Re: [tsvwg] Alissa Cooper's Discuss on draft-ietf-tsvwg-rfc5405bis-18: (with DISCUSS)

"Eggert, Lars" <lars@netapp.com> Fri, 14 October 2016 13:23 UTC

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From: "Eggert, Lars" <lars@netapp.com>
To: Gorry Fairhust <gorry@erg.abdn.ac.uk>
Thread-Topic: Alissa Cooper's Discuss on draft-ietf-tsvwg-rfc5405bis-18: (with DISCUSS)
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Date: Fri, 14 Oct 2016 13:22:16 +0000
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Cc: "tsvwg@ietf.org" <tsvwg@ietf.org>, "David L. Black" <david.black@emc.com>, Alissa Cooper <alissa@cooperw.in>, "draft-ietf-tsvwg-rfc5405bis@ietf.org" <draft-ietf-tsvwg-rfc5405bis@ietf.org>, The IESG <iesg@ietf.org>, "tsvwg-chairs@ietf.org" <tsvwg-chairs@ietf.org>
Subject: Re: [tsvwg] Alissa Cooper's Discuss on draft-ietf-tsvwg-rfc5405bis-18: (with DISCUSS)
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Applied

> On 2016-10-12, at 18:49, Gorry Fairhurst <gorry@erg.abdn.ac.uk> wrote:
> 
> See below.
> 
> On 12/10/2016 15:49, Alissa Cooper wrote:
>> Alissa Cooper has entered the following ballot position for
>> draft-ietf-tsvwg-rfc5405bis-18: 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://www.ietf.org/iesg/statement/discuss-criteria.html
>> for more information about IESG DISCUSS and COMMENT positions.
>> 
>> 
>> The document, along with other ballot positions, can be found here:
>> https://datatracker.ietf.org/doc/draft-ietf-tsvwg-rfc5405bis/
>> 
>> 
>> 
>> ----------------------------------------------------------------------
>> DISCUSS:
>> ----------------------------------------------------------------------
>> 
>> = Section 3.17 =
>> 
>> "An application sending ECN-capable datagrams MUST provide an
>>       appropriate congestion reaction when it receives feedback
>>       indicating that congestion has been experienced.  This must result
>>       in reduction of the sending rate by the UDP congestion control
>>       method (see Section 3.1) that is not less than the reaction of TCP
>>       under equivalent conditions."
>> 
>> Is the second "must" meant to be normative? If so, this worries me a bit.
>> RFC 6679 I believe retains flexibility for endpoints to react to
>> congestion in ways that are different from TCP and dependent on specific
>> codecs, topologies, and other factors. RFC 3551 provides a lot of
>> qualification in the requirements it places around equivalence to TCP's
>> behavior. So I would be concerned about how this requirement, if
>> normative, would affect RTP and other protocols.
>> 
>> If it's not meant to be normative, I would suggest using "ought to" or
>> some other word.
> I don't think the second "must" is a normative, because that would make it potentially contradict other RFCs (as you say). I think it describes the principle for design, so "ought to" would reflect that.
> 
> Gorry
> 
>