Category: NTP Basics

Using NTP Networks

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Network Time Protocol is by far the most widely used application for synchronizing computer time across local area networks and wider areas networks (LANs and WANs). The principles behind NTP are fairly simple. It checks the time on a system clock and compares it with an authoritative, single source of time, making corrections to the devices to ensure they are all synchronized to the time source.

Selecting the time source to use is perhaps the fundamentally most important thing in setting up a NTP network. Most network administrators opt, quite rightly to use a source of UTC time (Coordinated Universal Time). This is a global timescale and means that a computer network synchronized to UTC is not only using the same timescale as every other UTC synchronized network but also there is no need to worry about different time zones around the globe.

NTP uses different layers, known as strata, to determine the closeness and therefore accuracy, to a time source. As UTC is governed by atomic clocks, any atomic clock giving out a time signal is referred to as stratum 0 and any device that receives the time directly from an atomic clock is stratum 1. Stratum 2 devices are devices that receive the time from stratum 1 and so on. NTP supports over 16 different stratum levels although accuracy and reliable decrease with each stratum layer further away you get.

Man network administrators opt to use an internet source of UTC time. Apart from the security risks of using a time source from the internet and allowing it access through your firewall. Internet time servers are also stratum 2 devices in that they are normally servers that receive the time from single stratum 1 device.

A dedicated NTP time server on the other had are stratum 1 devices in themselves. They receive the time directly from atomic clocks, either via GPS or long wave radio transmissions. This makes them far more secure than internet providers as the time source is external to the network (and firewall) but also it makes them more accurate.

With a stratum 1 time server a network can be synchronized to within a few milliseconds of UTC without risk of compromising your security.

Perfect Time Synchronization for Windows

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Most Windows operating systems have an integrated time synchronisation service, installed by default that can synchronise the machine or indeed a network. However, for security reasons, it is highly recommended by Microsoft, amongst others, that an external time source is used.

NTP time servers
securely and accurately receive the UTC time signal from the GPS network or the WWVB radio transmissions (or European alternatives).  NTP time servers can synchronize a single Windows machine or an entire network to within fractions of a second of the correct UTC time (Coordinated Universal Time).

A NTP time server provides precise timing information 24 hours-a-day, 365 days-a-year anywhere on the entire globe. A dedicated NTP time server is the only secure, safe and reliable method of synchronizing a computer network to UTC (Coordinated Universal Time). External to the firewall, an NTP time server does not leave a computer system vulnerable to malicious attacks unlike Internet timing sources via the TCP-IP port.

A NTP time server is not only secure, it receives a UTC time signal direct from atomic clocks unlike Internet timing sources which are really time servers themselves. NTP servers and other time synchronization tools can synchronize entire networks, single PCs, routers and a whole host of other devices. Using either GPS or the North American WWVB signal, a dedicated NTP time server from will ensure all your devices are running to within a fraction of UTC time.

A NTP time server will:

•    Increase network security
•    Prevent data loss
•    Enable logging and tracking of errors or security breaches
•    Reduce confusion in shared files
•    Prevent errors in billing systems and time sensitive transactions
•    Can be used to provide incontestable evidence in legal and financial disputes

Computer Network Timing Solutions

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Computer networks and the internet have dramatically changed the way we live our lives. Computers are now in constant communication with each other making possible transactions such as online shopping, seat reservation and even email.

However, all this is only possible thanks to accurate network timing and in particular the use of Network Time Protocol (NTP) used to ensure all machines on a network are running the same time.

Timing synchronization is crucial for computer networks. Computers use time in the form of timestamps as the only marker to separate two events, without synchronization computers have difficulty in establishing the order of events or indeed if an event has happened or not.

Failing to synchronize a network can have untold effects. Emails may arrive before they are sent (according to the computer’s clock), data may get lost or fail to store and worst-of-all, the entire network could be vulnerable to malicious users and even fraudsters.

