Improving efficiency-friendliness tradeoffs of TCP congestion control algorithm

Abstract

It has been recognized that current TCP (mostly TCP-Reno) throughput deteriorates in high-speed networks with large bandwidth-delay-product. A number of protocols, such as high speed TCP and scalable TCP, have been proposed to address this problem. However, their lack of friendliness to existing protocols has hampered their wide deployment in public networks. In this paper, we propose TCP-AR (adaptive Reno) to ensure friendliness to TCP-Reno, as well as efficiency in high-speed networks. A key feature of TCP-AR is that it dynamically adjusts the TCP response function based on congestion level estimation via RTT measurement. Namely, it increases congestion window faster and decreases the window less than TCP-Reno when it recognizes no congestion. As the congestion level increases, it tunes the response function so that it behaves like TCP-Reno. Simulation results show that TCP-AR maintains friendliness to TCP-Reno in networks with varying buffer capacities with or without RED, and flows with varying RTTs, while it achieves much higher throughput than TCP-Reno or even high speed TCP.