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Mark Knecht wrote: |
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> 1) What causes a 'collision' on a network interface? |
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|
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As Paul pointed out via his e-mail (via the previous thread), collisions |
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are when two packets try and talk over an ethernet cable at the same time. |
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|
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In terms of a hub, it's very common, esp. when the hub becomes loaded as |
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2/4/8/32, etc. machines are all essentially using the same bit of |
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cable (what with a hub being nothing more than a repeater). |
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|
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If an interface detects a collision, the transfer is stopped and a it |
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waits a random amount of time before trying to send it again. This goes |
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round and round until it's sent. |
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|
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For a switch on the other hand, its not so common, as there are only |
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ever two machines on the cable - the switch and the computer. Although |
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31% collision rate on dragonfly does seam alot. |
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|
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Again, Paul is probably right, with half-duplex being the problem. In |
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this case, the same 'cable' us used for both sending and receiving |
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traffic. If one conflicts the other, you'll get a collision. With |
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Full-duplex, sends and receives are independent and therefore you can't |
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get collisions: |
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|
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jwright on jonathan [ ~ ] --> /sbin/ifconfig eth0 |
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eth0 Link encap:Ethernet HWaddr 00:02:B3:87:89:03 |
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inet addr:10.0.0.10 Bcast:10.0.0.255 Mask:255.255.255.0 |
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UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 |
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RX packets:3481762 errors:0 dropped:0 overruns:0 frame:0 |
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TX packets:3664852 errors:0 dropped:0 overruns:0 carrier:0 |
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collisions:0 txqueuelen:1000 |
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RX bytes:1212745301 (1156.5 Mb) TX bytes:1002484102 (956.0 Mb) |
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|
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jwright on jonathan [ ~ ] --> ssh -t kenny /sbin/ifconfig eth0 |
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eth0 Link encap:Ethernet HWaddr 00:50:8B:4C:9C:EA |
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inet addr:10.0.0.2 Bcast:10.0.0.255 Mask:255.255.255.0 |
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UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 |
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RX packets:18415888 errors:0 dropped:0 overruns:0 frame:0 |
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TX packets:17153032 errors:0 dropped:0 overruns:0 carrier:0 |
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collisions:0 txqueuelen:100 |
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RX bytes:2907452267 (2772.7 Mb) TX bytes:960767410 (916.2 Mb) |
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Interrupt:11 Base address:0x2000 Memory:42100000-42100038 |
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|
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Connection to kenny closed. |
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jwright on jonathan [ ~ ] --> ssh -t kyle /sbin/ifconfig eth0 |
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eth0 Link encap:Ethernet HWaddr 00:08:C7:7F:CF:A7 |
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inet addr:10.0.0.1 Bcast:10.0.0.255 Mask:255.255.255.0 |
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UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 |
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RX packets:34264896 errors:0 dropped:0 overruns:0 frame:0 |
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TX packets:33334375 errors:0 dropped:0 overruns:0 carrier:0 |
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collisions:0 txqueuelen:1000 |
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RX bytes:3580726012 (3414.8 MB) TX bytes:196135708 (187.0 MB) |
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Interrupt:9 Base address:0x2000 Memory:42100000-42100038 |
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|
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Connection to kyle closed. |
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|
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> 2) How can I eliminate them? (Including hardware changes if required.) |
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> The two machines are connected through a small LinkSys switch. model EZXS55W: |
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|
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When I first read that I thought 'cheap built-in hub', so only 10MBps @ |
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HD, however looking at it, 100MBps-FD shouldn't be a problem. A good |
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tool to look at is mii-tool (emerge mii-diag): |
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|
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root on jonathan [ ~ ] --> mii-tool |
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eth0: negotiated 100baseTx-FD flow-control, link ok |
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root on jonathan [ ~ ] --> mii-tool -v |
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eth0: negotiated 100baseTx-FD flow-control, link ok |
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product info: Intel 82555 rev 4 |
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basic mode: autonegotiation enabled |
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basic status: autonegotiation complete, link ok |
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capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD |
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advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD |
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flow-control |
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link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD |
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flow-control |
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|
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Then you can run: |
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|
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root on jonathan [ ~ ] --> mii-tool -F 100baseTx-FD |
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|
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Which should put the computer into 100MBps via Full Duplex. Give that a |
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go - it should work. If there's a problem putting it into that (and you |
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can run 'mii-tool -r' to re-negotiate), it may be the switch and/or the |
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cable. |
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|
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-- |
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Jonathan Wright ~ mail at djnauk.co.uk |
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~ www.djnauk.co.uk |
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-- |
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2.6.12-gentoo-r6-djnauk-b2 AMD Athlon(tm) XP 2100+ |
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up 11:04, 4 users, load average: 3.06, 5.30, 6.56 |
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-- |
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"People sometimes think I'm gay because I once played a gay in a |
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movie. It's funny. Audiences don't think you're a murderer if |
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you play a murderer, but they do think you're gay if you play a |
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gay." |
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|
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~ Perry King |
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-- |
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