3Com 10014298 manual Multicast Protocol

6

MULTICAST PROTOCOL

This chapter includes information on the following:

■IP Multicast Overview

■Configuring Common Multicast

■Configuring IGMP

■IGMP Snooping

■Configuring PIM-DM

■Configuring PIM-SM

■GMRP

IP Multicast Overview Many transmission methods can be used when the destination (including data, voice and video) is the secondary use of the network. If the multicast method is used you should establish an independent data transmission path for each user. The broadcast method can be used if you intend to send the information to all users on the network. In either case, the end users will receive the information. For example, if the same information is required by 200 users on the network, the traditional solution is to send the information 200 times in unicast mode. In the broadcast mode, the data is broadcast over the entire network. However, both of the methods waste bandwidth resources. In addition, the broadcast mode cannot ensure information security.

IP multicast technology solves this problem. The multicast source sends the information only once. Multicast routing protocols establish tree-type routing for multicast packets (see Figure 26) so that information can be correctly sent, with high efficiency, to each user.