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. NTP was developed over twenty-five years ago at the University of Delaware by Dr D. Mills, it remains one of the oldest protocols in constant use. 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 daemon can act as a server or client and can easily be configured to synchronise with an Internet based NTP server. 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 a number of security features that allow service ristrictions and server authentication. 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.
Computer servers and workstations have integrated real-time clocks that are based on simple, cheap, crystal oscillators. The real-time clock is battery backed and maintains system time even when the computer is switched off. However, crystal oscillators characteristics change significantly with temperature variation, which can cause the time to drift by several minutes each day. This article describes how Internet or Intranet based NTP servers can be utilised to maintain accurate time on a computer system.
NTP, or Network Time Protocol, was originally developed over 25 years ago as a means of distributing accurate time around the Internet. It is one of the oldest network protocols still in use today. NTP allows network time clients to synchronise to Internet based NTP time servers. It is an integral part of the Internet network structure.
Many operating systems including Microsoft Windows, LINUX, UNIX and Novell Netware integrate the ability to synchronise their system time by utilising NTP or its reduced sister protocol SNTP (Simple Network Time Protocol). Most NTP clients only require a single, or multiple, NTP server address to be specified and will periodically synchronise with the specified NTP server.
There a large number of Internet hosted NTP servers. Most synchronise with external timing reference such as GPS or time and frequency radio broadcasts. NTP servers that synchronise to an external timing reference are designated as stratum 1 time servers, this is because they sit at the head of the network time hierarchy. NTP servers that synchronise to stratum1 time server are designated stratum 2 and so on.
Below is a list of a small number of the most popular NTP servers available across the Internet. You should choose a NTP server close to you geographic locality, so as to reduce network round trip delays.
ntp.my-inbox.co.uk - Locality: United Kingdom. time.nist.gov - Locality: United States. canon.inria.fr - Locality: France. ptbtime1.ptb.de - Locality: Germany. clock.isc.org - Locality: Canada.
Most NTP servers are based on the LINUX operating system. The NTP software distribution is a freely downloadable application supplied under the GNU public licence. NTP source code and documentation can be obtained from the 'ntp.org' web-site. Under LINUX, NTP runs a daemon, periodically contacting specified NTP servers and synchronising system time.
Microsoft Windows operating systems utilise Microsoft's proprietary time synchronisation service 'Windows Time'. The Windows Time service can be configured via registry settings to synchronise with network time servers at specified intervals.
To conclude, Internet based NTP servers are readily available free sources of precise time. Additionally, most modern operating systems have the ability to contact and synchronise with NTP servers without the need for additional software. So, provided your network has an Internet connection, there is no longer any need to continue with inaccurate system time.
David Evans has sinced written about articles on various topics from Computers and The Internet, Personal Desktop and Computers and The Internet. David Evans is a respected technical author who has written a number of articles about computer and computer network time synchronisation systems. Previous articles include information about NTP authentication, security and NTP server reference clocks. Pl. David Evans's top article generates over 18100 views. to your Favourites.