Intelligent Gateway TCP Westwood Algorithm Implement And Improved Research In The Heterogeneous Networks

TCP/IP protocol group is the foundation of Internet, its congestion control mechanism ensures the stability and reliability of data transmission through the Internet high-levels. The wireless network has many characteristics, as high BER, often changes of bandwidth, long delay and etc. The traditional TCP protocol is not adapted to poorer link quality environment of the wireless network. If we also use TCP protocol in the wireless network, when packet is lost by link errors, TCP protocol will start congestion control, halve the sending windows, reduce the throughput and increase the system delay, at last, it will reduce the bandwidth utilization of network. Therefore, it is an important task that how to improve the transmission control protocol effectively in the heterogeneous network.Based on the TCP protocol and the intelligent gateway model, we analysis the problems of traditional TCP protocol in wireless network. In this article, we propose a model of intelligent gateway which has the function of boundary accessing control between such heterogeneous network, and add the TCP Westwood algorithms into the intelligent gateway model, the theoretical model is composed of wire network,intelligent gateway and wireless network. TCP Westwood algorithm which uses the congestion control mechanism of AIAD(Additive Increase Adaptive Decrease), it is more suitable for the wireless network environment. The intelligent gateway model with the TCP Westwood algorithm strengthens the access control function of boundary, improves the flow control and congestion control algorithm. With the improvement of the network bandwidth estimation accuracy, the sending windows and sending rate are optimized. The new model improves transmission performance of the wireless network. At last, we do some simulation experiments in the NS2 environment.The result shows that the effective throughput and utilization of bandwidth are improved obviously in the heterogeneous network. The scheme which takes a part of instructing and promoting function in applying the intelligent gateway from the theoretic research to the practical network environment.