U42093-J-Z716-1-74
Operating Manual
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.
SCC Addressing structure
Peripheral Device Addressing LUN structure
Bit
Byte
7
6
5
4
3
2
1
0
n
Address Method
Address Method Specific
n+1
Address Method Specific
Bit
Byte
7
6
5
4
3
2
1
0
n
0
0
Bus
n+1
Target/LUN
