Subject: WG Review: Bidirectional Forwarding Detection (bfd)

From: The IESG <[email-masked]>
Date: Wed, 19 May 2004 10:38:33 -0400

A new IETF working group has been proposed in the Routing Area. The IESG has not 
made any determination as yet. The following description was submitted, and is 
provided for informational purposes only. Please send your comments to the IESG 
mailing list ([email-masked]) by May 26th.

Bidirectional Forwarding Detection (bfd)
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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.