|
Hi,
Section 8 mentions "It is also assumed that at
target, incoming data (read data)
MAY be kept for recovery or it can be re-read from
a device server."
Is it assumed here that the data from the device
server is idempotent i.e will not
change when tried to re-read. If that is not the
case and we have more than one
Data In PDU being sent in the response (for one of
which a retransmission is
requested), it will result in in-correct view of
the data being given to the initiator.
As an example, consider that the following response
needs to be given
------------------
| 1 | 2 | 3 | 4 |
-----------------
which gets transmitted in two Data In PDUs like
this
--------
---------
| 1 | 2
| |
3 | 4 |
--------
---------
Now if a re-read generates
------------------
| 1 | 3 | 4 | 5 |
------------------
and retransmission is requested for 2nd PDU. It will get transmitted like
--------
| 4 | 5 |
--------
which means the initiator neither got 1,2,3,4 nor got 1,3,4,5 (both of
which are
valid snapshots at some point in time), instead it got 1,2,4,5 which never
existed
at the target.
If we try to re-read only data pertaining to retransmitting PDU, the
problem persists.
Regards,
Rahul
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