The Effect Of DTN Custody Transfer In Deep-space Communications

Delay/disruption tolerant networking (DTN) is considered a suitable technology forspace communications. A key parameter of the DTN architecture is the “custody transfer”option. DTN utilizes the well-known store-and-forward mechanism together with custodytransfer option for which a node agrees to hold a file in storage until its successfulreception is acknowledged by the next node. The effectiveness of DTN’s custody transferoption has been a topic of controversy for years. In this paper, we present an experimentalinvestigation of custody transfer in deep-space communications characterized by the verylong propagation delay, lengthy link disruptions and high data-loss rate that are typical ofdeep-space links. The intent is to determine the utility of custody transfer in deep-spacecommunications when running BP with various underlying “convergence layer” protocols:the Licklider Transmission Protocol (LTP), the Transmission Control Protocol (TCP) andthe Internet’s User Datagram Protocol (UDP).ADTN implementation named Interplanetary Overlay Network (ION), developed by theJet Propulsion Laboratory (JPL) in US, was adopted to conduct the file transfer experimentfor the proposed study. Analytical models are built to characterize the file delivery timeand the goodput performance of LTPCL with and without custody transfer (in bundleprotocol (BP)) in an extremely long signal propagation delay, lengthy link disruptions,highly lossy channels that are typical of deep-space links. The models are verified byfile-transfer experiments using a PC-based test-bed.