Information Transmission In The Multicast Mode - H3C S3100-52P Operation Manual

Operation Manual – Multicast
H3C S3100-52P Ethernet Switch
Source
Server
Figure 1-2 Information transmission in the broadcast mode
Assume that Hosts B, D, and E need the information. The source server broadcasts this
information through routers, and Hosts A and C on the network also receive this
information.
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 specific users;
moreover, broadcast occupies large bandwidth.

1.1.3 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.
Multicast solves this problem. When some users on a network require specified
information, the multicast information sender (namely, the multicast source) sends the
information only once. With multicast distribution trees established for multicast data
packets through multicast routing protocols, the packets are duplicated and distributed
at the nearest nodes, as shown in
Packets for all the network
Host A
Receiver
Receiver
Receiver
Host E
Figure 1-3:
1-3
Chapter 1 Multicast Overview
Host B
Host C
Host D