[off topic] Bomb Threat.

You are quite correct, but let me expand on it. Most customers do get only one circuit to a backbone, and yes the things go down. T1 or T3, or whatever you have, 99.9 percent of the time it goes thru _one_ CSU and/or _one_ router. If the CSU dies or the router starts flapping, the customer gets very upset. It is possible to have a customer home multiple circuits into multiple routers (it is a bit difficult, and not terribly efficient), but it just ain't done that way. The problem lies within the confines of the POPs. On a greater scale, just as the ARPA people envisioned, the backbones are very bulletproof. If a circuit goes down between two POPs (largish ones, anyway), there will always be another circuit to take the load. Sure, it may go thru an extra transit router or two, and may saturate them, but the net will still be up. Thank goodness that most of the equipment deployed to make the Internet is built like tanks. William Donzelli william(a)ans.net