Given that not all device ports support NL-Port operation,
I'd prefer to see you propose using a new bit. That way devices that do
not support the feature can return CHECK CONDITION for an Invalid Field in CDB
and easily point to the new bit.
Regards,
Michael Banther
Hewlett-Packard Ltd.
Telephone +44 (117)
312-9503
From: owner-t10@t10.org
[mailto:owner-t10@t10.org] On Behalf Of Kevin D Butt Sent: 27
March 2006 22:15 To: t10@t10.org Subject: ADC-2: Topology
Auto configuration
ADC WG,
In ADC-2, 6.2.2.3.3 Fibre Channel descriptor parameter
format, there is defined the topology lock bit. <<< A topology lock
(TOPLOCK) bit set to one forces the DT device primary port to operate only in
the mode selected by the P2P bit. A
TOPLOCK bit set to zero indicates the DT device primary port may negotiate the
topology (see FC-FS). If the TOPLOCK bit
is set to zero in a MODE SELECT command (see SPC-3), the P2P bit shall be
ignored.
A point-to-point (P2P) bit
set to one indicates the DT device primary port is configured to operate in
point-to-point mode. If the P2P bit is
set to one and the TOPLOCK bit is set to one, the RHA bit, LIV bit, and FC-AL
LOOP ID field shall be ignored in a MODE
SELECT command. A P2P bit set to zero indicates the DT device primary port is
configured to operate in arbitrated loop
mode. >>>
IBM drives have had the option since FC2G devices were
implemented, to select configurations of N-Port, L-Port, LN-Port, and NL-Port in
our terminology. That is, 1) N-Port (force Fabric Topology), 2) L-Port
(Force Arbitrated Loop), 3) LN-Port (Auto-Configure tryin L-Port or Arbitrated
Loop first), and 4) NL-Port, (Auto-Configure trying N-Port or Fabric Topology
first). There is no way in the ADC to distinuguish between LN-Port and
NL-Port.
It is IBM's desire to add
the capability to distinguish between LN-Port and NL-Port to ADC-2. If
FC-AL-2 is strictly followed, a device will attempt FC-AL and then, if
unsuccessful, fall into OLD_PORT state (i.e. port operating as an N-Port).
This would match our LN-Port. However, it is not known that all
current implementations interpret the settings this way.
The are two possible solutions that I am contemplating
proposing: 1) Use the P2P bit when the
TOPLOCK bit is set to zero. If P2P is set to one use NL-Port, if P2P is
set to zero then use LN-Port. 2) Use a
new bit from the reserved bits to indicate NL-Port.
Any comments?
Thanks,
Kevin D. Butt SCSI
& Fibre Channel Architect, Tape Firmware MS 6TYA, 9000 S. Rita Rd.,
Tucson, AZ 85744 Tel: 520-799-2869 / 520-799-5280 Fax: 520-799-2723
(T/L:321) Email address:
kdbutt@us.ibm.com http://www-03.ibm.com/servers/storage/