Receiving Time Signals with GPS

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Accurate time is one of the most important aspects to keeping a computer network secure and safe. Places such as stock exchanges, banks and air traffic control rely on secure and accurate time. As computers rely on time as their only reference for when events happen, a slight error in a time code could lead to all sorts of errors, from millions being wiped off share prices to aeroplane flight paths being incorrect.

And time doesn’t just need to be accurate for these organizations, but secure too. A malicious user who interferes with a timestamp could cause all sorts of trouble, so ensuring time sources are both secure and accurate is vital.

Security is increasingly important for all sorts of organisations. With so much trade and communication conducted over the internet, using a source of accurate and secure time is as important a part of network security as anti-virus and firewall protection.

Despite the need for accuracy and security, many computer networks still rely on online time servers. Internet sources of time are not only unreliable, with inaccuracies commonplace, and distance and latency affecting the precision, but an Internet time server is also unsecure and able to be hijacked by malicious users.

But an accurate, reliable and completely secure source of time is available everywhere, 365 days a year—GPS.

While commonly thought of as a means of navigation, GPS actually provides an atomic clock time code, direct from the satellite signals. It is this time code that navigation systems use for calculating position but it is just as effective to provide a secure time stamp for a computer network.

Organizations that rely on accurate time for safety and security all use GPS, as it is a continuous signal, that never goes down, is always accurate and can’t be interfered with by third parties.

To utilise GPS as a source of time, all that is required is a GPS time server. Using an antenna, the time server receives the GPS signal, while NTP (Network Time Protocol) distributes it around the network.

With a GPS time server, a computer network is able to maintain accuracy to within a few milliseconds of the atomic clock time signal, which is translated into UTC time (Coordinated Universal Time) thanks to NTP, ensuring the network is running the same accurate time as other networks also synchronised to a UTC time source.

Importance of the GPS Antenna

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The global positing system is one of the most used technologies in the modern world. So many people rely on the network for either satellite navigation or time synchronisation. The majority of road users now rely on some form of GPS or mobile phone navigation, and professional drivers are almost completely reliant on them.

And its not just navigation that GPS is useful for. Because GPS satellites contain atomic clocks—it is the time signals these clocks put out that are used by satellite navigation systems to accurately work out positioning—they are used as a primary source of time for a whole host of time sensitive technologies.

Traffic lights, CCTV networks, ATM machines and modern computer networks all need accurate sources of time to avoid drift and to ensure synchronicity.  Most modern technologies, such as computers, do contain internal time pieces but these are only simple quartz oscillators (similar type of clock as used in modern watches) and they can drift. Not only does this lead to the time slowly becoming inaccurate, when devices are hooked up together this drifting can leave machines unable to cooperate as each device may have  a different time.

This is where the GPS network comes in, as unlike other forms of accurate time sources, GPS is available anywhere on the planet, is secure (for a computer network it is received externally to the firewall) and incredibly accurate, but GPS does have one distinct disadvantage.

While available everywhere on the planet, the GPS signal is pretty weak and to obtain a signal, whether for time synchronisation or for navigation, a clear view of the sky is needed. For this reason, the GPS antenna is fundamental in ensuring you get a good quality signal.

As the GPS antenna has to go outdoors, it’s important that it s not only waterproof, able to operate in the rain and other weather elements, but also resistant to the variation in temperatures experienced throughout the year.

One of the leading causes of GPS NTP server failure (the time servers that receive GPS time signals and distribute them around a network using Network Time Protocol) is a failed or failing antenna, so ensuring you GPS antenna is waterproof, and resistant to seasonal temperature changes can eliminate the risk of future time signal failures.

Waterproof GPS Antenna

Our Time and Travel Reliance on GPS

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Since the Global Positioning System (GPS) first became available for civilian use in the early 1990’s, it has become one of the most commonly used modern pieces of technology. Millions of motorists use satellite navigation, while shipping and airline industries are heavily dependent on it.

And its not just wayfinding that we use GPS for, many technologies from computer network to traffic lights, to CCTV cameras, use the GPS satellite transmissions as a method of controlling time—using the onboard atomic clocks to synchronise these technologies together.

