University of Wisconsin-Madison
We develop two network tools, Pathrate and Pathload, for measuring the capacity and available bandwidth, respectively, of Internet paths. Pathrate is based on an adaptive variation of the packet-pair approach, in which the capacity of a path is estimated from the dispersion that a burst of packets encounters in the path. Pathrate is adaptive because the length of the bursts, which is the critical parameter in this method, is determined during run-time at the receiver, based on the statistics of the measurements.
Pathload, on the other hand, measures the delay variations and loss rate of a packet stream that randomly "samples" the path's state. The measured delay variations and loss rate are used in a metric which is positively correlated with the available bandwidth in the path. We will use Pathload to examine experimentally the dynamics of the available bandwidth, which is a question of major importance for real-time applications and traffic engineering.