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WWVB Explained

Thursday, May 7th, 2009

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.

Security and Synchronisation

Tuesday, May 5th, 2009

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.

Choosing the Right Time Signal for Your Network

Wednesday, April 22nd, 2009

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.

Types of Atomic Clock Receivers

Saturday, April 18th, 2009

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.

Receiving the Time and Finding the Correct Time Source

Monday, April 6th, 2009

So you have decided to synchronize your network to UTC (Coordinated Universal Time), you have a time server that utilizes NTP (Network Time Protocol) now the only thing to decide on is where to receive the time from.

NTP servers do not generate time they simply receive a secure signal from an atomic clock but it is this constant checking of the time that keeps the NTP server accurate and in turn the network that it is synchronizing.

Receiving an atomic clock time signal is where the NTP server comes into its own. There are many sources of UTC time across the Internet but these are not recommended for any corporate use or for whenever security is an issue as internet sources of UTC are external to the firewall and can compromise security – we will discuss this in more detail in future posts.

Commonly, there are two types of time server. There are those that receive an atomic clock source of UTC time from long wave radio broadcasts or those that use the GPS network (Global Positioning System) as a source.

The long wave radio transmissions are broadcast by several national physics laboratories. The most common signals are the USA’s WWVB (broadcast by NIST – National Institute for Standards and Time), the UK’s MSF (broadcast by the UK National Physical Laboratory) and the German DCF signal (Broadcast by the German National Physics Laboratory).

Not every country produces these time signals and the signals are vulnerable to interference from topography. However, in the USA the WWVB signal is receivable in most areas of North America (including Canada) although the signal strength will vary depending on local geography such as mountains etc.

The GPS signal on the other hand is available literally everywhere on the planet as along as the GPS antenna attached to the GPS NTP server can have a clear view of the sky.

Both systems are a truly reliable and accurate method of UTC time and using either will allow synchronization of a computer network to within a few milliseconds of UTC.

NTP GPS Server Using Satellite Time Signals

Tuesday, March 24th, 2009

The NTP GPS server is a dedicated device that uses the time signal from the GPS (Global Positioning System) network. GPS is now a common tool for motorists with satellite navigation devices fitted to most new cars. But GPS is far more than just an aid for positioning, at the very heart of the GPS network is the atomic clocks that are inside each GPS satellite.

The GPS system works by transmitting the time from these clocks along with the position and velocity of the satellite. A satellite navigation receiver will work out when it receives this time how long it took to arrive and therefore how far the signal travelled. Using three or more of these signals the satellite navigation device can work out exactly where it is.

GPS can only do this because of the atomic clocks that it uses to transmit the time signals. These time signals travel, like all radio signals, at the speed of light so an inaccuracy of just 1 millisecond (1/1000 of a second) could result in the satellite navigation being nearly 300 kilometres out.

Because these clocks have to be so accurate, they make an ideal source of time for a NTP time server. NTP (Network Time Protocol) is the software that distributes the time from the time server to the network. GPS time and UTC (Coordinated Universal Time) the civil timescale is not quite the same thing but are base don the same timescale so NTP has no trouble converting it. Using a dedicated NTP GPS server a network can be realistically synchronised to within a few milliseconds of UTC

The GPS clock is another term often given to a GPS time server. The GPS network consists of 21 active satellites (and a few spare) 10,000 miles in orbit above the Earth and each satellite circles the Earth twice a day. Designed for satellite navigation, A GPS receiver needs at least three satellites to maintain a position. However, in the case of a GPS clock just one satellite is required making it far easier to obtain a reliable signal.

Each satellite continuously transmits its own position and a time code. The time code is generated by an onboard atomic clock and is highly accurate, it has to be as this information is used by the GPS receiver to triangulate a position and if it was just half a second out the Sat Nav  unit would be inaccurate by thousands of miles.

Does My Business Need Accurate Time Synchronisation Five question (part 1)

Thursday, February 19th, 2009

Time synchronisation can be crucial for many computer networks. Correct synchronisation can protect a system from all sorts of security threats it will also ensure that the network is accurate and reliable but are dedicated NTP time server systems really necessary or can a network be run securely without a network time server?

Here are five questions to ask yourself to see if your network needs to be adequately synchronised.

1.  Does your network conduct time sensitive transactions across the internet?

If yes then accurate network time synchronisation is essential. Time is the only point of reference a computer has to identify two events so when it comes to a transaction across the internet such as sending an email, if it comes from an unsynchronised network, it may arrive before it was technically sent. This may lead to the email not being received as a computer cannot handle negative values when it comes to time.

