Impact of source counter on DTN routing control under resource constraints

We study routing schemes for resource constrained Disruption Tolerant Networks (DTNs) where transmission bandwidth is scarce resource. In such a setting, a key issue is how to schedule the transmission of packets under limited bandwidth to optimize performance. Such a scheduling consists of source control (i.e., source nodes choosing a routing scheme) and the local buffer management scheme adopted by each node. Existing works typically focus on transmission buffer management, but due to theoretical and practical difficulties, only heuristics have been proposed. In this work, we explore alternative ways to improve DTN routing performance via source control. We focus on spray-and-wait counter-based routing scheme. We first show that there exists an optimal counter value to achieve minimum average network-wide packet delivery delay. Then as a first step towards understanding multi-hop multicopy DTN routing schemes, we model a two-hop multi-copy DTN routing via a continuous time Markov Chain. Our modeling analysis provides insights into the impact of counter on routing performance and further suggests the existence of optimal counter value. In this process, we derive the capacity region of DTN routing (i.e., the maximum sustainable per-node throughput), and provide an accurate analysis of the average packet delivery delay of the two-hop single copy relaying scheme. Relying on the insights gained via simulations and modeling, we propose an adaptive scheme that allow nodes to adjust their counter values to achieve minimum packet delivery delay, in a distributed and asynchronous fashion. Simulations demonstrate the effectiveness of our scheme and suggest the potential of exploring this rich area for improving DTN routing performance.