SWITCH FABRIC END-TO-END CONGESTION AVOIDANCE MECHANISM

• US 20080198746A1
• Filed: 02/15/2008
• Published: 08/21/2008
• Est. Priority Date: 02/21/2007
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Agarwal, Puneet, Kwan, Bruce H.
• Granted Patent: US 8,520,517 B2
• Time in Patent Office: Days
• US Class Current: 370/231
• 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 47/18 End to end
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 49/506 Backpressure
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Aspects of a switch fabric end-to-end congestion avoidance mechanism are presented. Aspects of a system for end-to-end congestion avoidance in a switch fabric may include at least one circuit that enables reception of a congestion notification message that specifies a traffic flow identifier. The circuitry may enable increase or decrease of a current rate for transmission of data link layer (DLL) protocol data units (PDU) associated with the specified traffic flow identifier as a response to the reception of the congestion notification message.

Claims

1. A method for controlling data transmission in a communications system, the method comprising:

receiving a congestion notification message that specifies a traffic flow identifier; and

increasing or decreasing a current rate for transmitting data link layer (DLL) protocol data units (PDU) associated with said specified traffic flow identifier as a response to said received congestion notification message.

2. The method according to claim 1, comprising determining said response to said received congestion notification message is determined based on at least one of:

a congestion avoidance mode, and a congestion notification timer value.

3. The method according to claim 2, comprising transitioning said congestion avoidance mode from a first congestion state to a second congestion state based on said received congestion notification message.

4. The method according to claim 2, comprising transitioning said congestion avoidance mode from a second congestion state to a first congestion state when a congestion notification timer value is greater than a timeout value.

5. The method according to claim 4, wherein said congestion notification timer value measures a time duration following a time instant at receipt of a last congestion notification message.

6. The method according to claim 1, wherein said congestion notification message comprises at least one of:

a transmitter index, a path index, a priority group identifier, a receiver index, and a transmission rate modification request.

7. The method according to claim 6, wherein said transmission rate modification request comprises one of:

an increase request, and a decrease request.

8. The method according to claim 7, wherein said decreasing said current rate occurs when said transmission rate modification request is said decrease request, and a decrease wait timer value is greater than or equal to a minimum decrease wait time value.

9. The method according to claim 8, wherein said decrease wait timer value measures a time duration following a time instant of a last decrease in a rate for transmitting said DLL PDUs.

10. The method according to claim 8, comprising computing a subsequent rate for transmitting said DLL PDUs by dividing said current rate by a decrease factor.

11. The method according to claim 7, wherein said increasing said current rate occurs when said transmission rate modification request is said increase request, and an increase wait timer value is greater than or equal to a minimum increase wait time value.

12. The method according to claim 11, wherein said increase wait timer value measures a time duration following a time instant of a last increase in a rate for transmitting said DLL PDUs.

13. The method according to claim 11, comprising computing a subsequent rate for transmitting said DLL PDUs by multiplying said current rate by a multiplicative increase factor.

14. The method according to claim 11, comprising computing a subsequent rate for transmitting said DLL PDUs by adding said current rate and an additive increase factor.

15. The method according to claim 11, wherein said increased said current rate is less than or equal to a maximum rate.

16. A system for controlling data transmission in a communications system, the system comprising:

at least one circuit that enables reception of a congestion notification message that specifies a traffic flow identifier; and

said at least one circuit enables increase or decrease of a current rate for transmission of data link layer (DLL) protocol data units (PDU) associated with said specified traffic flow identifier as a response to said reception of said congestion notification message.

17. The system according to claim 16, wherein said response to said reception of said congestion notification message is determined based on at least one of:

a congestion avoidance mode, and a congestion notification timer value.

18. The system according to claim 17, wherein said at least one circuit enables transition of said congestion avoidance mode from a first congestion state to a second congestion state based on said reception of said congestion notification message.

19. The system according to claim 17, wherein said at least one circuit enables transition of said congestion avoidance mode from a second congestion state to a first congestion state when a congestion notification timer value is greater than a timeout value.

20. The system according to claim 19, wherein said congestion notification timer value measures a time duration following a time instant at receipt of a last congestion notification message.

21. The system according to claim 16, wherein said congestion notification message comprises at least one of:

a transmitter index, a path index, a priority group identifier, a receiver index, and a transmission rate modification request.

22. The system according to claim 21, wherein said transmission rate modification request comprises one of:

an increase request, and a decrease request.

23. The system according to claim 22, wherein said decrease of said current rate occurs when said transmission rate modification request is said decrease request, and a decrease wait timer value is greater than or equal to a minimum decrease wait time value.

24. The system according to claim 23, wherein said decrease wait timer value measures a time duration following a time instant of a last decrease in a rate for transmitting said DLL PDUs.

25. The system according to claim 23, wherein said at least one circuit enables computation of a subsequent rate for transmitting said DLL PDUs by division of said current rate by a decrease factor.

26. The system according to claim 22, wherein said increase of said current rate occurs when said transmission rate modification request is said increase request, and an increase wait timer value is greater than or equal to a minimum increase wait time value.

27. The system according to claim 26, wherein said increase wait timer value measures a time duration following a time instant of a last increase in a rate for transmitting said DLL PDUs.

28. The system according to claim 26, wherein said at least one circuit enables computation of a subsequent rate for transmission of said DLL PDUs by multiplication of said current rate by a multiplicative increase factor.

29. The system according to claim 26, wherein said at least one circuit enables computation of a subsequent rate for transmission of said DLL PDUs by addition of said current rate and an additive increase factor.

30. The system according to claim 26, wherein said increase of said current rate is less than or equal to a maximum rate.