The Concept of Time

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Time is something that we are all familiar with, it governs our lives even more so than money and we are constantly ‘at war’ with time as we battle to conduct our daily tasks before it runs out.

Yet when we start to examine time we discover that the concept of time we begin to realise that a non-ending linear distance between different events that we call time is purely a human invention.

Of course time exists but it certainly doesn’t follow the rules that the human concept of time does. It is not never ending or constant and changes and warps depending on speed of observers and the pull of gravity. In fact it was Einstein’s theories on relativity that gave human kind its first glimpse as to what time really is and how it affects our daily lives.

Einstein described a four-dimensional space-time, where time and space are inextricably woven together. This space-time gets warped and bent by gravity slowing time (or our perception of it). Einstein also, he suggested that the speed of light was the only constant in the universe and time altered depending on the relative speed to it.

When it comes to keeping track of time, Einstein’s theories can hamper any attempts at chronology. If both gravity and relative speed can affect time then it becomes difficult to measure time accurately.

We long ago abandoned the idea of using the celestial bodies and Earth’s rotation as a reference for our timekeeping as it was recognised in the early twentieth century that Earth’s rotation wasn’t at all accurate or reliable. Instead, we have depended n the oscillations of atoms to keep track of time. Atomic clocks measure atomic ticks of particular atoms and our concept of time is based on these ticks with every second being equal to over 9 billion oscillation of the caesium atom.

Even though we now base time on atomic oscillations, technologies such as GPS satellites (Global Positioning System) still have to counter the effects of lower gravity. In fact the effects of time can be monitored so accurately thanks to atomic clocks that those at different altitudes above sea level run at slightly differing speeds which has to be compensated for.

Atomic clocks can also be used to synchronise a computer network ensuring that they are running as accurately as possible. Most NTP time servers operate by utilising and distributing the time signal broadcast by an atomic clock (either through GPS or long wave) using the protocol NTP (Network Time Protocol).

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.

WWVB Explained

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The NTP time server (Network Time Protocol) is an essential tool for keeping networks synchronised. Without adequate synchronization, computer networks can be left vulnerable to security threats, data loss, fraud and may find it impossible to interact with other networks across the globe.

Computer networks are normally synchronised to the global timescale UTC (Coordinated Universal Time) enabling them to communicate efficiently with other networks also running UTC.

Whilst UTC time sources are available across the Internet these are not secure (being outside the firewall) and many are either too far away to provide adequate precision or are too inaccurate to begin with.

The most secure methods of receiving a UTC time source are to use a dedicated NTP Time Server. These devices can receive a secure and accurate time signal either the GPS network (Global Positioning System) available anywhere across the globe with a good view of the sky or through specialist radio transmission broadcast by national physics laboratories.

In the US the National Institute for Standards and Time (NIST) broadcast a time signal from near Fort Collins, Colorado. The signal, known as WWVB can be received all over North America (including many parts of Canada) and provides an accurate and secure method of receiving UTC.

As the signal is derived from atomic clocks situated at the Fort Collins site, WWVB is a highly accurate method of synchronising time and is also secure as a dedicated NTP time server acts as an external source.

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.

Security and Synchronisation

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Security is often the most worried about aspect of running a computer network. Keeping unwanted users out whilst allowing freedom for users to access network applications is a full time job. Yet many network administrators fail to pay any heed to one of the most crucial aspects of keeping a network secure – time synchronisation.

Time synchronisation is not just important but it is vital in network security and yet it is staggering how many network administrators disregard it or fail to have their systems properly synchronised.

Ensuring the same and correct time (ideally UTC – Coordinated Universal Time) is on each network machine is essential as any time delays can be an open door for hackers to slip in undetected and what is worse if machines do get hacked are not running the same time it can be near impossible to detect, repair and get the network back up and running.

Yet time synchronisation is one of the simplest of tasks to employ, particularly as most operating systems have a version of the time protocol NTP (Network Time Protocol).

