NTP Development of Network Time Protocol

The first implementation of Network Time Protocol (NTP) is recorded in Internet Engineering Notes, and its accuracy is several hundred milliseconds. Later, the specification of the first time protocol, RFC-778, was named DCNET Internet Time Service, which provided this service with the help of the Internet Control Message Protocol (ICMP), that is, the timestamp and timestamp response message in the Internet Control Message Protocol as NTP. This name first appeared in RFC-958, also known as NTP v0, and its purpose is to provide time synchronization for ARPA networks. It has completely separated from ICMP, and it is an independent protocol to complete higher time synchronization requirements. It describes basic operations, such as error estimation and accuracy of local clock, characteristics of reference clock, packet data on the network and its message format. But there is no compensation for frequency error, and there is no algorithm for filtering and synchronization. David L .Mills of the University of Delaware presided over the network time synchronization project funded by DARPA, NSF and NSWC, and successfully developed the NTP protocol of 1, 2 and 3 versions. NTP version 1 appeared in June of 1988, and RFC- 1059 described the first complete NTP specification and related algorithms. This version adopts client/server mode and symmetrical operation, but does not support authorization authentication and NTP control messages. 1September 1989, NTP v2 version, namely RFC-119, was introduced to replace RFC-958 and RFC- 1059. Almost at the same time, DEC also introduced a time synchronization protocol, Digital Time Synchronization Service (DTSS). 1March, 1992, NTP v3 version RFC- 1305 came out, which summarized and integrated the previous NTP version and DTSS, formally introduced the correction principle, improved the algorithm of clock selection and clock filtering, and also introduced the broadcast of time message transmission. After the release of NTP v 3, it has been continuously improved. An important function of NTP is to adjust the clock of computer operating system. While researching and launching NTP v3, the research on improving the timing function in the operating system kernel is also in parallel. RFC- 1589 was introduced in 1994, which is called the kernel model of accurate time Keening, that is, the kernel model of accurate time 0 1. This implementation can keep the time accuracy of computer operating system in the order of microseconds. Suggestions for improvement were put forward almost at the same time. The local clock adjustment algorithm, communication mode, new clock driver and improvement of NTP v4 adaptation rules are described. As of June 20 10, the latest NTP version is the fourth edition (NTPv4), and its standardized document is RFC 5905, which is inherited from NTP v3 described in RFC 1305. Network time synchronization technology will also develop in the direction of higher accuracy, stronger compatibility and stronger multi-platform adaptability. NTP is one of the standards of Internet time synchronization. Its purpose is to synchronize the computer clock with UTC. Its accuracy can reach 0. 1ms in the local area network and 1- 50ms in most places on the Internet. It is worth mentioning that a simple NTP(SNTP) version 4 has been described in RFC2030. Major NTP product suppliers: Global Time &; Symmetric communication company