From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx11.netapp.com (mx11.netapp.com [216.240.18.76]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "mx11.netapp.com", Issuer "VeriSign Class 3 International Server CA - G3" (not verified)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 8766321F229 for ; Fri, 29 Nov 2013 02:20:45 -0800 (PST) X-IronPort-AV: E=Sophos;i="4.93,796,1378882800"; d="asc'?scan'208";a="80864646" Received: from vmwexceht01-prd.hq.netapp.com ([10.106.76.239]) by mx11-out.netapp.com with ESMTP; 29 Nov 2013 02:20:45 -0800 Received: from SACEXCMBX01-PRD.hq.netapp.com ([169.254.2.244]) by vmwexceht01-prd.hq.netapp.com ([10.106.76.239]) with mapi id 14.03.0123.003; Fri, 29 Nov 2013 02:20:45 -0800 From: "Eggert, Lars" To: =?iso-8859-1?Q?Toke_H=F8iland-J=F8rgensen?= Subject: Re: One-way delay measurement for netperf-wrapper Thread-Topic: One-way delay measurement for netperf-wrapper Thread-Index: AQHO7OdL4tgcis7S6UabctRViyvmZJo8hZ2A Date: Fri, 29 Nov 2013 10:20:44 +0000 Message-ID: <5392347C-BC88-4836-BB53-F48523210237@netapp.com> References: <87zjoojr5u.fsf@toke.dk> <87mwknk0hw.fsf@toke.dk> In-Reply-To: <87mwknk0hw.fsf@toke.dk> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-originating-ip: [10.106.53.51] Content-Type: multipart/signed; boundary="Apple-Mail=_FB673BBC-4D1E-4894-AD6E-B95529DA6AB6"; protocol="application/pgp-signature"; micalg=pgp-sha1 MIME-Version: 1.0 Cc: Midori Kato , "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: Fri, 29 Nov 2013 10:20:46 -0000 --Apple-Mail=_FB673BBC-4D1E-4894-AD6E-B95529DA6AB6 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Hi, On 2013-11-29, at 10:42, Toke H=F8iland-J=F8rgensen = wrote: > Well, what the LINCS people have done (the link in my previous mail) = is > basically this: Sniff TCP packets that have timestamps on them (i.e. > with the TCP timestamp option enabled), and compute the delta between > the timestamps as a latency measure. we tried this too. The TCP timestamps are too coarse-grained for = datacenter latency measurements, I think under at least Linux and = FreeBSD they get rounded up to 1ms or something. (Midori, do you = remember the exact value?) > Putting timestamps into the TCP stream and reading them out at the = other > end might work; but is there a way to force each timestamp to be in a > separate packet? No, but the sender and receiver can agree to embed them every X bytes in = the stream. Yeah, sometimes that timestamp may be transmitted in two = segments, but I guess that should be OK? > Do you know how that worked more specifically and/or do you have a = link > to the source code? http://e2epi.internet2.edu/thrulay/ is the original. There are several = variants, but I think they also have been abandoned: http://thrulay-hd.sourceforge.net/ http://thrulay-ng.sourceforge.net/ Lars --Apple-Mail=_FB673BBC-4D1E-4894-AD6E-B95529DA6AB6 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- iQCVAwUBUphqedZcnpRveo1xAQIodAP+JCl4RbAM0dokktANPCeBcDK9cHgxtrTf uOyWrSsaOnsYP/RxvLDG09Ix1upaWYQEEEdJ3nE4vV2AlcW2kwPUEwUGfPSLNXoF 5UXd7J3Hd/1aOEKc6nEfH03kPhfULpUL30v8Yg/snbumnaFGyGZoQRkrmjw86RvT fZi+kRob6co= =Lfym -----END PGP SIGNATURE----- --Apple-Mail=_FB673BBC-4D1E-4894-AD6E-B95529DA6AB6--