Time Synchronisation

NTP (Network Time Protocol) is an internet based protocol designed to synchronise the clocks on a computer network. It is the main time synchronisation software used in computer networks and is also packaged with most operating systems.

An NTP server is a dedicated device that receives a single time source then distributes it amongst all devices on a network. The protocol NTP monitors the drift of the internal clocks on a network and corrects for them.

An NTP server can receive a time source from either a national physical laboratory such as the UK’s National Physical Laboratory (NPL), however, these time signals are broadcast via long wave radio and have  finite range.

GPS NTP servers are designed to receive the time source generated by the atomic clocks onboard GPS satellites (Global Positioning System). GPS is available anywhere on the planet as a time source as long as there is a clear view of the sky.

Without correct synchronisation all sorts of potential problems can occur such as leaving a computer system vulnerable to fraud, malicious users and hackers. An unsynchronised computer network may also lose data and be difficult to audit.

A global timescale called UTC (Coordinated Universal Time) has been developed to ensure the entire world uses the same timescale. The NTP server utilise UTC ensuring the computer network is telling the same time as every other computer network.

Computer network synchronisation is often perceived as a headache for many system administrators but keeping accurate time is essential for any network to remain secure and reliable. Failing to have an accurate synchronised network can lead to all sorts of errors when dealing with time sensitive transactions.

The protocol NTP (Network Time Protocol) is the industry standard for time synchronisation. NTP distributes a single time source to an entire network ensuring all machines are running the exact same time.

One of the most problematic areas in synchronising a network is in the selection of the time source. Obviously if you are spending time getting a network synchronised then the time source would have to be a UTC (Coordinated Universal Time) as this is the global timescale used by computer networks all over the world.

UTC is available across the internet of course but internet time sources are not only notoriously inaccurate but using the internet as a time source will leave  computer system open to security threats as the source is external to the firewall.

A far better and secure method is to use a dedicated NTP time server. The NTP server sits inside the firewall and can receive a secure time signal from highly accurate sources. The most commonly used these days is the GPS network (Global Positioning System) this is because the GPS system is available literally anywhere on the planet. Unfortunately it does require a clear view of the sky to ensure the GPS NTP server can ‘see’ the satellite.

There is another alternative however, and that is to use the national time and frequency transmissions broadcast by several national physics laboratories. These have the advantage in that being long wave signals they can be received indoors. Although it must be noted these signals are not broadcast in every country and the range is finite and susceptible to interference and geographical features.

Some of the main transmissions broadcast are known as: the UK’s MSF signal, Germany’s DCF-77 and the USA’s WWVB.

In selecting a timing source to synchronise a computer network to using a NTP server (Network Time Protocol) it is important that the time source is accurate, secure and a source of UTC (Coordinated Universal Time). UTC is a global timescale used by computer networks, business and commerce across the globe.

Whilst UTC is freely available across the Internet it is neither accurate nor secure (being as it is external to your firewall).  Also Internet time sources cannot be authenticated which is NTP’s own method of ensuring a time source is what it says it is. There are two secure, accurate and reliable methods for receiving UTC via a NTP server and both come with their own advantages and drawbacks.

The first method is to use the GPS network (Global Positioning System).The main advantage of using the signals transmitted from a GPS satellite’s onboard atomic clock is that a signal is available anywhere on the planet. However it does come with a downside. As the signals are all line-of-sight it means that the GPS antenna needs to be placed on a roof to ensure connectivity with a satellite.

An alternative to the GPS signal but equally as accurate and reliable is to make use of the long wave radio transmissions broadcast by several national physics laboratories. These signals, such as the UK’s MSF, Germany’s DCF-77 and the United States’ WWVB transmissions, can often be picked up inside buildings making them ideal for a solution if a rooftop is unavailable for a GPS antenna. It must be noted that not every country broadcasts such a signal and whilst most transmissions can be picked up in neighbouring countries the signals are vulnerable to interference and local geography.

Time synchronisation in the modern age is highly precise. Modern atomic clocks can keep time so accurately that in 100 million years these timekeeping devices will not lose even a second.

Bit is this sort of accuracy necessary in the modern world? How important can a second possibly be, after all, a second has always been seen as one of the smallest units of time.

However, when you consider modern technology such as the satellite navigation then a second suddenly becomes a huge gulf in time. Modern satellite navigation devices work by calculating distance by using the time form the atomic clocks on GPS (Global Positioning System) satellites.

However, when you consider that the speed of light is close to 300, 000 km a second then you can understand that if a GPS clock is a second out then your navigation could be inaccurate by hundreds of thousands of kilometres.

The same is true for modern computer networks. Computers can process thousands of transactions a second so when it comes to global network communication a second can be a huge amount of time.

That is why modern NTP server’s, responsible for synchronising networks offer precision to the millisecond, ensuring that network across the globe are within a hare’s breath of each other.

NTP (Network Time Protocol) is an internet based protocol designed to synchronise the clocks on a computer network. It is the main time synchronisation software used in computer networks and is also packaged with most operating systems.

