draft-ietf-mpls-tp-linear-protection-03.txt		draft-ietf-mpls-tp-linear-protection-04.txt
	Network Working Group S. Bryant, Ed.		Network Working Group S. Bryant, Ed.
	Internet-Draft E. Osborne		Internet-Draft E. Osborne
	Intended status: Standards Track Cisco		Intended status: Standards Track Cisco
	Expires: April 27, 2011 N. Sprecher, Ed.		Expires: July 30, 2011 N. Sprecher, Ed.
	Nokia Siemens Networks		Nokia Siemens Networks
	A. Fulignoli, Ed.		A. Fulignoli, Ed.
	Ericsson		Ericsson
	Y. Weingarten		Y. Weingarten
	Nokia Siemens Networks		Nokia Siemens Networks
	October 24, 2010		January 26, 2011
	MPLS-TP Linear Protection		MPLS-TP Linear Protection
	draft-ietf-mpls-tp-linear-protection-03.txt		draft-ietf-mpls-tp-linear-protection-04.txt
	Abstract		Abstract
	The Transport Profile for Multiprotocol Label Switching (MPLS-TP) is		The Transport Profile for Multiprotocol Label Switching (MPLS-TP) is
	being specified jointly by IETF and ITU-T. This document addresses		being specified jointly by IETF and ITU-T. This document addresses
	the functionality described in the MPLS-TP Survivability Framework		the functionality described in the MPLS-TP Survivability Framework
	document [SurvivFwk] and defines a protocol that may be used to		document [SurvivFwk] and defines a protocol that may be used to
	fulfill the function of the Protection State Coordination for linear		fulfill the function of the Protection State Coordination for linear
	protection, as described in that document.		protection, as described in that document.
	skipping to change at page 1, line 48		skipping to change at page 1, line 48
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on April 27, 2011.		This Internet-Draft will expire on July 30, 2011.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2011 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 3, line 18		skipping to change at page 3, line 18
	1.1. Protection architectures . . . . . . . . . . . . . . . . . 4		1.1. Protection architectures . . . . . . . . . . . . . . . . . 4
	1.2. Scope of the document . . . . . . . . . . . . . . . . . . 5		1.2. Scope of the document . . . . . . . . . . . . . . . . . . 5
	1.3. Contributing authors . . . . . . . . . . . . . . . . . . . 6		1.3. Contributing authors . . . . . . . . . . . . . . . . . . . 6
	2. Conventions used in this document . . . . . . . . . . . . . . 6		2. Conventions used in this document . . . . . . . . . . . . . . 6
	2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 7		2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 7
	2.2. Definitions and Terminology . . . . . . . . . . . . . . . 7		2.2. Definitions and Terminology . . . . . . . . . . . . . . . 7
	3. Protection switching control logic . . . . . . . . . . . . . . 7		3. Protection switching control logic . . . . . . . . . . . . . . 7
	3.1. Protection switching control logical architecture . . . . 7		3.1. Protection switching control logical architecture . . . . 7
	3.1.1. Local Request Logic . . . . . . . . . . . . . . . . . 8		3.1.1. Local Request Logic . . . . . . . . . . . . . . . . . 8
	3.1.2. Remote Requests . . . . . . . . . . . . . . . . . . . 10		3.1.2. Remote Requests . . . . . . . . . . . . . . . . . . . 10
	3.1.3. PSC Process Logic . . . . . . . . . . . . . . . . . . 11		3.1.3. PSC Control Logic . . . . . . . . . . . . . . . . . . 11
	3.1.4. PSC Message Generator . . . . . . . . . . . . . . . . 11		3.1.4. PSC Message Generator . . . . . . . . . . . . . . . . 12
	3.1.5. Wait-to-Restore (WTR) timer . . . . . . . . . . . . . 12		3.1.5. Wait-to-Restore (WTR) timer . . . . . . . . . . . . . 12
	3.1.6. PSC Control States . . . . . . . . . . . . . . . . . . 12		3.1.6. PSC Control States . . . . . . . . . . . . . . . . . . 12
	4. Protection state coordination (PSC) protocol . . . . . . . . . 13		4. Protection state coordination (PSC) protocol . . . . . . . . . 14
	4.1. Transmission and acceptance of PSC control packets . . . . 14		4.1. Transmission and acceptance of PSC control packets . . . . 14
	4.2. Protocol format . . . . . . . . . . . . . . . . . . . . . 14		4.2. Protocol format . . . . . . . . . . . . . . . . . . . . . 15
	4.2.1. PSC Ver field . . . . . . . . . . . . . . . . . . . . 15		4.2.1. PSC Ver field . . . . . . . . . . . . . . . . . . . . 16
	4.2.2. PSC Request field . . . . . . . . . . . . . . . . . . 15		4.2.2. PSC Request field . . . . . . . . . . . . . . . . . . 16
	4.2.3. Protection Type (PT) . . . . . . . . . . . . . . . . . 16		4.2.3. Protection Type (PT) . . . . . . . . . . . . . . . . . 17
	4.2.4. Revertive (R) field . . . . . . . . . . . . . . . . . 17		4.2.4. Revertive (R) field . . . . . . . . . . . . . . . . . 17
	4.2.5. Fault path (FPath) field . . . . . . . . . . . . . . . 17		4.2.5. Fault path (FPath) field . . . . . . . . . . . . . . . 18
	4.2.6. Data path (Path) field . . . . . . . . . . . . . . . . 17		4.2.6. Data path (Path) field . . . . . . . . . . . . . . . . 18
	4.3. Principles of Operation . . . . . . . . . . . . . . . . . 18		4.3. Principles of Operation . . . . . . . . . . . . . . . . . 18
	4.3.1. Basic operation . . . . . . . . . . . . . . . . . . . 18		4.3.1. Basic operation . . . . . . . . . . . . . . . . . . . 19
	4.3.2. Priority of inputs . . . . . . . . . . . . . . . . . . 19		4.3.2. Priority of inputs . . . . . . . . . . . . . . . . . . 20
	4.3.3. Operation of PSC States . . . . . . . . . . . . . . . 20		4.3.3. Operation of PSC States . . . . . . . . . . . . . . . 20
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 29		6. Security Considerations . . . . . . . . . . . . . . . . . . . 31
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29		Appendix A. PSC state machine tables . . . . . . . . . . . . . . 31
	8.1. Normative References . . . . . . . . . . . . . . . . . . . 29		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
	8.2. Informative References . . . . . . . . . . . . . . . . . . 29		8.1. Normative References . . . . . . . . . . . . . . . . . . . 35
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30		8.2. Informative References . . . . . . . . . . . . . . . . . . 35
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
	1. Introduction		1. Introduction
	The MPLS Transport Profile (MPLS-TP) [TPFwk] is a framework for the		The MPLS Transport Profile (MPLS-TP) [TPFwk] is a framework for the
	construction and operation of packet-switched transport networks		construction and operation of packet-switched transport networks
	based on the architectures for MPLS ([RFC3031] and [RFC3032]) and for		based on the architectures for MPLS ([RFC3031] and [RFC3032]) and for
	Pseudowires (PWs) ([RFC3985] and [RFC5659]) and the requirements of		Pseudowires (PWs) ([RFC3985] and [RFC5659]) and the requirements of
	[RFC5654].		[RFC5654].
	Network survivability is the ability of a network to recover traffic		Network survivability is the ability of a network to recover traffic
	skipping to change at page 5, line 21		skipping to change at page 5, line 21
	In the 1:1 architecture, a recovery transport path is dedicated to		In the 1:1 architecture, a recovery transport path is dedicated to
	the working transport path of a single service and the traffic is		the working transport path of a single service and the traffic is
	only transmitted either on the working or the recovery path, by using		only transmitted either on the working or the recovery path, by using
	a selector bridge at the source of the protection domain. A selector		a selector bridge at the source of the protection domain. A selector
	at the sink of the protection domain then selects the path that		at the sink of the protection domain then selects the path that
	carries the normal traffic. Since the source and sink need to be		carries the normal traffic. Since the source and sink need to be
	coordinated to ensure that the selector bridge at both ends select		coordinated to ensure that the selector bridge at both ends select
	the same path, this architecture must support a PSC protocol.		the same path, this architecture must support a PSC protocol.
	The 1:n protection architecture extends the 1:1 architecture above by		The 1:n protection architecture extends the 1:1 architecture above by
	sharing the recovery path amongst n services. Again, the recovery		sharing the recovery path among n services. Again, the recovery path
	path is fully allocated and disjoint from any of the n working		is fully allocated and disjoint from any of the n working transport
	transport paths that it is being used to protect. The normal data		paths that it is being used to protect. The normal data traffic for
	traffic for each service is transmitted either on the normal working		each service is transmitted either on the normal working path for
	path for that service or, in cases that trigger protection switching		that service or, in cases that trigger protection switching (as
	(as defined in [SurvivFwk]), may be sent on the recovery path. The		defined in [SurvivFwk]), may be sent on the recovery path. The
	switching action is similar to the 1:1 case where a selector bridge		switching action is similar to the 1:1 case where a selector bridge
	is used at the source. It should be noted that in cases where		is used at the source. It should be noted that in cases where
	multiple working path services have triggered protection switching		multiple working path services have triggered protection switching
	that some services, dependent upon their Service Level Agreement		that some services, dependent upon their Service Level Agreement
	(SLA), may not be transmitted as a result of limited resources on the		(SLA), may not be transmitted as a result of limited resources on the
	recovery path. In this architecture there may be a need for		recovery path. In this architecture there may be a need for
	coordination of the protection switching, and also for resource		coordination of the protection switching, and also for resource
	allocation negotiation. The procedures for this are for further		allocation negotiation. The procedures for this are for further
	study and may be addressed in future documents.		study and may be addressed in future documents.
