Method and apparatus for analyzing a media path for an internet protocol (IP) media session

• US 7,496,044 B1
• Filed: 03/09/2004
• Issued: 02/24/2009
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Wing, Daniel G.
• Primary Examiner(s): Nguyen; Brian D
• Application Number:
  US10/797,689
• Time in Patent Office: 1,813 Days
• Field of Search: 370/242, 370/255
• US Class Current: 370/242
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

Time To Live (TTL) values are modified in media packets to intentionally cause rejection of the media packets at intermediate nodes in a media path. Rejection notices caused by the TTL modified media packets are then analyzed to isolate Quality of Service (QoS) problems in the media path.

Claims

1. A method for analyzing a media path in a packet switched network, comprising:

providing media trace packets configured to use the same application protocol as actual media payload packets to be sent along the media path and further configured to match, at a protocol layer other than that of the application protocol, a priority indicator to be provided by the actual media packets to specify a desired one of a plurality of priority levels available in the network, wherein the media trace packets have the same class of service bits and same ports as the actual media payload packets, and wherein the media trace packets have a different synchronization identifier than the actual media payload packets;

varying a Time To Live (TTL) value in the media trace packets to intentionally cause faults at intermediate nodes in the media path; and

analyzing fault notices received from the intermediate nodes in the media path caused by the media trace packets.

2. The method according to claim 1 including providing media trace packets configured to use Real Time Protocol (RTP) as the application protocol and further configured to use Differentiated Services Code Point (DSCP) bits as the priority indicator.

3. The method according to claim 1 including:

conducting a media signaling protocol that establishes the media path between a source and destination endpoint;

using a same media header format for the media trace packets and media payload packets; and

setting a first set of TTL values in the media trace packets to a low enough value to cause a fault condition in one of the intermediate modes in the media path such that a portion of each media trace packet causing the fault condition is returned in a corresponding reject notice to the source endpoint.

4. The method according to claim 3 including setting a second set of TTL values so that at least some of the media trace packets reach the destination endpoint.

5. The method according to claim 4 including setting a member bit in the media trace packets that cause the destination endpoint to immediately generate, using a Real Time Control Protocol (RTCP), a media path analysis report for the media trace packets.

6. The method according to claim 5 including determining whether or not to transmit a media stream over the media path according to contents of the media path analysis report.

7. The method according to claim 1 including causing the media trace packets to play out low volume noise when received by a destination endpoint by inserting the low volume noise into media payload fields of the media trace packets before sending the media trace packets along the media path, said low volume noise inserted at a quantity creating uniformly-sized trace packets suitable for thwarting traffic analysis.

8. The method according to claim 1 including:

setting a first TTL value in a first set of the media trace packets that cause a first intermediate node in the media path to reject the first set of media trace packets and send back a first rejection notice; and

setting a second larger TTL value in a second set of the media trace packets that allow the first intermediate node to forward the second set of the media trace packets while causing a second intermediate node in the media path to reject the second set of the media trace packets and send back a second rejection notice.

9. A system for analyzing a media path in a packet switched network, comprising:

means for providing media trace packets configured to use the same application protocol as actual media payload packets to be sent along the media path and further configured to match, at a protocol layer other than that of the application protocol, a priority indicator to be provided by the actual media payload packets to specify a desired one of a plurality of priority levels available in the network, wherein the media trace packets have the same class of service bits and same ports as the actual media payload packets, and wherein the media trace packets have a different synchronization identifier than the actual media payload packets;

means for varying a Time To Live (TTL) value in the media trace packets to intentionally cause faults at intermediate nodes in the media path; and

means for analyzing fault notices received from the intermediate nodes in the media path caused by the media trace packets.

10. A system according to claim 9 including means for providing media trace packets configured to use Real Time Protocol (RTP) as the application protocol and further configured to use Differentiated Services Code Point (DSCP) bits as the priority indicator.

11. A system according to claim 9 including:

means for conducting a media signaling protocol that establishes the media path between a source and destination endpoint;

means for using a same media header format for the media trace packets and media payload packets; and

means for setting a first set of TTL values in the media trace packets to a low enough value to cause a fault condition in one of the intermediate modes in the media path such that a portion of each media trace packet causing the fault condition is returned in a corresponding reject notice to the source endpoint.

12. A system according to claim 11 including means for setting a second set of TTL values so that at least some of the media trace packets reach the destination endpoint.

13. A system according to claim 12 including means for setting a member bit in the media trace packets that cause the destination endpoint to immediately generate, using a Real Time Control Protocol (RTCP), a media path analysis report for the media trace packets.

14. A system according to claim 13 including means for determining whether or not to transmit a media stream over the media path according to contents of the media path analysis report.

15. A system according to claim 9 including means for causing the media trace packets to play out low volume noise when received by a destination endpoint by inserting the low volume noise into media payload fields of the media trace packets before sending the media trace packets along the media path.

16. A system according to claim 9 including:

means for setting a first TTL value in a first set of the media trace packets that cause a first intermediate node in the media path to reject the first set of the media trace packets and send back a first rejection notice; and

means for setting a second larger TTL value in a second set of the media trace packets that allow the first intermediate node to forward the second set of the media trace packets while

causing a second intermediate node in the media path to reject the second set of the media trace packets and send back a second rejection notice.

17. A computer readable medium having stored thereon computer executable instructions for analyzing a media path in a packet switched network that, when executed by a processor, causes the processor to perform the method of:

providing media trace packets configured to use the same application protocol as actual media payload packets to be sent along the media path and further configured to match, at a protocol layer other than that of the application protocol, a priority indicator to be provided by the actual media payload packets to specify a desired one of a plurality of priority levels available in the network, wherein the media trace packets have the same class of service bits and same ports as the actual media payload packets, and wherein the media trace packets have a different synchronization identifier than the actual media payload packets;

varying a Time To Live (TTL) value in the media trace packets to intentionally cause faults at intermediate nodes in the media path; and

analyzing fault notices received from the intermediate nodes in the media path caused by the media trace packets.

18. A computer readable medium according to claim 17 including providing media trace packets configured to use Real Time Protocol (RTP) as the application protocol and further configured to use Differentiated Services Code Point (DSCP) bits as the priority indicator.

19. A computer readable medium according to claim 17 including:

conducting a media signaling protocol that establishes the media path between a source and destination endpoint;

using a same media header format for the media trace packets and media payload packets; and

setting a first set of TTL values in the media trace packets to a low enough value to cause a fault condition in one of the intermediate modes in the media path such that a portion of each media trace packet causing the fault condition is returned in a corresponding reject notice to the source endpoint.

20. A computer readable medium according to claim 19 including setting a second set of TTL values so that at least some of the media trace packets reach the destination endpoint.

21. A computer readable medium according to claim 20 including setting a member bit in the media trace packets that cause the destination endpoint to immediately generate, using a Real Time Control Protocol (RTCP), a media path analysis report for the media trace packets.

22. A computer readable medium according to claim 21 including determining whether or not to transmit a media stream over the media path according to contents of the media path analysis report.

23. A computer readable medium according to claim 17 including causing the media trace packets to play out low volume noise when received by a destination endpoint by inserting the low volume noise into media payload fields of the media trace packets before sending the media trace packets along the media path.

24. A computer readable medium according to claim 17 including:

setting a first TTL value in a first set of the media trace packets that cause a first intermediate node in the media path to reject the first set of the media trace packets and send back a first rejection notice; and

setting a second larger TTL value in a second set of the media trace packets that allow the first intermediate node to forward the second set of the media trace packets while causing a second intermediate node in the media path to reject the second set of the media trace packets and send back a second rejection notice.