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    iSCSI Draft 11 Comments and MaxCmdSN rule



    Julian & All,
    
    I have two comments on the draft 11 file.
    (http://www.haifa.il.ibm.com/satran/ips/draft-ietf-ips-iscsi-11.pdf)
    
    (1) Editional Comment
      On page 31, This sentence appers twice in this page.
      (Line 3 and Line 20)
      
       "The target MUST NOT transmit a MaxCmdSN that is less than the last
       ExpCmdSN. For non-immediate commands, the CmdSN field can take any
       value from ExpCmdSN to MaxCmdSN. The target MUST silently ignore any
       non-immediate command outside of this range or non-immediate duplicates
       within the range."
    
    (2)MaxCmdSN rule
      I think that this sentence should change as Ayman says.
      This sentence is a confusing expression.
    
      On Page 31, Line 3
       "The target MUST NOT transmit a MaxCmdSN that is less than the last
       ExpCmdSN. "
    
                             change to
    
       "The target MUST NOT transmit a MaxCmdSN that is less than the last
       ExpCmdSN-1. "
    
    
    -------------------
    Yoshihiro Hasebe
    NEC Corporation
    -------------------
    
    -------------------- Attached Mail -------------------------------
    
    Please consider also carefully the Serial Arithmetic rules with regard to
    "lower/higher" and the bounds on the ExpComdSN and MaxCmdSN difference.
    
    Julo
    ----- Forwarded by Julian Satran/Haifa/IBM on 08-02-02 02:26 -----
                                                                                                 
                        "Ayman Ghanem"                                                           
                        <aghanem@cisco       To:     <ips@ece.cmu.edu>                           
                        .com>                cc:                                                 
                        Sent by:             Subject:     RE: iSCSI: MaxCmdSN rule               
                        owner-ips@ece.                                                           
                        cmu.edu                                                                  
                                                                                                 
                                                                                                 
                        08-02-02 00:53                                                           
                                                                                                 
                                                                                                 
    
    
    
    This sentence should be changed to:
    
    "The target MUST NOT transmit a MaxCmdSN that is less than the last
    ExpCmdSN-1"
    
    The paragraph above this states:
    
    "If the PDU MaxCmdSN is less than the PDU ExpCmdSN-1 (in Serial Arithmetic
    Sense), they are both ignored."
    
    which allows MaxCmdSN = ExpCmdSN-1,valid, for the case when the target's
    command window is closed.
    
    -Ayman
    
     -----Original Message-----
     From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
     Buck Landry
     Sent: Thursday, February 07, 2002 2:40 PM
     To: ips@ece.cmu.edu
     Subject: iSCSI: MaxCmdSN rule
    
     Hi all, I'm struggling over how to interpret this rule in section 1.2.2 of
     draft v10:
    
     >>> The target MUST NOT transmit a MaxCmdSN that is less than
             the last ExpCmdSN.
     <<<
    
     This confuses me because it says to me (in some cases) that a target must
     be able to handle an unlimited number of commands.  For example, let's say
     the target has just about reached the limit of the commands it can handle:
    
     T=>(Nop-In) (MaxCmdSN = 1, ExpCmdSN = 1)
    
     I=>(Scsi Read Cmd) (CmdSN = 1)
    
     T=>(Data-in) (MaxCmdSN = 1, ExpCmdSN = 2 /* acknowledging scsi read cmd
     */)
    
     Now the target may have many more data-ins to transmit.  But according to
     the rule, since the last ExpCmdSN the target transmitted was 2, the target
     is now forced to send a MaxCmdSN of 2:
    
     T=>(Data-in) (MaxCmdSN = 2, ExpCmdSN = 2)
    
     But this allows the initiator to send another command, even though the
     target can't handle it!
    
     Obviously something is wrong with my reasoning here (perhaps my
     interpretation of 'last ExpCmdSN', or when I"m supposed to acknowledge the
     scsi cmd); can anybody clarify?
    
     --buck
    
    
    
    
    ----- Forwarded by Julian Satran/Haifa/IBM on 08-02-02 02:26 -----
                                                                                                 
                        "Buck Landry"                                                            
                        <blandry@cross       To:     <ips@ece.cmu.edu>                           
                        roads.com>           cc:                                                 
                        Sent by:             Subject:     iSCSI: MaxCmdSN rule                   
                        owner-ips@ece.                                                           
                        cmu.edu                                                                  
                                                                                                 
                                                                                                 
                        07-02-02 22:40                                                           
                                                                                                 
                                                                                                 
    
    
    
    Hi all, I'm struggling over how to interpret this rule in section 1.2.2 of
    draft v10:
    
    >>> The target MUST NOT transmit a MaxCmdSN that is less than
            the last ExpCmdSN.
    <<<
    
    This confuses me because it says to me (in some cases) that a target must
    be able to handle an unlimited number of commands.  For example, let's say
    the target has just about reached the limit of the commands it can handle:
    
    T=>(Nop-In) (MaxCmdSN = 1, ExpCmdSN = 1)
    
    I=>(Scsi Read Cmd) (CmdSN = 1)
    
    T=>(Data-in) (MaxCmdSN = 1, ExpCmdSN = 2 /* acknowledging scsi read cmd */)
    
    Now the target may have many more data-ins to transmit.  But according to
    the rule, since the last ExpCmdSN the target transmitted was 2, the target
    is now forced to send a MaxCmdSN of 2:
    
    T=>(Data-in) (MaxCmdSN = 2, ExpCmdSN = 2)
    
    But this allows the initiator to send another command, even though the
    target can't handle it!
    
    Obviously something is wrong with my reasoning here (perhaps my
    interpretation of 'last ExpCmdSN', or when I"m supposed to acknowledge the
    scsi cmd); can anybody clarify?
    
    --buck
    


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Last updated: Thu Mar 07 02:18:15 2002
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