Finding an accurate time server can sometimes be problematic particularly if the network is synchronised across the internet as this can raise other security issues such as having an open port in the firewall and a lack of possible authentication by NTP to ensure the signal is trusted.

However, an easier method for time synchronisation, being both accurate and secure, is to use a dedicated NTP time server (also known as network time server). An NTP server will take a time signal direct from GPS or from the national time and frequency radio transmissions put out by organisations such as NIST or NPL.

By using a dedicated NTP server the network will become a lot securer and if the worst does happen and the system does fall victim to malicious users then having a synchronised network will ensure it is easily solvable.

What is the Best Source of UTC Time?

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UTC (Coordinated Universal Time) is the world’s global timescale and replaced the old time standard GMT (Greenwich Meantime) in the 1970’s.

Whilst GMT was based on the movement of the Sun, UTC is based on the time told by atomic clocks although it is kept inline with GMT by the addition of ‘Leap Seconds’ which compensates for the slowing of the Earth’s rotation allowing both UTC and GMT to run side by side (GMT is often mistakenly referred to as UTC – although as there is no actual difference it doesn’t really matter).

In computing, UTC allows computer networks all over the world to synchronise to the same time making possible time sensitive transactions from across the globe. Most computer networks used dedicated network time servers to synchronise to a UTC time source. These devices use the protocol NTP (Network Time Protocol) to distribute the time across the networks and continually checks to ensure there is no drift.

The only quandary in using a dedicated NTP time server is selecting where the time source comes from which will govern the type of NTP server you require. There are really three places that a source of UTC time can be easily located.

The first is the internet. In using an internet time source such as time.nist.gov or time.windows.com a dedicated NTP server is not necessarily required as most operating systems have a version of NTP already installed (in Windows just double click the clock icon to see the internet time options).

*NB it must be noted that Microsoft, Novell and others strongly advise against using internet time sources if security is an issue. Internet time sources can’t be authenticated by NTP and are outside the firewall which can lead to security threats.

The second method is to use a GPS NTP server; these devices use the GPS signal (most commonly used for satellite navigation) which is actually a time code generated by an atomic clock (from onboard the satellite). Whilst this signal is available anywhere on the globe, a GPS antenna does need a clear view of the sky which is the only drawback in using GPS.

Alternatively, many countries’ national physics laboratories such as NIST in the USA and NPL in the UK, transmit a time signal from their atomic clocks. These signals can be picked up with a radio referenced NTP server although these signals are finite and vulnerable to local interference and topography.

How to Synchronise a Computer to an Atomic Clock

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Time synchronisation is often a much underrated aspect of computer management. Generally time synchronisation is only crucial for networks or for computers that a take in time sensitive transactions across the internet.

Time synchronisation with modern operating systems such as Windows Vista, XP or the different versions of Linux is relatively easy as most contain the time synchronisation protocol NTP (Network Time Protocol) or a simplified version at least (SNTP).

NTP is an algorithm based program and works by using a single time source that can be distributed amongst the network (or a single computer) and is constantly checked to ensure the network’s clocks is running accurately.

For single computer users, or networks where security and precision are not primary concerns (although for any network security should be a main issue) then the simplest method of synchronising a computer is to use an internet time standard.

With a Windows operating system this can easily be done on a single computer by double clicking the clock icon and then configuring the internet time tab. However, it must be noted that in using an internet based time source such as nist.gov or windows.time, a port will have to be left open in the firewall which could be taken advantage of by malicious users.

For network users and those not wanting to leave vulnerabilities in their firewall then the most suitable solution is to use a dedicated network time server. Most of these devices also use the protocol NTP but as they receive a time reference externally to the network (usually by way of GPS or long wave radio) the leave no vulnerabilities in the firewall.

These NTP server devices are also far more reliable and accurate than internet time sources as they communicate directly with the signal from an atomic clock rather than being several tiers (in NTP terms known as strata) from the reference clock as most internet time sources are.

