Category: ntp server

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.

Atomic Clocks the Key to Network Synchronisation

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Sourcing the correct time for network synchronisation is only possible thanks to atomic clocks. Compared to standard timing devices and atomic clock is millions of times more accurate with the latest designs providing accurate time to within a second in a 100,000 years.

Atomic clocks use the unchanging resonance of atoms during different energy states to measure time providing an atomic tick that occurs nearly 9 billion times a second in the case of the caesium atom. In fact the resonance of caesium is now the official definition of a second having been adopted by the International System of Unit (SI).

Atomic clocks are the base clocks used for the international time, UTC (Coordinated Universal Time). And they also provide the basis for NTP servers to synchronise computer networks and time sensitive technologies such as those used by air traffic control and other high level time sensitive applications.

Finding an atomic clock source of UTC is a simple procedure. Particularly with the presence of online time sources such as those provided by Microsoft and the National Institute for Standards and Time (windows.time.com and nist.time.gov).

However, these NTP servers are what are known as stratum 2 devices that mean they are connected to another device which in turn gets the time from an atomic clock (in other words a second-hand source of UTC).

While the accuracy of these stratum 2 servers is unquestionable, it can be affected by the distance the client is from the time servers, they are also outside the firewall meaning that any communication with an online time server requires an open UDP (User Datagram Protocol) port to allow the communication.

This can cause vulnerabilities in the network and are not used for this reason in any system that requires complete security. A more secure (and reliable) method of receiving UTC is to use a dedicated NTP time server. These time synchronisation devices receive the time direct from atomic clocks either broadcast on long wave by places like NIST or NPL (National Physical Laboratory – UK). Alternatively UTC can be derived from the GPS signal broadcast by the constellation of satellites in the GPS network (Global Positioning System).

Atomic Clock to be attached to International Space Station

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One of the world’s most accurate atomic clocks is to be launched into orbit and attached to the International Space Station (ISS) thanks to an agreement signed by the French space agency.

The PHARAO (Projet d’Horloge Atomique par Refroidissement d’Atomes en Orbite) atomic clock is to attached to the ISS in an effort to more accurately test Einstein’s theory of relatively as well as increasing the accuracy of Coordinated Universal Time (UTC) amongst other geodesy experiments.

PHARAO is a next generation caesium atomic clock with an accuracy that corresponds to less than a second’s drift every 300,000 years. PHARAO is to be launched by the European Space Agency (ESA) in 2013.

Atomic clocks are the most accurate timekeeping devices available to mankind yet they are susceptible to changes in gravitational pull, as predicted by Einstein’s theory, as time itself is slewed by the Earth’s pull. By placing this accurate atomic clock into orbit the effect of Earth’s gravity is lessened allowing PHARAO to be more accurate than Earth based clock.

While atomic clocks are not new to orbit, as many satellites; including the GPS network (Global Positioning System) contain atomic clocks, however, PHARAO will be among the most accurate clocks ever launched into space, allowing it to be used for far more detailed analysis.

Atomic clocks have been around since the 1960’s but their increasing development has paved the way for more and more advanced technologies. Atomic clocks form the basis of many modern technologies from satellite navigation to allowing computer networks to communicate effectively across the globe.

Computer networks receive time signals from atomic clocks via NTP time servers (Network Time Protocol) which can accurately synchronise a computer network to within a few milliseconds of UTC.

Atomic Clocks and Gravity

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We couldn’t live our lives without them. They affect almost every aspect of our daily lives and many of the technologies that we take for granted in today’s world, just couldn’t function without them. In fact, if you are reading this article on the Internet the there is a chance you are using one right now.

Without knowing it, atomic clocks govern all of us. From the Internet; to mobile phone networks and satellite navigation, without atomic clocks none of these technologies would be possible.

Atomic clocks govern all computer networks using the protocol NTP (network time protocol) and network time servers, computer systems around the world remain in perfect synchronisation.

And they will continue to do so for several million years as atomic clocks are so accurate they can maintain time to within a second for well over 100 million years. However, atomic clocks can be made even more accurate and a French team of scientists are planning to do just that by launching an atomic clock into space.

Atomic clocks are limited to their accuracy on Earth because of the effects of he gravitational pull of the planet on time itself; as Einstein suggested time itself is warped by gravity and this warping slows down time on Earth.

However, a new type of atomic clock named PHARAO (Projet d’Horloge Atomique par Refroidissement d’Atomes en Orbit) is to be placed aboard the ISS (international space station) out of reach from the worst effects of Earth’ gravitational pull.

