Transport OAM — BFD, Y.1731, CFM

Bidirectional Forwarding Detection

BFD is a lightweight protocol that detects forwarding path failures between two adjacent or remote systems in milliseconds. BFD establishes a session between peers and exchanges periodic control packets at configurable intervals — typically three hundred milliseconds with a detect multiplier of three, providing sub-second failure detection. When a peer stops receiving BFD packets within the detection time, it declares the forwarding path down and notifies upper-layer protocols like OSPF, IS-IS, or BGP to trigger fast reroute. BFD operates independently of the routing protocol and can detect…