Patent ID: 7668207
Filing Date: 2010-02-23
Classification: G04G,G06F

Abstract:
1. A method for synchronizing first and second time-of-day clocks on first and second computers, respectively, the first computer having a third clock on a first network interface card, the second computer having a fourth clock on a second network interface card, the first and second network interface cards communicating with one another via a communication network, the method comprising: generating a first message having a first time difference value and a second time stamp value and transmitting the first message from the first network interface card, the first time difference value corresponding to a time difference between the first time-of-day clock and the third clock, the second time stamp value corresponding to a time determined by the third clock on the first network interface card when the first message is transmitted from the first network interface card; receiving from the second network interface card a second message having the first time difference value, the second time stamp value, a third time stamp value, a fourth time difference value, and a fifth time stamp value, the third time stamp value corresponding to a time determined by the fourth clock on the second network interface card when the first message is received by the second network interface card, the fourth time difference value corresponding to a time difference between the second time-of day clock and the fourth clock, the fifth time stamp value corresponding to a time determined by the fourth clock when the second message is transmitted from the second network interface card; determining a sixth time stamp value associated with the second message, the sixth time stamp value corresponding to a time determined by the third clock when the second message is received by the first network interface card; and determining a seventh time difference value corresponding to a time difference between the first and second time-of-day clocks based on the first time difference value, the second time stamp value, the third time stamp value, the fourth time difference value, the fifth time stamp value, and the sixth time stamp value.