[mpls] Re: Poll: IOAM and PSD

[Loa Andersson <[e-mail]>]

Greg,

I think Michael is right.

DEX is useful and we need it, but it does not solve all and any problem.

I thought DEX was about transporting data/info generated by a node, and 
outgoing packet. This data is by defiintion immutable and is for example 
never hashed for load sharing purposes

The issue with mutable data, e.g. the sequence number, is that it is in 
an incoming packet and mutable. If the network is doing ECMP by scanning 
the label stack, then the sequence number can't in the first 20 bits of 
an LSE.

Right?

/Loa

Den 04/08/2024 kl. 22:58, skrev Greg Mirsky:
> Hi Michael,
> I don't think that "IOAM requires mutable data" is an accurate 
> statement. RFC 9326 IOAM Direct Export 
> <https://datatracker.ietf.org/doc/rfc9326/> indeed defines optional 
> parameters, Flow ID and Sequence Number, to ease the correlation 
> process of collected telemetry data. For some applications, e.g., 
> DetNet over MPLS <https://datatracker.ietf.org/doc/rfc8964/>, both 
> these parameters already are present as part of the DetNet MPLS 
> encapsulation as S-label (Service) and Sequence Number in d-CW or 
> d-ACH, respectively. Furthermore, the IPPM WG draft on collecting 
> telemetry data 
> <https://datatracker.ietf.org/doc/draft-ietf-ippm-hybrid-two-step/> can 
> be used without the use of the optional IOAM-DEX fields, i.e., Flow-ID 
> and Sequence Number.
>
> Regards,
> Greg
>
> On Sat, Aug 3, 2024 at 6:43 AM Michael Menth <[e-mail]> 
> wrote:
>
>     Hi all,
>
>     we're not operators but researchers who implemented some IOAM
>     flavors in combination with SR using P4 on Tofino. We've presented
>     some results at an interim meeting before:
>     https://datatracker.ietf.org/meeting/interim-2024-mpls-01/session/mpls
>
>     IOAM requires mutable data. In combination with multiple labels,
>     e.g., for SR, these mutable data need to be near the bottom of the
>     stack, otherwise they get popped along the way. Moving them to PSD
>     makes encoding more efficient without increasing the effective
>     header length that needs to be parsed. Therefore, we think PSD is
>     the better option for applications like IOAM.
>
>     Regards
>
>     Michael
>
>     Am 30.07.2024 um 17:25 schrieb Tony Li:
>>
>>     [WG chair hat: on]
>>
>>     Hi all,
>>
>>     We’ve had many discussions about IOAM and PSD over the last few
>>     years. We need to reach consensus on the problems that need to be
>>     addressed in these areas. Therefore, we would like to hear from
>>     everyone, especially independent operators:
>>
>>     1.
>>
>>         There are many flavors of IOAM.  Which ones would you like to
>>         deploy/implement with MNA?
>>
>>     2.
>>
>>         Do you have other applications of MNA that have not been
>>         proposed yet?
>>
>>      This poll will close in two weeks, at 9am PDT, Aug 13.
>>
>>     Regards,
>>
>>     MPLS chairs
>>
>>
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>
>     -- 
>     Prof. Dr. habil. Michael Menth
>     University of Tuebingen
>     Faculty of Science
>     Department of Computer Science
>     Chair of Communication Networks
>     Sand 13, 72076 Tuebingen, Germany
>     phone: [phone]
>     mailto:[e-mail]  <mailto:[e-mail]>
>     http://kn.cs.uni-tuebingen.de
>
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-- 
Loa Andersson
Senior MPLS Expert
Bronze Dragon Consulting
[e-mail]
[e-mail]