An optimized implementation of a fault-tolerant clock synchronization circuit



Publisher: National Aeronautics and Space Administration, Langley Research Center, Publisher: National Technical Information Service, distributor in Hampton, Va, [Springfield, Va

Written in English
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Edition Notes

StatementWilfredo Torres-Pomales.
SeriesNASA technical memorandum -- 109176.
ContributionsLangley Research Center.
The Physical Object
FormatMicroform
Pagination1 v.
ID Numbers
Open LibraryOL17012426M
OCLC/WorldCa33155527

Such a fault-tolerant system needs a clock synchronization algorithm that works despite faulty behavior by some processes and clocks. This paper describes three such algorithms. It is easy to construct fault-tolerant synchronization algorithms if one restricts the type of failures that are permitted. However, it is difficult to find algorithms. – A clock is derived from another clock signal (e.g., different clock rate or phase) – Relationship is known • Typical implementation is done with clocks that are integer multiples of each other • E.g., MHz bus and MHz processor – Logic for the derived clock . Title: Fault-tolerant clock synchronization in distributed systems - Computer Author: IEEE Created Date: 2/25/ AM. Further developments are described in Verification of an optimized fault-tolerant clock synchronization circuit: A case study exploring the boundary between formal reasoning systems by Paul S. Miner and Steven D. Johnson, presented at the conference on Designing Correct Circuits in Bastad, Sweden in September

Six provably correct fault-tolerant clock synchronization algorithms are examined. These algorithms are all presented in the same notation to permit easier comprehension and comparison. The advantages and disadvantages of the different techniques are examined and issues related to the implementation of these algorithms are discussed. synchronization information is processed by software in the processor and not at the hardware level, then there are significant latencies that impede to achieve a high precision in the clock synchronization. Figure 1. Architecture of a CAN network In addition to software implementations, the hardware implementation of the Time-Triggered CAN. Qnamic Fault-Tolerant Clock Synchronization protocol here.) The crucial point is that since we do not use averaging, it is not necessary that the majority of processors be correct. Moreover, our algorithm requires the transmission of at most n 2 messages per synchronization (where n is the total number of processors in the system). The problem of fault-tolerant synchronization is of great importance for the design of reliable real-time multiprocessor systems. Most of the current solutions of this problem typically employ globality assumptions, or central control, and can not provide initial self-bootstrapping.

Fault-tolerant clock synchronization validation methodology. By Ricky W. Butler, Sally C. Johnson and Daniel L. Palumbo. Abstract. A validation method for the synchronization subsystem of a fault-tolerant computer system is presented. The high reliability requirement of flight-crucial systems precludes the use of most traditional validation. Briefing Slides. Network Time Protocl (NTP) General Overview PostScript | PowerPoint | PDF; NTP Achitecture, Protocol And Algorithms PostScript | PowerPoint | PDF. Importance of the Problem. Accurate, reliable time synchronization among the computers sharing a data network is vital for such things as file archive systems, cryptographic key management and real-time applications such as. Fault-Tolerant Clock Synchronization for Safety-Critical Applications In a distributed system the discrepancy between a node's view of current time and the rest of a system can cause critical deadlines to be missed. (2) Internal clock synchronization: Each node shares their physical clock time value with other nodes and set their new clock value accordingly for clock synchronization. Issues in Clock Synchronization. A simple method of clock synchronization is that each node has to send a request message ‘time=?’ to the real-time server.

An optimized implementation of a fault-tolerant clock synchronization circuit Download PDF EPUB FB2

An optimized implementation of a fault-tolerant clock synchronization circuit A fault-tolerant clock synchronization circuit was designed and tested. A comparison to a previous design and the procedure followed to achieve the current optimization are included. The report also includes a description of the system and the results of tests.

In previous work, we explored the interaction between different formal hardware development techniques in the implementation of a fault-tolerant clock synchronization circuit.

This case study. Fault-Tolerant Clock Synchronization In the previous lectures, we assumed that the world is a happy place without any kind of faults. This is not a realistic assumption in large-scale systems, and it is an issue in high reliability systems as well.

After all, if the system clock fails, there may be no further computations at all. Fault-tolerant clock synchronization in CAN. FAULT-TOLERANT CLOCK SYNCHRONIZATION Joseph Y.

Halpern Barbara Simons Ray Strong IBM Research Laboratory San Jose, California Danny Dolce Hebrew University, Givat Ram Jerusalem, Israel Abstract: This paper gives two simple efficient dis. ‹Nr.› Rationale e Common notion of time is crucial for almost all application e Ethernet has become the only viable communication medium a Performance is highly customizable a Bandwidth, fault tolerance, latency e One single communication medium both for and time a R.I.P.

Legacy time transfer systems e Ethernet is asynchronous a Time transfer has to be packet based. In this paper we present a new fault tolerant clock synchronization algorithm, the Fault Tolerant Daisy Chain algorithm.

It is intended for internal clock synchronization of systems using a broadcast bus with Time Division Multiple Access (TDMA) communication, or other systems where clock readings are broadcast at regular intervals.

In this paper, a new "Sliding Window" clock synchronization algorithm is presented. It offers two significant advantages. First, it can tolerate considerably higher percentages of faults than any known algorithm. In addition, it achieves clock synchronization tightness that is tighter than or as tight as that of other algorithms.

