Chinese Journal of Computers   Full Text
Title	EHSTCP: Enhanced TCP in High-Speed Networks
Authors	LONG Cheng-Nian1) YANG Hui-Long1) LI Xin1) GUAN Xin-Ping2)
Address	1)(Centre for Networking Control and Bioinformatics (CNCB), Institute of Electrical Engineering, Yanshan University, Qinhuangdao, Hebei 066004) 2)(Department of Automation, School of Electronic Information and Electrical Engineering, Shanghai Jiaotong University, Shanghai 200240)
Year	2008
Issue	No.3(440—449)
Abstract &   Background	Abstract TCP doesn’t perform well in high bandwidth-delay product networks, and its main limitations are low throughput and large oscillation of congestion window. HSTCP solves the primary limitations of regular TCP, but there exists large number of packet loss upon congestion epoch and serious RTT unfairness with drop-tail gateway. To overcome the above deficiency, this paper proposes an improved algorithm, called EHSTCP, which switches between two congestion avoidance modes in congestion avoidance phase. To locate the switch point, this paper presents a new prediction method for end-to-end available bandwidth using history congestion window dynamics. Simultaneously, it introduces the RTT fairness factor to eliminate the serious RTT unfairness in HSTCP. NS2 simulation results validate the effectiveness of the proposed scheme. keywords HSTCP; congestion control; TCP; packet loss; RTT unfairness background As computing, communications and storage technology of rapid development, the global grid system has provided the enough capacity and the high speed effective hardware environment for the computation and the scientific research. Development of the new generation network, the challenge is the existing network control algorithm and the resource allocation algorithm can not be extended to the next generation of high-bandwidth communications network. The main evidence is that, in the high-speed network environment, the existing protocol algorithm can not guarantee the required QoS (Quality of Service), for example low packet loss rate, low delay and delay jitter. Due to the inefficient congestion control algorithm which led to the uncooperative users competition and greed occupied bandwidth, it will even leads to instability in the entire network operation, significantly reducing the QoS. In high-bandwidth network environment, HSTCP algorithm solves the major performance deficiencies of standard TCP algorithm. The proposed solution is simple to implement, which has been adopted by the IETF. However, HSTCP adopts non-linear growth pattern in congestion avoidance. There will be a large amount of data packet loss and RTT unfairness when the sudden flow generated at the point of congestion. To resolve these issues, the authors propose an improved HSTCP algorithm in this paper. The basic idea of the proposed algorithm is to choose different congestion avoidance manners under different network congestion statues. In this paper, the authors present a new end-to-end available bandwidth prediction method based on the history values of congestion window. Based on the prediction information, it can achieve a suitable switch point for different congestion avoidance stages. Simultaneously, the authors introduce the RTT fairness factor to eliminate the serious RTT unfairness in HSTCP. NS2 simulation results validate the effectiveness of the proposed scheme. This work was supported in part by the National Science Fund for Distinguished Young Scholars of China under grant No.60525303 and National Natural Science Foundation of China under grant No.60404022.