From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-x233.google.com (mail-ob0-x233.google.com [IPv6:2607:f8b0:4003:c01::233]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id B0FC421F3E2; Thu, 14 May 2015 12:13:55 -0700 (PDT) Received: by obbkp3 with SMTP id kp3so60240677obb.3; Thu, 14 May 2015 12:13:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:cc:content-type; bh=ZBz7tdMNVsrEzJcVNS1MopJvHpiUA7HmMY07UO9DSN4=; b=huta8fGq/ux3WbBh2H0VR2PzjG+Ezm3LS0Q5h/GmVOri/j+QUDCzrLEl/Jrh+BFrHa Y17qpV29zmss/aGuOjUq2eYwkcDLB5A/JETp8WIER5iN8i7GR5lK++ROxKJgQS5sBmUZ DT9V/9gMp4gaqpgxvTjJU8H9ouDqbZOrjyExg9ui0KfA+gCeI3ytvSZTzDQVbVZAMs1K gd/D9z+r7FV1ip1mVLk8Tj0GbK565ef2PY2ER3fs5hVZFx77zw93SqKcK3SK2eNvZxY6 nm/HJcVNowgqmTwaab627QjOZnfn+6imwwhUoXt59Wv3jhOXZYD1wGWHg3I+Rr4GYXR4 1pHQ== MIME-Version: 1.0 X-Received: by 10.182.138.68 with SMTP id qo4mr4866555obb.56.1431630828415; Thu, 14 May 2015 12:13:48 -0700 (PDT) Received: by 10.202.71.139 with HTTP; Thu, 14 May 2015 12:13:48 -0700 (PDT) Date: Thu, 14 May 2015 12:13:48 -0700 Message-ID: From: Dave Taht To: cake@lists.bufferbloat.net, "cerowrt-devel@lists.bufferbloat.net" , bloat Content-Type: text/plain; charset=UTF-8 Cc: Greg White , "Klatsky, Carl" Subject: [Cake] heisenbug: dslreports 16 flow test vs cablemodems X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 14 May 2015 19:14:51 -0000 One thing I find remarkable is that my isochronous 10ms ping flow test (trying to measure the accuracy of the dslreports test) totally heisenbugs the cable 16 (used to be 24) flow dslreports test. Without, using cake as the inbound and outbound shaper, I get a grade of C to F, due to inbound latencies measured in the seconds. http://www.dslreports.com/speedtest/479096 With that measurement flow, I do so much better, (max observed latency of 210ms or so) with grades ranging from B to A... http://www.dslreports.com/speedtest/478950 I am only sending and receiving an extra ~10000 bytes/sec (100 ping packets/sec) to get this difference between results. The uplink is 11Mbits, downlink 110 (configured for 100) Only things I can think of are: * ack prioritization on the modem * hitting packet limits on the CMTS forcing drops upstream (there was a paper on this idea, can't remember the name (?) ) * always on media access reducing grant latency * cake misbehavior (it is well understood codel does not react fast enough here) * cake goodness (fq of the ping making for less ack prioritization?) * ???? I am pretty sure the cable makers would not approve of someone continuously pinging their stuff in order to get lower latency on downloads (but it would certainly be one way to add continuous tuning of the real rate to cake!) Ideas? The simple test: # you need to be root to ping on a 10ms interval # and please pick your own server! $ sudo fping -c 10000 -i 10 -p 10 snapon.lab.bufferbloat.net > vscabletest_cable.out start a dslreports "cable" test in your browser abort the (CNTRL-C) ping when done. Post processing of fping's format $ cat vscabletest_cable.out | cut -f3- -d, | awk '{ print $1 }' > vscabletest-cable.txt import into your favorite spreadsheet and plot.