Date: Sat, 14 Nov 1998 20:16:41 -0600 From: David Kelly <dkelly@hiwaay.net> To: Dave Bodenstab <imdave@mcs.net> Cc: questions@FreeBSD.ORG Subject: Re: Are collisions normal on a local net Message-ID: <199811150216.UAA28559@n4hhe.ampr.org> In-Reply-To: Message from Dave Bodenstab <imdave@mcs.net> of "Thu, 12 Nov 1998 21:54:06 CST." <199811130354.VAA11666@base486.home.org>
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Dave Bodenstab writes: > Is this normal or do I have something wrong with my setup? Could it be > something with the fxp driver or hardware trying to go at 100M instead of > 10M? I notice that the fxp driver can be ifconfig'ed with a media type > and options... I tried -media 10baseT/UTP but it didn't seem to affect > anything. I've been searching for the Really Good Collision URL I once had filed away. Seems it didn't survive housecleaning one day. But it was at SGI if that rings any bells. In that SGI article it was suggested that as much as a 200% collision rate should not cause worry. It was pointed out an early collision happens in the first 64 octets, so a backoff and retry doesn't cost much bandwidth. Late collisions are after this 64 octet window and are a bad thing suggesting a collision with another host too far down the wire. That's a real eye opener when one starts worrying about the length of wire over which the speed of light isn't fast enough (I know about velocity factors, typically 60% but possibly 80% in some coaxial cables, so Big Fat Hairy Deal, its only 60% of C). One other thing SGI mentioned is that different ethernet hardware used in various SGI system report collisions differently. I've noticed my 3com card at work (forgot model, uses the vx driver) almost never reports a collision. OTOH the 8-port hub its plugged into may have its collision light on solid. -- David Kelly N4HHE, dkelly@nospam.hiwaay.net ===================================================================== The human mind ordinarily operates at only ten percent of its capacity -- the rest is overhead for the operating system. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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