How Does NTP Work ?

NTP or Network Time Protocol is a standard protocol for the transfer of time between computers. Typically, GPS time server’s use the network time protocol to synchronise large networks of computers to the correct time. Synchronisation of time is very important in large distributed networks in order to ensure events occur in an ordered manner.

NTP is used to ensure that the time on computers is synchronised to a single accurate reference clock. All the computers can then be provided with a synchronised time from which to operate.

In fact not only computers can use NTP, many other networks products use it to get accurate time, such as; routers, switches, telephone systems, CCTV systems, digital video recorders (DVR’s) and networked clocks, amongst others.

NTP operates in a hierarchical manner. At the highest level, stratum-1, a NTP time server device obtains accurate time from a hardware time source such as GPS. It uses the accurate time reference to synchronise its internal clock. Precise time is then passed on to stratum-2 NTP servers, who in turn use it to synchronise their internal clocks and so on down the line. Each lower level, or stratum, sees a slight decline in accuracy. The hierarchical system allows the load of a large number of clients to be shared between a number of lower-level stratum devices, rather than all trying to access the higher-level device.

A NTP client synchronizes by periodically requesting time from a NTP server. The server responds by providing an accurate time stamp. Each NTP request and response is time-stamped, so that round-trip delay calculations can be performed to further improve accuracy.

 

 

About the Author.
Andy Shinton has spent his entire career within the IT industry, mainly in the Time and Frequency sector. Since 2002, he has headed TimeTools Research and Development Division. Andy regularly writes white-papers and articles about NTP and Network Timing Solutions.

 

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