Re: WGLC for BFD Multipoint documents (last round)

"Carlos Pignataro (cpignata)" <> Tue, 19 December 2017 02:20 UTC

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From: "Carlos Pignataro (cpignata)" <>
To: Greg Mirsky <>
CC: "" <>
Subject: Re: WGLC for BFD Multipoint documents (last round)
Thread-Topic: WGLC for BFD Multipoint documents (last round)
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Date: Tue, 19 Dec 2017 02:20:11 +0000
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Hi, Greg,

Thank you for the thoughtful, detailed reply.

Please find a corresponding follow-up:

You say that bfd.SessionType in RFC 7880 is used “to reflect S-BFD role the node performs in S-BFD session”, but that is incorrect. When you read the RFC, it says:
   o  bfd.SessionType: This is a new state variable that describes
      the type of a particular session.  Allowable values for S-BFD
      sessions are:

You say that bfd.SessionType in draft-ietf-bfd-multipoint-* is used to “reflect topology of the BFD session, i.e. whether it is p2p or p2mp”. However, that is incorrect. When you read the document it says:
         The type of this session.
And "point-to-point" and "point-to-multipoint" do not denote “topology”.

Consequently, in either case, both cases refer to the Type of session.

RFC 7880 defines values “allowable for S-BFD”, and draft-ietf-bfd-multipoint-, since it defines a new type of BFD session, needs to defined values allowable for BFD (i.e., PointToPoint, MultipointHead, and MultipointTail).

If at some point someone wants to define S-BFD p2mp, it can be done with the same variable.

Adding a new state variable for this results in unnecessary complexity.

Carlos Pignataro,<>

“Sometimes I use big words that I do not fully understand, to make myself sound more photosynthesis."

On Dec 16, 2017, at 4:31 PM, Greg Mirsky <<>> wrote:

Hi Carlos,
thank you very much for pointing this out. Sorry I've missed it. I agree that it requires resolution but I think that the resolution is different from what you've proposed in your original comment. The names of the new variable in RFC 7880 and draft-ietf-bfd-multipoint/draft-ietf-bfd-multipoint-active-tails are identical but, I believe, semantics are different:

  *   RFC 7880 uses bfd.SessionType to reflect S-BFD role the node performs in S-BFD session
  *   draft-ietf-bfd-multipoint-* are using bfd.SessionType to reflect topology of the BFD session, i.e. whether it is p2p or p2mp

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.

Greatly appreciate comments, suggestions. Let's make holiday presents to our AD!


On Fri, Dec 15, 2017 at 10:02 PM, Carlos Pignataro (cpignata) <<>> wrote:
Hi, Greg,

It seems the comments regarding bfd.SessionType are not addressed:


Sent from my iPad

On Dec 15, 2017, at 5:15 PM, Greg Mirsky <<>> wrote:

Dear All,
attached please find diffs and the updated version of the draft-ietf-bfd-multipoint-active-tail. All changes are editorial. Please review changes and share your comments.


On Wed, Dec 13, 2017 at 11:24 AM, Jeffrey Haas <<>> wrote:
Working Group,

In an attempt to give our AD a holiday gift, we're at the point where we may
now work to conclude WGLC on the BFD multipoint documents.  We did one pass
of last call June-July of this year, and held off approval pending review
from ALU who has an implementation of the base spec.  ALU has since
responded that they're fine with the contents.

To provide the working group one last opportunity to review the documents,
we're running a final last call and will send off the changes to our AD

The prior WGLC thread is here:

The documents are here:

The intent is to conclude this WGLC at end of year.

-- Jeff

<Diff_ draft-ietf-bfd-multipoint-active-tail-05.txt - draft-ietf-bfd-multipoint-active-tail-06.txt.html>