Abstract: A method, performed by an access point of a cellular network, obtains time information by identifying a control channel cycle boundary; at a beginning of the control channel cycle boundary, sending a request to a time server; receiving a response from the time server, the request including a server time; and obtaining the timing information using the server time. Obtaining the timing information includes using the server time and a first reference time to obtain an integer and a fraction; using the fraction to obtain a time difference; and using the time difference to obtain the timing information.

Abstract: To study and gain a better understanding of the power system dynamics, the concept of building a frequency monitoring network (FNET) was proposed in 2000 [1] and has been realized in 2003. The FNET system consists of many high dynamic precision frequency and phasor estimation devices, also known as frequency disturbance recorders (FDR). These FDRs can be used at any 110 V or 220 V wall outlet and transmit measured data remotely via the Ethernet. The FDRs can measure power system parameters including frequency, voltage, and phase angle. There are currently more than 40 FDRs placed strategically in different locations within the North America power grids to monitor the entire power network. Furthermore, the FDRs are currently synchronized in time via a GPS receiver. This paper discusses the feasibility study of the Internet timing synchronization. The motivation for Internet timing synchronization was ignited during the research for a more portable and economical yet still highly accurate FDR design. Test results are presented from several different NTP implementation methods. Based on the correlation between time synchronization and phasor accuracy, it was concluded that the current NTP is not yet a feasible synchronization tool for accurate phasor measurement.

Abstract: A weak point in network-based applications is that they commonly open some known communication port(s), making themselves targets for denial of service (DoS) attacks. Considering adversaries that can eavesdrop and launch directed DoS attacks to the applications' open ports, solutions based on pseudo-random port-hopping have been suggested. As port-hopping needs that the communicating parties hop in a synchronized manner, these solutions suggest acknowledgment-based protocols between a client-server pair or assume the presence of synchronized clocks. Acknowledgments, if lost, can cause a port to be open for a longer time and thus be vulnerable to DoS attacks; Time servers for synchronizing clocks can become targets to DoS attack themselves. Here we study the case where the communicating parties have clocks with rate drift, which is common in networking. We propose an algorithm, BigWheel, for servers to communicate with multiple clients in a port-hopping manner, thus enabling support to multi-party applications as well. The algorithm does not rely on the server having a fixed port open in the beginning, neither does it require from the client to get a "first-contact" port from a third party. We also present an adaptive algorithm, HoPerAA, for hopping in the presence of clock-drift, as well as the analysis and evaluation of the methods. 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. Provided that one has an estimation of the time it takes for the adversary to detect that a port is open and launch an attack, the method we propose doesnot make it possible to the eavesdropping adversary to launch an attack directed to the application's open port(s).

Abstract: The invention relates to a precision and stability monitor method for a clock, comprising: a clock supporting NTP standard is directly set to be a NTP server mode, and the clock not supporting NTP standard acquiring time by a synchronous monitor device; a dispatching center sets a NTP client-side which is connected with each NTP server terminal by a NTP communication mode; when the NTP client-side inquires the time of the monitored clock, each NTP server terminal transmits time to the NTP client-side in real time by a NTP protocol; the NTP client-side is compared with a setting optimum reference time resource to obtain a time difference for evaluating precision and stability of the monitored clock equipment. The invention sets a time monitor network by a NTP standard, and the NTP client-side compares the monitor clock time with the optimum reference clock resource time to be judged whether consistent for evaluating precision and stability of each monitored clock equipment. The invention is convenient in use and uniform management, which saves the cost.

Abstract: Measuring delay in a network segment and/or through a network device is disclosed. A method includes a sender preparing a real-time transport protocol with a transmit timestamp based on the time received from a remote, well-known time server, and a receiver computing a one way delay based on a receive time obtained from a remote, well-known time server and the transmit timestamp. A method in a single system includes a sender preparing a real-time transport protocol with a transmit timestamp based on the system, and a receiver computing a one way delay based on a receive time obtained from the system and the transmit timestamp. The method may be performed on one or more network cards and in one or more network testing systems, and may be implemented by one or more computing devices.

