The Delay-Tolerant Networking Experimental Network Constructing a Cross-agency Supported Internetworking Testbed
Edward J. Birrane · SpaceOps 2012 Conference · 2012
Delay-Tolerant Networking (DTN) protocols implement packetized, multi-path communications amongst space assets. The resulting internetworking model enables data sharing across multiple missions from multiple space agencies. Individual DTN protocols are being standardized in the Consultative Committee for Space Data Systems (CCSDS). NASA is additionally prototyping the routing, security, and management utilities necessary to deploy an operational network based on these CCSDS standards. These utilities require a testbed that simulates both the physical characteristics of a space network and the security and configuration challenges incumbent in coordinating devices across space agencies. The DTN Engineering Network (DEN) is such a testbed comprised of physical and virtual machines and flight-like hardware located at different NASA-centers and supporting universities. The DEN is configured with reference implementations of advanced communication protocols, including the Bundle Protocol and Licklider Transmission Protocol. It may be configured to simulate necessary signal propagation delays and link disruptions. As a distributed, heterogeneous set of machines independently managed by a variety of NASA centers, the DEN also represents a ground-based analog of the space internetworking model. This has allowed NASA to validate both software implementations and decentralized operational concepts. This paper describes the design, construction, test execution, and anticipated evolution of the DEN. This includes a discussion of the unique testing requirements of space internetworking, including the ability to operate across agency boundaries using heterogeneous hardware. The paper concludes with a discussion of lessons learned and how to extend the DEN configuration to include hardware managed by other space agencies, more flight-like hardware, and, potentially, a node on the International Space Station (ISS). Ultimately, the DEN provides the mechanism necessary to raise the TRL of both software and CONOPs so that missions may more comfortably adopt internetworking standards.