|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI: Use of the A bityes - I think that the latest text does just that. Julo "Rod Harrison" <rod.harrison@win To: Julian Satran/Haifa/IBM@IBMIL, John Hufferd/San driver.com> Jose/IBM@IBMUS cc: "Mallikarjun C." <cbm@rose.hp.com>, 18-03-02 23:29 <ips@ece.cmu.edu>, <owner-ips@ece.cmu.edu> Please respond to Subject: RE: iSCSI: Use of the A bit "Rod Harrison" Can we explicitly allow the status and data ACKs to be at the same time? Otherwise we prevent sending the status ACK (expStatSn) in the data ACK SNACK PDU. - Rod -----Original Message----- From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of Julian Satran Sent: Monday, March 18, 2002 8:23 PM To: John Hufferd Cc: Mallikarjun C.; ips@ece.cmu.edu; owner-ips@ece.cmu.edu Subject: Re: iSCSI: Use of the A bit John, comments in text - JUlo John Hufferd/San Jose/IBM@IBMUS 18-03-02 19:17 Please respond to John Hufferd To: Julian Satran/Haifa/IBM@IBMIL cc: "Mallikarjun C." <cbm@rose.hp.com>, ips@ece.cmu.edu, owner-ips@ece.cmu.edu Subject: Re: iSCSI: Use of the A bit Julian the following statement is confusing: "An initiator MUST ONLY acknowledge the status for command that produced Data-In PDUs after acknowledging the Data-In PDUs if Data-In PDU acknowledgment is requested by the target. A status acknowledgement for a command that generated Data-In PDUs is considered by the target as an implicit acknowledgement of the Data-In PDUs if such an acknowledgement was requested by the target." What did you intend to say. All commands MUST have t status acknowledge, via ExpStatSN, so I do not understand the first sentence. And if the Data-In PDUs must be acknowledged (if the A bit is set), what is the meaning of the last statement. +++ The first statement says that IF data-ack is requested it MUST be sent by the initiator before it acknowledges status. +++ Since I do not believe there is a need to ack the last Data-In PDU, I am hoping you agree. But it is not clear. +++ In fact the target may want a data ack as the status ack might be delayed for various reasons. The second statement says that if the target sees a status ack that is also an ack for the data The first statement says that the initiator must send ack if asked - and send status ack only afterwards. The second says that when status is received the data are acked and target should wait no longer (i.e., no recovery action). +++ If the Target sets the A bit on the last Data-In PDU, which also has good status set -- and the Initiator has a PDU ready to send to which it can attach the value of ExpStatSN, which will show that the Data-In PDU was received -- there should be no reason to send a extra SNACK for the Data-In PDU. Please tell me that is what you intended to say in the above quoted text. . . . 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, Cell: (408) 499-9702 Internet address: hufferd@us.ibm.com "Julian Satran" <Julian_Satran@il.ibm.com>@ece.cmu.edu on 03/17/2002 05:52:46 PM Sent by: owner-ips@ece.cmu.edu To: "Mallikarjun C." <cbm@rose.hp.com> cc: ips@ece.cmu.edu, owner-ips@ece.cmu.edu Subject: Re: iSCSI: Use of the A bit Dear all, The text for the A bit part (9.7.2) reads now: A (Acknowledge) bit For sessions with ErrorRecoveryLevel 1 or higher, the target sets this bit to 1 to indicate that it requests a positive acknowledgement from the initiator for the data received. The target should use the A bit moderately; it MAY set the A bit to 1 only once every MaxBurstSize bytes or on the last Data-In PDU that concludes the entire requested read data transfer for the task from the target's perspective, and MUST NOT do so more frequently than this. On receiving a Data-In PDU with the A bit set to 1, the initiator MUST issue a SNACK of type DataACK. If the initiator has detected holes in the input sequence, it MUST postpone issuing the SNACK of type DataACK until the holes are filled. An initiator MUST ONLY acknowledge the status for command that produced Data-In PDUs after acknowledging the Data-In PDUs if Data-In PDU acknowledgment is requested by the target. A status acknowledgement for a command that generated Data-In PDUs is considered by the target as an implicit acknowledgement of the Data-In PDUs if such an acknowledgement was requested by the target. The ITT mandating text in 9,16.1 will read: For Status SNACK and DataACK, the Initiator Task Tag is reserved. In all other cases, the Initiator Task Tag field MUST be set to the Ini-tiator Task Tag of the referenced command. Julo
Home Last updated: Mon Mar 18 18:18:12 2002 9189 messages in chronological order |