Abstract: Synchronizing clocks in a distributed system is an indeed challenging task. Although there exists a various class of applications, like synchronizing the clock of a PC with the network time protocol, where an accuracy of several milliseconds is sufficient, many applications, such as synchronized test and measurement or localization services in wireless LANs require a higher confidentiality in the time domain. This paper enlights some of the key restrictions and possibilities in the case of IEEE 802.3 Ethernet. As this case not only challenges the state of the art oscillator models, but also timestamping techniques, a novel, highly accurate approach for that is proposed. Moreover, a highly accurate deterministic approach also concerns the behavior of the physical layer devices and their influence on the asymmetry, as well as the underlying control loops an analysis of the behavior of both is given together with some preliminary results for Ethernet based clock synchronization in the nanosecond range.

Abstract: PROBLEM TO BE SOLVED: To make a clock being a reference for the fixed-time meter-reading and fixed-time transmission of a unit wattmeter in each house in a feeding supervisory control system for remote meter-reading cope with a low cost. SOLUTION: An NTP server 1 gives a time update instruction to a gateway GWa connected thereto by a wire, such as an intracompany optical fiber network at a time t0 that becomes prescribed periodic timing such as once a day, and successively puts the time of low-order unit wattmeters T5-1, T5-2;T4-1, T4-2, T4-3, T4-4 right by radio from the gateway GWa that has received the time update instruction, thus using the accurate clock in common even in an inexpensive network configuration without connecting each unit wattmeter T to a high-cost network such as ISDN capable of acquiring accurate time information and mounting high-cost equipment for acquiring the accurate time information of a GPS receiver or the like. COPYRIGHT: (C)2009,JPO&INPIT

Abstract: The National Institute of Standards and Technology (NIST) operates 22 network time servers at various locations. These servers respond to requests for time in a number of different formats and provide time stamps that are directly traceable to the NIST atomic clock ensemble in Boulder. The link between the servers at locations outside of the NIST Boulder Laboratories and the atomic clock ensemble is provided by the Automated Computer Time Service (ACTS) system, which has a direct connection to the clock ensemble and which transmits time information over dial-up telephone lines with a two-way protocol to measure the transmission delay. I will discuss improvements to the ACTS servers and to the time servers themselves. These improvements have resulted in an improvement of almost an order of magnitude in the performance of the system. (Some figures in this article are in colour only in the electronic version)

Abstract: This paper presents a renovative priority queuing algorithm for jitter-sensitive MPEG-2 Transport Stream distribution on home network. Upon the dissemination of broadband access networks, there are many technical studies of IP-based video distribution (IPTV). In addition, it is becoming common for individual residences to use Ethernet home networks to interconnect PCs and home appliances. Under these circumstances, the home network will be a common traffic channel for them within residences. On the home network, it is difficult to comply with MPEG-2 Systems requirements in which the distribution delay jitter of Program Clock Reference in its stream should be suppressed to less than plusmn500 ns to synchronize system clocks between a transmitter and receivers. In this paper, we propose a Constant Delay Queuing (CDQ) scheduler to suppress the forwarding delay jitter, which is suitable for consumer Ethernet hubs to distribute the IPTV flow on home networks. By using an experimental hub which implements the CDQ scheduler, we demonstrate that the CDQ scheduler suppresses the jitter to less than plusmn500 ns. Furthermore, we discuss applications of CDQ to IPTV distribution on home networks and to improving synchronization stability of Network Time Protocol.

Abstract: A primary time server of a Coordinated Timing Network remains as current time server, even if time code information of the primary time server is unavailable. The primary time server receives the necessary or desired timing information from a secondary time server and uses that information to maintain time synchronization within the Coordinated Timing Network.

