3Com Switch 7750 Configuration Guide

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MULTICAST OVERVIEW
n
“Router” or a router icon in this document refers to a router in a generic sense or
an Ethernet switch running a routing protocol. This will not be otherwise
described in this manual.
Multicast Overview With development of networks on the Internet, more and more interaction
services such as data, voice, and video services are running on the networks. In
addition, services highly dependent on bandwidth and real-time data interaction,
such as e-commerce, web conference, online auction, video on demand (VoD),
and tele-education have come into being. These services have higher requirements
for information security, legal use of paid services, and network bandwidth.
In the network, packets are sent in three modes: unicast, broadcast and multicast.
The following sections describe and compare data interaction processes in unicast,
broadcast, and multicast.
Information
Transmission in the
Unicast Mode
In unicast, the system establishes a separate data transmission channel for each
user requiring this information, and sends separate copy information to the user,
as shown in Figure 100:
Figure 100 Information transmission in the unicast mode
Assume that users B, D and E need this information. The source server establishes
transmission channels for the devices of these users respectively. As the
Source
Server
Receiver
Receiver
Receiver
Host A
Host B
Host C
Host D
Host E
Packets for Host B
Packets for Host D
Packets for Host E