Abstract: Utilities and operators are looking for new packet-based time synchronization solutions with Global Positioning System (GPS) level accuracies beyond those attainable using the traditional packet method like Network Time Protocol (NTP). Advances in high speed packet switching and communications over wide areas has made time synchronization over packet networks an attractive solution for many industries. This paper provides a tutorial discussion on the role of time synchronization in a power system environment. It provides an overview of current methods for time synchronization and also emerging packet-based alternatives that provide comparable performance over high speed communication links. These newer solutions have a number of potential applications in power system automation and also for wide area measurement systems (WAMS).

Abstract: The invention discloses an embedded-type high-precision network time server system which is composed of a clock source switch-on module, a clock source decoding module, a microsecond time counting module, a time information register module, a network time server port module, a network time server module, a system storage module and a system remote access module. The embedded-type high-precision network time server system is capable of automatically choosing global position system signals, range instrument group (IRIG-B) codes or big dipper signals as system external time reference signals according to signal quality, and microsecond-level time is produced through constant temperature crystal oscillator in the interior of the embedded-type high-precision network time server system, system reference time source precision is improved, and at the same time network time protocol (NTP), simple network time protocol (SNTP) and daytime protocol (daytime) are provided for carrying out time calibration to other clients in the network. In addition, system network addresses can be further inquired reversely and set by the embedded-type high-precision network time server system through remote manners, and network management difficulties can be reduced. The embedded-type high-precision network time server system is capable of achieving network time timing service with o.1 millisecond-level error and making up defects that the traditional time server time reference signals are difficult to change, low in time precision and inconvenient to manage.

Abstract: The invention provides a positioning method and device. The positioning method includes the steps of obtaining a time server list maintained by a terminal and an A-GPS server list maintained by the terminal when first positioning is performed or positioning time exceeds a preset time threshold value, determining a time server with the shortest response time in the time server list and an A-GPS server with the shortest response time in the A-GPS server list, and positioning the terminal according to the time server with the shortest response time and the A-GPS server with the shortest response time. The search speed and the speed for obtaining the current time on the time server in the positioning process are improved, and therefore the positioning speed is improved.

Abstract: We present a new software-based clock synchronization scheme that provides high precision time agreement among distributed memory nodes. The technique is designed to minimize variance from a reference chimer during runtime and with minimal time-request latency. Our scheme permits initial unbounded variations in time and corrects both slow and fast chimers (clock skew). An implementation developed within the context of the MPI message passing interface is described, and time coordination measurements are presented. Among our results, the mean time variance for a set of nodes improved from 20.0 milliseconds under standard Network Time Protocol (NTP) down to 2.29 secs under our scheme.

Abstract: Time synchronization is a key requirement in many automation systems. There are currently two predominant technologies for time synchronization in automation systems: SNTP (Simple Network Time Protocol) and PTP (Precision Time Protocol). PTP is the preferred technology and has several advantages over SNTP including far better accuracy in most if not all situations. However, legacy systems in many situations have to rely on SNTP. This is a challenge since the requirements on accuracy increase while the systems become larger and more complex. Thus, it is of interest to investigate what kind of accuracy level can be expected with the use of SNTP in modern switched networks. This paper shows that accuracies at the milliseconds level can be achieved for small networks. It is also analyzed how the network infrastructure and the end nodes contribute to the measured inaccuracy.

Abstract: The utility model provides a marine local area network time unification system which comprises a time server, a time synchronization client, a display screen device, a GPS receiver and a GPS antenna, wherein the GPS antenna is connected with the GPS receiver, the GPS receiver and the time server are connected through serial port equipment, the time synchronization client is in communication connection with the time server through an IP address of a configuration server, and the display screen device is respectively connected with the time server and the time synchronization client. The marine local area network time unification system has the following beneficial effects: UTC time synchronization service, Beijing time synchronization service and dynamic local time synchronization service can be simultaneously provided for users of a local area network of mobile ships, the synchronization precision can reach a millisecond level, and the various business application requirements of ships can be fully met; and whether the time synchronization client in a local area network is synchronous can be monitored and displayed at regular time to evaluate the stability and the precision of system equipment, and statistical analysis can be carried out easily.

