From owner-freebsd-hackers Fri Nov 30 16:35:31 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from exuma.irbs.com (exuma.irbs.com [216.86.160.252]) by hub.freebsd.org (Postfix) with ESMTP id B457A37B416 for ; Fri, 30 Nov 2001 16:35:28 -0800 (PST) Received: by exuma.irbs.com (Postfix, from userid 2500) id DA8FD17406; Fri, 30 Nov 2001 19:35:22 -0500 (EST) Date: Fri, 30 Nov 2001 19:35:22 -0500 From: John Capo To: Matthew Dillon Cc: Nate Williams , Alexander Haderer , freebsd-hackers@FreeBSD.ORG Subject: Re: Found the problem, w/patch (was Re: FreeBSD performing worse than Linux?) Message-ID: <20011130193522.A36097@exuma.irbs.com> Reply-To: jc@irbs.com References: <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011128104629.A43642@walton.maths.tcd.ie> <5.1.0.14.1.20011130181236.00a80160@postamt1.charite.de> <200111302047.fAUKlT811090@apollo.backplane.com> <200111302130.fAULUU324648@apollo.backplane.com> <15367.64883.390696.863120@caddis.yogotech.com> <200111302200.fAUM0hD27448@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2i In-Reply-To: <200111302200.fAUM0hD27448@apollo.backplane.com>; from dillon@apollo.backplane.com on Fri, Nov 30, 2001 at 02:00:43PM -0800 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Quoting Matthew Dillon (dillon@apollo.backplane.com): > > The question here is... is it actually packet loss that is creating > this issue for you and John, or is it something else? The only way > to tell for sure is to run tcpdump on BOTH the client and server > and then observe whether packet loss is occuring by comparing the dumps. > Packet loss is the problem for sure. I am dumping on the server and client side. http://www.irbs.net/server-dump.html http://www.irbs.net/client-dump.html In 60Ms the server pushed out about 200 segments. My test writes 1 byte at a time on an existing ssh conection so the payload per segment is small, 48 bytes. (48 + IP + TCP) * 200 is around 17KB in 60Ms which probably overflowed the frame switch queue. The client is on a fractional T1, the server is on a 10Mb -> OC3 connection 1200 network miles away. Jonathan Lemon pointed out in the TCP Anomalies thread that slow start seems to be broken. John Capo To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message