Edge Node for a network domain

• US 20100034090A1
• Filed: 11/10/2006
• Published: 02/11/2010
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bader, Attila, Csaszar, Andras, Takacs, Attila
• Granted Patent: US 8,509,085 B2
• Time in Patent Office: Days
• US Class Current: 370/236
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/26 using explicit feedback to the source, e.g. choke packets
• CPC Class Codes: H04L 47/31 by tagging of packets, e.g. using discard eligibility [DE] bits

Abstract

An egress node is proposed for a network domain that comprises at least one ingress node for receiving and routing data units belonging to a plurality of flows into said network domain, a plurality of interior routers for routing said data units through said network domain, and said egress node(s). One or more of the interior routers is arranged to detect whether it is subject to a congestion condition and to congestion mark routed data units if it is subject to said congestion condition. The egress node comprises a control element arranged for performing a congestion handling function that comprises a part for detecting the presence of congestion marked data units arriving at said edge node, and a part for reacting to the detection of the presence of congestion marked data units by invoking a congestion control process. The congestion control comprises sending to said ingress node an instruction for terminating one or more flows to thereby reduce a traffic load, waiting a predetermined period of time and then determining whether congestion marked data units are still arriving at said edge node, and if congestion marked data units are still arriving, repeating the sending and waiting steps.

Claims

1. An edge node for a network domain that comprises at least one ingress node for receiving and routing data units belonging to a plurality of flows into said network domain, a plurality of interior routers for routing said data units through said network domain, and at least one egress node for routing said data units out of said network domain, at least one of said interior routers being arranged to detect whether it is subject to a congestion condition and to congestion mark routed data units if it is subject to said congestion condition, said edge node being arranged to act as said egress node and comprising:

a control element arranged for performing a congestion handling function that comprises

a detecting part, for detecting the presence of congestion marked data units arriving at said edge node,

a reacting part for reacting to the detection of the presence of congestion marked data units by invoking a congestion control process that comprises;

a) sending to said ingress node an instruction for terminating one or more flows to reduce a traffic load,

b) waiting a predetermined period of time and then determining whether congestion marked data units are still arriving at said edge node, and

c) if congestion marked data units are still arriving, repeating steps a) and b).

2. The edge node of claim 1, wherein said control element is arranged such that said congestion control process further comprises setting a value of a load reduction parameter in response to the detection of congestion marked data units, and instructing said ingress node to terminate one or more flows to reduce traffic load in accordance with said value of said load reduction parameter.

3. The edge node of claim 2, wherein said control element is arranged such that said load reduction parameter is expressed in terms of one of an absolute load and a relative load.

4. The edge node of claim 2, wherein said control element is arranged such that said congestion control process further comprises a flow detection routine for detecting which flows are affected by congestion, and from which one or more flows are to be terminated in accordance with said value of said load reduction parameter.

5. The edge node of claim 4, wherein said control element is arranged such that said congestion control process furthermore comprises a flow selection routine for selecting which flows to terminate, and an indication of said selected flows.

6. The edge node of claim 2, wherein said congestion marked data units may comprise a first marker or a second marker, said first marker indicating that a traffic load at an interior node exceeds a first load threshold and said second marker indicating that a traffic load at an interior node exceeds a second load threshold corresponding to a higher load than said first load threshold, and said control element is arranged such that said congestion control process further comprises setting said load reduction parameter to a first load reduction value in response to detecting said first marker and to a second load reduction value in response to detecting said second marker, said second load reduction value corresponding to larger load reduction than said first load reduction value.

7. The edge node of claim 6, wherein said control element is arranged such that said second load reduction value corresponds to a load reduction that is equal to the difference between the second load threshold and the first load threshold.

8. The edge node of claim 6, wherein said control element is arranged such that said second load reduction value corresponds to a load reduction that is equal to the quotient of the difference between the second load threshold and the first load threshold, divided by the second load threshold.

9. The edge node of claim 6, wherein said control element is arranged for

d) sending to said ingress node said instruction for terminating one or more flows to reduce a traffic load corresponding to a momentary first load reduction value,

e) waiting said predetermined period of time and then determining whether congestion marked data units containing said first marker are still arriving at said edge node, and

f) if said first marker is still detected, setting said load reduction parameter to a new momentary first load reduction value smaller than the previous momentary value and repeating steps d) and e).

10. The edge node of claim 9, wherein said control element is arranged such that said setting of said new momentary first load reduction value smaller than the previous momentary value is a sum of an overall sequence of consecutively set momentary first load reduction values is smaller than or equal to the second load reduction value.

11. The edge node of claim 1, wherein said control element is arranged such that said predetermined period of time is a fixed value.

12. The edge node of claim 1, wherein said predetermined period of time is an adaptable value and said control element is arranged such that an adaptation routine for said predetermined period of time is provided.

13. The edge node of claim 12, wherein said control element is arranged such that said congestion handling function comprises a routine for determining a data unit propagation time from said ingress node to said egress node, and said adaptation routine is arranged for adapting said predetermined period of time on the basis of a data unit propagation time.

