> what part of the standard defines this error recovery? i was looking at
> 10.3 of the ST standard which says the timing out of this operation is the
> responability of the ULP, which in this case is SCSI. then the ST
> standard says that error recovery happens at the level of the transaction.
If you look at the state tables for the various FSMs you'll see that
the actions required to be triggered at various timeouts are clearly
defined. The ULP case may apply to transactions outside of sequences
covered in various FSMs. SCSI uses the Read/Write sequences - which
are defined.
> in the context of gig ethernet what defines this potential retransmision
> done by the nic itself? is this something defined by STP? are you
> talking about some other protocol running on gig ethernet sitting below
> STP doing this retransmision?
The GbE nic doesn't do any retransmission; in the general case, such
transactions would be beyond the scope of STP (they would be extremely
media dependent - like micropackets on GSN..; the implication to STP
would be that it sits on a reliable physical medium)
> do you envision the transmission of a CTS being initiated by the host or
> by the nic itself? how is it anticipated that SCSI transactions would be
> broken up into blocks. do you picture a SCSI transaction basically to
> consist of a block or two or something closer to one block = one frame?
> i would think the CTS would have to be initiated by the host itself, not
> the nic. if this is the case then it would probably be prefereable to
> minimize the number of blocks per transaction in order to minimize the
> host/nic interaction. this would mean that a resent CTS corresponds to
> the retransmission of a large number of individual frames.
CTS retransmission will be initiated by the host only! One could
implement the whole stack in the NIC - but thats not a desirable/
useful option. The concept of blocks implies the granularity at which
the host operates the protocol stack.
The block size used is a tradeoff between the desire the minimize
the host/nic interaction, and cost of retransmission on errors.
Block size to be used is determined by the configuration of the NIC,
and options submitted by the ULP. The ULP doesn't have to chunk the
transfer into blocks; for read/write sequences that part is handled
by the protocol stack (the FSM).
:a
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