Category: Time Synchronisation

History of Timekeeping from Stonehenge to the NTP Server

  |   By

Keeping track of time has been as integral part of helping human civilisation to develop. It could be argued that the greatest step that mankind took was in the development of farming, allowing humans to free up more time to develop sophisticated cultures.

However, farming was fundamentally reliant on timekeeping. Crops are seasonal and knowing when to plant them is the key to all horticulture. It is believed that ancient monuments such as Stonehenge were elaborate calendars helping the ancients to identify the shortest and longest days (solstice).

As human civilisation developed, telling increasingly accurate time became more and more important. And identifying days of the year was one thing but calculating how far into a day was another.

Timing was extremely inaccurate up until the middle ages. People would rely on comparisons of time as a time reference such as how long it took to walk a mile or the time of day would be estimated from when the sun was highest (noon).

Fortunately the development of clocks during the middle of the last millennium meant that for the first time humans could tell with some degree of precision the time of day. As clocks developed so did their accuracy and civilisation became more efficient as events could be more accurately synchronised.

When electronic clocks arrived at the turn of the last century, accuracy was further increased and new technologies started to develop but it wasn’t until the rise of the atomic clock that the modern world really took shape.

Atomic clocks have enabled technologies such as satellites, computer networks and GPS tracking possible as they are so accurate – to within a second every hundred million years.

The atomic clocks were even discovered to be even more accurate than the spin of the Earth that varies, thanks to the Moon’s gravity and extra seconds have to be added to the length of a day – The leap second.

Atomic clocks mean that a global timescale accurate to within a thousandth of second has been developed called UTC – Coordinated Universal Time.

Computer networks to communicate with each other from across the globe in perfect synchronisation to UTC if they use a NTP time server.

An NTP server will synchronise an entire computer network to within a few milliseconds of UTC time allowing global communications and transactions.

Atomic clocks are still being developed the latest strontium clocks are promising accuracy to within a second every billion years.

Time Server Manufacturers

  |   By

Time servers come in several shapes and sizes. The primary difference between most dedicated time servers is in the way they receive  a timing source.

Some time servers utilise national time and frequency transmissions that are broadcast on long wave while other use the GPS network.

Some time servers are designed to be rack-mountable perfect for the average U system of racks allowing the sever to be snugly fitted into your existing rack.

Other time servers are nothing more than small boxes that can be discretely hidden.

Here is a list of top time server manufacturers:

Galleon Systems

Elproma

Symmetricom

Meinberg

Time Tools

Time Server History and The changing ways of recording time

  |   By

The NTP server or network time server as it is often called is the culmination of centuries of horology and chronology. The history of keeping track of time has not been as smooth as you may think.

What month was the Russian October revolution? I’m sure you have guessed that it is a trick question, in fact if you trace the days back to the October revolution that changed the shape of Russia in 1917 you will find it didn’t start until November!

One of the first decisions the Bolsheviks, who had won the revolution, chose to make was to join the rest of eh world by taking up the Gregorian calendar. Russia was last to do adopt the calendar, which is still in use throughout the world today.

This new calendar was more sophisticated that the Julian calendar which most of Europe had been using since the Roman Empire. Unfortunately the Julian calendar did not allow for enough leap years and by the turn of the century this had meant that the seasons had drifted, so-much-so, that when Russia finally adopted the calendar on after Wednesday, 31 January 1918 the following day became Thursday, 14 February 1918.

So whilst the October revolution occurred in October in the old system, to the new Gregorian calendar it meant it had taken place in November.

Whilst the rest of Europe adopted this more accurate calendar earlier than the Russians they still also had to correct the seasonal drift, so in 1752 when Britain changed systems they lost eleven days which according to the populist painter of the time, Hogarth, caused rioters to demand the return of their lost eleven days.

This problem of inaccuracy in keeping track of time was thought to be solved in the 1950’s when the first atomic clocks were developed. These devices were so accurate that they could keep time for a million years without losing a second.

However, it was soon discovered that these new chronometers were in fact too accurate – compared with the Earth’s rotation anyway. The problem was that while atomic clocks could measure the length of a day to the nearest millisecond, a day is never the same length.

The reason being is that the Moon’s gravity affects the Earth’s rotation causing a wobble. This wobble has the effect of slowing down and speeding up the Earth’s spin. If nothing was done to compensate for this then eventually the time told by atomic clocks (International Atomic Time- TAI) and the time based on the Earth’s rotation used by farmers, astronomers and you and I (Greenwich Meantime- GMT) would drift that eventually noon would become midnight (albeit in many millennia).

