In Mobile Adhoc Network (MANET) packets can be transferred only if link between the nodes are established. If link is not established then packets will be lost. So packet delivery ratio will be decreased in MANET. To overcome this problem, Delay Tolerant Network (DTN) is used. In DTN each node has some storage capacity. So if the links of nodes are not established then packets will be stored in the storage. DTN is able to provide communication services in unreachable & unfriendly environments. There is no end to end connectivity between source & destination in DTN. Delay tolerant network use store & carry forward the data from one node to other node In this paper we have introduced DTN and its routing protocols. We have also compared these protocols and mentioned future research work in DTN.
Keywords: DTN, MANET, Routing, Flooding, Forwarding