST Special Publication (SP) 800–60. National Institute of Standards and Technology. 49. Vijayaraman, B. S., & Ramakrishna, H. V., (1993). Disaster preparedness of small businesses with micro-computer based information systems. Journal of Systems Management, 44(6), 28. 50. Vinogradova, E. Y., Andreeva, S. L., Babkin, A. V., & Galimova, A. I., (2017). Corporate information system—Element of efficient human resources management of the industrial-economic complex. In: 2017 IEEE VI Forum Strategic Partnership of Universities and Enterprises of Hi-Tech Branches (Science. Education. Innovations) (SPUE) (Vol. 1, pp. 63–66). IEEE. 51. Vlahos, G. E., & Ferratt, T. W., (1996). A comparative study between managers of corporations in Greece and the US regarding their use and perceived value of computer-based information systems in supporting decision making. In: Proceedings of the 1996 ACM SIGCPR/SIGMIS Conference on Computer Personnel Research (Vol. 1, pp. 103–113). 52. Vlahos, G. E., Ferratt, T. W., & Knoepfle, G., (2000). Use and perceived value of computer-based information systems in supporting the decision making of German managers. In: Proceedings of the 2000 ACM SIGCPR Conference on Computer Personnel Research (Vol. 1, pp. 111–123). 53. Wade, M., & Hulland, J., (2004). The resource-based view and information systems research: Review, extension, and suggestions for future research. MIS Quarterly, 1, 107–142. 54. Walls, J. G., & Turban, E., (1992). Selecting controls for computerbased information systems using heuristics and logic programming. Accounting, Management and Information Technologies, 2(4), 241– 261.

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55. Wennberg, J., & Gittelsohn, A., (1973). Small area variations in health care delivery: A population-based health information system can guide planning and regulatory decision-making. Science, 182(4117), 1102– 1108. 56. Yew, B. K., (2008). A perspective on a management information systems (MIS) program review. Journal of Information Technology Education: Research, 7(1), 299–314. 57. Yousefi, M., Ghalehaskar, S., Asghari, F. B., Ghaderpoury, A., Dehghani, M. H., Ghaderpoori, M., & Mohammadi, A. A., (2019). Distribution of fluoride contamination in drinking water resources and health risk assessment using geographic information system, northwest Iran. Regulatory Toxicology and Pharmacology, 1(7), 104–408.

CHAPTER

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FUNDAMENTALS OF COMPUTER NETWORKS

CONTENTS 3.1. Introduction ...................................................................................... 72 3.2. Models of Computer Networks ......................................................... 74 3.3. Types of Computer Network.............................................................. 75 3.4. Data Communication Media Technology .......................................... 77 3.5. Network Topology ............................................................................ 85 3.6. Network Connectivity and Procedures .............................................. 90 3.7. Network Services .............................................................................. 96 3.8. Devices for Network Connecting .................................................... 100 References ............................................................................................. 115

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3.1. INTRODUCTION According to the fundamental assumptions that underpin all forms of communication, efficient communication seems to need the presence of three components. In the beginning, there must be both a sender and a receiver. Those two have such a lot of things to talk about. Second, the object that may be shared has to be sent over some kind of means. This serves as the medium for transmission. In the end, you will be tasked with selecting a variety of distinct standards or protocols. These three criteria are useful for every kind of communication you could engage in (Meinel & Sack, 2014). The following three elements of a computer system will be the primary focus of this chapter. However, first of all, and foremost, what exactly is meant by the term “computer network”? The reader must be made aware that from this point forward, the phrase “computer network” will be used to refer to a conventional computer system. A computer system is a dispersed system that is composed of computers that are only tenuously linked to one another (Wang et al., 2006). Through the use of a medium of communication, any two of these devices can communicate with one another. From this point forward, we shall refer to these communication mediums as network equipment or transmission elements. For this collection of interconnected devices to be referred to as a communication network, there must be a predetermined set of guidelines, sometimes known as a protocol, so each device should adhere to them to have a successful conversation with some other device that is part of the network. The integration of software and hardware results in the creation of a computerized communication network, more often mentioned simply as a computer system. A diagram of a computer network is shown in Figure 3.1 (Jingna, 2010). Networking devices are a collection of nodes that make up the hardware component. These nodes involve end systems like hosts as well as intermediate step switching elements like port facilities, routers, bridges, and gateways. For the sake of clarity, we will refer to these nodes collectively as system components. The hardware part is made up of networking devices (Akyildiz et al., 2012). Each component of the network has capabilities either locally or internationally. The term “network software” refers to all software applications and communications networks that are utilized to coordinate, synchronize, and carry out the tasks of data sharing and exchange among the

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various components of a network. The pooling of costly network resources is another function that may be performed by network software (Cocchi et al., 1993). The cooperation of networking devices, network software, and users enables a single user to conversation messages and then pool possessions on some other organizations that may non be willingly accessible locally. This is possible because of the interconnected nature of the internet. Even if the network nodes and the resources they access could make use of a wide range of hardware technology, and even though the software might be as varied as is humanly conceivable, the whole system must function in harmony (Donoso & Fabregat, 2016).

Figure 3.1. Networking of computers. Source: https://link.springer.com/book/10.1007/978–3-319–55606–2.

The technology of computer networks makes it possible to link different types of networks and get them to speak with one another seamlessly. This is accomplished via the use of a wide range of specialized software technologies and hardware programs. The smooth functioning of every computer communication network is guaranteed by the low-level procedures that are present in the network components as well as the software that is present in the high-level telecommunications services that are present in the communication elements. Before we get into the specifics of how networks function, let’s take a look at many kinds of networks (Sarkar, 2006).

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3.2. MODELS OF COMPUTER NETWORKS Several configuration types make up a computer system. The greatest shared models are central and dispersed. In a central model, many supercomputers and devices remain linked and may interact with respectively other. All communications should, though, go via the master, which is the only central computer. Surrogate mothers, or dependent computers, may well have restricted local resources like memory, while the master manages sharable global resources from the center (LAUGHLAND, 1992; Takagi, 1991). Different from the central system, the dispersed network is composed of interconnected processors connected through a distributed communication system containing linking devices and channels of communication. The machines might have local resources or may be required during the development from a distant server. These devices are known by including congregation, several names, customers, and bulge. Uncertainty a congregation has properties that additional hosts demand, it is labeled as a server (LaRowe & Elliott, 2001). Instead of regulating communication or sharing resources, the central computer provides for just any communication between the two network units (Berting, 1984; Wilkov, 1972).

Figure 3.2. A centralized network structure. Source: https://link.springer.com/book/10.1007/978–3-319–55606–2.

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Figure 3.3. A framework for dispersed networks. Source: https://link.springer.com/book/10.1007/978–3-319–55606–2.

Centralized network architecture is shown in Figure 3.2, while a fully distributed framework is depicted in Figure 3.3 (Kocaoglu et al., 2012).

3.3. TYPES OF COMPUTER NETWORK Computer systems originated in various dimensions. Every net is composed of a set of nodes in the network as well as the resources that go with it. The cluster size determines the network type. Local part networks (LAN) and wide-area networks (WAN) are the two kinds of networks (WAN) (Wilson et al., 2009).

Figure 3.4. A LAN is a local area network. Source: https://www.amazon.com/Computer-Network-Security-Communications-Networks/dp/1447145429.

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3.3.1. Local Area Networks (LANs) A local area network (LAN) is a system that links various computer systems or groupings of computers as well as their assets via a communications platform that wants to share protocols and is limited to a small geographic area, such as a concrete floor, a constructing, or another few surrounding buildings (LAN) (Kameda et al., 2000). A LAN’s advantage is that a few network components are near together, allowing for speedier data transfer across communication channels. Because the communication components are so close together, high-cost, high-quality communicating parts are employed to increase service and dependability. A LAN network is seen in Figure 3.4 (Tipper & Sundareshan, 1990).

3.3.2. Wide Area Networks (WANs) A wide area network (WAN) is a network consisting of one or even more groups of networking devices and associated resources that are scattered throughout a broad geographic region, such as a state’s region, numerous nations, or the whole world like the Web, instead of being restricted to a limited region ability to disseminate services to a broader population as well as the access to a broad variety of software and hardware components which might not be available on a LAN are among the advantages of a WAN. Though, as of the vast topographical regions served by the WAN, communiqué methods are sluggish and sometimes unfeasible. A WAN is seen in Figure 3.5 (Morgan & Levin, 1977).

3.3.3. Metropolitan Area Networks (MANs) A medium network termed the metropolitan area network (MAN) exists between both the WAN and the LAN, spanning a somewhat bigger territory than LAN but not as vast also as a WAN. Public webs that conceal a city or a section of a city are a decent instance of a person. Because they remain typically outshone by relatives LAN to the leftward and wide area network to a right, MANs are seldom considered (Pawar & Anuradha, 2015).

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Figure 3.5. A wide-area network (WAN). Source: https://www.amazon.com/Computer-Network-Security-Communications-Networks/dp/1447145429.

3.4. DATA COMMUNICATION MEDIA TECHNOLOGY A system’s transmission media technologies have a substantial influence on its performance. Consider the following two scenarios (Leblanc et al., 2011).

3.4.1. Transmission Technology The medium over which data must remain carried determines the signals to be used. In certain mass media, only analog transmissions are permitted. Digital and Analog transmissions are supported by certain systems. As a consequence, based on the media and other conditions, the inputs might be shown as an analog or digital signal (Kumar et al., 1995). Information is transmitted as a series of steady electromagnetic radiation over some time in analog format, expressing things like music and video, and is transmitted across a range of outlets, including copper cables, twisting coaxial pairs or cable, fiber optic, or wireless. These media will be examined in more detail later. Information is directed as a digital indication in a digital medium, which is made up of an arrangement of electrical pulses that may be described as a stream of dual bits. Data is usually expressed either as digital or analog, and it may be transmitted both in digital and analog forms (D’Amico & Whitley, 2008).

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Transmission is the process of sending and receiving a digital signal through network nodes. The notion of expressing data for transmission as just a digital or analog signal is referred to as an encoding technique. The encoding is then delivered across a secure transmission means that connects all network parts. Techniques for digital and analog encoding are accessible. Analog encoding generates analog signals that encode analog signals such as complete surfs and vocal sounds. Digital encoding transmits digital signals that reflect both an analog or even a digital signal representing digital information of dual streams using two reference voltages. We’ll focus on digital encoding since we’re interested in online networking in just this book (King & Xia, 1997).

3.4.1.1. Analog Encoding of Digital Information It’s essential to mention that digital data can be represented by 1s and 0s. Digital data should be encoded utilizing demodulation and modulation to produce analog signals to transmit this information via analog mediums with limited capacities, such as a telephone line. The carrier’s signal is generated with a fixed frequency which is used to encode a sine wave or other steady oscillation wave. The carrier’s three inflection characteristics are rate, amplitude, and phase move. The communicated data is then demodulated and modulated to use a modem, a demodulation–modulation pair, based on one or more of the three carrier qualities. The resultant wave, as seen below, encompasses a broad range of frequency on both sides of a center (WatsonManheim & Bélanger, 2007): •

•

•

Amplitude: Every binary value is modulated with a particular carrier amplitude-frequency. A 0 may indicate a lack of or a lower carrier frequency, while a 1 can indicate anyone else frequency. However, since this is a relatively inefficient modulation method, it is only used on speech grade lines with frequencies up to 1,200 bits per second. Frequency: Two binary numbers are modulated at near frequencies to the carrier’s frequency. Higher frequencies are represented by a 1 while different frequencies are represented by a 0. The system remains even less vulnerable to errors. Phase Shift: By modifying the transporter’s wave’s timing, modulating adjusts the carrying phases to encode information. A 1 is expressed by a 180° phase difference in the carrier frequency,

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whereas a 0 is indicated by a 0 phase shift. With a transfer rate of up to 9,600 bit/sec, it’s the most practicable of the three methods.

3.4.1.2. Digital Encoding of Digital Information This encoding system, which is the extreme shared and simplest approach to sending digital data, uses two dual numbers to represent two independent voltages. In a computer, these voltages are commonly 0 then 5 V. Additional method uses two symbol codes: non-return to zero level (NRZ-L), wherein negative voltage equals binary one of these and positive voltage equals binary zero, and non-return to zero, inverted on the aces (NRZ-I) (NRZ-I) (Larson & Kulchitsky, 2000). For just an example of these two codes, see Figures 3.6 and 3.7. The information is transmitted by a progressive transition through one voltage level to another when a 1 appears in NRZ-L. One challenge with NRZ signaling pathways is the necessity for flawless synchronization here between receiver and transmitter clocks. This may be reduced, though, by sending a separate clock signal. The Manchester and differentiated Manchester are two main forms that encode clocks information along with data (Liu et al., 2019).

Figure 3.6. Non-return to zero level code NRZ-L N. Source: https://www.amazon.com/Computer-Network-Security-Communications-Networks/dp/1447145429.

Figure 3.7. On one’s presentation code, NRZ-I stands for non-return to zero inverts. Source: https://www.amazon.com/Computer-Network-Security-Communications-Networks/dp/1447145429.

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One would question why to go to the effort of digital encoding and transmission. Digital encoding has a variety of benefits over analog encoding. Several of them are as follows (Sitkin et al., 1992): • • • • •

The cost of digital circuitry is decreasing. Integration of video, voice, text, and images has been improved. Noise or other signal degradation is reduced when repeaters are used. The system capacity is maximized using digital approaches. When opposed to analog transmission, digital transmission has stronger encryption and hence security.

3.4.1.3. Multiplexing of Transmission Signals The amount of information sent regularly exceeds the channel’s capacity throughout the majority of data transmission via a transmission medium. It may also be able to distribute a communication method among several signal carriers if this happens. This is known as multiplexing. Close are two kinds of multiplexing: frequency-division multiplexing (FDM) and timedivision multiplexing (TMD) (Chen et al., 2008). With FDM, all info links are converted to analog first. Meanwhile, a carrier may transport multiple signals, every analog modulated signal by a different and distinct carrier signal, which allows for demultiplexing recovery. The frequencies then are merged just on a carrier. Just at the headset end, the demultiplexer may choose the proper haulier frequency and use it to get the digital signals for that circuit without available bandwidth overlapping. The ability to converse in a full-duplex is a benefit of FDM (Fonner & Roloff, 2012). TDM, on either hand, splits the channels into time frames to which data streams are allotted before transmission. The receiver may easily recover and recreate the initial streams of data uncertainty if the dispatcher and recipient agree just on time-slot assignments at both ends of the communication. Several digital transmissions are conducted on a single carrier via combining parts of respectively sign in a real period (Wijayanayake & Higa, 1999).

3.4.2. Transmission Media By way of earlier said, each kind of communication necessitates the use of an average over which the statement could income place. As a consequence, web components need a medium to communicate. If a system didn’t have

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such a broadcast average, there’d be no connection between both transmittal rudiments. The network’s functionality is heavily influenced by the broadcast medium (Kahai et al., 2012). The transmission medium does have a considerable influence just on the quality, longevity, and performance overall of a network. The broadcast medium regulates a web’s volume for delivering intended internet traffic, effectiveness for network connectivity, network size concerning the distance covered, and communication capacity. System broadcast media are divided into two categories: wireless and wired (Ziemann et al., 2002).

3.4.2.1. Wired Transmission Media Wire transmitters are rummage-sale to physically link each system node in based networks. The most common forms of physical media include copper cables, twisted pairs, optical fibers, and coaxial cables (Pea et al., 2012). Copper cables as they have a lower resistance to electrical currents, they’ve been used in communication for a long time. This allows messages to go farther. Copper cables, on the other side, are susceptible to electromagnetic interference from the atmosphere, demanding constant insulation. Twisted pair A couple is a group of cables made containing insulating copper wires enfolded in a twisting pattern around together. A unified communications channel is created by connecting the twisting, insulated copper wires (Williams & Merten, 2011). The wires are looped to reduce the cable’s susceptibility to electrical radiation and the transmission of broadcast noises, which might interfere with nearby electrical components and cables. To improve the efficiency of the transmission medium, over one couple of warped cables might be joined together beneath a protective covering. Warped duos remained widely used in telecommunication systems because they were less costly, easier to manage, and provided high audio quality data. However, they are restricted in their ability to scale up in transmissions. A twisted pair is shown in Figure 3.8 (Murray & Peyrefitte, 2007). Coaxial cables have a common internal conductor covered by an insulating material in the wire’s core, as well as an outer conductor that covers the insulation. Coaxial cables get their name from the fact that the core conductors are shared. Solid copper wire is usually used during the inner layer conduction; however, the stranded wire may also be utilized. Braided wires are used as the outer conductor (Ambrose et al., 2008).

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Figure 3.8. A twisted couple. Source: https://usermanual.wiki/Document/Guide20To20Computer20Network20Security203rd20Edition2020Joseph20Migga20Kizza2020Springer.28023928/help.

Figure 3.9. Cable with coaxial connectors. Source: https://www.researchgate.net/publication/253687458_A_Guide_to_ Computer_Network_Security.

Figure 3.10. Fiber optics. Source:https://www.researchgate.net/publication/253687458_A_Guide_to_ Computer_Network_Security.

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But it has a protecting tube surrounding its inner conductor, which is normally made of metal foil or a combination of both. This outer conductor is further protected by an extra covering known as the sheath. Figure 3.9 shows a helical wire. Copper wires are often used in television broadcasts. Unlike twisted pairs, coaxial wires may be utilized over long distances. The two types of twisted pair are thinnet, which would be a lightweight and elastic cabling material that is simple and inexpensive to construct, and the presence of heavy, which is stronger and tough to shake and can transmit more information over a larger distance than thinnet (Hollingshead, 1996). A fiber optic is just a small channel made of glass as well as polymers that transmits an optical beam. That’s the greatest cable for data transport since it can handle very considered to be significant and has fewer concerns with electronic radiation than twisted pair. It can also sustain cable runs of up to many kilometers. Fiber optic cables, on the other side, have two disadvantages: cost and difficulty of deployment. As illustrated in Figure 3.10, basic fiber optics has a central core formed of thin transparent plastic fibers (Martínez‐Moreno et al., 2009; Perse & Courtright, 1993). The fibers are protected by a cladding composed of glass or plastic. Even though the wrapping is made of the same material as the center, it has special properties that enable it to reflect obliquely struck core rays. A plastic sleeve protects the sheathing from the outdoors. The outer fiber is protected by the jacket against twisting and scratches from the outside environment. Before sending data signals, optical fiber connections transform them to light signals. The conveyed light is emitted at the source by a light-emitting diode (LED) or an injector laser diode (ILD). A photodetector just at the headset end collects the emitted photons and converts them back into their original form (ElShinnawy & Markus, 1998).

3.4.2.2. Wireless Communication Communication systems including wireless connections have developed in response to the fast advancement of technology, computing, and people’s choices and need for flexibility. Wi-Fi is divided into three types based on their distance from the user (Webster & Trevino, 1995): • •

Restricted Proximity Network: A combination of fixed and mobile local networks make up this network (LANs). Intermediate/Extended Network: A wirelessly component connects two static LAN elements in this wireless connection.

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The bridges might be used to link LANs in two towers or even farther apart (Ogilvie et al., 2018). • Mobile Network: It is a Wi-Fi network connecting two separate network units. A few of these components are usually a transportable device that connects to the local network through wireless or satellite technology (fixed). These three forms of wireless connections are connected via basic media including ultraviolet, laser light, bandpass filter and dispersed radio, microwaves, and communication satellites. (2nd) (Daft et al., 1987). Infrared: A network device produces and delivers wavelengths of infrared light to a receiver system component through an infrared transmission, which carries coded instructions. As soon because no defining elements of the conveyed light, the headset gets the teaching. Ultraviolet works greatest in a limited area, such as when a television remote interacts with television around 100 feet. In a tiny area like this, infrared is quite fast and can handle a massive bandwidth capacity of active to 10 Mbps (Treviño et al., 2000). High-Frequency Radio: RF transmissions are strong electromagnetic radio signals or radio waves that are created by the transmitters and managed to pick up by the receivers throughout a radio connection. Mobile computer components may communicate across a bigger place without having to position the transceiver in a direct line of sight so because the broadcasting band has a longer range than infrared; the signals can be reflected off bright buildings, walls, and environmental factors. Radio Frequency broadcasts stand especially excellent over extended distances once joined with satellites to bend the wireless signals (McGinn & Croson, 2004). Microwaves: Microwaves stand a higher-frequency form of wireless waves that, unlike radio waves, may stand directed in only one direction (Ruppel et al., 2013). A couple of parabolic antennae that emit and receive small, highly directed signals enable microwave communications. To be responsive to indications, equally the communication and receipt of the antenna should attention within a confined region. As a consequence, the broadcast signal must be aligned through a receiver by fine-tuning both the transmittal and reception antennas. Microwave communication may be terrestrial (when it

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is near to the ground) or satellites (when it is far away from the ground) (when it is far from the earth). These two types employ similar frequencies and technology, yet there are considerable differences between them (Cunha et al., 2016). Laser: Using a laser beam, data may be sent thousands of meters through airways and optics fibers. This is only possible when there are no impediments. Laser beams, like microwaves, may be used in several applications, and beams must be reflected across long distances to be effective (Harwood, 2000).

3.5. NETWORK TOPOLOGY Computer systems, whether they be local area networks, MANs, or wide area networks, are designed using topologies. Many of the most prevalent topologies are listed here (Walsh & Maloney, 2007).

3.5.1. Mesh A meshes topology, unlike some other kinds of topologies, enables a variety of connecting linkages between network components. But when a single web system flops, the system does not close down; instead, it just discovers a way toward the faulty piece and continues to function, the availability of several access lines connecting network elements promotes network reliability. Mesh network topology is frequently used in MAN links. Figure 3.11 illustrates a mesh link (Ganesh et al., 2005).

Figure 3.11. A network of meshes. Source: https://cds.cern.ch/record/1565824/files/9781848009165_TOC.pdf.

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Figure 3.12. The structure of a tree. Source: https://cds.cern.ch/record/1565824/files/9781848009165_TOC.pdf.

3.5.2. Tree Type A extra public kind of network architecture is tree network topology. The tree network topology organizes system basics into a graded system, with the root being the most pivotal factor and other network elements having a child-parent relationship. Inverted trees do not seem to have complete loops, as do conventional trees (Bashan et al., 2012). As a consequence, based on where a failed element is now in the structure, responding regarding network failures could be difficult. If the root element of a deeply ingrained tree, for example, quits, the network bursts and separates into two fragments. The two halves can’t communicate with one another. As a consequence, the general operation of the network is significantly impeded. A network thought up of a tree network is seen in Figure 3.12 (Boss et al., 2004).

3.5.3. Bus A bus network topology is more normally used, particularly in LANs. All components in such a bus network topology network utilize a bus and thereby have fair opportunities for other LAN capabilities. Every networking unit just on a bus has a full-duplex connection to the transmission standard, which enables it to lead data (Gu et al., 2019). Because each computer unit is physically linked to the transmitting medium, each signal sent through one element travels the length of a channel in both directions, enabling all system components to receive it. As a consequence, additional measures are necessary to be reserved to verify that messages projected for one element are delivered by that very same element. If two or more components try to send data at the same time, the network should have a method in place

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to resolve the conflict. The strategy mitigates the risk of signal collision and guarantees that they will be rapidly resolved. It’s also critical to ensure network justice so other parts may interact as required. Take a glance at Figure 3.13 for an example (Tangmunarunkit et al., 2002).

Figure 3.13. Topology of the bus. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

By permitting only a single part inside the organization to manage the bus for a slightly single period, a collision control strategy that leverages a bus topology should also improve the efficiency of the network. The master device is therefore the network node, whereas the slaves are the only other parts. This criterion avoids network collisions by prohibiting components from using the bus during the same period. The bus topology is common in LANs (Speedy et al., 1987).

3.5.4. Star Another popular architecture, especially in Local area network technologies, is just the star topology. A conspicuous central node links most other network parts, forming a star architecture. As a consequence, each piece of the network is connected to a single node. Each network component inside a star topology is connected and paired in a moment in time way via a central element, and interaction between this pair of components must pass through this central element (Milchtaich, 2006). The center component, or node, may function as a broadcasting device, transmitting data from one element to all connected elements, or as an active switch, transferring incoming information only to one component, the nearest one in path. In networks, the main drawback of the star topology is that if the center component fails, the whole network collapses. Figure 3.14 depicts a star topology (Lin et al., 2013).

