From owner-freebsd-net Mon Dec 17 0:21:10 2001 Delivered-To: freebsd-net@freebsd.org Received: from niwun.pair.com (niwun.pair.com [209.68.2.70]) by hub.freebsd.org (Postfix) with SMTP id 63DBD37B431 for ; Mon, 17 Dec 2001 00:20:52 -0800 (PST) Received: (qmail 20812 invoked by uid 3193); 17 Dec 2001 08:20:51 -0000 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 17 Dec 2001 08:20:51 -0000 Date: Mon, 17 Dec 2001 03:20:51 -0500 (EST) From: Mike Silbersack X-Sender: To: Thomas Zenker Cc: , Subject: Re: USB ethernet problem In-Reply-To: <20011217090920.A763@mezcal.tue.le> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 (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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message