3Com Switch 8800 Configuration Guide Chapter 23 IP Multicast Overview
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over the network if there is a large number of users in need of this infomration. As the
bandwidth would turn short, the unicast mode is incapable of massive transmission.
II. Data transmission in broadcast mode
In broadcast mode, every user on the network receives the information regardless of
their needs. See Figure 23-2 Data transmission in broadcast mode.
Server
Broadcast
User A
User B
User C
User D
User E
Figure 23-2 Data transmission in broadcast mode
Suppose the Users B, D, and E need the information, the information source Server
broadcasts the information through the router; User A and User C can also receive the
information. In that case, information security and rewards to services are not
guaranteed. Moreover, bandwidth is terribly wasted when only a few part of users are in
need of the information.
In short, the unicast mode is useful in networks with scattered users, and the multicast
mode is suitable for networks with dense users. When the number of users is uncertain,
the adoption of unicast or multicast mode results in low efficiency.
23.1.2 Advantages of Multicast I. Multicast
IP multicast technology solves those problems. When some users in the network need
specific information, it allows the multicast source to send the information only once.
With the tree route established by the multicast routing protocol, the information will not
be duplicated or distributed until it reaches the bifurcation point as far as possible. See
Figure 23-3 Data transmission in multicast mode.