Showing papers on "Precision Time Protocol published in 2016"
TL;DR: The application of White Rabbit precision time protocol in long-distance optical fiber links has been investigated and two implementations of WR-PTP in the existing communication fiber networks are discussed.
Abstract: The application of White Rabbit precision time protocol (WR-PTP) in long-distance optical fiber links has been investigated. WR-PTP is an implementation of PTP in synchronous Ethernet optical fiber networks, originally intended for synchronization of equipment within a range of 10 km. This paper discusses the results and limitations of two implementations of WR-PTP in the existing communication fiber networks. A 950-km WR-PTP link was realized using unidirectional paths in a fiber pair between Espoo and Kajaani, Finland. The time transfer on this link was compared (after initial calibration) against a clock comparison by GPS precise point positioning (PPP). The agreement between the two methods remained within ${\pm }{2}\; \text{ns}$ over three months of measurements. Another WR-PTP implementation was realized between Delft and Amsterdam, the Netherlands, by cascading two links of 137 km each. In this case, the WR links were realized as bidirectional paths in single fibers. The measured time offset between the starting and end points of the link was within 5 ns with an uncertainty of 8 ns, mainly due to the estimated delay asymmetry caused by chromatic dispersion.
106 citations
01 Sep 2016
TL;DR: The interaction between L1 syntonisation and PTP synchronisation in a WR device and the architecture of its Phase-Locked Loop (PLL) are explained and improvements that might be useful for different types of WR applications are proposed.
Abstract: White Rabbit (WR) extends the Precision Time Protocol (PTP) to provide synchronisation with sub-nanosecond accuracy and sub-50 picoseconds precision. The protocol aspects of the WR extension are currently studied and integrated into the upcoming revision of PTP. In the context of this PTP revision, mechanisms are added to allow the control of the Layer 1 (L1) syntonisation by the PTP protocol. This article focuses on the frequency transfer characteristics of the L1 syntonisation in WR. We first explain the interaction between L1 syntonisation and PTP synchronisation in a WR device and describe the architecture of its Phase-Locked Loop (PLL). We then characterize the frequency transfer through a WR network in two ways: measuring the characteristics of the WR switch according to the Synchronous Ethernet (SyncE) metrics defined in ITU-T G.8262, and performing phase noise analysis. The results of the measurements allow us to propose improvements that might be useful for different types of WR applications. Metrology laboratories might be interested in the optimisations made to significantly reduce the phase noise. On the other hand, the telecom industry might be interested in the modifications that make the WR switch SyncE-compliant but deteriorate its performance. Notably, the latter was achieved merely by modifying the software that implements the WR PLL.
26 citations
01 Sep 2016
TL;DR: The TSTP protocol's cross-layer architecture is explored to speculatively peek through the timestamps and geographic info present in message headers, implementing high-accuracy clock synchronization with minimal insertion of explicit messages, resulting in energy savings and precision.
Abstract: Time synchronization is a keystone of Wireless Sensor Networks (WSN). It is fundamental to coordinate the action of nodes in a network and it is also a critical element of several security mechanisms. In this paper, we discuss and evaluate the time synchronization strategy behind the Trustful Space-Time Protocol (TSTP), which explores the protocol's cross-layer architecture to speculatively peek through the timestamps and geographic info present in message headers, implementing high-accuracy clock synchronization with minimal insertion of explicit messages. We evaluate the protocol analytically and experimentally. The analytic evaluation is based on the model defined by Schmid [15] for the Virtual High-resolution Time (VHT), while the experimental evaluation was performed on the IEEE 802.15.4-compliant EPOSMote platform running EPOS and TSTP. Our results demonstrate that nodes in the network can be consistently synchronized with sub-microsecond precision while exchanging far less messages than they would with an ordinary, non-speculative implementation, resulting in energy savings. Indeed, precision and energy savings are higher for networks with higher traffic, since more messages are available for peeking. In an experiment scenario in which messages were exchanged between devices every 15 seconds, nodes in the network achieved a synchronization error of approximately 15 microseconds in the worst case, while in a scenario in which messages were exchanged every 3 seconds, synchronization error was less than 0.5 microseconds in the worst case, and approximately 0.25 microseconds on average.
