82 Switch FeaturesProtocol Independent Multicast—Dense ModeProtocol Independent Multicast (PIM) is a standard multicast routingprotocol that provides scalable inter-domain multicast routing across theInternet, independent of the mechanisms provided by any particular unicastrouting protocol. The Protocol Independent Multicast-Dense Mode (PIM-DM) protocol uses an existing Unicast routing table and a Join/Prune/Graftmechanism to build a tree. PIM-DM creates source-based shortest-pathdistribution trees, making use of reverse path forwarding (RPF).Protocol Independent Multicast—Sparse ModeProtocol Independent Multicast-Sparse Mode (PIM-SM) is used to efficientlyroute multicast traffic to multicast groups that may span wide area networks,and where bandwidth is a constraint. PIM-SM uses shared trees by defaultand implements source-based trees for efficiency. This data threshold rate isused to toggle between trees.Protocol Independent Multicast—Source Specific MulticastProtocol Independent Multicast—Source Specific Multicast (PIM-SSM) is asubset of PIM-SM and is used for one-to-many multicast routingapplications, such as audio or video broadcasts. PIM-SSM does not use sharedtrees.Protocol Independent Multicast IPv6 SupportPIM-DM and PIM-SM support IPv6 routes.MLD/MLDv2 (RFC2710/RFC3810)MLD is used by IPv6 systems (listeners and routers) to report their IPmulticast addresses memberships to any neighboring multicast routers. Theimplementation of MLD v2 is backward compatible with MLD v1.MLD protocol enables the IPv6 router to discover the presence of multicastlisteners, the nodes that want to receive the multicast data packets, on itsdirectly attached interfaces. The protocol specifically discovers whichmulticast addresses are of interest to its neighboring nodes and provides thisinformation to the multicast routing protocol that make the decision on theflow of the multicast data packets.
