Re: [Isis-wg] [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions

Peter Psenak <ppsenak@cisco.com> Tue, 20 February 2018 20:03 UTC

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Date: Tue, 20 Feb 2018 21:03:39 +0100
From: Peter Psenak <ppsenak@cisco.com>
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To: Alia Atlas <akatlas@gmail.com>
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Subject: Re: [Isis-wg] [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions
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Hi Alia,

On 20/02/18 18:35 , Alia Atlas wrote:
> Hi Peter,
>
> Thanks very much for the feedback.
>
> On Tue, Feb 20, 2018 at 12:27 PM, Peter Psenak <ppsenak@cisco.com
> <mailto:ppsenak@cisco.com>> wrote:
>
>     Hi Alia,
>
>     1. I see a benefit in having the BIER a way to map to any of the IGP
>     algorithms. Simply because IGPs already provide paths to all nodes
>     in the domain and BIER can simply use these paths instead of
>     computing its own.
>
>
> Makes sense.
>
>     2. Not sure if people plan to deploy the BIER in a model where it
>     does its own topology related computations, independent of IGPs. If
>     they do, I'm not objecting that.
>
>
> That is what I'm hearing as a requirement.
>
>     The encoding of the BAR though must be done in a way that it easily
>     supports both (1) and (2).
>
>
> There's the rub :-)  The challenge seems to be when there are
> BIER-specific constraints and also other more generic constraints.

we should be able to say BIER BAR X means (1) or (2), not both.

thanks,
Peter

>
> Regards,
> Alia
>
>     my 2c,
>     Peter
>
>
>
>
>     On 19/02/18 22:51 , Alia Atlas wrote:
>
>         As the Sponsoring AD for draft-ietf-bier-isis-extensions-07 and
>         draft-ietf-bier-ospf-extensions-12, I have been following the
>         discussion
>         on the mailing list with interest.
>
>         I have not seen clear consensus for any change.
>
>         Let me be clear on what I see the options are from the
>         discussion.  Then
>         I'll elaborate
>         a bit on how you can express your perspective most usefully.
>
>         1) Current Status:  Bier Algorithm (BAR) field is 8 bits.
>         Currently,
>         only value 0 is specified.  The drafts do not have an IANA
>         registry -
>         with the expectation that one will be created when the first
>         additional
>         use is clear.  It is possible that there will be objections from the
>         IESG to progressing without an IANA registry.  Given the lack of
>         clarity
>         for future use-cases and after discussion, I decided not to
>         force one
>         after my AD review - but I will not push back against having a
>         BIER IANA
>         registry if raised by others.
>
>         2) Option B:  Add a BAR sub-type of 8 bits.  This would modify the
>         current TLVs.
>              Define an IANA registry for the BAR type.  The meaning of
>         the BAR
>         sub-type derives
>              from the BAR type.   We can debate over the registration
>         policy for
>         the BAR type.
>
>         3) Option C: Change the BAR field to be 16 bits and define an IANA
>         registry.  Part of the range can be FCFS with Expert Review,
>         part can be
>         Specification Required, and part can be IETF Consensus.
>
>         4) Option D: At some point in the future, if there is an actual
>         understood and documented need, a BAR sub-type could be added a
>         sub-TLV.  The length of the BAR sub-type could be determined
>         when the
>         sub-TLV is defined.
>
>         Given
>
>             a) option D exists
>             b) there is currently only one defined value for BAR
>             c) I do not see strong consensus for change to one
>         particular other
>         option
>
>         I see no current reason for a change and I certainly see
>         absolutely no
>         reason for
>         a delay in progressing the documents.
>
>         I do want to be clear about what the WG wants to do on this issue.
>         Therefore, here is
>         my following request.
>
>         Please send your feedback to the mailing list as follows:
>
>         IF you prefer or can accept the current status, please say so.
>         No more
>         justification
>         or reasoning is required. I just don't want the bulk of folks
>         who are
>         content to be
>         overlooked by those suggesting change.
>
>         IF you prefer or can accept the current status, but think there
>         should
>         be an IANA registry
>         as is usual for managing code-points, please say so.  No more
>         justification is needed.
>
>         IF you prefer Option B, C, and/or D, please say so with your
>         explanation.  More technical depth than "'we might need it" would be
>         helpful; the availability of sub-TLVs already
>         provides future proofing.
>
>         IF you have a clear technical objection to why the Current
>         Status is not
>         acceptable,
>         please express that - with clear details.
>
>         IF you feel that additional code-points should be allocated in a BAR
>         IANA Registry or
>         have thoughts on the appropriate policy, please say so with your
>         explanation for what
>         those should be.
>
>         Unless I see clear and strong consensus for something other than the
>         Current Status,
>         that will remain.
>
>         IF there is clear and strong consensus for Option B, C, or D, or
>         adding
>         an IANA registry with particular values, then it will be possible to
>         have a change up through this Weds night - with a 1 week WGLC on
>         that
>         particular technical change.
>
>         My priority is to have the base BIER specifications published as
>         Proposed Standards so that more BIER implementations and
>         deployment can
>         be done.  I would like the WG to wrap up the core work (as
>         expressed in
>         the proposed recharter) so that you all can look
>         at how to use it.
>
>         Given this topic was raised last Weds and given that there are no
>         technical objections raised to the documents as are, there isn't
>         much
>         time - so please just respond to this email ASAP.  My deadline for a
>         decision is 6pm EST on Weds.
>
>         Regards,
>         Alia
>
>
>
>         _______________________________________________
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>         <https://www.ietf.org/mailman/listinfo/bier>
>
>
>