	skipping to change at page 8, line 19		skipping to change at page 8, line 19
	| | | |		| | | |
	V V V V		V V V V
	+---------------+ +-------+		+---------------+ +-------+
	| Local Request |<--------| WTR |		| Local Request |<--------| WTR |
	| logic |WTR Exps | Timer |		| logic |WTR Exps | Timer |
	+---------------+ +-------+		+---------------+ +-------+
	| ^		| ^
	Highest local|request |		Highest local|request |
	V | Start/Stop		V | Start/Stop
	+-----------------+ |		+-----------------+ |
	Remote PSC | PSC Process |------------+		Remote PSC | PSC Control |------------+
	------------>| logic |		------------>| logic |
	Request +-----------------+		Request +-----------------+
	|		|
	| Action +------------+		| Action +------------+
	+---------------->| Message |		+---------------->| Message |
	| Generator |		| Generator |
	+------------+		+------------+
	|		|
	Output PSC | Message		Output PSC | Message
	V		V
	Figure 1: Protection switching control logic		Figure 1: Protection switching control logic
	Figure 1 describes the logical architecture of the protection		Figure 1 describes the logical architecture of the protection
	switching control. The Local Request logic unit accepts the triggers		switching control. The Local Request logic unit accepts the triggers
	from the OAM, external operator commands, from the local control		from the OAM, external operator commands, from the local control
	plane (when present), and the Wait-to-Restore timer. By considering		plane (when present), and the Wait-to-Restore timer. By considering
	all of these local request sources it determines the highest priority		all of these local request sources it determines the highest priority
	local request. This high-priority request is passed to the PSC		local request. This high-priority request is passed to the PSC
	Process logic, that will cross-check this local request with the		Control logic, that will cross-check this local request with the
	information received from the far-end LER. The PSC Process logic		information received from the far-end LER. The PSC Control logic
	uses this input to determine what actions need to be taken, e.g.		uses this input to determine what actions need to be taken, e.g.
	local actions at the LER, or what message should be sent to the far-		local actions at the LER, or what message should be sent to the far-
	end LER, and the current status of the protection domain.		end LER, and the current status of the protection domain.
	3.1.1. Local Request Logic		3.1.1. Local Request Logic
	The protection switching logic processes input triggers from five		The protection switching logic processes input triggers from five
	sources:		sources:
	o Operator command - the network operator may issue commands that		o Operator command - the network operator may issue commands that
	skipping to change at page 9, line 35		skipping to change at page 9, line 35
	transport path and this SHOULD input an indication to the Local		transport path and this SHOULD input an indication to the Local
	Request Logic.		Request Logic.
	o WTR expires - The Wait-to-Restore timer is used in conjunction		o WTR expires - The Wait-to-Restore timer is used in conjunction
	with recovery from failure conditions on the working path in		with recovery from failure conditions on the working path in
	revertive mode. The timer SHALL signal the PSC control process		revertive mode. The timer SHALL signal the PSC control process
	when it expires and the end point SHOULD revert to the normal		when it expires and the end point SHOULD revert to the normal
	transmission of the user data traffic.		transmission of the user data traffic.
	The Local request logic SHALL process these different input sources		The Local request logic SHALL process these different input sources
	and, based on the priorities between them, SHOULD produce a current		and, based on the priorities between them (see section 4.3.2), SHALL
	local request. The different local requests that may be output from		produce a current local request. If more than one local input source
	the Local Request Logic are:		generates an indicator, then the Local request logic SHALL select the
			higher priority indicator and block any lower priority indicator. As
			a result, there is a single current local request that is passed to
			the PSC Control logic. The different local requests that may be
			output from the Local Request Logic are:
	o Clear - if the operator cancels an active local administrative		o Clear - if the operator cancels an active local administrative
	command, i.e. LO/FS/MS.		command, i.e. LO/FS/MS.
	o Lockout of Protection (LO) - if the operator requested to disable		o Lockout of Protection (LO) - if the operator requested to disable
	the protection path.		the protection path.
	o Signal Fail (SF) - if any of the Server Layer, Control plane, or		o Signal Fail (SF) - if any of the Server Layer, Control plane, or
	OAM indications signaled a failure condition on either the		OAM indications signaled a failure condition on either the
	protection path or one of the working paths.		protection path or one of the working paths.
	o Signal Degrade (SD) - if any of the Server Layer, Control plane,		o Signal Degrade (SD) - if any of the Server Layer, Control plane,
	or OAM indications signaled a degraded transmission condition on		or OAM indications signaled a degraded transmission condition on
	either the protection path or one of the working paths		either the protection path or one of the working paths
	o Clear Signal Fail - if all of the Server Layer, Control plane, or		o Clear Signal Fail - if all of the Server Layer, Control plane, or
	OAM indications are no longer indicating a failure condition on a		OAM indications are no longer indicating a failure condition on a
	path that was peviously indicating a failure condition.		path that was previously indicating a failure condition.
	o Forced Switch (FS) - if the operator requested that traffic be		o Forced Switch (FS) - if the operator requested that traffic be
	switched from one of the working paths to the protection path.		switched from one of the working paths to the protection path.
	o Manual Switch (MS) - if the operator requested that traffic be		o Manual Switch (MS) - if the operator requested that traffic be
	switched from its current path to the other path. This is only		switched from its current path to the other path. This is only
	relevant if there is no currently active Fault condition or		relevant if there is no currently active Fault condition or
	Operator command.		Operator command.
	o WTR Expires - generated by the WTR timer completing its period.		o WTR Expires - generated by the WTR timer completing its period.
	If none of the input sources have generated any input then the		If none of the input sources have generated any input then the Local
	current local request SHALL be a No Request (NR) request.		request logic SHALL generate a No Request (NR) request as the current
			local request .
	3.1.2. Remote Requests		3.1.2. Remote Requests
	In addition to the local requests generated as a result of the local		In addition to the local requests, generated as a result of the local
	triggers indicated in the previous subsection, the PSC Control Logic		triggers, indicated in the previous subsection, the PSC Control Logic
	SHALL accept PSC messages from the far-end LER of the transport path.		SHALL accept PSC messages from the far-end LER of the transport path.
	These remote messages indicate the status of the transport path from		These remote messages indicate the status of the transport path from
	the viewpoint of the far-end LER, and may indicate if the local MEP		the viewpoint of the far-end LER, and may indicate if the local MEP
	SHOULD initiate a protection switch operation.		SHOULD initiate a protection switch operation.
	The following remote requests may be received by the PSC process:		The following remote requests may be received by the PSC process:
	o Remote LO - indicates that the remote end point is in Unavailable		o Remote LO - indicates that the remote end point is in Unavailable
	state due to a Lockout of Protection operator command.		state due to a Lockout of Protection operator command.
	skipping to change at page 11, line 25		skipping to change at page 11, line 28
	o Remote DNR - indicates that the remote end point has determined		o Remote DNR - indicates that the remote end point has determined
	that the failure condition has recovered and will continue		that the failure condition has recovered and will continue
	transporting traffic on the protection path due to operator		transporting traffic on the protection path due to operator
	configuration that prevents automatic reversion to the Normal		configuration that prevents automatic reversion to the Normal
	state.		state.
	o Remote NR - indicates that the remote end point has no abnormal		o Remote NR - indicates that the remote end point has no abnormal
	condition to report.		condition to report.
	3.1.3. PSC Process Logic		3.1.3. PSC Control Logic
	The PSC Process Logic SHALL accept as input -		The PSC Control Logic SHALL accept as input -
	a. the Local request output from the Local Request Logic,		a. the current local request output from the Local Request Logic
			(see section 3.1.1),
	b. the remote request message from the remote end point of the		b. the remote request message from the remote end point of the
	transport path, and		transport path, and
	c. the current state of the PSC Control Logic (maintained internally		c. the current state of the PSC Control Logic (maintained internally
	by the PSC Control Logic).		by the PSC Control Logic).
	Based on the priorities between the different inputs, the PSC Process		Based on the priorities between the different inputs, the PSC Control
	Logic SHALL determine the new state of the PSC Control Logic and what		Logic SHALL determine the new state of the PSC Control Logic and what
	actions need to be taken.		actions need to be taken.
	The new state information should be retained by the PSC Process		The new state information SHALL be retained by the PSC Control Logic,
	Logic, while the requested action SHALL be sent to the PSC Message		while the requested action SHALL be sent to the PSC Message Generator
	Generator (see subsection 3.1.4) to generate and transmit the proper		(see subsection 3.1.4) to generate and transmit the proper PSC
	PSC message to be transmitted to the remote end point of the		message to be transmitted to the remote end point of the protection
	protection domain.		domain.
	3.1.4. PSC Message Generator		3.1.4. PSC Message Generator
	Based on the action output from the Process Logic this unit formats		Based on the action output from the Control Logic this unit formats
	the PSC protocol message that is transmitted to the remote end point		the PSC protocol message that is transmitted to the remote end point
	of the protection domain. When the PSC information has changed,		of the protection domain. When the PSC information has changed,
	three PSC messages SHOULD be transmitted in quick succession, and		three PSC messages SHOULD be transmitted in quick succession, and
	subsequent messages should be transmitted continually at a lower		subsequent messages should be transmitted continually at a lower
	rate.		frequency.
	The transmission of three rapid packets allows for fast protection		The transmission of three rapid packets allows for fast protection
	switching even if one or two PSC messages are lost or corrupted. For		switching even if one or two PSC messages are lost or corrupted. For
	protection switching within 50ms, it is RECOMMENDED that the default		protection switching within 50ms, it is RECOMMENDED that the default
	interval of the first three PSC messages SHOULD be no larger than		interval of the first three PSC messages SHOULD be no larger than
	3.3ms. The subsequent messages SHOULD be transmitted with an		3.3ms. The subsequent messages SHOULD be transmitted with an
	interval of 5 sec, to avoid traffic congestion.		interval of 5 sec, to avoid traffic congestion.
