Category: timing source

Importance of Atomic Clock Time Sources for Technology

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Timekeeping and accuracy is important in the running of our day-to-day lives. We need to know what time events are occurring to ensure we don’t miss them, we also need to have a source of accurate time to prevent us from being late; and computers and other technology are just as reliant on the tine as we are.

For many computers and technical systems, the time in the form of a timestamp is the only tangible thing a machine has to identify when events should occur, and in what order. Without a timestamp a computer is unable to perform any task—even saving data is impossible without the machine knowing what time it is.

Because of this reliance on time, all computer systems have in-built clocks on their circuit boards. Commonly these are quartz based oscillators, similar to the electronic clocks used in digital wrist watches.

The problem with these system clocks is that they are not very accurate. Sure, for telling the time for human purposes they are precise enough; however, machines quite often require a higher level of accuracy, especially when devices are synchronised.

For computer networks, synchronisation is crucial as different machines telling different times could lead to errors and failure of the network to perform even simple tasks. The difficult with network synchronisation is that the system clocks used by computers to keep time can drift. And when different clocks drift by differing amounts, a network can soon fall into disarray as different machines keep different times.

For this reason, these system clocks are not relied on to provide synchronisation. Instead, a far more accurate type of clock is used: the atomic clock.

Atomic clocks don’t drift (at least not by more than a second in a million years) and so are ideal to synchronise computer networks too. Most computers use the software protocol NTP (Network Time Protocol) which uses a single atomic clock time source, either from across the internet, or more securely, externally via GPS or radio signals, in which it synchronises every machine on a network to.

Because NTP ensures each device is kept accurate to this source time and ignores the unreliable system clocks, the entire network can be kept synchronised to with each machine within fractions of a second of each other.

How GPS Keeps Clocks Accurate

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While many of us are aware of GPS (Global Positioning System) as a navigational tool and many of us have ‘sat navs’ in our cars, but the GPS network has another use that is also important to our day-to-day lives but few people realise it.

GPS satellites contain atomic clocks which transmit to earth an accurate time signal; it is this broadcast that satellite navigation devices use to calculate global position. However, there are other uses for this time signal besides navigation.

Nearly all computer networks are kept accurate to an atomic clock. This is because miniscule accuracies across a network can lead to until problems, from security issues to data loss. Most networks use a form of NTP (Network Time Protocol) to synchronise their networks, but NTP requires a main time source to sync to.

GPS is ideal for this, not only is it an atomic clocks source, which NTP can calculate UTC (Coordinated Universal Time) from, which means that the network will be synchronised to every other UTC network on the globe.

GPS is an ideal source of time as it is available literally everywhere on the planet as long as the GPS antenna has a clear view of the sky. And it is not only computer networks that require atomic clock time, all sorts of technologies require accurate synchronisation: traffic lights, CCTV cameras, air traffic control, internet servers, indeed many modern applications and technology without us realising is being kept true by GPS time.

Top use GPS as a source of time, a GPS NTP server is required. These connect to routers, switches or other technology and receive a regular time signal from the GPS satellites. The NTP server then distributes this time across the network, with the protocol NTP continually checking each device to ensure it is not drifting.

GPS NTP servers are not only accurate they are also highly secure. Some network administrators use internet time servers as a source of time but this can lead to problems. Not only is the accuracy of many of these sources questionable, but the signals can be hijacked by malicious software which can breach the network firewall and cause mayhem.

Keeping a Windows 7 Network Secure, Reliable and Accurate

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Many modern computer networks are now running Microsoft’s latest operating system Window 7, which has many new and improved features including the ability to synchronise time.

When a Windows 7 machine is booted up, unlike previous incarnations of Windows, the operating system automatically attempts to synchronise to a time server across the internet to ensure the network is running accurate time. However, while this facility is often useful for residential users, for business networks it can cause many problems.