The solution has been to devise a timescale that is based on atomic time but also accounts for this wobble of the Earth’s rotation. The solution was called UTC (Coordinated Universal Time) and accounts for the Earth’s variable rotation by having ‘leap seconds’ occasionally added. There have been over thirty leap seconds added to UTC since its inception in the 1970’s.

UTC is now a global timescale used throughout the world by computer networks to synchronise too. Most computer networks use a NTP server to receive and distribute UTC time.

Network Time Protocol Security

  |   By

The protocol used by most network time servers is NTP (Network Time Protocol) and has been around for quite a long time yet it is constantly being updated and developed offering ever higher levels of accuracy and security.

Synchronisation is an essential part of modern computer networks and is essential for keeping a system secure. Without NTP and time synchronisation a computer network can be vulnerable o malicious attacks and even fraud.

Even with a perfectly synchronised network security can still be an issue but there are a few key steps that can be taken to ensure your network is kept secure.

Always use a dedicated Network Time Server. Whilst Internet time sources are common place they are a time source situated outside the firewall. This will have obvious security draw backs as a malicious user can take advantage of the ‘hole’ left in your firewall to communicate with the NTP server. A dedicated NTP server will receive a time signal from an external source.

Normally these types of dedicated time servers will utilise either the GPS network (Global Positioning System) or specialist national time and frequency radio transmissions. Both these time sources offer an accurate and reliable method of UTC time (coordinated universal time) whilst also being secure.

Another way to ensure security is to take advantage of NTP’s built-in security mechanism – authentication. Authentication is a set of encrypted keys that are used to establish if the time source is coming from where it is claiming to come from.

Authentication verifies that each timestamp has come from the intended time reference by analysing a set of agreed encryption keys that are sent along with the time information. NTP, using Message Digest encryption (MD5) to un-encrypt the key, analyses it and confirms whether it has come from the trusted time source by verifying it against a set of trusted keys.

Trusted authentication keys are listed in the NTP server configuration file (ntp.conf) and are stored in the ntp.keys file. The key file is normally very large but trusted keys tell the NTP server which set of subset of keys is currently active and which are not. Different subsets can be activated without editing the ntp.keys file using the trusted-keys config command.

Authentication is highly important in protecting a NTP server from malicious attack; however Internet time sources can’t be authenticated which doubles the risk of using an Internet based time reference.

Next Generation of Atomic Clocks Accurate to a Second in 200 Million Years

  |   By

Atomic clocks have been around since the 1950’s. They have provided incredible accuracy in timekeeping with most modern atomic clocks not losing a second in time in a million years.

Thanks to atomic clocks many technologies have become possible and have changed the way we live our lives. Satellite communication, satellite navigation, internet shopping and network communication are only possible thanks to atomic clocks.

Atomic clocks are the basis for the world’s global timescale Universal Coordinated Time (UTC) and are the reference that many computer networks use as a time source to distribute amongst its devices using NTP (Network Time Protocol) and a time server.

Atomic clocks are based on the atom caesium -133. This element has been traditionally used in atomic clocks as its resonance or vibrations during a particular energy state, or extremely high (over 9 billion) and therefore can provide high levels of accuracy.

However, new types of atomic clocks are on the horizon that will boast even more accuracy with the next generation of atomic clocks neither gaining nor losing a second in 200 million years.

The next generation of atomic clocks no longer rely on the caesium atom but use elements such as mercury or strontium and instead of using microwaves such as the caesium clocks these new clocks use light which has higher frequencies.

Strontium’s resonance also exceeds over 430 trillion which is vastly superior to the 9.2 billion vibrations that caesium manages.

Currently atomic clocks can be utilised by computer systems by using either a radio or GPS clock or dedicated NTP time server. These devices can receive the time signal transmitted by atomic clocks and distribute them amongst network devices and computers.

However, the National Institute for Standards and Technology (NIST) have revealed a miniature atomic clock that measures just 1.5 millimetres on a side and about 4 millimetres tall. It  consumes less than 75 thousandths of a watt, and has a stability of about one part in 10 billion, equivalent to a clock that would neither gain nor lose more than a second in 300 years.

In the future these devices could be integrated into computer systems, replacing the current real time clock chips, which are notoriously inaccurate and can drift.

Time Server Top Tips for Time Synchronisation

  |   By

Time synchronisation is an integral part of modern computer networking particularly with the Internet and online communication having become so dominant.

Communicating with machines across the globe requires exact time synchronisation otherwise many of the online tasks we take for granted would not be possible. Time in the form of timestamps is the only form of reference a computer has to identify the order of events. So with time sensitive transactions time synchronisation is pivotal.

Here are some tips to ensure your network is running precise and accurate time as possible:

NTP (Network Time Protocol) is the world’s leading time synchronisation software. There are other time protocols but NTP is the most widely used and best supported.

