Remote calibration of time from NTP servers

Douglas, Rob; Charbonneau, Andre; Gertsvolf, Marina

doi:10.1088/1681-7575/aae940

Cited by 9 publications

(4 citation statements)

References 2 publications

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“…Therefore, a timekeeping error of a hundred microseconds in an NTP system built over a LAN with a symmetrical path and no more than 2-3 interconnection elements between two NTP servers is considered optimum [11][12][13]. In contrast, for synchronization accuracy on a WAN a time error is, usually, below 10 ms in a 200-node WAN [14].…”

Section: Theoretical Approachmentioning

confidence: 99%

Assessment of an NTP service calibration over a Local Area Network

Vélez,

Díaz,

Osuna

et al. 2024

Meas. Sci. Technol.

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Nowadays, timekeeping is an essential component in modern computing. The Network Time Protocol (NTP) is a distributed service based on a hierarchical network protocol used to synchronize computer clocks over a network in an easy and scalable manner. Currently, this protocol is the main mechanism used on the internet to provide a common notion of time to all computers. The Real Instituto y Observatorio de la Armada (ROA) realizes Spanish legal time and disseminates it via the internet from two publicly accessible NTP time servers. In this study, it is assessed the implementation and calibration of two NTP time servers over a Local Area Network (LAN) in client-to-server and server-to-server modes from the side of NTP protocol and all its functionalities. These calibrations aim to analyze the client-to-server mode operation, forcing the polling interval at different values, and to verify the consistency of the results by employing the ppstest tool to compare one pulse‐per‐second (1PPS) from the UTC(ROA) with the client time offset. This comparison corroborates the proper operation of the NTP time server configured as stratum 1 and referred directly to UTC(ROA), and shows how a real deployment can be professionally deployed with the aim of distributing time over a public service using NTP.

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Section: Theoretical Approachmentioning

confidence: 99%

Assessment of an NTP service calibration over a Local Area Network

Vélez,

Díaz,

Osuna

et al. 2024

Meas. Sci. Technol.

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“…After the initial synchronization the TCG switches to using RC 1PPS signal and becomes a stratum-1 server itself. The time-of day information of the TCG is compared regularly with that derived from the RC GPS feed and is also monitored externally from NRC using NRC Monitored NTP service [18].…”

Section: System Design and Performancementioning

confidence: 99%

Remote time and frequency calibration with holdover traceability from a new treatment of non-white noise in rubidium clocks

2021

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A new method of uncertainty analysis for non-white noise is presented and used to evaluate traceable holdover capabilities of a new NRC system for time and frequency dissemination to remote rubidium-cell (Rb) clocks. As in many similar systems, these remote clocks are disciplined to track UTC using the Global Positioning System and the common view time transfer method. When disciplining data is unavailable, we extend traceability into this holdover period with evaluations of uncertainty from the measurements of the Rb clock's non-white noise: modelled, matched, and simply presented as a time dependent dispersion in Monte Carlo simulations. This leads to improved simplicity, reliability and economy for the new method, with a post processed standard uncertainty down to 6 ns when disciplined, with a holdover period of t seconds introducing an uncertainty component of 1.82 × 10 −3 t nanoseconds (combined standard uncertainty of 160 ns for a 24 h holdover).

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“…However, the time offset measured by these methods is prone to jumps because of congestion or exceptions generated by the calibrator and local routers [18][19][20]. Other methods set up only one calibrator in the same lab with the reference server, which measures both the time offset between the calibrator and NTP servers and the time offset between the calibrator and reference server [21,22]. If the calibrator is placed in a laboratory in another city, the measurement results might be different.…”

Section: Introductionmentioning

confidence: 99%

Traceability of network time service to UTC(NIM): online calibration

Zhang

Wang

Liu

et al. 2021

Meas. Sci. Technol.

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Network time service provided by Network Time Protocol (NTP) servers is widely used to synchronize the clocks of computers and other networked equipment. With the rapid development of smart devices and their applications, more NTP servers as time sources need to be calibrated to a legal time reference. This work proposes using a low-cost and convenient calibration method to investigate the time service capability of ten NTP servers located at different cities in China. The uncertainties (k = 2) of the time offsets between Coordinated Universal Time (National Institute of Metrology) and network time from NTP servers for a single measurement are generally less than 150 ms, and the uncertainties (k = 2) of the mean time offsets for 24 h are less than 85 ms. Calibration results were found at the same level when applying the two time references, which were maintained a time offset less than 10 ns and located more than 1000 km apart.

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Remote calibration of time from NTP servers

Cited by 9 publications

References 2 publications

Assessment of an NTP service calibration over a Local Area Network

Assessment of an NTP service calibration over a Local Area Network

Remote time and frequency calibration with holdover traceability from a new treatment of non-white noise in rubidium clocks

Traceability of network time service to UTC(NIM): online calibration

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