Firstly, to allow this synchronisation process to happen, the company firewall must have an open port (UDP 123) to allow the regular time transference. This can cause security issues as malicious users and bots can take advantage of the open port to penetrate into the company network.

Secondly, while the internet time servers are often quite accurate, this can often depend on your distance from the host, and any latency caused by network or internet connection can further cause inaccuracies meaning that you system can often be more than several seconds away from the preferred UTC time (Coordinated Universal Time).

Finally, as internet time sources are stratum 2 devices, that is they are servers that do not receive a first-hand time code, but instead receive a second hand source of time from a stratum 1 device (dedicated NTP time server – Network Time Protocol) which also can lead to inaccuracy – these stratum 2 connections can also be very busy preventing your network from accessing the time for prolonged periods risking drifting.

To ensure accurate, reliable and secure time for a Windows 7 network, there is really no substitute than to use your own stratum 1 NTP time server. These are readily available from many sources and are not very expensive but the peace of mind they provide is invaluable.

Stratum 1 NTP time servers receive a secure time signal direct from an atomic clock source. The time signal is external to the network so there is no danger of it being hijacked or any need to have open ports in the firewall.

Furthermore, as the time signals come from a direct atomic clock source they are very accurate and don’t suffer any latency problems. The signals used can be either through GPS (Global Positioning System satellites’ have onboard atomic clocks) or from radio transmissions broadcast by national physics laboratories such as NIST in the USA (broadcast from Colorado), NPL in the UK (transmitted form Cumbria) or their German equivalent (from Frankfurt).

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.

Origin of Synchronisation (Part 2)

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Continued…

Most towns and cities would have a main clock, such as Big Ben in London, and for those living near-by, it was fairly easy to look out the window and adjust the office or factory clock to ensure synchronicity; however, for those not in view of these tower clocks, other systems were used.

Commonly, somebody with a pocket watch would set the time by the tower clock in the morning and then go around businesses and for a small fee, let people know exactly what the time was, thus enabling them to adjust the office or factory clock to suit.

When, however, the railways began, and timetables became important it was clear a more accurate method of time keeping was needed, and it was then that the first official time-scale was developed.

As clocks were still mechanical, and therefore inaccurate and prone to drift, society again turned to that more accurate chronometer, the sun.

It was decided that when the sun was directly above a certain location, that would signal noon on this new time-scale. The location: Greenwich, in London, and the time-scale, originally called railway time, eventually became Greenwich Meantime (GMT), a time-scale that was used until the 1970’s.

Now of course, with atomic clocks, time is based on an international time-scale UTC (Coordinated Universal Time) although its origins are still based on GMT and often UTC is still referred to as GMT.

Now with the advent of international trade and global computer networks, UTC is used as the basis of nearly all international time. Computer networks deploy NTP servers to ensure that the time on their networks are accurate, often to a thousandth of a second to UTC, which means all around the world computers are ticking with the same accurate time – whether it is in London, Paris, or New York, UTC is used to ensure that computers everywhere can accurately communicate with each other, preventing the errors that poor time synchronisation can cause.

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.

An End to British Summer Time?

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The new UK government is to look again at the perennial debate about changing the clocks during the summer months from GMT (Greenwich Mean Time) to British Summer Time (BST).

While the move is controversial, with many in Scotland in the north of the UK, unwilling to adopt the change due to the longer dark days of winter they experience over the rest of the country – the move would help synchronise Britain with the rest of Europe.

Despite its positing in the European Union, Britain holds a different timescale to the rest of Europe. People from the UK who travel abroad have to advance their watches an hour every-time they travel to mainland Europe.

In the new proposals, daylight saving time will still continue but the standard winter time will be advanced an hour and a further advancement of an hour for the summer – know as double British Summertime – allowing the UK to have the same time as Europe.

However, despite the problems such a change would have to people; technology will not be affected by any alteration in daylight saving time.

UTC Time

Technology, such as computer networks, all use a universal time – UTC (Coordinated Universal Time). UTC is a global timescale, kept true by an international conglomeration of atomic clocks. This means whether you have a UK based computer network, or a one on the other side of the world, to the technologies – the time is the same.

