Time Synchronisation

Linux operating systems are becoming increasingly popular partly due to the many advantages they have over commercial systems like Windows or OS X. Linux offers increased security (as there are only a handful of viruses that can infect a Linux based system), better stability and in most cases it is free.

It is no wonder more and more home and business users alike are opting to switch to a Linux based operating systems and whether it is Redhat, Mandrake, Ubuntu or the myriad of other UNIX and LINUX based systems, keeping accurate time is relatively straight forward.

Time synchronisation is vital in many time-sensitive applications and most business users find it would be impossible to conduct any online transactions without a synchronized network. Even home-users find an advantage in ensuring their system is running accurate time, emails no longer arrive before they are sent and security is increased.

Most Linux based operating systems contain a version of Network Time Protocol (NTP) an Internet protocol designed to synchronise time on a network. For those that do not contain a pre-packed version, NTP is open source and freely available at ‘NTP.org’.

While NTP is available for most versions of Windows; Linux users have the advantage in that it has traditionally been the primary development platform for NTP. It works by using a timing source either from the Internet or via a dedicated network time server.
These reference clocks run UTC time (coordinated universal time) a global timescale which is relayed to them from atomic clocks that are accurate to a few nanoseconds (a nanosecond is a billionth of a second).

Put simply, the NTP daemon (a service program that runs in the background) compares the time on the computer with the timing source at regular intervals and adjusts it depending on any drift.

The NTP daemon is configured using the ‘NTP.conf’ file. The configuration file is where the location of the NTP timing servers are stored. If attempting to use a public internet timing source it is advised to visit http://www.pool.ntp.org which has a collection of over 200 servers.

However Microsoft and Novell, strongly advise that internet based timing sources are not used as they are unauthenticated and can leave a gateway open for malicious attacks.

Alternatively and most preferably, dedicated NTP time servers are available which provide better accuracy and are far more secure. These time servers receive a timing source from either a national radio broadcast (such as WWVB in the US or MSF in the UK) or via the GPS system.

Once installed these systems continually check the time on all the network computers’ clocks and adjusts them for any drift. A typical GPS receiver can provide timing information to within a few nanoseconds of UTC while national time and frequency transmissions are accurate to 1 – 20 milliseconds (a millisecond is 1/1000 of a second).

Time synchronisation is extremely important for modern computer networks. In some industries time synchronisation is absolutely vital especially when you are dealing with technologies such as air traffic control or marine navigation where hundreds of lives could be put at risk by lack of precise time.

Even in the financial world, correct time synchronisation is vital as millions can be added or wiped off share prices every second. For this reason the entire world adheres to a global timescale known as coordinated universal time (UTC). However, adhering to UTC and keeping UTC precise are two different things.

Most computer clocks are simple oscillators that will slowly drift either faster or slower. Unfortunately this means that no matter how accurate they are set on Monday they will have drifted by Friday. This drift may be only a fraction of a second but it soon won’t take long for the originally UTC time to be over a second out.

In many industries this may not mean a matter of life and death of the loss of millions in stocks and shares but lack of time synchronisation can have unforeseen consequences such as leaving a company less protected from fraud. However, receiving and keeping true UTC time is quite straight forward.

Dedicated network time servers are available that uses the protocol NTP (Network Time Protocol) to continually check the time of a network against a source of UTC time. These devices are often referred to as an NTP server, time server or network time server. The NTP server constantly adjusts all devices on a network to ensure that the machines are not drifting from UTC.

UTC is available from several sources including the GPS network. This is an ideal source of UTC time as it is secure, reliable and available everywhere on the planet. UTC is also available via specialist national radio transmissions which are broadcast from national physics laboratories although they are not available everywhere.

Time synchronisation is often described as a ‘headache’ by network administrators. Keeping computers on a network all running the same time is increasingly important in modern network communications particularly if a network has to communicate with another network running independently.

For this reason UTC (Coordinated Universal Time) has been developed to ensure all networks are running the same accurate timescale. UTC is based on the time told by atomic clocks so it is highly precise, never losing even a second. Network time synchronisation is however, relatively straight forward thanks to the protocol NTP (Network Time Protocol).

UTC time sources are widely available with over a thousand online stratum 1 servers available on the Internet. The stratum level describes how far away a time server is to an atomic clock (an atomic clock that generates UTC is known as a stratum 0 device). Most time servers available on the Internet are in fact not stratum 1 devices but stratum in that they get their time from a device that in turn receives the UTC time signal.

