RE: iSCSI - ExpDataSN

[pat_thaler@agilent.com]

Julian,

 

Looks good.

 

For completeness, "The target MAY also  send no more Data-In ! PDUs if it sent all its data in PDUs with DataSN

   ^ not sure what that character was suppose to be

less than ExpDataSN." should be

"The target MAY also send no more Data-In PDUs if all data has been acknowledged."

because ExpDataSN might be 0 and all the data was already acknowledged. If all the PDUs had DataSN less than ExpDataSN, then all the data was also acknowledged so this change covers both cases.

 

Pat

 

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Friday, August 16, 2002 4:02 AM
To: ips@ece.cmu.edu
Subject: iSCSI - ExpDataSN

Mallikarjun has 
expressed a lingering concern that we should allow the value 0 
for the field ExpDataSN in a TASK REASSIGN TM function to 
say "give me all unacked data" (as we do for SNACK). 
Please observe that we already allow the target to do 
this on its own and this change does not affect 
any recovery mechanism. To do it I am suggesting the following rephrasing 
of 9.5.6 

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 acknowldge-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. 

Please let me know what you think. 

Julo