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    Re: iSCSI Change - New NOP-Out/In text



    Sorry for the previous mail, which was sent accidentally.
    
    Julian,
    
    I have some questions.
    
    * Section 1.1  NOP-Out
    
                                                The NOP-Out may be useful
       in the case where an initiator has been waiting a long time for the
       response to some command, and the initiator suspects that there is some
       problem with the connection. .....
       
       If the initiator does not receive the NOP-In within some
       time (determined by the initiator),
            
          A NOP-Out should also be used to confirm a changed ExpStatSN if there is
       no other PDU to carry it for a long time.
    
        ? The draft doesn't say what a long time is? 
        
        Section 7.11.1 says as follows:
    
             The timeout value to be used by a target is outside the scope 
               of this document.  
        and
             The timeout value to be used by an initiator is outside the 
               scope of this document. 
    
        ? How the initiator/target times out is not defined? Then what that long time refers 
        to?
    
    * Section 1.1.3     Ping Data
    
       Ping data is reflected in the NOP-In Response. Note that the length of
       the reflected data is limited to 4096 bytes and the initiator should
       avoid sending more than 4096 bytes. The length of ping data is indicated
       by the Data Segment Length.  0 is a valid value for the Data Segment
       Length - and indicates the absence of ping data.
    
        ? The text starts abruptly that ping data is reflected....
           It doesn't say what the ping data is?
    
    
    - asai.
    
    
    
    ----- Original Message ----- 
    From: Julian Satran <Julian_Satran@il.ibm.com>
    To: <ips@ece.cmu.edu>
    Sent: Thursday, August 16, 2001 08:39 PM
    Subject: iSCSI Change - New NOP-Out/In text
    
    
    Here  is the new NOP-Out/In text (2.12 & 2.13):
    
    1.1  NOP-Out
    
    
       Byte /    0       |       1       |       2       |       3       |
          /              |               |               |               |
         |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
         +---------------+---------------+---------------+---------------+
        0|X|I| 0x00      |1| Reserved (0)                                |
         +---------------+---------------+---------------+---------------+
        4| Reserved (0)  | DataSegmentLength                             |
         +---------------+---------------+---------------+---------------+
        8| LUN or Reserved (0)                                           |
         +                                                               +
       12|                                                               |
         +---------------+---------------+---------------+---------------+
       16| Initiator Task Tag or Reserved (0xffffffff)                   |
         +---------------+---------------+---------------+---------------+
       20| Target Transfer Tag or Reserved (0xffffffff)                  |
         +---------------+---------------+---------------+---------------+
       24| CmdSN                                                         |
         +---------------+---------------+---------------+---------------+
       28| ExpStatSN                                                     |
         +---------------+---------------+---------------+---------------+
       32/ Reserved (0)                                                  /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
       48| Digests if any...                                             |
         +---------------+---------------+---------------+---------------+
         / DataSegment - Ping Data (optional)                            /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
    
       The NOP-Out with the Initiator Task Tag set to valid value (not the
       reserved 0xffffffff) acts as a "ping command".
    
       This form of the NOP-Out can be used to verify that a connection is
       still active and all its components are operational. This command MAY
       use in-order delivery or immediate delivery. The NOP-Out may be useful
       in the case where an initiator has been waiting a long time for the
       response to some command, and the initiator suspects that there is some
       problem with the connection.  When a target receives the NOP-Out with a
       valid Initiator Task Tag, it should respond with a Nop-In Response,
       duplicating the data that was provided in the NOP-Out (if any) as much
       as possible.  If the initiator does not receive the NOP-In within some
       time (determined by the initiator), or if the data returned by the
       NOP-In is different from the data that was in the NOP-Out, the initiator
       may conclude that there is a problem with the connection. The initiator
       then closes the connection and may try to establish a new connection.
    
       A NOP-Out should also be used to confirm a changed ExpStatSN if there is
       no other PDU to carry it for a long time.
    
