A Message Transfer Framework for Enhanced Reliability in Delay-Tolerant Networks

Delay-tolerant networks (DTNs) can tolerate disruption on end-to-end paths by taking advantage of temporal links emerging between nodes as nodes move in the network. Intermediate nodes store messages before forwarding opportunities become available. A series of encounters (i.e., coming within mutual transmission range) among different nodes will eventually deliver the message to the desired destination. The message delivery performance in a DTN (such as delivery ratio and end-to-end delay) highly depends on the time elapsed between encounters 52 www.macrothink.org/npa Network Protocols and Algorithms ISSN 1943-3581 2015, Vol.7, No.3 and the time two nodes remain in each others communication range once a contact is established. As messages are forwarded opportunistically among nodes, it is important to have sufficient contact opportunities in the network for faster, more reliable delivery of messages. We propose a simple yet efficient method for improving the performance of a DTN by increasing the contact duration of encountered nodes (i.e., mobile devices). Our proposed sticky transfer framework and protocol enable nodes in DTNs to collect neighbors’ information, evaluate their movement patterns and amounts of data to transfer in order to make decisions of whether to “stick” with a neighbor to complete the necessary data transfers. The sticky transfer framework can be combined with any DTN routing protocol to improve its performance. We evaluate our framework through simulations and measure several network performance metrics. Simulation results show that the proposed framework can improve the message delivery ratio, end-to-end delay, overhead ratio, buffer occupancy, number of disrupted message transmissions and so on. It can be well adopted for challenged scenarios where larger messages sizes need to be delivered with application deadline constraints. Furthermore, performance of the DTN improved (upto 43%) at higher node densities and (up to 49%) under increased mobility conditions.