Stability and Transient Performance Analysis of TCP

transfer services in packed-switched networks. TCP (Transmission Control Protocol), a sort of feedback-based congestion control mechanisms, has been widely used in the current Internet. In this thesis, we are devoted to studying a congestion control mechanism of TCP, which controls a congestion level of the network by regulating a window size of a source host according to feedback information obtained from the network. Another version of TCP called TCP Vegas has been proposed and studied in the literature. It can achieve better performance than the current TCP Reno. In previous studies, however, steady-state behavior of a window-based flow control mechanism based on TCP Vegas has been analyzed for a simple network topology. In this thesis, we extend the analysis to a generic network topology where each connection has a different propagation delay and there exists multiple bottleneck links. We first derive equilibrium values of window sizes of TCP connections and the number of packets waiting in a router's buffer. We also derive throughput of each TCP connection in steady state, and investigate the effect of control parameters of TCP Vegas on fairness among TCP connections. We then present several numerical examples, showing how control parameters of TCP Vegas should be configured for achieving both stability and better transient performance