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3.5.5. Ring Lastly, common web architecture is the ring network topology. In a ring topographic anatomy network, an individual computer unit is linked straight to the transmission medium by a linear linking, enabling data delivered across the transmission medium to spread to all computer units in the system (Fencl et al., 2011).

Figure 3.14. Topology of stars. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

Figure 3.15. Topology of rings. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

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a method of passing data from one place to another the ring via taking turns Figure 3.15 depicts a ring network topology network. When transmitting information, a tokens system is utilized to keep track of who is taking turns. A symbol is a unit of system-wide data that assures the bus master is now in charge. Other network components are not permitted to transmit on the bus while it is transporting the token. When such a component is in use right now (Lee et al., 2008) (Figure 3.16).

Figure 3.16. Hub of the token ring. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

When the process of transferring data and maintaining the symbol is ended, the symbol is sent downriver to the next nearest neighbor. The token technique is an excellent tool for preventing collisions and ensuring fairness (Briers, 2002). Although network elements are critical in Local area networks, they are impacted by a range of factors such as the type of data transmission, network reliability, network size, or planned future growth. Topologies including star, bus, and ring have lately been the most prevalent LAN topology. The most common bus- and star-based Networking architecture, and the most common ring-based LAN structure, is the Internet (Barford et al., 2001).

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3.6. NETWORK CONNECTIVITY AND PROCEDURES In the initial times of the internet, computers stayed used as separate devices, and all cross-computing jobs get completed by hand. Discs were used to share data from one system to another. Cross-computing, in which many computers interact with each other and vice versa, became necessary as a consequence. As a consequence of this, a new method was created. The open standard movement asked that software and hardware suppliers create a means to do this. This, however, necessitated the standardization of software services (Roos et al., 2017). The International Organization for Standardization (ISO) developed the Open System Interconnection (OSI) paradigm to help in this attempt and simplify computer communication. The OSI is just an open architectural idea that acts as a network communication protocol standard, albeit it wasn’t the most often utilized. The Transport Control Protocol/Internet Protocol (TCP/IP), which is a rival to OSI, is the most widely-used paradigm. Both OSI and TCP/IP models employ two protocol stacks, one from the source and another at the terminus (Siegel et al., 2016).

3.6.1. Open System Interconnection (OSI) The OSI methodology was built on the concept that an internetwork task may be divided into seven layers, each reflecting a distinct part of the operation. Various levels of the protocols provide various services to ensure that each level can only interact with its surroundings. That is, the protocols of every layer are based on the standards of previous levels (Smith et al., 2011). First, from the top levels, activities, and data move down the protocol till they reach the bottom layer, where they are transferred via the network medium from the data source to the destination. The task or information progresses through the levels until the gets to the top, where it will be delivered. Every layer is designed to take requests from the level above and transfer them through to the layer underneath it, and vice versa. To enable multilayer interaction simpler, the interconnections between both the layers are regulated. Every layer, on either hand, is self-contained and may be constructed as such, and the functioning of one layer should not interfere with the performance of layers up or down it (Zhou et al., 2010). An OSI model with seven levels and explanations of the services offered in each tier is shown in Table 3.1 (Jarrahi et al., 2015).

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Table 3.1. ISO Protocols Layers with Their Accompanying Layers 1 2 3 4 5 6 7

Protocol Physical Data link Network Transport Session Presentation Application

Figure 3.17. Framework for logical peer communication defined by ISO. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

As information flows from node to node on the sender computer, layer prefixes are attached, allowing the data packet to expand in size. For every layer, the layer headers contain information about the remote system’s peer. This data might indicate how well the packets should be transported through the networks and what should be performed with them when it is sent up the structure to the recipient machine (Schroeder et al., 1987). Table 3.2. OSI Datagrams Include a Header for Each Tier No Header No header H5 H4 H3 H2 H1

Data Data Data Data Data Data Data

Application Physical Data link Network Transport Session Presentation

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A logical architecture of communication between the two peer computers based on ISO is shown in Figure 3.17. The datagram as it passes through the levels is shown in Table 3.2, with modified header information. Although now the OSI model was developed to serve as a base for most other patent systems and to be as comprehensive of all existing models as possible, it never entirely replaced many of the competing models it was meant to replace in actuality, this “all-in-one” concept failed the marketplace because it became too advanced. Due to its late arrival on the scene, it was unable to achieve somewhat network compatibility (Toppi et al., 2016).

3.6.2. Transport Control Protocol/Internet Protocol (TCP/IP) Model Because the TCP/IP protocol was substantially less advanced and well for the period the OSI was announced, it’s one of the OSI’s rivals. The OSI model and the TCP/IP model vary somewhat. For example, instead of the OSI model’s seven levels, that has two to three. It was created for the Department of Defense Advanced Research Projects Agency (DARPA) in the United States, although it has been modified throughout time (Gili et al., 2013). Table 3.3. TCP/IP Protocols Have Many Layers Layer

Delivery Unit

Application Message

Protocols File Transfer Protocol (FTP), Name Server Protocol (NSP), Simple Mail Transfer Protocol (SMTP), Simple Network Management Protocol (SNMP), HTTP, Remote file access (telnet), Remote file access (telnet), Remote file access (telnet), Remote file access (telnet), Remote (File Transfer Protocol), Network File System (NFS), Domain Name System (DNS), HTTP, TFTP, SNMP, DHCP, DNS, BOOTP The Applications, Sessions, and Display Levels of the Osi Reference Model are Unified. High-Level Procedures Should Be Addressed

Transport

Segment

Add Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) to the list of transport layer protocols (UDP)

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Datagram

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protocols such as Internet Protocol (IP), Internet Control Message Protocol (ICMP), and Internet Group Management Protocol (IGMP) are required (IGMP) Facilitate the transfer of source packets over any connection and guarantee that they reach their intended destination independent of the route and connections they took. Every layer manages of choosing the optimal route and switching packets.

Data link

Frame

Protocols that require IP packets to cross a physical connection among one device, as well as another, are covered The relevant networks were included WAN stands for wide-area network LAN (local area network) is a computer network that connects two or more computers

Physical

Bitstream

Drivers for all network cards

Figure 3.18. Application layers’ data frame. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

Its popularity has soared, it’s now the Internet and several smaller networks’ de-facto standard. TCP/IP is made up of binary core protocols: Transmission Control Protocol (TCP) and IP. Table 3.3 lists the levels and methods for each tier (Tursich et al., 2015). Let’s focus on TCP/layers IP since it’s the most widely used network security protocol on the Net in many internal networks (Petkov et al., 2000).

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3.6.2.1. Application Layer That layer, which is equivalent to an application-level in the OSI paradigm, offers the essential interaction with sources rich in application functions. It permits all operations and includes numerous methods on a database, as shown in Figure 3.18. It’s made up of bit streams (Boedecker et al., 2009).

Figure 3.19. Data frames sent via TCP. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

Figure 3.20. Data frames sent via UDP. Source: https://www.springerprofessional.de/en/guide-to-computer-networksecurity/18047080.

3.6.2.2. Transport Layer That layer is similar to the OSI modeling process level in that it is significantly removed from the consumer and concealed from view. Its main purpose is to send application-level communications with communication protocol within their header between the hosting and the servers. Two main protocols make up the Web’s transport layer: Transport Control Protocol (TCP) and User Datagram Protocol (UDP). TCP is a connection-oriented strategy that provides that all application-level packets arrive at their desired location. Two methods contribute to this confirmation (Aertsen et al., 1989). Whenever the network is congested, the sources element’s data transmission is throttled, as well as the flowing control mechanism attempts

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to synchronize the flow rate and decrease packet loss rate by linking sending and receiving speeds. TCP guarantees the delivery of packets at the application layer, but UDP does not. It provides simple, no-frills service that focuses only on delivery and appreciation. It is, however, significantly more efficient and the standard of choice for real data including broadcasting music and video. Packets and protocols are sent from the transport layer to the network level through the transport coating. Figure 3.19 depicts the TCP data assembly, whereas Figure 3.20 depicts the UDP statistics format (Loggia et al., 2013).

3.6.2.3. Network Layer This layer moves datagrams (packets) through one router to another along the path from an origin to a destination host. Among some of the protocols, it implements are the IP, the ICMP, and the IGMP. IP Protocol is by far the most widely used network layer protocol. IP uses packet headers from transport protocols, such as packet data sending and receiving port numbers obtained from IP addresses, as well as TCP header and IP information, to transfer packets of data from gateway to router across the network (Touroutoglou et al., 2015).

Figure 3.21. An IP datagram’s structure. Source: https://link.springer.com/book/10.1007/978–3-319–55606–2.

The optimal pathways in the system are found using routing algorithms. Figure 3.21 depicts the IP datagram arrangement (Elton et al., 2014). The typical IP address has indeed been IPv4, which is a 32-bit addressing mechanism. Due to the fast expansion of internet innovation, there was fear that numbers may be running out, hence IPv6, a new 64-bit addressing mechanism, was created. The network layer sends multiple protocols to the link layer (Morgan et al., 2016).

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3.6.2.4. Data Link Layer That layer offers internet services including such linking lines that enable packets to be transported through one packet switching, including a router, to the next. That layer further guarantees that packets from the network level are delivered properly via connections. At the most basic level of interaction, it contains the network interface card (NIC) and operating system (OS) protocols. This tier includes the Internet, asynchronous communication mode (ATM), and additional protocols like data transfer. The link-layer process unit, the frame, may be moved from the sender to the receiver using different link-layer protocols at different connections along the route (Yu et al., 2019).

3.6.2.5. Physical Layer This coat is answerably and used for bit-by-bit physical transmission of data connection datagrams through networks as well as between network elements. The protocols in this area make use of and are contingent on the characteristics of the connected medium as well as the indications sent across the situation (Brunetti et al., 2017).

3.7. NETWORK SERVICES In need of a communication network to operate successfully, data should be able to transfer from one network to another. This is only conceivable if the data-transfer computer networks are operational. For communication systems, these activities are classified into two categories (Guha et al., 2004): •

•

Data interchange between two network functioning endpoints with the lowest amount of data damage and even in the smallest period feasible is enabled by connection services. Switching services to enable data transfer from one host to another through a linked mesh of hubs, crowds, connections, gateways, also routers are more efficient (Venkataraman et al., 1996).

3.7.1. Connection Services Where could we contract the link distribution pieces to talk to each other via the internet? Connection services are divided into two categories: there are two types of connections: those that are related to each other and those that aren’t (Brynildsen et al., 2006).

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3.7.1.1. Connected-Oriented Services In such a connection-oriented organization, a three-way handshake is necessary before a consumer may transmit packets carrying actual data to a server. In the next chapters, the three-way handshake would be defined. A three-way handshake, on either hand, is used to establish a session before beginning real dialogue (Edlow, 2021). Creating a session generates a network route of emulated connections between both the end systems, guaranteeing the preservation and creation of fixed communication channels as well as other resources necessary for exchanging data first before data is sent for as soon as the channel is needed. Whenever we make phone conversations, for example, the channels are scheduled and established again for a call before we spar. This approach is considered reliable since it assures that data reaches in the same order that it was sent. In a summary, the following characteristics are included in the service (Liu et al., 2017): • Every data exchange involving end systems is acknowledged. • During data transmission, dynamic network control is used. • Controlling congestion issues through the transmission. Depending upon the type of base stations in use and the activities to be offered by the communicative systems, correlation approaches may be used at the data link or distribution layer of the routing algorithm, although the current tendency is to use it largely at the network layer. TCP, for instance, is a correlation transport protocol at the transport layer. Two more connectionoriented computer networks are frames re-laid with ATMs (Xia et al., 2017).

3.7.1.2. Connectionless Service In such a wireless link, there are no shaking hands to establish a session with communication end systems, no flows, and no queueing control. This means that a client may connect with a service without having to wait for that to be prepared; it just delivers flows of data packets from its transmitting port towards the server’s linking ports in single point-to-point transfers with no dynamic interactions among packets and destination computers (Fu et al., 2019). This kind of connection service provides benefits as well as drawbacks. In a word, the connection is quicker because it eliminates the need for lengthy handshaking and enables frequent burst transfers of huge volumes of data. However, since there has been no prior monitoring or acknowledgement, this service simply offers the most basic features and

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offers no protections or warranties to the donor (Boveroux et al., 2010). Further, the services lack the consistency of the correlations technique and offer no error correction or packet order; moreover, every packet selfidentifies, resulting in enormous headers; and lastly, packets arrived in no particular sequence. Such as the connection-oriented technique, this facility may be used at the statistics link and transportation levels. UDP, a unicast service, is used at the transport layer, for example (Ying et al., 2012).

3.7.2. Network Switching System Before we go into communication systems, let us just take a detour and discuss data transport through a switching element. This is a means of transferring data from one site to another through the width and length of a networking mesh made up of servers, ports, bridges, routers, and gateways. This procedure is known as data shifting. The kind of data operating mode used by the network has an impact on how data are transported between both the two-way communication components and across the network. Data switching methods are divided into two classifications: packet switching and circuit switching (Goveas et al., 2011).

3.7.2.1. Circuit Switching Before constructing a practical means of communication in circuit-switched networks, all services must be allocated. The physical connection is only utilized for two end systems, which are generally contributors, for the period of the communication. The primary benefit of this form of linking is that it delivers a secure data proportion station that equally customers must utilize (Tu et al., 2013). Before consumers may start utilizing a telephone network link, for example, a connected line between the two sites should be reserved. One area of contention within the circuit-switched argument is the claimed waste of money and effort throughout the so-called inaudible hours, whenever the linking remains completely functioning nonetheless not existence utilized by the gatherings. Whenever a landline receiver, for example, is not jammed after usage throughout a telephone service period, the connection is left open. Though nobody is utilizing the session line during this period, it remains accessible (Kesler et al., 2013).

3.7.2.2. Packet Switching In contrast, frame relay networks do not require any characteristics to be allocated before the commencement of data transmission. Within those links,

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the transmitting host, on the other side, must arrange the data streams to be delivered hooked on packages. When a single communication is too big to fit into a single packet, it is divided into many smaller ones (Greicius et al., 2008). Packet headers include the input and output network information of the two communicating end systems. The packets are subsequently transmitted through communication cables or across packet switches (routers). Upon reception, the router recognizes the address of the destination present in each packet. Each router then transmits the packets to use its routing table and the maximum bit rate accessible on the better facilities (DeRamus et al., 2021).

Figure 3.22. Packet switching network. Source: https://networkinterview.com/what-is-packet-switching/.

Each packet is transmitted on the proper connection when it arrives at each successive router, intermingled with other messages traveling on just that path. Every router confirms that it is the owner of the package by checking the address of the destination, but even then reconfigures the packet through into the final letter. In a bandwidth network, the significance of routers is seen in Figure 3.22 (Schrantee et al., 2018). Package switches store-and-forward spreaders, connotation they require receiving the whole packet beforehand retransmission or forwarding things to a whole new switch. Because these packets have no predetermined routing, the time taken to reassemble the actual statement can be unexpected. In addition, the network may not be capable of properly transporting all packets to their desired targets. Every packet does have a maximum length that must be met for the system to maintain a constant transit time. Packet switching networks are plagued by a variety of difficulties, including the following (Castañeda, 2010):

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•

The frequency of packet transfer between two the switching elements is determined by the optimal transmission of the connection linking two switching elements, and the shifts themselves • There are usually small interruptions while the switch is to come for a complete packet. The delay is related to packet length. • Every switching component has a fixed cushion for packets. As a consequence, a packet could only go as far as the buffer, which is already overflowing with earlier packets. When this occurs, the afresh received packet is lost rather than being kept, a procedure called packet dipping. During busy periods, servers could drip a stream of packs. One gauge of traffic jams used during congestion management systems is the chance of packet loss. Packet switching links are often known as packet webs for various details. Asynchronous networks are indeed known as packet-switched networks, and packets are ideal in these networks because capacity is shared, removing the necessity of establishing commitments for the projected transfer. The following are the two types of packet-switched networks (McDowell & Shankari, 2000): • •

A packet routing is deliberate and then turned into a rational link earlier being routed through a circuit-switched network. That book is about datagram networks.

3.8. DEVICES FOR NETWORK CONNECTING Let’s go through the network architecture one more before we talk about getting it installed appropriately. A network is a web of interconnected network components (also referred to as network nodes) connected by a conductive medium. Such network elements may be found at the mesh’s borders as consumers or in the center as transmitting components. A local network, such as a LAN, uses special connecting and carrying equipment to transport online behavior from one node to another. When a system is a large Internetwork (a collection of networks such as Local Area Networks (LANs), it is linked to other unique intermediary network equipment, allowing the Web to function as a single gigantic system. Let’s take a closer look at network elements that are linked, and focus on two types: those that are utilized in networking (such as Local area networks) and those that are not (Simó-Ten et al., 2017).

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3.8.1. LAN Connecting Devices Since LANs are small systems, the strategies that link them are usually low-powered and have limited capabilities. The usage of repeaters, hubs, bridges, and switches is common (Carretero & García, 2014).

3.8.1.1. A Hub It is the most basic internet-connected gadget since it uses the very same protocol to link Local network components. It receives and re-transmits all imports in their entirety. It can switch between digital and analog data. Each node should be pre-set to be ready to analyze the incoming information. If indeed the initial information is digital, the hubs must send it as packets; whether it is analog, the hub would convey this as a signal. As depicted in Figures 3.23 and 3.24, there appear to be two types of hubs: basic or multiplex port hubs. Many port hubs can host a large number of computers, up to a certain number of ports, and will therefore be used to plan for future network coverage when additional computers are added. Network hubs interface through network interfaces and cables and typically run at 10 to 100 Mbps; although, many hubs could operate for both speeds. Hubs that can link computers with various speeds and run at 10/100 Mbps are suitable (Song et al., 2014).

Figure 3.23. A straightforward hub. Source: https://cds.cern.ch/record/1565824/files/9781848009165_TOC.pdf.

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Figure 3.24. Hubs with many ports. Source: https://www.researchgate.net/publication/253687458_A_Guide_to_ Computer_Network_Security.

3.8.1.2. A Repeater A system repeating firearm is a low-cost communication device that gathers network signals, amplified them to full intensity, and then re-transmits these at the physical layer to some other device in the network. Repeating firearms are used in a link for just a multitude of reasons, including signal attenuation over lengthy ranges and extending the LAN’s range beyond the stated limit. Because they function at the bottom of the network stacks tier, these are less proactive than their counterparts in the higher levels of a network mass, like switches, bridges, routers, and gateways. Take a glance at Figure 3.25 for an example (Doshi et al., 2018).

3.8.1.3. A Bridge A bridge is comparable to a repetition, except that a repeater increases electrical impulses since it’s positioned just at the protocol stack, whereas a bridge is placed at the data network and magnifies digital data. It duplicates frames in digital form. It permits panels from one section of a LAN, or from a separate LAN using the latest techniques, to be transmitted to some other portion of the LAN. When scanning and separating a frame through one networking to another or another segment of the same networking, the bridge, on either hand, will not transport a faulty frame through one end of the connection to another. Because packets are filtered, the bridge doesn’t alter the form or quality of the information transmitted (Gladisch et al., 2018).

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. Figure 3.25. In an OSI structure, a repeater. Source: https://link.springer.com/book/10.1007/978–3-319–55606–2.

Figure 3.26. A straightforward bridge. Source: https://www.amazon.com/Computer-Network-Security-Communications-Networks/dp/1447145429.

A bridge filters the frames before sending or discarding them. All “noise” packets are not transmitted (collisions, power surges, bad writing, and so on) (Bohn et al., 2005). The bridge filters and transmits packets on the network to use a changeable bridge counter. The originally available bridge board stores the LAN address for every computer within the LAN, and the address of every bridge connection that links the LAN to additional LANs. Like bridges, Hud

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may be humble or contain several ports. A basic bridge, the multi-ported bridge, and the position of the bridge are such an OSI procedure stack are shown in Figures 3.26, 3.27, and 3.28, correspondingly (Medaglia & Serbanati, 2010).

Figure 3.27. Multiple ports on a bridge. Source: https://slideplayer.com/slide/6445855/.

Figure 3.28. A bridge’s position in an OSI process stack. Source: https://www.geeksforgeeks.org/difference-between-bridge-and-repeater/.

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3.8.1.4. A Switch The switch is a switch that connects two local networks (Local area networks) or sections of a system, such as the Internet or system in the context of LANs. In the same way that the bridges do, it employs a variable table to screen and forward messages across the system. That point-to-point technique allows the switch to connect several pairs of components at the same period, enabling several computers to send information at the same time, giving them an efficient edge over their bridge counterparts (Labib et al., 2019).

Figure 3.29. A router’s role in the OSI protocol stack. Source: https://www.router-switch.com/faq/network-layers-in-osi-model-features-of-osi.html.

3.8.2. Internetworking Devices Different networking devices can connect local networks, including such Local area networks, to construct much bigger networks, like the Web. Let us just look at two such plugs: the routers and gateways (Trestian et al., 2009).

3.8.2.1. Routers Routers are multipurpose equipment that use IP subnetworks or unregistered point-to-point links to link two or more connected protocols. Usually, dedicated particularly unique computers with separate source and destination nodes for each linked network are employed. They’re used in the network layer of the protocol stack. Figure 3.29 shows where the router fits within the OSI IP suite.

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RFC 1812 states that a router performs the following functions (Patouni et al., 2013). • •

•

• •

• •

• •

•

Complies with particular Web Services listed in the 1812 specification, including IP, ICMP, or as appropriate. Allows users to join two or even more packet networks at the same time. The router must execute the duties that the network requires since it is a part of every network connection. These functions are commonly used in the following ways: The use of connected network sessions to summarize and decapsulate IP datagrams. The Internet headers and confirmation must be inserted if the connecting connection is an Internet Local area network, for instance (Diaz-Sanchez et al., 2011). Transmitters IP datagrams up to a maximum transmission medium (MTU) of the network. Each IP address range is transformed into an access point that is compatible with the associated network. When Internet cards are required, those are all of the hardware addresses just on NIC. As if the router were just a PC just on the network, every network talks with it. Each router, therefore, is a member of the systems to which it connects. As a result, it has a computer system for that network, as well as an interface address for each network to which it is connected. Each router interface has its Address Resolution Protocol (ARP) modules, LAN address (network card address), and IP identity as a result of this unusual feature (Putland, 2020). Dynamic network management and, if required, error alerts are handled. It receives and transmits Internet datagrams. This procedure requires congestion control, buffer management, and fairness. The router must do the following to do this: – Recognize error situations and produce appropriate ICMP error and informational packets. Datagrams containing a 0 time-to-live field should be discarded. As required, fragment datagrams to fall inside the maximum transmission units of the underlying network (MTU) (Turchet et al., 2016). Based on the information in its routed databases, it selects just one next location for every Data packet.

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Allows other gateways in the very same autonomous system to use an interior gateway protocol (IGP) to perform distributed routing and Wi-Fi tethering algorithms. Furthermore, specific routers must provide an exterior gateway protocol to exchange topological information with some other autonomous systems (EGP). Loading, status reporting, debugging, control, and exception reporting are some of the network management and systems and services available (Itao, 2007). Consider the case when server A in LAN1 tries to transfer a packet to server B in LAN2. Hosts A and B everyone has dual addresses: a Local network address as well as an IP address. This ARP translates Local network addresses to IP addresses, and also the data is acquired or saved inside the Arp cache, which is similar to Table 3.4. Also, it’s worth mentioning that now the router contains two network ports, one is for LAN1 and the other for LAN2 (for connecting to a greater link like the web). Each connection has a Local area networks (host) identity and an IP address again for networks to which it is connected (Dressler & Fischer, 2015) (Figure 3.30).

Figure 3.30. A useful router. Source: https://www.softwaretestinghelp.com/types-of-routers-routing-table/. Table 3.4. ARP Table is a Kind of Table That is Used to IP Address

LAN Address

Time

127.76.1.12

07–1A-EB-17-F6

10:03

127.0.0.5

16–73-AX-E4–01

10:03

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Table 3.5. Interface 1 Routing Table Address 192.76.1.12 127.0.0.1

Interface 2 1

Time 10:03 10:01

As we’re seeing in later chapters, at 10:01, host A directs a packet to router 1 that includes, among other things, both destination IP address and addresses message type of host B. As shown in Table 3.5, the packet comes to the router’s connection 1; the router analyzes it and constructs row 1 of the direction-finding table (Grailet et al., 2016).

