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Ask any network administrator or IT engineer and ask them how important network time synchronization is and you’ll normally get the same answer – very.

Time is used in almost all aspects of computing for logging when events have happened. In fact timestamps are the only reference a computer can use to keep tracks of tasks it has done and those that it has yet to do.

When networks are unsynchronized the result can be a real headache for anybody tasked with debugging them. Data can be often lost, applications fail to commence, error logging is next to impossible, not to mention the security vulnerabilities that can result if there is no synchronized network time.

NTP (Network Time Protocol) is the leading time synchronisation application having been around since the 1980′s. It has been constantly developed and is used by virtually every computer network that requires accurate time.

Most operating systems have a version of NTP already installed and using it to synchronise a single computer is relatively straight forward by using the options in the clock settings or task bar.

However, by using the inbuilt NTP application or daemon on a computer will result in the device using a source of internet time as a timing reference. This is all well and good for single desk top machines but on a network a more secure solution is required.

It is vital on any computer network that there are no vulnerabilities in the firewall which can lead to attacks from malicious users. Keeping a port open to communicate with an internet timing source is one method an attacker can use to enter a network.

Fortunately there are alternatives to using the internet as a timing source. Atomic clock time signals can be received using long wave radio or GPS transmissions.

Dedicated NTP time server devices are available that make the process of time synchronisation extremely easy as the NTP servers receives the time (externally to the firewall) and can then distribute to all machines on a network – this is done securely and accurately with most networks synchronised to an NTP server working to within a few milliseconds of each other.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other NTP time server solution.

Author: Richard N Williams
Article Source: EzineArticles.com
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A time server is a crucial piece of kit for any network. Time synchronisation is imperative in keeping a network secure and reliable. Time synchronisation, however, need not be the headache many administrators assume it is going to be.

Most of the difficulties of time synchronisation have been taken care of thanks to the protocol NTP (Network Time Protocol). Whilst NTP is not the only time synchronisation software available it is by far the most widely used (due mainly to the fact that it has been around since the 1980′s and is sill being developed today).

NTP uses a single time source and distributes it from machine-to-machine checking each PC or device for drift then adjusting for it. NTP is normally installed on Windows and Linux systems (or at least a simplified version called SNTP) although it is freely downloadable from the NTP homepage. While NTP can quite easily receive any time source from the Internet this can cause major security issues no to mention a lack of accuracy that many online NTP servers suffer from.

The most accurate and secure method is to use an external network time server as these sit within the firewall. They are also receive a UTC (Coordinated Universal Time) reference direct from an atomic clock which makes them stratum 1 devices. Most internet time servers are stratum 2 servers. NTP uses strata to define how far away a server is from the source so an atomic clock is a stratum 0 device while a computer that receives time direct from a NTP server becomes a stratum 2 device and so on.

The only decision that really needs to be made when installing a dedicated NTP time server is which time reference is best. There are two main methods of receiving a secure, accurate and authenticated UTC time reference; the GPS network (Global Positioning System) or national physics laboratories long wave radio transmissions.

The latter system is not available in every country although the USA, UK and Germany have strong signals known as WWVB, MSF and DCF respectively. These can often be picked up outside the borders of these countries although the signals are vulnerable to interference, outages and local topography.

A GPS NTP server system is less vulnerable to these things and as long as there is a clear view of the sky (such as a rooftop or open window) the GPS time signal can be picked up anywhere on the globe.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a Galleon NTP server or other NTP server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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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.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other network time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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Time synchronization is vital in modern computer networks. Having one machine running a slower clock than another can cause a myriad of all sorts of problems. From the benign, such as emails arriving before they were sent, to the more serious such as being unable to debug a system or have it vulnerable to malicious hackers.

Computers have two clocks, a software clock that runs in the background while the computer is running and a system clock that is battery backed and provides a reference for the software clock when the machine is switched on.

Unfortunately neither is very accurate which is why most administrators opt to synchronize their networks to an atomic clock source that relays the global Coordinated Universal Time (UTC). This has an advantage of not just providing the most accurate synchronization but also ensuring that the network is synchronized, not just with itself, but also with networks all around the world.

Like other operating systems, Windows uses a version of NTP (Network Time protocol) to deal with time synchronization. NTP is a protocol that transfers time information over the Internet or Local Area Network (LAN) by ‘packets’, allowing other computers to synchronize the time on their clocks to it.

By using NTP one server or work station can be used to synchronize dozens of other computers and devices. As NTP is also hierarchical, meaning servers that get their time from one machine can also use it to synchronize the time on other computers, in theory thousands of machines can be synchronized with just one NTP server receiving a UTC source. However, although the lower down the hierarchy or strata a machine is, the less accurate it will be.

