From owner-freebsd-net Mon Nov 6 14:53:43 2000 Delivered-To: freebsd-net@freebsd.org Received: from Awfulhak.org (tun.AwfulHak.org [194.242.139.173]) by hub.freebsd.org (Postfix) with ESMTP id 21E9837B479; Mon, 6 Nov 2000 14:53:30 -0800 (PST) Received: from hak.lan.Awfulhak.org (root@hak.lan.awfulhak.org [172.16.0.12]) by Awfulhak.org (8.11.1/8.11.0) with ESMTP id eA6MjiT02058; Mon, 6 Nov 2000 22:45:44 GMT (envelope-from brian@hak.lan.Awfulhak.org) Received: from hak.lan.Awfulhak.org (brian@localhost [127.0.0.1]) by hak.lan.Awfulhak.org (8.11.1/8.11.1) with ESMTP id eA6Mk9T13715; Mon, 6 Nov 2000 22:46:09 GMT (envelope-from brian@hak.lan.Awfulhak.org) Message-Id: <200011062246.eA6Mk9T13715@hak.lan.Awfulhak.org> X-Mailer: exmh version 2.2 06/23/2000 with nmh-1.0.4 To: Kris Kennaway Cc: "Richard A. Steenbergen" , David Greenman , freebsd-net@FreeBSD.ORG, brian@Awfulhak.org Subject: Re: tcp sendspace/recvspace In-Reply-To: Message from Kris Kennaway of "Sun, 05 Nov 2000 17:57:22 PST." <20001105175722.A8886@citusc17.usc.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 06 Nov 2000 22:46:09 +0000 From: Brian Somers Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > On Sun, Nov 05, 2000 at 08:36:14PM -0500, Richard A. Steenbergen wrote: > > On Sun, 5 Nov 2000, Kris Kennaway wrote: > >=20 > > > On Sun, Nov 05, 2000 at 02:02:44PM -0800, David Greenman wrote: > > > > I've been messing around with the net.inet.tcp.sendspace and=20 > > > > net.inet.tcp.recvspace parameters on ftp.freesoftware.com and have fo= > und > > > > that there is a significant performance improvement when increasing t= > hese > > > > to 32768 bytes. Apparantly there are enough systems out there with hi= > gher > > > > window maxes that it really does make a difference. By significant=20 > > > > improvement, I mean about a average of a 20% increase in Mbps per use= > r, > > > > and this was just the change over a 30 minute period with lots of con= > nections > > > > still using the old 16K values. > > > > Any objections to increasing the defaults in FreeBSD to 32K? > > >=20 > > > Won't this impact the latency of multiple connections over a slow PPP l= > ink? > >=20 > > Thats what the congestion window is for. Any limitation of transmits based > > on the advertised memory limitation window is totally improper. > > Perhaps it was a bug, but I used to see e.g. FTP transfers which were > running at full speed totally monopolizing my modem bandwidth (then a > 14.4k), and other sessions not being able to receive their "fair > share". Tweaking net.inet.tcp.recvspace to give only a second or two > worth of data transfer reduced the latency to acceptable levels. > > Maybe this has been fixed by now - I haven't noticed it since I > upgraded to a 56k modem. I'll try increasing my system to 32768 > and see if it has any effect. Have a look at ppp's ``set urgent'' and ``set ifqueue'' commands. These will effect interactive performance over a (slow) link.... Setting tcp.sendspace to a low value would probably make these ppp values more sensitive. > Kris -- Brian Don't _EVER_ lose your sense of humour ! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message