Bidirectional Forwarding Detection
charter-ietf-bfd-09

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
  hardware.

• 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
  course).

• Ability to be bootstrapped by any other protocol that automatically
  forms peer, neighbor or adjacency relationships to seed BFD endpoint
  discovery.

The working group is currently chartered to complete the following work items:

1. 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,
   SPRING.

2. Extend BFD to allow it to detect whether a path between two systems
   is capable of carrying a payload of a particular size.

3. Define a use of the BFD Echo where the local system supports BFD but
   the adjacent system does not support BFD.

4. Provide an optimization to BFD authentication to reduce computational
   demand while still providing desirable security properties.

5. Provide a Meticulous Keyed mode for BFD authentication.

6. Define experimental extensions to measure BFD stability.

The working group will maintain a relationship with the MPLS working group.