TCP-friendly congestion control to guarantee smoothness by Slack Term

With the rapid advance of network technologies over the past decade, more and more real-time multimedia applications, such as telephony and video conference, are widely deployed in the Internet. These multimedia applications are commonly implemented using UDP because some characteristics of TCP, for example, the burst transmission and frequent window variation, are not suitable for them. However, since UDP does not employ any congestion control, the unfair treatment towards TCP occurs. For these reasons, a new concept, “TCP-friendliness” is advocated. A TCP-friendly flow will share bandwidth similar to competing TCP flows. In this paper, we present a new TCP-friendly congestion control, Slack Term, by patching TCP-Friendly Rate Control (TFRC) and TCP Emulation At Receivers (TEAR). Slack Term limits the variation of sending rate to guarantee the smoothness, records the deficit/excess of bandwidth, and then compensates/returns it in the future to assure the friendliness. Simulation results show that our algorithm can enhance TFRC and TEAR with the smoother transmission rate and achieve the similar TCP-friendliness.