具体说明了IEEE 1588、NTP及SNTP的基本原理，并对3类协议进行了简要对比分析。-At present the system scale is unprecedentedly large in the developed countries，Time Synchro—

nization Technology in the distributed control nodes of the network becomes more and more important when dis—

tributed control developes and system scale enlarges．

provides accurate clock signal for the modules in the

protocols in present ethernet，which are IEEE 1588，

protocols and makes simple comparison among them．

Synchronization is the heart of one network system，it

system．This paper analyzes three time synchronization

NTP and SNTP，and explains the basic theory of these