Routing in future space‐terrestrial integrated networks with SATNET‐OSPF

Abstract

Summary Connectivity in satellite networks is governed by the spacecraft nodes' orbital dynamics together with the planet's continuous rotation where ground nodes are located. The resulting time‐dynamic but predictable topology demands the design of specific distributed routing schemes. However, terrestrial Internet routing schemes' maturity, proven scalability, and efficiency shall be leveraged whenever possible to facilitate space‐terrestrial integration while reducing risk and costs. In line with this reflection, we introduce SATNET‐OSPF: a backward‐compatible satellite extension for the widely used Open Shortest Path First routing protocol. The key features of SATNET‐OSPF are (a) accurate routing interface mapping to inter‐satellite links and ground‐to‐satellite links, (b) accelerated link‐up/link‐down event detection adapted to space‐specific wireless technologies, (c) proactive routing and forwarding mechanism to take advantage of predicted link‐down events, and (d) low memory footprint topology model to efficiently propagate the forthcoming space connectivity events via constrained telecommand links. Leveraging existing IPv6 and OSPFv3 open‐source stacks, we implemented SATNET‐OSPF in an actual space router comprising a space‐grade SPARC V8 CPU and a radiation‐hardened FPGA. Furthermore, we present the details of an emulation test bench supporting various configurations with COTS terrestrial OSPF routers that enabled a realistic performance evaluation of the SATNET‐OSPF. Results show that SATNET‐OSPF reduced OSPFv3 routing protocol overhead by up to 31%; shortened the link event detection delay by four orders of magnitude; decreased the routing outage by a factor of 22; and ensured flooding control message generation and forwarding times, as well as routing computing time, satisfy the original requirements (192, 37, and 17 ms, respectively).