From owner-freebsd-net@FreeBSD.ORG Tue Jul 12 14:39:54 2005 Return-Path: X-Original-To: freebsd-net@freebsd.org 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 CB36016A41C; Tue, 12 Jul 2005 14:39:54 +0000 (GMT) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id 70FCA43D45; Tue, 12 Jul 2005 14:39:54 +0000 (GMT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.13.1/8.13.3) id j6CEdUZU079462; Tue, 12 Jul 2005 09:39:30 -0500 (CDT) (envelope-from dan) Date: Tue, 12 Jul 2005 09:39:30 -0500 From: Dan Nelson To: David Malone Message-ID: <20050712143930.GJ5116@dan.emsphone.com> References: <200507121048.ab72454@salmon.maths.tcd.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200507121048.ab72454@salmon.maths.tcd.ie> X-OS: FreeBSD 5.4-STABLE X-message-flag: Outlook Error User-Agent: Mutt/1.5.9i Cc: Danny Braniss , freebsd-net@freebsd.org, freebsd-stable@freebsd.org, Luigi Rizzo Subject: Re: tcp troughput weirdness 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, 12 Jul 2005 14:39:54 -0000 In the last episode (Jul 12), David Malone said: > > did the trick! now can someone remind me what inflight does? and > > could someone explain why increasing sendspace alone did not do the > > trick? (i had it at 64k, which got things better, but not > > sufficient). > > TCP inflight limiting is supposed to guess the bandwidth-delay > product for a TCP connection and stop the window expanding much > above this. It's a pretty neat idea for DSL links that often have > huge buffers at the far end, where inflight limiting can prevent > delays to interactive traffic. > > However, some of the guys I know that work on TCP dynamics reckon > that they can they can come up with situations where inflight > limiting will break. Unfortunately, I haven't had time to talk > this through with them. I guess you may have found one of those > situations ;-) You might want to apply the patch at the bottom of http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/75122 ; without it, new connections get a random initial bandwidth. -- Dan Nelson dnelson@allantgroup.com