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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI: changing MaxPDUDataLength
I think that even the text I suggested is more than it is needed. Quiescing
the connection is not practical - many large box builder will find this
unacceptable and obviously an implementation can go away without it. As I
pointed out for retries you need only the offset at the change point and
anything that happens later require retransmission of everything from the
known point.
Julo
Eddy Quicksall
<eddy_quicksall@i To: Julian Satran/Haifa/IBM@IBMIL, ips@ece.cmu.edu
vivity.com> cc:
Subject: RE: iSCSI: changing MaxPDUDataLength
06/11/2002 08:56
PM
Please respond to
Eddy Quicksall
I see a case where the target could still end up sending PDU's of different
lengths for a given command.
It would be much safer if the initiator was required to idle the commands
before sending the new MaxRecvDataSegmentLength. That way there is nothing
for the target to do other than change the size.
Eddy
-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Tuesday, June 11, 2002 11:34 AM
To: ips@ece.cmu.edu
Subject: RE: iSCSI: changing MaxPDUDataLength
Importance: High
I suggest the following text in 11.13
A change of MaxRecvDataSegmentLength by an initiator or target
becomes effective after all commands preceding the negotiation
end-ing request have been processed by the target and their status
is acknowledged.
I also realized that we don't have "negotiation prompt" from the target.
I am not sure that we need one.
If some of you think we need we may want one additional code in the Asynch
Message.
Please comment TODAY.
Julo
----- Forwarded by Julian Satran/Haifa/IBM on 06/11/2002 06:29 PM -----
Julian Satran
To: Eddy Quicksall
<eddy_quicksall@ivivity.com>
06/11/2002 04:04 cc: ips@ece.cmu.edu,
pat_thaler@agilent.com
PM From: Julian
Satran/Haifa/IBM@IBMIL
Subject: RE: iSCSI: changing
MaxPDUDataLength(Document link: Julian Satran - Mail)
That is a fair request - we may slip in a recommendation to that effect (in
chapter 11?)
Julo
Eddy Quicksall
<eddy_quicksall@i To: Julian
Satran/Haifa/IBM@IBMIL
vivity.com> cc: ips@ece.cmu.edu,
pat_thaler@agilent.com
Subject: RE: iSCSI:
changing
MaxPDUDataLength
06/11/2002 04:28
AM
Please respond to
Eddy Quicksall
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> To: Julian
Satran/Haifa/IBM@IBMIL
cc: ips@ece.cmu.edu,
06/11/2002 12:32 AM pat_thaler@agilent.com
Please respond to Eddy Quicksall 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> To:
Sent by: owner-ips@ece.cmu.edu pat_thaler@agilent.com
cc: ips@ece.cmu.edu
Subject: RE: iSCSI:
06/08/2002 10:54 PM changing MaxPDUDataLength
Please respond to Eddy Quicksall
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
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