Using NIST Time Servers

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The National Institute for Standards and Technology (NIST) is one of the world’s leading atomic clock laboratories, and is the leading American time authority. Part of a constellation of national physics laboratories, NIST help ensure the worlds atomic clock time standard UTC (Coordinated Universal Time) is kept accurate and is available for the American people to use as a time standard.

All sorts of technologies rely on UTC time. All the machines on a computer network are usually synchronised to source of UTC, while technologies such as ATM’s, closed-circuit television (CCTV) and alarm systems require a source of NIST time to prevent errors.

Part of what NIST does is to ensure that sources of UTC time are readily available for the technologies to utilise, and NIST offer several means of receiving their time standard.

The Internet

The internet is the easiest method of receiving NIST time and in most Windows based operating systems, the NIST time standard address is already included in the time and date settings, allowing easy synchronisation. If it isn’t, to synchronise to NIST you simply need to double click on the system clock (bottom right hand corner) and enter the NIST server name and address. A full list of NIST Internet servers, here:

The Internet, however, is not a particularly secure location to receive a source of NIST time. Any Internet time source will require and open port in the firewall (UDP port 123) for the time signal to get through. Obviously, any gap in a firewall can lead to security issues, so fortunately NIST provide another method of receiving their time.

NTP Time Servers

NIST, from their transmitter in Colorado, broadcasts a time signal that all of North America can receive. The signal, generated and kept true by NIST atomic clocks, is highly accurate, reliable and secure, received externally to the firewall by using a WWVB timeserver (WWVB is call sign for the NIST time signal).

Once received, the protocol NTP (Network Time Protocol) will use the NIST time code and distribute it around the network and will ensure each device keeps true to it, continually making adjustments to cope with drift.

WWVB NTP time servers are accurate, secure and reliable and a must-have for anybody serious about security and accuracy who wants to receive a source of NIST time.

Most Accurate Atomic Clock Yet

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A new atomic clock as accurate as any produced has been developed by the University of Tokyo which is so accurate it can measure differences in Earth’s gravitational field—reports the journal Nature Photonics.

While atomic clocks are highly accurate, and are used to define the international timescale UTC (Coordinated Universal Time), which many computer networks rely on to synchronise their NTP servers to, they are finite in their accuracy.

Atomic clock use the oscillations of atoms emitted during the change between two energy states, but currently they are limited by the Dick effect, where noise and interference generated by the lasers used to read the frequency of the clock, gradually affect the time.

The new optical lattice clocks, developed by Professor Hidetoshi Katori and his team at the University of Tokyo, get around this problem by trapping the oscillating atoms in an optical lattice produced by a laser field. This makes the clock extremely stable, and incredibly accurate.

Indeed the clock is so accurate Professor Katori and his team suggest that not only could it man future GPS systems become accurate to within a couple of inches, but can also measure the difference in the gravitation of the Earth.

As discovered by Einstein in his Special and General Theories of Relativity, time is affected by the strength of gravitational fields. The stronger the gravity of a body, the more time and space is bent, slowing down time.

Professor Katori and his team suggest that this means their clocks could be used to find oil deposits below the Earth, as oil is a lower density, and therefore has a weaker gravity than rock.

Despite the Dick Effect, traditional atomic clocks currently used to govern UTC and to synchronise computer networks via NTP time servers, are still highly accurate and will not drift by a second in over 100,000 years, still accurate enough for the majority of precise time requirements.

However, a century ago the most accurate clock available was an electronic quartz clock that would drift by a second a day, but as technology developed more and more accurate time pieces were required, so in the future, it is highly possible that these new generation of atomic clocks will be the norm.

The Fragility of Time Japanese Earthquake Shortens the Day

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The recent and tragic earthquake that has left so much devastation in Japan has also highlighted an interesting aspect about the measurement of time and the rotation of the Earth.

