From owner-freebsd-current@FreeBSD.ORG Wed Mar 10 13:08:20 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 B035A16A4CE; Wed, 10 Mar 2004 13:08:19 -0800 (PST) Received: from rms04.rommon.net (rms04.rommon.net [212.54.2.140]) by mx1.FreeBSD.org (Postfix) with ESMTP id A917743D1F; Wed, 10 Mar 2004 13:08:18 -0800 (PST) (envelope-from pete@he.iki.fi) Received: from he.iki.fi (h81.vuokselantie10.fi [193.64.42.129]) by rms04.rommon.net (8.12.9p1/8.12.9) with ESMTP id i2AL82cM081405; Wed, 10 Mar 2004 23:08:02 +0200 (EET) (envelope-from pete@he.iki.fi) Message-ID: <404F83B0.7020803@he.iki.fi> Date: Wed, 10 Mar 2004 23:08:00 +0200 From: Petri Helenius User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Brooks Davis 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> <20040310192255.GD14892@Odin.AC.HMC.Edu> In-Reply-To: <20040310192255.GD14892@Odin.AC.HMC.Edu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Thu, 11 Mar 2004 05:24:08 -0800 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 21:08:20 -0000 Brooks Davis wrote: >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. > > > BER is usually combatted with technologies which embed redundant bits into the datastream so an occasional bit error does not take out a packet. In conjuction of 10GbE this would probably mean G.709. I would be happy to learn whether the typical link has BER of 10E-15 or 10E-12 and how fast retransmit plays in the picture of losing a bit every ten minutes or so. Pete