Online Routing of Stochastically Arriving Bundles in Delay Tolerant Networks

Future networks will expand current capabilities to service "outpost" regions in performance-challenging environments, in which link connectivity is intermittent, propagation delay may be extremely long, and/or communication conditions may be hostile. In such performance-challenging environments, a network is likely to be partitioned most of the time, and the message delivery mechanisms must have an opportune series of link-by-link transmittals from source to destination. The current Internet suite of protocols is less than adequate for networking in such performance-challenging environments, and new architecture and protocols, based on bundle transport, are being considered. A bundle is a message unit larger than a packet; it comprises a set of data that is sufficiently useful or meaningful to the application without additional data. In this paper, we focus on the online routing decision for a system in which bundle arrival times and bundle sizes are stochastic. We also model the time-varying link rates by stochastic processes. Then, we present an approach to "online" bundle routing based on "offline" traffic engineering. In this approach, we pre-compute nominal traffic flows based on the average available transmission rates of all links and the average rates of offered traffic for all source-destination node pairs. Then, online routing decisions are made on the basis of the nominal flows computed offline.