From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-x22f.google.com (mail-it0-x22f.google.com [IPv6:2607:f8b0:4001:c0b::22f]) (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 8B2583B2BC; Sat, 4 Jun 2016 13:10:39 -0400 (EDT) Received: by mail-it0-x22f.google.com with SMTP id f67so13292039ith.1; Sat, 04 Jun 2016 10:10:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding; bh=PJtY2Pbq9vAvUngs9uAHwIN9tCnX4nXazZ3pRsVX7pk=; b=aG4biwyTEtmoh8qHc+fOzS9i2PQMIvaMAIUPksuQbt5vwaPq6ms5NrIVyVvFAVuKQK OYjb428m/mEY+umVDrS3wO0mo1O+o9VOKdrmd2YMZ8IoxfTEjglOXw7LgWpA1pBsnXTY 8ZOim7N9Rm0MA2NZV987ZfsdcOnSJuARhXIrLW5p1HxNbkCpvDHSR+W5NRfkPrrQ+kTs CKb56+Py7v8qf07vAhuW9l+ctBz/7rP4WXrzWq/YpURJWIDYYPpCiJ21tlftR5GZ5WRk NKx4ifI79IHiURaPr2QDpu2FS6hMKPD98HvWoLn07HDbrMu5VrtQr21EFcQ9esdD/DXT 4hOw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:cc:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding; bh=PJtY2Pbq9vAvUngs9uAHwIN9tCnX4nXazZ3pRsVX7pk=; b=PnKzpEGaB37VGHcyNbeI9DNyLqcGyzyto0aoLJZxbkzDIv5pOHK2S+xwTe46/YnyVx x+uc0IWNCwqA+8Gn6Oecmgg3eDYoSXinNKOA4bkBzADsAecbY2GegpMx2Q8M7Ng4URIp woqi8JyLvn3Kn7smbCG17KcxfOOVWXozQ2k8ibY9IH2HW9utjYe+PbKaNEKMMqrERiMx g7WxoFIJBTjamB8Jmj8w4dTaQPnuSlHYw0MJ6Cj5Lmcax5vA3oXbC2znSIspwkzsM5rF NWy4I2YPVZ97X3HqgdiEOSj88+cQjyS7xqY9wjk04EiFdLIqAL0YRdPC1YVAPEb7l5Qg yOgg== X-Gm-Message-State: ALyK8tI1UFtDF+mnQCYDE+FDrrJ65meA9EnAAZ/GxcA4kEEf0RbBW9ZJKWyTCt53BmMZAQ== X-Received: by 10.36.71.7 with SMTP id t7mr7081091itb.9.1465060239089; Sat, 04 Jun 2016 10:10:39 -0700 (PDT) Received: from ?IPv6:2601:404:381:a21:fcb6:90dd:9164:a6bf? ([2601:404:381:a21:fcb6:90dd:9164:a6bf]) by smtp.gmail.com with ESMTPSA id 28sm4808238ios.4.2016.06.04.10.10.38 (version=TLSv1/SSLv3 cipher=OTHER); Sat, 04 Jun 2016 10:10:38 -0700 (PDT) To: Jonathan Morton , Andrew McGregor References: <22371476-B45C-4E81-93C0-D39A67639EA0@gmx.de> <857AEE56-E7DB-4981-B32E-82473F877139@gmail.com> <8AB0D25D-C1CA-45F1-889E-2F73CF8C44F7@gmail.com> <323AFC22-A092-4F59-8197-AF21EF73FD58@gmail.com> <274D3A0FA900FD47AA6B56991AAA32FDC5529FC8@wtl-exchp-1.sandvine.com> <574478B4.7080103@taht.net> <39F38477-A877-4C1B-9B7F-BB3358425F17@gmail.com> <0eb223f9-2873-7f53-c2ce-c6867ddec17c@gmail.com> <48A25043-19E2-4BB7-B634-A4003F7BE6F8@gmail.com> <01BEA343-7C07-46FA-8DC4-07BF26309FC8@gmail.com> Cc: cake@lists.bufferbloat.net, "codel@lists.bufferbloat.net" From: Noah Causin Message-ID: <10d58240-e106-ff1f-a038-df5bc0ee7a36@gmail.com> Date: Sat, 4 Jun 2016 13:10:35 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <01BEA343-7C07-46FA-8DC4-07BF26309FC8@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Codel] [Cake] Proposing COBALT X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 04 Jun 2016 17:10:39 -0000 I notice that issue with Steam. Steam uses lots of ECN, which can be nice for saving bandwidth with large games. The issue I notice is that Steam is the one application that can cause me to have ping spikes of over 100ms, even though I have thoroughly tested my network using both flent and dslreports. I also notice that I get large sparse delays in the cake stats during steam downloads. The highest I can remember right now is like 22ms. On 6/4/2016 9:55 AM, Jonathan Morton wrote: >> On 4 Jun, 2016, at 04:01, Andrew McGregor wrote: >> >> ...servers with ECN response turned off even though they negotiate ECN. > It appears that I’m looking at precisely that scenario. > > A random selection of connections from a packet dump show very high marking rates, which are apparently acknowledged using CWR, but a subsequent dropped packet (probably due to queue overflow) takes many seconds to be retransmitted (I’m using a rather high memory limit for observation purposes). > > Overall the TCP behaviour is approximately normal for NewReno on a dumb FIFO, and the ECN signalling is completely ignored. This doesn’t rule out the possibility that it’s a different Reno relative, such as Westwood+ or Compound. > > There’s often more than one CWR per RTT. This isn’t a consistent characteristic; some connections have normal-looking CWRs while others issue them every three packets, as if they’re fishing for “more accurate” ECN feedback. It might vary by host; I didn’t keep track of that. But this can’t be DCTCP; even that should back off in the face of a 100% marking rate, which is often achieved at my low bandwidth and with very persistent queues. > > Other servers respond normally to ECN signals, ruling out interference by my ISP. It’s possible the ECE flag is wiped and the CWRs are faked, but there’s no legitimate reason to do that. The CWRs ultimately make no difference, since at 100% CE marks, every ack has ECE set anyway. > > Turning off ECN negotiation at the client results in a much better managed queue with similar throughput. It’s not immediately obvious whether that’s due to a functioning congestion response or simply the AQM clearing out the queue the hard way. It’ll be interesting to see what effect COBALT has here, when I get it to actually work. > > As for who these servers are: Valve Software’s Steam platform. I did say they were large and popular. > > - Jonathan Morton >