3.8.2.2. Gateways Routers’ capabilities are far more limited than among gateways. They act as professional translators for computers or networks that interact using different protocols and operate on network segments, such as OSI and TCP/ IP, and they convert protocols between various types of networks, topologies, or applications. Every network would have its route techniques, web domain server, interfaces, and network management procedures and standards due to the varied technologies employed (Kukulska-Hulme, 2015).

Figure 3.31. A gateway’s operation. Source: https://www.researchgate.net/figure/Standard-gateway-position-onthe-companys-network_fig2_322343260.

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Table 3.6. A Routing Table for Gateways Network

Interface

Gateway

127.123.0.1

2

198.24.0.1

0.0.0.0

1

192.133.1.1

Gateways will handle all of the functions of such a router and much more. Protocol conversion is a gateway that converts data between various network protocols and applications. Figure 3.31 depicts the installation of a gateway inside a network (Vallati et al., 2016). Gateways offer capabilities such as packet size and/or volume translation, protocol transformation, data translating, terminal emulator, and multiplexer. Although they perform the more complex operation of protocol translation, gateways operate slowly and manage few connections. Let’s take a closer look into how a package might go through one or even more gates on its journey to its end destination. Whenever a router gets a datagram, it inspects the destination address and verifies it is not in the local network (Jokela et al., 2015). As a consequence, it uses the default route to send it. This default gateway is currently searching its database for the destination address. If a default gateway determines that the specific location is not connected directly to all the networks with which it is linked, it must identify other gateways to pass the data through (Tokunaga et al., 2002). That data comes from such a gateway navigation database, that links connections to gateways that really can access them. With default paths, the list starts with 0.0.0.0, which is a capture networking entry. Every packet is sent to this unnamed network using the default gateway. Table 3.6 illustrates the gateway forwarding table. When choosing between such a router, a link, and gateways, capability, and speed must be balanced. Gateways, as stated previously, provide a variety of functions; yet, owing to their slowness, portals could become blockages in just such a system (Chinnici et al., 2019). Network nodes may be individually constructed for smaller Local area networks (LAN or continuously produced for larger networks using routing supervisor software.

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3.9. NETWORK TECHNOLOGIES Smaller networks (LANs) reflect the limited area, whereas bigger ones cover wider regions, as we discussed before in this section (WANs). In the final half of this section, we’ll take a look at several communication networks in these fields (Aoki et al., 2010).

3.9.1. LAN Technologies Recall how we defined a local area network (LAN) at the outset of such a chapter? A local area network (Local area network) is a tiny data transfer system composed of a group of devices all of which are linked to the system and cover a specified geographic region, such as a structure or a single floor. Furthermore, a Local area network is often controlled by a single organization, such as a company. According to IEEE 802.3 Council on Local network Specifications, a Local area network is just a small, globally shared peer-to-peer network technology that transmits information over a basic physical channel in a point-to-point manner without the need for an intermediary switching device. Today, several prevalent communication networks, including such Internet, fall within this heading (Koper & Tattersall, 2004).

3.9.1.1. Star-Based Ethernet (IEEE 802.3) LAN The IEEE 802.3 Council on Standardization has defined Online services, that is the most frequently utilized of all Transmission control protocol. Both the media access control (MAC) level and the core network are described in the IEEE 802.3 specifications. The Network MAC employs a CSMA/ CD technique (carrier sense channels antenna with collision detections). Every network node seeking to broadcast using CSMA must first monitor to a medium to confirm that no other nodes are sending. Medium carriers sensing is the term for this. The element trying to communicate waits if the medium is currently used by other nodes; otherwise, it sends (Nolan et al., 2016).

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Figure 3.32. A framework for the internet. Source: https://www.gatevidyalay.com/ethernet-ethernet-frame-format/.

Interruption happens when two or even more components attempt to communicate at the same moment, jeopardizing the evidence’s credibility for all. On either hand, the element could be completely oblivious of this. As a consequence, it waits for the recipient node to respond. The waiting time varies depending on the maximal round-trip delay time or any unexpected delays. If the element receives no response at that time, it concludes there was still a collision and also that the transmission failed, and must be rebroadcast (Abboud et al., 2016). Whether there are additional collisions, the elements first must double their delay period, then the delay period must be doubled again, and so on. The medium could be idle while the two components are in a delay period following a collision, causing inefficiencies. Rather than just going in delayed mode, the components must continue to listen to the media while broadcasting to correct the situation. They would hardly be conducting carrier sense in this situation, and also monitoring a collision, resulting in Carrier sense multiple. The CSMA/CD mechanism, according to Siemens, follows algorithms (Balatsoukas et al., 2015): • • •

Uncertainty an average is inactive in some way, transmit. If a medium is busy, wait until it is calm before transmitting. Transmit a jamming signal to several network parts as a “collision warning” if a collision is detected. • Before trying to engage after plugging the signals, pause an arbitrary quantity of time component. The IEEE 802.3 standards are used in a variety of Ethernet LANs, including (Jones, 2002):

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•

10 BASE-X (where X equals 2, 5, T, and F; T is for twisted pair, while F stands for fiber optics) • BASE-T 100 (where the T choice contains TX, T4, and FX) • BASE-T 1,000 (where T choices contain CX, SX, T, then LX) As shown in Figure 3.32, a frame is by far the most basic Internet transmission structure. LAN dialogues of the procedure xx-xx-xx-xx are stored in the sending and receiving fields. The error-detecting field is a four-byte field used to identify errors, which is generally done utilizing the cyclic redundancy check (CRC) system, where the value of such bits is synchronized between both the sending and receiving components (Hartman et al., 1991).

3.9.1.2. Token Ring/IEEE 805.2 While not quite as prevalent as that of the Web, systems in the context of Computer networks based on The IEEE 805.2 remain widely utilized in business and minor networked systems. The standards employ a networkwide identifier that is accessible to all endpoints. Token passing technology, which we’ve seen, uses a technique to send the token throughout the system so all computer networks get fair opportunities for it (Vazquez & Salmeron, 2003). Whenever broadcasting, a network device would wait for such a token to arrive at the organism’s ring communication link. Whenever the token comes to a point, the component catches it and changes a single bit of that too to become the beginning bit of both the data frames that the element will broadcast. They attach more important data to the ring before sending the payload, including location data and other data. After that, it waits for the token to complete a circuit and also be delivered before proceeding. The structure’s source MAC address should be recognized by the recipient host. Upon reception, the server checks for the last column showing that the MAC address is acknowledged it its own (Vokhmina et al., 2015).

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Figure 3.33. A token data frame. Source: https://www.cisco.com/en/US/docs/internetworking/troubleshooting/ guide/tr1906.html.

The hosting then duplicates the contents of a frame, which is subsequently circulated again. Whenever the network element with the token is found, it takes this from the rings and replaces it with a new token for yet another network component that may need to be broadcast (Gruber et al., 2009). A round nature of the token ring approach guarantees that each network device has a reasonable casual of conveying if so needs. The network, though, will grind to a halt if a token is only ever lost. The configuration of a token data frame is shown in Figure 3.33, while the creation of a token ring is shown in Figure 3.16. A token ring, like the Internet, uses many technologies depending on the transmission speeds (Liu & Effenberger, 2016).

3.9.2. WAN Technologies As stated previously, WANs have data connections that are similar to Local area networks that cover a larger geographical region. WANs provide lesser services to clients than Local area networks because of their larger size. The high-speed communication network (ISDN), X.25, frames relay, and the widely used Web are all included in this section (Christin et al., 2010).

3.9.2.1. Integrated Services Digital Network (ISDN) International Standard Digital Network (ISDN) is a digital phone connection technology that enables data to be transported across the globe in real-time using endwise communications technology. It also is a system that enables the broadcast of video, audio, and statistics. System coordination for all of

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these networks is a crucial advantage in making systems more desirable since the transmission of diverse forms of data, especially graphics, exerts such a broad range of demand just on the transmission line. According to ISDN guidelines, users should be given a variety of items (Delgado et al., 2006). The BRI system comprises two 64-kbps B lines (carrier channels) and one comprehensive 16-kbps D route (data channel). The B band is dedicated to digital voice, while another is used for data transfer. Instrumentation and network control data are sent through the D line. The price is for a single user. •

PRI services, A maximum of kbit is provided through 23 64 kbps B channel one and 64 kbps D station. This tax is imposed on all large users. Consumers that have an ISDN phone service within 18,000 feet (approximately 3.4 miles or 5.5 kilometers) of the telecoms company’s headquarters are qualified for BRI. If not, expensive repeating equipment such as ISDN terminal converters or ISDN routers would’ve been required (Gray et al., 2015).

3.9.2.2. X.25 The X.25 standard, which was developed by the International Telecommunications Union (ITU) in 1993, may give compatibility to a broad variety of data transmission wide area networks (WANs), often called open networks, which are owned by private corporations, institutions, and government entities. According to X.25, that’s how data gets to and from access to the public communications systems. The physically, connections, and packet levels, correspondingly, represent the OSI layer, OSI data-link surface, and OSI core network. The hardware is much like the OSI physical layer, the link layer is like the OSI link layer, as well as the packet layer is the same as the OSI system level. X.25 is a three-level correlation and packet-switched broadband service protocol that corresponds to the OSI figure’s link, physically, and packet levels (Dimmick et al., 2007).

3.9.3. Wireless LANs For its quick improvements, compactness, then ubiquity, wireless technology has ushered in a new era of LAN technology. As a consequence of worker movement and migration, businesses have been forced to embrace new kinds of wireless technologies (Guy et al., 2010).

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CONTENTS 4.1. Introduction .................................................................................... 130 4.2. Memory Hierarchy .......................................................................... 133 4.3. Handling the Memory Hierarchy .................................................... 136 4.4. Caches............................................................................................ 141 4.5. Main Memory ................................................................................. 148 4.6. Future and Current Research Problems ........................................... 154 References ............................................................................................. 159

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4.1. INTRODUCTION A computer system is made up of three basic parts, as depicted in Figure 4.1: (i) To execute operations on data, units of calculation are used (Processors, for example, as we saw in the previous knowledge), (ii) storage (or memory) devices that retain data to be archived or processed, (iii) Communication units that transmit data between storage and compute units (Adrianson & Hjelmquist, 1993). Typically, the memory/storage units fall into two categories: (i) the memory system serves as a working storage space for the data that has been processed via running applications, and (ii) the backup storage system, such as a hard disk, that serves as secondary storage, permanently keeping data for a longer period. This chapter would concentrate on the communication of computer memory systems (Hollingshead & Brandon, 2003).

Figure 4.1. Computing system. Source: https://kilthub.cmu.edu/articles/journal_contribution/Memory_Systems/6469010/1.

The memory system is a data storage system from which the processor may update and retrieve data. During the operation of a computer system, the processor reads data from the memory system, executes calculations on the data, and then writes the modified data back into the memory system, continuing this process till all required computations have been done on all required data (Yan et al., 2001) (Figure 4.2).

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Figure 4.2. Computer memory systems are arranged in a hierarchy. Source: https://www.tutorialandexample.com/computer-memory.

4.1.1. Metrics and Basic Concepts The entire quantity of data that a memory system may store has been its capacity. A distinctive address is assigned to each item of data contained in the memory system. The 1st bit of data, for instance, has an address of 0 and the final bit of data has an address of capacity –1. The address space of the memory system refers to the whole range of potential addresses, which ranges from 0 to capacity –1. As a result, to retrieve a specific bit of data from the memory system, the processor should provide the memory system with its address (Peltokorpi & Hood, 2019). Various significant metrics define the efficiency of a memory system: (i) parallelism, (ii) bandwidth, and (iii) latency. Higher parallelism, higher bandwidth, and lower latency are all characteristics of a high-efficiency memory system. The length of time required for the CPU to retrieve one piece of information from the memory system is referred to as latency. The pace at which the CPU may receive information from the memory system has been measured in bandwidth, often referred to as throughput. Upon first

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glance, bandwidth, and latency seem to be completely opposed (Carter et al., 1995). For instance, if accessing one bit of data requires T seconds, it’s tempting to infer that 1/t sets of data may be accessible in one second. This isn’t always the case, though. To properly comprehend the link between bandwidth and latency, we should also consider the memory system’s 3rd performance indicator. The quantity of simultaneous memory system accesses has been referred to as parallelism. When a memory system seems to have a parallelism of one, all accesses have been handled once at a time, and bandwidth has been the opposite of latency throughout this situation (Hsu et al., 2012; Delp, 1988). However, if a memory system supports greater than one parallelism, simultaneous accesses to distinct locations might be handled at the same time, and overlap their latencies. Whenever the parallelism has been equal to 2, for instance, second access is provided in parallel during the time it takes to service one access (T). As a result, whereas the latency of individual access stays constant at T, the memory system’s bandwidth increases to 2/T. The link between parallelism, bandwidth, and latency of a memory system may be described in more generic terms as below (Ren & Argote, 2011).

Whereas bandwidth may be expressed in terms of accesses per time (the above equation), it may also be expressed in terms of bytes per time, which has been the quantity of data accessible per time (the below equation) (Palazzolo et al., 2006).

Cost is another property of a memory system. The memory system cost has been the needed investment to deploy it. Cost is tightly tied to the memory system’s efficiency and capacity: typically, improving the efficiency and capacity of a memory system also increases its cost (Tam et al., 1990).

4.1.2. Two Elements of the Memory System When building a memory system, computer architects improve the system such that it includes all three of the features described above: cheap cost, good efficiency, and great capacity. A memory system with both a big

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capacity and great performance is, though, quite costly (Riedl et al., 2012). Whenever one wishes to expand the memory’s capacity, for instance, the memory’s latency nearly always improves as well. Whenever constructing a memory system inside a suitable budget cost, there happens a basic trade-off between efficiency and capacity: it is feasible to attain either big capacity or higher efficiency, but not both simultaneously in a cost-efficient way (Lewis, 2004). Consequently, of the trade-off involving efficiency and capacity, a contemporary memory system often contains two elements: (i) a tiny but comparatively faster to access element, and (ii) a big but comparatively slower to access main memory element. Amongst two, the main memory has been the comprehensive primary repository its capacity has been typically selected to reduce storage system accesses. If the memory system consisted just of primary storage, meanwhile, all memory system accesses will be handled via main memory, which has been sluggish (Li & Hudak, 1989; Agarwal et al., 1994). Because of this, a memory system often additionally consists of a cache: Because of this, a memory system often additionally consists of a cache: despite being considerably smaller than the main memory, a cache has been extremely quick (precisely because of its diminutive size). The memory system employs the cache by transferring a subset of the data from primary memory to the cache, so allowing the cache to service certain memory system accesses more rapidly. The cache stores duplicates of the data already present in primary memory (Brandon & Hollingshead, 2004) (Figure 4.3).

Figure 4.3. Main memory system and cache. Source: https://www.apogeeweb.net/article/160.html.

4.2. MEMORY HIERARCHY A perfect memory system will have the following characteristics: higher efficiency (higher bandwidth and lower latency), cheap cost, and higher capacity. However, technical, and physical limits prevent the building of

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a memory system that simultaneously possesses all three features. Instead, one attribute may only be enhanced at the expense of another, that is, a basic trade-off association exists between the capacity, efficiency, and price of a memory system (Fatahalian et al., 2006). (To ease the topic, we would suppose that lower cost has always been desired, limiting ourselves to a “zero-sum” trade-off amid capacity and performance) For instance, main memory has been an element of the memory system that has a huge capacity but comparatively poor efficiency, whereas a cache has been an element of the memory system that has a modest capacity but great performance. Thus, main memory and caches occupy opposing sides of the performance versus capacity trade-off continuum (Alpern et al., 1994). We have already noted that contemporary memory systems include both main memory and caches. To get the best of both worlds (efficiency and volume), i.e., a memory system with the higher efficiency of a cache and the enormous capacity of main memory. When the memory system just consisted of main memory, then all memory system accesses will be subject to the higher latency (that is, poor efficiency) of main memory (MellorCrummey et al., 2021). Though, if caches have been employed in addition to main memory, then certain memory system accesses will be provided by the caches with lower latency, whereas the other accesses will locate their data in main memory with a high delay because of its enormous capacity. As a consequence of utilizing both the main memory and the caches, the actual latency of the memory system (such as average latency) has been lower than those of the main memory, although the main memory’s capacity remains the same (Balasubramonian et al., 2000). Main memory and caches have been stated to be components of a memory hierarchy inside a memory system. A memory hierarchy, in more technical terms, describes how distinct parts (such as main memory and cache) with varied capacity/efficiency qualities are joined to build the memory system. As shown in Figure 4.4, the element that is the quickest to access (but also the smallest) is located at the “top-level” of the memory hierarchy, whereas the one that is the slowest to access (but the largest) is located at the “bottom level” of the memory hierarchy (Mei & Chu, 2016; Van Dijck, 2008). The memory hierarchy normally comprises numerous levels of caches (such as the L1, L2, and L3 caches in Figure 4.4, which stand for level-1, level-2, and level-3) with every level having a larger capacity than the one that came before it, and a single level of main memory with the highest possible capacity at the very bottom. The utmost recent cache was the one located at

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the very bottom of the hierarchy (e.g., the L3 cache in Figure 4.4, which is directly above the main memory) (Hallnor & Reinhardt, 2005).

Figure 4.4. A memory hierarchy having three levels of caches is an instance. Source: https://kilthub.cmu.edu/articles/journal_contribution/Memory_Systems/6469010/1.

In most cases, the processor will access the memory system in a sequential approach, beginning with the top element and checking to see if it already possesses the essential data before moving on to the next element. when the data has been located, we refer to the access as having “hit” in the top element, and the access is granted there and then, bypassing the need to search the lower elements of the memory hierarchy (Yotov et al., 2005). If the data is not found, the access has been said not to have “hit” in any element. If the data has not been located, the access has been said to have “missed” in the top element. If this does not happen, the access has been said to have “missed” in the top element, and it is then sent down to the element in the memory hierarchy that is right below it (Jones, 2014). If this continues to happen, the access will eventually succeed. Therefore, the access can once again suffer either a hit or a miss depending on the circumstances. As access moves down into the hierarchy, the likelihood of a hit increases due to the growing capacity of the lower elements, and this trend continues down until the access reaches the lowest level of the hierarchy, at which point it has been assured to always be successful (assume the information has been stored in main memory) (Asadi et al., 2005).

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4.3. HANDLING THE MEMORY HIERARCHY As was previously stated, each item of data inside a memory system has been assigned a unique address. The address space has been the collection of all potential addresses for a memory system, and it extends from zero to capacity-1, wherein capacity has been the size of the memory system (Crisp, 1997; Goldberg et al., 1999). Normally, whenever software programmers construct computer programs, they depend upon the memory system and expect that program data may be stored at specified locations without limitation, so long as the addresses are legitimate, that is, they don’t exceed the address space allowed by the memory system. Consequently, in reality, the memory system doesn’t immediately disclose its address space to computer applications. There are two explanations for this (Lioris et al., 2010). To begin, a software developer constructing a computer program does not have any way of knowing the memory system on which the program will run because there is currently no such thing as virtual memory. For example, the program can run on a computer with a very small memory system that has a very large capacity (such as one terabyte) and a very small memory system (for example one MB capacity) (Zhou et al., 2009; Peltokorpi & Hood, 2019). Although a memory address of one gigabyte can be accepted by the first memory system, it cannot be accepted by the second memory system since it is more than the maximum allowable address space limit of one megabyte. Therefore, if the program has direct access to the address space of the memory system, the software developer cannot be confident whether the addresses are valid and whether they may be used to store program data. This is because the program has direct access to the memory system (Youseff et al., 2008) (Figure 4.5).

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Figure 4.5. Hierarchy representation of computer memory. Source: https://en.wikipedia.org/wiki/Memory_hierarchy.

Secondly, while writing a computer program, the software programmer has no means of knowing which many other programs would be running at the same time as the program. Whenever the consumer executes the application, for instance, it can operate on the same machine as several other programs, each of which can utilize a similar address (e.g., address 0) to keep a bit of data (Nieplocha et al., 2006). Whenever one program updates the data at a certain location, it rewrites the data of another program that had been placed at a similar address, which isn’t supposed to happen. As a consequence, if the memory system’s address space has been directly uncovered to the program, many applications may overwrite and damage every other’s data, causing all of the programs to execute incorrectly (Choi et al., 2011).

4.3.1. Physical Versus Virtual Address Spaces Like a solution to such two issues, a memory system creates the appearance of an incredibly vast address space that has been distinct for every individual application rather than explicitly exposing its address space (Figure 4.6).

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Figure 4.6. Virtual memory may work in tandem with the actual memory of a computer to offer quicker, more fluid processes. Source: https://www.enterprisestorageforum.com/hardware/virtual-memory/.

Whereas the idea of a wide address space overcomes the 1st issue of varying memory system capacities, the illusion of a distinct huge address space for every unique application solves the 2nd issue of many programs altering data at a similar address (Sanghavi et al., 1996). They are known as virtual address spaces because such big and independent address spaces are merely an illusion offered to the programmer to keep her life simpler while assembling programs. The physical address space, on the other hand, refers to the memory system’s real underlying address space. In using real numbers from today’s systems (approximately 2013), a typical eight GB memory system’s physical address space varies from zero to eight GB 1, while a program’s virtual address space generally extends from zero to 256 TB-1 (Yim, 2005).

4.3.2. Virtual Memory System Virtual memory refers to the complete technique discussed so far by which the OS maps and translates among physical and virtual addresses. Whenever building a virtual memory system is composed of an OS, there have been three things to keep in mind (Kandemi & Choudhary, 2002) (Figure 4.7): •

whenever a virtual address should be mapped to a physical address;

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the granularity of the mapping; whenever physical addresses aren’t any longer available, what should you do?

Figure 4.7. Virtual memory system. Source: http://www.cburch.com/books/vm/.

For starters, many virtual memory systems map a virtual address ondemand when it has been utilized for the 1st time. In the other words, a virtual address has never been mapped to a physical address since it was never used (Basak et al., 2019; Hockney & Curington, 1989). Even though the virtual address space is enormous (e.g., 256 TB), most applications only use a small portion of it in practice. As a result, mapping the whole virtual address space to the physical address space is pointless, as the vast majority of virtual addresses would never be used. Not to mention that now the virtual address space has been significantly bigger than the physical address space, therefore mapping all virtual addresses is impossible to start with (Sankaranarayanan et al., 2013) (Figure 4.8).

Figure 4.8. The virtual memory’s overall scheme. Source: https://edux.pjwstk.edu.pl/mat/264/lec/main85.html.

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Secondly, a granularity for mapping addresses from the virtual address space to the physical address space needs to be chosen for a virtual memory system before the system can be used. For instance, if the granularity has been set to one byte, the virtual memory system will divide the physical and virtual addresses into “chunks” that are each one byte in size. These “chunks” will correspond to the virtual address and the physical address, accordingly (Hajj et al., 1998). After then, the system for managing virtual memory can map a one-byte virtual chunk to every one-byte physical chunk, provided that the physical chunk in question is vacant. A significant drawback, although, of this precise split of the address spaces into a huge number of little portions is that it makes the virtual memory system more complicated. Whenever a mapping among a pair of virtual and physical chunks has been formed, it has been necessary for the system that manages virtual memory to memorize the mapping in question (Pohl et al., 2020). Therefore, a high number of virtual and physical chunks implies a high number of potential mappings between the 2, which increases the amount of bookkeeping overhead associated with remembering the mappings. The majority of virtual memory systems roughly partition the address spaces into a lower number of chunks, with each chunk being referred to as a page and having a size that is typically 4 KB in size. This is done to decrease such an overhead (Bellens et al., 2009; Irony et al., 2004). A portion of the virtual address space that is 4 KB in size has been known as a virtual page, while a portion of the physical address that is also 4 KB in size has been known as a physical page (conversely, a frame). When an OS maps a virtual page to a physical page, it stores the mapping information in a data structure known as the page table. This allows the OS to maintain a record of the mapping and retrieve it when necessary (Tuomenoksa & Siegel, 1982). Thirdly, when a program initially accesses a novel virtual page, the system of virtual memory transfers the virtual page to an available physical page. Whether it occurs often, the physical address space can be bushed, meaning that no physical pages have been available because they have all been mapped to virtual pages (Huang et al., 2018). Now, the system of virtual memory should reclaim one of the mapped physical pages to “generate” a free physical page. This is accomplished through the virtual memory system, which does so by removing the data from a physical page from the main memory and “un-mapping” the physical page from its corresponding virtual page. The virtual memory system may transfer a free physical page to a new virtual page after it has been generated in this way (Lin et al., 2001) (Figure 4.9).

