Showing papers on "Precision Time Protocol published in 2012"

Use of Precision Time Protocol to Synchronize Sampled-Value Process Buses

Abstract: Transmission smart grids will use a digital platform for the automation of high-voltage substations. The IEC 61850 series of standards, released in parts over the last ten years, provide a specification for substation communication networks and systems. These standards, along with IEEE Std 1588-2008 Precision Time Protocol version 2 (PTPv2) for precision timing, are recommended by both the IEC Smart Grid Strategy Group and the National Institute of Standards and Technology Framework and Roadmap for Smart Grid Interoperability Standards for substation automation. IEC 61850, PTPv2, and Ethernet are three complementary protocol families that together define the future of sampled-value (SV) digital process connections for smart substation automation. A time synchronization system is required for an SV process bus; however, the details are not defined in IEC 61850-9-2. PTPv2 provides the greatest accuracy of network-based time transfer systems, with timing errors of less than 100 ns achievable. The suitability of PTPv2 to synchronize sampling in a digital process bus is evaluated, with preliminary results indicating that steady-state performance of low-cost clocks is an acceptable 300 ns but that corrections issued by grandmaster clocks can introduce significant transients. Extremely stable grandmaster oscillators are required to ensure that any corrections are sufficiently small that time synchronizing performance is not degraded.

Evaluation of Time Gateways for Synchronization of Substation Automation Systems

Abstract: The International Electrotechnical Commission (IEC) 61850 standard is widely used in substation automation system (SAS), even if some aspects related to the network-based time synchronization are still under investigation. The latest version of the IEC 61850 standard introduces IEEE 1588 Precision Time Protocol (PTP) for distributing time in the station and process buses, in addition to the previously used Simple Network Time Protocol (SNTP). Some time synchronization problems may arise when mixing old and new IEC 61850 devices in the same system; the IEEE 1588 PTP and SNTP technologies have somewhat different time representations and synchronization schemes, requiring time gateways for smooth integration. This paper introduces and compares the performance of some compact time gateways with different implementation architectures. All the examined gateways have the same external structure: They are transparent two-port devices which are inserted in the last network link between the switch and the end device, in order to perform the time conversion from IEEE 1588 PTP to SNTP. The time gateways are built using the same hardware platform based on a Field Programmable Gate Array that enables the creation of real embedded prototypes. The experimental results show that all the considered time gateways are applicable to SAS, but some of them have better performance than others in terms of synchronization accuracy. Moreover, the authors identify the bottleneck in the SNTP implementation of the time gateway architecture. A careful analysis of the behavior of SNTP is proposed, and useful suggestions for trading off between synchronization accuracy and time gateway complexity are given.

Pluggable synchronization clocks, networks, systems and methods related thereto

Abstract: A pluggable synchronization clock comprising: a pluggable transceiver and a system clock synchronization subsystem embodied within the pluggable transceiver. The system clock synchronization subsystem may be adapted to implement a packet based precision time protocol. The system clock synchronization subsystem may be further adapted to include a time stamp unit capable of adding a time stamp to a frame using hardware or software.

Highly Accurate Timestamping for Ethernet-Based Clock Synchronization

Abstract: It is not only for test and measurement of great importance to synchronize clocks of networked devices to timely coordinate data acquisition. In this context the seek for high accuracy in Ethernet-based clock synchronization has been significantly supported by enhancements to the Network Time Protocol (NTP) and the introduction of the Precision Time Protocol (PTP). The latter was even applied to instrumentation and measurement applications through the introduction of LXI. These protocols are usually implemented in software; however, the synchronization accuracy can only substantially be improved by hardware which supports drawing of precise event timestamps. Especially, the quality of the timestamps for ingress and egress synchronization packets has a major influence on the achievable performance of a distributed measurement or control system. This paper analyzes the influence of jitter sources remaining despite hardware support and proposes enhanced methods for up to now unmatched timestamping accuracy in Ethernet-based synchronization protocols. The methods shown in this paper reach sub-nanosecond accuracy, which is proven in theory and practice.

