Multicast Overview; Introduction To Multicast - 3Com Switch 4800G 24-Port Configuration Manual

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Introduction to
Multicast
Comparison of
Information
Transmission Techniques
M
ULTICAST
n
This manual chiefly focuses on the IP multicast technology and device operations.
Unless otherwise stated, the term "multicast" in this document refers to IP
multicast.
As a technique coexisting with unicast and broadcast, the multicast technique
effectively addresses the issue of point-to-multipoint data transmission. By
allowing high-efficiency point-to-multipoint data transmission over a network,
multicast greatly saves network bandwidth and reduces network load.
With the multicast technology, a network operator can easily provide new
value-added services, such as live Webcasting, Web TV, distance learning,
telemedicine, Web radio, real-time videoconferencing, and other bandwidth- and
time-critical information services.
Unicast
In unicast, the information source sends a separate copy of information to each
host that needs the information, as shown in Figure 162.
Figure 162 Unicast transmission
Source
Server
Packets for Host B
Packets for Host D
Packets for Host E
Assume that Hosts B, D and E need this information. The information source
establishes a separate transmission channel for each of these hosts.
O
VERVIEW
Receiver
Host A
Receiver
Host B
Host C
Receiver
Host D
Host E