Operation Manual – Multicast
H3C S3600 Series Ethernet Switches-Release 1510 Chapter 1 Multicast Overview
1-4
In the multicast mode, network components can be divided in to the following roles:
z An information sender is referred to as a multicast source.
z Multiple receivers receiving the same information form a multicast group. Multicast
group is not limited by physical area.
z Each receiver receiving multicast information is a multicast group member.
z A router providing multicast routing is a multicast router. The multicast router can
be a member of one or multiple multicast groups, and it can also manage
members of the multicast groups.
For a better understanding of the multicast concept, you can assimilate a multicast
group to a TV channel. A TV station is a multicast source. It sends data to the channel.
The audiences are the receivers. After turning on a TV set (a computer), they can select
a channel to receive a program (namely join a group) and then watch the program.
Therefore, a multicast group should be an agreement between the sender and the
receivers, like the frequency of a channel.
Caution:
A multicast source does not necessarily belong to a multicast group. A multicast source
sends data to a multicast group, and it is not necessarily a receiver. Multiple multicast
sources can send packets to the same multicast group at the same time.
There may be routers that do not support multicast on the network. A multicast router
encapsulates multicast packets in unicast IP packets in the tunnel mode, and then
sends them to the neighboring multicast routers through the routers that do not support
multicast. The neighboring multicast routers remove the header of the unicast IP
packets, and then continue to multicast the packets, thus avoiding changing the
network structure greatly.
1.1.4 Advantages and Applications of Multicast
I. Advantages of multicast
Advantages of multicast include:
z Enhanced efficiency: Multicast decreases network traffic and reduces server load
and CPU load.
z Optimal performance: Multicast reduces redundant traffic.
z Distributive application: Multicast makes multiple-point application possible.
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