Clock synchronization based on predefined grandmaster

Abstract: In one embodiment, a method includes storing a grandmaster candidate list at a precision time protocol device, receiving a message identifying a synchronization hierarchy for use in clock synchronization at the precision time protocol device, the synchronization hierarchy having a grandmaster, determining if the grandmaster identified in the message is on the grandmaster candidate list, and performing synchronization in accordance with the synchronization hierarchy at the precision time protocol device if the grandmaster identified in the message is on the grandmaster candidate list. An apparatus is also disclosed.

Evaluation of Precision Time synchronisation methods for substation applications

Abstract: Many substation applications require accurate time-stamping. The performance of systems such as Network Time Protocol (NTP), IRIG-B and one pulse per second (1-PPS) have been sufficient to date. However, new applications, including IEC 61850-9-2 process bus and phasor measurement, require accuracy of one microsecond or better. Furthermore, process bus applications are taking time synchronisation out into high voltage switchyards where cable lengths may have an impact on timing accuracy. IEEE Std 1588, Precision Time Protocol (PTP), is the means preferred by the smart grid standardisation roadmaps (from both the IEC and US National Institute of Standards and Technology) of achieving this higher level of performance, and integrates well into Ethernet based substation automation systems. Significant benefits of PTP include automatic path length compensation, support for redundant time sources and the cabling efficiency of a shared network. This paper benchmarks the performance of established IRIG-B and 1-PPS synchronisation methods over a range of path lengths representative of a transmission substation. The performance of PTP using the same distribution system is then evaluated and compared to the existing methods to determine if the performance justifies the additional complexity. Experimental results show that a PTP timing system maintains the synchronising performance of 1-PPS and IRIG-B timing systems, when using the same fibre optic cables, and further meets the needs of process buses in large substations.

Time synchronization method and system for synchronous messages of IEEE1588 (Precision Time Protocol) master-slave clocks of intelligent transformer substation

Abstract: The invention discloses a time synchronization method and a time synchronization system for synchronous messages of IEEE1588 master-slave clocks of an intelligent transformer substation. The method comprises the following steps of: establishing a master clock synchronous message, and sending the timestamp t1 of the sending moment of the message to the clock in a broadcasting manner; recording a receiving moment t2 of the master clock synchronous message; recording an absolute receiving moment TT2 when the master clock synchronous message is received by a slave clock; establishing a slave clock responding message, sending the slave clock responding message to the master clock in a peer-to-peer manner, and recording the timestamp t3 of the sending moment of the message; recording an absolute sending moment TT3 when the slave clock sends the clock responding message; recording an acquiring moment t4 when the master clock acquires the message; calculating a time deviation, and calculating asymmetry errors according to the timestamp t1, the absolute receiving moment TT2, the absolute sending moment TT3 and the acquiring moment t4; and carrying out time correction on the slave clock by the time deviation and the asymmetry errors. According to the time synchronization method and the time synchronization system for synchronous messages of IEEE1588 master-slave clocks of the intelligent transformer substation, the influences of the asymmetry errors can be eliminated, and the time synchronization precision of the master-slave clocks is improved.

Precision time protocol offloading in a PTP boundary clock

Abstract: In a data network node implementing the Precision Time Protocol, low-touch PTP packet processing functions are moved from a PTP processing unit into an efficient network processor. An example network node thus includes a time -transfer protocol processing unit that generates negotiation messages and management messages for a time-transfer protocol and forwards said negotiation and management messages to one or more clients. The network node also includes a separate network processor unit, which is adapted to: receive a configuration message from the time-transfer protocol processing unit, the configuration message comprising stream configuration data for a first type of repetitive time -transfer message; generate a plurality of time-transfer messages according to the first type of repetitive time -transfer message, using the stream configuration data; and forward said plurality of time-transfer messages to the one or more remote network nodes, via the one or more line ports.

