Re: [tcpm] Comments on draft-ietf-tcpm-accurate-ecn

Joe Touch <touch@strayalpha.com> Fri, 13 July 2018 05:23 UTC

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From: Joe Touch <touch@strayalpha.com>
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Date: Thu, 12 Jul 2018 22:23:23 -0700
Cc: =?utf-8?Q?Mirja_K=C3=BChlewind?= <mirja.kuehlewind@tik.ee.ethz.ch>, Yuchung Cheng <ycheng@google.com>, "draft-ietf-tcpm-accurate-ecn@ietf.org" <draft-ietf-tcpm-accurate-ecn@ietf.org>, "tcpm@ietf.org" <tcpm@ietf.org>
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To: Praveen Balasubramanian <pravb=40microsoft.com@dmarc.ietf.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tcpm/B-ncchJzvnEC_7KDJktK55O9V8E>
Subject: Re: [tcpm] Comments on draft-ietf-tcpm-accurate-ecn
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Let’s please be clear:

> On Jul 12, 2018, at 9:25 AM, Praveen Balasubramanian <pravb=40microsoft.com@dmarc.ietf.org> wrote:
> 
> Re. GRO/LRO/RSC: https://docs.microsoft.com/en-us/windows-hardware/drivers/network/exception-conditions-that-terminate-coalescing <https://docs.microsoft.com/en-us/windows-hardware/drivers/network/exception-conditions-that-terminate-coalescing> see condition 4 for an exception that terminates coalescing: "The segment contains one or more TCP options other than the TCP timestamp option". So while software implementations of coalescing can be updated, existing hardware will cause poor performance with new TCP options that are present in a lot of data packets. 

While that may be true, it is also true that such performance optimizations always violated TCP. If we avoid updating the protocol as defined because of such existing violations, we might as well engrain TCP coalescing as legitimate in the protocol and deprecate all options other than timestamp.

Joe