From owner-freebsd-questions@FreeBSD.ORG Wed Jun 30 03:09:15 2004 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B162016A4CE for ; Wed, 30 Jun 2004 03:09:15 +0000 (GMT) Received: from internet.potentialtech.com (h-66-167-251-6.phlapafg.covad.net [66.167.251.6]) by mx1.FreeBSD.org (Postfix) with ESMTP id 80EA343D46 for ; Wed, 30 Jun 2004 03:09:15 +0000 (GMT) (envelope-from wmoran@potentialtech.com) Received: from working.potentialtech.com (pa-plum-cmts1e-68-68-113-64.pittpa.adelphia.net [68.68.113.64]) by internet.potentialtech.com (Postfix) with ESMTP id CB9E369A39; Tue, 29 Jun 2004 23:08:18 -0400 (EDT) Date: Tue, 29 Jun 2004 23:08:17 -0400 From: Bill Moran To: Charles Swiger Message-Id: <20040629230817.0f6d230e.wmoran@potentialtech.com> In-Reply-To: <1133CD52-CA07-11D8-99F8-003065ABFD92@mac.com> References: <20040629140231.7b57dedf.wmoran@potentialtech.com> <1187B403-C9FC-11D8-99F8-003065ABFD92@mac.com> <20040629153855.300b3888.wmoran@potentialtech.com> <1133CD52-CA07-11D8-99F8-003065ABFD92@mac.com> Organization: Potential Technologies X-Mailer: Sylpheed version 0.9.12 (GTK+ 1.2.10; i386-portbld-freebsd4.9) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit cc: questions@freebsd.org Subject: Re: REPOST: Performance problems with FTP X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Jun 2004 03:09:15 -0000 Charles Swiger wrote: > >> Can you reproduce by moving ftp to a different port #? (Perhaps some > >> quality-of-service thingy is providing different bandwidth by port...) > > > > I haven't tried that, but I forgot to mention that a Debian box located > > right next to the problem box (on the same network) gets speeds equal > > to what would be expected. To me, that ruled out QOS, routing and > > other > > beyond-my-control Internet problems. Again, I'm happy to be corrected > > if there's something here I'm not aware of. > > Well, that does tend to rule out a bunch of issues. Have you tried > changing the MTU of the FreeBSD box down to 1400 or so (or even 512), > just to see whether that does anything? OK. I've had a bit of success here ... By setting the MTU down to ~650, I get the best performance I've seen with this setup (about 27k/sec ... which isn't too bad) I set "SocketOptions maxseg 650" in the proftpd.conf file for now, which seems to help a good bit. But I'm really confused. Why does reducing the MTU improve performance? I would have thought it would hurt performance by increasing the # of packets, thus increasing overhead. I did some captures using Ethereal, and I'm seeing a weird pause (with the MTU at the default) where the client will send three packets, there'll be a pause, then the ack comes back, then three packets, pause, ack ... You'd think that reducing the MTU would make this worse because there's less data in the three packets, thus more pauses, but when I drop the MTU, the pause reduces significantly. There's something with TCP going on here that I don't understand. (Thanks a LOT for your assistance so far!) -- Bill Moran Potential Technologies http://www.potentialtech.com