Bidirectional Forwarding Detection (BFD) is a network protocol used to detect faults between two MEP endpoints connected by a link. The BFD establishes a session between these endpoints over a particular link by exchanging control packets.

Both MEPs exchange BFD control packets at a regular interval. The local MEP sends Continuity Check (CC) packets at a defined “CC Interval” and the remote MEP monitors the arrival of the CC packets and detects loss of Continuity (LOC) if the packets fail to appear over a certain time period.

If the link or path is protected, separate BFD sessions (BFD CC Supervision) are automatically established in the working and protection LSP to monitor both links.