Subject: iSCSI : NOP-OUT & NOP-IN issues.

From: Santosh Rao <[email-masked]>
Date: Sat, 06 Jan 2001 20:19:31 -0800

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

---

From: [email-masked]
Date: Sun, 7 Jan 2001 19:37:23 +0200

My reply in the text - thanks, Julo

Santosh Rao <[email-masked]> on 07/01/2001 06:19:31

Please respond to Santosh Rao <[email-masked]>

To:   IPS Reflector <[email-masked]>
cc:
Subject:  iSCSI : NOP-OUT & NOP-IN issues.

Julian,

Section 2.12 NOP-OUT PDU

<js> Bit 7 of the second byte (it was a typo) should read P - it is fixed
in 03.txt
</js>

<js> read ExpDataRN.  Correction and an explanation for the field have been
added
</js>

<js> In and Out are always relative to the initiator.
A receiver of a NOP knows if the NOP is originated by the target through
the target task tag.
The code differentiation is meant for a stateless protocol analyzer
<js>

Section 2.13. NOP-IN PDU

Thanks,
Santosh

<js> corections where made - this typo was reported by several people </js>

---

From: [email-masked]
Date: Sun, 7 Jan 2001 19:40:50 +0200

Santosh,

I will consider renaming. However the codes have now overloaded meaning
(for that we have earlier two different NOPs - and I don't feel easy having
a NOP response to no command.

Regards,
Julo

Santosh Rao <[email-masked]> on 07/01/2001 06:29:13

To:   Julian Satran/Haifa/IBM@IBMIL
cc:   [email-masked]
Subject:  Re: iSCSI : NOP-OUT & NOP-IN issues.

Julian,

If NOP-OUT and NOP-IN were to be re-named to NOP Command and NOP Response
PDUs, this would further enhance ease of understanding of the NOP operation
semantics, removing any issues about target originating the NOP operation
through the use of NOP-IN.

Thanks & Regards,
Santosh

sip - Santosh Rao wrote:

>  The NOP-OUT should be intended for the originator of the NOP
> and the responder of the NOP should reply with NOP-IN.