23 citations
22 Sep 2016
TL;DR: The design of Network Time Security considers the special requirements of precise timekeeping which are described in Security Requirements of Time Protocols in Packet Switched Networks [RFC7384].
Abstract: This document describes Network Time Security (NTS), a collection of
measures that enable secure time synchronization with time servers
using protocols like the Network Time Protocol (NTP) or the Precision
Time Protocol (PTP). Its design considers the special requirements of
precise timekeeping which are described in Security Requirements of
Time Protocols in Packet Switched Networks [RFC7384].
17 citations
02 Mar 2016
TL;DR: In this article, the authors present a detailed threat analysis of the PTP standard, in which they highlight the security properties that should be addressed by any security extension and suggest to replace Annex K's symmetric cryptography by an efficient elliptic-curve public-key signatures.
Abstract: The Precision Time Protocol (PTP) aims to provide highly accurate and synchronized clocks. Its defining standard, IEEE 1588, has a security section (“Annex K”) which relies on symmetric-key secrecy. In this paper we present a detailed threat analysis of the PTP standard, in which we highlight the security properties that should be addressed by any security extension. During this analysis we identify a sequence of new attacks and non-cryptographic network-based defenses that mitigate them. We then suggest to replace Annex K's symmetric cryptography by an efficient elliptic-curve Public-Key signatures. We implemented all our attacks to demonstrate their effectiveness, and also implemented and evaluated both the network and cryptographic defenses. Our results show that the proposed schemes are extremely practical, and much more secure than previous suggestions.
14 citations
01 Sep 2016
TL;DR: This paper serves as an introduction to LibPTP, which is an OMNeT++-based simulation framework for PTP networks that enables designers to study different configuration options, to compare delay mechanisms, or switch between clock servos.
Abstract: IEEE 1588 specifies the Precision Time Protocol (PTP). The design space for PTP implementations is large, and system designers have to make trade-offs. A sophisticated and extensible simulation tool can assist PTP system designers when exploring the design space. This paper serves as an introduction to LibPTP, which is an OMNeT++-based simulation framework for PTP networks. LibPTP facilitates building PTP networks using Ordinary, Boundary, and Transparent clocks. For instance, it enables designers to study different configuration options, to compare delay mechanisms, or switch between clock servos. The paper gives an overview of the current feature set of LibPTP, and demonstrates LibPTP's capabilities through exemplary experiments. The demonstrations encompass analyzing the choice of synchronization intervals, the impact of path asymmetry, and daisy chaining of clocks.
14 citations
25 Feb 2016
TL;DR: This document describes a convention for using the Cryptographic Message Syntax (CMS) to protect the messages in the Network Time Security (NTS) protocol.
Abstract: This document describes a convention for using the Cryptographic
Message Syntax (CMS) to protect the messages in the Network Time
Security (NTS) protocol. NTS provides authentication of time servers
as well as integrity protection of time synchronization messages using
Network Time Protocol (NTP) or Precision Time Protocol (PTP).
11 citations
TL;DR: This work proposes a solution to estimate the random delay's bias and improve the synchronization accuracy of IEEE 1588, which is easy to implement and is compatible with the current version of the protocol.
Abstract: In the context of the IEEE 1588 Precision Time Protocol (PTP), estimating the delay's bias is a problem that appears in both one-way (using transparent devices) or two-way message exchange mechanisms. For estimating the offset via the two-way message exchange mechanism, it is usually assumed that the expected value of delays in forward and reverse directions are equal. However, this is not a realistic assumption for packet-based wide area networks, where delays in down-link and up-link directions may have a significant difference. In this work, we propose a solution to estimate the random delay's bias and improve the synchronization accuracy of IEEE 1588. Our method is easy to implement and is compatible with the current version of the protocol. We compared our results to no bias correction and the Boot-strap method. In addition to the improvement in synchronization accuracy, our method allows us to update the slave clock recursively. The proposed method works well even in the presence of large frequency offsets and can also be implemented by using different filters.
