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Is cable length relevent?

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.. wrote:
> I've had occasion to go beyond 300' a time or two and saw speed drop
> but no appreciable loss or degredation of data. If you want to insure

Right, the 300 is more or less a guideline.

> >I'd read about someone else doing it, so thought I would too. Crimped on
> >a RJ45 at each end of a 1,000 foot spool of cat5 and tried to network.
> >Worked fine, probably was limited to 10Mbs, that was still faster than
> >the internet connection I was testing it on. But that 300' or 100 meter
> >limit is mostly theoretical, not a brick wall.


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.. wrote:
> I've had occasion to go beyond 300' a time or two and saw speed drop
> but no appreciable loss or degredation of data. If you want to insure
> that speed and data remain constant then make your run about 200 to
> 250 feet into a switch, then come from that switch into your device,
> or into another switch then out again if you need to go longer yet.
> The switches don't need to be expensive rigs either. Most any 5-porter
> (e.g. Linksys, D-link, etc.) that you can get for around $20.00 will
> do the trick.

300' is approximately the maximum length where any packet will fill the
entire cable. This is not very important when you have a single
connection through the cable. In that case signal attenuation and
degradation is more important, and higher speeds are more sensitive to
those effects, hence the speed drop. Switches may clean up and amplify
the signal, so using them as repeaters may prove effective.

When multiple connections request use of the cable, the "collision
detection" part of the ethernet link layer protocol (CSMA/CD) is
important. If the cable is too long, some collisions may not be
detected, and packets are sent simultaneously through the same cable
segment. This is an undetected collision, which leads to packet errors,
often not discovered immediately. Late discovery leads to late
retransmission, which amplifies packet buildup and network saturation.

With some luck the network may still work with multiple nodes on both
ends of the long stretch, but any load inrease will probably have a huge
impact on network performance.
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