Extending equation-based congestion control to high-speed long-distance networks: smoothness analysis

TCP-friendly rate control (TFRC), an equation-based congestion control protocol, has been a promising alternative to TCP for streaming multimedia applications. However, TFRC using the TCP response function has the same bandwidth scalability problem as TCP in high-speed long-distance networks. In this paper, we propose high-speed equation-based rate control (HERC) for streaming multimedia transfer over high-speed long-distance networks, as an extension of TFRC by replacing the TCP response function with a high-speed response function. Our result indicates that while HERC achieves better bandwidth scalability than TFRC, it has worse smoothness than TFRC with the same loss history size. We prove that the smoothness index measured by the coefficient of variation of sending rates is approximately equal to 1.09d/√LCoV[θ] where d is the exponent parameter of the response function, L is the loss history size, and CoV[θ] is the coefficient of variation of loss intervals. Furthermore, we show that by setting L to 32d², HERC with any value of d can achieve the same smoothness as TFRC under the same loss interval distribution.