Computer network synchronisation is essential in the modern world. Many of the world’s computer networks are all synchronised to the same global timescale UTC (Coordinated Universal Time).
To govern synchronisation the protocol NTP (Network Time Protocol) is used in most cases as it is able to reliably synchronise a network to a few milliseconds off UTC time.
However, the accuracy of time synchronisation is solely dependent on the accuracy of whatever time reference is selected for NTP to distribute and here lies one of the fundamental errors made in synchronising computer networks.
Many network administrators rely on Internet time references as a source of UTC time, however, apart from the security risks they pose (being as they are on the wrong side of a network firewall) but also their accuracy can not be guaranteed and recent studies have found less than half of them providing any useful accuracies at all.
For a secure, accurate and reliable method of UTC there really are just two choices. Utilise the time signal from the GPS network or rely on the long wave transmissions broadcast by national physics laboratories such as NPL and NIST.
To select which method is best then the only factor to consider is the location of the NTP server that is to receive the time signal.
GPS is the most flexible in that the signal is available literally everywhere on the planet but the only downside to the signal is that a GPS antenna has to be situated on the roof as it needs a clear view of the sky. This may prove problematic if the time server is located in the lower floors of a sky scraper but on the whole most users of GPS time signals find that they are very reliable and incredibly accurate.
If GPS is impractical then the national time and frequencies provide an equally accurate and secure method of UTC time. These longwave signals are not broadcast by every country however, although the US WWVB signal broadcast by NIST in Colorado is available in most of North America including Canada.
There are various versions of this signal broadcast throughout Europe including the German DCF and the UK MSF which prove to be the most reliable and popular. These signals can often be picked up outside the nation’s borders too although it must be noted long wave transmissions are vulnerable to local interference and topography.
For complete peace of mind, dual system NTP servers that receive signals from both the GPS and national physics laboratories are available although they tend to be a little more expensive than single systems although utilising more than one time signal makes them doubly reliable.