Non-deterministic software delay estimation method and system for packet based data network systems

• US 20020006115A1
• Filed: 05/18/2001
• Published: 01/17/2002
• Est. Priority Date: 05/18/2000
• Status: Abandoned Application

• Current Assignee: EXFO Service Assurance, Inc. (11172239 Canada, Inc.)
• Original Assignee: EXFO Service Assurance, Inc. (11172239 Canada, Inc.)
• Inventors: Hedayat, Kaynam, DesRochers, Steven A., Harvell, Laco Scott, Tavana, Sadredin
• Application Number:
  US09/860,296
• Publication Number:
  US 20020006115A1
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04J 3/0661 using timestamps
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6489 Buffer Management, Threshold setting, Scheduling, Shaping
• CPC Class Codes: H04L 43/50 Testing arrangements
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 69/32 Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level

Abstract

A method of characterizing a propagation delay of a data element propagating from a software source to a physical medium destination includes associating, in software, a first time code with the data element when the software source dispatches the data element to the physical medium destination. The method further includes associating, via a time-stamping circuit, a second time code with the data element when the data element reaches the physical medium destination. The method also includes subtracting the first time code from the second time code so as to calculate the propagation delay. In a similar manner, the method may also be used to characterize the propagation delay of the data element in the reverse direction, i.e., from the physical medium to the software source.

Claims

1. A method of characterizing a propagation delay of a data element propagating from a software source to a physical medium destination, comprising:

associating, in software, a first time code with the data element when the software source dispatches the data element to the physical medium destination;

associating, via a time-stamping circuit, a second time code with the data element when the data element reaches the physical medium destination; and

, subtracting the first time code from the second time code so as to calculate the propagation delay.

2. A method according to claim 1, further including characterizing an incoming propagation delay of an incoming data element propagating from the physical medium to the software source, comprising:

associating, via the time-stamping circuit, a third time code with the incoming data element when the incoming data element is taken from the physical medium destination;

associating, in software, a fourth time code with the incoming data element when the software source receives the data element; and

,

subtracting the third time code from the fourth time code so as to calculate the incoming propagation delay.

3. A method according to claim 1, further including providing a time source and sampling the first time code from the time source when the software source dispatches the data element to the physical medium destination.

4. A method according to claim 1, further including providing a time source and sampling the second time code from the time source when the data element reaches the physical medium destination.

5. A method according to claim 1, wherein the physical medium destination includes a network medium interface, the data element includes a data packet to be transmitted on the network medium, and the software source includes a software application for compiling the data packet.

6. A method according to claim 5, wherein the software source compiles the data packet in an IP format.

7. A method according to claim 1, further including generating two or more data elements, and for each data element:

(i) associating, in software, the first time code with the data element when the software source dispatches the data element to the physical medium destination;

(ii) associating, via the time-stamping circuit, the second time code with the data element when the data element reaches the physical medium destination;

(iii) subtracting the first time code from the second time code so as to calculate the propagation delay;

and further generating statistical values that characterize the propagation delays for the two or more data elements.

8. A method according to claim 7, wherein the statistical values are selected from the group consisting of a minimum propagation delay, a maximum propagation delay, a mean of the two or more propagation delays, a median of the two or more propagation delays, a variance of the two or more propagation delays, and combinations thereof.

9. A method according to claim 7, wherein the two or more data elements include data packets.

10. A method according to claim 7, wherein the two or more data elements include at least two data elements of different sizes.

11. A method according to claim 7, wherein the two or more data elements include at least two data elements of different format types.

12. A method according to claim 1, further including calculating the propagation delay of the data element independent of the software source generating and dispatching the data elements.

13. A method according to claim 1, further including specifying one or more predetermined characteristics of the data element to the software source, such that the software source dispatches a predetermined data element, and characterizing the propagation delay of the predetermined data element.

14. A method according to claim 13, wherein the one or more characteristics of the data element are selected from the group consisting of size, format, data content, and combinations thereof.

15. A method of measuring a propagation delay of an IP data packet propagating from a software source to a physical network medium interface, comprising:

associating, in software, a first time code with the IP data packet when the software source dispatches the IP data packet to the physical network medium interface;

associating, via a time-stamping circuit, a second time code with the IP data packet when the IP data packet reaches the physical network medium interface; and

,

subtracting the first time code from the second time code so as to calculate the propagation delay.

16. A method according to claim 15, further including characterizing an incoming propagation delay of an incoming IP data packet propagating from the physical network medium interface to the software source, comprising:

associating, via the time-stamping circuit, a third time code with the incoming data packet when the incoming data packet is taken from the physical network medium interface;

associating, in software, a fourth time code with the incoming data packet when the software source receives the data packet; and

,

subtracting the third time code from the fourth time code so as to calculate the incoming propagation delay.

17. A method according to claim 15, further including providing a time source and sampling the first time code from the time source when the software source dispatches the data packet to the network medium interface.

18. A method according to claim 15, further including providing a time source and sampling the second time code from the time source when the data packet reaches network medium interface.

19. A method according to claim 15, further including generating two or more data packets, calculating the propagation delay for each of the two or more data packets, and generating statistical values that characterize the propagation delays for the two or more data packets.

