Re: [Idr] WG adoption call for draft-scudder-idr-entropy-label-01 (9/6/2022 to 9/20/2022)

[[e-mail]]

Sue,

Thank you for your clarification questions.
Please see inline.



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From: Susan Hares <[e-mail]>
Sent: Friday, September 9, 2022 8:09 PM
To: DECRAENE Bruno INNOV/NET <[e-mail]>; [e-mail]
Subject: RE: [Idr] WG adoption call for draft-scudder-idr-entropy-label-01 (9/6/2022 to 9/20/2022)

Bruno and John:

The target for the adoption for draft-scudder-idr-entropy-label-01
is a bis draft for [RFC6790] to fix a bad RFC.

The IDR chairs did start this call for draft-scudder-idr-entropy-label-01
to compete with draft-ietf-idr-next-hop-capability-08.txt or
other drafts regarding next hops or bgp attributes
(e.g. draft-scudder-idr-entropy-label-01 as a "bis" document).


Thanks for the info. Why is there a desire from IDR chairs to bring a second solution (draft-scudder-idr-entropy-label) to compete with the first (draft-ietf-idr-next-hop-capability)?
- Is this that in general two solutions are better than one?
- Is this that the WG expressed comments/limitations on draft-ietf-idr-next-hop-capability?

Bruno argues that it would be better to include this in
draft-ietf-next-hop-capability-08.txt as a fix.

For this shepherd to monitor this portion of the adoption call,
I need John and Bruno to provide additional input:

John: you need to address Bruno's comments on

"So ELCv2 is not to be used. But this draft is more or less saying the opposite in Appendix A, therefore I object the content of Appendix A.
ELCv2 is a proprietary solution. Migrating away of ELCv2 may be handled without the IETF."

Bruno: if we are going to consider draft-ietf-next-hop-capability-08.txt
as alternate short term fix to [RFC 6790] I need to know the following:
Why do you say that draft-ietf-next-hop-capability is a short term fix, while it 1) fixes the problem and 2) it provides a generic tools to advertise BGP Next-Hop dependent capability which will be needed for current MPLS WG evolutions (In Stack Data, Post Stack Data)?
Why are you considering draft-ietf-next-hop-capability as the possible alternate while it's the solution been adopted by the IDR WG. In my opinion those qualifiers "alternate" and "if we are going to consider" would better apply to the recent individual draft (draft-scudder-idr-entropy-label)

1) Do you have a specific proposal for adding this fix to
draft-ietf-next-hop-capability?

If the WG express the need for a non-transitive BGP attribute in order to avoid the software upgrade on the RR it seems straightforward for draft-ietf-next-hop-capability to replace the non-transitive attribute with a transitive attribute recording the latest BGP NH which has modified the attribute. I don't recall such request from the IDR WG.

2) what is the implementation status is for draft-ietf-next-hop-capability-08.txt.
 [how many implementations and how many features]?

I'm not aware of any publically announced implementation.


How
MPLS transitioning away from "Entropy Label for the New Thing"
does not really impact a "bis" draft.  The focus here is publishing a fix
to a broken draft.

- If the focus is publishing a fix for a broken draft, we already have a WG document for this: draft-ietf-idr-next-hop-capability
- IMO, as we know that we need the signal more than ELC, it looks more futureproof to work on a generic solution. draft-ietf-idr-next-hop-capability provides this generic solution, draft-scudder-idr-entropy-label does not

Thank you,
Regards,
--Bruno

As shepherd, I expect that John Scudder and Bruno will answer
these questions as part of their upcoming posts.

