>This has nothing whatsoever to do with the problems of interference with >USB cables, which carry serial data streams, not packets, and are >subject to external electromagnetic interference.
I think you are mixing logical layer concepts (packets) with physical layer concepts (stream of bits). At the physical level, both Ethernet and USB are performing serial communication: that is, sending streams of bits. Both will be subject to electrical noise. Staying in the physical world, USB cables are surrounded by a metal shield. This is a costly, but very effective means to block electrical noise. Ethernet is not shielded so must rely on more sophisticated techniques. Ethernet signals are sent using a differential circuit (actually, several of them). A differential circuit uses a pair of wires and puts an opposite and equal signal across the pair. It depends on noise putting an equal signal across the pair. So a differential circuit looks only at the difference between each wire of the pair, thus it is able to ignore the noise. I think Ethernet twists per foot has more to do with crosstalk than noise rejection. I will leave that to someone else to look up. ************************************************************************* ** List info, subscription management, list rules, archives, privacy ** ** policy, calmness, a member map, and more at http://www.cguys.org/ ** *************************************************************************
