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.

Auditable Time Synchronization with an NTP Server

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Time synchronization is crucial for many modern applications. Whilst computer networks all have to be running in perfect time to prevent errors and ensure security other systems require time synchronization for legal reasons.

Average speed cameras, traffic light cameras, CCTV, parking meters and alarm systems to name but a few, all require accurate time synchronization not just to ensure the correct operation of the systems but also to provide an auditable and legal trail for use in prosecutions.

Failure to do so can lead to the system being completely useless as any legal case based around the technology would need to be provable.

For instance, a CCTV network that is not synchronized would not be admissible in court, a defendant could easily claim that an image of them on a camera could not be them as they were not in the vicinity at the time and unless the camera system can be audited and proved to be accurate then reasonable doubt would see any case against the suspect dropped.

For this reason, systems like those mentioned above require complete auditable time synchronisation that can be proven beyond reasonable doubt in a court system.

An auditable system of time synchronization is only possible by using a dedicated NTP time server (Network Time Protocol). NTP servers not only provide an accurate method of synchronization being accurate to a few milliseconds they also provide a full audit trail that can’t be disputed.

NTP server systems use the GPS network or specialist radio transmissions to receive the atomic clock time which is so accurate the chance of it being even a second out from UTC time (Universal Coordinated Time) is over 3 billion to one which is even greater than the accuracy of other legal evidences such as DNA.

Benefits of Accurate Network Time Synchronization

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Your computer probably does hundreds and thousands of tasks a day. If that is part of a network then the number of tasks could be millions. From sending emails to saving data, and everything else your computer is tasked to do, they are all logged by the computer or server.

Computers use timestamps to logo processes and indeed, timestamps are used as the only method a computer has to indicate when and if a task or application has been conducted. Timestamps are normally a 16 or 32 bit integer (one long number) that counts back the seconds from a prime epoch – normally 01 January 1970.

So for every task you computer does it will be stamped with the number of seconds from 1970 that the transaction was conducted. These timestamps are the only piece of information a computer system has to ascertain what tasks have been completed and what tasks have yet to be instigated.

The problem with computer networks of more than one machine is that the clocks on individual devices are not accurate enough for many modern time sensitive applications. Computer clocks are prone to drift they are typically based on inexpensive crystal oscillator circuits and can often drift by over a second a day.

This may not seem much but in today’s time sensitive world a second can be a long time indeed especially when you take into account the needs of industries like the stock exchange where a second can be the difference in price of several percent or online seat reservation, where a second can make the difference between an available seat and one that is sold.

This drift is also accumulative so within only a few months the computer systems could be over a minute out of sync and this can have dramatic effects on time sensitive transactions and can result in all sorts of unexpected problems from emails not arriving as a computer thinks they have arrived before they have been sent to data not being backed up or lost completely.

A NTP time server or network time server are increasingly becoming crucial pieces of equipment for the modern computer network. They receive an accurate source of time from an atomic clock and distribute it to all devices on the network. As atomic clocks are incredibly accurate (they won’t drift by a second even in a 100,000 years) and the protocol NTP (Network Time Protocol) continually checks the devices time against the master atomic clock time – it means the computer network will be able to run perfectly synchronised with each device within a few milliseconds of the atomic clock.

Reasons for Atomic Clock Timing

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Atomic clocks have, unbeknown to most people, revolutionised our technology. Many of the ways we trade, communicate and travel are now solely dependent on timing from atomic clock sources.

A global community often means that we have to communicate with people on other areas of the world and in other time zones. For this purpose a universal time zone was developed, known as UTC (Coordinated Universal Time), which is based on the time told by atomic clocks.

Atomic clocks are incredibly accurate, losing only a second in every hundred million years, which is staggering when you compare it to digital clocks that will lose that much time in a week.

But why do we need such accuracy in timekeeping? Much of the technology we employ in modern times is designed for global communication. The Internet is a good example. So much trade is done across continents in fields such as the stock exchange, seat reservation and online auctioning that exact time is crucial. Imagine you are bidding for an item on the Internet and you place a bid a few seconds before the end, the last and highest bid, would it be fair to lose the item because the clock on your ISP was a little fast and the computer therefore thought the bidding was over. Or what about seat reservation; if two people on different sides of the globe book a seat at the same time, who gets the seat. This is why UTC is vital for the internet.

Other technologies too such as global positioning and air traffic control are reliant on atomic clocks to provide accuracy (and in the case of air traffic is paramount for safety). Even traffic lights and speed cameras have to be calibrated with atomic clocks otherwise speeding ticket may not be valid as they could be questioned in court.

For computer systems NTP time servers are the preferred method for receiving and distributing a source of UTC time.

Using Atomic Clocks to Synchronize a Network

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Most computer networks have to be synchronized to some degree. Allowing the clocks on computers across a network to all be telling different times is really asking for trouble. All sorts of errors can occur such as emails not arriving, data getting lost, and errors get unnoticed as the machines struggle to makes sense of the paradoxes that unsynchronized time can cause.

The problem is computers use time in the form of timestamps as the only point of reference between different events. If these don’t match then computers struggle to establish not only the order of events but also if the events took place at all.

Synchronizing a computer network together is extremely simple, thanks largely to the protocol NTP (Network Time Protocol). NTP is installed on most computer operating systems including Windows and most versions of Linux.