This new type of atomic clock will allow hyper accurate synchronization with other atomic clocks, here on Earth (which in effect will make synchronization to an NTP server even more precise).

Pharao is expected to reach accuracies of around one second each 300 million years and will allow further advances in time reliant technologies.

Network Time Protocol Time Synchronisation Made Easy

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One of the most important aspects of networking is keeping all devices synchronised to the correct time. Incorrect network time and lack of synchronisation can play havoc with system processes and can lead to untold errors and problems debugging.

And failing to ensure devices are continually checked to prevent drift can also lead to a synchronised network slowly becoming unsynchronised and leading to the kinds of problems aforementioned.

However, ensuring a network not only has the correct time but that that time is not drifting is achieved using the time protocol NTP.

Network Time Protocol (NTP) is not the only time synchronisation protocol but it is by far the most widely used. It is an open source protocol but is continually updated by a large community of Internet time keepers.

NTP is based around an algorithm that can work out the correct and most accurate time from a range of sources. NTP allows a single time source to be used by a network of hundreds and thousands of machines and it can keep each one accurate to that time source to within a few milliseconds.

The easiest way of synchronising a network with NTP is to use a NTP time server, also known as a network time server.

NTP servers use an external source of time, either from the GPS network (Global Positioning System), or from broadcasts from national physics laboratories such as NIST in the US or NPL in the UK.

These time signals are generated by atomic clocks which are many times more accurate than the clocks on computers and servers. NTP will distribute this atomic clock time to all devices on a network it will then keep checking each device to ensure there is no drift and correcting the device if there is.

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.

Choosing a Time Source for UTC Synchronization

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Ensuring a computer network is time synchronized is vital in modern computer networks. Synchronization, not just between different machines on a network, but also each computer network that communicates with other networks needs to be synchronized with them too.

UTC (Coordinated Universal Time) is a global timescale that allows networks on other sides of the globe to be synchronized together. Synchronizing a network to UTC is relatively straightforward thanks to NTP (Network Time Protocol) the software protocol designed for this very purpose.

Most operating systems, including the latest Microsoft incarnation Windows 7, have a version of NTP (often in a simplified form known as SNTP), that allows a single time source to be used to synchronize every computer and device on a network.

Selecting a source for this time reference is the only real difficulty in synchronizing a network. There are three main locations where UTC time can accurately be received from:

Internet Time

There are many sources of internet time and the latest version of Windows (Windows 7) automatically synchronizes to Microsoft’s time server time.windows.com, so if Internet time is adequate Windows 7 users need not alter their settings. However, for computer networks where security is an issue then internet time sources can leave a system vulnerable as the time has to be received through the firewall forcing a UDP port to be left open. This can be utilised by malicious users. Furthermore, there is no authentication with an internet time source so the timecode could be hijacked before it arrives at your network.

GPS Time

Available literally everywhere on the globe, GPS provides a 24-hour, 365 days-a-year source of UTC time. Delivered externally to the firewall via the GPS satellite signal, time synchronization with GPS is accurate and secure.

Radio Transmissions

Usually broadcast by national physics laboratories such as NIST in the US and the UK’s NPL, the time signals are received via longwave and are also external to the firewall so are secure and accurate.

A dedicated NTP time server can receive both radio and GPS time signal guaranteeing accuracy and security.

How Computers Keep Abreast of Time

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Time governs our lives and keeping abreast of it is vital if we want to get to work on time, make it home for dinner or watch our favourite shows of an evening.

It is also crucial for computer systems. Computers use time as a point of reference, indeed, time is the only point of reference it can use to distinguish between two events and it is crucial that computers operating in networks are synchronized together.

Time synchronization is when all computers that are connected together run the same time. Time synchronization, however, is not simple to implement, primarily because computers are not good time keepers.

We are all used to the time being displayed on the bottom right hand of our computer desktops but this time is normally generated by the onboard crystal oscillator (normally quartz) on the motherboard.

Unfortunately these onboard clocks are prone to drift and a computer clock may lose or gain a second or so each day. While this may not sound like much, it can soon accumulate and with some networks consisting of hundreds and even thousands of machines, if they are all running different times its not hard to imagine the consequences; emails may arrive before they are sent, data may fails to backup, files will get lost and the networks will be amass of confusion and nearly impossible to debug.

To ensure synchronization throughout a network all devices must connect to a single time source. NTP (Network Time Protocol) has been devised for this very purpose and can distribute a time source to all devices and ensure that any drift is countered.

