Re: CmdSN during login

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

Mallikarjun,

I do realize that there are cases when the whole of the login sequence have
to be executed "out of order".
There are however cases when the login has to be executed in order (e.g.,
after an abort or after a logoout).
This is why I think that no new mechanism is needed (not considering them
unnumbered by default) and the Immediate command flag will cover all the
needs (together with the "one outstanding command" rule that holds for
login).
The confusion previously quote is when does numbering start and that is
from the first command of the first login.
For the leading login (the one creating a session) having the commands
immediate or not is less relevant as
those are the only commands arriving and no other connection can be
established.

Regards,
Julo

"Mallikarjun C." <cbm@rose.hp.com>@ece.cmu.edu on 10-08-2001 17:54:38

Please respond to cbm@rose.hp.com

Sent by:  owner-ips@ece.cmu.edu


To:   Julian Satran/Haifa/IBM@IBMIL
cc:   ips@ece.cmu.edu
Subject:  Re: CmdSN during login



Julian,

I tend to agree with Mark and Sanjay.

In cases where all connections in a session failed and a new
connection is being added to the existing session state (before
the session timeout), an initiator must issue the Login as an
immediate command to avoid the possibility of a deadlock - since
the initiator does not know for sure if target received all commands
on the failed connections.

Since this appears to be a mandatory requirement, I suggest that
we make it the default behavior - that Login PDUs never *consume*
CmdSNs (though the leading login carries a valid "seed" CmdSN),
including the leading login PDU.  There are no conditionals this way.

Sorry, I can't find the reasoning you offered earlier for rev07
behavior, in the middle of my travel.  Please comment if I missed
something.
--
Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668 Hewlett-Packard, Roseville.
cbm@rose.hp.com

Julian Satran wrote:
>
> Sanjay,
>
> If you want to ignore CmdSN and expedite Login processing you can do so
by
> having the commands being issued as immediate.
> This will help us keep away from creating ambiguity about (or another
> conditional) for when CmdSN is to be used or not.
>
> Julo
>
> Mark Bakke <mbakke@cisco.com>@ece.cmu.edu on 09-08-2001 23:55:25
>
> Please respond to Mark Bakke <mbakke@cisco.com>
>
> Sent by:  owner-ips@ece.cmu.edu
>
> To:   Sanjay Goyal <sanjay_goyal@ivivity.com>
> cc:   "Ips (E-mail)" <ips@ece.cmu.edu>
> Subject:  Re: CmdSN during login
>
> Sanjay-
>
> I absolutely agree with this; CmdSN is owned by the session, and
> should not be used until the connection has fully joined the session,
> which means full feature phase.
>
> This should also clean up any ambiguity on when to start
> using CmdSN.
>
> --
> Mark
>
> Sanjay Goyal wrote:
> >
> > Hi
> >
> >  Assuming Target and Initiator support multiple connections and the
> session
> > is having multiple connections. Assuming out-of-order CmdSN is a
> possibility
> > for this session.
> >
> >  Connection #   1       |       2       |       3
> > -------------------------------------------------------
> > Login Cmd  CmdSN=0      |   CmdSN=8     |  CmdSN=9
> > Txt   Cmd  CmdSN=1      |               |
> >                                 |               |
> >                                 |               |
> > Login Cmd  CmdSN=7      |  CmdSN=10     |  CmdSN=11
> > -------------------------------------------------------
> > Data Cmd   CmdSN=12     | CmdSN=14      | CmdSN=15
> > Data Cmd   CmdSN=13     |               |
> >                                 |               |
> >
> > CmdSN=7 is last of the Login sequence and it is acknowledged by the
> Target
> > with "accept login" response.
> >
> > Target would receive the PDUs in this CmdSN order
> >  0 to 7, 8, 9, 12, 10, 11, 13, 14, 15
> >
> > Now as Login and Text PDUs are being processed even though you have
> received
> > Data Cmd PDUs, you can not pass them to iSCSI layer and hence you are
> adding
> > latency.
> >
> > What I want to convey from this example is why not use CmdSN just
during
> the
> > FullFeature phase only.
> >
> > Regards
> > Sanjay Goyal
> >
> >
>
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>
> >
> >    Part 1.2    Type: application/ms-tnef
> >            Encoding: base64
>
> --
> Mark A. Bakke
> Cisco Systems
> mbakke@cisco.com
> 763.398.1054