Overview
Bidirectional forwarding detection (BFD) provides a general-purpose, standard, medium- and protocol-independent fast failure detection mechanism. It can detect and monitor the connectivity of links in IP to detect communication failures quickly so that measures can be taken to ensure service continuity and enhance network availability.
BFD can uniformly and quickly detect the failures of the bidirectional forwarding paths between two devices for upper-layer protocols such as routing protocols and MPLS. The hello mechanism used by upper-layer protocols needs seconds to detect a link failure, while BFD can provide detection measured in milliseconds.
BFD can be used for single-hop and multihop detections.
Single-hop detection—Detects the IP connectivity between two directly connected systems.
Multihop detection—Detects any of the paths between two systems. These paths have multiple hops, and might overlap.