Research On Time - Based Routing Algorithm And Congestion Control Strategy In DTN

With the rapid development of computer and communication technology, lots of communication equipments have to configure the mobile ability in order to meet the needs of the job, such as star network, wireless sensor network, wild animal tracking network, military networks, etc. Based on this requirement, Kevin and other scientists proposed a network named "the DTN (Delay/Disruption Tolerant Network)" in international conference of SIGCOMM2002. DTN is a frequently changed topology of network and has intermittent connectivity, but most of network architectures and protocols cannot work well to conquer these challenges for now. On routing algorithms of DTN network, multi-copy routing has higher packet delivery ratio than single-copy routing. To some extent, these routing protocols can satisfy the delivery of messages, however, these protocols cannot either improve message delivery ratio or lower reduce the network delay and overhead at the same time. Moreover, it cannot work well in reducing network congestion. Therefore, a reliable and effective multi-copy routing algorithm is of paramount importance. Multi-copy routing can cause node cache congestion and excessive consumption of network resources. Effective congestion control strategy can treat the node cache and messages distribution to make the multi-copy routing having great performance when the network state is not good. Therefore, incorporating congestion control mechanism into multi-copy routing is crucial to DTN.Based on the current research work on routing protocol and congestion control strategies, this thesis propose a routing algorithm based on time factor, and then add congestion control strategy on this algorithm. The contents and innovations can be summarized as follows.1. This thesis takes the influence of time factor into account on the forwarding probability, improving the forwarding probability of traditional probabilistic routing algorithm. This thesis proposes a routing algorithm based on time factor called TFRA algorithm for short. This algorithm defines the time parameters by analyzing the way of the connection mode among nodes to obtain the forwarding probability. In packet forwarding process, according to the improvement of the forwarding probability, the next hop node is chosen, and packets forwarding number is dynamically distributed. It solves the problem of the relay node selection blindness in the "Spray and Wait" routing algorithm.2. This paper analyses the shortcomings of the existing congestion control, and the congestion control strategy based on time factor routing algorithm is proposed by analysis the time factor routing algorithm. The strategy analyzes the effect of node disconnects duration on network congestion and measures the reserving value of message by defining it retention rate. The algorithm increases congestion control strategy that can reduce the redundant packet forwarding, so as to improve the network delivery rate, reduce the delay and overhead.3. The experimental simulation uses "The ONE" emulator to simulate for the proposed time-based routing algorithm and congestion strategy. Analysis and extensive simulation results show that the proposed algorithm in this thesis has better performance compared with traditional algorithms.