Additional Comments and Actions on FCP, Rev007a, PLEASE REVIEW

Bob Snively Bob.Snively at
Thu Jan 20 06:41:36 PST 1994

Review by the FCSI has revealed two additional comments on FCP, Revision 007a.

001	T	PRLI behavior in fabrics

In section 6.1, a PRLI request to modify an image pair for which
a PRLI request has already been performed is said to remove the existing
image pair and create a new image pair having the new properties.
Frames in the fabric on behalf of the original image pair must
be allowed to flow out of the fabric before any new exchanges can
be initiated.


The following sentence is put in the last paragraph of section 6.1
before the laste sentence of the paragraph:

"If all outstanding exchanges were not completed before
execution of the PRLI, no new exchanges shall be initiated for
the PRLI for at least R_A_TOV."

002	T	Management of open Exchanges during Abort operations

In section 7.1.2, three multiple abort functions are defined:

	TARGET RESET 	(resets the target activities and states from all
			initiators for all LUNs on the Target)

	CLEAR TASK SET	(aborts all tasks in the task set, including
			all tasks from all initiators for the specified LUN)

	ABORT TASK SET	(aborts all tasks from the originating 
			initiator for the specified LUN)

Each of these operations may require the elimination of open Exchanges
on the FC-PH in addition to the clearing of the Exchange resources
performed by the Task Management function.


For each of these tasks, the description will be modified to indicate
that the following steps are performed:

	a)	The Task Management IU is transferred to the Target.

	b)	The initiator and target shall clear all Exchange resources
		for Exchanges that can be unambiguously cleared.

	c)	Exchanges for which the state of the Exchange is
		ambiguous shall be terminated by using an ABTS/LS
		sequence initiated by the initiator or target that
		has determined that the state of the exchange is

		The definition of ambiguous is:

		An exchange is in ambiguous state if the N_Port
		has sequence initiative and there exists an
		unacknowledged frame for the sequence or if the
		N_Port has transferred sequence initiative but
		the transfer of initiative has not been confirmed.

		An exchange is also in an ambiguous state if the
		exchange exists between the target N_Port and an
		N_Port other than the initiator N_Port that 
		performed the Task Management function.

		If the Exchange resources for the ambiguous Exchange
		have already been cleared by the N_Port that is
		the sequence recipient of the ABTS, the ABTS response will be
		a BA_RJT.  

		If the Exchange resources for the ambiguous Exchange
		have not yet been cleared by the N_Port that is the
		sequence recipient of the ABTS, the ABTS response will
		have the LS bit set and will terminate the sequence and
		the Exchange, establishing a Recovery Qualifier.

		The Recovery Qualifier shall be removed by an
		RRQ command after R_A_TOV.

The goal of this is to clear the vast majority of the open exchanges
instantly and with no recovery processes on the Fibre Channel.
The remaining exchanges that are in a state where it is impossible to
verify that they will be properly cleared by both involved N_Ports
are cleared by a standard Abort Task (ABTS/LS) sequence.

The CLEAR TASK QUEUE and TARGET RESET operations will also clear
sequences on initiators other than the one that sent the task management

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