Archive for the 'ntp 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.

Useful NTP server related resources

NTP.org – The home for the NTP Project who provides support and additional development resources for the Official Reference Implementation of NTP.

NTP Project support pages

THE NTP pool – list of public servers

NPL – The National Physical Laboratory in the UK who control the MSF radio signal.

The University of Delaware and David Mills’ information page, Professor Mills is the original inventor and developer of NTP

David Mills’ list of Public NTP Time Servers a list of public NTP servers

National Institute of Standards and Technology (NIST) who operate the USA’s WWVB radio signal

Europe’s largest supplier of NTP server related products.

Galleon UK – NTP server products for the UK

ntp-time-server.com – one of the largest time and frequency suppliers in the United States

NTP – Wikipedia article on NTP

NTP server checker – free tool to ensure time server accuracy

NTP server – Instruments of Precision

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

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

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

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

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

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

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 – common acronyms explained:

NTP – Network Time Protocol

SNTP – Simple Network Time Protocol

GPS – Global Positioning System

UTC – Coordinated Universal Time

MSF – Radio Time Signal for United Kingdom

WWVB – Radio Time Signal for American

DCF – Radio Time Signal for Germany

LAN – Local Area Network

UDP – User Datagram Protocol

TCP – Transmission Control Protocol

IP – Internet Protocol

TDF – Radio Time Signal for France

CHU – Radio Time Signal for Canada

JJY – Radio Time Signal for Japan

HBG – Radio Time Signal for Switzerland

USB – Universal Serial Bus

RTC – Real Time Clock

AM – Amplitude Modulation

APM – Automatic Power Management

DES – Data Encryption Standard

ESD – Electrostatic Discharge

FM – Frequency Modulation

IETF – Internet Engineering Task Force

IRIG – Inter-Range Instrumentation Group

MD5 – Message Digest

PPM – Part Per Million

PPS – Pulse Per Second

RFC – Request For Comments

SA – Selective Availability

TAI – International Atomic Time

SI – International System of Units