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Re: [tcpm] On Sender Control of Delayed Acks in TCP

Jonathan Morton <chromatix99@gmail.com> Wed, 29 April 2020 21:33 UTC

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From: Jonathan Morton <chromatix99@gmail.com>
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Date: Thu, 30 Apr 2020 00:33:35 +0300
Cc: "Scheffenegger, Richard" <rs.ietf@gmx.at>, "tcpm@ietf.org" <tcpm@ietf.org>
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To: Neal Cardwell <ncardwell=40google.com@dmarc.ietf.org>
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Subject: Re: [tcpm] On Sender Control of Delayed Acks in TCP
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> On 30 Apr, 2020, at 12:07 am, Neal Cardwell <ncardwell=40google.com@dmarc.ietf.org> wrote:
> 
> The Linux TCP approach of sending an immediate ACK upon receiving a
> packet with CWR set (see Richard's link above) helps a lot with this
> case. But that's a non-standard heuristic, and doesn't help for
> senders that have a congestion control that does not use ECN CWR
> signals (e.g. Accurate ECN). Unless I'm missing something, it seems
> like endpoints using Accurate ECN are going to run into this same
> latency issue. To avoid this, I guess they may want to either use a
> cwnd >= 2, or make use of some new explicit ACK-pull mechanism.

Just to note, this is a problem that SCE wouldn't be affected by, as it doesn't change the ECE/CWR handling.

 - Jonathan Morton

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