Licklider Transmission Protocol (LTP)-Based DTN for Long-Delay Cislunar Communications

Delay/disruption tolerant networking (DTN) technology offers a new solution to highly stressed communications in space environments, especially those with long link delay and frequent link disruptions in deep space missions. To date, little work has been done in evaluating the effectiveness of the available DTN protocols when they are applied to an interplanetary Internet. In this paper, we present an experimental evaluation of the Bundle Protocol (BP) running over various "convergence layer" protocols in a simulated cislunar communications environment characterized by varying degrees of signal propagation delay and data loss. We focus on the Licklider Transmission Protocol (LTP) convergence layer adapter running on top of UDP/IP (i.e., BP/LTPCL/UDP/IP). The performance of BP/LTPCL/UDP/IP in realistic file transfers over a PC-based testbed is compared with that of two other DTN protocol stacks, BP/TCPCL/TCP/IP and BP/UDPCL/UDP/IP. The experiment results show that LTPCL has a significant performance advantage over TCPCL for link delays longer than 4 sec when bit error rate (BER) is 10E-6 or lower. For a lossy channel with a BER of around 10E-5, LTPCL has a significant goodput advantage over TCPCL at all the link delay levels studied, with an advantage of around 3000 bytes/s for delays longer than 1.5 sec.