Death to I_T_L_Q nexus

Ralph Weber Ralph.Weber at
Mon Jun 16 14:42:14 PDT 2014

Formatted message: <a href="">HTML-formatted message</a>

... and I am cheering for that attempt to across the finish line.
From: George Penokie [george.penokie at]
Sent: Monday, June 16, 2014 4:21 PM
To: Ralph Weber
Cc: T10 Reflector
Subject: Re: Death to I_T_L_Q nexus
There are not very many cases where one plus the other wording is needed. In
most cases command identifier can be substituted for I_T_LQ nexus.
And yes this is an execution attempt.
Bye for now,
George Penokie
Avago Technologies
3033 41 St NW
Rochester , MN 55901
george.penokie at
On Wed, Jun 11, 2014 at 2:03 PM, Ralph Weber
<Ralph.Weber at> wrote:
I would worry about 'I_T_L nexus plus command identifier' only if there are
dozens of them. If use of the phrase can be limited to a handful of places,
then 'I_T_L_Q nexus' has clearly fallen to the level of an almost useless
term. In this regard, I am opposed to creating a new term just to have a
My much less profound question of mine is whether this effort constitutes
"executing I_T_L_Q nexuses'. Sorry, if only George gets this joke. It is
based on a very old T10 food fight, but the fight was the basis for the
requirement that commands be processed, not executed.
All the best,
From: owner-t10 at<mailto:owner-t10 at>
[owner-t10 at<mailto:owner-t10 at>] on behalf of Kevin D Butt
[kdbutt at]
Sent: Wednesday, June 11, 2014 1:22 PM
To: George Penokie
Cc: owner-t10 at<mailto:owner-t10 at>; T10 Reflector
Subject: Re: Death to I_T_L_Q nexus
I have no objections with the concept of this direction. I was initially
concerned with the terminology used since FCP-4 also used the term.  However,
upon further review this seems to fall right into place.
FCP-4 Terms:
Command Identifier = 3.1.7 command identifier: The information that uniquely
identifies a command. See Annex A and SAM-5.  This is synonymous with OX_ID
(Note that If retransmission is enabled, the task retry identifier is also
used to construct the command identifier.)
I do have a concern with using "I_T_L nexus plus command identifier"
throughout all the standards.  I would prefer we come up with a term to
describe this.	Perhaps something like "Fully qualified command identifier". 
I know that doesn't really save words or letters when typing it, but it does
better convey, I think, the concept for which it is used.
Annex terminology mapping seems to have inconsistencies in it.
For SAM-3 command identifier = task tag
For SAM-4 command identifier = I_T_L_Q nexus
I think, perhaps for SAM-4 mapping it should be "I_T_L nexus plus command
identifier = I_T_L_Q nexus"
Also, there is a typo of "poert" instead of "port" in in the SCSI
Initiator Port box
Kevin D. Butt
SCSI Architect, Tape Firmware, T10 Standards
Data Protection & Retention
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280<tel:520-799-5280>
Fax: 520-799-2723<tel:520-799-2723> (T/L:321)
Email address: kdbutt at
From:	     George Penokie
<george.penokie at>
To:	   T10 Reflector <t10 at<mailto:t10 at>>,
Date:	     06/11/2014 08:35 AM
Subject:	Death to I_T_L_Q nexus
Sent by:	<owner-t10 at<mailto:owner-t10 at>>
If don't reached SAM overload yet this proposal should push you over the
edge. Here is the overview:
There has been a long standing problem with the I_T_L_Q nexus as it combines
routing information with a command identifier. The routing part is the I, the
T, and the L. The command identifier is the Q. In addition the nexus really
does not have a satisfactory home in the SAM-5 UML model.
This proposal solves the UML issue by adding a Management Application Client
class that is a “kind of” Application Client class. The new Management
Application Client class has I_T Nexus Identifier attributes and I_T_L Nexus
Identifier attributes. The Management Application Client class is the class
that goes out and finds all the nexuses in the SCSI domain. The method used
for the Management Client class to do this is protocol specific. For example
in SAS the discovery is defined in the SPL standard.
This also separates Q from nexus and replaces that with a standard alone
attribute called a Command Identifier attribute. The effect of this is that
all the I_T_L_Q nexus terms will be replaced with either Command Identifier
or I_T_L nexus and command identifier. This causes extensive changes to
several standards but has the largest effect on SPL, then SAM, then SPC, and
finally SBC. To prevent issues with existing published standards the term
I_T_L_Q nexus will have to remain but it will be defined as being synonymous
with I_T_L nexus plus command identifier.
Your request to upload a file or files to the T10 site has been accepted.
Your PDF file will be posted at:
Bye for now,
George Penokie
Avago Technologies
3033 41 St NW
Rochester , MN 55901
george.penokie at

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