How to Use Multicast in Your Network

Multicast is a “one source to many destinations” method of simultaneously sending information over a network using the most efficient delivery strategy over each link. Only the end stations that explicitly indicate a need to receive a given multicast stream will receive it.

Applications that take advantage of multicast include video conferencing, streaming video, corporate communications, distance learning, and distribution of software, stock quotes, and news.

Multicast technology includes the following protocols:

• Internet Group Management Protocol (IGMP) for IPv4, Multicast Listener Discovery (MLD) for IPv6
• Distance Vector Multicast Routing Protocol (DVMRP)
• Protocol Independent Multicast (PIM)

Unlike unicast and broadcast, multicast uses network infrastructure efficiently because only one copy of the source traffic is sent throughout the network, going only to interested receivers, minimizing the burden placed on the sender, network, and receiver. The routers in the network take care of replicating the packet, where necessary, to reach multiple receivers. If a router decides that there are no interested users downstream from itself, it prunes the stream back to the next router. Thus, unwanted streams are not sent to the pruned routers, saving bandwidth and preventing unwanted packets from being sent.