Abstract: In modern real-time Ethernet networks for substation automation, several protocols are adopted to guarantee the strict synchronization and availability requirements imposed by applications. The management of these networks is more and more complex, since several (cross-influencing) configuration parameters affect the performance of the overall system. In this paper the attention has been focused on synchronization systems applied to redundant network infrastructures for substation automation: in these systems the reconfiguration of the network after a fault may affect the synchronization performance of the nodes. As a test case the SNTP (Simple Network Time Protocol) synchronization has been simulated (with different fault conditions) using two network topologies typically adopted in Substation Automation Systems: RSTP (Rapid Spanning Tree Protocol) and PRP (Parallel Redundancy Protocol). The performance of the two cases has been compared by means of suitable metrics: PRP, as opposed to RSTP, guarantees seamless synchronization performance in case of a single fault.

Abstract: An IEEE 1588 based application scheme was proposed to achieve accurate time synchronization for a deep seafloor observatory network based on the communication topological structure of the Zhejiang University Experimental and Research Observatory. The principles of the network time protocol (NTP) and precision time protocol (PTP) were analyzed. The framework for time synchronization of the shore station, undersea junction box layer, and submarine science instrument layer was designed. NTP and PTP network signals were decoded by a PTP master clock on a shore station that receives signals from the Global Positioning System and the BeiDou Navigation Satellite System as reference time sources. These signals were remotely transmitted by a subsea optical-electrical composite cable through an Ethernet passive optical network. Accurate time was determined by time synchronization devices in each layer. Synchronization monitoring experiments performed within a laboratory environment indicated that the proposed system is valid and has the potential to realize microsecond accuracy to satisfy the time synchronization requirements of a high-precision seafloor observatory network.

Abstract: Methods and apparatus for a secure time service are disclosed. A time server including a time source, a cryptographic key and a cryptographic engine is instantiated within a provider network. A time service endpoint receives a timestamp request from a client. The endpoint transmits a representation of the request to the time server, and receives, from the time server, an encryption of at least a timestamp generated using the time source. A response comprising the encryption of at least the timestamp is transmitted to the requesting client.

Abstract: A distribute control requires to maintain time synchronization to the degree of precision depending on a particular application domain. Many large distributed systems employ Ethernet or even full TCP/IP stack for communication. Two prevalent protocols are used for clock synchronization in these networks, in particular, Network Time Protocol (NTP) and Precise Time Protocol (PTP). In this short paper, we present a method for practical performance evaluation of clock synchronization within a distributed environment consisting of nodes running a commodity real-time operating system. The results of measurement provide us a hint on the degree of synchronization that can be practically achieved among the set of distributed devices. The main contribution of this paper is to provide a simple method for practical evaluation of synchronization methods for a distributed control system and presenting some preliminary data from the measurement. A complete result set may be used, e.g., for defining a performance estimation functions in a platform-based design approach to networked control systems.

Abstract: The invention relates to the technical field of communication and internet and particularly relates to a method for achieving synchronization of a network device and a time server Under the condition that a server address is not required to be preset on the network device, discovery messages are transmitted to the network through a network device broadcasting mode, the address of the time server of the network can be obtained, the time synchronization of the network device and the server can be achieved, the step that the time server address is preset on the network device is omitted, and the automatic motility and the intellectualization of the time synchronization of the network device in the network and the network are improved

Abstract: In order to improve the synchronization accuracy of NTP(Network Time Protocol) for switch-oriented power monitoring networks,an improved protocol,SN-NTP(Switch Networks-NTP),is proposed,which enhances the synchronization accuracy to 17 times the original theoretically.SN-NTP is based on the priority scheduling foundation of switch protocol IEEE802.1p.First,NTP client continuously sends the short packets with higher priority to NTP server to block the switch path and make other data packets in waiting state.Then,NTP client sends NTP request packet with highest priority to NTP server to seize the switch path of short packets.By the above two steps,the maximum waiting time of request packet under SN-NTP becomes one seventeenth of that under NTP and the synchronization accuracy is improved.SN-NTP performance test of ship power monitoring network shows that the synchronization accuracy is improved to 15 to 24 times the original,coinciding with theoretical analysis.

