The Routing And Congestion Control Strategy Concerned On The Encounter Regularity Of Node In DTN

Traditional Internet has obtained great success by using TCP/IP protocol to realize message exchange between different networks. Although heterogeneity between different networks was shielded by TCP/IP protocol, the TCP/IP has many hypotheses for the underlying transport protocol, such as end to end must keep continuous and stable connection.In the limited network, communication environment is extremely bad and there is no stable end-to-end connection between nodes. The performance of TCP/IP protocol will be deteriorated sharply. The traditional routing protocols can’t normally run, either.In order to achieve the interconnection among the limited network, a new covering network architecture was putted forward in 2003, called the DTN (Delay Tolerant Network). It uses storage-carry-forward and regulation transmission mechanism to deal with condition that there is no stable end-to-end connection between nodes. As a result, reliable transmission is realized.DTN nodes forward the message to the destination node by the opportunity connection. The success rate of message delivery is low and the average delay is greater.In order to improve the DTN network performance, DTN often adopts multiple copies routing algorithm based on the quota. But this algorithm has two problems:how to determine the number of copies and how to select the nodes. In the real world, meet of all the network nodes have certain regularity. So to do research on the characteristics of node encounter regularity and to put forward high-efficiency multiple copies routing algorithm have the vital significance.Due to the node storage resources is limited, multiple copies of DTN routing algorithm is easy to cause the occurrence of congestion. In addition, each node needs to cooperate on the submitted message. If a hop can’t reach the destination node, the appropriate relay node’s retransmission can be applied in order to increase the success probability of submitted message. Because message transfer task is excessively heavy, the relay nodes are more likely to be congested. In case that specific routing algorithm can increase congestion control strategy, it’s as far as possible to avoid unreasonable usage of storage resources. It can effectively relieve node’s storage burden and play important significance on routing performance.The first part mainly introduces the concept, the network characteristics, the system structure, practical application of the DTN, and several typical routing algorithms. In the second part, in-depth analysis for binary spray and wait routing algorithm is given and analyzed. The following improvement is put forward:Firstly, due to binary spray and wait routing algorithm in selecting relay node and the number of message copies has certain blindness. This thesis proposes an adaptive spray and wait routing algorithm concerned on the encounter regularity of node. The algorithm let the traditional one-dimensional routing information table expand into a two-dimensional matrix, by comparing the rate of the relay node capacity, dynamically to adjust the message forwarding strategy. It not only considers the possibility of two node meet directly, but also analyzes whether there is a better intermediate node between two nodes and depends on the intermediate node as a bridge to assist transfer message. It can expand the selection scope of routing, solve the problem that current node and destination node encounter probability is low, and increase the success rate of submitted message.Secondly, due to the copies routing algorithm is easy to cause network congestion, but adaptive spray and wait routing algorithm concerned on the encounter regularity of node does not consider whether the congestion of relay nodes responsible for the transfer of message happen or not. In this thesis, a new congestion control strategy is added based on adaptive spray and wait routing algorithm concerned on the encounter regularity of node. Considering the perspective of the receiver of a message, when congestion occurs, the node first discards the message which has the shortest life cycle and is carried to the destination node by relay node whit lowest probability. Instead, this approach can not only control congestion, and free up storage space to receive more new message. The success rate of submitted message is enhanced. It also makes the adaptive spray and wait routing algorithm concerned on the encounter regularity of node have a better performance.Thirdly, the ONE simulator is used to simulate and assess the routing algorithm and congestion control strategy concerned on the encounter regularity of node in DTN. And then the simulation results are analyzed and compared.