MPLS Working Group                                        I. Busi (Ed)
Internet Draft                                          Alcatel-Lucent
Intended status: Informational                    B. Niven-Jenkins (Ed)
                                                                   BT
                                                         D. Allan (Ed)
                                                             Ericsson

Expires: January April 2010                                    July 13,                                   October 26, 2009

                           MPLS-TP OAM Framework
                  draft-ietf-mpls-tp-oam-framework-01.txt
                  draft-ietf-mpls-tp-oam-framework-02.txt

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Abstract

   Multi-Protocol Label Switching (MPLS) Transport Profile (MPLS-TP) is
   based on a profile of the MPLS and pseudowire (PW) procedures as
   specified in the MPLS Traffic Engineering (MPLS-TE), pseudowire (PW)
   and multi-segment PW (MS-PW) architectures complemented with
   additional Operations, Administration and Maintenance (OAM)
   procedures for fault, performance and protection-switching management
   for packet transport applications that do not rely on the presence of
   a control plane.

   This document provides describes a framework that supports to support a comprehensive set of
   OAM procedures that fulfills the MPLS-TP OAM requirements [11]. [12].

Table of Contents

   1. Introduction.................................................3 Introduction.....................................................3
      1.1. Contributing Authors....................................4 Authors........................................4
   2. Conventions used in this document............................4 document................................4
      2.1. Terminology.............................................4 Terminology.................................................4
      2.2. Definitions.............................................5 Definitions.................................................5
   3. Functional Components........................................7 Components............................................8
      3.1. Maintenance Entity......................................9
      3.2. Point-to-multipoint scenario............................9
      3.3. Entity (ME) and Maintenance Entity Group (MEG)..9
      3.2. MEG End Points (MEPs)..........................10
      3.4. Maintenance (MEPs)......................................12
      3.3. MEG Intermediate Points (MIPs).................12
      3.5. (MIPs).............................14
      3.4. Server MEPs............................................12 MEPs................................................15
      3.5. Tandem Connection..........................................15
   4. Reference Model.............................................13 Model.................................................16
      4.1. MPLS-TP Section Monitoring.............................15 Monitoring.................................19
      4.2. MPLS-TP LSP End-to-End Monitoring......................16 Monitoring..........................20
      4.3. MPLS-TP LSP Tandem Connection Monitoring...............17 Monitoring...................21
      4.4. MPLS-TP PW Monitoring..................................19 Monitoring......................................23
      4.5. MPLS-TP MS-PW Tandem Connection Monitoring.............19 Monitoring.................23
   5. OAM Functions for pro-active monitoring.....................21 proactive monitoring..........................24
      5.1. Continuity Check and Connectivity Verification.........21 Verification.............25
         5.1.1. Defects identified by CC-V........................22
            5.1.1.1. Loss Of Continuity defect....................22
            5.1.1.2. Mis-connectivity defect......................22
            5.1.1.3. MEP misconfiguration defect..................23
            5.1.1.4. Period Misconfiguration defect...............23 CC-V............................26
         5.1.2. Consequent action.................................23 action.....................................28
         5.1.3. Configuration considerations......................24 considerations..........................29
         5.1.4. Applications for proactive CC-V...................25 CC-V.......................29
      5.2. Remote Defect Indication...............................26 Indication...................................30
         5.2.1. Configuration considerations......................26 considerations..........................31
         5.2.2. Applications for Remote Defect Indication.........26 Indication.............31
      5.3. Alarm Reporting........................................27 Reporting............................................31
      5.4. Lock Reporting.........................................28 Reporting.............................................33
      5.5. Lock Indication........................................29
      5.6. Packet Loss............................................29
         5.6.1. Loss Monitoring.....................................33
         5.5.1. Configuration considerations......................29
         5.6.2. considerations..........................33
         5.5.2. Applications for Packet Loss......................30
      5.7. Loss Monitoring...............33

      5.6. Client Signal Failure Indication..............................30
         5.7.1. Indication...........................34
         5.6.1. Configuration considerations......................31
         5.7.2. considerations..........................34
         5.6.2. Applications for Remote Defect Indication.........31
      5.8. Client Signal Failure Indication.....34
      5.7. Delay Measurement......................................31
         5.8.1. Measurement..........................................35
         5.7.1. Configuration considerations......................32
         5.8.2. considerations..........................35
         5.7.2. Applications for Packet Loss......................32 Delay Measurement....................36
   6. OAM Functions for on-demand monitoring......................32 monitoring..........................36
      6.1. Connectivity Verification..............................32 Verification..................................36
         6.1.1. Configuration considerations......................33 considerations..........................38
      6.2. Packet Loss............................................34 Loss Monitoring.....................................38
         6.2.1. Configuration considerations......................34 considerations..........................38
         6.2.2. Applications for On-demand Packet Loss............34 Loss Monitoring.....39
      6.3. Diagnostic.............................................34 Diagnostic.................................................39
      6.4. Route Tracing..........................................35 Tracing..............................................39
      6.5. Delay Measurement......................................35 Measurement..........................................40
         6.5.1. Configuration considerations......................35 considerations..........................40
         6.5.2. Applications for Delay Measurement................35 Measurement....................41
      6.6. Lock Instruct..........................................36 Instruct..............................................41
   7. Security Considerations.....................................36 Considerations.........................................41
   8. IANA Considerations.........................................36 Considerations.............................................41
   9. Acknowledgments.............................................36 Acknowledgments.................................................41
   10. References.................................................37 References.....................................................43
      10.1. Normative References..................................37 References......................................43
      10.2. Informative References................................37 References....................................43

1. Introduction

   As noted in [8], MPLS-TP defines a profile of the MPLS-TE and (MS-)PW
   architectures defined in RFC 3031 [2], RFC 3985 [5] and [7] which is
   complemented with additional OAM mechanisms and procedures for alarm,
   fault, performance and protection-switching management for packet
   transport applications.

   [Editor's note - The draft needs to be reviewed to ensure support of
   OAM for p2mp transport paths]

   In line with [12], [13], existing MPLS OAM mechanisms will be used wherever
   possible and extensions or new OAM mechanisms will be defined only
   where existing mechanisms are not sufficient to meet the
   requirements.

   The MPLS-TP OAM framework defined in this document provides a
   comprehensive set of OAM procedures that satisfy the MPLS-TP OAM
   requirements [11]. [12]. In this regard, it is defines similar to OAM
   functionality as for existing SONET/SDH and OTH OTN OAM mechanisms (e.g.
   [16]).

1.1. Contributing Authors

   Dave Allan, Italo Busi, Ben Niven-Jenkins, Annamaria Fulignoli,
   Enrique Hernandez-Valencia, Lieven Levrau, Dinesh Mohan, Vincenzo
   Sestito, Nurit Sprecher, Huub van Helvoort, Martin Vigoureux, Yaacov
   Weingarten, Rolf Winter

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [1].

2.1. Terminology

   AC   Attachment Circuit

   DBN  Domain Border Node

   FDI  Forward Defect Indication

   LER  Label Edge Router

   LME  LSP Maintenance Entity

   LSP  Label Switched Path

   LSR  Label Switch Router

   LTCME LSP Tandem Connection Maintenance Entity

   [Editor's note - Difference or similarity between tandem connection
   monitoring (TCM)_and Path Segment Tunnel (PST) need to be defined and
   agreed]

   ME   Maintenance Entity

   [Editor's note - There is a need to define whether to support OAM on
   p2mp transport path there is a need to introduce the

   MEG concept]  Maintenance Entity Group

   MEP  Maintenance Entity Group End Point

   MIP  Maintenance Entity Group Intermediate Point

   PHB  Per-hop Behavior

   PME  PW Maintenance Entity
   PTCME PW Tandem Connection Maintenance Entity

   PSN  Packet Switched Network

   PW   Pseudowire

   SLA  Service Level Agreement

   SME  Section Maintenance Entity

2.2. Definitions

   ME: The collection

   Note - the definitions in this section are intended to be in line
   with ITU-T recommendation Y.1731 in order to have a common,
   unambiguous terminology. They do not however intend to imply a
   certain implementation but rather serve as a framework to describe
   the necessary OAM functions for MPLS-TP.

   Domain Border Node (DBN): An LSP intermediate MPLS-TP node (LSR) that
   is at the boundary of MEPs an MPLS-TP OAM domain. Such a node may be
   present on the edge of two domains or may be connected by a link to
   an MPLS-TP node in another OAM domain.

   Maintenance Entity (ME): Some portion of a transport path that
   requires management bounded by two points, and MIPs the relationship
   between those points to which maintenance and their association monitoring operations
   apply (details in section 3.1).

   Maintenance Entity Group (MEG): The set of one or more maintenance
   entities that maintain and monitor a transport path in an OAM domain.

   MEP: A MEP MEG end point (MEP) is capable of initiating (MEP Source) and
   terminating (MEP Sink) OAM messages for fault management and
   performance monitoring. MEPs reside at the boundaries of an ME
   (details in section 3.3). 3.2).

   MEP Source: A MEP acts as MEP source for the an OAM messages that message when it
   originates and inserts the message into the transport path for its
   associated ME. MEG.

   MEP Sink: A MEP acts as a MEP sink for the an OAM messages that message when it
   terminates and processes the messages received from its associated ME.
   MEG.

   MIP: A MIP MEG intermediate point (MIP) terminates and processes OAM
   messages and generates may generate OAM messages in reaction to received OAM
   messages. It never generates unsolicited OAM messages itself. A MIP
   resides within a
   ME an MEG between MEPs (details in section 3.4). 3.2).

   OAM domain: A domain, as defined in [10], [11], whose entities are grouped
   for the purpose of keeping the OAM confined within that domain.

   Note - within the rest of this document the term "domain" is used to
   indicate an "OAM domain"

   OAM flow: An OAM flow is a flow Is the set of all OAM packets between a pair of MEPs
   or messages originating with a specific
   MEP and a MIP that is used to monitor and maintain a ME
   [Editor's note - a MEG depending on what we decide for this point].
   An OAM flow is associated to instrument one direction of a unique ME and contains the MEG.

   OAM
   monitoring, signalling and notification messages necessary to monitor
   and maintain that ME. The exact mix information element: An atomic piece of message types information exchanged
   between MEPs in MEG used by an OAM flow
   will be dependent on the technology being monitored and the exact
   deployment scenario of that technology (e.g. some deployments may
   proactively monitor the connectivity of all transport paths whereas
   other deployments may only reactively monitor transport paths). application.

   OAM Message: An One or more  OAM information element elements that when
   exchanged between MEPs or between MEPs and MIPs performs some OAM
   functionality (e.g. continuity check and or connectivity verification)

   OAM Packet: A packet that carries one or more OAM messages (i.e. OAM
   information elements).

   Path: See Transport Path

   Signal Fail: A condition declared by a MEP when the data forwarding
   capability associated with a transport path has failed in the sense that a defect condition (not being a
   degraded defect) is detected. failed, e.g. loss of
   continuity.

   Tandem Connection: A tandem connection is an arbitrary part of a
   transport path that can be monitored (via OAM) independently from the
   end-to-end monitoring (OAM).  It may be a monitored segment or a
   monitored concatenated segment of a transport path. The tandem connection may also include
   the forwarding engine(s) of the node(s) at the edge(s) boundaries of the segment or concatenated segment.
   tandem connection.

