They buzz away next to the system’s servers and few people ever give them a moment’s thought, but network time servers are a crucial aspect to any computer network. Understanding their importance is important for maintain a healthy network, as time errors can lead to all sorts of problems, such as security breaches, data loss, or application failure.
Network time servers are responsible for providing a network’s time. Of course, all computers have their own onboard clocks built into the motherboards, but these devices are only cheap oscillators and are prone to drift. When you have a network of hundreds or even thousands of PCs and devices, if there was no synchronisation to a single network time source, all the machines could be relaying completely different times, often several minutes apart.
To maintain synchronicity all devices on a network need to have access to a single time source, which needs to be as accurate and precise as possible. Furthermore, a network also needs a means of maintaining this time accurately, to avoid drift and maintain synchronisation with each other.
Network time servers do this by using a single, highly accurate time source, which they can then distribute around a network. Furthermore, they continue to check the times on devices such as PC consoles, to make sure there is no drift, and if there is, the network time server adjusts the offending machine it to keep in synchronised with the rest of the network.
Most network time servers run Network Time Protocol (NTP) to achieve this, which is a highly efficient time synchronisation protocol able to maintain accuracies to a few milliseconds. With NTP, a single time source can be distributed to all devices on a network, ensuring complete synchronisation. NTP continually checks and adjusts machines for drift.
Types of Network Time Server
Network time servers come in several flavours. Firstly, there is the radio referenced time server, which receives its time from a radio signal. These transmissions are usually put out by organisations such as the UK’s National Physical Laboratory (NPL) or the United States’ National Institute for Standards and Time (NIST). Because these signals are generated by atomic clocks, they are incredibly accurate, enabling networks to utilise this same precision.
Another type of network time server is one that utilises GPS. The GPS network (Global Positioning System) also transits atomic clock signals sent from the satellites. These clock systems are what satellite navigation systems use to work out where they are in the world, but are just as useful as a source of atomic clock time. GPS time servers, receive the signals from a rooftop antenna, and then distributes the time around a network.
Some network time servers use a dual system, which receives the time from both radio and GPS sources. Dual time servers are therefore more accurate, as NTP can take an average of both time sources before it distributes it around a network. They also maintain accuracy when, for instance, interference or outage blocks the radio signal, or when the antenna loses track of the satellites, which is rare, but can happen after a power outage or other system reboot.