From owner-freebsd-net@FreeBSD.ORG Wed Mar 19 14:30:16 2008 Return-Path: Delivered-To: freebsd-net@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6CF44106568B for ; Wed, 19 Mar 2008 14:30:16 +0000 (UTC) (envelope-from scf@FreeBSD.org) Received: from mail.farley.org (farley.org [67.64.95.201]) by mx1.freebsd.org (Postfix) with ESMTP id 348718FC29 for ; Wed, 19 Mar 2008 14:30:16 +0000 (UTC) (envelope-from scf@FreeBSD.org) Received: from thor.farley.org (thor.farley.org [192.168.1.5]) by mail.farley.org (8.14.2/8.14.2) with ESMTP id m2JEUBbF088247; Wed, 19 Mar 2008 09:30:14 -0500 (CDT) (envelope-from scf@FreeBSD.org) Date: Wed, 19 Mar 2008 09:30:11 -0500 (CDT) From: "Sean C. Farley" To: David DeSimone In-Reply-To: <20080318223404.GB24011@verio.net> Message-ID: References: <47DE4E96.8080507@FreeBSD.org> <20080318223404.GB24011@verio.net> User-Agent: Alpine 1.00 (BSF 882 2007-12-20) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.4 X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on mail.farley.org Cc: freebsd-net@FreeBSD.org Subject: Re: Frequent pauses with Linux-based router X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Mar 2008 14:30:16 -0000 On Tue, 18 Mar 2008, David DeSimone wrote: > Sean C. Farley wrote: >> >> An ICMP test showed that there were occasional pauses and packet >> loss. The fix: use 100Mb instead of 10Mb. :) For some reason I do >> not recall, I had forced the interface connected to the DSL router to >> 10Mb. When I noticed XP did not have the same problem and that it >> had a 100Mb connection to the router, I found and removed the "media >> 10baseT/UTP mediaopt full-duplex" from /etc/rc.conf for the >> interface. That appears to have fixed it. > > The fix here is not that you moved to 100 Mb, it's that you stopped > forcing duplex, and allow auto-negotiation to take place. > > With the forced duplex in effect, your NIC does not auto-negotiate > with the other end (the router), and it falls back to half duplex, > which leads to large numbers of collision errors. Ah! I tried it again at 10Mb without setting it to full-duplex, and it worked. Out of curiosity, is it normal that 100Mb will default to full-duplex yet 10Mb will not, or is it dependent on the hardware? >> The pause always seemed to be for packets from the router to the >> computer. > > Yep, whenever the router would try to send, if your end happened to be > sending a frame, the router's NIC would stop to avoid the collision, > leading to packet loss. This is a classic duplex-mismatch scenario. My wife was getting tired of hearing the thump of my head on the wall. Maybe one more to make sure I remember this next time. :) Thank you for the explanation. Sean -- scf@FreeBSD.org