Methods and apparatus for network congestion control

• US 7,327,680 B1
• Filed: 11/05/2002
• Issued: 02/05/2008
• Est. Priority Date: 11/05/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Kloth, Raymond J.
• Primary Examiner(s): Chan; Wing
• Assistant Examiner(s): ROBERTS, BRIAN S
• Application Number:
  US10/289,090
• Time in Patent Office: 1,918 Days
• Field of Search: None
• US Class Current: 370/235
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 47/39 Credit based

Abstract

Methods and apparatus are provided for controlling congestion in a network such as a fiber channel network. Techniques are provided for detecting congestion at a shared resource such as a network node. When a controller sends data to a shared resource, the delay between sending the data and receiving a credit is measured. If the delay is significant, it is assumed that the path towards the destination associated with the data is congested and subsequent traffic from the port associated with the data is blocked.

Claims

1. A method, comprising:

identifying a received data sequence at a buffer controller in a fibre channel network, the received data sequence having a source corresponding to a port among a plurality of ports coupled to the buffer controller and having a destination reachable through a shared resource coupled to the buffer controller, wherein the shared resource is used by traffic associated with the plurality of ports coupled to the buffer controller to reach a plurality of destinations;

forwarding the received data sequence to the shared resource;

receiving a transmission credit from the shared resource, wherein the port associated with the received data sequence is blocked after the transmission credit is received if the transmission credit is not received from the shared resource within a predetermined period of time.

2. The method of claim 1, wherein the port is blocked if the transmission credit is not received within a period of time identified as a congestion latency.

3. The method of claim 1, wherein the port is blocked by masking the port.

4. The method of claim 1, wherein data is forwarded to the shared resource from the plurality of ports in round robin fashion.

5. The method of claim 1, wherein the plurality of ports are coupled to a plurality of fibre channel switches.

6. The method of claim 1, wherein the plurality of destinations comprise fibre channel switches, hosts, and disks.

7. The method of claim 1, wherein the shared resource is in a depleted state when the received data sequence is sent to the shared resource.

8. The method of claim 7, wherein the port associated with the received data sequence is unblocked when the shared resource is no longer in the depleted state.

9. The method of claim 7, wherein the shared resource is no longer in the depleted state and enters the shared state when the number of free buffers associated with the shared resource is greater than a depletion threshold.

10. The method of claim 7, wherein the shared resource is a memory and the depletion threshold indicates the level when fewer than 10% of total buffers remain.

11. The method of claim 7, wherein the port associated with the received data sequence is unblocked when a starvation criterion is reached.

12. The method of claim 11, wherein the starvation criterion is reached when a predetermined number of data sequences have been forwarded by the shared resource and the port associated with the received data sequence has not been unblocked.

13. The method of claim 11, wherein the starvation criterion is reached after a predetermined period of time has elapsed.

14. An apparatus comprising:

means for identifying a received data sequence at a buffer controller in a fibre channel network, the received data sequence having a source corresponding to a port among plurality of ports coupled to the buffer controller and having a destination reachable through a shared resource coupled to the buffer controller, wherein the shared resource is used by traffic associated with the plurality of ports coupled to the buffer controller to reach a plurality of destinations;

means for forwarding the received data sequence to the shared resource;

means for receiving a transmission credit from the shared resource, wherein the port associated with the received data sequence is blocked after the transmission credit is received if the transmission credit is not received from the shared resource within a predetermined period of time.

15. The apparatus of claim 14, wherein the predetermined period of time is a congestion latency.

16. The apparatus of claim 14, wherein the port is blocked by masking the port.

17. The apparatus of claim 14, wherein data is forwarded to the shared resource from the plurality of ports in round robin fashion.

18. The apparatus of claim 14, wherein the plurality of ports are coupled to a plurality of fibre channel switches.

19. The apparatus of claim 14, wherein the plurality of destinations comprise fibre channel switches, hosts, and disks.

20. The apparatus of claim 14, wherein the shared resource is in a depleted state when the received data sequence is sent to the shared resource.

21. An apparatus comprising:

a plurality of input ports configured to receive data sequences having destinations reachable through a shared resource,

a buffer controller configured to pull a received data sequence from one of the plurality of input ports, forward the received data sequence to the shared resource, and receive a transmission credit from the shared resource after a predetermined period of time has elapsed, wherein an input port associated with the received data sequence is blocked after the transmission credit is received to control congestion in a fibre channel network if the transmission credit is not received from the shared resource within a predetermined period of time.

22. The apparatus of claim 21, wherein the port is blocked if the transmission credit is not received within a period of time identified as a congestion latency.

23. The apparatus of claim 21, wherein the port is blocked by masking the port.

24. The apparatus of claim 21, wherein data is forwarded to the shared resource from the plurality of ports in round robin fashion.

25. The apparatus of claim 21, wherein the plurality of ports are coupled to a plurality of fibre channel switches.

26. The apparatus of claim 21, wherein the plurality of destinations comprise fibre channel switches, hosts, and disks.

27. The apparatus of claim 21, wherein the shared resource is in a depleted state when the received data sequence is sent to the shared resource.

28. The apparatus of claim 27, wherein the port associated with the received data sequence is unblocked when the shared resource is no longer in the depleted state.

29. The apparatus of claim 27, wherein the shared resource is no longer in the depleted state and enters the shared state when the number of free buffers associated with the shared resource is greater than a depletion threshold.

30. The apparatus of claim 27, wherein the shared resource is a memory and the depletion threshold indicates the level when fewer than 10% of total buffers remain.

31. The apparatus of claim 27, wherein the port associated with the received data sequence is unblocked when a starvation criterion is reached.

32. The apparatus of claim 31, wherein the starvation criterion is reached when a predetermined number of data sequences have been forwarded by the shared resource and the port associated with the received data sequence has not been unblocked.

33. The apparatus of claim 31, wherein the starvation criterion is reached after a predetermined period of time has elapsed.