Abstract: A time setup device and a method therefor are provided to set a time accurately regardless of the operation of an image display device A storing unit(190) stores current time information included in broadcasting information of a broadcasting signal received from the outside A communication unit(170) communicates with an NTP(Network Time Protocol) server(300) through the Internet(200) and receives global time information A user interface unit(110) receives a request command of a user If an NTP clock is selected through the user interface unit(110), a control unit(160) outputs a control signal to set current time on the basis of the time information received from the NTP server(300) A time setup unit(180) compares the time information received through the NTP server(300) with the time information stored in the storing unit(190) according to the control signal of the control unit(160), and sets the current time on the basis of the time information received through the NTP server(300)

Abstract: Wireless sensor networks (WSNs) have emerged as an interesting research area in the last few years. The applications envisioned for such networks require collaborative execution of a distributed task amongst a large set of sensor nodes. The collaborative execution is realized by exchanging messages that are time-stamped using the local clocks on the nodes. Hence, time synchronization becomes indispensable in such distributed systems. For years, protocols such as network time protocol (NTP) have kept the clocks of networked systems in perfect synchronization. However, wireless sensor networks has a large density of nodes and very limited energy resource at every node which leads to improved scalability requirements while limiting the resources. This paper proposes a technique called level-based time synchronization to provide redundant ways for each node to synchronize its clock with the common source, so that it can tolerate partially missing or false synchronization information provided by compromised nodes. The efficacy of this technique is evaluated via simulations.

Abstract: The invention discloses an improved method for the key parameter statistic as well as the transmission of the wireless stream media, and the method is invented for alleviating the computing capability of a client during the stream media playing process and realizing the reliable transmission of the statistic parameter of the wireless stream media. The method comprises the following steps: firstly, the deposited position of the statistic parameter is confirmed, and the round-trip time valve is calculated out by a server; secondly, the server and the client carry out the negotiation on transmitting the parameter, and the valve of the network time protocol is submitted by the client; thirdly, the throughput is obtained by calculating; fourthly, the server establishes a session stream and sends out the real time transport protocol data packet to the client; fifthly, the client terminal sends out the real time transmission control protocol packet or the real-time stream protocol packet to the server, and the server counts the lost condition of the data packet; sixthly, the server counts the one trial parameter after the session stream is disconnected, and the server calculates the related parameter of the client terminal. The invention changes the statistic position of the statistic parameter, and improves the usability and the reliability of the statistic parameter transmission.

Abstract: PROBLEM TO BE SOLVED: To synchronize time of a built-in clock by using time information of a network server even in a control terminal which is not provided with a function for acquiring the time information of a network time server. SOLUTION: A network terminal 3 is provided with an interface 31 for acquiring time information from an NTP server 1 through the Internet NT and an interface 32 for connecting a control terminal 2 and transferring the time information to the control terminal 3. When the control terminal 2 requests time synchronization of a built-in clock 21 to the network terminal 3, the network terminal 3 requests time information to the NTP server 1 and transfers the acquired time information to the control terminal 2. In the operation, the control terminal 2 acquires the time information and synchronizes the time of the built-in clock 21. COPYRIGHT: (C)2008,JPO&INPIT

Abstract: PROBLEM TO BE SOLVED: To provide a time synchronizing system capable of accurately synchronizing the times of a plurality of electronic devices. SOLUTION: The time synchronizing system 10 comprises the plurality of electronic devices (for example, sensor device) 12, and at least one cradle 14 for charging the electronic devices. The cradle 14 acquires time information for synchronizing it with the standard time, for example, time information from an NTP (Network Time Protocol) server 16, and periodically provides accurate time information to the electronic devices 12. The electronic devices 12 performs clocking over a predetermined period, and corrects a time conversion parameter based on a count value according to the internal clock based on the time information provided from the external cradle 14. Whenever the correction is performed, the time interval required for clocking is set long, and further correction is performed. Thus, times of all electronic devices can be synchronized accurately. COPYRIGHT: (C)2008,JPO&INPIT

Abstract: The invention relates to a selecting method of NTP time server, firstly, setting the maximum permissible selecting times N and the priority of each time server (11), then in each timing interval, a network element device (12) selects time servers (11) according to the maximum permissible selecting times N and the priority in order. The method selects time servers through setting the priority and simple counting, is completely suitable for network element devices, solves the problems that the computing capacity and the speed of a chip on the network element device fall behind the selection algorithm of NTP which sets a time server by itself.

