Subject: RE: ISCSI: CmdSN in non-leading login

From: [email-masked]
Date: Fri, 10 May 2002 14:04:51 -0400

> There is a certain ambiguity about 9.12.8.  The text describes how in a 
> leading connection, the target takes must accept and use a non-zero CmdSN,

> but it does not explain what should be present for a non-leading
connection.
>
> There are a couple of problems here for the target.  At what point is a 
> non-leading connection considered to be part of the session ?   Is it the 
> moment that the login request is received with a non-zero TSIH ?  Or is it

> only when the non-leading login succeeds and it enters full feature phase
?

My recollection is the latter, so a non-leading login carries a CmdSN
that only applies to that login, and it starts using session-wide CmdSN
numbering when it enters full-feature phase.  I see the ambiguity in the
9.12.8 text, and believe the answer is that a non-leading login can use
any CmdSN it likes, but only for login purposes, and starts using the
session CmdSN numbering when it enters full-feature phase.

> So, should an initiator set the CmdSN in the first login request to zero 
> and only synchronise with the session command stream after full feature
> phase is established ?  This is my preferred option.

Synchronization in full feature phase should be required.  Zero should
be allowed, but not required.  As long as the Initiator chooses the
number and can use what it wants, Mark's initiators are free to choose
zero.  Text would need to be added to explain this.

> What happens if the initiator tries using the current session command 
> sequence number is that whilst the login negotiation occurs, other 
> connections within the session can be issuing new commands, so by the time

> that the login is finished the CmdSN exchanged in the initial request is 
> invalid anyway.

Non-leading login should not affect the session until it enters full-
feature phase.

Thanks,
--David
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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
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From: "Mark S. Edwards" <[email-masked]>
Date: Fri, 10 May 2002 19:13:54 +0100

David,

>session CmdSN numbering when it enters full-feature phase.

We can live with that.  The text as it stands is applicable only to the 
leading connection, it just needs additional words to describe the more 
limited scope of a CmdSN in a non-leading connection.

>zero.  Text would need to be added to explain this.

Fine, our target will just echo the CmdSN that the initiator chooses.  All 
we wanted was text to clarify that whatever this value is in a non-leading 
connection is meaningless within the context of the real session CmdSN.

>Non-leading login should not affect the session until it enters full-

That's exactly what I wanted to hear ... over to you Julian :)

Mark.