Research Of DTN Congestion Avoidance Algorithms Based On Concurrent Data Forwarding

In recent years, delay tolerant network(DTN) has become a hot research issue. There are numerous differences between DTN and traditional networks. For example, DTN is usually faced with long interruptions of forwarding(such as interplanetary network communication)or high delay caused by intermittent connection. In addition, DTN cannot ensure the end-to-end connections for a long time between a source node and a destination node compared with the traditional networks. The energy and buffer resources that the nodes in the network have are limited because the nodes are on the move. These obvious characteristics of network have brought a lot of challenges when some core functions were designed, such as routing mechanism, congestion control mechanism and so on. Therefore, how .to design efficient DTN congestion algorithm has become one of the key issues.Based on the research and analysis of the existing congestion algorithms, three congestion avoidance algorithms are proposed in this paper. These three algorithms can effectively avoid the congestion of in DTN from different views. In this paper, the main work is as follows:Firstly, a congestion avoidance algorithm based on concurrent data forwarding controlled by token is proposed. The algorithm assigns a token to the nodes in each packet by grouping the nodes in the network periodically and schedules tokens in packets through time slice cycling scheduling so that nodes between packets can realize concurrent data forwarding. And the algorithm divides the priorities of nodes in the network so that the high-priority nodes have longer time for the message forwarding. The algorithm can effectively avoid congestion in the network.Secondly, aiming at the probability routing algorithm,a congestion avoidance algorithm with a few copies for probability routing is proposed. On the basis of probability routing, the algorithm sets the priorities of the packet messages firstly. Then, the algorithm confirms the threshold of the number of message copies which a single message can generate in the network according to different priorities between messages. Finally, the algorithm limits the total number of messages in the network by limiting the number of copies of each message.The algorithm not only avoids the congestion, but also considers the delivery rate of the packets in the network.At last, comprehensive the congestion avoidance algorithm based on concurrent data forwarding controlled by token and congestion avoidance algorithm with a few copies for probability routing, a congestion avoidance algorithm with data forwarding based for probability routing is proposed. On the basis of probability routing, the algorithm reduces the total amount of messages in the network by reducing the number of message copies that a single message can generate in the network. The algorithm groups the nodes in the network periodically and assigns tokens to the nodes in the network by allocating tokens dynamically and periodically. The algorithm schedules token in packets through time slice cycling scheduling so that nodes between packets can realize concurrent data forwarding. And the algorithm divides the priorities of nodes in packets of network so that the high-priority nodes have longer time for the message forwarding. The algorithm can effectively avoid congestion in the network.