[OSPF] Alvaro Retana's Discuss on draft-ietf-isis-sbfd-discriminator-02: (with DISCUSS)

"Alvaro Retana" <aretana@cisco.com> Wed, 18 November 2015 17:06 UTC

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Subject: [OSPF] Alvaro Retana's Discuss on draft-ietf-isis-sbfd-discriminator-02: (with DISCUSS)
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Alvaro Retana has entered the following ballot position for
draft-ietf-isis-sbfd-discriminator-02: Discuss

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The document, along with other ballot positions, can be found here:
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----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------

It has been pointed out during the processing of this document (and other
similar ones, draft-ietf-ospf-sbfd-discriminator, for example) that the
functionality provided is only the advertisement of S-BFD discriminators,
but not a mechanism to map these discriminators to specific applications
or use-cases in the nodes.  That mapping has been declared out of scope.

However, the Base S-BFD draft (draft-ietf-bfd-seamless-base) assumes that
the advertisers of the multiple discriminators will in fact provide the
ability for the mapping.  Specifically, the base S-BFD document reads in
Section 3. (Seamless BFD Overview):

   An S-BFD module on each network node allocates one or more S-BFD
   discriminators for local entities, and creates a reflector BFD
   session.  Allocated S-BFD discriminators may be advertised by
   applications (e.g., OSPF/IS-IS).  Required result is that
   applications, on other network nodes, possess the knowledge of the
   mapping from remote entities to S-BFD discriminators.

This text reads to me that S-BFD is expecting the mapping to be somehow
provided by the "applications (e.g., OSPF/IS-IS)".  There's no other
explicit discussion about the mapping in that document.

I'm putting a DISCUSS on this document to hold its processing while the
requirements from the S-BFD point of view are clarified.  The answer to
that question should be a discussion in the BFD WG (cc'd in this
message), in coordination with the providers of the advertisements (so
far the isis, ospf and l2tpext WGs have active drafts in this area).

One possible outcome of this required discussion is clearly that the
mapping is in fact outside the scope of advertising protocols (such as
IS-IS).  Other possible outcomes may require this document to be
modified.