Cheerily, Sue



From: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Sent: Thursday, September 8, 2022 10:20 AM
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Subject: RE: [Idr] WG adoption call for draft-scudder-idr-entropy-label-01 (9/6/2022 to 9/20/2022)


Sue,




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From: Idr <[e-mail]<mailto:[e-mail]>> On Behalf Of Susan Hares
Sent: Tuesday, September 6, 2022 10:32 PM
To: [e-mail]<mailto:[e-mail]>
Subject: [Idr] WG adoption call for draft-scudder-idr-entropy-label-01 (9/6/2022 to 9/20/2022)

This begins a 2 week WG Adoption and IPR call for:
https://datatracker.ietf.org/doc/draft-scudder-idr-entropy-label/

The co-authors should respond to this message with an IPR statement.

The specification revised the BGP attribute for Entropy Label Capability.
The abstract of the document states:

  "This specification defines the Entropy Label Capability Attribute
   version 3 (ELCv3), a BGP attribute that can be used to inform an LSP
   ingress router about an LSP egress router's ability to process
   entropy labels.  This version of the attribute corrects a
   specification error in the first version, and an improper code point
   reuse in the second.



1)    We already have a solution for this; an IDR WG document. https://datatracker.ietf.org/doc/html/draft-ietf-idr-next-hop-capability-08

"This document also defines a Next-Hop capability to advertise the

   ability to process the MPLS Entropy Label as an egress LSR for all

   NLRI advertised in the BGP UPDATE.  It updates RFC 6790<https://datatracker.ietf.org/doc/html/rfc6790> with regard

   to this BGP signaling."

I don't recall that the WG expressed an issue on this solution. Nor asked for the use of a non-transitive attribute.
Now if there is a compelling reason to use a transitive attribute, this can be discussed by the WG as part of regular WG work on draft-ietf-idr-next-hop-capability. If needed, both drafts may also be merged.


2) Initiating a technical comparison of transitive vs non-transitive attribute:

Non-transitive:
- require the software upgrade of PE, ASBR, RR

Transitive:
- require the software upgrade of PE, ASBR.
- require the re-implementation, test and debugging of the non-transitive-like filtering.

All in all, small gain in term of deployability at a small cost in term of implementation. Obviously, "small" is in the eye of the beholder.
Regarding software upgrade, the only difference is the BGP Route Reflector which: is a small number of nodes (typically at least two order of magnitude smaller), control plane only / no impact on customers, typically centralized in a very small number of locations, control plane only so very possibly we are talking about a VM or container. I would not call this a 'forklift upgrade'.

Again, this is a discussion that we can have on the WG document that we have (draft-ietf-idr-next-hop-capability)

3) lack of feature coverage
draft-ietf-idr-next-hop-capability is a generic tool allowing the advertisement of different kind of BGP Next-hop dependent capabilities. Entropy label is one, but the MPLS WG is currently defining new data plane features (In Stack Data, Post Stack Data) which will require to advertise different type de capabilities, possibly with related parameters. Therefore the general tool is needed. (and some people in the MPLS WG have even proposed to deprecate the Entropy Label for the New Thing, so defining a new BGP Capability just for Entropy Label may seem a bit late). There are other usages for other dataplane such as IOAM (another IDR WG using draft-ietf-idr-next-hop-capability)

4) In all cases, I don't think we need two solutions for this simple problem. (the operational differences are small, a few %)


In your comments consider:
1) Does this specification fixes errors in versions 1 and 2?

2) Are there any additional errors or weakness in this specification
of version 3?  For example, has this specification clearly described what
happens if version 1, 2 and 3 exist in a network?

Not really. As already expressed on the list, what happens if ELCv2 and ELCv1 exist in the network is BGP sessions reset with a major impact on the network.
So ELCv2 is not to be used. But this draft is more or less saying the opposite in Appendix A, therefore I object the content of Appendix A.
ELCv2 is a proprietary solution. Migrating away of ELCv2 may be handled without the IETF.

3) Will deployment of version 3 of Entropy Label Capability
BGP attribute aid in fixing problems in current networks?

4) Are there enough implementations that this draft should
Be moved quickly to WG LC?

There are no implementations of ELCv3.

Regards,
--Bruno

Cheerily, Sue


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