4000 Router Series IP Multicast Configuration Guide

a separate copy of the same information to each of these hosts. Sending many copies can place a

tremendous pressure on the information source and the network bandwidth.

Unicast is not suitable for batch transmission of information.

Broadcast

In broadcast transmission, the information source sends information to all hosts on the subnet, even if

some hosts do not need the information.

Figure 2 Broadcast transmission

In Figure 2, assume that only Host B, Host D, and Host E need the information. If the information is

broadcast to the subnet, Host A and Host C also receive it. In addition to information security issues,

broadcasting to hosts that do not need the information also causes traffic flooding on the same subnet.

Broadcast is not as efficient as multicast for sending data to groups of hosts.

Multicast

Unicast and broadcast techniques cannot provide point-to-multipoint data transmissions with the

minimum network consumption.

Multicast transmission can solve this problem. When some hosts on the network need multicast

information, the information sender, or multicast source, sends only one copy of the information.

Multicast distribution trees are built through multicast routing protocols, and the packets are replicated

only on nodes where the trees branch.