How Atomic Clocks Control our Transport Systems

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Getting from A to B has been a primary concern for societies ever since the first roads were built. Whether it is horseback, carriage, train, car or plane – transportation is what enables societies to grow, prosper and trade.

In today’s world, our transportation systems are highly complex due to the sheer numbers of people who are all trying to get somewhere – often at similar times such as rush hour. Keeping the motorways, highways and railways running, requires some sophisticated technology.

Traffic lights, speed cameras, electronic warning signs, and railway signals and point systems have to be synchronised for safety and efficiency. Any differences in time between traffic signals, for instance, could lead to traffic queues behind certain lights, and other roads remaining empty. While on the railways, if points systems are being controlled by an inaccurate clock, when the trains arrive the system may be unprepared or not have switched the line – leading to catastrophe.

Because of the need for secure, accurate and reliable time synchronisation on our transport systems, the technology that controls them is often synchronised to UTC using atomic clock time servers.

Most time servers that control such systems have to be secure so they make use of Network Time Protocol (NTP) and receive a secure time transmission either utilising atomic clocks on the GPS satellites (Global Positioning System) or by receiving a radio transmission from a physics laboratory such as NPL (National Physical Laboratory) or NIST (National Institute of Standards and Time).

In doing so, all traffic and rail management systems that operate on the same network are accurate to each other to within a few milliseconds of this atomic clock generated time and the NTP time servers that keep them synchronised ensures they stay that way, making minute adjustments to each system clock to cope with the drift.

NTP servers are also used by computer networks to ensure that all machines are synced together. By using a NTP time server on a network, it reduces the probability of errors and ensures the system is kept secure.

Do I Really Need an NTP Time Server?

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NTP (Network Time Protocol) is one of the oldest protocols still in use today. It was developed in the 1980’s when the internet was still in its infancy and was designed to help computers synchronise together, preventing drift and ensuring devices can communicate with unreliable time causing errors.

NTP is now packaged in most operating systems and forms the basis for time synchronisation in computers, networks and other technologies. Most technologies and networks use a network time server (commonly called an NTP time server) for this task.

These time servers are external devices that receive the time from a radio frequency or GPS signal (both generated by atomic clocks). This time signal is then distributed across the network using NTP ensuring all devices are using the exact same time.

As NTP is ubiquitous in most operating systems and the internet is awash with sources of atomic clock time, this begs the question of whether NTP time servers are still necessary for modern computer networks and technology.

There are two reasons why networks should always use a NTP time server and not rely on the internet as a source of time for synchronisation. Firstly, internet time can never be guaranteed. Even if the source of time is 100% accurate and kept true (incidentally most sources of internet time are derived using an NTP time server at the host’s end) the distance from the host can lead to discrepancies.

Secondly, and perhaps fundamentally more important to most business networks is security. NTP time servers work externally to the network. The source of time either radio of GPS, is secure, accurate and reliable and as it is external to the network it can’t be tampered with en-route, or used to disguise malicious software and bots.

NTP servers don’t require an open port in the firewall, unlike internet sources of time which can be used as an entry point by malicious users and software.

From Pennies to NTP Servers the Intricacies of Keeping Time

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Keeping accurate time is an essential aspect of our day to day lives. Nearly everything we do is reliant on time from getting up for work in the morning to arranging meetings, nights out or just when it’s time for dinner.

Most of us carry some kind of clock or watch with us but these timepieces are prone to drift which is why most people regularly use another clock of device to set their time too.

In London, by far the most common timepiece that people use to set their watches too is Big Ben. This world famous clock can be seen for miles, which is why so many Londoners use it to ensure their watches and clocks are accurate – but have you ever wondered how Big Ben keeps itself accurate?

Well the unlikely truth lies in a pile of old coins. Big Ben’s clock mechanism uses a pendulum but for fine tuning and ensuring accuracy a small pile of gold coins resting on the top of the pendulum.  If just one coin is removed then the clock’s speed will change by nearly half a second

Ensuring accuracy on a computer network is far less archaic. All computer networks need to run accurate and synchronised time as computers too are completely reliant on knowing the time.

