Cisco Networkers

Citation preview

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

1

Deploying Scalable IP Multicast Session RST-220

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

3

Geekometer

Agenda

• IP Multicast Review • Configuring IP Multicast • Multicast Issues at Layer 2 • Multicast Scalability

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

4

PIM-DM Flood and Prune Initial Flooding

Source

(S, G) State created in every router in the network!

Multicast Packets

Receiver RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

5

PIM-DM Flood and Prune Pruning Unwanted Traffic

Source

Multicast Packets Prune Messages Receiver RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

6

PIM-DM Flood and Prune Results After Pruning

Source

(S, G) State still exists in every router in the network!

Multicast Packets

Flood and Prune process repeats every 3 minutes!!! RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

Receiver 7

PIM-SM Shared Tree Join

RP

(*, G) State created only along the Shared Tree.

(*, G) Join Shared Tree Receiver

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

8

PIM-SM Sender Registration

RP

Source

(S, G) State created only along the Source Tree.

Traffic Flow Shared Tree Source Tree (S, G) Register

(unicast)

Receiver

(S, G) Join

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

9

PIM-SM Sender Registration

RP

Source

Traffic Flow

(S, G) traffic begins arriving at the RP via the Source tree.

Shared Tree Source Tree (S, G) Register

(unicast)

RP sends a Register-Stop back to the first-hop router to stop the Register process.

(S, G) Register-Stop

(unicast)

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

Receiver

10

PIM-SM Sender Registration

RP

Source

Traffic Flow

Source traffic flows natively along SPT to RP.

Shared Tree Source Tree

From RP, traffic flows down the Shared Tree to Receivers. Receiver

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

11

PIM-SM SPT Switchover

RP

Source

Last-hop router joins the Source Tree.

Traffic Flow Shared Tree Source Tree (S, G) Join

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

Additional (S, G) State is created along new part of the Source Tree. Receiver

12

PIM-SM SPT Switchover

RP

Source

Traffic Flow Shared Tree Source Tree (S, G)RP-bit Prune

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

Traffic begins flowing down the new branch of the Source Tree. Receiver

Additional (S, G) State is created along along the Shared Tree to prune off (S, G) traffic.

13

PIM-SM SPT Switchover

RP

Source

(S, G) Traffic flow is now pruned off of the Shared Tree and is flowing to the Receiver via the Source Tree.

Traffic Flow Shared Tree Source Tree Receiver

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

14

PIM-SM SPT Switchover

RP

Source

(S, G) traffic flow is no longer needed by the RP so it Prunes the flow of (S, G) traffic.

Traffic Flow Shared Tree Source Tree (S, G) Prune

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

Receiver

15

PIM-SM SPT Switchover

RP

Source

(S, G) Traffic flow is now only flowing to the Receiver via a single branch of the Source Tree.

Traffic Flow Shared Tree Source Tree Receiver

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

16

Agenda

• IP Multicast Review • Configuring IP Multicast • Multicast Issues at Layer 2 • Multicast Scalability

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

17

PIM Configuration Steps • Enable Multicast Routing on every router • Configure every interface for PIM • Configure the RP (if using PIM-SM) Anycast/Static RP addressing RP address must be configured on every router Note: Anycast RP requires MSDP Using Auto-RP or BSR Configure certain routers as Candidate RP(s) All other routers automatically learn elected RP RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

18

Enabling Multicast on the Router

• Global Configuration Command ip multicast-routing

Enables IP multicast forwarding in the router Configure on EVERY router in the network

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

19

Which Mode—Sparse or Dense • Dense mode Flood and Prune behavior very inefficient Can cause problems in certain network topologies Creates (S, G) state in EVERY router Even when there are no receivers for the traffic Complex Assert mechanism Mixed control and data planes Results in (S, G) state in every router in the network Can result in non-deterministic topological behaviors No support for shared trees

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

20

PIM-DM Assert Problem Initial Flow Duplicate Traffic

Receiver

Receiver

Multicast Packets

Source RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

21

PIM-DM Assert Problem Sending Asserts Loser

Receiver

Receiver

Winner

Multicast Packets Assert Messages Source RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

22

PIM-DM Assert Problem Assert Loser Prunes Interface Loser

Receiver

Receiver

Winner

Multicast Packets

Source RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

23

PIM-DM Assert Problem Assert Winner Fails Traffic flow is cutoff until Prune times out on Assert Loser.