Configuring a Windows to act as a client server is relatively straightforward. Simply create a new DWORD value, or modify the existing “LocalNTP” and set it to:

System Key: [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeParameters]
Value Name: LocalNTP
Data Type: REG_DWORD (DWORD Value)
Value Data: (0 = disabled, 1 = enabled)
Selecting a UTC source is another consideration when running a NTP server. There are several methods of doing this.

The first is to use one of the myriad of Internet time references available. However, some are more accurate that others and distance from a host can play a factor too. Another consideration to take into account in using an Internet timing reference is that of security. To use an Internet source a hole must be kept open in a firewall and NTP’s inbuilt security system called authentication isn’t possible over the Internet.

A far better solution is to use the national time and frequency signals broadcast by several countries’ large physics laboratories. Alternatively the timing signal broadcast by the onboard atomic clocks of the GPS (Global Positioning System) network can be used. Both these methods are far more secure than receiving a timing signal over the Internet and dedicated NTP servers are available that can receive

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a network time server or other ntp server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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There are hundreds of internet based timing sources that allow computers running NTP to synchronise to a UTC time – however, there are several drawbacks in relying on the Internet for a timing reference:

Security is paramount for most computer networks and NTP, one of the Internet’s oldest protocols, is equipped with its own security measures in the form of authentication. 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 timing information.

Unfortunately, internet time sources can not be authenticated and Microsoft, Novell and others “strongly recommend” that internet sources are not used for a timing reference as it could leave a network vulnerable and open to malicious hackers, viruses or even a DDoS attack (Distributed Denial of Service – where a server is inundated with traffic rendering it useless).

Also a survey by MIT (Massachusetts Institute of Technology) of over 900 internet time references, discovered nearly half were offset by over ten seconds (one by a staggering six years – but there were fortunately not many peers) and less that a third where described as being at all “useful”.

The report also discovered that many internet time reference hosts were too far away from their peers to allow any accurate time synchronisation to take place.
Fortunately a dedicated NTP network time server can receive other sources of UTC time which do offer complete security, authentication and are far more accurate and reliable.

The first is the national time and frequency broadcasts transmitted by several countries. In the US the signal is referred to as WWVB and is broadcast by NIST (National Institute for Standards and Technology) in Colorado. In the UK the National Physical Laboratory (NPL) broadcasts the MSF signal from Cumbria and similar systems are broadcast in Germany (DCF-77), Japan (JJY) and France (TDF).

Another, equally accurate and secure method is to use the timing signals broadcast by the American GPS (Global Positioning System).

The GPS is currently the world’s only Global Navigation Satellite System, although Europe’s Galileo and the Russian GLONASS system are expected to be up and running over the next five years.

It is a consequence of needing accurate timing information to be able to pin-point positioning that GPS satellites all contain an atomic clocks and the signal that is broadcast can be received and used by a network time server.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a network time server or other ntp server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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Windows 7 is the very latest operating system from Microsoft. Replacing the rather disappointing Windows Vista, Windows 7 promises to correct the flaws that made its predecessor so unpopular.

One of the changes Windows 7 makes is that it automatically synchronizes the time using the Windows Time service located at windows.time.com. Whilst this is an accurate stratum 2 time server , managed by Microsoft, it can be changed for another source of Internet time. However, even Microsoft recommend that Internet time sources should not used for computer networks as they can’t be authenticated by the time protocol NTP (Network Time protocol). Furthermore, an internet time source needs a port left open in the firewall for the time signals to make it through. Any open port in a firewall can be used by a malicious user to gain access to the network.

For a secure, authenticated and accurate method of synchronizing a Windows 7 network, then it is wise to use a dedicated network time server. Most of these time servers use the protocol NTP (Network Time Protocol) which can easily distribute a single time server throughout a network of hundreds and even thousands of machines.

Time servers plug directly into the router/switch for the network or can be installed on a single machine. Rather than rely on the Internet for a source of time and risk leaving the firewalls UDP port open, dedicated NTP servers use either the GPS signals or long wave radio broadcasts transmitted from national physics laboratories such as the MSF signal broadcast by the UK’s NPL and the USA WWVB signal broadcast by NIST.

As these signals are external to the firewall and are able to be authenticated by NTP to establish the authority of the signals and are a more accurate and secure method of synchronizing a Windows 7 network.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other NTP time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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NTP time servers are quite simply devices in the sense that they are used for the purposes of time synchronisation, receiving an external source of the time which is then distributed throughout a computer network using NTP (Network Time Protocol).