A generic synchronized data acquisition solution for distributed automation systems

Abstract: This paper presents a novel approach for data acquisition in distributed, heterogeneous automation systems as a basis for new condition monitoring, anomaly detection and visualization applications. The described solution enables process data acquisition in real time Ethernet systems, using the Precision Time Protocol (PTP) from IEEE 1588 for synchronization and the OPC Unified Architecture for data presentation. As a proof of concept the architecture is implemented using standard hardware components and a x86/x64 architecture without any special operating system. As verified later this setup already achieves a synchronization accuracy of <10ms, sufficient for the majority of production processes to be monitored.

System and method for passively determining own position listening to wireless time synchronization communications

Abstract: The system and method of the present invention provides a mobile node (e.g., target), such as an aircraft, vehicle or mobile piece of equipment, the ability to determine its own position by passively listening to wireless time synchronization communications, such as IEEE 1588 Precision Time Protocol (PTP) messages, exchanged between nodes over a wireless network.

Method and device for time synchronization convergence based on precision time protocol

Abstract: The invention discloses a method and a device for time synchronization convergence based on the precision time protocol. The method comprises the followings steps of: interacting a synchronization message with a grandmaster clock node at each passive port by a slave clock node, performing time synchronization calculation, and establishing and maintaining the alternative time information corresponding to the passive port according to a result of the time synchronization calculation; when the slave clock node detects that an upstream clock synchronization network of a slave port or any passive port undergoes topology change, triggering BMC (Best Master Clock) computation, determining a port with the optimal clock priority information according to a BMC computation result, if the port with the optimal clock priority information is a passive port, switching the passive port into a slave port, and performing time synchronization processing on a local clock according to the alternative time information corresponding to the passive port. With the method and the device, the out-of-step time of the slave clock node can be reduced during the topology change of the network.

Method for improving accuracy in computation of one-way transfer time for network time synchronization

Abstract: A method for improving accuracy in the computation of a one-way transfer time between two networked devices. In one aspect, variability in time transfer latency that is caused by cache loading, data structure setup time, and scheduling variability in software is reduced by initiating a first sequence of loading data structures into cache and priming scheduling, and then initiating a second sequence of calibrating the timing of a subsequent synchronization message so that the completion of the first sequence occurs just in time for the reception of the synchronization message. The method is applicable for any network time synchronization protocol, including Network Time Protocol (NTP) and Precision Time Protocol (PTP).

Power system time synchronization device based on precision time protocol

Abstract: The utility model discloses a power system time synchronization device based on a precision time protocol, which comprises an E1/Ethernet network bridge, a 1588 clock signal receiving unit, a message analyzing module, an embedded microprocessor, a local clock signal generating unit and an output interface unit, wherein the E1/Ethernet network bridge converts a 1588 master clock time message conforming to an SDHE1 protocol into a TCP/IP (transmission control protocol/internet protocol) protocol, then the 1588 master clock time message is analyzed by the message analyzing module so as to obtain a 1588 clock signal; the embedded microprocessor is provided with a time delay compensation module for calculating to obtain asymmetric switching delay of an SDH (synchronous digital hierarchy) network; the local clock signal generating unit locks the 1588 clock signal, and performs time delay compensation on the 1588 clock signal so as to generate a local clock signal, and then outputs the local clock signal to the output interface unit. According to the power system time synchronization device, IEEE1588 master clock time message signals are taken as an input source, and the asymmetric handover delay of the SDH network is eliminated, so that compared with the coordinated universal time, 1 microsecond is preceded, thereby meeting the synchronization accuracy requirements of power systems.

