Category: Time Synchronisation

Five Reasons why your Network needs a NTP Server

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Accurate timekeeping if quite often overlooked as a priority for network administrators yet many are risking both security and data loss by not ensuring their networks are synchronised as precisely as possible.

Computers do have their own hardware clocks but these are often just simple electronic oscillators such as exist in digital watches and unfortunately these system clocks are prone to drift, often by as much as several seconds in a week.

Running different machines on a network that have different times – even by only a few seconds – can cause havoc as so many computer tasks rely on time. Time, in the form of timestamps, is the only reference computers use to distinguish between different events and failure to accurately synchronize a network can lead to all sorts of untold problems.

Here are some of the major reasons why your network should be synchronised using Network Time Protocol, prefasbly with a NTP time server.

Data Backups – vital to safeguard data in any business or organization, a lack of synchronisation can lead to not only back ups failing but older versions of files replacing more modern versions.

Malicious Attacks – no matter how secure a network, somebody, somewhere will eventually gain access to your network but without accurate synchronisation it may become impossible to discover what compromises have taken place and it will also give any unauthorised users extra time inside a network to wreak havoc.

Error logging – when faults occur, and they inevitably do, the system logs contain all the information to identify and correct problems. However, if the system logs are not synchronised it can sometimes be impossible to figure out what went wrong and when.

Online Trading – Buying and selling on the internet is now commonplace and in some businesses thousands of online transactions are conducted every second from seat reservation to buying of shares and a lack of accurate synchronisation can result in all sorts of errors in online trading such as items being bought or sold more than once.

Compliance and legality – Many industrial regulations systems require an auditable and accurate method of timing. A unsynchronised network will also be vulnerable to legal issues as the exact time an event is alleged to have taken place can not be proved.

Did you Remember the Leap Second this Year?

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When you counted down on New Year’s Eve to mark the beginning of the next year did you start at 10 or 11? Most revelers would have counted down from ten but they would have been premature this year as there was an extra second added to last year – the leap second.

Leap seconds are normally inserted once or twice a year (normally on New Year’s Eve and in June) to ensure the global timescale UTC (Coordinated Universal Time) coincides with the astronomical day.

Leap seconds have been used since UTC was first implemented and they are a direct result of our accuracy in timekeeping. The problem is that modern atomic clocks are far more accurate timekeeping devices than the earth itself. It was noticed when atomic clocks were first developed that the length of a day, once thought to be exactly 24 hours, varied.

The variations are caused by the Earth’s rotation which is affected by the moons gravity and tidal forces of the Earth, all of which minutely slow down the earth’s rotation.

This rotational slowing, while only minuscule, if it is not checked then the UTC day would soon drift into the astronomical night (albeit in several thousands of years).

The decision on whether a Leap Second is needed is the remit of the International Earth Rotation Service (IERS), however, Leap Seconds are not popular with everybody and they can cause potential problems when they are introduced.

UTC is used by NTP time servers (Network Time Protocol) as a time reference to synchronise computer networks and other technology and the disruption Leap seconds can cause is seen as not worth the hassle.

However, others, such as astronomers, say that failing to keep UTC in line with the astronomical day would make studying of the heavens nearly impossible.

The last leap second inserted before this one was in 2005 but there have been a total of 23 seconds added to UTC since 1972.

Using NTP to Synchronise a Digital Signage System

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Digital signage is advancing quite rapidly for such a burgeoning new industry. Fantastic new innovations and content styles are being developed all the time and there are some really fantastic campaigns out there and more and more adventurous implementations are springing up all the time.

One of a growing number of trends is the use of complicated, scheduled and synchronised campaigns on multiple machines. These are incredibly eye-catching especially when the content is synchronised to provide passers-by with an almost interactive experience.

Synchronised content can be really challenging to implement and this sort of content is certainly not for the beginner as setting up such a sophisticated campaign can be really difficult.

One of the essential aspects of these types of scheduled digital signage campaigns is to ensure all displays are synchronized together. Synchronization is perhaps the most crucial aspect of these types of sophisticated digital signage campaigns. There are multiple methods of synchronising this type of campaign.

One solution is to a network time server which receives a single time source and distributes it amongst all devices on that network using the time protocol NTP (Network Time Protocol).

NTP servers receive the time from an external source (normally GPS or long wave radio) so there is no need to have the network connected to the internet although it is just as possible to synchronise to an internet time source although this can be problematic if there is any disturbance in the internet connection.

Any large network of digital signage displays also need to be protected, especially if media players or PCs are being used to generate content. The best option for ensuring total security is to place both the screen and media device in a display enclosure, often referred to as an LCD enclosure.

Rubidium Oscillators Additional Precision for NTP Serve (Part 1)

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Oscillators have been essential in the development of clocks and chronology. Oscillators are just electronic circuitry that produces a repetitive electronic signal. Often crystals such as quartz are used to stabilise the frequency of the oscillation,

Oscillators are the primary technology behind electronic clocks. Digital watches and battery powered analogue clock are all controlled by an oscillating circuit usually containing a quartz crystal.

