| The NTP server (Network Time Protocol) is one of | | | | can obviously cause its own security issues. |
| the most used but least understood computer | | | | Internet timing sources are also notoriously inaccurate. |
| networking items. | | | | A survey by MIT (Massachusetts Institute of |
| A NTP Server is just a time server that uses the | | | | Technology) found less than a quarter of Internet |
| protocol NTP. Other time protocols do exist but NTP is | | | | timing sources were any where near accurate and |
| by far the most widely used. The terms ‘NTP | | | | often those that were, were too far away from clients |
| server’, ‘time server’ and ‘network time | | | | to provide a reliable timing source. |
| server’ are interchangeable and often the terms | | | | The most common, secure and accurate method for |
| ‘radio clock’ or ‘GPS time server’ are | | | | receiving timing source is the GPS system (Global |
| used but these simply describe the method which the | | | | Positioning System). While a GPs signal can be |
| time servers receive a time reference. | | | | received anywhere on the planet there are still |
| NTP servers receive a time source that they can then | | | | common installation issues. |
| distribute amongst a network. NTP will check a | | | | A GPS antenna has to have a good clear view of the |
| devices system clock and advance or retreat the time | | | | sky; this is because the GPs satellite broadcast their |
| depending on how much it has drifted. By regularly | | | | signal by line of sight. He signal can not penetrate |
| checking the system clock with the time server, NTP | | | | buildings and therefore the antenna has to be situated |
| can ensure the device is synchronised. | | | | on the rood. Another common issue with a GPS time |
| The NTP server is a simple device to install and run. | | | | server is that they need to be left for at least 49 |
| Most connect to a network via an Ethernet cable and | | | | hours to ensure the GPS receiver gets a good satellite |
| the software included is easily configured. However, | | | | fix. Many users find that they are receiving an |
| there are some common troubleshooting problems | | | | intermittent signal this is normally due to impatience and |
| associated with NTP servers and in particular with | | | | not letting the GPS system obtain a solid fix. |
| receiving timing sources: | | | | The other secure and reliable method for receiving a |
| A dedicated NTP server will receive a time signal from | | | | timing signal is the national radio transmissions. In the |
| various sources. The Internet is probably the most | | | | UK this is called MSF but similar systems exist in the |
| common sources of UTC time (Coordinated Universal | | | | US (WWVB), Germany (DCF) and several other |
| Time), however, using the Internet as a timing source | | | | countries. There are usually less problems faced when |
| can be a cause for several time server problems. | | | | using the MSF/DCF/WWVB signal. Although the radio |
| Firstly Internet timing sources can’t be | | | | signal can penetrate buildings it is susceptible to |
| authenticated; authentication is NTP’s in-built | | | | interference from topography and other electrical |
| security measure and ensures that a timing reference | | | | appliances. Any issues with a MSF time server can |
| is coming from where it says it is. On a similar note to | | | | normally be resolved by moving the server to another |
| use an Internet timing source would mean that a gap | | | | locale or often just angling the server so its in-built |
| would have to be created in the network firewall, this | | | | antenna is perpendicular to the transmission. |