Re: rationale to send PDUs in increasing CmdSn onsingle connection

Julian, below you said "no" to #2. But is there a restriction in the RFC (maybe I just don't remember it)? I agree it has no practical value but I have used it to test my re-ordering logic with only one connection.

Eddy
  ----- Original Message ----- 
  From: Julian Satran 
  To: Parav Pandit 
  Cc: [email protected] 
  Sent: Friday, August 31, 2007 11:53 AM
  Subject: Re: [Ips] rationale to send PDUs in increasing CmdSn onsingle connection




  Parav Pandit <[email protected]> wrote on 31/08/2007 12:52:04:

  > Hi,
  >  
  > RFC 3720, section 3.2.2.1 says 
  > 
  > "On any connection, the iSCSI initiator MUST send the
  > commands in increasing order of CmdSN, except for
  > commands that are retransmitted due to digest error
  > recovery and connection recovery. "
  > 
  > (Assuming Single TCP connection ISCSI session)
  > 
  > 1. I interpret above 3.2.2.1 statement as 
  > SCSI layer gives SCSI commands to the ISCSI stack in
  > the order of Cmd-1 and Cmd-2. 
  > Cmd-1 will have CmdSn = 10.
  > Cmd-2 will have CmdSn = 11.
  > ISCSI stack CAN send PDUs to the TCP layer in
  > following order ONLY.
  > PDU-1 with Cmd-1.
  > PDU-2 with Cmd-2.
  > 
  > Is this correct interpretation?
  > Or
  > 
  Yes 
  > 2. On a SINGLE connection can ISCSI stack send the 
  > PDU-1 with Cmd-2 followed by 
  > PDU-2 with Cmd-1?
  > 
  NO
  > Assuming the answer of the question #2 is No,
  > 
  > 3. If there are multiple connections in a session then
  > command MAY any way reach out of order. And targets
  > need to wait for the previous expected commands.
  > 
  > So targets will receive out of order ISCSI PDUs from
  > the TCP layer and ISCSI stack handles them.
  > 
  > So then why initiators have restriction of sending
  > command in the increasing order of CmdSn on SINGLE TCP
  > connection?
  > 
  To simplify recovery and to...
  > Is it to simplify the implementation of targets
  > supporting only single TCP connection?
  > 
  > 

  and there was no visible motivation for out of order commands on a single connection 

  > Regards,
  > Parav Pandit
  > 
  > 
  > 
  >        
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