| Walt Mankowski on 31 Aug 2006 20:54:03 -0000 |
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On Thu, Aug 31, 2006 at 04:25:11PM -0400, gyoza@comcast.net wrote: > Actually, a link that someone posted said 90 meters/295 feet. Here it > is again: http://en.wikipedia.org/wiki/Cat5e > > In any case, patch cables are usually short, but, in reality, I don't > think it matters that much. The guidelines are safe numbers for maximum > performance. It's not a matter of performance, it's a matter of being able to detect collisions on the line. Ethernet does collision detection by sending a packet out on the line and then listening if anyone else on the line is also trying to send something. If they are, they each wait a random amount of time and try again. The amount of time it waits is dependent on knowing what the maximum cable length is, because it needs to wait for the packet to reach the end of the cable. If it waits that amount of time without hearing anything, then the entire cable must have been clear when it sent it. If you try to use a cable longer than the maximum length, then you risk throwing off the timing of the protocol. Walt Attachment:
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