Date: Wed, 10 Mar 2004 11:22:56 -0800 From: Brooks Davis <brooks@one-eyed-alien.net> To: Petri Helenius <pete@he.iki.fi> Cc: freebsd-current@freebsd.org Subject: Re: Who wants SACK? (Re: was My planned work on networking stack) Message-ID: <20040310192255.GD14892@Odin.AC.HMC.Edu> In-Reply-To: <404F40EB.6040702@he.iki.fi> 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>
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[-- Attachment #1 --] On Wed, Mar 10, 2004 at 06:23:07PM +0200, Petri Helenius wrote: > Brooks Davis wrote: > > >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 -- 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 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFAT2sPXY6L6fI4GtQRAt8QAJ9PoSpeV5C5XC/QkSqz1ZVYVQ1YyACgsWu2 4WosEDYE2UlkV+6gvX+W5/I= =ZZPZ -----END PGP SIGNATURE-----
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