However, with a myriad of ‘free’ time servers available on the internet many network administrators take the decision that NTP time servers are not necessary pieces of equipment and that their network can do without it. However, there are a huge number of pitfalls in relying on the internet as a time reference; Microsoft and the USA physics laboratory NIST (National Institute of Standards and Time) highly recommend external NTP time servers rather than internet providers.

Here is what Microsoft says:

“We highly recommend that you configure the authoritative Time Server to gather the time from a hardware source. When you configure the authoritative Time Server to sync with an Internet time source, there is no authentication.”

Authentication is a security measure implemented by NTP to ensure that the time signal that is sent comes from where it claims to come from. In other words authentication is the first line of defence in protecting against malicious users. There are other security issues too with using the internet as a time source as any communication with an internet time source is going to require the TCP/IP port to be left open in the firewall this could also be manipulated by malicious users.

NIST too recognise the importance of NTP time server systems for prevention and detection of security threats in their Guide to Computer Security Log Management they suggest:

“Organizations should use time synchronization technologies such as Network Time Protocol (NTP) servers whenever possible to keep log sources’ clocks consistent with each other.”

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other NTP time server systems.

Author: Richard N Williams
Article Source: EzineArticles.com
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If you are reading this then you are probably aware of the importance time plays in IT systems and computer networks. Most computer administrators appreciate that precise accurate synchronisation are an important aspect of keeping a computer network error free and secure.

And yet, despite its importance many network administrators still rely on the Internet as a source of UTC for their networks (UTC – Coordinated Universal Time), primarily because they see it as a quick and more importantly a free method of time synchronisation.

However, the drawbacks in using these free services may cost a lot more than the money saved on a dedicated NTP server.

NTP (Network Time Protocol) is now present on nearly all computers and it is NTP that is used to synchronise computer systems. However, if an Internet time source is used then the source is outside the network firewall and this creates a serious vulnerability. Any external source will require a port to be left open in the firewall to allow the information packets through and this opening is too easy a way to exploit a network which can become victim to a DDOS attack (Distributed Denial of Service) or even allow malicious programmes through to take control of the machines themselves.

Another problem is the availability of stratum 1 time sources across the internet. Most online time sources come from stratum 2 ntp servers. These are devices that receive UTC time another NTP server (stratum 1) that originally gets the information from an atomic clock (stratum 0). While stratum 2 devices can be just as accurate as stratum 1 servers, across the internet without NTP authentication the actual accuracy can not be guaranteed.

Furthermore, internet sources of UTC have never been considered accurate or precise with surveys showing over half being inaccurate by over a second and the rest dependent on the distance from client as to whether they can provide any useful accuracy. Even organisations such as NIST publish advisory notices on their time server pages about it unable to guarantee security or accuracy and yet millions of networks are still receiving UTC from across the internet.

With the decline in cost of dedicated radio referenced NTP servers or GPS NTP servers there has never been a better time to get one. And when you consider the cost of a computer breach or crashed network the NTP time server will have paid for itself many times over.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or for other NTP time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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Computer network synchronisation is often perceived as a headache for many system administrators but keeping accurate time is essential for any network to remain secure and reliable. Failing to have an accurate synchronised network can lead to all sorts of errors when dealing with time sensitive transactions.

The protocol NTP (Network Time Protocol) is the industry standard for time synchronisation. NTP distributes a single time source to an entire network ensuring all machines are running the exact same time.

One of the most problematic areas in synchronising a network is in the selection of the time source. Obviously if you are spending time getting a network synchronised then the time source would have to be a UTC (Coordinated Universal Time) as this is the global timescale used by computer networks all over the world.

UTC is available across the internet of course but internet time sources are not only notoriously inaccurate but using the internet as a time source will leave computer system open to security threats as the source is external to the firewall.

A far better and secure method is to use a dedicated NTP time server. The NTP server sits inside the firewall and can receive a secure time signal from highly accurate sources. The most commonly used these days is the GPS network (Global Positioning System) this is because the GPS system is available literally anywhere on the planet. Unfortunately it does require a clear view of the sky to ensure the GPS NTP server can ‘see’ the satellite.

There is another alternative however, and that is to use the national time and frequency transmissions broadcast by several national physics laboratories. These have the advantage in that being long wave signals they can be received indoors. Although it must be noted these signals are not broadcast in every country and the range is finite and susceptible to interference and geographical features.

