Performance of TCP in a wide-area network: influence of successive bottlenecks and exogenous traffic

Many works have studied the performance of TCP by modeling the network as a single bottleneck node. It has been proved that, in addition to the main bottleneck, upstream nodes can affect the behavior of the protocol, especially during the slow start phase. We show that two successive bottlenecks seriously impact the performance of TCP, even during congestion avoidance. We derive analytical expressions for the maximum window size, throughput and round-trip time of a TCP connection. The fluid-based model we propose allows one to locate losses according to the nodes parameters. It consequently gives valuable guidelines for the dimensioning of network buffers so as to improve the performance of TCP.