From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail2.tohojo.dk (mail2.tohojo.dk [144.76.141.112]) (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 BC04121F1D1 for ; Mon, 2 Dec 2013 00:34:08 -0800 (PST) X-Virus-Scanned: amavisd-new at example.com Sender: toke@toke.dk DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toke.dk; s=201310; t=1385973206; bh=X70gQi/auTi1wk/bcSNskJ41zNvSn7Vnd4M1fq6qrkk=; h=From:To:Cc:Subject:References:Date:In-Reply-To; b=oid/yaqNtw/bjqeoW/eBs4vLThF1FZ67PsthW0i1JuD47fOfPNzILUgmgihMC15WN 0j+D66p0cw0bYFfWrh9vlbBlSVVdArPRMObOTsu9TXzqdBYCEJaU5Q3H4yv2e2Yrsd IAQ3YIbdazTNvLesAnfD9Ya36dYm2WBdxdG6+4iE= Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id B7ACFE68A; Mon, 2 Dec 2013 08:34:12 +0000 (GMT) From: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= To: Hal Murray Subject: Re: One-way delay measurement for netperf-wrapper References: <20131202054526.523C0406060@ip-64-139-1-69.sjc.megapath.net> Date: Mon, 02 Dec 2013 08:34:10 +0000 In-Reply-To: <20131202054526.523C0406060@ip-64-139-1-69.sjc.megapath.net> (Hal Murray's message of "Sun, 01 Dec 2013 21:45:26 -0800") Message-ID: <87ob4z1wjh.fsf@toke.dk> Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Cc: bloat-devel@lists.bufferbloat.net X-BeenThere: bloat-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Developers working on AQM, device drivers, and networking stacks" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Dec 2013 08:34:09 -0000 --=-=-= Content-Type: text/plain Hal Murray writes: > How long are you running the tests? Not longer than a few minutes at a time, normally. > How accurate do you expect the timings to be? As accurate as possible, I suppose... > ntpd assumes the network delays are symmetric. It's easy to break that > assumption by sending a lot of traffic in one direction. ntpd tries to > avoid that problem. It remembers the last 8 packets to a server and > uses the one with the shortest round trip time. If you run tests for > long enough you will overflow that buffer. The time scale is somewhere > between minutes and hours. Right, well I'm not too worried then; especially not for the case where there actually is a well-synchronised clock. -Toke --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQEcBAEBCAAGBQJSnEYCAAoJEENeEGz1+utP3i8H/3oEJ2lOe6GTUA5c68g6++ne OHEsPxbRRTliTry5Dvo7CgvN5THXdiHP49OUhpCQzjtol2nvs0U5nz2+xFKd3fVC oLEOeYXwE3PUx+r6E3u2fi4PIpyU/iAMM/U9CWWwHSfmJKzFXhOjQ/Yt5ti3y+tJ Nz+Tw5RA6oZz37LltdnQo8457MZi9LRjG+BxW00VZFzhT1tgU9ABA6bHRnqohKy2 RN8ptdUCMjJmsmintRN0QatLuW8ojsz2Pm4b37nbgZba/myvdUjJ1pLSXqiVgJi3 qEfgV+0DTCRciosoS8ewsGnVgCxBkowX4epR8ofYMi+OyIMWgOBfEdWyb3+SEfw= =ldI4 -----END PGP SIGNATURE----- --=-=-=--