Posts by: Richard N Williams

Common Internet Time Synchronisation Issues

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Keeping the clock on a PC system synchronised is important for many systems, networks and users that need time accuracy for applications and transactions. Nearly everything on a modern computer system is time reliant so when synchronisation fails all sorts of issues can arise from data getting lost and debugging becoming near impossible.

There are several methods of synchronising a computer system’s clock but the majority of them rely on the time synchronisation protocol NTP (Network Time Protocol).

By far the most common method is to make use of the myriad of online NTP time servers that relay the UTC time (Coordinated Universal Time). However, there are many common issues in using internet based time servers – here are some of them:

Can’t access the Internet time server

A common occurrence with Internet time sources is the inability to access them. This can be caused by several reasons:

• Too much traffic trying to access the server
• Website is down
• Your connection is down

The time from the time server is innacuurate

Most online sources of time are what are known as stratum 2 time servers. This means they get their time from another time server (stratum 1) that it connected to an atomic clock (stratum 0). If there is an error with the stratum 1 device the stratum 2 device will be wrong (and every device that is trying to get the time from it).

The time server is leading to security problems with the firewall

Another common problem caused by the fact that all online time servers need access through your firewall. Unfortunately this gives the opportunity for malicious users to make use of this back door into your system.

Eliminating Time Server Issues

Internet time sources are neither guaranteed to be accurate, reliable or secure so for any serious time synchronisation requirements an external source of time should be used. NTP time servers that plug into a network and receive the time from GPS or radio sources are a much more secure and reliable alternative. These NTP servers are also highly secure as they do not operate across the Internet.

GPS as a Timing Reference for NTP servers

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The GPS system is familiar to most people. Many cars now have a GPS satellite navigation device in their cars but there is more to the Global Positioning System than just wayfinding.

The Global Positioning System is a constellation of over thirty satellites all spinning around the globe. The GPS satellite network has been designed so that at any point in time there is at least four satellites overhead – no matter where you are on the globe.

Onboard each GPS satellite there is a highly precise atomic clock and it is the information from this clock that is sent through the GPS transmissions which by triangulation (using the signal from multiple satellites) a satellite navigation receiver can work out your position.

But these ultra precise timing signals have another use, unbeknown to many users of GPS systems. Because the timing signals from the GPS atomic clocks are so precise, they make a good source of time for synchronising all sorts of technologies – from computer networks to traffic cameras.

To utilise the GPS timing signals, a GPS time server is often used. These devices use NTP (Network Time Protocol) to distribute the GPS timing source to all devices on the NTP network.

NTP regularly checks the time on all the systems on its network and adjusts it accordingly if it has drifted to what the original GPS timing source is.

As GPS is available anywhere on the planet it provides a really handy source of time for many technologies and applications ensuring that whatever is synchronised to the GPS timing source will remain as accurate as possible.

A single GPS NTP server can synchronize hundreds and thousands of devices including routers, PCs and other hardware ensuring the entire network is running perfectly coordinated time.

A Guide to Network Time Protocol

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NTP (Network Time Protocol) is perhaps the oldest and most commonly used protocol employed by computers and yet it is probably the least understood.

NTP is used by nearly all computers, networks and other devices that are involved in communicating across the internet or internal networks. It was developed in the very earliest stages of the internet when it became evident that some method of ensuring accuracy over distance was required.

The protocol works by selecting a single time source, of which NTP has the ability to establish the accuracy and reliability of, which it then distributes around every device on the NTP network.

Each device is regularly checked against this reference clock and adjusted if any drift is noticed. A version of NTP is now deployed with virtually every operating system allowing any machine to be synchronized to a single time source.

Obviously if every network in the world selected a different time source as its reference, the reason for of all this synchronization would be lost.

Fortunately, a global timescale based on an international consortium of atomic clocks has been developed to provide a single time source for the purposes of global synchronisation.

