Re: [Int-area] Alissa Cooper's Discuss on draft-ietf-intarea-frag-fragile-15: (with DISCUSS and COMMENT)

Well, there’s the tautology that “it worked when it worked”.

Given that’s basically the rule that defines *everything* in the Internet, it’s baffling we need to say it again here, but if we did, we could simply state:

“The Internet is a best-effort system and lacks a formal validation or conformance mechanism. Like any other protocol feature, IP fragmentation is useful only when it actually works - both by successfully traversing routers and other in-network devices and when it is correctly supported by endpoints. As a consequence, like any other protocol feature, IP fragmentation MAY be used by new protocols that validate its successful traversal and provide an alternate as a backup.”

(and yes, if we’re going to try to imply that frag is limited, it really should be clear that this is *no different than any other protocol feature* in the Internet)

Joe

> On Aug 15, 2019, at 6:59 AM, Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org> wrote:
> 
> Folks,
> 
> Has anyone proposed text that:
> 
> a) satisfies Alissa's request
> b) satisfies the WG
> 
> If not, do we believe that such text could possibly exist?
> 
>                                              Ron
> 
> 
> 
> 
> Juniper Business Use Only
> 
> -----Original Message-----
> From: Brian E Carpenter <brian.e.carpenter@gmail.com> 
> Sent: Tuesday, August 6, 2019 8:55 PM
> To: Alissa Cooper <alissa@cooperw.in>; Tom Herbert <tom@herbertland.com>
> Cc: Joel Halpern <joel.halpern@ericsson.com>; draft-ietf-intarea-frag-fragile@ietf.org; int-area <int-area@ietf.org>; IESG <iesg@ietf.org>; intarea-chairs <intarea-chairs@ietf.org>
> Subject: Re: [Int-area] Alissa Cooper's Discuss on draft-ietf-intarea-frag-fragile-15: (with DISCUSS and COMMENT)
> 
> On 07-Aug-19 12:11, Alissa Cooper wrote:
>> Hi Tom,
>> 
>>> On Aug 6, 2019, at 5:41 PM, Tom Herbert <tom@herbertland.com> wrote:
>>> 
>>> On Tue, Aug 6, 2019 at 1:30 PM Alissa Cooper via Datatracker 
>>> <noreply@ietf.org> wrote:
>>>> 
>>>> Alissa Cooper has entered the following ballot position for
>>>> draft-ietf-intarea-frag-fragile-15: Discuss
>>>> 
>>>> When responding, please keep the subject line intact and reply to 
>>>> all email addresses included in the To and CC lines. (Feel free to 
>>>> cut this introductory paragraph, however.)
>>>> 
>>>> 
>>>> Please refer to 
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ietf.org_ie
>>>> sg_statement_discuss-2Dcriteria.html&d=DwIFaQ&c=HAkYuh63rsuhr6Scbfh0
>>>> UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThKP
>>>> 8&m=IUZsPOprgYi_5nBSPGeqNCLb8LwDMKCxRNeEBfcUZ5c&s=c7tAk-Lfr6pcQSMn1x
>>>> 1tdfjkQsL8F_NryIiq3caZ26k&e= for more information about IESG DISCUSS 
>>>> and COMMENT positions.
>>>> 
>>>> 
>>>> The document, along with other ballot positions, can be found here:
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.iet
>>>> f.org_doc_draft-2Dietf-2Dintarea-2Dfrag-2Dfragile_&d=DwIFaQ&c=HAkYuh
>>>> 63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF
>>>> 2EfpHcAwrDThKP8&m=IUZsPOprgYi_5nBSPGeqNCLb8LwDMKCxRNeEBfcUZ5c&s=lb6u
>>>> 0SVhJIFnTV7TdqeLiDBfadRxJkAxNEDqOvFqhyQ&e=
>>>> 
>>>> 
>>>> 
>>>> --------------------------------------------------------------------
>>>> --
>>>> DISCUSS:
>>>> --------------------------------------------------------------------
>>>> --
>>>> 
>>>> Thanks for writing this document.
>>>> 
>>>> Section 6.1 says:
>>>> 
>>>> "Developers MAY develop new protocols or applications that rely on IP
>>>>  fragmentation if the protocol or application is to be run only in
>>>>  environments where IP fragmentation is known to be supported."
>>>> 
>>>> I'm wondering if there should be a bit more nuance here to make the 
>>>> recommendation clearer. Do we think there is a case where an 
>>>> application protocol developed in the IETF will be known to only run 
>>>> in environments where fragmentation is supported? If we don't think 
>>>> developing such a protocol would be in scope for the IETF, then I'm 
>>>> wondering if that case should be called out explicitly with a stronger normative requirement.
>>>> 
>>> Alissa,
>>> 
>>> Are you distinguishing between protocol development and application 
>>> development?
>> 
>> I’m specifically wondering about application protocols (as distinct from other protocols) developed in the IETF (as distinct from developed elsewhere). Sometimes we use BCPs to guide future work in the IETF specifically, and it seemed to me that in that specific slice — IETF-developed application protocols — we may be able to make a stronger recommendation since we can’t be sure of the environment in which any given application protocol would be deployed (I think, but would be open to arguments otherwise).
> 
> fwiw, I agree with what I think Alissa is saying. Unless we actually *implement* a mechanism to define and support limited domains (draft-carpenter-limited-domains) protocol designers cannot safely make assumptions such as "fragmentation works".
> 
> Maybe this paragraph needs to be more of a health warning than a somewhat dubious RFC2119 statement. At least, "should not ... unless" might be a better formulation than "MAY ... if".
> 
>   Brian
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