Proposal for modifications to PRLI/PRLO to meet both FCP and FC-SB requirements

Bob Snively Bob.Snively at eng.sun.com
Mon Apr 25 18:08:24 PDT 1994


To:	fiber-chan-ext at think.com,  scsi at wichitaks.ncr.com

From:	Bob Snively (bob.snively at sun.com)

Date:	April 24, 1994

Subject:	Proposal for resolving the PRLI/PRLO problems

At the Fibre Channel meeting and the FCP meeting the
week of April 18-22, the PRLI/PRLO implementation proposed
by FC-SB was found to be excessively limiting.  After much
discussion, I believe that the following proposal would
resolve the problems.

This resolution would provide a basis for correcting 
comments 82-108 and 156-166 against the FCP document.

The goals for PRLI/PRLO are:
   1)	PRLI should be optional.  Implicit PRLI is acceptable.
   2)	PRLI should be able to provide information without
	forming a mandatory image pair relationship.
	This information can be used to form an image pair.
   3)	PRLI should be able to perform assymetrical logins, such
	that the originator or responder that does not use
	Process Associators internally can use the PAs of the 
	corresponding responder or originator to perform normal
	operations. 	
   4)	PRLI should be able to form mandatory image pair
	relationships as required by FC-SB.
   5)	PRLI can only be performed after a valid N_Port Login
	is successful, since information about the capability
	of an N_Port to support Process Associators is required
	to properly execute the PRLI protocols.
   6)	Name services and other magic should not be required
	for normal operation.  TPLS and SCN are optional.
	and not necessary for normal operation.
   7)   Rules for the requirement for an association header
	must be clearly defined.  Every new exchange
	shall have the required initial association header in 
	its first frame.  If the FC-4 grants initiative to the
	responder, the required final association header shall
	be included in the first frame from the responder.
	If no X_ID reassignment is taking place, those two
	association headers are the only association headers
	required in the entire exchange.
	For other cases, the rules of FC-PH,
	section 25.3.2 shall be used to determine if an
	association header is required.  

These goals require the following changes to the FC-SB protocol.  These
changes must also be propagated to FC-EP.


   PA images can exist in the following relationships.
  	Any of these relationships can be established
	as a default condition using mechanisms not
	specified by the standards.

	PA not supported:
		If PAs are not supported by one or both of
		of the originator and responder, no valid
		Process Associator shall be specified in 
		any frame of any exchange.  

		PRLI and PRLO commands shall have no more than a 
		single page for the Common Service Parameters and an
		additional single page for each additional
		type supported by the originator or responder.
		Each page shall indicate that both the
		originator PA and responder PA are invalid.
		
		The Login/Logout can be thought of as enabling
		and disabling the specified services for the
		entire N_Port.

	PA required by Originator, supported by Responder:
		If PAs are required by the Originator, the
		Originator is expected to communicate only when
		a valid PA is included in the initial Association
		Header.  The responder shall provide a final
		Association Header and provide other 
		Association Headers as required by FC-PH.
		The PA establishes a routing to
		a particular host process.  There is
		no relationship between PAs identified
		through one N_Port of a host system
		and another N_Port from the same host.
		FC-EP may define Hunt and Stripe Groups
		using N_Port aliases.  If so, then a process
		defined by a PA for the alias of the group shall 
		be considered as the same process for all N_Ports
		of the group.  The PA may additionally be used by 
		the FC-4 in an FC-4 dependent manner.

		The PLRI request pages shall have valid Originator process
		associator values and invalid responder process
		associator values.  This PLRI will inform the
		responder of the originator requirements and
		capablities for each type of FC-4.

		The PLRI and PRLO can be thought of as enabling
		and disabling the access of each Originator
		Process to the Responder N_Port.

