Conditional shortest path routing in Delay tolerant networks

This article studies Delay tolerant networks (DTNs) where each node knows the probabilistic distribution of contacts with other nodes. Delay tolerant networks are characterized by the sporadic connectivity between their nodes and therefore the lack of stable end-to-end paths from source to destination. Since the future node connections are mostly unknown in these networks, opportunistic forwarding is used to deliver messages. Based on the observations about human mobility traces and the findings of previous work, we introduce a new metric called conditional intermeeting time. We propose Conditional Shortest Path Routing (CSPR) protocol that route the messages over conditional shortest paths in which the cost of links between nodes is defined by conditional intermeeting times rather than the conventional intermeeting times. When a node receives a message from one of its contacts, it stores the message in its buffer and carries the message until it encounters another node which is at least as useful (in terms of the delivery) as itself. Through trace-driven simulations, we demonstrate that CSPR achieves higher delivery rate and lower end-to-end delay compared to the shortest path based routing protocols that use the conventional intermeeting time as the link metric.