RE: iSCSI - positive data ack - change proposal

["John Hufferd" <hufferd@us.ibm.com>]

Rod,
I think having iSCSI get the data off of the physical device to respond to
a resend request, may add more complexity then you are currently thinking
about.  That is because, it may be going back to get data that has been
changed by a write that could have come in from another connection.  This
gets all very complicated to control.

.
.
.
John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/SSG San Jose Ca
Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
Home Office (408) 997-6136
Internet address: hufferd@us.ibm.com


"Rod Harrison" <rod.harrison@windriver.com>@ece.cmu.edu on 09/25/2001
06:09:54 AM

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


To:   Julian Satran/Haifa/IBM@IBMIL, <ips@ece.cmu.edu>
cc:
Subject:  RE: iSCSI - positive data ack - change proposal



Julian,

     The NOP mechanism is awkward, no question, but I wasn't thinking it
was something we should specify and mandate. Rather it is something
that a target might do under extreme, and hopefully unlikely
conditions.

     - Rod

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
Julian Satran
Sent: Tuesday, September 25, 2001 1:02 PM
To: ips@ece.cmu.edu
Subject: RE: iSCSI - positive data ack - change proposal


Matthew,

I can fix the text and the ack for the last - we can dispense with,
but
unlike we gather more support we will have to drop this.   I think
that the
NOP mechanism is awkward but is awkward and as the target shares the
penalty for SNAK it has no real incentive to the F bit in every PDU.

Julo



                    "BURBRIDGE,MATTH
                    EW                     To:     Julian
Satran/Haifa/IBM@IBMIL,
                    (HP-UnitedKingdo        ips@ece.cmu.edu
                    m,ex2)"                cc:
                    <matthew_burbrid       Subject:     RE: iSCSI -
positive data ack -
                    ge@hp.com>              change proposal

                    24-09-01 12:38
                    Please respond
                    to
                    "BURBRIDGE,MATTH
                    EW
                    (HP-UnitedKingdo
                    m,ex2)"





Julian

This looks good!

A couple of comments:

Please could you add a paragraph to state that a target does not
necessarily
need to wait for the acknowledgment of a sequence before starting
transmission of the next sequence - for performance reasons.

In section 3.7.1 it states that "Upon receiving an Data-In PDU with
the F
set to 1 in a session with ErrorRecoveryLevel 1 or higher the
initiator
MUST
issue a DataACK type of SNACK indicating the next expected DataSN for
this
task".  Is this true for all incoming data sequences including the
final
sequence of the transfer?

Cheers

Matthew


-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Sunday, September 23, 2001 2:46 AM
To: ips@ece.cmu.edu
Subject: Re: iSCSI - positive data ack - change proposal


Here is updated version (in the previous I had excluded the sequences
ended
with Status with no good reason.

Julo

(See attached file: ack.txt)

----- Forwarded by Julian Satran/Haifa/IBM on 23-09-01 04:41 -----



                    Julian Satran

                                         To:     ips@ece.cmu.edu

                    22-09-2001           cc:

                    14:04                From:   Julian
Satran/Haifa/IBM@IBMIL
                                         Subject:     iSCSI - positive
data
ack - change
                                          proposal










Dear colleagues,

As  I mentioned earlier all the elements needed for positive data-ack
are
already in place.

I am suggesting the following changes to the document to reintroduce
the
data-ACK.

Comments?

Julo

**** Attachment ack.txt has been removed from this note on 23
September
2001 by Julian Satran ****