Interface Implementation 21
Interface Implementation
Addresses
Each Fibre Channel port also has a Port Address which is assigned during
loop initialization and/or Fabric Login. This is a 24-bit value in the following
format:
The AL_PA is the Arbitrated Loop Physical Address. This is normally assigned
dynamically during loop initialization.
If the loop is not attached to a fabric (in other words, when it is private,) the top
two bytes will be zero. If the loop is attached to a fabric, the tape drive is
assigned the top two bytes when it logs into the fabric.
Together, the three bytes provide a unique address on the Fibre Channel fabric
that is used for frame addressing. It forms the equivalent of the Target ID or
Initiator ID in SCSI.
HP’s Implementation of Names and Addresses
The HP implementation uses three adjacent IEEE Registered Names:
■ The first (last bits = 00) is used as the Port A World Wide Name.
■ The second (last bits = 01) is used as the Port B World Wide Name.
■ The third name (last bits = 10) is used for the Device World Wide Name.
(These are assigned during manufacture from HP’s pool of names, although
only the first will actually be stored in the drive NV-RAM).
The port addresses will be assigned using the ‘standard’ AL_PA initialization
mechanisms. The ‘Fibre Channel Port Control mode page’ controls this. The
drive has the ability to support hard addresses as part of this scheme.