   The following terms are defined in [10] RFC 5654 [11] as follows:

   Associated bidirectional path: A path that supports traffic flow in
   both directions but which that is constructed from a pair of unidirectional
   paths (one for each direction) which that are associated with one another
   at the path's ingress/egress points.  The forward and backward
   directions are setup, monitored monitored, and protected independently. As a consequence
   consequence, they may or may not follow the same route (links and
   nodes) across the network.

   Concatenated Segment: A serial-compound link connection as defined in
   G.805 [17]. A concatenated segment is a contiguous part of an LSP or
   multi-segment PW that comprises a set of segments and their
   interconnecting nodes in sequence.  See also "Segment".

   Co-routed bidirectional path: A path where the forward and backward
   directions follow the same route (links and nodes) across the
   network.  Both directions are setup, monitored and protected as a
   single entity.  A transport network path is typically co-routed.

   Layer network: Layer network is defined in G.805 [17]. A layer
   network provides for the transfer of client information and
   independent operation of the client OAM.  A Layer Network layer network may be
   described in a service context as follows: one layer network may
   provide a (transport) service to higher client layer network and may,
   in turn, be a client to a lower layer lower-layer network.  A layer network is a
   logical construction somewhat independent of arrangement or
   composition of physical network elements.  A particular physical
   network element may topologically belong to more than one layer
   network, depending on the actions it takes on the encapsulation
   associated with the logical layers (e.g. (e.g., the label stack), and thus
   could be modeled as multiple logical elements.  A layer network may
   consist of one or more sublayers.  Section 1.3 1.4 (of RFC 5654) provides
   a more detailed overview of what constitutes a layer network.  For
   additional explanation of how layer networks relate to the OSI
   concept of layering layering, see Appendix I of Y.2611 [19].

   Section Layer Network: A section layer is a server layer (which may
   be MPLS-TP or a different technology) which that provides for the transfer
   of the section layer section-layer client information between adjacent nodes in the
   transport path
   transport-path layer or transport service layer.  A section layer may
   provide for aggregation of multiple MPLS-TP clients.  Note that G.805
   [17] defines the section layer as one of the two layer networks in a
   transmission media
   transmission-media layer network.  The other layer network is the
   physical media
   physical-media layer network.

   Path: See Transport Path

   Segment: A link connection as defined in G.805 [17]. A segment is the
   part of an LSP that traverses a single link or the part of a PW that
   traverses a single link (i.e. (i.e., that connects a pair of adjacent
   {Switching|Terminating} Provider Edges). See also "Concatenated
   Segment".

   Sublayer: Sublayer is defined in G.805 [17]. The distinction between
   a [editors: concept should be layer network and specific.. suggesting
   that the part of a sublayer is PW that traverses a sublayer is not single physical link is a
   segment means a segment is pretty much bounded by duct ends, and by
   devices completely clueless as to the existence of the PW, visibility
   of the wrong layer, To group: we have a definition conflict between
   G.805 and usage of segment in IETF (e.g. PWE3), not sure how to
   resolve this, for discussion Nov 3]
   Sublayer: Sublayer is defined in G.805 [17]. The distinction between
   a layer network and a sublayer is that a sublayer is not directly
   accessible to clients outside of its encapsulating layer network and
   offers no direct transport service for a higher layer (client)
   network. [editors: messy definition as it is context specific. Given
   MPLS has no PID, the transport path will always exist in a sublayer
   as the PW or PID label which has no forwarding context will be bottom
   of stack. Whether or not you actually think of the PW label as being
   a sublayer itself entirely dependant on usage SS or MS-PW, for
   discussion Nov 3rd]

   Transport Path: A network connection as defined in G.805 [17]. In an
   MPLS-TP environment, a transport path corresponds to an LSP or a PW.

   Transport Path Layer: A (sub-)layer (sub)layer network that provides
   point-to-point or point-to-multipoint transport paths.  It provides is
   instrumented with OAM mechanisms that are independent (of of the client) OAM when transporting its clients. clients
   it is transporting. [editor: if you look at the sublayer discussion
   above, this term pretty much universally must be a transport path
   sub-layer. The transport path cannot be a layer to itself in the
   MPLS_TP architecture unless we are discussing multi-segment dry
   martini, for discussion Nov 3rd]

   Unidirectional path: A path that supports traffic flow in only one
   direction.

   The term 'Domain Border Node' is defined in [14] as follows:

   Domain Border Node: To be defined

   [Editor's note - There is no definition of Domain Border Node in RFC
   5151]

   The term 'Per-hop Behavior' is defined in [13] [14] as follows:

   Per-hop Behavior: a description of the externally observable
   forwarding treatment applied at a differentiated services-compliant
   node to a behavior aggregate.

3. Functional Components

   MPLS-TP defines a profile of the MPLS and PW architectures ([2], [5]
   and [7])  that is designed to transport service traffic complying where the
   characteristics of information transfer between the transport path
   endpoints can be demonstrated to comply with certain performance and
   quality requirements. guarantees. In order to verify and maintain these performance
   and quality requirements, guarantees, there is a need to not only apply OAM
   functionality on a transport path granularity (e.g. LSP or MS-PW),
   but also on arbitrary parts of transport paths, defined as Tandem
   Connections, between any two arbitrary points along a path.

   MPLS-TP OAM operates in the context of Maintenance Entities (MEs).

   A Maintenance Entity is

   In order to describe the collection required OAM functionality, this document
   introduces a set of two (or more) Maintenance
   End Points (MEPs) and their association. The MEPs high-level functional components. [Note -
   discussion in Munich -tues concluded that form TCM not possible with PWs -
   can monitor a single PW segment - but attempting to monitor more than
   one segment converts the PW into an LSP and therefore the intervening
   SPEs are unable to see the PW as a PW due to the differences in how
   OAM flows are disambiguated.] [editors: if true this IMO is a huge
   problem as the one place I would really want TCM is a multi-domain
   MS-PW, else I have to control plane peer at two layers, for
   discussion Nov 3rd]

   When a control plane is not present, the management plane configures
   these functional components. Otherwise they can be configured either
   by the management plane or by the control plane.

   These functional components should be instantiated when the path is
   created by either the management plane or by the control plane (if
   present). Some components may be instantiated after the path is
   initially created (e.g. TCM).

3.1. Maintenance Entity (ME) and Maintenance Entity Group (MEG)

   [editors: rather than fight chicken and egg, we made two sections
   into one]

   MPLS-TP OAM operates in the context of Maintenance Entities (MEs)
   that are a relationship between two points of a point to point
   [editors: why has this restriction been added, for discussion Nov 3rd]
   transport path to which maintenance and monitoring operations
   apply. These two points are called Maintenance Entity Group End
   Points (MEPs). In between these two points zero or more intermediate
   points, called Maintenance Entity Group MEG Intermediate Points
   (MIPS), MAY exist and can be shared by more than one ME in a MEG.

   The MEPs that form an MEG are configured and managed to limit the
   scope of an OAM flow within the
   ME MEG the MEPs belong to (i.e. within
   the domain of the transport path or segment, in the specific layer
   network, that is being monitored and managed).

   An example A misbranching fault
   may cause OAM packets to be delivered to a MEP that is not in the MEG
   of origin.

   The abstract reference model for an ME with more than two MEPs is a point-to-multipoint
   ME monitoring a point-to-multipoint transport path (or point-to-
   multipoint tandem connection).

   Each MEP resides at the boundaries of the ME that they are part of.
   An ME may also include a set of zero or more Maintenance Intermediate
   Points (MIPs), which reside within the Maintenance Entity, between
   the MEPs.

   MEPs and MIPs are associated with only one Maintenance Entity.

   The abstract reference model for a ME with MEPs and MIPs and MIPs is
   described in Figure 1 below:

                            +-+    +-+    +-+    +-+
                            |A|----|B|----|C|----|D|
                            +-+    +-+    +-+    +-+

                   Figure 1 ME Abstract Reference Model

   The instantiation of this abstract model to different MPLS-TP
   entities is described in section 4. In this model, nodes A, B, C and
   D can be LER/LSR for an LSP or the {S|T}-PEs for a MS-PW. Nodes MEPs reside
   in nodes A and D are MEPs while MIPs reside in nodes B and C are MIPs. C. The links
   connecting adjacent nodes can be either physical links links, sub-layer LSPs or lower-level LSPs.
   lower layer TCMs.

   This functional model defines the relationships between all OAM
   entities from a maintenance perspective, to allow each Maintenance
   Entity to monitor and manage the layer network under its
   responsibility and to localize problems efficiently.

   When

   [Dave: given how these definitions are shaking out, should the MEG
   and ME not be confined to a control plane sub-layer, there is not present, no such thing as a
   completely self contained "layer" in the management plane configures
   MEPs and MIPs. Otherwise they architecture to which a MEG
   can be configured apply, for Nov 3rd]

   An MPLS-TP maintenance entity group can cover either by the
   management plane whole end-
   to-end or by a Tandem Connection of the control plane.

3.1. Maintenance Entity transport path. A Maintenance
   Entity Group may be defined to monitor the transport path for fault and
   and/or performance management unidirectional point-to-point or point-to-
   multipoint transport paths or tandem connections, or co-routed
   bidirectional point-to-point transport paths and tandem connections
   in an MPLS-TP layer network. management.

   In case of associated bi-directional paths, two independent
   Maintenance Entities are define defined to independently monitor each
   direction.

   An MPLS-TP maintenance entity can be either the whole end-to-end
   transport path This has implications for transactions that terminate at
   or query a Tandem Connection of the transport path. MIP as a return path from MIP to source MEP does not exist
   in a unidirectional ME.

   The following properties apply to all MPLS-TP MEs:

   o They can be nested but not overlapped, e.g. a an ME may cover a
      segment or a concatenated segment of another ME, and may also
      include the forwarding engine(s) of the node(s) at the edge(s) of
      the segment or concatenated segment, but all its MEPs and MIPs are
      no longer part of the encompassing ME. It is possible that MEPs of
      nested MEs reside on a single node.

   o Each OAM flow is associated with a single Maintenance Entity.

   o OAM packets are subject to the same forwarding treatment (e.g. (i.e.
      fate share) as the data traffic, but they traffic and in some cases may be required
      to have common queuing discipline E2E with the class of traffic
      monitored. OAM packets can be distinguished from the data traffic
      using the GAL and ACH constructs [9] for LSP and Section or the
      ACH construct [6]and [9] for (MS-)PW.

3.2. Point-to-multipoint scenario (MS-)PW.

   [Propose from Munich - rewrite to describe the MEG as collection of
   one or more maint entities and then immediately define an ME.

   [editors: much of this comment is actually either ME or MEP/MIP
   specific, not MEG specific, hence we are struggling as to what to do
   with this, for discussion Nov 3rd]

   A key point in the definition of an ME is the end-points are defined
   by location of the logical function MEP

   Later in the framework we will discuss the precision with which we
   can identify the location of a MEP/MIP i.e, ingress i/f, egress i/f
   or node.

   We need to distinguish between the point of interception of an OAM
   msg and the point where the action takes place.

   Somewhere we need to distinguish between the OAM control function and
   the OAM measurement function. i.e. we set up a loop back (a control
   function, in which case the OAM message may be intercepted and
   actioned anywhere convenient), and the measurement function (i.e.
   looping the packet to determine that it reached a particular part of
   the network) which needs to be actioned at a precisely know and
   stipulated point in the network/equipment.

