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Proceedings ArticleDOI

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.
Citations
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Patent
06 Jul 2012
TL;DR: In this paper, a method for synchronizing the operating clock and the timing clock of a subordinate domain (236) of an automation network was proposed, where a single synchronization message (212) serves to synchronize the sync slaves with respect to their respective operating clock (216) and timing clock (204).
Abstract: A method for synchronizing the operating clock and the timing clock of a subordinate domain (236) of an automation network, wherein sync slaves (218,224,230) are synchronized by a clock sync master (200) with respect to an operating clock (216), a clock sync master (206) forms part (200) of a subordinate domain, a single synchronization message (212) serves to synchronize the sync slaves with respect to their respective operating clock (216) and timing clock (204), wherein the method comprises providing a notification of the difference (214) between the timing clock (204) and the operating clock (216) using the synchronization message, and accepting this difference (214) into the synchronization message (212) as additional information.
Patent
丁懋卿, 丁汉, 吴建华, 熊振华, 许雄 
07 Sep 2011
TL;DR: The method provided by the invention solves the real-time communication scheduling problem caused by combination of the real -time communication and the clock synchronization.
Abstract: The invention discloses a real-time communication and clock synchronization method of a chain network, comprising the following steps that: A, a primary device enumerates and configures each slave device, starts a forwarding function of each slave device and forms an Ethernet chain network structure; B, the primary device and the slave device or the slave devices mutually exchange a delay request message and a delay response message to obtain related time stamps, and then, calculate a path delay between the current device and the next slave device and store the path delay in the current device; C, the primary device sends an initial deviation correcting signal message, each slave device orderly finishes initial deviation correction on a local clock after receiving the initial deviation correcting signal message; D, the primary device periodically communicates with each slave device in real time in a manner of collecting total frames, wherein a clock synchronization process is embedded in the real-time communication process. The method provided by the invention solves the real-time communication scheduling problem caused by combination of the real-time communication and the clock synchronization.
Journal ArticleDOI
TL;DR: A network simulation environment is proposed which allows to gain new knowledge about the synchonization behaviour in non-static real-world cases and the simulator will give insights into the importance of the influence on the accuracy of the different network layers.

Cites background from "Enhancements to the time synchroniz..."

  • ...A potential drawback for clock synchronization in switched Ethernet together with effects of a proposed solution shall be evaluated as well: switch delay latency and transparent clocks (Jasperneite et al., 2004)....

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Patent
03 Feb 2016
TL;DR: In this article, the global synchronisation using the global master node and the global slave nodes (GS) is also performed in the pre-determined sub-networks (SN1, SN2, SN3) using the local master node (LM) and the local slaves nodes (LS).
Abstract: One or a plurality of sub-networks (SN1, SN2, SN3, SN4) are defined in the communications network, which each comprise a plurality of network nodes (N1, N2, N14) from the communications network, wherein one or a plurality of the sub-networks represent pre-determined sub-networks (SN1, SN2, SN3), in which respective pre-determined network nodes (N1, N3, N5) have both the function of a global slave node (GS) and the function of a local master node (LM), and the one or the other network nodes (N2, N4, N6, N8) of the respective pre-determined sub-networks (SN1, SN2, SN3) are local slave nodes (LS). The method is characterised in that, in addition to global synchronisation using the global master node (GM) and the global slave nodes (GS), local synchronisation is also performed in the pre-determined sub-networks (SN1, SN2, SN3) using the local master node (LM) and the local slave nodes (LS). It is thus achieved that, in the event of an error outside a pre-determined sub-network (SN1, SN2, SN3), the local synchronisation can be continued, whereas the global synchronisation is aborted. It is thus avoided that an erroneous synchronisation is propagated into corresponding sub-networks.
Patent
29 Apr 2007
TL;DR: In this article, a method for realizing a chain between Ethernet network node apparatus and method for synchronizing is presented, which is not compatible with products from different manufacturers to increase the use of cost and other issues.
Abstract: 本发明公开了一种实现以太网链状网络节点间同步的装置和方法。 The present invention discloses a method for realizing a chain between Ethernet network node apparatus and method for synchronizing. 它解决了目前以太网链状网络结构中实现各网络节点间精确同步动作时成本较高,不能兼容不同厂家产品,增加使用成本等问题,它具有结构简单,使用方便,兼容性好等优点。 It solves the Ethernet chain network structure among network nodes accurately synchronized action at higher cost, is not compatible with products from different manufacturers to increase the use of cost and other issues, it has a simple structure, easy to use, good compatibility. 其结构为:它包括至少一个控制器和若干个网络节点,控制器能枚举和配置各网络节点,控制器分配给各网络节点一个单独的节点号,所述控制器具有至少一个通信接口,各节点具有至少两个通信接口,控制器的通信接口通过数据线连接到某节点的一个通信接口上,然后该节点的另一个通信接口通过数据线连接到下一个节点的一个通信接口上,这样彼此连接下去,形成一个链状网络结构;在各节点上还设有定时器。 Its structure is: it comprises at least one controller and a number of network nodes, the controller can enumerate and configure each network node, the controller assigned to each network node a separate node number, the controller has at least one communication interface, each node having at least two communication interfaces, another communication interface of the communication controller via a data line connected to a communication interface of a node, then the node interface connected to a communication interface of the next node through the data line, so that connected to each other down, forming a chain network structure; on each node also has a timer.
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

Journal ArticleDOI
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

Proceedings ArticleDOI
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

Journal ArticleDOI
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