Re: [spring] "This solution does not require any SRH data plane change" in draft-filsfilscheng-spring-srv6-srh-compression-02

4.  SRv6 Specific Requirements

4.1.  SRv6 Based

*   Description: A solution to compress SRv6 SID Lists SHOULD be based on
 the SRv6 architecture, control plane and data plane. * The compression
   solution MAY be based on a different data plane and control plane,
   provided that it derives sufficient benefit.

It is clearly a requirement. It is not an exclusive requirement, but that
does not make it of any less importance as evaluation criteria. Analysis
draft provides comparison table in section 3.1

But please let's not derail this thread as I provided a specific question
to John.

Many thx,
R.

On Tue, Oct 26, 2021 at 10:01 PM Ron Bonica <rbonica@juniper.net> wrote:

> Robert,
>
>
>
> Which requirement was that?
>
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>
>                                     Ron
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> Juniper Business Use Only
>
> *From:* spring <spring-bounces@ietf.org> *On Behalf Of *Robert Raszuk
> *Sent:* Tuesday, October 26, 2021 3:41 PM
> *To:* John Scudder <jgs@juniper.net>
> *Cc:* draft-filsfilscheng-spring-srv6-srh-compression@ietf.org;
> spring@ietf.org
> *Subject:* Re: [spring] "This solution does not require any SRH data
> plane change" in draft-filsfilscheng-spring-srv6-srh-compression-02
>
>
>
> *[External Email. Be cautious of content]*
>
>
>
> Hello John,
>
>
>
> May I inquire what was not definitive as part of my answer ?
>
>
>
> Please observe that below documents which are product of this WG go in
> depth to evaluate compression against the requirement not to change SRv6
> data plane:
>
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> https://datatracker.ietf.org/doc/html/draft-srcompdt-spring-compression
> -requirement
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-srcompdt-spring-compression-requirement__;!!NEt6yMaO-gk!W8DcKe4AgQyCCvA2v_GW3_9ZaJ_RJ2Ll6-kbhylSgO0YHbi3AQVZRHMPrQcnZRJk$>
>
> https://datatracker.ietf.org/doc/html/draft-srcompdt-spring-compression
> -analysis
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-srcompdt-spring-compression-analysis__;!!NEt6yMaO-gk!W8DcKe4AgQyCCvA2v_GW3_9ZaJ_RJ2Ll6-kbhylSgO0YHbi3AQVZRHMPrft1hBsN$>
>
>
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> Would your enquiry be satisfied if the draft in question s/SRH data
> plane/SRv6 data plane/ ?
>
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> Kind regards,
>
> Robert
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> On Tue, Oct 26, 2021 at 7:55 PM John Scudder <jgs@juniper.net> wrote:
>
> (For clarity: I’m not wearing any hats other than “WG contributor”.)
>
> Hi All,
>
> Since there hasn’t been any definitive answer from the authors, nor any
> update to the draft to address the issue, and given that the disputed
> statement seems to be an important premise for evaluation of the fitness of
> the draft for adoption (at least, the authors considered it fundamental
> enough to put in the abstract): I’m opposed to adoption of the draft until
> this question has been settled, or at least meaningfully addressed.
>
> Regards,
>
> —John
>
> P.S.: I will also follow up to the main adoption thread to assist with
> issue tracking.
>
> > On Oct 13, 2021, at 6:28 PM, John Scudder <jgs=
> 40juniper.net@dmarc.ietf.org> wrote:
> >
> >
> > Hi Folks,
> >
> > I’m struggling with the claim repeated throughout the beginning of
> draft-filsfilscheng-spring-srv6-srh-compression-02 (Abstract, §1, §3) that
> “this solution does not require any SRH data plane change”.
> >
> > I’m not aware of a standardized formal definition of “data plane”, it
> seems to follow Justice Stewart’s maxim of “I know it when I see it”.
> However, here’s an attempt, cribbed from some Washington University course
> slides: a “local, per-router function that determines how a datagram
> arriving on a router input port is forwarded to a router output port”.
> Seems reasonable.
> >
> > I also am not aware of a standardized formal definition of the term “SRH
> data plane”, in fact this draft, its predecessors, some associated blog
> posts, and Clarence’s dissertation, are the only places a search finds the
> phrase (but it’s not formally defined in any of them). So I’m just going to
> assume it means the data plane, as applied to packets that include an SRH.
> (I’m not sure why we should disregard packets that are encoded using
> NEXT-C-SID that omit the SRH, but let’s overlook that for now.)
> >
> > If this solution does not require any SRH data plane change, presumably
> it would be true that if I take a packet that includes an SRH and place
> within it a series of SIDs encoded with (for example) the REPLACE-C-SID
> flavor, then that packet would be able to successfully traverse a network
> of routers that support plain vanilla RFC 8754. That is, it would arrive at
> its first hop router which according to a local, per-router function, would
> determine how to take the datagram arriving on the router input port and
> forward it to (the correct) router output port. Then that process would be
> repeated across the rest of the network.
> >
> > But that is patently incorrect: when it’s delivered to the first hop,
> the plain vanilla RFC 8754 router will be unable to apply the REPLACE-C-SID
> behavior, and forwarding to the next hop will fail. It seems that a
> different local, per-router function is required (in fact, the local,
> per-router function defined in the draft) in order for the forwarding to
> succeed. By the definitions I’m using here, that is exactly a data plane
> change.
> >
> > What, precisely, is then being claimed?
> >
> > Thanks,
> >
> > —John
> > _______________________________________________
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