Loser

Receiver

Receiver

X Winner

Multicast Packets

Source RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

24

Potential PIM-DM Route Loop Normal Steady-State Traffic Flow

Source Interface previously Pruned by Assert Process

RPF Interface

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

25

Potential PIM-DM Route Loop Interface Fails

X Source This Router converges first

RPF Interface

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

26

Potential PIM-DM Route Loop New Traffic Flow

X Source But wait . . . This Router still hasn’t converged yet

Multicast Route Loop ! ! RPF Interface

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

27

Which Mode—Sparse or Dense • Sparse mode Must configure a Rendezvous Point (RP) Statically (on every Router) Using Auto-RP (Routers learn RP automatically) Using BSR (Routers learn RP automatically) Very efficient Uses Explicit Join model Traffic only flows to where it’s needed Separated control and data planes Router state only created along flow paths Deterministic topological behavior Scales better than dense mode Works for both sparsely or densely populated networks RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

28

Which Mode—Sparse or Dense

CONCLUSION Virtually all production networks should be configured to run in Sparse mode!

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

29

Enabling Multicast on an Interface • Interface Configuration Commands Enables multicast forwarding on the interface. Controls the interface’s mode of operation. ip pim dense-mode

Interface mode is set to Dense mode operation. ip pim sparse-mode

Interface mode is set to Sparse mode operation. ip pim sparse-dense-mode

Interface mode is determined by the Group mode. If Group is Dense, interface operates in Dense mode. If Group is Sparse, interface operates in Sparse mode.

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

30

Enabling Multicast on an Interface

• Multi-Layer Switching (MLS) Interface Configuration Commands Permits multicast to be switched in hardware. Catalyst 6500 MLS interface command mls ip multicast

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

31

Configure PIM on Every Interface Classic Partial Multicast Cloud Mistake src

no ip pim dense-mode

T1/E1

56K/64K ip pim dense-mode

X

We’ll just use the spare 56K line for the IP Multicast traffic and not the T1. RST-220

RPF Failure!!!!! Network Engineer

© 2001, Cisco Systems, Inc. All rights reserved.

rcvr 32

Group Mode vs. Interface Mode Common Misconception • Interface Mode controls Group Mode. “If I set all interfaces to ‘ip pim sparse-mode’, the router will always operate in Sparse mode and never fall back into Dense mode” Bzzzztt!!! I’m sorry, but that’s the incorrect answer Group mode is independent of interface mode Interface mode only controls how the interface operates Group mode is controlled by RP information!!!

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

33

Group Mode vs. Interface Mode • Avoid Group/Interface mode mismatches Group and Interface mode should be the same Otherwise you may get unwanted/unpredictable results

• Sparse-Dense interfaces always match the Group mode Should normally be used if running Auto-RP Permits Auto-RP groups to automatically run in Dense mode All other groups run in Sparse mode. (Assuming an RP is defined for all other groups) Can also be used for Sparse-only or Dense-only networks

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

34

Group Mode vs. Interface Mode • Let Group mode control Interface mode Use ‘ip pim sparse-dense-mode’ command Allows maximum flexibility No need to ever change interface configuration

• Control Group mode with RP info If RP info exists, Group = Sparse Therefore interface mode = Sparse for this group If RP info does not exist, Group = Dense Therefore interface mode = Dense for this group RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

35

Avoiding falling back to Dense Mode

To always guarantee Sparse mode operation (and avoid falling back to Dense mode), make sure that every router always knows of an RP for every group.

