Delay Tolerant Networks (DTN) are deployed to establish communications in challenging environments with frequent disruptions and delays due to intermittently connecting nodes, such as sparsely distributed wireless sensor networks and mobile ad hoc networks. Routing in such networks is difficult as nodes have little information about the state of the network that has time evolving topology. Therefore, nodes must store, carry, and forward messages towards destinations during opportunistic contacts. In recent years, numerous simulation based studies have been conducted for DTN protocols under various platforms, parameters, and mobility scenarios. However, most of the evaluations were limited in terms of: (a) number of protocols compared, (b) simulation parameters, and (c) DTN scenarios. This paper performs a detailed comparative analysis of ten popular DTN routing protocols. The protocols are benchmarked for the performance metrics, such as: (a) delivery ratio, (b) latency, and (c) message overhead, under the variance of: (a) buffer capacity, (b) message size, (c) message rate, and (d) size of network. The simulation results provide a deeper insight into a protocol’s strengths and weaknesses under diverse network conditions. As a further contribution, we proposed enhancements in the models of three routing schemes for DTNs. The proposed schemes autonomously adapt to the varying network conditions to reduce the messages’ replication frequency by finding optimal routes for messages among sources and destinations nodes. Simulation results indicated significant improvement in performance of the proposed enhanced schemes. © 2016, Springer Science+Business Media New York.