For many applications this can be accurate enough but as these timing sources are on the Internet there is very little you can do to ensure both their accuracy and their precision. In fact even if an Internet source is highly accurate the distance away form it can cause delays int eh time signal.

Internet time sources are also unsecure as they are situated outside of the firewall forcing the network to be left open for the time requests. For this reason network administrators serious about time synchronisation opt to use their own external stratum 1 server.

These devices, often called a NTP server, receive a UTC time source from a trusted and secure source such as a GPS satellite then distribute it amongst the network. The NTP server is far more secure than an Internet based time source and are relatively inexpensive and highly accurate.

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.

Keeping accurate time on a network with a NTP time server is highly important here is the second part of the article that explains why.

Legal protection – Whether it is a payment dispute with a supplier or customer or even a case of fraud committed against your company only an accurate method of synchronisation will be accepted as a legal defence. An NTP time server is legally auditable and can be used as evidence in a court of law.

Company Credibility:
Being victim to any of these potential hazards can have devastating effects on your own business but also that of your suppliers and customers. Once word gets out too it will soon become common knowledge amongst your competitors, customers and suppliers as news travels quickly in the business world. Keeping credibility is a good enough reason in itself to ensure a computer network is adequately synchronised.

If you have answered yes to any of the above questions then it is time your company invested in a dedicated NTP time server to accurately synchronise you computer network to. Dedicated time servers use the protocol NTP (Network Time Protocol) as a method of distributing a single time source around the internet. UTC (Coordinated Universal Time) is the preferred time standard that most networks are synchronised to.

An NTP time server can receive a secure and accurate UTC time signal from the GPS network or from long wave radio transmissions broadcast by several national physics laboratories.

Time synchronisation in the modern age is highly precise. Modern atomic clocks can keep time so accurately that in 100 million years these timekeeping devices will not lose even a second.

Bit is this sort of accuracy necessary in the modern world? How important can a second possibly be, after all, a second has always been seen as one of the smallest units of time.

However, when you consider modern technology such as the satellite navigation then a second suddenly becomes a huge gulf in time. Modern satellite navigation devices work by calculating distance by using the time form the atomic clocks on GPS (Global Positioning System) satellites.

However, when you consider that the speed of light is close to 300, 000 km a second then you can understand that if a GPS clock is a second out then your navigation could be inaccurate by hundreds of thousands of kilometres.

The same is true for modern computer networks. Computers can process thousands of transactions a second so when it comes to global network communication a second can be a huge amount of time.

That is why modern NTP server’s, responsible for synchronising networks offer precision to the millisecond, ensuring that network across the globe are within a hare’s breath of each other.

Time synchronisation is vital for the modern computer network particularly when computer networks across the globe need to communicate with each other.

A lack of synchronisation would make impossible many online activities such as Internet auctions, seat reservation and trading in stocks and shares. It can also leave a system open to security threats and even fraud.

The NTP server (Network Time Protocol) can provide the most secure and accurate method of synchronising a network.  Many NTP servers are rack-mountable devices that can connect to a network and distributes time information between all devices on that system.

They work by using a single time reference, most commonly a source of UTC (Coordinated Universal Time), which NTP then checks all the system clocks to ensure all devices are keeping the same time. When it finds a computer or device that is drifting it advances or retreats the system clock until it matches UTC.

A NTP server will receive a timing source from either across the Internet (although not very secure or accurate), a specialist long-wave radio transmission or from the GPS network (global positioning system).

By utilising dedicated NTP server, not only can all devices on a network be synchronised together but also by using UTC the network will be synchronised with millions of computer networks all over the world.

Time synchronisation is now a critical aspect of network management enabling time sensitive applications to be conducted from across the globe. Without correct synchronisation computer systems would be unable to communicate with each other and transactions such as seat reservation, Internet auctions and online banking would be impossible.

For effective time synchronisation the global timescale UTC (Coordinated Universal Time) is a prerequisite. While a computer network can be synchronised to any single time source, UTC is employed by computer networks all over the world. By synchronising to a UTC time source a computer network can therefore be synchronised to every other computer network across the globe that also use UTC as their time source.

Receiving a reliable UTC time source is not as easy as it sounds. Many network administrators opt to use a UTC Internet time source. Whilst many of these time sources are accurate enough, they can be too far away to provide reliability and there are plenty of Internet time sources that are vastly inaccurate.

Another reason why Internet time sources should not be used as a source of time synchronisation is because an Internet time source is outside of a firewall and leaving a gap in the firewall to receive timing information can leave a system open to abuse.

