15 IGMP Snooping Configuration
15.1 Overview
15.1.1 Understanding IGMP
Before understanding the IGMP, let us first describe the concept and function of IP multicast.
On the Internet, the multimedia services such as video conference and video on demand
(VOD) with the sending mode of single point to multiple-point are becoming an important
part of information transmission. The point-to-point unicast transmission mode cannot
accommodate such service transmission feature, since the server must provide every
receiver with a same copy of the IP packet. In addition, the same packets are transmitted
repeatedly on the network, occupying enormous resources. Similarly, IP broadcast cannot
meet such requirements. Despite the IP broadcast allows the host to send one IP packet to
all the hosts of one network, the network resources are still wasted since not all hosts need
such packets. In this situation, the multicast emerges, providing a solution to the method for
one host to send messages to multiple designated receivers. See the figure below.
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