Abstract: The invention relates to the network technology, particularly to the communication network time synchronization technology. An application of a precision time protocol to a smart substation comprises the precision time protocol operating in the smart substation, an ordinary clock, a boundary clock and a management node, wherein the ordinary clock is only provided with a communication port of the precision time protocol, while the boundary clock is provided with more than two communication ports of the precision time protocol, and each communication port of the precision time protocol provides independent precision time protocol communication. An accurate clock synchronization protocol related with network communication, local calculation and distributed objects in a measurement and control network is defined, has the advantages that high-accuracy synchronization at the submicrosecond level can be achieved, and the protocol is incomparable for the network time protocol (NTP) with the synchronization accuracy only up to the millisecond level.

Abstract: Network time protocol (NTP) has become widely used across the Internet to synchronize clocks on computers and, more recently, on a wide variety of handheld devices. You are using NTP on a daily basis without even knowing it?when you set your mobile phone to get its time from the local network, you are linking into a global network of NTP servers that coordinate time across the entire Internet.

Abstract: In peer-to-peer (P2P) overlay networks, a group of n (= 2) peer processes have to cooperate with each other. Each peer directly sends messages to every peer and receives messages from every peer in a group. In group communications, each message sent by a peer is required to be causally delivered to every peer. Types of logical clocks like linear clock (LC) and vector clock (VC) are used to causally order messages. Some pair of messages not to be causally ordered are unnecessarily ordered since message length is O(1) in the LC protocol. On the other hand, no message is unnecessarily ordered in the VC protocol. However, the vector clock cannot be adopted in a scalable group due to the message length O(n). Recently, processes on each computer can read more precise physical clock which is synchronized with a time server in NTP. In this paper, we discuss how to causally deliver messages in a scalable group with hybrid clock (HC) which takes advantage of LC and PC in order to reduce the number of messages unnecessarily ordered. The HC protocol is implemented and some experimentations are presented in this paper. We show unnecessarily ordered messages can be reduced in the HC protocol compared with the LC protocol through the experimentations.

Abstract: This is a network based application, while transferring file from client to server attackers may hack the files. Internet grows rapidly since it was created. With this network, users can share their information. The use of such networks had a tremendous growth. Meanwhile, attacks to such networks also have increased. There are several types of such attacks. An attacker can possibly launch a DoS attack by studying the flow or path of network. Earlier solutions for this problem are based on port-hopping between single pair of processes which are synchronous. Adversaries have the ability to identify open ports and launch directed attacks to those ports. This problem is named as Port-Hopping. The Solution proposed in this paper extend port-hopping to support multiparty applications. The server communicate with multiple clients in a port-hopping manner without the need for group synchronization. The solutions are simple, based on each client interacting with the server independently of the other clients, without the need of acknowledgments or time server.

Abstract: The invention relates to a time synchronization technique of a relevant server in an internet, in particular to a method for time synchronization of a network time protocol (NTP) server used for an internet monitoring system. The overall technical scheme of the method is that time synchronization with each server is carried out through additional arrangement of NTP-S time synchronization servers, the time synchronization is carried out between the NTP-S time synchronization servers and each relevant server, the time synchronization is carried out between the NTP-S time synchronization servers and each NTP-T server in a fixed period, problems of blocking and delaying caused by the fact that a distance between an upper layer NTP-T server and each server is long and number of visiting users is large are solved, and time of each server can effectively synchronized. The method has the advantages of achieving time synchronization of each server, avoiding confusion of clocks of each server, and accordingly enabling each relevant server based on the time synchronization to accurately and stably work. The method is particularly suitable to internet time synchronization servers.

