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 and the Different Time Sources

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NTP servers are essential devices for computer network time synchronisation. Ensuring a network coincides with UTC (Coordinated Universal Time) is vital in modern communications such as the Internet and is the primary function of the network time server (NTP server).

As their name suggests, these time servers use the protocol NTP (Network Time Protocol) to handle the synchronisation requests. NTP is already installed in many operating systems and synchronisation is possible without an NTP server by utilising an Internet time source, this can be unsecure and inaccurate for many network needs.

Network time servers receive a far more accurate and secure time signal. There are two methods of receiving the time using a time server: utilising the GPS network or receiving long wave radio transmissions.

Both these methods of receiving a time source are secure as they are external to any network firewall. They are also accurate as both sources of time are generated directly by atomic clocks rather than an Internet time service that are normally NTP devices connected to a third party atomic clock.

The GPS network provides an ideal source of time for NTP servers as the signals are available anywhere. The only downside of using the GPS network is that a view of the sky is required to lock-on to a satellite.

Radio referenced time sources are more flexible in that the long wave signal can be received indoors. They are limited in strength and not every country has a time signal although some signals such as the German DCF and the USA WVBB are available in neighbouring states.

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 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.

Keeping Accurate Time and The Importance of a Network Time Server

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A network time server can be one of the most crucial devices on a computer network as timestamps are vital for most computer applications from sending and email to debugging a network.

Tiny inaccuracies in a timestamp can cause havoc on a network, from emails arriving before they have technically been sent, to leaving an entire system vulnerable to security threats and even fraud.

However, a network time server is only as good as the time source that it synchronises to. Many network administrators opt to receive a timing code from the Internet, however, many Internet time sources are wholly inaccurate and often too far away from a client to provide any real accuracy.

Furthermore, Internet based time sources can’t be authenticated. Authentication is  a security measure used by NTP (Network Time Protocol which controls the network time server) to ensure the time server is exactly what it says it is).

To ensure accurate time is kept it is vital to select a time source that is both secure and accurate. There are two methods which can ensure a millisecond accuracy toUTC (coordinated universal time – a global timescale based on the time told by atomic clocks).

The first is to use a specialist national time and frequency transmission broadcast in several countries including the UK, USA, Germany, France and Japan. Unfortunately these broadcasts can’t be picked up everywhere but the second method is to use the timing signal broadcast by the GPS network which is available literally everywhere on the face of the planet.

A network time server will use this timing code and synchronise an entire network to it using NTP which is why they are often referred to as a NTP server or NTP time server. NTP continually adjusts the network’s clocks ensuring there is no drift.

Choosing the Right Time Signal for Your Network

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Computer network synchronisation is essential in the modern world. Many of the world’s computer networks are all synchronised to the same global timescale UTC (Coordinated Universal Time).

To govern synchronisation the protocol NTP (Network Time Protocol) is used in most cases as it is able to reliably synchronise a network to a few milliseconds off UTC time.

However, the accuracy of time synchronisation is solely dependent on the accuracy of whatever time reference is selected for NTP to distribute and here lies one of the fundamental errors made in synchronising computer networks.

Many network administrators rely on Internet time references as a source of UTC time, however, apart from the security risks they pose (being as they are on the wrong side of a network firewall) but also their accuracy can not be guaranteed and recent studies have found less than half of them providing any useful accuracies at all.

For a secure, accurate and reliable method of UTC there really are just two choices. Utilise the time signal from the GPS network or rely on the long wave transmissions broadcast by national physics laboratories such as NPL and NIST.

To select which method is best then the only factor to consider is the location of the NTP server that is to receive the time signal.

GPS is the most flexible in that the signal is available literally everywhere on the planet but the only downside to the signal is that a GPS antenna has to be situated on the roof as it needs a clear view of the sky. This may prove problematic if the time server is located in the lower floors of a sky scraper but on the whole most users of GPS time signals find that they are very reliable and incredibly accurate.

