BFD

networking

Stands for: Bidirectional Forwarding Detection

Bidirectional Forwarding Detection - a tiny, protocol-agnostic hello stream that detects a dead path in milliseconds, so routing protocols can fail over before users notice.

Routing protocols keep deliberately slow hellos (seconds) for stability; BFD (RFC 5880) runs the fast heartbeat for them: two endpoints exchange minimal control packets at intervals commonly tuned to tens of milliseconds, declare the path down after a few misses, and notify every registered client - BGP, OSPF, IS-IS, static routes, VRRP - in one stroke. One session protects them all, which is the elegance: liveness becomes a shared service instead of per-protocol timer surgery. The echo function pushes detection into the forwarding plane itself. The practical rule of thumb: anywhere failover matters and the media will not signal loss of link, BFD is the difference between 50 milliseconds and 30 seconds.

Also known as: bfd, echo function, liveness detection

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