PIM is a multicast routing protocol which uses Hello messages to detect adjacent node failure. This mechanism is very slow and leads to control plane overhead when interval between hello messages is set to minimum.

BFD is a protocol designed to detect link failures superfast, routing protocols such as OSPF, ISIS uses BFD to get link failure notification.

BFD detects the link failure immediately after the original DR fails and triggers new DR election. The BFD protocol uses control packets and shorter detection time limits to more rapidly detect failures in a network.