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Figure 4.9. Virtual memory enhancement. Source: https://www.bsc.es/research-development/research-areas/computerarchitecture-and-codesign/improving-virtual-memory.

4.4. CACHES A cache, in general, has been any structure which stores information which is anticipated to be requested again (e.g., often accessed data or latest accessed data) to prevent the long latency operation necessary to obtain the data with a very slower structure (Kgil et al., 2008; Bershad et al., 1991). Web servers, for instance, frequently utilize caches to save the most prominent photos or news items so that they may be promptly accessed and given to the end consumer. A cache is a tiny yet fast element of the memory hierarchy that caches the most often accessed data between all data in the memory system. Data kept in the cache may be retrieved rapidly by the processor because it has been planned to be quicker than the main memory (Aga et al., 2017) (Figure 4.10).

Figure 4.10. Memory caches (CPU caches) employ high-speed static RAM (SRAM) chips, while disk caches have been often a portion of main memory consisting of standard dynamic RAM (DRAM) chips. Source: https://www.pcmag.com/encyclopedia/term/cache.

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The efficacy of a cache is determined by the proportion of memory accesses that “hit” in the cache and, as a consequence, are fed from the cache rather than the considerably slower main memory. Because Several computer programs exhibit locality in the way they access memory, a cache can achieve a greater hit rate while having a very limited capacity. This is because data that has been accessed in the past are likely to be accessed once more shortly. Thus the cache stores the data that were most recently accessed (or that are accessed the most often), a tiny cache, its capacity has been significantly smaller than those of main memory, can handle the majority of memory accesses (McFarling, 1989).

4.4.1. Primary Considerations of Design There have been three fundamental design factors to consider whenever implementing a cache: (i) capacity, (ii) physical substrate, and (iii) granularity of data management. We’ll go through each of them one by one in the sections below (Hill & Smith, 1989). Firstly, the physical substrate utilized to implement the cache should be capable of delivering much lower latencies than the physical substrate utilized to implement the main memory. Because of this, SRAM (pronounced “es-ram”) has been and continues to be the most frequent physical substrate for caches. SRAM’s primary advantage is that it can operate at speeds comparable to those of the CPU (Iyer, 2004). Furthermore, SRAM has been made up of the same sort of semiconductor-based transistors as the CPU. As a result, a lower-cost SRAM-based cache may be installed beside the CPU on the same semiconductor chip, enabling even reduced latencies. An SRAM cell, which generally has six transistors, has been the smallest unit of SRAMThe six transistors collectively store a one-of-a-kind data value, either one or zero, in the form of an electrical voltage that may be either “low” or “high” (Wolf et al., 1996). Whenever the processor reads information from an SRAM cell, the transistors provide the CPU with the data value that corresponds to the voltage levels at which they are operating. On the one hand, whenever the CPU writes into an SRAM cell, the voltage of the transistors has been adjusted to display the updated data value that has been written. On the other hand, the voltage of the transistors has not been affected (Mueller, 2000). Secondly, while establishing a cache’s capacity, it’s important to strike a balance between the necessity for a cheap cost, higher hit rate, and lower latency. Whereas a huge cache has been more likely to have a higher hit rate,

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it does have two drawbacks. Firstly, because of the higher transistor count necessary to construct a huge cache, it contains a high cost (Dusser et al., 2009; Bhaskar et al., 2020). Secondly, a huge cache will almost certainly have longer latency. It’s because controlling the operation of a large number of transistors has been a difficult undertaking with additional delays (e.g., determining the location of an address can take more time). In reality, a cache s designed large enough to attain a higher hit rate while avoiding a major increase in cost and delay (Nesbit et al., 2007). Finally, a cache has been broken down into several little bits known as cache blocks. The granularity with which the cache maintains data has been defined as a cache block. In current memory systems, a cache block is typically 64 bytes in size. A 64 KB cache, for instance, is made up of 1024 distinct cache blocks. Any single one of these cache blocks may store data from any “chunk” of the address space that is 64 bytes long. For instance, every cache block that is 64 bytes long can store data from address 0, address 64, address 128, address 192, and so on. As a result, a cache block needs a “label” which specifies the location of the data saved in the cache block (Eklov & Hagersten, 2010) (Figure 4.11).

Figure 4.11. Cache data. Source: https://kilthub.cmu.edu/articles/journal_contribution/Memory_Systems/6469010/1.

4.4.2. Logical Organization The logical structure of a cache, which is defined as how it transfers 64byte parts of the address space onto its 64-byte cache blocks, is something that the computer architect is responsible for determining. In addition to the fundamental considerations that have already been discussed, this decision ought to be made as well. Because the memory system’s address space is substantially larger than the capacity of the cache, there have been a significantly greater number of chunks than there have been cache

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blocks (Bhattacharjee, 2013). This is because the capacity of the cache is significantly smaller. As a direct consequence of this, the mapping between cache pieces and chunks of data must always be “many-to-few.” The computer architect, on the other hand, may create a cache for every unique chunk of the address space that may map the chunk to (i) only one cache block or (ii) any of its cache blocks. Whenever mapping a chunk to a cache block, such two logical groups show two opposing ends of the degree of freedom. In reality, as discussed below, this flexibility poses a critical tradeoff between cache complexity and use (Laoutaris et al., 2006). On either side, a completely-associative structure refers to a cache that allows the most flexibility in mapping a chunk to a cache block. A completely-associative cache doesn’t impose any restrictions on whether a new chunk may be stored when it has been brought in from the main memory, the chunk may be kept in any of the cache blocks. As a result, as soon as the cache contains a minimum of one empty cache block, the chunk will be saved in the cache without the need to evict an already occupied (that is, non-empty) cache block (LaMarca & Ladner, 1999). A completelyassociative cache is the most effective at utilizing all of the cache blocks in this regard. The disadvantage of a completely-associative cache is that every time the processor uses the cache, it should search all cache blocks exhaustively because any one of the cache blocks might have the data that the processor requires. However, scanning throughout all cache blocks not only consumes a significant amount of time (resulting in higher access latency) but also consumes a significant amount of energy (Ranganathan et al., 2000) (Figure 4.12).

Figure 4.12. Logical organization. Source: https://slideplayer.com/slide/16157911/.

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A direct-mapped organization, on either side, refers to a cache that allows the least amount of flexibility in mapping a portion to a cache block. A direct-mapped cache enables a fresh chunk to be fetched from the main memory and stored in only a single cache block. Consider the following scenario as shown in the figure, a 64 KB cache have 1024 cache chunks (64 bytes). A fundamental direct-mapped cache implementation will assign each 1024th chunk of the address space (64 bytes) to the same cache block (Laoutaris et al., 2004). For instance, chunks starting at address 0, address 64K, address 128K, and so on will all map to the cache’s 0th cache block. This is because each chunk is 1024 bytes long. However, if the cache block is already filled by another chunk, the old chunk should 1st be evicted before a new chunk may be put there. When two separate chunks (represented by two multiple addresses) compete for the same cache block, this has been known as a conflict. Conflicts may arise at one cache block in a direct-mapped cache even if all other cache blocks have been empty. In this aspect, a directmapped cache performs the poorest in terms of effectively utilizing all cache blocks. The advantage of a direct-mapped cache is that the processor may rapidly decide if the cache has the data it needs by searching only one cache block. As a result, a direct-mapped cache has a short access latency (Kamble & Ghose, 1997). There has been a 3rd option termed the set-associative organization, which allows a chunk to map to one of several cache blocks inside a cache, even though not all cache blocks, serve as a compromise between the two companies (completely associative versus direct-mapped). In a cache that has N cache blocks, an associative organization will map a chunk to every one of the cache blocks, but a direct-mapped organization will only map a chunk to a single cache block even if the cache contains N cache blocks (Ross, 1997; Chi et al., 2016). The idea of sets, which have been tiny non-overlapping groupings of cache blocks, has been used in a set-associative organization. In a set-associative cache, a chunk has been mapped to only one set, comparable to a direct-mapped cache. A set-associative cache, on either hand, has been comparable to a fully-associative cache in that the chunk may map to any cache block in the set. As an instance, consider a 2-way set-associative cache, which is a set-associative cache with every set consisting of two cache blocks. A chunk is first mapped to one particular set out of all N/2 sets using such a cache. The chunk may then map to one of the two cache blocks that make up the set inside the set (Hill, 1988).

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4.4.3. Handling Various Caches We’ve just discussed design concerns and management strategies for a single cache so far. A memory hierarchy, on the other hand, often comprises greater than one cache, as explained previously. The rules that control how several caches inside the memory hierarchy communicate with one another are discussed in the following sections: (i) write handling policy, (ii) inclusion policy, and (iii) segregating policy (Kessler & Hill, 1992) (Figure 4.13).

Figure 4.13. A distributed cache combines the RAM of numerous computers into a single in-memory data store that serves as a data cache. Source: https://hazelcast.com/glossary/distributed-cache/.

Firstly, in addition to main memory, the memory hierarchy can have numerous tiers of caches. The superset of all data stored from any of the caches has always been kept in the main memory, which is the lowest level. To put it another way, main memory includes caches. Furthermore, based on the memory system’s inclusion strategy, the same relationship cannot exist between one cache and another. There have been three distinct policies for inclusion: (i) non-inclusive, (ii) exclusive, and (iii) inclusive. Firstly, a bit of data inside one cache can or cannot be discovered at higher layers of caches under the non-inclusive policy (Agarwal & Pudar, 1993). Secondly, under the exclusive policy, a bit of data stored in one cache has been guaranteed to be absent from all subsequent cache levels. Thirdly, a piece of information in one cache has been guaranteed to be discovered in all higher layers of caches under the inclusive policy. The exclusive and inclusive policies are

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opposed, whereas any other policies that fall between the two are classified as non-inclusive. However, the exclusive strategy has the advantage of not wasting cache capacity by not storing duplicate copies of the same material in all caches. The inclusive strategy, on either hand, has the benefit of ensuring data searching is easier when the computer system has numerous processors (Jaleel et al., 2008) (Figure 4.14).

Figure 4.14. Single vs multi-level caches. Source: memory/.

https://pediaa.com/difference-between-cache-memory-and-virtual-

Second, whenever new data is written by the processor into a cache block, the data that had been stored in that cache block has been updated and becomes distinct from the data that had been initially placed into the cache. This happens because the cache is a volatile storage medium. Even though the cache stores the most up-to-date version of the data, all of the lower layers of the memory hierarchy (including caches and main memory) continue to store an older version of the data (Flautner et al., 2002). On the other hand, when writing access hits in a cache, a discrepancy occurs between the updated cache block and the lower levels of the memory structure. This discrepancy can only be resolved by clearing the cache and restarting the application. This inconsistency can be rectified as a result of the memory system implementing a write handling policy. There have been two kinds of write-handling policies: (i) write-back and (ii) write-through (Yang, et al., 2000). Finally, a cache at a given level can be divided into two small caches, which have been allocated into one of two kinds of data: (i) data or (ii) instruction. Instructions are a sort of data which enables a computer how to alter (e.g., subtract, add, or move other data. There are two benefits to having two distinct caches (a data cache and an instruction cache) (Seznec,

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1994). For instance, it keeps one sort of data from dominating the cache. Whereas the processor requires both kinds of data to operate, when the cache has been partially occupied, the processor can be forced to retrieve the other data from low levels of the memory hierarchy, resulting in a significant delay. Furthermore, it enables every cache to be located closer to the CPU, reducing the time it takes to deliver data and instructions to the processor (Cekleov & Dubois, 1997).

4.4.4. Specialized Caches for Virtual Memory In virtual memory systems, specialized caches are utilized to expedite address translation. The most prevalent of these caches is known as a (translation lookaside buffer) TLB. The translation lookaside buffer has been responsible for caching the most currently utilized virtual-to-physical address interpretations by the processor. This makes it possible for the TLB to facilitate the quick translation of virtual addresses that have been cached. The translation lookaside buffer, or TLB, is a cache that holds sections of the page table that the processor has only very recently viewed (Cohen & Kaplan, 2001).

4.5. MAIN MEMORY In contrast to caches, which have been primarily geared for higher speed, the primary objective of main memory has been to offer as much capacity as feasible at a cheap cost and with reasonable latency. DRAM (dynamic random-access memory, pronounced “dee-ram”) is hence the ideal physical substrate for constructing main memory. A DRAM cell has been the smallest unit of DRAM, comprising one capacitor (1C) and one transistor (1T) (Dell, 1997). A DRAM cell maintains a single piece of data (1 or 0) as an electrical charge (“discharged” or “charged”) inside its capacitor. The fundamental benefit of DRAM over SRAM is its smaller cell size: DRAM cells need fewer electrical elements (1C and 1T) than SRAM cells (6T). Consequently, far more DRAM cells may be packed on a similar area of a semiconductor chip, allowing DRAM-dependent main memory to reach a significantly greater capacity for roughly the same price (Garcia-Molina & Salem, 1992) (Figure 4.15).

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Figure 4.15. Kinds of DRAM. Source: https://fr.transcend-info.com/Support/FAQ-1263.

SRAM-dependent caches are often built onto a similar semiconductor chip as the CPU. DRAM-dependent main memory, on the other hand, has been implemented utilizing one or many specialized DRAM chips independent from the CPU chip. This has been because of two factors. To begin with, a big capacity of main memory necessitates so many DRAM cells that they may not all fit on a similar chip as the CPU (Qureshi et al., 2009). Secondly, the process technology used to make DRAM cells (and associated capacitors) is incompatible with the process technology used to make processor chips at a cheap cost. As a result, combining DRAM and logic will dramatically raise the cost of today’s systems. Alternatively, primary memory has been implemented as one or more DRAM chips with a significant number of DRAM cells allocated to it. Main memory that is based on a DRAM is usually referred to as “off-chip” main memory from the perspective of the CPU since it is not located on the same chip as the processor (DeWitt et al., 1984) (Figure 4.16).

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Figure 4.16. Kinds of DRAMs. Source: https://www.javatpoint.com/dram-in-computer-organization.

Memory bus cables connect the CPU to DRAM chips. A CPU’s memory controller interfaces with DRAM chips through the memory bus. The memory controller sends and receives electrical signals over the memory bus to access DRAM data. Signals may be classified into three categories: (i) data, (ii) command, and (iii) address (Deng et al., 2011). The address gives information about the data location that has been accessed, the command gives information about how the data has been accessed (e.g., write or read), and the data gives the definite data value that has been accessed. A data bus, a command bus, and an address bus are the three subsets of wires that make up a memory bus. Every subset has been responsible for transmitting a different kind of signal. Only the data bus among such three is bi-directional because the memory controller may transmit data to and obtain data from the DRAM chips. On the other hand, the command and address buses are uni-directional because only the memory controller may transmit addresses and commands to the DRAM chips (Stonebraker & Weisberg, 2013).

4.5.1. The Organization of DRAM The logical organization of a DRAM-dependent main memory system is (i) ranks, (ii) channels, and (iii) banks. Banks have been the shortest memory structures which may be accessed simultaneously. Bank-level parallelism is the term for this. A rank, on the other hand, is a group of DRAM chips (and associated banks) that function in lockstep. Usually, a DRAM rank

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comprises 8 DRAM chips, each with 8 banks (Levandoski et al., 2013). The rank contains just eight separate banks, which are the set of the ith bank throughout all chips, due to the chips’ lockstep operation. Banks in various ranks have been completely isolated from their chip-level electrical operations, resulting in superior bank-level parallelism than banks in a similar rank. All memory bus-communicating banks form a channel (data, command, address buses). Banks on a similar channel can’t be visited independently, while banks on other channels can. Two memory dictates that access to a similar bank be provided sequentially, although DRAM enables differing levels of parallelism. Why? Analyze the memory controller’s logical DRAM bank structure (Manegold et al., 2002).

Figure 4.17. DRAM organization. Source: https://kilthub.cmu.edu/articles/journal_contribution/Memory_Systems/6469010/1.

Figure 4.17 illustrates the logical structure of a DRAM bank. A DRAM bank is a 2D arrangement of DRAM cells with capacitors. This has been viewed as a set of rows, with every row containing multiple columns. Consequently, every cell has been assigned its own unique set of addresses, which are comprised of a column address as well as a row address. Every bank has what’s called a row buffer, which is just a collection of sense amplifiers. A sense-aim amplifier reads cell information by sensing the cell’s small electrical charge. Alternately, while writing to a cell, the senseamplifier functions as an electrical driver and trains the cell by either filling or emptying the cell’s stored charge. This occurs while the cell is being trained (Crisp, 1997) (Figure 4.18).

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Figure 4.18. Bank organization.

Wires that have been referred to as bit lines span the length of a bank in the direction of the column, and every bitline can link a sense-amplifier to any of the cells that have been located in the same column as it. It has been determined by a wire known as the wordline, of which there is one per row, whether or not correlating row of cells has been linked to the bit lines (Zhou et al., 2009).

4.5.2. Bank Operation The memory controller sends three commands to a bank in the sequence that has been detailed below. These commands are used to fulfill a memory request which accesses data at a certain column and row address. Every command initiates a predetermined chain of actions inside the bank, which allows access to the cell (or cells) that are linked with the address (Ekman & Stenstrom, 2005). •

ACTIVATE (assigned a row address): The complete row is loaded into the buffer of the row. • WRITE /READ (assigned a column address): You may retrieve the data that is stored in a column by using the row buffer. To perform a READ operation, move the data from the row buffer into the processor. Modify the data in the row buffer so that it corresponds to the data that was received from the processor while performing a WRITE operation. • PRECHARGE: Remove the row buffer. While being processed by the DRAM chip, every DRAM instruction generates a delay. When a command is given before the prior command has been completely processed, unexpected behavior can occur. To avoid this, whenever giving orders to a DRAM chip, the memory controller should adhere to a set of temporal limitations (Strohman & Croft, 2007). Such limitations specify when a command has been prepared to be scheduled

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concerning all previous instructions delivered to a similar channel, rank, or bank before it. The timing limitations’ precise values are given in the datasheet of each DRAM chip and vary from one to the next. The 3 DRAM commands (WRITE/READ, ACTIVATE, and PRECHARGE), on the other hand, each require roughly 15ns. We recommend Kim et al. for further details on the organization and functioning of a DRAM bank (Kim et al., 2000).

4.5.3. Schedule of Memory Request When a large number of memory requests have been awaiting access to DRAM, the memory controller should determine which memory request to schedule subsequently. The memory controller does this by implementing a memory scheduling algorithm its purpose, in several modern highefficiency systems, is to pick the most advantageous memory request to reduce total memory request latency. Consider the case when a memory request is pending to access a row that has been currently loaded in the rowbuffer (Balkesen et al., 2013). Because the row has been in the row buffer in this situation, the memory controller may bypass the PRECHARGE and ACTIVATE directives and go straight to the WRITE /READ command. Consequently, the memory controller may respond swiftly to that specific memory request. A row-buffer hit is a memory request which accesses the row in the row buffer. Several memory scheduling techniques make use of row-buffer hits’ short latency and prioritize them over other requests. We suggest the reader to current publications that have looked into memory request scheduling for further detail (Kemper & Neumann, 2011).

4.5.4. Refresh Data is stored as a charge on a capacitor in a DRAM cell. That charge slowly drains over time, allowing the data to be lost. Because the charge on DRAM fluctuates over time, this has been called “dynamic” RAM. The charge in every DRAM cell should be maintained or refreshed regularly to maintain data integrity. DRAM cells have been revitalized at the granularity of a row through reading this out and writing this back in, which is similar to sending the row a PRECHARGE and an ACTIVATE in that order (Zhang & Swanson, 2015).

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4.6. FUTURE AND CURRENT RESEARCH PROBLEMS In practical, in all computer systems, the memory system remains a critical bottleneck (particularly in words of efficiency and power/energy usage). This has become an even bigger bottleneck in today’s and future computer systems: more and more different agents and processor cores have been sharing sections of the memory system; Applications which operate on cores are becoming more data and memory demanding; memory consumes a considerable amount of power and energy in current systems (Al-Motarreb et al., 2010); and scaling long-lasting memory technologies, like DRAM, to smaller technological nodes has been getting challenging. As a result, effectively managing memory throughout all stages of the transformational hierarchy, both in hardware and software, has become increasingly crucial. Approaches or sets of method combines the best concepts at various levels to handle the tough efficiency, the efficiency of energy, reliability, accuracy, and security concerns we face in memory system design and management currently looks promising (Groves et al., 2003).

4.6.1. Caches 4.6.1.1. Effective Use Several replacement policies were developed to enhance the basic LRU policy to accurately use a cache’s limited capacity. The LRU policy isn’t necessarily the best option for all memory access patterns with varying degrees of proximity. For instance, with the LRU policy, even though the data contains low locality, the most currently accessed data has been stored in the cache (e.g., it’s uncertain to be accessed again) (Eklov & Hagersten, 2010). To complicate things, the lower-locality data has been kept in the cache for an inordinate amount of time. It is due to the LRU policy always adding material into the cache as the most currently accessed and only ejects it after it has become the least currently accessed. Consequently, academics are employing a mix of three methodologies to construct complex replacement plans. Firstly, a cache block must not always be put as the most currently accessed when this has been allotted in the cache. Cache blocks having poor locality must instead be put as the least currently accessed as they have been swiftly ejected from the cache to create a way for the blocks of cache with higher locality (e.g., (McFarling, 1989). Secondly, whenever a cache block has been ejected from the cache, it must not necessarily be the block of cache that has been read the least recently. Preferably, “dead” cache blocks

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(those that would never be visited again) must be evicted whether or not they have been the least-currently accessed. Thirdly, when deciding which cache block to evict, the cost of fetching the cache block from the main memory must be factored in. If all other factors are equal, the cache block with the lowest likelihood of requiring a fetch from the main memory must be evicted (Aga et al., 2017) (Figure 4.19, Figure 4.20).

Figure 4.19. Management of cache. Source: https://www.webroam.com/cache-management.php.

Figure 4.20. Transferring a cache block. Source: https://slideplayer.com/slide/14569058/.

4.6.1.2. Quality-of-Service In a multi-core system, the CPU has been divided into several cores, and each may run a different application. Components of the memory hierarchy can be shared amongst some or all cores in such a system. The last-level cache

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in a processor, for instance, has been usually shared by all cores. Though the last cache has a big capacity, having several last-level caches independently for every core has been prohibitively costly. Furthermore, in this instance, this is critical to guarantee that the mutual final-level cache has been used fairly by all cores (Ranganathan et al., 2006). Instead, a program operating on the cores can fill the last-level cache containing exclusively their data, evicting data required by other programs. Researchers have developed techniques to provide quality service whenever a cache has been shared by many cores to avoid these events. One method is to divide the shared cache amongst cores whereby every core has its devoted part where just the data of that core has been kept (Kamble & Ghose, 1997). A core’s partition must preferably be only large enough to retain the data which the core has been currently accessing (the core’s working set) and no more. Moreover, if the size of a core’s working set varies over time, the partition core size must dynamically grow or decrease suitably (Laoutaris et al., 2006).

4.6.1.3. Low Power One of the major issues that computer architects confront has been maximizing the fuel efficiency of computing systems. Because caches need a high number of transistors, which all consume power, they have been a prominent target for improving energy efficiency. Researchers proposed, for instance, decreasing the operating voltage of the transistors of the cache to minimize power usage. Furthermore, this offers significant tradeoffs that should be managed when constructing a cache: whereas a lower voltage cache uses low power, this can also be slow and more error-prone. Researchers are looking for ways to allow low-voltage caches that are both reliable and affordable (LaMarca & Ladner, 1999).

4.6.2. Main Memory 4.6.2.1. Challenges in DRAM Scaling DRAM is the most ideal physical substrate for constructing main memory, due to its lower cost for one bit. Furthermore, as DRAM process technology expanded to combine DRAM cells into a similar space on a semiconductor chip, the cost-per-bit of DRAM has steadily reduced. Furthermore, because of rising manufacturing cost/complexity and decreased cell dependability, enhancing DRAM cell density through lowering cell size, as it has been done in the past, is becoming more challenging. Consequently, researchers

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have been looking at new ways to improve DRAM’s efficiency and energy efficiency while keeping costs low. Current recommendations, for instance, include lowering DRAM access latency, increasing DRAM parallelism, and reducing the frequency of DRAM revives (Garcia-Molina & Salem, 1992) (Figure 4.21).

Figure 4.21. DRAM scaling challenges. Source: https://semiwiki.com/semiconductor-services/297904-spie-2021-applied-materials-dram-scaling/.

