thanks for thinking and writing it down.
I think there are actually a couple of different traffic measurements of interest. traffic volume, traffic elasticity, and traffic usability.
Traffic volume is fairly simple, but also mostly useless. Measure the total traffic exchange through the local exchange point (e.g. peak 2Mbps in St. Louis) and that is a definition of traffic exchanged by the local ISPs that isn't going across transit lines to upstream providers. Harder to measure is how 'local' any of the ISPs actually are. In the st. louis case, all of the ISPs operate in at least two states, and two of them operate in more than two states. None of them, as far as I know, have tried to break up their routing into geographic regions.
Traffic elasticity is an interesting issue. How much traffic is being exchanged, which wouldn't otherwise be exchanged? In other words is the existance of the local exchange point actually causing more traffic to be generated. This is a what if question. If you didn't have the local exchange, would you still haul highly elastic traffic like USENET across your long-haul links? Or is it highly elastic traffic like at-home students or employees who use a local ISP modem pool for access instead of dialing directly into the remote institution.
And finally, usability. The I know it when I see it issue. The right combination of adequate speed, low latency, and little congestion that gives the end-user a 'good' connection. Since we still have a hard time defining what is 'good' this is the hardest one to measure. I can really only measure this indirectly, such as the number of customer compliants or through surveys of non-customers. In general, customers of ISPs connected to the local exchange point report better connections to resources on ISPs also attached to the local exchange point than to those same ISPs before the exchange point. -- Sean Donelan, Data Research Associates, Inc, St. Louis, MO Affiliation given for identification not representation