Re: WGLC for BFD Multipoint documents (last round)

Jeffrey Haas <jhaas@pfrc.org> Tue, 19 December 2017 16:01 UTC

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Date: Tue, 19 Dec 2017 11:05:37 -0500
From: Jeffrey Haas <jhaas@pfrc.org>
To: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
Cc: Greg Mirsky <gregimirsky@gmail.com>, "rtg-bfd@ietf.org" <rtg-bfd@ietf.org>
Subject: Re: WGLC for BFD Multipoint documents (last round)
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References: <20171213172443.GC8708@pfrc.org> <CA+RyBmX6PHczvwEzc4UNqBioK8qv=wTfyeHg9j04EJNe1Uv0wA@mail.gmail.com> <746F74E2-7DFC-41A7-879F-4054CF95475C@cisco.com> <CA+RyBmWqGPTkBek+a0N+BaFr9QZ+xEKvWT5oRxPBuhFsQcizcw@mail.gmail.com> <38B53F72-66B9-4E8F-8BCE-C28A2C283D38@cisco.com>
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[Speaking as an individual contributor.]

On Tue, Dec 19, 2017 at 02:20:11AM +0000, Carlos Pignataro (cpignata) wrote:
> S-BFD currently specified for p2p but I don't see a reason why S-BFD cannot be applied to p2mp cases. So, for a BFD node that supports both RFC 7880 and draft-ietf-bfd-multipoint values of variables may be SBFDInitiator and PointToPoint. And, at some time, there will be interest to define behavior of the SBFDInitiator/MultipointHead and SBFDReflector/MultipointTail combinations.
> 
> Thus I see this issue as name conflict that can be resolved by changing the name in draft-ietf-bfd-multipoint-* to something other than bfd.SessionType. Perhaps we can change the name to bfd.SessionTopology.

I concur with Carlos.  This really isn't a topology, simply a session type.
(And one that is core to even the original BFD spec, albeit simply a bit
that wasn't well defined!)

I also agree that the solution to permitting S-BFD with multipoint is to
simply have a value that expresses that combination.  At this point, S-BFD
with multipoint is undefined.

At this point it is also worth noting that the session type has no
centralized location covering their enumerations.  This leads to two
interesting observations:
- We could have an IANA registry for such things.  However, I'm not sure
  this is really need.  But this also means:
- Here's another case why some pieces of the BFD yang module likely shoudl
  be IANA maintained.  In this case, the bfd-path-type identity as the
  relevant example.

-- Jeff