IP packet identification method and system for TCP connection and UDP stream

• US 20020039371A1
• Filed: 05/18/2001
• Published: 04/04/2002
• Est. Priority Date: 05/18/2000
• Status: Active Grant

• Current Assignee: EXFO Incorporated (11172239 Canada, Inc.)
• Original Assignee: EXFO Service Assurance, Inc. (11172239 Canada, Inc.)
• Inventors: Hedayat, Kaynam, Pyrik, Daniel S., DesRochers, Steven A.
• Granted Patent: US 7,512,069 B2
• Time in Patent Office: Days
• US Class Current: 370/516
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6489 Buffer Management, Threshold setting, Scheduling, Shaping
• CPC Class Codes: H04L 43/026 using flow identification
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 43/087 Jitter
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

A method of measuring jitter of a packet flow includes identifying the data packet flow at each of a first and second network locations by analyzing the data fields of each of the packets in the flow. The method associates a transmit time code with each packet transmitted from the first location, and associates a receive time code with each packet received at the second location. The method calculates inter-arrival times for consecutive pairs of packets by (i) subtracting the transmit time code of the first packet from the transmit time code of the second packet, (ii) subtracting the receive time code associated with the first packet from the receive time code associated with the second packet, and (iii) subtracting the results. The method includes calculating a jitter value as a smoothed version of two or more inter-arrival times, smoothed over a predetermined number of pairs of consecutive packets.

Claims

1. A method of measuring jitter characteristics of a specific data packet flow, including one or more packets, at a first location on a network relative to a second location on the network, comprising:

identifying, at each one of the first and second locations on the network, the specific data packet flow by analyzing data in one or more data fields of each of the packets in the packet flow;

associating a transmit time code with each of the packets transmitted from the first location, associating a receive time code with each of the packets received at the second location, and calculating, for each packet, a propagation delay from the first location to the second location by subtracting the associated transmit time code from the associated receive time code;

for each pair of consecutive packets received at the second location, calculating a delay variation as the difference between the propagation delays calculated for the pair of consecutive packets; and

,

calculating a jitter value as an average delay variation, averaged over a predetermined number of pairs of consecutive packets.

2. A method according to claim 1, wherein the packet flow includes an IP packet flow.

3. A method according to claim 2, wherein identifying the specific data flow further comprises analyzing data in four fields of each of the packets, including a source address field, a source port field, a destination address field and a destination port field.

4. A method according to claim 2, further comprising identifying a particular data packet within a data flow by analyzing data in an IP identifier field of each of the packets.

5. A method of measuring jitter characteristics of a specific data packet flow, including one or more packets, at a first location on a network relative to a second location on the network, comprising:

identifying, at each one of the first and second locations on the network, the specific data packet flow by analyzing data in one or more data fields of each of the packets in the packet flow;

associating a transmit time code with each of the packets transmitted from the first location, associating a receive time code with each of the packets received at the second location, and calculating, for each consecutive pair of packets, an inter-arrival time by (i) subtracting the transmit time code associated with the first packet from the transmit time code associated with the second packet so as to produce a transmit time delta, (ii) subtracting the receive time code associated with the first packet from the receive time code associated with the second packet so as to produce a receive time delta, and (iii) subtracting the transmit delta from the receive delta; and

,

calculating a jitter value as a smoothed version of two or more inter-arrival times, smoothed over a predetermined number of pairs of consecutive packets.

6. A method according to claim 5, wherein the smoothed version of the two or more inter-arrival times is characterized as J_n=J_n−

1+(|D(p<sub>n−

1</sub>,p_n)|−

J<sub>n−

1</sub>)/G.

7. A method according to claim 5, wherein the data packet flow includes an IP packet flow.

8. A method of passively identifying individual packets within an IP packet flow at a first location on a network, comprising:

for each individual packet passing the first location on the network, analyzing data in four fields of the packet, including a source address field, a source port field, a destination address field and a destination port field, so as to identify a particular IP packet flow; and

,

for each individual packet within the particular packet flow, analyzing data in the IP identifier field of the packet so as to identify the individual packet.

9. A method according to claim 8, further including identifying a packet loss event by identifying an individual packet that occurs at the first location and not the second location, or an individual packet that occurs at the second location and not the first location.

10. A method according to claim 8, further including identifying the flow and individual packets at a second location on the network, associating a time code with each packet at the first location, and associating a time code with each packed at the second location.

11. A method according to 10, further including calculating a latency value for each individual packet by subtracting the time code associated with the packet at the first location from the time code associated with the packet at the second location.

12. A method according to 11, further including calculating a jitter value by subtracting the latency values corresponding to two consecutive packets.

