Research On Buffer Management Of Terminal Node In Delay Tolerant Networks

Delay tolerant networking (DTN) is an approach to computer network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. In DTN, terminal nodes relay messages using ’store-carry-forwards’ mode. In order to improve the success rate of message forwarding, multiple copies of the same message will be spread in the network at the same time. The copies of the message will quickly consume buffer space of the nodes. The message stored for a long time and multiple copies in the network will inevitably lead to fierce competition of the storage space, network bandwidth and other resources. In the current study, there is no qualitative analysis of the buffer size, the study of the buffer allocation strategy is ongoing, and how to determine the life-cycle of the data has not been discussed. So the study that how to make a theoretical analysis of buffer size and then design a appropriate buffer management is of great importance. The result is to enhance the overall performance in DTN networks while having low delay and high resource utilization.This paper is mainly on the scenario of the hand-held Delay Tolerant Networks organized by a large number of mobile devices such as ad hoc terminal nodes. And the paper studies the process of data storage, carrying and forwarding in the network that is expensive or not convenient while people need provide data sharing services. We start with the capacity theoretical derivation of the terminal node, and setting the lifetime of the data, as well as the replacement algorithm between the adjacent nodes. The descriptions of the three parts are as follows:1) First is the buffer capacity theoretical analysis of the terminal nodes. We use independent and identically distributed and queuing theory to estimate nodes’ required buffer capacity that used to carry out the data forwarding. Then we provide rational planning use of the storage resources and evaluate the feasibility. This part is to avoid excessive waste of resources caused by the large buffer, and optimize buffer performance with limited resources.2) Second, according to the buffer management issues and the message timeliness requirements, we calculate the average depth of the dissemination of the message. Then we propose the method of setting time-to-live to improve the performance of delay tolerant network.3) Third, we analyze the existing buffer management schemes, establish ACK message logging table of every nodes, and propose the message delete scheme (MSGDS) based on ACK records. Then we describe the update algorithm of the TRACK queue. At last, we estimate the number of copies in the network through the exchanged information between the nodes. Combined the number of copies and timeless of the message, we propose the message replacement scheme. (MSGRS).4) Finally, we study the simulation of the proposed buffer capacity theory and analyze the effects of different buffer sizes on the latency and packet forwarding rate. Then the simulation study of different algorithms are provided. Through extensive simulations, we compare with different buffer management schemes and find that our schemes can improve the latency and forwarding rate.