Abstract: The invention discloses a time synchronization method of an observation instrument of ocean bottom observatory network and the synchronization method based on network time protocol (NTP) and picture transfer protocol (PTP) technology. An NTP synchronization signal and a PTP synchronization signal which are output by a primary connecting junction box are input to a second-layer switchboard of a secondary connecting junction box. The PTP synchronization signal which is output by the second-layer switchboard is received by PTP from a clock and decodes and outputs a P2P-streaming (PPS) signal. The signal PPS signal conducts quantative allocation and power amplification by a PPS distribution amplifier. The PPS signal, the NTP synchronization signal and the PTP synchronization signal are transmitted to the observation instrument through a cable. An inner circuit of the observation instrument isolates and amplifies the PPS signal so as to achieve driving capability. Meanwhile, the NTP synchronization signal or the PTP synchronization signal are encoded and time synchronization is achieved. The time synchronization method of the observation instrument of the ocean bottom observatory network takes great importance to achieving accurate time of observation instrument such as a seismometer.

Abstract: The invention provides a time synchronizing system, which comprises a main station time server, sub-station time servers, a multiple-E1 (European basic muliplex rate)/PTP (precision time protocol) time channel adapter and single-E1/PTP time channel adapters, wherein the multiple-E1/PTP time channel adapter exchanges information with the single-E1/PTP time channel adapters through a transmission network, so as to realize time synchronizing. Since the number of equipment participating in the whole time synchronizing process is little, and the data exchange is only carried out among the main station time server, the multiple-E1/PTP time channel adapter, the single-E1/PTP time channel adapters and the sub-station time servers, the delay is greatly reduced, and the time synchronizing precision is greatly improved.

Abstract: The embodiment of the invention provides a time synchronization method and a time synchronization device The time synchronization method comprises the following steps of actively acquiring a standard time from a time server when a palm computer is successfully connected with the network of a time server; and synchronizing the local time of the palm computer with the standard time According to the time synchronization method and the time synchronization device, in the situation that the network is normally connected, the standard time can be obtained from the time server by the time synchronization device in a built-in palm computer, so that synchronous setting on the local time of the palm computer with the standard time is finished According to a time synchronization process, manual participation of a user is not needed, the accuracy of the local time of the palm computer can be greatly improved, and convenience is provided for the user

Abstract: In an energy management system for a data center, intelligent power distribution units are synchronized by a time server. Measurements carried out by the intelligent power distribution units are commenced and stopped synchronously. Each intelligent power distribution unit carries out a calculation based upon the Unix Epoch Time of receipt of a sampling command from the energy management system.

Abstract: PROBLEM TO BE SOLVED: To solve the problem of not capable of receiving GPS signals in a tunnel when GPS is used to synchronize transmission timing between each base station, and to obtain a synchronization method without NTP (Network Time Protocol) device.SOLUTION: In a radio communication system according to the present invention, a first base station recognizes that next synchronous timing is after the lapse of 1-t1/2 second after a reference signal reception time. Also, a second base station recognizes that next synchronous timing is after the lapse of 1-(t1/2+t2/2) second after a reference signal reception time. A third base station recognizes that next synchronous timing is after the lapse of 1-(t1/2+t2/2+t3/2) second after a reference signal reception time. As such, each base station can perform synchronization using the lapse of (1-channel delay time) after a reference signal reception time to be the reference signal time of a central device.

Abstract: NTP accuracy at the server is masked to the user by internet and other asymmetries, and can also be degraded by the properties of and load on the client computer. This paper provides some examples and attempts to quantify the performance.