Abstract: In this article, an Internet-based remote control system is designed and implemented. The communication is based on the master-slave structure. The master PC communicates with the slave from about 40 km away by UDP protocol. In order to guarantee the master and slave clocks to be synchronized, the NTP (network time protocol) is used in both sides. The packets are sent together with time-stamps. The controller design (master) relies on a remote observer that achieves a state prediction of the application (slave), despite the variable communication delays. The Slave comprises a PC and a robot Miabot of Merlin company. The protocol Bluetooth is used between the local PC and the robot. Internet-based remote systems are subject to variable time delays (including communication and data-sampling delays) and data packets losses (due to the unstable Internet network). We have continuously tested the RTT (round-trip-time) between the two PCs in the daytime and nighttime by the protocol ICMP (Internet Control Message). From these tests, an evaluation of the maximal time delay is obtained. Our structure allows one to guarantee an exponential stabilization performance, which is proven via a Lyapunov-Krassovski functional technique and involves the estimated delay upperbound. This means that the guaranteed decay rate is computed (via some LMI optimization) in relation to some maximal value of the communication delays. Of course, for greater delay values, the performance cannot be guaranteed anymore and an alternative solution has to be considered. In our system, we give a command for the robot to stop until the communication comes back to a sufficient quality.

Abstract: This paper introduces knowledge related on the NTP protocol,gives configuration and attention point of set up NTP client under windows system,include the independent host,the working group,and the domain.And give approach to set up a NTP server in Windows system.

Abstract: The invention relates to a method for synchronous time calibration by a network element equipment. The method uses a standard network time protocol (NTP) for time synchronization. The method also includes the following steps: a plurality of standard NTP servers (11) are provided in the network and priority levels are set; when the network element equipment (12) selects the NTP servers (11) according to the priority level order for time calibration, N times of the selection to the maximum permitted corresponding to each NTP server (11) can be carried out before success. The method, through priority level setting and simple counting for the selection of the NTP servers, is totally applicable to the network element equipment. The problem that calculation ability and rate of a chip in the network element equipment cannot satisfy requirements of NTP server selection algorithm set by the NTP is solved.

Abstract: A time synchronization method includes the following steps. First, network communication equipment receives time information sent by at least two time servers respectively, in which the time information includes time synchronization status information of each of the time servers. Then, it is determined whether time synchronization status of each of the time servers is normal or not according to the time synchronization status information. Finally, the network communication equipment selects to employ the time information provided by the time servers with the normal time synchronization status from the at least two time servers. Network communication equipment and a network communication system are also provided correspondingly. The network communication equipment is capable of employing the time information provided by the time server with the normal time synchronization status according to the time synchronization status of each of the time servers, thereby improving precision and reliability of the time information obtained by the network communication equipment.

Abstract: This paper proposes a small SNTP server to set the correct time for in-home electric appliances In-home electric appliances obtain the correct time through the Internet by using SNTP The proposed method was implemented in a verification system with an embedded microprocessor, RTOS and the small resources of 18 MB which are assumed to be required for consumer use and was verified As a result, the correct time was provided with a precision within 1 ms for an SNTP server, and the RTC was able to set it

Abstract: The system has slave clocks (NU1-NU5) attached to a central clock (ZU) over a data network i.e. local area network (LAN). The central clock transmits time information and actual time zone to the slave clocks using a network time protocol (NTP) and a multicast protocol respectively. The slave clocks determine actual time from the received time information and the time zone. The slave clocks are divided into time zone groups (ZZG1, ZZG2), and a determined time zone is transmitted to each time zone group. The central clock periodically transmits a time zone table to the associated slave clock.

Abstract: This paper considers synchronization of multiple plants over networks. The effect of time-varying transmission delay is compensated by a switching observer which uses the time-stamp information. To calculate the instantaneous value of transmission delay length via the time-stamp, the clocks of sending and receiving computers must be synchronized. It is shown that the correction of the difference of the quartz frequencies of the computers and the clock adjustment via NTP (Network Time Protocol) can provide the time synchronization within a required accuracy for moderate sampling periods. Proposed method is demonstrated by an experiment of synchronization of DC-motors over a real network.

