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Showing papers on "Precision Time Protocol published in 2007"


Proceedings ArticleDOI
19 Nov 2007
TL;DR: The results show that master clock failure as well as network failures can be handled with very low impact on synchronization quality and the combination of PTP and PRP is studied.
Abstract: High availability applications typically count on the network's ability to reconfigure in case of a failure. Since the precision time protocol (PTP) measures the delay of communication paths, it has to cope with network topology changes. The concept of peer-to-peer transparent clocks (TC), introduced with PTP version 2, facilitates the handling of path switchover by measuring the link delays from each node to its neighbors in advance. The parallel redundancy protocol (PRP) follows a different approach from the well-known reconfiguration protocols. It makes use of two independent Ethernet networks. Frames are replicated by the sending node and transmitted over both networks. Duplicates are discarded by the receiving node. There is no distinction between a working and a backup path. The combination of PTP and PRP is studied in this paper. Different models are presented and evaluated with respect to synchronization switchover and implementation issues. An experimental implementation is outlined. The results show that master clock failure as well as network failures can be handled with very low impact on synchronization quality.

46 citations


Proceedings ArticleDOI
19 Nov 2007
TL;DR: Analysis of the factors that affect the synchronization performance in using the precision time protocol provides a theoretical ground for the understanding of simulation results as well as guidelines for choosing both system and control parameters when applying FTP.
Abstract: This paper analyzes the factors that affect the synchronization performance in using the precision time protocol (FTP). We first study the influence of jitter under the assumption of no frequency drifts. Then we study the influence of frequency drift in the absence of jitter. The analytic formulas provide a theoretical ground for the understanding of simulation results as well as guidelines for choosing both system and control parameters when applying FTP.

35 citations


Patent
18 Sep 2007
TL;DR: In this article, the PTP emulation service enables seamless PTP-style clock synchronization over a data communication network using any combination of legacy switches, PTP boundary switches and PTP switches.
Abstract: Precision Time Protocol (PTP) emulation service for a data communication network of a type that is adapted to support circuit emulation services (CES). The PTP emulation service enables seamless PTP-style clock synchronization over such a network using any combination of legacy switches, PTP boundary switches and PTP switches. The PTP emulation service is delivered through the expedient of external PTP emulation devices that are associated with legacy switches and PTP boundary switches.

28 citations


Journal ArticleDOI
TL;DR: An algorithm built on top of a precision time protocol (PTP) implementation that allows for synchronization, syntonization and absolute time referencing to coordinated universal time (UTC), including the estimation of timestamp uncertainty is described.
Abstract: In this paper, we describe an algorithm built on top of a precision time protocol (PTP) implementation that allows for synchronization, syntonization and absolute time referencing to coordinated universal time (UTC), including the estimation of timestamp uncertainty. We call this the software grandmaster (SWGM) algorithm, since it provides similar services to a PTP grandmaster clock. We show that SWGM allows timestamps to be coordinated between multiple participants in a distributed measurement system with typical performance of plusmn 86 ns [root mean square (rms)] over commodity switched Ethernet connections using hardware PTP and hardware-derived timestamps. We further show that when software-derived timestamps are used the uncertainty in the timestamps is primarily driven by the latency of the system calls to read the PTP hardware, and may be on the order of 15-25 s (rms) depending on process priority, hardware bus speed, and host processor clock rate. We also show that SWGM is robust against dropped network packets up to approximately 60% loss of packets.

22 citations


Proceedings ArticleDOI
01 May 2007
TL;DR: A new simulation model of IEEE1588 PTP is presented and discussed, highlighting some special features introduced by authors: modelization of drift and rate variations in the local oscillator and packet timestamping at any level of the protocol stack.
Abstract: This paper deals with time synchronization of distributed systems over Industrial Ethernet network. A new simulation model of IEEE1588 PTP is presented and discussed. The development platform used for simulation is OPNETtrade. Architecture of the proposed model is explained in details, highlighting some special features introduced by authors: modelization of drift and rate variations in the local oscillator and packet timestamping at any level of the protocol stack. Three typical industrial application scenarios have been simulated using the proposed model. Effects of bandwidth usage and network topology have been studied and results are reported. For instance, standard deviation of time offset in the order of 5 mus can be obtained in networks with 48 nodes and cycle time of 1 ms.