Abstract: The distributed control systems are applied widely in communication, navigation and power fields. With growing in both systems complexity and speed of data exchange, the real time performance of systems is required. Existing clock synchronization techniques include those for wide-area network (WAN) applications with large propagation delays, e.g., the Network Time Protocol (NTP), and those for control systems over local-area networks (LANs), e.g., the IEEE 1588 Precise Time Protocol (PTP). However, NTP-like protocols have only millisecond-scale precision, which is too coarse for many LAN applications such as instrument monitoring systems, high-quality digital audio systems and sensor networks. The 1588 PTP like protocols, which are still under development, require support of a highly precise hardware clock. The key point of the existing Ethernet test and measurement is that the method needs to achieve precision clock synchronization between different terminals. In this paper, an improved method is proposed with consideration of the time drift and propagation delay, expressing master-slave synchronization as a linear relationship and inducting the line of least squares fitting algorithm that traded as linear matrix form. The precision time protocol (PTP) is also analyzed in this paper. The experiment results show that the synchronization accuracy reaches sub-microsecond grade, which is the same as the PTP. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2832 Full Text: PDF

Abstract: A method for adding a network clock to a modem comprises the steps as follows: the modem is communicated with a time server to acquire network time; taking the acquired network time as a standard, the local system time is synchronized; and a timer is started, and an alarm is given out when the timing time is up. By adopting the method disclosed by the invention, through the time server, the local system time is updated; the timer is started in a local system, the alarm is given out when the timing time is up, thus a network clock function is achieved, and further the network clock function of the modem is achieved.

Abstract: The utility model provides a multi-stage time synchronizing system mainly including a second-stage time server and a third-stage time server. The second-stage time server mainly receives PTP signals sent by a main clock for time synchronization and sends the PTP signals to the three-stage time server. The third-stage timer server receivers the PTP signals sent from the second-stage time server for time synchronization. The second-stage time server includes a boundary clock, a synchronous digital hierarchy algorithm module and a PTP output port. The synchronous digital hierarchy algorithm module is used for tracking and synchronizing PTP signals from a synchronous digital hierarchy network accurately and stably. The boundary clock is used for supplementing and correcting the PTP signals received from the main clock by the synchronous digital hierarchy algorithm module by utilizing pulse per second generated when upstream signals are synchronized to the main clock in the second-stage timer server and sending new PTP signals generated after the supplementation and correction to the PTP output port. The PTP output port sends the PTP signals to the third-stage time server.

Abstract: We consider a stochastic model of clock synchronization in a wireless network consisting of N sensors interacting with one dedicated accurate time server. For large N we find an estimate of the final time sychronization error for global and relative synchronization. Main results concern a behavior of the network on different time scales $t=t_N \to \infty$, $N \to \infty$. We discuss existence of phase transitions and find exact time scales on which an effective clock synchronization of the system takes place.

Abstract: The purpose of this paper is to describe a problem of precise time synchronization between elements in a distributed automation system. At the beginning, to present current state of art, Network Time Protocol is described. Further, the main focus is placed on describing this problem in context of systems in which interconnection is done with RS-485 serial communication. The issue is presented based on the solution used for active power calculations in a modular motor control system. In this case, to determine the power factor, precise calculation of the delay between voltage and current zero crossings measured by discrete modules is required. The developed solution of this problem can be extended to most of distributed systems interconnected with a serial interface. Further in the article the method to validate algorithm accuracy for different voltage and current plots was presented.

Abstract: The Metrological laboratory for angle and length calibration (ML160) uses a geodetic class double-frequency GPS receiver as a time standard. Time correction terms are delivered to laboratory computers via Network Time Protocol (NTP). We tested NTP parameters within the intranet environment with the respect to the quality of GPS measurements. The 24 hours experiment showed that the characteristics of time delivered to NTP clients is influenced by the quality of GPS data received by our Stratum 1. We suggested methods for improving the reliability of GPS disciplined time corrections. Jitter 13TF054