14. The edge node of claim 13, wherein said routine for determining a data unit propagation time comprises monitoring one or more periodic refresh messages, dedicated query and response messages and keep-alive signalling messages exchanged between said ingress node and said egress node.

15. An interior router for a network domain that comprises at least one ingress node for receiving and routing data units belonging to a plurality of flows into said network domain, a plurality of interior routers for routing said data units through said network domain, and at least one egress node for routing said data units out of said network domain, said interior router comprising:

a control element arranged to detect whether a load at said interior router exceeds a first load threshold or a second load threshold higher than said first load threshold, and to generate congestion marked data units comprising a first marker if the traffic load exceeds the first load threshold and a second marker if the traffic load exceeds the second load threshold.

16. A method for controlling an egress node for a network domain that comprises at least one ingress node for receiving and routing data units belonging to a plurality of flows into said network domain, a plurality of interior routers for routing said data units through said network domain, and at least one egress node for routing said data units out of said network domain, at least one of said interior routers being arranged to detect whether the egress node is subject to a congestion condition and to congestion mark routed data units if it is subject to said congestion condition, the method comprising:

detecting the presence of congestion marked data units arriving at said edge node,

reacting to the detection of the presence of congestion marked data units by invoking a congestion control process that comprises

a) a terminating instruction to said ingress node an instruction for terminating one or more flows to reduce a traffic load,

b) waiting a predetermined period of time and then determining whether congestion marked data units are still arriving at said edge node, and

c) if congestion marked data units are still arriving, repeating steps a) and b).

17. The method of claim 16, further comprising

setting a value of a load reduction parameter in response to the detection of congestion marked data units, and arranging said terminating instruction to terminate one or more flows to reduce traffic load in accordance with said value of said load reduction parameter.

18. The method of claim 17, wherein said load reduction parameter is expressed in terms of one of an absolute load and a relative load.

19. The method of claim 17, wherein said congestion control process further comprises a flow detection routine for detecting which flows are affected by congestion, and said terminating instruction comprises an indication of flows from which one or more are to be terminated in accordance with said value of said load reduction parameter.

20. The method of claim 19, wherein said congestion control process furthermore comprises a flow selection routine for selecting which flows to terminate, and wherein said instruction comprises an indication of said selected flows.

21. The method of claim 17, wherein said congestion marked data units may comprise a first marker or a second marker, said first marker indicating that a traffic load at an interior node exceeds a first load threshold and said second marker indicating that a traffic load at an interior node exceeds a second load threshold corresponding to a higher load than said first load threshold, and said congestion control process furthermore comprises setting said load reduction parameter to a first load reduction value in response to detecting said first marker and to a second load reduction value in response to detecting said second marker, said second load reduction value corresponding to larger load reduction than said first load reduction value.

22. The method of claim 21, wherein said second load reduction value corresponds to a load reduction that is equal to the difference between the second load threshold and the first load threshold.

23. The method of claim 21, wherein said second load reduction value corresponds to a load reduction that is equal to the quotient of the difference between the second load threshold and the first load threshold, divided by the second load threshold.

24. The method of claim 21, wherein said congestion control process further

d) sending to said ingress node said instruction for terminating one or more flows to thereby reduce a traffic load corresponding to a momentary first load reduction value,

e) waiting said predetermined period of time and then determining whether congestion marked data units containing said first marker are still arriving at said edge node,

f) if said first marker is still detected, setting said load reduction parameter to a new momentary first load reduction value smaller than the previous momentary value and repeating steps d) and e).

25. The method of claim 24, wherein said setting of said new momentary first load reduction value smaller than the previous momentary value is arranged such that a sum of an overall sequence of consecutively set momentary first load reduction values is smaller than or equal to the second load reduction value.

26. The method of claim 16, wherein said control element is arranged such that said predetermined period of time is a fixed value.

27. The method of claim 16, wherein said predetermined period of time is an adaptable value and said control element is arranged such that an adaptation routine for said predetermined period of time is provided.

28. The method of claim 27, further comprising

said congestion handling function determining a data unit propagation time from said ingress node to said egress node, and

said adaptation routine adapting said predetermined period of time on the basis of said data unit propagation time.

29. The method of claim 28, wherein said routine for determining a data unit propagation time comprises monitoring one or more periodic refresh messages, dedicated query and response messages and keep-alive signalling messages exchanged between said ingress node and said egress node.

30. A method of controlling an interior router for a network domain that comprises at least one ingress node for receiving and routing data units belonging to a plurality of flows into said network domain, a plurality of interior routers for routing said data units through said network domain, and at least one egress node for routing said data units out of said network domain, comprising:

detecting whether a load at said interior router exceeds a first load threshold or a second load threshold higher than said first load threshold, and

generating congestion marked data units comprising a first marker if the traffic load exceeds the first load threshold and a second marker if the traffic load exceeds the second load threshold.

31-32. -32. (canceled)