Using Periodic Contacts for Efficient Routing in Delay Tolerant Networks
Rugved Jathar, Vikas Yadav and Arobinda Gupta
In Delay Tolerant Networks (DTNs), nodes come in contact with each other intermittently, causing parts of an end-to-end path to be formed at different times, though a complete end-to-end path may not exist at any time. Routing in such networks follow a store-and-forward approach where a node buffers a packet for some time if the path to the destination does not exist, and then forwards it to the next hop when it comes in contact with it. In many real life scenarios, contacts between nodes are periodic in nature, with the contacts repeating in certain time sequence over multiple periods with high probability. The knowledge about the sequencing and the periodicity of these contacts can be effectively utilized to predict the time of future contacts to improve the delivery ratio in routing. In this paper, we first propose a routing protocol for DTNs called PROCS that uses both the repetitive contacts arising out of this periodicity and their time sequencing to improve the delivery ratio. The protocol does not replicate any message, and hence can work with low buffer size and low power in mobile nodes. The novel feature of this protocol is the use of periodicity of contacts which has not been used in earlier protocols. Simulation results show that the proposed protocol achieves high message delivery ratio with no message replication compared to some of the existing protocols.We also present an extension of the protocol that uses limited replication if needed to deliver messages within some specified expiry time.
Keywords: Delay tolerant networks, routing, periodicity