RE: Initiator Task Tag

Jacob,

An iSCSI session is an I_T nexus - see the definitions of session
and I_T nexus in section 2.1 of RFC 3720.  Hence initiator task tags
have to be unique across an I_T nexus.

The language in Section 3.5.1.1 says that to identify a specific
SCSI command (I_T_L_x nexus), one needs the Task Tag to identify
the command.  In other words, session (I_T nexus) + ITT identifies
a specific command (I_T_L_x nexus).  If you need to know the LUN
(L), the command will contain that information.

Thanks,
--David
----------------------------------------------------
David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email protected]        Mobile: +1 (978) 394-7754
----------------------------------------------------

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] 
> Sent: Tuesday, September 19, 2006 12:13 PM
> To: [email protected]
> Subject: [Ips] Initiator Task Tag
> 
> Should the Initiator task tag be unique for an I_T nexus or for an
I_T_L
> nexus?
> 
> Section 3.2.1 says:
> Initiator identifying elements, such as the Initiator Task Tag, are
> global across the session regardless of the connection on which they
are
> sent or received.
> 
> and 
> 
> Sections 10.2.1.8 says:
> While a task exists, this tag MUST uniquely identify the task
session-wide.
> SCSI may also use the initiator task tag as part of the SCSI task
> identifier when the timespan during which an iSCSI initiator task tag
> must be unique extends over the timespan during which a SCSI task tag
> must be unique.
> 
> (which seems to imply I_T nexus wide uniqueness)
> 
> 
> 
> Section 3.5.1.1 says:
> IN arguments such as task attributes, Expected Data Transfer Length
for
> one or both transfer directions (the latter for bidirectional
commands),
> and Task Tag (as part of the I_T_L_x nexus).
> 
> (which seems to follow the broadest definition allowed by SAM)
> 
> 
> What was the intention of the designers?
> 
> 
> Thanks,
> Jacob 
> 
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