[mpls] Re: Poll: IOAM and PSD

[Joel Halpern <[e-mail]>]

I wondeer if we can find some better terminology.  You are correct that 
the sequence number on packets is not the same in successive packets in 
a flow.  So, depending upon how you use the term "mutable" it is mutable 
between packets in a flow.  It is not changed (mutatated) by the devices 
that process it.  We have other use cases where we use "mutable" to mean 
that.   Can we disentangle them?

Thanks,

Joel

On 8/3/2024 11:44 PM, Loa Andersson wrote:
> 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
>>>
>>>
>>>     _______________________________________________
>>>     mpls mailing list [e-mail]
>>>     To unsubscribe send an email [e-mail]
>>
>>     --     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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