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 Slow Start phase. In this paper, we show that two successive bottlenecks seriously impact the performance of TCP, even during Congestion Avoidance. We derive analytical expressions for maximum window size, throughput and round-trip time of a TCP connection. The fluid-based model we propose allows to locate losses according to nodes parameters. It consequently gives valuable guidelines for the dimensioning of network buffers so as to improve the performance of TCP.