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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI: changing MaxPDUDataLengthI 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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