Routing protocols in Delay Tolerant Networks - a survey

Delay Tolerant Networks (DTN) are a class of networks that lack continuous connectivity between nodes due to limited wireless radio coverage, widely scattered mobile nodes, constrained energy resources, high levels of interference or due to some other similar channel impairment. Examples of such networks are those operating in mobile networks or extreme terrestrial environments, or simply as planned networks in space. The term disruption-tolerant network is also occasionally used in place of DTN. Routing in DTN is challenging because of frequent and long duration periods of non-connectivity. Several routing protocols have been proposed with strategies ranging from flooding to opportunistic approaches. Due to the diversity of available strategies, there is a need to properly classify and evaluate their performance with various angles. In this paper, we study state of the art routing protocols and give a comparison between them with respect to the characteristic features and methodology involved. The pros and cons of each, their performance and open research issues are also discussed.