© 1999, Cisco Systems, Inc. 9-1 Chapter 10 Controlling Campus Device Access Chapter 9 Multicast...

© 1999, Cisco Systems, Inc. 9-1

Chapter 10

Controlling Campus Device Access

Chapter 9Chapter 9

Multicast OverviewMulticast OverviewMulticast OverviewMulticast Overview

© 1999, Cisco Systems, Inc. 10-1

© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—9-2

Objectives

Upon completion of this chapter, you will be able to perform the following tasks:• Match the correct transmission method to the appropriate

definition

• Reconcile a set of IP multicast addresses to Ethernet addresses

• Describe the functional differences between IGMPv1 and IGMPv2

• Describe the setup procedure in which routers and switches facilitate multicast traffic

• Identify the appropriate multicast routing protocol for a given network requirement


Multicast Overview

• Multicast overview

• Addressing in a multicast environment

• Managing multicast traffic in a campus network

• Routing multicast traffic

• Multicast routing protocols

In this chapter, we discuss the following topics:


Multicast Overview

In this section, we discuss the following topics:• Multicast Overview

– Unicast Traffic

– Broadcast Traffic

– Multicast Traffic

– IP Multicast Characteristics• Addressing in a Multicast Environment

• Managing Multicast Traffic in a Campus Network

• Routing Multicast Traffic

• Multicast Routing Protocols


Unicast Traffic

VideoServer

Receiver Receiver Receiver Not AReceiver

• Unicast applications send one copy of each packet to every client unicast address


1.5 Mb x 3 = 4.5 Mb

1.5 Mb x 2 = 3 Mb 1.5 Mb x 1 = 1.5 Mb

1.5 Mb x 1 = 1.5 Mb

1.5 Mb x 1 = 1.5 Mb1.5 Mb x 1 = 1.5 Mb

Unicast Traffic (cont.)Unicast Traffic (cont.)

VideoServer



Unicast Traffic (cont.)

. . .

1.5 Mb x 100 = 150 Mb

1.5 Mb x 100 = 150 Mb

1.5 Mb x 100 = 150 Mb

Receiver 1 Receiver 100

1.5 Mb x 100 = 150 Mb

VideoServer


Broadcast Traffic

I don’t want to receive this video stream, but my CPU still needs to process that 1.5 MB

of data!

1.5 Mb

1.5 Mb 1.5 Mb

1.5 Mb 1.5 Mb 1.5 Mb 1.5 Mb

VideoServer


• Hosts not using a multimedia application must still process the broadcast traffic


Multicast Traffic

1.5 Mb

1.5 Mb 1.5 Mb

1.5 Mb 1.5 Mb 1.5 Mb

VideoServer


• A multicast server sends out a single data stream to multiple clients using a special broadcast address


IP Multicast Characteristics

• Transmits to a host group

• Delivers with “best effort” reliability

• Supports dynamic membership

• Supports diverse numbers and locations

• Supports membership in more than one group

• Supports multiple streams host


Multicast Overview


• Addressing in a Multicast Environment

– IP Multicasting Address Structure

–Mapping MAC addresses to IP Multicast Addresses


• Routing Multicast Traffic• Multicast Routing Protocols


Multicast IP Address Structure

• A Class D address consists of 1110 as the higher order bits in the first octet, followed by a 28-bit group address.

• Class D addresses range from 224.0.0.0 through 239.255.255.255. The high-order bits in the first octet identify this 224-base address.

Multicast Group ID1 1 01Class D

28 bits


Mapping IP Multicast to Ethernet Addresses

0000000100000000 011011110

Class D IP Address

48-Bit Ethernet Address

1110

0 7 8 15 16 23 24 31

Not

Used

Low-Order 23 Bits of Multi-cast

Group ID Copied to Ethernet Address

01 00 5E

224


0 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01

224 10 8 5- - -

1 1 1 0 0 0 0 0

01 00- -

Multicast Address:

Ethernet Address:

Mapping Multicast to Ethernet Addresses: Example 1


5E 0A- 08- 05-

0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1



1 0 0 0 1 0 10 0 0 0 0 1 0 00 0 0 0 0 0 1 01

224 10 8 5- - -

1 1 1 0 1 0 1 0

01 00- -

Multicast Address:

Ethernet Address:

5E 0A- 08- 05-

0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1


Multicast Overview




– Subscribing and Maintaining Groups

– IGMPv1

– IGMPv2

– Handling Multicast Trafficin the Switch

• Routing Multicast Traffic



Facilitating Multimedia Traffic

• Coordinate multicast operations of network devices

• Establish a path between between source and destination

• Forward multicast traffic through the network

Source

Destination


Group Membership

Host A Host B Host C

Host DI’m not a

member so I won’t respond.

I’m a member so I will

respond.


respond.


respond.

Are there any members for Group XYZ?

