IP Multicast allows an arbitrary number of IP hosts on disparate IP networks to have IP datagrams simultaneously routed to them. This mechanism is exploited to provide Internet wide "broadcast" material such as audio and video transmissions and other novel applications.
Kernel Compile Options:
Networking options ---> [*] TCP/IP networking .... [*] IP: multicasting
A suite of tools and some minor network configuration is required. Please check the Multicast-HOWTO for more information on Multicast support in Linux.