Analysis on adjustment-based TCP-friendly congestion control: fairness and stability

In this paper, we focus on understanding the binomial congestion control algorithms (Bansal et al., 2001) and can generalize TCP-style additive-increase by increasing inversely proportional to a power k of the current window (for TCP, k=0) and generalize TCP-style multiplicative-decrease by decreasing proportional to a power l of the current window (for TCP, l=1). We discuss their global fairness and stability. We prove that such congestion control algorithms can achieve (p, k+l+1)-proportional fairness globally no matter what the network topology is and how many users there are. We also study their dynamical behavior through a control theoretical approach. The smoothness of the congestion control results in a less stable system and slower convergence to fair bandwidth allocation. The modeling and discussion in this paper are quite general and can be easily applied to equation-based TCP-friendly congestion control schemes, another category of TCP-friendly transport protocols.