11 citations
Posted Content•
TL;DR: A detailed threat analysis of the Precision Time Protocol standard is presented, in which the security properties that should be addressed by any security extension are highlighted and an efficient elliptic-curve Public-Key signatures are suggested.
Abstract: The Precision Time Protocol (PTP) aims to provide highly accurate and synchronised clocks. Its defining standard, IEEE 1588, has a security section ("Annex K") which relies on symmetric-key secrecy. In this paper we present a detailed threat analysis of the PTP standard, in which we highlight the security properties that should be addressed by any security extension. During this analysis we identify a sequence of new attacks and non-cryptographic network-based defenses that mitigate them. We then suggest to replace Annex K's symmetric cryptography by an efficient elliptic-curve Public-Key signatures. We implemented all our attacks to demonstrate their effectiveness, and also implemented and evaluated both the network and cryptographic defenses. Our results show that the proposed schemes are extremely practical, and much more secure than previous suggestions.
10 citations
TL;DR: In REVERSEPTP, a clock synchronization scheme for software-defined networks SDNs is introduced, which is based on the Precision Time Protocol PTP, but is conceptually reversed; all nodes switches in the network distribute timing information to a single software-based central node the SDN controller, which tracks the state of all the clocks in a network.
Abstract: We introduce REVERSEPTP, a clock synchronization scheme for software-defined networks SDNs. REVERSEPTPi¾?is based on the Precision Time Protocol PTP, but is conceptually reversed; in REVERSEPTP, all nodes switches in the network distribute timing information to a single software-based central node the SDN controller, which tracks the state of all the clocks in the network. Hence, all computations and bookkeeping are performed by the central node, whereas the 'dumb' switches are only required to periodically send it their current time. In accordance with the SDN paradigm, the 'brain' is implemented in software, making REVERSEPTP flexible and programmable from an SDN programmer's perspective. We present the REVERSEPTPi¾?architecture and discuss how it can be used in typical SDN architectures. Our experimental evaluation of a network with 34 REVERSEPTP-enabled nodes demonstrates the effectiveness and scalability of using REVERSEPTP. Copyright © 2016 John Wiley & Sons, Ltd.
10 citations
29 Sep 2016
TL;DR: The study evaluates the scalability of the WR extensions to PTPv2 for the achievement of ultra-accurate time transfer in networks with linear topology and results are relevant for applications where the scalable of the timing solution is a fundamental ingredient for addressing novel applications and markets.
Abstract: Due to an increase of timing requirements in many actual and future applications, improvements are needed in current synchronization protocols. New scenarios as the Internet of Things or the next generation of 5G Mobile telecommunication networks, where a large number of devices must be interconnected, will stand in need of a better synchronization accuracy and a highly scalable protocol. White Rabbit (WR) is a multi-collaborative open project aiming at the distribution of timing with sub-nanosecond accuracy to thousand of nodes connected within an Ethernet network. It is built as an extension of the Precision Time Protocol (PTP). In order to improve the PTP's accuracy, WR incorporates some enhancements such as a precise link delay model, fine delay phase measurement and clock syntonization over the physical layer. In this paper we focus on the scalability analysis of the WR solution with networks of more than 15 hops connected in a daisy-chain configuration, using the WR Light Embedded Node (WR-LEN) which includes the White Rabbit PTP Core Dual Port. The study evaluates the scalability of the WR extensions to PTPv2 for the achievement of ultra-accurate time transfer in networks with linear topology. The contribution results are relevant for applications where the scalability of the timing solution is a fundamental ingredient for addressing novel applications and markets.