Latency determination in substation networks

Abstract: The present disclosure relates to latency determination in a substation network. One aspect relates to a method being performed in a first electronic device of the substation network. Another aspect relates to a method being performed in a relay device of the substation network. Yet another aspect relates to a method being performed in a second electronic device of the substation network. Latency is determined using a precision time protocol, such as the IEEE 1588v2 protocol. However, no GPS based master clock timing is required. Instead at least one data value is included as payload in a message of the precision time protocol. The relay device adds a residence time duration and a link latency to the message. The message is then forwarded to the second electronic device. A corresponding first electronic device, relay device, and second electronic device as well as a computer program and computer program product are also provided.

L-PTP: A novel clock synchronization protocol for Powerline networks

Abstract: This paper proposes a Lightweight version of the Precision Time Protocol, called L-PTP, for implementation on Powerline communication systems. The aim of this novel protocol is to reduce the number of messages exchanged to achieve synchronization, without penalizing its quality. L-PTP introduces several modifications to the original PTP and can be implemented on COTS devices. The paper focuses on the protocol and on the benefits of its combination with a virtual clock computation performed by a dynamic clock synchronization algorithm.

Method and system for robust precision time protocol synchronization

Abstract: A method and system for maintaining clock synchronization in a communication network having multiple clocks are disclosed. According to one aspect, the invention provides a first precision time protocol (PTP) instance and second PTP service instance. Dynamic PTP parameters and tuning PTP parameters are periodically cloned from the first PTP service instance to the second PTP service instance substantially in real time.

Clock synchronizing method for NTP network and PTP network

Abstract: The invention discloses a clock synchronizing method for an NTP (Network Time Protocol) network and a PTP (Precision Time Protocol) network, which comprises the following steps: a PTP network side is configured as a master clock, an NTP network side is configured as a slave clock, and a message processing server is arranged between the master and slave clocks; a clock synchronizing message sent from the PTP network side is received by the message processing server, converted into message with an NTP message format, and finally transmitted to the NTP network side; and after response message sent from the NTP network and for the clock synchronizing message, the response message is converted into delay request message with a PTP message format, and the delay request message is transmitted to the PTP network side. The method achieves the clock synchronizing of the NTP network and the PTP network, enables the most conventional NTP network can be communicated with the PTP network, and obtains technical effects including cost conversation and precision improvement.

Testing phasor measurement units using IEEE 1588 precision time protocol

Abstract: As the electric power grid is changing to a smarter more dynamically controlled system, there is increasing need for measurements that show the global status of the system for wide-area monitoring and control. These measurements require time synchronization across the grid. This synchronization is obtained by the use of GPS clocks. As the number of such synchronized devices increases there is a need to have an efficient, accurate, and reliable method of time distribution within power substations. The power industry is increasingly turning to the use of IEEE 1588 network Precision Time Protocol to meet this need in substation Intelligent Electronic Devices (IEDs). This paper examines this need in relation to the use of Phasor Measurement Units. This also paper describes the errors associated with this protocol and its application to the calibration of PMUs.

Ethernet passive optical network (EPON) system and method for realizing end-to-end transparent clock in system

Abstract: The invention discloses an Ethernet passive optical network (EPON) system and a method for realizing an end-to-end transparent clock (E2ETC) in the system, wherein the method effectively reduces the cost of the EPON system. The method comprises the steps that: when precision time protocol (PTP) information is received, a first network unit records first time of receiving information and places the recorded first time in the PTP information and transmits the PTP information to a second network unit; and the second network unit receives the PTP information, wherein the detention time of the PTP information which is calculated according to the first time and the current time is carried in the PTP information which is transmitted to lower equipment or upper equipment. By adopting the technical scheme, the existing EPON system equipment is fully utilized, the E2ETC function in the IEEE1588-2008 protocol is realized under the situation that additional hardware assistance is required, the application scenario of the EPON system is satisfied, the cost of the EPON system is truly and effectively reduced and certain economic benefits are brought about.