11 citations


Proceedings ArticleDOI
19 Nov 2007
TL;DR: This paper describes the performance requirements of example applications, then describes a general application interface in abstract terms, and describes realizations of the interface that can meet theperformance requirements for selected applications.
Abstract: The protocol specified in IEEE 1588, together with a profile, define a timing system that may be used to supply precise timing to applications. However, IEEE 1588 does not say anything about the interface to the applications. In designing this interface, the application performance requirements (e.g., jitter, wander, time synchronization) must be considered. For example, an application that requires microsecond or better time synchronization needs a hardware or firmware interface; a software interface can result in exceeding the synchronization requirement by a factor of 1000 or more. This paper describes the performance requirements of example applications. It then describes a general application interface in abstract terms. Finally, it describes realizations of the interface that can meet the performance requirements for selected applications.

10 citations


Proceedings ArticleDOI
19 Nov 2007
TL;DR: This paper details the work for Boeing's 787 which deployed these technologies to build an innovative system capable of providing gigabit data throughput with sub-microsecond synchronization.
Abstract: Large-scale data acquisition and recording systems have long sought to benefit from the bandwidth, scalability, and low-cost of Ethernet and Internet protocol (IP). However, these systems' requirement for reliable correlation of data with time is impeded by Ethernet's inherently non-deterministic transit delay. With the advent of precision time protocol (PTP), these challenges can now be overcome by deploying synchronized data sources that timestamp data at the source. Furthermore, data producers and consumers constitute a multicast data distribution model, where a single data source is observable by any interested subscribers. This paper details our work for Boeing's 787 which deployed these technologies to build an innovative system capable of providing gigabit data throughput with sub-microsecond synchronization.

9 citations


Proceedings ArticleDOI
19 Nov 2007
TL;DR: A telecom circuit-emulation system that uses the precision time protocol aka IEEE1588 for frequency distribution and the advantages of the use of PTP compared with traditional clock recovery mechanism are discussed.
Abstract: This paper describes a telecom circuit-emulation system that uses the precision time protocol (PTP) aka IEEE1588 for frequency distribution. The advantages of the use of PTP compared with traditional clock recovery mechanism are discussed. The architecture and its main design consideration are reviewed and preliminary performance tests results are demonstrated.

8 citations


Proceedings ArticleDOI
19 Nov 2007
TL;DR: This study describes the objectives, details, and implementation of the simulator that aims to model a semiconductor factory network and will provide a practical perspective to study the accuracy achievable and potential network factors contributing to accuracy degradation of factory-wide time synchronization.
Abstract: In today's semiconductor fabrication facilities ("fabs"), coordination of time-based information throughout the factory and enterprise has become necessary to support fab-wide diagnostics, control, and information management. This has driven the need to have time synchronization at all levels of the enterprise. Time synchronization protocols such as network time protocol (NTP) and precision time protocol (PTP) have been defined for performing synchronization over distributed systems. Lack of time synchronization among the various subsystems is seen as a factor of poor data quality in equipment data acquisition (EDA) and advanced process control (A PC) analysis. The focus of our study is to investigate the extent and precision of time synchronization that can be practically applied with the available protocols at various levels of the semiconductor factory environment to meet next generation manufacturing requirements. To this end, we describe the objectives, details, and implementation of the simulator that aims to model a semiconductor factory network This will provide a practical perspective to study the accuracy achievable and potential network factors contributing to accuracy degradation of factory-wide time synchronization.

