Re: [aqm] TCP ACK Suppression

Christian Huitema <huitema@microsoft.com> Fri, 09 October 2015 02:08 UTC

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From: Christian Huitema <huitema@microsoft.com>
To: David Lang <david@lang.hm>
Thread-Topic: [aqm] TCP ACK Suppression
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Cc: "LAUTENSCHLAEGER, Wolfram \(Wolfram\)" <wolfram.lautenschlaeger@alcatel-lucent.com>, Greg White <g.white@CableLabs.com>, "aqm@ietf.org" <aqm@ietf.org>, Joe Touch <touch@isi.edu>
Subject: Re: [aqm] TCP ACK Suppression
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On Thursday, October 8, 2015 5:43 PM, David Lang wrote:
> ...
> For example, in the fq_codel/cake development, we're finding that there are
> some transports that bundle very large numbers of packets together to send
> at one time in order to maximize the transport bandwidth. (for example, 4x4
> wifi sends a LOT of data in one transmit timeslot). Treating that large
> aggregate as a single packet seriously hurts fairness and latency on the next
> hop. So 'pulling apart' this aggregate into the individual packets/streams and
> making decisions based on the pieces ends up being a serious win in fairness
> and latency.

Define "bundle" please. If they are making sure that several IP packets are sent back to back in a single Wi-Fi slot, then it is of course perfectly fine for AQM to handle the IP packets one by one. Does 4x4 Wi-Fi do something else?

> Suggesting that the queues that build up produce a special enough case to
> consider thinning out the duplicate acks is a far cry from 'making a
> recommendation that breaks other recommendations'

That definitely contradicts the TCP specs. So it is very much in "don't go there" territory...

-- Christian Huitema