Geographic-based Auxiliary Routing Scheme in SDN-based Mega Constellation Networks

Recently, large-scale and mega low earth orbit (LEO) constellations have become the primary development trends in satellite networks.Considering the complex topology and limited processing capabilities of LEO satellites, traditional distributed routing algorithms with significant flooding overhead are not suitable for the era of mega constellations. In this context, centralized routing technology based on Software Defined Network (SDN) architecture has been widely applied. However, centralized routing technology exhibits a slower response to inter-satellite link (ISL) changes due to longer informing path, which induce that longer time is required to restore traffic in the event of ISL terminal or satellite /hardware faults. To this end, this paper proposes a lightweight Geographic-based Auxiliary Routing Scheme (GARS), adapted to Walker Delta constellation, as a traffic fast restoration strategy for SDN-based centralized routing scheme. This scheme has an ultralow computation complexity of O(1),enabling the rapid calculation and establishment of temporary paths to restore service during the SDN controller in ground station rerouting. In addition, an optimized geometric routing algorithm with anti-loop mechanism is proposed to enhance the stability and reliability of geometric routing algorithm. Simulation results show that (1) compared with traditional centralized routing system, the routing scheme proposed in this paper shortens interruption time of traffic by at least 65.5% and reduces mean packet loss ratio by at least 67.2% without increasing link load. (2) Compared to other traditional geometric routing algorithms without advanced anti-loop mechanism, GARS with the optimized anti-loop mechanism also effectively ensures the continuity of service, reducing packet loss rate and interruption time byat most 96%.