Method and system for preventing deadlock in fibre channel fabrics using frame priorities

• US 20050174936A1
• Filed: 03/11/2004
• Published: 08/11/2005
• Est. Priority Date: 02/05/2004
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: QLogic Corporation (Marvell Technology Group Limited)
• Inventors: Betker, Steven M.
• Granted Patent: US 7,480,293 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04L 47/2433 Allocation of priorities to traffic types
• CPC Class Codes: H04L 47/2458 Modification of priorities while in transit
• CPC Class Codes: H04L 47/39 Credit based
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 47/522 Dynamic queue service slot or variable bandwidth allocation
• CPC Class Codes: H04L 47/6215 Individual queue per QOS, rate or priority
• CPC Class Codes: H04L 47/6265 past bandwidth allocation
• CPC Class Codes: H04L 49/357 Fibre channel switches
• CPC Class Codes: H04L 49/552 by ensuring the integrity of packets received through redundant connections

Abstract

A method and system for transmitting frames using a fibre channel switch is provided. The method includes, determining a frame'"'"'s priority based on a hop count for the frame; placing a frame in a priority queue, where the priority queue is dedicated to frames having similar priorities; selecting a frame for transmission based on the frame'"'"'s priority, if credit is available, where a frame with a higher priority is sent before a frame with a lower priority; and selecting a frame with a lower priority if enough higher priority frames have been sent. The system includes a switch with at least two priority queues for placing frames with different priorities; a counter that keeps track of frames that are transmitted from the two priority queues; and a credit control module that determines if credit is available before sending a particular frame.

Claims

1. A method for transmitting frames using a fibre channel switch, comprising:

determining a frame'"'"'s priority based on a hop count for the frame;

placing a frame in a priority queue, where the priority queue is dedicated to frames having similar priorities;

selecting a frame for transmission based on the frame'"'"'s priority, if credit is available, where a frame with a higher priority is sent before a frame with a lower priority; and

selecting a frame with a lower priority if enough higher priority frames have been sent.

2. The method of claim 1, where a counter maintains count of frames that are transmitted from a priority queue, and is used to send lower priority frames if enough higher priority frames have been sent.

3. The method of claim 1, where a frame with a higher hop count has lower priority compared to a frame with a lower hop count.

4. A system for transmitting fibre channel frames, comprising:

a fibre channel switch with a transmit port with at least two priority queues for placing frames with different priorities, where a frame'"'"'s priority is based on a hop count depending upon the frame'"'"'s destination;

a counter that keeps track of frames that are transmitted from the two priority queues; and

a credit control module that determines if credit is available before sending a particular frame.

5. The system of claim 4, where a frame'"'"'s priority is inversely proportional to the frame'"'"'s hop count.

6. A fibre channel switch having a receive and transmit port for transmitting frames, comprising:

at least two priority queues for placing frames with different priorities, where a frame'"'"'s priority is based on a hop count depending upon the frame'"'"'s destination;

a counter that keeps track of frames that are transmitted from the two priority queues; and

a credit control module that determines if credit is available before sending a particular frame.

7. The switch of claim 6, where a frame'"'"'s priority is inversely proportional to the frame'"'"'s hop count.

8. A system for transmitting fibre channel frames, comprising:

means for placing a frame in a priority queue, where the priority queue is dedicated to frames having similar priorities;

means for selecting a frame for transmission based on the frame'"'"'s priority, if credit is available, where a frame with a higher priority is sent before a frame with a lower priority; and

means for selecting a frame with a lower priority if enough higher priority frames have been sent.

9. The system of claim 8, further comprising:

means for maintaining a count of frames that are transmitted from a priority queue, and the count is used to send lower priority frames if enough higher priority frames have been sent.

10. The system of claim 8, where a frame with a higher hop count has lower priority compared to a frame with a lower hop count.

11. A fibre channel switch having a receive port and a transmit port for transmitting fibre channel frames, comprising:

means for placing a frame in a priority queue, where the priority queue is dedicated to frames having similar priorities;

means for selecting a frame for transmission based on the frame'"'"'s priority, if credit is available, where a frame with a higher priority is sent before a frame with a lower priority; and

means for selecting a frame with a lower priority if enough higher priority frames have been sent.

12. The switch of claim 11, further comprising:

means for maintaining a count of frames that are transmitted from a priority queue, and the count is used to send lower priority frames if enough higher priority frames have been sent.

13. The switch of claim 11, where a frame with a higher hop count has lower priority compared to a frame with a lower hop count.