TETHER: Transparent Handoff for Elastic Transport in Hybrid Earth-Space Routing

Abstract

While compute and application state for networked services are typically hosted on terrestrial servers, a specific subset of workloads such as multi-party interactive applications can benefit from in-orbit compute, particularly in regions with sparse terrestrial network infrastructure. Hosting stateful services on LEO satellites, however, introduces a fundamental challenge: the satellite serving a user changes every few minutes due to orbital motion, threatening to disrupt users' active connection sessions. This paper presents TETHER, a network abstraction that preserves application-visible connectivity despite continual satellite movement. TETHER combines persistent virtual IPs, anticipatory state migration, and transport continuity mechanisms to transparently relocate application state between satellites before performance degradation occurs. The system leverages Linux Checkpoint/Restore In Userspace (CRIU) for process migration and exploits predictable orbital trajectories to proactively schedule migrations. We explore two migration policies with different trade-offs between latency and overhead. directly-above migrates application state to the satellite closest to the user, minimizing latency at the cost of more frequent migrations. In contrast, edge-of-reachability migrates state to a satellite that can stay under an acceptable latency budget the longest, reducing migration frequency while tolerating higher latency. We evaluate both policies using the xeoverse LEO network emulator. Our results show that anticipatory migration preserves long-lived TCP sessions across satellite transitions and enables applications to trade latency tolerance against migration overhead.