	3.1.5. Wait-to-Restore (WTR) timer		3.1.5. Wait-to-Restore (WTR) timer
	The WTR timer is used to delay reversion to Normal state when		The WTR timer is used to delay reversion to Normal state when
	recovering from a failure condition on the working path and the		recovering from a failure condition on the working path and the
	protection domain is configured for revertive behavior. The WTR may		protection domain is configured for revertive behavior. The WTR may
	be in one of two states - either Running or Stopped. The WTR timer		be in one of two states - either Running or Stopped. The WTR timer
	MAY be started or stopped by the PSC Process Logic.		MAY be started or stopped by the PSC Control Logic.
	If the WTR timer expires prior to being stopped it SHALL generate a		If the WTR timer expires prior to being stopped it SHALL generate a
	WTR Expires local signal that shall be processed by the Local Request		WTR Expires local signal that shall be processed by the Local Request
	Logic. If the WTR timer is running, sending a Stop command SHALL		Logic. If the WTR timer is running, sending a Stop command SHALL
	reset the timer but SHALL NOT generate a WTR Expires local signal.		reset the timer but SHALL NOT generate a WTR Expires local signal.
	If the WTR timer is not running, a Stop command SHALL be ignored.		If the WTR timer is not running, a Stop command SHALL be ignored.
	3.1.6. PSC Control States		3.1.6. PSC Control States
	The PSC Control Logic SHOULD maintain information on the current		The PSC Control Logic SHOULD maintain information on the current
	state of the protection domain. The state information SHALL include		state of the protection domain. The state information SHALL include
	information of the current state and an indication of the cause for		information of the current state and an indication of the cause for
	the current state (e.g. unavailable due to local LO command,		the current state (e.g. unavailable due to local LO command,
	protecting due to remote FS). In particular, the state information		protecting due to remote FS). In particular, the state information
	SHOULD include an indication if the state is related to a remote or		SHOULD include an indication if the state is related to a remote or
	local condition.		local condition. If there are both a local indicator and remote
			indicator for the state then the state shall be considered a local
			state. For example, if the LER enters into a Protecting failure
			state due to a remote SF input, and then a local SF indication is
			received then even though this was initially a remote Protecting
			failure state, by receiving the local SF input the LER is considered
			to be in local Protecting failure state.
	It should be noted that when referring to the "transport" of the data		It should be noted that when referring to the "transport" of the data
	traffic, in the following descriptions and later in the document that		traffic, in the following descriptions and later in the document that
	the data will be transmitted on both the working and the protection		the data will be transmitted on both the working and the protection
	paths when using 1+1 protection, and on either the working or the		paths when using 1+1 protection, and on either the working or the
	protection path exclusively when using 1:1 protection. When using		protection path exclusively when using 1:1 protection. When using
	1+1 protection, the receiving LER should select the proper		1+1 protection, the receiving LER should select the proper
	transmission, according to the state of the protection domain.		transmission, according to the state of the protection domain.
	The states that are supported by the PSC Control Logic are:		The states that are supported by the PSC Control Logic are:
	skipping to change at page 13, line 27		skipping to change at page 13, line 39
	SF/SD condition on the working path that is being controlled by		SF/SD condition on the working path that is being controlled by
	the Wait-to-Restore (WTR) timer.		the Wait-to-Restore (WTR) timer.
	o Do-not-revert state - The protection domain is recovering from a		o Do-not-revert state - The protection domain is recovering from a
	Protecting state, but the operator has configured the protection		Protecting state, but the operator has configured the protection
	domain to not automatically revert to the Normal state upon		domain to not automatically revert to the Normal state upon
	recovery. The protection domain SHALL remain in this state until		recovery. The protection domain SHALL remain in this state until
	the operator issues a command to revert to the Normal state or		the operator issues a command to revert to the Normal state or
	there is a new trigger to switch to a different state.		there is a new trigger to switch to a different state.
	See section 4.3.1 for details on what actions are taken by the PSC		See section 4.3.3 for details on what actions are taken by the PSC
	Process Logic for each state and the relevant input.		Process Logic for each state and the relevant input.
			3.1.6.1. Local and Remote state
			An end-point may be in a given state as a result of either a local
			input indicator, e.g. OAM, WTR timer, or as a result of receiving a
			PSC message from the far-end LER. If the state is entered as a
			result of a local input indicator, then the state SHOULD be
			considered a local state. If the state is entered as a result of a
			PSC message, in the absence of a local input, then the state SHOULD
			be considered a remote state. This differentiation affects how the
			LER should react to different inputs, as described in section 4.3.3.
			The PSC Control logic should maintain, together with the current
			state, an indication of whether this is a local or remote state.
			In any instance where the LER has both a local and remote indicators
			that cause the PSC Control logic to enter a particular state, then
			the state SHOULD be considered a local state, regardless of the order
			in which the indicators were processed. If, however, the LER has
			local and remote indicators that would cause the PSC Control logic to
			enter different states, e.g. a Local SF on working and a Remote
			Lockout message, then the state with the higher importance will be
			the deciding factor and the source of that indicator will determine
			whether it is local or remote. In the given example the result would
			be a Remote Unavailable state transmitting SF(1,0) messages.
	4. Protection state coordination (PSC) protocol		4. Protection state coordination (PSC) protocol
	Bidirectional protection switching, as well as unidirectional 1:1		Bidirectional protection switching, as well as unidirectional 1:1
	protection, requires coordination between the two end points in		protection, requires coordination between the two end points in
	determining which of the two possible paths, the working or recovery		determining which of the two possible paths, the working or recovery
	path, is transmitting the data traffic in any given situation. When		path, is transmitting the data traffic in any given situation. When
	protection switching is triggered as described in section 3.1, the		protection switching is triggered as described in section 3.1, the
	end points must inform each other of the switch-over from one path to		end points must inform each other of the switch-over from one path to
	the other in a coordinated fashion.		the other in a coordinated fashion.
	skipping to change at page 14, line 21		skipping to change at page 15, line 11
	state. In addition, limiting the transmission to a single path		state. In addition, limiting the transmission to a single path
	avoids possible conflicts and race conditions that could develop if		avoids possible conflicts and race conditions that could develop if
	the PSC messages were sent on both paths.		the PSC messages were sent on both paths.
	When the PSC information is changed due to a local input, three PSC		When the PSC information is changed due to a local input, three PSC
	messages SHOULD be transmitted as quickly as possible, to allow for		messages SHOULD be transmitted as quickly as possible, to allow for
	rapid protection switching. This set of three rapid messages allows		rapid protection switching. This set of three rapid messages allows
	for fast protection switching even if one or two of these packets are		for fast protection switching even if one or two of these packets are
	lost or corrupted. When the PSC information changes due to a remote		lost or corrupted. When the PSC information changes due to a remote
	message there is no need for the aforementioned rapid transmission of		message there is no need for the aforementioned rapid transmission of
	three messages. The exception (e.g. when the rapid tranmission is		three messages. The exception (e.g. when the rapid transmission is
	still required) is when going from WTR state to Normal state as a		still required) is when going from WTR state to Normal state as a
	result of a remote NR message.		result of a remote NR message.
	The frequency of the three rapid messages and the separate frequency		The frequency of the three rapid messages and the separate frequency
	of the continual transmission SHOULD be configurable by the operator.		of the continual transmission SHOULD be configurable by the operator.
	For protection switching within 50ms, the default interval of the		For protection switching within 50ms, the default interval of the
	first three PSC messages is RECOMMENDED to be no larger than 3.3ms.		first three PSC messages is RECOMMENDED to be no larger than 3.3ms.
	The continuous transmission interval is RECOMMENDED to be 5 seconds.		The continuous transmission interval is RECOMMENDED to be 5 seconds.
	If no valid PSC specific information is received, the last valid		If no valid PSC specific information is received, the last valid
	skipping to change at page 16, line 4		skipping to change at page 16, line 34
	has switched traffic to the protection path as a result of an		has switched traffic to the protection path as a result of an
	administrative command. The Fpath field SHALL indicate that the		administrative command. The Fpath field SHALL indicate that the
	working path is being blocked (i.e. Fpath set to 1), and the Path		working path is being blocked (i.e. Fpath set to 1), and the Path
	field SHALL indicate that user data traffic is being transported		field SHALL indicate that user data traffic is being transported
	on the protection path (i.e. Path set to 1).		on the protection path (i.e. Path set to 1).
	o (0110) Signal Fail - indicates that the transmitting end point has		o (0110) Signal Fail - indicates that the transmitting end point has
	identified a signal fail condition on either the working or		identified a signal fail condition on either the working or
	protection path. The Fpath field SHALL identify the path that is		protection path. The Fpath field SHALL identify the path that is
	reporting the failure condition (i.e. if protection path then		reporting the failure condition (i.e. if protection path then
	Fpath set to 0 and if working path then Fpath set to 1), and the		Fpath is set to 0 and if working path then Fpath is set to 1), and
	Path field SHALL indicate where the data traffic is being		the Path field SHALL indicate where the data traffic is being
	transported (i.e. if protection path is blocked then Path set to 0		transported (i.e. if protection path is blocked then Path is set
	and if working path is blocked then Path set to 1).		to 0 and if working path is blocked then Path is set to 1).
	o (0101) Signal Defect - indicates that that the transmitting end		o (0101) Signal Defect - indicates that that the transmitting end
	point has identified a degradation of the signal, or integrity of		point has identified a degradation of the signal, or integrity of
	the packet transmission on either the working or protection path.		the packet transmission on either the working or protection path.
