Delay tolerant network routing: Beyond epidemic routing

In this paper, we identify two distinct classes of routing algorithms for Delay or Disruption Tolerant Networks (DTN). The purpose of this classification is to clearly delineate the assumptions they work under and to facilitate mapping of applications to these algorithms. Algorithms based on opportunistic contact and some variant of epidemic routing use minimal topology knowledge and the most resources due to replication. The island-based algorithms find routes between connected islands and are closer to real applications such as tactical military networks. The general consensus is that there is no single routing solution that will minimize delay at the same maximizing throughput for DTNs. Majority of the algorithms assume non-standard and diverse scenarios which makes comparative evaluation difficult. Mapping applications to algorithms also poses a problem as many of the known applications do not match in scale the rigor of the proposed algorithms. Further efforts in standardization and verifiable evaluation using application context are the way forward.