FPGA-based embedded system architecture for power quality measurements

Abstract: The main objective of this paper is to describe a technique for optimize the capturing and processing of voltage and current signals at various points of the power system. The FPGA enables parallel processing of multiple signals. We present preliminary results with FPGA-based embedded system architecture for six-processing signals. A second objective is use of Precision Time Protocol to Synchronise Sampled Value with high precision. Therefore, we use a Software Based IEEE 1588-2008 for synchronization of the captures of event for Power Quality measurements.

Method and device for monitoring time synchronization

Abstract: Disclosed are a method and a device for monitoring time synchronization, which relate to the communications technology, so as to solve the problem in the prior art that time synchronization cannot be monitored in real time. The technical solution provided in an embodiment of the present invention comprises: receiving a precision time protocol 1588v2 time signal, and acquiring a precision time protocol 1588v2 time stamp of the precision time protocol 1588v2 time signal; performing frequency locking and phase locking on the precision time protocol 1588v2 time stamp, so as to obtain a precision time protocol 1588v2 pulse per second (PPS) of the precision time protocol 1588v2 time signal; performing phase detection on the precision time protocol 1588v2 PPS and a satellite PPS of a satellite signal, so as to obtain a decimal part of a precision time protocol 1588v2 time deviation of a base station; and reporting the decimal part of the precision time protocol 1588v2 time deviation. The embodiments of the present invention may be applied in industrial automation, measurement, and communications procedures.

Realizing device of accurate time synchronization protocol

Abstract: The invention is applicable in the technical field of network communication, and provides a realizing device of accurate time synchronization protocol, the device comprises a system initialization unit, initializing the realizing device of PTP (precision time protocol), preparing for running of PTP(precision time protocol); a human-computer interaction unit, providing one or more interactive interfaces, providing interact between users and the realizing device of the PTP(precision time protocol); a protocol engine unit, running PTP(precision time protocol); a hardware communication unit, stamping time for all PTP(precision time protocol) messages of engine unit organization of the protocol , transmitting the PTP(precision time protocol) messages with stamp between the master clock device and the vice clock device. The invention of realizing device of PTP(precision time protocol) runs the PTP(precision time protocol) in the network, realizing high-precision synchronization of the network clock, and solving all kinds of problems caused by error of clock synchronization or asynchronization in the current industrial control.

Method and system for improving PTP time synchronization precision

Abstract: The invention provides a method and a system for improving PTP (Precision Time Protocol) time synchronization precision. The method comprises the following steps: sealing a timestamp on each transmitted or received PTP message on the connection part of the connection medium access control layer and the physical layer; obtaining the adjusted PTP count time through adjusting the time shift and the time deviation; judging whether the PTP count time is between -1/2f and +1/2f of whole second while the PTP message is triggered at second pulse, and transmitting the second pulse while the PTP count time is between -1/2f and +1/2f of the whole second. The invention judges whether transmitting the PTP clock output signal through turning a PTP counter in seconds when nanosecond is between the allowed precision range, so the synchronization precision is improved for double than the PTP count resolution ratio, and the nanosecond synchronization precision is realized from the connection between the main node and secondary node enabled by PTP.

Method, device and system for recognizing precision time protocol massages

Abstract: The embodiment of the present invention discloses a method, a device and a system for recognizing precision time protocol massages, which relates to the field of communication. The present invention is invented for shortening the time of network equipment recognizing precision time protocol massages. The method for recognizing precision time protocol massages is applied to a multi-label transmitting network, which comprises the following steps: the precision time protocol massages are captured; a label retaining layer carrying recognizing labels is added in a label zone of the precision time protocol massages; and the precision time protocol massages are transmitted. Another method for recognizing the precision time protocol massages is applied to a multi-label protocol transmitting network, which comprises the following steps: massages carrying the label retaining layer in the label zone are captured; the precision time protocol massages are recognized through recognizing labels in the retaining label layer; and the precision time protocol massages are transmitted. The present invention can be applied to transmit the precision time protocol massages.

