Delay and Disruption Tolerant Networks (DTN) can provide an underlying base to support mobility environments. DTN is equipped with advanced features such as custody transfer and hop by hop routing which can tackle the frequent disconnections of mobile devices by buffering bundles and dynamically making hop-by-hop routing decisions under intermittent connectivity environment. In this paper, we have proposed a DTN routing protocol HALF (Handoff-based And Limited Flooding) which can manage and improve performance of disrupted and challenging communication between mobile nodes in the presence of an infrastructure network consisting of fixed interconnected nodes (routers). HALF makes use of the general handoff mechanisms intended for the IP network, in a DTN way and also integrates a limited flooding technique to it. Simulation results show that HALF attains better performance than other existing DTN routing protocols under diverse network conditions. As the traffic intensity changes from low to high, delivery ratio of other DTN routing protocols decreased by 50% to 75% whereas in HALF such ratio is reduced by less than 5%. HALF can deliver about 3 times more messages than the other protocols when the disrupted network has to deal with larger size of messages. If we calculate the overhead ratio in terms of 'how many extra (successful) transfer' is needed for each delivery, HALF gives less than 20% overhead ratio while providing a good delivery ratio.

Custody transfer in delay tolerant networks (DTNs) provides reliable end-to-end data delivery by delegating the responsibility of data transfer among special nodes (custodians) in a hop-by-hop manner. However, storage congestion occurs when data increases and/or the network is partitioned into multiple sub-networks for a long time. The storage congestion can be alleviated by message ferries which move around the network and proactively collect data from the custodians. In such a scenario, data should be aggregated to some custodians so that message ferries can collect them effectively. In this paper, we propose a scheme to aggregate data into selected custodians, called aggregators, in a fully distributed and autonomous manner with the help of evolutionary game theoretic approach. Through theoretical analysis and several simulation experiments, taking account of the uncooperative behavior of nodes, we show that aggregators can be selected in a self-organized manner and the number of aggregators can be controlled to a desired value.