BFD — Bidirectional Forwarding Detection
BFD is how networks achieve sub-second failover — without it, BGP takes 90+ seconds to detect a peer failure. Any high-availability design (active-active DC, SD-WAN, carrier) relies on BFD for fast convergence.
What It Defines
BFD provides fast, protocol-independent failure detection between forwarding engines. Sends hellos at 50 ms–1 s intervals over UDP port 3784 (control) or 3785 (echo). Operates in asynchronous or demand mode. Used by BGP, OSPF, IS-IS, static routes, and MPLS LSPs to trigger sub-second failover without waiting for BGP holddown or OSPF dead intervals.
Canonical (Normative)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
BGP stitches the internet together — every AS, CDN, cloud provider, and multi-homed network runs it. Understanding AS path, communities, and prefix aggregation is essential for cloud networking, CDN design, and any serious network engineering role.
OSPF is the interior routing protocol of choice for enterprise and carrier networks. Understanding area design, LSA types, and SPF convergence is essential for data center networking, WAN design, and network certification paths.
IS-IS is the IGP of choice in most Tier-1 and Tier-2 carrier networks and large-scale DC fabrics (Meta, Amazon). It runs under BGP in many hyperscale designs. Essential for service provider and large-scale DC networking roles.
MPLS is the forwarding substrate of carrier networks, MPLS VPNs, and traditional WAN services. Understanding FEC, LDP, and LSP concepts is essential for service provider or enterprise WAN networking.