	PA required by Responder, supported by Originator:
		If PAs are required by the Responder, the
		Responder is expected to communicate only when
		a valid Responder PA is included in the initial Association
		Header.  The responder shall provide a final
		Association Header and provide other 
		Association Headers as required by FC-PH.
		The PA establishes a routing to
		a particular responder process.  There is
		no relationship between PAs identified
		through one N_Port of a responder
		and another N_Port from the same responder.
		FC-EP may define Hunt and Stripe Groups
		using N_Port aliases.  If so, then a process
		defined by a PA for the alias of the group shall 
		be considered as the same process for all N_Ports
		of the group.  The PA may additionally be used by 
		the FC-4 in an FC-4 dependent manner.

		The PLRI request pages shall have valid Responder process
		associator values and invalid Originator process
		associator values.  The Responder Process Associator
		values shall be those obtained through an 
		informative PRLI operation or by other methods not
		specified.

		The PLRI and PRLO can be thought of as enabling
		and disabling the access of each Responder
		Process to the Originating N_Port.


	PA Required by Originator and Responder:

		Communication can only take place between an
		Originator and a Responder when valid PAs are 
		provided for Processes in the initial process
		associator.  FC-EP may define Hunt and Stripe Groups
		using N_Port aliases.  If so, then a process
		defined by a PA for the alias of the group shall 
		be considered as the same process for all N_Ports
		of the group.  The PA may additionally be used by 
		the FC-4 in an FC-4 dependent manner.

		The PLRI request pages shall have valid responder
		and associator values defined to create image
		pairs in an exclusive manner.  Communication with
		image pairs that have not been established is
		not allowed, even if both PAs exist and have the
		proper requirements and capabilities.

		The PRLI pages with incomplete Originator PA and Responder
		PA information are informative.  The PRLI and PRLO
		pages with complete Originator PA and Responder PA
		information enable or disable communication between
		the specified image pair.

PRLI Operation:

      PRLI has two modes of operation.

	Informative mode:
		Information is exchanged using the PRLI to
		enable negotiation for proper image pairs.	   

	Exclusive mode:
		Information is exchanged that explicitly
		establishes a relationship between
		processes in communicating N_Ports.  The
		relationship does not allow any communication
		types or paths other than those established
		by the PRLI.

		Exclusive mode is determined by the completeness
		of the page information with respect to the
		PLOGI requirements specified for Initial Process
		Associators.  If the PA validiy information is complete, the
		resulting PLOGI is exclusive.  If the PA validity
		is not complete enough to meet the requirements of
		the PLOGI, the resulting PLOGI is informative.
	
		The service parameters included in a page may be
		either requirements or capabilities.  Capabilities
		indicate those FC-4 properties that describe the
		role and state of the node in the FC-4.  Such capabilities
		include channel or device (FC-SB), initiator or
		target (FCP), and similar values.  Requirements indicate
		those FC-4 properties that must be agreed upon by
		both nodes for operation with an FC-4.  Requirements
		include values such as the paramters controlling the 
		FCP IUs that shall be used in communication.
		

	The PRLI protocol is performed in the following manner:

	   If IPAs are required by both the Originator and Responder:

	   	In the Request payload:
		The request pages shall identify an
		Originator PA / Responder PA pair.  The 
		requirements shall be set to those that 
		correspond to the combined understanding
		expected to be agreed to by the responder,
		given the knowledge that the originator PA
		has of the responder PA.  The capabilities shall
		be those of the originator only.

	   	In the Responder payload:
		The response shall be in exclusive mode.
		All pages from the request shall be returned
		with the same
		Originator PA / Responder PA pair.  The 
		requirements shall be set to those that 
		are agreed to by the responder.  
		The capabilities shall
		be those of the responder only.
		Error responses are possible.

		The use of an exclusive PRLI page requires that the
		originator have precise and detailed knowledge of the
		PAs and capabilities available in the responder.  That
		information may be obtained from Name Services (not
		presently defined), implicitly from configuration
		information obtained outside the scope of FC, or by
		performing a PRLI with informative pages.

