From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-x229.google.com (mail-qk0-x229.google.com [IPv6:2607:f8b0:400d:c09::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id B77AF3BA8E for ; Thu, 30 Nov 2017 03:00:27 -0500 (EST) Received: by mail-qk0-x229.google.com with SMTP id d141so7730143qkc.12 for ; Thu, 30 Nov 2017 00:00:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=74uoCd1l2MehVUb//lRJmwGPQRa64enxMcXjOn9sCFI=; b=cSHb+hQqjCY5uzfq+jEcefkpESAl/Eq4JOmWyz97TzuX0YMhwE9xqVD8NrYcZpggy4 SQIWAM5IQ+4mPrfAqUQxvbeFIggYzBE75Nbll2tAdplCDxZ+WqmuDpIhYD8KhV56/Xm0 oZiD3dBAddRdMuUpod3yjZQmnLx4l958eVHJfUI4A6md9PpPYsQAPnNk7lYRKQerlOha +P6M1wGwudDPFG7OqP0z05d8hM6w590sXhXEXIEeCKvExC9Gf8z0v/MxB6kOMGGpy7yn 2rC0HOtHxOD2TU5pRKKgZfOJqeyZqlawuGxFpnt+3uwNhXcWdnwLw79d94MUsLiUJu1B peMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=74uoCd1l2MehVUb//lRJmwGPQRa64enxMcXjOn9sCFI=; b=aeSalQW6owMEloq8PPlHasTeHAoY4I6dg3J50+IEz6P1iuE5Cpb521QkCrODJbqj6s cRIG0tfRI2pPFvONiHNF8vJLViO+Gjb0Kl4l9432KxgPtFtB4QfXle5AiykyjYfnlFzn BXek/3K/Xvj0VArmwLeOvz6od1ytXv/OYEO461ihbH08ex9ygjkqRR2jAZcXnHcWmlmj zUq/qIR3eVSvf1PULnolXfbHj3YNvmC0mhkjoQNA2eeopuzFk8wZHDtw5VQ7ohzgJizT hNDhcPl9+qwbypPcGHnSWFz+MAqg73S8HKP3MFf6/4iBJvLs2lb30WYH490NqJUC4ilh ukOw== X-Gm-Message-State: AKGB3mKY2CvQFCrk6kOhGf2I5dBriFvwXCniY2WBubaxqrxRsnCHRgCA oY8ekucpPJL17msiD2ZTeLlubJNaNpxJCnxAabk= X-Google-Smtp-Source: AGs4zMYf36tr4XCoAlxcNb0G47JPy+xsIhFWeL5fv/HHpJf7qQ6+0JkNttPPaNB97dT5HbFwaV2uEzg2wRGBFifrjdc= X-Received: by 10.55.210.194 with SMTP id f185mr1415655qkj.330.1512028827288; Thu, 30 Nov 2017 00:00:27 -0800 (PST) MIME-Version: 1.0 Received: by 10.12.191.227 with HTTP; Thu, 30 Nov 2017 00:00:26 -0800 (PST) In-Reply-To: References: <4D0E907C-E15D-437C-B6F7-FF348346D615@gmx.de> <7B92DF4D-B6B5-4A64-9E10-119DCA2D4A6F@ifi.uio.no> From: Luca Muscariello Date: Thu, 30 Nov 2017 09:00:26 +0100 Message-ID: To: Jonathan Morton Cc: Michael Welzl , David Ros , bloat Content-Type: multipart/alternative; boundary="94eb2c04e8d2240c47055f2ea5dd" Subject: Re: [Bloat] benefits of ack filtering X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Nov 2017 08:00:27 -0000 --94eb2c04e8d2240c47055f2ea5dd Content-Type: text/plain; charset="UTF-8" Agree and think this is a lucid analysis of the problem(s) and solution(s). But, what can be done to let clients upgrade orders of magnitude faster than today? Move transport in user space inside the app? Else? On Thu, Nov 30, 2017 at 8:48 AM, Jonathan Morton wrote: > I do see your arguments. Let it be known that I didn't initiate the > ack-filter in Cake, though it does seem to work quite well. > > With respect to BBR, I don't think it depends strongly on the return rate > of acks in themselves, but rather on the rate of sequence number advance > that they indicate. For this purpose, having the receiver emit sparser but > still regularly spaced acks would be better than having some middlebox > delete some less-predictable subset of them. So I think BBR could be a > good testbed for AckCC implementation, especially as it is inherently paced > and thus doesn't suffer from burstiness as a conventional ack-clocked TCP > might. > > The real trouble with AckCC is that it requires implementation on the > client as well as the server. That's most likely why Google hasn't tried > it yet; there are no receivers in the wild that would give them valid data > on its effectiveness. Adding support in Linux would help here, but aside > from Android devices, Linux is only a relatively small proportion of > Google's client traffic - and Android devices are slow to pick up new > kernel features if they can't immediately turn it into a consumer-friendly > bullet point. > > Meanwhile we have highly asymmetric last-mile links (10:1 is typical, 50:1 > is occasionally seen), where a large fraction of upload bandwidth is > occupied by acks in order to fully utilise the download bandwidth in TCP. > Any concurrent upload flows have to compete with that dense ack flow, which > in various schemes is unfair to either the upload or the download > throughput. > > That is a problem as soon as you have multiple users on the same link, eg. > a family household at the weekend. Thinning out those acks in response to > uplink congestion is a solution. Maybe not the best possible solution, but > a deployable one that works. > > - Jonathan Morton > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat > > --94eb2c04e8d2240c47055f2ea5dd Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Agree and think this is a lucid analysis of the problem(s)= and solution(s).

But, what can be done to let clients u= pgrade orders of magnitude faster than today?
Move transport in u= ser space inside the app? Else?



On T= hu, Nov 30, 2017 at 8:48 AM, Jonathan Morton <chromatix99@gmail.com> wrote:

I do = see your arguments.=C2=A0 Let it be known that I didn't initiate the ac= k-filter in Cake, though it does seem to work quite well.

With respect to BBR, I don't think it depends strongly o= n the return rate of acks in themselves, but rather on the rate of sequence= number advance that they indicate.=C2=A0 For this purpose, having the rece= iver emit sparser but still regularly spaced acks would be better than havi= ng some middlebox delete some less-predictable subset of them.=C2=A0 So I t= hink BBR could be a good testbed for AckCC implementation, especially as it= is inherently paced and thus doesn't suffer from burstiness as a conve= ntional ack-clocked TCP might.

The real trouble with AckCC is that it requires implementati= on on the client as well as the server.=C2=A0 That's most likely why Go= ogle hasn't tried it yet; there are no receivers in the wild that would= give them valid data on its effectiveness.=C2=A0 Adding support in Linux w= ould help here, but aside from Android devices, Linux is only a relatively = small proportion of Google's client traffic - and Android devices are s= low to pick up new kernel features if they can't immediately turn it in= to a consumer-friendly bullet point.

Meanwhile we have highly asymmetric last-mile links (10:1 is= typical, 50:1 is occasionally seen), where a large fraction of upload band= width is occupied by acks in order to fully utilise the download bandwidth = in TCP.=C2=A0 Any concurrent upload flows have to compete with that dense a= ck flow, which in various schemes is unfair to either the upload or the dow= nload throughput.

That is a problem as soon as you have multiple users on the = same link, eg. a family household at the weekend.=C2=A0 Thinning out those = acks in response to uplink congestion is a solution.=C2=A0 Maybe not the be= st possible solution, but a deployable one that works.

- Jonathan Morton


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