Using MLD in Your Network

Multicast Listener Discovery (MLD) enables each IPv6 router to discover the presence of nodes wishing to receive multicast packets on its directly attached links, and determines which multicast addresses are of interest to those neighboring nodes. MLD provides the discovered information to the routing protocol used by the router, in order to ensure that multicast packets are delivered to all links where there are interested receivers.

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. See Multicast Configuration for a detailed multicast discussion.

The S- K- and 7100-Series platforms support MLD version 1 (RFC 2710) and version 2 (RFC 3810). MLD defaults to version 2.

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.