UTC (Coordinated Universal Time) is used by computer networks worldwide as a time reference which means any device that is synchronised to UTC with NTP will in effect be synchronised with every network that uses UTC as its base time.

There are many different methods that NTP can access UTC time. The internet is a common location although this does provide security and firewall issues. A more secure (and accurate) method is to use a dedicated NTP time server that takes the time from external sources such as the GPS network (GPS works by broadcasting an atomic clock timestamp that is easily converted to UTC by a NTP server).

With NTP, a dedicated time server and access to UTC an entire network can be synchronised to within a few milliseconds of the universal time providing a secure and accurate network that can operate in complete synchronicity with other networks across the globe.

Synchronizing a PC to an Atomic Clock

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Atomic clocks are without doubt the most accurate time pieces on the face of the planet. In fact the accuracy of an atomic clock in incomparable to any other chronometer, watch or clock.

While an atomic clock will not lose even a second in time in thousands upon thousands of years, you’re average digital watch will perhaps lose a second in just a few days which after a few weeks or months will mean your watch is running slow or fast by several minutes.

The same can also be said for the system clock that controls your computer the only difference is that computers rely even more heavily on time than we ourselves do.

Nearly everything a computer does is reliant on timestamps, from saving work to performing applications, debugging and even emails are all reliant on timestamps which can be a problem if the clock on your computer is running too fast or slow as errors can quite often occur, especially if you are communicating with another computer or device.

Fortunately, most PCs are easily synchronized to an atomic clock meaning they can be accurate as these powerful time keeping devices so any tasks performed by your PC can be in perfect synchronicity with whatever device you are communicating with.

In most PC operating systems an inbuilt protocol (NTP) allows the PC to communicate with a time server that is connected to an atomic clock. In most versions of Windows this is accessed through the date and time control setting (double clicking the clock in the bottom right).

However, for business machines or networks that require secure and accurate time synchronization, online time servers are just not secure or accurate enough to ensure your network is not vulnerable to security flaws.

However, NTP time servers that receive the time direct from atomic clocks are available that can synchronize entire networks. These devices receive a broadcasted timestamp distributed by either national physics laboratories or via the GPS satellite network.

NTP servers enable entire networks to all have exactly synchronized time which is as accurate and secure as is humanly possible.

Technologies that rely on Atomic Clocks (Part 2)

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GPS is not the only technology that is dependent on atomic clocks. The high levels of accuracy that are supplied by atomic clocks are used in other crucial technologies that we take for granted everyday.

Air traffic Control Not only are all aeroplanes and airliners now equipped with GPS to enable pilots and ground staff to know their exact location but atomic clocks are also used by air traffic controllers who need precise and accurate measurements and time between planes.

Traffic Lights and Road Congestion Systems – Traffic lights are another system that relies on atomic clock timing. Accuracy and synchronization is vital for traffic light systems as small errors in synchronization could lead to fatal accidents.

Congestion cameras and other systems such as parking metres also use atomic clocks as a basis of their timekeeping as this prevents any legal issues when issuing penalty notices.

CCTV – Closed circuit television is another large scale user of atomic clocks. CCTV cameras are often used in the fight against crime but as evidence they are ineffective in a court of law unless the timing information on the CCTV camera can be proved to be accurate. Failure to do so could lead to criminals escaping prosecution because despite the identification by the camera, proof that it was at the time and date of the offence can’t be clarified without accuracy and synchronization.

Internet – Many of the applications we now entrust to the internet are only made possible thanks to atomic clocks. Online trading, internet banking and even online auction houses all need accurate and synchronized time.

Imagine taking your savings from your bank account only finding that you can withdraw them again because another computer has a slower clock or imagine bidding on an internet auction site only to have your bid rejected by a bid that came before yours because it was made on a computer with a slower clock.

