On Estimating the Bandwidth Share of TCP Connections in Presence of Reverse Traffic

To improve the performance of TCP under different network scenarios, the idea of adjusting congestion window according to the bandwidth share estimation has been widely used. Various estimators are proposed in the literature. Some estimate the acquired bandwidth share, and some estimate the volume of traffic or packets queued in the buffers along the end-to-end path. We evaluate these estimation techniques with a common and effective performance metric, the number of DATA packets queued in the buffers and notice that because most estimators do not distinguish explicitly between the queuing delay on the forward path and that on the reverse path, in presence of large volumes of traffic on the reverse path these estimators become fragile. To address this problem, we propose a one-way queuing delay estimation scheme which only requires simple modifications to current TCP implementation (through a TCP option). With this estimation scheme, a one-way packet in queue estimator (OPQE) is proposed to provide a more robust and accurate estimation of the number of DATA packets queued along the forward path of a TCP connection. Simulation results show that OPQE has a good performance under different scenarios, even in the presence of reverse traffic.