RE: iSCSI: Use of the A bit

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

Thanks for catching 2.5.3.4 conflict (it was not updated together with 9).
It reads now:

With the SNACK Request, the initiator requests retransmission of num-bered-responses or data from the target. A single SNACK request covers a contiguous set of missing items called a run of a given type of items (the type is indicate in a type field in the PDU header). The run is composed of an initial item (StatSN, DataSN, R2TSN) and the number of missed Status, Data, or R2T PDUs. For long data-in sequences, the target may request (at predefined minimum intervals) a positive acknowledgement for the data sent. A SNACK request with a type field that indicates ACK and the number of Data-In PDUs acknowl-edged conveys this positive acknowledgement. 

SNACKs can be rejected when the target does not have the data or status or has never sent it (error in error recovery :-)).

Julo

Michael Schoberg <michael_schoberg@cnt.com> Sent by: owner-ips@ece.cmu.edu 15-03-02 01:14 Please respond to Michael Schoberg

To:        "IPS Reflector (E-mail)" <ips@ece.cmu.edu>         cc:                 Subject:        RE: iSCSI: Use of the A bit

9.4.3 I have a  more general SNACK question.  When would one use use the iSCSI, SCSI Response message with sense (reason -> SNACK rejected)?  The reason for using this hasn't jumped out at me yet.  Does it have to do with connection recovery?

9.16 States that SNACK support is optional.  Since "ErrorRecoveryLevel" controls SNACK support, can something in the SNACK message description reference how this feature is negotiated?

Also a cleanup is needed for SNACK- "RunLength".

  2.5.3.4   SNACK Request

          With the SNACK Request, the initiator requests retransmission of num-
          bered-responses or data from the target. A single SNACK request covers
          a contiguous set of missing items called a run of a given type of
          items (the type is indicate in a type field in the PDU header). The
          run is composed of an initial item (StatSN, DataSN, R2TSN) and the
          number of additional missed Status, Data, or R2T PDUs (0 means only
          the initial). For long data-in sequences, the target may request (at
          predefined minimum intervals) a positive acknowledgement for the data
          sent. A SNACK request with a type field that indicates ACK and the
          number of Data-In PDUs acknowledged conveys this positive acknowl-
          edgement.

9.16
          The SNACK request is used to request the retransmission of numbered-
          responses, data, or R2T PDUs from the target.  The SNACK request indi-
          cates the missed numbered-response or data "run" to the target, where
          the run starts with the first missed StatSN, DataSN, or R2TSN and
          indicates also the number of missed Status, Data, or R2T PDUs (0 has
          the special meaning of "all after the initial").