After detecting a fault on a peer, BFD immediately instructs the PIM module to trigger a new Designated router (DR) election rather than waits until the neighbor relationship times out. This minimizes the multicast data interruptions and improves the reliability of multicast data transmission.
Generally, if the active DR on a shared network segment is faulty, other PIM neighbors triggers a new round of DR election only after the neighbor relationship times out. The data transmission interruption duration (usually for some seconds) is not shorter than the timeout period of the neighbor relationships.
BFD for PIM can detect a link's status on a shared network segment within milliseconds and respond quickly to a fault on a PIM neighbor. When BFD detects that a peer is faulty, BFD immediately reports this fault to PIM. PIM then triggers a new round of DR election without waiting for the timeout of neighbor relationships. This minimizes service interruptions and improves the multicast network reliability.
PIM BFD also applies to the assert election on a shared network segment. It can fast respond to the fault of the interface that wins the assert election.