Why a GPS Time Server is the Number One Choice for Time Synchronization

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When it comes to synchronizing a computer network there are several choice to ensure each device is running the same time. NTP (Network Time Protocol) is the preferred choice of time synchronization protocols but there are a multitude of methods in how NTP receives the time.

The NTP Daemon is installed on most operating systems such as windows and applications such as Windows Time are quite capable of receiving a source of UTC time (Coordinated Universal Time) from across the internet.

UTC time is the preferred time source used by computer networks as it is kept true by atomic clocks. UTC, as the name suggests, is also universal and is used by computer networks all over the world as a source to synchronize too.

However, internet sources of UTC are to recommended for any organisation where security and accuracy are a concern. Not only can the distant from host (internet time server) to the client (your computer network) can never be accurately measured leading to a drop in precision. Furthermore, any source of internet time will need access through the firewall (usually through the UDP 123 port). And by leaving this port open, malicious users and hackers can take advantage and gain access to the system.

Dedicated NTP time servers are a better solution as they receive the time from an external source. There are really two types of NTP server, the radio reference time server and the GPS time server.
Radio reference time servers use signals broadcast by places like NPL (National Physical Laboratory in the UK) or NIST (National Institute of Standards and Time). While these signals are extremely accurate, precise and secure they are affected by regular maintenance on the transmitters that broadcast the signal. Also being long wave they are vulnerable to local interference.

GPS time servers on the other hand receive the time directly from GPS satellites. This GPS time is easily converted to UTC by NTP (GPS time is UTC – 17 seconds exactly as no leap seconds have been added.) As the GPS signal is available everywhere on the earth 24 hours a day, 365 days a week, there is never a risk of a loss of signal.
A single dedicated GPS time server can synchronize a computer network of hundreds, and even thousands of machines to within a few of milliseconds of UTC time.

Time Servers and the Internet

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Timing is becoming increasingly crucial for computer systems. It is now almost unheard of for a computer network to function without synchronisation to UTC (Coordinated Universal Time). And even single machines used in the home are now equipped with automatic synchronisation. The latest incarnation of Windows for instance, Windows 7, connects to a timing source automatically (although this application can be turned off manually by accessing the time and date preferences.)

The inclusion of these automatic synchronisation tools on the latest operating systems is an indication of how important timing information has become and when you consider the types of applications and transactions that are now conducted on the internet it is of no surprise.

Internet banking, online reservations, internet auctions and even email can be reliant on accurate time. Computers use timestamps as the only point of reference they have to identify when and if a transaction has occurred. Mistakes in timing information can cause untold errors and problems, particularly with debugging.

The internet is full of time servers with over a thousand time sources available for online synchronisation however; the accuracy and usefulness of these online sources of UTC time do vary and leaving a TCP/IP open in the firewall to allow the timing information through can leave a system vulnerable.

For network systems where timing is not only crucial but where security is also a paramount issue then the internet is not a preferred source for receiving UTC information and an external source is required.

Connecting a NTP network to an external source of UTC time is relatively straightforward if a network time server is used. These devices that are often referred to as NTP servers, use the atomic clocks onboard GPS (Global Positioning System) satellites or long wave transmissions broadcast by places such as NIST or NPL.

Time Synchronization Using the GPS Network

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The GPS (Global Positioning System) systems has revolutionized navigation for pilots, mariners and drivers a like. Nearly every brand new car is sold with an inbuilt satellite navigation system already installed and similar detachable devices continue to sell in their millions.

Yet the GPS system is a multi purpose tool thanks mainly to the technology it employs to provide navigational information. Each GPS satellite contains an atomic clock which signal is used to triangulate positioning information.

GPS has been around since the late 1970’s but it was only in 1983 that is stopped from being purely a tool of the military and was opened up to allow free commercial access following an accidental shooting down of a passenger airliner.

To utilise the GPS system as a timing reference, a GPS clock or GPS time server is required. These devices usually rely on the time protocol NTP (Network Time Protocol) to distribute the GPS time signal that arrives via the GPS antenna.

GPS time is not the same as UTC (Coordinated Universal Time) which is normally used  NTP for time synchronization via radio transmissions or the internet. GPS time did originally match UTC in 1980 during its inception but sine that time there have been leap seconds added to UTC to counteract the variations of the earth’s rotation, however the on-board satellite clocks are corrected to compensate for the difference between GPS time and UTC, which is 17seconds, as of 2009.

By utilising a GPS time server an entire computer network can be synchronized to within a few milliseconds of UTC ensuring that all computers are safe, secure and able to deal effectively with time sensitive transactions.

Reported GPS Fears Should Not Affect Time Synchonisation

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Following recent media reports on the lack of investment in the USA’s Global Navigation Satellite System – GPS (Global Positioning System) and the potential failure of navigational receivers in recent years, time synchronisation specialists, Galleon Systems, would like to ensure all their customers that any failure of the GPS network will not affect current GPS NTP time servers.

Recent media reports following a study by the US government’s accountability office (GAO), that concluded mismanagement and a lack of investment meant some the current number of 31 operational satellites may fall to below 24 at times in 2011 and 2012 which would hamper its accuracy.

