Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Tom Herbert <tom@herbertland.com> Fri, 22 May 2020 15:34 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Fri, 22 May 2020 08:34:39 -0700
Message-ID: <CALx6S34Dj67F58W5hvETYttqKytB72hw6QrLMCdhZ26eqtZ+Hw@mail.gmail.com>
Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH
To: "Ketan Talaulikar (ketant)" <ketant=40cisco.com@dmarc.ietf.org>
Cc: "Joel M. Halpern" <jmh@joelhalpern.com>, "rtg-ads@ietf.org" <rtg-ads@ietf.org>, "spring@ietf.org" <spring@ietf.org>, 6man <6man@ietf.org>
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On Thu, May 21, 2020 at 10:21 PM Ketan Talaulikar (ketant)
<ketant=40cisco.com@dmarc.ietf.org> wrote:
>
> Hi Joel,
>
> I'll point you to RFC7855, RFC8355 and RFC8402 that cover both the data-planes for Spring. Then the RFC8354 which is focussed on SRv6. All this body of work along with a whole lot of discussion and brainstorming happening in the Spring WG provided the architecture, use-cases, applicability and requirements for SRH (RFC8754).

Ketan,

There was also a whole lot of discussion that took place in 6man when
SRH draft was being worked on. There were fundamental aspects of SRH
that were questioned such as: why does SRH require its own TLVs and
why aren't Destination Options before the Routing Header sufficient,
why does SRH need flags and tag field, why does it require its own
header authentication instead of just relying on AH (which in fact SRH
actually breaks AH), what are the mutability requirements of the
header. There were also questions about the overhead of carrying lists
of 128 bit addresses, as well as implications of using IPv6 addresses
as SIDs. Of course, SRH motivated the whole discussion about extension
header insertion and deletion.

Some of these questions were answered, some were not and the draft
advanced with noted objections-- but, in all those discussions I don't
believe any of these questions were answered by someone just referring
us to an architecture or requirements document.

