Reproducible measurements of TCP BBR congestion control

Abstract The complexity of evaluating TCP congestion control has increased considerably since its initial development in the 1980s. Several congestion control algorithms following different approaches have been proposed to match the requirements of modern computer networks. We present a framework to analyze different congestion control algorithms using network emulation. The framework is publicly available which provides easy repeatability of our experiments and reproducibility of the results. As a case study, we use our framework to analyze the bottleneck bandwidth and round-trip time (BBR) congestion control algorithm, which was published by Google in 2016. Because of promising initial results, BBR has gained wide-spread attention. As such it has been subject analysis, which showed an increase in performance, but also revealed critical flaws. We verify our framework by reproducing experiments from related work which confirm weaknesses of the current BBR implementation. We also contribute an analysis of BBR’s inter-flow synchronization behavior and its interaction when competing with other congestion control algorithms. Our results show that BBR flows on their own have difficulty to reach a fairness equilibrium and suppress other congestion control algorithms. BBR is still work in progress, thus the framework is useful to validate further updates of BBR by rerunning the given experiments.