Wide-area actuator RPC over GridStat with timeliness, redundancy, and safety

GridStat is a QoS-managed middleware framework designed to replace the power grid's aging, inflexible, and slow data communications system. GridStat is a specialization of the publish-subscribe paradigm that takes advantage of the semantics of periodic updates of cached sensor data to provide data delivery with a per-subscriber rate, latency, and redundant paths. While GridStat is well-suited for delivery of sensor data over a wide-area network, its baseline one-way mechanisms are not suitable for round-trip invocations such as setting an actuator or calling between control centers. In this paper we present the design, implementation and experimental evaluation of Ratatoskr, a tunable remote procedure call mechanism that builds on the QoS semantics of GridStat and supports three kinds of redundancy. Additionally, user-defined pre- and post-condition predicates over GridStat status variables are built into the call semantics.