Experiences from architecting a DTN Testbed
Efthymios Koutsogiannis, Sotiris Diamantopoulos, Georgios I Papastergiou, Ioannis Komnios, Aggelis Aggelis, Nestor Peccia · 2009
As the number of space elements increases, space communications enter a new era, where internetworking grad- ually replaces traditional telecommunication protocols. Delay Tolerant Networking (DTN) has emerged as the most prominent solution for such challenged networks; however, extensive testing and evaluation of all mechanisms is required prior to the wide deployment of DTN. In this paper, we present our experiences from architecting a state-of-the-art DTN testbed, capable of emulating future space communications and appropriate to evaluate proposed protocols and mechanisms. Several evaluation results have been drawn so far, including reliability (CFDP over LTP), routing (Contact Graph Routing versus other DTN routing protocols) and interoperability issues (communication between DTN and Space Packet nodes). the major design challenges and technical obstacles such as immaturity of existing technology; and second, the experimen- tal perspective, where we discuss the appropriate scenarios to evaluate DTN protocols for Space along with experiences from using DTN itself, based on the results we have obtained by using the testbed. Unlike a simulation tool, a testbed allows for more realisti c scenarios, uncovers practical software or hardware malfunc- tions and, in general, constitutes an environment where be- havior of participating entities is unpredictable, unsche duled and involves a wide spectrum of parameters. In this context, a testbed can be far more reliable than a simulation tool; however, comparatively, it suffers from limited flexibilit y and limited scalability - let alone the higher costs of construc tion. In order to cancel that major disadvantage of the DTN testbed, we took two specific measures: • We incorporated heterogeneity - to deal with scala- bility. In particular, the testbed includes satellite link s capable of repeating communication patterns that em- ulate realistic propagation delays and space conditions. Therefore, space time can be realistically achieved in the experiments through ping-pong operations. Fur- thermore, internetworked links, including intercontinen - tal links between Europe (DUTH, Xanthi, Greece) and America (MIT, Boston, USA) are also included, allowing for evaluation of scenarios of space-data distribution on Earth. According to its design objectives, DTN may form an overlay that binds earth and space communications; in this context, data dissemination on Earth, possibly of huge volume and occasionally over congested links, will be possible.