A node selects a source of timing information using network topology and the timing status of network nodes

摘要

In a synchronous network, such as a synchronous digital hierarchy network (SDH), a node can obtain synchronisation or timing information from any one of a plurality of sources, such as a PRC, SSU or SEC. If the chosen source fails then a new timing source must be selected. The present invention detects the topology of the network and the timing status of each network node, and uses this information to select a new timing source in the event of failure of an existing timing source. Using the present invention it is possible to avoid the selection of timing sources which would result in the creation of a timing loop. Preferably the detection operations are performed using a spanning-tree algorithm.