Jim Ray wrote:
Where "shape" is defined as a square wave on an oscilloscope, sure. Degradation of "shape" or "height" in that respect are all byproducts of attenuation, and as I mentioned earlier a hub will correct for attenuation related problems. What it won't correct for is timing issues. Consider a 100m cable run, operating at 100MBits / second. Remember that both ends have the potential to attempt to talk at the same time, this isn't a frame or token based network where everyone talks in an agreed-upon order. So let's say one end raises the voltage to 5v (I don't recall the actual voltages on Ethernet, these are for example purposes) - the other end won't see that voltage raise due to propagation across the copper for _at_best_ 334 nanoseconds (assuming the speed of light in a vacuum, in practice it's much slower, thus longer). If the voltage ever goes to 10v, it means that two stations tried to talk at once and a collision occurs, and everyone has to try again. The farther / longer that signal has to travel before being received by everyone else on that unswitched segment, then the higher your chances of collisions. As a final note, if you only have two machines on the segment, and they're operating in full duplex mode, this problem is really a moot point - but if that's the case it's highly unlikely that you're also going to have a classic hub involved. :)Do note that a traditional, old school, hub does not "reform" the
packets in the manner that you're attempting to do, to extend an
Ethernet segment. You need to use a switch in that situation.
[JR>] signals propagating in active digital transmission circuits whether hub or switch go through transistors that snap 0's and 1's back into shape.
I'll freely admit that I'm stretching the limits of my knowledge at this point, but if someone with a stronger physics or EE background wants to step in and clarify the velocity (to borrow an RF term) of Cat-V cable, feel free.
Aaron S. Joyner -- TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug TriLUG Organizational FAQ : http://trilug.org/faq/ TriLUG Member Services FAQ : http://members.trilug.org/services_faq/ TriLUG PGP Keyring : http://trilug.org/~chrish/trilug.asc