An NTP server is a dedicated device that receives a single time source then distributes it amongst all devices on a network. The protocol NTP monitors the drift of the internal clocks on a network and corrects for them.

An NTP server can receive a time source from either a national physical laboratory such as the UK’s National Physical Laboratory (NPL), however, these time signals are broadcast via long wave radio and have  finite range.

GPS NTP servers are designed to receive the time source generated by the atomic clocks onboard GPS satellites (Global Positioning System). GPS is available anywhere on the planet as a time source as long as there is a clear view of the sky.

Without correct synchronisation all sorts of potential problems can occur such as leaving a computer system vulnerable to fraud, malicious users and hackers. An unsynchronised computer network may also lose data and be difficult to audit.

A global timescale called UTC (Coordinated Universal Time) has been developed to ensure the entire world uses the same timescale. The NTP server utilise UTC ensuring the computer network is telling the same time as every other computer network.

Time servers are incredibly important but an often overlooked part of a computer network. They are essential devices ensuring that all computers and devices connected to the network are synchronised to the same time. This prevents any problems from occurring when networks run sporadic time such as emails arriving before they were sent or even more serious security issues.

Time servers are similar to other servers but their sole role is to receive the time from a trusted source and distribute it amongst the network. The network time server can receive this time source from several places but in doing so one must have in mind two questions: How accurate is the time reference supplying the time? And how secure is it?

There are two highly accurate and completely secure methods of receiving the time for a time server. Both methods supply UTC (Coordinated Universal Time) which is a global timescale maintained by highly accurate atomic clocks. The first is to utilise the Global Positioning System (GPS) whose satellites all have onboard an atomic clock or the second is to use the national physics’ laboratories time and frequency transmissions.

Once a timing reference is received it is distributed to machines on a network using the protocol NTP (Network Time Protocol). NTP is based on an algorithm that not only corrects the time on any device but also ensures that the UTC time being received is secure, stable and precise.

NTP is one of the oldest Internet based protocols having been around since the 1980’s yet it is a testament to its developers that over twenty years on it is not only still in use but is by far the most common time protocol in use.

The Global Positioning System along with the Internet has changed the way we live our lives. Thousands of motorists use them daily to navigate their around the country’s roads while airline pilots and ship’s captains use them for the same purpose on our seas and in our skies.

But GPS has more uses than just navigation as the technology that GPS utilises is based around the atomic clock. Atomic clocks are highly accurate devices, so accurate that within a billion years they will not lose a second in time.

It is this accuracy that allows satellite navigation devices to triangulate the positioning by measuring the time it takes for the GPS signals to arrive. As radio waves, such as those broadcast by the GPS satellites travel at the speed of light, an inaccuracy of just one second could see the positioning device inaccurate by 300,000 km (the speed light travels per second).

This timing signal broadcast by the satellites can also be utilised by a GPS time server. GPS time servers use the atomic clock signal and convert it into UTC (Coordinated Universal Time) which can be used by network time servers.

These time servers are often referred to as a GPS time server as they use GPS as a timing source to synchronise entire computer networks to.  GPS signals are highly accurate and available anywhere on the planet.

A simple source of UTC (Coordinated Universal Time) is the Global Positioning System. GPS offers reliable, worldwide coverage and the potential for extremely accurate timing via a GPS time server.
When you use a GPS time server to receive, be sure to let it obtain a good satellite lock so it can update correctly.

This is the main cause for GPS time servers to display the incorrect time. To test the accuracy of a GPS time server, you should verify the accuracy of your GPS’ displayed UTC by comparing it against an accurate time standard such as the MSF signal or by using a guaranteed source of UTC from across the Internet – details of which are posted on the NTP pool.

Reliable, precision timing is available from the Global Positioning System by using a GPS time server as they use the GPS 1PPS signal. Such units provide the current UTC to an accuracy of 1/1000 of a second or better.

NTP GPS server is a time server that uses the protocol NTP (Network Time Protocol) receives its authoritative time source from the GPS satellite network (Global Positioning System).

Other varieties of time server exist most if not all dedicated devices use NTP as it is universally excepted as the most superlative time protocol, there are however numerous ways a network time server (whether NTP or not) can receive a time signal.

The internet is a common source for timing information although very few administrators who have a dedicated time server device would use the Internet. This is because external time sources across the Internet are the wrong side of a uses firewall and therefore pose a potential security risk not-to-mention many Internet timing sources are not very accurate and also most are stratum 2 devices and therefore further away from the original time source than a stratum 1 dedicated NTP server (stratum 0 devices are atomic clocks).

The other methods a dedicated NTP server (often called network time server) can receive a timing signal is via GPS or radio transmissions that are broadcast from national physics laboratories.

Radio signal are a good source of UTC time (coordinated universal time) as they are maintained and run by organisations such NPL (National Physical Lab. UK) or NIST (National Institute for Standards and Time – US). However, these long wave transmissions are not broadcast in every country and the signals are susceptible to local interference and topography.

On the other hand a dedicated NTP GPS server receives its time signal from the GPS satellite system (each satellite contains an atomic clock). These signals offer excellent accuracy and furthermore are available everywhere on the planet where there is a clear view of the sky.

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.