From what I understand often the difference between the de jure path and
I just wanted to take a moment to thank everyone for helping me out with this. I've a much better handle on the nature of the problem and likely issues associated with it. the de facto path are due to a combination of: 1) Interfaces belonging to one AS that sit in a router belonging to another AS. 2) A router not announcing an AS that sits behind it. 3) Adminitsrative issues (eg, purely human failures to keep the ASes updated properly). 4) Network topology (peer to peer links between ASes and such). 5) Hand of fate. All in all I've come to the conclusion that my initial assumption (which is that the BGP tables provide a relatively accurate macroscopic map of network topology) is correct. I'll probably need to exapnd on this more if I ever write a paper on my work but I'm still not sure I'm doing anything really useful yet. Chris Rapier PSC/NCNE/NLANR