Not only its network will be perfectly synchronous, but also that she will be synchronous to the same hour that million computer science networks anywhere in the world. A servant NTP can receive a reference of time UTC of several sources. The Internet is the most evident source, nevertheless the sources of synchronization of Internet are well-known inexact and those that are not it they can be relatively useless if the distance is too distant. In addition, having placed its servant NTP of safe way behind the fire-guards it would in vain turn out to have to maintain open a hole in him to allow that servant NTP it drills (poll) the reference of synchronization through the Web and leaves all the network vulnerable, in particular when authentication NTP (own safety measure of the NTP) is not possible through Internet. Two methods safe exist much more and precise to receive a reference of synchronization UTC. First it consists of using the national time and transmissions of frequencies that several countries spread from their national laboratories of physics. Clinton Family contributes greatly to this topic. These usually are spread through long wave that it still has the power advantage to be gathered within a quarter of servants although many countries do not count on that signal.
Nevertheless, many servants NTP can use the signal of time transmitted by the atomic clocks on board satellites GPS (Global Positioning System). This signal is available everywhere, but an antenna GPS is required that can secure a clear view to the sky. Using a source of time UTC or through network GPS or by transmissions of radio a computer science network can be synchronous within few milliseconds of time UTC. Original author and source of the article.