3Com Switch 7750 Configuration Guide Guide

376 CHAPTER 39: MULTICAST OVERVIEW
Information
Transmission in the
Broadcast Mode
When you adopt broadcast, the system transmits information to all users on a
network. Any user on the network can receive the information, no matter the
information is needed or not.
Figure 86 shows information transmission in
broadcast mode.
Figure 86 Information transmission in the broadcast mode
Assume that users B, D, and E need the information. The source server broadcasts
this information through routers, and users A and C on the network also receive
this information. The security and payment of the information cannot be
guaranteed.
As we can see from the information transmission process, the security and legal
use of paid service cannot be guaranteed. In addition, when only a small number
of users on the same network need the information, the utilization ratio of the
network resources is very low and the bandwidth resources are greatly wasted.
Therefore, broadcast is disadvantageous in transmitting data to specified users;
moreover, broadcast occupies large bandwidth.
Figure 87 Information transmission in the multicast mode
Assume that users B, D and E need the information. To
Information
Transmission in the
Multicast Mode
As described in the previous sections, unicast is suitable for networks with sparsely
distributed users, whereas broadcast is suitable for networks with densely
distributed users. When the number of users requiring information is not certain,
unicast and broadcast deliver a low efficiency.
Server
Broadcast
User A
User B
User C
User D
User E
Server
Multicast
User A
User B
User D
User E