RE: iSCSI: DataACK SNACK

["Julian Satran" <Julian_Satran@il.ibm.com>]

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" <chuck.micalizzi@qlogic.com> 15-02-02 23:14

To:        Julian Satran/Haifa/IBM@IBMIL         cc:        <ips@ece.cmu.edu>         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: ips@ece.cmu.edu; owner-ips@ece.cmu.edu
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" <chuck.micalizzi@qlogic.com> Sent by: owner-ips@ece.cmu.edu 14-02-02 21:02

To:        <ips@ece.cmu.edu>        cc:                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.