iSCSI: Question on StatRN usage

["Mallikarjun C." <cbm@rose.hp.com>]

Julian,

Could you please comment on the following on StatRN usage?  Let me
know if I am misinterpreting the draft.

Current iSCSI draft seems to allow StatRN values from 0 through
2**32-1.  It does not qualify the value of 0 as it does for CmdRNs.
Assuming that 0 is legal, how would a receiving initiator distinguish
between the target implementation that numbers (assigns StatRNs) 
read data PDUs and the one that doesn't?  A StatRN of 0 in a read data
packet could be miscontrued and scoreboarded at the initiator, when
all the target was saying is that it doesn't implement StatRN for 
data (assuming that 0 happens to be a legal StatRN at the moment).

Options are:
- explicitly state that StatRN value of 0 is not legal.  This is
  simple, and my preference.  A statRN of 0 in data PDUs in this case 
  indicates non-implementation.
- rely on a login dialogue to call out the capability.

Even if we choose the first option, I propose introducing a login/text 
key request/response through which an initiator can ask a target not
to number iSCSI data PDUs since he cannot scoreboard all the (potentially
unlimited # per each read command) data PDUs.  Note that the converse 
case for target is not critical since target controls the write data transfers
and can hope to have scoreboarding room always available.

Thanks!
--
Mallikarjun 
M/S 5601			
Networked Storage Architecture
HP Storage Organization
Hewlett-Packard, Roseville.
cbm@rose.hp.com