Patent ID: 7716375

Claim:
A method for synchronization in a network in which a local time is updated at various nodes in the network, the method comprising: determining, in a network, a higher-level node and a lower-level node; receiving, at the lower-level node, a time message sent from the higher-level node; reading, by the lower-level node, a local time of the higher-level node from the time message; adding, by the lower-level node, a minimum delay time for a message to be transmitted between the higher-level node and the lower-level node, thereby generating a comparison time, comparing, by the lower-level node, the comparison time to a local time of the lower-level node; updating the local time of the lower-level node if the comparison time is newer than the local time of the lower-level node and not updating the local time of the lower-level node if the comparison time is older than the local time of the lower-level node; if the local time of the lower-level node is not updated, monitoring, at the lower-level node, a non-zero time interval starting from a most recent update of the local time at the lower-level node; producing a virtual local time at the lower-level node if the local time at the lower-level node has not been updated before the time interval exceeds a predetermined value, the virtual local time lagging behind the local time at the lower-level node; and updating the local time of the lower-level node if the comparison time is newer than the virtual local time; wherein the local time of the lower-level node is undated such that the local time of the lower-level node is set to the comparison time.