	The specifics for the method of identifying this degradation is		The specifics for the method of identifying this degradation is
	out-of-scope for this document. The details of the actions to be		out-of-scope for this document. The details of the actions to be
	taken for this situation is left for future specification.		taken for this situation is left for future specification.
	o (0100) Manual switch - indicates that the transmitting end point		o (0100) Manual switch - indicates that the transmitting end point
	has switched traffic as a result of an administrative Manual		has switched traffic as a result of an administrative Manual
	skipping to change at page 18, line 33		skipping to change at page 19, line 18
	| ?< | | >? |		| ?< | | >? |
	| \|\\ Protection Path //|/ |		| \|\\ Protection Path //|/ |
	+-----+ \\=======================// +-----+		+-----+ \\=======================// +-----+
	|--------Protection Domain--------|		|--------Protection Domain--------|
	Figure 3: Protection domain		Figure 3: Protection domain
	4.3.1. Basic operation		4.3.1. Basic operation
	The purpose of the PSC protocol is to allow the end points of the		The purpose of the PSC protocol is to allow an end point of the
	protection domain to notify their peer of the status of the domain		protection domain to notify its peer of the status of the domain that
	that is known at the end point and coordinate the transmission of the		is known at the end point and coordinate the transmission of the data
	data traffic. The current state of the end point is expressed in the		traffic. The current state of the end point is expressed in the
	values of the Request field [reflecting the local requests at that		values of the Request field [reflecting the local requests at that
	end point] and the Fpath field [reflecting knowledge of a blocked		end point] and the Fpath field [reflecting knowledge of a blocked
	path]. The coordination between the end points is expressed by the		path]. The coordination between the end points is expressed by the
	value of the Path field [indicating where the data traffic is being		value of the Path field [indicating where the user data traffic is
	transmitted]. The value of the Path field SHOULD be identical for		being transmitted]. The value of the Path field SHOULD be identical
	both end points at any particular time. The values of the Request		for both end points at any particular time. The values of the
	and Fpath fields may not be identical between the two end points.In		Request and Fpath fields may not be identical between the two end
	particular it should be noted that a remote message MAY not cause the		points. In particular it should be noted that a remote message MAY
	end point to change the Request field that is being transmitted while		not cause the end point to change the Request field that is being
	it does affect the Path field (see details in the following		transmitted while it does affect the Path field (see details in the
	subsections).		following subsections).
	The protocol is a single-phase protocol. Single-phase implies that		The protocol is a single-phase protocol. Single-phase implies that
	each end point notifies its peer of a change in the operation		each end point notifies its peer of a change in the operation
	(switching to or from the protection path) and makes the switch		(switching to or from the protection path) and makes the switch
	without waiting for acknowledgement.		without waiting for acknowledgement.
	The following subsections will identify the messages that SHALL be		The following subsections will identify the messages that SHALL be
	transmitted by the end point in different scenarios. The messages		transmitted by the end point in different scenarios. The messages
	are described as REQ(FP, P) - where REQ is the value of the Request		are described as REQ(FP, P) - where REQ is the value of the Request
	field, FP is the value of the Fpath field, and P is the value of the		field, FP is the value of the Fpath field, and P is the value of the
	skipping to change at page 19, line 28		skipping to change at page 20, line 13
	traffic.		traffic.
	4.3.2. Priority of inputs		4.3.2. Priority of inputs
	As noted above (in section 3.1.1) the PSC Control Process accepts		As noted above (in section 3.1.1) the PSC Control Process accepts
	input from five local input sources. There is a definition of		input from five local input sources. There is a definition of
	priority between the different inputs that may be triggered locally.		priority between the different inputs that may be triggered locally.
	The list of local requests in order of priority are (from highest to		The list of local requests in order of priority are (from highest to
	lowest priority):		lowest priority):
	1. Clear (Operator command)		1. Clear (Operator command)
	2. Lockout of protection (Operator command)		2. Lockout of protection (Operator command)
	3. Signal Fail on protection (OAM/Control Plane/Server Indication)		3. Signal Fail on protection (OAM/Control Plane/Server Indication)
	4. Forced switch (Operator command)		4. Forced switch (Operator command)
	5. Signal Fail on working (OAM/Control Plane/Server Indication)		5. Signal Fail on working (OAM/Control Plane/Server Indication)
	6. Signal Degrade on working (OAM/Control Plane/Server Indication)		6. Signal Degrade on working (OAM/Control Plane/Server Indication)
	7. Clear Signal Fail/Degrade (OAM/Control Plane/Server Indication)		7. Clear Signal Fail/Degrade (OAM/Control Plane/Server Indication)
	8. Manual switch (Operator command)		8. Manual switch (Operator command)
	9. WTR expires (WTR Timer)		9. WTR expires (WTR Timer)
			10. No request (default)
			As was noted above, the Local request logic SHALL always select the
			local input indicator with the highest priority as the current local
			request. All local inputs with lower priority than this current
			local request will be blocked.
	The determination of whether a remote message is accepted or ignored		The determination of whether a remote message is accepted or ignored
	is a function of the current state of the local LER and the current		is a function of the current state of the local LER and the current
	local request (see section 3.1.3). Part of this consideration will		local request (see section 3.1.3). Part of this consideration will
	be included in the following subsections describing the operation in		be included in the following subsections describing the operation in
	the different states.		the different states.
	4.3.3. Operation of PSC States		4.3.3. Operation of PSC States
			The following sub-sections present the operation of the different
			states defined in section 3.1.6. For each state we define the
			reaction, i.e. the new state and the message to transmit, to each
			possible input - either the highest priority local input or the PSC
			message from the remote LER. If the definition states to "ignore"
			the message, the intention is that the LER should remain in its
			current state and continue transmitting (as presented in section 4.1)
			the current PSC message.
	4.3.3.1. Normal State		4.3.3.1. Normal State
	When the protection domain has no special condition in effect, the		When the protection domain has no special condition in effect, the
	ingress LER SHALL forward the user data along the working path, and,		ingress LER SHALL forward the user data along the working path, and,
	in the case of 1+1 protection, the Permanent Bridge will bridge the		in the case of 1+1 protection, the Permanent Bridge will bridge the
	data to the recovery path as well. The receiving LER SHALL read the		data to the recovery path as well. The receiving LER SHALL read the
	data from the working path.		data from the working path.
	When the end point is in Normal State it SHALL transmit a NR(0,0)		When the end point is in Normal State it SHALL transmit a NR(0,0)
	message, indicating - Nothing to report and data traffic is being		message, indicating - Nothing to report and data traffic is being
	transported on the working path.		transported on the working path.
	When the LER (assume LER-A) is in Normal State the following		When the LER (assume LER-A) is in Normal State the following
	transitions are relevant in reaction to a local input (new state		transitions are relevant in reaction to a local input (new state
	SHOULD be marked as local):		SHOULD be marked as local):
	o A local Lockout of protection input SHALL cause the LER to go into		o A local Lockout of protection input SHALL cause the LER to go into
	Unavailable State and begin transmission of a LO(0,0) message to		local Unavailable State and begin transmission of a LO(0,0)
	the far-end LER (LER-Z).		message.
	o A local Forced switch input SHALL cause the LER to go into		o A local Forced switch input SHALL cause the LER to go into local
	Protecting administrative state and begin transmission of a		Protecting administrative state and begin transmission of a
	FS(1,1) message to the far-end LER (LER-Z).		FS(1,1) message.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail indication on the protection path SHALL cause
	the LER to go into Unavailable state and begin transmission of a		the LER to go into local Unavailable state and begin transmission
	SF(0,0) message to the far-end LER (LER-Z).		of a SF(0,0) message.
	o A local Signal Fail indication on the working path SHALL cause the		o A local Signal Fail indication on the working path SHALL cause the
	LER to go into Protecting failure state and begin transmission of		LER to go into local Protecting failure state and begin
	a SF(1,1) message to the far-end LER (LER-Z).		transmission of a SF(1,1) message.
	o A local Manual switch input SHALL cause the LER to go into		o A local Manual switch input SHALL cause the LER to go into local
	Protecting administrative state and begin transmission of a		Protecting administrative state and begin transmission of a
	MS(1,1) message to the far-end LER (LER-Z).		MS(1,1) message.
	o All other local inputs SHOULD be ignored.		o All other local inputs SHALL be ignored.
	In Normal state, remote messages would cause the following reaction		In Normal state, remote messages would cause the following reaction
	from the LER (new state SHOULD be marked as remote):		from the LER (new state SHOULD be marked as remote):
	o A remote Lockout of protection message SHALL cause the LER (LER-A)		o A remote Lockout of protection message SHALL cause the LER to go
	to go into Unavailable state, while continuing to transmit the		into remote Unavailable state, while continuing to transmit the
	NR(0,0) message.		NR(0,0) message.
	o A remote Forced switch message SHALL cause the LER (LER-A) to go		o A remote Forced switch message SHALL cause the LER to go into
	into Protecting administrative state, and transmit a NR(0,1)		remote Protecting administrative state, and begin transmitting a
	message.		NR(0,1) message.
	o A remote Signal Fail message that indicates that the failure is on		o A remote Signal Fail message that indicates that the failure is on
	the protection path SHALL cause the LER (LER-A) to go into		the protection path SHALL cause the LER (LER-A) to go into remote
	Unavailable state, while continuing to transmit the NR(0,0)		Unavailable state, while continuing to transmit the NR(0,0)
	message.		message.
	o A remote Signal Fail message that indicates that the failure is on		o A remote Signal Fail message that indicates that the failure is on
	the working path SHALL cause the LER (LER-A) to go into Protecting		the working path SHALL cause the LER to go into remote Protecting
	failure state, and transmit a NR(0,1) message.		failure state, and transmit a NR(0,1) message.
	o A remote Manual switch message SHALL cause the LER (LER-A) to go		o A remote Manual switch message SHALL cause the LER to go into
	into Protecting administrative state, and transmit a NR(0,1)		remote Protecting administrative state, and transmit a NR(0,1)
	message.		message.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHALL be ignored.