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

36

Configuring Rendezvous Points

• Auto-RP • Bootstrap Router (BSR) • Static RP’s • Anycast RP’s

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

37

Auto-RP Overview • All routers automatically learn RP address No configuration necessary except on: Candidate RPs Mapping Agents

• Makes use of Multicast to distribute info Two specially IANA assigned Groups used Cisco-Announce—224.0.1.39 Cisco-Discovery—224.0.1.40 These groups typically operate in Dense mode

• Permits backup RP’s to be configured Warning: Can fall back into Dense mode if misconfigured

• Can be used with Admin-Scoping RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

38

C-RP 1.1.1.1

C

Announce

MA B Announce

Announce

A

Announce

Announce

MA

D Announce

Announce

Auto-RP—From 10,000 Feet

Announce

C-RP 2.2.2.2

RP-Announcements multicast to the Cisco Announce (224.0.1.39) group Announce RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

39

MA

C-RP 1.1.1.1

C

Dis cov ery

A

Disc over y

MA

Dis cov ery

B Disc over y

Dis cov ery

Disc over y

Dis cov ery

Auto-RP—From 10,000 Feet

Disc over y

D

C-RP 2.2.2.2

RP-Discoveries multicast to the Cisco Discovery (224.0.1.40) group Discovery RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

40

Auto-RP Fundamentals • Candidate RPs Configured via global config command ip pim send-rp-announce scope [group-list acl]

Multicast RP-Announcement messages Sent to Cisco-Announce (224.0.1.39) group Sent every rp-announce-interval (default: 60 sec) RP-Announcements contain: Group Range (default = 224.0.0.0/4) Candidate’s RP address Holdtime = 3 x RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

41

Auto-RP Fundamentals • Mapping agents Configured via global config command ip pim send-rp-discovery [] scope

Receive RP-Announcements Select highest C-RP IP addr as RP for group range Stored in Group-to-RP Mapping Cache with holdtimes Multicast RP-Discovery messages Sent to Cisco-Discovery (224.0.1.40) group Sent every 60 seconds or when changes detected RP-Discovery messages contain: Contents of MA’s Group-to-RP Mapping Cache RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

42

Auto-RP Fundamentals • All Cisco routers Join Cisco-Discovery (224.0.1.40) group Automatic No configuration necessary Receive RP-Discovery messages Stored in local Group-to-RP Mapping Cache Information used to determine RP for group range RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

43

Configuring Rendezvous Points

• Auto-RP • Bootstrap Router (BSR) • Static RP’s • Anycast RP’s

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

44

BSR Overview • A single Bootstrap Router (BSR) is elected Multiple Candidate BSR’s (C-BSR) can be configured Provides backup in case currently elected BSR fails C-RP’s send C-RP announcements to the BSR C-RP announcements are sent via unicast BSR stores ALL C-RP announcements in the “RP-set” BSR periodically sends BSR messages to all routers BSR Messages contain entire RP-set and IP address of BSR Messages are flooded hop-by-hop throughout the network away from the BSR All routers select the RP from the RP-set All routers use the same selection algorithm; select same RP

• BSR cannot be used with Admin-Scoping RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

45

BSR—From 10,000 feet

G

PIMv2 Sparse Mode

F

BSR A

D

CRP Ad v (un ertis ica em en st) t

t en m e rtis ve st) d A ica RP (un C

C-RP

B

C

C-RP

E

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

46

BSR—From 10,000 feet

G BSR Msgs

PIMv2 Sparse Mode BSR Msgs

BSR

F BSR Msgs

A BSR Msgs

D

C-RP

B

C

C-RP

E BSR Msgs Flooded Hop-by-Hop RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

47

BSR Fundamentals • Candidate RPs Configured via global config command ip pim rp-candidate [group-list acl]

Unicast PIMv2 C-RP messages to BSR Learns IP address of BSR from BSR messages Sent every rp-announce-interval (default: 60 sec) C-RP messages contain: Group Range (default = 224.0.0.0/4) Candidate’s RP address Holdtime = 3 x

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

48

BSR Fundamentals • Bootstrap router (BSR) Receive C-RP messages Accepts and stores ALL C-RP messages Stored in Group-to-RP Mapping Cache w/holdtimes Originates BSR messages Multicast to All-PIM-Routers (224.0.0.13) group (Sent with a TTL = 1) Sent out all interfaces. Propagate hop-by-hop Sent every 60 seconds or when changes detected BSR messages contain: Contents of BSR’s Group-to-RP Mapping Cache IP Address of active BSR RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

