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Multicast overview
NOTE:
This document focuses on the IP multicast technology and device operations. Unless otherwise stated,
the term
multicast
in this document refers to IP multicast.
Introduction to multicast
As a technique that coexists with unicast and broadcast, the multicast technique effectively addresses the
issue of point-to-multipoint data transmission. By enabling high-efficiency point-to-multipoint data
transmission over a network, multicast greatly saves network bandwidth and reduces network load.
By using multicast technology, a network operator can easily provide new value-added services, such as
live webcasting, web TV, distance learning, telemedicine, web radio, realtime video conferencing, and
other bandwidth-critical and time-critical information services.
Comparison of information transmission techniques
Unicast
In unicast transmission, the information source must send a separate copy of information to each host
that needs the information.
Figure 1 Unicast transmission
Source
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
IP network
In Figure 1, assume that Host B, Host D and Host E need the information. A separate transmission
channel must be established from the information source to each of these hosts.
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