2006 Reports

LinkWidth: A Method to measure Link Capacity and Available Bandwidth Using Single-End Probes

Chakravarty, Sambuddho; Stavrou, Angelos; Keromytis, Angelos D.

We introduce LinkWidth, a method for estimating capacity and available bandwidth using single-end controlled TCP packet probes. To estimate capacity, we generate a train of TCP RST packets "sandwiched" between two TCP SYN packets. Capacity is obtained by end-to-end packet dispersion of the received TCP RST/ACK packets corresponding to the TCP SYN packets. Our technique is significantly different from the rest of the packet-pair-based measurement techniques, such as CapProbe, pathchar and pathrate, because the long packet trains minimize errors due to bursty cross-traffic. TCP RST packets do not generate additional ICMP replies preventing cross-traffic interference with our probes. In addition, we use TCP packets for all our probes to prevent some types of QoS-related traffic shaping from affecting our measurements. We extend the Train of Packet Pairs technique to approximate the available link capacity. We use pairs of TCP packets with variable intra-pair delays and sizes. This is the first attempt to implement this technique using single-end TCP probes, tested on a wide range of real networks with variable cross-traffic. We compare our prototype with pathchirp and pathload, which require control of both ends, and demonstrate that in most cases our method gives approximately the same results.