   Note that not all functionality / processing of an OAM pkt needs to
   take place at the point of measurement.

   We considered that an OAM function can be decomposed into the
   following components

   - Instruction or command

   - Execution

   - Addressing (node, interface etc) is ttl/LSP enough - do we need
      sub-addressing to cause execution on a specific component in the
      node - i.e. egress interface

   - Response via OAM

   - Reporting to mgt interface

   It is useful to further decompose this into an initiator and a
   responder in general an initiator is the source mep and the responder
   is a mip or a sink mep. There are exceptions to this such as a mip
   initiating an AIS msg or lock indication.]
   Another OAM construct is referred to as Maintenance Entity Group,
   which is a collection of one or more MEs that belongs to the same
   transport path and that are maintained and monitored as a group.

   A use case for an MEG with more than one ME is point-to-multipoint
   OAM. The reference model for the p2mp scenario MEG is represented in Figure 4. 2.

                                                 +-+
                                              /--|D|
                                             /   +-+
                                          +-+
                                       /--|C|
                            +-+    +-+/   +-+\   +-+
                            |A|----|B|        \--|E|
                            +-+    +-+\   +-+    +-+
                                       \--|F|
                                          +-+

                   Figure 2 Reference Model for p2mp MEG

   In case of p2mp transport paths, the OAM measurements operations are different independent
   for each [Root, Leaf] relationship ME (A-D, A-E and A-F):

   o Fault conditions - depending from where the failure is located

   o Packet loss - depending from where the packets are lost

   o Packet delay - depending on different paths

   Each leaf (i.e. D, E and F) terminates OAM messages to monitor its
   own [Root, Leaf] relationship ME while the root (i.e. A) generates OAM messages to
   monitor all the [Root, Leaf] relationships MEs of the p2mp
   transport path.

   [Editor's note - Further considerations regarding MEG. In this particular case, the
   p2mp case will
   be added in transport path is monitored by a future version MEG that consists of this document]

3.3. Maintenance three MEs.
   Nodes B and C might implement a MIP in the corresponding MEGs.

3.2. MEG End Points (MEPs)

   Maintenance

   MEG End Points (MEPs) are the end points of a ME. an MEG. In the context of
   an MPLS-TP LSP, only LERs can be implement MEPs while in the context of
   an LSP Tandem Connection both LERs and LSRs can be implement MEPs.

   In the context of
   Regarding MPLS-TP PW, only T-PEs can be implement MEPs while in the
   context of for a PW
   Tandem Connection both T-PEs and S-PEs can implement MEPs. In the
   context of MPLS-TP Section, any MPLS-TP NE can implement MEPs.

   [Munich: See note about PW Tandem monitoring earlier, and whether a
   PW can be MIPs. a tandem connection]
   MEPs are responsible for activating and controlling all of the OAM
   functionality for the ME. MEG. A MEP is capable of initiating and
   terminating OAM messages for fault management and performance
   monitoring. These OAM messages are encapsulated into an OAM packet
   using the G-ACh as defined in RFC 5586 [9]: in this case the G-ACh
   message is an OAM message and the channel type indicates an OAM
   message. A MEP terminates all the OAM packets it receives from the
   MEG it belongs to. The MPLS label identifies the MEG the OAM packet
   belongs to.

   Once an MEG is configured, the operator can configure which OAM
   functions to use on the MEG but the MEPs are always enabled. A node
   at the edge of an MEG always support a MEP.

   MEPs have to prevent OAM packets corresponding to a ME MEG from leaking
   outside that ME: MEG:

   o A MEP sink terminates all the OAM packets that it receives
      corresponding to its ME MEG and does not forward them further along
      the path. If the pro-active CC-V OAM tool detects an unintended
      connectivity, all traffic on the path is blocked (i.e. all
      received packets are dropped, including user-data packets).

   [Editor's note - Need to discuss whether to keep the last sentence in
   the bullet above regarding the MEP behavior in case of
   misconnections]

   o A MEP source in a tandem connection tunnels all the OAM packets that it
      receives, upstream from the associated ME, via label stacking. These packets
      are not MEG to prevent them from
      being processed within the ME as they belong to another ME.

   [Editor's - Need to rephrase associated MEG. The usage of the bullet above label
      stacking mechanism allows all the MEPs and MIPs within the MEG to clarify what it
   actually means]
      distinguish tunneled OAM packets from OAM packets that belong to
      that MEG.

   MPLS-TP MEP passes a fault indication to its client (sub-)layer
   network.

   A MEP of a tandem connection is not necessarily coincident with the
   termination of the MPLS-TP transport path (LSP or PW). Within the
   boundary of the tandem connection it can monitor the MPLS-TP
   transport path for failures or performance degradation (e.g. count
   packets).

   [Editor's note - The MEP of
   network as a TCM monitors the transport paths'
   connectivity within the scope consequent action of the TCM. This means that failures or
   performance degradations within the TCM are detected by the TCM MEP
   while failures fault detection. [ editor:
   interesting case, is this always sink, or performance degradations outside the TCM are not
   detected by we considering
   loopbacks where inserting fault indication into the TCM MEP.

   Improve client (s)layer
   is comparatively useless. We wrestled with same problem with RSVP
   errors in the text above to explain this concept.] past ..., for Nov 3rd]

   A MEP of an MPLS-TP transport path (Section, LSP or PW) coincides
   with transport path termination and monitors it for failures or
   performance degradation (e.g. based on packet counts) in an end-to-end end-to-
   end scope. Note that both MEP source and MEP sink coincide with
   transport paths' source and sink terminations.

   [Editor's note - Add some text regarding

   A MEP identification as well
   as about what of an MPLS-TP tandem connection is not necessarily coincident
   with the termination of the MPLS-TP transport path (LSP or PW) and
   monitors the transport path for failures or performance degradation
   (e.g. based on packet counts) within the boundary of the MEG for the
   tandem connection.

   It may occur in TCM that two MEPs are set on both sides of the
   forwarding engine such that the MEG is entirely internal to the node.

   Note that a MEP can only exist at the beginning and end of a MEP should sub-
   layer i.e. an LSP or PW. If we need to add a monitoring point within
   an LSP we create a new sub-layer. We need to describe the migration
   process for adding a TCM segment.

   We have the case of a MIP sending msg to a MEP. To do if this it receives an unexpected OAM
   packet]

3.4. Maintenance uses
   the LSP label - i.e. the top label of the stack at that point.
   [editors: clarify in section 3.4]

3.3. MEG Intermediate Points (MIPs)

   A Maintenance MEG Intermediate Point (MIP) is a point between the two MEPs in an ME.

   In the context of an MPLS-TP LSP and LSP Tandem Connections, LSRs can
   be MIPs.

   In the context of MPLS-TP PW and PW Tandem Connection, S-PEs can be
   MIPs.
   ME.

   A MIP is capable of reacting to some OAM packets and forwarding all
   the other OAM packets while ensuring fate sharing with data plane
   packets.

   A However, a MIP does not initiate unsolicited [unsolicited OAM - editors:
   this text was removed in the commented .rtf document from Munich but
   not tracked as a revision, validate this change Nov 3rd] packets, but
   may be addressed by OAM packets initiated by one of the MEPs of the
   ME. A MIP can generate OAM packets only in response to OAM packets
   that are sent on the ME MEG it belongs to.

   [Editor's note - It is needed to provide

   An intermediate node within an high-level description
   about how this is achieved (e.g. TTL expiry).]

   MIPs are unaware of any MEG can either:

   o not support MPLS-TP OAM flows running between MEPs or between
   MEPs and other MIPs. (i.e. no MIPs per node)

   o support per-node MIP (i.e. a single MIP per node)

   o support per-interface MIP (i.e. two MIPs per node on both sides of
      the forwarding engine)

   A node at the edge of an MEG can only receive also support a MEP and process a per-
   interface MIP at the two sides of the forwarding engine.

   When sending an OAM packets
   addressed packet to a MIP, the source MEP should set the
   TTL field to indicate the number of hops necessary to reach the node
   where the MIP itself.

   A MIP takes no action on resides. It is always assumed that the "pipe" model of
   TTL handling is used by the MPLS transport profile.

   The source MEP should also include Target MIP information in the MPLS-TP transport path.

   [Editor's note - Add some text regarding OAM
   packets sent to a MIP to allow proper identification as well
   as about what a of the MIP should do if it receives an unexpected
   within the node. The MEG the OAM
   packet]

3.5. packet belongs to is inferred from
   the MPLS label.

   Once an MEG is configured, the operator can enable/disable the MIPs
   on the nodes within the MEG.

3.4.  Server MEPs

   A server MEP is a MEP of an ME that is either:

   o defined in a layer network below the MPLS-TP layer network being
      referenced, or

   o defined in a sub-layer of the MPLS-TP layer network that is below
      the sub-layer being referenced.

   A server MEP can coincide with a MIP or a MEP in the client (MPLS-TP)
   layer network.

   A server MEP provides also interacts with the client/server adaptation
   function between the client (MPLS-TP) layer network and the server
   layer network. As a
   consequence The adaptation function maintaints state on the server MEP is aware
   mapping of the MPLS-TP transport paths that are setup over that server
   layer's transport path.

   For example, a server MEP can be either:

   o A termination point of a physical link (e.g. 802.3), an SDH VC or
      OTH ODU for the MPLS-TP Section layer network, defined in section
      4.1;

   o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section 4.2;

   o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section 4.4;

   o An MPLS-TP LSP Tandem Connection MEP for higher-level LTCMEs,
      defined in section 4.3;

   o An MPLS-TP PW Tandem Connection MEP for higher-level PTCMEs,
      defined in section 4.5.

   The server MEP can run appropriate OAM functions for fault detection
   within the server (sub-)layer network, and notifies server (sub-)layer network, and notifies a fault
   indication to its client MPLS-TP layer network. Server MEP OAM
   functions are outside the scope of this document.

3.5. Tandem Connection

   A tandem connection is instantiated to support tandem connection
   monitoring (TCM).

   TCM for a given portion of a transport path is implemented by first
   creating a hierarchical LSP that that has a 1:1 association with
   portion of the transport path that is to be uniquely monitored such
   that there is direct correlation between all FM and PM information
   gathered for the tandem connection AND the monitored portion of the
   E2E path. The tandem connection is monitored using normal LSP
   monitoring. There are a number of implications to this approach:

   1) The hierarchical LSP would use the uniform model of EXP code
      point copying between sub-layers for diffserv such that the E2E
      markings and PHB treatment was preserved in the tandem
      connection.

   2) The hierarchical LSP would use the pipe model for TTL handling
      such that MIP addressing for the E2E entity would be distinct
      from the tandem connection.

   3) PM statistics need to be adjusted for the overhead of the
      additional sub-layer.

   4) The server sub-layer LSP is viewed as single hop by the client
      LSP. The E2E ME source MEPs cannot direct transactions to tandem
      connection MIPs.

