Re: [Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-ls-segment-routing-msd-17: (with COMMENT)

Alvaro Retana <aretana.ietf@gmail.com> Wed, 06 May 2020 21:22 UTC

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From: Alvaro Retana <aretana.ietf@gmail.com>
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To: Benjamin Kaduk <kaduk@mit.edu>, Jeff Tantsura <jefftant.ietf@gmail.com>
Cc: Susan Hares <shares@ndzh.com>, idr-chairs@ietf.org, draft-ietf-idr-bgp-ls-segment-routing-msd@ietf.org, The IESG <iesg@ietf.org>, idr@ietf.org
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Subject: Re: [Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-ls-segment-routing-msd-17: (with COMMENT)
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On May 6, 2020 at 1:56:07 PM, Benjamin Kaduk wrote:


Ben:

Hi!

...
> It sounds like you are intending this to work the way that I was hoping it
> would work, which is reassuring. That said (and this relates to a later
> comment as well), I think we may want to double-check the wording in one
> spot: in Section 3 we define the "Node MSD is the smallest MSD supported by
> the node on the set of interfaces configured for use." This definition
> seems to disallow advertising a Node MSD that is larger than any specific
> Link MSD for that node. My question here was about whether a receiving
> node was expected to enforce this (surprising) aspect of the definition.
> If, instead, the definition should be changed to say only that the Node MSD
> is the MSD to be used for interfaces on this node in the absence of an
> interface-specific value, then there is no longer any enforcement needed.

§5 does say this: "When Link MSD is present for a given MSD-type, the
value of the Link MSD MUST take precedence over the Node MSD."

Is that what you're looking for.

Keep in mind that the expectation of BGP-LS is to simply transport
information; the rules around that information and how the consumer
should process it come form the IGP documents.  IOW, in this case
we're bound by what those published documents already say (see RFC8491
and RFC8476).


Thanks!

Alvaro.