From owner-freebsd-net@FreeBSD.ORG Tue Jul 17 11:15:17 2007 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 2913616A401 for ; Tue, 17 Jul 2007 11:15:17 +0000 (UTC) (envelope-from rrs@cisco.com) Received: from sj-iport-5.cisco.com (sj-iport-5.cisco.com [171.68.10.87]) by mx1.freebsd.org (Postfix) with ESMTP id 003EC13C4C4 for ; Tue, 17 Jul 2007 11:15:16 +0000 (UTC) (envelope-from rrs@cisco.com) Received: from sj-dkim-1.cisco.com ([171.71.179.21]) by sj-iport-5.cisco.com with ESMTP; 17 Jul 2007 04:15:16 -0700 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ao8CAM9BnEarR7MV/2dsb2JhbAA X-IronPort-AV: i="4.16,546,1175497200"; d="scan'208"; a="166946911:sNHT29501001" Received: from sj-core-1.cisco.com (sj-core-1.cisco.com [171.71.177.237]) by sj-dkim-1.cisco.com (8.12.11/8.12.11) with ESMTP id l6HBFGnN018164; Tue, 17 Jul 2007 04:15:16 -0700 Received: from xbh-sjc-231.amer.cisco.com (xbh-sjc-231.cisco.com [128.107.191.100]) by sj-core-1.cisco.com (8.12.10/8.12.6) with ESMTP id l6HBFGA2009629; Tue, 17 Jul 2007 11:15:16 GMT Received: from xfe-sjc-211.amer.cisco.com ([171.70.151.174]) by xbh-sjc-231.amer.cisco.com with Microsoft SMTPSVC(6.0.3790.1830); Tue, 17 Jul 2007 04:15:16 -0700 Received: from [127.0.0.1] ([171.68.225.134]) by xfe-sjc-211.amer.cisco.com with Microsoft SMTPSVC(6.0.3790.1830); Tue, 17 Jul 2007 04:15:15 -0700 Message-ID: <469CA4F3.4080302@cisco.com> Date: Tue, 17 Jul 2007 07:16:03 -0400 From: Randall Stewart User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.13) Gecko/20070601 X-Accept-Language: en-us, en MIME-Version: 1.0 To: James Healy , Mark Allman References: <469AF916.6090901@swin.edu.au> <469AFE80.2090304@swin.edu.au> <469B5069.6080706@cisco.com> <469C27CB.9090906@swin.edu.au> In-Reply-To: <469C27CB.9090906@swin.edu.au> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 17 Jul 2007 11:15:15.0796 (UTC) FILETIME=[C05C9940:01C7C863] DKIM-Signature: v=0.5; a=rsa-sha256; q=dns/txt; l=3177; t=1184670916; x=1185534916; c=relaxed/simple; s=sjdkim1004; h=Content-Type:From:Subject:Content-Transfer-Encoding:MIME-Version; d=cisco.com; i=rrs@cisco.com; z=From:=20Randall=20Stewart=20 |Subject:=20Re=3A=20Odd=20congestion=20window=20behaviour=20[=20was=3A=20 Draft=20email=20to=20freebsd-net=0A=20] |Sender:=20; bh=edIJDUbrGQQSkOJolBQK/SXWVbpQWUiXRIonyWjFCAI=; b=RX7dCyDReNfyDrcwP4QsrDdFDUYnn01vcHsRj3uCKyf/xZZAAECyWtuBDFAQkthXgkvz4vMr CFz31kbTIQ+2yXOYC1xrZCpc8lQxlf8dF4kohC92ns09wRCm/Fkjhxt+tgCU8vXnQNUsUBA5Cs 5uniAdxecAJ5GghQH80oesc68=; Authentication-Results: sj-dkim-1; header.From=rrs@cisco.com; dkim=pass (sig from cisco.com/sjdkim1004 verified; ); Cc: freebsd-net@freebsd.org, Andrew Subject: Re: Odd congestion window behaviour [ was: Draft email to freebsd-net ] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Jul 2007 11:15:17 -0000 James Healy wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > >>I.e. where we keep past connection state and use that >>as a reference for the initial cwnd. I asked Mark about >>this in the past.. and he said that his paper was >>mis-interpreted and this is incorrect behavior. If you >>have no connections up to a peer you should not use any >>past value for the cwnd... > > > So it's possible that the inital cwnd shouldn't be set by the hostcache > at all? > > If this was the case, does that mean we'd just use the rfc 3390 logic if > enabled, with fallback to the manual sysctl variables as a last resort? > IMO if you want to follow the true spirit of RFC3390 and RFC2581 then yes.. you should ONLY use RFC3390 (or 2581) to set your initial cwnd. I am adding Mark Allman on this to get his opinion.. Mark, here is your big chance to chime in on something that has had your name in comments in FreeBSD code for years... Basically let me referesh your memory in case you are not on net@freebsd.org (or you can go look at the thread). Currently FreeBSD will dig into its hostcache and set the cwnd of a new connection to the previous value with some constraints.. James posted these a fe days ago when noting funny behavior. I chimed in and said really IMO using the previous cwnd of old connections is NOT a good idea.. (I can see using the previous ssthresh.. but not cwnd).. and it is exactly why our SCTP implementation DOES NOT do this.. What do you think Mark (since your name is in the comments to justify this action).. R > James > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.7 (FreeBSD) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iD8DBQFGnCfL4oawkrbYo/kRAuRMAJ47fESbkRB076y7w4hUA25FJp8i+wCcCg13 > aMQJpkHxjy6RdWXVoGmHhX4= > =QYKp > -----END PGP SIGNATURE----- > > Swinburne University of Technology > CRICOS Provider Code: 00111D > > NOTICE > This e-mail and any attachments are confidential and intended only for the use of the addressee. 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We do not accept liability in connection with computer virus, data corruption, delay, interruption, unauthorised access or unauthorised amendment. > > Please consider the environment before printing this email. > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > -- Randall Stewart NSSTG - Cisco Systems Inc. 803-345-0369 803-317-4952 (cell)