Method and system for keeping a fibre channel arbitrated loop open during frame gaps

• US 20050018671A1
• Filed: 07/20/2004
• Published: 01/27/2005
• 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., Papenfuss, Gary M., Kohlwey, Ernest G.
• Granted Patent: US 7,420,982 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04L 12/42 Loop networks
• CPC Class Codes: H04L 47/245 using preemption

Abstract

A method and system for keeping an arbitrated loop open during a frame gap using a fibre channel switch element is provided. The switch element includes a port control module having a receive and transmit segment, wherein the transmit segment activates a timer whose value determines a duration during which the arbitrated loop remains open; determines if a last frame from a sequence of frames from a source port has been transmitted; modifies the timer value if a higher priority frame for transmission is unavailable; and keeps the arbitrated loop open until the timer reaches a certain value. If a higher priority frame is available for transmission before the timer value is modified then the higher priority frame is transmitted and the timer value is re-initialized.

Claims

1. A method for keeping an arbitrated loop open during a frame gap using a fibre channel switch element, comprising:

activating a timer whose value determines a duration during which the arbitrated loop remains open;

determining if a last frame from a sequence of frames from a source port has been transmitted;

modifying the timer value if a higher priority frame for transmission is unavailable; and

keeping the arbitrated loop open until the timer reaches a certain value.

2. The method of claim 1, wherein if a higher priority frame is received when the arbitrated loop is being held open, the higher priority frame is transmitted without regard to the timer value.

3. The method of claim 1, wherein if a higher priority frame is available for transmission before the timer value is modified then the higher priority frame is transmitted and the timer value is re-initialized.

4. The method of claim 1, wherein a frame from the same source if available, is transmitted before the timer value is modified.

5. The method of claim 1, wherein the timer value is pre-programmed by using a processor.

6. A fibre channel switch element coupled to an arbitrated loop of a fibre channel network, comprising:

a port control module having a receive and transmit segment, wherein the transmit segment activates a timer whose value determines a duration during which the arbitrated loop remains open;

determines if a last frame from a sequence of frames from a source port has been transmitted;

modifies the timer value if a higher priority frame for transmission is unavailable; and

keeps the arbitrated loop open until the timer reaches a certain value.

7. The fibre channel switch element of claim 6, wherein if a higher priority frame is received, when the arbitrated loop is being held open, the higher priority frame is transmitted without regard to the timer value.

8. The fibre channel switch element of claim 6, wherein if a higher priority frame is available for transmission before the timer value is modified then the higher priority frame is transmitted and the timer value is re-initialized.

9. The fibre channel switch element of claim 6, wherein a frame from the same source if available, is transmitted before the timer value is modified.

10. The method of claim 7, wherein the timer value is pre-programmed by using a processor.

11. An arbitration module in fibre channel switch element with a port control module having a receive and transmit segment coupled to an arbitrated loop of a fibre channel network, comprising:

a loop hold timer whose value determines a duration during which the arbitrated loop remains open;

determines if a last frame from a sequence of frames from a source port has been transmitted; and

modifies the timer value if a higher priority frame for transmission is unavailable; and

keeps the arbitrated loop open until the timer reaches a certain value.

12. The fibre channel switch element of claim 11, wherein if a higher priority frame is received after the timer value is modified then the higher priority frame is transmitted and the timer value is re-initialized.

13. The fibre channel switch element of claim 11, wherein if a higher priority frame is available for transmission before the timer value is modified then the higher priority frame is transmitted and the timer value is re-initialized.

14. The fibre channel switch element of claim 11, wherein a frame from the same source if available, is transmitted before the timer value is modified.

15. The method of claim 13, wherein the timer value is pre-programmed by using a processor.