Research Of Data Reliable Delivery Based On Custody Transfer Mechanism In Space Networks

With the development of China space technologies and spatial applications, especially the established goal of constructing the space laboratory and Space Station, the spatial duty presents a series of characters:diversity, protracted and complexity etc. From the perspectives of networks,Space Information Network has the features of network topology changes greatly with laws,far distance and long delay between nodes,link short-time interrupt but restores frequently. The space data how to carry on the reliable delivery under such network environment, directly influences the validity of space information network.Firstly, this paper analyzes the requirements of space network and its development in the world. By studying the structure of the space information network, this paper summarizes the features of the network from the view of networking. Then, by combining the related researches of DTN network and the characteristics of the space communications, the paper analyses several representative transport protocols for space communications network. According to comparison, the paper draw the conclusion that the DTN network protocol and custody transfer mechanism is suitable for using in the space information networks to solve the problem of the reliable delivery of space data.Then, this paper proposes a"Storage Routing Based On Heterogeneous Filtrations Schem(eSR-HFS)algorithm".The algorithm can adapt to the characteristics of the space networks that the storage resources of one node is very limited. By integrating filter control mechanism and buffer management strategies, the SR-HFS separate the storage management of nodes from the routing problem. Through the operations of " Heterogeneous Filtrations", " Ring Search" of "Push" and "Content Retrieval" of the "Pull", the algorithm extends the local memory storage of one node and integrates the network resource effectively. Thus, the SR-HFS can achieve the optimal allocation of node buffer and improve the reliability of data transmission in the space network.Finall,by modifying the ONE (Opportunistic Networking Environment) simulator, this paper establishes simulation scenarios based on the characteristics of the space network and involved communication node. The simulation scenarios combine six typical routing algorithms of DTN, such as Direct Delivery, First Contact, Spray-and-Wait, PRoPHET, Max-Prop and Epidemic. By selecting the Epidemic protocol which has higher possibility to facing the exhaustibility of network resource, this paper validates the performance of the SR-HFS algorithm by changing the parameters of simulation time, TTL, message size, rate of the message generated and so on. The simulation results show that under the same condition, the rate of message transmitted can be increased by about 10% after adding the SR-HFS algorithm, and the rate of packet loss and the ratio of network overhead can be reduced by about 50%. Also, the inceasing of the network average delay is acceptable, which is increased by less than 1%. Based on the simulation results,this paper draws the conclusion that the SR-HFS algorithm is suitable to solve the challenge of transmitting message reliabley in the space network with high latency and continual interruption.