		Information pages are requested of the Responder
		by using request pages that do not have the Originator
		or Responder PA indicated as valid. The Responder returns
		pages describing its PAs, requirements, and capabilities.
		The Responder may also return exclusive pages.

	   If IPAs are required by the Originator and 
			supported by the Responder.

		In the Request payload:
		The request pages shall identify the Originator
		PA and specify the Responder PA as invalid.  The
		requirements shall be those
		expected to be agreed to by the responder.
		The capabilites shall be those of the originator only.

		In the Responder payload:
		The pages shall be returned for the same request
		pages using the same Originator/invalid pair.  The
		requirements shall be set to those that are agreed
		to by the responder.  The capabilities shall be
		those of the responder only for the specified type
		of operation.

		The pages identify exclusive communications between
		the Originator's multiple images and the single
		image provided by the Responder.

	   If IPAs are supported by the Originator and required by
			the Responder.

		In the Request payload:
		A request page shall be provided for each
		type of operation with both the Originator
		and Responder PA specified as invalid.
		The request pages shall identify specify the
		requirements expected to be agreed to by the
		responder.  The capabilities shall be those
		of the originator only.

		In the Responder payload:
		Pages shall be returned for each Responder PA with
		the orignator PA specified as invalid.  The
		requirements shall be those committed to by the
		responder.  The capabilities shall be those of
		the responder for the specified type of operation.

		The pages identify those exclusive communication
		paths established between the single image of
		the Originator and the multiple images of the Responder.

	A PRLI effects only those PAs or image pairs
	specifically referenced by the pages.  A new PRLI
	page to an already established image pair replaces
	the previous parameters with new PRLI parameters.
	New PRLI pages can be mixed in any combination
	with pages that address established image pairs.
	If the change in parameters affects any outstanding
	actions, those sequences and exchanges shall be
	terminated with ABTS, ABTS/LS, or ABTX actions.
	Only actions established for the referenced image
	pairs are affected.  
	The definition of an affected action may vary
	depending on the FC-4.	

   PRLO operates in the following manner:

	A PRLO operates by referencing by
	referencing particular PA image pairs.  Pages
	can be mixed in any
	combination in a PRLO request.  The PRLO accept
	payload is required to present a response page
	for every request page.  Pages may be individually
	marked as being in error.

	A PRLO page identifies a particular image pair
	to logout by marking both the Originator Process
	Associator and the Responder Process Associator
	as valid.  Only that image pair is logged out.
	No further communication under the affected
	FC-4 is possible between these two images.  
	Those sequences and exchanges outstanding between
	image pairs at the time of the PRLO shall be
	terminated with ABTS, ABTS/LS, or ABTX actions.
	On-going activities and states
	for other image pairs are not affected.

	A PRLO page identifies an image pair where only
	the Originator or only the Responder requires IPA by
	marking only the Originator PA or only the Responder
	PA as valid.  The image pair that is specified by
	the single PA and the opposite N_Port is logged out.
	No further communication under the affected
	FC-4 is possible between these two images.
	Those sequences and exchanges outstanding between
	those image pairs shall be terminated with ABTS, ABTS/LS,
	or ABTX as required.  On-going activities and states
	for other image pairs are not affected.

	A PRLO page identifies an image pair where neither
	the Originator or Responder supports IPA by marking the
	Originator PA and Responder PA as invalid.  No further
	communication under the affected FC-4 is possible
	between those two N_Ports.
	Those sequences and exchanges outstanding between
	those image pairs shall be terminated with ABTS, ABTS/LS,
	or ABTX as required.  On-going activities and states
	for other image pairs are not affected.
		
	If a PA is not logged in:

	Attempts to communicate with a PA instance that has
	not been logged in or has been logged out shall be
	acknowledged in the normal manner.  The Responder
	shall then perform a PRLO operation for the PA
	instance to indicate that the PA has been logged out.








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