Joe,

All things are fragile. That's one of life's realities.

But some things are more fragile than others.

                                                           Ron



Juniper Business Use Only

-----Original Message-----
From: Joe Touch <to...@strayalpha.com> 
Sent: Thursday, August 15, 2019 10:21 AM
To: Ron Bonica <rbonica=40juniper....@dmarc.ietf.org>
Cc: Brian E Carpenter <brian.e.carpen...@gmail.com>; Alissa Cooper 
<ali...@cooperw.in>; Tom Herbert <t...@herbertland.com>; Joel Halpern 
<joel.halp...@ericsson.com>; draft-ietf-intarea-frag-frag...@ietf.org; int-area 
<int-area@ietf.org>; IESG <i...@ietf.org>; intarea-chairs 
<intarea-cha...@ietf.org>
Subject: 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....@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.carpen...@gmail.com>
> Sent: Tuesday, August 6, 2019 8:55 PM
> To: Alissa Cooper <ali...@cooperw.in>; Tom Herbert 
> <t...@herbertland.com>
> Cc: Joel Halpern <joel.halp...@ericsson.com>; 
> draft-ietf-intarea-frag-frag...@ietf.org; int-area 
> <int-area@ietf.org>; IESG <i...@ietf.org>; intarea-chairs 
> <intarea-cha...@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 <t...@herbertland.com> wrote:
>>> 
>>> On Tue, Aug 6, 2019 at 1:30 PM Alissa Cooper via Datatracker 
>>> <nore...@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_i
>>>> e
>>>> sg_statement_discuss-2Dcriteria.html&d=DwIFaQ&c=HAkYuh63rsuhr6Scbfh
>>>> 0 
>>>> UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThK
>>>> P 
>>>> 8&m=IUZsPOprgYi_5nBSPGeqNCLb8LwDMKCxRNeEBfcUZ5c&s=c7tAk-Lfr6pcQSMn1
>>>> x 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.ie
>>>> t 
>>>> f.org_doc_draft-2Dietf-2Dintarea-2Dfrag-2Dfragile_&d=DwIFaQ&c=HAkYu
>>>> h 
>>>> 63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AW
>>>> F 
>>>> 2EfpHcAwrDThKP8&m=IUZsPOprgYi_5nBSPGeqNCLb8LwDMKCxRNeEBfcUZ5c&s=lb6
>>>> u 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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