However, the UK’s National Physical Laboratory are confident that any potential problems of the GPS navigation facilities will not affect timing information utilised by GPS NTP servers.

A spokesman for the UK’s National Physical Laboratory confirmed that timing information should be unaffected by any potential future satellite failure.

“There is estimated to be a 20% risk that in 2011-2012 the number of satellites in the GPS constellation could drop below 24 at times.

“If that were to happen, there could be a slight reduction in the position accuracy of GPS receivers at some periods, and in particular they might take longer to acquire a fix in some locations when first powered up. However, even then the effect would be a degradation of performance, rather than complete failure to operate.

“A GPS timing receiver is unlikely to be affected significantly since, once it has determined its position when turned on, every satellite it observes provides it with useful timing information. A small reduction in the number of satellites in view should not degrade its performance much.”

MSF Outage 11 June NPL Maintenance

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The UK’s MSF signal broadcast from Anthorn, Cumbria and utilised by UK NTP server users is be turned off for a four hour period on 11 June for scheduled maintenance. The MSF 60 kHz time and frequency standard will be off between 10.00 and 14:00 BST (9:00 – 13:00 UTC).

Users of NTP time servers that utilise the MSF signal should be aware of the outage but shouldn’t panic. Most network time servers that use the Anthorn system should still function adequately and the lack of a timing signal for four hours should not create any synchronisation problems or clock drift.

However, any testing of time servers that utilise MSF should be conducted before or after the scheduled outage. Further information is available from NPL.

Any network time server users that require ultra-precise precision or are feel temporary loss of this signal could cause repercussions in their time synchronisation should seriously consider utilising the GPS signal as an additional means of receiving a time signal.

GPS is available literally anywhere on the planet (as long as there is a good clear view of the sky) and is never down due to outages.

For further information on GPS NTP server can be found here.

Computers, Communications, Atomic Clocks and the NTP Server

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Time synchronisation on computer networks is often conducted by the NTP server. NTP time servers do not generate any timing information themselves but are merely methods of communicating with an atomic clock.

The precision of an atomic clock is widely talked about. Many of them can maintain time to nanosecond precision (billionths of a second) which means they won’t drift beyond a second in accuracy in hundreds of millions of years.

However, what is less understood and talked about is why we need to have such accurate clocks, after-all the traditional methods of keeping time such as mechanical clocks, electronic watches and using the rotation of the Earth to keep track of the days has proved reliable for thousands of years.

However, the development of digital technology over recent years has been nearly solely reliant on the ultra high precision of an atomic clock. One of the most widely used applications for atomic clocks is in the communications industry.

For several years now telephone calls taken in most industrialized countries are now transmitted digitally. However, most telephone wires are simply copper cables (although many telephone companies are now investing in fibre optics) which can only transmit one packet of information at a time. Yet telephone wires have to carry many conversations down the same wires at the same time.

This is achieved by computers at the exchanges switching from one conversation to another thousands of times every second and all this has to be controlled by nano-second precision otherwise  the calls will become out of step and get jumbled – hence the need for. Atomic clocks; mobile phones, digital TV and Internet communications use similar technology.

The accuracy of atomic clocks is also the basis for satellite navigation such as GPS (global positioning system). GPS satellites contain an onboard atomic clock that generates and transmits a time signal. A GPS receiver will receive four of theses signals and use the timing information to work out how long the transmissions took to reach it and therefore the position of the receiver on Earth.

Current GPS systems are accurate to a few metres but to give an indication of how vital precision is, a one second drift of a GPS clock could see the GPS receiver be inaccurate by over 100 thousand miles (because of the  huge distances light and therefore transmissions take in one second).

Many of these technologies that depend on atomic clocks utilise NTP servers as the preferred way to communicate with atomic clocks making the NTP time server one of the most crucial pieces of equipment in the communication industries.

The NTP Time Server Essential Network Protection

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There are a myriad of hardware and software methods of protecting computers. Anti-virus software, firewalls, spyware and routers to name but a few yet perhaps the most important tools for keeping a network safe is often the most overlooked.

One of the reasons for this is that the network time server’s often referred to as the NTP time server (after the protocol Network Time Protocol) primary task is time synchronisation and not security.

The NTP server’s primary task is to retrieve a time signal from a UTC source (Coordinated Universal Time) which it then distributes it amongst the network, checking the clock on each system device and ensuring its running in synchronisation with UTC.

Here is where many network administrators fall down. They know that time synchronisation is vital for computer security. Without it, errors can not be logged (or even spotted) network attacks can’t be countered, data can be lost and if a malicious user does get into the system it is near impossible to discover what they were up to without all machines on a network corresponding to the same time.

However, the NTP server is where many network administrators think they can save a little money. ‘Why bother?’ ‘They say, ‘when you can log on to an Internet NTP server for free.’

Well, as the old saying goes there is no such thing as a free lunch or as it goes a free source of UTC time. Using internet time providers may be free but this is where many computer networks leave themselves open to abuse.