So powerful was the 9.0 magnitude earthquake, it actually shifted Earth axis by 165mm (6½ inches) according to NASA.

The quake, one of the most powerful felt on Erath over the last millennia, altered the distribution of the planet’s mass, causing the Earth to rotate on its axis that little bit faster and therefore, shortening the length of every day that will follow.

Fortunately, this change is so minute it is not noticeable in our day to day activities as the Earth slowed by less than a couple of microseconds (just over a millionth of a second), and it isn’t unusual for natural events to slow down the speed of the Earth’s rotation.

In fact, since the development of the atomic clock in the 1950’s, it has been realised the Earth’s rotation is never continual and in fact has been increasing very slightly, most probably for billions of years.

These changes in the Earth’s rotation, and the length of a day, are caused by the effects of the moving oceans, wind and the gravitational pull of the moon. Indeed, it has been estimated that before humans arrived on Earth, the length of a day during the Jurassic period (40-100 million years ago) the length of a day was only 22.5 hours.

These natural changes to the Earth’s rotation and the length of a day, are only noticeable to us thanks to the precise nature of atomic clocks which have to account for these changes to ensure that the global timescale UTC (Coordinated Universal Time) doesn’t drift away from mean solar time (in other words noon needs to remain when the sun is highest during the day).

To achieve this, extra seconds are occasionally added onto UTC. These extra seconds are known as leap seconds and over thirty have been added to UTC since the 1970’s.

Many modern computer networks and technologies rely on UTC to keep devices synchronised, usually by receiving a time signal via a dedicated NTP time server (Network Time Protocol).

NTP time servers are designed to accommodate these leap seconds, enabling computer systems and technologies to remain accurate, precise and synchronised.

How the Moon Affects Time on Earth

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We take it for granted that a day is twenty-four hours. Indeed, our body’s circadian rhythm is finally tuned to cope with a 24-hour-day. However, a day on Earth was not always 24 hours long.

In the early days of the Earth, a day was incredibly short – just five hours long, but by the time of the Jurassic period,  when dinosaurs roamed the Earth, a day had lengthened to about 22.5 hours.

Of course now, a day is 24-hours and has been since humans evolved, but what has caused this gradual lengthening. The answer lies with the Moon.

The moon used to be a lot closer to the Earth and the effect of its gravity was therefore, a lot stronger. As the moon drives tidal systems, these were a lot stronger in the early days of the Earth, and the consequence was that the Earth’s spin slowed, the tugging of the moon’s gravity and tidal forces on the Earth, acing like a brake on the rotation of the planet.

Now the moon is farther away, and is continuing to move away even farther, however the effect of the moon is still felt on Earth, with a consequence that Earth’s day is still slowing down, albeit minutely.

With modern atomic clocks, it is now possible to account for this slowing and the global timescale used by most technologies to ensure time synchronisation, UTC (Coordinated Universal Time), has to account for this gradual slowing, otherwise, because of the extreme accuracy of atomic clocks, eventually day would slip into night as the Earth slowed and we didn’t adjust our clocks.

Because of this, once or twice a year, an extra second is added to the global timescale. These leap-seconds, as they are known, have been added since the 1970’s when UTC was first developed.

For many modern technologies where millisecond accuracy is required, this can cause problems. Fortunately, with NTP time servers (Network Time Protocol) these leap seconds are accounted for automatically, so any technologies hooked up to an NTP server need not worry about this discrepancy.

NTP servers are used by time sensitive technology and computer networks worldwide to ensure precise and accurate time, all the time, regardless of what the heavenly bodies are doing.

Computer Time Synchronisation The Basics

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With so much automated in the modern world and with computer networks running everything from finance to health services, keeping, storing and transferring information needs to be secure, accurate and reliable.

The time is crucial for computer systems to ensure this. Timestamps are the only information computers have to assess if a task has been completed, is due, or that information has been successfully received, sent or stored. One of the most common causes of computer errors comes from inadequate synchronisation of timings.

