Patent ID: 8576883

Claim:
A system for synchronizing time clocks within a distributed network, comprising: a master timing unit configured to broadcast a synchronization message with a known time interval, the synchronization message including a master time stamp reflecting an instantaneous time value measured at the master timing unit; a network data path connected to the master timing unit and providing a data path for the synchronization message; at least one network device connected to the network data path and adapted to receive the synchronization message, the network device comprising: a network core element; and a time stamping unit; a time pulse generator configured to output a periodic timing pulse; and a time pulse distribution network connecting the time pulse generator to the time stamping unit of the at least one network device; wherein the time pulse network is separate from the network data path; the time stamping unit further includes a timebase based on a local oscillator that is locked to the periodic timing pulse of the time pulse generator and used to drive a local slave time clock; and the time stamping unit is further adapted to: utilize the local slave time clock to measure a time interval between an arrival of the synchronization message at the network core element and a departure of the synchronization message from the network core element, in order to calculate a residence time of the synchronization message within the network core element; and update the synchronization message to add a time offset to the master time stamp that corresponds to the residence time within the network core element; wherein: the at least one network device is further configured to send a delay request packet back to the master timing unit through the network data path upon receiving the synchronization message from the master timing unit, wherein the delay request packet includes a time stamp reflecting a time measured by the local slave time clock when the delay request message leaves the at least one network device; the master timing unit is further configured to send a delay response packet back to the at least one network device that includes a time stamp reflecting a time at which the delay request packet arrived at the master timing unit; and the at least one network device is further configured to calculate a transport time of the synchronization message from the master timing unit and to shift a phase of the local slave time clock to compensate for the transport time of the synchronization message.