IEEE 1588 synchronization in distributed measurement systems for electric power networks

Abstract: Modern electric power systems can be considered as the consequence of the continuous technological evolution, often pushed by economical, political and social requirements. As an example, the main transformations in electric distribution systems arise from the diffusion of “Distributed Generation” (DG), i.e. small production plants, often supplied through renewable energy sources, whose presence has significant implications on both energy management (since “active networks” are needed to take into account bidirectional energy flows by means of innovative devices) and protection systems (since adaptive protections can be used to automatically reconfigure the network in the case of fault occurrence). In general, in both transmission and distribution networks, monitoring, control and protection tasks are usually performed by Intelligent Electronic Devices (IEDs), which can be, by their nature, connected to each other by suitable communication links. A famous example of this approach is represented by the series of Standard IEC 61850 (Communication Networks and Systems in Substations). These standards are related to networks and communication systems within the substation, but are used as a reference in all those circumstances in which an electrical system is managed through the use of IEDs communicating with each other (as in the case of active distribution networks). In this way, control and protection schemes practically become algorithms, whose correct behavior is determined firstly by the availability of data measured in strategic points of the network. The critical role of the above mentioned applications, which clearly emerges from their implications on safety, as well as from economical considerations, makes it of fundamental importance the evaluation of correctness and trustworthiness of the information on which such actions are based. Many of these applications implemented for control and protection purposes in electric power networks require the acquisition of information by Wide Area Monitoring System (WAMS) from strategic points of the system and need that the acquired data have an extremely accurate common time reference. Generally, amplitudes and phases of the positive sequence voltages are the quantities to be estimated in the network nodes. Because of the extension of power networks, suitable measurement devices should be used to ensure proper synchronization between the collected data. Thus, the key components of WAMSs are represented by Phasor Measurement Units (PMUs) designed to measure synchronized phasors (synchrophasors). Typical synchronization specifications for synchrophasors measurement are in the order of few microseconds. Such a tight synchronization requirements lead to the need of highly accurate clock settings, such as the ones bases on satellite systems. Currently, the Global Positioning System (GPS) is the only system to provide a time reference with sufficient availability and accuracy for most distributed monitoring and control applications in power systems. As an alternative, in situations where many devices are located in a geographically limited sub-area (e.g. a substation) of the system and are connected to each other by suitable communication networks (as described by the series of standard IEC 61850), it could be advantageous to distribute the time reference of a high accuracy clock to the devices through suitable network synchronization protocols. Between them, the PTP (Precision Time Protocol) defined in the Standard IEEE 1588 offers the best accuracy performance. It is worth mentioning that the Standard IEC 61850-9-2 practically indicates Ethernet as a preferred communication solution, thus offering an optimal support to implement 1588 synchronization in electric power plants. In this context, it should be recalled that the IEEE 1588 profile for power system applications (project PC37.238) is being developed under IEEE Power System Relaying Committee (PSRC) and Power System Substation Committee (PSSC). The scope covers all power system applications, including Synchrophasors. The group works in close coordination with TC57 WG10, which plans to adopt the PTP profile in the next revision of IEC 61850. In the first part of this thesis, the state of the art regarding power system evolution, IEEE Standard on synchrophasor measurements and synchronization system is presented. In particular, the problems related to the evolution of the power system along with some possible advantages due to the implementation of Phasor Measurement Units in Wide Area Monitoring Systems are introduced. After a general description of the architecture of a distributed measurement system based on PMUs, the new synchrophasors standard is analysed, highlighting the differences with previous versions, the requirements for the measurement of synchrophasors and the definition of synchrophasor under steady-state and dynamic conditions. Moreover, a summary of the possible synchronization solutions is introduced. For each solution, advantages and disadvantages are highlighted. In particular, satellite system and network based protocol are analysed in detail. In the second part of the thesis, a synchronization solution able to exploit the worldwide availability of the GPS and the possibility to disseminate the synchronization signal with high accuracy by means of the network synchronization protocol IEEE 1588 is proposed. This solution is used for the synchronization of PMUs. The objective of this work is to analyse the possibility to synchronize PMUs via PTP and to study the impact that such a synchronization solution has on the performance of measurement systems under both steady-state and anomalous operating conditions, as well as its effects on the applications that make use of their data. Two different versions of the PTP are used: the first one uses hardware-assisted time-stamp mechanism whereas the second one uses software-only time-stamp mechanism. Two experimental systems are characterized in detail with an accurate description of all the used hardware and software components, and their synchronization performances under different operative conditions are analysed. Finally, among all the sources which may contribute to the uncertainty introduced by PMUs, the last part of this thesis analyses the impact of the phasor estimation models on the accuracy of these devices, with particular attention to algorithms proposed in literature for the estimation of dynamic phasors and studies their performances under several different conditions.

