A Discussion on Periodic Communication Disruption in LEO Satellite Constellations

There are few IP unreachable areas outside the Internet coverage by terrestrial or wired link. Low Earth Orbit (LEO) satellite constellations may cover such IP unreachable areas. Starlink by SpaceX (Space Exploration Technologies Corp.), which is a major LEO satellite constellation service, is reported to disrupt communication at the fixed timing due to handover periodically. It is, however, still unclear how periodic communication breakdowns occur and how they affect traditional transport protocols such as TCP and UDP. This paper confirms the periodic communication breakdowns of Starlink and evaluates how TCP and UDP are affected. We have confirmed that handover surely occurs at the fixed interval of 15 seconds and the fixed timing of 12, 27, 42, and 57 seconds for each minute due to handover. We then observed that handover times ranged from 139 ms to 384 ms, which is longer than previously reported. In addition, Starlink may buffer or retransmit packets somewhere in its network, and some packet losses may be avoided.