While plenty of advantages to using GPS for both navigation and time synchronisation exist, it’s accurate in both time and positioning and is available, literally everywhere on the planet with a clear view to the sky. However, a recent report by the Royal Academy of Engineering this month has warned that the UK is becoming dangerously dependent on the USA run GPS system.

The report suggests that with so much of our technology now reliant on GPS such as road, rail and shipping equipment, there is a possibility that any loss in GPS signal could lead to loss of life.

And GPS is vulnerable to failure. Not only can GPS satellites be knocked out by solar flares and other cosmological phenomenon, but GPS signals can be blocked by accidental interference or even deliberate jamming.

If the GPS system does fail then navigation systems could become inaccurate leading to accidents, however, for technologies that use GPS as a timing signal, and these range from important systems at air traffic control, to the average business computer network, then fortunately, things should not be that disastrous.

This is because GPS time servers that receive the satellite’s signal use NTP (Network Time Protocol). NTP is the protocol that distributes the GPS time signal around a network, adjusting the system clocks on all the devices on the network to ensure they are synchronised. However, if the signal is lost, then NTP can still remain accurate, calculating the best average of the system clocks. Consequently if the GPS signal does go down, computers can still remain accurate to within a second for several days.

For critical systems, however, where extremely precise time is required constantly, dual NTP time servers are commonly used. Dual time servers not only receive a signal from GPS, but also can pick-up the time standard radio transmissions broadcast by organisations such as NPL or NIST.

A Galleon Systems NTP GPS Time Server

How GPS Keeps Clocks Accurate

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While many of us are aware of GPS (Global Positioning System) as a navigational tool and many of us have ‘sat navs’ in our cars, but the GPS network has another use that is also important to our day-to-day lives but few people realise it.

GPS satellites contain atomic clocks which transmit to earth an accurate time signal; it is this broadcast that satellite navigation devices use to calculate global position. However, there are other uses for this time signal besides navigation.

Nearly all computer networks are kept accurate to an atomic clock. This is because miniscule accuracies across a network can lead to until problems, from security issues to data loss. Most networks use a form of NTP (Network Time Protocol) to synchronise their networks, but NTP requires a main time source to sync to.

GPS is ideal for this, not only is it an atomic clocks source, which NTP can calculate UTC (Coordinated Universal Time) from, which means that the network will be synchronised to every other UTC network on the globe.

GPS is an ideal source of time as it is available literally everywhere on the planet as long as the GPS antenna has a clear view of the sky. And it is not only computer networks that require atomic clock time, all sorts of technologies require accurate synchronisation: traffic lights, CCTV cameras, air traffic control, internet servers, indeed many modern applications and technology without us realising is being kept true by GPS time.

Top use GPS as a source of time, a GPS NTP server is required. These connect to routers, switches or other technology and receive a regular time signal from the GPS satellites. The NTP server then distributes this time across the network, with the protocol NTP continually checking each device to ensure it is not drifting.

GPS NTP servers are not only accurate they are also highly secure. Some network administrators use internet time servers as a source of time but this can lead to problems. Not only is the accuracy of many of these sources questionable, but the signals can be hijacked by malicious software which can breach the network firewall and cause mayhem.

Origin of Synchronisation (Part 2)

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Continued…

Most towns and cities would have a main clock, such as Big Ben in London, and for those living near-by, it was fairly easy to look out the window and adjust the office or factory clock to ensure synchronicity; however, for those not in view of these tower clocks, other systems were used.

Commonly, somebody with a pocket watch would set the time by the tower clock in the morning and then go around businesses and for a small fee, let people know exactly what the time was, thus enabling them to adjust the office or factory clock to suit.

When, however, the railways began, and timetables became important it was clear a more accurate method of time keeping was needed, and it was then that the first official time-scale was developed.

As clocks were still mechanical, and therefore inaccurate and prone to drift, society again turned to that more accurate chronometer, the sun.

It was decided that when the sun was directly above a certain location, that would signal noon on this new time-scale. The location: Greenwich, in London, and the time-scale, originally called railway time, eventually became Greenwich Meantime (GMT), a time-scale that was used until the 1970’s.

Now of course, with atomic clocks, time is based on an international time-scale UTC (Coordinated Universal Time) although its origins are still based on GMT and often UTC is still referred to as GMT.

