Accession Number : ADP009132

Title :   The NIST Internet Time Service,

Corporate Author : NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO

Personal Author(s) : Levine, Judah

Report Date : 02 DEC 1993

Pagination or Media Count : 7

Abstract : We will-describe the NIST Network Time Service which provides time and frequency information over the internet. Our first time server is located in Boulder, Colorado, a second backup server is under construction there, and we plan to install a third server on the East Coast later this year. The servers 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 DAYTIME 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 Time notice is based on the US transition dates of the first Sunday in April and the last one in October. The NTP is a more complex protocol that is suitable for larger machines; it is normally run as a demon 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 'demon processes (such as NTP) that continuously correct the time of the local clock based on periodic calibrations.

Descriptors :   *TIME STANDARDS, *COMMUNICATIONS NETWORKS, *RADIO LINKS, *SYNCHRONISM, CALIBRATION, CLOCKS, DAYLIGHT, FORMATS, TIME, UNCERTAINTY.

Subject Categories : Computer Systems
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE