From owner-freebsd-current@FreeBSD.ORG Wed Mar 10 11:23:07 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4C4DB16A4CE; Wed, 10 Mar 2004 11:23:07 -0800 (PST) Received: from odin.ac.hmc.edu (Odin.AC.HMC.Edu [134.173.32.75]) by mx1.FreeBSD.org (Postfix) with ESMTP id 317AF43D39; Wed, 10 Mar 2004 11:23:07 -0800 (PST) (envelope-from brdavis@odin.ac.hmc.edu) Received: from odin.ac.hmc.edu (IDENT:brdavis@localhost.localdomain [127.0.0.1]) by odin.ac.hmc.edu (8.12.10/8.12.3) with ESMTP id i2AJMuaN015420; Wed, 10 Mar 2004 11:22:57 -0800 Received: (from brdavis@localhost) by odin.ac.hmc.edu (8.12.10/8.12.3/Submit) id i2AJMunX015415; Wed, 10 Mar 2004 11:22:56 -0800 Date: Wed, 10 Mar 2004 11:22:56 -0800 From: Brooks Davis To: Petri Helenius Message-ID: <20040310192255.GD14892@Odin.AC.HMC.Edu> References: <20040309214205.3EE2D5D07@ptavv.es.net> <20040309160821.P705@odysseus.silby.com> <20040310123237.V61186@beagle.fokus.fraunhofer.de> <20040310154139.GA14892@Odin.AC.HMC.Edu> <404F40EB.6040702@he.iki.fi> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="DrWhICOqskFTAXiy" Content-Disposition: inline In-Reply-To: <404F40EB.6040702@he.iki.fi> User-Agent: Mutt/1.5.4i X-Virus-Scanned: by amavisd-milter (http://amavis.org/) on odin.ac.hmc.edu cc: freebsd-net@freebsd.org cc: freebsd-current@freebsd.org Subject: Re: Who wants SACK? (Re: was My planned work on networking stack) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Mar 2004 19:23:07 -0000 --DrWhICOqskFTAXiy Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Mar 10, 2004 at 06:23:07PM +0200, Petri Helenius wrote: > Brooks Davis wrote: >=20 > >For that matter, there are sufficent drops on 10GbE from data errors to > >insure that two boxes connected back to back won't achieve line speed on > >a single TCP session. > > > Do you have data to back this up or are you just using broadcom chipsets? I looked for the paper I paraphrased, I'm pretty sure if was one by Sally Floyd. I didn't find it, but this paper talks a bit about the issue on page 7: http://www.calit2.net/research/labs/features/CACM/CACMDefanti.pdf The problem is that the BER of a typical optical link is high enough that the link will almost certantly discard at least one packet before you get out of slow-start and once that happens it, AIMK means it take hours or even days to get back up to the top even assuming you don't lose further packets. This isn't a problem for most people, but it's definalty a problem for the HPC community. -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 --DrWhICOqskFTAXiy Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFAT2sPXY6L6fI4GtQRAt8QAJ9PoSpeV5C5XC/QkSqz1ZVYVQ1YyACgsWu2 4WosEDYE2UlkV+6gvX+W5/I= =ZZPZ -----END PGP SIGNATURE----- --DrWhICOqskFTAXiy--