Utilising GPS for a Stratum 1 NTP Server
The Network Time Protocol was originally developed over 25 years ago as a means of synchronising computers on the Internet. NTP is a suite of applications that provide synchronisation of time to an accurate timing reference. Originally developed for Linux\UNIX, NTP has since been rewritten for the Microsoft Windows operating systems. NTP allows a network time client to synchronise to within milliseconds of an accurate external time reference.
Combining an accurate external timing reference with the NTP application provides a highly accurate network timing device. This article describes how to utilise a low-cost GPS receiver in combination with the NTP software distribution to provide an accurate stratum 1 NTP server timing reference.
The NTP source code can be obtained from the NTP website and must be compiled on the local machine. The downloadable NTP tar file extracts to a directory where scripts are available to make compilation and configuration very straight-forward. Many Linux distributions provide pre-installed versions of the software. To set up and install a stratum 1 time server a stable external timing reference is required. The NTP software provides a large number of reference clock drivers that can be utilised to interface with a range of hardware timing references. Hardware timing references can generally be fairly expensive pieces of equipment. However, the popularity of GPS navigation devices has reduced the cost of GPS technology. Low-cost GPS receivers are now readily available from around $100. Many GPS receivers have a RS232 serial communications port, which can easily be connected to a PC. Many low-cost GPS devices use the NMEA protocol, which is a standard GPS protocol for providing location and timing information. The timing information can be utilised by the NTP software as an accurate timing reference to provide a stratum 1 NTP server.
The NTP software needs to be compiled with the NMEA reference clock driver to interface with the GPS receiver. Once compiled the application must be configured to utilise the correct serial port. When correctly installed and configured, the NTP application will provide your network with an accurate, stable timing reference.
Most computers such as Linux and Microsoft Windows servers and network devices such as routers and switches can synchronise time with a NTP server. Any network device that has an integrated NTP client can be configured to synchronise time with the NTP server. Generally, clients only need the IP address of the NTP server for synchronisation. With a NTP server, you can synchronise almost any device on your network.
By : David Evans
Keyword : Utilising GPS,Stratum 1 NTP Server