Using atomic clocks as a source for time is relatively straight forward for many technologies. Radio signals and even the GPS transmissions can be used as a source of atomic clock time and for computer systems, the protocol NTP (Network Time Protocol) will ensure any sized network will be synchronized perfectly together. Dedicated NTP time servers are used throughout the world in technologies and applications that require precise time.

Technologies that rely on Atomic Clocks (Part 1)

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Atomic clocks are the most accurate timekeeping devices known to man. There accuracy is incomparable to other clocks and chronometers in that whilst even the most sophisticated electronic clock will drift by a second every week or two, the most modern atomic clocks can keep running for thousands of years and not lose even a fraction of a second.

The accuracy of an atomic clock is down to what they use as their basis for time measurement. Instead of relying on an electronic current running through a crystal like an electronic clock, an atomic clock uses the hyperfine transition of an atom in two energy states. Whilst this may sound complicated, it is just an unfaltering reverberation that ‘ticks’ over 9 billion times each second, every second.

But why such accuracy really necessary and what technologies are atomic clocks employed in?

It is by examining the technologies that utilise atomic clocks that we can see why such high levels of accuracy are required.

GPS – Satellite navigation

Satellite navigation is a huge industry now. Once just a technology for the military and aviators, GPS satellite navigation is now used by road users across the globe. However, the navigational information provided by satellite navigation systems like GPS is solely reliant on the accuracy of atomic clocks.

GPS works by triangulating several timing signals that are deployed from atomic clocks onboard the GPS satellites. By working out when the timing signal was released from the satellite the satellite navigational receiver can just how far away it is from the satellite and by using multiple signals calculate where it is in the world.

Because of these timing signals travel at the speed of light, just one second inaccuracy within the timing signals could lead to the positing information being thousands of miles out. It is testament to the accuracy of GPS atomic clocks that currently a satellite navigation receiver is accurate to within five metres.

Synchronizing a Computer Network with a Dedicated Network Time Server

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Synchronization is vital for most computer networks. Timestamps are the only reference a computer can use to analyse when and if processes or applications are completed. Synchronized timestamps are also vital for security, debugging and error logging.

Failure to keep a network adequately synchronized can lead to all sorts of problems. Applications fail to commence, time sensitive transactions will fail and errors and data loss will become commonplace.

However, ensuring synchronization no matter the size of network is straight forward and not costly, thank to the dedicated network time server and the time protocol NTP.

Network Time Protocol (NTP)

NTP has been around even longer than the internet but is the most widely used synchronization protocol available. NTP is free to use and makes synchronization very straight forward. It works by taking a single time source (or multiple ones) and distributes it amongst the network. It will maintain high levels of accuracy even when it loses the original time signal and can make judgements on how accurate each time reference.

NTP Time Server

These come in several forms. Firstly there are a number of virtual time servers across the internet that distributes time free of charge. However, as they are internet based a network is taking a risk leaving a firewall port open for this time communication. Also there is no control over the time signal so if it goes down (or becomes unstable or wholly inaccurate) your network can be left without adequate synchronization.

Dedicated NTP time servers use GPS or radio references to receive the time. This is far more secure and as GPS and radio signals like WWVB (from NIST) are generated by atomic clocks there accuracy is second to none.

Because the NTP protocol is hierarchical it also means that only one dedicated time server needs to be used for a network, no matter the size, as other devices on the network can act as time servers after having rece9ved the time from the primary NTP server.

MSF Downtime on March 11

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The National Physical Laboratory has announced scheduled maintenance this week (Thursday) meaning the MSF60kHz time and frequency signal will be temporarily turned off to allow the maintenance to be conducted in safety at the Anthorn radio Station in Cumbria.

Normally these scheduled maintenance periods only last a few hours and should not cause any disturbance to anybody relying on the MSF signal for timing applications.
NTP (Network Time Protocol) is well suited to these temporary losses of signal and little if no drift should be experienced by any NTP time server user.