49

BSR Fundamentals • Candidate bootstrap router (C-BSR) Configured via global config command ip pim bsr-candidate [priority ]

Determines IP address

Sets RP selection hash mask length

Sets the C-BSR priority (default = 0) C-BSR with highest priority elected BSR C-BSR IP address used as tie-breaker (Highest IP address wins) The active BSR may be preempted New router w/higher BSR priority forces new election RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

50

BSR Fundamentals • All PIMv2 routers Receive BSR messages Stored in local Group-to-RP Mapping Cache Information used to determine active BSR address Selects RP using Hash algorithm Selected from local Group-to-RP Mapping Cache All routers select same RP using same algorithm Permits RP-load balancing across group range

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

51

Auto-RP vs BSR • Auto-RP Easy to configure Supports Admin. Scoped Zones Works in either PIMv1 or PIMv2 Cisco networks Cisco proprietary

• BSR Easy to configure Does not support Admin. Scoped Zones Non-proprietary (PIMv2 networks only)

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

52

Configuring Rendezvous Points

• Auto-RP • Bootstrap Router (BSR) • Static RP’s • Anycast RP’s

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

53

Static RP’s • Hard-coded RP address When used, must be configured on every router All routers must have the same RP address RP fail-over not possible Exception: If Anycast RPs are used. (More on that later.) Group can never fall back into Dense mode.

• Command ip pim rp-address [group-list ] [override]

Optional group list specifies group range Default: Range = 224.0.0.0/4 (Includes Auto-RP Groups!!!!) Override keyword “overrides” Auto-RP information Default: Auto-RP learned info takes precedence

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

54

Configuring Rendezvous Points

• Auto-RP • Bootstrap Router (BSR) • Static RP’s • Anycast RP’s

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

55

Avoiding DM Fallback • Define an “RP-of-last-resort” Configure as a Static RP on every router Will only be used if all Candidate-RP’s fall Can be a dummy address Recommendation: Use lowest priority C-RP address Use ACL to avoid breaking Auto-RP ip pim rp-address 10 access-list 10 deny 224.0.1.39 access-list 10 deny 224.0.1.40 access-list 10 permit any RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

56

Anycast RP—Overview • Uses single statically defined RP address Two or more routers have same RP address RP address defined as a Loopback Interface Loopback address advertised as a Host route Senders and Receivers Join/Register with closest RP Closest RP determined from the unicast routing table Can never fall back to Dense mode Because RP is statically defined

• MSDP session(s) run between all RPs Informs RPs of sources in other parts of network RPs join SPT to active sources as necessary

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

57

Anycast RP—Overview

Src RP1

X RST-220

RP2

MSDP

A 10.1.1.1

Rec

Src

SA

Rec

© 2001, Cisco Systems, Inc. All rights reserved.

SA

B 10.1.1.1

Rec

Rec

58

Anycast RP—Overview

Src

RP2

A 10.1.1.1

B 10.1.1.1

X

RP1

Rec

RST-220

Src

Rec

© 2001, Cisco Systems, Inc. All rights reserved.

Rec

Rec

59

Anycast RP Configuration

RP1 A

MSDP

RP2 B

ip pim rp-address 10.1.1.1

ip pim rp-address 10.1.1.1

X

Y

Interface loopback 0 ip address 10.1.1.1 255.255.255.255

Interface loopback 0 ip address 10.1.1.1 255.255.255.255

Interface loopback 1 ip address 10.0.0.2 255.255.255.255 ! ip msdp peer 10.0.0.1 connect-source loopback 1 ip msdp originator-id loopback 1

Interface loopback 1 ip address 10.0.0.1 255.255.255.255 ! ip msdp peer 10.0.0.2 connect-source loopback 1 ip msdp originator-id loopback 1

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

60

Beginner’s Guide to IP Multicast RP/Mapping Agent A

B

PIM Sparse Mode C

On every router:

