Time Synchronisation

Network Time Protocol (NTP) designed to synchronise computers an devices on a network to an authoritative time source such as UTC (Universal Coordinated Time).
NTP distributes the timing information to all the devices on a network that require synchronisation and adjusts the clocks of these devices accordingly to keep it in line with the timing source.

May network administrators opt to use the Internet to retrieve timing information despite the fact that several surveys have found that many Internet based timing sources are inaccurate. There are Internet sources that are accurate to UTC but to use them as a timing source they need to be close as the distance travelled can reduce the accuracy. Furthermore, Internet timing sources can’t be authenticated. Authentication is a security measure utilised by NTP to ensure the timing source is what it says it is and not a malicious user.

There are several options available to receive an authenticated accurate timing source the first being the national time and frequency transmissions broadcast by several countries. However, these transmissions are not available everywhere and even in the country of origin the signal can be blocked by local geographical features.

The most assured way of receiving a UTC timing source is to use the onboard atomic clocks of the American GPS (Global Positioning System) network.
GPS, commonly known as a satellite navigation system actualy relays timing information. It is this information that is received by GPS receivers that can then triangulate the position of the receiver by working out how long the signal has taken to arrive from various satellites (four being the minimum to receive an accurate location).

Although this timing information is not in a UTC format, because it is from an atomic clock and incredibly accurate, NTP can convert the information into UTC and distribute it through the network using a NTP GPS time server.

A NTP GPS server can receive the signal from a GPS aerial although this does need to have a good view of the sky as the satellites relay their transmissions via line-of-sight.

Using a dedicated NTP GPS server a computer network can be synchronised to within a few milliseconds of NTP (milli=1000th of a second) and provide security and authentication.

Following the dramatic rise of GPS technology over the last few years, NTP GPS servers are now relatively inexpensive and are simple and straight forward systems to install.

Richard Hawkesford © 2009