| Popis: |
Delay /Disruption Tolerant Network (DTN) is an emerging architecture for internetworking with regional networks of different characteristics as a single entity. The first part of the paper briefs terrestrial and space applications of DTN, different implementations available, real world projects already deployed, the open problems, and the research activities in the area. The paper discusses CCSDS (Consultative Committee for Space Data System) effort to define DTN for interplanetary networking and next generation space internet. The paper also reviews the loose ends in the bundle protocol which is the underlying protocol of DTN architecture and the solutions for the issues. The second part of the paper brings out the need for a test bed to be used for performance evaluation and protocol validation of DTN before its deployment. The authors have developed a test bed and evaluated DTN2 reference implementation for its operation on three nodes network. On the test bed, a three node (ground, orbiter and rover) intermittently connected network was simulated and proved the concept of telecommand / telemetry operation from ground to rover through an orbiter as a relay. A contact graph based static routing was established at all nodes indicating contact time and duration for the operation. As part of initial study on DTN, a three node network was also simulated on NS2 for assessing the advantage of DTN over TCP for large latency satellite links. The results were promising in favour of DTN and are presented. Paper concludes by suggesting more simulation study on the test bed for various configurations for evaluation and experimentation in space towards making DTN operational. |
