iSCSI: TSIH clarifications

["Martin, Nick" <Nick.Martin@compaq.com>]

Julian,

Some comments/questions about TSIH

Draft 11-94 text:

9.12.6  TSIH

     TSIH MUST be valid only in the final response.  The target is gener-
     ates and uses it and its internal format and content are not defined 
     by this  protocol except for the value 0 that is reserved and used by 
     the initiator to indicate a new session.  It is given to the target, 
     during additional connection establishment for the same session, to 
     identify the associated session for the target.
      
The above paragraph is under Login Request.  (The word "is" in the second sentence should be removed.)  However it seems to describe the field more from the Login Response point of view.  Here is some alternate text to instruct the initiator constructing the Login Request PDU, and the target interpreting it.

9.12.6  TSIH

     TSIH must be set in the first Login Request.  The reserved value 0 
     MUST be used on the first connection for a new session.  Otherwise 
     the TSIH sent by the target at the conclusion of successful login of 
     the first connection for this session MUST be used.  The TSIH 
     identifies to the target, the associated existing session for this 
     new connection.  The target will verify that a session with this TSIH 
     exists, and that all other session identifying parameters of this 
     connection also match that session.

     All Login requests within the Login phase MUST carry the same TSIH.

     The target MUST use the value presented with the first login request.


Draft 11-94 text:

9.13.3  TSIH

     The TSIH is the target assigned component of the session identifier 
     (SSID).  TSIH MUST be valid only in the final response.  The target is 
     generating and using it and its internal format and content are not 
     defined by this protocol except for the value 0 that is reserved and 
     used by the initiator to indicate a new session.  It is given to the 
     target, during additional connection establishment for the same ses-
     sion, to identify the associated session for the target. 

The above paragraph is under Login Response.  My question is regarding the sentence "TSIH MUST be valid only in the final response.".  This could be read to mean that the TSIH, if known by the target at some earlier point, must not be supplied to the initiator in any non-final login response.  Was it intended to mean this for some security reason?  Or does it mean only that the initiator must not use the value until the final login response.

Which of the following best represents the intent of that sentence?
    A) "TSIH only MUST be valid in the final response."
    B) "TSIH MUST be valid in the final response.  Otherwise it is reserved."
    C) "TSIH MUST be valid in the final response.  Otherwise it MUST be 0."

The above primarily applies to the leading connection of a new session.  In the case of a connection other than the first in a session, the TSIH was supplied by the initiator in the first (and every) Login Request for this connection, should this value not be copied into every login response?

Thanks,
Nick
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Nick Martin
Systems Engineer
Server Storage Products
Compaq Computer Corporation