Enhancements to the time synchronization standard IEEE-1588 for a system of cascaded bridges
22 Sep 2004-pp 239-244
TL;DR: In this paper, a bypass clock instead of the boundary clock is proposed as an enhancement of the IEEE-1588 standard for bridged networks, where the local clock adjustment can be modeled by a corresponding control loop.
Abstract: The IEEE-1588 standard for a high precision time synchronization now exists since 2002. For using this standard in bridged networks a so-called boundary clock is defined, where the local clock adjustment can be modeled by a corresponding control loop. At the field level of industrial automation systems, the line topology is very important. By using Ethernet at the field level, the resulting chain of bridges leads to a cascade of control loops and may lead to instabilities and deviations of the distributed clocks, which are not acceptable. For this application a bypass clock instead of the boundary clock is proposed as an enhancement of the IEEE-1588 standard. The effectiveness of this extension to be evaluated by simulation technique.
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25 Sep 2006
TL;DR: This paper presents a novel approach for cascaded synchronized clocks to monitor their own quality without major further communication effort by using the wellknown Allan deviation.
Abstract: Clock synchronization in distributed computer systems is an enabler for the introduction of real-time. So far, many approaches are published which implement clock synchronization on a protocol basis over state of the art packet oriented networks. One very recent example is the introduction of real-time into industrial Ethernet networks, like in Profinet or Powerlink. In addition to this usually flat hierarchy of clock synchronization, also cascaded systems are in use. One application is telecom data transmission, another are power line communication (PLC) networks. In addition to synchronizing their clocks, nodes in these systems still need to know about the actual quality of their local clock. This paper presents a novel approach for cascaded synchronized clocks to monitor their own quality without major further communication effort by using the wellknown Allan deviation.
13 citations
Patent•
30 Jan 2008
TL;DR: In this article, a clock synchronization device (DA1) is proposed to aid a master station (SM) of a wireless network in performing time synchronizations, this master station comprising a master clock (HM) represented by the value of a master counter (CM) and means (MG1) for generating wireless frames of IP packets containing in particular PTP messages of first and second types.
Abstract: A device (DA1) is intended to aid a clock synchronization device (DS1) of a master station (SM) of a wireless network in performing time synchronizations, this master station (SM) comprising a master clock (HM) represented by the value of a master counter (CM) and means (MG1) for generating wireless frames of IP packets containing in particular PTP messages of first and second types. The aid device (DA1) comprises detection means (MD1) for, in case of detection by the physical layer of the master station (SM) of a frame pulse received from the network, triggering the sampling of the value of the master counter (CM)
13 citations
21 May 2008
TL;DR: A new approach to evaluate coexistence of RTE protocols by means of a distributed RTE traffic emulator/logger that can simultaneously inject Rte traffic and measure its effect on existing infrastructure is introduced.
Abstract: The definition of several real-time Ethernet (RTE) protocols for industry use implies that new automation systems can include more than one technology. In the future different RTE protocols could share the same network infrastructure, raising the problem of coexistence. The paper introduces a new approach to evaluate coexistence of RTE protocols by means of a distributed RTE traffic emulator/logger that can simultaneously inject RTE traffic and measure its effect on existing infrastructure. In order to experimentally show effectiveness of the proposed method, a prototype instrument has been used to evaluate consequences of mixing RTE protocols that use IEEE 1588 for synchronization and RTE protocols based on time division multiple access. Measurements taken with the proposed instrument have uncertainty in the order of 50 ns.
13 citations
Cites background from "Enhancements to the time synchroniz..."
...It can achieve time offset error between participants in the order of tenths of nanoseconds [7,9]....
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TL;DR: A SP longer-term strategy based on SDN and NFV approach that will offer rapid end-to-end service provisioning and centralized network control is proposed that helps SP maintain good profit margin and best customer experience.
13 citations
Cites background from "Enhancements to the time synchroniz..."
...This approach offers also more flexibility to SP designers to leverage existing infrastructure and avoid upgrading network elements to support embedded Boundary clocks or SyncE [59,60]....
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TL;DR: In this article, a hybrid architecture considering Global Positioning System (GPS) and Precision Time Protocol (PTP) for applications in electric power systems, with reference to one of the most challenging measurement problems, namely the measurement of synchrophasors, is presented.
