Patent ID: 8125907

Claim:
A method for time calibration in nodes of a network utilizing characterizations of multiple disparate communication paths across the network which vary in transmission behavior frequently over time, the method comprising: sending from a peer node a request message to a network control point (NCP) over a first communication path and a duplicate request message to the NCP over a second communication path different from the first communication path, wherein the request message and the duplicate request message are both tagged with a send time according to a peer node clock in the peer node; selecting the request message or the duplicate request message as the first request message received in the NCP and tagged with an arrival time by a master clock in the NCP; sending from the NCP in response to the first request message a reply message to the peer node over the first communication path and a duplicate reply message to the peer node over the second communication path, wherein the reply message and the duplicate reply message are both tagged with a reply send time according to the master clock in the NCP, wherein the reply message and the duplicate reply message both include the send time; selecting the reply message or the duplicate reply message as the first reply message received in the peer node and tagged with a reply arrival time according to the peer node clock; and calibrating a network time at the peer node to the master clock in the NCP based on the send time according to the peer node clock, the reply send time according to the master clock in the NCP, and the reply arrival time according to the peer node clock, wherein the calibrating comprises: generating a slope value based on a ratio of an average reply send time versus an average reply arrival time for at least two samples of the reply send time and at least two samples of the reply arrival time; and generating the network time at the peer node based on an evaluation of the slope value multiplied by a current time at the peer node plus one half of a difference between the send time and the reply arrival time.