RP/Mapping Agent

D

ip multicast-routing ip pim rp-address group-list 10 access-list 10 deny 224.0.1.39 access-list 10 deny 224.0.1.40 access-list 10 permit all

On every interface:

ip pim sparse-dense-mode

On routers B and C:

ip pim send-rp-announce loopback0 scope ip pim send-rp-discovery loopback0 scope

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

61

Agenda

• IP Multicast Review • Configuring IP Multicast • Multicast Issues at Layer 2 • Multicast Scalability

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

62

L2 Multicast Frame Switching Problem: Layer 2 Flooding of Multicast Frames PIM

• Typical L2 switches treat multicast traffic as unknown or broadcast and must “flood” the frame to every port • Static entries can sometimes be set to specify which ports should receive which group(s) of multicast traffic

Multicast M

• Dynamic configuration of these entries would cut down on user administration

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

63

L2 Multicast Frame Switching Solution 1: IGMPv1-v2 Snooping • Switches become “IGMP” aware • IGMP packets intercepted by the NMP or by special hardware ASICs

PIM

Requires special hardware to maintain throughput

• Switch must examine contents of IGMP messages to determine which ports want what traffic IGMP membership reports IGMP leave messages

IGMP

• Impact on low-end Layer-2 switches: Must process ALL Layer 2 multicast packets Admin. load increases with multicast traffic load Generally results in switch Meltdown Meltdown!!!

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

IGMP 64

Typical L2 Switch— 1st Join Router A

LAN Switch

IGMP Report 224.1.2.3

1 (IGMP Snooping Enabled)

Switching 0 Engine

CPU

CAM Table 2 MAC Address

4

5

Ports

Host 1 RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 2

Host 3

Host 4 65

Typical L2 Switch— 1st Join Router A 1 (IGMP Snooping Enabled)

LAN Switch

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

4

5

Ports 0,1,2

Entry Added RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 1

Host 2

Host 3

Host 4 66

Typical L2 Switch— 2nd Join Router A

LAN Switch

IGMP Report 224.1.2.3

1 (IGMP Snooping Enabled)

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

4

5

Ports 0,1,2

Host 1 RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 2

Host 3

Host 4 67

Typical L2 Switch— 2nd Join Router A

LAN Switch

1 (IGMP Snooping Enabled)

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

4

5

Ports 0,1,2 ,5

Host 1

Port Added RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 2

Host 3

Host 4 68

Typical L2 Switch Meltdown! 1.5Mbps !!! Choke, Gasp, Wheeze!!

LAN Switch

Router A 1 (IGMP Snooping Enabled)

Switching 0 Engine

CPU CPU

1.5Mbps MPEG Video

CAM Table 2 MAC Address 0100.5e01.0203

3

5

Ports 0,1,2 ,5

Host 1 Host 2 (MPEG Server) RST-220

4

© 2001, Cisco Systems, Inc. All rights reserved.

Host 3

Host 4 69

L3 Aware Switch

Router A

LAN Switch

CPU

1 (IGMP Snooping Enabled)

Switching Engine 0 (w/L3 ASICs)

CAM Table 2 MAC Address 0100.5exx.xxxx

L3 IGMP

4

5

Ports 0

IGMP Processing Entry RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 1

Host 2

Host 3

Host 4 70

L3 Aware Switch 1st Join Router A

LAN Switch

CPU

1 (IGMP Snooping Enabled)

Switching Engine 0 (w/L3 ASICs) IGMP Report 224.1.2.3

CAM Table 2 MAC Address 0100.5exx.xxxx 0100.5e01.0203

L3 IGMP !IGMP

4

5

Ports 0 1,2

Host 1 RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 2

Host 3

Host 4 71

L3 Aware Switch 2nd Join Router A

LAN Switch

CPU

IGMP Report 224.1.2.3

1 (IGMP Snooping Enabled)

Switching Engine 0 (w/L3 ASICs)

CAM Table 2 MAC Address 0100.5exx.xxxx 0100.5e01.0203

L3 IGMP !IGMP

4

5

Ports 0 1,2 ,5

Port Added RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 1

Host 2

Host 3

Host 4 72

L3 Aware Switch

Ahhh, That’s more like it!

