draft-ietf-opsawg-oam-overview-02.txt		draft-ietf-opsawg-oam-overview-03.txt
	Operations and Management Area Working Group T. Mizrahi		Operations and Management Area Working Group T. Mizrahi
	Internet Draft Marvell		Internet Draft Marvell
	Intended status: Informational N. Sprecher		Intended status: Informational N. Sprecher
	Expires: April 2011 Nokia Siemens Networks		Expires: July 2011 Nokia Siemens Networks
	E. Bellagamba		E. Bellagamba
	Ericsson		Ericsson
	Y. Weingarten		Y. Weingarten
	Nokia Siemens Networks		Nokia Siemens Networks
	October 7, 2010		January 24, 2011
	An Overview of		An Overview of
	Operations, Administration, and Maintenance (OAM) Mechanisms		Operations, Administration, and Maintenance (OAM) Mechanisms
	draft-ietf-opsawg-oam-overview-02.txt		draft-ietf-opsawg-oam-overview-03.txt
	Status of this Memo		Status of this Memo
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	Abstract		Abstract
	Operations, Administration, and Maintenance (OAM) is a general term		Operations, Administration, and Maintenance (OAM) is a general term
	that refers to a toolset that can be used for detecting and reporting		that refers to a toolset that can be used for fault detection and
	connection failures or measurement of connection performance		localization, and for performance measurement. OAM mechanisms have
	parameters. OAM mechanisms have been defined for various layers in		been defined for various layers in the protocol stack, and are used
	the protocol stack, and are used with a variety of protocols.		with a variety of protocols.
	This document presents an overview of the OAM mechanisms that have		This document presents an overview of the OAM mechanisms that have
	been defined and are currently being defined by the IETF, as well as		been defined and are currently being defined by the IETF, as well as
	a comparison to other OAM mechanisms that have been defined by the		a comparison to other OAM mechanisms that have been defined by the
	IEEE and ITU-T.		IEEE and ITU-T.
	Table of Contents		Table of Contents
	1. Introduction................................................4		1. Introduction................................................4
	2. Conventions used in this document............................8		2. Conventions used in this document............................8
	3. Basic Terminology...........................................8		3. Basic Terminology...........................................8
	3.1. Abbreviations..........................................8		3.1. Abbreviations..........................................8
	3.2. Terminology used in OAM Standards.......................9		3.2. Terminology used in OAM Standards.......................9
	3.2.1. General Terms......................................9		3.2.1. General Terms......................................9
	3.2.2. OAM Maintenance Entities and Communication Links...10		3.2.2. OAM Maintenance Entities and Communication Links...10
	3.2.3. OAM Maintenance Points............................10		3.2.3. OAM Maintenance Points............................10
	3.2.4. Link Failures.....................................11		3.2.4. Connectivity Verification and Continuity Checks....11
	3.2.5. Connectivity Verification and Continuity Checks....11		3.2.5. Link Failures.....................................11
	3.2.6. Summary of OAM Terms used in the Standards.........11		3.2.6. Summary of OAM Terms used in the Standards.........12
	4. OAM Functions..............................................13		4. OAM Functions..............................................13
	4.1. ICMP Ping.............................................13		4.1. ICMP Ping.............................................13
	4.2. Bidirectional Forwarding Detection (BFD)...............13		4.2. Bidirectional Forwarding Detection (BFD)...............13
	4.2.1. Overview.........................................13		4.2.1. Overview.........................................13
	4.2.2. BFD Control.......................................13		4.2.2. BFD Control.......................................13
	4.2.3. BFD Echo.........................................14		4.2.3. BFD Echo.........................................14
	4.3. LSP Ping..............................................14		4.3. LSP Ping..............................................14
	4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...15		4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...15
	4.5. IP Performance Metrics (IPPM)..........................15		4.5. IP Performance Metrics (IPPM)..........................16
	4.5.1. Overview.........................................15		4.5.1. Overview.........................................16
	4.5.2. Control and Test Protocols........................16		4.5.2. Control and Test Protocols........................16
	4.5.3. OWAMP............................................16		4.5.3. OWAMP............................................17
	4.5.4. TWAMP............................................17		4.5.4. TWAMP............................................17
	4.6. ITU-T Y.1711..........................................17		4.6. ITU-T Y.1711..........................................18
	4.6.1. Overview.........................................17		4.6.1. Overview.........................................18
	4.6.2. Connectivity Verification (CV)....................18		4.6.2. Connectivity Verification (CV)....................18
	4.6.3. Fast Failure Detection (FFD)......................18		4.6.3. Fast Failure Detection (FFD)......................19
	4.6.4. Forward Defect Indication (FDI)...................18		4.6.4. Forward Defect Indication (FDI)...................19
	4.6.5. Backward Defect Indication (BDI)..................19		4.6.5. Backward Defect Indication (BDI)..................19
	4.7. ITU-T Y.1731..........................................19		4.7. ITU-T Y.1731..........................................19
