The NIST Internet Time Service

Judah Levine

Abstract: We will describe the NIST Network Time Service which provides time and frequency information over the internet. Our first time sewer is located in Boulder, Colorado, a second backup server is under construction there, and we plan to install a third sewer on the East Coast later this year. The sewers are synchronized to UTC(NIST) with an uncertainty of about 0.8 ms RMS and they will respond to time requests from any client on the internet in several different formats including the DAYTIME, TIME and NTP protocols. The DAYTlME and TIME protocols are the easiest to use and are suitable for providing time to PCs and other small computers. In addition to UTC(NIST), the DAYTIME message provides advance notice of leap seconds and of the transitions to and from Daylight Saving Time. The Daylight Saving Tim notice is based on the US transition dates of the first Sunday in April and the Just one in October. The NTP is a more complex protocol that is suitable for larger machines; it is normally run as a "daemon" process in the background and can keep the time of the client to within a few milliseconds of UTC(NIST). We will describe the operating principles of various kinds of client software ranging from a simple program that queries the server once and sets the local clock to more complex "daemon" processes (such as NTP) that continuously correct the time of the local clock based on periodic calibrations.
Published in: Proceedings of the 25th Annual Precise Time and Time Interval Systems and Applications Meeting
November 29 - 2, 1993
Ritz-Carlton Hotel
Marina Del Rey, California
Pages: 505 - 514
Cite this article: Levine, Judah, "The NIST Internet Time Service," Proceedings of the 25th Annual Precise Time and Time Interval Systems and Applications Meeting, Marina Del Rey, California, November 1993, pp. 505-514.
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