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

• US 7,512,069 B2
• Filed: 05/18/2001
• Issued: 03/31/2009
• Est. Priority Date: 05/18/2000
• Status: Expired due to Term

• Current Assignee: EXFO Incorporated (11172239 Canada, Inc.)
• Original Assignee: EXFO Service Assurance, Inc. (11172239 Canada, Inc.)
• Inventors: DesRochers, Steven A., Hedayat, Kaynam, Pyrik, Daniel S.
• Primary Examiner(s): Moe; Aung S
• Assistant Examiner(s): Grey; Christopher P.
• Application Number:
  US09/860,287
• Publication Number:
  US 20020039371A1
• Time in Patent Office: 2,874 Days
• Field of Search: 370/252, 370/241, 370/253, 370/232, 370/230, 370/230.1, 370/235, 370/242, 370/244, 370/245, 370/248, 370/254, 370/352, 370/356, 370/412, 370/428, 370/429, 370503-507, 370516-519, 370/528, 375/226, 702/69, 714/1, 714/2, 714/55, 714/25, 714/798, 714/799, 714/814, 709/220, 709/233, 709/234, 709/248
• US Class Current: 370/230.1
• 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 of normal network traffic, 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, a specific IP packet flow of normal network traffic by analyzing data in one or more data fields of each of the IP packets in the IP packet flow and identifying each IP packet in the IP data flow at said locations;

associating passively a transmit time code with each identifed IP packet in the IP packet flow transmitted from the first location associating passively a receive time code with each of the identified IP packets received at the second location the transmit and receive time codes derived from respective time code generators without requiring synchronization therebetween, and calculating, for each consecutive pair of IP packets, an inter-arrival time by (i) subtracting the transmit time code associated with the first IP packet from the transmit time code associated with the second IP packet so as to produce a transmit time delta, (ii) subtracting the receive time code associated with the first IP packet from the receive time code associated with the second IP 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 IP packets, wherein the jitter value is indicative of network performance,

wherein the smoothed version of the two or more inter-arrival times is characterized as J_n=J<sub>n−

1</sub>+(|D(p<sub>n−

1</sub>,p_n)|−

J<sub>n−

1</sub>)/G, wherein J_n is an average jitter value, J<sub>n−

1</sub> is a previously calculated average jitter value, D(p<sub>n−

1</sub>,p_n) is a variance in delay computed using the n^th and n−

1^th packets, and G is a gain parameter.

2. A method according to claim 1, wherein identifying the IP packet flow further comprises analyzing data in four fields of each of the IP packets, including a source address field, a source port field, a destination address field and a destination port field.

3. A method according to claim 1, further comprising identifying a particular IP packet within the IP packet flow by analyzing data in an IP identifier field of each of the IP packets.

4. A method according to claim 1, wherein associating passively each of the transmit and receive time codes with each identified IP packet is accomplished without modifying the specific data packet flow.

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

for each individual IP packet passing the first location on the network, analyzing data in four fields of the IP 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 of normal network traffic;

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

identifying the IP packet flow and individual IP packets at a second location on the network, associating a time code with each IP packet at the first location, and associating a time code with each IP packet at the second location, wherein the associated time codes at the first and second location are derived from respective time code generators without requiring synchronization therebetween;

calculating a latency value for each individual IP packet by subtracting the time code associated with the IP packet at the first location from the time code associated with the IP packet the second location;

calculating a jitter value by subtracting the latency values corresponding to two consecutive IP packets; and

calculating a smoothed jitter value by combining two or more jitter values according to the formula given by J_n=J<sub>n−

1</sub>+(|D(p<sub>n−

1</sub>, p_n)|−

J<sub>n−

1</sub>)/G, wherein J_n is an average jitter value, J<sub>n−

1</sub> is a previously calculated average jitter value, D(p<sub>n−

1</sub>, p_n) is a variance in delay computed using the n^th and n−

1^th packets, and G is a gain parameter.

6. A system for measuring jitter characteristics of a specific data packet flow of normal network traffic, 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 IP packet flow and to identify the individual IP packets, and associating passively a transmit time code with each of the IP 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 a specific IP packet flow and to identify the individual IP packets, and associating passively a receive time code with each of the IP packets as the packet traverses the second location, so as to form a packet-time code association for each IP packet;

wherein the responder passes the packet-time code associations to the controller, and the controller calculates, for each consecutive pair of IP packets, an inter-arrival time without requiring synchronization to the responder, by

(i) subtracting the transmit time code associated with the first IP packet from the transmit time code associated with the second IP packet so as to produce a transmit time delta,

(ii) subtracting the receive time code associated with the first IP packet from the receive time code associated with the second IP packet so as to produce a receive time delta,

(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 IP packets, wherein the jitter value is indicative of network performance,

(iv) calculating a latency value for each individual IP packet by subtracting the time code associated with the IP packet at the first location from the time code associated with the IP packet at the second location,

(v) calculating a jitter value by subtracting the latency values corresponding to two consecutive IP packets, and

(vi) calculating a smoothed jitter value by combining two or more jitter values according to the formula given by J_n=J<sub>n−

1</sub>+(|D(p<sub>n−

1</sub>, p_n)|−

J<sub>n−

1</sub>)/G, wherein J_n, is an average jitter value, J<sub>n−

1</sub> is a previously calculated average jitter value, D(p<sub>n−

1</sub>,p_n) is a variance in delay computed using the n^th and n−

1^th packets, and G is a gain parameter.

7. A system according to claim 6, 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.

8. A system according to claim 6, wherein the controller analyzes, for each of the IP packets, a source address field, a source port field a destination address field and a destination port field, so as to identify the particular IP packet flow.

9. A system according to claim 8, wherein the responder analyzes, for each of the IP packets, an IP identifier field, so as to identify a particular IP packet within the IP packet flow.

10. A system according to claim 6, wherein the responder passes each packet-time code association to the controller via an out of band channel.

11. A system according to claim 6, wherein the responder passes each packet-time code association to the controller via the same channel utilized by the IP packet flow.

12. A system according to claim 6, further including a configuration device for providing configuration data to the controller and to the responder, and for receiving infomation regarding the IP packet flow, the individual IP packets, and the jitter values.

13. A system according to claim 12, wherein the configuration device communicates with the controller and with the responder via an out of band channel.

14. A system according to claim 12, wherein the configuration device communicates with the controller and the responder via the same channel utilized by the packet flow.

15. A system according to claim 6, wherein associating passively each of the transmit and receive time codes with each identified IP packet accomplished without modifying the specific data packet flow.