All computer networks need to be synchronised, and not just all the devices on a network, either. With so much global communication these days, all computer networks across the globe need to be synchronised together, otherwise when they communicate errors may occur, data can get lost, and it can pave the way for security problems as time discrepancies can be used by malicious users and software.

But how do computers synchronise together? Well, it is made possible by to innovations. The first is the international timescale, UTC (Coordinated Universal Time), kept true by atomic clocks and the same the world over, regardless of time-zones. The second, NTP (Network Time Protocol) is a computer program designed to keep PCs synchronised together.

Both NTP and UTC operate in tandem. The computer time server (NTP server) receives a UTC time source, either from radio, GPS (Global Positioning System) or the internet (although an insecure method of receiving UTC and not recommended).

NTP then distributes this time around a network, checking the time on each device at periodic intervals and adjusts them for any drift in time. Most computer networks that utilise NTP time servers in this way have each machine on the network within milliseconds of UTC time, enabling accurate and precise global communication.

NTP time servers are the only secure and accurate method of computer network synchronisation and should be used by any computer system that requires reliability, accuracy and security.

Finding an Online NTP Time Source

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Finding a source of time to synchronise a computer network to can be a challenge as there are a myriad of online time sources, all pertaining to be accurate and reliable; however, the truth can be rather different with many online sources either in too much demand, too far away or inaccurate.

NTP (Network Time Protocol) requires a source of UTC time (Coordinated Universal Time) which is kept true by atomic clocks. Online time sources are not themselves atomic clocks but NTP server devices that receive the time from an atomic clock which is then relayed to the devices that connect to the online time server.

There are two types of online time server: stratum 1 devices – devices that receive the time directly from an atomic clock, either using GPS or a radio reference signal. Stratum 2 devices  on the other hand are one step further away in that they are receive their time from a stratum 1 time server.

Because of demand, finding an online stratum 1 time server is next to impossible, and those that do take request usually do so under a subscription, which leaves the only choice for most people being a stratum 2 device.

There are plenty of resources on the internet that provide locations for online time servers such as https://support.microsoft.com/en-us/help/262680/a-list-of-the-simple-network-time-protocol-sntp-time-servers-that-are

But there are drawbacks to using such devices; firstly, online stratum 2 time sources can’t be guaranteed and several surveys taken have found that the reliability and accuracy of many of them can’t be taken for granted.  Secondly, online sources of time require an open firewall port which can be manipulated by malicious bots or users – leading to security risks.

A far better solution for most networks is to install your own stratum 1 NTP server. These time server devices sync to atomic clocks outside the firewall (using GPS or radio signals) and therefore are not security risks. They are also accurate to a few milliseconds ensuring the network will always be accurate to UTC.

The Effects of No Time Signal

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NTP servers (Network Time Protocol) are an essential tool in the modern computer network. They control the time, ensuring every device on the network is synchronised.

Because of the importance of time in controlling nearly every aspect of computer networking accurate and synchronised time is essential which is why so many system administrators deploy a NTP time server.

These time servers use a single time source as a base to set all the clocks on a network to; the time is often got from the GPS network or radio signals broadcast from physics laboratories such as NPL in the UK (whose signal is broadcast from Cumbria).

Once this signal is received by the time server, the time protocol NTP then distributes it around the network – comparing the system clock of every device to the time reference and adjusting each device. By regularly assessing the drift of these devices and correcting for them NTP keeps clocks accurate to within milliseconds of the time signal and when this signal emanates from an atomic clock – it ensures the network is as accurate as physically possible, but what happens if you lose the time signal?

Damaged GPS antennas, maintenance of time signal transmitters or technical faults can lead to a NTP time sever failing to receive a time signal. Often, this is only temporary and normal service is resumed within a few hours but what happens if it doesn’t, and what is the effect of having a failed time signal?

