Graceful port shutdown protocol for fibre channel interfaces

• US 20060087963A1
• Filed: 10/25/2004
• Published: 04/27/2006
• Est. Priority Date: 10/25/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Gupta, Shashank, Jain, Praveen, Jain, Sachin, Rajagopalan, Ranganathan, Janakiraman, Ramsundar
• Granted Patent: US 7,593,324 B2
• Time in Patent Office: Days
• US Class Current: 370/217
• 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 port shutdown protocol coordinates among various components involved in the process of administratively bringing down a link at both ends of a link connecting two switches. Execution of the protocol avoids or reduces frame drops and/or reordering. In this protocol, peer switches perform various actions when bringing down an ISL in a synchronized manner. In one implementation, this protocol uses the Exchange Peer Protocol (EPP) as the underlying transport to carry the port shutdown protocol frames.

Claims

1. In a Fibre Channel switch coupled to an inter-switch link, a method of gracefully shutting down said inter-switch link, the method comprising:

determining that the inter-switch link is to be shut down;

modifying forwarding parameters to ensure that no further frames are forwarded from the switch onto the link;

communicating with a peer switch on the other side of the inter-switch link to synchronize actions between the two switches on the inter-switch link; and

ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

2. The method of claim 1, further comprising aborting and/or completing any pending changes for the inter-switch link.

3. The method of claim 2, wherein the aborting and/or completing is performed prior to modifying said forwarding parameters.

4. The method of claim 1, wherein synchronizing actions between the two switches on the inter-switch link comprises

(a) informing the peer switch that the inter-switch link is being shut down;

and

(b) receiving an acknowledgment from the peer switch indicating that the peer switch will take or has taken actions in preparation for shutting down the inter-switch link.

5. The method of claim 1, wherein synchronizing actions between the two switches on the inter-switch link comprises communicating in an EPP protocol.

6. The method of claim 1, wherein synchronizing actions between the two switches on the inter-switch link comprises communicating using a protocol other than EPP.

7. The method of claim 1, wherein modifying said forwarding parameters comprises updating a forwarding table on said switch.

8. The method of claim 7, wherein modifying said forwarding parameters further comprises informing other switches on a network fabric with said switch, but not on the inter-switch link, that said inter-switch link will shut down in order to cause said other switches to update their forwarding tables.

9. The method of claim 1, wherein ensuring that no frames remain queued on the switch comprises waiting for a defined period of time for any queued frames to drain onto the inter-switch link.

10. The method of claim 1, wherein ensuring that no frames remain queued on the switch comprises deterministically confirming that there are no queued packets in the switch for transmission on the inter-switch link.

11. The method of claim 1, further comprising, after ensuring that no frames remain queued on the switch,

(i) informing the peer switch that the link can be shut down;

and

(ii) receiving confirmation from said peer switch that it is prepared for the link to come down.

12. The method of claim 1, further comprising bringing down the inter-switch link after ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

13. A computer program product comprising a machine readable medium on which is provided instructions gracefully shutting down said inter-switch link coupled to a Fibre Channel switch, the instructions comprising:

determining that the inter-switch link is to be shut down;

modifying forwarding parameters to ensure that no further frames are forwarded from the switch onto the link;

communicating with a peer switch on the other side of the inter-switch link to synchronize actions between the two switches on the inter-switch link; and

ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

14. The computer program product of claim 13, further comprising instructions for aborting and/or completing any pending changes for the inter-switch link.

15. The computer program product of claim 13, wherein the instructions for synchronizing actions between the two switches on the inter-switch link comprises instructions for

(a) informing the peer switch that the inter-switch link is being shut down;

and

(b) receiving an acknowledgment from the peer switch indicating that the peer switch will take or has taken actions in preparation for shutting down the inter-switch link.

16. The computer program product of claim 13, wherein the instructions for synchronizing actions between the two switches on the inter-switch link comprises instructions for communicating in an EPP protocol.

17. The computer program product of claim 13, wherein the instructions for modifying said forwarding parameters comprises instructions for updating a forwarding table on said switch.

18. The computer program product of claim 17, wherein the instructions for modifying said forwarding parameters further comprises instructions informing other switches on a network fabric with said switch, but not on the inter-switch link, that said inter-switch link will shut down in order to cause said other switches to update their forwarding tables.

19. The computer program product of claim 13, wherein the instructions for ensuring that no frames remain queued on the switch comprises instructions for waiting for a defined period of time for any queued frames to drain onto the inter-switch link.

