mod1 intro multicast

© 2008 Extreme Networks, Inc. All rights reserved. ExtremeXOS Implementing Multicast Routing (EIMR), Version 12.1. Part # DOC-01616.

Introduction to IP Multicasting

Student Objectives

Upon successful completion of this module, the student will be able to:

Describe IP multicast and its applications

Describe differences between broadcast and multicast traffic

Describe packet replication

List bandwidth and server load considerations for multicasting

List the range of IP addresses that are reserved for multicast

• List addresses reserved for link-local multicast addresses

• List addresses reserved for administratively scoped multicast addresses

Map an IP multicast address to a MAC address

Slide 2

Multicast Applications

Slide 3

IP Unicast and Broadcast

Slide 4

11001010 00001010 00001010 11111111198 10 10 255

subnet host

A

198.10.10.1

B

198.10.10.2

C

198.10.10.3

D

192.1.1.1L2

LAN

Routers forward unicast packets but block

broadcasts

IP Multicast

Multicast OperationMulticast data is received

by a router then forwarded out of each

interface towards member hosts

Receiver

Receiver

Source

Packet Replication

Slide 6

The difference between packet replication at the source versus replication at the network layer.

2

Source

12 3 4

1

3

4

Unicast Replication

Source

Multicast Replication

S1

S1

S1 S

1

S1

Bandwidth Considerations

Slide 7

Clients

1 20 40 60 80 100

0

2

4

6

8

10

12

14

Bandwidth Mbps

Unicast Video

Multicast

Unicast versus Multicast Bandwidth for Audio and Video

Unicast Audio

Server Load

Slide 8

Live video streaming server

Live video streaming server

Unicast IP Multicast IP

Many simultaneous requests for traffic can overload a

unicast server

Multicast Issues

Unreliable User Datagram Protocol (UDP)

Network must be multicast enabled

Multicast routers must maintain state information of active multicast groups which costs CPU processing time and memory

• Extreme Networks switches make fdb entries in hardware for every multicast stream.

• Multicasting has no effect on the forwarding capacity of Extreme Networks switches.

Slide 9

Ethernet Multicast MAC Address

Slide 10

00000001 00000000 01011110 0XXXXXXX XXXXXXXX XXXXXXXX

07 7 7 7 7 70 0 0 0 0

Broadcast / Multicast Bit (Bit 0)

Locally Administered address Bit (Bit 1)

01 00 5E XX XX XX

Multicast Group Addresses

Slide 11

Class D -- Multicast Address

224.0.0.0 through 239.255.255.255

1110XXXX XXXXXXXX XXXXXXXX XXXXXXXX

Multicast IP addressing uses the Class D IP address space. The address range is reserved by the IANA and

spans from 224.0.0.0 to 239.255.255.255

Address Mapping

Slide 12

24 bits 23 bits

01 00 5e 0

1110

Class D

5 lost bits

23 bits

28 bit multicast addressThe last 23 bits of a multicast IP address are mapped to the

MAC address

Performance Impact

Slide 13

1110XXXX X 0000001 00000001 00000001

Mapped to MAC address

224 - 239?

129 or 1 1 1

01 00 5E 01 01 01

224.1.1.1224.129.1.1225.1.1.1225.129.1.1

239.1.1.1239.129.1.1

Every multicast MAC address can denote any one of 32 IP addresses. This can have a performance impact

on receiving hosts.

Address Mapping Exercise

Calculate the Ethernet MAC address for the following IP Multicast addresses.

• 224.100.10.10

• 224.24.1.1

• 239.100.10.10

• 239.24.10.10

• 225.228.10.10

Slide 14

01 00 5e 0

1110

23 bits

IP multicast address

Ethernet multicast address

Link-Local Reserved Addresses

Slide 15

Address Usage

224.0.0.1 All Hosts

224.0.0.2 All Routers

224.0.0.3 Unassigned

224.0.0.4 DVMRP Routers

224.0.0.5 OSPF All Routers

224.0.0.6 OSPF Designated Routers

224.0.0.7 ST Routers

224.0.0.8 ST Hosts

224.0.0.9 RIP2 Routers

224.0.0.10 IGRP Routers

224.0.0.11 Mobile-Agents

224.0.0.12 DHCP Server/Relay Agent

224.0.0.13 All PIM Routers

224.0.0.14 RSVP-Encapsulation

224.0.0.15 All CBT Routers

224.0.0.16 Designated-SBM

224.0.0.17 All SBMS

224.0.0.18 VRRP

224.0.0.24 OSPF-TE

224.0.0.X

Not forwarded by routers

Additional Reserved Addresses

Slide 16

Address Usage

224.0.1.0 VMTP Managers Group

224.0.1.1 NTP-Network Time Protocol

224.0.1.2 SGI-Dogfight

224.0.1.3 Rwhod

224.0.1.6 NSS-Name Service Server

224.0.1.8 SUN NIS+ Information Service

224.0.1.20 Any Private Experiment

224.0.1.21 DVMRP on MOSPF

224.0.1.32 Mtrace

224.0.1.33 RSVP-encap-1

224.0.1.34 RSVP-encap-2

224.0.1.39 Cisco-RP-Announce

224.0.1.40 Cisco-RP-Discovery

224.0.1.52 Mbone-VCR-Directory

224.0.1.78 Tibco Multicast 1

224.0.1.79 Tibco Multicast 2

224.0.1.125 PolyCom Relay1

224.0.1.128 CNN

224.0.1.X

Forwarded by routers

The SSM Address Block

Source Specific Multicast (SSM) is an extension of IP Multicast

Multicast packets are forwarded "only" to receivers that have explicitly expressed interest in receiving packets from those specific multicast sources.

• Source-Specific Multicast Addresses Block: 232.0.0.0 to 232.255.255.255

• Addresses in the SSM block must not be used for other purposes.

Slide 17

Administratively Scoped Address

Slide 18

239.X.X.X

Private multicast address scheme, contained within a private network

Summary

You should now be able to:

Describe IP multicast and its applications

Describe differences between broadcast and multicast traffic

Describe packet replication

List bandwidth and server load considerations for multicasting

List the range of IP addresses that are reserved for multicast

• List addresses reserved for link-local multicast addresses

• List addresses reserved for administratively scoped multicast addresses

Map an IP multicast address to a MAC address

Slide 19


Review Questions


This presentation contains forward-looking statements that involve risks and uncertainties, including statements regarding our expectations as to products, trends and our performance. There can be no assurances that any forward-looking statements will be achieved, and actual results could differ materially from forecasts and estimates. For factors that may affect our business and financial results please refer to our filings with the Securities and Exchange Commission, including, without limitation, under the captions: “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and “Risk Factors,” which is on file with the Securities and Exchange Commission (http://www.sec.gov). We undertake no obligation to update the forward-looking information in this release.

© 2008 Extreme Networks, Inc. All rights reserved. ExtremeXOS Implementing Multicast Routing (EIMR), Version 12.1. Part # DOC-01616.© 2008 Extreme Networks, Inc. All rights reserved. ExtremeXOS Implementing Multicast Routing (EIMR), Version 12.1. Part # DOC-01616.

mod1 intro multicast

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