iSCSI : On the subject of R2T and Task Tags.

[Santosh Rao <santoshr@cup.hp.com>]

On the subject of R2T and task tags .....

Section 2.16. R2T
=============
1) Differing nomenclatures "Target Task Tag" and
"Target Transfer Tag" for the same field. Only 1 of the 2 should
be used. The current semanticsof this field seem to call for a
"Target R2T Tag" name and not a "Target Task Tag",
since this is not per task.

2) The READ I/O PDUs do not use a "Target Task Tag".
The WRITE I/O PDUs use a "Target Task Tag" per R2T
and not per task.

It seems like the only unique per I/O identifier is the Initiator
Task Tag. (?) Is it the intention of iSCSI that targets should be
using the Initiator Task Tag as the per I/O lookup tag ?

If this is true, then, the name "Initiator Task Tag" is a misnomer
and it should just be "Task Tag", since it is used by both initiators
and
targets.

Explicitly stating the semantics of "Target Task Tag" in
Section 2.2 would help, particularly since, it seems like iSCSI's
concept of "Target Task Tag" differs from the semantics of the
equivalent(?) RX_ID in the Fibre Channel header.

iSCSI seems to be more closely aligned with Parallel SCSI's
single Queue Tag model than Fibre Channel's OX_ID/RX_ID
tag model.

3) Quoting from the draft :
"The present document does not limit the number of outstanding
datatransfers."

As we had discussed earlier, this needs to be removed, since
MaxOutstandingR2T bounds the number of outstanding R2Ts.

Thanks,
Santosh
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