Data-gram Protocol (UDP) which is in-turn reliant on the TCP/IP protocol. NTP messages are communicated using UDP port 23, which is reserved solely for the apply of NTP traffic. The protocol basically consists of a number of fields, which specify: clock-offset, round-trip delay and dispersion relative to a precise time source. The facts stored in each NTP packet allow a network time client to accurately synchronise time with a NTP server. NTP is a structured protocol that operates in a hierarchical manner. At the top of the tree, a primary time reference is known as a stratum 1 time server. Servers that synchronise to a stratum 1 server are known as stratum 2 servers and so on down each level of the hierarchy. As the stratum increases, so generally precision decreases. Over a number of years NTP has been enhanced to operate with a plethora of precision hardware clock devices, or reference clocks. NTP reference clocks are available for GPS hardware and also many of the
National Radio Time and Frequency standards such as MSF, DCF-77 and WWVB. A number of third-party timing hardware manufacturers have installed precision crystals into their reference clocks to provide an accurate backup timing reference, . A spin-off of the NTP protocol is SNTP or Simple Network Time Protocol, which is basically as the honour implies, a simplified version of NTP. SNTP is generally used in small low-powered computing devices such as micro-controllers. It allows low-powered devices the ability to synchronise time to NTP servers over a network. To summarise, NTP is a long-standing and widely used protocol for synchronising time between time critical processes. It has a straightforward hierarchical structure that allows synchronisation of large numbers of network time clients. For applications that require critical timing, NTP provides a de-facto morals solution. Full text: http://computerandtechnologies.com/computers-and-technology/news_2008-05-27-15-30
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