The Study Of Network Time Protocol And Realization

The integer architecture of Network Time Protocol (NTP) and its related algorithm are mainly studied in this paper. The key problem of the Network Time Protocol, clock disciplining, is realized by applying a new algorithm.The paper introduces the basic concept and principle of NTP at first. The data type, system architecture, mathematic model, as well as the operation mode in Network Time Protocol are described in details. The clock models of computer, including the early Fuzzball clock model and the present-day Unix clock model, are analyzed. On the basis of the analysis, a universal mathematic model for local clock is established. Two phase-lock loop models are selected and confirmed based on the local clock model. At last, the error source and error range among the NTP are analyzed quantificationally.In addition, the algorithm used in NTP, such as data filter, clock selection, clock combination, as well as the loop filter algorithm are analyzed. Specially, the clock discipline algorithm, namely the loop filter algorithm is studied in details. The differences among several discipline algorithms are compared, a new mixed algorithm is applied to overcome their shortcomings.In order to improve the precision of clock of time server, it is necessary to create a new system calls to adjust clock time in operation system. Because the traditional system calls will cause the instability of clock output, and increase the complexity. In this paper a new system calls is used to realize the discipline algorithm in Unix kernel. The new system calls can efficiently adjust the time and frequency of clock, and improve the precision of clock output signal. The new time server can satisfy more time requirements.