14 Mar 2016
TL;DR: An approach to remove the drift factor of frequency of crystal oscillators on the master and slave clocks without any additional message exchanges added to the conventional PTP protocol and an approach to reduce the asymmetric delays caused by the imbalanced hardware processing latencies between downlink and uplink paths are provided.
Abstract: In this work, an improved Precision Time Protocol (PTP) used to synchronize clocks in industrial Wireless Local Area Network (WLAN) communication systems is addressed. In order to enhance the accuracy of the PTP synchronization, we first provide an approach to remove the drift factor of frequency of crystal oscillators on the master and slave clocks without any additional message exchanges added to the conventional PTP protocol. Then, we show an approach to reduce the asymmetric delays caused by the imbalanced hardware processing latencies between downlink and uplink paths. The simulation results show that the first and second approaches can improve the synchronization accuracy about 30% and 50%, respectively, as compared with the conventional PTP protocol. In addition, the PTP message exchanges are aggregated to reduce transmission overheads for the fast communication systems.
Patent•
07 Oct 2016TL;DR: In this article, the authors propose a protocol for relaying a time synchronizing signal between a master and a slave that transmits PTP (Precision Time Protocol) signals.
Abstract: A communication apparatus, for relaying a time synchronizing signal between a master and a slave that transmit PTP (Precision Time Protocol) signals, stores a first time of the communication apparatus at a point in time that the communication apparatus receives a first time synchronizing signal addressed to the slave, obtains a second time of the master at a point in time that the first time synchronizing signal is transmitted from the master, from the first time synchronizing signal or the like, obtains an amount of offset that is a difference between a reference time of the master and a reference time of the communication apparatus, using the first time as a time of the slave and the second time as the time of the master in a time synchronizing algorithm of the PTP, and corrects the reference time of the communication apparatus using the amount of offset.
Patent•
23 Mar 2016
TL;DR: In this article, an SOPC (System on a Programmable Chip) networking based sub-microsecond level clock synchronizing method is proposed for time synchronization and frequency synchronization, which includes the steps of synchronizing UTC (Universal Time Coordinated) of a remote reference primary parent clock with UTC from an external GPS (global positioning system) clock or a Big Dipper system clock.
Abstract: The invention provides an SOPC (System on a Programmable Chip) networking based sub-microsecond level clock synchronizing method The clock synchronizing method comprises the steps of synchronizing UTC (Universal Time Coordinated) of a remote reference primary parent clock with UTC from an external GPS (Global Positioning System) clock or a Big Dipper system clock; synchronizing each node of a local first-level PTP (Precision Time Protocol) domain with the remote reference primary parent clock through a network switching device which supports a transparent clock function; receiving an optimal primary clock from a network at the same level by each Zynq platform based slave clock which supports IEEE158V2 protocol and gigabit Ethernet for time synchronization and frequency synchronization; when a PTP domain at the next level synchronizes with the primary parent clock through a border clock, performing clock synchronization by a primary clock at the upper level; and during the period that the PTP domain at the same level masters an independent clock synchronization control right, selecting the optimal primary clock as the primary clock of the network at the same level through an optimal primary clock algorithm The invention also provides an SOPC networking based sub-microsecond level clock synchronizing system which adopts the clock synchronizing method
Patent•
13 Jan 2016
TL;DR: In this article, the authors proposed a clock synchronization device consisting of a delay measurement module, a clock extraction module, and a delay compensation module, where delay measurement is used for measuring a delay value of a message passing through a hardware delay node in real time, and transmitting the delay value to the delay compensation mechanism.
Abstract: The invention discloses a clock synchronization device and a clock synchronization method. The device comprises a delay measurement module, a clock extraction module and a delay compensation module, wherein the delay measurement module is used for measuring a delay value of a message passing through a hardware delay node in real time, and transmitting the delay value to the delay compensation module; the clock extraction module is used for extracting a timestamp stamped before a precision time protocol message enters the hardware delay node when the message is determined to be the precision time protocol message, and transmitting the timestamp to the delay compensation module; and the delay compensation module is used for correspondingly performing delay compensation according to the received delay value and the received timestamp. Compared with the delay value, computed as a fixed value, of the precision time protocol (PTP) message passing through a certain hardware delay node, the delay value, measured in real time, of the PTP message passing through the certain hardware delay node is more precise. Therefore, corresponding timestamp regulation can be performed according to the precise delay value and the extracted timestamp, and the synchronization accuracy of the precision time protocol message is further improved.
