Methods and apparatus for device access fairness in fibre channel arbitrated loop systems

• US 20040085994A1
• Filed: 07/10/2003
• Published: 05/06/2004
• Est. Priority Date: 07/02/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Vixel Corporation (Broadcom, Inc.)
• Inventors: White, Michael L., Warren, Bruce Gregory, Goodwin, William, Johnson, Bruce E., Mies, Carl, Eng, Warren
• Granted Patent: US 7,660,316 B2
• Time in Patent Office: Days
• US Class Current: 370/462
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/20 Traffic policing

Abstract

Methods and apparatus for switching Fibre Channel Arbitrated Loop Systems is provided between a plurality of Fibre Channel Loop devices. In one aspect of the invention, the system switches based at least in part on arbitrated loop primitives. An exemplary interconnect system may include a first port and a second port, both including port logic to monitor certain arbitrated loop primitives, a connectivity apparatus, a route determination apparatus including a routing table consisting of ALPA addresses and their associated ports, the route determination apparatus coupled to each port and the connectivity apparatus, where the connectivity apparatus creates paths between the ports based on arbitrated loop primitives. In one embodiment, the connectivity apparatus is a crossbar switch. Examples of the arbitrated loop primitives that cause the switch to create paths between ports includes one or more of the following: ARB, OPN and CLS. In yet other aspects, the system ensures device access fairness through one or more techniques, including a rotating priority system, a counter to count the number of OPNs, especially sequential OPNs, and/or priority based on port type. Device zoning may be implemented. In one implementation, the system includes trunking such that frames may be transferred on multiple ports.

Claims

1. A system for interconnecting Fibre Channel Arbitrated Loop Devices employing the Fibre Channel Arbitrated Loop protocol including the access fairness algorithm, comprising:

a plurality of Fibre Channel Arbitrated Loop ports each including port logic,

a route determination apparatus,

a connectivity apparatus, and

logic implementing predefined loop control criteria to enforce fairness in addition to the access fairness algorithm.

2. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein the fairness logic serves to limit the number of times a connected device opens another device.

3. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 2, wherein the fairness logic serves to limit the number of times a connected device sequentially opens another device.

4. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, further including a counter to count the number of opens.

5. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 4, wherein the counter counts sequential opens.

6. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein the logic proactively closes a device.

7. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein the ports are assigned different access priorities.

8. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein when a port is granted a connection due to the receipt of an OPN, it is moved to the bottom of the list and the lower priority ports are moved up toward the top of the list.

9. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein priority levels of fairness are predefined.

10. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 9 wherein the predefined levels of fairness include a higher level which wins loop arbitration before the lower levels.

11. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 9 wherein the predefined priority levels are separate from the Fibre Channel Arbitrated Loop address priorities.

12. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 1, wherein fairness is enforced in a string cascade architecture.

13. A system for interconnecting Fibre Channel Arbitrated Loop Devices of claim 12 wherein the fairness is enforced in part where a device wins an arbitration when an ARB has traveled between the switch and the interconnected switches on the string.