RE: iSCSI: changing MaxPDUDataLength

["Rod Harrison" <rod.harrison@windriver.com>]

	I don't see an issue with this, although I would prefer to see it
mandated rather than recommended.

	- Rod

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
Julian Satran
Sent: Tuesday, June 11, 2002 8:11 AM
To: Eddy Quicksall
Cc: ips@ece.cmu.edu; pat_thaler@agilent.com
Subject: RE: iSCSI: changing MaxPDUDataLength



That is a fair request - we may slip in a recommendation to that
effect (in chapter 11?)

Julo


Eddy Quicksall <eddy_quicksall@ivivity.com>
06/11/2002 04:28 AM
Please respond to Eddy Quicksall

        To:        Julian Satran/Haifa/IBM@IBMIL
        cc:        ips@ece.cmu.edu, pat_thaler@agilent.com
        Subject:        RE: iSCSI: changing MaxPDUDataLength




How about if we say that an initiator must not change the
MaxPDUDataSize unless it first idles the commands (at least the ones
with the R bit) or if ErrorRecoveryLevel==0?

That would simplify target code greatly and would meet the design
goals; and since it should be rare to change it, it would be of little
impact to idle the commands for a split second.


Eddy
-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Monday, June 10, 2002 8:06 PM
To: Eddy Quicksall
Cc: ips@ece.cmu.edu; pat_thaler@agilent.com
Subject: RE: iSCSI: changing MaxPDUDataLength


I said only that when you change length you can ask for all PDUs after
the ack! (no need to keep a tall - the old offsets are good up to the
hole).

Julo

Eddy Quicksall <eddy_quicksall@ivivity.com>
06/11/2002 12:32 AM
Please respond to Eddy Quicksall
       To:        Julian Satran/Haifa/IBM@IBMIL
       cc:        ips@ece.cmu.edu, pat_thaler@agilent.com
       Subject:        RE: iSCSI: changing MaxPDUDataLength





Julian,

Another problem here is that the target has to calculate the offset
from the DataSN #. And as BegRun can be any value. E.g., BegRun=4 and
RunLngth=0 means starting DataSN=4, send all the data for that
sequence.

I think it would be a performance hit and waist of memory to keep a
tally of all PDU sizes just for an occasional SNACK.

It's not that it can't be done ... it is more that it is messy and I
think there is a solution that will satisfy the design requirements
but keep the software simpler.

Eddy
-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Saturday, June 08, 2002 10:16 PM
To: Eddy Quicksall
Cc: ips@ece.cmu.edu; owner-ips@ece.cmu.edu; pat_thaler@agilent.com
Subject: RE: iSCSI: changing MaxPDUDataLength


That is not completely accurate.
The only problem is when PDU size decreases and then SNACK must be for
all data.
Target can also keep a mapping of numbers/to offsets (the list should
be small and if it gets long ask for ack (A-bit).

Julo
Eddy Quicksall <eddy_quicksall@ivivity.com>
Sent by: owner-ips@ece.cmu.edu
06/08/2002 10:54 PM
Please respond to Eddy Quicksall
      To:        pat_thaler@agilent.com
      cc:        ips@ece.cmu.edu
      Subject:        RE: iSCSI: changing MaxPDUDataLength






Thanks,

As a target, I won't be able to let it change until all of the
outstanding
commands are finished (running with ErrorRecoveryLevel>=1). This is
because
I must use the PDU size to compute the offset from a SNACK's
BegRun/RunLength.

So, I plan to not give the text response for a MaxPDURecvDataLength in
FFP
until I get back an ExpStatSN == next StatSN.

This will cause a delay of unknown time before the PDU size can
actually
change ... do you see any problem with this?

Eddy

-----Original Message-----
From: pat_thaler@agilent.com [mailto:pat_thaler@agilent.com]
Sent: Friday, June 07, 2002 1:13 PM
To: eddy_quicksall@ivivity.com; ips@ece.cmu.edu
Subject: RE: iSCSI: changing MaxPDUDataLength


Eddy,

If one uses a message sync and steering that relys on the transport
segments
carrying a full PDU, e.g. TCP ULP Framing Protocol (TUF), then if the
path
MTU changes one would want to change the PDU data length to fit the
new path
MTU.

Pat

-----Original Message-----
From: Eddy Quicksall [mailto:eddy_quicksall@ivivity.com]
Sent: Wednesday, June 05, 2002 12:24 PM
To: ips@ece.cmu.edu
Subject: iSCSI: changing MaxPDUDataLength


Does anybody know a case where it is necessary to support a new PDU
data
length during full feature phase?

Eddy
mailto: Eddy_Quicksall@iVivity.com