Utility Based Routing Mechanism In DTNs

DTN(Delay Tolerant Network)is developed in recent years an emerging network technology. Mainly used in large delays, long waiting times. intermittent connectivity and other extreme environments of network communications. The ability to adapt to extreme communications environment, with the emergence of delay tolerant networks, it will be favored, in the military, transportation, marine monitoring, wildlife tracking, satellite communications and other aspects have been applied, and it become a national research focus. delay tolerant network robustness has led to routing algorithm complexity and diversity. In recent years, scholars have for different applications, developed different algorithms and protocols. Its research focus includes three aspects: routing, node mobility model and DTN-based data distribution and retrieval. This thesis concentrates on the routing mechanism.As DTN particularity, DTN existing uncertainty, such as the structural characteristics of dynamic topology, the queue cache, node lifetime, duration of connection. etc., so routing is DTN technology has been difficult and hot spots.Specificity for the DTN environment, many routing protocols have been proposed, which have more impact Epidemic. Spray and Wait, Prophet, etc. These routing protocols may be divided into single-copy and multi-copy algorithm, the single-copy program, there is only one node can relay the message. for example, the copy of the message is forwarded based on a utility function when encounter any othr node; in a multi-copy program, allowed or not allowed to copy the message several times spread out. In the encounter case, the mutual exchange of data between nodes. When the copy message is limited, we must adopt a change in approach to distribution. including only the source node can distribute message to the other nodes and relay nodes can distribute message to another encounter before arrive to the destination.In Epidemic mechanism, the Bundle number can not be controlled in the network, bound to the network overhead become lager. Spray and Wait mechanism control the number of bundle is L at source side, but did not give how the values were L. Prophet mechanism is by a mixture of Epidemic routing and utility-based routing mechanism. where the utility is a probability value, which be calculated based on historical information meet. but this protocal control the number of the bundle in the network does not have the convergence. As long as meet the P value of encounter bigger than itself, the node would deliver message to encounter. The mechanism is essentially a controlled flooding, and control the granularity is coarse. There is also a message can not deliver, for example, if the source end node to the destination node is the probability of 0.9, it may not exist a relay node, which the probability is glarger than 0.9, in this case, the mechanism degradation to deliver directly, or even impossible to deliver.In this paper, we first analyze and summarize the concepts of DTN. its architecture, and a variety of common routing algorithms, then, in response to these problems, we propose the following programs:1. A hybrid forwarding strategy, redundancy and utility based mixed--alterable utility-based DTN routing mechanism. It has two parameters, one is the number of the message has been delivered. And the oter is P value between encounter node and destination. With two parameters to decide how to forward. It has the following characteristics:it overcome the single-copy has low deliver rate; it overcome flooding has a high network overhead; it overcome the PROPHET routing protocol packets in the network may be an infinite number, which greatly reduces the possibility of degradation for the direct deliver.2. Another hybrid forwarding strategy, redundancy and utility based mixed--Increasing utility-based DTN routing mechanism. According PROPHET improvement:each message associated with a utility value, each node also has a utility value to the other nodes, using the two utility value to decide whether the message forwarding to encounter node. Since reducing the number delivered, but each time were delivered to a large utility value node, thereby enhancing the delivery ratio, reduce the delay.