Date: Fri, 13 Nov 1998 14:06:12 -0800 From: David Greenman <dg@root.com> To: Eddie Irvine <eirvine@tpgi.com.au> Cc: Dave Bodenstab <imdave@mcs.net>, questions@FreeBSD.ORG Subject: Re: Are collisions normal on a local net Message-ID: <199811132206.OAA02240@root.com> In-Reply-To: Your message of "Sat, 14 Nov 1998 08:46:47 %2B1100." <364CA8C7.3A461F3C@tpgi.com.au>
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>> When I do a ``netstat -i'' on either of the machines with the ne2000 >> cards, I see no collisions, but I do see a few IERRS, ie: >> >> Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll >> ed0 1500 <Link>00.40.05.52.8d.ad 8352016 15 5678032 0 0 >> ed0 1500 10 base486 8352016 15 5678032 0 0 >> >> However, from the 3.0 box, I see: >> >> Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll >> fxp0 1500 <Link> 00.a0.c9.49.6f.9e 199825 0 363568 0 30635 >> fxp0 1500 10/24 base686 199825 0 363568 0 30635 >> > >Seems a tad excessive for a small network. > >> ed0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > ^^^^^^^ > >Use the MS-DOS setup disk that came with the ed0 card to make certain >it really is in SIMPLEX mode and not DUPLEX. > >This seems to be a problem with the ISA NE2000 cards (not just for >FreeBSD but >W95 as well). PCI NE2000 cards seem to be OK. A couple of things...first, "SIMPLEX" above refers to whether the card/driver will see it's own packet transmissions and does not refer to the (half/full) duplex of the link. A collision rate of 10% is not very high and is not a problem. For half duplex circuits, packet acknowledges will collide with the traffic in the other direction, and depending on the timing, this can cause lots of collisions or relatively few. Even a collision rate of 100% (average of one collision for every packet sent) will only reduce your network throughput by perhaps 15%, so a collision rate of 10% is in the noise. The reason that the Pro/100B cards have more collisions is because the inter-packet spacing for transmitted packets is the minimum allowed for IEEE 802.3 and this doesn't leave much room for another transmitter to start talking without a collision. If you mix slow cards with fast ones, the effect is exaggerated. The bottom line is "Don't worry about it, it's not a problem". -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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