	4.7.1. Overview.........................................19		4.7.1. Overview.........................................19
	4.7.2. ETH-CC...........................................19		4.7.2. ETH-CC...........................................19
	4.7.3. ETH-LB...........................................20		4.7.3. ETH-LB...........................................20
	4.7.4. ETH-TST..........................................20		4.7.4. ETH-TST..........................................20
	4.7.5. ETH-LT...........................................20		4.7.5. ETH-LT...........................................21
	4.7.6. ETH-AIS..........................................20		4.7.6. ETH-AIS..........................................21
	4.7.7. ETH-LCK..........................................20		4.7.7. ETH-LCK..........................................21
	4.7.8. ETH-RDI..........................................21		4.7.8. ETH-RDI..........................................21
	4.7.9. ETH-APS..........................................21		4.7.9. ETH-APS..........................................21
	4.7.10. ETH-LM..........................................21		4.7.10. ETH-LM..........................................21
	4.7.11. ETH-DM..........................................21		4.7.11. ETH-DM..........................................22
	4.8. IEEE 802.1ag..........................................22		4.8. IEEE 802.1ag..........................................23
	4.8.1. Overview.........................................22		4.8.1. Overview.........................................23
	4.8.2. Continuity Check..................................22		4.8.2. Continuity Check..................................23
	4.8.3. Loopback.........................................22		4.8.3. Loopback.........................................23
	4.8.4. Linktrace........................................23		4.8.4. Linktrace........................................23
	4.9. IEEE 802.3ah..........................................23		4.9. IEEE 802.3ah..........................................23
	4.9.1. Overview.........................................23		4.9.1. Overview.........................................23
	4.9.2. Remote Failure Indication.........................23		4.9.2. Remote Failure Indication.........................23
	4.9.3. Remote Loopback...................................23		4.9.3. Remote Loopback...................................24
	4.9.4. Link Monitoring...................................23		4.9.4. Link Monitoring...................................24
	4.10. MPLS-TP OAM..........................................23		4.10. MPLS-TP OAM..........................................24
	4.10.1. Overview........................................23		4.10.1. Overview........................................24
	4.10.2. Generic Associated Channel.......................24		4.10.2. Generic Associated Channel.......................25
	4.10.3. MPLS-TP OAM Toolset..............................24		4.10.3. MPLS-TP OAM Toolset..............................25
	4.10.3.1. Continuity Check and Connectivity Verification25		4.10.3.1. Continuity Check and Connectivity Verification25
	4.10.3.2. Diagnostic Tests............................25		4.10.3.2. Diagnostic Tests............................26
	4.10.3.3. Route Tracing...............................25		4.10.3.3. Route Tracing...............................26
	4.10.3.4. Lock Instruct...............................25		4.10.3.4. Lock Instruct...............................26
	4.10.3.5. Lock Reporting..............................26		4.10.3.5. Lock Reporting..............................26
	4.10.3.6. Alarm Reporting.............................26		4.10.3.6. Alarm Reporting.............................26
	4.10.3.7. Remote Defect Indication....................26		4.10.3.7. Remote Defect Indication....................27
	4.10.3.8. Client Failure Indication...................26		4.10.3.8. Client Failure Indication...................27
	4.10.3.9. Packet Loss Measurement.....................26		4.10.3.9. Packet Loss Measurement.....................27
	4.10.3.10. Packet Delay Measurement...................27		4.10.3.10. Packet Delay Measurement...................27
	4.11. Summary of OAM Functions..............................27		4.11. Summary of OAM Functions..............................28
	4.12. Summary of Continuity Check Mechanisms................29		4.12. Summary of Continuity Check Mechanisms................29
	5. Security Considerations.....................................30		5. Security Considerations.....................................30
	6. IANA Considerations........................................30		6. IANA Considerations........................................30
	7. Acknowledgments............................................30		7. Acknowledgments............................................30
	8. References.................................................30		8. References.................................................31
	8.1. Normative References...................................30		8.1. Normative References...................................31
	8.2. Informative References.................................32		8.2. Informative References.................................33
	1. Introduction		1. Introduction
	OAM is a general term that refers to a toolset that can be used for		OAM is a general term that refers to a toolset that can be used for
	detecting and reporting connection failures or measurement of		detecting, isolating and reporting connection failures or measurement
	connection performance parameters. The term OAM has been used over		of connection performance parameters. The term OAM has been used over
	the years in several different contexts, as discussed in [OAM Soup].		the years in several different contexts, as discussed in [OAM Soup].
