Threshold-based Message Copies Control in Delay Tolerant Networks

Delay Tolerant Networks (DTN) generally lack end-to-end connectivity and multiple message copies routing protocols are often used to improve the efficiency that messages are delivered successfully, but network load is increased due to a large number of message copies. A new scheme based on threshold is presented to control message copies efficiently in the networks. A contact counter is added in every node for Epidemic routing scheme and the counter of every node records the number of nodes, which it contacts, with the same copy for a message. If the counter value of a node reaches the threshold which was set, then the node drops message copy. We analysis threshold in theory and derive the lower bound of threshold in delay tolerant networks. According to the lower bound of threshold, we can set a proper threshold in the networks. Using the new scheme message copies reduce obviously and are dropped completely in the end. The successful delivery ratio is no less than Epidemic routing and message copies are controlled efficiently. We show that it is validity in our scheme by comparing with the trends of message copies among different thresholds in two mobility scenes.