Re: [spring] Penultimate Segment Popping and RFC8200 (Was Re: We don't seem to be following our processes (Re: Network Programming - Penultimate Segment Popping))

"Adrian Farrel" <adrian@olddog.co.uk> Sat, 07 December 2019 21:26 UTC

Return-Path: <adrian@olddog.co.uk>
X-Original-To: spring@ietfa.amsl.com
Delivered-To: spring@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9BD6112082F for <spring@ietfa.amsl.com>; Sat, 7 Dec 2019 13:26:49 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.598
X-Spam-Level:
X-Spam-Status: No, score=-2.598 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_NONE=0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id AW9dAIJ-qf2z for <spring@ietfa.amsl.com>; Sat, 7 Dec 2019 13:26:47 -0800 (PST)
Received: from mta7.iomartmail.com (mta7.iomartmail.com [62.128.193.157]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 3974212004A for <spring@ietf.org>; Sat, 7 Dec 2019 13:26:47 -0800 (PST)
Received: from vs1.iomartmail.com (vs1.iomartmail.com [10.12.10.121]) by mta7.iomartmail.com (8.14.4/8.14.4) with ESMTP id xB7LQjsb006573; Sat, 7 Dec 2019 21:26:45 GMT
Received: from vs1.iomartmail.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F12D62207F; Sat, 7 Dec 2019 21:26:44 +0000 (GMT)
Received: from asmtp3.iomartmail.com (unknown [10.12.10.224]) by vs1.iomartmail.com (Postfix) with ESMTPS id DC3F32207E; Sat, 7 Dec 2019 21:26:44 +0000 (GMT)
Received: from LAPTOPK7AS653V ([84.93.96.25]) (authenticated bits=0) by asmtp3.iomartmail.com (8.14.4/8.14.4) with ESMTP id xB7LQiFd023455 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sat, 7 Dec 2019 21:26:44 GMT
Reply-To: <adrian@olddog.co.uk>
From: "Adrian Farrel" <adrian@olddog.co.uk>
To: "'Brian E Carpenter'" <brian.e.carpenter@gmail.com>, "'SPRING WG'" <spring@ietf.org>
References: <f2a0ad13-0eba-6f5a-1d3c-e45e2780f201@si6networks.com> <D666EA6E-E8E9-439A-9CDE-20857F03CB65@employees.org> <4255AD3B-379C-45BF-96E1-D3D9141A684F@liquidtelecom.com> <d59de54e-c7f8-be67-1e77-b051735d40a6@gmail.com> <3bce7b18-ea45-d29f-5dfb-1d3258b07d1e@si6networks.com> <c6e1f690-b0bf-9f45-8fa7-92ed182c5b04@gmail.com> <a2cc5cbd-ac06-e193-307c-3ffe5b21b0b1@si6networks.com> <80A78F48-9802-4DA9-B264-1A8920C1DDF9@kaloom.com> <MWHPR11MB1600C5E0821814913110DA16C15E0@MWHPR11MB1600.namprd11.prod.outlook.com> <a3b37257-9673-8d0b-b862-e94e094c62fa@gmail.com>
In-Reply-To: <a3b37257-9673-8d0b-b862-e94e094c62fa@gmail.com>
Date: Sat, 7 Dec 2019 21:26:43 -0000
Organization: Old Dog Consulting
Message-ID: <04b601d5ad45$062786a0$127693e0$@olddog.co.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AQFGAnnmlEKLPVHeDLpaNkShcWbBAwFMr39dAkCPsKMBugG/wAIcmGotAXkY5CQB74zAKAJfz7/sAdMGP9cCGMSP0qhFw6gw
Content-Language: en-gb
X-Originating-IP: 84.93.96.25
X-Thinkmail-Auth: adrian@olddog.co.uk
X-TM-AS-GCONF: 00
X-TM-AS-Product-Ver: IMSVA-9.0.0.1623-8.2.0.1013-25090.003
X-TM-AS-Result: No--24.310-10.0-31-10
X-imss-scan-details: No--24.310-10.0-31-10
X-TMASE-Version: IMSVA-9.0.0.1623-8.2.1013-25090.003
X-TMASE-Result: 10--24.309600-10.000000
X-TMASE-MatchedRID: IeZYkn8zfFrgQ1B1MOCRzT/vQrzBjp6UNtQas3JOHmjaOIP2b6ZfX9Rl myjfMuuvG86r2sytqhn2xPYX08NXspNLuA4iPC3wTNDKZy5/hvQYOnQDwWp0xC62hjZS0WoYkKa 0W/D+XilDQvyrk4qfvJZ7rfN9VJLwTGrxUPD863Lmu6GrtSORDxmyTBaqiJvcRP5pzC9VlZg3jG r4Y9HXMX4GcCB9LiTQ4slG5grepOg9YosDr+D/+/HkpkyUphL9yeUl7aCTy8hQdwGfvSIlB0Y/F nCqVhStybz368KglmEBU9vJN4D7byWcfeJKQl9YuoibJpHRrFlnXBVFJwvSMAAheUymmndfcQ2a h832eukQSK75DSbBzo4FH7MC6NcGEnaXhoxT5343X0+M8lqGUjdI0wuKhB4t6NfipxutJCf5vLc kcCULVMlov5iwmAe67Gg2NYxPtKgeMiLfxDfeySQ7ls378/zHJuJX9LfoIjj7jZ40qn7f4fznNg amBrh08vwsrbfwnUSDGJYLgMxhqF0ieHN50/kHLyz9QvAyHjqpvf+jmz45w8Hx9l2YYLoQt0LfP CopieE3Opzody2+qtCWKyZBDwPhoIutGEGtrEMD2WXLXdz+ATmKihe1K2IeC/U4++8MvOwjXowQ GjrACs0YxsHTpdZNo1iPgKgiLB1UHLGrNupy0FyuZHgmvm5ozIs/K2gEmgWiyxjC+6hq+4tYef8 EoZUCTs5apCH0JNKDSuJUOBtVJPx8QbDyWf2LLjsmuOashGK8xE2H2EuMWTXSEULATMS5Laxx5K hV9JQQ4ddDw+W7F2itnBG1/u/BCa4ersRYGFqeAiCmPx4NwFkMvWAuahr8m5N2YHMD0b8MyrfP9 j+C1d934/rDAK3zUc1+O1X9AzE=
X-TMASE-SNAP-Result: 1.821001.0001-0-1-12:0,22:0,33:0,34:0-0
Archived-At: <https://mailarchive.ietf.org/arch/msg/spring/qoLxBUCW5UPtOfpiK9Y-Af8FFCY>
Subject: Re: [spring] Penultimate Segment Popping and RFC8200 (Was Re: We don't seem to be following our processes (Re: Network Programming - Penultimate Segment Popping))
X-BeenThere: spring@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Source Packet Routing in NetworkinG \(SPRING\)" <spring.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/spring>, <mailto:spring-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/spring/>
List-Post: <mailto:spring@ietf.org>
List-Help: <mailto:spring-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/spring>, <mailto:spring-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sat, 07 Dec 2019 21:26:49 -0000

