[mpls] Re: Working Group Last Call on draft-ietf-mpls-mna-hdr (2nd WG call)

[Fabian Ihle <[e-mail]>]

Hi all,

we updated our P4 implementation to meet the latest version of the 
encoding draft.

The challenges we faced in our implementation at the interim meeting were:

 1. The initial opcode could not carry AD LSE. Back then we proposed to
    redefine fields in the bSPL to eliminate the initial opcode
    encoding. The draft got updated and now supports AD LSE with a new
    length field in the initial opcode LSE. Further, the draft states
    that TC and TTL values should not have special meanings due to
    compatibility with MNA unaware solutions. Therefore, this issue is
    resolved.
 2. Mutable data with ISD is not efficient and not possible with SR.
    Therefore PSD should be used IF a network action requires mutable
    data. This discussion is still ongoing.

We currently have two implementations in P4: one using ISD only, and one 
using "PSD only". For the PSD only, we use a minimum-sized NAS and the P 
bit from the jags draft to indicate the presence of PSD. This means we 
need 2 LSEs: one Format A, and one Format B with the P bit set. For the 
PSD only implementation, LSEs are wasted, as we need two LSEs to 
indicate PSD with a single bit. This scales even worse with multiple 
scopes. We have some ideas on how to tackle this and are currently in 
the process of putting all the pieces together. However, this might 
require more changes than redefining the semantics of a reserved bit in 
the encoding draft.

For the ISD implementation, I'd like to hear about the RLD from other 
vendors. An implementation supporting maximum-sized NAS means that each 
NAS requires 17 LSE. Having a select-scoped NAS, and a HBH NAS at one 
node then already requires 34 LSE (excluding the forwarding labels). Our 
implementation is capable of this, how about others?

Best,

Fabian

On 26.09.24 18:28, Dongjie (Jimmy) wrote:
>
> Hi Tarek,
>
> Before the 1st WG LC, some implementation experience with the -04 
> version of this draft was presented on an interim meeting: 
> https://datatracker.ietf.org/meeting/interim-2024-mpls-01/session/mpls. 
> That implementation was from Academia.
>
> As shown in the meeting materials, the implementors met some 
> challenges with the encodings in -04 version, they asked some 
> questions and also gave some proposals for possible optimization. As 
> part of the WG LC, it would be important to check whether the issues 
> raised at that time have be addressed by the latest version. It would 
> be helpful if some feedback on the latest version can be provided by 
> those implementors.
>
> At IETF 120 I asked one question about the implementation report. Are 
> we aware of any other implementation of this document, besides the 
> implementation of the -04 version from Academia? This would be 
> important to gauge the maturity of the document and the interest in 
> implementing it.
>
> Best regards,
>
> Jie
>
> *From:*Tarek Saad <[e-mail]>
> *Sent:* Tuesday, September 24, 2024 9:25 PM
> *To:* [e-mail]
> *Cc:* MPLS Working Chairs <[e-mail]>; 
> [e-mail]
> *Subject:* [mpls] Working Group Last Call on draft-ietf-mpls-mna-hdr 
> (2nd WG call)
>
> Dear WG,
>
> This email starts a two-week Working Group last call for 
> draft-ietf-mpls-mna-hdr 
> <https://datatracker.ietf.org/doc/draft-ietf-mpls-mna-hdr/>. This is 
> the 2^nd WG last call for this document.
>
> Please indicate your support or concern for this draft. If you are 
> opposed to the progression of the draft to RFC, please articulate your 
> concern. If you support it, please indicate that you have read the 
> latest version, and it is ready for publication in your opinion. As 
> always, review comments and nits are most welcome.
>
> Please send your comments to the mpls WG mailing list ([e-mail])
>
> If necessary, comments may be sent unidirectional to the WG chairs.
>
> Note, currently there are 5 IPR disclosures against this document at 
> https://datatracker.ietf.org/ipr/search/?submit=draft&id=draft-ietf-mpls-mna-hdr 
> <https://datatracker.ietf.org/ipr/search/?submit=draft&id=draft-ietf-mpls-mna-hdr>
>
> This poll runs until October 8, 2024.
>
> Thank you,
>
> Tarek (for the MPLS WG co-chairs)
>
>
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-- 
Fabian Ihle
Universität Tübingen
Fachbereich Informatik Lehrstuhl Kommunikationsnetze
Wilhelm-Schickard-Institut für Informatik
Sand 13, 72076 Tübingen

Raum: B303
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