Re: [tcpm] Linux doesn’t implement RFC3465

Yuchung Cheng <ycheng@google.com> Mon, 09 August 2021 20:53 UTC

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From: Yuchung Cheng <ycheng@google.com>
Date: Mon, 9 Aug 2021 13:52:40 -0700
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To: Mark Allman <mallman@icir.org>
Cc: Neal Cardwell <ncardwell@google.com>, Vidhi Goel <vidhi_goel@apple.com>, Extensions <tcpm@ietf.org>
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Subject: Re: [tcpm] =?utf-8?q?Linux_doesn=E2=80=99t_implement_RFC3465?=
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On Mon, Aug 9, 2021 at 10:05 AM Mark Allman <mallman@icir.org> wrote:

>
> > (2) Implementations that don't pace will generally be causing
> > large bursts for many different reasons anyway (data and/or ACK
> > aggregation in the network or end hosts), restart from idle,...)
> > so having a constant L does not provide enough protection from
> > bursts to justify the cost in reduced performance (in the form of
> > slower slow-start). In support of this, experience with this as
> > the default behavior in Linux TCP over the 2013-2021 period
> > suggests this works well enough in practice.
>
> I think at some point someone should put some meat on the bones of
> "suggests this works well enough in practice".
>
Good point. We could add anecdotal words on the degree of stretched ACK.

Maybe we can also cite priori discussions on ACK compression / decimation a
couple years ago in tcpm / tsvwg. Are there research papers on stretch ACK
degrees too?


> It isn't enough for linux to have implemented this.  Or, even had it
> turned on.  E.g., if L=\infinity yet receivers ACK every other
> packet then there is an effective L of 2.  We see lots of people
> saying this scenario isn't the prevalent scenario these days.  If
> that's true then it should be easy to provide a summary of
> experience with L=\infinity.
>
> This would all just seem better with some concrete experience rather
> than the quite hand wavy statements we've seen so far.
>
> allman
>