Most computer networks across the globe are synchronised to UTC (Coordinated Universal Time). This is a global timescale based on the time told by atomic clocks. Always use a UTC source to synchronise too.

Always use an external hardware source as a timing reference as time sources from the Internet can not be authenticated. Authentication is a security measure used by NTP to ensure a timing reference is coming from where it says it is from. Also using an Internet timing source means that the reference is outside your networks firewall, this can cause added security risks.

Dedicated time servers can receive UTC signals from radio transmissions and the GPs network. These offer the most secure, accurate and reliable method of receiving a UTC time reference.

Networks based in Britain, Germany, the USA and Japan have access to long-wave time and frequency transmissions that are broadcast by national physics labs. These broadcasts are accurate and reliable and often the dedicated time servers that receive them are less expensive than their GPS alternatives.

GPS is available everywhere on the globe as a source of UTC time. GPS antennas do good a good 180 degree view of the sky and require a good 48 hours to receive a stable ‘locked’ satellite fix.

Arrange your network into strata. Stratum levels signify the distance from a timing source. A stratum 0 server is an atomic clock while a stratum 1 server is a dedicated time server that receives the time from a stratum 0 source. Stratum 2 devices are machines that receive their timing source from a stratum 1 server but stratum 2 devices can also be used to pass on timing information. By ensuring you have enough stratum levels you will avoid congestion in your network and time server.

How to Configure an Authoritative Time Server in Windows Server 2008

  |   By

Time synchronisation in modern computer networks is essential, all computers need to know the time as many applications, from sending an email to storing information are reliant on the PC knowing when the event took place.

Microsoft Windows Server from 2000 onwards has a time synchronisation utility built into the operating system called Windows Time (w32time.exe) which can be configured to operate as a network time server.

Windows Server 2008 can easily set the system clock to use UTC (Coordinated Universal Time, the World’s time standard) by accessing an Internet source (either: time.windows.com or time.nist.gov).

To achieve this, a user merely has to double click the clock on their desktop and adjust the settings in the Internet Time tab.

It must be noted however, that Microsoft and other operating system manufacturers strongly advise that external timing references should be used as Internet sources can’t be authenticated.

To configure the Windows Time service to use an external time source, click Start, Run and type regedit then click OK.

Locate the following subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type
In the right pane, right-click Type then click Modify, in edit Value type NTP in the Value data box then click OK.

Locate the following subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags.
In the right pane, right-click AnnounceFlags and click Modify. The ‘AnnounceFlags’ registry entry indicates whether the server is a trusted time reference, 5 indicates a trusted source so in the Edit DWORD Value box, under Value Data, type 5, then click OK.

Network Time Protocol (NTP) is an Internet protocol used for the transfer of accurate time, providing time information along so that a precise time can be obtained
To enable the Network Time Protocol; NTPserver, locate and click:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpServer\
In the right pane, right-click Enabled, then click Modify.

In the Edit DWord Value box, type 1 under Value data, then click OK.

Now go back and click on
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer
In the right pane, right-click NtpServer, then Modify, in the Edit DWORD Value under Value Data type In the right pane, right-click NtpServer, then Modify, in the Edit DWORD Value under Value Data type the Domain Name System (DNS), each DNS must be unique and you must append 0x1 to the end of each DNS name otherwise changes will not take effect.

Now click Ok.

Locate and click the following
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient\SpecialPollInterval
In the right pane, right-click SpecialPollInterval, then click Modify.

In the Edit DWORD Value box, under Value Data, type the number of seconds you want for each poll, ie 900 will poll every 15 minutes, then click OK.
To configure the time correction settings, locate:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\config
In the right pane, right-click MaxPosPhaseCorrection, then Modify, in the Edit DWORD Value box, under Base, click Decimal, under Value Data, type a time in seconds such as 3600 (an hour) then click OK.
Now go back and click:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\config
In the right pane, right-click MaxNegPhaseCorrection, then Modify.

In the Edit DWORD box under base, click Decimal, under value data type the time in seconds you want to poll such as 3600 (polls in one hour)
Exit Registry Editor
Now, to restart windows time service, click Start, Run (or alternatively use the command prompt facility) and type:

net stop w32time && net start w32time
And that’s it your time server should be now up and running.

Windows Time Server Synchronising Your Network With NTP

  |   By

Nearly all a computers activity involves time whether logging a timestamp for when a network was accessed to sending an email, knowing the time is crucial for computer applications.

All computers have an on-board clock that provides time and date information. These Real Time Clock (RTC) chips are battery backed so that even when off they can maintain time, however these RTC chips are mass produced and cannot maintain accurate time and tend to drift.

