Category: gps time server

Choosing a Time Server for your Network

  |   By

Any network administrator will tell you how important time synchronization is for a modern computer network. Computers rely on the time for nearly everything, especially in today’s age of online trading and global communication where accuracy is essential.

Failing to ensure that computers are accurately synced together could lead to all manner of problems: data loss, security vulnerabilities, unable to conduct time sensitive transactions and difficulties debugging can all be caused by a lack of, or not adequate enough, time synchronization.

But ensuring every computer on a network has the exact same time is simple thanks to two technologies: the atomic clock and the NTP server (Network Time Protocol).

Atomic clocks are extremely accurate chronometers. They can keep time and not drift by as much of a second in thousands of years and it is this accuracy that has made possible technologies and applications such as satellite navigation, online trading and GPS.

Time synchronization for computer networks is controlled by the network time server, commonly referred to as the NTP server after the time synchronization protocol they use, Network Time Protocol.
When it comes to choosing a time server, there are really only two real type – the radio reference NTP time server and the GPS NTP time server.

Radio reference time servers receive the time from long wave transmission broadcast by physics laboratories like NIST in North America or NPL in the UK. These transmissions can often be picked up throughout the country of origin (and beyond) although local topography and interference from other electrical devices can interfere with the signal.

GPS time servers, on the other hand, use the satellite navigation signal transmitted from GPS satellites. The GPS transmissions are generated by atomic clocks onboard the satellites so they are a highly accurate source of time just like the atomic clock generated time broadcast by the physics laboratories.

Apart from the disadvantage of having to have a roof top antenna (GPS works by line of sight so a clear view of the sky is essential), GPS is obtainable literally everywhere on the planet.

As both types of time server can provide an accurate source of reliable time the decision of which type of time server should be based on the availability of long wave signals or whether it is possible to install a rooftop GPS antenna.

Using GPS as a source of Accurate Time

  |   By

The Global Positioning System (GPS) is an increasingly popular tool, used throughout the world as a source of wayfinding and navigation. However, there is much more to the GPS network than just satellite navigation as the transmissions broadcast by the GPS satellites can also be used as a highly accurate source of time.

GPS satellites are actually just orbiting clocks as each one contains atomic clocks that generate a time signal. It is the time signal that is broadcast by the GPS satellites that satellite navigation receivers in cars and planes use to work out distance and position.

Positioning is only possible because thee time signals are so accurate. Vehicle sat navs for instance use the signals from four orbiting satellites and triangulate the information to work out the position. However, if there is just one second inaccuracy with one of the time signals then the positing information could be thousands of miles out – proving useless.

It is testament to the accuracy of atomic clocks used to generate GPS signals that currently a GPS receiver can work out its position on earth to within five metres.

Because GPS satellites are so accurate, they make an ideal source of time to synchronise a computer network to. Strictly speaking GPS time differs from the international timescale UTC (coordinated Universal Time) as UTC has had additional leap seconds added to it to ensure parity with the earth’s rotation meaning it is exactly 18 seconds ahead of GPS but is easily converted by NTP the time synchronisation protocol (Network Time Protocol).

GPS time servers receive the GPS time signal via a GPS antenna which has to be placed on the roof to receive the line of sight transmissions. Once the GPS signal is received the NTP GPS time server will distribute the signal to all devices on the NTP network and corrects any drift on individual machines.

GPS time servers are dedicated easy to use devices and can ensure millisecond accuracy to UTC without any of the security risks involved in using an internet time source.

Common Issues in Time Synchronisation

  |   By

Time synchronization is essential in modern computer networking especially with the amount of time sensitive transactions conducted over the internet these days. Without adequate synchronization computer systems will:

  • Be vulnerable to malicious attacks
  • Susceptible to data loss
  • Unable to conduct time sensitive transactions
  • Difficult to debug

Fortunately ensuring a computer network is accurately synchronized is relatively straight forward. There different methods of synchronizing a network to the global timescale UTC (Coordinated Universal Time) but occasionally some common issues do arise.

My dedicated time server is unable to receive a signal

Dedicated NTP time servers receive the time from either long wave transmissions or GPS networks. If using a GPS NTP server then a GPS antenna needs to be situated on a roof to obtain a clear view of the sky. However, a NTP radio receiver does not need a roof mounted aerial although the signal can be vulnerable to interference and the correct angle toward the transmitter should be attained.

I am using a public time server across the Internet but my devices are not synchronised.

As public time servers can be used by anyone they can receive high levels of traffic. This can cause problems with bandwidth and mean that your time requests can’t get through. Public NTP servers can also fall victim to DDoS attacks and some high profile incidents of NTP vandalism have occurred.

Internet time servers are also stratum 2 devices, in other words they themselves have to connect to a time server to receive the correct time and because of this some online time references are wildly inaccurate.

*NB – internet time servers are also incapable of being authenticated to allow NTP to establish if the time source is coming from where it claims to be, combined with the problem of ensuring the firewall is open to receive the time requests, can mean that internet time servers present a clear risk to security.

The time on my computer seems to be off by a second to standard UTC time

You need to check if a recent leap second has been added to UTC. Leap seconds are added once or twice a year to ensure UTC and the Earth’s rotation match. Some time servers experience difficulties in making the leap second adjustment.

Why a GPS Time Server is the Number One Choice for Time Synchronization

  |   By

When it comes to synchronizing a computer network there are several choice to ensure each device is running the same time. NTP (Network Time Protocol) is the preferred choice of time synchronization protocols but there are a multitude of methods in how NTP receives the time.

The NTP Daemon is installed on most operating systems such as windows and applications such as Windows Time are quite capable of receiving a source of UTC time (Coordinated Universal Time) from across the internet.

UTC time is the preferred time source used by computer networks as it is kept true by atomic clocks. UTC, as the name suggests, is also universal and is used by computer networks all over the world as a source to synchronize too.

However, internet sources of UTC are to recommended for any organisation where security and accuracy are a concern. Not only can the distant from host (internet time server) to the client (your computer network) can never be accurately measured leading to a drop in precision. Furthermore, any source of internet time will need access through the firewall (usually through the UDP 123 port). And by leaving this port open, malicious users and hackers can take advantage and gain access to the system.

Dedicated NTP time servers are a better solution as they receive the time from an external source. There are really two types of NTP server, the radio reference time server and the GPS time server.
Radio reference time servers use signals broadcast by places like NPL (National Physical Laboratory in the UK) or NIST (National Institute of Standards and Time). While these signals are extremely accurate, precise and secure they are affected by regular maintenance on the transmitters that broadcast the signal. Also being long wave they are vulnerable to local interference.

GPS time servers on the other hand receive the time directly from GPS satellites. This GPS time is easily converted to UTC by NTP (GPS time is UTC – 17 seconds exactly as no leap seconds have been added.) As the GPS signal is available everywhere on the earth 24 hours a day, 365 days a week, there is never a risk of a loss of signal.
A single dedicated GPS time server can synchronize a computer network of hundreds, and even thousands of machines to within a few of milliseconds of UTC time.