Some of the main transmissions broadcast are known as: the UK’s MSF signal, Germany’s DCF-77 and the USA’s WWVB.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a Galleon NTP server or other NTP server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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Network Time Protocol (NTP) is an Internet protocol used for the transfer of accurate time, providing time information so that a precise time can be obtained and maintained on a network

Most UNIX and Linux operating systems provide built-in time synchronisation functionality with its NTP (Network Time Protocol) daemon. If the NTP service is not available on your version of UNIXLinux, NTP version 4 is open source and can easily be downloaded and configured, compiled and installed from http://www.ntp.org.

Network Time Protocol is the standard service for time dissemination across TCP/IP networks. It provides accuracies of 1-50 milliseconds, depending on the characteristics of the synchronization source and network paths.

The configuration file fro the NTP daemon is named ntp.conf and contains a list of reference clocks that it can synchronise too. The command ‘server’ specifies the reference clock, any characters after the ‘#’ symbol are comments, example:
server time-a.nist.gov # Public NTP server: NIST
driftfile /var/lib/ntp/ntp.drift

The drift file command identifies the location where the drift is recorded (sometimes referred to as a ‘frequency error). This value can be offset by NTP to ensure of increased accuracy. When configured, NTP can be controlled using the commands ‘ntpd start’ ‘ntpd stop’ ‘ ntpq -p’ (displays status)

NTP can also authenticate timing resources Note: It is strongly recommends that you configure a time server with a hardware source rather than from the internet where there is no authentication. Authentication codes are specified in the ‘ntp.keys’ file.

Specialist NTP servers are available that can receive transmissions from either GPS or national time reference broadcasts. They are relatively cheap and the signal is authenticated providing a secure time reference.

Authentication allows passwords to be specified by the NTP server and its clients. NTP passwords or keys are stored in the ntp.keys file in the following format: number M (The M stands for MD5 encryption), password:

1 M mypassword

3 M my2ndpassword

5 M my3rdpassword

Authentication for NTP has been developed to prevent malicious tampering with system synchronisation just as firewalls have been developed to protect networks from attack but as with any system of security it only works if it is utilised.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other network time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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All computers have clocks of course although the real time chips (RTC) that inhabit most PC’s are not the most accurate of timepieces and are prone to drift.

This may not matter much to the average home user although when it comes to time sensitive applications this inaccuracy can be at best annoying (an email arriving before its been sent) or at worst leaving your machine open to security threats.

A universal time (UTC) does exist and allows the global industry to communicate and trade even across time zones. UTC was developed to ensure that everybody used the same time reference, preventing problems with time sensitive transactions such as on the stock exchange.

Windows Vista has an inbuilt time synchronization facility already installed called Windows Time and it is pretty easy to setup and to synchronize a machine with UTC over the Internet. This will ensure that the clock on your computer is accurate to UTC time and is constantly updated to ensure the time does not drift.

To synchronize your Windows Vista machine to an Internet UTC source simply follow these instructions:

1. Right click the clock in the system tray.

2. Click adjust time and date.

3. Click the Internet time tab.

4. Click change settings.

5. If you are prompted for a password or for confirmation, type the password, or click Continue.

6. Select the server you want to use (such as windows.time)

7. Click the Update now button.

8. Click Ok twice.

If problems occur then another method of synchronizing your computer is possible via the command prompt by running w32tm / resync. This should activate the windows time service.

Note: Microsoft and other operating system manufacturers recommend that an external hardware source should be used to synchronize a computers clock as Internet time servers can not be authenticated leaving systems vulnerable to security threats.

There are specialist time servers that connect to a UTC source using either the GPS network or a specialist radio transmission. These servers use NTP (Network Time Protocol) to synchronize machines on a network to one UTC source and are easily installed and relatively inexpensive.

Window Vista also has a facility to add extra clocks to the system tray. This allows different times from different time zones to be displayed on the computer. If the clock has been synchronized with a UTC source then all these clock will present UTC time converted to whatever time zone is required.

To add additional clocks simply follow these instructions:

Choose change date and time settings.

1. Left click the clock and click Additional Clocks tab.

4. Put a check mark in Show this Clock.

5. Select the time zone.

6. Enter a name for your new clock.

7. Click apply, then when you click on the Clock icon you’ll see your new clocks.

Copyright 2008 Richard N Williams

Richard N Williams is a technical author and a specialist in the telecommunications and network time synchronisation industry helping to develop dedicated time server products; ethernet clocks, GPS time servers, NTP servers, digital wall clocks, atomic clock servers and SNTP time servers. Please visit us for more information about NTP products and NTP servers This article may be republished and reprinted in its complete form or in part without seeking permission providing a relevant link to this site is maintained. It is a violation of copyright law to reprint or publish this content without following these terms.

