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Asynchronous Message Service (1 of 3)

Asynchronous Message Service (1 of 3). In addition to file transfer, event-driven asynchronous message exchange may also be useful for deep space communications with and among spacecraft : streaming engineering (housekeeping) data real-time commanding

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Asynchronous Message Service (1 of 3)

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  1. Asynchronous Message Service (1 of 3) • In addition to file transfer, event-driven asynchronous message exchange may also be useful for deep space communications with and among spacecraft : • streaming engineering (housekeeping) data • real-time commanding • continuous collaborative operation among robotic craft • NASA’s proposed new Command, Control, Communications, and Information (C3I) architecture is based on this model. • Challenges in large-scale asynchronous message exchange: • Heterogeneity: platforms, security regimes, communication environments, QOS requirements, performance requirements, cost tolerance. • Changing topology: requires autonomous discovery of communication endpoints, automatic reconfiguration. • Publish/subscribe message exchange model scales better than client/server.

  2. Asynchronous Message Service (2 of 3) • But most asynchronous message exchange systems are: • proprietary, licensed products (e.g., TIBCO Rendezvous, NDDS) rather than open international standards; • not designed for operation on deep space robots. • Proposed CCSDS Asynchronous Message Service (AMS) standard is based on proven NASA technology: no commercial licensing, designed for spacecraft flight operations. • Tramel (Task Remote Asynchronous Message Exchange Layer) was developed in JPL’s Flight Systems Testbed (FST) in 1995-1996; mature and stable since 1998. • Real-time spacecraft simulation in FST (1994-1999). • Software fault tolerance experiments at JPL (1998). • X-34 Integrated Vehicle Health Management testbed (2003). • Baselined for inclusion in C3I.

  3. Asynchronous Message Service (3 of 3) • AMS features: • Platform-neutral, UT-layer neutral. • Designed to scale from very small to very large configurations. • Self-configuring and fault-tolerant, via silent “meta-AMS” protocol. • “Remote AMS” adaptations enable efficient, delay-tolerant publish/subscribe capability over interplanetary distances. • Status: • Concept paper (tentative protocol specification) ready for review. • Fully-functional, well-documented prototype (Tramel) has been mature for six years.

  4. Deep Space Communications Architecture User application AMS CFDP file system functions 7 CFDP unacknowledged transmission (no retransmission, no store-and-forward) UT adapter UT adapter Bundling store-and-forward (bandwidth management) TCP end-to-end retransmission 4 IP network routing 3 “UT layer” LTP point-to-point retransmission COP/P retransmission 2 TM/TC, AOS Prox-1 Ethernet R/F, optical wire 1

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