Method for creating accurate time-stamped frames sent between computers via a network

• US 7,080,160 B2
• Filed: 11/28/2001
• Issued: 07/18/2006
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Tionesta, Llc
• Original Assignee: Qosmetrics, Inc.
• Inventors: Cognet, Yves, Ovanesian, Joseph, Aynillan, Armen
• Primary Examiner(s): Etienne, Ario
• Assistant Examiner(s): NANO, SARGON N
• Application Number:
  US09/996,490
• Publication Number:
  US 20020073228A1
• Time in Patent Office: 1,693 Days
• Field of Search: 709/202, 709/203, 709/205, 709/224, 709/227, 709/228, 709/233, 709/248
• US Class Current: 709/248
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04L 12/2874 Processing of data for distribution to the subscribers
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method for creating time-stamped frames sent between computers includes receiving and generating a universal coordinated time reference signal using a global positioning system. Clocks independent of operating systems of the sending and receiving computer are synchronized with the reference signal. A test frame is created including a tag having reserved fields for transmit and receive time stamps. The transmit time stamp is inserted into the reserved transmit time stamp field, without intervention of the sending computers central processing unit, that corresponds to the time on the synchronized clock at the instant the test frame is sent. The test frame having the transmit time stamp is received by the receiving computer, and a receive time stamp is inserted into the reserved receive time stamp field corresponding to the time on the synchronized clock of the receiving computer when the test frame was received.

Claims

1. A method for creating accurate time-stamped frames sent between computers via a network, comprising the steps of:

receiving a universal coordinated time reference signal;

synchronizing clocks electronically connected to universal coordinated time reference signal receivers and associated with sending and receiving computers, but operating independently of operating system clocks of the sending or receiving computers, with the universal coordinated time reference signal by initializing the clocks with the received universal coordinated time reference signal;

using the clocks to create sub-microsecond time values corresponding to a fractionalized universal coordinated time reference signal;

over time, adjusting the clock into synchronization with the universal coordinated time reference signal;

creating a test frame including a tag having reserved fields for transmit and receive time stamps representing the universal coordinated time reference signal and the sub-microsecond time values;

inserting a transmit time stamp into the reserved transmit time stamp field corresponding to the time on the synchronized clock of the sending computer at the instant the test frame is sent onto the network without intervention of the sending computer'"'"'s central processing unit; and

receiving the test frame having the transmit time stamp and inserting a receive time stamp into the reserved receive time stamp field corresponding to the time on the synchronized clock of the receiving computer when the test frame was received by the receiving computer.

2. The method of claim 1, wherein the universal coordinated time signal is received via a global positioning system receiver.

3. The method of claim 2, wherein the clock and global positioning system receiver are electronically connected on a device which is attachable to an existing multi-master bus of either the sending or receiving computer.

4. The method of claim 3, wherein the device comprises a card interfacing with a multi-master bus of the receiving or sending computer.

5. The method of claim 1, wherein the adjusting step includes the steps of altering the voltage applied to a voltage controlled crystal oscillator associated with the clock to maintain synchronization with the universal coordinated time signal.

6. The method of claim 1, wherein a receiving device, without intervention from the receiving computer, automatically attaches a receive time stamp corresponding to the synchronized time that the frame was received for each frame received.

7. The method of claim 1, wherein a receiving device, without intervention from the receiving computer, detects the tag of each test frame and attaches a receive time stamp corresponding to the synchronized time that the frame was received to only the test frames.

8. The method of claim 1, wherein the creating step includes the step of creating complimentary time information in the reserved transmit and receive time stamp fields to enable the insertion of the synchronized transmit and receive time stamps upon transmit and receipt, respectively, in order to preserve an original TCP or UDP checksum.

9. The method of claim 1, wherein the synchronized clocks have a resolution of between 10 and 100 nanoseconds.

14. The method of claim 1, wherein the inserting step includes inserting the transit time stamp into the reserved transit time stamp field at the instant a last byte of the test frame is sent onto the network;

and wherein the receiving step includes the step of inserting a receive time stamp into the reserved receive time stamp field when a first byte of the test frame is received by the receiving computer.