       The NOP-Out can be sent by an initiator because of a NOP-In with the
       Target Transfer Tag set to a valid value (not the reserved 0xffffffff).
       In this case the NOP-Out Target Transfer Tag must contain a copy of
       NOP-In Target Task Tag.
    
    
    1.1.1     Initiator Task Tag
    
       An initiator assigned identifier for the operation.
    
       The NOP-Out must have the Initiator Task Tag set to a valid value only
       if a response in the form of NOP-In is requested.
       If the Initiator Task Tag does not contain a valid value, the CmdSN
       field contains as usual the next CmdSN but CmdSN is not advanced and the
       I bit must be set to 1.
    
    1.1.2     Target Transfer Tag
    
       A target assigned identifier for the operation.
    
       The NOP-Out MUST have the Target Transfer Tag set only if it is issued
       in response to a NOP-In with a valid Target Transfer Tag, in which case
       it copies the Target Transfer Tag from the NOP-In PDU.
    
       When the Target Transfer Tag is set, the LUN field MUST be also copied
       from the NOP-In.
    
    1.1.3     Ping Data
    
       Ping data is reflected in the NOP-In Response. Note that the length of
       the reflected data is limited to 4096 bytes and the initiator should
       avoid sending more than 4096 bytes. The length of ping data is indicated
       by the Data Segment Length.  0 is a valid value for the Data Segment
       Length - and indicates the absence of ping data.
    
    
    
    1.2  NOP-In
    
    
       Byte /    0       |       1       |       2       |       3       |
          /              |               |               |               |
         |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
         +---------------+---------------+---------------+---------------+
        0|1|1| 0x20      |1| Reserved (0)                                |
         +---------------+---------------+---------------+---------------+
        4| Reserved (0)  | DataSegmentLength                             |
         +---------------+---------------+---------------+---------------+
        8| LUN or Reserved (0)                                           |
         +                                                               +
       12|                                                               |
         +---------------+---------------+---------------+---------------+
       16| Initiator Task Tag or Reserved (0xffffffff)                   |
         +---------------+---------------+---------------+---------------+
       20| Target Transfer Tag or Reserved (0xffffffff)                  |
         +---------------+---------------+---------------+---------------+
       24| StatSN                                                        |
         +---------------+---------------+---------------+---------------+
       28| ExpCmdSN                                                      |
         +---------------+---------------+---------------+---------------+
       32| MaxCmdSN                                                      |
         +---------------+---------------+---------------+---------------+
       36/ Reserved (0)                                                  /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
       48| Digests if any...                                             |
         +---------------+---------------+---------------+---------------+
         / DataSegment - Return Ping Data                                /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
    
    
       When a target receives the NOP-Out with a valid Initiator Task Tag (not
       the reserved value 0xffffffff), it MUST respond with a NOP-In with the
       same Initiator Task Tag that was provided in the NOP-Out Command. It
       SHOULD also duplicate up to first 4096 bytes of the initiator provided
       Ping Data. For such a response, the Target Transfer Tag MUST be
       0xffffffff.
    
    1.2.1     Target Transfer Tag
    
       A target assigned identifier for the operation.
    
       A target may issue a NOP-In on its own to test the connection and the
       state of the initiator. If the target wants to test the initiator, it
       sets the Target Task Tag to a valid value (not the reserved 0xffffffff)
       in order to ask for an answer from the initiator. In this case the
       Initiator Task Tag MUST be 0xffffffff and the LUN field MUST contain a
       valid LUN. If the target wants only to test the connection, both tags
       MUST hold the reserved value 0xffffffff and the LUN field is reserved.
    
       A target may also issue a NOP-In on its own to carry a changed ExpCmdSN
       and/or MaxCmdSN if there is no other PDU to carry them for a long time.
    
       Whenever the NOP-In is not issued in response to a NOP-Out the StatSN
       field will contain as usual the next StatSN but StatSN for this
       connection is not advanced.
    
    
    1.2.2     LUN
    
       A LUN MUST be set to a correct value when the Target Transfer Tag is
       valid (not the reserved value 0xffffffff).
    
    
    


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