Bidirectional Forwarding Detection
Bidirectional Forwarding Detection WG
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The BFD Working Group is chartered to standardize and support the
bidirectional forwarding detection protocol (BFD) and its extensions. A
core goal of the working group is to standardize BFD in the context of
IP routing, or protocols such as MPLS that are based on IP routing, in a
way that will encourage multiple, inter-operable vendor implementations.
The Working Group will also provide advice and guidance on BFD to other
working groups or standards bodies as requested.
BFD is a protocol intended to detect faults in the bidirectional path
between two forwarding engines, including physical interfaces,
subinterfaces, data link(s), and to the extent possible the forwarding
engines themselves, with potentially very low latency. It operates
independently of media, data protocols, and routing protocols. An
additional goal is to provide a single mechanism that can be used for
liveness detection over any media, at any protocol layer, with
a wide range of detection times and overhead, to avoid a proliferation
of different methods.
Important characteristics of BFD include:
- Simple, fixed-field encoding to facilitate implementations in
- Independence of the data protocol being forwarded between two systems.
BFD packets are carried as the payload of whatever encapsulating
protocol is appropriate for the medium and network.
- Path independence: BFD can provide failure detection on any kind of
path between systems, including direct physical links, virtual
circuits, tunnels, MPLS LSPs, multihop routed paths, and
unidirectional links (so long as there is some return path, of
- Ability to be bootstrapped by any other protocol that automatically
forms peer, neighbor or adjacency relationships to seed BFD endpoint
The working group is currently chartered to complete the following work items:
1. Develop further MIB modules for BFD and submit them to the IESG for
publication as Proposed Standards.
2a. Provide a generic keying-based cryptographic authentication
mechanism for the BFD protocol developing the work of the KARP
working group. This mechanism will support authentication through
a key identifier for the BFD session's Security Association rather
than specifying new authentication extensions.
2b. Provide extensions to the BFD MIB in support of the generic keying-
based cryptographic authentication mechanism.
2c. Specify cryptographic authentication procedures for the BFD protocol
using HMAC-SHA-256 (possibly truncated to a smaller integrity check
value but not beyond commonly accepted lengths to ensure security) using
the generic keying-based cryptographic authentication mechanism.
3. Provide an extension to the BFD core protocol in support of point-to-
multipoint links and networks.
4. Provide an informational document to recommend standardized timers
and timer operations for BFD when used in different applications.
5. Define a mechanism to perform single-ended path (i.e. continuity)
verification based on the BFD specification. Allow such a mechanism to
work both proactively and on-demand, without prominent initial delay.
Allow the mechanism to maintain multiple sessions to a target entity and
between the same pair of network entities. In doing this work, the WG
will work closely with at least the following other WGs: ISIS, OSPF,
The working group will maintain a relationship with the MPLS working group.