Non cooperative path characterization using packet spacing techniques

Non cooperative network path measurements assume that there is no cooperation from the other end of a path. Such methods have to cleverly exploit standard protocol options to initiate probing traffic. Performing measurements in this framework for the ´reverse path´ is particularly challenging. We describe the design of iPathmeter2, non cooperative tool to measure capacity and available bandwidth on the reverse path. The probing traffic of iPathmeter2 consists of a chirp of packet-pairs with appropriate spacing. The spacing between the ACKs from the measuring host and the size of the advertised receive window help shape the transmitting pattern from the remote host to the measuring node. Thus, iPathmeter2 adapts the existing cooperative packet spacing techniques for reverse path, non-cooperative measurements. A utilization based estimator for the available bandwidth is also described. iPathmeter2 is validated by performing measurements under controlled conditions. Results from live tests on the Internet are also reported.