Performance Comparison of Four Unicast Routing Schemes in DTNs

Disruption tolerant network(DTN)s have been proposed to provide data communications in challenging network scenarios where an instantaneous end-to-end path between a source and destination may not exist. In this paper, we focus on comparing the performance of four recently proposed unicast routing schemes, namely (i) Multihop Routing with Custody Transfer (MRCT), (ii) Two-Hop Relay with Erasure-Coding (THEC), (iii) MaxProp, and (iv) Prophet. We conduct performance studies for different DTN scenarios, e.g., DTNs with different node densities, DTNs with different mobility models, networks with different percentage of nodes supporting DTN functionality, etc. Our results indicate that (i) the custody transfer concept significantly improves the delivery ratio in a sparsely connected network for all four schemes, (ii) multihop routing approach achieves higher delivery ratio with lower message delivery latency than the two-hop routing approach but incurs higher transmission overhead, (iii) MRCT scheme provides the best delivery performance by achieving high delivery ratio and low average delay, (iv) both MRCT and THEC schemes perform better with Zebranet than with the random waypoint (RWP) mobility model but MaxProp and Prophet performs worse with Zebranet than with the RWP model, (v) among the three multihop schemes, the transmission overhead for MaxProp and Prophet is higher than that incurred using the MRCT scheme. All these four schemes do not perform well when the network is very sparse (when each node has fewer than 1.5 neighbors within its transmission range) and hence an adaptive scheme that allows nodes to act as message ferries when its local neighborhood is very sparse is needed for such scenarios.