Intelligent supervision for configuration of precision time protocol (ptp) entities

Abstract: An intelligent supervisor located at a management node in the PTP network determines the PTP roles and configuration of the client nodes. The intelligent supervisor communicates with intelligent supervisor agents located at client nodes in the PTP network. The intelligent supervisor agents at the client nodes feed back information, such as the PTP properties of the client nodes, to the intelligent supervisor. The intelligent supervisor analyzes the data to determine the roles and appropriate configuration for the client nodes.

Time synchronization realizing method and clock node

Abstract: The invention relates to a time synchronization realizing method and a clock node. The method comprises the following steps: the clock node extracts an SSM (synchronization status message) best master clock according to the SSM, wherein the SSM best master clock is a best master clock for frequency synchronization; the clock node sets a precision time protocol (PTP) port status of a port according to the line of the SSM best master clock; and the clock node obtains a master clock data set and a best master clock data set for time synchronization according to the received notification message. Through the time synchronization realizing method and clock node provided by the invention, the PTP best master clock algorithm can be simplified.

High-precision network clock server of LTE (Long Term Evolution) system

Abstract: The utility model discloses a high-precision network clock server of an LTE (Long Term Evolution) system, which comprises a three-in-one satellite receiving unit, a 1588 clock interface unit and a local clock signal generating unit. The three-in-one satellite receiving unit is used for automatically selecting to receive any one effective satellite clock input signal in a GPS (Global Positioning System), a BeiDou satellite or a GLONASS (GLObal NAvigation Satellite System); the 1588 clock interface unit is used for acquiring a 1588 clock input signal; the local clock signal generating unit is used for generating a local clock signal according to the satellite clock input signal or the 1588 clock input signal and outputting the local clock signal to output interfaces; and the output interfaces comprise 10MHz, E1, PTP (Precision Time Protocol), 1PPS (Pulse Per Second)+TOD (Time Of Date) and IRIG-B (InterRange Instrumentation Group B) interfaces. The high-precision network clock server has the capacity of automatically switching among three satellite systems and supports to use a PTP input as a clock reference source; the clock source can be provided for the system under the condition that the three-in-one satellite receiving unit goes wrong; and the reliability of the operation of the system is greatly improved.

Method for setting security authentication in precision time protocol (PTP)

Abstract: The invention discloses a method for setting security authentication in a precision time protocol (PTP). The method comprises the following steps of: setting keys on a time synchronous source and time synchronous equipment in advance, and adding an identity authentication field in the transmitted PTP message when the time synchronous source transmits synchronous information to the time synchronous equipment, wherein the field comprises a first MD5 value, and the MD5 value consists of a sequence ID field and key logic operation; performing corresponding logic operation on the sequence ID field in the message and a locally preset key when the time synchronous equipment receives the PTP message to obtain a second MD5 value; comparing the two MD5 values, passing the PTP authentication if the PTP messages are the same, otherwise discarding the messages. Thus, the communication safety of PTP is guaranteed, so that equipment for operating the PTP is hardly influenced by hostile attack from an internet.