01 Sep 2016
TL;DR: Redundant Ethernet topologies such as Rapid Spanning Tree Protocol (RSTP), High-availability Seamless Redundancy (HSR) and ParallelRedundancy Protocol (PRP) are used in automation systems to monitor PTP functionality.
Abstract: Redundant Ethernet topologies such as Rapid Spanning Tree Protocol (RSTP), High-availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP) are used in automation systems. Commonly Precision Time Protocol (PTP) is used to synchronize nodes in such networks. The redundant topology can be utilized to monitor PTP functionality — such as to detect asymmetries, non-functional devices and to help during installation and operation.
TL;DR: This study examined how the IEEE 1588 Precision Time Protocol can be used for clock correction to synchronize the sound of all devices in an Ethernet synchronous audio playback system.
Abstract: A Dante network card and development template developed by Audinate were used as a platform for realizing an Ethernet synchronous audio playback system. A personal computer (PC) was connected to each Dante device through a switch hub and Ethernet cable PC to transmit sound before TAS3204EVM was applied in digital signal processing and EQ adjustment for application in a live music concert. The expensive wire and cable currently used in live music concerts can be replaced with an Ethernet cable, substantially reducing costs. To ensure that the Dante devices deliver sound simultaneously, an artificial delay was introduced to enable devices closer to the sound source to delay the playback time while devices farther from the sound source play back sound with the other devices. This study examined how the IEEE 1588 Precision Time Protocol can be used for clock correction to synchronize the sound of all devices. Zero Configuration Networking (ZCN) was used to enable the devices to obtain an Internet Protocol address, and the Multicast Domain Name System was employed to obtain the device names, thus ensuring that User Datagram Protocol control instructions can be correctly delivered to control interdevice channel connections.
Patent•
07 Dec 2016
TL;DR: In this article, a system and a method for video playback synchronization using a precision time protocol (PTP) is presented. But the system is not suitable for the use of multimedia applications.
Abstract: The present invention relates to a system and a method for video playback synchronization system using a precision time protocol, and more particularly to, a system and a method for video playback synchronization system using a precision time protocol, wherein a master server and one or more slave terminals are connected through a network, and the time among the master server and the slave terminals are synchronized by using a precision time protocol (PTP), the system comprising: a calculation unit calculating a time error (Td) of the master server time (Tm) and the slave terminal time (Ts); an extraction unit extracting a moving-picture playback time stamp (hereinafter, referred to as Tstc) from input video data; and a playback unit summing the time error (Td) calculated from the calculation unit and the Tstc extracted from the extracting unit to playback the video data. According to the present invention, since the time among the master server and the slave terminals which are connected through a network are synchronized with each other in order to synchronize the playback of video output from one or more slave terminals, and the video is played back such that time errors calculated while being synchronized during the playback are added to a video playback time of each slave terminal, it is possible to provide a system and method for video playback synchronization system using a precision time protocol in which the playback of each slave terminal can be synchronized.
01 Sep 2016
TL;DR: An overview of the general approach and some key components being standardized as part of both the IEEE 1588 Precision Time Protocol (PTP) and the IETF Network Time Security (NTS) efforts are discussed.
Abstract: Security has historically not been a top consideration for the developers of time synchronization protocols. However, in recent years rising awareness of the overall importance of security in general along with increasing examples of targeted vulnerability analysis and incidents exploiting the underlying weaknesses of existing solutions has increased the demand for standards based security mechanisms for network time synchronization protocols. This paper provides an overview of the general approach and discusses some key components being standardized as part of both the IEEE 1588 Precision Time Protocol (PTP) and the IETF Network Time Security (NTS) efforts. It also discusses the underlying motivation and requirements driving these efforts and identifies some next steps and possible avenues of further investigation.
