Time-efficient transient loops avoiding in snapshot routing algorithm

Snapshot routing algorithm is widely applied in satellite networks to reduce the impact caused by the dynamic varying topology. When the satellite network topology changes, the snapshot routing table in each satellite switches to the predefined new one automatically. Originally, snapshot routing tables switch synchronously in all satellites, and a major part of the network routing paths change in a flash. As a result, a lot of rollback traffic caused by the routing path changes produces many transient routing loops. In this paper, we analyzed the cause of the transient routing loops in satellite networks, such as predictable and unpredictable network topology changes. Based on the ordering update method and time-based update method, we proposed the group partitioning synchronous (GPS) update method for the predictable topology changes and the source routing based multicast (SRM) update method for the unpredictable changes. Results show that our methods can efficiently avoid the transient routing loops in satellite networks with acceptable convergence time, reduced transmission hops and lower network overhead.