Fortunately, NTP time servers are designed to accurately and reliably keep entire computer networks synchronised. NTP (Network Time Protocol) is a software protocol designed to keep networks accurate and it works by using a single time source that it uses to correct drift on

Most network operators synchronise their computers to a form of UTC time (Coordinated Universal Time) as this is governed by atomic clocks (highly accurate timepieces that never drift – not for several thousand years, anyway).

A source of atomic clock time can be received by a NTP server by using either GPS satellite (Global Positioning System) signals or radio frequencies broadcast by national physics laboratories.

NTP servers ensure that computer networks all across the globe are synchronised, accurate and reliable.

The Time According to UTC (Coordinated Universal Time)

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The modern world is a small one. These days, in business you are just as likely to be communicating across the Atlantic as you are trading with you neighbour but this can cause difficulties – as anybody trying to get hold of somebody across the other-side of the world will know.

The problem, of course, is time. There are 24 time zones on Earth which means that people you may wish to talk to across the other side of the world, are in bed when you are awake – and vice versa.

Communication is not jus a problem for us humans either; much of our communication is conducted through computers and other technologies that can cause even more problems. Not just because time-zones are different but clocks, whether they are those that power a computer, or an office wall clock, can drift.

Time synchronisation is therefore important to ensure that the device you are communicating with has the same time otherwise whatever transaction you are conducting may result in errors such as the application failing, data getting lost or the machines believing an action has taken place  when it has not.

Coordinated Universal Time

Coordinated Universal Time (UTC) is an international timescale. It pays no heed to time-zones and is kept true by a constellation of atomic clocks – accurate timepieces that do not suffer from drift.

UTC also compensates for the slowing of the Earth’s spin by adding leap seconds to ensure there is no drift that would eventually cause noon to drift towards night (albeit in many millennia; so slow is the slowing of the Earth).

Most technologies and computer networks across the globe use UTC as their source of time, making global communication more feasible.

Network Time Protocol and NTP Time Servers

Receiving UTC time for a computer network is the job of the NTP time server. These devices use Network Time Protocol to distribute the time to all technologies on the NTP network. NTP time servers receive the source of time from a number of different sources.

  • The internet – although  internet time sources can be insecure and unreliable
  • The GPS (Global Positioning System) – using the onboard atomic clocks from navigation satellites.
  • Radio signals – broadcast by national physics laboratories like NPL and NIST.

Using Atomic Clocks for Time Synchronisation

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The atomic clock is unrivalled in its chronological accuracy. No other method of maintaining time comes close to the precision of an atomic clock. These ultra-precise devices can keep time for thousands of years without losing a second in drift – in comparison to electronic clocks, perhaps the next most accurate devices, which can drift up to a second a day.

Atomic clocks are not practical devices to have around though. They use advanced technologies such as super-coolant liquids, lasers and vacuums – they also require a team of skilled technicians to keep the clocks running.

Atomic clocks are deployed in some technologies. The Global Positioning System (GPS) relies on atomic clocks that operate onboard the unmanned orbiting satellites. These are crucial for working out accurate distances. Because of the speed of light that the signals travel, a one second inaccuracy in any GPS atomic clock would lead to positing information being out by thousands of kilometres – but the actual accuracy of GPS is within a few metres.

While these wholly accurate and precise instruments for measuring time are unparalleled and the expensive of running such devices is unobtainable to most people, synchronising your technology to an atomic clock, in actual fact, is relatively simple.

The atomic clocks onboard the GPS satellites are easily utilised to synchronise many technologies to. The signals that are used to provide positioning information can also be used as a source of atomic clock time.

The simplest way to receive these signals is to use a GPS NTP server (Network Time Protocol). These NTP servers use the atomic clock time signal from the GPS satellites as a reference time, the protocol NTP is then used to distribute this time around a network, checking each device with the GPS time and adjusting to ensure accuracy.

Entire computer networks can be synchronised to the GPS atomic clock time by using just one NTP GPS server, ensuring that all devices are within milliseconds of the same time.

The Hierarchy of a NTP Time Server Stratum Levels Explained

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When it comes to time synchronisation and using Network Time Protocol (NTP) to ensure accuracy on a computer network, it is important to understand the hierarchy of NTP and how it affects distance and accuracy.

NTP has a hierarchical structure known as stratum levels. In principle the lower the stratum number the closer the device is (in accuracy terms) to an original time source.