Abstract: A method of measuring temporal drift of an electronic apparatus linked to a network and capable of providing a time-stamp including capturing at least two messages including a gauge reference time circulating around the network, and determining precision of the time-stamping function of the apparatus as a function of the gauge reference time and of a time-stamp provided by the apparatus. The apparatus can be a network analyser and each message captured includes at least one Ethernet frame including a gauge reference time in accordance with NTP (Network Time Protocol).

Abstract: PROBLEM TO BE SOLVED: To allow television conference apparatuses to synchronize each other for time even if no time information is available from an NTP server existing on a network. SOLUTION: A television conference apparatus 12 that fails in acquiring time information from an NTP server existing on a network 13 requests and receives the time information from a television conference apparatus 11 that has succeeded in acquiring time information from the NTP server existing on the network 13, and then it sets time according to the time information. The invention can be applied to, for example, a television conference system. COPYRIGHT: (C)2008,JPO&INPIT

Abstract: A method for testing an accuracy of a real time clock is provided. The method includes: applying parameters that comprise a predetermined repetition count on testing the RTC, a predetermined time period, and an acceptable error margin of the RTC; communicating with a local network time protocol (NTP) server for acquiring a system time of the local NTP server; applying a current time of the RTC according to the system time at the beginning of testing the accuracy of the RTC; acquiring the current system time of the local NTP server when the predetermined time period lapse; computing a time difference between the system time of the local NTP server and the current time of the RTC; and determining if the RTC is accurate or not by comparing the time difference and the acceptable error margin, and generating a testing result according to the determination.

Abstract: PROBLEM TO BE SOLVED: To provide a technology for enhancing the accuracy of time information to be acquired in a communication apparatus that acquires time information from a time server through a network. SOLUTION: A complex machine acquires a congestion degree representing a degree of congesting a network in time information acquisition processing (S120) and acquires time information from a time server thereafter (S140), wherein the acquired congestion degree is compared with a reference congestion degree prior to acquiring the time information and in a case where the congestion degree indicates that the network is congested more than the reference congestion degree (S130:YES), the idea of acquiring the time information is abandoned (S150). This is because, during network congestion a more communication time is required because of frequent packet loss occurrence and accuracy of acquired time information may become adverse. Thus, according to the multifunction peripheral, time information with a high possibility of adverse accuracy is prevented from being acquired, accuracy of time information to be acquired can be enhanced. COPYRIGHT: (C)2010,JPO&INPIT

Abstract: : Next generation Navy platform designs are evolving towards generalized multipurpose infrastructures based on open standards and commercial products. These platforms will support a wide range of new and expanding applications in a more flexible and dynamic manner than in previous designs. This new paradigm creates significant network time synchronization challenges. The Navy has been deploying the Network Time Protocol (NTP) in shipboard computing infrastructures to meet the current network time synchronization requirements. Additionally, a new standard, IEEE 1588 or the Precision Time Protocol (PTP), has emerged. It holds the promise of more precise synchronization through the use of hardware assists. New international standardization efforts intend to leverage NTP and PTP for a next generation of time synchronization protocols. This paper examines the emerging work in the International Standards communities in the area of precise network time synchronization. Additionally, it looks at preliminary evaluations of NTP and PTP in the types of products commonly used in Navy shipboard applications. Finally, this paper proposes potential focus areas for Navy standardization and experimentation efforts.

Abstract: A time server and method for improving the input precision of the time server are provided. The time server includes: a time receiver (21), used for receiving time information of the time source, and outputting the absolute moment signal and the time code after processing; a time delay controller (22), used for compensating the time delay for the absolute moment signal from said time receiver according to the previsional transmission time delay to form the third time signal; a time generator, used for combining the time code from said time receiver and the third time signal from said time delay controller, and converting them into the forth time signal with a designated time output format, then transmitting them outward.