If GPS is impractical then the national time and frequencies provide an equally accurate and secure method of UTC time. These longwave signals are not broadcast by every country however, although the US WWVB signal broadcast by NIST in Colorado is available in most of North America including Canada.

There are various versions of this signal broadcast throughout Europe including the German DCF and the UK MSF which prove to be the most reliable and popular. These signals can often be picked up outside the nation’s borders too although it must be noted long wave transmissions are vulnerable to local interference and topography.

For complete peace of mind, dual system NTP servers that receive signals from both the GPS and national physics laboratories are available although they tend to be a little more expensive than single systems although utilising more than one time signal makes them doubly reliable.

Atomic Clocks Explained

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Is an Atomic Clock Radioactive?

An atomic clock keeps time better than any other clock. They even keep time better than the rotation of the Earth and the movement of the stars. Without the atomic clock, GPS navigation would be impossible, the Internet would not synchronise, and the position of the planets would not be known with enough accuracy for space probes and landers to be launched and monitored.

An atomic clock is not radioactive, it doesn’t rely on atomic decay. Rather, an atomic clock has an oscillating mass and a spring, just like ordinary clocks.

The big difference between a standard clock in your home and an atomic clock is that the oscillation in an atomic clock is between the nucleus of an atom and the surrounding electrons. This oscillation is not exactly a parallel to the balance wheel and hairspring of a clockwork watch, but the fact is that both use oscillations to keep track of passing time. The oscillation frequencies within the atom are determined by the mass of the nucleus and the gravity and electrostatic “spring” between the positive charge on the nucleus and the electron cloud surrounding it.

What Are The Types of Atomic Clock?

Today, though there are different types of atomic clock, the principle behind all of them remains the same. The major difference is associated with the element used and the means of detecting when the energy level changes. The various types of atomic clock include:

The Cesium atomic clock employs a beam of cesium atoms. The clock separates cesium atoms of different energy levels by magnetic field.

The Hydrogen atomic clock maintains hydrogen atoms at the required energy level in a container with walls of a special material so that the atoms don’t lose their higher energy state too quickly.

The Rubidium atomic clock, the simplest and most compact of all, use a glass cell of rubidium gas that changes its absorption of light at the optical rubidium frequency when the surrounding microwave frequency is just right.

The most accurate commercial atomic clock available today uses the cesium atom and the normal magnetic fields and detectors. In addition, the cesium atoms are stopped from zipping back and forth by laser beams, reducing small changes in frequency due to the Doppler effect.

When Was The Atomic Clock Invented? atomic clock

In 1945, Columbia University physics professor Isidor Rabi suggested that a clock could be made from a technique he developed in the 1930s called atomic beam magnetic resonance. By 1949, the National Bureau of Standards (NBS, now the National Institute of Standards and Technology, NIST) announced the world’s first atomic clock using the ammonia molecule as the source of vibrations, and by 1952 it announced the first atomic clock using cesium atoms as the vibration source, NBS-1.

In 1955, the National Physical Laboratory (NPL) in England built the first cesium-beam atomic clock used as a calibration source. Over the next decade, more advanced forms of the atomic clocks were created. In 1967, the 13th General Conference on Weights and Measures defined the SI second on the basis of vibrations of the cesium atom; the world’s time keeping system no longer had an astronomical basis at that point! NBS-4, the world’s most stable cesium atomic clock, was completed in 1968, and was used into the 1990s as part of the NPL time system.

In 1999, NPL-F1 began operation with an uncertainty of 1.7 parts in 10 to the 15th power, or accuracy to about one second in 20 million years, making it the most accurate atomic clock ever made (a distinction shared with a similar standard in Paris).

How Is Atomic Clock Time Measured?

The correct frequency for the particular cesium resonance is now defined by international agreement as 9,192,631,770 Hz so that when divided by this number the output is exactly 1 Hz, or 1 cycle per second.

The long-term accuracy achievable by modern cesium atomic clock (the most common type) is better than one second per one million years. The Hydrogen atomic clock shows a better short-term (one week) accuracy, approximately 10 times the accuracy of a cesium atomic clock. Therefore, the atomic clock has increased the accuracy of time measurement about one million times in comparison with the measurements carried out by means of astronomical techniques.

