document updated 17 years ago, on Mar 22, 2008

There are lots of design guidelines floating about for UTP signals or other differential signals.

http://pcdandf.com/cms/cms/content/view/4005/95/
USB board layout guidelines
PCI-E board layout guidelines
this says that signal integrity analysis is becoming increasingly important with high-speed interconnects, so.... study this, which has lots of useful infos