   [editors: the text from Munich suggested that a fault
   indication to its client MPLS-TP layer network. Server MEP OAM
   functions are outside tandem connection
   could be N:1, we've stuck with 1:1 such that there would be direct
   correlation of PM stats between the scope tandem connection and the
   monitored portion of this document. the transport path, a N:1 hierarchical LSP IF WE
   INSIST on including, should be documented as a separate procedure]

4. Reference Model

   The reference model for the MPLS-TP framework builds upon the concept
   of an ME, MEG, and its associated MEPs and MIPs, to support the
   functional requirements specified in [11]. [12].

   The following MPLS-TP MEs are specified in this document:

   o A Section Maintenance Entity (SME), allowing monitoring and
      management of MPLS-TP Sections (between MPLS LSRs).

   o A LSP Maintenance Entity (LME), allowing monitoring and management
      of an end-to-end LSP (between LERs).

   o A PW Maintenance Entity (PME), allowing monitoring and management
      of an end-to-end SS/MS-PWs (between T-PEs).

   o An LSP Tandem Connection Maintenance Entity (LTCME), allowing
      monitoring and management of an LSP Tandem Connection between any
      LER/LSR along the LSP.

   o A MS-PW Tandem Connection Maintenance Entity (PTCME), allows
      monitoring and management of a SS/MS-PW Tandem Connection between
      any T-PE/S-PE along the (MS-)PW.

   The [Munich: Please clarify that an LTCME is
      JUST an ordinary hierarchical LSP (RFC3031).

     Note - TCM only makes sense for LSPs as previously noted.]The MEs
   specified  in  this  MPLS-TP  framework  are  compliant  with  the
   architecture framework for MPLS MS-PWs [7] and MPLS LSPs [2].

   Hierarchical LSPs are also supported. In this case, each LSP Tunnel
   in the hierarchy is a different sub-layer network that can be
   monitored independently from higher and lower level LSP tunnels in
   the hierarchy, end-to-end (from LER to LER) by an LME. Tandem
   Connection monitoring via LTCME are applicable on each LSP Tunnel in
   the hierarchy.

   [Munich: There was discussion on above para - and it was suggested
   that it be removed.] [ for discussion Nov 3rd, TCM and hierarchical
   LSPs...]
           Native  |<------------------- MS-PW1Z ------------------->|  Native
           Layer   |                                                 |   Layer
          Service  |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |  Service
           (AC1)   V    V   LSP   V    V   LSP   V    V   LSP   V    V   (AC2)
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        |TPE1|   | |   |SPE3|         |SPEX|   | |   |TPEZ|       +----+
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     | CE1|--------|........PW13.......|...PW3X..|........PWXZ.......|-------|CE2 |
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+
                   .                   .         .                   .
                   |                   |         |                   |
                   |<---- Domain 1 --->|         |<---- Domain Z --->|
                   .-------------------
                   ^------------------- PW1Z  PME -------------------.
                   .---- -------------------^
                   ^---- PW13 PTCME ---.         .---- ---^         ^---- PWXZ PTCME ---.
                        .---------.                   .---------. ---^
                        ^---------^                   ^---------^
                         PSN13 LME                     PSNXZ LME

                        .---. .---.    .---------.    .---. .---.

                        ^---^ ^---^    ^---------^    ^---^ ^---^
                        Sec12 Sec23       Sec3X       SecXY SecYZ
                         SME   SME         SME         SME   SME

   TPE1: Terminating Provider Edge 1                 SPE2: Switching Provider Edge 3
   TPEX: Terminating Provider Edge X                 SPEZ: Switching Provider Edge Z

   .---.

   ^---^ ME    .    ^     MEP   ====   LSP      .... PW

           Figure 3 Reference Model for the MPLS-TP OAM Framework

   Figure 3 depicts a high-level reference model for the MPLS-TP OAM
   framework. The figure depicts portions of two MPLS-TP enabled network
   domains, Domain 1 and Domain Z. In Domain 1, LSR1 is adjacent to LSR2
   via the MPLS Section Sec12 and LSR2 is adjacent to LSR3 via the MPLS
   Section Sec23. Similarly, in Domain Z, LSRX is adjacent to LSRY via
   the MPLS Section SecXY and LSRY is adjacent to LSRZ via the MPLS
   Section SecYZ. In addition, LSR3 is adjacent to LSRX via the MPLS
   Section 3X.

   Figure 3 also shows a bi-directional MS-PW (PW1Z) between AC1 on TPE1
   and AC2 on TPEZ. The MS-PW consists of three bi-directional PW
   Segments: 1) PW13 segment between T-PE1 and S-PE3 via the bi-
   directional PSN13 LSP, 2) PW3X segment between S-PE3 and S-PEX, via
   the bi-directional PSN3X LSP, and 3) PWXZ segment between S-PEX and
   T-PEZ via the bi-directional PSNXZ LSP.

   The MPLS-TP OAM procedures that apply to an instance MEG of a given ME transport
   path are expected to operate independently from procedures on other
   instances
   MEGs of the same ME transport path and certainly MEGs of other MEs. transport
   paths. Yet, this does not preclude that multiple MEs MEGs may be affected
   simultaneously by the same network condition, for example, a fibre
   cut event.

   Note that there are no constrains imposed by this OAM framework on
   the number, or type, type (p2p, p2mp, LSP or PW), of MEs MEGs that may be
   instantiated on a particular node. In particular, when looking at
   Figure 1, 3, it should be possible to configure one or more MEPs on the
   same node if that node is the endpoint of one or more MEs. MEGs.

   Figure 3 does not describe a PW3X PTCME because typically TCMs are
   used to monitor an OAM domain (like PW13 and PWXZ PTCMEs)   rather
   than the segment between two OAM domains. However the OAM framework
   does not pose any constraints on the way TCM are instantiated as long
   as they are not overlapping.

   The subsections below define the MEs specified in this MPLS-TP OAM
   architecture  framework  document.  Unless  otherwise  stated,  all
   references to domains, LSRs, MPLS Sections, LSP, LSPs, pseudowires and MEs
   in this Section section are made in relation to those shown in Figure 3.

4.1. MPLS-TP Section Monitoring

   An MPLS-TP Section ME (SME) is an MPLS-TP maintenance entity intended
   to monitor the forwarding behaviour of an MPLS Section as defined in
   [10]. [11]. An SME may be configured on
   any MPLS section. SME OAM packets must fate share with the user data
   packets sent over the monitored MPLS Section.

   [Editor's note - Is OAM monitoring only the forwarding behaviour? If
   not, we need to clarify what it is monitoring]

   An SME is intended to be deployed for applications where it is
   preferable to monitor the link between topologically adjacent (next
   hop in this layer network) MPLS (and MPLS-TP enabled) LSRs rather
   than monitoring the individual LSP or PW segments traversing the MPLS
   Section and the server layer technology does not provide adequate OAM
   capabilities.

                   |<------------------- MS-PW1Z ------------------->|
                   |                                                 |
                   |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |
                   V    V   LSP   V    V   LSP   V    V   LSP   V    V
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        |TPE1|   | |   |SPE3|         |SPEX|   | |   |TPEZ|       +----+
     |    |  AC1   |    |=========|    |=========|    |=========|    |  AC2  |    |
     | CE1|--------|........PW13.......|...PW3X..|.......PWXZ........|-------|CE2 |
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+

                        .--.  .--.     .--------.     .--.  .--.

                        ^--^  ^--^     ^--------^     ^--^  ^--^
                        Sec12 Sec23       Sec3X       SecXY SecYZ
                         SME   SME         SME         SME   SME

          Figure 4 Reference Example of MPLS-TP Section MEs (SME)

   Figure 4 shows 5 Section MEs configured in the path between AC1 and
   AC2: 1) Sec12 ME associated with the MPLS Section between LSR 1 and
   LSR 2, 2) Sec23 ME associated with the MPLS Section between LSR 2 and
   LSR 3, 3) Sec3X ME associated with the MPLS Section between LSR 3 and
   LSR X, 4) SecXY ME associated with the MPLS Section between LSR X and
   LSR Y, and 5) SecYZ ME associated with the MPLS Section between LSR Y
   and LSR Z.

4.2. MPLS-TP LSP End-to-End Monitoring

   An MPLS-TP LSP ME (LME) is an MPLS-TP maintenance entity intended to
   monitor the forwarding behaviour of an end-to-end LSP between two
   (e.g., a point-to-point LSP) or more (e.g., a point-to-multipoint
   LSP) LERs. An LME may be configured
   on any MPLS LSP. LME OAM packets must fate share with user data
   packets sent over the monitored MPLS-TP LSP.

   An LME is intended to be deployed in scenarios where it is desirable
   to monitor the forwarding behaviour of an entire LSP between its LERs, rather than, say,
   monitoring individual PWs.

                   |<------------------- MS-PW1Z ------------------->|
                   |                                                 |
                   |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |
                   V    V   LSP   V    V   LSP   V    V   LSP   V    V
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        |TPE1|   | |   |SPE3|         |SPEX|   | |   |TPEZ|       +----+
     |    |  AC1   |    |=========|    |=========|    |=========|    |  AC2  |    |
     | CE1|--------|........PW13.......|...PW3X..|........PWXZ.......|-------|CE2 |
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+

                        .---------.                   .---------.

                        ^---------^                   ^---------^
                         PSN13 LME                     PSNXZ LME

                Figure 5 Examples of MPLS-TP LSP MEs (LME)

   Figure 5 depicts 2 LMEs configured in the path between AC1 and AC2:
   1) the PSN13 LME between LER 1 and LER 3, and 2) the PSNXZ LME
   between LER X and LER Y. Note that the presence of a PSN3X LME in
   such a configuration is optional, hence, not precluded by this
   framework. For instance, the SPs may prefer to monitor the MPLS-TP
   Section between the two LSRs rather than the individual LSPs.

4.3. MPLS-TP LSP Tandem Connection Monitoring

   An MPLS-TP LSP Tandem Connection Monitoring ME (LTCME) is an MPLS-TP
   maintenance entity intended to monitor the forwarding behaviour of an arbitrary part of an LSP
   between a given pair of LSRs independently from the end-to-end
   monitoring (LME). An LTCME can monitor an LSP segment or concatenated
   segment and it may also include the forwarding engine(s) of the
   node(s) at the edge(s) of the segment or concatenated segment.

   Multiple LTCMEs MAY be configured on any LSP. The LSRs that terminate
   the LTCME may or may not be immediately adjacent at the MPLS-TP
   layer. LTCME OAM packets must fate share with the user data packets
   sent over the monitored LSP segment.

   A LTCME can be defined between the following entities:

        o LER and any LSR of a given LSP.

        o Any two LSRs of a given LSP.

   An LTCME is intended to be deployed in scenarios where it is
   preferable to monitor the behaviour of a part of an LSP rather than
   the entire LSP itself, for example when there is a need to monitor a
   part of an LSP that extends beyond the administrative boundaries of
   an MPLS-TP enabled administrative domain.

   Note that LTCMEs are equally applicable to hierarchical LSPs.

                   |<--------------------- PW1Z -------------------->|
                   |                                                 |
                   |    |<--------------PSN1Z LSP-------------->|    |
                   |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |
                   V    V  S-LSP  V    V  S-LSP  V    V  S-LSP  V    V
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        | PE1|   | |   |DBN3|         |DBNX|   | |   | PEZ|       +----+
     |    |  AC1   |    |=======================================|    |  AC2  |    |
     | CE1|--------|......................PW1Z.......................|-------|CE2 |
     |    |        |    |=======================================|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+
                   .                   .         .                   .
                   |                   |         |                   |
                   |<---- Domain 1 --->|         |<---- Domain Z --->|

                        .---------.                   .---------.