For many applications this can be quite adequate, however if a computer is on a network and needs to talk to other machines, failing to be synchonised to the correct time can mean many time-sensitive transactions can not be completed and can even leave the network open to security threats.

All versions of Windows Server since 2000 have included a time synchronization facility, called Windows Time Service (w32time.exe), built into the operating system. This can be configured to operate as a network time server synchronizing all machines to a specific time source.

Windows Time Service uses a version of NTP (Network Time Protocol), normally a simplified version, of the Internet protocol which is designed to synchronise machines on a network, NTP is also the standard for which most computer networks across the global use to synchronise with.

Choosing the correct time source is vitally important. Most networks are synchronized to UTC (Coordinated Universal Time) source. UTC is a global standardized time based on atomic clocks which are the most accurate time sources.

UTC can be obtained over the Internet from such places as time.nist.gov (us Naval Observatory) or time.windows.com (Microsoft) but it must be noted that internet time sources can not be authenticated which can leave a system open to abuse and Microsoft and others advise using an external hardware source as a reference clock such as a specialized NTP server.

NTP servers receive their time source from either a specialist radio transmission from national physics laboratories which broadcast UTC time taken from an atomic clock source or by the GPS network which also relays UTC as a consequence of needing it to pin point locations.

NTP can maintain time over the public Internet to within 1/100th of a second (10 milliseconds) and can perform even better over LANs.

Keeping accurate time on Linux

  |   By

If you want to be sure that your computer clock is accurate you can configure your system to use NTP (Network Time Protocol), one of the oldest Internet protocols and the industry standard for time synchronisation.

NTP on will synchronise your computer’s clock to a pool of time servers around the world that are official ‘timekeepers’. It is best to choose the closest to you so response time is minimized and to use more than one in case one goes down. There are more than 1.500 servers to choose from, but some areas are better served than others. Many servers on the internet are extremely inaccurate and Internet time references should not be used as a replacement for a dedicated time server.

However, for basic time synchronisation purposes, Internet providers will suffice. The first step should be to select three servers close to you – preferably in your country, or if there aren’t enough, in your ‘zone. Go to ntp home and browse through the tree of zones and servers to select which ones are best for you. The follow these commands to configure:

1. Configure /etc/ntp.conf
Edit this file with a text-editor. Replace
server <example-server-name>
with your servers, such as:

server 0.br.pool.ntp.org
server 1.br.pool.ntp.org
server 2.br.pool.ntp.org

2. Synchronise your clock manually
If your clock is drifting too NTP might refuse to synchronise it, but it can be done manually:

ntpdate 0.br.pool.ntp.org (server name that you choose)

3. Make your ntp daemon executable

chmod +x /etc/rc.d/rc.ntpd

4. Start NTP now without rebooting
Again, a simple command:

/etc/rc.d/rc.ntpd start

Basic Time Server Information

  |   By

All PC’s and networking devices use clocks to maintain an internal system time. These clocks, called Real Time Clock chips (RTC) provide time and date information. The chips are battery backed so that even during power outages, they can maintain time.

Computer networks rely on timekeeping for nearly all their applications, from sending an email to saving data, a timestamp is necessary for computer to keep track. All routers and switches need to run at the same rate, out of sync devices can lead to data being lost and even entire connections.

For some transactions it is necessary for computers to be perfectly synchronised, even a few seconds difference between machines can have serious effects, such as finding an airline ticket you had booked had been sold moments later to another customer or you could draw your savings out of a cash machine and when your account is empty you could quickly going to another machine and withdraw it all again.

However, personal computers are not designed to be perfect clocks, their design has been optimized for mass production and low-cost rather than maintaining accurate time. However, these internal clocks are prone to drift and although for many application this can be quite adequate, often machines need to work together on a network and if the computers drift at different rates the computers will become out of sync with each other and problems can arise particularly with time sensitive transactions.

Time servers are like other computer servers in the sense they are usually located on a network. A time server gathers timing information, usually from an external hardware source and then synchronises the network to that time.

Most time servers use NTP (Network Time Protocol) which is one of the Internet’s oldest protocols still used, invented by Dr David Mills from the University of Delaware, it has been in utilized since 1985. NTP is a protocol designed to synchronize the clocks on computers and networks across the Internet or Local Area Networks (LANs).

NTP utilises an external timing reference and then synchronises all devices on the network to that time.

There are various sources that a NTP time server can use as a timing reference. The Internet is an obvious source, however, internet timing references from the Internet such as nist.gov and windows.time can not be authenticated, leaving the time server and therefore the network vulnerable to security threats.

Often time servers are synchronised to a UTC (Coordinated Universal time) source which is the global standard time scale and allows computers all over the world to synchronised to exactly the same time. This has obvious importance in industries where exact timing is crucial such as the stock exchange or airline industry.