From owner-freebsd-net Mon Dec 17 1:18:20 2001 Delivered-To: freebsd-net@freebsd.org Received: from smtp.www-service.de (smtp.www-service.de [212.77.161.16]) by hub.freebsd.org (Postfix) with SMTP id 3D5B037B419 for ; Mon, 17 Dec 2001 01:18:14 -0800 (PST) Received: (qmail 26446 invoked from network); 17 Dec 2001 09:18:02 -0000 Received: from pd90065db.dip.t-dialin.net (HELO fw.tue.le) (217.0.101.219) by smtp.www-service.de with SMTP; 17 Dec 2001 09:18:02 -0000 Received: from mezcal.tue.le (mezcal.tue.le [192.168.201.20]) by fw.tue.le (8.8.8/8.8.8) with ESMTP id KAA23066; Mon, 17 Dec 2001 10:17:49 +0100 (CET) (envelope-from thz@mezcal.tue.le) Received: (from thz@localhost) by mezcal.tue.le (8.11.6/8.11.6) id fBH9HmW01434; Mon, 17 Dec 2001 10:17:48 +0100 (CET) (envelope-from thz) Date: Mon, 17 Dec 2001 10:17:48 +0100 From: Thomas Zenker To: Mike Silbersack Cc: freebsd-net@freebsd.org Subject: Re: USB ethernet problem Message-ID: <20011217101748.A1395@mezcal.tue.le> Mail-Followup-To: Mike Silbersack , freebsd-net@freebsd.org References: <20011217090920.A763@mezcal.tue.le> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from silby@silby.com on Mon, Dec 17, 2001 at 03:20:51AM -0500 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Mon, Dec 17, 2001 at 03:20:51AM -0500, Mike Silbersack wrote: > > (Moving over to -net, please remove -stable from any cc's) > > On Mon, 17 Dec 2001, Thomas Zenker wrote: > > > I allways wondered, why the initial slowstart window is set to one > > (well some years I didn't look into the tcp code though). 9 years > > ago I had to develope the firmware for a store&foreward radio > > network, where I applied a lot of the ideas from the then net/2 tcp > > stack. The rtt in such a network is really horrible and packetsizes > > have to be taken in account. Anyway the optimal initial window there > > was 2. With a window of two there much more probability to get a > > connection going, because you send two packets in the beginning, > > if the first is lost, the receiption of the second one gets the > > first one resent long before the timeout. Otherway round, if the > > second is lost... the third is on its way already. With a intital > > window of 1 the only recovery is by timeout. The argument against > > bigger than two was (at least in my case) not to defeat the intention > > of the slowstart. Anyway, in tcp probably something between 2 and > > 4 could be considered. > > > > Thomas > > RFC 2581 suggests that 4 is a good value (well, not exactly 4, they have a > formula which comes out to about 4 in most cases.) I'm inclined to agree > that something between 2-4 would be a good value for our non-local > slowstart flightsize as well. Maybe after 4.5 is released we can go look > into it. (It's too late to be changing stuff now.) > > Mike "Silby" Silbersack ok. everybody can try this anyway: sysctl net.inet.tcp.slowstart_flightsize=2 -- Thomas Zenker c/o Lennartz electronic GmbH Bismarckstrasse 136, D-72072 Tuebingen, Germany Phone: +49-(0)7071-93550 Email: thz@lennartz-electronic.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message