Research And Design Of Congestion Control Algorithm On DTN

DTN (Delay Tolerant Network) is a emerging network architecture with the feature of high latency, low data rate and connection frequently interrupt. In order to achieve interconnection and interoperability and reliable transmission of asynchronous messages between heterogeneous opportunity networks, DTN provides Bundle and custody transfer and store-and-forward mechanism. DTN has broad application prospects like deep space network, sensor networks, military Ad hoc networks, vehicles Ad hoc networks, global mobile networks, underwater acoustic modulation communication, and so on. DTN differs from the traditional network to a large extent, therefore the traditional mature routing algorithm and congestion control policy can not be directly applied to DTN. DTN routing and congestion control algorithm become a promising research field which many scholars are driven to address.This paper focuses on the delay tolerant network congestion study, and the emphasis is to solve the problem congestion avoidance and congestion control. For these two types of questions, this paper raises some congestion strategy, and summarized as follows:(1) In terms of congestion avoidance, the main idea is utilizing single copy strategy for routing so as to reduce the risk of congestion caused by limited storage space due to the multiple copies for congestion avoidance policy. When choosing next hop, we use probabilistic routing to maximize the expectations ensuring the messages reach the destination node. We suggest the entire network be divided equally into a plurality of regions, calculate the probability of each node occurring in each region, and maintain a probability matrix, according to which nodes select the best hop node. Since every time, the maximum probability is the basis during hop choosing for reaching the destination node, then the success rate of message transmission is increased. The experimental results show that congestion avoidance algorithm based on area partition can effectively to avoid the routing path that may cause congestion and increase the transmission success rate by the assist of probability matrix.(2) when congestion occurs, the main idea is releasing the message package within the congestion node storage space in order to avoid the phenomenon, where congestion deepens resulted by congestion node refuses to accept the new message because of the lack of free storage space. Introduced the AMED routing algorithm for congestion control, this algorithm calculates the routing path when congestion occurs, then the congestion node through dump the stored message to neighboring nodes so that it will no longer refuse receiving new messages because storage capacity overflow, thus largely relieve the congestion degree. The experimental results show that congestion control algorithm based on distributed storage can not only effectively alleviate the congestion occurs but also balanced the consumption of the whole network storage to extend the lifetime of it.