ADT-2: SCSI Command IU to Initiator Only port
Kevin D Butt
kdbutt at us.ibm.com
Mon Nov 26 12:19:45 PST 2007
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07-438r0 suggests that we change "acts as" a SCSI target/initiator port to
"is" a SCSI target/initiator port. and that we add the following to ADT-2:
If a port that does not support SCSI target functions receives a SCSI
Command IU or a SCSI Task Management IU, then it shall transmit a NAK IU
with a status code of UNSUPPORTED FRAME TYPE FOR SELECTED PROTOCOL (see
table 14) and discard the IU.
Note x: The exchange originator should not interpret this response as an
indication that the port does not have SCSI target port capabilities, only
that it does not have SCSI target port capabilities enabled at this time
Discussion about "acts as" vs "is"
First, I think "acts as" is more correct than "is". A port that is a SCSI
target/initiator port (this term does not exist in SAM-4) acts as a SCSI
initiator port and a SCSI target port.
Each instance of a SCSI Port class shall contain:
a) one SCSI target port that shall contain:
A) one task router;
b) one SCSI initiator port; or
3.1.94 SCSI initiator port: A SCSI initiator device object that acts as
the connection between application clients
and the service delivery subsystem through which requests, indications,
responses, and confirmations are routed.
In all cases when this term is used it refers to an initiator port or a
SCSI target/initiator port <<operating as>> a SCSI
3.1.99 SCSI target port: A SCSI target device object that contains a task
router and acts as the connection
between device servers and task managers and the service delivery
subsystem through which indications and
responses are routed. When this term is used it refers to a SCSI target
port or a SCSI target/initiator port <<operating
as>> a SCSI target port.
3.1.101 SCSI target/initiator port: A SCSI device resident object that has
all the characteristics of a SCSI target
port and a SCSI initiator port.
Discussion about adding the suggested text:
The issue that this proposal intends to solve is that of a port receiving
a command IU when that port is an initiator port only or that is an
initiator/target port that has not yet been configured to act as a target
port. One of the concerns about what is returned is that the port
initiating this command IU not take the rejection to mean that this port
will never accept a command IU.
There are really two behaviors that a plausible. One behavior is that
mentioned in the proposal of the transport layer returning a NAK IU with a
status code of UNSUPPORTED FRAME TYPE FOR SELECTED PROTOCOL. The other is
to treat the port as being a target port but not having a valid logical
unit so the response would be at a higher layer.
It seems to me that returning a LOGICAL UNIT NOT CONFIGURED would be more
accurate. Further it does not imply that the logical unit does not exist
or is not supported. It just implies that it needs configured before it
can be communicated with. This is exactly the scenario we are in. The
one concern I have with this approach is that no LU exists and no
well-known LU either.
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
"Banther, Michael" <michael.banther at hp.com>
Sent by: owner-t10 at t10.org
11/26/2007 10:39 AM
"t10 at t10.org" <t10 at t10.org>
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