Most technologies receive this time from an atomic clock source using devices known as NTP servers (after the time protocol: Network Time Protocol). NTP servers take advantage of the atomic clocks onboard GPS satellites so they can not only supply an accurate source of time but they can assure that the time source never drifts.

Other methods of getting an atomic clock source of time include using medium wave transmissions broadcast by places like the UK’s National Physical Laboratory (NPL) or the American National Institute for Standards and Time.

NTP servers ensure that no matter where you are in the world the source of time your computers and technology utilise is always Coordinated Universal Time – no matter what the time of year.



Using Windows 7 and Reasons Your Network Still Needs an NTP Server

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Time synchronisation becomes more and more relevant as we become more dependent on the internet. With so many time sensitive transactions conducted across the globe, from banking and commerce to sending emails, the correct and accurate time is vital in preventing errors and ensuring security.

Increasingly, more and more people are relying on sources of internet time especially with many of the modern flavours of Microsoft’s Windows such as Windows 7 having NTP and time synchronisation abilities already installed.

Windows 7 and Time Synchronisation

Windows 7 will, straight out of the box, attempt to find a source of internet time; however, for a networked machine this does not necessarily mean the computer will be synchronised accurately or securely.

Internet time sources can be wholly unreliable and unsecure for a modern computer network. Internet time has to come through the firewall and as a gap is left for these time codes to come through, malicious software can take advantage of this firewall hole too.

Not only can the accuracy of these devices vary depending on the distance away your network is but also an internet time source very rarely comes direct from an atomic clock.

In fact, most internet time sources are known as stratum 2 devices. This means they connect to another device – a stratum 1 device – namely a NTP time server which gets the time directly from the clock and transmits it to the stratum 2 device.

Stratum 1 NTP time servers

For true accuracy and security, there is no replacement for your network’s own stratum 1 NTP server. Not only are these devices secure, receiving a time source externally to the firewall (often using GPS) but also they receive these signals direct from atomic clocks (The GPS satellite that transmits this signal has an onboard atomic clock that generates the time.

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

When Time Servers go Bad

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“Time is what prevents everything from happening at once,’ said eminent physicist John Wheeler. And when it comes to computers his words couldn’t be any more relevant.

Timestamps are the only method that a computer has to establish if an event has occurred, is meant to occur or shouldn’t be occurring just yet. For a home PC, the computer relies on the inbuilt clock that displays the time on the corner of your operating system, and for most home uses this is satisfactory enough.

However for computer networks that have to communicate with each other, relying in individual system clocks can cause untold problems:

All clocks drift, and computer clocks are no different and problems occur when two machines are drifting at different rates as the time does not match up. This poses a conundrum for a computer as it is unsure of which time to believe and time critical events can fail to occur and even simple tasks like sending an email can cause time confusion on a network.

For these reasons, time servers are commonly used to receive the time from an external source and distribute it around the network. Most of these devices use the protocol NTP (Network Time Protocol) which is designed to provide a method of synchronising time on a network.

However, time servers are only as good as the time source that they rely on and when there is a problem with that source, synchronisation will fail and the problems mentioned above can occur.

The most common cause for time server failure or inaccuracy is the reliance on internet based sources of time. These can neither be authenticated by NTP nor guaranteed to be accurate and they can also lead to security issues with firewall intrusion and other malicious attacks.

Ensuring the NTP time server continues to get a source of highly accurate time is fairly straight forward and is all a matter of choosing an accurate, reliable and secure time source.

In most parts of the world there are two methods that can provide a secure and reliable source of time:

  • GPS time signals
  • Radio referenced time signals

GPS signals are available anywhere on the planet and are based on GPS time which is generated by atomic clocks onboard the satellites.

Radio referenced signals like MSF and WWVB are broadcast on long wave from physics laboratories like NIST and NPL.