Date Added: Aug 2010
Delay Tolerant Networks (DTNs) have evolved from Mobile Ad Hoc NETworks (MANET). It is a network, where contemporaneous connectivity among all nodes doesn't exist. This leads to the problem of how to route a packet from one node to another, in such a network. This problem becomes more complex, when the node mobility also is considered. The researchers have attempted to address this issue for over a decade. They have found that communication is possible in such a challenged network. The design of routing protocol for such networks is an important issue. This paper surveys the literature and classifies the various routing approaches.