Bidirectional PIM (BIDIR-PIM) is a variant of PIM Sparse-Mode (PIM-SM) that builds bidirectional shared trees connecting multicast sources and receivers as specified in RFC5015.

BIDIR-PIM dispenses with both encapsulation and source state by allowing packets to be natively forwarded from a source to the Rendezvous Point (RP) using shared tree state.

BIDIR-PIM uses the same tree for traffic from source towards RP and from RP to receivers.