ADC-2: Topology Auto configuration

Gerry.Houlder at Gerry.Houlder at
Wed Mar 29 08:19:32 PST 2006

Attachment #1: <A HREF="r060330b_banthermichae.vcf">banthermichae.vcf</A>

It sounds like Kevin would like a 2 bit field to cover the four cases he
want to distinguish. Can P2P bit be expanded into a two bit field? As
always, implementations are not required to support all 4 cases and can
respond with CHECK CONDITION status when an unsupported combination is sent
in that field.
	     <michael.banther@						To>		       "Kevin D Butt" <kdbutt at>, 
	     Sent by:		       <t10 at>			   
	     owner-t10 at						cc 
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				       RE: ADC-2: Topology Auto 	   
	     03/29/2006 07:25						   
Hi Kevin,
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.
Michael Banther
Hewlett-Packard Ltd.
Telephone +44 (117) 312-9503
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Kevin D
Sent: 27 March 2006 22:15
To: t10 at
Subject: ADC-2: Topology Auto configuration
In ADC-2, 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?
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 at (See attached file: BANTHER,MICHAEL

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