4.6.2.2. Three-Dimensional Stacked Memory A memory bus connects a DRAM chip to the CPU chip. Electrical lines on a motherboard are used to implement the memory bus in today’s computers. However, there are three drawbacks to this approach: increased cost, higher power, and limited bandwidth. To begin with, transferring an electrical signal across a motherboard cable requires a huge amount of power due to its length and thickness. Secondly, because it requires high power to send several electrical signals in rapid sequence, the bandwidth that a motherboard cable can supply is limited (Stonebraker & Weisberg, 2013). Thirdly, every processor and DRAM chip has a stub (referred to as a pin) with which each end of a motherboard wire has been attached. Pins, however, are not cheap. As a result, a memory bus with a lot of motherboard wires (and just multiple pins on the chips) raises the price of the memory system. Rather than putting them beside each other upon the motherboard, researchers have anticipated stacking one more DRAM chip directly on top of a processor chip. The processor chip may interconnect directly having the DRAM chips in this three-dimensional (3D) stacked configuration, eradicating the need for motherboard pins and wires (DeWitt et al., 1984) (Figure 4.22).

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Figure 4.22. The architecture of a three-dimensional stacked DRAM. Source: https://www.researchgate.net/figure/Architecture-of-a-3D-stackedDRAM-based-on-39–92_fig2_333077335.

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CHAPTER

5

INTERCONNECTION NETWORKS

CONTENTS 5.1. Introduction .................................................................................... 170 5.2. Questions About Interconnection Networks .................................... 171 5.3. Uses of Interconnection Networks .................................................. 173 5.4. Network Basics ............................................................................... 183 References ............................................................................................. 192

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5.1. INTRODUCTION Digital systems are ubiquitous in contemporary culture. Digital computers can simulate real systems, manage vast databases, and prepare publications, among other duties. Digital communication networks transmit Online information, voice calls, and video transmission. Entertainment audio and video are progressively transmitted and handled digitally. Almost everything things, including autos and household appliances, is digitally managed (Feng, 1981). A digital system has three fundamental components: logic, memory, and transmission. By conducting mathematical operations or taking decisions, for instance, logic alters and mixes data. Memory retains information for eventual retrieval, shifting it over time. Data is transferred from one point to another through interaction. This text focuses on the communication aspect of digital systems. In particular, it investigates the connection systems utilized to transmit information between components of a digital system (Wu & Feng, 1980). Many digital systems’ efficiency nowadays is restricted by their connection or connectivity, not just by the reasoning or storage. In an elevated system, the majority of power is needed to drive cables, and the majority of clock cycles are focused on wire lag rather than gate lag (Akers & Krishnamurthy, 1989). As technology advances, memory, and computers become more compact, quick, and affordable. Nonetheless, the velocity of light stays unaffected. Pin complexity and wire density, which controls linkages among parts of the system, are growing more slowly than the parts themselves. In addition, the pace of interaction between parts lags significantly behind the clock speeds of contemporary CPUs. The combination of these variables makes interconnectivity the determining factor for the benefit of future communications circuits (Owens et al., 2007). As developers seek to make more effective usage of limited connectivity capacity, connection systems are developing as a practically ubiquitous resolution for system-level communication issues in contemporary digital systems. Interconnection networks are starting to substitute buses as the basic system connection. Initially designed to meet the demanding information needs of multicomputer, connection networking is starting to substitute buses as the normal system-level connections. As developers

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learn that routing packages are quicker and more cost-effective than routing cables, they are also substituting specialized cabling based on a systematic (Biberman & Bergman, 2012).

5.2. QUESTIONS ABOUT INTERCONNECTION NETWORKS Before proceeding, we shall address some fundamental problems concerning network interfaces. What is a system of interconnections? Where are they located? Why are they essential (Agarwal, 1991)?

5.2.1. What Is an Interconnection Network? Figure 5.1 demonstrates that an interconnection network is a configurable system that transmits information across endpoints. Six terminals, T1 through T6, are shown linked to a connection in the diagram. Whenever endpoint T3 desires to transfer data to endpoint T5, it transmits a message comprising of the information in the network, which then transmits the message to T5 (Blumrich et al., 2003). The system is configurable in the fact that it establishes important linkages at various times. The network shown in the image is capable of delivering a signal from T3 to T5 in one phase and using a similar capacity to convey a signal from T3 to T1 in the subsequent cycle. The system is a combination since it consists of several parts that work with each other to convey information: buffers, channels, switches, as well as controllers (Monien & Sudborough, 1990). Systems fulfilling this wide description exist in a variety of sizes. Within a computer node, on-chip networking might move information across memory arrays, registers, as well as arithmetic modules. Board- and systemlevel systems enable processors and memory or incoming and outgoing terminals. Local- as well as wide-area systems ultimately unite different systems inside a company or across the world. This book focuses on the lower sizes, from the hardware level to the network level. There is already a multitude of great literature covering the greater scale. Yet, difficulties at the network level and lower, when links are narrow and data speeds are very fast, are distinctly separate from those at massive distances and need distinct solutions (Navaridas et al., 2009).

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Figure 5.1. A useful representation of a connection network. Source: https://er.yuvayana.org/metrics-for-interconnection-networks-andperformance-factors/.

Note: Utilizing channels, endpoints (designated T1 thru T6) are linked to the system. The arrows at both ends of the channel show that it is bilateral, allowing data to flow either to and from the network interface (Ridruejo Perez & Miguel-Alonso, 2005).

5.2.2. Where Do You Find Interconnection Networks? They are utilized in the vast majority of digital systems which are big enough to link two parts. Computer systems & communication switches are by far the most typical uses of interconnection networks. They link CPUs to memory and input/output (I/O) units to I/O controllers in computer networks. The link input pins to output terminals in networking devices and communication gateways. Additionally, they link sensors and devices to control system CPUs. Wherever bits are transferred across two parts of the system, an interconnection network is probable to happen (GB III & Siegel, 1982).

5.2.3. Why Are Interconnection Networks Important? Since they are a problem, especially for several systems. Memory latency and memory bandwidth, two crucial performance characteristics in a computing device, are mostly determined by the network between CPU and memory. In a communication switching, the capacity (data transfer rate as well as the amount of ports) is primarily influenced by the efficiency of the interconnection network (also referred to as the fabric in this regard). Since

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this request for connections has increased faster than the capacity of the underlying cables, interconnection is becoming a bottleneck for the majority of networks (Puente et al., 2002). Interconnection networks are an interesting alternative to specialized wire since they enable multiple low-duty-factor signals to utilize limited wiring facilities. Assume, in Figure 5.1, that every port must exchange one letter with other terminals per 100 phases (Kruskal & Snir, 1986). We might offer a worldwide dedicated section amongst each circuit element, which would need a maximum of 30 single connections. Every channel, though, would’ve been inactive 99% of the time. If the six endpoints are then connected in a ring, just six lines are required. (T1 is linked to T2, T2 to T3, and so on, with T6 linking back to T1). The ring network decreases the number of channels by a factor of 5 as well as increases the channel duty rate from 1% to 12.5% (Chen et al., 2011).

5.3. USES OF INTERCONNECTION NETWORKS It’s helpful to look at how connectivity systems are employed in digital systems to comprehend the constraints imposed on their design. Therefore, in part, we’ll look at three main types of interconnection networks as well as how they influence network needs. We’ll look at in which way every application chooses the upcoming network settings for every implementation (Dandamudi & Eager, 1990): • • • • • • • •

The count of connections Every terminal’s maximum bandwidth Every terminal’s mean bandwidth The necessary delay The dimension of the text or a range of message lengths The projected traffic pattern(s) The necessary level of service excellence The interconnectivity network’s needed dependability and accessibility The count of endpoints, or connections, in a network, correlates to the set of parts that must be linked to the system, as we’ve previously seen. The designer must also understand how the endpoints will interface with the system with the number of terminals (Feng, 1981).

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Every endpoint will need a specific quantity of bandwidth, which is commonly measured in bits per second (bit/s). Except as otherwise specified, we consider that the endpoint bandwidths are equal, meaning that the incoming and outgoing bandwidths are identical. The largest data speed that a port will seek from the system in a brief period is the maximum bandwidth, while the typical bandwidth is the typical data speed that a port will demand. Understanding either the maximum and mean bandwidths get critical when attempting to reduce the interconnection network’s operational costs, as shown in the next section on the design of processor-memory interconnects (Gratz et al., 2007). Additional to the rate where the messages should be received and sent by the system, the network’s message latency (the longer it takes to send a single message) also is stated. Whereas an ideal network would have either high bandwidth plus low latency, there is frequently a compromise across the two. A system that offers high bandwidth, for instance, generally keeps network capacity active, resulting in resource contention (Hosein & Jung, 2019). Whenever two or even more communications try to access a similar network common resource, there is contention. Each and one of such messages would have to delay for that service is becoming available, lengthening the message’s latency. Alternatively, if resource consumption was reduced by lowering bandwidth requirements, latency will be reduced as well (Nayebi et al., 2007). Another key design concern is message length or the size of a statement in bytes. When messages are tiny, network operating costs may have a greater influence on the effectiveness than when overheads are absorbed well throughout a bigger message. There are a variety of message sizes available in different systems (Soteriou et al., 2006). The traffic sequence of a network is defined by how signals from every endpoint are spread over all potential destination endpoints. Every endpoint, for instance, may transmit messages to other endpoints with uniform chances. That’s the sequence of unpredictability in traffic. If, on the other hand, endpoints prefer to transmit messages primarily to other endpoints nearby, the underlying network may make use of this spatial locality to save money. Nonetheless, in the other networks, the requirements must remain true for a wide range of traffic patterns (Kiamilev et al., 1991).

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Quality of service (QoS) will be required by certain networks. In general, QoS refers to the equitable distribution of resources underneath a service policy. Whenever numerous messages compete for a similar network resource, for instance, the conflict might be addressed in a range of methods. Messages might be sent in a first-come, first-served order depending on how hard people have been waiting for the service. Another method prioritizes the message which has spent the most time in the system. The decision across these and various allocation strategies are determined by the network’s necessary services (Krishnamoorthy et al., 1992). Lastly, the dependability and accessibility that an interconnection network must provide have an impact on design considerations. The frequency with which the network accomplishes the duty of transmitting mail is referred to as reliability. In most cases, communications must be sent on schedule and without error 100% of the time. Installing special hardware to identify and rectify mistakes, a higher-level programming interface, or a combination of such technologies may be used to achieve a 100% reliable connection (Marescaux et al., 2002). It’s also conceivable that the system might lose a tiny percentage of data, as we’ll see in the part on data communication fibers below. The accessibility of a network refers to the percentage of time it is up and running. In most cases, a 99.999% accessibility is stated in an Internet router, implying fewer than 5 minutes of total downtime annually. The difficulty in achieving this degree of reliability is that the parts that are used to build the system often malfunction many times each minute. As a consequence, the network should be built to identify and rebound fast from such faults whereas the remaining operational (Jiang et al., 2009).

5.3.1. Processor-Memory Interconnect Figure 5.2 depicts two techniques for connecting processors to memory through a network interface. Figure 5.2(a) depicts a dance-hall design whereby an interconnection network connects P CPUs to M memory banks. The integrated-node arrangement depicted in Figure 5.2 is used by the majority of current computers (b) (Fan & Bruck, 2000).

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Figure 5.2. An interconnectivity link is used to link the CPU and memory. Source: https://dl.acm.org/doi/pdf/10.5555/2821589.

Note: (a) (b)

Dance-hall architecture with the processor (P) and memory (M) connections that are separated. An integrated-node design with a single memory bank as well as a shared CPU as well as memory interfaces (Hoefler et al., 2007).

Table 5.1. Parameters of Processor-Memory Interconnection Networks Parameter

Value

Processor ports

1–2,048

Memory ports Peak bandwidth Average bandwidth Message latency Message size Traffic patterns Quality of service Reliability Availability

0–4,096 8 Gbytes/s 400 Mbytes/s 100 ns 64 or 576 bits arbitrary none no message loss 0.999 to 0.99999

In an interconnected node, CPUs, and memory are merged. Every CPU may reach its memory unit through a connection switch C instead of using the network in this configuration (Abd-El-Barr & Al-Somani, 2011).

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The networking requirements imposed by each setup are described in Table 5.1. The frequency of processor terminals may range from thousands to hundreds of thousands, as in a Cray T3E with 2,176 processor terminals, to as low as one for a single CPU. In modern global systems, 64 to 128 processor combinations are typical, and so this list is growing. All such processor links are also memory links in the mixed node design. On the other hand, with a dance-hall arrangement, the frequency of memory terminals is often substantially more than the quantity of CPU lines. One high-end vector processor, for instance, has 32 processor interfaces and may require 4,096 memory banks. This big ratio optimizes memory bandwidth while reducing the likelihood of bank conflicts, which occur when two processors need an approach to a similar memory bank at a similar time (Siegel, 1979). A contemporary microprocessor can perform roughly 109 instructions per second, which together may take two 64-bit phrases from memory (one for the command itself and one for information). If one of such references is not found in the caches, a block of eight words is typically retrieved from memory. If we were required to retrieve two words from memory per cycle, we’d require 16Gbytes/s of bandwidth. However, only around a 1/3 of all commands relate to data stored in memory, as well as caches help to limit the bunch of times a memory bank must be referenced (Biberman & Bergman, 2012; Yu et al., 2016). The mean bandwidth is more than just a magnitude fewer with normal cache-miss ratios—around 400 Mbytes/s. Nevertheless, most computers should still be capable to retrieve one letter per command from the main memory at a maximum rate of one letter per instruction to prevent enhancement in memory latency due to serialization. A rapid rush of memory queries might soon block the processor’s network interface if we reduced this peak bandwidth too much. Serialization raises message delay by pushing a high-bandwidth wave of queries down a lowerbandwidth network interface, akin to a clogged sink gradually emptying. A maximum bandwidth of 8Gbytes/s is required to prevent serialization in spikes of queries (Reed & Grunwald, 1987). Memory latency, and thus the delay of the network interface as to which storage queries and answers are delivered, has a significant impact on system throughput. Since this is the fundamental latency of a common main memory with no network, we mention a delay need of 100ns in Table 5.1. We have increased the effective cognitive delay if our network introduces another 100ns of latency (Akers & Krishnamurthy, 1989).

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Whenever load/store commands skip the processor’s cache (and aren’t targeted to a memory location in an integrated-node system), they’re transformed into read-request as well as write-request packages and sent across the network to the relevant memory. Every read-request header carries the main memory to be read, as well as a word or cache column to be cached. After receiving a request packet, the relevant memory bank conducts the required operation as well as provides a read-reply or writereply packet (Abad et al., 2007). In this network, you’ll see that we’ve started to discriminate among messages and packages. A message is a component of transmission from the channel’s users to the net (e.g., CPUs and memory). A message may generate one or more packages at the network connection. Huge messages may be divided into multiple smaller packages, or uneven duration messages could be divided into fixed-length packaging, allowing the base system to be simplified. We presume a one-to-one relationship across messages and packages since the messages generated in this CPU interface are quite modest (Owens et al., 2007).

Figure 5.3. The two message forms needed for the processor-memory link are shown. Source: https://www.amazon.com/Principles-Practices-Interconnection-Networks-Architecture/dp/0122007514.

The read-request and write-reply packages contain no information, but they do save a location. The network’s address, together with a certain header as well as package data, fits easily inside 64 bits. Read-reply and write-request packages share 64 bits of the header as well as address data, as well as the data of a 512-bit cache line, for a total of 576 bits. Figure 5.3 depicts the two different packet forms (Kachris et al., 2013). We do not need any particular QoS, as is usual with the processormemory connection. Since the system is fundamentally self-throttling, this is the case. Memory demands might take more time to be serviced if the

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network gets overloaded. Because the computers can only handle a certain amount of queries at a time, they would begin to idle while having to wait for responses (Uwase et al., 2010). The network congestion is decreased since the computers are not producing new demands when they are idle. Self-throttling is the term for this self-soothing action. Most QoS assurances only affect the network whenever it’s crowded, while self-throttling tries to minimize overcrowding, trying to make QoS in processor-memory couplers less beneficial (Gupta & Dally, 2006).

5.3.2. I/O Interconnect Interconnection systems can also be utilized in computer networks to link I/O equipment to CPUs and/or memory, like hard disks, screens, and networking devices. Figure 5.4 depicts the basic I/O network utilized to connect a group of host ports to an arrangement of storage devices (at the bottom of the figure). The networking works in the same way as the processor-memory connection, but also with distinct granularities and time. Such variations, notably a higher tolerance for delay, influence network design in fundamentally different ways (Siegel & Smith, 1978).

Figure 5.4. A typical I/O network links a few host adapters to a greater number of I/O equipment, such as a disk drive. Source: https://www.elsevier.com/books/principles-and-practices-of-interconnection-networks/dally/978–0-12–200751–4.

Table 5.2 lists the specifications of a high-performance I/O connectivity network. That system can support up to 64 host adapters, with multiple devices, like hard disks, connected to every host adapter. There are up to 64

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I/O connections per host adapter in this instance, for a total of 4,096 gadgets. In more common setups, just several host adapters link to a dozen or more gadgets (Navaridas et al., 2010). The peak-to-average bandwidth ratio of the disk connectors is quite high. A disk can recover files at up to 200Mbytes/s while it is transmitting successive sectors. The peak bandwidth in the list is determined by this value. In most cases, the disk should shift its head across sectors in an aggregate of 5 milliseconds (or more), based on a total bit rate of one 4-Kbyte sector per 5 milliseconds, or less than 1 megabyte per second. The host lines have a poorer peak-to-average bandwidth ratio because they manage the average traffic across 64 disk devices (Lebeck & Sohi, 1994). Because of the large variation across peak and average bandwidth at device terminals, a network structure with focus is required. While designing a network to serve the maximum bandwidth over all channels at the same time is undoubtedly adequate, the resultant system would be highly costly (Portz, 1991). Instead, we may build the network to accommodate merely the median bandwidth, however, this increases serialization delay, as explained in the procedure or memory interconnection instance. This serialization delay would just be relatively considerable due to the high peak-to-average bandwidth ratio. The failure repair for a bad I/O operation is far more elegant than for a failed memory reference, hence concentrating the demands of different systems onto one modest actual loss is acceptable (Bhuyan, 1983). Table 5.2. Parameters of I/O Interconnection Networks Parameter

Value

Device ports

1–4,096

Host ports

1–64

Peak bandwidth

200 Mbytes/s

Average bandwidth

1 Mbytes/s (devices) 64 Mbytes/s (hosts)

Message latency

10 μs

Message size

32 bytes or 4 Kbytes

Traffic patterns

arbitrary

Reliability

no message loss

Availability

0.999 to 0.99999

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“Aggregate” port is a kind of port. The aggregate terminal’s average bandwidth is dependent on the number of devices using it. Since equipment seldom seeks peak bandwidth from the net, it’s doubtful that more than a few of the different systems are requesting maximum bandwidth from the aggregated terminal. We were able to lower the ratio between the maximum and mean bandwidth consumption by focusing, resulting in a less costly system with minimal serialization delay (Chen et al., 1981). The signal packet size is bimodal, much like the CPU connection, but with a wider dispersion between the two methods. To demand read operations, confirm write operations, as well as execute disk management, the network sends brief (32-byte) messages. Reading responses and sending request messages, on the other extreme, need very lengthy (8-Kbyte) communications (Chen & Peh, 2003). The system is not extremely latency-sensitive due to the huge inherent latency of disk operations (milliseconds) and the massive quantity of data transported as a unit (4Kbyte). The efficiency would be minimal if the delay was increased to 10s. It’s considerably easier to design an efficient I/O network with these flexible latency criteria than it is to construct a formerly identical processor-memory connection with a high latency requirement (Pinkston & Warnakulasuriya, 1997).

Figure 5.5. Interconnection networks are used as a switching fabric by certain network routers, moving messages across line devices that receive and send packets through cable networks. Source: http://cva.stanford.edu/books/ppin/.

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5.3.3. Packet Switching Fabric Interconnection networks have taken over as the shifting fiber for information network routers and switches, displacing buses as well as slats. In this use, an interconnection network serves as a gateway for a wider network (local-area or wide-area). Such implementation is shown in Figure 5.5. The big network pathways (often optic fibers having 2.5 Gbits/s or 10 Gbits/s bandwidth) are terminated by an arrangement of line adapters (Melsa et al., 1990; Ho et al., 1998). Every package or cell is processed by the line cards to establish its route, check conformity with the service contract, update different areas of the message, and modify statistics monitors. Every package is then sent to the fabric via the interface card. Every package is then sent by the fabric out of its origin device connected to its target line card. The package is stored and prepared for delivery on the export cable network at the target (Lemieux & Lewis, 2004). The parameters of a common network interface using it as a shifting fabric are shown in Table 5.3. The main distinctions between switch fabric needs and processor memory as well as I/O infrastructure components are the switch fabric’s relatively high throughput and the necessity for service quality (Gaughan & Yalamanchili, 1993). A switching fabric’s huge data packet, combined with its latency insensitivity, network control design since latency and message overhead does not need to be substantially tuned. The actual package sizes are determined by the router’s protocols (Aggarwal & Huang, 1988). Table 5.3. Parameters of a Packet Switching Fabric Parameter

Value

Ports

4–512

Peak Bandwidth Average Bandwidth Message Latency Packet Payload Size Traffic Patterns Reliability

10 Gbits/s 7 Gbits/s 10 μs 40–64 Kbytes arbitrary < 10−15 loss rate

Quality of Service Availability

needed 0.999 to 0.99999

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Packet sizes for Internet protocol (IP) vary between 40 bytes to 64Kbytes, with many of these packages being 40, 100, or 1,500 bytes long. Packets, as in our previous two instances, are separated into brief control packets as well as massive data transmissions (Smith & Siegel, 1979). A switched network fabric, unlike a processor-memory or I/O connection, does not self-throttle. Irrespective of fabric congestion, every line card remains to send a continuous stream of bits, and the network should offer fixed bandwidth to specific courses of packaging (Kumar & Wang, 1991). The fabric should be non-interfering to achieve that reliable service. That is, and although messages meant a or communications headed for b share resources across the fabric, an overflow of traffic destined for linecard a, maybe owing to a brief overflow, must not interact with or “steal” frequency band from traffic destined for a separate line card b. A need for non-interference puts specific requirements on the network switch fabric’s technology involved (Navaridas et al., 2011).

5.4. NETWORK BASICS To achieve the performance requirements of a specific input, like those outlined previously, the designer must execute the geometry, forwarding, as well as packet filtering of the network while adhering to technological limits. As stated in the preceding sections, the sharing of communication facilities is crucial to the effectiveness of network interfaces (Usman, 2020). Rather than building a new channel among every terminal pairing, the interconnection system is made of common router nodes linked by shared channels. The topology is defined by the connectivity sequence of such nodes. Messages are then sent across displays through many hops via shared channels as well as networks, from the source side to the target interface. A good topology maximizes network capacity by using the attributes of the channel’s active packaging, like the number of nodes on a processor’s container or the number of wires that may be linked to various cabinets (Breeding, 2009).

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Once one topology has been selected, there are several different pathways (patterns of nodes as well as links) that even a communication might follow to arrive across the network. The routing process decides which of the above various pathways a message goes. A good selection of pathways reduces their length, which is often measured in terms of nodes and channels traversed, whilst minimizing the load on the network’s common resources. The duration of a route affects the latency of a signal traveling over a system, and the request or load on a service indicates how frequently that service has been accessed. If one source is overly being used while another is idle, termed as a load imbalance, the network’s overall capacity for delivering messages is lowered (Marin, 2005). Over the period, flow control determines that communications have accessibility to certain network resources. That impact of flow gets increasingly crucial as memory usage rises, and excellent flow transmits packages with little lag as well as prevents resources from idling during heavy loads (Gemmill, 2005).

5.4.1. Topology Interconnection networks are made up of a collection of the common gateway, connections, and streams, and the channel’s topology relates to how such nodes and networks are organized. An interconnection network’s topology is similar to a strategic plan. Data packets (like automobiles) are transported through one routing node (crossings) to the other with routes (like highways) (Williams & Rast, 2020). The network seen in Figure 5.6, for instance, is made up of 16 terminals, which are linked to eight routes, one to every neighbor and the other from every neighbor. The topology of such a system is a torus. The terminals are represented by circles, as well as each set of routes, one for each side, is represented by a line connecting two terminals in the diagram. One such topology is likewise a straight network, with a port attached to every one of the topology’s 16 components (Macfarlane, 2007). A good topology makes use of the properties of the current packaging industry to suit the user’s bandwidth as well as latency needs at a low cost (Tennant, 1992).

