The designers of synchronous switched digital communications networks have a large number of possibilities from which to choose a timing/synchronization system. Various combinations of the timing/synchronization system features described here can be used to characterize these possibilities. Advantages and disadvantages of employing different timing/synchronization features are examined, and their relationships to the more commonly discussed mutual and master-slave methods of network timing/synchronization are described. The need for particular timing system options is dependent on system applications. Significant differences in needed capability result from differences between civilian and military application. These differences are discussed, and the relationship between timing/ synchronization requirements of a wartime worldwide synchronous switched digital military communications network and timing system features is explored.