33
IP M
ULTICAST
This chapter covers the following topics:
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IP Multicast Overview
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IP Multicast Addresses
■
IP Multicast Features
■
IP Multicast Routing Protocols
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IP Multicast Packet Forwarding
■
IP Multicast Application
IP Multicast Overview
When the destination addresses carrying information (data, voice, and video)
transmit with only a few subscribers in the network, multiple transmission
methods such as unicast and broadcast can be employed. Unicast transmission
means establishing a separate data transmission channel for each subscriber, while
broadcast transmissionmeans sending the message to all the subscribers in the
network no matter whether they need it or not. If 200 subscribers in network
require receiving the same message, traditionally there are two solutions for this.
One is to send such message 200 times to ensure that all the subscribers are able
to get it. The other one is to transmit the data within the whole network to enable
subscribers to get the necessary data directly from the network by adopting the
broadcast method.
Using the unicast method to transmit to 200 subscribers results in wasted
bandwidth. Using the broadcast method risks information security and
confidentiality. IP multicast technology solves both of these problems. The
multicast source sends the information only once. The transmitted information is
duplicated and distributed continuously at key network nodes. In this way, the
information can be sent accurately and efficiently to each subscriber who requires
it.
In simple terms, IP multicast is a bandwidth-saving technology. It sends a single
information flow to several receivers simultaneously to reduce network traffic. In
case a router does not support multicast in the network, the router can employ
the tunnel method to encapsulate the multicast packets in the unicast packets,
and send them to the adjacent multicast router. Adjacent multicast routers drop
the unicast IP header, and then continue the multicast transmission to avoid
causing a change to the network structure.
IP Multicast Addresses
IP multicasting uses Class D addressing. Each multicast address stands for a
multicast group, not for a host. Because the maximum four-digit number of a
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Страница 1: ...http www 3com com 3Com Router Configuration Guide Published March 2004 Part No 10014299 ...
Страница 4: ...VPN 615 RELIABILITY 665 QOS 681 DIAL UP 721 ...
Страница 6: ...2 ABOUT THIS GUIDE ...
Страница 7: ...I GETTING STARTED Chapter 1 3Com Router Introduction Chapter 2 3Com Router User Interface ...
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Страница 16: ...12 CHAPTER 1 3COM ROUTER INTRODUCTION ...
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Страница 60: ...56 CHAPTER 3 SYSTEM MANAGEMENT ...
Страница 88: ...84 CHAPTER 5 CONFIGURING NETWORK MANAGEMENT RouterA interface ethernet 0 RouterA Ethernet0 rmon promiscuous ...
Страница 98: ...94 CHAPTER 6 DISPLAY AND DEBUGGING TOOLS ...
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Страница 114: ...110 CHAPTER 8 INTERFACE CONFIGURATION OVERVIEW ...
Страница 158: ...154 CHAPTER 10 CONFIGURING WAN INTERFACE ...
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Страница 188: ...184 CHAPTER 13 CONFIGURING PPPOE CLIENT ...
Страница 192: ...188 CHAPTER 14 CONFIGURING SLIP Router ip route static 0 0 0 0 0 0 0 0 10 110 0 1 ...
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Страница 292: ...288 CHAPTER 18 CONFIGURING HDLC Enable HDLC packet debugging debugging hdlc packet interface type number ...
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Страница 330: ...326 CHAPTER 20 CONFIGURING IP ADDRESS ...
Страница 362: ...358 CHAPTER 21 CONFIGURING IP APPLICATION ...
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Страница 482: ...478 CHAPTER 30 CONFIGURING BGP ...
Страница 494: ...490 CHAPTER 31 CONFIGURING IP ROUTING POLICY ...
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Страница 514: ...510 CHAPTER 34 CONFIGURING IGMP ...
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Страница 532: ...528 CHAPTER 37 CONFIGURING TERMINAL ACCESS SECURITY ...
Страница 550: ...546 CHAPTER 38 CONFIGURING AAA AND RADIUS PROTOCOL ...
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