                        ^---------^                   ^---------^
                        PSN13 LTCME                   PSNXZ LTCME
                        .---------------------------------------.
                        ^---------------------------------------^
                                        PSN1Z LME

   DBN: Domain Border Node

        Figure 6 MPLS-TP LSP Tandem Connection Monitoring ME (LTCME)

   Figure 6 depicts a variation of the reference model in Figure 3 where
   there is an end-to-end PSN LSP (PSN1Z LSP) between PE1 and PEZ. PSN1Z
   LSP consists of, at least, three stitched LSP Concatenated Segments: PSN13,
   PSN3X and PSNXZ. In this scenario there are two separate LTCMEs
   configured to monitor the forwarding behaviour of the PSN1Z LSP: 1) a LTCME monitoring the PSN13
   LSP Concatenated Segment on Domain 1 (PSN13 LTCME), and 2) a LTCME
   monitoring the PSNXZ LSP Concatenated Segment on Domain Z (PSNXZ
   LTCME).

   It is worth noticing that LTCMEs can coexist with the LME monitoring
   the end-to-end LSP and that LTCME MEPs and LME MEPs can be coincident
   in the same node (e.g. PE1 node supports both the PSN1Z LME MEP and
   the PSN13 LTCME MEP).

4.4. MPLS-TP PW Monitoring

   An MPLS-TP PW ME (PME) is an MPLS-TP maintenance entity intended to
   monitor the end-to-end forwarding behaviour of a SS-PW or MS-PW between a pair of T-PEs. A PME MAY be
   configured on any SS-PW or MS-
   PW. MS-PW. PME OAM packets must fate share
   with the user data packets sent over the monitored PW.

   A PME is intended to be deployed in scenarios where it is desirable
   to monitor the forwarding behaviour of an entire PW between a pair of MPLS-TP enabled T-PEs
   rather than monitoring the LSP aggregating multiple PWs between PEs.

                   |<------------------- MS-PW1Z ------------------->|
                   |                                                 |
                   |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |
                   V    V   LSP   V    V   LSP   V    V   LSP   V    V
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        |TPE1|   | |   |SPE3|         |SPEX|   | |   |TPEZ|       +----+
     |    |  AC1   |    |=========|    |=========|    |=========|    |  AC2  |    |
     | CE1|--------|........PW13.......|...PW3X..|........PWXZ.......|-------|CE2 |
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+

                   .---------------------PW1Z PME--------------------.

                   ^---------------------PW1Z PME--------------------^

                       Figure 7 MPLS-TP PW ME (PME)

   Figure 7 depicts a MS-PW (MS-PW1Z) consisting of three segments:
   PW13, PW3X and PWXZ and its associated end-to-end PME (PW1Z PME).

4.5. MPLS-TP MS-PW Tandem Connection Monitoring

   An MPLS-TP MS-PW Tandem Connection Monitoring ME (PTCME) is an MPLS-
   TP maintenance entity intended to monitor the forwarding behaviour of an arbitrary part of an  MS-PW MS-
   PW between a given pair of PEs independently from the end-to-end
   monitoring (PME). An A PTCME can monitor a PW segment or concatenated
   segment and it may alos also include the forwarding engine(s) of the
   node(s) at the edge(s) of the segment or concatenated segment.

   Multiple PTCMEs MAY be configured on any MS-PW. The PEs may or may
   not be immediately adjacent at the MS-PW layer. PTCME OAM packets
   fate share with the user data packets sent over the monitored PW
   Segment.

   A PTCME can be defined between the following entities:

   o T-PE and any S-PE of a given MS-PW
   o Any two S-PEs of a given MS-PW. It can span several PW segments.

   A PTCME is intended to be deployed in scenarios where it is
   preferable to monitor the behaviour of a part of a MS-PW rather than
   the entire end-to-end PW itself, for example to monitor an MS-PW
   Segment within a given network domain of an inter-domain MS-PW.

                   |<------------------- MS-PW1Z ------------------->|
                   |                                                 |
                   |    |<-PSN13->|    |<-PSN3X->|    |<-PSNXZ->|    |
                   V    V   LSP   V    V   LSP   V    V   LSP   V    V
                   +----+   +-+   +----+         +----+   +-+   +----+
     +----+        |TPE1|   | |   |SPE3|         |SPEX|   | |   |TPEZ|       +----+
     |    |  AC1   |    |=========|    |=========|    |=========|    |  AC2  |    |
     | CE1|--------|........PW13.......|...PW3X..|........PWXZ.......|-------|CE2 |
     |    |        |    |=========|    |=========|    |=========|    |       |    |
     +----+        | 1  |   |2|   | 3  |         | X  |   |Y|   | Z  |       +----+
                   +----+   +-+   +----+         +----+   +-+   +----+

                   .----

                   ^---- PW1 PTCME ----.         .---- ----^         ^---- PW5 PTCME ----.
                   .---------------------PW1Z PME--------------------. ----^
                   ^---------------------PW1Z PME--------------------^

        Figure 8 MPLS-TP MS-PW Tandem Connection Monitoring (PTCME)

   Figure 8 depicts the same MS-PW (MS-PW1Z) between AC1 and AC2 as in
   Figure 7. In this scenario there are two separate PTCMEs configured
   to monitor the forwarding behaviour of MS-PW1Z: 1) a PTCME monitoring the PW13 MS-PW Segment on
   Domain 1 (PW13 PTCME), and 2) a PTCME monitoring the PWXZ MS-PW
   Segment on Domain Z with (PWXZ PTCME).

   It is worth noticing that PTCMEs can coexist with the PME monitoring
   the end-to-end MS-PW and that PTCME MEPs and PME MEPs can be
   coincident in the same node (e.g. TPE1 node supports both the PW1Z
   PME MEP and the PW13 PTCME MEP).

5. OAM Functions for pro-active proactive monitoring

5.1. Continuity Check and Connectivity Verification

   [Editor's note - There is a need to decide whether pro-active CC and
   CV functions need

   [Munich: Note the fwk needs to be combined in explicit about the same tool or separated into
   different tools. This version mapping of
   functions to the document combines the two
   functions. Future versions will tools we have chosen.] [editors: shouldn't it be aligned with the decision taken
   about whether
   other way around?]

   In this document, proactive monitoring refers to combine or not CC OAM operations that
   are either configured to be carried out periodically and CV.]

   Proactive continuously
   or preconfigured to act on certain events such as alarm signals.

5.1. Continuity Check and Connectivity Verification (CC-V)

   Proactive Continuity Check functions are used to detect a loss of
   continuity (LOC), defect (LOC) between two MEPs in an MEG.

   Proactive Connectivity Verification functions are used to detect an
   unexpected connectivity defect between two MEs MEGs (e.g. mismerging or
   misconnection), as well as unexpected connectivity within the ME MEG
   with an unexpected MEP.

   Execution of proactive CC-V is

   Both functions are based on the (proactive) generation of
   CC-V OAM packets
   by the source MEP that are processed by the sink MEP.  Each As a
   consequence these two functions are grouped together into Continuity
   Check and Connectivity Verification (CC-V) OAM packets.

   In order to perform pro-active Connectivity Verification function,
   each CC-V OAM packet MUST also include a globally unique ME
   identifier, Source MEP
   identifier. When used to perform only pro-active Continuity Check
   function, the CC-V OAM packet MAY not include any MEG identifier.

   Different formats of MEP identifiers are defined in [10] to address
   different applications. When MPLS-TP is deployed in transport network
   applications as defined by ITU-T, the ICC-based format for MEP
   identification is the DEFAULT and MANDATORY identification scheme.
   When MPLS-TP is deployed in IP-based environment, the IP-based MEP
   identification is the DEFAULT and MANDATORY identification scheme.

   As a consequence, it is not possible to detect misconnections between
   two MEGs monitored only for Continuity while it is possible to detect
   any misconnection between two MEGs monitored for Continuity and
   Connectivity or between an MEG monitored for Continuity and
   Connectivity and one MEG monitored only for Continuity.

   CC-V OAM packets MUST be transmitted at a regular, operator's
   configurable, rate. The default CC-V transmission periods are
   application dependent (see section 5.1.4).

   Proactive CC-V OAM packets are transmitted with the "minimum loss
   probability PHB" within a single network operator. This PHB is
   configurable on network operator's basis. PHBs can be translated at
   the network borders.

   [Editor's note - Describe the relation between the previous paragraph
   and the fate sharing requirement. Need to clarify also in the
   requirement document that for proactive CC-V the fate sharing is
   related to the forwarding behavior and not to the QoS behavior]
   In a bidirectional point-to-point transport path, when a MEP is
   enabled to generate pro-active CC-V OAM packets with a configured
   transmission rate, it also expects to receive pro-active CC-V OAM
   packets from its peer MEP at the same transmission rate. In a
   unidirectional transport path (either point-to-point or point-to-
   multipoint), only the source MEP is enabled to generate CC-V OAM
   packets and only the sink MEP is configured to expect these packets
   at the configured rate.

   MIPs, as well as intermediate nodes not supporting MPLS-TP OAM, are
   transparent to the pro-active CC-V information and forward these pro-
   active CC-V OAM packets as regular data packets.

   To initialize the proactive CC-V monitoring on a configured ME
   without affecting traffic, the MEP source function (generating pro-
   active CC-V packets) should be enabled prior to the corresponding MEP
   sink function (detecting continuity and connectivity defects).  When
   disabling the CC-V proactive functionality, the MEP sink function
   should be disabled prior to the corresponding MEP source function.

5.1.1. Defects identified by CC-V

   Pro-active CC-V functions allow a sink MEP to detect the following defect conditions.
   conditions described in the following sub-sections. For all of these the
   described defect cases, the sink MEP SHOULD notify the equipment
   fault management process of the detected defect.

   [Editor's note - Investigate whether in case there is a
   misconfiguration on the minimum loss probability PHB on the two MEPs
   a defect can be useful to notify the misconfiguration to the
   operator.]

5.1.1.1. Loss Of Continuity defect

   When proactive CC-V is enabled, a sink MEP detects a loss of
   continuity (LOC) defect when it fails to receive pro-active CC-V OAM
   packets from the peer MEP.

   o Entry criteria:  if no pro-active CC-V OAM packets from the peer
      MEP (i.e. with the correct ME and peer MEP identifiers) are
      received within the interval equal to 3.5 times the receiving
      MEP's configured CC-V transmission period.

   o Exit criteria: a pro-active CC-V OAM packet from the peer MEP
      (i.e. with the correct ME and peer MEP identifiers) is received.

5.1.1.2. Mis-connectivity defect

   When a pro-active CC-V OAM packet is received, a sink MEP identifies
   a mis-connectivity defect (e.g. mismerge or misconnection) with its
   peer source MEP when the received packet carries an incorrect ME
   identifier.

   o Entry criteria: the sink MEP receives a pro-active CC-V OAM packet
      with an incorrect ME ID.

   o Exit criteria: the sink MEP does not receive any pro-active CC-V
      OAM packet with an incorrect ME ID for an interval equal at least
      to 3.5 times the longest transmission period of the pro-active
      CC-V OAM packets received with an incorrect ME ID since this
      defect has been raised. This requires the OAM message to self
      identify the CC-V periodicity as not all MEPs can be expected to
      have knowledge of all MEs.

