Technical analysis and engineering reference.
Traditional IP routing protocols like OSPF and IS-IS assume static physical topology where links rarely change. In Low Earth Orbit (LEO), satellites travel at 7.6 km/s, causing inter-plane optical link geometry, Doppler shifts, and line-of-sight angles to change continuously. Running link-state flood updates across thousands of orbital nodes consumes excessive bandwidth and triggers routing oscillations.
Unlike vehicular mobile ad-hoc networks (MANETs) on the ground, satellite trajectories are mathematically predictable weeks in advance: - Contact Graph Routing (CGR) precomputes dynamic link contact start times, durations, and available data rates based on orbit propagators. - Packets are queued along Dijkstra shortest paths evaluated in the time-expanded graph domain. - Eliminating link-state advertisement broadcast storms entirely.
When ground gateways experience localized precipitation fading or congestion, spaceborne routers dynamically recalculate laser link pathweights, diverting packet bursts across polar crosslinks to dry ground stations on adjacent continents.