Delay and disruption tolerant networks have been proposed to address data communication challenges in network scenarios where an instantaneous end-to-end path between a source and destination may not exist, and the links between nodes may be opportunistic, predictably connectable, or periodically-(dis)connected. In this paper, we describe the store-and-forward and custody transfer concepts that are used in DTNs. Then, we present simulation results that illustrate the usefulness of the custody transfer feature, and a message ferry in improving the end-to-end message delivery ratio in a multihop scenario where link availability can be as low as 20%. In particular, our results indicate that one can achieve a delivery ratio as high as 90-99% with appropriate buffer allocations. We also provide some preliminary insights on the design factors that influence the end to end delivery ratio, e.g., the link availability patterns and buffer allocation strategies.