• Multicast uses query and report messages to

establish and maintain group membership


IGMPv1—Packet Format

• Version Code Version = 1

• Type:– 1 = Host Membership Query– 2 = Host Membership Report

• Group Address:– Multicast Group Address

7 15 23 31

Ver Unused ChecksumType

4

Group Address


IGMPv1—Joining a Group

• Joining member sends report to 224.1.1.1 immediately upon joining

H3

224.1.1.1

Report

IGMPv1

H1 H2


IGMPv1—General Queries

• The router periodically sends general queries to 224.0.0.1 to determine memberships

General Query to 224.0.0.1

IGMPv1 MulticastRouter

H3H1 H2


IGMPv1—Maintaining a Group

IGMPv1

#1#1 Router sends periodic queries#2#2 One member per group per subnet report

224.1.1.1

#2#2

#3#3 Other members suppress reports

224.1.1.1

X#3#3

H3H1 H2

Query to224.0.0.1 #1#1

Report Suppressed


• Router sends periodic queries• Hosts silently leave group• Router continues sending periodic queries

Query to224.0.0.1

IGMPv1—Leaving a Group

IGMPv1

• No reports for group received by router• Group times out

H3H1 H2


IGMPv2—Packet Format

• Multiple message types

• Max. Resp. Time– Max. time before sending a responding report in 1/10 secs (default = 10 secs)

• Group Address:– Multicast Group Address (0.0.0.0 for General Queries)

Max. Resp. Time Checksum

Group Address

Type

7 15 31


IGMPv2—Joining a Group

• Joining member sends report to 224.1.1.1 immediately upon joining (same as IGMPv1)

224.1.1.1

Report

172.16.41.141

H1

172.16.41.1 172.16.41.2 172.16.41.3

RTR141

H3H2


IGMPv2—Joining a Group (cont.)

172.16.41.141

H1

172.16.41.1 172.16.41.2 172.16.41.3

RTR141

E0

H2 H3

RTR141>show ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:02:31 172.16.41.2


IGMPv2—Querier Election

• Intially all routers send out a query

• Router with lowest IP address “elected” querier

• Other routers become non-queriers

IGMPv2

H1 H2 H3

Query Query

IGMP QuerierIGMP

Non-Querier172.16.41.141

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.143


IGMPv2—Querier Election

• Locating the designated querier router

RTR141>show ip igmp interface e0Ethernet0 is up, line protocol is up Internet address is 172.16.41.141, subnet mask is 255.255.255.0 IGMP is enabled on interface Current IGMP version is 2 CGMP is disabled on interface IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Inbound IGMP access group is not set Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 172.16.41.141 (this system) IGMP querying router is 172.16.41.141 (this system) Multicast groups joined: 224.0.1.40 224.2.127.254


IGMPv2—Maintaining a Group

Router sends periodic queries

Query

IGMPv2

• One member per group per subnet report

224.1.1.1

Report

• Other members suppress reports

224.1.1.1

SuppressedX

H2 H3

172.16.41.141

172.16.41.1 172.16.41.2 172.16.41.3

H1


IGMPv2—Leaving a Group

H1 H2 H3

RTR141

• IGMP state in RTR141 before leave

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.141

RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:02:31 172.16.41.2


IGMPv2—Leaving a Group (cont.)

• H2 leaves group; sends leave message

H1 H2 H3H2

Leave to224.0.0.2

224.1.1.1

#1#1

• Router sends group-specific query

Group SpecificQuery to 224.1.1.1

#2#2

• A remaining member host sends report;

Report to224.1.1.1

224.1.1.1

#3#3

group remains active

RTR141

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.141

#1#1

#2#2

#3#3



H1 H2 H3

RTR141

• IGMP state in RTR141 after H2 leaves

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.141

RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:01:47 172.16.41.3


IGMPv2—Leaving a Group (Cont.)

• Last host leaves group; sends Leave message

H1 H3H3

Leave to224.0.0.2

224.1.1.1

#1#1

• Router sends group-specific query;

Group-specificQuery to 224.1.1.1

#2#2

no report is received, group times out

H2

#1#1

#2#2

RTR141

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.141



RTR141>sh ip igmp groupIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter

H1 H2

RTR141

• IGMP state in RTR141 after H3 leaves

172.16.41.1 172.16.41.2 172.16.41.3

172.16.41.141

H3


Multicast Overview



• Managing Multicast Traffic in a Campus Network Routing

–GCMP• Routing Multicast Traffic



Layer 2 Multicast

I don’t want to receive this video stream, but my CPU still needs to process that 1.5 MB

of data!

1.5 Mb

1.5 Mb 1.5 Mb

1.5 Mb 1.5 Mb 1.5 Mb 1.5 Mb

Receiver Receiver Receiver Not A Receiver

VideoServer


CGMP

0000.0c12.3456

IGMP Join Request 0000.0c12.3456 would like to join multicast

group XYZ.

0000.0c12.3456 would like to join multicast

group XYZ.

• CGMP is a Cisco-developed protocol

• CGMP allows Catalyst switches to learn about the existence of multicast clients from Cisco routers


CGMP (cont.)

Device 0000.0c12.3456wants to join

Group 234.10.8.5

Device 0000.0c12.3456wants to join

Group 234.10.8.5

CGMP Message

0000.0c12.3456

CGMP Message

I have no knowledge of

device 0000.0c12.3456

I have no knowledge of

device 0000.0c12.3456

I can reach device0000.0c12.3456

out of Port 1. I will add 234.10.8.5 to my switch

forwarding table.


