Method and system for improving bandwidth and reducing idles in fibre channel switches

• US 7,583,597 B2
• Filed: 07/20/2004
• Issued: 09/01/2009
• 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., Papenfuss, Gary M., Verba, Craig M.
• Primary Examiner(s): Yao; Kwang B
• Assistant Examiner(s): Lai; Andrew
• Application Number:
  US10/894,726
• Publication Number:
  US 20050018649A1
• Time in Patent Office: 1,869 Days
• Field of Search: 370/300, 370/360, 370/428, 370/229, 370/230, 370/230.1, 370/235, 370/236, 370/237, 370/238, 370/392
• US Class Current: 370/230.1
• CPC Class Codes: H04L 12/5602 Bandwidth control in ATM Networks, e.g. leaky bucket

Abstract

A method for routing fibre channel frames using a fibre channel switch element is provided. The switch element includes, a receiving segment in a fibre channel port for receiving the frames and a transmit segment that transmits the received frames. The method includes requesting an early frame transfer, wherein the transmit segment of a fibre channel port requests an early frame transfer from a receiving segment of the fibre channel port before a frame has arrived at the transmit segment; activating an early frame transfer; determining if there is a need for aborting the early frame transfer request; and selecting a different source port if there is a need for aborting an early frame transfer request.

Claims

1. A method for routing fibre channel frames using a fibre channel switch element having a plurality of ports, where each port includes a receive segment for receiving fibre channel frames and a transmit segment for transmitting fibre channel frames;

comprising;

(a) requesting an early frame transfer of a fibre channel frame from a memory location of the receive segment of a fibre channel port to the transmit segment of the fibre channel port, before the transmit segment completes a status check, wherein the transmit segment sends a request to the receive segment for the early frame transfer;

(b) activating an early frame transfer;

wherein the early frame transfer is activated at the receive segment;

(c) after completing the status check, determining if there is a need for aborting the early frame transfer request sent to the receive segment in step (a);

wherein the transmit segment determines if there is a need for aborting the early frame transfer request and if there is a need, generates a request-abort command to abort the early frame transfer request and sends the request abort command to the receive segment; and

(e) after aborting the early frame transfer, selecting another frame from a different source port while continuing to have the memory location in step (a) available for the transmit segment to re-request the frame transfer from the same memory location.

2. The method of claim 1, further comprising:

transferring the fibre channel frame if there is no need to abort the early frame transfer request gene rated by the transmit segment.

3. The method of claim 1, wherein firmware executed by the fibre channel switch element enables a request-abort feature permitting the transmit segment to send the early frame transfer request and aborting the early frame transfer request if the status check fails.

4. The method of claim 1, wherein the request-abort command is generated if a frame'"'"'s status field lacks a destination bit value.

5. The method of claim 1, wherein the request-abort command is generated if a frame'"'"'s status indicates that not enough of the frame has arrived properly at the receive segment.

6. The method of claim 1, wherein the request abort command is generated if a frame'"'"'s status information used to determine that credit is unavailable for the frame.

7. The method of claim 1, wherein the request abort command is generated if the transmit segment does not have sufficient space to hold the frame.

8. The method of claim 1, wherein a request-abort command is generated if a plurality of R_RDYs, a primitive indicating available credit at the receive segment of the port, are transmitted by the transmit segment to another port.

9. The method of claim 1, wherein the request abort command is generated by firmware and used by the fibre channel switch element.

10. A fibre channel switch element for routing fibre channel frames, comprising:

a receive segment in a fibre channel port of the fibre channel switch element for receiving the fibre channel frames and a transmit segment that transmits the received fibre channel frames;

wherein the transmit segment of the fibre channel port requests an early frame transfer of a fibre channel frame from a memory location of the receive segment of the fibre channel port to the transmit segment, before the transmit segment completes a status check; and

in response to the earl;

frame transfer request, the receive segment activates an early frame transfer; and

wherein, after completing the status check, the transmit segment determines if there is a need for aborting the early frame transfer request;

generates a request abort command to abort the early frame transfer request if there is a need for aborting the early frame transfer request and sends the request abort command to the receive segment; and

wherein after the early frame transfer request is aborted, another frame from a different source port is selected while the receive segment continues to have the memory location available for the transmit segment to re-request the frame transfer from the same memory location.

