Re: IG clarifications: Login Response & Reject reason codes

[Julian Satran <Julian_Satran@xxxxxxxxxx>]

Mallikarjun,

If we allow for multiple outstanding
Login Requests we will have to allow for multiple outstanding Login Responses.

Regards,
Julo

"Mallikarjun C." <cb_mallikarjun@xxxxxxxxx>

28/12/06 21:45

To	Julian Satran/Haifa/IBM@IBMIL
cc	IPS <ips@xxxxxxxx>
Subject	Re: IG clarifications: Login Response & Reject reason codes

Julian,
 
Thanks for the inputs, I somehow overlooked
to respond to this email earlier.

I agree with you on the "Task in progress" Reject reason code.
 There is no 
 
Unless I hear new objections, I would like
to note "Negotiation Reset" Reject reason code as obsolete.  Based
on the silence so far, like you, I do not believe it is in use.
 
On the "no more than one outstanding
Login Response" semantics, your comments seem to be around Login Request
PDU (and I believe we have such text for Login Request PDU) - do you see
any cases wherein there can be multiple outstanding Login Responses on
the wire?  The request I got was to clarify if there is a plausible
use case.  
 
Thanks!
 
Mallikarjun
----- Original Message ----
From: Julian Satran <Julian_Satran@xxxxxxxxxx>
To: Mallikarjun C. <cb_mallikarjun@xxxxxxxxx>
Cc: IPS <ips@xxxxxxxx>
Sent: Monday, December 11, 2006 1:34:41 PM
Subject: Re:  IG clarifications: Login Response & Reject reason
codes



"Mallikarjun C." <cb_mallikarjun@xxxxxxxxx> wrote on 11/12/2006
20:15:23:

> All:
> 
> I received some offline feedback on the implementers' guide draft
> from  a few reviewers who preferred to be anonymous.  Please
review & comment.
> 
> 1) RFC 3720 does not explicitly call out that there cannot be more
> than one outstanding Login-Response PDU on one iSCSI connection at
> any given time (although the C-bit text indirectly implies it).
> 
> 

This is intentional. At the time we where playing with the idea of pipelining
the login. 
However it is common practice to have a single outstanding Login Request.
I think that the only thing that becomes problematic is the phase change
request (there you can have only one outstanding).
There is already text that says that all changes to key values become final
only at the end (when consistency can be reasonably checked).

> Section 10.10 on Text Request PDU (which should cover Login Request
> PDU semantics as well) says: "An initiator MUST have at most
one 
> outstanding Text Request on a connection at any given time."
 
> Essentially, an analog for Login/Text Response is missing (or so it
seems).
> 
> 2) RFC 3720 does not specify the use case for Reject reason code 
> "Task in progress" (0x07).
> 
> I vaguely recall we put in this reason code for task reassignment
> attempts while a task is in progress, but then we subsequently added
> a TMF response reason code for that case (Julian?).  So I'm not
sure
> if reason code 0x07 is used by implementations any longer.  
> 

The reject can used when the initiator attempts to start a new task but
a task with the same ITT is still active for those cases when the target
can't be sure this is a protocol error (e.g., a race between a logout and
a reissued SCSI command). 

> The other non-obvious case is that of a "negotiation reset"
Reject 
> reason code.  What is this used for by implementations, if at
all?  
> If I don't hear any objections, I will deprecate these two reason
codes.
> 

The negotiating can't be continued by one of the parties but the partial
results (e.g., previous stage) are OK and no renegotiation is deemed necessary.
I have no clue if somebody uses it but I felt at the time that the purists
will object if I'd suggest restarting the login :-)

> Mallikarjun
> 
> 
>  
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