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CesiumSpray: a Precise and Accurate Global Time Service for Large-scale Systems

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Abstract

In large-scale systems, such as Internet-based distributed systems, classical clock-synchronization solutions become impractical or poorly performing, due to the number of nodes and/or the distance among them. We present a global time service for world-wide systems, based on an innovative clock synchronization scheme, named CesiumSpray. The service exhibits high precision and accuracy; it is virtually indefinitely scalable; and it is fault-tolerant. It is deterministic for real-time machinery in the local area, which makes it particularly well-suited for, though not limited to, large-scale real-time systems. The main features of our clock synchronization scheme can be summarized as follows: hybrid external/internal synchronization protocol improves effectiveness of synchronization; heterogeneous failure semantics for clocks and processors improves previous lower bounds on processors; two-level hierarchy improves scalability. The root of the hierarchy is the GPS satellite constellation, which “sprays” its reference time over a set of nodes provided with GPS receivers, one per local network. The second level of the hierarchy performs internal synchronization, further “spraying” the external time inside the local network.

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Authors and Affiliations

  1. Univ. of Lisboa Faculdade de Ciencias, Lisboa, Portugal

    Paulo Veríssimo, Luís Rodrigues & Antonio Casimiro

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  1. Paulo Veríssimo
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  2. Luís Rodrigues
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  3. Antonio Casimiro
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Veríssimo, P., Rodrigues, L. & Casimiro, A. CesiumSpray: a Precise and Accurate Global Time Service for Large-scale Systems. Real-Time Systems 12, 243–294 (1997). https://doi.org/10.1023/A:1007949113722

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