Reducing latency of message diffusion on congested DTNs

We propose a broadcast method for Delay Tolerant Networks (DTNs) to achieve small latency for message diffusion in a congested situation. In the existing DTN broadcast methods, nodes tend to transfer a limited variant of messages to the contacted nodes, and thus cause an inefficient bandwidth use. That leads to a large latency of message diffusion. This paper proposes a new transfer message selection method called ESF (Estimated Slowest First) which estimates the diffusion rate of messages and precedes the message that has the smallest diffusion rate for its elapsed time from creation, i.e. the slowest message, at the time of node contact. By preceding the slowest message, a variant of the transferred messages is diversified in congested situations and the latency is reduced. The simulation results show that our method can reduce the latency of diffusion completion by 46% more than existing methods in a DTN in a congested situation.