3Com Switch 7757, Руководство по настройке, Страница: 416 / 940

416 C
HAPTER
41: M
ULTICAST
O
VERVIEW
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Each receiver receiving multicast information is a multicast group member.
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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.
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CAUTION: A multicast source does not necessarily belong to a multicast group. A
multicast source sends packets 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 router that
do no 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.
Advantages and
Applications of
Multicast
Advantages of multicast
Advantages of multicast include:
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Enhanced efficiency: Multicast decreases network traffic and reduces server
load and CPU load.
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Optimal performance: Multicast reduces redundant traffic.
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Distributive application: Multicast makes multiple-point application possible.
Application of multicast
The multicast technology effectively addresses the issue of point-to-multipoint
data transmission. By enabling high-efficiency point-to-multipoint data
transmission, over an IP network, multicast greatly saves network bandwidth and
reduces network load.
Multicast provides the following applications:
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Applications of multimedia and flow media, such as Web TV, Web radio, and
real-time video/audio conferencing.
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Communication for training and cooperative operations, such as remote
education.
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Database and financial applications (stock), and so on.
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Any point-to-multiple-point data application.
Multicast Architecture
The purpose of IP multicast is to transmit information from a multicast source to
receivers in the multicast mode and to satisfy information requirements of
receivers. You should be concerned about:
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Host registration: What receivers reside on the network?
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Technologies of discovering a multicast source: Which multicast source should
the receivers receive information from?
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Multicast addressing mechanism: Where should the multicast source transports
information to?