[Hmmm, there were a lot of people in the to/cc fields. I trimmed a bit because (hopefully) some of them are subscribed to the mailing lists.]

Brian,

I think some of the notion of "popping an SRH" may be associated with the idea of having more than one SRH present. Whether that is a good idea is a different question.

Cheers,
Adrian

-----Original Message-----
From: spring <spring-bounces@ietf.org> On Behalf Of Brian E Carpenter
Sent: 07 December 2019 19:49
To: Ketan Talaulikar (ketant) <ketant@cisco.com>om>; Suresh Krishnan <Suresh@kaloom.com>om>; Fernando Gont <fgont@si6networks.com>om>; SPRING WG <spring@ietf.org>
Cc: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>rg>; int-ads@ietf.org; Andrew Alston <Andrew.Alston@liquidtelecom.com>om>; rtg-ads <rtg-ads@ietf.org>rg>; Bob Hinden <bob.hinden@gmail.com>om>; Ole Troan <otroan@employees.org>
Subject: Re: [spring] Penultimate Segment Popping and RFC8200 (Was Re: We don't seem to be following our processes (Re: Network Programming - Penultimate Segment Popping))

Ketan,
On 07-Dec-19 23:13, Ketan Talaulikar (ketant) wrote:
> +1
> 
>  
> 
> For some strange reason the PSP behaviour is being mixed with EH insertion and likely there is some misunderstanding here.

I found the language in draft-ietf-spring-srv6-network-programming very hard to understand, and your comment and those from Robert Raszuk really don't clear it up. No insult intended, but it seems that SRH exponents are so close to SRH that you don't understand why others find it hard to understand.

So let me ask for clarification on three points in the draft. (Please keep me in CC as I'm not on the spring list.)

(1) Where the draft uses the word "insert", does it refer *only* to the encapsulating node at the SR domain ingress?

(2) What does the phrase ""Pop the SRH" mean? Does it mean "delete" a header inserted as in (1),
at the same time as decapsulating the packet?

(3) In *very* elementary language, what is "updated SL" in statement S14.2? It isn't defined elsewhere as far as I can see. It may just be sloppy writing, because if "Segments Left" is a variable, then perhaps "updated SL" just means the current value of "Segments Left" after executing S14.