Tom

>
> It may be so that many people in 6man focussed on only the IPv6 specific aspects as is their design expertise. But there were others (in 6man, Spring and other WGs) that were able to look at the solution in a holistic manner thanks to the body of work behind it.
>
> Net-PGM builds on top of RFC8402 and RFC8754.
>
> To give a real world analogy, let us understand what kind of a car we are trying to build (to carry goods/passengers or both and how much/many, what terrain it is meant for, what weather/environment conditions, how much speed/performance/fuel efficiency parameters required, etc.) before we start designing tyres for it.
>
> Thanks,
> Ketan
>
> -----Original Message-----
> From: Joel M. Halpern <jmh@joelhalpern.com>
> Sent: 22 May 2020 10:02
> To: Ketan Talaulikar (ketant) <ketant@cisco.com>
> Cc: spring@ietf.org; 6man <6man@ietf.org>rg>; rtg-ads@ietf.org
> Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH
>
> Ketan, I am trying to figure out which documents you think were adopted and approved elsewhere to drive the 6man work on SRH.
>
> I did find RFC 8354, which was a use case.  It is not a problem statement.  It is most definitely not an architecture.  The only architecture documents I can find are general SR documents.  Those did not justify a need for SRH.  And I (at least) did not object to SRH on the basis of that gap.
>
> Yes, SRH normatively references 8402.  But 8402 does not drive any need for SRH.  In fact, the actual text references to SRH are fairly cursory.
>   (The most significant is some terminology.)
>
> In fact, as far as I can tell, the ties are such that there is no evidence in the documents that SPRING had any say in SRH.  (the reality is more complex, I grant you.  But there was no formal approval or signoff.)
>
> As far as I can tell, there was no formal approval of anything by SPRING that can be read as a request to 6man to work on SRH.  (Do remember that the SRH document was adopted by 6man in December of 2015.)  The network programming draft did not even appear at 00 until March of 2017, 15 months later.
>
> How, given this history, can you claim that CRH needs something more.
> We have operators asking for this.
>
> Yours,
> Joel
>
> On 5/21/2020 11:53 PM, Ketan Talaulikar (ketant) wrote:
> > Hi Bob,
> >
> > Perhaps I will try to make my case to you (and everyone else here) …
> > one last time.
> >
> > This is how I've seen RH work being done in 6man until now (in a
> > matter that fits its charter).
> >
> > 1) There is a WG (not 6man) that defines the problem statement,
> > use-cases and architecture that requires RH
> >
> > 2) The 6man being the experts on IPv6 design, either take up the
> > document that specifies that RH (or even if it is done in another WG,
> > reviews it).
> >
> > So 6man has always had work done in (1) to reference and lean upon
> > when doing (2).
> >
> > My argument of the shortcut in the case of this specific adoption is
> > that we don't have (1).
> >
> > It is not in 6man charter nor expertise to take up (1) because CRH is
> > not purely IPv6 work. It is not meant for "Internet" but a specific
> > "limited domain". The SIDs that it introduces is a new "mapping ID"
> > concept. It is not an IPv6 address and neither it is MPLS. This is a
> > *_Routing_* Header and part of a new Source *_Routing_* solution.
> >
> > Therefore, without (1) being made available to 6man, I believe that
> > working on (2) in 6man is to me a shortcutting of the IETF technical
> > review process (specifically of the *_Routing_* area in this case) for
> > a solution and does not provide the necessary reference for 6man to work on.
> >
> > Why the rush?
> >
> > I close my arguments.
> >
> > Thanks,
> >
> > Ketan
> >
> > -----Original Message-----
> > From: Bob Hinden <bob.hinden@gmail.com>
> > Sent: 22 May 2020 09:03
> > To: Ketan Talaulikar (ketant) <ketant@cisco.com>
> > Cc: Bob Hinden <bob.hinden@gmail.com>om>; Brian Carpenter
> > <brian.e.carpenter@gmail.com>om>; Ron Bonica <rbonica@juniper.net>et>;
> > Chengli (Cheng Li) <c.l@huawei.com>om>; Zafar Ali (zali)
> > <zali@cisco.com>om>; Robert Raszuk <robert@raszuk.net>et>; spring@ietf.org;
> > 6man <6man@ietf.org>
> > Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of
> > CR in CRH
> >
> > Ketan,
> >
> >  > On May 21, 2020, at 8:12 PM, Ketan Talaulikar (ketant)
> > <ketant=40cisco.com@dmarc.ietf.org
> > <mailto:ketant=40cisco.com@dmarc.ietf.org>> wrote:
> >
> >  >
> >
> >  > Hi Brian,
> >
> >  >
> >
> >  > Please see my previous response to your comments.
> >
> >  >
> >
> >  > My argument is not legalistic. I am not as experience in IETF work
> > as you and Bob are. But what I understand is that the reason why we
> > have these "legal" process of charters and BoF is to enable a proper
> > technical discussion with the right context and details of the
> > proposal presented for review of the community.
> >
> >  >
> >
> >  > I do not see how shortcutting them helps anyone and I wonder why it
> > is being done in this case?
> >
> > There is no short cutting here.  The adoption call is to determine if
> > there is interest in the w.g. to take this work into 6man.   If it
> > becomes a w.g. draft, then the w.g. is responsible to decide what
> > happens next.
> >
> > It’s a first step, it is not a decision to publish it.
> >
> > Bob (w/ w.g. chair hat on)
> >
> >  >
> >
> >  > Thanks,
> >
> >  > Ketan
> >
> >  >
> >
> >  > -----Original Message-----
> >
> >  > From: Brian E Carpenter <brian.e.carpenter@gmail.com
> > <mailto:brian.e.carpenter@gmail.com>>
> >
> >  > Sent: 22 May 2020 04:18
> >
> >  > To: Ketan Talaulikar (ketant) <ketant@cisco.com
> > <mailto:ketant@cisco.com>>; Ron Bonica <rbonica@juniper.net
> > <mailto:rbonica@juniper.net>>; Chengli (Cheng Li) <c.l@huawei.com
> > <mailto:c.l@huawei.com>>; Zafar Ali (zali) <zali@cisco.com
> > <mailto:zali@cisco.com>>; Robert Raszuk <robert@raszuk.net
> > <mailto:robert@raszuk.net>>
> >
> >  > Cc: spring@ietf.org <mailto:spring@ietf.org>; 6man <6man@ietf.org
> > <mailto:6man@ietf.org>>
> >
> >  > Subject: Re: CRH is back to the SPRING Use-Case - Re: Size of CR in
> > CRH
> >
> >  >
> >
> >  > On 22-May-20 05:26, Ketan Talaulikar (ketant) wrote:
> >
> >  > ...> It is the 6man charter that precludes it from defining a new
> > Source Routing solution..
> >
> >  >> “It is not chartered to develop major changes or additions to the
> > IPv6 specifications.”
> >
> >  >
> >
> >  > If this addition was major, that would be true. But adding a new RH
> > type is well within the scope of maintenance, IMHO. We have already
> > done it quite recently.
> >
> >  >
> >
> >  > In any case, legalistic arguments about WG charters are really not
> > how we should take technical decisions.
> >
> >  >
> >
> >  > Regards
> >
> >  >    Brian
> >
> >  >
> >
> >  >
> >
> >  > _______________________________________________
> >
> >  > spring mailing list
> >
> >  > spring@ietf.org <mailto:spring@ietf.org>
> >
> >  > https://www.ietf.org/mailman/listinfo/spring
> >
> >
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