Design And Implementation Of Routing Algorithm And Buffer Management Mechanism In Delay Tolerant Networks

With the rapid development of wireless communication technology and applications, there are many challenging communication networks, such as interplanetary network, wildlife monitoring network and war-time communication network. Nodes in those challenging networks typically have mobility, also their bandwidth and energy are usually limited, which results in the frequent link breaks, the dynamic changes of network topology, the high delivery latency, and the increasing error rate.To deal with those problems raised by challenging networks, Kevin Fall and other researchers propose a kind of new network called Delay Tolerant Network(DTN).The basic assumptions of TCP/IP protocol can not be applied to DTN because DTN doesn’t maintain a stable end to end link.Therefore the message routing and buffer management mechanisms in traditional network can not be used in DTN. DTN provides custody transfer services by using permanent storage,and adopts Store-Carry-Forward message exchange technology to ensure reliable delivery of messages.This paper proposes a routing algorithm and a buffer management technique for DTN.The major contributions of this paper are described bellow:(1) To solve the problem of low delivery ratio and high delivery latency in DTN, a new DTN routing algorithm HIBR(History Information Based Routing) based on history information is proposed. HIBR defines the degree of intimacy between nodes by using historical meeting frequency and duration, and then chooses the relay nodes based on the intimacy between nodes. HIBR also defines the degree of activity by using the number of nodes a node encountered in the most recent period, and distributes copies of the message among the relay nodes according to the degree of activity.(2) To deal with the problem of low delivery ratio and high transmission delay resulted from congestion, a buffer management strategy PBBM(Priority Based Buffer Management) based on the priority of messages is proposed.PBBM defines the quality of message and the quality of node, then defines the message priority by considering the quality of message and the quality of current node. High-priority messages are sent preferentially during message forwarding, and low-priority messages are firstly discarded when the node is congested.(3) The superiorities of our algorithms are verified on the Opportunistic Network Environment simulator(ONE) by comparing with existing algorithms.