Now with the advent of international trade and global computer networks, UTC is used as the basis of nearly all international time. Computer networks deploy NTP servers to ensure that the time on their networks are accurate, often to a thousandth of a second to UTC, which means all around the world computers are ticking with the same accurate time – whether it is in London, Paris, or New York, UTC is used to ensure that computers everywhere can accurately communicate with each other, preventing the errors that poor time synchronisation can cause.

The Accuracy of the Speaking Clock

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The UK speaking clock has been around for nearly eighty years. It was started in 1936 when time keeping started to become more important to people’s lives. Initially available only in the London it was rolled out to the whole country during World War II.

There have been four people that have had honour of providing the permanent voice to the speaking clock over the last 70. And over 70 million calls are made to the speaking clock making it an important from of accurate time but have you ever wondered how accurate it is and where the time comes from and how accurate it is?

The speaking clock is controlled by a major British telecoms company who took over the General Post Office (GPO) and the time was originally supplied by the National Physical Laboratory (NPL) who also provide the MSF signal that NTP time servers use as a source of atomic clock synchronisation.

NPL no longer help with the speaking clock but the time is still controlled by NTP servers, either GPS or MSF, which ensures that the time you hear on the end of the telephone is accurate.

NTP servers are also commonly used by computer networks to ensure that IT systems, from traffic light signals to the office PC are all running an accurate form of time.

NTP time servers can either receive the MSF radio signal broadcast by NPL or, more commonly now, GPS signals beamed directly from space.

Often network administrators opt to use online NTP servers that send time signals over the internet but these are not as accurate and cause security problems so it is far better to have a dedicated NTP time server to control the time if you wish to have a computer network that is running accurately.

Solar Flares and the Vulnerability of GPS

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Whilst GPS is commonly associated with satellite navigation and wayfinding, many technologies and computer networks rely on the GPS satellite system for a source of accurate time.

GPS time servers utilise the onboard atomic clocks of the global positing satellites and use this stable and accurate time source as a basis for their NTP synchronisation (Network Time Protocol)

GPS has become the preferred source of atomic clock time for many network operators. There are other methods where UTC (Coordinated Universal Time) can be used; radio signals and across the internet to name but two sources, but none is as secure or readily available as GPS.

Unlike radio signals, GPS is available everywhere on the planet, is never down for scheduled maintenance and is not commonly vulnerable to interference. It also doesn’t have any security implications like connecting across an internet firewall to an online time server can.

However, this doesn’t mean GPS is completely invulnerable as recent news reports have suggested.
It has been recently reported that a sunspot (sunspot 1092) the size of the Earth has flared up and a massive coronal ejection (solar flare), described in the press as a “solar tsunami” which was suggested to be large enough to satellites and wreck power and communications grids.

Solar activity, such as sunspots and solar flares (ejected hot plumes of plasma and radiation from the sun), have long been known to be able to damage and even disable satellites.

GPS is particularly vulnerable because of the high orbits of geostationary satellites (some 22,000 miles up) this leaves them unprotected by the earth’s magnetic field.

However, following the recent solar activity there has been no reported damage to the GPS system but as so many people rely on satellite navigation and GPS time for NTP servers could a future solar storm lead to havoc on Earth?

Well the short answer is yes; GPS satellites have been in orbit for several decades and while redundant satellites were introduced into the system many have been used up due to previous failures and it would only take a couple of disabled satellite to cause real problems for the network.

Fortunately, help is at hand as the Europeans, Russians and Chinese are all working on their own GPS equivalents which should work hand-in-hand with the American GPS network allowing GPS receivers to pick and choose from all four GNSS networks (Global Navigational Satellite Systems) ensuring that even if a really violent solar storm hits in the future there will be more than enough geo stationary satellites to ensure no loss of signal.

MSF Downtime No Signal 26th and 27th July

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The UK’s time and frequency signal MSF, provided by the National Physical Laboratory out of Cumbria, will be down for essential maintenance on 26 and 27 July.