Synchonising to an Atomic Clock

The simplest way to synchonise to an atomic clock is to use a dedicated NTP server. These devices will receive either the GPS ataomic clock signal or radio waves from places like NIST or NPL.

Types of Atomic Clock Receivers

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MSF atomic clock receiver

The controlling radio signal for the National Physical Laboratory‘s atomic clock is transmitted on the MSF 60kHz signal via the transmitter at , CumbriaAnthorn, operated by British Telecom. This radio atomic clock time signal should have a range of some 1,500 km or 937.5 miles. All of the British Isles are of course within this radius.
The National Physical Laboratory’s role as keeper of the national time standards is to ensure that the UK time-scale agrees with Co-ordinated Universal Time (UTC) to the highest levels of accuracy and to make that time available across the UK. As an example, the MSF (MSF being the three-letter call sign to identify the source of the signal) radio broadcast provides the time signal for, electronic share trading, the clocks at most railway stations and for BT’s speaking clock.

DCF atomic clock receiver

The controlling radio signal for the German clock is transmitted via long wave from the DCF 77kHz transmitter at Mainflinger, near Dieburg, some 25 km south east of Frankfurt – the transmitter of German National Time Standards. It is similar in operation to the Cumbria transmitter, however there are two antennas (radio masts) so the radio atomic clock time signal can be maintained at all times.

Long wave is the preferred radio frequency for transmitting radio atomic clock time code binary signals as it performs most consistently in the stable lower part of the ionosphere. This is because the long wave signal carrying the time code to your timepiece travels in two ways; directly and indirectly. Between 700 km (437.5 miles) to 900 km (562.5 miles) of each transmitter the carrier wave can travel directly to the timepiece. The radio signal also reaches the timepiece via being bounced off the underside of the ionosphere. During the hours of daylight a part of the ionosphere called the “D layer” at an altitude of some 70 km (43.75 miles) is responsible for reflecting the long wave radio signal. During the hours of darkness when the sun’s radiation is not acting from outside the atmosphere, this layer rises to an altitude of some 90 km (56.25 miles) becoming the “E layer” in the process. Simple trigonometry will show that signals thus reflected will travel further.

A large part of the European Union area is covered by this transmitter facilitating reception for those who travel widely in Europe. The German clock is set on Central European Time – one hour ahead of U.K. time, following an inter-governmental decision, from the 22nd October, 1995, U.K. time will always be 1 hour less than European Time with both the U.K. and mainland Europe advancing and retarding clocks at the same “time”.

WVVB atomic clock receiver

A radio atomic clock system is available in North America set up and operated by NIST – the National Institute of Standards and Technology, located in Fort Collins, Colorado.

WWVB  has high transmitter power (50,000 watts), a very efficient antenna and an extremely low frequency (60,000 Hz). For comparison, a typical AM radio station broadcasts at a frequency of 1,000,000 Hz. The combination of high power and low frequency gives the radio waves from MSF a lot of bounce, and this single station can therefore cover the entire continental United States plus much of Canada and Central America.

The radio atomic clock time codes are sent from WWVB using one of the simplest systems possible, and at a very low data rate of one bit per second. The 60,000 Hz signal is always transmitted, but every second it is significantly reduced in power for a period of 0.2, 0.5 or 0.8 seconds:

• 0.2 seconds of reduced power means a binary zero • 0.5 seconds of reduced power is a binary one. • 0.8 seconds of reduced power is a separator.

The time code is sent in BCD (Binary Coded Decimal) and indicates minutes, hours, day of the year and year, along with information about daylight savings time and leap years. The time is transmitted using 53 bits and 7 separators, and therefore takes 60 seconds to transmit.

A clock or watch can contain an extremely small and relatively simple radio atomic clock antenna and receiver to decode the information in the signal and set the atomic clock time accurately. All that you have to do is set the time zone, and the atomic clock will display the correct time.