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Figure 5.6. The configurations of nodes, marked by rings labeled 00 to 33, and the routes linking the endpoints make up a network topology. Source: https://www.bookdepository.com/Principles-Practices-Interconnection-Networks-William-James-Dally/9780122007514.

Note: Every line in the diagram represents a couple of lines, one in every direction. Every node in this 44, 2-D torus, or 4-are 2-cube, topology is linked to eight networks: one to and one from every one of its four neighbors (Diez et al., 2014). To optimize bandwidth, a topology must fill the binary search bandwidth or the bandwidth given by the basic packing technique over the system’s middle. Figure 5.7, for instance, depicts how the system from Figure 5.6 may be packed. On upright circuit boards, four categories are arranged. Four circuits are joined to use a backplane electronic circuit, similar to how PCI cards are hooked into a computer’s motherboard. The bisection bandwidth for such a device refers to the total bandwidth that may be transmitted via this backplane. The overall bisection bandwidth is 256Gbits/s if the backplane is broad enough to accommodate 256 channels, all running at a bit rate of 1Gbit/s (Al-Taie & Kadry, 2017). Returning to Diagram 5.6, the middle of our topology is crossed by precisely 16 unilateral channels—recall that the arcs in the figure indicate

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two routers, in all directions. Every channel traversing the bisection must be 256/16 = 16 data broad to overload the 256 signal bisection. To overload a bisection of 256 data, every route traversing the bisection must be 16 signals broad, or 256/16 (Khan et al., 2015). In addition, we should consider the fact that every node would be packed on a single IC chip. For this instance, every chip has just 128 signal-carrying pins. Because our architecture needs an overall of 08 channels per unit, the pin restriction of every chip restricts the router width to 128/8 = 16 signals. The amount of signals necessary to overload the bisection bandwidth corresponds perfectly to the channel width imposed by pin constraints (Zupan, 2003). Observe, in comparison, the 16-node circular network seen in Figure 5.8. Every node is linked to four channels, hence pin limitations restrict the bandwidth to 128/4 = 32 signals. Four streams traverse the bisection; hence we would want to construct such channels to be 256/4 = 64 signals wide to overload the bisection, however, the pins restrict the bandwidth to just half of this value. Consequently, the ring topology offers only 1/2 the bandwidth of the toroidal topology under equal technological restrictions. Bandwidthwise, the torus is better, since it provides the entire 32Gbits/s of bandwidth per node throughout the system’s middle (Lyon, 2008).

Figure 5.7. Packaging of a 16-node torus topology. Source: https://www.oreilly.com/library/view/principles-and-practices/9780122007514/chapter-02.html.

Note: On the separate printed circuit, sets of four terminals are packed, with four of them coupled to a common backplane card. The third column’s backplane ports are visible all along the backplane’s right-hand side. The binary search bandwidth of such packages is determined by the amount of signals over the breadth of the backplane (256) (Armstrong et al., 2013).

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Figure 5.8. A 16-node network device has shorter latency than that of the 16node, 2-D torus of Figure 5.6 for the limitations of our scenario. This delay comes at the cost of reduced capacity. Source:https://catalog.library.vanderbilt.edu/discovery/fulldisplay/ alma991043603552703276/01VAN_INST:vanui.

Therefore, high bandwidth isn’t the essential criterion for a topology’s success. Assume we have such a new app that demands just 16Gbits/s of bandwidth as well as the lowest feasible latency under similar technological limitations. Furthermore, imagine this program sends 4,096-bit packets. To reduce the total latency, the topology should strike a compromise between both the goal for a low average range across nodes and the need for reduced serialization delay (Casey, 2011). The hop count, or range across nodes, is defined as the mean size of the network and endpoints a message should travel to reach its target. Raising the number of nodes is required to reduce this gap (the number of channels coming and going out of every terminal). Since every node has a set pin constraint, raising the quantity of channels results in smaller channel sizes. Serialization delay is caused by squeezing a big packet through a limited channel. We return the two 16-node designs, however, this time we concentrate on signal latency to explore how this tradeoff influences topology choice (Ward et al., 2008). To calculate delay owing to hop count, a traffic sequence must first be considered. For convenience, we utilize arbitrary traffic, wherein every node delivers the same amount of data to one another. With arbitrary traffic, the mean hop count is simply the average length across endpoints. The average difference for our torus topology is 2, whereas the average difference for the circle is 4. The delay per hop in a typical network can be 20ns, leading to an overall hop latency of 40ns for the torus as well as 80ns for the circle (Cullen et al., 2014). The ring, on the other hand, has a substantially reduced serialization delay because of its large channel. A 4,096-bit packet needs 4,096/32 = 128 network cycles to convey over a 32-signal network. Because our 1GHz

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signaling rate equates to a 1ns interval, the ring’s serialization delay is 128ns. If our network is structured effectively, we have only to spend that serialization period once, resulting in an average lag of 80 + 128 = 208ns per package across the circle. The torus has a serialization latency of 256ns and an overall lag of 296ns, according to identical estimates. Despite having a higher average number of hops, the circle has better connectivity for such lengthy packets due to physical packaging restrictions (Camarán & De Miguel, 2008).

5.4.2. Routing A network’s routing technique specifies the route a packet takes from a supply data point to a target data point. A path or route is an ordered collection of networks in which the output unit of channel ci matches the input node of network ci+1, the supply is the source to channel c1, and the target is the outputs of channel ck (Omondi & Rajapakse, 2006). In certain systems, there is just one pathway from every resource to every destination, however, in others, including the torus network seen in Figure 5.6, there are several alternative routes. A smart network design distributes load equitably among routes irrespective of the provided traffic sequence when there are several pathways. Continuing with our example of a road map, while the topology provides the map, roads, and junctions, the routing technique guides the automobile, determining which direction to go at each intersection. To avoid having one route become clogged while neighboring roads are vacant, it is necessary to divide the traffic among several roadways (Sayama, 2015).

5.4.3. Flow Control Flow control regulates the distribution of network capacity to packages as they traverse a network. Principal elements in the majority of network interfaces are routes and buffering. The function of channels in carrying packets across nodes has previously been covered (Daryanani, 1976). Buffers are node-implemented storage, like registers or memory, which let packages be briefly retained at the networks. Continuing with our example, the topology sets the route map, the routing technique directs the automobile, and the control valve regulates the traffic lights, defining whether a car may go across the next section of the road (channels) or must pull off into a parking lot (buffer) to let other traffic drive (Adedeji & Hamam, 2020) (Figure 5.9).

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Figure 5.9. Two routes from 01 to 22 on the 2-D torus are seen in Figure 5.6. Source:https://catalog.library.vanderbilt.edu/discovery/fulldisplay/ alma991043603552703276/01VAN_INST:vanui.

Note: (a)

Dimension-order routing transfers the packet first along the x dimension and then along the y dimension. (b) A non-minimal route necessitates a longer path than the minimum path length (Goldberg, 2017). To reach the full potential of the topology as well as routing approach, the flow-control approach must prevent potential conflicts that might cause an idle link. It does not, for instance, block a package that can utilize an idle channel because it is waiting for a buffer held by a packet that is stopped on a busy channel. This circumstance is equivalent to an automobile awaiting for a gap in traffic to make a left turn obstructing the path of a car that wishes to continue ahead. In flow control and also on the road, the answer is to establish a (left turn) lane to decouple the resource requirements, enabling the stalled packet or vehicle to go without waiting (Habiba & Hossain, 2018). A smart flow control method is equitable and prevents bottlenecks. Similar to a motorist attempting to make a left turn from a busy street without a signal, an unfair flow management method might lead a packet to wait forever. Deadlock happens when a cycle of packets are waiting for one another to release resources, and are thus stalled forever – a condition analogous to gridlock in our example of a road network (Sen et al., 2017).

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Figure 5.10 depicts a kind of time-space diagram that is often used to demonstrate flow control methods. Time-space diagrams for (a) store-andforward flow control and (b) cut-through flow control are shown in the figure. In both pictures, the horizontal axis represents time and the vertical axis represents space. Time is measured by cycles. By specifying the channels utilized to transmit the packet, space is shown. Each packet has five flits of fixed size. A flow control digit, or flit, is the smallest unit of information that the flow control technique recognizes (Umlauft & Reichl, 2009). Choosing a modest, fixed-size simplifies the design of routers without incurring a significant penalty for packets whose length is not a multiple of the flit size. Each flit of a single packet, shown by labeled boxes, is transmitted over four network channels. During the cycle when a specific flit is using the bandwidth of a channel, a box is shown in the figure. As shown in Figure 5.10, the choice of flow control strategies may have a substantial impact on the network latency of a packet (Díaz-Cacho Medina et al., 2011).

Figure 5.10. A time-space diagram illustrating two ways of flow control. The vertical axis represents space (channels), whereas the horizontal axis represents time (cycles). Source: https://dl.acm.org/doi/pdf/10.5555/2821589.

Note: (a) With store-and-forward flow control, a packet comprising five flits is entirely broadcast over one channel before transmission on the next channel begins. (b) With cut-through flow control, packet transmission across the channels is pipelined, with each flit immediately forwarded over the next channel upon arrival (Papo et al., 2014).

5.4.4. Router Architecture Figure 5.11 depicts a simplified depiction of one of the 16 nodes in the network seen in Figure 5.6 Each of the four input channels is paired with a buffer, and these buffers store incoming flits until they are granted the appropriate resources for departure. Once a flit is guaranteed buffer space

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at the subsequent router along its path, the downstream router may compete for access to the crossbar switch (Kizza J. & Kizza F., 2008). The crossbar switch may be designed to link any router input buffer to any output channel, with the restriction that each input can only be connected to one output and each output can only be connected to one input. Allocators are responsible for resolving all potential requests to the router’s crossbar and other shared resources. A flit in one of the input buffers must be assigned space in a buffer on the next node of its route, bandwidth on the next channel of the route, and win the allocation to traverse the crossbar switch to move to the next router (Nothias, 2020) (Figure 5.12).

Figure 5.11. A simplification of a router’s block diagram. Source: https://www.elsevier.com/books/principles-and-practices-of-interconnection-networks/dally/978–0-12–200751–4.

Figure 5.12. Architecture of a router.

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MOBILE COMMUNICATION NETWORKS

CONTENTS 6.1. Introduction .................................................................................... 200 6.2. Historical Background .................................................................... 201 6.3. Foundation ..................................................................................... 204 6.4. MCN Architecture........................................................................... 204 6.5. MCN Platforms ............................................................................... 207 6.6. Information Diffusion In MCN ........................................................ 208 6.7. Key Applications ............................................................................. 210 6.8. Future Directions ............................................................................ 212 References ............................................................................................. 214

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6.1. INTRODUCTION Mobile communication networks (MCN) are a type of telecommunication system that have a set of endpoints, organizations, and components that are linked together through connections to allow communication across endpoint customers. The entities show persons who are talking with one another through texts or telephony signaling while using transportable mobile phones. Numerous techniques, including the Global System for Enhanced Data Rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Mobile Communications (GSM), High-Speed Downlink Packet Access (HSDPA), and Long-Term Evolution (LTE), support, and provide MCN (LTE) (Bisong & Jianhua, 2010). Several scientific research shows that humans are sociable creatures by nature. That is, people engage with one another to build relationships that enable them to live out their lives as well as share knowledge and ideas. The appropriate person to interact with and communicate with is represented by communications systems. People have utilized many techniques and practices to interact with one another throughout history, including mail, fax, telegram, telefax, signal repeaters, telephones, smartphones, and e-mail communications (Hu et al., 2010). Because of its ability to be used everywhere and at any moment, mobile communications systems have become the most popular means for individuals to interact with one another. It began with two-way radio systems and progressed to 4G technologies, which carry high-quality video and phone communications through mobile networks. At first, massive, and heavy equipment was employed, but they eventually evolved into gadgets that were extremely light and compact. These characteristics have an impact on people’s conduct and communication. People sometimes used to see one another, mail one another, and contact one another on the telephone, but today they could deliver a text, send a picture, or have a video call (Costa et al., 2007). because of the widespread adoption of mobile technology, designers have begun to release a plethora of mobile apps that make connectivity even simpler and assist people in managing their clinical, economic, academic, and social lives by providing a quick approach to information irrespective of where they’re from but where the data is displayed. People may use mobile apps to wait for the outcome of their clinical checks, have their health history in their hands in times of emergency, experience new cultures, research their

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programs, spread information, have important meetings among partners and stakeholders, and more (England & Finney, 2011) (Figure 6.1).

Figure 6.1. Structure of the mobile cell communication system. Source: https://www.researchgate.net/figure/Diagram-of-the-Mobile-CellularCommunication-Network-Under-Study_fig1_288057997.

6.2. HISTORICAL BACKGROUND More than a century earlier, the discovery of “mobile radio” marked the beginning of a period in the path of information. Since the start, cell phones have accelerated the transmission of data from the velocity of humans to the light speed. In the last two decades, the mobile phone is now the most popular way of communicating (Frenkiel, 2002). In 1857, the Scottish mathematician James Clerk Maxwell formulated two equations whose solutions anticipated the propagation of electromagnetic waves at light speed (Frenkiel 2000). In 1899, Guglielmo Marconi utilized radiotelegraph broadcasts for mobile radio contact from a boat in New York Harbor to the Twin Lights in Highlands, New Jersey (Greenstein 1999). In three years, Marconi was capable of transmitting radio signals over the Atlantic Ocean. In 1905, analog audio communication was utilized by the army (Greenstein, 1999).

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6.2.1. Two-Way Radio Systems The earliest vehicles to employ two-way radio equipment were cabs, police vehicles, and other shuttle buses in which cab drivers, as well as policemen, interacted with one other or a centralized base. In 1928, the Detroit police department implemented the very first communications system (land mobile). In 1929, radiotelephony for customers was introduced aboard transatlantic ships (Nubarrón, 2011) (Figure 6.2).

Figure 6.2. Demonstrates two-way radio systems. Source: https://www.radiodepot.com/blogs/resources/radio-101-the-completetwo-way-radio-guide.

6.2.2. Two-Way Cell Phones Cell phone telecommunications consists of specialized radios which connect to a phone system through a live operator. The system was linked to the phone system and distinguished itself from radio broadcast technology by being linked to the phone system. 1947 marked the beginning of current phone technology, whenever Douglas H. Ring and W. Rae Young of Bell Labs invented hexagonal cells for cell devices. Early “mobile” telephones were cumbersome, costly, and provided poor mobility operations (LópezPintado, 2008).

6.2.3. Cell Areas In 1967, the concept of cellphone towers as well as cell regions that receive and send signals developed. Such cell regions were not able to transfer

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mobile phone calls from one access point to the other, preventing customers from continuing their conversations while moving from one cell to the other (Mahdi et al., 2009).

6.2.4. 1G Networks Amos Edward Joel created the first-generation (1G) of mobile operators in the 1970s. He created the call offloading system through which sensor readings were transferred across towers, eliminating lost calls as customers traveled from one telecommunications room to the other. 1G systems were lighter and far less costly than their predecessors (Valente, 2005). AT&T presented a request for mobile phone service to the FCC in 1971. Subsequently, major 1G system standards like Nordic Mobile Telephone (NMT), Total Access Communication Systems (TACS), and Advanced Mobile Phone System (AMPS), were implemented (NMT). The analog AMPS service was offered from 1982 until 1990 when it was superseded by the digital service (Zhu et al., 2011).

6.2.5. 2G Networks: GSM Networks In the early nineties, second-generation (2G) cellphones using the Global System for Mobile Communications (GSM) were released. Voicemail systems rely on digital encoding to increase communication efficiency and effective delivery. Using 2G technology, extra services like pagers, faxes, text messages, and phones were provided. Nonetheless, the 2G network provided limited data capabilities, including WAP, HSCSD, and MLS (Leon-Garcia & Widjaja, 2000).

6.2.6. 2.5G Networks: GPRS Networks In the 1990s, 2.5G connections were available. It employs the GPRS specification, which provides packet-switched digital abilities to current GSM networks (Hill, 2011) and enables users to transmit graphical data as packages. The EDGE network is a kind of 2.5G mobile technology (Onnela et al., 2007).

6.2.7. 3G Networks The third-generation (3G) mobile phone system was released in 2007 so that users may access audio, visual, and video apps. It is easy to access

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videos and conduct video phone calls using 3G technology. 3G technology facilitates combined packet- and circuit-switched information exchange provides worldwide roaming, and provides internet access from any point in the globe. The Universal Mobile Telecommunications System (UMTS) is another name for 3G technology (Marsch et al., 2012).

6.2.8. 4G Networks The Fourth Generation (4G) of mobile telephony was launched lately to give high rates of transfer and Quality of Service (QoS) capabilities. That capability lets the usage of telephone apps that involve the high-performance transmission of multimedia material also and enhances video conferencing performance. 4G mobile brings communications technology to standard cell devices and gives a higher QoS and a bigger bandwidth for accessing the Internet as well as watching various tv networks. Table 6.1 (Li et al., 2009).

6.3. FOUNDATION MCNs are a special sort of vast system. Networks, like social networking sites, transport systems, cell neural nets, and communications systems, represent complexities in the actual world as channels (Bisong & Jianhua, 2010). Every complicated system has distinct topological characteristics that define its connectedness and have a significant effect on the development of network operations (Costa et al. 2007).

6.4. MCN ARCHITECTURE MCN is a broadcasting network that covers geographical regions and has at minimum one cell network or ground station for every. Every ground station offers radio transmission availability over a specific geographical area, allowing a huge proportion of wearable electronics to connect with others while traveling from one ground station to the next. MCN is independent of any physical link across audio & video, and it also can switch from one unit to the other (Lambiotte et al., 2008) (Figure 6.3).

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Figure 6.3. The MCN architecture’s key entities. Source: https://www.researchgate.net/figure/Key-entities-of-the-MCN-Architecture_fig4_303480811.

The coming up are the primary elements of MCN’s infrastructure (Bellofiore et al., 2002).

6.4.1. Mobile Station It comprises cell phones and the Subscriber Identity Module (SIM), which offers mobility, and is utilized by mobile phone service users. Whenever a SIM card is inserted into a smartphone, users may use it to surf the web, exchange text messages, as well as accept and dial phone calls (Gomez et al., 2014) (Figure 6.4).

Figure 6.4. A mobile station is shown schematically. Source: https://www.wikiwand.com/en/Mobile_station.

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6.4.2. Base Station Subsystem It is in charge of the mobile station’s radio connection. One or even more Base Transceiver Stations (BTS) and a Base Station Controller make up the system (BSC). The BTS is made up of radio antennas and communications equipment that form a cell as well as manage radio communication systems with the Base Stations. The BSC is in charge of one or more BTS resources. It controls the handoffs of one cell to the other, as well as available radio creation and carrier frequency (Ruban et al., 2017) (Figure 6.5).

Figure 6.5. Base station subsystem architecture. Source: https://teltechinsight.blogspot.com/2018/08/base-station-subsystembss-in-system.html.

6.4.3. Network Switching Subsystem Its most important component is the Mobile Switching Center (MSC), which handles call shifting across fixed and mobile users on the network. MSC is in charge of mobile management systems including enrollment, verification, and geolocation updates (Zhou et al., 2019; Zhan, 2014).

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Table 6.1. Summary of the Development of Technologies Year

Technology

Description

1857

Electromagnetic waves

Established by James Clerk Maxwell

1899

Radiotelegraph transmission

Created by Guglielmo Marconi

1905

Analog (voice) transmission Consumed by defenses applications

1928

Two-way radio systems

Detroit police placed the first radio network (land mobile)

1929

Two-way radio systems

Boats in the Atlantic utilized radiotelephony for customers

1947

Two-way cell phones

Began whenever Douglas H. Ring and W. Rae Young invented hexagonal cells for cellphones Heavy and costly with reduced and incomplete mobility facilities

1967

Cell areas

– Incapable of handing off cell phone calls from one ground station to another

The 1970s

1G networks

Created by Amos Edward Joel Analog signs were given off across towers Call not canceled whenever going from one cell region to another Less heavy and costly

The early 1990s

2G: GSM networks

Based on a digital variation Recovers the broadcast value and attention of cellphone call facilities Provides paging, faxes, SMS, and voice mail facilities Incomplete data facilities like MLS, WAP, and HSCSD,

The late 1990s

2.5G: GPRS networks

Usages GPRS typical Graphics data delivered as packages EDGE network is a case

Recently

4G networks

Provides high transmission rates with Quality of Service (QoS) features Improves the quality of video conferencing Works as television with wider bandwidth

6.5. MCN PLATFORMS Communications Systems of mobiles include Mobile Ad Hoc Networking (Mobile Network) and Mobile Social Networks (MSN) (Baccelli & Zuyev, 1996) (Figure 6.6).

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Figure 6.6. Systems for integrated mobile networks. Source: https://www.securitymagazine.com/articles/94433-the-push-to-talkecosystem-cellular-wi-fi-and-unified-platforms.

MSN is a grouping of people that connect via social mobile apps like WhatsAppTM as well as BBMTM. By utilizing such mobile apps, including non-digital people can conduct a variety of information and digital activities. They examine their e-mail, give a quick telephone call, or deliver a text. They submit blog posts, maintain their social accounts, and upload images and videos to express their preferences, ideas, and emotions to the globe. Owing to the rise in phone use, data may be rapidly disseminated across a huge population on the network. This phenomenon is referred to as information dissemination (Braun, 2014).

6.6. INFORMATION DIFFUSION IN MCN Diffusion is the transfer of knowledge or ideas from one individual (node) to the other with network interconnections and connections (links) (Van den Berg et al., 2008). In a small space of time, individuals in a network share ideas and information with others. Irrespective of the qualities of the individuals, the social connection structure is important to the project implementation period (Mahdi et al. 2009). In actuality, the features of a player do not give it almost more receptive to embracing new technologies than other actors. The

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location of each player in a system and their connections are the primary elements that form it much more susceptible to the method of diffusion (Smith-Clarke et al., 2014). Mobile social media network apps enable users to engage with one another via microblogging and text transmission. This sort of connection between individuals results in the spread of knowledge since people affect one another by their very nature. Multiple facets were discovered to explain user engagement. Firstly, the total actions of users mimic the user’s everyday work routine with a somewhat longer length and regular occurrence (Konglin Zhu et al. 2011). Secondly, user contacts in social media and mobile reflect the heavy-tailed distribution found in tiny social groups, and customer interactions obey the Pareto principle, in which around 20% of users have close relationships with the other 80%. Third, the connection route between two mobile terminals is often less than six hops (links), and data dispersion employing an epidemic technique reveals that 50% of the population is aware in the short future and 80% in the long run (Davronbekov & Matyokubov, 2020) (Figure 6.7).

Figure 6.7. The design of a complicated wireless communication network in the twenty-first century, including linkages to wired backhauls. Source: https://www.semanticscholar.org/paper/Diffusion-Models-for-Information-Dissemination-in-Cheng-Karyotis/71c7493f9a55c85a47d587c48fe711 e2b692c84f.

Various mathematical, as well as networking methods, as well as networking methods, are utilized to examine the dissemination of inventions

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in MCN (Lopez-Pintado, 2004). The macro model is a very well dispersion method used to determine the pace of dissemination and the invention and copying ratios. In addition to assessing the rate of diffusion, the autocorrelation-correlation approach assesses the spread of artifacts, infections, and other behaviors across surrounding regions. A third approach is the network system, in which each person is related to other people by social accounts and interactions, establishing a net of players and relationships wherein network impacts are represented by a social identity approach (Valente, 2005). Throughout this exposure model, the amount to which every person adopts new ideas rises as the number of linked individuals in his or her network grows (Zdarsky & Schmitt, 2004).

6.7. KEY APPLICATIONS Healthcare, clinical, amusement, cultural, educational, efficiency, industry, money, and life are just a few of the sectors in which mobile communication apps have been created. Because such mobile apps may be utilized whenever and wherever they are currently the most popular method for individuals to interact (Gawas, 2015) (Figure 6.8).

Figure 6.8. People-focused mobile communication apps. Source: https://www.tutorialspoint.com/communication_technologies/mobile_ communication_protocols.htm.

