Date: Mon, 17 Dec 2001 10:17:48 +0100 From: Thomas Zenker <thz@Lennartz-electronic.de> To: Mike Silbersack <silby@silby.com> Cc: freebsd-net@freebsd.org Subject: Re: USB ethernet problem Message-ID: <20011217101748.A1395@mezcal.tue.le> In-Reply-To: <Pine.BSF.4.30.0112170314380.14582-100000@niwun.pair.com>; from silby@silby.com on Mon, Dec 17, 2001 at 03:20:51AM -0500 References: <20011217090920.A763@mezcal.tue.le> <Pine.BSF.4.30.0112170314380.14582-100000@niwun.pair.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20011217101748.A1395>