From owner-freebsd-net Mon Nov 26 6:46:30 2001 Delivered-To: freebsd-net@freebsd.org Received: from prism.flugsvamp.com (cb58709-a.mdsn1.wi.home.com [24.17.241.9]) by hub.freebsd.org (Postfix) with ESMTP id ECEF437B405 for ; Mon, 26 Nov 2001 06:46:26 -0800 (PST) Received: (from jlemon@localhost) by prism.flugsvamp.com (8.11.0/8.11.0) id fAQEhu185094; Mon, 26 Nov 2001 08:43:56 -0600 (CST) (envelope-from jlemon) Date: Mon, 26 Nov 2001 08:43:56 -0600 (CST) From: Jonathan Lemon Message-Id: <200111261443.fAQEhu185094@prism.flugsvamp.com> To: serg@sirena2000.ru, net@freebsd.org Subject: Re: decreasing TIME_WAIT duration(T/TCP?) X-Newsgroups: local.mail.freebsd-net In-Reply-To: References: Organization: Cc: 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 In article you write: >Lars Eggert wrote: >> >> > In article >> > you write: >> > >Hello! >> > > >> > >It is important to me to have duration of TIME_WAIT state of TCP >> > >connection as short time as possible. >> > >> > Tweak net.inet.tcp.msl, which specifies the 2MSL timeout. >> >> And know what you are doing, it's there for a reason. If you need to >> dramatically change this value, I'd wager your system would benefit from a >> design change. >> >> Lars >> -- >> Lars Eggert Information Sciences Institute >> http://www.isi.edu/larse/ University of Southern California > > >Alan Cox wrote: >| >| > Machine is web serwer with reather big traffic. Why there is >| > so much connections in TIME_WAIT state ? >| >| >| "2 mintues" may be how the Linux kernel does it, but it's not the way >| TCP says it should be done. >| >| TIME_WAIT should last for 2*MSL (maximum segment lifetime). I know >it's >| hard to calculate MSL, and if you make up a hard-coded value it has to >| be long enough for the slowest connections. It could be that FreeBSD >| 4.0 does do this calculation. If we can calculate semi-accurate MSLs >| for each connection, TIME_WAIT states would be minimized. >| >| Even over a slow Internet link, the MSL can't be much longer than 10 >| seconds or so. By then a segment has either been TTL'd out, or is >| lost. I don't buy "MSL == 1 minute" at all. > >How to turn on this calculation for 4.x ? Unfortunately, this is not calculated; we still rely on a static (default 30sec) MSL quiet period. Ideally, it should be possible to set MSL based on some multiple of RTT for the connection, and default to a hard coded value if there are not enough samples to calculate RTT. -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message