System and method for intelligently analyzing performance of a device under test

• US 8,004,994 B1
• Filed: 11/01/2006
• Issued: 08/23/2011
• Est. Priority Date: 11/01/2006
• Status: Expired due to Fees

• Current Assignee: Azimuth Systems, Inc. (Anritsu Corporation)
• Original Assignee: Azimuth Systems, Inc. (Anritsu Corporation)
• Inventors: Spilman, Jeremy, Graziani, Jose, Darisi, Prashant
• Primary Examiner(s): Harper; Kevin C
• Assistant Examiner(s): ANDREWS, LEON T
• Application Number:
  US11/555,324
• Time in Patent Office: 1,756 Days
• Field of Search: 370/230, 370/231, 370/232, 370/235, 370/236, 370/241.1, 370/242, 370/245, 370/247, 370/248, 370/253, 370/277, 370/395.65, 370/395.7, 370/395.71, 370/395.72, 370/516, 370/519, 370/252, 370/395.6, 714/748
• US Class Current: 370/241
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER

Abstract

A method and apparatus is provided that enables accurate measurement of drop rate and delay in a System Under Test (SUT) by one or more monitoring devices even when the frame error rate of the monitoring devices may be imperfect. During a packet drop measurement process, ancillary information is identified and analyzed to determine if the ancillary information can be used to infer receipt of packets when explicit information regarding receipt is not present. A delay measurement process incorporates the time required to re-transmit packets into the delay measurement to more accurately reflect SUT operation.

Claims

1. A method of measuring a quality of service statistic of a system under test (SUT) includes the steps of:

monitoring traffic exchanged between a Source Device Under Test (Source DUT) and a Destination Device Under Test (Destination DUT), including storing packets of the traffic in a source list;

monitoring traffic received by the Destination DUT, including storing packets of received traffic in a destination list;

generating a dropped packet list by comparing the source list and the destination list to identify packets that are in the source list but not in the destination list;

validating the dropped packet list using ancillary information to determine whether a packet in the dropped packet list was actually received by the Destination DUT;

calculating the quality of service statistic based on the validated dropped packet list; and

outputting the quality of service statistic in tangible form.

2. The method of claim 1, wherein the step of monitoring traffic exchanged between the Source DUT and Destination DUT includes the steps of recording acknowledgements received by the Source DUT in response to source packet transmissions, and wherein the ancillary information includes the recorded acknowledgements.

3. The method of claim 2 wherein the Source DUT and the Destination DUT communicate using an 802.11 WiFi protocol, and wherein the acknowledgement is an 802.11 ACK packet.

4. The method of claim 1, wherein the step of validating infers receipt of a packet in the dropped packet list when an acknowledgement is received for the dropped packet by the Source DUT within a protocol acknowledgement window (PAW).

5. The method of claim 4 wherein the step of validating further removes the packet from the dropped packet list when the acknowledgement for the packet is received within the PAW.

6. The method of claim 1 further including the step of generating a gap list, where each gap in the gap list specifies a range of packets that are found on the source list but not on the destination list.

7. The method of claim 6 wherein the step of validating the dropped packet list uses the gap list to identify ancillary information of interest for validating packet drops.

8. An analyzer in a System Under Test (SUT) comprising a computer processor including a computer readable medium having program code stored thereon, the analyzer comprising:

program code for generating a dropped packet list by comparing a source list of packets exchanged between a Source Device Under Test (Source DUT) and a Destination DUT to a destination list of packets received by the destination DUT to identify packets that are in the source list but not in the destination list;

program code for validating the dropped packet list using ancillary information of the source list to identify packets that are in the source list but not in the destination list, and were actually received by the Destination DUT;

program code for calculating a quality of service statistic based on the validated dropped packet list; and

program code for outputting the quality of service statistic in tangible form.

9. The analyzer of claim 8, further including program code for generating a gap list comprising a plurality of gap entries, each gap entry identifying ancillary information that may be used to determine whether receipt of a packet can be inferred.

10. The analyzer of claim 8, wherein the ancillary information includes an acknowledgement for a packet that is received within a protocol acknowledgement window (PAW).

11. A method of measuring a delay of a System Under Test (SUT) includes the steps of:

monitoring traffic exchanged between a Source Device Under Test (Source DUT) and a Destination Device Under Test (Destination DUT) including maintaining in a source list a time stamp of each packet transmitted and received by the Source DUT, and maintaining in a destination list a time stamp of each packet transmitted and received by the Destination DUT;

selecting a packet from the source list including storing a packet transmission timestamp (PTT) for the packet;

searching the source list to locate a valid acknowledgement associated with the packet, wherein the valid acknowledgement includes an acknowledgement to a re-transmitted version of the packet;

locating a matching entry in the destination list, the matching entry comprising the retransmitted version of the packet in the destination list, including retrieving a time stamp for the matching entry (D-MATCH);

computing delay of the packet using the PTT and the D-MATCH and

outputting the delay of the SUT in tangible form.

12. The method of claim 11 wherein the valid acknowledgement packet is an acknowledgement packet that is received within a Protocol Acknowledgement Window (PAW) for the retransmitted packet.

13. An analyzer in a System Under Test (SUT) comprising a computer processor including a computer readable medium having program code stored thereon, comprising:

program code for searching a list of packets exchanged between a Source Device Under Test (Source DUT) and a Destination Device Under Test (Destination DUT) to measure a delay of the System Under Test (SUT), including program code for comparing a time stamp of a transmitted packet to a time stamp of a matching entry in the destination list, the matching entry corresponding to a retransmission of the transmitted packet to determine the delay associated with the transmitted packet;

program code for outputting a quality of service statistic based on the determined delay in tangible form.