20. A method according to claim 19, wherein the statistical values is selected from a group consisting of a minimum propagation delay, a maximum propagation delay, a mean of the two or more propagation delays, a median of the two or more propagation delays, a variance of the two or more propagation delays, and combinations thereof.

21. A system for characterizing a propagation delay of a data element propagating from a software source to a physical medium destination, comprising:

a module of software code for associating a first time code with the data element when the software source dispatches the data element to the physical medium destination;

a time-stamping circuit for associating a second time code with the data element when the data element reaches the physical medium destination; and

,

a difference calculator for subtracting the first time code from the second time code so as to calculate the propagation delay.

22. A system according to claim 21, wherein (i) the time-stamping circuit associates a third time code with the data element when the data element is taken from the physical medium destination, (ii) the module of software code associates a fourth time code with the data element when the software source receives the data element, and (iii) the difference calculator subtracts the third time code from the fourth time code so as to calculate an incoming propagation delay.

23. A system according to claim 21, wherein the module of software code samples a time source to acquire the first time code when the software source dispatches the data element to the physical medium destination.

24. A system according to claim 21, wherein the time-stamping circuit samples a time source to acquire the second time code when the data element reaches the physical medium destination.

25. A system according to claim 21, wherein the physical medium destination includes a network medium interface, the data element includes a data packet to be transmitted on the network medium, and the software source includes a software application for compiling the data packet.

26. A system according to claim 25, wherein the software source compiles the data packet in an IP format.

27. A system according to claim 21, wherein the module of software code generates two or more data elements, and for each data element,

(i) the module of software code associates a first time code with the data element when the software source dispatches the data element to the physical medium destination;

(ii) the time-stamping circuit associates a second time code with the data element when the data element reaches the physical medium destination;

(iii) the difference calculator calculates the propagation delay for each of the two or more data elements;

wherein a statistics calculator receives the propagation delays of the two or more data elements and calculates statistical values thereof.

28. A system according to claim 27, wherein the statistical values are selected from the group consisting of a minimum propagation delay, a maximum propagation delay, a mean of the two or more propagation delays, a median of the two or more propagation delays, a variance of the two or more propagation delays, and combinations thereof.

29. A system according to claim 27, wherein the two or more data elements include data packets.

30. A system according to claim 27, wherein the two or more data elements include at least two data elements of different sizes.

31. A system according to claim 27, wherein the two or more data elements include at least two data elements of different format types.

32. A system according to claim 21, wherein the difference calculator calculates the propagation delay of the data element independent of the software source generating and dispatching the data elements.

33. A system according to claim 21, wherein the software source dispatches a data element having one or more predetermined characteristics.

34. A system according to claim 33, wherein the one or more predetermined characteristics of the data element are selected from the group consisting of size, format, data content, and combinations thereof.

35. A system for measuring a propagation delay of an IP data packet propagating from a software source to a physical network medium interface, comprising:

a module of software code for associating a first time code with the IP data packet when the software source dispatches the IP data packet to the physical network medium interface;

a time-stamping circuit for associating a second time code with the IP data packet when the IP data packet reaches the physical network medium interface; and

,

a difference calculator for subtracting the first time code from the second time code so as to calculate the propagation delay.

36. A system according to claim 35, wherein (i) the time-stamping circuit associates a third time code with the data packet when the data packet is taken from the physical network medium interface, (ii) the module of software code associates a fourth time code with the data packet when the software source receives the data packet, and (iii) the difference calculator subtracts the third time code from the fourth time code so as to calculate an incoming propagation delay.

37. A system according to claim 35, wherein the module of software code samples a time source to acquire the first time code when the software source dispatches the IP data packet to the physical network medium interface.

38. A system according to claim 35, wherein the time-stamping circuit samples a time source to acquire the second time code when the IP data packet reaches the physical network medium interface.

39. A system according to claim 35, wherein the module of software code generates two or more IP data packets, and for each data packet,

(i) the module of software code associates a first time code with the data packet when the software source dispatches the data packet to the physical network medium interface;

(ii) the time-stamping circuit associates a second time code with the data packet when the data element reaches the physical network medium interface;

(iii) the difference calculator calculates the propagation delay for each of the two or more data packets;

wherein a statistics calculator receives the propagation delays of the two or more data packets and calculates statistical values thereof.

40. A system according to claim 39, wherein the statistical values include a minimum propagation delay, a maximum propagation delay, a mean of the two or more propagation delays, a median of the two or more propagation delays, a variance of the two or more propagation delays, and combinations thereof.

41. A system according to claim 39, wherein the two or more data packets include at least two data elements of different sizes.

42. A system according to claim 39, wherein the two or more data packets include at least two data packets of different format types.

43. A system according to claim 35, wherein the difference calculator calculates the propagation delay of the data packets independent of the software source generating and dispatching the data packets.

44. A system according to claim 35, wherein the software source dispatches a data packets having one or more predetermined characteristics.

45. A system according to claim 44, wherein the one or more predetermined characteristics of the data packets are selected from the group consisting of size, format, data content, and combinations thereof.