	4.3.3.2. Unavailable State		4.3.3.2. Unavailable State
	When the protection path is unavailable - either as a result of a		When the protection path is unavailable - either as a result of a
	Lockout operator command, or as a result of a SF or SD detected on		Lockout operator command, or as a result of a SF detected on the
	the protection path - then the protection domain is in the		protection path - then the protection domain is in the unavailable
	unavailable state. In this state, the data traffic is transported on		state. In this state, the data traffic is transported on the working
	the working path.		path and is not protected. When the domain is in unavailable state
			the PSC messages may not get through and therefore the protection is
			more dependent on the local inputs rather than the remote messages
			(that may not be received).
	The protection domain will exit the unavailable state and revert to		The protection domain will exit the unavailable state and revert to
	the normal state when, either the operator clears the Lockout command		the normal state when, either the operator clears the Lockout command
	or the protection path recovers from the signal fail or degraded		or the protection path recovers from the signal fail or degraded
	situation. Both ends will resume sending the PSC packets over the		situation. Both ends will resume sending the PSC packets over the
	protection path, as a result of this recovery.		protection path, as a result of this recovery.
	When in unavailable state the data traffic is being transported on
	the working path and is not protected. When the domain is in
	unavailable state the PSC messages may not get through and therefore
	the protection is more dependent on the local inputs rather than the
	remote messages (that may not be received).
	When the LER (assume LER-A) is in Unavailable State the following		When the LER (assume LER-A) is in Unavailable State the following
	transitions are relevant in reaction to a local input (new state		transitions are relevant in reaction to a local input (new state
	SHOULD be marked as local):		SHOULD be marked as local):
	o A local Clear input SHOULD be ignored if the LER is in remote		o A local Clear input SHOULD be ignored if the LER is in remote
	Unavailable state. If in local Unavailable state due to a Lockout		Unavailable state. If in local Unavailable state due to a Lockout
	command, then the input SHALL cause the LER to go to Normal state		command, then the input SHALL cause the LER to go to Normal state
	and begin transmitting a NR(0,0) message.		and begin transmitting a NR(0,0) message.
	o A local Lockout of protection input SHALL cause the LER to remain		o A local Lockout of protection input SHALL cause the LER to remain
	in Unavailable State and begin transmission of a LO(0,0) message		in local Unavailable State and transmit a LO(0,0) message to the
	to the far-end LER (LER-Z).		far-end LER (LER-Z).
	o A local Clear SF in local Unavailable state due to a Signal Fail		o A local Clear SF of the protection path in local Unavailable state
	on the protection path and the Clear SF indicates that the		that is due to a SF on the protection path SHALL cause the LER to
	protection path is now cleared, then the input SHALL cause the LER		go to Normal state and begin transmitting a NR(0,0) message. If
	to go to Normal state and begin transmitting a NR(0,0) message.		the LER is in remote Unavailable state but has an active local SF
	If the LER is in remote Unavailable state but is under a local SF
	condition, then the local Clear SF SHALL clear the SF local		condition, then the local Clear SF SHALL clear the SF local
	condition and the LER SHALL begin transmitting NR(0,0) messages,		condition and the LER SHALL remain in remote Unavailable state and
	maintaining the remote Unavailable state. In all other cases the		begin transmitting NR(0,0) messages. In all other cases the local
	local Clear SF SHOULD be ignored.		Clear SF SHOULD be ignored.
	o A local Forced switch SHOULD be ignored by the PSC Process Logic.		o A local Forced switch SHALL be ignored by the PSC Control Logic.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail on the protection path input when in local
	the LER to remain in Unavailable state and begin transmission of a		Unavailable state [by implication this is due to a local SF on
	SF(0,0) message.		protection] SHALL cause the LER to remain in local Unavailable
			state and transmit a SF(0,0) message.
	o All other local inputs SHOULD be ignored.		o A local Signal Fail on the working path input when in remote
			Unavailable state SHALL cause the LER to remain in remote
			Unavailable state and transmit a SF(1,0) message.
			o All other local inputs SHALL be ignored.
	If remote messages are being received over the protection path then		If remote messages are being received over the protection path then
	they would have the following affect:		they would have the following affect:
	o A remote Lockout of protection message SHALL cause the LER to		o A remote Lockout of protection message SHALL cause the LER to
	remain in Unavailable state, and continue transmission of the		remain in Unavailable state, (note that if the LER was previously
	current message (either NR(0,0) or LO(0,0) or SF(0,0))		in local Unavailable state due to a Signal Fail on the protection
			path, then it will now be in remote Unavailable state) and
			continue transmission of the current message (either NR(0,0) or
			LO(0,0) or SF(0,0))
	o A remote Signal Fail message that indicates that the failure is on		o A remote Signal Fail message that indicates that the failure is on
	the protection path SHALL cause the LER to remain in Unavailable		the protection path SHALL cause the LER to remain in Unavailable
	state and continue transmission of the current message (either		state and continue transmission of the current message (either
	NR(0,0) or SF(0,0) or LO(0,0)).		NR(0,0) or SF(0,0) or LO(0,0)).
	o A remote No Request, when the LER is remote Unavailable state		o A remote No Request, when the LER is in remote Unavailable state
	SHALL cause the LER to go into Normal state and begin transmission		SHALL cause the LER to go into Normal state and continue
	of a NR(0,0) message. When in local Unavailable state, the		transmission of the current message (either NR(0,0) or SF(0,0)).
	message SHALL be ignored.		If there is a local SF indicator this may cause an immediate state
			change after switching into Normal state. When in local
			Unavailable state, the remote message SHALL be ignored.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHALL be ignored.
	4.3.3.3. Protecting administrative state		4.3.3.3. Protecting administrative state
	In the protecting state the user data traffic is being transported on		In the protecting state the user data traffic is being transported on
	the protection path, while the working path is blocked due to an		the protection path, while the working path is blocked due to an
	operator command, i.e. Forced Switch or Manual Switch.		operator command, i.e. Forced Switch or Manual Switch. The
			difference between a local FS and local MS affects what local
			indicators may be received - the Local request logic will block any
			local SF when under the influence of a local FS, whereas the SF would
			override a local MS. In general, a MS will be canceled in case of
			either a local or remote SF or LO condition.
	The following describe the reaction to local input:		The following describe the reaction to local input:
	o A local Clear SHOULD be ignored if in remote Protecting state. If		o A local Clear SHOULD be ignored if in remote Protecting
	in local Protecting administrative state then this input SHALL		administrative state. If in local Protecting administrative state
	cause the LER to go into Normal state and begin transmitting a		then this input SHALL cause the LER to go into Normal state and
	NR(0,0) message.		begin transmitting a NR(0,0) message.
	o A local Lockout of protection input SHALL cause the LER to go into		o A local Lockout of protection input SHALL cause the LER to go into
	Unavailable state and begin transmission of a LO(0,0) message.		local Unavailable state and begin transmission of a LO(0,0)
			message.
	o A local Forced switch input SHALL cause the LER to remain in		o A local Forced switch input SHALL cause the LER to remain in local
	Protecting administrative state and begin transmission of a		Protecting administrative state and transmit a FS(1,1) message.
	FS(1,1) message.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail indication on the protection path SHALL cause
	the LER to go into Unavailable state and begin transmission of a		the LER to go into local Unavailable state (i.e. overriding the MS
	SF(0,0) message.		related Protection administrative state) and begin transmission of
			a SF(0,0) message.
	o A local Signal Fail indication on the working path SHOULD be		o A local Signal Fail indication on the working path SHALL cause the
	filtered by the Local Request Logic if the protecting state was		LER to go into local Protecting failure state and begin
	entered due to an active local Forced switch operator command. If		transmitting a SF(1,1) message, if the current state is due to a
	the protecting state is due to a remote Forced switch message,		(local or remote) Manual switch operator command. If the LER is
	then this local indication SHOULD be filtered by the PSC Process		in remote Protecting administrative state due to a remote Forced
	Logic. If the current state is due to a (local or remote) Manual		Switch command, then this local indication SHALL cause the LER to
	switch operator command, it SHALL cause the LER to go into		remain in remote Protecting administrative state and transmit a
	Protecting failure state and begin transmitting a SF(1,1) message.		SF(1,1) message. If the LER is in local Protecting administrative
			state due to a local Forced Switch command then this indication
			SHALL be ignored (i.e. the indication should have been blocked by
			the Local request logic).
	o A local Clear SF when in remote Protecting administrative state		o A local Clear SF when in remote Protecting administrative state
	SHOULD clear any local SF condition that may exist. The LER SHALL		SHOULD clear any local SF condition that may exist. The LER SHALL
	stop transmitting the SF(1,1) message and begin transmitting an		stop transmitting the SF(x,1) message and begin transmitting an
	NR(0,1) message.		NR(0,1) message.
	o A local Manual switch input SHALL be filtered by the Local Request		o A local Manual switch input SHALL be ignored if in remote
	Logic if there is an active local Forced switch. If the		Protecting administrative state is due to a remote Forced switch
	protecting state is due to a remote Forced switch command, then		command. If the current state is due to a (local or remote)
	this local indication SHOULD be filtered by the PSC Process Logic.		Manual switch operator command, it SHALL cause the LER to remain
	If the current state is due to a (local or remote) Manual switch		in local Protecting administrative state and transmit a MS(1,1)
	operator command, it SHALL cause the LER to remain in Protecting		message.
	administrative state and begin transmission of a MS(1,1) message.
	o All other local inputs SHOULD be ignored.		o All other local inputs SHALL be ignored.
