  == Dialup ==  The bit about dialup, in the intro, being an overlay on the telephone network seems a bit out of place. It confused me enough to have to reread the intro. If i'm not mistaken, I understand that any physical transmission medium can be overlayed with a communication network, so would it be better to state that and use dialup as example? Or is that example not about the physical telephone network but about the protocols used to implement the telephone network and dialup connection sequences riding on top of those protocols? -Isha