[mpls] Re: Request WG adoption for draft-jags-mpls-ps-mna-hdr-03.txt

[Loa Andersson <[e-mail]>]

Rakesh, Tnx for this, I think we are close with what you say here and 
what I said in my review of draft-mb-mpls-ioam-dex 
[https://datatracker.ietf.org/doc/review-mb-mpls-ioam-dex-06-rtgdir-early-andersson-2024-06-17/]

The -dex drafts would fit much nicer if we carried the AD as PSD.

I also have a comment on your bullet 2 below.

2. IOAM data field format (32-bit) does not fit well into 32-bit ISD
    LSE due to S bit (e.g., in 31-bit Format D), and it can result in
    limitations, kind of defeats the use of standard IOAM formats

    There is an additional problem in Format D also the bit zero is "taken",
    it is set to "1", to avoid confusing the it with a bSPL. You only have
    30 bits available, this does not make it easier.

    And, if you are going to transport a 22-bit sequence number that is by
    definition mutable,  and can't be transported in bit 1-19. It has to in
    the 11 bit 10-22 and 24-31. Since it is 22 bits it will take 2 Format D
    LSEs and make it even more different from the nice 32-bit aligned fields
    in the original dex-draft.

    I think this is a pretty good example of "case 2" in my previous 
mail, it
    possible to solve as >ISD, but becomes pretty awkward. Points to a PSD
    based solution.

/Loa

Den 2024-06-26 kl. 21:08, skrev Rakesh Gandhi:
> Hi Joel,
>
> Thanks for your review comment.
>
> Based on my understanding, some of the main motivations for adding 
> IOAM direct export data fields in PSD instead of ISD would be:
>
>  1. IOAM data fields such as 32-bit Sequence Number or 32-bit
>     Timestamp in an ISD LSE can lead to undesired ECMP behavior on
>     nodes that use labels for ECMP hashing
>  2. IOAM data field format (32-bit) does not fit well into 32-bit ISD
>     LSE due to S bit (e.g., in 31-bit Format D), and it can result in
>     limitations, kind of defeats the use of standard IOAM formats
>  3. IOAM direct export supports extensibility to optionally add
>     “unlimited” number of data fields. When added as ISD, node RLD
>     would make it difficult to process the entire label stack
>  4. IOAM data fields for direct export (e.g., timestamp, sequence
>     number, flow identifier, Namespace-ID, IOAM Option-Type, etc.)
>     represent metadata (extra baggage) in the received packets
>       * NPU simply exports these metadata (extra baggage) and does not
>         really process them, there is not much motivation to place
>         them in ISD.
>
>
> Based on the discussion, will update draft-gandhi-mpls-mna-ioam-dex-01 
> <https://datatracker.ietf.org/doc/html/draft-gandhi-mpls-mna-ioam-dex-01>. 
>
>
> Thanks,
> Rakesh
>
>
>
> On Wed, Jun 26, 2024 at 10:06 AM Joel Halpern <[e-mail]> wrote:
>
>     Rakesh, I tried to understand the explanation in your draft for
>     why the iOAM DEX needs to be post-stack data.  I could not parse
>     it.  Could you write an email that explains why you think it is
>     needed?
>
>     Thank you,
>
>     Joel
>
>     On 6/26/2024 9:12 AM, Rakesh Gandhi wrote:
>>     Thanks Jags.
>>
>>     The PSD solution for MNA defined in draft-jags-mpls-ps-mna-hdr-03
>>     is used for IOAM and IOAM DEX in draft-gandhi-mpls-mna-ioam-dex-01:
>>
>>         https://datatracker.ietf.org/doc/html/draft-gandhi-mpls-mna-ioam-dex-01
>>
>>
>>     IOAM and IOAM DEX use-cases for MNA are defined in
>>     draft-ietf-mpls-mna-usecases-10:
>>     https://datatracker.ietf.org/doc/html/draft-ietf-mpls-mna-usecases-10
>>
>>     The PSD solution is useful for IOAM and IOAM-DEX, I support the
>>     request for WG adoption for draft-jags-mpls-ps-mna-hdr-03 (as
>>     co-author).
>>
>>     P.S. I understand this email was not the WG adoption poll
>>     initiated by the chairs.
>>
>>     Thanks,
>>     Rakesh
>>
>>
>>
>>
>>
>>     On Tue, Jun 25, 2024 at 10:52 PM Jaganbabu Rajamanickam
>>     (jrajaman) <jrajaman=[e-mail]> wrote:
>>
>>         Hello Chairs,
>>
>>            We would like to request WG adoption for
>>         draft-jags-mpls-ps-mna-hdr.
>>
>>            Updated the draft with the initial review comments and the
>>         latest MNA header format.
>>
>>           Welcome your review comments and suggestions.
>>
>>         Thanx,
>>
>>         Jags
>>
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-- 
Loa Andersson
Senior MPLS Expert
Bronze Dragon Consulting
[e-mail]
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