Multicast Overview




• Routing Multicast Traffic–Routing Protocols

–Distribution Trees

–Scope of Delivery• Multicast Routing Protocols


Unicast Routing

Host A172.13.107.5

Network172.13.0.0

Network172.45.0.0

Server B172.45.37.10

172.13.107.5 172.45.37.10

DestinationAddress

SourceAddress


Multicast Routing

Host A172.13.107.5

Host B172.45.37.10

Network172.45.0.0

Network172.45.0.0

Network172.6.0.0

B

I don’t have anyclients in group 234.10.8.5 but Router B has.

I don’t have anyclients in group 234.10.8.5 but Router B has. A

01-00-5e-10-8-5234.10.8.5Multimedia Stream for Group XYZ


Distribution Trees

I am a member of Group XYZ.




I am NOT member of Group XYZ.

I am NOT member of Group XYZ.

Packet Duplicationat This Point Only


Source Distribution Tree

Server 1Group ABC

Host 1Group ABC

A B C D

E F G

• Source-specific trees use the shortest path from the sender to each receiver

Host 2Group ABC

Host 3Group ABC


Source Distribution Tree (cont.)

Server 1Group ABC

Host 1Group ABC

A B C D

E F G

Host 2Group ABC

• If the link between the local router and the neighboring router is not the shortest path, the packet is not forwarded on that link


Shared Distribution Tree

Source 1

A B C D

E F G

Source 2

• Multicast traffic for each group is sent and received over the same delivery tree, regardless of the source


Scope of Delivery

Acme Manufacturing, Inc.

Human Resources

EngineeringPersonnel Payroll

TTL Threshold = 15

TTL Threshold = 31TTL Threshold = 127

• Assigning a TTL threshold to each interface limits the scope of multicast transmission


Time To Live Threshold

E0 E1

E2E3

E1: (TTL Threshold = 16)E2: (TTL Threshold = 0)E3: (TTL Threshold = 64)

Multicast Packetw/TTL=24

Packet Not Forwarded!


Multicast Overview




• Routing Multicast Traffic• Multicast Routing Protocols

–Dense Mode Routing Protocols

–Sparse Mode Routing Protocols


Dense Mode Routing Protocols

• Densely distributed receivers• Plentiful bandwidth• Majority of routers forwarding multicast traffic• Protocols– DVMRP– MOSPF– PIM DM


Distance Vector Multicast Routing Protocol

This is amulticast packet for Group XYZ.

This is amulticast packet for Group XYZ.

• Reverse path flooding floods a packet on all paths except the path leading back to the source.


Multicast Open Shortest Path First (MOSPF)

I have a newmember for Group XYZ.

I have a newmember for Group XYZ.

Source 1

Group XYZ

A B C D

E F G

Group XYZ

DesignatedRouter

Router F has a new member for Group XYZ.

Router F has a new member for Group XYZ.

• Uses OSPF link-state advertisements to construct distribution trees

• Trees must be recomputed when a link-state change occurs


Protocol Independent Multicast Dense Mode (PIM DM)

This is a multicast packet for Group XYZ.

This is a multicast packet for Group XYZ.

• Protocol-independent means the protocol is not dependent

on any unicast routing protocol

I have nomembers forGroup XYZ.

I have nomembers forGroup XYZ.

Prune Message


Sparse-Mode Routing Protocols

• Sparsely distributed receivers• Limited bandwidth• Add branches as a result of

explicit joins• Protocols– CBT– PIM SM


Core-Based Tree

Core Router

I have a memberwho wants to join

Group XYZ.

I have a memberwho wants to join

Group XYZ.

AB

C D E

Join Message

Source 1

Join Message

Source 2

• CBT protocol constructs a single tree shared by all members of the group

• A CBT shared tree has a core router that is used to construct the tree

I am already abranch of that tree.I will acknowledge the join message.

I am already abranch of that tree.I will acknowledge the join message.


Protocol Independent Multicast Sparse Mode (PIM SM)

Rendezvous Point

I want to start receiving

multicast packetsto Group XYZ

I want to start receiving


A

C

BD

Optimized Path

InitialPath

InitialPath

I want to start sending


I want to start sending


InitialPath


Written ExerciseWritten Exercise

• Following is the written exercise for this chapter


Summary

• Multicast is the most efficient method for data transmission to multiple client.

• IP Multicast employs special addressing.

• IGMP allows clients to join and leave multicast groups.

• CGMP allows switches to handle multicast traffic.

• Special routing protocols are used to route multicast traffic through the network.

• Multicast routing protocols are divided into two categories.


Review

• Discuss the three types of transmission methods and the effect each one has on network bandwidth.

• Explain how routers and switches handle the impact of multicast addressing techniques.

• Discuss different multicast routing protocols and identify which ones are most effective in a campus network.

© 1999, Cisco Systems, Inc. 9-1 Chapter 10 Controlling Campus Device Access Chapter 9 Multicast...

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