	In the context of this document OAM refers to Operations,		In the context of this document OAM refers to Operations,
	Administration, and Maintenance, i.e., this document refers to OAM in		Administration, and Maintenance, i.e., this document refers to OAM in
	the context of monitoring communication links. Other aspects		the context of monitoring communication entities, e.g., nodes, paths,
	associated with the OAM acronym, such as management, are not		physical links, or logical links. Other aspects associated with the
	described in this document.		OAM acronym, such as management, are outside the scope of this
			document.
	OAM was originally used in the world of telephony, and has been		OAM was originally used in the world of telephony, and has been
	adopted in packet based networks. OAM mechanisms are used in various		adopted in packet based networks. OAM mechanisms are used in various
	layers in the protocol stack, and are applied to a variety of		layers in the protocol stack, and are applied to a variety of
	different protocols.		different protocols.
	The IETF has defined OAM for several protocols, and is currently		The IETF has defined OAM for several protocols, and is currently
	working on defining several new OAM protocols. A summary of these		working on defining several new OAM protocols. A summary of these
	protocols, old and new, is listed below:		protocols, old and new, is listed below:
	skipping to change at page 9, line 18		skipping to change at page 9, line 18
	LSR Label Switching Router		LSR Label Switching Router
	MA Maintenance Association		MA Maintenance Association
	ME Maintenance Entity		ME Maintenance Entity
	MEG Maintenance Entity Group		MEG Maintenance Entity Group
	MEP Maintenance End Point		MEP Maintenance End Point
			MHF MIP Half Function
	MIP Maintenance Intermediate Point		MIP Maintenance Intermediate Point
	MP Maintenance Point		MP Maintenance Point
	MPLS Multiprotocol Label Switching		MPLS Multiprotocol Label Switching
	MPLS-TP MPLS Transport Profile		MPLS-TP MPLS Transport Profile
	OAM Operations, Administration, and Maintenance		OAM Operations, Administration, and Maintenance
	skipping to change at page 10, line 13		skipping to change at page 10, line 13
	some of the OAM related terminology.		some of the OAM related terminology.
	This section presents a comparison of the terms used in various OAM		This section presents a comparison of the terms used in various OAM
	standards, without fully quoting the definition of each term. For a		standards, without fully quoting the definition of each term. For a
	formal definition of each term, refer to the references at the end of		formal definition of each term, refer to the references at the end of
	this document. The comparison focuses on three basic terms, and is		this document. The comparison focuses on three basic terms, and is
	summarized in section 3 ..2.6.		summarized in section 3 ..2.6.
	3.2.2. OAM Maintenance Entities and Communication Links		3.2.2. OAM Maintenance Entities and Communication Links
	A Maintenance Entity (ME) can be either a point-to-point or a point-		A Maintenance Entity (ME) is a point-to-point relationship between
	to-multipoint relationship between two or more Maintenance Points		two Maintenance Points (MP). The connectivity between these
	(MP). The connectivity between these Maintenance Points is managed		Maintenance Points is managed and monitored by the OAM protocol.
	and monitored by the OAM protocol.
	A pair of MPs engaged in an ME are connected by a communication Link.		A pair of MPs engaged in an ME are connected by a communication Link.
	Link in this context may refer to a physical connection, or to a		The term "Link" in this context is a generic term that may refer to
	logical path such as an MPLS LSP. The term Link is used throughout		one of several types of connection, e.g. a single physical
	this document to refer to the connection between the MPs that is		connection, a set of physical connections, or a virtual link such as
	monitored by an OAM protocol.		an MPLS LSP. The term Link is used throughout this document to refer
			to the connection between the MPs that is monitored by an OAM
			protocol.
	The term Maintenance Entity (ME) is defined in ITU-T standards (e.g.		The term Maintenance Entity (ME) is defined in ITU-T standards (e.g.