For true accuracy the single time source should be a source of UTC (Coordinated Universal Time) which is a global timescale that is used across continents and pays no heed to timezones, this allows networks on opposite sides of the Earth to be synchronized together.

A source of UTC should also be governed by an atomic clock as any drift in the time will mean that your network will be out of sync with UTC. By far the easiest, most efficient, secure, accurate and reliable method of receiving an atomic clock source of UTC is to use a dedicated NTP time server. NTP servers receive the UTC time from either the GPS network (Global Positioning System) or from radio transmission broadcast by national physics laboratories such as NIST or NPL.

Closed Circuit Cameras are Useless Without a Network Time Server

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For those of us that live in Britain, the CCTV camera (closed circuit TV) will be a familiar site on the high streets. Over four million cameras are in operation throughout the British Isles with every major city being monitored by state funded cameras which has cost the British taxpayer over £200 million ($400 million).

The reasons for use of such widespread surveillance have always been declared as to prevent and detect crime. However, critics argue that there is little evidence that CCTV cameras have done anything to dent the rising street crime on the UK’s streets and that the money could be better well spent.

One of the problems of CCTV is that many cities have both cameras controlled by local councils and privately controlled cameras. When it comes to crime detection the police often have to obtain as much evidence as possible which often means combining the different local authority controlled CCTV cameras with the privately controlled systems.

Many local authorities synchronise their CCTV cameras together, however, if the police have to obtain images from a neighbouring borough or from a private camera these may not be synchronised at all, of if so, synchronised to a different time completely.

This is where CCTV falls down in the fight against crime. Just imagine a suspected criminal is spotted on one CCTV camera committing a criminal act. The time on the camera could say 11.05pm but what if the police follow the suspects movements across a city and use footage from a privately owned camera or from other boroughs and while the CCTV camera that caught the suspect in the act may say 11.05, the other camera could spot the suspect minutes later only for the time to be even earlier. You could imagine a good defence lawyer taking full advantage of this.

To ensure their worth in the fight against crime, it is imperative that CCTV cameras are time synchronized using a network time server. These times servers ensure every device (in this case camera) is running the exact same time. But how do we ensure all cameras are synchronised to the same time source. Well fortunately, a global time source known as UTC (coordinated Universal Time) has been developed for this exact purpose. UTC is what governs computer networks, air traffic control and other time sensitive technologies.

A CCTV camera using a NTP server that receives a UTC time source from an atomic clock will not only be accurate but the time told on the devices will be provable in court and accurate to a thousandth of a second (millisecond).

Keeping Your Network Secure A Beginners Guide

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Network security is vitally important for most business systems. Whilst email viruses and denial-of-service attacks (DoS attack) may cause us headaches on our home systems, for businesses, these sorts of attacks can cripple a network for days – costing businesses hundreds of millions each year in lost revenue.

Keeping a network secure to prevent this type of malicious attack is usually of paramount importance for network administrators, and while most invest heavily in some forms of security measures there is often vulnerabilities inadvertently left exposed.

Firewalls are the best place to begin when you are trying to develop a secure network. A firewall can be implemented in either hardware or software, or most commonly a combination of both. Firewalls are used to prevent unauthorized users from accessing private networks connected to the Internet, especially local intranets. All traffic entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified criteria.

Anti-virus software works in two ways. Firstly it acts similarly to a firewall by blocking anything that is identified in its database as possibly malicious (viruses, Trojans, spyware etc). Secondly Anti-virus software is used to detect, and remove existing malware on a network or workstation.

One of the most over-looked aspects of network security is time synchronization. Network administrators either fail to realise the importance of synchronization between all devices on a network. Failing to synchronize a network is often a common security issue. Not only can malicious users take advantage of computers running at different times but if a network is struck by an attack, identifying and rectifying the problem can be near impossible if every device is running on a different time.

Even when a network administrator is aware of the importance of time synchronization they often make a common security mistake when attempting to synchronize their network. Instead of investing in a dedicated time server that receives a secure source of UTC (Coordinated Universal Time) externally from their network using atomic clock sources like GPS, some network administrators opt to use a shortcut and use a source of Internet time.

There are two major security issues in using the Internet as a time server. Firstly, to allow the time code through the network a UDP port (123) has to be left open in the firewall. This can be taken advantage of by malicious users who can use this open port as an entrance to the network. Secondly, the inbuilt security measure used by the time protocol NTP, known as authentication, doesn’t work across the Internet which means that NTP has no guarantee the time signal is coming from where it is supposed to.

To ensure your network is secure isn’t it time you invested in an external dedicated NTP time server?