Information delivery in delay tolerant networks

Modern Internet protocols demonstrate inefficient performance in those networks where the connectivity between end nodes has intermittent property due to dynamic topology or resource constraints. Network environments where the nodes are characterized by opportunistic connectivity are referred to as Delay Tolerant Networks (DTNs). Because of numerous applications such as low-density mobile ad hoc networks, command/response military networks and wireless sensor networks, DTNs have been one of the growing topics of interest characterized by a significant amount of research efforts invested in this area over the past decade. Routing is one of the major components that significantly affects the overall performance of DTN networks in terms of resource consumption, data delivery and latency. Over the past few years a number of routing protocols have been proposed. The focus of this paper is on description, classification and comparison of these protocols. We discuss the state-of-the-art routing schemes and methods in opportunistic networks and classify them to two main deterministic and stochastic routing categories. Finally, we introduce the recently proposed network coding concept, and discuss recent researches regarding coding-based routing protocols in intermittent networks.