Contact Graph Routing (CGR) for Delay/Disruption Tolerant Networking (DTN) space-based networks makes use of the predictable nature of node contacts to make real-time routing decisions given unpredictable traffic patterns. The contact graph will have been disseminated to all nodes before the start of route computation. CGR was designed for space-based networking environments where future contact plans are known or are independently computable (e.g., using known orbital dynamics). For each data item (known as a bundle in DTN), a node independently performs route selection by examining possible paths to the destination. Route computation could conceivably run thousands of times a second, so computational load is important.
This work refers to the simulation software model of Enhanced Contact Graph Routing (ECGR) for DTN Bundle Protocol in JPL’s MACHETE simulation tool. The simulation model was used for performance analysis of CGR and led to several performance enhancements. The simulation model was used to demonstrate the improvements of ECGR over CGR as well as other routing methods in space network scenarios. ECGR moved to using earliest arrival time because it is a global monotonically increasing metric that guarantees the safety properties needed for the solution’s correctness since route re-computation occurs at each node to accommodate unpredicted changes (e.g., traffic pattern, link quality). Furthermore, using earliest arrival time enabled the use of the standard Dijkstra algorithm for path selection. The Dijkstra algorithm for path selection has a well-known inexpensive computational cost. These enhancements have been integrated into the open source CGR implementation. The ECGR model is also useful for route metric experimentation and comparisons with other DTN routing protocols particularly when combined with MACHETE’s space networking models and Delay Tolerant Link State Routing (DTLSR) model.
This work was done by John S. Segui, Esther H. Jennings, and Loren P. Clare of Caltech for NASA’s Jet Propulsion Laboratory. The software used in this innovation is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
Enhanced Contact Graph Routing (ECGR) MACHETE Simulation Model
(reference NPO-47650) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the Enhanced Contact Graph Routing (ECGR) and the MACHETE Simulation Model. It is part of NASA Tech Briefs and is intended to disseminate information on aerospace-related developments with potential technological, scientific, or commercial applications.
The ECGR is a routing protocol designed for Delay/Disruption Tolerant Networking (DTN), which is crucial for communication in environments where traditional networking methods may fail due to long delays or intermittent connectivity, such as in space missions. The document outlines the challenges faced in space networking, including routing loops, latency, and computational requirements, and presents solutions to enhance the efficiency and reliability of data transmission.
The document also describes simulations conducted under the MACHETE model, which tested four solar system scenarios: Lunar, Lunar Polar, Martian Historic, and Martian Future. These simulations aimed to evaluate the performance of the ECGR in various environments, demonstrating its ability to decrease network load and increase the delivery ratio of data packets over a finite horizon.
The research presented in this document was shared at the IEEE GLOBECOM Conference in Houston, Texas, on December 8, 2011, by authors John Seguí, Esther Jennings, and Scot Burleigh. The findings contribute to the broader field of space communication, providing insights that could enhance future interplanetary missions and improve the robustness of data networks in challenging environments.
The document emphasizes the importance of compliance with U.S. export regulations and includes contact information for further inquiries related to the research and technology discussed. It also includes a disclaimer stating that the U.S. Government does not assume liability for the use of the information contained within the document.
In summary, this Technical Support Package serves as a comprehensive resource on ECGR and its applications in space networking, highlighting the innovative approaches being developed at JPL to address the unique challenges of communication in space.
