Most computer networks have to be synchronized to some degree. Allowing the clocks on computers across a network to all be telling different times is really asking for trouble. All sorts of errors can occur such as emails not arriving, data getting lost, and errors get unnoticed as the machines struggle to makes sense of the paradoxes that unsynchronized time can cause.
The problem is computers use time in the form of timestamps as the only point of reference between different events. If these don’t match then computers struggle to establish not only the order of events but also if the events took place at all.
Synchronizing a computer network together is extremely simple, thanks largely to the protocol NTP (Network Time Protocol). NTP is installed on most computer operating systems including Windows and most versions of Linux.
NTP uses a single time source and ensures that every device on the network is synchronized to that time. For many networks this single time source can be anything from the IT manager’s wrist watch to the clock on one of the desktop machines.
However, for networks that have to communicate with other networks, have to deal with time sensitive transactions or where high levels of security are required then synchronization to a UTC source is a must.
Coordinated Universal Time (UTC) is a global timescale used by industry all over the world. It is governed by a constellation of atomic clocks making it highly accurate (modern atomic clocks can keep time for 100 million years without losing a second).
For secure synchronization to UTC there is really only one method and that is to use a dedicated NTP time server. Online NTP servers are used by some network administrators but they are taking a risk not only with the accuracy of the synchronization but also with security as malicious users can imitate the NTP time signal and penetrate the firewall.
As dedicated NTP servers are external to the firewall, relying instead on the GPS satellite signal or specialist radio transmissions they are far more secure.