Gord', You said:
"... But what if the big four no longer see the need to upgrade their bandwidth INTO and OUT OF exchange points? what happens to the "secondary ten" when they get some large customers who see their packects die between Sprints mae east router and the nearest sprint backbone POP if that pipe is over crowded. "
The argument can be made, and there might be empirical data to back it up, that the private interconnects actually offload *at least in the short term* the participants' pipes into the public exchange points. For example, if a significant fraction (1/4th to 1/3rd) of the S and M and ... traffic into a public exchange is S and M and ... talking among each other, then offloading much of it at some other place might reduce the fractions (maybe to 1/10th to 1/5th). Of course, if their business models do not include eventual upgrading of their pipes into public exchanges, they will have to balance the reduced <performance|reachability> to the Internet at large as seen by their customers against any savings from not upgrading. (Disclaimer: I pulled the numbers out of thin air, so anybody who quotes them is as foolish as I for having put numbers in writing in the first place.) --Steve