Time server – Synchronisation Methods

A time server is an essential piece of equipment responsible for ensuring all devices on a computer network are running the same time. Most time servers are dedicated devices that receive a time signal, normally UTC (Coordinated Universal Time), and distribute it to all devices on a network.

Most time servers use the Internet protocol NTP (Network Time Protocol) to synchronise all devices and are often referred to as NTP servers. NTP distributes a single time source throughout the network which is normally a UTC source (Coordinated Universal Time).

There are several places a time server can receive a time signal from. The internet is an obvious source for many although online time sources are not very accurate, can be too far away to give any useful precision, and more importantly are not secure being as they are external to the firewall.

As a dedicated time server is an external device they are extremely secure and impossible for malicious users to tamper with. Dedicated time server can receive a time signal from two sources the GPS network (Global Positioning System) , a highly accurate method and available everywhere on the globe with a good view of the sky; or the specialist long wave radio transmissions broadcast by national physics laboratories.

In Europe the two main radio transmissions are the UK’s MSF signal broadcast by NPL (National Physical Laboratory) in Cumbria, England and the German DCF-77 broadcast near Frankfurt.

These long wave signals are also highly accurate and can be picked up in most neighbouring countries too. The USA has a similar system called WWVB,  transmitted by the National Institute for Standards and Technology (NIST) from Boulder, Colorado.

Time Server – FAQS

What is a time server?

A time server is a hardware device that distributes a single time source amongst a network to ensure all computers and devices are synchronised

What is NTP?

Network Time Protocol is a set of software instructions designed to distribute time across computers. NTP uses a complex algorithm to work out d inaccuracies and compensates for them by advancing or retarding the system clock.

What is UTC?

Coordinated Universal Time (UTC) is the offical global timescale. It is used by computer networks throughout the world. It is based on the time told by atomic clocks but compensates for the slowing of the Earth’s rotation by adding Leap Seconds, this also keeps it inline with GMT (Greenwich Meantime) sometimes referred to as UT1.

How does a time server receive UTC?

UTC can be received by either tuning in to a national time and frequency broadcast on long-wave administered by national physics laboratories, although not every country has one. Alternatively as GPS satellites (Global Positioning System) all carry an onboard atomic clock which transmits timing information this can be used also as a timing source for network time servers.

Can’t I use the Internet as a timing source?

You can, and there are many sources of UTC time on the Internet but very few offer any useful accuracy and for those that do the distance away can cause a drop-off in precision. More importantly, Internet time sources are exterior to your firewall and therefore a port needs to be left open to ensure communication, this can be taken advantage of by malicious users. Also Internet timing sources can’t be authenticated; authentication is a security measure that ensures that a timing reference is what it says it is.

Which method is best for me a radio referenced time server or one that utilises the GPS network?

This depends on location. While GPS signals are available everywhere on the planet the antennas do have to have a clear view of the sky to receive the signal, alternatively radio transmissions are limited in their availability although where available the signals can be received indoors.

How accurate are time servers?

A radio referenced network time server can provide UTC time to an accuracy of 100 microseconds, while the GPS network can fare even better with accuracies of a few milliseconds reasonably possible.

Galleon’s Time Servers

One of the World’s leading suppliers of time servers are Galleon Systems based in the UK and Europe.

Their time servers provide:

* Automatic update of time with no user intervention required.

* Simple Installation

* Customised products: As the specialist supplier, with the widest product range of dedicated Time Servers in the World if we haven’t got the time synchronisation product you want contact us because we can modify the standard products to your specific requirements.

* Full product range, From Dedicated Rack Mount NTP Time Servers that synchronize the time of thousands of computers across a network to simple Atomic Clocks that connect to a single PC.

* Cost Effective by being a specialist in Time synchronisation, Galleon offers a full product range so you buy the correct product for you needs, not one designed for a Multinational corporation.

* Reliable, Galleon Atomic Clocks and NTP Time Servers are used by organizations world-wide and provide reliable time synchronization 24 hours a day 365 days a year.

* 3 Year warranty. Galleon offers a 3 year warranty on ServerARC, ServerGPS, WorkstationARC and WorkstationGPS NTP Time Server products

* Lifetime Technical support. At Galleon we believe that technical support should be free for as long as you want to use a Galleon product for.

* MSF and GPS: Uses the NPL MSF time signal or GPS satellites time. The MSF time signal provides the strongest radio time signal in the UK and can be received up to about a range of 937.5 miles. GPS satellites time can be received anywhere in the world. You can have both time sources linked to your Galleon NTP Time Server for redundancy in the event that one time source is not available.

Please given Galleon a call, before you LOSE TRACK OF TIME:

+44 (0)121 608 4433

Time Server – security and legal protection

Dedicated time servers are used throughout the world to ensure computer networks are synchronised. Not only does a synchronised network offer more security but synchronisation using a dedicated time server can offer legal protection.

Because dedicated time servers use such a secure and reliable method of keeping time (atomic clock signals from either the GPS network or radio broadcasts) the time can be legally audited to few milliseconds. However, networks synchronised using an Internet timing source can not be audited and this can leave these systems open to abuse or even fraud.

Dedicated time servers are also based behind a firewall ensuring the system is protected from any intrusion while an internet based timing source has to have access through the firewall through an open port.

Any company that requires security in its network or protection from fraud must ensure they are using either a  GPS or radio referenced time server.