TL;DR: An embedded protocol stack for a Field Programmable Gate Array (FPGA) capable of high-throughput data transmission and clock synchronization and a versatile stack architecture for the User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) over Internet Protocol (IP) such as Address Resolution Protocol (ARP).
Abstract: State of the art detector readout electronics require high-throughput data acquisition (DAQ) systems. In many applications, e. g. for medical imaging, the front-end electronics are set up as separate modules in a distributed DAQ. A standardized interface between the modules and a central data unit is essential. The requirements on such an interface are varied, but demand almost always a high throughput of data. Beyond this challenge, a Gigabit Ethernet interface is predestined for the broad requirements of Systems-on-a-Chip (SoC) up to large-scale DAQ systems. We have implemented an embedded protocol stack for a Field Programmable Gate Array (FPGA) capable of high-throughput data transmission and clock synchronization. A versatile stack architecture for the User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) over Internet Protocol (IP) such as Address Resolution Protocol (ARP) as well as Precision Time Protocol (PTP) is presented. With a point-to-point connection to a host in a MicroTCA system we achieved the theoretical maximum data throughput limited by UDP both for 1000BASE-T and 1000BASE-KX links. Furthermore, we show that the random jitter of a synchronous clock over a 1000BASE-T link for a PTP application is below 60 ps.
Patent•
25 May 2016
TL;DR: In this article, a voice data processing method, device and system and a controlled device are described, where the time of the controlled device is synchronized with that of the main control device through an IEEE1588 precision time protocol.
Abstract: The invention discloses a voice data processing method, device and system and a controlled device. The voice data processing method is used for the controlled device. The controlled device is connected with a main control device; the time of the controlled device is synchronized with that of the main control device through an IEEE1588 precision time protocol; the main media clock signal of the main control device and the IEEE1588 reference clock signal of the main control device adopt the same frequency source; the voice data processing method comprises following steps: converting a first media voice digital signal into a first network voice digital signal synchronous with the main media clock signal; the first media voice digital signal is the voice digital signal synchronous with the media clock signal of the controlled device; and the first network voice digital signal is sent to the main control device. In application of the technical solution of the invention to a video session system, the demand for the processing capacity of a video session host can be reduced; therefore, more microphones can be cascaded with the video session host; and the scalability of the voice data processing system can be improved.
01 Sep 2016
TL;DR: Conclusions have made that the PTP profiles divergence tendency still presents now in the Time and Frequency (T&F) world.
Abstract: IEEE 1588-2008 protocol, or Precision Time Protocol (PTP) has found it's implementation in different applications for time and frequency distribution through both local and IP-networks. PTP profiles standardized by different international organizations just for adopting PTP to a field existing network are analyzed and compared each other to see a trend of their mutual compatibility providing. Conclusions have made that the PTP profiles divergence tendency still presents now in the Time and Frequency (T&F) world.
Patent•
08 Apr 2016
TL;DR: In this paper, the authors present techniques for a master to distribute AV data encoded with one or more time markers to a plurality of processing nodes, indexed to a precision time protocol (PTP) time stamp used as a time reference.
Abstract: The present aspects relate to techniques of timing synchronization of audio and video (AV) data in a network. In particular, the techniques for a AV master to distribute AV data encoded with one or more time markers to a plurality of processing nodes. The one or more time markers may be indexed to a precision time protocol (PTP) time stamp used as a time reference. In one technique, the nodes extract the time markers to determine an offset value that is applied to a PLL to synchronize AV data packets at a distribution node or a processing node. In another technique the distribution node or the processing node determines the worst case path, which corresponds to a system offset value. The distribution node then reports the system offset value to the AV master, which in turn adjusts the phase based on the report.