Fortunately, NTP has back-up systems for just such an eventuality. If a time signal fails and there is no other source of time, NTP cleverly uses the average time from all the clocks on its network. So if some clocks have drifted a few milliseconds faster, and others a few milliseconds slower – then NTP takes the average of this drift ensuring that the time remains accurate for as long as possible.

Even if a signal has failed for several days – or even weeks – without knowledge of the system users, this does not mean the network will drift apart. NTP will still keep the entire network synchronised together, using the average drift, and while the longer the time signal remains off the les accurate the network will be it can still provide millisecond accuracy even after a few days of no time reference.

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 Internet Time for Computer Synchronization

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Ensuring your network is synchronized is a vital part of modern computing. Failure to do so, and having different machines telling different times is a recipe for disaster and can cause untold problems, not to mention making it almost impossible to debug or log errors.

And it is not just your own network you need to synchronize to either. With so many networks talking to each other, it is important that all networks synchronize to the same time-scale.

UTC (Coordinated Universal Time) is just such a global timescale. It is controlled by an international constellation of atomic clocks and enables computers all over the world to talk to each other in perfect synchronicity.

But how do you sync to UTC?

The internet is awash with sources of internet time. Most modern operating systems, especially in the Windows flavour, are set up to do this automatically (just by clicking the time/date tab on the clock menu). The computer will then regularly check the time server (usually at Microsoft or NIST, although others can be used) and adjust the computer to ensure its time matches.

Most internet time servers are known as stratum 2 devices. This means they take the time from another device but where does that get the time from?

NTP time servers

The answer is that somewhere on the stratum tree there will be a stratum 1 device. This will be a time server that receives the time direct from an atomic clock source. Often this is by GPS but there are radio referenced alternatives in several countries. These stratum 1 NTP (Network Time Protocol) time servers then provide the stratum 2 devices with the correct time – and its these devices we get our internet time from.

Drawbacks to Internet time

There are several drawbacks to relying on the Internet for time synchronisation. Accuracy is one consideration. Normally, a stratum 2 device will provide ample enough precision for most networks; however, for some users who require high levels of accuracy or deal in a lot of time sensitive transactions a stratum 2 time server may not be accurate enough.

Another problem with internet time servers is that they require an open port in the firewall. Keeping the NTP access on UDP port 123 open all the time could lead to security issues, especially as internet time sources can’t be authenticated or guaranteed.

Using a Stratum 1 NTP Time server

Stratum 1 NTP time servers are easily installed on most networks. Not only will they provide a higher accurate source of time but as they receive the time externally (from GPS or radio) they are highly secure and can’t be hijacked by malicious users or viral software.

MSF Downtime No Signal 26th and 27th July

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The UK’s time and frequency signal MSF, provided by the National Physical Laboratory out of Cumbria, will be down for essential maintenance on 26 and 27 July.

The unplanned downtime is to allow essential maintenance to be carried out in safety. The MSF transmitter will stop broadcasting the MSF signal on 26 and 27 July between 08.00 and 20.00 (BST – 07:00 GMT/UTC) although it is possible the maintenance may be finished ahead of schedule in which case the signal will be turned on earlier.

Future maintenance is scheduled for the following times when the signal will also be turned off:

• 9 September 2010 from 10:00 BST to 14:00 BST
• 9 December 2010 from 10:00 UTC to 14:00 UTC
• 10 March 2011 from 10:00 UTC to 14:00 UTC

Problems for Time Synchronisation

Generally, most NTP time servers should be able to maintain a stable time during these brief outages and users of MSF time synchronisation devices should not experience any difficulties with the lack of MSF signal.

However, those users who require high levels of accuracy and reliability and find the MSF outages affect them should perhaps look to a GPS NTP server.

GPS time servers receive their time signals from the GPS network which is available 24 hours a day, 365 days a year and never experiences any outages.

MSF Downtime – No Signal 26/27 July