Clock Synchronization in Distributed Real-Time Systems

  title={Clock Synchronization in Distributed Real-Time Systems},
  author={Hermann Kopetz and Wilhelm Ochsenreiter},
  journal={IEEE Transactions on Computers},
The generation of a fault-tolerant global time base with known accuracy of synchronization is one of the important operating system functions in a distributed real-time system. [] Key Method In the last section, the functions of a VLSI clock synchronization unit, which improves the synchronization accuracy and reduces the CPU load, are described. With this unit, the CPU overhead and the network traffic for clock synchronization in state-of-the-art distributed real-time systems can be reduced to less than 1…

Figures and Tables from this paper

Fault-tolerant clock synchronization in CAN

A new fault-tolerant clock synchronization algorithm designed for the Controller Area Network (CAN) that provides all correct processes of the system with a global timebase, despite the occurrence of faults in the network or in a minority of processes.

Synchronized universal time coordinated for distributed real-time systems

Fault-tolerant clock synchronization for embedded distributed multi-cluster systems

  • M. PaulitschW. Steiner
  • Computer Science
    15th Euromicro Conference on Real-Time Systems, 2003. Proceedings.
  • 2003
This paper addresses fault-tolerant clock synchronization of clusters for TT systems that are already internally synchronized by addressing systematic and stochastic errors of cluster times differently and achieves a significant improvement to known synchronization algorithms.

Efficient synchronization of clocks in a distributed system

A probabilistic clock synchronization algorithm is proposed where processors in the system exchange time stamps and synchronize to a common clock value. Most of the previous algorithms for this

Generating a fault tolerant global clock in a high speed distributed system

  • Y. Ofek
  • Computer Science
    [1989] Proceedings. The 9th International Conference on Distributed Computing Systems
  • 1989
A technique is described for constructing a fault-tolerant global clock in a point-to-point distributed system with an arbitrary topology, which constitutes a wide-area network that is possible to estimate accurately intermodal delays and thereby to achieve a much tighter synchronization than with other methods.

Clock synchronization in MAFT

The steady-state clock synchronization algorithm of MAFT (multicomputer architecture for fault tolerance), an extremely reliable system for real-time applications, is discussed and the maximum skew between nonfaulty clocks is derived in terms of basic system parameters.

An interval-based framework for clock rate synchronization

A basic system model and suitable building blocks for a generic rate synchronization algorithm that employs a convergence function are introduced and it is revealed that the clock rate stability takes over the role of maximum hardware drift rate in traditional clock synchronization approaches.

Distributed time-management in transputer networks

The design and simulation of such an algorithm for a distributed system consisting of transputers is described, based on second order filtered adjustment of the clock rates rather than updating the clock values at once.

Software-Based Fault-Tolerant ClockSynchronization for Distributed UNIXEnvironments

It is shown that a software implementation of the FTMA algorithm is sensitive to environmental aspects such as process priority, CPU and network load, and that it is possible to obtain a more stable algorithm by using a technique referred to as adaptive exponential averaging.



A Paradigm for Reliable Clock Synchronization

Existing fault-tolerant clock synchronization protocols are shown to result from refining a single clock synchronization paradigm. In that paradigm, a reliable time source periodically issues

A new fault-tolerant algorithm for clock synchronization

A new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem for a system of distributed processes that communicate by sending messages, which solves the problem of maintaining closely synchronized local times, assuming that processes' local times are closely synchronized initially.

Time, clocks, and the ordering of events in a distributed system

A distributed algorithm is given for synchronizing a system of logical clocks which can be used to totally order the events, and a bound is derived on how far out of synchrony the clocks can become.

Synchronizing clocks in the presence of faults

Three algorithms for maintaining clock synchrony in a distributed multiprocess system where each process has its own clock work in the presence of arbitrary clock or process failures, including “two-faced clocks” that present different values to different processes.

SIFT: Design and analysis of a fault-tolerant computer for aircraft control

SIFT (Software Implemented Fault Tolerance) is an ultrareliable computer for critical aircraft control applications that achieves fault tolerance by the replication of tasks among processing units by using a novel fault-tolerant synchronization method.

Reaching approximate agreement in the presence of faults

This paper considers a variant of the Byzantine Generals problem, in which processes start with arbitrary real values rather than Boolean values or values from some bounded range, and in which

Inexact agreement: accuracy, precision, and graceful degradation

Use of the protocols for clock synchronization in a distributed system is explained, and two fault-tolerant protocols for Inexact Agreement are described.

Maintaining the time in a distributed system

To a client of a loosely-coupled distributed system, one of the simplest services is a time service. Usually the client simply requests the time from any subset of the time servers making up the

Maintaining knowledge about temporal intervals

An interval-based temporal logic is introduced, together with a computationally effective reasoning algorithm based on constraint propagation. This system is notable in offering a delicate balance