	While in Protecting administrative state the LER may receive and		While in Protecting administrative state the LER may receive and
	react as follows to remote PSC messages:		react as follows to remote PSC messages:
	o A remote Lockout of protection message SHALL cause the LER to go		o A remote Lockout of protection message SHALL cause the LER to go
	into Unavailable state and begin transmitting a NR(0,0) message.		into remote Unavailable state and begin transmitting a NR(0,0)
	It should be noted that this automatically cancels the current		message. It should be noted that this automatically cancels the
	Forced switch or Manual switch command and data traffic is		current Forced switch or Manual switch command and data traffic is
	reverted to the working path.		reverted to the working path.
	o A remote Forced switch message SHOULD be ignored by the PSC		o A remote Forced switch message SHOULD be ignored by the PSC
	Process Logic if there is an active local Forced switch operator		Process Logic if there is an active local Forced switch operator
	command. If the Protecting state is due to a remote Forced switch		command. If the Protecting administrative state is due to a
	message then the LER SHALL remain in Protecting administrative		remote Forced switch message then the LER SHALL remain in remote
	state and continue transmission of the last message. If the		Protecting administrative state and continue transmitting the last
	Protecting state is due to either a local or remote Manual switch		message. If the Protecting administrative state is due to either
	then the LER SHALL remain in Protecting administrative state		a local or remote Manual switch then the LER SHALL remain in
	(updating the state information with the proper relevant		remote Protecting administrative state (updating the state
	information) and begin transmitting a NR(0,1) message.		information with the proper relevant information) and begin
			transmitting a NR(0,1) message.
	o A remote Signal Fail message indicating a failure on the		o A remote Signal Fail message indicating a failure on the
	protection path SHALL cause the LER to go into Unavailable state		protection path SHALL cause the LER to go into remote Unavailable
	and begin transmitting a NR(0,0) message. It should be noted that		state and begin transmitting a NR(0,0) message. It should be
	this automatically cancels the current Forced switch or Manual		noted that this automatically cancels the current Forced switch or
	switch command and data traffic is reverted to the working path.		Manual switch command and data traffic is reverted to the working
			path.
	o A remote Signal Fail message indicating a failure on the working		o A remote Signal Fail message indicating a failure on the working
	path SHALL be ignored if there is an active local Forced switch		path SHALL be ignored if there is an active local Forced switch
	command. If the Protecting state is due to a local or remote		command. If the Protecting state is due to a local or remote
	Manual switch then the LER SHALL go to Protecting failure state		Manual switch then the LER SHALL go to remote Protecting failure
	and begin transmitting a NR(0,1) message.		state and begin transmitting a NR(0,1) message.
	o A remote Manual switch message SHALL be ignored by the PSC Process		o A remote Manual switch message SHALL be ignored by the PSC Control
	Logic if in Protecting state due to a local or remote Forced		Logic if in Protecting administrative state due to a local or
	switch. If in Protecting state due to a remote Manual switch then		remote Forced switch. If in Protecting administrative state due
	the LER SHALL remain in Protecting administrative state and		to a remote Manual switch then the LER SHALL remain in remote
	continue transmitting the current message. If in Protecting state		Protecting administrative state and continue transmitting the
	due to an active local Manual switch then the LER SHALL remain in		current message. If in local Protecting administrative state due
			to an active Manual switch then the LER SHALL remain in local
	Protecting administrative state and continue transmission of the		Protecting administrative state and continue transmission of the
	MS(1,1) message.		MS(1,1) message.
	o A remote DNR(0,0) message SHALL be ignored if in Protecting state		o A remote DNR(0,1) message SHALL be ignored if in local Protecting
	due to a local input. If in Protecting state due to a remote		administrative state. If in remote Protecting administrative
	message then the LER SHALL go to Do-not-revert state and begin		state then the LER SHALL go to Do-not-revert state and continue
	transmitting a NR(0,0) message.		transmitting the current message.
	o A remote NR(0,0) message SHALL be ignored if in Protecting state		o A remote NR(0,0) message SHALL be ignored if in local Protecting
	due to a local input. If in Protecting state due to a remote		administrative state. If in remote Protecting administrative
	message then the LER SHALL go to Normal state and begin		state then the LER SHALL go to Normal state and begin transmitting
	transmitting a NR(0,0) message.		a NR(0,0) message.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHOULD be ignored.
	4.3.3.4. Protecting failure state		4.3.3.4. Protecting failure state
	When the protection mechanism has been triggered and the protection		When the protection mechanism has been triggered and the protection
	domain has performed a protection switch, the domain is in the		domain has performed a protection switch, the domain is in the
	protecting failure state. In this state the normal data traffic is		protecting failure state. In this state the normal data traffic is
	transported on the protection path.		transported on the protection path. When an LER is in this state it
			implies that there was either a local SF condition or received a
			remote SF PCS message. The SF condition or message indicated that
			the failure is on the working path.
			This state may be overridden by the Unavailable state triggers, i.e.
			Lockout of Protection or SF on the protection path, or by issuing a
			FS operator command. This state will be cleared when the SF
			condition is cleared. In order to prevent flapping due to an
			intermittent fault, the LER SHOULD employ a Wait-to-restore timer to
			delay return to Normal state until the network has stabilized (see
			section 3.1.5)
	The following describe the reaction to local input:		The following describe the reaction to local input:
	o A local Clear SF SHOULD be ignored if in remote Protecting state.		o A local Clear SF SHALL be ignored if in remote Protecting failure
	If the Clear SF indicates that the protection path is now cleared		state. If the Clear SF indicates that the protection path is now
	(but working is still in SF condition) then the indicateion SHOULD		cleared (but working is still in SF condition) then the indication
	be ignored. If in local Protecting failure state and the LER is		SHALL be ignored. If in local Protecting failure state and the
	configured for revertive behavior then this input SHALL cause the		LER is configured for revertive behavior then this input SHALL
	LER to go into Wait-to-restore state, start the WTR timer, and		cause the LER to go into Wait-to-restore state, start the WTR
	begin transmitting a WTR(0,1) message. If in local Protecting		timer, and begin transmitting a WTR(0,1) message. If in local
	failure state and the LER is configured for non-revertive behavior		Protecting failure state and the LER is configured for non-
	then this input SHALL cause the LER to go into Do-not-revert state		revertive behavior then this input SHALL cause the LER to go into
	and begin transmitting a DNR(0,1) message.		Do-not-revert state and begin transmitting a DNR(0,1) message.
	o A local Lockout of protection input SHALL cause the LER to go into		o A local Lockout of protection input SHALL cause the LER to go into
	Unavailable state and begin transmission of a LO(0,0) message.		Unavailable state and begin transmission of a LO(0,0) message.
	o A local Forced switch input SHALL cause the LER to go into		o A local Forced switch input SHALL cause the LER to go into
	Protecting administrative state and begin transmission of a		Protecting administrative state and begin transmission of a
	FS(1,1) message.		FS(1,1) message.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail indication on the protection path SHALL cause
	the LER to go into Unavailable state and begin transmission of a		the LER to go into Unavailable state and begin transmission of a
	SF(0,0) message.		SF(0,0) message.
	o A local Signal Fail indication on the working path SHALL cause the		o A local Signal Fail indication on the working path SHALL cause the
	LER to remain in Protecting failure state and begin transmitting a		LER to remain in local Protecting failure state and transmit a
	SF(1,1) message.		SF(1,1) message.
	o All other local inputs SHOULD be ignored.		o All other local inputs SHOULD be ignored.
	While in Protecting failure state the LER may receive and react as		While in Protecting failure state the LER may receive and react as
	follows to remote PSC messages:		follows to remote PSC messages:
	o A remote Lockout of protection message SHALL cause the LER to go		o A remote Lockout of protection message SHALL cause the LER to go
	into Unavailable state and if in protecting failure state due to a		into remote Unavailable state and if in local Protecting failure
	local SF condition then the LER SHALL begin transmitting a SF(1,0)		state then the LER SHALL transmit a SF(1,0) message, otherwise it
	message, otherwise it SHALL transmit a NR(0,0) message. It should		SHALL transmit a NR(0,0) message. It should be noted that this
	be noted that this may cause loss of user data since the working		may cause loss of user data since the working path is still in a
	path is still in a failure condition.		failure condition.
	o A remote Forced switch message SHALL cause the LER go into		o A remote Forced switch message SHALL cause the LER go into remote
	Protecting administrative state and if in protecting failure state		Protecting administrative state and if in local Protecting failure
	due to a local SF condition the LER SHALL begin transmitting the		state the LER SHALL transmit the SF(1,1) message, otherwise it
	SF(1,1) message, otherwise it SHALL begin transmitting NR(0,0).		SHALL transmit NR(0,1).
	o A remote Signal Fail message indicating a failure on the		o A remote Signal Fail message indicating a failure on the
	protection path SHALL cause the LER to go into Unavailable state		protection path SHALL cause the LER to go into remote Unavailable
	and if in protecting failure state due to a local SF condition		state and if in local Protecting failure state then the LER SHALL
	then the LER SHALL begin transmitting a SF(1,0) message, otherwise		transmit a SF(1,0) message, otherwise it SHALL transmitting
	it SHALL begin transmitting NR(0,0) message. It should be noted		NR(0,0) message. It should be noted that this may cause loss of
	that this may cause loss of user data since the working path is		user data since the working path is still in a failure condition.
	still in a failure condition.
	o If in Protecting state due to a remote message, a remote Wait-to-		o If in remote Protecting failure state, a remote Wait-to-Restore
	Restore message SHALL cause the LER to go into Wait-to-Restore		message SHALL cause the LER to go into remote Wait-to-Restore
	state and continue transmission of the current message.		state and continue transmission of the current message.
	o If in Protecting state due to a remote message, a remote Do-not-		o If in remote Protecting failure state, a remote Do-not-revert
	revert message SHALL cause the LER to go into Do-not-revert state		message SHALL cause the LER to go into remote Do-not-revert state
	and continue transmission of the current message.		and continue transmission of the current message.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHOULD be ignored.
