Forwarding and Replication Strategies for DTN with Resource Constraints

Disruption tolerant network (DTN) refers to the type of sparse mobile ad hoc network where the nodes are connected intermittently. A common strategy to cope with intermittent network connectivity is to use multiple-copy routing for message delivery. However, the resultant replicates of messages incur significant burden on the bandwidth and storage requirements of each node. In this paper, we investigate the effect of excessive message-replications in multiple-copy routing in DTNs under communication bandwidth and buffer constraints. By modeling the message delivery process as a Markov chain, we first analytically derive the delivery latency as a function of message-replication limit for the single-message-delivery case. The performance of the multiple-message-multiple-flow case is then evaluated via extensive simulations. For the latter, we observe that there is an optimal value for the message-replication limit of each message beyond which network performance will degrade. Finally, we propose an alternative forwarding and message-dropping strategy to address the problem of unfairness found in the basic FIFO-with-blocking strategy. Our results show that the average message delivery delay can be reduced by as much as 25% with the proposed scheme.