The clock synchronization algorithm by Srikanth and Toueg [27] guarantees a bound of O(D) on the clock skew between any two nodes at all times and is thus asymptotically optimal. The algorithm is further fault-tolerant and achieves an accuracy with respect. – A clock is derived from another clock signals (e.g., different clock rate or phase) – Relationship is known – Logic for the derived clock should be separated from regular logic and manually synthesized (e.g., special delay line or PLL) – A system with derived clock can still be treated and analyzed as a synchronous system.

FAULT-TOLERANT CLOCK SYNCHRONIZATION • At the beginning of an iteration, all nodes transition to state ready (or, initially, start) within a bounded time span. This resets the flags. • Nodes wait in this state until they are sure that all correct nodes reached it. Then, when a local timeout expires, they transition to propose.

Clock synchronization schemes in the presence of faults have been investigated extensively in recent years to increase reliability in real-time systems. Among the clock synchronization schemes, hardware-based clock synchronization scheme is preferable one for the time-critical applications that need tight and reliable clock synchronization.

Abstract: Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization.

A clock-fault tolerant architecture and circuit for reliable nanoelectronics system Abstract: Due to discrepancies in manufacturing process and the probabilistic nature of quantum mechanical phenomenon, nanoelectronic devices cannot be made as reliable as current microelectronic devices.

FAULT-TOLERANT ALGORITHM FOR CLOCK SYNCHRONIZATION 3 synchronization, in the face of clock drift, uncertainty in the message delivery time, and arbitrary process faults. This variant is also presented. We consider the main contributions of this paper to be the following. A simulation framework for fault-tolerant clock synchronization in industrial automation networks are highly optimized.

useful during the implementation of a synchronization simulation. We describe a new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem.

The algorithm is designed for a system of distributed processes that communicate by sending messages. Each process has its own read-only physical clock whose drift. remote clock reading error, p is the maximum drift rate of a correct hardware clock and rman is the max- imum duration of a synchronization round.

1 Introduction Tight internal clock synchronization is essential for many real-time and fault-tolerant applications. Inter- nal clock synchronization requires that (1) at any time. Many safety-relevant real-time systems require a reliable time source, which leads to the requirement of fault-tolerant clock synchronization.

This paper proposes a fault-tolerant synchronization. The paper is organized as follows. Section 2 presents an overview of the clock synchronization algorithm.

Section 3 describes our proposed benchmark. Section 4 presents the results of our experiments. We conclude in Section 5. 2 Clock Synchronization Overview In a network with a fault-tolerant con guration, switches and end systems assume the roles.

Fault-Tolerant Clock Synchronization is the scope of this presentation. Page 9 Overview Ensuring Reliable Networks 1. Introduction 2. Rationale for and use of fault-tolerant clock synchronization 3.

A short history on the development of fault-tolerant. The design of clock synchronization has several challenges. Clock synchronization must take two factors, the network transmission delays and clock drift, into account.

First, because the network transmission delay is variable, a processor cannot achieve values of remote clocks immediately.

of loss of synchronization. Also, this ap- proach may induce very high traffic to the system. This article compares and contrasts ex- isting fault-tolerant clock synchronization algorithms.

The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost. Elementary Fault-Tolerant Clock Synchronization III.

Extended FT CS Approaches – Integrating Internal and External CS – Interval-based CS – Clock Rate Synchronization – Hardware Assistance. Novel FT CS Approaches – CS in Shared Memory Multiprocessor Systems – Biological CS – CS in Wireless Networks – CS in Systems-on-Chip.

We present a novel approach for the on-chip generation of a fault-tolerant clock. Our method is based on the hardware implementation of a tick synchronization algorithm from the distributed systems community. We discuss the selection of an appropriate algorithm, present the refinement steps necessary to facilitate its efficient mapping to hardware, and elaborate on the key challenges we had to.

clock synchronization algorithm. Unfortunately, some of its features also make the implementation of a fault-tolerant clock synchronization service a non-trivial task.

Our algo-rithm addresses both the positive and the negative aspects of CAN. Introduction. systems need a fault-tolerant, clock synchronization service.

A clock synchronization service ensures that spatially dispersed processors in a distributed system share a common notion of time. This clock synchronization service must deal with communication delay uncertainties, clock imprecision and drift, as well as link and processor faults.

This. ternal and internal clock synchronization for as long as no more than F reference time servers out of a total of 2F+1 are faulty. When the number of faulty refer- ence time servers exceeds F, the algorithm degrades to a fault-tolerant internal clock synchronization algo- rithm.

We prove that at. We describe a new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem. The algorithm is designed for a system of distributed processes that communicate by sending messages. Each process has its own read-only physical clock whose drift rate from real time is very small.

CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): We describe a new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem. The algorithm is designed for a system of distributed processes that communicate by sending messages, Each process has its own read-only physical clock whose drift rate from real time is very small.

FAULT-TOLERANT CLOCK SYNCHRONIZATION. By. Abstract. Abstract: This paper gives two simple efficient dis-tributed algorithms: one for keeping clocks in a net-work synchronized and one for allowing new proc-essors to join the network with their clocks syn-chronized.

The algorithms tolerate both link and node failures of any type.The Resource An optimized implementation of a fault-tolerant clock synchronization circuit, Wilfredo Torres-Pomales, (microform).CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): We describe a new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem.

The algorithm is designed for a system of distributed processes that communicate by sending messages. Each process has its own read-only physical clock whose drift rate from real time is very small.