	4.3.3.5. Wait-to-restore state		4.3.3.5. Wait-to-restore state
	The Wait-to-Restore state is used by the PSC protocol to delay		The Wait-to-Restore state is used by the PSC protocol to delay
	reverting to the normal state, when recovering from a failure		reverting to the normal state, when recovering from a failure
	condition on the working path, for the period of the WTR timer to		condition on the working path, for the period of the WTR timer to
	allow the recovering failure to stabilize. While in the Wait-to-		allow the recovering failure to stabilize. While in the Wait-to-
	Restore state the data traffic SHALL continue to be transported on		Restore state the data traffic SHALL continue to be transported on
	the protection path. The natural transition from the Wait-to-Restore		the protection path. The natural transition from the Wait-to-Restore
	state to Normal state will occur when the WTR timer expires.		state to Normal state will occur when the WTR timer expires.
	When in Wait-to-Restore state the following describe the reaction to		When in Wait-to-Restore state the following describe the reaction to
	local inputs:		local inputs:
	o A local Lockout of protection command SHALL cause the LER to Stop		o A local Lockout of protection command SHALL cause the LER to Stop
	the WTR timer, go into Unavailable state, and begin transmitting a		the WTR timer, go into local Unavailable state, and begin
	LO(0,0) message.		transmitting a LO(0,0) message.
	o A local Forced switch command SHALL cause the LER to Stop the WTR		o A local Forced switch command SHALL cause the LER to Stop the WTR
	timer, go into Protecting administrative state, and begin		timer, go into local Protecting administrative state, and begin
	transmission of a FS(1,1) message.		transmission of a FS(1,1) message.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail indication on the protection path SHALL cause
	the LER to Stop the WTR timer, go into Unavailable state, and		the LER to Stop the WTR timer, go into local Unavailable state,
	begin transmission of a SF(0,0) message.		and begin transmission of a SF(0,0) message.
	o A local Signal Fail indication on the working path SHALL cause the		o A local Signal Fail indication on the working path SHALL cause the
	LER to Stop the WTR timer, go into Protecting failure state, and		LER to Stop the WTR timer, go into local Protecting failure state,
	begin transmission of a SF(1,1) message.		and begin transmission of a SF(1,1) message.
	o A local Manual switch input SHALL cause the LER to Stop the WTR		o A local Manual switch input SHALL cause the LER to Stop the WTR
	timer, go into Protecting administrative state and begin		timer, go into local Protecting administrative state and begin
	transmission of a MS(1,1) message.		transmission of a MS(1,1) message.
	o A local WTR expires input SHALL cause the LER to remain in Wait-		o A local WTR expires input SHALL cause the LER to remain in Wait-
	to-Restore state and begin transmitting a NR(0,1) message.		to-Restore state and begin transmitting a NR(0,1) message.
	o All other local inputs SHOULD be ignored.		o All other local inputs SHOULD be ignored.
	When in Wait-to-Restore state the following describe the reaction to		When in Wait-to-Restore state the following describe the reaction to
	remote messages:		remote messages:
	o A remote Lockout of protection message SHALL cause the LER to Stop		o A remote Lockout of protection message SHALL cause the LER to Stop
	the WTR timer, go into Unavailable state, and begin transmitting a		the WTR timer, go into remote Unavailable state, and begin
	NR(0,0) message.		transmitting a NR(0,0) message.
	o A remote Forced switch message SHALL cause the LER to Stop the WTR		o A remote Forced switch message SHALL cause the LER to Stop the WTR
	timer, go into Protecting administrative state, and begin		timer, go into remote Protecting administrative state, and begin
	transmission of a NR(0,1) message.		transmission of a NR(0,1) message.
	o A remote Signal Fail message for the protection path SHALL cause		o A remote Signal Fail message for the protection path SHALL cause
	the LER to Stop the WTR timer, go into Unavailable state, and		the LER to Stop the WTR timer, go into remote Unavailable state,
	begin transmission of a NR(0,0) message.		and begin transmission of a NR(0,0) message.
	o A remote Signal Fail message for the working path SHALL cause the		o A remote Signal Fail message for the working path SHALL cause the
	LER to Stop the WTR timer, go into Protecting failure state, and		LER to Stop the WTR timer, go into remote Protecting failure
	begin transmission of a NR(0,1) message.		state, and begin transmission of a NR(0,1) message.
	o A remote Manual switch message SHALL cause the LER to Stop the WTR		o A remote Manual switch message SHALL cause the LER to Stop the WTR
	timer, go into Protecting administrative state and begin		timer, go into remote Protecting administrative state and begin
	transmission of a NR(0,1) message.		transmission of a NR(0,1) message.
	o If the WTR timer is running then a remote NR message SHALL be		o If the WTR timer is running then a remote NR message SHALL be
	ignored. If the WTR timer is no longer running then a remote NR		ignored. If the WTR timer is no longer running then a remote NR
	message SHALL cause the LER to go into Normal state and begin		message SHALL cause the LER to go into Normal state and begin
	transmitting a NR(0,0) message.		transmitting a NR(0,0) message.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHOULD be ignored.
	4.3.3.6. Do-not-revert state		4.3.3.6. Do-not-revert state
	Do-not-revert state is a continuation of the protecting state when		Do-not-revert state is a continuation of the Protecting failure
	the protection domain is configured for non-revertive behavior.		state. When the protection domain is configured for non-revertive
	While in Do-not-revert state, data traffic continues to be		behavior. While in Do-not-revert state, data traffic continues to be
	transported on the protection path until the administrator sends a		transported on the protection path until the administrator sends a
	command to revert to the Normal state. It should be noted that there		command to revert to the Normal state. It should be noted that there
	is a fundemental difference between this state and Normal - whereas		is a fundamental difference between this state and Normal - whereas
	Forced Switch in Normal state actually causes a switch in the		Forced Switch in Normal state actually causes a switch in the
	transport path used, in Do-not-revert state the Forced switch just		transport path used, in Do-not-revert state the Forced switch just
	switches the state (to Protecting administrative state) but the		switches the state (to Protecting administrative state) but the
	traffic would continue to be transported on the protection path! The		traffic would continue to be transported on the protection path! To
	command to revert back to Normal state could either be a Lockout of		revert back to Normal state the administrator SHALL issue a Lockout
	protection (followed be a Clear command), a Clear command, or a new		of protection command followed by a Clear command.
	form of the Manual switch command [note: This would also require some
	kind of agreement, although it seems to have been adopted by ITU-T in
	G.8031 for Ethernet]. The following description of operation is
	based on the Lockout/Clear option mentioned!
	When in Do-not-revert state the following describe the reaction to		When in Do-not-revert state the following describe the reaction to
	local input:		local input:
	o A local Lockout of protection command SHALL cause the LER to go		o A local Lockout of protection command SHALL cause the LER to go
	into Unavailable state and begin transmitting a LO(0,0) message.		into local Unavailable state and begin transmitting a LO(0,0)
			message.
	o A local Forced switch command SHALL cause the LER to go into		o A local Forced switch command SHALL cause the LER to go into local
	Protecting administrative state and begin transmission of a		Protecting administrative state and begin transmission of a
	FS(1,1) message.		FS(1,1) message.
	o A local Signal Fail indication on the protection path SHALL cause		o A local Signal Fail indication on the protection path SHALL cause
	the LER to go into Unavailable state and begin transmission of a		the LER to go into local Unavailable state and begin transmission
	SF(0,0) message.		of a SF(0,0) message.
	o A local Signal Fail indication on the working path SHALL cause the		o A local Signal Fail indication on the working path SHALL cause the
	LER to go into Protecting failure state and begin transmission of		LER to go into local Protecting failure state and begin
	a SF(1,1) message.		transmission of a SF(1,1) message.
	o A local Manual switch input SHALL cause the LER to go into		o A local Manual switch input SHALL cause the LER to go into local
	Protecting administrative state and begin transmission of a		Protecting administrative state and begin transmission of a
	MS(1,1) message.		MS(1,1) message.
	o All other local inputs SHOULD be ignored.		o All other local inputs SHOULD be ignored.
	When in Do-not-revert state the following describe the reaction to		When in Do-not-revert state the following describe the reaction to
	remote messages:		remote messages:
	o A remote Lockout of protection message SHALL cause the LER to go		o A remote Lockout of protection message SHALL cause the LER to go
	into Unavailable state and begin transmitting a NR(0,0) message.		into remote Unavailable state and begin transmitting a NR(0,0)
			message.
	o A remote Forced switch message SHALL cause the LER to go into		o A remote Forced switch message SHALL cause the LER to go into
	Protecting administrative state and begin transmission of a		remote Protecting administrative state and begin transmission of a
	NR(0,1) message.		NR(0,1) message.
	o A remote Signal Fail message for the protection path SHALL cause		o A remote Signal Fail message for the protection path SHALL cause
	the LER to go into Unavailable state and begin transmission of a		the LER to go into remote Unavailable state and begin transmission
	NR(0,0) message.		of a NR(0,0) message.
	o A remote Signal Fail message for the working path SHALL cause the		o A remote Signal Fail message for the working path SHALL cause the
	LER to go into Protecting failure state, and begin transmission of		LER to go into remote Protecting failure state, and begin
	a NR(0,1) message.		transmission of a NR(0,1) message.
	o A remote Manual switch message SHALL cause the LER to go into		o A remote Manual switch message SHALL cause the LER to go into
	Protecting administrative state and begin transmission of a		remote Protecting administrative state and begin transmission of a
	NR(0,1) message.		NR(0,1) message.
	o All other remote messages SHOULD be ignored.		o All other remote messages SHOULD be ignored.