01 Nov 2016
TL;DR: This paper proposes to use Timed Colored Petri Nets (TCPN) to model PTP and formally represent with temporal dimension and will verify the model by means of simulation techniques.
Abstract: Precision Time Protocol (PTP) is clock synchronization protocol that is used in computer networks. It is one of the most widely used clock synchronization protocol in the domains where the high degree of precision is required. Accuracy of the PTP goes in the sub-microsecond range. A lot of works have been done for verification and simulation of the protocol. There are still lacks of formal model representations of the PTP in temporal interactions aspects. This paper proposes to use Timed Colored Petri Nets (TCPN) to model PTP and formally represent with temporal dimension. We will verify the model by means of simulation techniques.
01 Sep 2016
TL;DR: It is concluded that clock frequency offset and network transmission delay are the main influence factors for synchronization and the feasibility of maintaining submicrosecond-level synchronization accuracy within multi-level switch topology is proved.
Abstract: This paper proposed a universal method for implementing PTP (Precision Time Protocol) for test systems with the 1000M Ethernet Interface. To achieve the synchronization accuracy of sub-microsecond, the configurable real-time clock and the time stamp module were realized in the programmable logic which makes the PHY and MAC to be free of time stamp functions in the communication link. PTPd (Precision Time Protocol deamon, an open source implementation) was modified and transplanted into the embedded Linux system to realize PTP state machine while the IEEE 1588 IP core device driver was developed to provide the application layer with access to the accurate time-stamp obtained in link layer by IEEE 1588 IP core. This project structure makes the transplantation process concentrate on the time adjustment algorithm design in the application layer regardless of obtaining a precise time stamp in the hardware. The proposed method was evaluated on the Xilinx Zynq-7000 SOC platform by outputting PPS (Pulse Per Second) which can verify the synchronization accuracy of all nodes (master and slaves) in the network. After quantifying the accuracy and stability of the synchronization offset, we concluded that clock frequency offset and network transmission delay are the main influence factors for synchronization and proved the feasibility of maintaining submicrosecond-level synchronization accuracy within multi-level switch topology.
Posted Content•
TL;DR: The implementation of realistic clock noise and its synchronization via PTP in OMNeT++ is discussed and the components presented in this paper are intended to assist engineers with the configuration of PTP networks.
Abstract: Real-time systems rely on a distributed global time base. As any physical clock device suffers from noise, it is necessary to provide some kind of clock synchronization to establish such a global time base. Different clock synchronization methods have been invented for individual application domains. The Precision Time Protocol (PTP), which is specified in IEEE 1588, is another interesting option. It targets local networks, where it is acceptable to assume small amounts of hardware support, and promises sub-microsecond precision. PTP provides many different implementation and configuration options, and thus the Design Space Exploration (DSE) is challenging. In this paper we discuss the implementation of realistic clock noise and its synchronization via PTP in OMNeT++. The components presented in this paper are intended to assist engineers with the configuration of PTP networks.
01 Sep 2016
TL;DR: In this article, the authors provide an update on a joint project employing commercial equipment to send national timing signals through a telecommunication network in the United States using the Precision Time Protocol (PTP).
Abstract: There is a need to back up critical timing infrastructure at the national level. This paper provides an update on a joint project employing commercial equipment to send national timing signals through a telecommunication network in the United States. This experiment connects the UTC(NIST) time scale located in Boulder, Colorado with the UTC(USNO) Alternate Master Clock time scale located at Schriever Air Force Base in Colorado via a telecommunication provider's optical network. Timing signals using the Precision Time Protocol (PTP) were sent in the usual two-way fashion, but each one-way delay was measured, because we had UTC time scales at both ends of the network that were within 10 ns of each other. This part of the experiment is now nearly complete. The experiment was started in April 2014 and extensions of the project will run through the end of 2016. It appears that there is at least one commercial transport mechanism that could serve to back up GPS for time transfer at the 100 ns level. We found that the asymmetry of the PTP time transfer resulted in 10's of microseconds of time transfer error, but that the stability through the entire connection was less than 100 ns, as long as the connection remained complete. This implies that if the time delays of the network could be calibrated, it could maintain under 100 ns accuracy as long as it did not go down. We have established the likely causes of the bias, as well as run simulations of various configurations in a laboratory. Thus, we have some certainty that similar results will apply if this technique were used as a service across the country. While many researchers have shown that fiber can transfer time and frequency with high accuracy, this experiment addresses the practicality of using the US telecom infrastructure for timing.
