On 9/23/05, Jonathan Wright <[EMAIL PROTECTED]> wrote: > Mark Knecht wrote: > > 1) What causes a 'collision' on a network interface? > > As Paul pointed out via his e-mail (via the previous thread), collisions > are when two packets try and talk over an ethernet cable at the same time. > > In terms of a hub, it's very common, esp. when the hub becomes loaded as > 2/4/8/32, etc. machines are all essentially using the same bit of > cable (what with a hub being nothing more than a repeater). > > If an interface detects a collision, the transfer is stopped and a it > waits a random amount of time before trying to send it again. This goes > round and round until it's sent. > > For a switch on the other hand, its not so common, as there are only > ever two machines on the cable - the switch and the computer. Although > 31% collision rate on dragonfly does seam alot. > > Again, Paul is probably right, with half-duplex being the problem. In > this case, the same 'cable' us used for both sending and receiving > traffic. If one conflicts the other, you'll get a collision. With > Full-duplex, sends and receives are independent and therefore you can't > get collisions: > <SNIP> > > > 2) How can I eliminate them? (Including hardware changes if required.) > > The two machines are connected through a small LinkSys switch. model > > EZXS55W: > > When I first read that I thought 'cheap built-in hub', so only 10MBps @ > HD, however looking at it, 100MBps-FD shouldn't be a problem.
I bought the switch base don it being able to do 100Mb FD. Thanks to your suggestion about mii-tool I'm not so sure right now that it's actually doing it... > A good > tool to look at is mii-tool (emerge mii-diag): YES!! VERY HELPFUL! Thanks! > > root on jonathan [ ~ ] --> mii-tool > eth0: negotiated 100baseTx-FD flow-control, link ok Now, I'm thinking that this is setting the mii on my PC, correct? (Not on the switch.) Unfortunately it appears that Dragonfly cannot/will not do 100baseTx-FD or HD! dragonfly ~ # mii-tool eth0: 10 Mbit, full duplex, link ok dragonfly ~ # mii-tool -F 100baseTx-FD dragonfly ~ # mii-tool eth0: 100 Mbit, full duplex, no link dragonfly ~ # mii-tool -F 10baseT-FD dragonfly ~ # mii-tool eth0: 10 Mbit, full duplex, link ok dragonfly ~ # mii-tool -F 10baseT-HD dragonfly ~ # mii-tool eth0: 10 Mbit, half duplex, link ok dragonfly ~ # mii-tool -F 100baseTx-HD dragonfly ~ # mii-tool eth0: 100 Mbit, half duplex, no link dragonfly ~ # mii-tool -F 10baseT-FD dragonfly ~ # mii-tool eth0: 10 Mbit, full duplex, link ok dragonfly ~ # mii-tool -F 100baseTx-FD dragonfly ~ # mii-tool eth0: 100 Mbit, full duplex, no link dragonfly ~ # dragonfly ~ # lspci | grep Ethernet 0000:01:03.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) dragonfly ~ # Note that there is no link for any of the 100Mb settings. This is verified looking at the switch itself as the link light turns off. Actually, I had never noticed that the 100 light was not turning on before today. so much for plug and play! (My bad...me stupido...) ;-) dragonfly ~ # mii-tool -v eth0: 100 Mbit, full duplex, no link product info: vendor 00:00:00, model 0 rev 0 basic mode: 100 Mbit, full duplex basic status: no link capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD dragonfly ~ # dragonfly ~ # mii-tool -F 10baseT-FD dragonfly ~ # mii-tool -v eth0: 10 Mbit, full duplex, link ok product info: vendor 00:00:00, model 0 rev 0 basic mode: 10 Mbit, full duplex basic status: link ok capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD dragonfly ~ # So far, up to this point, I can at least see the world using 100baseT-FD. That should be better than what I had before. (I think...) > root on jonathan [ ~ ] --> mii-tool -v > eth0: negotiated 100baseTx-FD flow-control, link ok > product info: Intel 82555 rev 4 > basic mode: autonegotiation enabled > basic status: autonegotiation complete, link ok > capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD > advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD > flow-control > link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD > flow-control > > Then you can run: > > root on jonathan [ ~ ] --> mii-tool -F 100baseTx-FD > > Which should put the computer into 100MBps via Full Duplex. Give that a > go - it should work. If there's a problem putting it into that (and you > can run 'mii-tool -r' to re-negotiate), it may be the switch and/or the > cable. dragonfly ~ # mii-tool -r restarting autonegotiation... dragonfly ~ # mii-tool -v eth0: autonegotiation failed, link ok product info: vendor 00:00:00, model 0 rev 0 basic mode: autonegotiation enabled basic status: autonegotiation complete, link ok capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD dragonfly ~ # OK, so something is having trouble with this negotiation stuff. I'll drag out some new cables after I send this and see what happens with that. I looked at the LinkSys switch docs again. There are no user settings that I see to get the switch to support 100Mb/S. It's supposed to be automatic. Again, thanks very much. mii-tool is very helpful. I'll also have to look at mii-diag to see if it can help with this problem. cheers, Mark -- gentoo-user@gentoo.org mailing list
