3Com Switch 8800 Configuration Guide Chapter 23 IP Multicast Overview
23-1
Chapter 23 IP Multicast Overview Note:
An Ethernet switch functions as a router when it runs IP multicast protocol. A router that
is referred to in the following represents a generalized router or a layer 3 Ethernet
switch running IP multicast protocol.
23.1 IP Multicast Overview
23.1.1 Problems with Unicast/Broadcast
The constant development of the Internet and increasing interaction of versatile data,
voice and vedio information over the network, has promoted the emergence of new
services like e-commerce, network conference, online auction, vedio on demand (VoD),
and tele-education. These services require higher information security and greater
rewards.
I. Data transmission in unicast mode
In unicast mode, every user that needs the inforamtion receives a copy through the
channels the system separately establishes for them. See Figure 23-1.
Server
Unicast
User A
User B
User C
User D
User E
Figure 23-1 Data transmission in unicast mode
Suppose that Users B, D, and E need the information, the information source Server
establishes transmision channels with every of them. Since the traffic in transmission
increases with the number of users, excessive copies of the information would spread