And while electronic clocks are many times more accurate than a mechanical clock, a quartz oscillator will still drift by a second or two each week.

Atomic clocks of course are far more accurate. They still, however, use oscillators, most commonly caesium or rubidium but they do so in a hyper fine state often frozen in liquid nitrogen or helium. These clocks in comparison to electronic clocks will not drift by a second in even a million years (and with the more modern atomic clocks 100 million years).

To utilise this chronological accuracy a network time server that uses NTP (Network Time Protocol) can be used to synchronise complete computer networks. NTP servers use a time signal from either GPS or long wave radio that comes direct from an atomic clock (in the case of GPS the time is generated in a clock onboard the GPS satellite).

NTP servers continually check this source of time and then adjust the devices on a network to match that time. In between polls (receiving the time source) a standard oscillator is used by the time server to keep time. Normally these oscillators are quartz but because the time server is in regular communication with the atomic clock say every minute or two, then the normal drift of a quartz oscillator is not a problem as a few minutes between polls would not lead to any measurable drift.

To be continued…

Dealing with Time across the Globe

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No matter where we are in the world we all need to know the time at some point in the day but while each day lasts for the same amount of time no matter where you are on Earth the same timescale is not used globally.

The impracticality of Australians having to wake up at 17.00 or those in the US having to start work at 14.00 would rule out suing a single timescale, although the idea was discussed when the Greenwich was named the official prime meridian (where the dateline officially is) for the world some 125 years ago.

While the idea of a global timescale was rejected for the above reasons, it was later decided that 24 longitudinal lines would split the world up into different timezones. These would emanate from GMT around with those on the opposite side of the planet being +12 hours.

However, by the 1970’s a growth in global communications meant that a universal timescale was finally adopted and is still in much use today despite many people having never heard of it.

UTC, Coordinated Universal Time, is based on GMT (Greenwich Meantime) but is kept by a constellation of atomic clocks. It also accounts for variations in earth’s rotation with additional seconds known as ‘leap seconds’ added once of twice a year to counteract the slowing of the Earth’s spin caused by gravitational and tidal forces.

While most people have never heard of UTC or use it directly its influence on our lives in undeniable with computer networks all synchronised to UTC via NTP time servers (Network Time Protocol).

Without this synchronisation to a single timescale many of the technologies and applications we take for granted today would be impossible. Everything from global trading on stocks and shares to internet shopping, email and social networking are only made possible thanks to UTC and the NTP time server.

UTC What Time is it?

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From the early days of the industrial revolution, when railway lines and the telegraph spanned across time zones it became apparent that a global timescale was required that would allow the same time to be used no matter where you were in the world.

The first attempt at a global timescale was GMT – Greenwich Meantime. This was based on the Greenwich Meridian where the sun is directly above at 12 noon. GMT was chosen, primarily because of the influence of the British empire on the rest if the globe.

Other timescales had been developed such British Railway Time but GMT was the first time a truly global system of time was used throughout the world.

GMT remained as the global timescale through the first half of the twentieth century although people began referring to as UT (Universal Time).

However, when atomic clocks were developed in the middle of the twentieth century it soon became apparent that GMT was not accurate enough. A global timescale based on the time told by atomic clocks was desired to represent these new accurate chronometers.

International Atomic Time (TAI) was developed for this purpose but problems in using atomic clocks soon became apparent.

It was thought that the Earth’s revolution on its axis was an exact 24 hours. But thanks to atomic clocks it was discovered the Earth’s spin varies and since the 1970’s has been slowing. This slowing of the Earth’s rotation needed to be accounted for otherwise the discrepancies could build up and night would slowly drift in to day (albeit in many millennia).

Coordinated Universal Time was developed to counter this. Based on both TAI and GMT, UTC allows for the slowing of the Earth’s rotation by adding leap seconds every year or two (and sometimes twice a year).

UTC is now a truly global timescale and is adopted by nations and technologies across the globe. Computer networks are synchronised to UTC via network time servers and they use the protocol NTP to ensure accuracy.

NTP or SNTP That is the Question?

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While there are several protocols available for time synchronisation the majority of network time is synchronised using either NTP or SNTP.

Network Time Protocol (NTP) and Simple Network Time Protocol (SNTP) have been around since the inception of the Internet (and in the case of NTP, several years beforehand) and are by far the most popular and widespread time synchronisation protocols.

However, the difference between the two is slight and deciding which protocol is best for a ntp time server or a particular time synchronisation application can be troublesome.

As its name suggests, SNTP is a simplified version of Network Time Protocol but the question is often asked: ‘what exactly is the difference?’

The main difference between the two versions of the protocol is in the algorithm that is used. NTP’s algorithm can query multiple reference clocks an calculate which is the most accurate.

SNTP use for low processing devices – it is suited to less powerful machines, do not require the high level accuracy of NTP. NTP can also monitor any offset and jitter (small variations in waveform resulting from voltage supply fluctuations, mechanical vibrations or other sources) whilst SNTP does not.