20. The computer program product of claim 13, further comprising instructions for bringing down the inter-switch link after ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

21. A Fibre Channel switch comprising:

a backplane for running applications and services used by the switch

a port for connecting to an inter-switch link; and

port shutdown logic comprising instructions for

determining that the inter-switch link is to be shut down;

modifying forwarding parameters to ensure that no further frames are forwarded from the switch onto the link;

communicating with a peer switch on the other side of the inter-switch link to synchronize actions between the two switches on the inter-switch link; and

ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

22. The Fibre Channel switch of claim 21, wherein the shutdown logic further comprises instructions for aborting and/or completing any pending changes for the inter-switch link.

23. The Fibre Channel switch of claim 21, wherein the port shutdown logic instructions for modifying said forwarding parameters comprises instructions for updating a forwarding table on said switch.

24. The Fibre Channel switch of claim 23, wherein the port shutdown logic instructions for modifying said forwarding parameters further comprises instructions informing other switches on a network fabric with said switch, but not on the inter-switch link, that said inter-switch link will shut down in order to cause said other switches to update their forwarding tables.

25. The Fibre Channel switch of claim 21, wherein the port shutdown logic instructions for ensuring that no frames remain queued on the switch comprises instructions for waiting for a defined period of time for any queued frames to drain onto the inter-switch link.

26. The Fibre Channel switch of claim 21, further comprising port shutdown instructions for bringing down the inter-switch link after ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

27. A Fibre Channel switch for coupling to an inter-switch link comprising:

means for determining that the inter-switch link is to be shut down;

means for modifying forwarding parameters to ensure that no further frames are forwarded from the switch onto the link;

means for communicating with a peer switch on the other side of the inter-switch link to synchronize actions between the two switches on the inter-switch link; and

means for ensuring that no frames remain queued on the switch for transmission on the inter-switch link.

28. A method of gracefully shutting an inter-switch link between a first switch and a second switch on a Fibre Channel network, the method comprising:

(a) determining that the inter-switch link is to be shut-down;

(b) modifying forwarding parameters in the first switch to ensure that no further frames are forwarded from the first switch onto the inter-switch link and sending one or more communications to the second switch;

(c) sending a communication to the second switch informing it that the link is to be shut down;

(d) modifying forwarding parameters in the second switch to ensure that no frames are forwarded from second switch onto the inter-switch link;

(e) ensuring that no frames remain queued in the first switch for transmission on the inter-switch link;

(f) receiving confirmation from the second switch that it is prepared for the inter-switch link to shut down; and

(g) shutting down the inter-switch link.

29. The method of claim 28, further comprising aborting and/or completing any pending changes for the inter-switch link.

30. The method of claim 29, wherein the aborting and/or completing is performed prior to modifying said forwarding parameters.

31. The method of claim 28, wherein sending one or more communications between the switches to ensure that both switches will participate in a graceful shut down protocol comprises communicating in an EPP protocol.

32. The method of claim 28, wherein modifying said forwarding parameters comprises updating a forwarding table on said switch.

33. The method of claim 32, wherein modifying said forwarding parameters comprises informing other switches on a network fabric with said switch, but not on the inter-switch link, that said inter-switch link will shut down in order to cause said other switches to update their forwarding tables.

34. The method of claim 28, wherein ensuring that no frames remain queued on the switch comprises waiting for a defined period of time for any queued frames to drain onto the inter-switch link.

35. The method of claim 28, wherein ensuring that no frames remain queued on the switch comprises deterministically confirming that there are no queued packets in the switch for transmission on the inter-switch link.

36. A storage area network comprising:

a first Fibre Channel switch;

a second Fibre Channel switch; and

an inter-switch link coupling the first and second Fibre Channel switches,

wherein the first Fibre Channel switch comprises logic for

(a) determining that the inter-switch link is to be shut-down;

(b) modifying forwarding parameters in the first switch to ensure that no further frames are forwarded from the first switche onto the inter-switch link and sending one or more communications to the second switch;

(c) sending a communication to the second switch informing it that the link is to be shut down;

(d) ensuring that no frames remain queued in the first switch for transmission on the inter-switch link;

(e) receiving confirmation from the second switch that it is prepared for the inter-switch link to shut down; and

(f) shutting down the inter-switch link.

wherein the second Fibre Channel switch comprises logic for

(a) modifying forwarding parameters in the second switch to ensure that no frames are forwarded from second switch onto the inter-switch link;

(b) ensuring that no frames remain queued in the second switch for transmission on the inter-switch link; and

(c) sending a confirmation to the first switch that the second switch is prepared for the inter-switch link to shut down.