Time Synchronisation

Time synchronisation is extremely important for modern computer networks. In some industries time synchronisation is absolutely vital especially when you are dealing with technologies such as air traffic control or marine navigation where hundreds of lives could be put at risk by lack of precise time.

Even in the financial world, correct time synchronisation is vital as millions can be added or wiped off share prices every second. For this reason the entire world adheres to a global timescale known as coordinated universal time (UTC). However, adhering to UTC and keeping UTC precise are two different things.

Most computer clocks are simple oscillators that will slowly drift either faster or slower. Unfortunately this means that no matter how accurate they are set on Monday they will have drifted by Friday. This drift may be only a fraction of a second but it soon won’t take long for the originally UTC time to be over a second out.

In many industries this may not mean a matter of life and death of the loss of millions in stocks and shares but lack of time synchronisation can have unforeseen consequences such as leaving a company less protected from fraud. However, receiving and keeping true UTC time is quite straight forward.

Dedicated network time servers are available that uses the protocol NTP (Network Time Protocol) to continually check the time of a network against a source of UTC time. These devices are often referred to as an NTP server, time server or network time server. The NTP server constantly adjusts all devices on a network to ensure that the machines are not drifting from UTC.

UTC is available from several sources including the GPS network. This is an ideal source of UTC time as it is secure, reliable and available everywhere on the planet. UTC is also available via specialist national radio transmissions which are broadcast from national physics laboratories although they are not available everywhere.

A time server is an integral part of any network system. It ensures all machines on a network or keeping the exact same time, failure to do so could lead to all sorts of problems, particularly with time sensitive transactions.

Most computer networks are synchronised to UTC (coordinated Universal Time). UTC is a global time scale and used throughout the world. It is also highly precise as it is based on the time told by atomic clocks.

Atomic clocks are ideal sources of time as they do not drift whilst the standard electrical oscillators on our PC clocks can drift by a second every week. This drift can cause untold problems which is why most networks are synchronised to a time server that receives a time signal from an atomic clock.

Atomic clock time signals can be received from a myriad of sources. The Internet is an obvious choice but unless security and precision is not an issue then it is not recommended for any commercial networks as using an Internet times source can leave a system open to security threats.

For security and accuracy there are two options to synchronise to an atomic clock. One is to use a GPS time server that receives the time-code from the GPS system. The other method is to use a time server that can receive the long wave radio transmissions broadcast from several national physics laboratories.

Telling the time is not as straight forward as most people think. In fact the very question, ‘what is the time?’ is a question that even modern science can fail to answer. Time, according to Einstein, is relative; it’s passing changes for different observers, affected by such things as speed and gravity.

Even when we all live on the same planet and experience the passing of time in a similar way, telling the time can be increasingly difficult. Our original method of using the Earth’s rotation has since been discovered to be inaccurate as the Moon’s gravity causes some days to be longer than 24 hours and a few to be shorter. In fact when the early dinosaurs were roaming the Earth a day was only 22 hours long!

Whilst mechanical and electronic clocks have provided us with some degree accuracy, our modern technologies have required far more accurate time measurements. GPS, Internet trading and air traffic control are just three industries were split second timing is incredibly important.

So how do we keep track of time? Using the Earth’s rotation has proven unreliable whilst electrical oscillators (quartz clocks) and mechanical clocks are only accurate to a second or two per day. Unfortunately for many of our technologies a second inaccuracy can be far too long. In satellite navigation, light can travel 300,000 km in just over a second, making the average sat-nav unit useless if there was one second of inaccuracy.

The solution to finding an accurate method of measuring time has been to examine the very small – quantum mechanics. Quantum mechanics is the study of the atom and its properties and how they interact. It was discovered that electrons, the tiny particles that orbit atoms changed the path that they orbit and released a precise amount of energy when they do so.

In the case of the caesium atom this occurs nearly nine billion times a second and this number never alters and so can be used as an ultra reliable method of keeping track of time. Caesium atoms are use din atomic clocks and in fact the second is now defined as just over 9 billion cycles of radiation of the caesium atom.

Atomic clocks are the foundation for many of our technologies. The entire global economy relies on them with the time relayed by NTP time servers on computer networks or beamed down by GPS satellites; ensuring the entire world keeps the same, accurate and stable time.

An official global timescale, Coordinated Universal Time (UTC) has been developed thanks to atomic clocks allowing the whole world to run the same time to within a few thousandths of a second from each other.