From owner-freebsd-net@FreeBSD.ORG Thu Jan 13 19:13:03 2005 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 72B9316A4CE for ; Thu, 13 Jan 2005 19:13:03 +0000 (GMT) Received: from kyoto.netlab.nec.de (kyoto.netlab.nec.de [195.37.70.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id 63D3843D48 for ; Thu, 13 Jan 2005 19:13:02 +0000 (GMT) (envelope-from lars.eggert@netlab.nec.de) Received: from [10.1.1.112] (mito.netlab.nec.de [195.37.70.39]) by kyoto.netlab.nec.de (Postfix) with ESMTP id 6D6C11BACA9; Thu, 13 Jan 2005 20:12:57 +0100 (CET) Message-ID: <41E6C837.1020503@netlab.nec.de> Date: Thu, 13 Jan 2005 20:12:55 +0100 From: Lars Eggert Organization: NEC Network Laboratories User-Agent: [Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O) Gecko/20040906 Camino/0.8+] X-Accept-Language: en,de,es,ja,fr,it,nl,sv,no,da,fi,pt,zh-cn,zh-tw,ko MIME-Version: 1.0 To: Julian Elischer References: <41E5C9D8.4090209@elischer.org> <20050113055111.GA11141@odin.ac.hmc.edu> <41E6C564.50005@elischer.org> In-Reply-To: <41E6C564.50005@elischer.org> Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg=sha1; boundary="------------ms070605090401070409060605" cc: net@freebsd.org Subject: Re: TCP out-of-order packets. X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Jan 2005 19:13:03 -0000 This is a cryptographically signed message in MIME format. --------------ms070605090401070409060605 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit >>> I have a link which is provided by someone else that is 7 x E1s >>> aggregated. At leat it looks that way to me when I get to see it. >>> however I have only been able to get 60kB.sec across this, >>> despite having a tcp window size of 131072 bytes.. After >>> investigation it appears that the link is massively re-orderring >>> packets. groups of upto 10 packets may appear in random order. >>> (Maybe more, bu tI have seen 10) >>> >>> in fact packets are rarely IN order. >>> This plays havoc with the tcp sessions. A gap or jump in the ACK stream looks to TCP like a loss, no matter that it's caused by reordering. Multiple such things per window look like multiple losses and trigger a slow start under Reno. TCP/SACK should be more robust against reorderings (up to a degree, at least.) Does 4.x have the SACK code yet? What sort of link multiplexer is this? Decent ones jump through all sorts of hoops to try and reestablish the original packet order. 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