A non-replication multicasting scheme in delay tolerant networks

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Multicast is an important routing function that supports the distribution of data to a group of users, a service needed for many potential DTNs applications. While multicasting in the Internet and mobile ad hoc networks has been studied extensively, efficient multicasting in DTNs is a considerably different and challenging problem due to the probabilistic nature of contact among nodes. This paper aims to provide a non-replication multicasting scheme in DTNs while keeping the number of forwardings low. The address of each destination is not replicated, but is assigned to a particular node based on its contact probability level and node active level. Our scheme is based on a dynamic multicast tree where each leaf node corresponds to a destination. Each tree branch is generated at a contact based on the compare-split rule proposed in this paper. The compare part determines when a new search branch is needed, and the split part decides how the destination set should be partitioned. When only one destination is left in the destination set, we use either wait (no further relay) or focus (with further relay) to reach the final destination. The effectiveness of our approach is verified through extensive simulation.