11. The fibre channel switch element of claim 10, wherein the transmit segment transfers the fibre channel frame if there is no need to abort the early frame transfer request.

12. The fibre channel switch element of claim 10, wherein firmware executed by the fibre channel switch element enables a request-abort feature permitting the transmit segment to send the early frame transfer request and aborting the early frame transfer request if the status check fails.

13. The fibre channel switch element of claim 10, wherein the request abort command is generated if the frame'"'"'s status field lacks a destination bit value.

14. The fibre channel switch element of claim 10, wherein the request abort command is generated if the frame'"'"'s status indicates that not enough of a frame has arrived properly.

15. The fibre channel switch element of claim 10, wherein the request abort command is generated if the frame'"'"'s status information used to determine that credit is unavailable for the frame.

16. The fibre channel switch element of claim 10, wherein the request abort command is generated if the transmit segment does not have sufficient space to hold the frame.

17. The fibre channel switch element of claim 10, wherein the request abort command is generated if a plurality of R_RDYs, a primitive indicating available credit at the receive segment of the port, are transmitted by the transmit segment to another port.

18. The fibre channel switch element of claim 10, wherein the request abort command is generated by firmware used by the fibre channel switch element.

19. A switch element, comprising:

a receive segment of a port for receiving a frame; and

a transmit segment of the port for transmitting a frame; and

before the transmit segment completes a status check;

the transmit segment sends a request for an early frame transfer to the receive segment to transfer the frame from a memory location of the receive segment to the transmit segment; and

in response to the early frame transfer request, the receive segment activates an early frame transfer;

wherein, after completing the status check, the transmit segment determines if there is a need for aborting the early frame transfer request; and

if there is a need, generates a request to abort the early frame transfer request and sends the request to the receive segment so that the early frame transfer is aborted; and

wherein after the early frame transfer is aborted the receive segment continues to have the memory location available for the transmit segment to re-request the frame transfer from the same memory location.

20. The switch element of claim 19, wherein the transmit segment generates a request-abort command to abort the early frame transfer request.

21. The switch element of claim 20;

wherein the request-abort command to abort the early frame transfer is generated based on one or more of the following;

(a) the frame'"'"'s status field lacks a destination bit value;

(b) the frame'"'"'s status indicates that not enough of a frame has arrived properly;

(c) the frame'"'"'s status indicates that credit is unavailable for the frame;

(d) if the transmit segment does not have sufficient space to hold the frame;

(e) if a plurality of R_RDYs a primitive indicating available credit at the receive segment, are transmitted; and

(f) if firmware of the switch element generates the request-abort command.

22. A method for a switch element having a plurality of ports, each port having a receive segment for receiving frames and a transmit segment for transmitting frames;

comprising;

a. before the transmit segment completes a status check, requesting an early frame transfer of a frame from a memory location of the receive segment of a port to the transmit segment of the port;

wherein the transmit segment sends a request to the receive segment for the early frame transfer;

b. activating an early frame transfer;

wherein the early frame transfer is activated at the receive segment;

c. after completing the status check, determining if there is a need for aborting

the early frame transfer request sent to the receive segment in step (a);

wherein the transmit segment determines if there is a need for aborting the early frame transfer request and if there is a need, generates a request-abort command to abort the early frame transfer request and sends the request abort command to the receive segment; and

(d) after aborting the early frame transfer, selecting another frame while continuing to have the memory location in step (a) available for the transmit segment to re-request transfer of the frame from the same memory location of step (a).

23. The method of claim 22, wherein the request-abort command to abort the early frame transfer is generated based on one or more of the following:

(a) the frame'"'"'s status field lacks a destination bit value;

(b) the frame'"'"'s status indicates that not enough of a frame has arrived properly;

(c) the frame'"'"'s status indicates that credit is unavailable for the frame;

(d) if the transmit segment does not have sufficient spice to hold the frame; and

(E) if firmware of the switch element generates the request-abort command.