From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nm18.bullet.mail.ne1.yahoo.com (nm18.bullet.mail.ne1.yahoo.com [98.138.90.81]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 380C721F184 for ; Sun, 14 Sep 2014 10:51:46 -0700 (PDT) Received: from [98.138.100.102] by nm18.bullet.mail.ne1.yahoo.com with NNFMP; 14 Sep 2014 17:51:44 -0000 Received: from [98.138.87.3] by tm101.bullet.mail.ne1.yahoo.com with NNFMP; 14 Sep 2014 17:51:44 -0000 Received: from [127.0.0.1] by omp1003.mail.ne1.yahoo.com with NNFMP; 14 Sep 2014 17:51:44 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 903086.36773.bm@omp1003.mail.ne1.yahoo.com Received: (qmail 41006 invoked by uid 60001); 14 Sep 2014 17:51:44 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1410717104; bh=zh6CeYM5W0laiDAqmT4yyJLCZVtd4KheTtZSQlqpC7Q=; h=References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=I2JsWOEspVl83qD0YNkhWqMQl6ZoEU6i09ap4+WAHB4TLHyXvDZ2iZVNRUZoORHyG4VzrtgeDE71aJ93V32ultKMtc0jUGhrafhk/ja4fhn4AGh0cH/WcqkLJmjwrx28KXcI103BMYxqtlPXxNQ4tTMcO629rTfsAgUnCGrzCtg= X-YMail-OSG: jwlGb2kVM1l4tlTL3hcYuZpsclwBAlyB5AvnTLk0jzaYyIT hnFf.JcBQWtxfyQP2QW9GISFIloL3SWuwSEgFoDLogVMzBjGUyEMhp4BDwqz DVmfjMRD58K0FJARgbE_Ivk55WpH8nv2.rjwxVWl42TSTRl7U6IOO7SLIao3 RyrSF7U5u7Hx5dZMsYqzR60ygCvwNZOush4X5Xb.fRV.ZuZHzLItq9P1R9Rm EqmgM7JqMNp3aGB1pzxq_Y3XJN3E40E6ZuVPqgeeJjZpPWMJimAqo5kkMQ2P _Dryp2HN5YPK9p7_gMoa_7rbyLqNt4RLgT4fBC186wQtkCK7NjgRGm.GQ2gG LZLQF2PadnlxN0zqR7vn8EFW5k8Lij13FDttibEx5j5k4kkYmKlsNX8xAnrn P1iaT_j73w99f7Z2xHYdpxwW8eTuHm6Gz8R9qgUbczkfIR03LDwBm4zhdBF3 DLoK..QfPPAmyYJ2fCiaU4M11P5FP_GgkGktZ0sT7BNmEQ0MjWIInUJnV2Zo KuKLrwO1ewQcttiny6OpnZUIdHK45LK10Tvkc51mqm8rdYniQmg-- Received: from [86.175.18.205] by web122503.mail.ne1.yahoo.com via HTTP; Sun, 14 Sep 2014 10:51:44 PDT X-Rocket-MIMEInfo: 002.001, CgoKT29wcywgaW50ZW5kZWQgdG8gQ0MgdGhlIGxpc3QuLi4KCgoKPiBPbiBTdW5kYXksIFNlcHRlbWJlciAxNCwgMjAxNCAxMTozOSBBTSwgQWxleCBCdXJyIDxhamI0NC5nZW9AeWFob28uY29tPiB3cm90ZToKPiA.IAo.IAo.IAo.IAo.IAo.IE9uIFN1bmRheSwgU2VwdGVtYmVyIDE0LCAyMDE0IDEyOjMyIEFNLCBKb25hdGhhbiBNb3J0b24gCj4gPGNocm9tYXRpeDk5QGdtYWlsLmNvbT4gd3JvdGU6Cj4gCj4gCj4.IAo.PiAKPj4gIFRvIGV4cGFuZCBvbiB0aGlzOiB0byBtZWFzdXJlIG9uZS13YXkgZGVsYXkBMAEBAQE- X-Mailer: YahooMailWebService/0.8.203.696 References: <20140913194126.5B0D1406062@ip-64-139-1-69.sjc.megapath.net> <20418644-AB62-43AE-A09E-5F85ED42DBF4@gmx.de> <1410691150.20919.YahooMailNeo@web122503.mail.ne1.yahoo.com> Message-ID: <1410717104.12610.YahooMailNeo@web122503.mail.ne1.yahoo.com> Date: Sun, 14 Sep 2014 10:51:44 -0700 From: Alex Burr To: "bloat@lists.bufferbloat.net" In-Reply-To: <1410691150.20919.YahooMailNeo@web122503.mail.ne1.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: [Bloat] Fw: Measuring Latency X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list Reply-To: Alex Burr List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 14 Sep 2014 17:52:15 -0000 Oops, intended to CC the list... > On Sunday, September 14, 2014 11:39 AM, Alex Burr wrote: > > > > > > > On Sunday, September 14, 2014 12:32 AM, Jonathan Morton > wrote: > > >> >> >> To expand on this: to measure one-way delay, you would need finely > synchronised clocks (to within a >> couple of ms) at both ends. The average consumer doesn't have that > sort of setup - not even if they >> happen to use NTP. So it's not a goal worth pursuing at this level - > save it for scientific >> Investigations, where the necessary effort and equipment can be made > available. > > > This is true for absolute one way delay. But since we are interested in the > variation > with load, it's actually easier. When you take the difference of two delays, > the synchronisation offset cancels out, so you are left with just the drift. > That may still be an insurmountable problem, but I would suggest at least > putting timestamps in the packets, even if you don't estimate one-way delay > up-front. That way people can try and get clever with clients later, without > having to change the server. > > Alex >