SORT BY:

LIST ORDER
THREAD
AUTHOR
SUBJECT


SEARCH

IPS HOME


    [Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

    RE: iSCSI: changing MaxPDUDataLength



    I see a case where the target could still end up sending PDU's of different
    lengths for a given command.
    
    It would be much safer if the initiator was required to idle the commands
    before sending the new MaxRecvDataSegmentLength. That way there is nothing
    for the target to do other than change the size.
    
    Eddy
    
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Tuesday, June 11, 2002 11:34 AM
    To: ips@ece.cmu.edu
    Subject: RE: iSCSI: changing MaxPDUDataLength
    Importance: High
    
    
    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
    
    
    
    
    
    
    
    
    


Home

Last updated: Tue Jun 11 19:18:46 2002
10670 messages in chronological order