3Com 5500 SI - Switch - Stackable, Руководство по настройке

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18
M
ULTICAST
P
ROTOCOL
This chapter includes information on the following:
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IP Multicast Overview
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IGMP Snooping
■
Common Multicast Configuration
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Internet Group Management Protocol (IGMP)
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PIM-DM Overview
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PIM-SM Overview
IP Multicast Overview
The Switch 5500-EI supports all of the multicast protocols listed in this manual;
however, the Switch 5500-SI only supports the IGMP Snooping protocol.
Many transmission methods can be used when the destination (including data, voice
and video) is the secondary use of the network. If the multicast method is used you
should establish an independent data transmission path for each user. The broadcast
mode can be used if you intend to send the information to all users on the network.
In either case, the end users will receive the information. For example, if the same
information is required by 200 users on the network, the traditional solution is to
send the information 200 times in unicast mode. In the broadcast mode, the data is
broadcast over the entire network. However, both of the methods waste bandwidth
resources. In addition, the broadcast mode cannot ensure information security.
IP multicast technology solves this problem. The multicast source sends the
information only once. Multicast routing protocols establish tree-type routing for
multicast packets. The information being sent will be replicated and distributed as far
as possible (see Figure 78). Therefore, the information can be correctly sent, with high
efficiency, to each user.