Quality of service testing of communications networks

• US 20070076605A1
• Filed: 09/13/2005
• Published: 04/05/2007
• Est. Priority Date: 09/13/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Cidon, Israel, Zangiri, Benny, Sidi, Moshe, Horn, Lior
• Granted Patent: US 7,835,293 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04L 43/0847 Transmission error
• CPC Class Codes: H04L 43/0852 Delays
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

Network testing is conducted using a pair of traffic agents that acts as sender and receiver endpoints. The sending traffic agent generates and transmits a stream of packet batches, each batch being composed of high and low priority packets in a predetermined sending order. The receiving traffic agent analyzes the order of packet arrival in the stream relative to the sending order, and returns results to a traffic control module. Path speed and the priority classification of the traffic are parameters used to configure the tests. The tests are typically run periodically under different load conditions in order to evaluate the effects of other traffic being concurrently transiting the network.

Claims

1. A method of testing packet prioritization in a data network, comprising the steps of:

transmitting a stream of data packets over said network from a sender toward a receiver, wherein said stream is formed of a sequence of high priority packets and low priority packets in a predetermined sending order;

receiving said stream at said receiver;

determining a difference between a receiving order of packet arrival at said receiver of said high priority packets and said low priority packets in said stream relative to said sending order; and

responsively to said difference, evaluating performance of said packet prioritization in said network.

2. The method according to claim 1, wherein said step of determining a difference comprises determining a number of overtakings of said low priority packets by said high priority packets.

3. The method according to claim 1, and said step of determining a difference comprises determining differences between respective times of arrival at said receiver of said low priority packets and said high priority packets.

4. The method according to claim 1, wherein said high priority packets are RTP packets.

5. The method according to claim 1, wherein said low priority packets are TCP type packets created using a raw socket mechanism.

6. The method according to claim 1, wherein said sequence is arranged in groups, each of said groups having a predefined number of packet batches, said packet batches being transmitted successively with a predetermined time separation therebetween.

7. The method according to claim 6, wherein said packet batches each have a predefined sequence of said high priority packets and said low priority packets, all of said low priority packets preceding any of said high priority packets.

8. The method according to claim 1, wherein said step of transmitting comprises the steps of:

receiving error messages from said receiver; and

determining said receiving order of packet arrival at said receiver responsively to respective times of arrival of said error messages.

9. The method according to claim 8, wherein said step of transmitting further comprises assigning a common TTL value to a field of said high priority packets and a field of said low priority packets, and iteratively increasing said TTL value and repeating said step of transmitting using said increased TTL value.

10. A computer software product, including a computer-readable medium in which computer program instructions are stored, which instructions, when read by a computer, cause the computer to perform a method for testing packet prioritization in a data network, comprising the steps of:

transmitting a stream of data packets over said network from a sender toward a receiver, wherein said stream is formed of a sequence of high priority packets and low priority packets in a predetermined sending order;

receiving said stream at said receiver;

determining a difference between a receiving order of packet arrival at said receiver of said high priority packets and said low priority packets in said stream relative to said sending order; and

responsively to said difference, evaluating performance of said packet prioritization in said network.

11. The computer software product according to claim 10, wherein said step of determining a difference comprises determining a number of overtakings of said low priority packets by said high priority packets.

12. The computer software product according to claim 10, and said step of determining a difference comprises determining differences between respective times of arrival at said receiver of said low priority packets and said high priority packets.

13. The computer software product according to claim 10, wherein said sequence is arranged in groups, each of said groups having a predefined number of packet batches, said packet batches being transmitted successively with a predetermined time separation therebetween.

14. The computer software product according to claim 13, wherein said packet batches each have a predefined sequence of said high priority packets and said low priority packets, all of said low priority packets preceding any of said high priority packets.

15. The computer software product according to claim 13, wherein said step of transmitting comprises the steps of:

receiving error messages from said receiver; and

determining said receiving order of packet arrival at said receiver responsively to respective times of arrival of said error messages.

16. The computer software product according to claim 15, wherein said step of transmitting further comprises assigning a common TTL value to a field of said high priority packets and a field of said low priority packets, and iteratively increasing said TTL value and repeating said step of transmitting using said increased TTL value.

17. An apparatus for testing packet prioritization in a data network, comprising:

a sending traffic agent and a receiving traffic agent, which are respectively coupled to a sender endpoint and a receiver endpoint of a path through the network; and

a testing center coupled to said receiving traffic agent and to said sending traffic agent, said testing center being operative to instruct said sending traffic agent to transmit a stream of data packets to said receiving traffic agent, wherein said stream is formed of a sequence of high priority packets and low priority packets in a predetermined sending order, said stream being received by said receiving traffic agent, said receiving traffic agent being operative for determining an order of packet arrival at said receiver endpoint of said high priority packets and said low priority packets in said stream and for calculating responsively to said order of packet arrival a difference between a receiving order of packet arrival at said receiver endpoint of said high priority packets and said low priority packets in said stream relative to said sending order that represents a quality of said packet prioritization in said network.

18. The apparatus according to claim 17, wherein said receiving traffic agent is operative for calculating said difference by determining a number of overtakings of said low priority packets by said high priority packets.

19. The apparatus according to claim 17, wherein said receiving traffic agent is operative for calculating said difference by determining differences between respective times of arrival at said receiver endpoint of said low priority packets and said high priority packets.

20. The apparatus according to claim 17, wherein said sequence is arranged in packet batches, each of said packet batches being transmitted successively with a predetermined time separation therebetween.

21. The apparatus according to claim 20, wherein said packet batches each have a predefined sequence of said high priority packets and said low priority packets, all of said low priority packets preceding any of said high priority packets.

22. The apparatus according to claim 17, wherein said sending traffic agent is operative for receiving error messages from a receiver;

and

determining said receiving order of packet arrival at said receiver responsively to respective times of arrival of said error messages.

23. The apparatus according to claim 22, wherein said sending traffic agent is operative for assigning a common TTL value to a field of said high priority packets and a field of said low priority packets, and iteratively increasing said TTL value and executing retransmissions of said stream using a respective said increased TTL value.