15. The method of claim 3, wherein the device includes only hardware or firmware and not software.

16. The method of claim 5, wherein the adjusting step comprises the steps of comparing the received universal coordinated time reference signal with the created sub-microsecond time values and altering the voltage applied to the voltage controlled crystal oscillator associated with the clock to speed up or slow down and synchronize the sub-microsecond time values created by a counter in the clock with the universal coordinated time reference signal.

19. The method of claim 16, wherein the clock and global positioning system receiver are electronically connected on a device which is attachable to an existing multi-master bus of either the sending or receiving computer.

20. The method of claim 19, wherein the device comprises a card interfacing with a multi-master bus of the receiving or sending computer.

21. The method of claim 20, wherein the device includes only hardware or firmware and not software.

22. The method of claim 21, wherein the device does not consume any of the computer'"'"'s central processing resources.

10. A method for creating accurate time-stamped frames sent between computers via a network, comprising the steps of:

using a global positioning receiver in communication with sending and receiving computers to generate a universal coordinated time reference signal;

synchronizing clocks associated with the sending and receiving computers, but operating independently of operating system clocks of the sending or receiving computers, with the universal coordinated time reference signal by initializing the clocks with the received universal coordinated time reference signal and over time tracking and averaging the periodically received universal coordinated time reference signal and adjusting the clock to correspond to the universal coordinated time reference signal by altering the voltage applied to a voltage controlled crystal oscillator associated with the clock;

creating a test frame including a tag having reserved fields for transmit and receive time stamps;

creating complimentary time information in the reserved transmit and receive time stamp fields;

replacing the complimentary time information in the transmit time stamp field with a transmit time stamp corresponding to the time on the synchronized clock of the sending computer at the instant the test frame is sent onto the network without intervention of the sending computer'"'"'s central processing unit; and

automatically attaching a receive time stamp corresponding to the time on the synchronized clock of the receiving computer when the frame was received by the receiving computer to every frame received by the receiving computer.

11. The method of claim 10, wherein the clock and global positioning system receivers are electronically connected on a device which is attachable to an existing multi-master bus of either the sending or receiving computer.

12. The method of claim 11, wherein the device comprises a card interfacing with a multi-master bus of the receiving or sending computer.

13. The method of claim 10, wherein the synchronized clocks have a resolution of between 10 and 100 nanoseconds.

17. A method for creating accurate time-stamped frames to be sent between computers via a network, comprising the steps of:

receiving a universal coordinated time reference signal;

creating sub-microsecond time values corresponding to a fractionalized universal coordinated time reference signal using a clock operating independently of a computer clock and in direct electronic communication with a universal coordinated time reference signal receiver, wherein the universal coordinated time reference signal and the sub-microsecond time values together represent an absolute time;

over time, comparing the received universal coordinated time reference signal and the created sub-microsecond time values and adjusting the clock into synchronization with the universal coordinated time reference signal;

creating a test frame including a tag having reserved fields for transmit and receive time stamps representing the absolute time; and

inserting a transmit time stamp into the reserved transmit time stamp field corresponding to the absolute time the test frame is sent onto the network, without intervention of the computer'"'"'s central processing unit.

18. The method of claim 17, wherein the universal coordinated time signal is received via a global positioning system receiver.

23. The method of claim 17, wherein the adjusting step includes the steps of altering the voltage applied to a voltage controlled crystal oscillator associated with the clock to speed up or slow down and synchronize the sub-microsecond time values created by a counter in the clock with the universal coordinated time reference signal.

24. The method of claim 17, wherein the clock has a resolution of between 10 and 100 nanoseconds.

25. The method of claim 17, including the step of receiving the test frame having the transmit time stamp and inserting a receive time stamp into the reserved receive time stamp field corresponding to the time on the synchronized clock of a receiving computer when the test frame was received by the receiving computer.

26. The method of claim 24, wherein the receiving computer automatically attaches a receive time stamp corresponding to the synchronized time that a first byte of the frame was received for each frame received.

27. The method of claim 24, wherein the receiving computer detects the tag of each test frame and attaches a receive time stamp corresponding to the synchronized time that the frame was received to only the test frames.

28. The method of claim 24, wherein the creating step includes the step of creating complimentary time information in the reserved transmit and receive time stamp fields to enable the insertion of the synchronized transmit and receive time stamps upon transmit and receipt, respectively, in order to preserve an original TCP or UDP checksum.