Synchronization with NTP is relatively straight forward as most operating systems have a version of the time protocol already installed; however, choosing a timing reference to synchronize to is more challenging.

UTC (Coordinated Universal Time) is a global timescale governed by atomic clocks and is used by nearly all computer networks across the globe. By synchronizing to UTC a computer network is essentially synchronizing the network time with ever other computer network in the world that uses UTC.

The internet has plenty of sources of UTC available but security issues with the firewall means the only safe method of receiving UTC is externally. Dedicated NTP time servers can do this using either long wave radio or GPS satellite transmissions.

Using a NTP Server in your Network

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The Network Time Protocol server is used in computer networks all over the world. It keeps an entire network’s systems and devices synchronised to the same time, normally a source of UTC (Coordinated Universal Time).

But is a NTP time server a necessary requirement and can your computer network survive without one?  The short answer is perhaps yes, a computer network can survive without a NTP server but the consequences can be dramatic.

Computers are meant to make our lives easier but any network administrator will tell you they can cause an awful amount of difficulty when they inevitably go wrong and without adequate time synchronisation, identifying an error and putting it right can be nearly impossible.

Computers use the time in the form of a timestamp as the only reference they have to distinguish between two events. Whilst computers and networks will still function without adequate synchronisation they are extremely vulnerable. Not only is locating and correcting errors extremely difficult if machines are not synchronised the network will be vulnerable to malicious users and viral software that can take advantage of it.

Furthermore, failing to synchronise to UTC can cause problems if the network is to communicate with other networks that are synchronised. Any time sensitive transactions could fail and the system could be open to potential fraud or other legal implications as proving the time of a transaction could be near impossible.

NTP servers are easy to install and receive the UTC time signal from either long wave transmissions or the GPS satellite network which they then distribute amongst the network’s machines. As a dedicated NTP time server operates externally to the network firewall it does so without compromising security.

Dangers of Free Time

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We are all looking for freebies, particularly in the present financial climate and the internet is not short of them. Free software, free films, free music, almost everything these days has a free version. Even critical applications for our computers and networks such as anti-virus can come free. So it is understandable that when network administrators want to synchronize the time on computer networks they turn to free sources of UTC time (UTC – Coordinated Universal Time) to synchronize their networks using the operating systems’ own inbuilt NTP server.

However, just as there is no such thing as a free lunch, free time sources come with a cost too. To start with all time servers on the internet that are available for the public to use are stratum 2 servers. This means they are devices that receive the time from another device (a stratum 1 time server) that gets it from an atomic clock. While this second hand time source shouldn’t lose too much time compared to the original, for high levels of accuracy there will be a noticeable drift.

Furthermore, internet time sources are based outside the network firewall. For access to the time server a UDP port needs to be left open. This will mean the network firewall will intrinsically have a hole in it which could be manipulated y a malicious user or aggressive malware.

Another consideration is the inbuilt security that the time transfer protocol NTP (Network Time Protocol) uses to assess the time signal it receives is genuine. This is referred to as authentication but is unavailable across the internet. Meaning the time source may not be what it claims to be and with a hole in the firewall it could result in a malicious attack.

Internet time sources can also be unreliable. Many are too far from clients to provide any real accuracy some time sources available on the internet are wildly out (some by hours not just minutes). There are however, more reputable stratum 2 servers available and the NTP pool has details of those.

For real accuracy with none of the security threats the best solution is to use an external time source. The best method for doing this is to utilise a dedicated NTP server. These devices work exterior to the firewall and receive the time either direct from GPS satellites or via broadcasts by national physics labs such as NIST or NPL.

A Guide to Using a GPS Clock

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The Global Positioning System much loved by drivers, pilots and sea-farers as a method of finding location offers much more than just satellite navigation information. The GPS system work by using atomic clocks that broadcast signals that are then triangulated by the computer in a satellite navigation system.

