Development of a DTN bundle protocol convergence layer for SpaceWire

Delay-Tolerant Networks (DTNs) have been recently recognized as an alternative solution for building future space-based networks where communications are inherently intermittent due to orbital mechanics, resource constrains, or even spacecraft failures. Among the challenges to implement practical DTNs, the definition of a new communication protocol, which does not assume a persistent connectivity between the communication end points, has been addressed by the specification of the Bundle protocol (BP). Because Bundle Protocol operates as an overlay network over transport layers, it allows for different transport protocols to be used at different points along the path. In this context, in order to allow for proper transport of Bundle Protocol data units (bundles) over the various transport layers, Convergence Layer Adaptors (CLAs) are required. To this end several CLAs exists for LTP, TCP, UDP, among other transport protocols. However, despite SpaceWire is becoming the defacto low-cost, low-latency, and full-duplex standard for intra-spacecraft communication networks, to the best of our knowledge, there is no CLA available for this protocol. Since such a development would allow for extending DTNs to an intra-spacecraft domain, we implemented a prototype SpaceWire CLA in the Interplanetary Overlay Network (ION) stack and evaluated its performance on a LEON3FT-RTAX based on-board computer network test-bench. Finally, we compare the performance with existent CLA over Ethernet link layer.