	5. IANA Considerations		5. IANA Considerations
	To be added in future version.		This draft requires the allocation of a Channel Code from the G-ACh
			repository.
	6. Security Considerations		6. Security Considerations
	To be added in future version.		To be added in future version.
	7. Acknowledgements		7. Acknowledgements
	The authors would like to thank all members of the teams (the Joint		The authors would like to thank all members of the teams (the Joint
	Working Team, the MPLS Interoperability Design Team in IETF and the		Working Team, the MPLS Interoperability Design Team in IETF and the
	T-MPLS Ad Hoc Group in ITU-T) involved in the definition and		T-MPLS Ad Hoc Group in ITU-T) involved in the definition and
	specification of MPLS Transport Profile.		specification of MPLS Transport Profile.
			Appendix A. PSC state machine tables
			The PSC state machine is described in section 4.3.3. This appendix
			provides the same information but in tabular format. In the event of
			a mismatch between these tables and the text in section 4.3.3, the
			text is authoritative. Note that this appendix is intended to be a
			functional description, not an implmentation specification.
			For the sake of clarity of the table the six states listed in the
			text are split into thirteen states. The logic of the split is to
			differentiate between the different cases given in the conditional
			statements in the descriptions of each state in the text. In
			addition, the remote and local states were split for the Unavailable,
			Protecting failure, and Protecting administrative states.
			There is only one table for the PSC state machine, but it is broken
			into two parts for space reasons. The first part lists the thirteen
			possible states, the eight possible local inputs (that is, inputs
			which are generated by the node in question) and the action taken
			when a given input is received when the node is in a particular
			state. The second part of the table lists the thirteen possible
			states and the eight remote inputs (inputs which come from a node
			other than the one executing the state machine).
			There are thirteen rows in the table, headers notwithstanding. These
			rows are the thirteen possible extended states in the state machine.
			The text in the first column is the current state. Those states
			which have both source and cause are formatted as State:Cause:Source.
			For example, the string UA:LO:L indicates that the current state is
			'Unavailable', that the cause of the current state is a Lockoutof
			protection that was a Local input. In contrast, the state N simply
			is Normal; there is no need to track the cause for entry into Normal
			state.
			The thirteen extended states, as they appear in the table, are:
			N Normal state
			UA:LO:L Unavailable state due to local Lockout
			UA:P:L Unavailable state due to local SF on protection path
			UA:LO:R Unavailable state due to remote Lockout message
			UA:P:R Unavailable state due to remote SF message on protection path
			PF:W:L Protecting failure state due to local SF on working path
			PF:W:R Protecting failure state due to remote SF message on working
			path
			PA:F:L Protecting administrative state due to local FS operator
			command
			PA:M:L Protecting administrative state due to local MS operator
			command
			PA:F:R Protecting administrative state due to remote FS message
			PA:M:R Protecting administrative state due to remote MS message
			WTR Wait-to-restore state
			DNR Do-not-revert state
			Each state corresponds to the transmission of a particular set of
			Request, FPath and Path bits. The table below lists the message that
			is generally sent in each particular state. If the message to be
			sent in a particular state deviates from the table below, it is noted
			in the footnotes to the state-machine table.
			State REQ(FP,P)
			------- ---------
			N NR(0,0)
			UA:LO:L LO(0,0)
			UA:P:L SF(0,0)
			UA:LO:R NR(0,0)
			UA:P:R NR(0,0)
			PF:W:L SF(1,1)
			PF:W:R NR(0,1)
			PA:F:L FS(1,1)
			PA:M:L MS(1,1)
			PA:F:R NR(0,1)
			PA:M:R NR(0,1)
			WTR WTR(0,1)
			DNR DNR(0,1)
			The top row in each table is the list of possible inputs. The local
			inputs are:
			NR No Request
			OC Operator Clear
			LO Lockout of protection
			SF-P Signal Fail on protection path
			SF-W Signal Fail on working path
			FS Forced Switch
			CSF Clear Signal Fail
			MS Manual Switch
			WTRExp WTR Expired
			and the remote inputs are:
			LO remote LO message
			SF-P remote SF message indicating protection path
			SF-W remote SF message indicating working path
			FS remote FS message
			MS remote MS message
			WTR remote WTR message
			DNR remote DNR message
			NR remote NR message
			Section 4.3.3 refers to some states as 'remote' and some as 'local'.
			By definition, all states listed in the table of local sources are
			local states, and all states listed in the table of remote sources
			are remote states. For example, section 4.3.3.1 says "A local
			Lockout of protection input SHALL cause the LER to go into local
			Unavailable State". As the trigger for this state change is a local
			one, 'local Unavailable State' is by definition displayed in the
			table of local sources. Similarly, "A remote Lockout of protection
			message SHALL cause the LER to go into remote Unavailable state"
			means that the state represented in the Unavailable rows in the table
			of remote sources is by definition a remote Unavailable state.
			Each cell in the table below contains either a state, a footnote, or
			the letter 'i'. 'i' stands for Ignore, and is an indication to
			continue with the current behavior. See section 4.3.3. The
			footnotes are listed below the table.
			Part 1: Local input state machine
			| OC | LO | SF-P | FS | SF-W | CSF | MS | WTRExp
			--------+-----+-------+------+------+------+------+------+-------
			N | i |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i |PA:M:L| i
			UA:LO:L | N | i | i | i | i | i | i | i
			UA:P:L | i |UA:LO:L| i | i | i | [5] | i | i
			UA:LO:R | i |UA:LO:L| [1] | i | [2] | [6] | i | i
			UA:P:R | i |UA:LO:L|UA:P:L| i | [3] | [6] | i | i
			PF:W:L | i |UA:LO:L|UA:P:L|PA:F:L| i | [7] | i | i
			PF:W:R | i |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i | i | i
			PA:F:L | N |UA:LO:L|UA:P:L| i | i | i | i | i
			PA:M:L | N |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i | i | i
			PA:F:R | i |UA:LO:L|UA:P:L|PA:F:L| [4] | [8] | i | i
			PA:M:R | i |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i |PA:M:L| i
			WTR | i |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i |PA:M:L| [9]
			DNR | i |UA:LO:L|UA:P:L|PA:F:L|PF:W:L| i |PA:M:L| i
			Part 2: Remote messages state machine
			| LO | SF-P | FS | SF-W | MS | WTR | DNR | NR
			--------+-------+------+------+------+------+------+------+------
			N |UA:LO:R|UA:P:R|PA:F:R|PF:W:R|PA:M:R| i | i | i
			UA:LO:L | i | i | i | i | i | i | i | i
			UA:P:L | [10] | i | i | i | i | i | i | i
			UA:LO:R | i | i | i | i | i | i | i | [16]
			UA:P:R |UA:LO:R| i | i | i | i | i | i | [16]
			PF:W:L | [11] | [12] |PA:F:R| i | i | i | i | i
			PF:W:R |UA:LO:R|UA:P:R|PA:F:R| i | i | [14] | [15] | i
			PA:F:L |UA:LO:R|UA:P:R| i | i | i | i | i | i
			PA:M:L |UA:LO:R|UA:P:R|PA:F:R| [13] | i | i | i | i
			PA:F:R |UA:LO:R|UA:P:R| i | i | i | i | i | N
			PA:M:R |UA:LO:R|UA:P:R|PA:F:R| [13] | i | i | i | N
			WTR |UA:LO:R|UA:P:R|PA:F:R|PF:W:R|PA:M:R| i | i | [17]
			DNR |UA:LO:R|UA:P:R|PA:F:R|PF:W:R|PA:M:R| i | i | i
			The following are the footnotes for the table:
			[1] Remain in the current state (UA:LO:R) and transmit SF(0,0)
			[2] Remain in the current state (UA:LO:R) and transmit SF(1,0)
			[3] Remain in the current state (UA:P:R) and transmit SF(1,0)
			[4] Remain in the current state (PA:F:R) and transmit SF(1,1)
			[5] If the SF being cleared is SF-P, Transition to N. If it's SF-W,
			ignore the clear.
			[6] Remain in current state (UA:x:R), if the CSF corresponds to a
			previous SF then begin transmitting NR(0,0).
			[7] If the SF being cleared is SF-P, ignore the clear. If it's SF-W,
			transition to WTR, start the WTR timer, and send WTR(1,1)
			[8] Remain in PA:F:R and transmit NR(0,1)
			[9] Remain in WTR, send NR(0,1)
			[10] Transition to UA:LO:R continue sending SF(0,0)
			[11] Transition to UA:LO:R and send SF(1,0)
			[12] Transition to UA and send SF(1,0)
			[13] Transition to PF:W:R and send NR(0,1)
			[14] Transition to WTR state and continue to send the current
			message.
			[15] Transition to DNR state and continue to send the current
			message.
			[16] Transition to N state and continue to send the current message.
			[17] If the receiving node's WTR timer has expired, transition to N.
			If not, maintain current state and message.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,		[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
	and S. Ueno, "Requirements of an MPLS Transport Profile",		and S. Ueno, "Requirements of an MPLS Transport Profile",
	RFC 5654, September 2009.		RFC 5654, September 2009.
End of changes. 117 change blocks.
	264 lines changed or deleted		538 lines changed or added
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