Abstract: This paper presents a study on a hybrid architecture considering Global Positioning System (GPS) and Precision Time Protocol (PTP), defined in Standard IEEE 1588, for applications in electric power systems, with reference to one of the most challenging measurement problems, namely the measurement of synchrophasors. The proposed approach refers in particular to situations in which many measurement devices, connected to each other by suitable communication links, are located in a geographically limited subarea of the power system. A laboratory experimental setup has been built to evaluate the performance achievable with this solution. A detailed analysis of the obtained results is presented. Copyright © 2010 John Wiley & Sons, Ltd.
13 citations
References
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01 Jan 2003
TL;DR: OMNeT++ is fully programmable and modular, and it was designed from the ground up to support modeling very large networks built from reusable model components.
Abstract: The paper introduces OMNeT++, a C++-based discrete event simulation package primarily targeted at simulating computer networks and other distributed systems. OMNeT++ is fully programmable and modular, and it was designed from the ground up to support modeling very large networks built from reusable model components. Large emphasis was placed also on easy traceability and debuggability of simulation models: one can execute the simulation under a powerful graphical user interface, which makes the internals of a simulation model fully visible to the person running the simulation: it displays the network graphics, animates the message flow and lets the user peek into objects and variables within the model. These features make OMNeT++ a good candidate for both research and educational purposes. The OMNeT++ simulation engine can be easily embedded into larger applications. OMNeT++ is opensource, free for non-profit use, and it has a fairly large user
2,316 citations
TL;DR: The NTP synchronization system is described, along with performance data which show that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few milliseconds, even in cases of failure or disruption of clocks, time servers, or networks.
Abstract: The network time protocol (NTP), which is designed to distribute time information in a large, diverse system, is described. It uses a symmetric architecture in which a distributed subnet of time servers operating in a self-organizing, hierarchical configuration synchronizes local clocks within the subnet and to national time standards via wire, radio, or calibrated atomic clock. The servers can also redistribute time information within a network via local routing algorithms and time daemons. The NTP synchronization system, which has been in regular operation in the Internet for the last several years, is described, along with performance data which show that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few milliseconds, even in cases of failure or disruption of clocks, time servers, or networks. >
2,114 citations
"Enhancements to the time synchroniz..." refers background or methods in this paper
...The effectiveness of this extension will be evaluated by simulation technique....
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...This due to a decrease in price provoked by the office Ethernet market, high bandwidth, switching technology [3], priority features [4], full duplex operation [2], availability of Ethernet bridges as well as Ethernet-enabled products fulfilling industrial environmental requirements (e.g. [15])....
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27 Sep 2004
TL;DR: A protocol is provided in this standard that enables precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing, and distributed objects.
Abstract: A protocol is provided in this standard that enables precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing, and distributed objects. The protocol is applicable to systems communicating via packet networks. Heterogeneous systems are enabled that include clocks of various inherent precision, resolution, and stability to synchronize. System-wide synchronization accuracy and precision in the sub-microsecond range are supported with minimal network and local clock computing resources. Simple systems are installed and operated without requiring the management attention of users because the default behavior of the protocol allows for it.
1,428 citations
05 Dec 2002
TL;DR: This paper discusses the major features and design objectives of the IEEE-1588 standard, designed to serve the clock synchronization needs of industrial systems, and recent performance results of prototype implementations of this standard in an Ethernet environment are presented.
Abstract: This paper discusses the major features and design objectives of the IEEE-1588 standard. Recent performance results of prototype implementations of this standard in an Ethernet environment are presented. Potential areas of application of this standard are outlined.
1,112 citations
01 Apr 1994
TL;DR: In this article, the authors describe a series of incremental improvements in system hardware and software which result in significantly better accuracy and stability, especially in primary time servers directly synchronized to radio or satellite time services.
Abstract: This paper builds on previous work involving the Network Time Protocol, which is used to synchronize computer clocks in the Internet. It describes a series of incremental improvements in system hardware and software which result in significantly better accuracy and stability, especially in primary time servers directly synchronized to radio or satellite time services. These improvements include novel interfacing techniques and operating system features. The goal in this effort is to improve the synchronization accuracy for fast computers and networks from the tens of milliseconds regime of the present technology to the submillisecond regime of the future.In order to assess how well these improvements work, a series of experiments is described in which the error contributions of various modern Unix system hardware and software components are calibrated. These experiments define the accuracy and stability expectations of the computer clock and establish its design parameters with respect to time and frequency error tolerances. The paper concludes that submillisecond accuracies are indeed practical, but that further improvements will be possible only through the use of temperature-compensated local clock oscillators.
227 citations