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    RE: iSCSI: v15 R2T and DATA-OUT



    There should not be a requirement for the initiator to check for
    consistency. This would just serve to impact performance. It would be OK to
    check but the target should be responsible to set the LUN correctly and the
    initiator should just copy it as is.
    
    BTW, the LUN in the R2T only has use by the target ("are used by the target
    only"). If the target doesn't need it, then why should it take the time to
    supply it?
    
    Does anyone know why this is in the R2T anyway? It would seem like the TTT
    would say it all.
    
    Eddy
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Friday, July 26, 2002 5:04 AM
    To: ips@ece.cmu.edu
    Subject: RE: iSCSI: v15 R2T and DATA-OUT
    
    
    I will add a strong statement about field consistency somewhere in 2.
    
    Julo
    
    
     
    
                          "Rod Harrison"
    
                          <rod.harrison@win        To:       Julian
    Satran/Haifa/IBM@IBMIL                                                      
                          driver.com>              cc:       <ips@ece.cmu.edu>
    
                                                   Subject:  RE: iSCSI: v15 R2T
    and DATA-OUT                                                    
                          07/26/2002 03:08
    
                          AM
    
     
    
     
    
    
    
    
    Julian,
    
                 OK, that's the answer to my question then. The wording that's
    there
    right now doesn't say what the initiator should do if the LUN in an
    R2T doesn't match the LUN it sent in the command PDU.
    
                 So the resolution is that the initiator should treat a LUN
    inconsistency between R2T and command as a protocol error. I suggest
    we add a note to that effect where we talk about LUN in the R2T PDU
    description, that would be 9.8.5 in the v15 working draft.
    
                 - Rod
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Thursday, July 25, 2002 6:53 PM
    To: Rod Harrison
    Cc: ips@ece.cmu.edu
    Subject: RE: iSCSI: v15 R2T and DATA-OUT
    
    
    
    Rod,
    
    Probably a very long day. LUN is present in the command. Command is
    associated with ITT. R2T can be checked for a consistent ITT and LUN.
    End-story.
    
    Julo
    
    
    "Rod Harrison" <rod.harrison@windriver.com>
    07/25/2002 06:49 AM
    
            To:        <ips@ece.cmu.edu>
            cc:        Julian Satran/Haifa/IBM@IBMIL
            Subject:        RE: iSCSI: v15 R2T and DATA-OUT
    
    
    
    
    
                    OK, it's been a long day. Let me try this one more
    time.
    
                    I was write (almost) first time but I meant DATA-OUT
    instead of
    DATA-IN. Here's what I meant to say ...
    
                    There is a potential inconsistency in the description
    of the use of
    the LUN field in DATA-OUT and R2T in the working v15 draft.
    
                    9.7.3 Target Transfer Tag, for DATA-OUT last paragraph
    says ...
    
                    "If the Target Transfer Tag is provided, then the LUN
    field MUST hold
    a valid value and be consistent with whatever was specified with the
    command;"
    
                    9.8.5 Target Transfer Tag, for R2T says ...
    
                    "The Target Transfer Tag and LUN are copied in the
    outgoing data PDUs
    and are used by the target only."
    
                    Potentially a target could return a different LUN
    field in the R2T,
    for perhaps some funky LUN mapping or other internal reason expecting
    it to be copied to the DATA-OUT as per the R2T text.
    
                    I think we need to indicate what is expected of the
    initiator if the
    LUN field in the R2T does not match the LUN in the command PDU.
    
                    - Rod
    
    -----Original Message-----
    From: Rod Harrison [mailto:rod.harrison@windriver.com]
    Sent: Wednesday, July 24, 2002 8:57 PM
    To: Julian Satran
    Cc: ips@ece.cmu.edu
    Subject: RE: iSCSI: v15 R2T and DATA-OUT
    
    
    
                    Oops, I see the confusion. I said DATA-IN in my
    message when I meant
    DATA-OUT.
    
                    However, re-reading the section of v15 in question I
    now see that the
    third paragraph is referring to the DATA-IN LUN, not the DATA-OUT LUN.
    That wasn't clear to me when first scanned it because of the paragraph
    break.
    
                    Perhaps a note of clarification needs to be added?
    
                    - Rod
    
    -----Original Message-----
    From: Rod Harrison [mailto:rod.harrison@windriver.com]
    Sent: Wednesday, July 24, 2002 8:51 PM
    To: Julian Satran
    Cc: ips@ece.cmu.edu
    Subject: RE: iSCSI: v15 R2T and DATA-OUT
    
    
    Julian,
    
                    I think you've misread my message. I was questioning
    how the
    initiator should handle the LUN between an R2T and the DATA-OUT(s)
    that satisfy it.
    
                    DATA-OUT says copy the LUN from the command PDU, R2T
    says copy the
    LUN from the R2T to the DATA-OUT. Which is correct if the R2T contains
    a different LUN than that in the command PDU?
    
                    - Rod
    
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Wednesday, July 24, 2002 5:00 PM
    To: Rod Harrison
    Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
    Subject: Re: iSCSI: v15 R2T and DATA-OUT
    
    
    There is no TTT for data-In. Julo
    
    
    
                         "Rod Harrison"
                         <rod.harrison@win        To:
    <ips@ece.cmu.edu>
                         driver.com>              cc:
                         Sent by:                 Subject:  iSCSI: v15
    R2T and DATA-OUT
                          owner-ips@ece.cmu
                         .edu
    
    
                         07/24/2002 10:24
                         PM
    
    
    
    
    
    
    Folks,
    
                There is a potential inconsistency in the description of
    the
    use of
    the LUN field in DATA-OUT and R2T in the working v15 draft.
    
                9.7.3 Target Transfer Tag, for DATA-IN last paragraph
    says ...
    
                "If the Target Transfer Tag is provided, then the LUN
    field
    MUST hold
    a valid value and be consistent with whatever was specified with the
    command;"
    
                9.8.5 Target Transfer Tag, for R2T says ...
    
                "The Target Transfer Tag and LUN are copied in the
    outgoing
    data PDUs
    and are used by the target only."
    
                Potentially a target could return a different LUN field
    in the
    R2T,
    for perhaps some funky LUN mapping or other internal reason expecting
    it to be copied to the DATA-OUT as per the R2T text. I suspect we just
    want to say this is not allowed and the LUN field MUST be the same as
    the command PDU.
    
                Either way I think we need to indicate what is expected
    of the
    initiator if the LUN field in the R2T does not match the LUN in the
    command PDU.
    
                Apologies for not spotting this before the end of last
    call.
    
                - Rod
    
    
    
    
    


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