Research On Spray And Wait Routing Algorithm Based On Historic Throughput Ratio Of Nodes In DTN

The Internet has achieved great success in interconnecting a large number of communication devices of the global heterogeneous network in today’s society, and its achievements are based on TCP/IP protocol suite. But the different networks are appearing with the development of network and computer technology, featuring high latency, high error rate, being intermittently connected and resource-constrained, etc. They are different from the traditional network, there is no complete path between the source nodes and the destination nodes, which was named the challenged network (For example:military wireless ad hoc networks, interplanetary network and wireless sensor networks etc). In order to solve the difficult interconnection problem between these networks, Fall proposed a message-oriented overlay architecture in conference of ICIR, it is called Delay Tolerant Network (DTN). DTN consists of a number of heterogeneous area networks. In order to complete communications and interoperability between different network regions, a new protocol layer is added between application layer and the transport layer of the traditional network, called "bundle layer". DTN is different from the traditional network, so the traditional network’s way of forwarding messages through wire links don’t apply to the DTN network. Therefore, the DTN network use the way of "storage - carry - forward" to forward messages.DTN’s research focuses on the aspects of the routing protocols, transport protocols and security. Due to nodes relative dispersion, active variable node and limited resources in DTN, to design efficient DTN routing is still a huge challenge. The purpose of routing is to improve the success rate of forwarding packet to destination node and reduce latency. The design of DTN’s routing needs to be based upon the characteristics of DTN network to find an optimal path. The path is not only to improve the success rate of forwarding packet to destination node and reduce latency, but also can adapt to the dynamic topology changes of the DTN network.In this thesis, we first described the research background of DTN and research status both in China and abroad, then, we introduce the characteristics of DTN network and the architecture of DTN etc. In the third chapter, single-copy and multi-copy routing protocols are introduced in DTN network. Aimed at two kinds of routing algorithms, in this chapter some classical routing algorithms are listed. Also, the working process of the algorithms is made a detailed presentation and analyzes the advantages and disadvantages of each route.In order to overcome the disadvantages of Spray and Wait Routing Algorithm, we put forward a kind of algorithm in the fourth chapter, which is called spray and wait routing algorithm based on historic throughput ratio of nodes in DTN network (HTR-SW). Due to the influence of the node itself and limited resources in the real environment, the performance of nodes shows great differences in Delay Tolerant Network. In order to estimate the performance of nodes in a more effective way, this chapter put forwarded the concept of historic throughput ratio of nodes (HTR). Using HTR as a foundation, we proposed the spray and wait Routing algorithm based on the historic throughput ratio of nodes in DTN Network. The algorithm uses the ratio of HTR to assign the number of message copies to the encounter nodes dynamically and to select the right length of messages sprayed to the encounter nodes. It not only solves the problem of being random and blind when using the Binary Spray and Wait (BSW) routing to spray the number of message copies, but also assigns the right length of messages according to the performance of the encounter nodes. Finally, the algorithm of HTR-SW is simulated by The ONE simulation platform, The results show that compared with the BSW algorithm, HTR-SW algorithm can enhance the message delivery rate, reduce the average latency and network overhead. At the same time, it can also reduce the number of messages forwarded by relay-nodes in the DTN network significantly.