understanding the SCSI Specification.

HI all,
Im working on a storage protocol   which uses SCSI commands  set as
the command set and also the SCSI Task Management functions for
processing the Task Management.
The Architectural Model is based on SAM-5. The Command set is based on
SPC-4 and SBC-3. I have some doubts in trying to understanding some
SCSI terms and definitions.

For  using the send command transport protocol service request to
request a initiator  the following API is defined

[1]Send SCSI Command (IN (I_T_L_Q Nexus, CDB, Task Attribute, [Data-in
Buffer Size], [Data-
out Buffer], [Data-out Buffer Size], [CRN], [Command Priority], [First
Burst Enabled]))

Here  I want to know what relation does the I_T_L_Q tries to convey.
from what it says in SAM-5 Specification  section 4.8 tries to define
the Nexus as " nexus represents a relationship between a SCSI
initiator port, a SCSI target port, optionally a logical unit,
and optionally a command."
 how do we convey this information in the above [1].
Also can someone help me in how to map the initiator-target relation
to host-device  structure? thanks.

Warm Regards,
Ravi Kulkarni.





Warm Regards,
Ravi Kulkarni.