Using NIST Time Servers

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The National Institute for Standards and Technology (NIST) is one of the world’s leading atomic clock laboratories, and is the leading American time authority. Part of a constellation of national physics laboratories, NIST help ensure the worlds atomic clock time standard UTC (Coordinated Universal Time) is kept accurate and is available for the American people to use as a time standard.

All sorts of technologies rely on UTC time. All the machines on a computer network are usually synchronised to source of UTC, while technologies such as ATM’s, closed-circuit television (CCTV) and alarm systems require a source of NIST time to prevent errors.

Part of what NIST does is to ensure that sources of UTC time are readily available for the technologies to utilise, and NIST offer several means of receiving their time standard.

The Internet

The internet is the easiest method of receiving NIST time and in most Windows based operating systems, the NIST time standard address is already included in the time and date settings, allowing easy synchronisation. If it isn’t, to synchronise to NIST you simply need to double click on the system clock (bottom right hand corner) and enter the NIST server name and address. A full list of NIST Internet servers, here:

The Internet, however, is not a particularly secure location to receive a source of NIST time. Any Internet time source will require and open port in the firewall (UDP port 123) for the time signal to get through. Obviously, any gap in a firewall can lead to security issues, so fortunately NIST provide another method of receiving their time.

NTP Time Servers

NIST, from their transmitter in Colorado, broadcasts a time signal that all of North America can receive. The signal, generated and kept true by NIST atomic clocks, is highly accurate, reliable and secure, received externally to the firewall by using a WWVB timeserver (WWVB is call sign for the NIST time signal).

Once received, the protocol NTP (Network Time Protocol) will use the NIST time code and distribute it around the network and will ensure each device keeps true to it, continually making adjustments to cope with drift.

WWVB NTP time servers are accurate, secure and reliable and a must-have for anybody serious about security and accuracy who wants to receive a source of NIST time.


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Richard N Williams is a technical author and a specialist in the NTP Server and Time Synchronisation industry. Richard N Williams on Google+