Appendix B
Addressing, Structures and Operation
Fibre Channel and SCSI systems employ different methods of addressing devices. The inclusion of a bridge or router requires that a method of translating device IDs be implemented so that each SCSI device is mapped to the appro- priate Fibre Channel LUN. The SCSI bus establishes bus connections between devices. Targets on the SCSI bus may internally address logical units. The addressing of a specific SCSI device is represented by the BUS:TARGET:LUN triplet.
When a Fibre Channel initiator initializes on an arbitrated loop, the first order of business is to determine what devices exist on the loop. Device discovery is performed, and an FCP target device list is built. Each device is queried for FCP logical units. The logical units are the actual devices that the operating system will address. When an initiator addresses a logical unit, the LUN field used is consistent in form with the SCC defined fields. All current Fibre Channel host bus adapter drivers are consistent with these methods. The addressing used is the SCC Logical Unit Addressing and Peripheral Device Addressing methods, shown in Table “SCC Addressing structure” and “Peripheral Device Addressing LUN structure”. First level addressing is supported, so only the first 2 bytes of the 8 byte FCP LUN are used.
Bit | 7 | 6 | 5 |
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n | Address Method |
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n+1 |
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SCC Addressing structure |
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Bit | 7 | 6 | 5 |
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n | 0 | 0 |
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n+1 |
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Peripheral Device Addressing LUN structure
Operating Manual |