Because these atomic clocks are highly accurate and don’t drift by as much as a second even in a million years, they can be utilised as a method of synchronizing computer systems. GPS time, the time relayed by the GPS atomic clocks, is not strictly speaking the same as UTC (Coordinated Universal Time), the world’s global timescale, but as they are both based on International Atomic Time it can easily be converted. (GPS time is actual 17 seconds slower than UTC as there have been 17 leap seconds added to the global timescale since the GPS satellites where sent in to orbit).

A GPS clock is a device that receives the GPS signal and then translates it into the time. Most GPS clocks are dedicated time servers too as there is little point in receiving the exact time if you are to do nothing with it. GPS time servers use the protocol NTP (Network Time Protocol) which is one of the internet’s oldest protocols and designed to distribute timing information across a network.

A GPS clock, or GPS time server works by receiving a signal directly from the satellite. This unfortunately means the GPS antenna has to have a clear view of the sky to receive a signal. The time is then distributed from the time server to all devices on the network. The time on each device is regularly checked by NTP and if differs to the time from the GPS clock then it is adjusted.

Setting up a GPS clock for time synchronization is relatively easy. The time server (GPS clock) are often designed to fill a 1U space on a server rack. This is connected to the GPS antenna (usually on the roof) via a length of coax cable. The server is connected to the network and once it has locked on to the GPS system it can be set to begin synchronizing the network.

Choosing a Time Source what to do and what not to do

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Time synchronization is crucial for many of the applications that we do across the internet these days; internet banking, online reservation and even online auctions all require network time synchronization.

Failing to ensure their servers are adequately synchronized would mean many of these applications would be impossible to achieve; seat reservations could be sold more than once, lower bids could win internet auctions and it would be possible to withdraw you life savings from the bank twice if they didn’t have adequate synchronization (good for you not for the bank).

Even computer networks that on the face of it do not rely on time sensitive transactions also need to be adequately synchronized as it could be near impossible to track down errors or protect the system from malicious attacks if the timestamps on differ on various machines on the network.

Many organisations opt to use internet time servers as a source of UTC (Coordinated Universal Time) – the atomic clock controlled global timescale. Although there are many security issues in doing so such as leaving a hole in the firewall to communicate with the time server and not having any authentication for the time synchronization protocol NTP (Network Time Protocol).

However, in saying that many network administrators still opt to use online time servers as a UTC source regardless of the security implications although there are other issues that administrators should be aware of. On the internet there are two types of time server – stratum 1 and stratum 2. Stratum 1 servers receive a time signal direct from an atomic clock while stratum 2 servers receive a time signal from a stratum 1 server. Most internet stratum 1 servers are closed – unavailable to most administrators and there can be some shortfall in accuracy in using a stratum 2 server.

For the most accurate, secure and precise timing information external NTP time servers are the best option as these are stratum 1 devices that can synchronize hundreds of machines on a network to the exact same UTC time.

Milestones in Chronology From Crystals to Atoms

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Telling the time may seem a simple affair these days with the number of devices that display the time to us and with the incredible accuracy of devices such as atomic clocks and network time servers it is quite easy to see how chronology has been taken for granted.

The nanosecond accuracy that powers technologies such as the GPS system, air traffic control and NTP server systems (Network Time Protocol) is a long way from the first time pieces that were invented and were powered by the movement of the sun across the heavens.

Sun dials were indeed the first real clocks but they obviously did have their downsides – such as not working at night or in cloudy weather, however, being able to tell the time fairly accurately was a complete innovation to civilisation and helped for more structured societies.

However, relying on celestial bodies to keep track of time as we have done for thousands of years, would not prove to be a reliable basis for measuring time as was discovered by the invention of the atomic clock.

Before atomic clocks, electronic clocks provided the highest level of accuracy. These were invented at the turn of the last century and while they were many times more reliable than mechanical clocks they still drifted and would lose a second or two every week.

Electronic clocks worked by using the oscillations (vibrations under energy) of crystals such as quartz, however, atomic clocks use the resonance of individual atoms such as caesium which is such a high number of vibrations per second it makes the incredibly accurate (modern atomic clocks do not drift by even a second every 100 million years).

