Bidirectional Forwarding Detection (bfd)

Description of Working Group:
The BFD Working Group is chartered to specify a protocol for
bidirectional forwarding detection (BFD), as well as extensions to be
used within the scope of BFD and IP routing, or protocols such as MPLS
that are based on IP routing, in a way that will encourage multiple,
inter-operable vendor implementations.

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.

At this time the WG is chartered to complete the following work items
(additional items will require rechartering):

1. Develop the base BFD protocol specification and submit it to the
IESG
  for publication as a Proposed Standard
                                                                     
  2. Document BFD encapsulation and usage profile for single-hop IPv4
  and IPv6 adjacencies (e.g, physical links and IP/GRE tunnels for
  static routes, IS-IS, OSPFv2, OSPFv3, single-hop BGP) and submit the
  specification to the IESG for publication as a Proposed Standard.
                                                                     
3. Document BFD encapsulation and usage profile for MPLS LSPs and
submit
  the specification to the IESG for publication as a Proposed
Standard.
                                                                     
                                                                     

 
4. Develop the MIB module for BFD and submit it to the IESG for
  publication as a Proposed Standard.
                                                                     
5. Document BFD encapsulation and usage profile for multi-hop IPv4
  and IPv6 adjacencies (e.g. OSPF virtual links and iBGP sessions)
  and submit the specification to the IESG for publication as a
  Proposed Standard.

Topics for Possible Future Work:

1. Document BFD directly over 802.3 in close collaboration and
  synchronization with the IEEE.