Cluster-Based Replication: A Forwarding Strategy for Mobile Opportunistic Networks

Mutli-copy routing is an efficient and wide-spread approach for coping with the intermittent connectivity of mobile opportunistic networks. One popular multi-copy approach is known as “dynamic” replication; each node creates replicas on a contact basis using a utility that determines a node's fitness for delivering a message to its destination. This scheme is highly flexible, configurable with different utility functions and able to operate efficiently in networks with diverse characteristics. Nonetheless, its drawback is the tendency to produce a high number of replicas that consume limited resources such as energy and storage. Our approach to tackle this problem relies on the observation that, based on their utility values, the network nodes can be grouped into clusters that portray different delivery capabilities. Then, to avoid unnecessary replication, we exploit this finding to replicate a packet to nodes that belong to clusters with increasing delivery capability instead of replicating it to nodes with increasing utility. The new method works in synergy with the basic dynamic replication algorithms and is fully configurable, in the sense that it can be used with virtually any utility function. By conducting experiments in a diverse set of real-life networks, we empirically show that the method effectively reduces the overall number of replicas without hindering delivery efficiency.