Influence of parameters variation of TCP-Vegas in performance of congestion window over large bandwidth-delay networks

Major challenge for TCP is to keep up the new and modern generation in communications networks such as networks with large bandwidth and long delay because when TCP applies on next generation networks will suffer from degradation in performance. The reason behind this shortcoming in performance is due to the congestion control mechanisms supported by TCP variants where these mechanisms depending on linear or exponential growth to increasing the transmission window. In TCP-Vegas, in spite of the performance degrades if applied in large bandwidth-large delay networks, but it can give acceptable performance when TCP receiver support delayed acknowledgment (ACK). Vegas congestion control algorithm developed in different manner and not support the same techniques used in other TCP source variants, because it minimizes the delay in connection queue and also provides a far less in loss of packets where that increase the throughput of network. This article presents results from a series of simulation experiments designed to study TCP Vegas performance in large bandwidth and large delay network model using NS-2 network simulator. The analysis and observation of Vegas behavior performed using the main two parameters, alpha and beta, to configure the congestion window (cwnd) phases. After used multiple values, the behavior of cwnd of TCP Vegas is very sensitive to the variation of the parameters values and then we got a wide variety results corresponding to parameters variation.