Satellite system is regarded as important part of 5G networks. Software Defined Satellite Networking (SDSN), utilizing the advantages of Software Defined Networking (SDN), as believed in former work, can provide better performance. Different SDN architectures based on either multi-layer satellite constellation or sing-layer constellation have been proposed and the key technology has been validated. However, characteristics of satellites such as high propagation delay and coverage characteristics pose some problems on the network performance. In this paper, we analyze the characteristics of satellite networks and propose an onboard controller policy of LEO software defined networking according to these characteristics. We also simulate the network and compare both its propagation delay between switches and controllers and bandwidth with another SDN architecture of single-layer LEO constellation.