Archive for the 'ntp time server' Category

The NTP Server and Accurate Time

Accurate time on a network is essential for all businesses and institutions. Without an accurately synchronised system a computer network can be vulnerable to all sorts of problems, from malicious hackers and other security threats to fraud and data loss.

Network Time Protocol
is the key to keeping accurate time it is a software algorithm that has been constantly developed for over two decades. NTP takes a single time source that is received by the NTP server and distributes it across a network ensuring all machines in that network are running to exact same time.

Whilst NTP can maintain synchronisation of a network to within a few milliseconds it is only as good as the time source it receives. A dedicated NTP server will use a time signal from an external source and so keep the network secure as the firewall will not have to be disturbed.

The two preferred methods for most users of NTP servers is the GPS network (Global Positioning System) or specialist time and frequency transmissions put out be several national physics labs such as the UK’s NPL.

These time signals are UTC (Coordinated Universal Time) which is the world’s civil timescale. A NTP server receiving time source from either a frequency transmission or the GPS network can realistically provide accuracy to within a few milliseconds of UTC

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The NTP Server – Selecting a Time Source Check List

In selecting a timing source to synchronise a computer network to using a NTP server (Network Time Protocol) it is important that the time source is accurate, secure and a source of UTC (Coordinated Universal Time). UTC is a global timescale used by computer networks, business and commerce across the globe.

Whilst UTC is freely available across the Internet it is neither accurate nor secure (being as it is external to your firewall).  Also Internet time sources cannot be authenticated which is NTP’s own method of ensuring a time source is what it says it is. There are two secure, accurate and reliable methods for receiving UTC via a NTP server and both come with their own advantages and drawbacks.

The first method is to use the GPS network (Global Positioning System).The main advantage of using the signals transmitted from a GPS satellite’s onboard atomic clock is that a signal is available anywhere on the planet. However it does come with a downside. As the signals are all line-of-sight it means that the GPS antenna needs to be placed on a roof to ensure connectivity with a satellite.

An alternative to the GPS signal but equally as accurate and reliable is to make use of the long wave radio transmissions broadcast by several national physics laboratories. These signals, such as the UK’s MSF, Germany’s DCF-77 and the United States’ WWVB transmissions, can often be picked up inside buildings making them ideal for a solution if a rooftop is unavailable for a GPS antenna. It must be noted that not every country broadcasts such a signal and whilst most transmissions can be picked up in neighbouring countries the signals are vulnerable to interference and local geography.

MSF signal interruption – Notice from the National Physical Laboratory

For users of MSF time server or other NTP related devices:

Notice of Interruption MSF 60 kHz Time and Frequency Signal – NPL
The MSF 60 kHz time and frequency signal broadcast from Anthorn Radio Station will be shut down over the period:

11 December 2008 – from 10:00 UTC to 14:00 UTC

The interruption to the transmission is required to allow scheduled maintenance work to be carried out in safety.

If you require any additional information, please contact NPL

Or alternatively please see the NPL time website.

Free NTP server checker – available for download

Galleon’s free NTP Server Checker allows you to check the following items
* IP address – the time server you are checking.
* NTP Version
* Reference timestamp (the prime epoch ) used by NTP to work out the time from this set point
* Round trip delay (the time it takes request to arrive and come back in milliseconds)
* Local clock offset – time difference between host and client
* Leap indicator (if there is to be a leap second that day – normally only on 31 December)
* Mode 3 – indicates a client request
* Stratum level – which stratum level the NTP server is (a stratum 1 server receives the time from an atomic clock source a stratum 2 server receives the time from a stratum 1 server)
* Poll Interval (Will be 1 as only 1 requests is made by the SNTP client)
* Precision – how accurate in milliseconds
* Root Delay – This is a signed fixed-point number indicating the total roundtrip delay to the primary reference source at the root
* Root dispersion (in milliseconds)- The root dispersion is the maximum (worst case) difference between the local system clock and the root of the NTP tree (stratum 1 clock)
* Ref ID – the host name
* Originate time stamp (time before synchronisation request)
* Receive timestamp – the time the host got request
* Transmit timestamp – the time the host sends back to us
* Is response valid – synchronised or not

Please download from Galleon Systems

NTP Server – Using Stratum

NTP (Network Time Protocol) is the most prevalent time synchronisation software available. On of the reasons NTP is so successful is the way it organises its clients into a hierarchy.

The hierarchy of NTP is divided into stratum with each strata representing the distance from the original reference clock.  For instance an atomic clock that generates a UTC (coordinated universal time) signal is referred to as a stratum 0 device.

A NTP server that receives a stratum  1 time signal is referred to as a stratum 1 device and a device that receives a time source from a NTP server is a stratum 2 device. NTP can support up to 16 strata although the further away from the reference clock you get (stratum 0) the less accurate the device will be.

However, by arranging the network into stratum and allowing stratum 2 devices to pass on the time to a stratum 3 device (and so on) it reduced the demand on the NTP server and the network. By using a stratum based network, realistically thousands of machines can be synchronised to just one NTP server.

NTP Server –Telling the NTP Time

Network Time Protocol (NTP) is an Internet based protocol designed to distribute and synchronise time across a network.

NTP is in fact one of the oldest Internet protocols having been developed in the late 1980’s at Delaware University when the Internet was still in its infancy. It was devised by Professor David Mills and his team when they realised the need for accurate time synchronisation if computers were needed to communicate with each other.

A NTP server is a dedicated device that receives a single timing source and then distributes it amongst all network devices. A NTP server will receive the timing information through a number of ways but normally it is a UTC source (coordinated universal time) a global timescale based on the time as told by atomic clocks.

NTP handles the time in a different way to how humans perceive and deal with it. While we may split a time into seconds, minutes, hours, days, months and years; NTP regards time  as a single number which is the number of seconds since the ‘prime epoch’.

The prime epoch is a date set for when NTP began counting seconds. For NTP the prime Epoch is 00.01 on 1 January 1900 so that means on 1 January 2008 the time according to NTP will be 3405888000, which is the number of seconds since 1900.

The NTP Server – Trust in Time

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.