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

"Dolganow, Andrew (Nokia - SG/Singapore)" <> Tue, 20 February 2018 09:10 UTC

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From: "Dolganow, Andrew (Nokia - SG/Singapore)" <>
To: Senthil Dhanaraj <>
CC: Alia Atlas <>, BIER WG <>, " list" <>
Thread-Topic: [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions
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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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As per below i am not aware of a commercial deployment.

Some  implementation assume ability to use BIER specific algorithm. So if we keep 8 bits only, the IANA registry needs to allow that.  The registry being suggested as an option on the list will not allow BIER specific option ( and does not even support experimental bits at all) That would create a functional conflict unless the registry we use is BIER specific. But, as I pointed out, this option does not satisfy others.

Extending field as per Option B would require implementation change but can be accommodated but technically satisfies everyone’s needs I believe.


Sent from my iPhone

On Feb 20, 2018, at 4:34 PM, Senthil Dhanaraj <<>> wrote:

I’m not aware of any commercial (or sort of) deployments.

So I hope it’s early enough for the implementations to adjust - Just like the consensus we had on the other issue related to allowing 0 as a valid value for “label-range (now called as “max-si)” which in-fact had a interoperability issue for last SI.

I do understand/agree there would be backward/interop issue with older bier-igp drafts if we make a change (say option-B) now for BAR.
Peter Psenak / Ice – Comments ?


From: Alia Atlas []
Sent: 20 February 2018 10:45
To: Senthil Dhanaraj <<>>
Cc: BIER WG <<>>;<> list <<>>
Subject: RE: [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions

I have one additional question for those with implementations or testing them.

What is the impact of going with your preferred option in terms of interoperability?  It may be early enough that changes can happen, but more feedback is needed.

For those favoring Option B, could you send email to the list providing exact text so we have the details?

For those favoring the current status without an IANA registry, are you able to handle one being imposed during IESG Review?  It is an obvious concern to raise.  Are you just prolonging or postponing the discussion?


On Feb 19, 2018 11:53 PM, "Senthil Dhanaraj" <<>> wrote:
+1 to Option-B
Seems future proof to me.


From: BIER [<>] On Behalf Of Alia Atlas
Sent: 20 February 2018 03:21
To: BIER WG <<>>;<> list <<>>
Subject: [Bier] BAR field length in draft-ietf-bier-isis-extensions and draft-ietf-bier-ospf-extensions

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.


  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.


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