Re: Question On R2T Behaviour?

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

Suresh,

The only statement that can be made is that the target is the master of 
the data transfers.
For the case you describe any of the behaviors you describe is legal.
The behavior is defined by SSCSI (SAM).
The results are implementation dependent.
The only think that we might say is that the results "should match 
expectation" and "the residual counts should match transfers".
In practical terms you will find many targets that will terminate the 
transfer with an error status if an R2T  request is not properly 
fulfilled.

Julo





"Suresh Tanjore" <sureshtk@aarohicommunications.com>
Sent by: owner-ips@ece.cmu.edu
16-11-01 19:39
Please respond to "Suresh Tanjore"

 
        To:     <ips@ece.cmu.edu>
        cc: 
        Subject:        Question On R2T Behaviour?

 

Hi all,

On page 75 of iSCSi 0.8 revision

                 " The data length of the DATA PDU MUST *not exceed* the 
desired
                 data transer length specified in the R2T. If the R2T is 
answered
                 with a sequence of data PDUs the buffer offset and Length
                 must be within the range of those specfied by R2T, the 
last PDU
                 SHOULD have the F bit set to 1. The data-out PDU ordering 
is goverened
                 by  DataPDUInOrder."


My question is if the data length of the DATA PDU is less than
the desired data transfer length and the F bit is set, what should be the
behaviour of the target. For the sake of this discussion let us
assume DataPDUInOrder to be set to Yes.

                 1. It looks intutive that target may send another R2T 
with different
                    sequence number and collect the data initially that 
the host
                    was not able to send for the previous R2T request.

                 Or

                 2. It is an error that need to be detected by target that 
the host was not
                    able to fully satisfy the R2T request sent by the 
target in the first
place.

Please let me know what is the right behaviour and should this be 
documented
in the
specification if it is not already documented. If it is documented may be 
i
missed
reading this, please point to me where it is defined.

Thanks
sureshtk