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People may establish teams, share data, and send limitless photos, video, audio, as well as texts and emails using sociable mobile apps. Additionally, these programs allow users to create free videos as well as phone conversations. Many social programs analyze individuals’ Foursquare, Facebook, and Twitter connections to aid them to find and socialize with other users, colleagues, Facebook, and Twitter friends, business connections, and coworkers (Fei et al., 2006). As a result, individuals may go into any area, café, airport, retail mall, or park and see if they have something mutual with everyone else there, as well as see how well they are related to the individuals surrounding them. Other programs may be making TV viewing more enjoyable by allowing users to instantly recognize whatever is on TV and synchronize Sideshows to discuss TV episodes and films they enjoy with others who enjoy similar series. People can also view the greatest videos online as chosen by their colleagues and others they love about (Khattak et al., 2019; Swain & Ray, 2018). Other sociable mobile apps, on the other hand, permit customers to ask any questions and get responses about what is currently happening in areas of interest. This type of app assists users to figure out how to get there, what else to do, and what’s going on in their area right now by linking them with knowledgeable people and individuals who are currently on the spot. WhatsAppTM Messenger, BlackBerryR Messenger (BBMTM), ViberTM, SonarTM, MisoTM, ShowyouTM, and LocalmindTM are the very well apps throughout this area (Dai & Zhang, 2006). People may use wellness and exercise mobile apps to obtain quick reach to their patients’ information and test results, as well as save and distribute their vital patient data through e-mail or fax. Individuals may keep their patient data on their phones in times of emergency, arrange, and get prescription alerts, and plan and locate their upcoming laboratory visits. Furthermore, fitness apps enable users to monitor and regulate their weight to become in shape. Medical apps may also analyze (but not identify) diseases and conditions, as well as provide guidance to those who are experiencing health issues. Some of the health mobile apps include GazelleTM, MyNetDiaryTM, and Lose It!TM, and iChemoDiaryTM (Yu & Zhu, 2016). Smartphone games may provide enjoyment mobile apps since they rely on creating a network that enables several players to compete with others. Several games are available in this games industry that may be performed by much more than two people in various locations across the globe. Sketch something is a communal drawing game for apple iOS and AndroidR smartphones that is fun to play. High NoonTM, FarmVilleTM, and Mini CafeTM are three other entertaining mobile games (Stefani et al., 2021).

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Studying using education mobile apps is an attractive notion. Whilst e-Learning is not a new idea, it describes how education distribution has been established to satisfy dynamic nature as well as to harness a significant income stream via the use of technologies. Learners, instructors, and scientists may study on the fly by using these types of programs. Many instructors are now using educational programs such as dictionaries, unit converters, translators, and GPS as learning aids for their pupils. Moreover, academic mobile apps are displacing tangible items like textbooks, calculators, notes, and pens that were formerly taken about. Individuals may learn anything from chemistry to convey meaning via learning software (Cau et al., 2016; Wang et al., 2017). It assists students in various stages of English proficiency, from knowing how to read to honing composition and grammatical skills to studying great literature. It may also be used as a portable mathematician, with systems to enhance to study of numbers, master arithmetic, calculate algebraic expressions, understand statistics, and much more. Furthermore, educational programs enable users to explore the worlds of chemistry, anatomy, astronomy, biology, and all other fields of scientific discipline. Tutor.com To GoTM, Shake-a-PhraseTM, Graphing CalculatorTM, and TutorVideo: BiologyTM is just a few of the apps offered (Kim, 2018).

6.8. FUTURE DIRECTIONS The communications sector has been significantly impacted and therefore will remain to be transformed by the rapid emergence and spread of smartphone innovations. Scientists and researchers predict that in the near, a higher emphasis would be placed on safety, confidentiality, confidence, and reliability to maximize cellular routers in terms of QoS, network management, and self-organization. MCN’s future directions include ubiquitous (pervasive) computers, holograms, interactive media, and four dimensions (4D) (Xia et al., 2019). Pervasive computing would depend on multiple network elements doing different tasks even without the user’s knowledge. It is predicated on the notion that every gadget can be embedded with chips and connected to an infinite network of always-accessible devices. It is based on smartphone context-aware, which increases system reuse and flexibility (Pérez‐Escamilla & Engmann, 2019). Hologram technology is an optical projecting method that functions by guiding sunlight to the regions where people want to view an image. Optical

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holography, as well as electrical holography, are included (holo video). Holography relies on three-dimensional (3D) images with full-depth features (e.g., shading, texture gradients) and uses computer technology to make interactive visuals (Gardner & Lehnert, 2016). The electronic holography (holo video) technique, on either hand, blends the holographic method with the aid of optical modulation to create large, interactive, and high-resolution flowing visuals that provide an extraordinarily realistic sense of the video sequences. In the near, merging such techniques into smartphones would enable users to project small 3D holographic moving images of the person they are contacting, as well as play downloaded movies on a wall using a mobile device. Consequently, the employment of holographic technology will bring the Star Trek universe much closer to reality (Xu et al., 2014).

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CHAPTER

7

SECURITY FOR COMMUNICATION SYSTEMS

CONTENTS 7.1. Introduction .................................................................................... 220 7.2. Security Objectives ......................................................................... 222 7.3. Types of Attacks .............................................................................. 225 7.4. Security in Communication Protocols and Networks ...................... 227 References ............................................................................................. 236

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7.1. INTRODUCTION Industrial automation technologies are utilized in a variety of application areas, including process, discontinuous, and batch production; the production and distribution of electrical energy; the supply of water and gas; and mobility. The elements of industrial automation may be disseminated on a scale that spans from regional to broad to even international, depending on the details and operation of the system.. In the past, different automation systems were neither connected nor were they linked to open networks including the internet (Vitek et al., 1996). Companies are under a lot of pressure to make quick judgments that are also efficient with their finances in today’s market. To achieve this goal, precise, and updated information on the plants and the state of the process must not only be accessible just on factory floors, but at the leadership level within the company, and to members of the supply chain. As a consequence of this, there will be an increase in the amount of connectivity that exists between various automation systems including industrial automation and office networks. In the beginning, these kinds of connections were made via strategic communications methods and protocols that were only available to a select few. Gradually, technologies that are public and standardized on the internet and the network itself are being utilized for this purpose in the modern environment (Dzung et al., 2005) (Figure 7.1).

Figure 7.1. The network information infrastructure and the command, reconnaissance, and battle control system. Source: https://www.spiedigitallibrary.org/conference-proceedings-ofspie/11442/114420S/Security-of-communication-in-the-special-communications-systems/10.1117/12.2565307.full?SSO=1.

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When discussing the safety of information management, the word “risk” refers to the combination of two elements: a weakness and a hazard. The capacity to be damaged is what we mean when we talk about a vulnerability. A basic deficiency, a defect in the conceptual architecture of the system (such as a poorly designed protocol), or a problem in the implementation of the system (such as a programming error) may all contribute to the vulnerabilities of a data system (e.g., cryptographic keys and password that can be guessed). The presence of an attacker who is attempting to discover and take advantage of a vulnerability to cause harm is indicative of the existence of a threat. Weakness may also be exploited accidentally and without malicious intent, which might result in damage to the system (Coburn et al., 2005). Modern industrial communication networks are, for the most part, due to commercial operating systems (OSs), protocols implementation, and communication apps, all of which are well aware of their security flaws and may be exploited by malicious actors. When a device is connected to the Internet or any other kind of public network, whatever vulnerabilities it may have been made visible to prospective hackers. The attackers need to have the necessary skills and drive. Knowledge is readily accessible because of the open technology of the Internet. Attacks on industrial communication networks might be motivated by either politics or economics (Obeed et al., 2018): •

Computer control directs the flow of water, power, and other vital processes. In the event of a future crisis, a criminal cartel, terrorist organization, or foreign government may attempt to do economic harm by assaulting such essential networks. The danger is quite substantial. • Deregulation and competitiveness between power companies have provided “economic incentives for hostile penetration into the electricity generation business and marketplace players’ communications and computer systems,” according to IEEEUSA. In conclusion, big, and linked networking of commercial communication and automated systems are susceptible to electronic assaults, and there are risks to be concerned about. Because of this, ensuring one’s safety has emerged as a primary concern (Qi et al., 2019).

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7.2. SECURITY OBJECTIVES We may differentiate three basic approaches when searching for a security description for a given system that will serve as the foundation for a security protocol or system design (Dressler & Kargl, 2012) (Figure 7.2).

Figure 7.2. Framework for cyber-security. Source: https://cetome.com/training/nist-csf.

The first viewpoint considers how an attacker gains access to a specific information system (IS): physically, wherein situation the defenses are referred to as physical security, or electronically, in which case the defenses are referred to as network/security (Arfaoui et al., 2020). These 80 security goals listed below provide a framework for identifying and evaluating different systems’ security features (Wolf et al., 2004).

7.2.1. Confidentiality The security goal relates to protecting information from being disclosed to unauthorized individuals or systems. This is true both for domain-specific data, including manufacturing recipes or plant efficiency and widespread policy, and secrets related to the security processes themselves, including such passwords and encrypt, for automated systems (Sommestad et al., 2009).

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7.2.2. Integrity The integrity goal relates to avoiding unauthorized people or systems from changing information without being recognized. That applies to data including manufacturing recipes, sensor data, and control instructions in automated systems. This goal involves protection against data alteration on the system through message insertion, replaying, and delaying. Violations of integrity may result in safety hazards, such as damage to equipment or persons (Ericsson, 2010).

7.2.3. Availability The term “availability” relates to guaranteeing that unauthorized people or services cannot refuse authorized access to users or usage. All IT aspects of the plant, such as control systems, security systems, operating workstations, engineering workspaces, production executing systems, and the communications networks between such components and the outside world, are referred to as automated systems. Denial-of-service (DoS) attacks, often defined as availability violations, may result in not only financial losses but also safety concerns since administrators lose the responsibility to control and manage the process (Aiash et al., 2010).

7.2.4. Authentication Authentication is the act of determining a system user’s genuine identification and mapping that identification to a mechanism principal (e.g., legitimate user accounts) that the system recognizes. The majority of other security goals, most significantly authorization, employ authentication to differentiate between authorized and illegal users (Gao et al., 2014).

7.2.5. Authorization The authorization goal often termed network access, is focused on preventing unauthorized individuals or systems from accessing the system. Authorization, in a broader sense, is the process that differentiates between authorized and unauthorized individuals for other security goals, such as confidentiality, stability, and so on. The capacity to give directives to the facility management system is restricted by the limited meaning of access control. Violations of authorization may jeopardize one’s safety (Sun et al., 2019).

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7.2.6. Auditability The capacity to recreate the whole background of the system to analyze from previous recordings of all (relevant) operations performed on it is what audibility is all about. This security goal is particularly useful for determining the magnitude of a system breakdown or the implications of a security event just after facts, as well as discovering and determining the causes for systems breakdowns just after the reality. It’s worth noting that audibility without identification may be useful for diagnosing problems, but it doesn’t guarantee accountability (Stavroulakis & Stamp, 2010).

7.2.7. Nonrepudiability The non-reputability goal entails being ready to offer incontrovertible evidence to a third party as to who began a certain activity within the platform, even though the third party is unwilling to cooperate. That security goal is important for determining responsibility and culpability. This is particularly significant in the context of automated systems when it comes to regulatory standards, such as FDA clearance in the United States. Violations of this security goal usually have legal repercussions but no safety concerns (Rahman & Imai, 2002).

7.2.8. Third-Party Protection The third-party defense objective serves to prevent destruction to third parties caused by the IT framework, that is, significant harm which is not caused by the managed plant’s potential dangers: the satisfactorily attacked and circumvented automation system can be used for different attacks on independent third party IT structures, information, or users, for example, via Distributed DoS (DDoS) or maggot attacks. The repercussions might range from a tarnished image for the automated system’s operator to legal culpability for third-party losses. (Additional security goals, most particularly the registration management objective, include the hazard to third parties from probable workplace security problems resulting from attacks on the plant industrial automation.) Several of these security goals are rather independent of one another, but only a fraction of them would have top importance or be relevant even for most networks (Burg et al., 2017). The third point of view is associated with the amount of trust that may be placed in the techniques used by a given system to fulfill the appropriate security goals. The degree of trust might be expressed in terms of official

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certification outcomes, such as the Common Criteria (CC) assessment (see Section IV-A1), or even in terms of industry standards and procedures. When kinds of attacks including vulnerabilities emerge discovered, the degree of trust in a system’s security measures often declines over time, necessitating continuous reviews and updates to the safety design and implementation (Timotheou et al., 2014).

7.3. TYPES OF ATTACKS Every automation and control system must meet a subset of both the security goals outlined in Section II-A, based on its unique role and location. Any attack is defined as a deliberate breach of a security goal. Outsiders or inside may both launch attacks just on the facility. Planned and untargeted assaults are distinguished. Targeted assaults are designed to damage a certain communications network or system types, such as for economic espionage, terrorism or warfare. Untargeted attacks target any device that is found to be susceptible. Targeted assaults are usually preceded by a period of acquiring information on the target, such as via the use of offline and online resources, as well as specialized tools for locating weak devices on a network. The following are a few examples of common assaults (An et al., 2016) (Figure 7.3).

Figure 7.3. Types of cyber-attacks. Source: https://www.wallarm.com/what/what-is-a-cyber-attack.

7.3.1. DoS The goal of an attacker is to make the system less accessible for the purpose intended (Li et al., 2018).

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7.3.2. Eavesdropping The attacker’s purpose is to compromise the communication’s secrecy by scanning packets just on the Local area networks or capturing wireless broadcasts, for example (Lu et al., 2019).

7.3.3. Man-in-the-Middle In such a man-in-the-middle attack, an attacker behaves as if he or she is the intended, genuine participant at both ends of the connection. That allows for the modification of exchanged communications in addition to breaching confidentiality (integrity). Man-in-the-middle attacks may be used to acquire authority over data encryption sessions by exploiting flaws in the application or the use of particular key swap and verification protocols (Zhang et al., 2016).

7.3.4. Breaking Into a System The attacker gains the capacity to influence components of the behavior of the communication network and the linked plant at his whim by violating the identification and user access goals, including the ability to defeat security and privacy requirements. A break-in generally entails the simultaneous infiltration of numerous subsystems as well as the gradual upgrading of an attacker’s capabilities (Du et al., 2018).

7.3.5. Virus To implement the malicious software inserted by the attacker, a virus-based attack tries to manipulate a user’s identity to defeat identification and access control systems. Virus assaults are frequently untargeted that spread through susceptible applications and users in actuality. Virus assaults often limit the supply of compromised computers by using excessive processing capability or communication bandwidth, either explicitly or implicitly (Li et al., 2017).

7.3.6. Trojan The Trojan seems to be a virus in which the dangerous code is concealed behind user-desired and utilized capability. Trojans are often used to get around confidentiality and user access goals (Wang et al., 2019).

7.3.7. Worm A worm is a malicious program whose transmission techniques depend on the automated research and exploiting of weaknesses within the target

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network, with no human interaction. Worm infestations are untargeted and often cause difficulties with accessibility for the afflicted systems or even the entire Internet. Furthermore, the worm may include malicious code that allows all infected systems to conduct a widespread, targeted assault (Lin et al., 2019).

7.4. SECURITY IN COMMUNICATION PROTOCOLS AND NETWORKS Security protocols at various tiers of the communication system accomplish security goals in communications systems. The security protocols are designed to safeguard communication channels against network-based assaults. As discussed in this section, this may be given substantially independently of the applications, allowing commercial communication networks to depend on all these protocols for information security. User access challenges, on the other hand, are usually particular to the application’s needs. As a result, access control aspects are highlighted in Section III-C on safety in automated production protocols (Sharma & Kim, 2020). Any security services supplied by a level should safeguard the connection between both the layer’s exit points while being visible to a level above. IPSec and SSL, which are networking and transport layer security (TLS) technologies, are now the most extensively used (Hua et al., 2019) (Figure 7.4).

Figure 7.4. Communication networks secure routing protocol. Source: https://www.cs.cornell.edu/boom/2004sp/ProjectArch/SecureRouting/ srp_boom_simple.html.

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7.4.1. Link-Layer Security The password-based authentication protocol (PAP) and the tougher Challenging Handshake Authentication Protocol (CHAP) are security modifications to the Point-to-Point Protocol (PPP). The former employs a password-based system, while the latter uses a challenge/response system. The Expandable Authentication Protocol (EAP) is a generic identification framework (Xue et al., 2019) (Figure 7.5).

Figure 7.5. Module for link-layer security. Source: https://www.researchgate.net/figure/Link-layer-security-module_ fig2_260540463.

7.4.1.1. Security for Short-Range Wireless Links Bluetooth and IEEE 802.11 wireless Local area networks (WLANs) are examples of wireless short-range communications that are especially susceptible. DoS attacks using radio jammer are simple to carry out. In the end, there is no way to prevent such assaults, but they can at least be identified. More sophisticated attackers may be able to snoop on data or even breach into the automated system. Modern literary wireless communications technology, on the other hand, provides defense from espionage and

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proactive attacks (Bankey & Upadhyay, 2017).

7.4.1.2. Bluetooth A common “link key” is used by each pairing of Bluetooth devices for encryption and authentication. These devices should be “matched” the very first time they connect to one other, by inputting an identical personalized identifying number (PIN) from both devices, to create a connection key between the Bluetooth-enabled automated controllers and, for example, any portable config devices. Such pairing is crucial, and it should be done in an eavesdropper-proof setting. A few of the higher layer security protocols discussed below, especially IPSec, might be used as a substitute for a linklevel particular solution. Link-layer administration messages, on the other hand, would be unprotected and open to spoofing attacks as a result of this (Guo et al., 2018).

7.4.1.3. IEEE 802.11 Wireless LAN WLAN networks have a greater transmit power, i.e., a longer distance, than Bluetooth networks, making them more susceptible to espionage and active assaults. Wireless Equivalent Privacy (WEP), IEEE802.11 alternative security standards, provides an encrypted strategy focused on the RC4 cryptographic algorithm (symmetric encryption). However, because of its improper use of initialization vectors, WEP may be cryptographic keys cracked provided the attacker has enough data. The IEEE 802.11i task group addressed these issues by lengthening the key and enhancing the input value management in the RC4-based Wireless Protected Access (WPA) solution. The suggested long-term IEEE 802.11i solution uses AES to replace the encryption technique, although this necessitates hardware changes (Chen & Song, 2018). To generate the encrypted key for all sites, WEP uses a network-wide session key secret. WEP cannot be expanded to a large number of connections since automated session keys are not implemented. If just a small number of reconfigurable users are required, as is typically the case in industrial automation applications, encrypting with stable keys utilizing WEP or its enhanced descendants, along with MAC-address filtration, may be adequate. Clients and connections must be properly verified, and keys must be disseminated automatically in much more adaptable systems with high-security needs. IEEE 802.1X is a port-based network security protocol for Local area networks; IEEE 802.11i defines its usage for WLANs. The EAP is initially executed by the client computer and the WLAN base

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station when using IEEE 802.1X. Only when the client node has properly authenticated itself with the network does the access point provide its network connectivity. A remote management dial-in user server (RADIUS) is normally where the network keeps user information. The adoption of IPSec/VPN systems, as discussed below, is a valuable addition or alternative to secured WLAN operation (An et al., 2015).

7.4.2. Internet Layer Security Internet Protocol Security (IPSec) provides security at the Internet layer. IPSec is an additional modification to the Internet Protocol version 4 (IPv4), however, it is a required feature of IPv6, and most current operating aware and conscious of it (Gao et al., 2017) (Figure 7.6).

Figure 7.6. Protocol for network layer security. Source: https://www.tutorialspoint.com/network_security/network_security_ layer.htm.

IPSec offers a single layer of security for all UDP and TCP services since it is applied just at the IP layer. It is invisible to the top layers and meets the essential host-to-host interaction security requirements (Zhang et al., 2017): • • • •

(Only in encapsulated security payload (ESP) version); secrecy; (Only within authenticating header (AH) version); data source authentication; The authenticity of information (in ESP or AH versions); About the specific host, access control (in ESP and AH modes).

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IPSec’s ESP and AH phases are mentioned in detail. These modes may be used simultaneously or separately. IPSec key exchanges (IKE) also offer a framework for key security and management connection negotiation (e.g., the session key for symmetric encryption). IPSec offers machineto-machine protection but does not handle the individual authentication process. As a result, IPSec is most often used to create a virtual private network (VPNs), although it may also be used to secure end hosts. (A manin-the-middle attack on VPN connections described in References exploited implementation flaws.) Because the source and destination IP addresses are used to identify IPSec security relationships, IPSec setups may collapse if network address translation (NAT) alters IP addresses and ports. This issue has been addressed (Haider et al., 2020).

7.4.3. Transport Layer Security Applications running on top of TCP (but not UDP) can be secured by the secure sockets layer (SSL), or its extension, the TLS standard. Typical applications are HTTP and FTP, whose usage of SSL is indicated by the URL prefixes HTTPS and FTP, respectively. The main features of SSL are (Lu et al., 2017): •

The TLS standard, and the safeguard socket layer (SSL), could be used to secure applications that utilize TCP (but not UDP). HTTP and FTP are two popular applications, with the HTTPS prefix in the URL and the file transfer protocol (FTP) indicating not just whether they employ SSL. The above are some of the most important features of SSL: Encryption algorithms negotiations and session key distribution; • Server authentication using certificates; • Certificate-based server authenticating confidentiality; • Preservation of data security. Client authentication is indeed a possibility in SSL; however, it is seldom used since it needs client certifications. Instead, customer authentication is frequently performed independently at the application level, with the Encryption process providing secrecy protections (Fan et al., 2018) (Figure 7.7).

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Figure 7.7. TLS stands for transport layer security. Source: https://www.cloudflare.com/learning/ssl/transport-layer-security-tls/.

With remote access applications, the secured shell (SSH) transport layer protocol (SSH-TRANS) offers secrecy, server identification, session key exchanges, and integrity of data. The SSH Authentication Mechanism (SSHAUTH) and the SSH Connection Protocol (SSH-CONN), both of which operate on top of it, are supported by SSH-TRANS. Although SSH-AUTH enables user authentication, SSH-CONN offers a variety of communication networks, including highly secure login and secured TCP port forwarding, that Berkeley covers telnet and r-tools functionality, such as login (Zhang C. & Zhang G., 2020).

7.4.4. Application Layer Security The lowest layer security methods stated above can’t handle all security goals. The application server, in particular, is responsible for user and program authentication (Liu et al., 2017) (Figure 7.8).

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Figure 7.8. Protocols for application-level security. Source: https://www.tutorialspoint.com/network_security/network_security_ application_layer.htm.

The following are some common application-level security examples. •

•

•

Using a challenge/response method, HTTP digest authentication (DA) is used for user authentication. DA is expected to offer authentication processes and security standards by definition. The latter, on the other hand, is not always included in the implementation. If such an application doesn’t need secrecy and SSL or IPSec can’t be used due to space or speed constraints, DA may be used instead. Privacy is quite good (PGP). Encryption and sign data for asynchronous data transmission (e.g., through e-mail) and storage using PGP or its accessible version Gnu Privacy Guard (GnuPG). XML Web services: A self-documenting, living person eXtensible Markup Language (XML) is progressively being used to communicate data and trigger services across platforms and applications. For Html pages or XML components, many standards are now being established to fulfill the security requirements of fine-grained confidentiality, consistency, identification, and authorization, during both transmission and long-term storage.

7.4.5. Firewalls A firewall is a piece of network hardware or software that is installed at the program’s or network zone’s edge to prevent illegal access from adjacent zones (such as the Internet). It simply analyzes all arriving data packages’

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protocol particular elements and bases its admittance judgment on them (Wu et al., 2019) (Figure 7.9).

Figure 7.9. A simple example of firewal security. Source: https://www.wallarm.com/what/the-concept-of-a-firewall.

Firewall kinds and services differ depending on the network protocols they check and the reasoning they use to evaluate them. The above are the many kinds of firewalls (Andreotti et al., 2014). • • • •

Depending just on the packet’s IP input and output addresses, and the protocol type, filtering routers allow packets through or not. UDP and TCP header information such as port and flag is also used by packet-filtering firewalls to make admission decisions. For example, stateful firewalls keep track of session state to determine if an is something to a previously defined session. After verifying for acceptability depending on the application level data objects and requirements, application-level gateways transfer requests just on the application level between both the internally and externally networks (using different connections).

7.4.6. Intrusion Detection Systems Based on established attack characteristics and/or unexpected system activity, an intrusion detection system (IDS) attempts to identify assaults. The information obtained by a network-based IDS (NIDS) comes from the traffic monitoring on the subnetwork. (The kind, content, frequency, and course of the sent messages are all included in this data) (Nguyen, 2016) (Figure 7.10).

