Loss Synchronization of TCP Connections at a Shared Bottleneck Link

In this project, we study the degree of loss synchronization between TCP connections sharing a bottleneck network link, i.e., the fraction of the connections that lose a packet during a congestion instance. Loss synchronization determines the variability of the total TCP load on the link and therefore affects the loss, delay, and throughput characteristics of network applications. We conduct our investigation in the Open Network Laboratory (ONL) [Turner et al., 2005], a network testbed maintained by the Applied Research Laboratory at Washington University in St. Louis. To measure loss synchronization, we develop an ONL plugin that collects packet-level statistics (arrival time, size, flow affiliation, sequence number) at a router and communicates the recorded data to an end host for generating a log file. The statistics plugin and log-generating software can also be used in other ONL studies that require knowledge of packet-level dynamics at routers. Control parameters in our investigation of loss synchronization include the types and intensity of traffic, network topology, link capacities, propagation delays, and router buffer sizes. We report the loss rates, queue sizes, degree of TCP fairness, and link utilizations observed in our experiments.