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    RE: iSCSI: changing MaxPDUDataLength



    I suggest the following text in 11.13
    
           A change of MaxRecvDataSegmentLength by an initiator or target
           becomes effective after all commands preceding the negotiation
           end-ing request have been processed by the target and their status
           is acknowledged.
    
     I also realized that we don't have "negotiation prompt" from the target.
     I am not sure that we need one.
     If some of you think we need we may want one additional code in the Asynch
     Message.
     Please comment TODAY.
    
     Julo
    ----- Forwarded by Julian Satran/Haifa/IBM on 06/11/2002 06:29 PM -----
                                                                                                                                               
                          Julian Satran                                                                                                        
                                                   To:      Eddy Quicksall <eddy_quicksall@ivivity.com>                                        
                          06/11/2002 04:04         cc:      ips@ece.cmu.edu, pat_thaler@agilent.com                                            
                          PM                       From:    Julian Satran/Haifa/IBM@IBMIL                                                      
                                                   Subject: RE: iSCSI: changing MaxPDUDataLength(Document link: Julian Satran - Mail)          
                                                                                                                                               
                                                                                                                                               
                                                                                                                                               
                                                                                                                                               
                                                                                                                                               
                                                                                                                                               
    
    
    
    That is a fair request - we may slip in a recommendation to that effect (in
    chapter 11?)
    
    Julo
    
    
                                                                                                                                               
                          Eddy Quicksall                                                                                                       
                          <eddy_quicksall@i        To:       Julian Satran/Haifa/IBM@IBMIL                                                     
                          vivity.com>              cc:       ips@ece.cmu.edu, pat_thaler@agilent.com                                           
                                                   Subject:  RE: iSCSI: changing MaxPDUDataLength                                              
                          06/11/2002 04:28                                                                                                     
                          AM                                                                                                                   
                          Please respond to                                                                                                    
                          Eddy Quicksall                                                                                                       
                                                                                                                                               
                                                                                                                                               
    
    
    
    How about if we say that an initiator must not change the MaxPDUDataSize
    unless it first idles the commands (at least the ones with the R bit) or if
    ErrorRecoveryLevel==0?
    
    That would simplify target code greatly and would meet the design goals;
    and since it should be rare to change it, it would be of little impact to
    idle the commands for a split second.
    
    
    Eddy
          -----Original Message-----
          From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
          Sent: Monday, June 10, 2002 8:06 PM
          To: Eddy Quicksall
          Cc: ips@ece.cmu.edu; pat_thaler@agilent.com
          Subject: RE: iSCSI: changing MaxPDUDataLength
    
    
          I said only that when you change length you can ask for all PDUs
          after the ack! (no need to keep a tall - the old offsets are good up
          to the hole).
    
          Julo
    
                                                                              
       Eddy Quicksall                                                         
       <eddy_quicksall@ivivity.com>              To:        Julian            
                                         Satran/Haifa/IBM@IBMIL               
                                                 cc:        ips@ece.cmu.edu,  
       06/11/2002 12:32 AM               pat_thaler@agilent.com               
       Please respond to Eddy Quicksall          Subject:        RE: iSCSI:   
                                         changing MaxPDUDataLength            
                                                                              
                                                                              
                                                                              
    
    
    
    
          Julian,
    
          Another problem here is that the target has to calculate the offset
          from the DataSN #. And as BegRun can be any value. E.g., BegRun=4 and
          RunLngth=0 means starting DataSN=4, send all the data for that
          sequence.
    
          I think it would be a performance hit and waist of memory to keep a
          tally of all PDU sizes just for an occasional SNACK.
    
          It's not that it can't be done ... it is more that it is messy and I
          think there is a solution that will satisfy the design requirements
          but keep the software simpler.
    
          Eddy
          -----Original Message-----
          From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
          Sent: Saturday, June 08, 2002 10:16 PM
          To: Eddy Quicksall
          Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu; pat_thaler@agilent.com
          Subject: RE: iSCSI: changing MaxPDUDataLength
    
    
          That is not completely accurate.
          The only problem is when PDU size decreases and then SNACK must be
          for all data.
          Target can also keep a mapping of numbers/to offsets (the list should
          be small and if it gets long ask for ack (A-bit).
    
          Julo
                                                                              
       Eddy Quicksall                                                         
       <eddy_quicksall@ivivity.com>             To:                           
       Sent by: owner-ips@ece.cmu.edu    pat_thaler@agilent.com               
                                                cc:        ips@ece.cmu.edu    
                                                Subject:        RE: iSCSI:    
       06/08/2002 10:54 PM               changing MaxPDUDataLength            
       Please respond to Eddy Quicksall                                       
                                                                              
                                                                              
    
    
    
    
    
          Thanks,
    
          As a target, I won't be able to let it change until all of the
          outstanding
          commands are finished (running with ErrorRecoveryLevel>=1). This is
          because
          I must use the PDU size to compute the offset from a SNACK's
          BegRun/RunLength.
    
          So, I plan to not give the text response for a MaxPDURecvDataLength
          in FFP
          until I get back an ExpStatSN == next StatSN.
    
          This will cause a delay of unknown time before the PDU size can
          actually
          change ... do you see any problem with this?
    
          Eddy
    
          -----Original Message-----
          From: pat_thaler@agilent.com [mailto:pat_thaler@agilent.com]
          Sent: Friday, June 07, 2002 1:13 PM
          To: eddy_quicksall@ivivity.com; ips@ece.cmu.edu
          Subject: RE: iSCSI: changing MaxPDUDataLength
    
    
          Eddy,
    
          If one uses a message sync and steering that relys on the transport
          segments
          carrying a full PDU, e.g. TCP ULP Framing Protocol (TUF), then if the
          path
          MTU changes one would want to change the PDU data length to fit the
          new path
          MTU.
    
          Pat
    
          -----Original Message-----
          From: Eddy Quicksall [mailto:eddy_quicksall@ivivity.com]
          Sent: Wednesday, June 05, 2002 12:24 PM
          To: ips@ece.cmu.edu
          Subject: iSCSI: changing MaxPDUDataLength
    
    
          Does anybody know a case where it is necessary to support a new PDU
          data
          length during full feature phase?
    
          Eddy
          mailto: Eddy_Quicksall@iVivity.com
    
    
    
    
    
    
    
    
    
    


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Last updated: Wed Jun 12 16:18:42 2002
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