Are mobiles ready for BBR?

BBR is a new congestion control algorithm that has seen widespread Internet adoption in recent years with an estimated 40% of Internet traffic volume as BBR traffic. While many studies examine the performance and fairness of BBR on desktops and servers, there is still a question of how BBR would behave on mobile devices. This is especially important because mobiles represent a large segment of Internet devices. In this work, we study the potential performance bottlenecks of BBR if it were to be deployed on Android devices. We compare the performance of BBR and the default congestion control algorithm Cubic for different devices and device configurations. We find that BBR performs poorly compared to Cubic, especially under low-end device configurations. Further investigation reveals that this poor performance is because of packet pacing which is enabled in BBR by default. Pacing increases the computational overhead, which can affect performance for low-end devices. To address this problem, we propose a first cut solution that modifies BBR's pacing behavior to improve performance while still retaining the benefits of packet pacing.