Analysis of optimal RTO of DTN protocol in deep-space communications

The National Aeronautics and Space Administration (NASA) has proposed an end to end networking architecture named Delay/Disruption Tolerant Network (DTN) which is for reliable data delivery in deep-space vehicle communication. Bundle Protocol (BP), the main protocol of DTN, uses a store-and-forward mechanism and custody transfer option for transmission reliability. There has been some work in performance evaluation of DTN's BP and Retransmission Time-Out (RTO) timer setting for the use of BP for file transmission over a relay-based deep-space vehicle communication infrastructure characterized by long signal propagation delay, lengthy disruption, lossy data links and asymmetric channel rates which indicate that RTO timer is set equal or greater than Round-Trip Time (RTT). Unlike this, there is a possible efficient use of the deep-space data channel bandwidth: RTO is set to be less than RTT and that leads to maximum transmission performance of BP for deep-space mission in analytical and experimental manners. They have been previously validated by running file transfer experiments using a PC-based testbed. Furthermore, there is a mathematical proof proposed for analytical models that are built for transmission performance involving normalized RTO timer with respect to the total amount of data transmitted.