The unplanned downtime is to allow essential maintenance to be carried out in safety. The MSF transmitter will stop broadcasting the MSF signal on 26 and 27 July between 08.00 and 20.00 (BST – 07:00 GMT/UTC) although it is possible the maintenance may be finished ahead of schedule in which case the signal will be turned on earlier.

Future maintenance is scheduled for the following times when the signal will also be turned off:

• 9 September 2010 from 10:00 BST to 14:00 BST
• 9 December 2010 from 10:00 UTC to 14:00 UTC
• 10 March 2011 from 10:00 UTC to 14:00 UTC

Problems for Time Synchronisation

Generally, most NTP time servers should be able to maintain a stable time during these brief outages and users of MSF time synchronisation devices should not experience any difficulties with the lack of MSF signal.

However, those users who require high levels of accuracy and reliability and find the MSF outages affect them should perhaps look to a GPS NTP server.

GPS time servers receive their time signals from the GPS network which is available 24 hours a day, 365 days a year and never experiences any outages.

MSF Downtime – No Signal 26/27 July

Competition for GPS Ever Closer

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Written by Richard N Williams for Galleon Systems

Since its release to the civilian population the Global Positioning System (GPS) has greatly improved and enhanced our world. From satellite navigation to the precise time used by NTP servers (Network Time Protocol) and much or our modern world’s technology.

And GPS has for several years been the only Global Navigation Satellite Systems (GNSS) and is used the world over, however, times are now changing.

There are now three other GNSS systems on the horizon that will not only act as competition for GPS but will also increase its precision and accuracy.

Glonass is a Russian GNSS system that was developed during the Cold War. However, after the fall of the Soviet Union the system fell into disrepair but it has finally been revamped and is now back up and running.

The Glonass system is now being used as a navigational aid by Russian airlines and their emergency services with in-car GNSS receivers also being rolled out for the general population to use. And the Glonass system is also allowing time synchronisation using NTP time servers as it uses the same atomic clock technology as GPS.

And Glonass is not the only competition for GPS either. The European Galileo system is on track with the first satellites expected to be launched at the end of 2010 and the Chinese Compass system is also expected to be online soon which will make four fully operational GNSS systems orbiting above Earth’s orbit.

And this is good news for those interested in ultra high time synchronisation as the systems should all be interoperable meaning anyone looking to GNSS satellites can use multiple systems to ensure even greater accuracy.

It is expected that interoperable GNSS NTP time servers will soon be available to make use of these new technologies.

Choosing a Source of Time for Computer Network Synchronization

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You don’t need me to tell you how important computer network time synchronization is. If you are reading this then you are probably well aware of the importance in ensuring all your computers, routers and devices on your network are running the same time.

Failure to synchronize a network can cause all sorts of problems, although with a lack of synchronicity the problems may go unnoticed as error finding and debugging a network can be nigh on impossible without a source of synchronized time.

There are multiple options for finding a source of accurate time too. Most time sources used for synchronisation are a source of UTC (Coordinated Universal Time) which is the international timescale.
However, there are pro’s and con’s to all sources:

Internet time

There are an almost an endless number of sources of UTC time on the internet. Some of these time sources are wholly inaccurate and unreliable but there are some trusted sources put out by people like NIST (National Institute for Standards and Time) and Microsoft.

However, regardless of how trusted the time source is, there are two problems with internet time sources. Firstly, an internet time server is actually a stratum 2 device. In other words, an internet time server is connected to another time server that gets its time from an atomic clock, usually from one of the sources below. So an internet source of time is never going to be as accurate or precise as using a stratum 1 time server yourself.

Secondly, and more importantly, internet sources of time operate through the firewall so a potential security breach is available to any malicious user who wishes to take advantage of the open ports.

GPS Time

GPS time is far more secure. Not only is a GPS time signal available anywhere with a line of sight view of the sky, but also GPS time signals can be received externally to the network. By using a GPS time server the GPS time signals can be received and by using NTP (Network Time Protocol) this time can be converted to UTC (GPS time is currently 17 seconds exactly behind GPS time) then distributed around the network.

MSF/WWVB Time

Radio broadcasts in long wave are transmitted by several national physics labs. NIST and the UK’s NPL are two such organisations and they transmit the UTC signals MSF (UK) and WWVB (USA) which can be received and utilised by a radio referenced NTP server.