However, there are some high level users of network time servers or may have concerns on the accuracy of their technology during these scheduled periods of no signal. There is another solution for ensuring a continuous, secure and equally accurate time signal is always being used.

GPS, most commonly used for navigation and wayfinding it actually an atomic clock based technology. Each of the GPS satellites broadcasts a signal from their onboard atomic clock which is used by satellite navigation devices that work out the location through triangulation.

These GPS signals can also be received by a GPS NTP time server. Just as MSF or other radio signal time servers receive the external signal from the Anthorn transmitter, GPS time servers can receive this accurate and external signal from the satellites.

Unlike the radio broadcasts, GPS should never go down although it can sometimes be impractical to receive the signal as a GPS antenna needs a clear view of the sky and therefore should preferably be on the roof.

For those wanting to make doubly sure there is never a period when a signal is not being received by the NTP server, a dual time server can be used. These pick up both radio and GPS transmissions and the onboard NTP daemon calculates the most accurate time from them both.

The Vulnerability of GPS

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An increase in GPS ‘attacks’ has been causing some concern amongst the scientific community.  GPS, whilst a highly accurate and reliable system of transmitting time and positing information, relies on very weak signals that are being hampered by interference from the Earth.

Both unintentional interference such as from pirate radio stations or intentional deliberate ‘jamming’ by criminals is still rare but as technology that can hamper GPS signals becomes more readily available, the situation is expected to get worse.

And while the effects of signal failure of the GPS system may have obvious results for people who use it for navigation (ending up in the wrong location or getting lost) it could have more serious and profound repercussions for the technologies that rely on GPS for time signals.

As so many technologies now rely on GPS timing signals from telephone networks, the internet, banking and traffic lights and even our power grid any signal failure no matter how briefly, could cause serious problems.

The main problem with the GPS signal is that it is very weak and as it comes from space bound satellites, little can be done to boost the signal so any similar frequency being broadcast in a local area can easily drown out GPS.

However, GPS is not the only accurate and secure method of receiving the time from an atomic clock source. Many national physics laboratories from across the globe broadcast atomic clock signals via radio waves (usually long wave). In the USA these signals are broadcast by NIST (National Institute for Standards and Time (known as WWVB) whilst in the UK, it’s MSF signal is broadcast by NPL (National Physical Laboratory).

Dual time servers that can receive both signals are available and are a safer bet for any high technology company that can’t afford to risk losing a time signal.

Network Time Protocol and Computer Time Synchronization

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Ask any network administrator or IT engineer and ask them how important network time synchronization is and you’ll normally get the same answer – very.

Time is used in almost all aspects of computing for logging when events have happened. In fact timestamps are the only reference a computer can use to keep tracks of tasks it has done and those that it has yet to do.

When networks are unsynchronized the result can be a real headache for anybody tasked with debugging them. Data can be often lost, applications fail to commence, error logging is next to impossible, not to mention the security vulnerabilities that can result if there is no synchronized network time.

NTP (Network Time Protocol) is the leading time synchronisation application having been around since the 1980’s. It has been constantly developed and is used by virtually every computer network that requires accurate time.

Most operating systems have a version of NTP already installed and using it to synchronise a single computer is relatively straight forward by using the options in the clock settings or task bar.

However, by using the inbuilt NTP application or daemon on a computer will result in the device using a source of internet time as a timing reference. This is all well and good for single desk top machines but on a network a more secure solution is required.

It is vital on any computer network that there are no vulnerabilities in the firewall which can lead to attacks from malicious users. Keeping a port open to communicate with an internet timing source is one method an attacker can use to enter a network.

Fortunately there are alternatives to using the internet as a timing source. Atomic clock time signals can be received using long wave radio or GPS transmissions.

Dedicated NTP time server devices are available that make the process of time synchronisation extremely easy as the NTP servers receives the time (externally to the firewall) and can then distribute to all machines on a network – this is done securely and accurately with most networks synchronised to an NTP server working to within a few milliseconds of each other.