Cesiumspray : A Precise and Accurate Global Time Service for Large-scale Systems

Paulo Veríssimo, Luís Rodrigues, António Casimiro

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

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.
Original languageEnglish (US)
Pages (from-to)243-294
Number of pages52
JournalReal-Time Systems
Volume12
Issue number3
DOIs
StatePublished - Jan 1 1997
Externally publishedYes

ASJC Scopus subject areas

  • Control and Optimization
  • Modeling and Simulation
  • Computer Networks and Communications
  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering

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