Abstract: This paper analyzes in theory the factors affecting bandwidth estimation accuracy of TCP Westwood, and presents a method to average the ACK space time to eliminate measure error. By using this method, the bandwidth measurement accuracy can be improved. Further, congestion avoidance of TCP Westwood is divided into two phases according to the bottleneck length, making the sending process stay longer at a high level. Simulation results based on ns2 shows effectiveness of the modified TCP algorithm.

Key words: TCP Yolanda, bandwidth estimation, bit error rate, throughput