Method and system for detecting congestion and over subscription in a fibre channel network

• US 20050030893A1
• Filed: 07/20/2004
• Published: 02/10/2005
• Est. Priority Date: 07/21/2003
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: QLogic Corporation (Marvell Technology Group Limited)
• Inventors: Dropps, Frank R., Ross, Edward C.
• Granted Patent: US 7,522,529 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/266 Stopping or restarting the source, e.g. X-on or X-off
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04L 47/39 Credit based
• CPC Class Codes: H04L 49/357 Fibre channel switches

Abstract

A method and system for detecting congestion and over-subscription in a fibre channel switch element is provided. A counter is updated if a frame cannot be transmitted due to lack of credit; then the counter value is compared to a threshold value; and an event is triggered if the counter value varies from the threshold value. Also, provided is a first register that maintains information regarding a rate at which a source port can transfer data; a counter that counts entries corresponding to a number of frames to be transmitted at a given time; and a second register that determines an over-subscription rate.

Claims

1. A method for detecting congestion in a transmit side of a fibre channel switch element, comprising:

updating a counter if a frame cannot be transmitted from a transmit side of a switch due to lack of credit;

comparing the counter value to a threshold value; and

triggering a threshold event if the counter value varies from the threshold value.

2. A method for detecting congestion on a receive segment of a fibre channel switch element, comprising:

comparing a counter value to a threshold value, if a receive buffer is full; and

triggering a threshold event if the counter value varies from the threshold value.

3. A method for detecting congestion in a transmit segment of a fibre channel switch element, comprising:

determining if credit is available for transmitting a frame;

triggering an event based on a duration that the frame waits for transmission; and

notifying a processor based on such event.

4. The method of claim 3, where a first counter value is compared to a threshold value to trigger the event.

5. The method of claim 3, further comprising:

sending an interrupt to a processor after congestion is detected at the transmit segment.

6. A method for detecting congestion at a receive segment of a fibre channel switch element, comprising:

determining if a receive buffer has been full for a certain duration; and

triggering an event if the duration varies from a threshold value.

7. The method of claim 6, further comprising:

sending an interrupt to a processor if the duration varies from the threshold value.

8. A system for detecting congestion in a fibre channel switch element, comprising:

a first counter that counts a duration for which a frame waits for transmission, and the duration is compared to a threshold value to detect congestion.

9. The system of claim 8, where the threshold value may be programmed by firmware used by the fibre channel switch element.

10. The system of claim 8, where if the first counter value is greater than the threshold value, an event is triggered.

11. A system for detecting congestion at a receive segment of a fibre channel switch element, comprising:

a receive buffer log that indicates how quickly frames are moving through the receive segment.

12. The system of claim 11, further comprising:

a first counter that is incremented when a receive buffer is full and if the counter value varies from a threshold value, an event is generated.

13. The system of claim 12, further comprising:

a register that maintains count for frames that are routed to another switch element.

14. A system for determining over-subscription in a transmit segment of a fibre channel switch element, comprising:

a first register that maintains information regarding a rate at which a source port can transfer data;

a first counter that counts entries corresponding to a number of frames to be transmitted at a given time; and

a second register that determines an over-subscription rate.

15. A method for determining over-subscription in a transmit port of a fibre channel switch element, comprising:

determining an over-subscription value based on a source port'"'"'s data rate, a transmit port'"'"'s data rate and an entry corresponding to a number of frames that are to be transmitted from the transmit port at a given time; and

notifying a processor of the over-subscription rate if the over-subscription value is different from a threshold value.

16. The method of claim 15, where the threshold value may be programmed.