Once this type of time telling accuracy was discovered it became apparent that our tradition of using the rotation of the earth as a means of telling time was not as accurate as these atomic clocks. Thanks to their accuracy it was soon discovered the Earth’s rotation was not precise and would slow and speed up (by minute amounts) each day. To compensate for this the world’s global timescale UTC (Coordinated Universal Time) has additional seconds added to it once or twice a year (Leap seconds).

Atomic clocks provide the basis of UTC which is used by thousands of NTP servers to synchronise computer networks to.

Heroes of Time

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Chronology – the study of time- has provided science and technology with some incredible innovations and possibilities. From atomic clocks, NTP servers and the GPS system, true and accurate chronology has changed the shape of the world.

Time and the way it is counted has been a preoccupation of mankind since the earliest civilisations. Early chronologists spent their time trying to establish calendars but this proves to be more complicated than first imagined primarily because the earth takes a quarter of a day more than 365 days to orbit the sun.

Establishing the right number of leap days was one of the first challenges and it took several attempts at calendars until the modern Gregorian calendar became adopted by the globe.

When it came to monitoring time at a smaller level great advances were made by Galileo Galilei who would have built the first pendulum clock if only his death hadn’t interrupted his plans. Pendulums were finally invented by Christiaan Huygens and provided the first true glimpse of accurately monitoring the time throughout the day.

The next steps in chronology couldn’t take place though until we had a better understanding of time itself. Newton (Sir Isaac) had the first ideas and had the notion time was absolute” and would flow “equably” for all observers. This would have been an obvious idea to Newton as many of us regard time as unchanging but it was Einstein in his special theory of relativity that proposed that in fact time wasn’t a constant and would differ to all observers.

It was Einstein’s ideas that proved correct and his model of time and space paved the way for many of the modern technologies we take for granted today such as the atomic clock.

However, chronology doesn’t stop there, timekeepers are constantly looking for ways of increasing accuracy with modern atomic clocks so precise they would not lose a second in millions of years.

There are other notable figures in the modern world of chronology too. Professor David Mills from the University of Delaware devised a protocol in the 1980’s to synchronise computer networks.

His Network Time Protocol (NTP) is now used in computer systems and networks all over the world via NTP time servers. A NTP server ensures computers on opposite sides of the globe can run exactly the same time.

How to Synchronise Your PC to an Atomic Clock

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The world’s technologies have advanced dramatically over the last few decades with innovations likes the internet and satellite navigation having changed the way we live our lives.

Atomic clocks pay a key role in these technologies; their time signals are what are used by GPS receivers to plot location and many applications and transactions across the internet if it wasn’t for highly precise synchronisation.

In fact a global timescale has been developed that is based on the time told by atomic clocks. UTC (Coordinated Universal Time) ensures that computer networks across the globe can be synchronised to the exact same time.

Synchronising computers and networks to atomic clocks is relatively straight forward thanks in part to NTP (Network Time Protocol), a version of which is included in most operating systems and is also thanks to the number of public NTP servers that exist on the internet.

To synchronise a Windows PC to an atomic clock is done by simply double clocking the clock on the task bar and then configuring the Internet Time tab to a relevant NTP server. A list of public NTP servers can be found at the NTP pool website.

When configuring networks to UTC however, a public NTP server is not suitable as there are security issues about polling a time source outside the firewall. Public servers are also known as stratum 2 servers which means they receive the time from another device that gets it from an atomic clock. This indirect method means that there is often a compromise in accuracy, furthermore if the internet connection goes down or the time server site then the network will soon drift away from UTC.

A far more secure and stable method is to invest in a dedicated NTP time server. These devices receive a time signal directly from an atomic clock, either produced by a national physics lab like NIST or NPL via long wave radio or from GPS satellites.

A single dedicated NTP server will provide a stable, reliable and highly precise source of UTC and allow networks of hundreds and even thousands of devices to be synchronised to NTP.