Improving Westwood over bandwidth instability

The design of TCP/IP is the key of the success of Internet. Due to the network considered as a "black box", the congestion control algorithm becomes the most important part of TCP. TCP Westwood provides an eligible rate estimation algorithm that improves upon the performance of TCP Reno in wired as well as wireless networks. The improvement is most significant in wireless networks with lossy links. In mobile communication, due to the node mobility, the bandwidth shifting requires higher demands to QoS. In mobile networks with high bandwidth, such as 3G/LTE, the bandwidth will shift rapidly in different positions. We call this bandwidth instability, which is the cause of the degradation of performance. However, Westwood TCP or the other popular TCP cannot response quickly to this situation. In this paper, we verify the problem mentioned above of varied TCP protocols. After that, we propose an improved fast recovery mechanism based on Westwood TCP. The new mechanism can adjust the congestion window in time when the bandwidth shifts.