Common GPS Queries

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Is the GPS time signal the same as the GPS positioning signal?

Yes. The signals that are broadcast by GPS satellites contain time information and the position of the satellite it came from (and its velocity). The timing information is generated by an onboard caesium atomic clock. It is this information used by satellite navigation devices (sat navs) that enables global positioning. Sat Navs use these signals from multiple satellites to triangulate a position.

How accurate is GPS positioning?

Because the time signal generated by GPS comes from an atomic clock it is accurate to within 16 nanoseconds (16 billionths of a second). As light travels nearly 186 000 miles in a second this equates to around 16 feet (5+metres) which means a GPS positioning system is usually accurate to this much.

Is GPS time the same as UTC?

No. GPS time, like UTC (Coordinated Universal Time)is based on International Atomic Time (TAI) – the time told by atomic clocks. However as the GPS system was developed several decades ago it is now 14 seconds (and soon to be 15) behind UTC because it has missed out on the Leap Seconds added to UTC to calibrate for the Earth’s slowing rotation.

How can I use GPS as a source of UTC then?

Fortunately a GPS time server will convert GPS to the current UTC time, which as od 1 January 2009 will mean it has to add exactly 15 seconds.

GPS Time Server and its Accuracy from space

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The GPS network (Global Positioning System), is commonly known as a satellite navigation system. It however, actually relays a ultra-precise time signal from an onboard atomic clock.

It is this information that is received by satellite navigation devices that can then triangulate the position of the receiver by working out how long the signal has taken to arrive from various satellites.

These time signals, like all radio transmissions travel at the speed of light (which is close to 300,000km a second). It is therefore highly important that these devices are not just accurate to a second but to a millionth of a second otherwise the navigation system would be useless.

It is this timing information that can be utilized by a GPS time server as a base for network time. Although this timing information is not in a UTC format (Coordinated Universal Time), the World’s global timescale, it easily converted because of its origin from an atomic clock.

A GPS time server can receive the signal from a GPS aerial although this does need to have a good view of the sky as the satellites relay their transmissions via line-of-sight.
Using a dedicated GPS time server a computer network can be synchronised to within a few milliseconds of NTP (milli=1000th of a second) and provide security and authentication.

Following the increase use of GPS technology over the last few years, GPS time servers are now relatively inexpensive and are simple and straight forward systems to install.

Next Generation of Accurate Atomic Clocks Starts Ticking as NIST scientists unveil new strontium clock

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Those chronological pioneers at NIST have teamed up with the University of Colorado and have developed the world’s most accurate atomic clock to date. The strontium based clock is nearly twice as accurate as the current caesium clocks used to govern UTC (Coordinated Universal Time) as it loses just a second every 300 million years.

Strontium based atomic clocks are now being seen as the way forward in timekeeping as higher levels of accuracy are attainable that are just not possible with the caesium atom. Strontium clocks, like their predecessors work by harnessing the natural yet highly consistent vibration of atoms.

However, these new generations of clocks use laser beams and extremely low temperatures close to absolute zero to control the atoms and it is hoped it is a step forward to creating a perfectly precise clock.

This extreme accuracy may seem a step too far and unnecessary but the uses for such precision are many fold and when you consider the technologies that have been developed that are based on the first generation of atomic clocks such as GPS navigation, NTP server synchronisation and digital broadcasting a new world of exciting technology based on these new clocks could just be around the corner.

While currently the world’s global timescale, UTC, is based on the time told by a constellation of caesium clocks (and incidentally so is t he definition of a second as just over 9 billion caesium ticks), it is thought that when the Consultative Committee for Time and Frequency at the Bureau International des Poids et Mesures (BIPM) next meets it will discuss whether to make these next generation of atomic clocks the new standard.

However, strontium clocks are not the only method of highly precise time. Last year a quantum clock, also developed at NIST managed accuracy of 1 second in 1 billion years. However, this type of clock can’t be directly monitored and requires a more complex scheme to monitor the time.