Author: Richard N Williams
Article Source: EzineArticles.com
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Time synchronization is a crucial aspect of computer networking. Ensuring all machines on a network are synchronised to the global timescale, UTC (Coordinated Universal Time), otherwise time sensitive transactions with other networks would be impossible.

Time synchronization is made easy thanks to the Network Time Protocol (NTP) which was devised in the early days of the Internet for that very purpose. It works be utilising a single time source (usually UTC) which is then distributed amongst all devices on the NTP network.

The UTC time source is often taken from the Internet on networks where security is not a great issue but as this involves leaving an open port in a network firewall for many networks the vulnerability this can leave isn’t worth the risk.

Dedicated network time servers (often referred to as NTP servers) are used by many networks as a secure and even more accurate method of receiving UTC. These devices receive the UTC time direct from an atomic clock source.

Furthermore, these dedicated time servers operate external to the firewall and network and use sources such as GPS or radio frequencies to pick up the time codes.

For ease of synchronisation there are various time synchronisation software packages that run hand-in-hand with NTP and allow, through browser interfaces, easy configuration of the time synchronization throughout the network.

Whilst these time synchronisation software packages aren’t essential in using most NTP servers, the standard software installed in operating systems is often lacking or quite complicated.

Most specialist producers of dedicated network time servers will produce a times service client to allow configuration and these are probably best suited for the device from that suppler. However, there are many freeware and open source time synchronisation software packages that are mostly compatible with many NTP servers.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a Galleon ntp time server or other ntp server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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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 synchronization 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 synchronize 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).

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronization helping to develop dedicated NTP clocks. Please visit us for more information about an Linux time server or other network time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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A NTP Server connects to a computer network with the purpose of synchronising all computers, routers and other devices to the exact same time. NTP servers use Network Time Protocol to adjust the drift of different machines to match the reference time.

NTP servers rely on using a reference clock; most networks that use a NTP server will use a UTC (Coordinated Universal Time) time source. UTC is based on the time told by the incredibly accurate and expensive atomic clocks.

Atomic clocks work on the principle that a single atom (in most cases the caesium -133) will resonate at an exact rate at certain energy levels. The accuracy of atomic clocks is so proficient that UTC was developed to allow international Atomic Time (TAI) and Greenwich Meantime (GMT) to be combined, allowing for the slowing of the Earth’s rotation by adding leap seconds and therefore keeping the Sun at the Earth’s meridian at noon.

Failure to account for this slowing in the Earth’s spin would result in the eventual drift of day and night (albeit in many millennia).

A NTP server can be set to receive a UTC time signal from across the Internet although these can vary tremendously in accuracy and are reliant on reasonably close distances from client and server.

Relying on an Internet based timing references can also leave a network open to malicious users as they can not utilise NTP authentication which is a security measure used to ensure a timing reference is what it says it is.

Many dedicated NTP servers are designed to receive a more accurate and authenticated timing reference. One method utilises radio transmissions that are broadcast by several national physics laboratories such as NIST (National Institute for Standards and Technology) in the US (WWVB signal) and NPL (National Physical Laboratory) in the UK (MSF signal). These signals are broadcast in long wave and can be picked up within the broadcast area although the signals can be blocked by local geographical features.

Another method to receive a UTC timing reference is to use the onboard atomic clocks on GPS (Global Positioning System) network. While GPS is most commonly known as a positioning system the satellite actually relays timing information which is used by GPS receivers to calculate the time it has travelled and therefore the distance.

While the GPS signals are not broadcast in UTC format they are highly accurate and NTP has no problem in converting them.

The NTP server checks the time stamp from the UTC source and uses the information to calculate if the network clocks are drifting and adds or subtracts a second to match the reference clock. The NTP server will do this at set intervals, normally every fifteen minutes to ensure perfect accuracy.

NTP is accurate to within 1/100th of a second (10 milliseconds) over the public Internet and can perform even better over LANs and WANS with accuracies of 1/5000th of a second (200 microseconds) not unheard of.

To ensure further accuracy the NTP service (or daemon on Linux) runs in the background and does not believe the time it is told until after several exchanges and each one has passed a protocol specification (a test), the server is then considered. It usually takes about five good samples) until a NTP server is accepted as a timing source.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a network time server or other ntp server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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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 utilized 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.

Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about an NTP server or other NTP time server solutions.

Author: Richard N Williams
Article Source: EzineArticles.com
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