iSCSI : NOP-OUT & NOP-IN issues.

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

Julian,

I have several concerns regarding the current semantics for the NOP
operation, as defined in the lastest iSCSI draft. (iSCSI-02.txt) :

Section 2.12 NOP-OUT PDU
=========================
1) Quoting from the draft :
"The NOP-Out can be sent by an initiator because of a NOP-In with the
 poll bit set, in which case the Target Tag will copy the NOP-In value."

There is no poll bit in the NOP-IN PDU. What is the intent of the
above ?

2) Quoting from the draft :
"The NOP-Out MUST have the Initiator Task Tag set only if the P bit is
 one or the DataRN field is set."

There is no DataRN field in the NOP-OUT PDU. Is the intent of this to
state
that :
"The NOP-OUT must have the Initiator Task Tag set if the NOP-OUT is
being
used to acknowledge DataRN[s] from received READ Data PDU[s]" ?
Some clarification would help here.

3) Quoting from the draft :
"The NOP-Out MUST have the Target Tag set only if it issued in
 response to a NOP-In with the P bit one, in which case it copies the
 Target Tag from the NOP-In PDU."

Some comments on the above :
i) There is no P bit in a NOP-IN PDU.

ii) If a target wanted to originate a NOP for some reason, it should use

NOP-OUT. The NOP-OUT should be intended for the originator of the NOP
and the
responder of the NOP should reply with NOP-IN.
This keeps the NOP semantics simple and intuitive.

ii) Why is there a need for a target to originate a NOP-OUT ? In the
interests
of simplicity, targets should be prohibited from originating the NOP
operation.

iii) With the above semantics, how is an initator to know if a received
NOP-IN
is being originated by a target [to which it needs to respond with a
NOP-OUT]
or the NOP-IN is being received in response to a transmitted NOP-OUT ?

The semantics of NOP-OUT used by the originator of the NOP operation and

NOP-IN used by the responder of the NOP operation seem more intuitive.

Section 2.13. NOP-IN PDU
=========================
1) References to a P bit in the NOP-IN PDU which does not exist.

2) This section specifies the use of 0 for Initiator Task Tag when the
target
originates a NOP operation. 0 is a valid value for Initiator Task Tag
and its
usage can confuse the initiator b/n a target originated NOP-IN and a
target
response to NOP-OUT sent on an initiator task tag of 0.
The reserved value for Initiator Task Tag should be 0xFFFFFFFF, as is
the case
with the Target Task Tag.

Thanks,
Santosh
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