To resolve the channel resources waste problem of current source-specific multicast (SSM) routing algorithm in low earth orbit (LEO) satellite IP networks

a new SSM algorithm called core-cluster-based source-specific multicast (CSSM) algorithm and its improved one (the weighted CSSM algorithm) are presented.The CSSM algorithm takes source node as initial core-cluster

and extends it step by step to construct entire multicast tree with the lowest tree cost by a shortest path scheme between newly-generated core-cluster and surplus group member nodes

which can greatly improve transport bandwidth utilization and transport efficiency.In the w-CSSM algorithm

end-to-end propagation delay can be decreased and meanwhile tree cost will be increased a bit by adaptively adjusting the weighted coefficient to meet strict end-to-end delay requirements of some real-time multicast applications.Finally

performance comparison of the two algorithms with the typical SSM algorithm (i.e.MRA) in LEO satellite networks is provided.Simulation results show that their tree cost performance is greatly better than that of MRA at the expense of a bit higher end-to-end propagation delay.