Subject: [Ips] section 5.1 ITT [draft-ietf-ips-iscsi-impl-guide-00.txt]

From: "Eddy Quicksall" <[email-masked]>
Date: Thu, 4 Aug 2005 21:46:08 -0400

In my mind, Section 5.1 ITT wording is in question:

Section 10.19 in [RFC3720] mentions this in passing but noted 
here again for making it obvious.  An ITT value of 0xffffffff is 
reserved and MUST NOT be used by the initiator.  The only 
instance it may be seen on the wire is in a target-initiated 
NOP-In PDU (and the initiator response to that PDU if 
necessary).

If taken in the context of 10.19, it doesn't make sense since the initiator does not issue NOP-In and hence the 2nd sentence seems out of place.

Or ---

Are you saying that the following is being withdrawn from the RFC?

10.18.1.  Initiator Task Tag

   .......  Otherwise, the Initiator Task Tag MUST be set to 0xffffffff.

   .........

   If the Initiator Task Tag contains 0xffffffff, the I bit MUST be set
   to 1 and the CmdSN is not advanced after this PDU is sent.

_______________________________________________
Ips mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/ips

---

From: William Studenmund <[email-masked]>
Date: Fri, 5 Aug 2005 09:12:41 -0700

On Aug 4, 2005, at 6:46 PM, Eddy Quicksall wrote:

> If taken in the context of 10.19, it doesn't make sense since the 
> initiator does not issue NOP-In and hence the 2nd sentence seems out 
> of place.

Do you mean the third sentence?

The point is that if the initiator ever uses an ITT of 0xffffffff, 
there is no way to tell a target-initiated NOP-IN from a response to an 
initiator-generated one.

>    to 1 and the CmdSN is not advanced after this PDU is sent.

No, that's the whole point. That's the "Initiator response" PDU.

I think the confusion is that setting the ITT field to 0xffffffff is 
not "using" it. At least not as I understand it. "Using" an ITT is 
having a task in the initiator that has an ITT with that value. Thus we 
are saying that the initiator MUST never start a task that as an ITT of 
  0xffffffff.

Put another way, the "pick an ITT" function in the initiator must never 
return 0xffffffff.

Does that make things clearer?

Take care,

Bill

---

From: "Eddy Quicksall" <[email-masked]>
Date: Fri, 5 Aug 2005 17:43:13 -0400

Actually I know what the paragraph is trying to say but I think it is not 
worded clearly. Also, paragraphs 10.18 and 10.19 are very clear on this 
subject so I also wonder why it has to be explained again. Explaining again 
in unclear terms can imply unwanted understanding.

"An ITT value of ... NOT be used by the initiator" ... paragraph 10.19 is 
talking about Nop-In's and the initiator does not send NOP-In's. Hence one 
wonders what this is trying to say. If one thinks of this as a reference to 
10.18 then the ffffffff contradicts the RFC. Hence the mind shifts back and 
forth trying to figure out why this paragraph is even here.

If you guys think it is clear after reviewing it, then I'll accept that.

Eddy

----- Original Message ----- 
From: "William Studenmund" <[email-masked]>
To: "Eddy Quicksall" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, August 05, 2005 12:12 PM
Subject: Re: [Ips] section 5.1 ITT [draft-ietf-ips-iscsi-impl-guide-00.txt]

Take care,

Bill

---

From: William Studenmund <[email-masked]>
Date: Fri, 5 Aug 2005 17:13:06 -0700

On Aug 5, 2005, at 2:43 PM, Eddy Quicksall wrote:

> Actually I know what the paragraph is trying to say but I think it is 
> not worded clearly. Also, paragraphs 10.18 and 10.19 are very clear on 
> this subject so I also wonder why it has to be explained again. 
> Explaining again in unclear terms can imply unwanted understanding.
>
> "An ITT value of ... NOT be used by the initiator" ... paragraph 10.19 
> is talking about Nop-In's and the initiator does not send NOP-In's. 
> Hence one wonders what this is trying to say. If one thinks of this as 
> a reference to 10.18 then the ffffffff contradicts the RFC. Hence the 
> mind shifts back and forth trying to figure out why this paragraph is 
> even here.
>

Well, I thought it was clear. However the fact we still have this 
thread active indicates it may not be.

All I can think to add is some text to the second sentence:

Section 10.19 in [RFC3720] mentions this in passing but noted here 
again for making it obvious.  An ITT value of 0xffffffff is reserved 
and MUST NOT be used by the initiator to identify an initiator task.  
The only instance it may be seen on the wire is in a target-initiated 
NOP-In PDU (and the initiator response to that PDU if necessary).

Is that better?

Take care,

Bill

---

From: "Eddy Quicksall" <[email-masked]>
Date: Fri, 5 Aug 2005 20:32:42 -0400

Maybe you can explain why 10.19 (and 10.18) needs clarification. To me they 
are clear on the use of the ITT.

Eddy

----- Original Message ----- 
From: "William Studenmund" <[email-masked]>
To: "Eddy Quicksall" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, August 05, 2005 8:13 PM
Subject: Re: [Ips] section 5.1 ITT [draft-ietf-ips-iscsi-impl-guide-00.txt]

Is that better?

Take care,

Bill

---

From: William Studenmund <[email-masked]>
Date: Fri, 5 Aug 2005 17:44:09 -0700

On Aug 5, 2005, at 5:32 PM, Eddy Quicksall wrote:

> Maybe you can explain why 10.19 (and 10.18) needs clarification. To me 
> they are clear on the use of the ITT.

I'm not sure; I don't know what discussions lead to this section.

However I would expect they stem from the fact that RFC 3720 (10.18 and 
10.19) never explicitly states that ITT 0xffffffff is reserved overall. 
Yes, it's in the NOP-OUT and NOP-IN section and they won't work if ITT 
0xffffffff isn't reserved. But it's a big thing that should have been 
mentioned, say in chapter 3 where we discussed primary concepts. "Don't 
use ITT 0xffffffff for an initiator task's ID" is a big thing. :-)

Take care,

Bill

---

From: "Mallikarjun C." <[email-masked]>
Date: Fri, 05 Aug 2005 18:28:38 -0700

>But it's a big thing that should have been
 > mentioned, say in chapter 3 where we discussed primary concepts.

Thanks.  That's basically the feedback I received, which I thought was a 
reasonable request.  I will wordsmth the text a bit to make it clearer.

Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
StorageWorks Division
Hewlett-Packard MS 5668
Roseville CA 95747
cbm [at] rose.hp.com

William Studenmund wrote:
> ------------------------------------------------------------------------
>

---

From: "Eddy Quicksall" <[email-masked]>
Date: Fri, 5 Aug 2005 21:46:58 -0400

Ahh, silly me. All this time I thought the paragraph was referring to 10.19 
only.

How about this then?

--- new wording ---
Except where expressly allowed in sections 10.18 and 10.19, an ITT value of 
0xffffffff is reserved and MUST NOT be used by the initiator.

Eddy

----- Original Message ----- 
From: "William Studenmund" <[email-masked]>
To: "Eddy Quicksall" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, August 05, 2005 8:44 PM
Subject: Re: [Ips] section 5.1 ITT [draft-ietf-ips-iscsi-impl-guide-00.txt]

Take care,

Bill