Time Server – The need for a reliable time source

A time server is a necessary part of any computer network. Time servers receive an authoritative time source that they then distribute amongst all devices on a network. Most time servers use a protocol such as NTP (Network Time Protocol) to distribute the single time source to all devices.

The accuracy of a time server depends entirely on the accuracy of the time source that it uses. Most networks require a UTC time source (coordinated universal time). UTC is a global timescale based on International atomic clock time (TAI) and used throughout the globe. Utilising UTC means that a computer network can be synchronised to the exact same time as a network on the other side of the globe allowing precise communications and time sensitive transactions to take place.

A time server can receive a UTC time source from only three places: the Internet, via a radio transmission or the GPS network.

The internet is by far the most commonly used source of UTC time. There are over a thousand time servers all claiming to relay UTC time. However, in surveys, less than half of these internet time sources are accurate and those that are, can be too far away to provide and real use as a timing source.

Using an internet timing source will also leave a computer network vulnerable. The hole left in the firewall to access the timing source can be used by malicious users and the built-in security method of NTP, authentication, can not ne utilised from across the Internet.

Fortunately, the two other methods of receiving UTC time offer both secure and reliable methods of receiving UTC time. The GPS network is available anywhere where there is a clear view of the sky whilst although not every country has a national time and frequency transmission, these longwave signals can be picked up by a radio referenced network time server from within a building.

Radio referenced time servers explained.

Atomic clocks use an atomic resonance frequency standard as their timekeeping element and are by far the most accurate chronometers possible with the latest Strontium based atomic clocks boasting a precision of a less than a second lost in several hundred million years.

The clocks maintain a continuous and stable time scale called International Atomic Time (TAI). However, for civil time, another time scale, Coordinated Universal Time (UTC)which  is derived from TAI, but synchronized using leap seconds to UTC, to keep it based on the rotation of the Earth.

UTC is a global timescale that is commonly used to synchronise the clocks on computer networks allowing machines from across the globe to communicate together and conduct time sensitive applications.

Unfortunately atomic clocks are highly expensive pieces of equipment and are generally only to be found in high technology physics laboratories or onboard satellites. However, several national physics laboratories broadcast the time told by their atomic clocks via a long wave radio transmission.

These signals are commonly picked up and utilized by radio controlled wall and desk clocks and by NTP time servers (Network Time Protocol).

The transmissions from the national standards agencies maintain an accuracy of 10-9 seconds per day (approximately 1 part in 1014). MSF is the signal broadcast by National Physical Laboratory in, Anthorn, Cumbria. Other countries boast their own signals the most common being the DCF77 transmission broadcast from Mainflingen near Frankfurt, Germany and the USA’s WWVB signal broadcast from Fort Collins, Colorado.

All these times signals work in a similar way. At the start of each second the strength of the signal is either reduced by between 6 and 10 dB

The Time Server – References and Strata

A time server is a computer server that reads the time from an accurate clock and distributes this information to its clients across a computer network.

The reference used by a time server is normally a UTC (coordinated universal time) time source. UTC is a global time scale adopted all over the world and based on the time told by atomic clocks The most common source for UTC time is now the GPS system (global positioning system).

The most widely-used protocol for distributing and synchronising time is Network Time Protocol (NTP) which has been around almost as long as the Internet itself, having been developed in 1985 by Professor David Mills.

NTP receives the time from the time server and then checks or clocks on its networks to see if they need advancing or retreat.

To prevent overload of networks requesting timing information, NTP is hierarchical.  The term “stratum” is used to label the nearness to a stratum 0 server – that atomic clock. The higher the stratum number the further away the server is. A GPS time server is normally a stratum 1 device as it receives time from a stratum 0 device. However, stratum 2 and stratum 3 devices can still synchronise with each other.

Types of Dedicated Time Server

Dedicated time servers are used despite the numerous Internet time sources available. The advantages of a dedicated time server is that the device is behind a firewall so preventing any security issues, dedicated time servers can also guarantee accuracy that is just not possible over the Internet.

The dedicated time server checks the time stamp from the UTC source (Coordinated Universal Time) and uses the information to calculate if the network clocks are drifting and adds or subtracts a second to match. The time server will do this at set intervals. Most time servers utilise NTP (network time protocol) although other protocols do exist NTP is by far the most widespread.

For NTP to distribute the time it first needs a timing source and this is where the differences in dedicated time servers come in. As UTC is based on the time told by atomic clocks, it is an atomic clocks that is the source for a time servers timing reference. Atomic clocks are extremely expensive, large, and require a multitude of maintenance engineers. For this reason they are only to be found in large scale physics laboratories.

However, the time from an atomic clock can still be utilised by using either a radio clock attached to a time server or a GPS clock. A radio clock is just a simple radio receiver that picks-up the long-wave signal broadcast by several national physics laboratories. This UTC signal is not available everywhere and the broadcast can be blocked by buildings, mountains and bad weather etc.

The other type of dedicated time server utilise the signals sent by the GPS satellites (global positioning system). These signals are available literally everywhere on the globe although the only downside is that a GPS antenna needs to have a clear view of the sky and therefore ideally needs to be situated on a roof which can cause some problems if the server room is along way from the top of the building.

Some dedicated time servers can actually receive both signals; the radio and GPS. In doing so they can continue receiving time signals even if one signal fails or gets temporarily blocked.