3 citations


Patent
04 Jul 2007
TL;DR: In this article, a time synchronization method in a residential Ethernet system is provided to synchronize time of day information of respective node devices in a timing master in the residential Ethernet systems to minimize transmission delay.
Abstract: A time synchronization method in a residential Ethernet system is provided to synchronize time of day information of respective node devices in a timing master in the residential Ethernet system to minimize transmission delay. A PTP(Precision Time Protocol) message frame for synchronizing times in respective nodes in a residential Ethernet system includes a preamble field(31), a DA(Destination Address) field(32), an SA(Source Address) field(33), a type field(34), a PTP message field(35), and an error correction field(36). The preamble field consists of eight-byte data. The DA field consists of 6-byte data and represents a source MAC(Media Access Control) data. The type field consists of 2-byte data and defines a data type. The PTP message field includes a PTP message to be transmitted. The error correction field consists of 4-byte data and checks an error in a transmission frame.

3 citations


01 Jan 2007
TL;DR: In this article, the authors describe an algorithm built on top of a precision time protocol (PTP) implementation that allows for synchronization, syntonization and absolute time referencing to coordinated universal time (UTC), including the estimation of timestamp uncertainty.
Abstract: In this paper, we describe an algorithm built on top of a precision time protocol (PTP) implementation that allows for synchronization, syntonization and absolute time referencing to coordinated universal time (UTC), including the estimation of timestamp uncertainty. We call this the software grandmaster (SWGM) algorithm, since it provides similar services to a PTP grandmaster clock. We show that SWGM allows timestamps to be coordinated between multiple participants in a distributed measurement system with typical performance of 86 ns (root mean square (rms)) over commodity switched Ethernet connec- tions using hardware PTP and hardware-derived timestamps. We further show that when software-derived timestamps are used the uncertainty in the timestamps is primarily driven by the latency of the system calls to read the PTP hardware, and may be on the order of 15-25 s (rms) depending on process priority, hardware bus speed, and host processor clock rate. We also show that SWGM is robust against dropped network packets up to approximately 60% loss of packets.

Proceedings ArticleDOI
01 May 2007
TL;DR: This paper shows how to transfer a theory from the literature concerning rank order filters for analog signals to the domain of time-stamped signals, discusses how to implement the resultingRank order filters efficiently, and shows the results on actual time-Stamped, measured data.
Abstract: The emerging availability of precision time synchronization, such as that provided by IEEE 1588 Precision Time Protocol, make it desirable to have signal processing methods available for signals that are sampled at non-uniform intervals but have the sample times accurately recorded, or time-stamped. Rank order filters, including median filters, are well known in discrete time signal processing. Such filters are used for such purposes as signal de-noising without ringing and robust esimation of signal mimimum and maximum values. The question considered in this paper, then, is: Are there efficient analogues in the domain of time stamped signals for rank order filters ? The answer is yes. This paper shows how to transfer a theory from the literature concerning rank order filters for analog signals to the domain of time-stamped signals, discusses how to implement the resulting rank order filters efficiently, and shows the results on actual time-stamped, measured data.

Proceedings ArticleDOI
22 Oct 2007
TL;DR: The LXI-based airborne missile remoteness test system improves the efficiency to locate the fault and cuts down the cost to maintain the equipment.
Abstract: The airborne-missile remoteness test and fault diagnosis is that the experts in academy and graduate school can test straightly the airborne-missiles and locate remotely the fault by the means of network and computers to shorten the time in locating the fault and decrease the cost in maintaining the airborne-missile. Due to network latency, the test process is possible to work abnormally in the normal remoteness test and fault diagnosis system sometimes it even leads to not executing exactly. LXI is a new instrumentation standard that builds on LAN communications standards. The instrument of LXI class A and B can synchronize their system clocks to a high degree of accuracy automatically and transparently according to IEEE STD 1588 Precision Time Protocol. To overcome the disorder of the test process in airborne-missile remoteness test, build the LXI-based airborne missile remoteness test system. The system improves the efficiency to locate the fault and cuts down the cost to maintain the equipment.