International Comparisons of Network Time Protocol Servers

Published

December 4, 2014

Author(s)

Michael A. Lombardi, Judah Levine, Jose M. Lopez, Francisco Jimenez, John Bernard, Marina Gertsvolf, Harold Sanchez, Oscar G. Fallas, Liz C. Hernandez Ferero, Ricardo de Carvalho, Mario Fittipaldi, Raul Solis, Franklin Espejo

Abstract

This paper describes a recently designed system that measures the time transmitted by network time protocol (NTP) servers located in North, Central, and South America. Direct measurements of the time transmitted by each server are obtained by comparing the received time stamps to the UTC(NIST) time scale at the National Institute of Standards and Technology (NIST) in Boulder, Colorado. International comparisons of the time differences between servers are obtained by utilizing UTC(NIST) as a common-view observation signal. Results of both direct and common-view measurements are published in real time via the web site of the Sistema Interamericano de Metrologia (SIM) Time and Frequency Metrology Working Group, providing verification of a given server's accuracy. The paper describes the NTP measurement system, and presents results from direct comparison and common-view measurements. It also discusses factors that contribute uncertainty to NTP measurements; in particular network asymmetry caused by inconsistent routing and/or network congestion.

Proceedings Title

Proceedings of the Precise Time and Time Interval Systems and Applications (PTTI) Meeting

Conference Dates

December 2-4, 2014

Conference Location

Boston, MA

Conference Title

Precise Time and Time Interval Systems and Applications (PTTI) Meeting

Pub Type

Conferences

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Keywords

international comparisons, Network Time Protocol (NTP), time, time transfer

Citation

Lombardi, M. , Levine, J. , Lopez, J. , Jimenez, F. , Bernard, J. , Gertsvolf, M. , Sanchez, H. , Fallas, O. , Hernandez, L. , de, R. , Fittipaldi, M. , Solis, R. and Espejo, F. (2014), International Comparisons of Network Time Protocol Servers, Proceedings of the Precise Time and Time Interval Systems and Applications (PTTI) Meeting, Boston, MA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917539 (Accessed March 16, 2025)