	[ITU-T Y.1731]). Various terms are used to refer to an ME. For		[ITU-T Y.1731]). Various terms are used to refer to an ME. For
	example, in MPLS terminology, an ME is simply referred to as an LSP.		example, in MPLS LSP Ping ([LSP Ping]) terminology, an ME is simply
	BFD does not explicitly use a term that is equivalent to ME, but		referred to as an LSP. BFD does not explicitly use a term that is
	rather uses the term "session", referring to the relationship between		equivalent to ME, but rather uses the term "session", referring to
	two nodes using a BFD protocol.		the relationship between two nodes using a BFD protocol.
	MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG)		MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG)
	in [MPLS-TP OAM FW], similar to the terms defined by ITU-T.		in [MPLS-TP OAM FW], similar to the terms defined by ITU-T.
	3.2.3. OAM Maintenance Points		3.2.3. OAM Maintenance Points
	A Maintenance Point (MP) is a function that is defined at a node in		A Maintenance Point (MP) is a functional entity that is defined at a
	the network, and either initiates or reacts to OAM messages. A		node in the network, and either initiates or reacts to OAM messages.
	Maintenance End Point (MEP) is one of the end points of an ME, and		A Maintenance End Point (MEP) is one of the end points of an ME, and
	can initiate OAM messages and respond to them. A Maintenance		can initiate OAM messages and respond to them. A Maintenance
	Intermediate Point (MIP) is a point between two MEPs, that is able to		Intermediate Point (MIP) is an intermediate point between two MEPs,
	respond to OAM frames, but does not initiate them.		that does not initiate OAM frames, but is able to respond to OAM
			frames that are destined to it, and to forward others.
	The terms MEP and MIP are defined in ITU-T standards (e.g. [ITU-T		The terms MEP and MIP are defined in ITU-T standards (e.g. [ITU-T
	Y.1731]). The term Maintenance Point is a general term for MEPs and		Y.1731]). The term Maintenance Point is a general term for MEPs and
	MIPs, and is used in [IEEE 802.1ag].		MIPs, and is used in [IEEE 802.1ag].
			The 802.1ag defines a finer distinction between Up MPs and Down MPs.
			An MP is a bridge interface, that is monitored by an OAM protocol
			either in the direction facing the network, or in the direction
			facing the bridge. A Down MP is an MP that receives OAM packets from,
			and transmits them to the direction of the network. An Up MP receives
			OAM packets from, and transmits them to the direction of the bridging
			entity.
	MPLS-TP has defined the terms MEP and MIP and their functional		MPLS-TP has defined the terms MEP and MIP and their functional
	characteristics in [MPLS-TP OAM FW], similar to the terms defined by		characteristics in [MPLS-TP OAM FW], similar to the terms defined by
	ITU-T.		ITU-T.
	3.2.4. Link Failures		3.2.4. Connectivity Verification and Continuity Checks
	The terms Failure, Fault, and Defect are intermittently used in the
	standards. In some standards, such as [IEEE 802.1ag], there is no
	distinction between these terms, while in other standards each of
	these terms refers to a different type of malfunction.
	The ITU-T distinguishes between these terms in [ITU-T G.806]. The
	term Fault refers to an inability to perform a required action, e.g.,
	an unsuccessful attempt to deliver a packet. The term Defect refers
	to an interruption in the normal operation, such as a consecutive
	period of time where no packets are delivered successfully. The term
	Failure refers to the termination of the required function. While a
	Defect typically refers to a limited period of time, a failure refers
	to a long period of time.
	3.2.5. Connectivity Verification and Continuity Checks
	Two distinct classes of failure management functions are used in OAM		Two distinct classes of failure management functions are used in OAM
	protocols, connectivity verification and continuity checks. The		protocols, connectivity verification and continuity checks. The
	distinction between these terms is defined in [MPLS-TP OAM], and is		distinction between these terms is defined in [MPLS-TP OAM], and is
	used similarly in this document.		used similarly in this document.
	Continuity checks are used to verify the liveness of a link, and are		Continuity checks are used to verify the liveness of a link, and are
	typically sent proactively, though they can be invoked on-demand as		typically sent proactively, though they can be invoked on-demand as
	well.		well.
