SORT BY:

LIST ORDER
THREAD
AUTHOR
SUBJECT


SEARCH

IPS HOME


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

    Re: iSCSI : Digest Error Problems & CmdSN/ExpCmdSN window issues



    Santosh,
    
    I guess I don't understand what it is that you think needs clarification.
    
    -Matt
    
    Santosh Rao wrote:
    > 
    > Matt,
    > 
    > (You may want to take another look at the thread.). Here's the details again :
    > 
    > > 3) The policy of "discard and restart" is also subject some race
    > > conditions in the CmdSN sliding window. At the time the digest error was
    > >
    > > detected at the initiator, the ExpCmdSN may not yet have acknowledged
    > > that
    > > command. This causes the initiator to restart the command with the same
    > > Initiator Task Tag, CmdSN and "retry" bit set.
    > >
    > > However, by the time the command gets to the target, the target may have
    > >
    > > updated its ExpCmdSN window having sent a later PDU which updated the
    > > ExpCmdSN. This results in the target discarding the received CmdSN since
    > >
    > > <js> at command restart you never really rely on the CmdSN. you will want
    > > to check
    > > the Initiator Task Tag and accept it in the above case. </js>
    > 
    > The draft states the following on this subject :
    > 
    > Section 5.1
    > =========
    > -    the initiator will reissue all outstanding commands with their
    >       original Initiator Task Tag and their original CmdRN if they
    >       are not acknowledged yet or a CmdRN of 0 (not-numbered) if they
    >       were acknowledged; the retry (X) flag in the command PDU will
    >       be set
    > 
    > Section 1.2.2.1
    > ===========
    > - The target MUST silently ignore any command
    >    outside this range or duplicates within the range not flagged with
    >    the retry bit (the X bit in the opcode).
    > 
    > This, to me, means :
    > - ignore all commands outside the (ExpCmdSN, MaxCmdSN) range.
    > - ignore all duplicate commands within the range that are not flagged with the
    > retry
    > bit. << "duplicate" added this time >>
    > 
    > Can you please clarify the intent of the text ?
    > 
    > Matt Wakeley wrote:
    > 
    > > Santosh Rao wrote:
    > > > Alright (so the cut & paste did'nt work)  ;-}
    > > >
    > > > The issue under discussion is a retried command [and thereby, a duplicate
    > > > CmdSN] that is OUTSIDE the (ExpCmdSn, MaxCmdSN) range. That falls under the
    > > > first criteria.
    > >
    > > And the point is?  What am I missing?
    > >
    > > -Matt
    


Home

Last updated: Tue Sep 04 01:05:41 2001
6315 messages in chronological order