5.1.1.3. MEP misconfiguration defect

   When a pro-active CC-V packet is received, a sink MEP identifies a
   MEP misconfiguration defect with its peer source MEP when the
   received packet carries a correct ME Identifier but an unexpected
   peer MEP Identifier which includes the MEP's own MEP Identifier.

   o Entry criteria: the sink MEP receives a CC-V pro-active packet
      with correct ME ID but with unexpected MEP ID.

   o Exit criteria: the sink MEP does not receive any pro-active CC-V
      OAM packet with a correct ME ID and unexpected MEP ID for an
      interval equal at least to 3.5 times the longest transmission
      period of the pro-active CC-V OAM packets received with a correct
      ME ID and unexpected MEP ID since this defect has been raised.

5.1.1.4. Period Misconfiguration defect

   If pro-active CC-V OAM packets is are received with a correct ME and MEP
   identifiers but with a transmission period different than its own
   configured transmission period, then a CC-V period mis-configuration
   defect is detected

   o Entry criteria: a MEP receives a CC-V pro-active packet with
      correct ME ID and MEP ID but with a Period field value different
      than its own CC-V configured transmission period.

   o Exit criteria: the sink MEP does not receive any pro-active CC-V
      OAM packet with a correct ME and MEP IDs and an incorrect
      transmission period for an interval equal at least to 3.5 times
      the longest transmission period of the pro-active CC-V OAM packets
      received with a correct ME and MEP IDs and an incorrect
      transmission period since this defect has been raised.

5.1.2. Consequent action

   [editors: IMO this would be better folded into the specific defect
   types, If agreed I will edit accordingly]

   A sink MEP that detects one of the defect conditions defined in
   section 5.1.1 MUST perform the following consequent actions. Some of
   these consequent actions SHOULD be enabled/disabled by the operator
   depending upon the application used (see section 5.1.4).

   If a MEP detects an unexpected ME Identifier, or an unexpected MEP,
   it MUST block all the traffic (including also the user data packets)
   that it receives from the misconnected transport path.

   If a MEP detects LOC defect and the CC-V monitoring is enabled it
   SHOULD block all the traffic (including also the user data packets)
   that it receives from the transport path if this consequent action
   has been enabled by the operator.

   It is worth noticing that the OAM requirements document [11] [12]
   recommends that CC-V proactive monitoring is enabled on every ME in
   order to reliably detect connectivity defects. However, CC-V
   proactive monitoring MAY be disabled by an operator on a an ME. In the
   event of a misconnection between a transport path that is pro-
   actively monitored for CC-V and a transport path which is not, the
   MEP of the former transport path will detect a LOC defect
   representing a connectivity problem (e.g. a misconnection with a
   transport path where CC-V proactive monitoring is not enabled)
   instead of a continuity problem, with a consequent wrong traffic
   delivering. For these reasons, the traffic block consequent action is
   applied even when a LOC condition occurs. This block consequent
   action MAY be disabled through configuration. This deactivation of
   the block action, action may be used for activating or deactivating the
   monitoring when it is not possible to synchronize the function
   activation of the two peer MEPs.

   If a MEP detects a LOC defect, an unexpected ME Identifier, or an
   unexpected MEP it MUST declare a signal fail condition at the
   transport path level.

   If a MEP detects an Unexpected Period defect it SHOULD declare a
   signal fail condition at the transport path level.

   [Editor's note - Transport equipment also performs defect correlation
   (as defined in G.806) in order to properly report failures to the
   transport NSM. NMS ]. The current working assumption, to be further
   investigated, is that defect correlations are outside the scope of
   this document and to be defined in ITU-T documents.]

5.1.3. Configuration considerations

   At all MEPs inside a ME, MEG, the following configuration information need
   needs to be configured when pro-active a proactive CC-V function is enabled:

   o ME MEG ID; the ME MEG identifier to which the MEP belongs;

   o MEP-ID; the MEP's own identity inside the ME; MEG;

   o list of peer MEPs inside the ME. MEG. For a point-to-point ME MEG the
      list would consist of the single peer MEP ID from which the OAM
      packets are expected. In case of the root MEP of a p2mp ME, MEG, the
      list is composed by all the leaf MEP IDs inside the ME. In case of
      the leaf MEP of a p2mp ME, MEG, the list is composed by the root MEP
      ID (i.e. each leaf MUST know the root MEP ID from which it expect
      to receive the CC-V OAM packets).

   o transmission rate; the default CC-V transmission periods are
      application dependent (see section 5.1.4)

   o PHB; it identifies the per-hop behaviour of CC-V packet. Proactive
      CC-V packets are transmitted with the "minimum loss probability
      PHB" previously configured within a single network operator. This
      PHB is configurable on network operator's basis. PHBs can be
      translated at the network borders.

   For statically provisioned transport paths the above information are
   statically configured; for dynamically established transport paths
   the configuration information are signaled via the control plane.

5.1.4. Applications for proactive CC-V

   CC-V is applicable for fault management, performance monitoring, or
   protection switching applications.

   o Fault Management: default transmission period is 1s (i.e.
      transmission rate of 1 packet/second)

   o Performance Monitoring: default transmission period Performance monitoring is 100ms (i.e.
      transmission rate only relevant
      when the transport path is defect free. CC-V contributes to the
      accuracy of 10 packets/second) PM statistics by permitting the defect free periods to
      be properly distinguished.

   o Protection Switching: in order to achieve sub-50ms recovery time the default transmission period is 3.33ms (i.e. transmission rate
      of 300 packets/second) although a transmission period defect
      entry criteria should resolve in less than 50msec, and should
      budget sufficient portion of 10ms can
      also the 50 msec. to be used. available for
      consequent action processing. In some cases, when a slower
      recovery time is acceptable, it is also possible to lengthen the
      transmission rate.

   It SHOULD be possible for the operator to configure these
   transmission rates for all applications, to satisfy his internal
   requirements.

   In addition, the operator should be able to define the consequent
   action to be performed for each of these applications.

5.2. Remote Defect Indication

   The Remote Defect Indication (RDI) is an indicator that is
   transmitted by a MEP to communicate to its peer MEPs that a signal
   fail condition exists.  RDI is only used for bidirectional
   connections and is associated with proactive CC-V activation. The RDI
   indicator is piggy-backed onto the CC-V packet.

   When a MEP detects a signal fail condition (e.g. in case of a
   continuity or connectivity defect or an AIS condition is detected), defect), it should begin transmitting an
   RDI indicator to its peer MEP.  The RDI information will be included
   in all pro-active CC-V packets that it generates for the duration of
   the signal fail condition's existence.

   [Editor's note - Add some forward compatibility information to cover
   the case where future OAM mechanisms that contributes to the signal
   fail detection (and RDI generation) are defined.]

   A MEP that receives the packets with the RDI information should
   determine that its peer MEP has encountered a defect condition
   associated with a signal fail.

   MIPs as well as intermediate nodes not supporting MPLS-TP OAM are
   transparent to the RDI indicator and forward these proactive CC-V
   packets that include the RDI indicator as regular data packets, i.e.
   the MIP should not perform any actions nor examine the indicator.

   When the signal fail defect condition clears, the MEP should clear
   the RDI indicator from subsequent transmission of pro-active CC-V
   packets.  A MEP should clear the RDI defect upon reception of a pro-
   active CC-V packet from the source MEP with the RDI indicator
   cleared.

5.2.1. Configuration considerations

   In order to support RDI indication, this may be a unique OAM message
   or an OAM information element embedded in a CV message. In this case
   the RDI transmission rate and PHB of the MEP OAM packets carrying RDI
   should be configured as part of the CC-V configuration. same as that configured for  CC-V.

5.2.2. Applications for Remote Defect Indication

   RDI is applicable for the following applications:

   o Single-ended fault management - A MEP that receives an RDI
      indication from its peer MEP, can report a far-end defect
      condition (i.e. the peer MEP has detected a signal fail condition
      in the traffic direction from the MEP that receives the RDI
      indication to the peer MEP that has sent the RDI information).

   o Contribution to far-end performance monitoring - The indication of
      the far-end defect condition is used as a contribution to the
      bidirectional performance monitoring process.

5.3. Alarm Reporting

   The Alarm Reporting function relies upon an Alarm Indication Signal
   (AIS) message used to suppress alarms following detection of defect
   conditions at the server (sub) layer. (sub-)layer.

   o A server MEP that detects a signal fail conditions in the server
      (sub-)layer, can generate packets with AIS information in a
      direction opposite to its peers MEPs to allow the suppression of
      secondary alarms at the MEP in the client (sub-)layer.

   A server MEP is responsible for notifying the MPLS-TP layer network
   MEP upon fault detection in the server layer network to which the
   server MEP is associated.

   [editor: the above is confused. The server layer passes signal fail
   or whatever notification to the adaptation function which has
   knowledge of the client layer transport paths, otherwise we are
   discussing a layer violation. These may be MEP co-located end points
   or MIPs. It is the OAM functionality co-located with the adaptation
   function that performs AIS insertion into the client layer MPLS-TP
   paths.... If agreed I will re-word accordingly]

   Only Server MEPs can issue MPLS-TP packets with AIS information. Upon
   detection of a signal fail condition the Server MEP can immediately
   start transmitting periodic packets with AIS information. These
   periodic packets, with AIS information, continue to be transmitted
   until the signal fail condition is cleared.  [editor: SEE ABOVE]

   Upon receiving a packet with AIS information an MPLS-TP MEP detects
   an AIS defect condition and suppresses loss of continuity alarms
   associated with all of its peer MEPs. [editor: There can only be one
   MEP for the ME AIS has been received in association with] A MEP
   resumes loss of continuity alarm generation upon detecting loss of
   continuity defect conditions in the absence of AIS condition.

   For example, let's consider a fiber cut between LSR 1 and LSR 2 in
   the reference network of Figure 3. Assuming that all the MEs
   described in Figure 3 have pro-active CC-V enabled, a LOC defect is
   detected by the MEPs of Sec12 SME, PSN13 LME, PW1 PTCME and PW1Z PME,
   however in transport network only the alarm associate to the fiber
   cut needs to be reported to NMS while all these secondary alarms
   should be suppressed (i.e. not reported to the NMS or reported as
   secondary alarms).

   If the fiber cut is detected by the MEP in the physical layer (in
   LSR2), LSR2 can generate the proper alarm in the physical layer and
   suppress the secondary alarm associated with the LOC defect detected
   on Sec12 SME. As both MEPs reside within the same node, this process
   does not involve any external protocol exchange. Otherwise, if the
   physical layer has not enough OAM capabilities to detect the fiber
   cut, the MEP of Sec12 SME in LSR2 will report a LOC alarm.

   In both cases, the MEP of Sec12 SME in LSR 2 generates AIS packets on
   the PSN13 LME in order to allow its MEP in LSR3 to suppress the LOC
   alarm. LSR3 can also suppress the secondary alarm on PW1 PTCME
   because the MEP of PW1 PTCME resides within the same node as the MEP
   of PSN13 LME. The MEP of PW1 PTCME in LSR3 also generates AIS packets
   on PW1Z PME in order to allow its MEP in LSRZ to suppress the LOC
   alarm.

