CFDP PDU Tunneling Service over DTN Between Heterogeneous Deep Space Communication Assets

In space exploration missions, the spacecraft have limited computing resources. In particular, the communications environments for these spacecraft, whether in deep space or the cislunar region, are characterized by intermittent connectivity loss, long signal-propagation delay, and high bit-error rates between spacecraft and their ground stations. Delay-Tolerant Network (DTN) has been introduced to enable automated, efficient communication among flight-mission entities in these environments. However, most flight-mission entities are not yet equipped for DTN; a mechanism is needed whereby DTN-enabled entities and non-DTN-enabled entities can easily interoperate. The CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) is supported in both DTN and non-DTN communication fabrics, so perhaps CFDP file transmission can serve as the common communication medium that bridges the two. When CFDP runs without a Bundle Protocol (BP), it requires a more complex CFDP implementation, and multi-hop communication is more difficult to configure. This paper presents a tunneling mechanism that relays CFDP protocol data units (PDUs) between a non-DTN-enabled CFDP entity and a DTN-enabled CFDP entity. This enables CFDP-over-link implementations to bridge into BP networks to simplify multi-hop forwarding through the BP network. A proof-of-concept implementation of the tunneling service has been developed and tested using the Interplanetary Overlay Network (ION) DTN software to evaluate this concept of CFDP PDU relay/forward functionality to enable communication between the two heterogeneous space communication fabrics. Test setup, test results, and future work on the tunneling service are also discussed.