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Book Formal Verification of a Fault Tolerant Clock Synchronization Algorithm

Download or read book Formal Verification of a Fault Tolerant Clock Synchronization Algorithm written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-24 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: A formal specification and mechanically assisted verification of the interactive convergence clock synchronization algorithm of Lamport and Melliar-Smith is described. Several technical flaws in the analysis given by Lamport and Melliar-Smith were discovered, even though their presentation is unusally precise and detailed. It seems that these flaws were not detected by informal peer scrutiny. The flaws are discussed and a revised presentation of the analysis is given that not only corrects the flaws but is also more precise and easier to follow. Some of the corrections to the flaws require slight modifications to the original assumptions underlying the algorithm and to the constraints on its parameters, and thus change the external specifications of the algorithm. The formal analysis of the interactive convergence clock synchronization algorithm was performed using the Enhanced Hierarchical Development Methodology (EHDM) formal specification and verification environment. This application of EHDM provides a demonstration of some of the capabilities of the system. Rushby, John and Vonhenke, Frieder Unspecified Center NASA-CR-4239, NAS 1.26:4239 NAS1-17067; RTOP 505-66-21-01...

Book Formal Techniques in Real Time and Fault Tolerant Systems

Download or read book Formal Techniques in Real Time and Fault Tolerant Systems written by Anders P. Ravn and published by Springer Science & Business Media. This book was released on 1998-09-02 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 5th International Symposium on Formal Techniques in Real-Time and Fault-Tolerant Systems, FTRTFT'98, held in Lyngby, Denmark, in September 1998. The 22 revised full papers presented were carefully selected and reviewed for inclusion in the book. Also included are four invited contributions and five tool demonstrations. The papers address the current aspects of the hot topic of embedded systems, in particular temporal logic, requirements engineering, analysis techniques, verification, model checking, and applications.

Book A Byzantine Fault Tolerant Self Stabilizing Protocol for Distributed Clock Synchronization Systems

Download or read book A Byzantine Fault Tolerant Self Stabilizing Protocol for Distributed Clock Synchronization Systems written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-07 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Embedded distributed systems have become an integral part of safety-critical computing applications, necessitating system designs that incorporate fault tolerant clock synchronization in order to achieve ultra-reliable assurance levels. Many efficient clock synchronization protocols do not, however, address Byzantine failures, and most protocols that do tolerate Byzantine failures do not self-stabilize. Of the Byzantine self-stabilizing clock synchronization algorithms that exist in the literature, they are based on either unjustifiably strong assumptions about initial synchrony of the nodes or on the existence of a common pulse at the nodes. The Byzantine self-stabilizing clock synchronization protocol presented here does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The proposed protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period. Proofs of the correctness of the protocol as well as the results of formal verification efforts are reported.

Book Formal Techniques in Real Time and Fault Tolerant Systems

Download or read book Formal Techniques in Real Time and Fault Tolerant Systems written by Jan Vytopil and published by Springer Science & Business Media. This book was released on 1991-12-11 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents state-of-the-art research results in the area of formal methods for real-time and fault-tolerant systems. The papers consider problems and solutions in safety-critical system design and examine how wellthe use of formal techniques for design, analysis and verification serves in relating theory to practical realities. The book contains papers on real-time and fault-tolerance issues. Formal logic, process algebra, and action/event models are applied: - to specify and model qualitative and quantitative real-time and fault-tolerant behavior, - to analyze timeliness requirements and consequences of faulthypotheses, - to verify protocols and program code, - to formulate formal frameworks for development of real-time and fault-tolerant systems, - to formulate semantics of languages. The integration and cross-fertilization of real-time and fault-tolerance issues have brought newinsights in recent years, and these are presented in this book.

Book A Byzantine Fault Tolerant Self Stabilizing Protocol for Distributed Clock Synchronization Systems

Download or read book A Byzantine Fault Tolerant Self Stabilizing Protocol for Distributed Clock Synchronization Systems written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-05-29 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Embedded distributed systems have become an integral part of safety-critical computing applications, necessitating system designs that incorporate fault tolerant clock synchronization in order to achieve ultra-reliable assurance levels. Many efficient clock synchronization protocols do not, however, address Byzantine failures, and most protocols that do tolerate Byzantine failures do not self-stabilize. Of the Byzantine self-stabilizing clock synchronization algorithms that exist in the literature, they are based on either unjustifiably strong assumptions about initial synchrony of the nodes or on the existence of a common pulse at the nodes. The Byzantine self-stabilizing clock synchronization protocol presented here does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The proposed protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period. Proofs of the correctness of the protocol as well as the results of formal verification efforts are reported.Malekpour, Mahyar R.Langley Research CenterCLOCKS; SYNCHRONISM; PROVING; FAULT TOLERANCE; CONVERGENCE; EMBEDDING; ALGORITHMS; SAFETY; PROTOCOL (COMPUTERS); PROGRAM VERIFICATION (COMPUTERS); FAILURE