	A connectivity verification function allows an MP to check whether it		A connectivity verification function allows an MP to check whether it
	is connected to a peer MP or not. A connectivity verification (CV)		is connected to a peer MP or not. A connectivity verification (CV)
	protocol typically uses a CV message, followed by a CV reply that is		protocol typically uses a CV message, followed by a CV reply that is
	sent back to the originator. A CV function can be applied proactively		sent back to the originator. A CV function can be applied proactively
	or on-demand.		or on-demand.
	Connectivity verification and continuity checks are considered		Connectivity verification and continuity checks are considered
	complementary mechanisms, and are often used in conjunction with each		complementary mechanisms, and are often used in conjunction with each
	other.		other.
			3.2.5. Link Failures
			The terms Failure, Fault, and Defect are intermittently used in the
			standards, referring to a malfunction that can be detected by a
			connectivity or a continuity check. In some standards, such as [IEEE
			802.1ag], there is no distinction between these terms, while in other
			standards each of these terms refers to a different type of
			malfunction.
			The ITU-T distinguishes between these terms in [ITU-T G.806]. The
			term Fault refers to an inability to perform a required action, e.g.,
			an unsuccessful attempt to deliver a packet. The term Defect refers
			to an interruption in the normal operation, such as a consecutive
			period of time where no packets are delivered successfully. The term
			Failure refers to the termination of the required function. While a
			Defect typically refers to a limited period of time, a failure refers
			to a long period of time.
	3.2.6. Summary of OAM Terms used in the Standards		3.2.6. Summary of OAM Terms used in the Standards
	Table 2 provides a comparison of the terminology used in different		Table 2 provides a comparison of the terminology used in different
	OAM standards.		OAM standards.
	+-----------+-------------+-----------+----------------------------+		+-----------+-------------+-----------+----------------------------+
	| |Maintenance |Maintenance|Link Failure Terminology |		| |Maintenance |Maintenance|Link Failure Terminology |
	| |Point |Entity | |		| |Point |Entity | |
	| |Terminology |Terminology| |		| |Terminology |Terminology| |
	+-----------+-------------+-----------+----------------------------+		+-----------+-------------+-----------+----------------------------+
	skipping to change at page 12, line 38		skipping to change at page 13, line 5
	+ --------- + ----------- + --------- + -------------------------- +		+ --------- + ----------- + --------- + -------------------------- +
	|ITU-T |-MEP | ME |-Fault, Defect, Failure: as |		|ITU-T |-MEP | ME |-Fault, Defect, Failure: as |
	|Y.1731 |-MIP | | defined in [ITU-T G.806] |		|Y.1731 |-MIP | | defined in [ITU-T G.806] |
	| | | | |		| | | | |
	+ --------- + ----------- + --------- + -------------------------- +		+ --------- + ----------- + --------- + -------------------------- +
	|MPLS-TP |-End Point, |-LSP |-Fault, Defect, Failure: as |		|MPLS-TP |-End Point, |-LSP |-Fault, Defect, Failure: as |
	|OAM | MEP |-PW | defined in [ITU-T G.806] |		|OAM | MEP |-PW | defined in [ITU-T G.806] |
	| |-Intermediate|-Section | |		| |-Intermediate|-Section | |
	| | Point, MIP | | |		| | Point, MIP | | |
	+ --------- + ----------- + --------- + -------------------------- +		+ --------- + ----------- + --------- + -------------------------- +
	|IEEE |-MEP | ME |-Failure |		|IEEE |-MP (Down,Up)| ME |-Failure |
	|802.1ag |-MIP | |-Fault |		|802.1ag | -MEP | |-Fault |
	| |-MP | |-Defect |		| | -MIP | |-Defect |
			| | -MHF | | |
	+ --------- + ----------- + --------- + -------------------------- +		+ --------- + ----------- + --------- + -------------------------- +
	|IEEE | DTE | Link |-Failure |		|IEEE | DTE | Link |-Failure |
	|802.3ah | | |-Fault |		|802.3ah | | |-Fault |
	+-----------+-------------+-----------+----------------------------+		+-----------+-------------+-----------+----------------------------+
	Table 2 Summary of OAM Terms		Table 2 Summary of OAM Terms
	4. OAM Functions		4. OAM Functions
	4.1. ICMP Ping		4.1. ICMP Ping
	skipping to change at page 15, line 6		skipping to change at page 15, line 21
	Class (FEC) and also Maximum Transmission Unit (MTU) problems. The		Class (FEC) and also Maximum Transmission Unit (MTU) problems. The
	traceroute functionality may be used to isolate and localize the MPLS		traceroute functionality may be used to isolate and localize the MPLS
	faults, using the Time-to-live (TTL) indicator to incrementally		faults, using the Time-to-live (TTL) indicator to incrementally
	identify the sub-path of the LSP that is successfully traversed		identify the sub-path of the LSP that is successfully traversed
	before the faulty link or node.		before the faulty link or node.