NTP time servers work by receiving a single time source and using this as a basis for all time on the network, however, a synchronised network will be only as accurate as the original time source and this is where stratum levels come in.

And atomic clock, either one sat in a large scale physics laboratory, or those aboard GPS satellites, are stratum 0 devices. In other words these are the devices that actually generate the time.

Stratum 1 devices are NTP time servers that get their source of time directly from these stratum 0 atomic clocks. Either by using a GPS receiver or a radio referenced NTP server, a stratum 1 device is as accurate as you can get without having your own multi-million dollar atomic clock in the server room. A stratum 1 NTP time server will typically be accurate to within a millisecond of the atomic clock time.

Stratum 2 devices are the next step down on stratum level chain. These are time servers that receive their time from a stratum 1 device. Most online time servers, for instance, are stratum 2 devices, getting their time from another NTP time server. Stratum 2 devices are obviously further away from the original time source and therefore are not quite as accurate.

The stratum levels on an NTP network continue on, with devices connecting to devices going all the way down to stratum 10, 11, 12 and so on – obviously the more links in the chain the less accurate the device will be.

Dedicated stratum 1 NTP time servers are by far the most accurate, reliable and secure method of synchronising a computer network and no business network should really be without one.

Time Synchronisation of Technology

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Many technologies are reliant and precise, accurate and reliable time. Time synchronisation is vital in many technical systems that we encounter everyday, from CCTV cameras and ATMs to air traffic control and telecommunication systems.

Without synchronisation and accuracy many of these technologies would become unreliable and in could cause major problems, even catastrophic ones in the case of air traffic controllers.

Precise time and synchronisation also plays an increasingly important part in modern computer networking, ensuring the network is secure, data is not lost, and the network can be debugged. Failing to ensure a network is synchronised properly can lead to many unexpected problems and security issues.

Ensuring accuracy

To ensure accuracy and precise time synchronisation modern technologies and computer networks the time controlling Network Time Protocol (NTP) is most commonly employed. NTP ensures all devices on a network, whether they are computers, routers, CCTV cameras or almost any other technology, are maintained at the exact same time as every other device on the network.

It works by using a single time source that it then distributes around the network, checking for drift, and correcting devices to ensure parity with the time source. It has many other features such as being able to assess errors and calculating the best time from multiple sources.

Obtaining the time

When using NTP, getting the most accurate source of time allows you to keep your network synchronised – not just together but also synchronised to every other device or network that uses that same time source.

A global timescale known as Coordinated Universal Time (UTC) is what most NTP servers and technologies use. A sit is a global timescale, and is not concerned with time zones and daylight saving, UTC allows networks across the world to communicate precisely with the exact same time source.

NTP time servers

Despite their being many sources of UTC across the internet, these are not recommended for accuracy and security reasons; to receive an accurate source of NTP there are really only two options: using a NTP time server that can receive radio transmissions from atomic clock laboratories or by using the time signals from GPS satellites.

Windows Server and the Importance of NTP

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Windows Server is the most common operating system used by business networks. Whether it is the latest Windows Server 2008 or a previous incarnation such as 2003, most computer networks used in trade and business have a version.

These network operating systems make use of the time synchronization protocol NTP (Network Time Protocol) to ensure synchronicity between all devices connected to the network. This is vital in the modern world of global communication and trade as a lack of synchronization can cause untold problems; data can get lost, errors can go undetected, debugging becomes near impossible and time sensitive transactions can fail if there is no synchronization.

NTP works by selecting a single time source and it be checking the time on all devices on the network, and adjusting them, it ensures the time is synchronised throughout. NTP is capable of keeping all PCs, routers and other devices on a network to within a few milliseconds of each other.

The only requirement for network administrators is to select a time source – and this is where many IT professionals commonly go wrong.

Internet time servers

Any source of time to synchronize a network to should be UTC (Coordinated Universal Time) which is a global timescale controlled by the world’s most accurate atomic clocks and the number one source for finding a UTC time server is the internet.

And many network administrators opt to use these online time servers thinking they are an accurate and secure source of time; however, this is not strictly the case. Internet time servers send the time signal through the network firewall which means viruses and malicious users can take advantage of this ‘hole.’