Book Validation of a Fault Tolerant Clock Synchronization System

Download or read book Validation of a Fault Tolerant Clock Synchronization System written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-06 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: A validation method for the synchronization subsystem of a fault tolerant computer system is investigated. The method combines formal design verification with experimental testing. The design proof reduces the correctness of the clock synchronization system to the correctness of a set of axioms which are experimentally validated. Since the reliability requirements are often extreme, requiring the estimation of extremely large quantiles, an asymptotic approach to estimation in the tail of a distribution is employed. Butler, R. W. and Johnson, S. C. Langley Research Center NASA-TP-2346, L-15799, NAS 1.60:2346 RTOP 505-34-13

Book A Verified Design of a Fault Tolerant Clock Synchronization Circuit

Download or read book A Verified Design of a Fault Tolerant Clock Synchronization Circuit written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Schneider demonstrates that many fault tolerant clock synchronization algorithms can be represented as refinements of a single proven correct paradigm. Shankar provides mechanical proof that Schneider's schema achieves Byzantine fault tolerant clock synchronization provided that 11 constraints are satisfied. Some of the constraints are assumptions about physical properties of the system and cannot be established formally. Proofs are given that the fault tolerant midpoint convergence function satisfies three of the constraints. A hardware design is presented, implementing the fault tolerant midpoint function, which is shown to satisfy the remaining constraints. The synchronization circuit will recover completely from transient faults provided the maximum fault assumption is not violated. The initialization protocol for the circuit also provides a recovery mechanism from total system failure caused by correlated transient faults. Miner, Paul S. Langley Research Center ALGORITHMS; CIRCUITS; CLOCKS; FAULT TOLERANCE; SYNCHRONISM; CONVERGENCE; PROTOCOL (COMPUTERS); PROVING; SYSTEM FAILURES...

Book Formal Techniques in Real Time and Fault Tolerant Systems

Download or read book Formal Techniques in Real Time and Fault Tolerant Systems written by Werner Damm and published by Springer Science & Business Media. This book was released on 2002-08-28 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of FTRTFT 2002, the International S- posium on Formal Techniques in Real-Time and Fault-Tolerant Systems, held at the University of Oldenburg, Germany, 9–12 September 2002. This sym- sium was the seventh in a series of FTRTFT symposia devoted to problems and solutions in safe system design. The previous symposia took place in Warwick 1990, Nijmegen 1992, Lub ̈ eck 1994, Uppsala 1996, Lyngby 1998, and Pune 2000. Proceedings of these symposia were published as volumes 331, 571, 863, 1135, 1486, and 1926 in the LNCS series by Springer-Verlag. This year the sym- sium was co-sponsored by IFIP Working Group 2.2 on Formal Description of Programming Concepts. The symposium presented advances in the development and use of formal techniques in the design of real-time, hybrid, fault-tolerant embedded systems, covering all stages from requirements analysis to hardware and/or software - plementation. Particular emphasis was placed on UML-based development of real-time systems. Through invited presentations, links between the dependable systems and formal methods research communities were strengthened. With the increasing use of such formal techniques in industrial settings, the conference aimed at stimulating cross-fertilization between challenges in industrial usages of formal methods and advanced research. Inresponsetothecallforpapers,39submissionswerereceived.Eachsubm- sion was reviewed by four program committee members assisted by additional referees. At the end of the reviewing process, the program committee accepted 17 papers for presentation at the symposium.

Book An Extension to Schneider s General Paradigm for Fault tolerant Clock Synchronization

Download or read book An Extension to Schneider s General Paradigm for Fault tolerant Clock Synchronization written by Paul S. Miner and published by . This book was released on 1992 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Formal Verification of an Oral Messages Algorithm for Interactive Consistency

Download or read book Formal Verification of an Oral Messages Algorithm for Interactive Consistency written by John Rushby and published by . This book was released on 1992 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: This example illustrates how delicate choices in the formulation of a problem can have significant impact on the readability of its formal specification and on the tractability of its formal verification."

Book An Extension to Schneider s General Paradigm for Fault Tolerant Clock Synchronization

Download or read book An Extension to Schneider s General Paradigm for Fault Tolerant Clock Synchronization written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1987, Schneider presented a general paradigm that provides a single proof of a number of fault tolerant clock synchronization algorithms. His proof was subsequently subjected to the rigor of mechanical verification by Shankar. However, both Schneider and Shankar assumed a condition Shankar refers to as a bounded delay. This condition states that the elapsed time between synchronization events (i.e., the time that the local process applies an adjustment to its logical clock) is bounded. This property is really a result of the algorithm and should not be assumed in a proof of correctness. This paper remedies this by providing a proof of this property in the context of the general paradigm proposed by Schneider. The argument given is a generalization of Welch and Lynch's proof of a related property for their algorithm. Miner, Paul S. Langley Research Center...