To utilise an internet source of time such as Microsoft’s, NIST or one of those on the NTP pool project may be free but they are also outside a networks firewall and these is where many network administrators come unstuck.

Bringing Atomic Clock Precision to your Desktop

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Atomic clocks have been a huge influence on our modern lives with many of the technologies that have revolutionised the way we live our lives relying on their ultra precise time keeping abilities.

Atomic clocks are far different to other chronometers; a normal watch or clock will keep time fairly accurately but will lose second or two each day. An atomic clock on the other hand will not lose a second in millions of years.

In fact it is fair to say that an atomic clock doesn’t measure time but is the foundations we base our perceptions of time on. Let me explain, time, as Einstein demonstrated, is relative and the only constant in the universe is the speed of light (though a vacuum).

Measuring time with any real precision is therefore difficult as even the gravity on Earth skews time, slowing it down. It is also almost impossible to base time on any point of reference. Historically we have always used the revolution of the earth and reference to the celestial bodies as a basis for our time telling (24 hours in a day = one revolution of the Earth, 365 days = one revolution of the earth around the Sun etc).

Unfortunately the Earth’s rotation is not an accurate frame of reference to base our time keeping on. The earth slows down and speeds up in its revolution meaning some days are longer than others.

Atomic clocks however, used the resonance of atoms (normally caesium) at particular energy states. As these atoms vibrate at exact frequencies (or an exact number of times) this can be used as a basis for telling time. So after the development of the atomic clock the second has been defined as over 9 billion resonance ’ticks’ of the caesium atom.

The ultra precise nature of atomic clocks is the basis for technologies such as satellite navigation (GPS), air traffic control and internet trading. It is possible to use the precise nature of atomic clocks to synchronise computer networks too. All that is needed is a NTP time server (Network Time Protocol).
NTP servers receive the time from atomic clocks via a broadcast signal or the GPS network they then distribute it amongst a network ensuring all devices have the exact same, ultra precise time.

Why the Need for NTP

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Network Time Protocol is an Internet protocol used to synchronize computer clocks to a stable and precise time reference. NTP was originally developed by Professor David L. Mills at the University of Delaware in 1985 and is an Internet standard protocol and is used in most network time servers, hence the name NTP server.

NTP was developed to solve the problem of multiple computers working together and having the different time. Whilst, time usually just advances, if programs are running on different computers time should advance even if you switch from one computer to another. However, if one system is ahead of the other, switching between these systems would cause time to jump forward and back.

As a consequence, networks may run their own time, but as soon as you connect to the Internet, effects become visible. Just Email messages arrive before they were sent, and are even replied to before they were mailed!

Whilst this sort of problem may seem innocuous when it comes to receiving email, however, in some environments a lack of synchronisation can have disastrous results this is why air traffic control was one of the first applications for NTP.

NTP uses a single time source and distributes it amongst all devices on a network it does this by using an algorithm that works out how much to adjust a system clock to ensure synchronisation.

NTP works on a hierarchical basis to ensure there are no network traffic and bandwidth problems. It uses a single time source, normally UTC (coordinated universal time) and receives time requests from the machines on the top of the hierarch which then pass the time on further down the chain.

Most networks that utilise NTP will use a dedicated NTP time server to receive their UTC time signal. These can receive the time from the GPS network or radio transmissions broadcast by national physics laboratories. These dedicated NTP time servers are ideal as they receive time direct from an atomic clock source they are also secure as they are situated externally and therefore do not require interruptions in the network firewall.

NTP has been an astronomical success and is now used in nearly 99 per cent of time synchronisation devices and a version of it is included in most operating system packages.

NTP owes much of its success to the development and support it continues to receives nearly three decades after its inception which is why t is now used throughout the world in NTP servers.

Increased Accuracy of Dual NTP Server Systems

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The NTP time server has revolutionised the synchronisation of computer networks over the last twenty years. NTP (Network Time Protocol) is the software  that  is responsible for distributing time from the time server to the entire network, adjusting machines for drift and assuring accuracy.

NTP can reliable maintain system clocks to within a few millimetres of UTC (Coordinated Universal Time) or whatever timescale it is fed with.

However NTP can only be as reliable as the time source that it receives and as UTC  is the global civil timescale it depends on where the UTC source comes from.

National time and frequency transmissions from physics labs like NIST in the USA or NPL in the UK are extremely reliable sources of UTC and NTP time servers are designed specifically for them. However, the time signals are not guaranteed, they can drop off throughout the day and are susceptible to interference; they are also regularly turned of for maintenance.

For most applications a few hours of your network relying on crystal oscillators will probably not cause too much problems in synchronisation. However, GPS (Global Positioning System) is far more reliable source for UTC time in that a GPS satellite is always overhead. They do require a line-of-sight reception which means an antenna has to go on the roof or outside an open window.

For applications where accuracy and reliability are essential the safest solution is to invest in a dual system NTP time server, these device can receive both the radio transmissions such  as MSF, DCF-77 or WWVB and the GPS signal.

On a dual system NTP server, NTP will take both time sources and to synchronise a network to ensuring increased accuracy and reliability.