Re: [mpls] Working Group Adoption Poll for draft-andersson-mpls-mna-fwk

["Dongjie (Jimmy)" <[e-mail]>]

Hi Chairs,

I agree that a framework document for MNA is needed, and the current draft-andersson-mpls-mna-fwk is the starting point.

While in order to make it useful in guiding the solution design, I do think this document needs to be further improved before it can be adopted.

Here are some major comments on this document, some of them has been raised in a previous review, but has not been addressed yet.


1.      The relationship between MNA label and NAS



It is clear that the MNA label (a bSPL) is needed regardless whether ISD or PSD or both are carried in the packet. For example, the framework should allow a solution with the combination of MNA label and PSD only.



In the current framework draft, the MNA label is defined as Network Action Sub-Stack Indicator (NSI), this could confuse people the MNA label is bound with in-stack data, while it makes more sense to treat the MNA label as a separate construct from the NAS/ISD, so that it could also be allowed to be used with PSD only.  Maybe it is better to call it "MNA indicator" instead of "NAS Indicator".



2.      The impact to MPLS architecture and forwarding model



The introduction of ISD and PSD to MPLS no only means possible changes to the MPLS label entry encoding, it also implies changes to the MPLS forwarding model of RFC 3031. For example, the traditional MPLS packet forwarding is only based on the top most label entry, however this will be changed by MNA. The changes like this need to be captured somewhere, and it seems the framework draft is the right place.



3.      Align with the ISD and PSD poll result



The result of the poll on ISD and PSD was: https://mailarchive.ietf.org/arch/msg/mpls/sFiqn-c8ThFGFLODKe2bTksPhcM/



"The Framework document must be solution independent and say:

         a packet may carry Ancillary Data using one or both of the  following methods:

    (1) in-stack, and

              (2) post-stack."

And



        "There is also a fairly strong opinion that solutions that specify the use of ISD, should take special care to provide the motivation for the use of ISD. "

        It shows there are concerns about the use of ISD, and people mentioned the use ISD needs to be minimized.

        However, the text in the beginning of section 2 structure is talking about a solution with multiple NAS (ISD):

"An MNA solution is envisioned as a set of network action sub-stacks, plus possible post-stack data."

          It is suggested this text be updated to reflect the consensus on ISD and PSD. It could be something like:

"An MNA solution is envisioned to carry either one or both of the in-stack data and post-stack data, while it needs to provide the motivation for the use of ISD."


4.      Imbalance in the text about ISD and PSD



In several places of the current document, detailed description about NAS/ISD are provided, while the same level of description of PSD is not provided. Assuming that they are equally important to the framework,  this could be solved by moving some NAS/ISD text to the solution documents, or borrow some architecture text about PSD from the MPLS extension header drafts.


Hope this helps.

Best regards,
Jie

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Sent: Tuesday, June 28, 2022 9:55 PM
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Subject: [mpls] Working Group Adoption Poll for draft-andersson-mpls-mna-fwk

Working Group,

This is to start a two week poll on adopting  draft-andersson-mpls-mna-fwk as a MPLS working group
document.

Please send your comments (support/not support) to the mpls working group mailing list ([e-mail]<mailto:[e-mail]>).
Please give a technical motivation for your support/not support, especially if you think that
the document should not be adopted as a working group document.

There are two IPRs disclosure against this document. Details can be found here:

https://datatracker.ietf.org/ipr/5703/
https://datatracker.ietf.org/ipr/5659/
An IPR poll was done, and all the authors and contributors have stated on the MPLS WG mailing list that
they are unaware of any other IPR that relates to this document

The working group adoption poll ends July 12th , 2022.

Nic