Computer systems utilise low-cost timing components that keep very poor time. The timing chips and oscillators used by many PC circuit board manufacturers can cause system time to drift wildly, by minutes every day. For environments that require synchronised time over a range of processes or devices, an alternative must be found. This is where the Network Time Protocol, or NTP, comes in. NTP provides a low-cost software solution to the problem of computer time synchronisation. This article describes how NTP and Internet based NTP servers can be utilised to eliminate drift and to maintain synchronisation across a number of networked devices.
There are a large number of Internet based time references that use the Network Time Protocol (NTP) to synchronise time clients. Dr David Mills of the University of Delaware introduced NTP over 25 years ago. The protocol was developed to provide accurate synchronisation of time between time servers and clients. Internet based NTP servers synchronise their time to accurate external reference clocks, such as GPS, national radio time standards or precise atomic clocks. Precise time is then disseminated around the network for the purpose of synchronisation.
Most present day computer operating systems have the ability to synchronise time with an accurate internet based NTP server. Linux, Unix, Microsoft Windows XP/2000/2003/Vista and Novell all have routines for NTP time synchronisation. Generally, client-side configuration consists of providing the client with the domain name of the NTP server.
The Microsoft Windows operating systems allow entry of a NTP server into the 'Internet Time' tab of the 'Time Properties' applet. Periodically, the NTP server will be contacted to obtain time and perform synchronisation.
The Linux and Unix operating systems have a NTP daemon available from the NTP web site at 'ntp.org'. The NTP daemon can be configured to otain time from other NTP servers or act as a server in its own right. The 'ntp.conf' configuration file contains a list of servers that can be contacted. Simply enter the IP address or domain name of a NTP server in the list.
To maintain accurate time on a computer system using NTP is very straightforward. However, there are many other more advanced features of the NTP protocol. There are security and authentication facilities that allow a server to limit client access and a client to authenticate a server. Additionally, there are numerous reference clock drivers available to synchronise NTP with a precise external reference - providing a full-blown NTP server installation.
To conclude, computer systems provide notoriously poor time keeping hardware. Without help, standard time keeping devices are just not up to the task of providing system-wide time synchronisation. The solution is to use the NTP protocol and get your computers synchronised to some of the most accurate clocks in the world.
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The author of this article, D. Evans, is a well-respected technical author in the field of NTP server systems and computer network time synchronisation. D. Evans is the author of many articles and white papers detailing the instillation and configuration of computer network timing systems. A number of articles also discuss precision timing references for NTP servers such as TCXO, OCXO and rubidium oscillators. Please go to our web site for more information about NTP server systems.
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