RE: iSCSI: Use of the A bit

[Paul Koning <ni1d@arrl.net>]

>>>>> "John" == John Hufferd <hufferd@us.ibm.com> writes:

 John> I like this response.  I think it is correct and the best
 John> response so far on this topic.

I think it's essentially correct, see below.  I agree with the
conclusion. 

 >> "BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)"
 >> <matthew_burbridge@hp.com> @ece.cmu.edu on 03/13/2002 10:39:27
 >> AM

 >> The target is quite within its rights to use the A bit when at
 >> recovery level 0.  If the session is re-established due to
 >> recovery 7.11.4 then the relevant command is aborted anyway and
 >> so there is no reason to keep hold of the data any way: With
 >> recovery level 0 there is no recovery mechanism that requires
 >> the target to keep the data.  Therefore the A bit is redundant
 >> when the recovery level is 0.

 >> The spec says that the initiator MUST issue a SNACK if the A
 >> bit is set.  However, the MaxBurstSize restriction is there to
 >> prevent the initiator from having to send a SNACK on every PDU
 >> in the case where a target inadvertently sets the A bit in (for
 >> example) every data in PDU. The target may set the A bit more
 >> often than the MaxBurstSize but it should not expect a SNACK
 >> more often than this.

The spec says that the target MUST NOT set the A it more often that
MaxBurstSize.  If it does, that would be a protocol violation.  Is is
perfectly reasonable for the initiator to ignore A bits that are
protocol violations; even if the spec had not stated so explicitly,
that would have been true.

     paul