ArcNet and the Pursuit of Multiple Topologies

On Oct 13, 13:10, Eric J. Korpela wrote: Yes, I'm afraid you have! 100baseTX uses the same pairs as 10baseT, no more, no less. 4+5 are definitely not used. However, they are used (along with 7+8) for 100baseT4, which uses a different encoding and modulation scheme to permit 100Mb/s operation over lower-grade cable, using all 4 pairs, and similarly 1000baseTX uses all four pairs. Nothing I know of (certainly no standard Ethernet technique) uses three pairs. In 100baseTX full-duplex (and 10baseT full-duplex which is an extension of the older standard, not always supported) the same pairs are used for transmit and receive as in half-duplex. The only difference is that both pairs are allowed to be active at the same time (which would be counted as a collision otherwise). -- Pete Peter Turnbull Network Manager University of York