How To Synchronize a LAN to a NTP Time Server

Most PC's usually have internal real-time clocks built in. They are not, however, very good at keeping time due to the parts used to carry out this function are often low-cost components. It is widely recognised that left to their own devices desktop computers are not reliable time-keepers. It is not unknown for them to drift by many minutes each day. This can, of course, have serious implications for computer networks in modern day applications. With each computer on a network issuing a different time-stamp applications such as transaction processing, updating files and event logging can be seriously compromised.

This problem can be overcome with the use of a Time Server. A time server enables an organisation to bring its network infrastructure in line to operate a uniform time-stamp, as the network can be synchronised to a single precise reference. A Time Server retrieves accurate time from an exte
al time reference and maintains this precise time. This information can then be shared with network clients bringing them all under the same time umbrella.

The Network Time Protocol, or NTP, is a standard form of network time synchronisation. NTP specifies packets of information that pass between the Time Server and the client for synchronisation. NTP client software is widely accessible, and is indeed free, over the Internet.
Also, numerous operating systems can utilise a dedicated local time server without installing additional software.

Configuring NTP client software is a very straight forward process. Usually, all that is required is the IP address of the NTP Server the client wishes to use.

There are various benefits in choosing to use a local server as opposed to the freely available Internet based time servers. One of the main advantages being that the local server will sit inside your firewall. Reference to an Internet based server outside your firewall could introduce significant security risks. Local time servers also tend to be more accurate having a direct link to the exte
al time reference. The accuracy of Internet based service providers has also been questioned, with a recent survey highlighting approx 78% were configured incorrectly.

Precise time can be obtained from various exte
al reference clocks. Modern applications preferred option is the 'Global Positioning System', or 'GPS' as it is more commonly known. A GPS system is able to provide timing information to within a few nanoseconds of the current time. The installation of a GPS system, however, can have cost implications. A GPS antenna ideally requires a good view of the sky which means a roof top would be the preferred location, giving a full 360 degree view. Radio Time and frequency broadcasts could be used as an alte
ative time reference. These can often be received indoors if located close to the host server. While this would be a cheaper option, problems with interference can significantly affect reception. Also radio time references are typically not as accurate as GPS signals.

To conclude, synchronising a PC and computer networks to a precise time reference is not a complicated procedure. NTP time servers are widely available, all feature advantages and disadvantages in their application. A local time server overcomes issues of security, associated with Internet based time servers, as well as issues of reliability linked to both Internet based and radio time references.