Routing Algorithm With Buffer Management Research Based On Transfer Utility In DTN

At present, the Internet is widely applied in the world, interconnecting tens of millions of communication equipment based on TCP/IP protocol suite. With the development of application scenarios, network technology has been used many extreme environments, for example, Military Network and Planetary Network etc. In these networks, the communication link is often intermittently connected, thereby the traditional end-to-end data transmission way and the existing protocol do not meet them. In 2002, Kevin Fall et al proposed the concept of DTN (Delay Tolerant Networks, DTN), which node is relatively sparse and intermittently connected. DTN uses bundle layer to transmit asynchronous messages. Bundle layer is a new protocol layer, located between the application layer and the transport layer, and it uses the way of store-carry-forward to transfer messages.Delay tolerant network is a kind of network evolving from Interplanetary Network, which can deal with intermittent connection, large delay and high error rate extreme network environments and handle the link instability among nodes caused by sparse distribution, movement and limited resources etc. There are three routing algorithms in DTN, including epidemic routing, spray and wait routing and probabilistic routing. The spray and wait routing protocol will blindly spray a half number of message copies to the relay node, without considering node’s receiving capability. It causes that the nodes can not receive new messages and discard old messages, resulting low delivery ratio and high overhead ratio. Therefore, based on spray and wait routing, the modified routing algorithm with buffer management policy is proposed, which nodes dynamically forward the number of message copies, thereby increasing the packet delivery utility and improving DTN performance.This thesis introduces the network architecture of DTN, the region of DTN and several major routing protocols. It studies spray and wait routing protocol in depth, the following works are completed.Firstly, this thesis uses the principles of Game Theory to conclude the concept of incentive and utility of DTN. Considering the limited buffer space and waiting time for each node are relatively short, and nodes are sparse, the transfer utility of node is proposed. According to node buffer space and the waiting time to calculate the transfer utility of node, the source node (relay node) sprays message copies dynamically based on the transfer utility of node.Secondly, this thesis proposes a spray and wait routing algorithm based on the transfer utility of node and a buffer management policy. By managing the buffer space to reduce redundant node’s message, nodes can store-carry-forward more useful messages. The algorithms not only enhance the delivery rate of messages but also improve the overall performance of network.Thirdly, this thesis uses the ONE to simulate the binary spray and wait routing protocol, the spray and wait routing based on the transfer utility of node, buffer management policy based on the transfer utility of node, and their results were compared.In summary, this thesis proposes a routing algorithm and buffer management policy to enhance the delivery rate of messages and ease the pressure of buffer space in the nodes, which has theory significance and useful value for further research in DTN.