Measurement Caveats

Representativeness of data set
Answer: Paths cross 9 of 11 of "large" ASes.

Could reflect failure on the reverse path
Solution: Correlate with failures from active probes.

Tells us about interfaces, not routers
Maybe even the outgoing interface of the return packet!
Solution: Alias resolution techniques.

Little information about AS boundaries
Solution: Use knowledge about the topology...