LAN Switch

CPU

Router A

1 (IGMP Snooping Enabled)

Switching Engine 0 (w/L3 ASICs) 1.5Mbps MPEG Video

CAM Table 2 MAC Address 0100.5exx.xxxx 0100.5e01.0203

L3 IGMP !IGMP

4

5

Ports 0 1,2 ,5

Host 1 RST-220

3

© 2001, Cisco Systems, Inc. All rights reserved.

Host 2

Host 3

Host 4 73

L2 Multicast Frame Switching Solution 2: CGMP—Cisco Group Multicast Protocol • Runs on both the switches and the router

PIM

• Router sends CGMP multicast packets to the switches at a well known multicast MAC address: 0100.0cdd.dddd

• CGMP packet contains : Type field—Join or Leave MAC address of the IGMP client Multicast address of the group

CGMP Commands

IGMP

• Switch uses CGMP packet info to add or remove a Layer-2 entry for a particular multicast MAC address RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

74

CGMP Basics

IGMP Report Dst MAC = 0100.5e01.0203 Src MAC = 0080.c7a2.1093 Dst IP = 224.1.2.3 Src IP = 192.1.1.1 IGMP Group = 224.1.2.3

CGMP Join 1/1

5/1

(a) RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

1/1

USA = 0080.c7a2.1093 GDA = 0100.5e01.0203

5/1

(b) 75

CGMP 1st Join Router A

IGMP Report 224.1.2.3

1 Simple LAN Switch

Switching 0 Engine

CPU

CAM Table 2 MAC Address

3

4

5

Ports

Host 1

Host 2

Host 3

Host 4

0080.c7a2.1093 RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

76

CGMP 1st Join Router A 1 Simple LAN Switch

Switching 0 Engine

CPU

CGMP Join USA 0080.c7a2.1093 GDA 0100.5e01.0204

CAM Table 2 MAC Address

3

4

5

Ports

Host 1

Host 2

Host 3

Host 4

0080.c7a2.1093 RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

77

CGMP 1st Join Router A 1 Simple LAN Switch

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

4

5

Ports 1,2

Entry Added RST-220

3

Host 1

Host 2

Host 3

Host 4

0080.c7a2.1093

© 2001, Cisco Systems, Inc. All rights reserved.

78

CGMP 2nd Join Router A

IGMP Report 224.1.2.3

1 Simple LAN Switch

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

3

4

5

Ports 1,2

Host 1

Host 2

Host 3

Host 4 0080.c7b3.2174

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

79

CGMP 2nd Join Router A 1 Simple LAN Switch

Switching 0 Engine

CPU

CGMP Join USA 0080.c7b3.2174 GDA 0100.5e01.0204

CAM Table 2 MAC Address 0100.5e01.0203

3

4

5

Ports 1,2

Host 1

Host 2

Host 3

Host 4 0080.c7b3.2174

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

80

CGMP 2nd Join Router A 1 Simple LAN Switch

Switching 0 Engine

CPU

CAM Table 2 MAC Address 0100.5e01.0203

4

5

Ports 1,2 ,5

Host 1

Port Added RST-220

3

Host 2

Host 3

Host 4 0080.c7b3.2174

© 2001, Cisco Systems, Inc. All rights reserved.

81

CGMP No Load on Switch Router A 1 Simple LAN Switch

Switching 0 Engine

CPU

1.5Mbps MPEG Video

CAM Table 2 MAC Address 0100.5e01.0203

3

5

Ports 1,2 ,5

Host 1 Host 2 (MPEG Server) RST-220

4

© 2001, Cisco Systems, Inc. All rights reserved.