Another major difference is in the way the two protocols adjust for any drift in network devices. NTP will speed up or slow down a system clock to match the time of the reference clock coming into the NTP server (slewing) while SNTP will simply step forward or backward the system clock.

This stepping of the system time can cause potential problems with time sensitive applications especially of the step is quite large.

NTP is used when accuracy is important and when time critical applications are reliant on the network. However, its complex algorithm is not suited to simple machines or those with less powerful processors. SNTP on the other hand is best suited for these simpler devices as it takes up less computer resources, however it is not suited for any device where accuracy is critical or where time critical applications are reliant on the network.

Network Time Protocol For When Time Matters

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There is a certain irony that the computer that sits on your desktop and may have cost as much as month’s salary will have a clock onboard that is less accurate than a cheap wristwatch bought at a petrol or gas station.

The problem is not that computers are in particularly made with cheap timing components but that any serious timekeeping on a PC can be achieved without expensive or advanced oscillators.

The onboard timing oscillators on most PCs are in fact just a back up to keep the computer clock synchronised when the PC is off or when network timing information is unavailable.

Despite these inadequate onboard clocks, timing on a network of PC’s can be achieved to within millisecond accuracy and a network that is synchronised to the global timescale UTC (Coordinated Universal Time) shouldn’t drift at all.

The reason this high level of accuracy and synchronicity can be achieved without expensive oscillators is that computers can use Network Timing Protocol (NTP) to find and maintain the exact time.

NTP is an algorithm that distributes a single source of time; this can be generated by the onboard clock of a PC – although this would see every machine on the network drift as the clock itself drifts – A far better solution is to use NTP to distribute a stable, accurate source of time, and most preferably for networks that conduct business across the internet, a source of UTC.

The simplest method of receiving UTC – which is kept true by a constellation of atomic clocks around the globe – is to use a dedicated NTP time server. NTP servers use either GPS satellite signals (Global Positioning System) or long wave radio broadcasts (usually transmitted by national physics laboratories like NPL or NIST).

Once received the NTP server distributes the timing source across the network and constantly checks each machine for drift (In essence the networked machine contacts the server as a client and the information is exchanged via TCP/IP.

This makes the onboard clocks of the computers themselves obsolete, although when the machines are initially booted up, or if there has been a delay in contacting the NTP server (if it is down or there is a temporary fault), the onboard clock is used to maintain time until full synchronisation is again achievable.

Time Servers and the Internet

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Timing is becoming increasingly crucial for computer systems. It is now almost unheard of for a computer network to function without synchronisation to UTC (Coordinated Universal Time). And even single machines used in the home are now equipped with automatic synchronisation. The latest incarnation of Windows for instance, Windows 7, connects to a timing source automatically (although this application can be turned off manually by accessing the time and date preferences.)

The inclusion of these automatic synchronisation tools on the latest operating systems is an indication of how important timing information has become and when you consider the types of applications and transactions that are now conducted on the internet it is of no surprise.

Internet banking, online reservations, internet auctions and even email can be reliant on accurate time. Computers use timestamps as the only point of reference they have to identify when and if a transaction has occurred. Mistakes in timing information can cause untold errors and problems, particularly with debugging.

The internet is full of time servers with over a thousand time sources available for online synchronisation however; the accuracy and usefulness of these online sources of UTC time do vary and leaving a TCP/IP open in the firewall to allow the timing information through can leave a system vulnerable.

For network systems where timing is not only crucial but where security is also a paramount issue then the internet is not a preferred source for receiving UTC information and an external source is required.

Connecting a NTP network to an external source of UTC time is relatively straightforward if a network time server is used. These devices that are often referred to as NTP servers, use the atomic clocks onboard GPS (Global Positioning System) satellites or long wave transmissions broadcast by places such as NIST or NPL.

NTP Servers and the Different Time Sources

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NTP servers are essential devices for computer network time synchronisation. Ensuring a network coincides with UTC (Coordinated Universal Time) is vital in modern communications such as the Internet and is the primary function of the network time server (NTP server).

As their name suggests, these time servers use the protocol NTP (Network Time Protocol) to handle the synchronisation requests. NTP is already installed in many operating systems and synchronisation is possible without an NTP server by utilising an Internet time source, this can be unsecure and inaccurate for many network needs.

Network time servers receive a far more accurate and secure time signal. There are two methods of receiving the time using a time server: utilising the GPS network or receiving long wave radio transmissions.

Both these methods of receiving a time source are secure as they are external to any network firewall. They are also accurate as both sources of time are generated directly by atomic clocks rather than an Internet time service that are normally NTP devices connected to a third party atomic clock.

The GPS network provides an ideal source of time for NTP servers as the signals are available anywhere. The only downside of using the GPS network is that a view of the sky is required to lock-on to a satellite.

Radio referenced time sources are more flexible in that the long wave signal can be received indoors. They are limited in strength and not every country has a time signal although some signals such as the German DCF and the USA WVBB are available in neighbouring states.