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Figure 7.10. Local area networks and intrusion detection systems. Source: https://www.researchgate.net/figure/Intrusion-Detection-Systems-andLocal-Area-Networks_fig1_339194281.

A host-based intrusion detection system (HIDS seeks to identify assaults based on information observed immediately on the server. A host-based IDS, for instance, gets its data through file system security checkers, which keep track of whether crucial file systems change for no apparent reason. A host-based IDS must protect the most essential and security-relevant hosts, including firewalls or NIDS services (Bankey & Upadhyay, 2017).

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CHAPTER

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FUTURE DIRECTIONS IN THE DESIGN OF DEPENDABLE COMMUNICATION SYSTEMS

CONTENTS 8.1. Introduction .................................................................................... 242 8.2. Research Directions in Software Failure Mitigation ......................... 246 8.3. Reliability of Wireless Communications .......................................... 249 8.4. Failure Models and Measures of Fault Tolerance ............................. 250 8.5. Resilience Considerations of an IP Backbone Network in the Interplay With an Agile Optical Layer ................................. 252 References ............................................................................................. 254

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8.1. INTRODUCTION It is impossible to offer accessibility that is 100% of the time, despite the countless efforts that have been made to enhance the Quality of the service in communication networks when there is a malfunction. Because errors with communications networks are usually unavoidable, it is not feasible to build communications networks that are error-free and to fully protect oneself against a variety of problems and risks (Agarwal et al., 2010). However, by providing a decent defense, detectors of unexpected events, restoration of negative impacts, and recovering to normal operating state (e.g., by applying the D2R2 + DR make a diagnosis and precision approach from (Alonso et al., 2013), which is sketched in Fig. 1), an organization will be able to minimize the effects of a potential attack. 8.1 It is possible to obtain a considerable improvement in recognizing the signs, which is defined as the capability of the system to provide for and maintain the level of offering in the face of a variety of failings and obstacles to normal operating conditions. This type of improved performance can be accomplished. According to the concept of resilience encompasses not only the ability to survive, but also the capacity to tolerate faults and disruptions, as well as reliability, performability, and safety (Avizienis et al., 2007). Under this position statement on dependable networking, we are especially interested in system performance, which is stated in as the continuation of proper service. This is because the network model is a key component of the reliability of a communication system (i.e., the ability to avoid service failures that are more frequent and more service than acceptable). Specifically, the purpose of this study is to lay out the research paths in network dependability that, in our view, are of the biggest relevance, as well as to highlight critical difficulties that will need to be handled in the future (Avizienis et al., 2004). We concentrate on a wide variety of research instructions in the area of information risk and quality. The basic layout of communication networks that are required to uphold the ISO/OSI communication system model includes seven layers: Physiological (L1), Link Layer (L2), Network (L3), Transport (L4), Session (L5), Presentation (L6), and Application (L7). Depending on this general framework, communications equipment is obligated to abide by the framework. As a result, we not just address problems relating to the dependability of the architecture of communications networks, but we also call attention to concerns that are associated with failed software (Balbuena et al., 1996) (Figure 8.1).

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Figure 8.1. Principal elements of the D2R2 + DR approach. Source: https://link.springer.com/article/10.1007/s11235-013-9816-9.

Specifically, the most recent research approaches to software error prevention are presented in this area. According to this, software issues are responsible for around 40–50% of all failures that occur in communication devices. Despite the use of formal approaches to cut down on the likelihood of software failures, the creation of error-free software seems to be an extremely unlikely possibility. In Section 8.2, in addition to presenting the categorization of failings, the authors have focused on the “Environmental community” idea to display the effect of global warming on failures and to indicate important and challenging issues for future investigation. In addition, the authors present the categorization of failures in this section (Beineke et al., 2002). In the following sections, we will discuss concerns related to the dependability of the infrastructures of communications systems. When it comes to wired networks terms, the research has so far paid a significant amount of attention to this particular topic. Various strategies have been suggested for the safety of communication links, such as the utilization of alternative pathways, also known as backup paths (BP), which are linked or nodded in conjunction with the primary pathways, also known as having to work or active paths (AP), that are under the security (Bhandari, 1999). Alternative pathways might either be deployed in advance as part of a protection plan or discovered dynamically in response to a failure as part of a recovery scheme. Thus, using a protection system will provide complete recovery of the required capacity, while using flexible restoration will only give backup pathways based on the best-effort criterion. Path, section, or link

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protection and restoration are among the most significant ideas concerning the breadth of backup routes (Colle et al., 2002). The primary goal of network administrators is to offer the requested service to consumers while simultaneously lowering the overall capacity and/or power consumption of the network as a whole. Nevertheless, from the point of view of a user, it is frequently more vital to enable rapid recovery of flows that have been disrupted by the breakdown (Cramp et al., 1992). Certain variations of algorithms that are used to find communication channels are designed for the safety either of static or dynamic traffic. This means that they take into account the amounts of traffic which do not alter significantly over time (e.g., in the core areas of the circuit), or that are highly time-dependent, following this distinction (De Maesschalck et al., 2002). Because the challenge of locating communication pathways in networks with limited capacity is an NP-complete one, effective solutions are not always possible (Wang et al., 2010) (Figure 8.2).

Figure 8.2. Illustrations of the active and backups pathways. Source: https://link.springer.com/article/10.1007/s11235–015–9987–7.

It has been suggested to use heuristic techniques to detect disjoint pathways. Such techniques appear to be the sole answer in the situation of dynamic network prevention because of time restrictions. The majority of the available techniques for finding disjoint pathways pertain to the situation of only one network. This means that in all path calculations, the price cij of links lij is assumed to be the same (for both working and BP). This presumption is often incorrect, for example when numerous backup pathways use the same connectivity. In this scenario, the value of a link in calculations for backups paths is typically a fraction of the

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comparable cost in use for functioning path calculations. That’s an instance of the so-called inter networks situation, which requires the employment of certain techniques to locate disjoint pathways. One such approach is the k-Penalty technique, which can be found in reference (Staessens et al., 2006). The scenario of random failures, in which nodes and connections experience problems independently of one another, is addressed by a significant number of proposed solutions. Because the properties of network parts themselves sometimes influence differential failure probability, this concept is frequently not practical. In addition, there is a big group of incidents that are the consequence of malevolent human actions. These activities are known as assaults, and they stand except for errors that are unpredictable by their very nature. The related ideas of attack-resistant routing techniques may be found (Wei et al., 2004). Due to the known geographical coordination of failures as just a consequence of, for example, natural catastrophes like intense rainfall falls, the concept of random failures is also inappropriate for use for estimating the susceptibility of wireless connections. This is because of the reported correlations of failures. When this occurs, the availability of connections shifts considerably over time. We are certain that it is an emerging field of study that will get a great deal of attention in the years to come. Specifically, there is a requirement to create reliable communication techniques that can react to failures in regions, which are defined as the simultaneous occurrence of several failures in circumscribed areas (Medeiros et al., 2003). The relevant Section 8.3, first underlines character traits of failings in wireless connections and then has shown two significant instructions for future studies, namely, offering the reliable data transmission in Wireless Mesh Networks (WMNs), and in wireless mobile networks (here for the situation of automotive communication systems in vehicular ad-hoc channels). In addition, the respective Section 8.3, provides a summary of the main takeaways from the study. In turn, Section four focuses on algorithmic elements and areas for future research in the construction of efficient ways to discover communication channels. Section 8.4 is broken down into the following subsections (Jajszczyk, 2009). In the next section of the article, we will be concentrating on future directions concerning the robustness of neural network models. There is no question that modern communications systems are multilayered, which means that they are made of a stack of networks operating in a relationship

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with the client. In multilayered networks, it is common practice for the lower-layer network to provide transportation services to the greater network (Ou et al., 2003). The two-layer IPover-Wavelength Division Multiplexing (WDM) structure seems to be the most promising design, with IP flows being serviced immediately by the WDM level. In general, the protection and restoration strategies that were discussed previously in this section are simply adaptable to offer to transmit protection in multiple hidden layers. Nevertheless, under this circumstance, it is essential to set appropriate norms of cooperation across the different levels of the network to guarantee multilayered resilience. That’s a good field, and the corresponding interworking techniques define, for example, the pattern of different networks to operate healing of impacted flows, and also a way of transferring the companies. consequently between both the link layer, have indeed been suggested. This is an area that has received a significant amount of attention (Campbell et al., 2015).

8.2. RESEARCH DIRECTIONS IN SOFTWARE FAILURE MITIGATION Because our society relies on systems and servers, these systems must be very dependable. According to numerous assessments, the fundamental reasons for system problems may be divided into three categories: hardware, user, and programming. Software has emerged as the primary source of equipment failures, accounting for between 40 to 50% of all problems (Lin et al., 2015). Although various articles have demonstrated that programming is one of the primary causes of failure, it appears that it is implicitly accepted that networking and telecommunication system problems are mostly driven by hardware (Singh et al., 2018). Developing failure software is just an exorbitant, if not impossible, undertaking, despite considerable breakthroughs in formal approaches, programming styles, and testing procedures. The number of residual defects may be reduced to one per 10,000 code lines with a good (and costly) development approach. Complicated systems with several flaws will be implemented. As a result, during operations, software fault tolerances become a vital component for dealing with software flaws and resulting equipment failure. Unfortunately, the research on software dependability has mostly concentrated on construction, debugging, and testing, ignoring the operating phase of computers (Jinno et al., 2010).

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To cope with problems during operations, the researchers advise using architectural diversity. Unfortunately, the expense of design variety has restricted its practical use; it can only be rationalized in existing systems (Ramamurthy et al., 2003). A question arises: Is it feasible to create software defect tolerance that is both economical and effective in dealing with problems that occur within operation (Kanoun, 2001)? Retry has typically been used to reduce hardware instantaneous failures, whereas rebooting or resetting the system has been used to cope with hardware periodic failures. In recent times, the same procedures have been employed to reduce transient or intermittent program failures produced by fundamental software defects. Following that logic, we believe that a software defect civility approach is based on reattempt, reboot, boot up, or losing to an exactly equal operating system (OS) replica (not a different version) to deal with failures induced by some kinds of software failings during operating condition is a cost-effective way to deal with software bugs (Liu et al., 2011). Software flaws are categorized as Bohrbugs (Bohs), Non-Aging-Related Mandelbugs (NAMs), and Aging-Related Bugs (ARBs) depending on their features. In 1985, Gray invented the name “Bohrbug.” It relates to flaws that are simple to pinpoint, duplicate, and so repair. Mandelbug, on the other hand, refers to defects that have a sufficiently complicated activation and/or erroneous propagation to cause “non-deterministic” behaviors. According to Dörner (Lyu et al., 1994), Mandelbugs are inextricably linked to software complexity. The following factors may contribute to its difficulty (Lyu et al., 1994): 1. 2. a. b. c.

A delay in the incidence of a breakdown between both the fault actuation and the incidence of a breakdown; or Secondary elements such as for example. connections between the software program and its internal hardware surroundings (hardware, system software, and other programs); the impact of inputs and operations time (compared to one another, or in terms of model duration or calendars time); and Whereas if inputs might have been performed in a different format and at minimum one of the alternative sequences would have not resulted in a failing, the ordering is deemed important.

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This software aging effect is caused by a kind of Mandelbug known as an aging-related bug. As software ages, it has a higher failure rate and suffers from gradual performance deterioration. This is particularly noticeable in long-running programs. Software regeneration has been employed as a preventive form of defense in the event of aging-related issues. Closing the program, cleansing its inner state and/or surroundings, and resuming it are the basis of software regeneration. The percentages of NAMs, BOH, and ARBs are 61.4, 32.1, and 4.4%, correspondingly, across various kinds of software (Maier & Pattavina, 2013). This taxonomy of software flaws is also not useful in theory, but in exercise: Each sort of software flaw necessitates a different technique for recovery. The categorization is useful for creating successful software defect stress tolerance and, if feasible, establishing the best preventative maintenance schedules (Zhang et al., 2012). The structure of the durations to aircraft systems of many NASA/JPL operations was investigated. An investigation of real-world TTF data like this may lead to improved prediction failures, potential preventative service intervals, better mitigation approaches, and, ultimately, great software layouts (Molisz & Rak, 2005) (Figure 8.3).

Figure 8.3. Classification tree for software fault/failure mitigation. Source: https://eg.uc.pt/handle/10316/48332.

We promote an economical software defect tolerance through environmental variety since the fraction of Mandelbugs in real-world software products is not insignificant. Environment diversity’s fundamental premise is whenever we redo a previously incorrect operation and it succeeds, that’s because the atmosphere in which the action was performed has altered enough to prevent Mandelbug activity. The operating system’s

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(OSs) capabilities, other programs running simultaneously and sharing the very same resources, convolution of activities, and concurrent, or synchronization are all examples of the ecosystem (Molisz & Rak, 2008). We addressed the various environmental diversity techniques used in eight NASA/JPL operations. Fix and patch proved to be the most popular method, as predicted. Environmental variety techniques, on the other hand, were employed to address a non-negligible proportion (about 11%) of problems caused by NAMs (Reboot, Retry, Restart, and Failover to identical copy). Only 1.6% of failures induced by Bohs were resolved using these techniques. That demonstrates the usefulness of the Environmental Diversification strategy in dealing with operational problems and related underlying defects (Molisz & Rak, 2008).

8.3. RELIABILITY OF WIRELESS COMMUNICATIONS Wireless technology durability is a comparatively recent study field. There are just a few ideas for wireless connections in comparison to the number of findings accessible in the research covering wired network dependability difficulties, and in particular, wired connection survival (Oki et al., 2017). Generally, wireless networking dependability is more difficult to accomplish, due to issues with the time-efficient capability of connections. Interruptions of many sorts commonly limit its capability (partially or fully), the most common of which are channel fading, crosstalks, and weather-related variables. Especially in mobile networks, wherein, effective connection capability is also a function of frequency variable range among nodes, the issue becomes much more pressing (Naumov & Gross, 2007). Wireless network dependability, we believe, will continue to be a study topic in the future years. To support this position, we can provide an overview of existing research findings on wireless communication dependability in this part, as well as some potential future study areas (Al-Tarawneh et al., 2020). Particularly, we focused on current failed theories and fault-tolerant techniques provided for wireless communication systems in earlier sections. Following that, we offer an overview of new strategies for ensuring communication dependability in two distinct wireless network situations, namely, Wireless Mesh Systems (with stationary nodes) and Vehicular Ad-

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hoc Networks—VANETs (with wireless nodes). For each example, we also talk about prospective study directions (Neumayer & Modiano, 2010) (Figure 8.3).

Figure 8.4. A strategy based on an environmental variety. Source: https://link.springer.com/article/10.1007/s11235–015–9987–7.

8.4. FAILURE MODELS AND MEASURES OF FAULT TOLERANCE The findings of a system of solitary random failures are presented in a vast number of research articles. The breakdowns of network parts in this paradigm are unrelated. Although such an assumption is reasonable for wireless connections, it seems to be insufficient for wireless technology. This is owing to the commonly found geographical association between wireless communication component failures caused by natural catastrophes (storms, torrential rain) or malevolent human activity (e.g., bomb blasts) (Brungard et al., 2009). The notion of a regional failure, which has been introduced, for example in Govardan et al., (2015), allows for constant failure of numerous network nodes placed within a specific area of negative effect. Most node and connection faults seem to be covered by this paradigm. During the latter instance, the functional capacity of connections may be reduced partially or completely.

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The geometric depiction of a failure zone is constructed by a concentric circle with a particular radius r, according to Brungard et al., (2009). This is particularly true in natural catastrophes like earthquakes when the risk of regarding network breakdowns is related to their distances from the epicenter of the breakdown (Ghonaim et al., 2015). Most researchers of research articles on regional failures presume that problems are limited to a single area at any one moment (Meddour et al., 2011), for example, contains the results of simulating many concurrent failures in several areas. Known techniques for area failure simulation may be classified as deterministic or stochastic failure-based depending on failure predictions. The very first class (see, for example, Wu et al., 2015) implies that any network system located within a given region will fail with possibility 1, whereas the latter category implies that the possibility of a network failure will be a repetitively reducing function of size between such a base station and the inability epicenter. Prediction methods appear to be more appropriate overall. They do, although, have certain limits. For example, in the model from (Eluwole et al., 2018), the circular failing area’s radius r is supposed to remain constant, which would be not the case. Another significant stumbling block (Figures 8.5 and 8.6).

Figure 8.5. An example of a failing in an area. A sphere of provided radial distance, positioned at the failing epicenter, represents the region of likely network breakdowns.

Source: https://tohoku.pure.elsevier.com/ja/publications/reliability-assessment-for-wireless-mesh-networks-under-probabili.

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Figure 8.6. Probabilities of area collapse as an example. Source: https://www.researchgate.net/publication/238522759_Reliability_Assessment_for_Wireless_Mesh_Networks_Under_Probabilistic_Region_Failure_Model.

The chance pi of link failure expressed as a distinct fixed value in each i-th region between two successive circumferential annuluses is the implementation of this concept in reality. As a consequence, failure rate estimates are either overestimated or understated (Andriolli et al., 2022). Real-world failure situations, in combination with a channel’s topological properties, have a direct impact on the channel’s overall dependability. Median connectivity, range connectivity, and route connectivity measurements may be used to assess the susceptibility of systems to higher failure. It contains the relevant concept for a wireless communication reliability metric for a regional loss situation (Zhang & Xin, 2019).

8.5. RESILIENCE CONSIDERATIONS OF AN IP BACKBONE NETWORK IN THE INTERPLAY WITH AN AGILE OPTICAL LAYER For several years, multi-layer (ML) communication has been considered. Despite a large number of publications, it still hasn’t been extensively used in real-world networks. Moreover, it has lately received more interest in the communication sector as a result of newly obtained connectivity, with the promise of additional cost reduction and better network management (Garrich et al., 2018) (Figure 8.7, Figure 8.8).

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Figure 8.7. An IP-over-optics network with A-/B-Plane architecture and how optical restoration is integrated into an ML resilience scheme are shown in this diagram. Source: https://www.comsoc.org/publications/journals/ieee-tnsm/cfp/recentadvances-design-and-management-reliable-communication.

Figure 8.8. A major paradigm shift is underway, moving away from fixed grid networking and toward a flexible modular optical transport network with adjustable reach and rate capabilities. Source: https://link.springer.com/article/10.1007/s11235-015-9987-7.

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INDEX

A Access control systems 227 accessibility 3 accounting 48, 50 active paths (AP) 247 Advanced Mobile Phone System (AMPS) 203 Aging-Related Bugs (ARBs) 251 algorithms 248 analog audio communication 201 authenticating header (AH) 233 Authentication 223, 229, 235 Authorization 224 automation systems 220

B backup paths (BP) 247 bandwidth 131, 132, 133, 157, 165 Base Station Controller 206 Base Transceiver Stations (BTS) 206 batch processing 45 binary value 78 Bohrbugs (Bohs) 251

broadcasting 5, 12, 13, 14, 18, 31, 32, 36, 37, 38 business management 50

C cache 133, 134, 141, 142, 143, 144, 145, 146, 147, 148, 154, 155, 156 Cell phone telecommunications 202 Centralized network architecture 75 Challenging Handshake Authentication Protocol (CHAP) 229 Civilization 3 Code Division Multiple Access (CDMA) 200 commercial transactions 44, 54, 56, 59 Common Criteria (CC) assessment 225 communication channels 76, 97 communication links 247 communication network 5 communications equipment 246 communication switching 172 completely-associative cache 144

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computer communication capabilities 5 computer communication network 73 computer communications 4, 5, 7, 12, 16, 17, 22, 24, 25, 27, 28, 29, 31, 32, 34, 38 computer interactions 2 computer network 72, 93, 117, 120, 121 computer science 5, 29 computer system 72, 74, 106 connection networking 170

D data communication 6 data management 142 data storage system 130 debugging 250 decision support networks 44 Decision Support Systems (DSS) 48 Denial-of-service (DoS) attacks 223 digital circuitry 80 Digital communication networks 170 Digital computers 170 Digital data 78 Digital encoding 78, 80 Digital systems 170 digital transmission 80 direct-mapped cache 145 distinctive address 131 distributed network 8

E electronic communications 8 e-mail communications 200

encapsulated security payload (ESP) 233 encoding system 79 Environmental community 247 Expandable Authentication Protocol (EAP) 229

F facility management system 224 file transfer protocol (FTP) 234 financial information systems (FIS) 50 financial management 49 Flow control 188 frequency-division multiplexing (FDM) 80

G General Packet Radio (GPRS) 200 global community 5 Global System 200, 203

Service

H hardware technology 73 High-Speed Downlink Packet Access (HSDPA) 200 human resource management (HRM) 50

I inclusion policy 146 Industrial automation technologies 220 Information reporting systems (IPS) 48 information system (IS) 42

Index

information technology 5 injector laser diode (ILD) 83 Integrated Services Digital Network (ISDN) 11, 24, 26 Interconnection networks 170, 173, 181, 182, 184, 192, 193, 195 Internet protocol (IP) 183 Internet Protocol Security (IPSec) 232 inter-personal communications 4 IPSec key exchanges (IKE) 233

K Knowledge Management Systems (KMS) 49

L latency 131, 133, 134, 141, 142, 144, 145, 148, 153, 157 light-emitting diode (LED) 83 Local part networks (LAN) 75 Long-Term Evolution (LTE) 200

M mail 200, 207, 208, 211 main memory 133, 134, 135, 140, 141, 142, 144, 145, 146, 147, 148, 149, 150, 155, 156, 160, 161, 163, 165, 166, 167 management information systems (MIS) 44, 65, 66, 67, 69 memory bandwidth 172, 177 Memory demands 178 memory hierarchy 134, 135, 141, 146, 147, 148, 155, 159, 160, 161, 162, 163, 164, 165, 166, 167 Memory latency 172, 177 memory system 130, 131, 132, 133,

261

134, 135, 136, 137, 138, 139, 140, 141, 143, 146, 147, 150, 154, 157, 165 Messages 175, 183 metropolitan area network (MAN) 76 Mobile Ad Hoc Networking (Mobile Network) 207 Mobile Communications 200, 203 mobile communications systems 200 mobile radio 201 Mobile Social Networks (MSN) 207 Mobile Switching Center (MSC) 206 multicomputer 170, 193, 197 multilayered networks 250 multi-layer (ML) communication 256 multiplexing 80

N network address translation (NAT) 234 network congestion 179 Networking devices 72 network interface 172, 175, 177, 182 network software 72 Non-Aging-Related Mandelbugs (NAMs) 251 Nordic Mobile Telephone (NMT) 203

O online networking 78 operating systems (OSs) 221 operations support systems 44 organizational records 44

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The Role of Communication in Computer Science

P parallelism 131, 150, 157, 160 password-based authentication protocol (PAP) 229 personalized identifying number (PIN) 231 phone system 202, 203 physical address 3 Point-to-Point Protocol (PPP) 229 process control systems 45 programming error 221 protocols implementation 221

Q Quality of service (QoS) 175

R radio broadcast technology 202 remote management dial-in user server (RADIUS) 232

S safeguard socket layer (SSL) 234 secure sockets layer (SSL) 234 segregating policy 146 Self-throttling 179 semiconductor chip 142, 148, 149, 156 set-associative cache 145 signal repeaters 200 smartphones 200, 211, 213 sociotechnical systems 42 Strategic Information Systems 50 Subscriber Identity Module (SIM) 205

T Telecommunications 4, 9

telecommunications services 73 telefax 200 telegram 200 telephone network 10, 15 time-division multiplexing (TMD) 80 topology 183, 184, 185, 186, 187, 188, 189 toroidal topology 186 Total Access Communication Systems (TACS) 203 transaction processing systems (TPS) 44 transport layer security (TLS) 228 Trojan 227

U Universal Mobile Telecommunications System (UMTS) 204

V Vehicular Ad-hoc Networks— VANETs 254 Virtual memory 138, 139, 141 virtual private network (VPNs) 234 Virus assaults 227

W Wavelength Division Multiplexing (WDM) 250 Web servers 141 wide-area networks (WAN) 75 Window, Icon, Menu, and Pointer (WIMP) interface 7 Wireless Equivalent Privacy (WEP) 231 wireless Local area networks (WLANs) 230

Index

Wireless Mesh Networks (WMNs) 249 wireless networking dependability 253 Wireless Protected Access (WPA) 231

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Wireless technology durability 253 workplace association systems 46 worm 227 write handling policy 146, 147