This is an initiator-defined component of the session identifier and is structured as follows (see [RFC3721] and Section 9.1.1 Conservative Reuse of ISIDs for details):
| Byte | 0 | 1 | 2 | 3 | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Bits | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| 8 | ||||||||||||||||||||||||||||||||
| 12 | ||||||||||||||||||||||||||||||||
The T field identifies the format and usage of A, B, C, and D as indicated below:
| T | Description |
|---|---|
| 00b | OUI-Format A&B are a 22 bit OUI (the I/G & U/L bits are omitted)C&D 24 bit qualifier |
| 01b | EN - Format (IANA Enterprise Number) A - Reserved B&C EN (IANA Enterprise Number) D - Qualifier |
| 10b | "Random" A - Reserved B&C Random D - Qualifier |
| 11b | A,B,C&D Reserved |
For the T field values 00b and 01b, a combination of A and B (for 00b) or B and C (for 01b) identifies the vendor or organization whose component (software or hardware) generates this ISID. A vendor or organization with one or more OUIs, or one or more Enterprise Numbers, MUST use at least one of these numbers and select the appropriate value for the T field when its components generate ISIDs. An OUI or EN MUST be set in the corresponding fields in network byte order (byte big-endian).
If the T field is 10b, B and C are set to a random 24-bit unsigned integer value in network byte order (byte big-endian). See [RFC3721] for how this affects the principle of "conservative reuse".
The Qualifier field is a 16 or 24-bit unsigned integer value that provides a range of possible values for the ISID within the selected namespace. It may be set to any value within the constraints specified in the iSCSI protocol (see Section 3.4.3 Consequences of the Model and Section 9.1.1 Conservative Reuse of ISIDs).
The T field value of 11b is reserved.
If the ISID is derived from something assigned to a hardware adapter or interface by a vendor, as a preset default value, it MUST be configurable to a value assigned according to the SCSI port behavior desired by the system in which it is installed (see Section 9.1.1 Conservative Reuse of ISIDs and Section 9.1.2 iSCSI Name, ISID, and TPGT Use). The resultant ISID MUST also be persistent over power cycles, reboot, card swap, etc. For details have a look in the [RFC3721]. @author Volker Wildi
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