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 -----
Sent: Friday, August 31, 2007 11:53
AM
Subject: Re: rationale to send PDUs
in increasing CmdSn onsingle connection
Parav Pandit <paravpandit@xxxxxxxxx> 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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