BAR : BBR with Adjusting RTprop for Inter-Protocol Fairness with CUBIC TCP

BBR has been proposed as a new congestion control algorithm avoiding bufferbloat and is one of the widely used one along with CUBIC in the current Internet. In this paper, we evaluate preliminary performance of BBR when it shares the bottleneck link with CUBIC. Evaluation results reveal that one of the reasons for unfairness between BBR and CUBIC is misestimation of BBR control parameter RTprop. We also reveal that by increase/decrease of RTprop, we can control delivery rate of BBR. Based on these insights, we propose a new BBR algorithm, BAR(BBR with Adjusting RTprop). BAR adjusts RTprop so that BBR obtains fair bandwidth with CUBIC. Our performance evaluation results show that inter-protocol fairness between BBR and CUBIC flows can be significantly improved by BAR with few packet losses.