H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 309)

28-3
Figure 28-2 Broadcast transmission
Assume that only Hosts B, D, and E need the information. If the information source broadcasts the
information, Hosts A and C also receive it. In addition to information security issues, this also causes
traffic flooding on the same network.
Therefore, broadcast is disadvantageous in transmitting data to specific hosts; moreover, broadcast
transmission is a significant usage of network resources.
Multicast
As discussed above, the unicast and broadcast techniques are unable to provide point-to-multipoint
data transmissions with the minimum network consumption.
The multicast technique has solved this problem. When some hosts on the network need multicast
information, the multicast source (Source in the figure) sends only one copy of the information. Multicast
distribution threes are built for the multicast packets through multicast routing protocols, and the
packets are replicated only on nodes where the trees branch, as shown in
Figure 28-3 :