RE: iSCSI - ExpDataSN

To: "'Julian Satran'" <Julian_Satran@il.ibm.com>, ips@ece.cmu.edu

Subject: RE: iSCSI - ExpDataSN

From: "KRUEGER,MARJORIE (HP-Roseville,ex1)" <marjorie_krueger@hp.com>

Date: Fri, 16 Aug 2002 15:01:26 -0400

Content-Type: multipart/alternative;boundary="----_=_NextPart_001_01C24557.5236A760"

If I understand correctly, this change will align the TASK REASSIGN task management function behavior with the SNACK request behavior wrt understanding that the value 0 means "send me all unacked data" - that makes sense to me.

In the 3rd sentence, it's not clear to me what you mean by "a new data acknowledgement ref. number" - shouldn't this be the requestor's ExpDataSN or 0? The use of the word "new" leave the impression that the requestor is somehow resetting this number and offering a new one?

Editorial comments: the 3rd sentence in the first paragraph seems to be missing a comma after "Bidirectional command"? And the word "acknowledgement" is mis-spelled in the hyphenated spot. I've corrected the text below:

For recovery purposes the iSCSI target and initiator maintain a data acknowledgement reference number - the first input DataSN number unacknowledged by the initiator. When issuing a new command this num-ber is set to 0. If the function is TASK REASSIGN, which establishes a new connection allegiance for a previously issued Read or Bidirec-tional command, ExpDataSN will contain either a new data acknowledge-ment reference number or the value 0 indicating that the data acknowledgement reference number is unchanged. The initiator MUST discard any data PDUs from the previous execution that it did not acknowledge and the target MUST transmit all Data-in PDUs (if any) starting with the data acknowledgement reference number. The number of retransmitted PDUs, may or may not be the same as the original transmission depending on if there was a change in MaxRecvDataSeg-mentLength in the reassignment. The target MAY also send no more Data-In ! PDUs if it sent all its data in PDUs with DataSN less than ExpDataSN.

The value of ExpDataSN MUST be either 0 or higher than the DataSN of the last acknowledged Data-In PDU but not larger than DataSN+1 of the last Data-IN PDU sent by the target. Any other value MUST be ignored by the target.

For other functions this field is reserved.