13. A method according to 12, further including calculating a smoothed jitter value by combining two or more jitter values according to a predetermined smoothing formula.

14. A method according to 12, further including calculating a smoothed jitter value by combining two or more jitter values according to the formula given by

J_n=J_n−

1+(|D(p<sub>n−

1</sub>,p_n)|−

J<sub>n−

1</sub>)/G.

18. A system according to claim 15, wherein the controller analyzes, for each of the packets, a source address field, a source port field, a destination address field and a destination port field, so as to identify the particular data flow

19. A system according to claim 18, wherein the responder analyzes, for each of the packets, an IP identifier field, so as to identify a particular data packet within the data flow.

20. A system according to claim 15, wherein the responder passes each packet-time code association to the controller via an out of band channel.

21. A system according to claim 15, wherein the responder passes each packet-time code association to the controller via the same channel utilized by the packet flow.

22. A system according to claim 15, further including a configuration device for providing configuration data to the controller and to the responder, and for receiving information regarding the packet flow, the individual packets, and the jitter values.

23. A system according to claim 22, wherein the configuration device communicates with the controller and with the responder via an out of band channel.

24. A system according to claim 22, wherein the configuration device communicates with the controller and the responder via the same channel utilized by the packet flow.

28. A system according to claim 25, wherein the controller analyzes, for each of the packets, a source address field, a source port field, a destination address field and a destination port field, so as to identify the particular data flow

29. A system according to claim 28, wherein the responder analyzes, for each of the packets, an IP identifier field, so as to identify a particular data packet within the data flow.

30. A system according to claim 25, wherein the responder passes each packet-time code association to the controller via an out of band channel.

31. A system according to claim 25, wherein the responder passes each packet-time code association to the controller via the same channel utilized by the packet flow.

32. A system according to claim 25, further including a configuration device for providing configuration data to the controller and to the responder, and for receiving information regarding the packet flow, the individual packets, and the jitter values.

33. A system according to claim 32, wherein the configuration device communicates with the controller and with the responder via an out of band channel.

34. A system according to claim 32, wherein the configuration device communicates with the controller and the responder via the same channel utilized by the packet flow.

15. A system for measuring jitter characteristics of a specific data packet flow, including one or more packets, at a first location on a network relative to a second location on the network, comprising:

a controller at the first location for observing packets on the network, analyzing data in one or more data fields of each of the packets in the packet flow so as to identify the specific data packet flow and the individual packets, and associating a transmit time code with each of the packets as the packet traverses the first location;

a responder at the second location for observing packets on the network, analyzing data in one or more data fields of each of the packets in the data flow so as to identify the specific data packet flow and the individual packets, and associating a receive time code with each of the packets as the packet traverses the second location, so as to form a packet-time code association for each packet;

wherein the responder passes each packet and associated time code to the controller, and the controller (i) calculates, for each packet, a propagation delay from the first location to the second location by subtracting the associated transmit time code from the associated receive time code, (ii) calculates, for each pair of consecutive packets received at the second location, a delay variation as the difference between the propagation delays calculated for the pair of consecutive packets, and (iii) calculates a jitter value as an average delay variation, averaged over a predetermined number of pairs of consecutive packets.

16. A system according to 15, wherein the packet flow includes an IP packet flow.

17. A system according to 15, wherein the one or more data fields includes a source address field, a source port field, a destination address field and a destination port field.

25. A system for measuring jitter characteristics of a specific data packet flow, including one or more packets, at a first location on a network relative to a second location on the network, comprising:

a controller at the first location for observing packets on the network, analyzing data in one or more data fields of each of the packets in the packet flow so as to identify the specific data packet flow and the individual packets, and associating a transmit time code with each of the packets as the packet traverses the first location;

a responder at the second location for observing packets on the network, analyzing data in one or more data fields of each of the packets in the data flow so as to identify the specific data packet flow and the individual packets, and associating a receive time code with each of the packets as the packet traverses the second location, so as to form a packet-time code association for each packet;

wherein the responder passes the packet-time code associations to the controller, and the controller calculates, for each consecutive pair of packets, an inter-arrival time by (i) subtracting the transmit time code associated with the first packet from the transmit time code associated with the second packet so as to produce a transmit time delta, (ii) subtracting the receive time code associated with the first packet from the receive time code associated with the second packet so as to produce a receive time delta, and (iii) subtracting the transmit delta from the receive delta, and the controller further calculates a jitter value as a smoothed version of two or more inter-arrival times, smoothed over a predetermined number of pairs of consecutive packets.

26. A system according to 25, wherein the packet flow includes an IP packet flow.

27. A system according to 25, wherein the one or more data fields includes a source address field, a source port field, a destination address field and a destination port field.