Bi-directional Protocol Independent Multicast (BIDIR-PIM)
This document discusses Bi-directional PIM, a variant of PIM Sparse-Mode that builds bi-directional shared trees connecting multicast sources and receivers. Bi-directional trees are built using a fail-safe Designated Forwarder (DF) election mechanism operating on each link of a multicast topology. With the assistance of the DF, multicast data is natively forwarded from sources to the Rendezvous-Point and hence along the shared tree to receivers without requiring source-specific state. The DF election takes place at RP discovery time and provides the route to the RP thus eliminating the requirement for data-driven protocol events.