Another problem with internet time servers is that their accuracy can’t be guaranteed. Often they are not as accurate as a profession network requires and factors such as distance away from the host can make differences in the time.

Dedicated NTP time server

Dedicated NTP time servers, however, get the time directly from atomic clocks – either from the GPS network or via secure radio transmissions from national physics laboratories. These signals are millisecond accurate and 100% secure.

For anyone running a network using Windows Server 2008 or other Microsoft operating system should seriously consider using a dedicated NTP server rather than the internet to ensure accuracy, reliability and security.

NTP Servers Which Signal is Best Radio or GPS?

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NTP time servers (Network Time Protocol) are an essential aspect of any computer or technology network. So many applications require accurate timing information that failing to synchronize a network adequately and precisely can lead to all sorts of errors and problems – especially when communicating with other networks.

Accuracy, when it comes to time synchronization, means only one thing – atomic clocks. No other method of keeping time is as accurate or reliable as an atomic clock. In comparison to an electronic clock, such as a digital watch, which will lose up to a second a day – an atomic clock will remain accurate to a second over 100,000 years.

Atomic clocks are not something that can be housed in an average server room though; atomic clocks are very expensive, fragile and require full time technicians to control so are usually only found in large scale physics laboratories such as the ones run by NIST (National Institute of Standards and Time – USA) and NPL (National Physical Laboratory – UK).

Getting a source of accurate time from an atomic clock is relatively easy. For a secure and reliable source of atomic clock time there are only two options (the internet can neither be described as secure nor reliable as a source of time):

  • GPS time
  • UTC time broadcast on long-wave

GPS time, from the USA’s Global Positioning System, is a time stamp generated onboard the atomic clocks on the satellites. There is one distinct advantage about using GPS as a source of time: it is available anywhere on the planet.

All that is required to receive and utilise GPS time is a GPS time sever and antenna; a good clear view of the sky is also needed for an assured signal. Whilst not strictly UTC time (Coordinated Universal Time) being broadcast by GPS (UTC has had 17 leap seconds added to it since the satellites were launched) the timestamp included the information needed for NTP to convert it to the universal time standard.

UTC, however, is broadcast directly from physics laboratories and is available by using a radio referenced NTP server. These signals are not available everywhere but in the USA (the signal is known as WWVB) and most of Europe (MSF and DCF) are covered. These too are highly accurate atomic clock generated time sources and as both methods come from a secure source the computer network will remain secure.

The Time According to Cumbria Using the UKs MSF Time and Frequency Signal

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Getting an accurate source of time for computer networks and other technologies is increasingly becoming more important. As technologies advance and global communications mean that we are just as liable to communicate with technology across the other side of the planet as we are at home.

The need for accurate time is therefore essential if you wish to prevent time sensitive applications on your network failing or to avoid debugging problems – not too mention keeping your system secure.

NTP time servers (Network Time Protocol) are common devices that many computer networks use to provide a source of accurate time as NTP is able to ensure entire networks are synchronised to just a few milliseconds to the time reference.

The time reference that NTP servers use can come from several locations:

  • The internet
  • GPS satellite
  • And National Physical Laboratories

In the UK, the National Physical Laboratory (NPL) produce a time signal that can be received by radio referenced NTP time servers. This used to be broadcast from rugby in central England but in recent years the transmission has been moved to Cumbria.

The Cumbrian signal, known as MSF, is broadcast from Anthorn with a signal strength of 100 microvolts per metre at a distance of 1000 km. This should mean that the signal is available everywhere in the UK; however, this is not strictly the case as many MSF clocks and time servers can run into trouble when first trying to receive this atomic clock generated signal.

However, a simple checklist should ensure that no matter what your location you should be able to receive a signal to your MSF clock or NTP time server:

  • Check the power. Perhaps the most common problem ensure the battery is inserted and if the clock uses both mains power and a battery, remember to switch the mains power on. It can take quite a few minutes for the clock to pick up the MSF signal, so be patient.
  • Try rotating the clock or time server. As the MSF signal is long wave the antenna needs to be perpendicular to the signal for best reception.
  • If all else fails move the clock or time server to a different location. The signal can be blocked by local interference from electrical and mechanical devices.

* Note the MSF signal is down for scheduled maintenence on Tuesday 9 September 2010 from 10:00 BST to 14:00 BST