A Comparative Evaluation of TCP Congestion Control Schemes over Low-Earth-Orbit (LEO) Satellite Networks

Low-Earth-Orbit (LEO) satellite constellations can provide global Internet connectivity with latency comparable to terrestrial networks, but their fast movement and frequent handovers result in highly dynamic connectivity changes, with an unknown impact on network congestion control design. In this paper we evaluate and compare the performance of four congestion control schemes over LEO satellite networks, especially their behavior in the face of path changes and delay variations caused by satellite movement. Our results show that, while dynamic connectivity leads to performance degradation in all the congestion control schemes we examined, the impact differs for different schemes: the loss-based schemes (NewReno and Cubic) suffer from high queuing delays, the delay-based scheme (Vegas) often achieves low throughput, and BBR can handle connectivity dynamics with moderate performance degradation. Furthermore, if a user terminal can only connect to one satellite at a time, the performance degradation is worse across all the examined schemes.