2. Do you store valuable data?

Data loss is another ramification of not having a synchronised network. When a computer stores data it is stamped with the time. If that time is from an unsynchronised machine on a network then a computer may consider the data already saved or it may overwrite new data with older versions.

3. Is security important to your business and network?

Keeping a network secure is essential if you have any sensitive data on the machines. Malicious users have a myriad of ways of gaining access to computer networks and using the chaos caused by an unsynchronised network is one method they frequently take advantage of. Not having a synchronised network may mean it is impossible to identify if your network has been hacked into too as all records left on log files are time reliant too.

NTP Server Time Tired of Inaccurate and Insecure Time

Monday, February 16th, 2009

The internet has been a marvellous resource for business over the last decade. High speed access and the proliferation of computers in homes and offices alike have turned the World Wide Web into the main business arena for many companies.

With more and more transactions being conducted from opposite ends of the world across the internet, the need for an accurate and precise clock to keep computer networks synchronised has never been greater.

Most of the world’s computer networks, synchronise to a source of UTC (Coordinated Universal Time) which is the worldwide standard and is controlled by atomic clocks. A worldwide standard for synchronising the clocks has been developed also. NTP (Network Time Protocol) is a software algorithm that distributes UTC amongst a network’s clocks and adjusts the time accordingly.

Many computer network administrators turn to the internet as a source of NTP server time as there are a multitude of sources of UTC time. However, many internet sources of NTP time cannot be relied upon to provide accurate time. Surveys have discovered more than half of all internet time servers were inaccurate by over a second and even those that are not, they could be too far away to provide any useful precision.

More importantly, however, is that internet based NTP servers are external to a network’s firewall so any regular communication with a NTP server will require the firewall port to be left open allowing easy access for malicious users to take advantage of.

The only solution for getting a source of NTP server time, whilst keeping a network secure, is to use an external stratum 1 NTP time server. These devices communicate directly with an atomic clock either via the GPS satellite network or long wave radio signals. Because these devices operate from with the firewall the entire network is kept secure whilst the NTP server distributes an accurate, precise and source of UTC time.

Using Time and Frequency Transmissions to Synchronise a Computer Network

Friday, February 13th, 2009

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.

(UTC) Coordinated Universal Time is The only time you will ever need to know

Friday, January 30th, 2009

We may think of their being only one time and therefore one timescale. Sure, we’re all aware of time zones where the clock has to be pushed back an hour but we all obey the same time surely?

Well actually we don’t. There are numerous different timescales all developed for different reasons are too numerous to mention them all but it wasn’t until the nineteenth century that the idea of a single timescale, used y everybody came into effect.

It was the advent of the railway that provoked the first national timescale in the UK (Railway time) before then people would use noon as a basis for time and set their clocks to it. It rarely mattered if your watch was five minutes faster than your neighbours but the invention of the trains and the railway timetable soon changed all that.

The railway timetable was only useful if people all used the same time scale. A train leaving at 10.am would be missed if a watch was five minutes slow so synchronisation of time became a new obsession.

Following railway time a more global timescale was developed GMT (Greenwich Meantime) which was based on the Sun’s position at noon which fell over the Greenwich Meridian line (0 degrees longitude). It was decided during a world conference in 1884 that a single world meridian should replace the numerous one’s already in existence. London was perhaps the most successful city in the world so it was decided the best place for it.

GMT allowed the entire world to synchronise to the same time and while nations altered their clocks to adjust for time-zones their time was always based on GMT.

GMT proved a successful development and remained the world’s global timescale until the 1970’s. By then that atomic clock had been developed and it was discovered in the use of these devices that Earth’s rotation wasn’t a reliable measure to base our time on as it actually alters day by day (albeit by fractions of a second).

Because of this a new timescale was developed called UTC (Coordinated Universal Time). UTC is based on GMT but allows for the slowing of the Earth’s rotation by adding additional ‘Leap Seconds’ to ensure that Noon remains on the Greenwich Meridian.

UTC is now used all over the World and is essential for applications such as air traffic control, satellite navigation and the Internet. In fact computer networks across the globe are synchronised to UTC using NTP time servers (Network Time Protocol). UTC is governed by a constellation of atomic clocks controlled by national physics laboratories such as NIST (National Institute of Standards and Time) and the UK’s NPL.