Boy, that was dumb of me, I didn't even notice that
statement in the very email I sent out.
Eddy
----- Original Message -----
Sent: Friday, October 19, 2007 5:23
PM
Subject: Re: rationale to send PDUs
in increasing CmdSn onsingleconnection
yes it is must and besides
being pointless sending out of order would break some assumptions about
detecting missing items (as Pat has nicely outlined in her note).
Julo
On Oct 19, 2007, at 8:03 AM, Eddy Quicksall
wrote:
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.
Parav quoted a MUST from the
RFC on this, so I'd call that a restriction. :-)
I
agree that it's a reasonable thing to do to test re-ordering logic. But I
think that test environments don't count in that to be a good test of error
handling, they _must_ break the spec. :-) Otherwise it's exceptionally
difficult to reproducibly test how devices handle error conditions. :-)
Take care,
Bill
---- Original Message ----- From: Julian Satran To:
Parav
Pandit Cc: ips@xxxxxxxx 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
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