NTP uses a single time source and ensures that every device on the network is synchronized to that time. For many networks this single time source can be anything from the IT manager’s wrist watch to the clock on one of the desktop machines.

However, for networks that have to communicate with other networks, have to deal with time sensitive transactions or where high levels of security are required then synchronization to a UTC source is a must.

Coordinated Universal Time (UTC) is a global timescale used by industry all over the world. It is governed by a constellation of atomic clocks making it highly accurate (modern atomic clocks can keep time for 100 million years without losing a second).

For secure synchronization to UTC there is really only one method and that is to use a dedicated NTP time server. Online NTP servers are used by some network administrators but they are taking a risk not only with the accuracy of the synchronization but also with security as malicious users can imitate the NTP time signal and penetrate the firewall.

As dedicated NTP servers are external to the firewall, relying instead on the GPS satellite signal or specialist radio transmissions they are far more secure.

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.

The NTP Time Server Essential Network Protection

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There are a myriad of hardware and software methods of protecting computers. Anti-virus software, firewalls, spyware and routers to name but a few yet perhaps the most important tools for keeping a network safe is often the most overlooked.

One of the reasons for this is that the network time server’s often referred to as the NTP time server (after the protocol Network Time Protocol) primary task is time synchronisation and not security.

The NTP server’s primary task is to retrieve a time signal from a UTC source (Coordinated Universal Time) which it then distributes it amongst the network, checking the clock on each system device and ensuring its running in synchronisation with UTC.

Here is where many network administrators fall down. They know that time synchronisation is vital for computer security. Without it, errors can not be logged (or even spotted) network attacks can’t be countered, data can be lost and if a malicious user does get into the system it is near impossible to discover what they were up to without all machines on a network corresponding to the same time.

However, the NTP server is where many network administrators think they can save a little money. ‘Why bother?’ ‘They say, ‘when you can log on to an Internet NTP server for free.’

Well, as the old saying goes there is no such thing as a free lunch or as it goes a free source of UTC time. Using internet time providers may be free but this is where many computer networks leave themselves open to abuse.

To utilise an internet source of time such as Microsoft’s, NIST or one of those on the NTP pool project may be free but they are also outside a networks firewall and these is where many network administrators come unstuck.

Why the Need for NTP

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Network Time Protocol is an Internet protocol used to synchronize computer clocks to a stable and precise time reference. NTP was originally developed by Professor David L. Mills at the University of Delaware in 1985 and is an Internet standard protocol and is used in most network time servers, hence the name NTP server.

NTP was developed to solve the problem of multiple computers working together and having the different time. Whilst, time usually just advances, if programs are running on different computers time should advance even if you switch from one computer to another. However, if one system is ahead of the other, switching between these systems would cause time to jump forward and back.

As a consequence, networks may run their own time, but as soon as you connect to the Internet, effects become visible. Just Email messages arrive before they were sent, and are even replied to before they were mailed!

Whilst this sort of problem may seem innocuous when it comes to receiving email, however, in some environments a lack of synchronisation can have disastrous results this is why air traffic control was one of the first applications for NTP.

NTP uses a single time source and distributes it amongst all devices on a network it does this by using an algorithm that works out how much to adjust a system clock to ensure synchronisation.

NTP works on a hierarchical basis to ensure there are no network traffic and bandwidth problems. It uses a single time source, normally UTC (coordinated universal time) and receives time requests from the machines on the top of the hierarch which then pass the time on further down the chain.

Most networks that utilise NTP will use a dedicated NTP time server to receive their UTC time signal. These can receive the time from the GPS network or radio transmissions broadcast by national physics laboratories. These dedicated NTP time servers are ideal as they receive time direct from an atomic clock source they are also secure as they are situated externally and therefore do not require interruptions in the network firewall.

NTP has been an astronomical success and is now used in nearly 99 per cent of time synchronisation devices and a version of it is included in most operating system packages.

NTP owes much of its success to the development and support it continues to receives nearly three decades after its inception which is why t is now used throughout the world in NTP servers.

Security and Synchronisation

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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.

How to Synchronise a Computer to an Atomic Clock

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Time synchronisation is often a much underrated aspect of computer management. Generally time synchronisation is only crucial for networks or for computers that a take in time sensitive transactions across the internet.

Time synchronisation with modern operating systems such as Windows Vista, XP or the different versions of Linux is relatively easy as most contain the time synchronisation protocol NTP (Network Time Protocol) or a simplified version at least (SNTP).

NTP is an algorithm based program and works by using a single time source that can be distributed amongst the network (or a single computer) and is constantly checked to ensure the network’s clocks is running accurately.

For single computer users, or networks where security and precision are not primary concerns (although for any network security should be a main issue) then the simplest method of synchronising a computer is to use an internet time standard.

With a Windows operating system this can easily be done on a single computer by double clicking the clock icon and then configuring the internet time tab. However, it must be noted that in using an internet based time source such as nist.gov or windows.time, a port will have to be left open in the firewall which could be taken advantage of by malicious users.

For network users and those not wanting to leave vulnerabilities in their firewall then the most suitable solution is to use a dedicated network time server. Most of these devices also use the protocol NTP but as they receive a time reference externally to the network (usually by way of GPS or long wave radio) the leave no vulnerabilities in the firewall.

These NTP server devices are also far more reliable and accurate than internet time sources as they communicate directly with the signal from an atomic clock rather than being several tiers (in NTP terms known as strata) from the reference clock as most internet time sources are.