Message prioritization support for space Delay/Disruption Tolerant Networks

Abstract

Due to the constraints of satellite platforms and Inter-Satellite Links (ISL), very limited ISLs can be equipped on the satellites, making the ISLs intermittently available. Meanwhile, the Ground-Satellite Links (GSL) are also intermittent due to the rotation between the constellation and the earth. Intermittent connectivity of both ISLs and GSLs makes the satellite constellation network a typical earth-orbiting space Delay/Disruption Tolerant Network (DTN), where routing solutions specifically designed for DTN have to be adopted. Moreover, traffic in space DTN, such as command and payload data, may have different reliability requirements, thus, message prioritization support should be provided for space DTN. Among the many proposals, Contact Graph Routing (CGR), originally designed by NASA Jet Propulsion Laboratory for deep space, seems particularly appealing. However, the directional epidemic forwarding strategy for critical bundles in CGR may produce high overhead in earth-orbiting space DTN which will deplete the limited network resources. This paper proposes a multipath forwarding (MPF) strategy for critical bundles to provide prioritization support for space DTN. The performances of different critical bundle forwarding strategies were evaluated through OPNET simulations under various network conditions. Simulation results indicate that MPF strategy for critical bundles is more efficient in earth-orbiting space DTN.