	It should be noted that LSP Ping does support unique identification		It should be noted that LSP Ping does support unique identification
	of the LSP within an addressing domain. The identification is checked		of the LSP within an addressing domain. The identification is checked
	using the full FEC identification. LSP Ping is easily extensible to		using the full FEC identification. LSP Ping is easily extensible to
	include additional information needed to support new functionality,		include additional information needed to support new functionality,
	by use of Type-Length-Value (TLV) constructs.		by use of Type-Length-Value (TLV) constructs. The usage of TLVs is
			typically not easy to perform in hardware, and is thus typically
			handled by the control plane.
	LSP Ping supports both asynchronous, as well as, on-demand		LSP Ping supports both asynchronous, as well as, on-demand
	activation. In addition, extensions for LSP Ping are being defined		activation. In addition, extensions for LSP Ping are being defined
	for point-to-multipoint LSPs in [P2MP LSP Ping] and for MPLS Tunnels		for point-to-multipoint LSPs in [P2MP LSP Ping] and for MPLS Tunnels
	in [MPLS LSP Ping].		in [MPLS LSP Ping].
	4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)		4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)
	VCCV, as defined in [VCCV], provides end-to-end fault detection		VCCV, as defined in [VCCV], provides end-to-end fault detection
	and diagnostics for PWs (regardless of the underlying tunneling		and diagnostics for PWs (regardless of the underlying tunneling
	skipping to change at page 18, line 23		skipping to change at page 18, line 41
	The CV function is used to detect connectivity defects in an LSP. CV		The CV function is used to detect connectivity defects in an LSP. CV
	frames are sent proactively at a rate of 1 per second. Each frame		frames are sent proactively at a rate of 1 per second. Each frame
	contains the Trail-Termination Source Identifier (TTSI), indicating		contains the Trail-Termination Source Identifier (TTSI), indicating
	the identity of the transmitting LSR.		the identity of the transmitting LSR.
	The CV function can detect any of the following defect conditions.		The CV function can detect any of the following defect conditions.
	o Loss of Connectivity Verification (LOCV): A loss of connectivity		o Loss of Connectivity Verification (LOCV): A loss of connectivity
	is detected when no CV OAM packets are received in a period of 3		is detected when no CV OAM packets are received in a period of 3
	consecutive transmission periods.		consecutive transmission periods.
			It should be noted that the LOCV defect is in fact loss of
			continuity when using the terminology defined in 3 ..2.4.
	o TTSI Mismatch: A TTSI mismatch is detected when a CV frame with an		o TTSI Mismatch: A TTSI mismatch is detected when a CV frame with an
	unexpected TTSI is received.		unexpected TTSI is received.
	o TTSI Mismerge: A TTSI mismerge is detected when the CV frames		o TTSI Mismerge: A TTSI mismerge is detected when the CV frames
	received in a given LSP contain some frame with an expected TTSI,		received in a given LSP contain some frame with an expected TTSI,
	and some frames with an unexpected TTSI.		and some frames with an unexpected TTSI.
	o Excess: An excess is detected when at least 5 CV frames are		o Excess: An excess is detected when at least 5 CV frames are
	received during a period of 3 consecutive transmission periods.		received during a period of 3 consecutive transmission periods.
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	failure detection and reporting, protection switching mechanisms		failure detection and reporting, protection switching mechanisms
	typically require faster detection. FFD is very similar to CV in		typically require faster detection. FFD is very similar to CV in
	terms of the packet format, and the possible defect conditions, but		terms of the packet format, and the possible defect conditions, but
	FFD allows a configurable transmission frequency. The default		FFD allows a configurable transmission frequency. The default
	transmission rate of FFD frames is 20 per second, i.e., every 50 ms,		transmission rate of FFD frames is 20 per second, i.e., every 50 ms,
	allowing fast detection for protection switching applications.		allowing fast detection for protection switching applications.
	4.6.4. Forward Defect Indication (FDI)		4.6.4. Forward Defect Indication (FDI)
	The FDI function is used by an LSR to report a defect to affected		The FDI function is used by an LSR to report a defect to affected
	client layers, allowing them to suppress alarms about this defect. An		client layers, allowing them to suppress alarms about this defect.
