Intel ZT8101 user manual Protocol-IndependentMulticast - Dense Mode PIM-DM

Switch Management and Operating Concepts

Protocol-Independent Multicast - Dense Mode (PIM-DM)

The Protocol Independent Multicast - Dense Mode (PIM-DM) protocol should be used in networks with a low delay (low latency) and high bandwidth because PIM-DM is optimized to guarantee delivery of multicast packets, not to reduce overhead. The switch supports PIM-DM v2.

The PIM-DM multicast routing protocol assumes that all downstream routers want to receive multicast messages and relies on explicit prune messages from downstream routers to remove branches from the multicast delivery tree that do not contain multicast group members.

PIM-DM has no explicit “join” messages. It relies on periodic flooding of multicast messages to all interfaces. It then waits for the following:

•A timer to expire (the join/prune interval)

•The downstream routers to transmit explicit “prune” messages indicating that there are no multicast members on their respective branches.

PIM-DM then removes these branches (“prunes” them) from the multicast delivery tree.

Because a member of a pruned branch of a multicast delivery tree may want to join a multicast delivery group (at some point in the future), the protocol periodically removes the prune information from its database and floods multicast messages to all interfaces on that branch. The interval for removing prune information is the join/prune interval.

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