Host 3

Host 4 82

L2 Multicast Frame Switching • Impact of IGMPv3 on IGMP Snooping IGMPv3 Reports sent to separate group (224.0.0.22) Switches listen to just this group. Only IGMP traffic—no data traffic. Substantially reduces load on switch CPU Permits low-end switches to implement IGMPv3 Snooping No Report Suppression in IGMPv3 Enables individual member tracking IGMPv3 supports Source-specific Includes/Excludes Permits (S,G) state to be maintained by switch Currently not implemented by any switches May be necessary for full IGMPv3 functionality RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

83

Summary—Frame Switches • IGMP snooping Switches with Layer 3 aware Hardware/ASICs High-throughput performance maintained Increases cost of switches Switches without Layer 3 aware Hardware/ASICs Suffer serious performance degradation or even Meltdown! Meltdown Shouldn’t be a problem when IGMPv3 is implemented

• CGMP Requires Cisco routers and switches Can be implemented in low-cost switches RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

84

Design Issue—Core Switch Video Server

Router A

7500 1.5MB MPEG Video Streams

Holy Multicast, Batman!! 3MB of unwanted data! (Choke, gasp, wheeze!)

Unnecessary Multicast Traffic !!!

T1 2500

Catalyst 5000

Router B

7500

Unnecessary Multicast Traffic !!!

Receiver Group 1 RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

WAN

Router D

7500

Router C

Receiver Group 2 85

Design Issue—Core Switch Video Server

Router A

7500 1.5MB MPEG Video Streams

Catalyst 5000

Router B

7500

Unnecessary Multicast Traffic !!!

Receiver Group 1 RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

T1 2500

WAN

Router-D

Move WAN Router to Another VLAN Segment Inside of Catalyst 5000

7500

Router C

Receiver Group 2 86

Design Issue—Core Switch • Problem Routers send PIM Join/Prunes at Layer 3 IGMP Join/Leaves not sent by routers Other routers on VLAN can override Prune Switches operate at Layer 2 Use IGMP Snooping to constrain multicast Must assume routers want all multicast traffic Need new Layer 2 Join/Prune mechanism Permits routers to send Join/Prunes to switch

• Solution: (RGMP) Router Group Management Protocol

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

87

Router Group Management Protocol • Runs on Core Routers and Switches Routers Identify themselves via RGMP Hello/Bye msg. Send special Layer 2 (*,G) Join/Prune messages Switches Do not forward multicast traffic to router ports until specifically requested

• Limitations: Only works with PIM-SM/PIM-SSM No Hosts permitted on VLAN Routers cannot detect sources since multicast flooding to routers is off by default RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

88

RGMP Initially, multicast forwarding to routers is disabled RGMP Switch

Switching 0 Engine

CPU

CAM Table 1 MAC Address 0100.5exx.xxxx

RST-220

Ports 0

© 2001, Cisco Systems, Inc. All rights reserved.

A

2 B

3 C

4 D

89

RGMP 1st Router receives a PIM (*,G) Join from downstream RGMP Switch

Switching 0 Engine

CPU

RGMP Join 0100.5e01.0101

CAM Table 1 MAC Address 0100.5e01.0101 0100.5exx.xxxx 0100.5exx.xxxx

Ports 2 0 0 Entry Added

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

A

2 B

3 C

4 D

PIM (*, 224.1.1.1) Join

90

RGMP 2nd Router receives a PIM (*,G) Join from downstream RGMP Switch

Switching 0 Engine

CPU

RGMP Join 0100.5e01.0101

CAM Table 1 MAC Address 0100.5e01.0101 0100.5exx.xxxx

Ports 2,4 0

Port Added

RST-220

A

2 B

3 C

4 D

PIM (*, 224.1.1.1) Join

© 2001, Cisco Systems, Inc. All rights reserved.

91

RGMP Multicast is constrained to routers B and D RGMP Switch

Switching 0 Engine

CPU

CAM Table 1 MAC Address 0100.5e01.0101 0100.5exx.xxxx

Ports 2,4 0

A

2 B

3 C

4 D

Source RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

92

Agenda

• IP Multicast Review • Configuring IP Multicast • Multicast Issues at Layer 2 • Multicast Scalability

RST-220

© 2001, Cisco Systems, Inc. All rights reserved.

93

Multicast Application Categories • One-to-Many Applications Video, TV, Radio, Concerts, Stock Ticker, etc.

• Few-to-Few Applications Small (