The Transmission Control Protocol (TCP) is the most popular transport layer protocol for the internet. Congestion Control is used to increase the congestion window size if there is additional bandwidthon the network, and decrease the congestion window size when there is congestion. This paper uses a classic TCP which we called Robust TCP with an accurate algorithm of congestion detection in order to improve the performance of TCP. Our TCP Robust only reacts when it receives an ECN (Explicit Congestion Notification) mark. The evaluation result shows a good performance in the terms of drop ratioand throughput.