Date: Mon, 01 Feb 1999 05:25:48 +1000 From: Greg Black <gjb@comkey.com.au> To: Greg Lehey <grog@lemis.com> Cc: FreeBSD Questions <questions@FreeBSD.ORG> Subject: Re: Excessive collisions on Ethernet Message-ID: <19990131192548.24006.qmail@alpha.comkey.com.au> In-Reply-To: <19990131110224.I8473@freebie.lemis.com> of Sun, 31 Jan 1999 11:02:25 %2B1030 References: <19990131110224.I8473@freebie.lemis.com>
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> In the last few days I've noticed a really high number of collisions > on my Ethernet. There are only 5 machines on the network, 3 of which > are barely active, yet I see: > > (allegro, running 2.2.6-STABLE) > ed0 1500 <Link> 00.00.c0.44.a5.68 43729816 45 43861788 12 977828 > ed0 1500 widecast allegro 43729816 45 43861788 12 977828 That's only 1.1%. > (freebie, running 4.0-CURRENT) > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll > ed2 1500 <Link> 00.80.48.e6.a0.61 11976144 12 13389307 0 988340 > ed2 1500 widecast freebie 11976144 12 13389307 0 988340 And that's only 3.9% -- it's worse than allegro, but not by a significant margin for the relatively small amount of traffic. On my Ethernet, I have machines that report 0.01%, 9.6%, 0.7%, 0.04% and 0.4%. The outlier is a machine that has been up a few hours and was used for a large file transfer which blew its average out of the water -- it'll be back to about 1% as time goes by. > I tried an ftp from panic, copying a file of 45 MB from freebie. The > transfer ran at about 1 MB/s with about 450 collisions per second on > the freebie side, none on the panic side. Here are the values before > and after: > > freebie: > Ipkts Ierrs Opkts Oerrs Coll > before 11978350 13 13392678 0 989089 > after 11994616 13 13424921 0 1009912 > diff 16266 0 32243 0 20823 > > panic: > Ipkts Ierrs Opkts Oerrs Coll > before 480 0 651 1 0 > after 32143 0 16679 1 0 > diff 31663 0 16028 0 0 > > Looking at these results (40% collision rate on freebie), it would > seem that something is seriously wrong in the network. On the other > hand, allegro also shows a large number of collisions. At the moment > I'm suspecting the (3 month old) Ethernet board in freebie, but I was > wondering if there were other reasons which might apply. I just did some 10 to 15 MB file transfers with NFS on my LAN (I don't have FTP set up), and saw collision rates ranging from 25% to 35% for those periods. I'd say that was pretty normal, given the way that Ethernet works. The more interesting statistics are the overall figures over time, and the ones you give at the start aren't too bad. Yes, freebie is a bit high -- but 4% compared with 1% is not a big factor, especially with the fairly low total amount of traffic. I'd watch it for a bit longer before deciding it was a real problem. After all, if you're getting 1 MB/s on a 10 Mb/s LAN, you're doing pretty well :-) -- Greg Black <gjb@acm.org> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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