RE: iSCSI: DLB [T.31] ErrorRecoveryLevel 0.5

["KRUEGER,MARJORIE (HP-Roseville,ex1)" <marjorie_krueger@hp.com>]

David,
I don't understand what you are aquiescing to?  It seems to me that what
Steve is proposing is a violation of the protocol - there is no way to
negotiate "level 0 + SNACK", therefore as Mallikarjun pointed out, it
wouldn't work.  If you've negotiated error level 0, the remote end of this
session won't support SNACK (or shouldn't).  This sort of interpretation
would create an interoperability (not to mention testing) nightmare - that's
why the error recover levels were defined in the first place.  I think your
original comment is valid.

Marjorie Krueger
Networked Storage Architecture
Networked Storage Solutions Org.
Hewlett-Packard

> -----Original Message-----
> From: Black_David@emc.com [mailto:Black_David@emc.com]
> Sent: Wednesday, July 10, 2002 12:57 AM
> To: reames@diskdrive.com; ips@ece.cmu.edu
> Subject: RE: iSCSI: DLB [T.31]
> 
> 
> Steve,
> 
>> From DLB's comments:
>> 
>>>[T.31] 9.16.1  Type
>>>
>>>   An iSCSI target that does not support recovery within connection MAY
>>>   reject the status SNACK with a Reject PDU. If the target supports
>>>   recovery within connection, it MAY reject the SNACK after which it
>>>   MUST issue an Asynchronous Message PDU with an iSCSI event that indi-
>>>   cates "Request Logout".
>>>
>>> This should be conditioned on the operational ErrorRecoveryLevel of the
>>> session, not whether the target supports recovery within connection.
>> 
>> I would prefer that this not be conditioned on the ErrorRecoveryLevel. If
>> I am writing code, I may choose to support recovery-within-connection,
but 
>> not all the features that would be required to move me up to 
>> ErrorRecoveryLevel 1. I would like SNACK and Reject PDUs to work properly

>> for my code, even though it is technically only "ErrorRecoveryLevel 0.5".
>> As I read it, changing the wording would allow the target to ignore
>> my improved error recovery efforts unless I have a full
ErrorRecoveryLevel 1 
>> implementation. David, I doubt that is what you intended, so maybe you
>> want to word it a little differently.
> 
> Actually, it was what I intended when I made that comment, 
> BUT, I had not considered the scenario you describe above ... 
> and so, I now agree with
> you.  Therefore I'll withdraw my [T.31] comment provided that the
> possibility of multiple "ErrorRecoveryLevel 0.5" levels of support is
> described in the overview section to be added on error recovery.
> 
> Thanks,
> --David
> ---------------------------------------------------
> David L. Black, Senior Technologist
> EMC Corporation, 42 South St., Hopkinton, MA  01748
> +1 (508) 249-6449            FAX: +1 (508) 497-8018
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