So that UTC time can be opted as a civil time throughout the world several national physics laboratories broadcast a UTC timing signal that can be received and utilised as a network time source. Unfortunately, however, these time signals are not available in every country and even in those areas where a signal exists; they can be quite often obstructed by interference and local topography.

Another method for receiving a source of UTC time is to use the GPS satellite network. Strictly speaking the Global Positioning System (GPS ) does not relay UTC but it is a time based on International Atomic Time (TAI) with a predefined offset. A GPS NTP clock can simply convert the GPS time into UTC for synchronisation purposes.

The main advantage of using GPS is that a GPS signal is available anywhere on the planet providing that there is a clear view of the sky above (GPS transmissions are broadcast via line-of-sight) so UTC synchronisation can be conducted anywhere.

Time synchronisation is often described as a ‘headache’ by network administrators. Keeping computers on a network all running the same time is increasingly important in modern network communications particularly if a network has to communicate with another network running independently.

For this reason UTC (Coordinated Universal Time) has been developed to ensure all networks are running the same accurate timescale. UTC is based on the time told by atomic clocks so it is highly precise, never losing even a second. Network time synchronisation is however, relatively straight forward thanks to the protocol NTP (Network Time Protocol).

UTC time sources are widely available with over a thousand online stratum 1 servers available on the Internet. The stratum level describes how far away a time server is to an atomic clock (an atomic clock that generates UTC is known as a stratum 0 device). Most time servers available on the Internet are in fact not stratum 1 devices but stratum in that they get their time from a device that in turn receives the UTC time signal.

For many applications this can be accurate enough but as these timing sources are on the Internet there is very little you can do to ensure both their accuracy and their precision. In fact even if an Internet source is highly accurate the distance away form it can cause delays int eh time signal.

Internet time sources are also unsecure as they are situated outside of the firewall forcing the network to be left open for the time requests. For this reason network administrators serious about time synchronisation opt to use their own external stratum 1 server.

These devices, often called a NTP server, receive a UTC time source from a trusted and secure source such as a GPS satellite then distribute it amongst the network. The NTP server is far more secure than an Internet based time source and are relatively inexpensive and highly accurate.

Time synchronisation is extremely important for modern computer networks. In some industries time synchronisation is absolutely vital especially when you are dealing with technologies such as air traffic control or marine navigation where hundreds of lives could be put at risk by lack of precise time.

Even in the financial world, correct time synchronisation is vital as millions can be added or wiped off share prices every second. For this reason the entire world adheres to a global timescale known as coordinated universal time (UTC). However, adhering to UTC and keeping UTC precise are two different things.

Most computer clocks are simple oscillators that will slowly drift either faster or slower. Unfortunately this means that no matter how accurate they are set on Monday they will have drifted by Friday. This drift may be only a fraction of a second but it soon won’t take long for the originally UTC time to be over a second out.

In many industries this may not mean a matter of life and death of the loss of millions in stocks and shares but lack of time synchronisation can have unforeseen consequences such as leaving a company less protected from fraud. However, receiving and keeping true UTC time is quite straight forward.

Dedicated network time servers are available that uses the protocol NTP (Network Time Protocol) to continually check the time of a network against a source of UTC time. These devices are often referred to as an NTP server, time server or network time server. The NTP server constantly adjusts all devices on a network to ensure that the machines are not drifting from UTC.

UTC is available from several sources including the GPS network. This is an ideal source of UTC time as it is secure, reliable and available everywhere on the planet. UTC is also available via specialist national radio transmissions which are broadcast from national physics laboratories although they are not available everywhere.

Time synchronisation in the modern age is highly precise. Modern atomic clocks can keep time so accurately that in 100 million years these timekeeping devices will not lose even a second.

Bit is this sort of accuracy necessary in the modern world? How important can a second possibly be, after all, a second has always been seen as one of the smallest units of time.

However, when you consider modern technology such as the satellite navigation then a second suddenly becomes a huge gulf in time. Modern satellite navigation devices work by calculating distance by using the time form the atomic clocks on GPS (Global Positioning System) satellites.

However, when you consider that the speed of light is close to 300, 000 km a second then you can understand that if a GPS clock is a second out then your navigation could be inaccurate by hundreds of thousands of kilometres.

The same is true for modern computer networks. Computers can process thousands of transactions a second so when it comes to global network communication a second can be a huge amount of time.

That is why modern NTP server’s, responsible for synchronising networks offer precision to the millisecond, ensuring that network across the globe are within a hare’s breath of each other.