Patent•
23 Jun 2016
TL;DR: In this article, a time synchronization monitoring method in a communication system that includes a master device and a slave device to which a PTP (Precision Time Protocol) is applied includes a step S4 where the master device 1a determines whether a monitoring time difference (T4-T3) is within a predetermined allowable range, and outputs a result of the determination.
Abstract: PROBLEM TO BE SOLVED: To provide a time synchronization monitoring method, a communication system and a master device, capable of achieving precision time synchronization between a master device and a slave device.SOLUTION: A time synchronization monitoring method in a communication system that includes a master device and a slave device to which a PTP (Precision Time Protocol) is applied includes a step S4 where a slave device 2a transmits a Clock_Req message S3 including information indicating a time T3 at the time T3 based on a slave clock and a master device 1a receives the Clock_Req message at a clock T4 based on a master clock. The master device 1a determines whether a monitoring time difference (T4-T3) is within a predetermined allowable range, and outputs a result of the determination.SELECTED DRAWING: Figure 4
01 Sep 2016
TL;DR: This paper presents a low-cost, re-configurable Modular Intelligent Node for Distribution systems (MIND), which can serve as a sustainable and general-purpose module for monitoring and automation of power distribution systems.
Abstract: This paper presents a low-cost, re-configurable Modular Intelligent Node for Distribution systems (MIND). It can serve as a sustainable and general-purpose module for monitoring and automation of power distribution systems. MIND is designed and built with low-cost hardware, interconnectivity with other modules, and highly reconfigurable design of hardware and software to support newly added monitoring and automation tasks. For tasks requiring limited computational power, MIND uses its local hardware, otherwise it uses the computational power of other MINDS within the same network or cloud services. The tests here show time synchronization and then application of MIND for power quality metering in an IEC 61850 framework. In this study, MIND is synchronized to the UTC time using the IEEE 1588 Precision Time Protocol (PTP) V2 protocol and the RMS calculation is done according to the IEC 6100-4-30 standard. Results show the accuracy of the time synchronization, the ability to track the voltage sags and swells, and the reporting latency.
01 Oct 2016
TL;DR: The proposed PTP switch can meet the microsecond-level requirement for time synchronization in cellular wireless networks and can provide accurate clock distribution along a three-hop path over 1 hour measurement.
Abstract: Software Defined Networking (SDN) is an emerging technology to enhance flexible control on networks through abstraction of lower-level switch functionality. Recently using SDN to construct mobile backhaul networks has attracted a lot of attention. Although IEEE has defined IEEE 1588 Precision Time Protocol (PTP) for providing accurate time synchronization in Ethernet networks, how to distribute accurate time in SDN to facilitate synchronization among wireless base stations is still not clear. In this paper, we present an implementation of a NetFPGA based PTP module to support time-synchronized SDN. The PTP module can be embedded inside an SDN switch or can be placed as an external add-on module to an SDN switch. Both solutions can turn a PTP unaware switch into PTP aware. In our system, an SDN controller can configure the PTP module to determine the routing paths for clock distribution. We have developed a frequency compensation circuit to increase the accuracy. In addition, a moving average technique is applied to stabilize the clock output. Experimental results show that our NetFPGA based SDN switch can provide accurate clock distribution with maximum 50 nsec deviation along a three-hop path over 1 hour measurement. The performance of the proposed PTP switch can meet the microsecond-level requirement for time synchronization in cellular wireless networks.