410
C
37: IP M
HAPTER
ULTICAST
Advantages of Multicast
O
VERVIEW
Figure 97 Data transmission in broadcast mode
Broadcast
Server
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.
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 98 "Data transmission in multicast mode".
Figure 98 Data transmission in multicast mode
Multicast
Multicast
Server
Server
Suppose the Users B, D, and E need the information, they need to be organized
into a receiver group to ensure that the information can reach them smoothly. The
routers on the network duplicate and forward the information according to the
User A
User B
User C
User D
User E
User A
User A
User B
User B
User C
User C
User D
User D
User E
User E