			In MPLS-TP OAM this function is referred to as Client Failure
			Indication.
	FDI packets are sent at a rate of 1 per second.		FDI packets are sent at a rate of 1 per second.
	4.6.5. Backward Defect Indication (BDI)		4.6.5. Backward Defect Indication (BDI)
	The BDI function is used to inform the LSR at an LSP trail		The BDI function is used by an LSR to inform a peer LSR about a
	termination source point about a defect condition in the forward		defect condition on an LSP for which they are the end points of.
	direction of an LSP. The LSR at the LSP trail termination sink point		In MPLS-TP OAM this function is referred to as Remote Defect
	transmits the BDI to the upstream LSR through the return path. BDI		Indication.
	packets are sent at the same transmission rate as FDI.
			BDI packets are sent at the same transmission rate as FDI.
	4.7. ITU-T Y.1731		4.7. ITU-T Y.1731
	4.7.1. Overview		4.7.1. Overview
	The [ITU-T Y.1731] defines a protocol for Ethernet OAM. It is		The [ITU-T Y.1731] defines a protocol for Ethernet OAM. It is
	presented in this document as a reference point. Y.1731 defines		presented in this document as a reference point. Y.1731 defines
	various OAM functions, including continuity and connectivity		various OAM functions, including continuity and connectivity
	verification, and functions for performance monitoring.		verification, and functions for performance monitoring.
	4.7.2. ETH-CC		4.7.2. ETH-CC
	The Ethernet Continuity Check function is a proactive function that		The Ethernet Continuity Check function is a proactive function that
	allows a MEP to detect loss of continuity with any of the other MEPs		allows a MEP to detect loss of continuity with any of the other MEPs
	in the MEG. This function also allows detection of other defect		in the MEG. This function also allows detection of other defect
	conditions, such as unintended connectivity between two MEGs. The		conditions, such as unintended connectivity between two MEGs (also
	ETH-CC function is used for one of three possible applications: fault		known as a mismerge). The ETH-CC function is used for one of three
	management, performance monitoring (see 4.6.10.), and protection		possible applications: fault management, performance monitoring (see
	switching.		4.6.10.), and protection switching.
	Continuity Check Messages (CCM) are transmitted periodically at a		Continuity Check Messages (CCM) are transmitted periodically at a
	constant rate. There are 7 possible transmission periods, from 3.33		constant rate. There are 7 possible transmission periods, from 3.33
	ms to 10 min. When the ETH-CC function detects a defect, it reports		ms to 10 min. When the ETH-CC function detects a defect, it reports
	one of the following defect conditions:		one of the following defect conditions:
	o Loss of continuity (LOC): Occurs when at least when no CCM		o Loss of continuity (LOC): Occurs when at least when no CCM
	messages have been received from a peer MEP during a period of 3.5		messages have been received from a peer MEP during a period of 3.5
	times the configured transmission period.		times the configured transmission period.
	skipping to change at page 23, line 13		skipping to change at page 23, line 40
	See 4.6.3.		See 4.6.3.
	4.8.4. Linktrace		4.8.4. Linktrace
	See 4.6.5.		See 4.6.5.
	4.9. IEEE 802.3ah		4.9. IEEE 802.3ah
	4.9.1. Overview		4.9.1. Overview
	The [IEEE 802.3ah] defines an Ethernet link-layer OAM, for single-hop		The [IEEE 802.3ah] defines Ethernet for the Last Mile (EFM). With
	Ethernet links. The OAM functions in this standard are described		respect to OAM, this standard was designed as an Ethernet link-layer
	below.		OAM, for single-hop Ethernet links, allowing to monitor remote
			networking devices that are not managed by a centralized management
			system. The OAM functions in this standard are described below.
	4.9.2. Remote Failure Indication		4.9.2. Remote Failure Indication
	This function allows a node to notify a peer about a defect in the		This function allows a node to notify a peer about a defect in the
	receive path. Some physical interfaces allow unidirectional traffic,		receive path. Some physical interfaces allow unidirectional traffic,
	where even if one direction of the link fails, the reverse direction		where even if one direction of the link fails, the reverse direction
	can still be used to convey the remote failure indication.		can still be used to convey the remote failure indication.
	4.9.3. Remote Loopback		4.9.3. Remote Loopback
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