   The generation of AIS packets for each MEs ME in the client (sub-)layer
   is configurable (i.e. the operator can enable/disable the AIS
   generation).

   AIS packets are transmitted with the "minimum loss probability PHB"
   within a single network operator. This PHB is configurable on network
   operator's basis.

   A MIP is transparent to packets with AIS information and therefore
   does not require any information to support AIS functionality.

5.4. Lock Reporting

   [Editor's note - Requirements for Lock Indication and Lock Reporting
   are still under discussion in draft-ietf-mpls-tp-oam-requirement-02.

   Lock Indication is not required by draft-ietf-mpls-tp-oam-
   requirement-02 This section will be aligned according to the final
   decision regarding the requirement.] AIS functionality.

5.4. Lock Reporting

   To be incorporated in a future revision of this document

5.5. Lock Indication

   [Editor's note - Requirements for Lock Indication and Lock Reporting
   are still under discussion in draft-ietf-mpls-tp-oam-requirement-02.

   Lock Indication is not required by draft-ietf-mpls-tp-oam-
   requirement-02 This section will be aligned according to the final
   decision regarding the requirement.]

   The Locked Indication Signal (LIS) is used to propagate an
   administrative locking of a source MEP and consequential interruption
   of data forwarding towards the sink MEP. It allows a sink MEP
   receiving LIS to differentiate between a defect condition and an
   administrative locking action at the source MEP. An example
   application that requires administrative locking of a MEP is the out-
   of-service test.

5.6. Packet Loss Monitoring

   Packet Loss Monitoring (LM) is one of the capabilities supported by
   the MPLS-TP Performance Monitoring (PM) function in order to
   facilitate reporting of QoS information for a transport path. LM is
   used to exchange counter values for the number of ingress and egress
   packets transmitted and received by the transport path monitored by a
   pair of MEPs.

   Pro-active

   Proactive LM is performed by periodically sending LM OAM packets from
   a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP
   (if a bidirectional transport path) during the life time of the
   transport path. Each MEP performs measurements of its transmitted and
   received packets. These measurements are then transactionally
   correlated with the peer MEP in the ME to derive the impact of packet
   loss on a number of performance metrics for the transport path. ME in the MEG. The LM
   transactions are issued such that the OAM packets will experience the
   same queuing discipline as the measured traffic while transiting
   between the MEPs in the ME.

   For a MEP, near-end packet loss refers to packet loss associated with
   incoming data packets (from the far-end MEP) while far-end packet
   loss refers to packet loss associated with egress data packets
   (towards the far-end MEP).

5.6.1.

5.5.1. Configuration considerations

   In order to support pro-active proactive LM, the transmission rate and PHB
   associated with the LM OAM packets originating from a MEP need be
   configured as part of the LM provisioning procedures. LM OAM packets
   should be transmitted with the PHB that yields the lowest packet loss
   performance among the PHB Scheduling Classes or Ordered Aggregates
   (see RFC 3260 [14]) [15]) in the monitored transport path for the relevant
   network domain(s).

5.6.2.

5.5.2. Applications for Packet Loss Monitoring

   LM is relevant for the following applications:

   o Single or double-end performance monitoring: determination of the
      packet loss performance of a transport path for SLS Service Level
      Agreement (SLA) verification purposes.

   o Single or double-end performance monitoring: determination of the
      packet loss performance of a PHB Scheduling Class or Ordered
      Aggregate within a transport path path.

   o Contribution to service unable time. Both near-end and far-end
      packet loss measurements contribute to performance metrics such as
      near-end severely errored seconds (Near-End SES) and far-end
      severely errored seconds (Far-End SES) respectively, which
      together contribute to unavailable time, in a manner similar to
      Recommendation G.826 [19] and Recommendation G.7710 [20].

5.7.

5.6. Client Signal Failure Indication

   The Client Signal Failure Indication (CSF) function is used to help
   process client defects and propagate a client signal defect condition
   from the process associated with the local attachment circuit where
   the defect was detected (typically the source adaptation function for
   the local client interface) to the process associated with the far-end far-
   end attachment circuit (typically the source adaptation function for
   the far-end client interface) for the same transmission path in case
   the client of the transmission path does not support a native
   defect/alarm indication mechanism, e.g. FDI/AIS.

   A source MEP starts transmitting a CSF indication to its peer MEP
   when it receives a local client signal defect notification via its
   local CSF function. Mechanisms to detect local client signal fail
   defects are technology specific.

   A sink MEP that has received a CSF indication report this condition
   to its associated client process via its local CSF function.
   Consequent actions toward the client attachment circuit are
   technology specific.

5.7.1.

   Either there needs to be a 1:1 correspondence between the client and
   the ME, or when multiple clients are multiplexed over a transport
   path, the CSF message requires additional information to permit the
   client instance to be identified.

5.6.1. Configuration considerations

   In order to support RCSF CSF indication, the CSF transmission rate and PHB
   of the CSF OAM packet message/information element should be configured as
   part of the CSF configuration.

5.7.2.

5.6.2. Applications for Remote Defect Client Signal Failure Indication

   CSF is applicable for the following applications:

   o Single-ended fault management - A MEP that receives a CSF
      indication from its peer MEP, can report a far-end client defect
      condition (i.e. the peer MEP has been informed of local client
      signal fail condition in the traffic direction from the client to
      the peer MEP that transmitted the CSF).

   o Contribution to far-end performance monitoring - The indication of
      the far-end defect condition may be used to account on network
      operator contribution to the bidirectional performance monitoring
      process.

   CSF supports the application described in Appendix VIII of ITU-T
   G.806 [18].

5.8.

5.7. Delay Measurement

   Delay Measurement (DM) is one of the capabilities supported by the
   MPLS-TP PM function in order to facilitate reporting of QoS
   information for a transport path. Specifically, pro-active DM is used
   to measure the long-term packet delay and packet delay variation in
   the transport path monitored by a pair of MEPs.

   Pro-active

   Proactive DM is performed by sending periodic DM OAM packets from a
   MEP to a peer MEP and by receiving DM OAM packets from the peer MEP
   (if a bidirectional transport path) during a configurable time
   interval.

   Pro-active DM can be operated in two ways:

   o One-way: a MEP sends DM OAM packet to its peer MEP containing all
      the required information to facilitate one-way packet delay and/or
      one-way packet delay variation measurements at the peer MEP. Note
      that this requires synchronized precision time at either MEP by
      means outside the scope of this framework.

   o Two-way: a MEP sends DM OAM packet with a DM request to its peer
      MEP, which replies with an a DM OAM packet as a DM response. The
      request/response DM OAM packets containing all the required
      information to facilitate two-way packet delay and/or two-way
      packet delay variation measurements from the viewpoint of the
      source MEP.

5.8.1.

5.7.1. Configuration considerations

   In order to support pro-active DM, the transmission rate and PHB
   associated with the DM OAM packets originating from a MEP need be
   configured as part of the LM DM provisioning procedures. DM OAM packets
   should be transmitted with the PHB that yields the lowest packet loss
   performance among the PHB Scheduling Classes or Ordered Aggregates
   (see RFC 3260 [14]) [15]) in the monitored transport path for the relevant
   network domain(s).

5.8.2.

5.7.2. Applications for Packet Loss Delay Measurement

   DM is relevant for the following applications:

   o Single or double-end performance monitoring: determination of the
      delay performance of a transport path for SLS SLA verification
      purposes.

   o Single or double-end performance monitoring: determination of the
      delay performance of a PHB Scheduling Class or Ordered Aggregate
      within a transport path

6. OAM Functions for on-demand monitoring transport path

6. OAM Functions for on-demand monitoring

[Munich: Note the fwk needs to be explicit about the mapping of
functions to the tools we have chosen.]

   In contrast to proactive monitoring, on-demand monitoring is
   initiated manually and for a limited amount of time, usually for
   operations such as e.g. diagnostics to investigate into a defect
   condition.

   [editor: we would have to babysit a lot fewer words if we folded this
   into section 5 and simply indicated which transactions existed in
   both proactive and reactive forms... if agreed I will edit accordingly]

6.1. Connectivity Verification

   In order to preserve network resources, e.g. bandwidth, processing
   time at switches, it may be preferable to not use pro-active proactive CC-V. In
   order to perform fault management functions functions, network management may
   invoke periodic on-demand bursts of on-demand CV packets.

   Use of on-
   demand on-demand CV is dependent on the existence of a bi-directional
   connection ME, because it requires the presence of a return path in
   the data plane.

   [Editor's note - Clarify in the sentence above and within the
   paragraph that on-demand CV requires a return path to send back the
   reply to on-demand CV packets]
   An additional use of on-demand CV would be to detect and locate a
   problem of connectivity when a problem is suspected or known based on
   other tools.  In this case the functionality will be triggered by the
   network management in response to a status signal or alarm
   indication.

   On-demand CV is based upon generation of on-demand CV packets that
   should uniquely identify the ME that is being checked.  The on-demand
   functionality may be used to check either an entire ME (end-to-end)
   or between a MEP to a specific MIP. This functionality may not be
   available for associated bidirectional paths as the MIP may not have
   a return path to the source MEP for the on-demand CV transaction.

   On-demand CV may generate a one-time burst of on-demand CV packets,
   or be used to invoke periodic, non-continuous, bursts of on-demand CV
   packets.  The number of packets generated in each burst is
   configurable at the MEPs, and should take into account normal packet-
   loss conditions.

   When invoking a periodic check of the ME, the source MEP should issue
   a burst of on-demand CV packets that uniquely identifies the ME being
   verified.  The number of packets and their transmission rate should
   be pre-configured and known to both the source MEP and the target MEP
   or MIP.  The source MEP should use the TTL field to indicate the
   number of hops necessary, when targeting a MIP and use the default
   value when performing an end-to-end check [IB => This is quite
   generic for addressing packets to MIPs and MEPs so it is better to
   move this text in section 2].  The target MEP/MIP shall return a
   reply on-demand CV packet for each packet received.  If the expected
   number of on-demand CV reply packets is not received at source MEP, a
   the LOC defect state is detected. entered.

   [Editor's note - We need to add some text for the usage of on-demand
   CV with different packet sizes, e.g. to discover MTU problems.]

   When a connectivity problem is detected (e.g. via a pro-active proactive CC-V
   OAM tool), on demand an on-demand CV tool can be used to check the path.  The
   series should check CV from MEP to peer MEP on the path, and if a
   fault is discovered, by lack of response, then additional checks may
   be performed to each of the intermediate MIP to locate the fault.

   [Dave: this seems a bit warped as the original discussion was about
   not spending resources on proactive CC-V, so can we just be honest
   about "when the incredibly pissed off customer calls, an on demand CV
   tool..."]

6.1.1. Configuration considerations

   For on-demand CV the MEP should support the configuration of the
   number of packets to be transmitted/received in each burst of
   transmissions and their packet size. The transmission rate should be either pre-
   configured or negotiated between the different nodes.

   In addition, when the CV packet is used to check connectivity toward
   a target MIP, the number of hops to reach the target MIP should be
   configured.

   The PHB of the on-demand CV packets should be configured as well.

