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RE: iSCSI: DataACK SNACK
How about moving bi-di to 40 and residual count to 44? Eddy -----Original Message----- From: John Hufferd [mailto:email@example.com] Sent: Tuesday, February 19, 2002 4:43 AM To: Julian Satran Cc: Chuck Micalizzi; firstname.lastname@example.org Subject: RE: iSCSI: DataACK SNACK Julian, If you include the TTT in the Data-In PDU, you will need to change the format of the Data-In PDU. The TTT is usually placed at displacement 20-23, if you do that, you will have to reformat the Data-In PDU. Perhaps the best thing to do is to move the residual count to displacement 44-47. This is the same displacement that is used by the SCSI Response PDU for the residual count for Bidirectional reads. The other PDU that has a residual count, is the SCSI Response PDU and it also has residual in bytes 20-23, so there is no perfect solution. What do you plan to do? If this change worth it? . . . 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: email@example.com Julian Satran/Haifa/IBM@IBMIL@ece.cmu.edu on 02/15/2002 11:52:06 PM Sent by: firstname.lastname@example.org To: "Chuck Micalizzi" <email@example.com> cc: firstname.lastname@example.org Subject: RE: iSCSI: DataACK SNACK Chuck, The Initiator Task Tag is thhe only reliable indicator the protocol provides today. If nobody shouts against it we might let the target provide a Target Transfer Task for Data-In PDUs that have the A bit set to be returned with the ACK for target convenience. Julo "Chuck Micalizzi" <email@example.com To: Julian m> Satran/Haifa/IBM@IBMIL cc: 15-02-02 23:14 <firstname.lastname@example.org> Subject: RE: iSCSI: DataACK SNACK Julian, Thank you for the response. Let me try to be more direct. If a target has been issued multiple read commands, with transfer counts that exceed the negotiated maxBurstSize. After the target sends a data sequence for one of these commands must it wait for a DataACK before sending a data sequence for another command. Or is it free to send a data sequence for each outstanding command? If the target can have a data sequence in flight for each active command then it must expect a DataACK for each sequence sent with the Acknowledge bit set. If the DataACK SNACK doesn't include a task Tag the target can't be certain as to which data sequence the initiator is acknowledging. So how can the target determine which resources to free or which sequence to send next? chuck -----Original Message----- From: Julian Satran [mailto:Julian_Satran@il.ibm.com] Sent: Friday, February 15, 2002 9:30 AM To: Chuck Micalizzi Cc: email@example.com; firstname.lastname@example.org Subject: Re: iSCSI: DataACK SNACK DataACK is a "bulk ack". Answering the last (in case of several) is good enough. I fail to see your point. Julo "Chuck Micalizzi" <email@example.com> To: Sent by: firstname.lastname@example.org <email@example.com> cc: 14-02-02 21:02 Subject: iSCSI: DataACK SNACK All, I have a question regarding DataACK. Rev. 10 section 10.16.1 states: For a Data/R2T SNACK, the Initiator Task Tag MUST be set to the Initiator Task Tag of the referenced Command. Otherwise, it is reserved. it also states: The DataACK is used to free resources at the target and not to request or imply data retransmission. Is the target allowed to have more than one DataACK outstanding on a connection? If multiple outstanding DataACKs are allowed per connection then in my opinion the DataACK must have a valid task tag inorder for the target to associate the DataACK with the appropriate resources to be freed. chuck micalizzi Qlogic Corp.
Last updated: Tue Feb 19 22:18:03 2002
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