[mpls] Re: Poll: IOAM and PSD

[Joel Halpern <[e-mail]>]

That would work for me.

Thank you,

Joel

On 8/5/2024 12:42 AM, Tony Li wrote:
> [WG chair hat: off]
>
> Towards that end, I would like to propose:
>
> Mutable data: data that changes while the packet is in transit.
>
> Variable data: data that is constant while the packet is in transit, 
> but may vary across packets in the same LSP.
>
> T
>
>
>> On Aug 3, 2024, at 9:31 PM, Greg Mirsky <[e-mail]> wrote:
>>
>> 
>> Hi Loa,
>> thank you for sharing your thoughts. Please find my notes below 
>> tagged GIM>>.
>>
>> Regards,
>> Greg
>>
>> On Sat, Aug 3, 2024 at 8:44 PM Loa Andersson <[e-mail]> wrote:
>>
>>     Greg,
>>
>>     I think Michael is right.
>>
>>     DEX is useful and we need it, but it does not solve all and any
>>     problem.
>>
>> GIM>> Can you point me to where these "all and any problem" DEX is 
>> expected to solve? Or IOAM in general?
>>
>>
>>     I thought DEX was about transporting data/info generated by a
>>     node, and
>>     outgoing packet. 
>>
>> GIM>> Perhaps some of my presentations, comments contributed to that 
>> misunderstanding. IOAM-DEX is not to transport data generated by the 
>> node but to separate the generation of the operational state and 
>> performance data from transporting them in the IOAM tagged packet 
>> that triggered the origination of data in the first place. IOAM-DEX 
>> allows operators use their preferred management plane mechanisms, 
>> e.g., IPFIX, protobuf, to collect data. Furthermore, raw data could 
>> be processed locally on the node that generated them and the results, 
>> e.g., mean, median, percentiles, exported.
>>
>>     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. 
>>
>> GIM>> As defined in RFC 9326 
>> <https://datatracker.ietf.org/doc/rfc9326/>, the Sequence Number is 
>> optional. And, as presented at the MPLS meeting in Vancouver, it, if 
>> needed, can use mutable 11 bits of LSE Format D. Hence, I think that 
>> the mutable concern, in my opinion, is addressed.
>>
>>     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.
>>
>> GIM>> Yes, the authors of draft-mb-mpls-ioam-dex 
>> <https://datatracker.ietf.org/doc/draft-mb-mpls-ioam-dex/> recognized 
>> that and propose the reasonable way to handle the situation.
>>
>>
>>     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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>>     >
>>     > _______________________________________________
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>>
>>     -- 
>>     Loa Andersson
>>     Senior MPLS Expert
>>     Bronze Dragon Consulting
>>     [e-mail]
>>     [e-mail]
>>
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