CONHIS: Contact history-based routing algorithm for a vehicular delay tolerant network

A vehicular delay tolerant network (VDTN) is a special type of delay tolerant network (DTN), where messages are carried by vehicles from one end to another end. End-to-end connectivity in a VDTN is episodic because an end-to-end path between different source nodes and destination nodes does not exist and therefore the possibility of delivering messages to the destination node reduces drastically. Underlying routing protocols of Mobile Ad-hoc Network (MANET) fail when applied to a VDTN because of the non-existence of an end-to-end path that is used to carry packets to the destination. Thus, routing becomes the challenging task in a VDTN. Different types of routing algorithms are proposed for a DTN in the literature but very few algorithms have been proposed that take into account the past history of nodes. In this paper, we propose a contact history based routing algorithm explicitly designed for a VDTN that exploits the history of a node to find the best candidate relay to take a decision to forward a message to the destination. This contact history contains every node's past encounters with relay nodes that had come in contact with this node in the past. We show that, our algorithm outperforms existing history based approaches as well as few non-history based approaches in terms of message delivery ratio, overhead ratio and average delivery latency.