   [Editor's note - We need to be better define the reason for such
   configuration]

6.2. Packet Loss Monitoring

   On-demand Packet Loss (LM) is one of the capabilities supported by
   the MPLS-TP Performance Monitoring function in order to facilitate
   diagnostic of QoS performance for a transport path. As Pro-active proactive LM,
   on-demand LM is used to exchange counter values for the number of
   ingress and egress packets transmitted and received by the transport
   path monitored by a pair of MEPs.

   On-demand LM is performed by periodically sending LM OAM packets from
   a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP
   (if a bidirectional transport path) during a pre-defined monitoring
   period. Each MEP performs measurements of its transmitted and
   received packets. These measurements are then correlated evaluate the
   packet loss performance metrics of the transport path. [Dave: again
   are we discussing simply discard eligibility and no other PHB
   impacts?]

6.2.1. Configuration considerations

   In order to support on-demand LM, the beginning and duration of the
   LM procedures,the procedures, the transmission rate and PHB associated with the LM
   OAM packets originating from a MEP must be configured as part of the
   on-demand LM provisioning procedures. LM OAM packets should be
   transmitted with the PHB that yields the lowest packet loss
   performance among the PHB Scheduling Classes or Ordered Aggregates
   (see RFC 3260 [14]) [15]) in the monitored transport path for the relevant
   network domain(s).

6.2.2. Applications for On-demand Packet Loss

   On-demand LM relevant
   network domain(s).

6.2.2. Applications for On-demand Packet Loss Monitoring

   On-demand LM is relevant for the following applications:

   o Single-end performance monitoring: diagnostic of the packet loss
      performance of a transport path for SLA trouble shooting purposes.

   o Single-end performance monitoring: diagnostic of the packet loss
      performance of a PHB Scheduling Class or Ordering Aggregate within
      a transport path for QoS trouble shooting purposes.

6.3. Diagnostic

   To be incorporated in a future revision of this document

   [Munich: Need to describe the two types of loopback - LBM/LBR and
   traffic loopback enhanced with variable sized packets in the on
   demand cases.

   One objective of diags is fault location, we need to make clear how
   we apply the tools to fault location.

   At the top of each section we need to describe the detailed
   requirements and then in the rest of the section describe how it is
   met.]

6.4. Route Tracing

   After e.g. provisioning an MPLS-TP LSP or for trouble shooting
   purposes, it is often necessary to trace a route covered by an ME
   from a source MEP to the sink MEP including all the MIPs in-between.
   The route tracing function is relevant for providing this functionality. Based on
   the following applications:

   o Single-end performance monitoring: diagnostic fate sharing requirement of OAM flows, i.e. OAM packets receive
   the packet loss
      performance of same forwarding treatment as data packet, route tracing is a transport path for SLS trouble shooting purposes.

   o Single-end performance monitoring: diagnostic of the packet loss
      performance of
   basic means to perform CV and, to a PHB Scheduling Class or Ordering Aggregate within much lesser degree, CC. For this
   function to work properly, a transport return path for QoS trouble shooting purposes.

6.3. Diagnostic

   To must be incorporated present.

   Route tracing might be implemented in a future revision of different ways and this
   document

6.4. does not preclude any of them. Route Tracing

   To trace could be incorporated
   implemented e.g. by an MPLS traceroute-like function [RFC4379].
   However, route tracing should always return the full list of MIPs and
   the peer MEP in it answer(s). In case a future revision defect exist, the route trace
   function needs to be able to detect it and stop automatically
   returning the incomplete list of this document OAM entities that it was able to
   trace.

   The configuration of the route trace function must at least support
   the setting of the trace depth (number of hops)_and the number of
   trace attempts before it gives up. Default setting need to be
   configurable by the operator, too.

6.5. Delay Measurement

   Delay Measurement (DM) is one of the capabilities supported by the
   MPLS-TP PM function in order to facilitate reporting of QoS
   information for a transport path. Specifically, on-demand DM is used
   to measure packet delay and packet delay variation in the transport
   path monitored by a pair of MEPs during a pre-defined monitoring
   period.

   On-Demand DM is performed by sending periodic DM OAM packets from a
   MEP to a peer MEP and by receiving DM OAM packets from the peer MEP
   (if a bidirectional transport path) during a configurable time
   interval.

   On-demand DM can be operated in two ways:

   o One-way: a MEP sends DM OAM packet to its peer MEP containing all
      the required information to facilitate one-way packet delay and/or
      one-way packet delay variation measurements at the peer MEP.

   o Two-way: a MEP sends DM OAM packet with a DM request to its peer
      MEP, which replies with an DM OAM packet as a DM response. The
      request/response DM OAM packets containing all the required
      information to facilitate two-way packet delay and/or two-way
      packet delay variation measurements from the viewpoint of the
      source MEP.

6.5.1. Configuration considerations

   In order to support on-demand DM, the beginning and duration of the
   DM procedures, the transmission rate and PHB associated with the DM
   OAM packets originating from a MEP need be configured as part of the
   LM provisioning procedures. DM OAM packets should be transmitted with
   the PHB that yields the lowest packet delay performance among the PHB
   Scheduling Classes or Ordering Aggregates (see RFC 3260 [14]) [15]) in the
   monitored transport path for the relevant network domain(s).

   In order to verify different performances between long and short
   packets (e.g., due to the processing time), it SHOULD be possible for
   the operator to configure of the on-demand OAM DM packet.

6.5.2. Applications for Delay Measurement

   DM is relevant for the following applications:

   o Single or double-end performance monitoring: determination of the
      packet delay and/or delay variation performance of a transport
      path for SLS SLA verification purposes.

   o Single or double-end performance monitoring: determination of the
      packet delay and/or delay variation a PHB Scheduling Class or
      Ordering Aggregate within a transport path

   o Contribution to service unable time. Packet delay measurements may
      contribute to performance metrics such as near-end severely
      errored seconds (Near-End SES) and far-end severely errored
      seconds (Far-End SES), which together contribute to unavailable
      time.

6.6. Lock Instruct

   To be incorporated in a future revision of this document

7. Security Considerations

   A number of security considerations are important in the context of
   OAM applications.

   OAM traffic can reveal sensitive information such as passwords,
   performance data and details about e.g. the network topology. The
   nature of OAM data therefore suggests to have some form of
   authentication, authorization and encryption in place. This will
   prevent unauthorized access to vital equipment and it will prevent
   third parties from learning about sensitive information about the
   transport network.

   Mechanisms that the framework does not specify might be subject to
   additional security considerations.

8. IANA Considerations

   No new IANA considerations.

9. Acknowledgments

   The authors would like to thank all members of the teams (the Joint
   Working Team, the MPLS Interoperability Design Team in IETF and the
   T-MPLS Ad Hoc Group in ITU-T) involved in the definition and
   specification of MPLS Transport Profile.

   This document was prepared using 2-Word-v2.0.template.dot.

10. References

10.1. Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997

   [2]  Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol Label
         Switching Architecture", RFC 3031, January 2001

   [3]  Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032,
         January 2001

   [4]  Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in
         Multi-Protocol Label Switching (MPLS) Networks", RFC 3443,
         January 2003

   [5]  Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge
         (PWE3) Architecture", RFC 3985, March 2005

   [6]  Nadeau, T., Pignataro, S., "Pseudowire Virtual Circuit
         Connectivity Verification (VCCV): A Control Channel for
         Pseudowires", RFC 5085, December 2007

   [7]  Bocci, M., Bryant, S., "An Architecture for Multi-Segment
         Pseudo Wire Emulation Edge-to-Edge", draft-ietf-pwe3-ms-pw-
         arch-05 (work in progress), September 2008

   [8]  Bocci, M., et al., "A Framework for MPLS in Transport
         Networks", draft-ietf-mpls-tp-framework-01 (work in progress),
         June 2009

   [9]  Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal, R.,
         "MPLS Generic Associated Channel ", Channel", RFC 5586, June 2009

   [10] Swallow, G., Bocci, M., "MPLS-TP Identifiers", draft-swallow-
         mpls-tp-identifiers-01 (work in progress), July 2009

10.2. Informative References

   [10]

   [11] Niven-Jenkins, B., Brungard, D., Betts, M., sprecher, N., Ueno,
         S., "MPLS-TP Requirements", draft-ietf-mpls-tp-requirements-09
         (work in progress), June RFC 5654, September 2009

   [11]

   [12] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in
         MPLS Transport Networks", draft-ietf-mpls-tp-oam-requirements-
         02
         03 (work in progress), June August 2009

   [12]

   [13] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, Y.,
         "MPLS-TP OAM Analysis", draft-sprecher-mpls-tp-oam-analysis-04
         (work in progress), May 2009

   [13]

   [14] Nichols, K., Blake, S., Baker, F., Black, D., "Definition of
         the Differentiated Services Field (DS Field) in the IPv4 and
         IPv6 Headers", RFC 2474, December 1998

   [14]

   [15] Grossman, D., "New terminology and clarifications for
         Diffserv", RFC 3260, April 2002.

   [15] Farrel, A., Ayyangar, A., Vasseur, JP., "Inter-Domain MPLS and
         GMPLS Traffic Engineering -- Resource Reservation Protocol-
         Traffic Engineering (RSVP-TE) Extensions", RFC 5151, February
         2008

   [16] ITU-T Recommendation G.707/Y.1322 (01/07), "Network node
         interface for the synchronous digital hierarchy (SDH)", January
         2007

   [17] ITU-T Recommendation G.805 (03/00), "Generic functional
         architecture of transport networks", March 2000

   [18] ITU-T Recommendation G.806 (01/09), "Characteristics of
         transport equipment - Description methodology and generic
         functionality ", January 2009

   [19] ITU-T Recommendation G.826 (12/02), "End-to-end error
         performance parameters and objectives for international,
         constant bit-rate digital paths and connections", December 2002

   [20] ITU-T Recommendation G.7710 (07/07), "Common equipment
         management function requirements", July 2007

   [21] ITU-T Recommendation Y.2611 (06/12), " High-level architecture
         of future packet-based networks", 2006

Authors' Addresses

   Dave Allan (Editor)
   Ericsson

   Email: david.i.allan@ericsson.com

   Italo Busi (Editor)
   Alcatel-Lucent

   Email: Italo.Busi@alcatel-lucent.it
   Ben Niven-Jenkins (Editor)
   BT

   Email: benjamin.niven-jenkins@bt.com

Contributing Authors' Addresses

   Annamaria Fulignoli
   Ericsson

   Email: annamaria.fulignoli@ericsson.com

   Enrique Hernandez-Valencia
   Alcatel-Lucent

   Email: enrique@alcatel-lucent.com

   Lieven Levrau
   Alcatel-Lucent

   Email: llevrau@alcatel-lucent.com

   Dinesh Mohan
   Nortel

   Email: mohand@nortel.com

   Vincenzo Sestito
   Alcatel-Lucent

   Email: vincenzo.sestito@alcatel-lucent.it

   Nurit Sprecher
   Nokia Siemens Networks

   Email: nurit.sprecher@nsn.com
   Huub van Helvoort
   Huawei Technologies

   Email: hhelvoort@huawei.com

   Martin Vigoureux
   Alcatel-Lucent

   Email: martin.vigoureux@alcatel-lucent.fr

   Yaacov Weingarten
   Nokia Siemens Networks

   Email: yaacov.weingarten@nsn.com

   Rolf Winter
   NEC

   Email: Rolf.Winter@nw.neclab.eu