H3C Technologies H3C SecPath F1000-E - Manual (Page 3)

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Assume that Host B, Host D and Host E need the information. A separate transmission channel needs to
be established from the information source to each of these hosts.
In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that
need the information. If a large number of hosts need the information, the information source must send
a separate copy of the same information to each of these hosts. This means a tremendous pressure on the
information source and the network bandwidth.
As we can see from the information transmission process, unicast is not suitable for batch transmission of
information.
Broadcast
In broadcast, the information source sends information to all hosts on the subnet, even if some hosts do
not need the information, as shown in Figure 2 .
Figure 2 Broadcast transmission
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, this also causes traffic
flooding on the same subnet.
Therefore, broadcast is disadvantageous in transmitting data to specific hosts; moreover, broadcast
transmission is a significant waste of network resources.
Multicast
As discussed above, unicast and broadcast techniques are unable to provide point-to-multipoint data
transmissions with the minimum network consumption.
Multicast well addresses 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 information is replicated only on nodes where
the trees branch. Figure 3 shows the delivery of a data stream to receiver hosts through multicast.