How,NTP,Server,Works,NetworkTi computer How a NTP Server Works
----------------------------------------------------------Permission is granted for the below article to forward,reprint, distribute, use for ezine, newsletter, website,offer as free bonus or part of a product for sale as longas no changes a Gone are those times when the companies and the organisations didn't need a hi-tech system to handle them. Owing to the considerable increase in the business sector and thus, an enormous increase in the complexity of the organisational struc
NetworkTime Protocol (NTP)is one of the Internets oldest protocols still in use. Invented by Dr DavidMills from the University of Delaware it has been utilized since 1985. NTP isdesigned to synchronize the clocks on computers and networks across theInternet or Local Area Networks (LANs). NTP(currently version 4) is actually threethings in one; a software program that runs in the background of Windows or UNIX;a protocol that exchanges time values between servers and clients; and a suiteof algorithms that process the time values to advance or retreat the systemclock. NTPuses an algorithm (Marzullos algorithm) to synchronise time on a network using a time reference. Although networks canbe synchronized with internal clocks or Internet based timing references, it ishighly recommended by Microsoft and others that an external timing referenceshould be used to guarantee authentication. An absolute timing reference shoulduse UTC (Coordinated Universal Time or TempsUniversel Coordonné) which supports such features as leap seconds - added tocompensate for the slowing of the Earths rotation. NTP works within the TCP/IP suite and relies on UDP, a less complexform of NTP exists called Simple Network Time Protocol (SNTP) that does notrequire the storing of information about previous communications, needed byNTP. It is used in some devices and applications where high accuracy timing isnot as important, it is also included in most Windows operating systems butmore recent versions have the full NTP already installed, which is also free todownload via the Internet. Synchronisationwith NTP is relatively simple, it synchronises time with reference to a reliable clock source suchas an atomic clock, although these are extremely expensive and are generallyonly to be found in large-scale physics laboratories, however NTP can useeither the Global Positioning system (GPS) network or specialist radio transmissionto receive UTC time from these clocks. NTP uses timestamps to represent the current time of the dayeach timestamp is ephemeral, in other words it is always greater than theprevious timestamp as time never runs backwards. NTP analyses the timestamp valuesincluding the frequency of errors and the stability. A NTP serverwill maintain an estimate of the quality of its referenceclocks and of itself. The distance from the reference clock is known as thestratum levels and they exist to prevent cycles in the NTP. Stratum 0 aredevices such as reference clocks connected directly to a computer. Stratum 1are computers attached to stratum 0 devices, while Stratum 2 are computers thatsend NTP requests to Stratum 1 servers. NTP can support up to 256 strata. NTP timestamps are in two formats but they relay the secondsfrom a set point in time (known as the prime epoch, set at 00:00 1 January1900) The NTP algorithm then uses this timestamp to determine the amount toadvance or retreat the system or network clock. The NTP program (known as a daemon on UNIX and a service onWindows) runs in the system background. NTP refuses to believe the time it istold until several packet exchanges have taken place, each passing a set oftests. Only if the replies from a server satisfy the test, known as protocolspecifications, the server is considered. It usually takes about five minutes(five good samples) until a NTP server is accepted as asynchronization source. A typical GPS time server can provide timing information towithin a few nanoseconds of UTC as long as there is an antenna situated with agood view of the sky. There are also a number of national time and frequency radiotransmissions that can be used to synchronise a NTP server. In Britain thesignal (called MSF) is broadcast by the National Physics Laboratory in Cumbriawhich serves as the United Kingdom's national time reference, thereare also similar systems in Colorado, US (WWVB) and in Frankfurt, Germany(DCF-77). These signals provides UTC time to an accuracy of 100 microseconds,however, the radio signal has a finite range and is vulnerable to interference.
How,NTP,Server,Works,NetworkTi