Arab J Sci Eng DOI 10.1007/s13369-012-0483-z RESEARCH ARTICLE - COMPUTER ENGINEERING AND COMPUTER SCIENCE QTCP: Improving Throughput Performance Evaluation with High-Speed Networks Barkatullah Qureshi · Mohamed Othman · Shamala Subramaniam · Nor Asila Wati Received: 4 April 2011 / Accepted: 10 January 2012 © King Fahd University of Petroleum and Minerals 2012 Abstract High-speed TCP (HSTCP) is one of the several popular variants of TCP aimed at the optimization of TCP for high-speed networks. Like all other variants, HSTCP also fails to take full shared bandwidth utilization and offers low throughput rate, high packet loss rate and poor fairness. To overcome these problems, a new adaptive congestion control algorithm with high-speed delay product network, named, the Quick Transport Control Protocol (QTCP) has been designed through this research. The basic idea of QTCP has been inspired by the HSTCP and CUBIC, which sup- ported to enhance the algorithm. Three main component of QTCP window control algorithm are α phase, β phase and multiplicative decrease. An experimental setup was designed for the evaluation of QTCP. In this experiment, the QTCP was evaluated based on average throughput and fairness between multiple flows with the same RTT. QTCP performs tuning of the sender side modification based on slow start and AIMD algorithms of HSTCP and CUBIC. QTCP pro- vides higher throughput and enhanced fairness as compared to most of the currently available TCP variants for high-speed networks. The improved throughput and fairness remains intact even in the presence of background traffic. NS-2 B. Qureshi (B ) · M. Othman · S. Subramaniam · N. A. Wati Department of Communication Technology and Network, Faculty of Computer Science and Information Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor D.E., Malaysia e-mail: qureshi5939@gmail.com M. Othman e-mail: mothman@fsktm.upm.edu.my S. Subramaniam e-mail: shamala@fsktm.upm.edu.my N. A. Wati e-mail: asila@fsktm.upm.edu.my simulator-based results with different configurations are pre- sented, discussed in detail, and evaluated with other popular algorithms. Keywords HSTCP · AIMD · Congestion control · Throughput · Fairness 1 Introduction The availability of high-speed networks coupled with high- end computational power has fuelled the development of distributed collaborative applications, which are used by scientists to analyze the large datasets. This development and 123