Evaluating the Performance of CGR Routing Strategies in Delay Tolerant Networks using DtnSim

Delay Tolerant Networking (DTN) networks have no continuous end-to-end connectivity and data undergoes store-and-forward mechanism of custody transfer where the bundles (data) are taken custody on a node-to-node basis. Nodes therefore deploy complex routing algorithms such as Contact Graph Routing (CGR) that predicts and generates time evolving graphs of the contacts for path computation. Different path computation techniques have been proposed for route list computations on DTN networks. Path computation techniques involve Dijkstra’s search, Yen’s model of K-Shortest paths [1] etc., with the metrics being the best delivery time (BDT), number of hops visited as per the ION implementation (by Jet Propulsion Laboratory, NASA). Recently, several volume-aware based route computation techniques have been proposed, which consider the volume consumption for delivery of a bundle and updates the residual volume for the contact/route while forwarding. In this research, we consider two contact plans for experimental analysis: a simple contact plan graph and a much denser graph of a deep space scenario. All required parameters for route computations are made available through the contact plan files. Contact Plan Designer is used to emulate deep space satellite networks and to design a feasible contact plan. DtnSim is the simulator used to simulate DTN network experiments for various volume aware route computations. DtnSim uses CGR implemented in ION 3.5 and facilitates additional models of routing currently proposed for further research. The experimental performance analysis includes studying throughput (bundles delivered, mean hops traversed, delivery ratio) and overhead metrics (number of Dijkstra searches, route table size, routes explored during forwarding, Shared Data Recorder (SDR) storage) on routing of bundle traffic using different types of volume aware routing techniques such as 1st contact volume aware, all contacts volume aware, and all contacts volume aware with source routing in extension block or header for various routing algorithms: 1) initial+anchor, 2) first-ending, 3) first-depleted, 4) one-best-path, and 5) per-neighbor-best-path. The effect of topology and contacts on routing performance, the wastage of route computations involved during enqueuing for packet losses during forwarding are not studied extensively. Therefore, in this work we studied and compared the above algorithms for deep space and essentially formulated important aspects, challenges, and limitations while designing a CGR routing algorithm for deep space.