There are 45 sites involved.
More are in US, but there are a few others.
The goals of this study from an end-user point of view.
Record each new traceroute path.
Map each IP address to one AS.
What is normal and what is abnormal?
Between NPD sites, there are one or 2 paths available.
See http://compute.merit.edu/stats/npd/npd.html for the detailed reports generated by this project.
There are more flaps during the middle of the day than there are at night. This is probably traffic related. Even so, the number of flaps is still small.
There is some concern that the use of traceroute as a tool for measuring route flapping is problematical.
Enke Chen notes that BGP has some provision to control loops.