Re: iSCSI - CmdSN and Retry

["Julian Satran" <Julian_Satran@il.ibm.com>]

The initiator has to timeout and resend (see chapter 6). Julo

Rohit B <b_rohitb@yahoo.com> Sent by: owner-ips@ece.cmu.edu 05-04-02 09:00 Please respond to Rohit B

To:        iSCSI <ips@ece.cmu.edu>         cc:                 Subject:        iSCSI -  CmdSN and Retry

Hello,
   Please consider the scenario described below

CmdSN (I)                  ExpCmdSN (T)               


  1  ---------------------->                    
   <------------------------  2     

  2  ---------------------->                    
   <------------------------  3     

  3  ---------------------->                    
   <------------------------  4     

  4  ---------------------->                    
   <------------------------  5     


This would be the order of processing if none of the
packets were lost. If for example the packet with
CmdSN = 2 was lost, but the others were received at
the Target

CmdSN (I)                  ExpCmdSN (T)               


  1  ---------------------->                    
   <------------------------  2     

  2  ----------dropped packet                    
  

  3  ---------------------->                    


  4  ---------------------->                    


The draft says that  "With the exception of the
commands marked for immediate delivery, the iSCSI
target layer MUST deliver the commands for execution
in the order specified by CmdSN." (Pg 30 draft 11).
This means that the target cannot process cmds 3 and 4
until it gets cmd 2. Is this interpretation correct? 

                 If YES,can the target acknowledge to the initiator
the receipt of cmds 3 and 4? If so, how? or is it the
responsibility of the initiator to timeout and retry
commands 2,3 and 4. This may be wasteful as 3 and 4
have already reached the target. 


Thanks,
Rohit

                  

  


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