With specific answers to those questions, the text would be easier to interpret.

Some diagrams of the encapsulation would be helpful, too.

Regards
   Brian

> 
>  
> 
> Fernando says:
> 
> 
> (pop when you are the destination but SL!=0 is essentially 'in the
> network removal’)
> 
>  
> 
> This is NOT what PSP is (refer https://tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05#section-4.16.1) – the “pop” is done when the SL becomes 0.
> 
>  
> 
> FWIW, this has been stated in different ways and clarified on the mailing list previously by the authors as well as others involved in SRv6 development and deployments. There is no violation of RFC8200 here.
> 
>  
> 
> Thanks,
> 
> Ketan
> 
>  
> 
> *From:*spring <spring-bounces@ietf.org> *On Behalf Of *Suresh Krishnan
> *Sent:* 07 December 2019 12:50
> *To:* Fernando Gont <fgont@si6networks.com>om>; SPRING WG <spring@ietf.org>
> *Cc:* Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>rg>; int-ads@ietf.org; Andrew Alston <Andrew.Alston@liquidtelecom.com>om>; rtg-ads <rtg-ads@ietf.org>rg>; Bob Hinden <bob.hinden@gmail.com>om>; Ole Troan <otroan@employees.org>rg>; Brian E Carpenter <brian.e.carpenter@gmail.com>
> *Subject:* [spring] Penultimate Segment Popping and RFC8200 (Was Re: We don't seem to be following our processes (Re: Network Programming - Penultimate Segment Popping))
> 
>  
> 
> (responding on spring mailing list)
> 
>  
> 
> Hi Fernando,
> 
> 
> 
>     On Dec 7, 2019, at 11:07 AM, Fernando Gont <fgont@si6networks.com <mailto:fgont@si6networks.com>> wrote:
> 
>      
> 
>     On 6/12/19 23:47, Brian E Carpenter wrote:
> 
>         Again, comment at the end...
>         On 07-Dec-19 14:37, Fernando Gont wrote:
> 
>             On 6/12/19 22:15, Brian E Carpenter wrote:
>             [...]
> 
> 
> 
>                     and if such a thing is required, an update to RFC8200 should be done.
> 
> 
>                 Why does that follow? Alternatively, draft-ietf-spring-srv6-network-programming could acknowledge that it deviates from RFC8200.
> 
> 
>             You can deviate from s "should", not from a "must". This is an outright
>             violation of a spec, rather than a mere "deviation".
> 
> 
> 
>                 Whether that's acceptable would be a question for the IETF Last Call rather than any single WG.
> 
> 
>             I would expect that a WG cannot ship a document that is violating an
>             existing spec, where the wg shipping the document is not in a position
>             of making decisions regarding the spec being violated.
> 
>             That would be like a waste of energy and time for all.
> 
> 
> 
> 
>                 At the moment, the draft only mentions RFC8200 in a context that discusses neither insertion nor removal of extension headers, which is beside the point. Like draft-voyer, if it describes a violation of RFC8200, shouldn't that be explicit in the text?
> 
>                 There's a lot of jargon in draft-ietf-spring-srv6-network-programming. I can't tell from the jargon whether "insert" means "insert on the fly" and whether "Pop the SRH" means "delete on the fly". Should those terms be clarified before the draft advances?
> 
> 
>             Well, if it's not clear to you, it would seem to me that the simple
>             answer would be "yes".
> 
> 
>         But if "insert" refers to the encapsulating node at the SR domain ingress, it's no problem, and if "pop" simply means doing normal routing header processing, it's no problem. It simply isn't clear in the text, at least not clear to me.
> 
> 
>     The fact that a folk that has been deeply involved with IPv6 cannot
>     unequivocally tell what they talking about should be an indication with
>     respect to how ready the document is to be shipped.
> 
>     (pop when you are the destination but SL!=0 is essentially 'in the
>     network removal’)
> 
>  
> 
> It is not obvious to me why you think this is a violation of RFC8200 though it is possible that I misread your comment. The relevant text I am looking at is
> 
>  
> 
> "  Extension headers (except for the Hop-by-Hop Options header) are not
> 
>    processed, inserted, or deleted by any node along a packet's delivery
> 
>    path, until the packet reaches the node (or each of the set of nodes,
> 
>    in the case of multicast) identified in the Destination Address field
> 
>    of the IPv6 header.”
> 
>  
> 
> which seems to permit it. Can you please clarify where there is a violation?
> 
>  
> 
> Regards
> 
> Suresh
> 

_______________________________________________
spring mailing list
spring@ietf.org
https://www.ietf.org/mailman/listinfo/spring