Performance Evaluation of CFDP in Deferred NAK Mode over Point-to-Point LEO-Satellite Links

The consultative committee for space data systems (CCSDS) file delivery protocol (CFDP) operates in a store-and-forward model to ensure the efficient transfer of information in a wide variety of mission configurations, from relatively low earth-orbiting spacecrafts to complex arrangements of inter-planetary space links. The performance of CFDP in the deferred NAK mode has been evaluated in a theoretical manner. In this paper, we present an experimental performance evaluation of CFDP in the deferred NAK mode over direct point to point low earth orbit (LEO)-satellite links simulated using a test-bed. We compare CFDP/TCP with the commonly used TCP and space communication protocol standards (SCPS) protocol stacks to see which one is more effective over a LEO-satellite link. The evaluation results show that CFDP outperform other two protocols over lossy and asymmetric channels. We found that CFDP is more tolerant of heavy noise and asymmetric channel rate. The superior performance of CFDP over lossy links is attributed to that data are stored pending transmission opportunity and portions of file can be made available to the user as soon as they arrive and its ability to minimize link traffic because of aggregated selective negative acknowledgements.