Routing in intermittently connected mobile ad hoc networks and delay tolerant networks: overview and challenges

Recently there has been much research activity in the emerging area of intermittently connected ad hoc networks and delay/disruption tolerant networks (DTN). There are different types of DTNs, depending on the nature of the network environment. Routing in DTNs is one of the key components in the DTN architecture. Therefore, in the last few years researchers have proposed different routing protocols for different types of DTNs. In this article we capture the state of the art in routing protocols in DTNs. We categorize these routing protocols based on information used. For deterministic time evolving networks, three main approaches are discussed: the tree approach, the space and time approach, and the modified shortest path approach. For stochastic time evolving networks, the following approaches are discussed: the epidemic or random forwarding approach, predication or history based approach (including per contact routing based on one hop information only and per contact routing based on average end to end