Patent ID: 8824332

Claim:
A method for selecting a clock source in a synchronization digital hierarchy network, comprising: network nodes in said synchronization digital hierarchy network generating standalone clock information packets from clock quality information and transmitting the clock information packets to neighbor network nodes, wherein each of said clock information packets contains information of a quality grade, a priority, a clock variance and a clock source identifier; and a clock module of every network node in said synchronization digital hierarchy network independently selecting a clock source by using said clock information packets, wherein the step of a clock module of every network node in said synchronization digital hierarchy network independently selecting a clock source by using said clock information packets comprises: for the received clock information packets sent by different neighbor network nodes, said each clock module comparing in turn the quality grades, priorities and clock variances in the clock information packets sent by the different neighbor network nodes and selecting a clock source according to a result of the comparison; and wherein the step of selecting a clock source according to a result of the comparison comprises: for the received clock information packets sent by different neighbor network nodes, selecting a clock source with the highest quality grade, if said clock source with the highest quality grade is not unique, selecting a clock source with the highest priority therefrom, and if said clock source with the highest priority is not unique, calculating clock variances of said clock sources with the highest priority, and selecting a clock source with the minimum clock variance.