Date: Wed, 19 Mar 2008 09:30:11 -0500 (CDT) From: "Sean C. Farley" <scf@FreeBSD.org> To: David DeSimone <fox@verio.net> Cc: freebsd-net@FreeBSD.org Subject: Re: Frequent pauses with Linux-based router Message-ID: <alpine.BSF.1.00.0803190924290.4462@thor.farley.org> In-Reply-To: <20080318223404.GB24011@verio.net> References: <alpine.BSF.1.00.0803161517370.56728@thor.farley.org> <47DE4E96.8080507@FreeBSD.org> <alpine.BSF.1.00.0803181459390.7409@thor.farley.org> <20080318223404.GB24011@verio.net>
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On Tue, 18 Mar 2008, David DeSimone wrote: > Sean C. Farley <scf@FreeBSD.org> 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
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