Internet Engineering Task Force (IETF)                 M. Vigoureux, Ed.
Request for Comments: 5860                                Alcatel-Lucent
Category: Standards Track                                   D. Ward, Ed.
ISSN: 2070-1721                                         Juniper Networks
                                                           M. Betts, Ed.
                                             M. C. Betts Consulting Ltd.
                                                                May 2010


   Requirements for Operations, Administration, and Maintenance (OAM)
                       in MPLS Transport Networks

Abstract

   This document lists architectural and functional requirements for the
   Operations, Administration, and Maintenance of MPLS Transport
   Profile.  These requirements apply to pseudowires, Label Switched
   Paths, and Sections.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5860.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Scope of This Document . . . . . . . . . . . . . . . . . .  3
     1.2.  Requirements Language and Terminology  . . . . . . . . . .  4
   2.  OAM Requirements . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Architectural Requirements . . . . . . . . . . . . . . . .  6
       2.1.1.  Scope of OAM . . . . . . . . . . . . . . . . . . . . .  6
       2.1.2.  Independence . . . . . . . . . . . . . . . . . . . . .  6
       2.1.3.  Data Plane . . . . . . . . . . . . . . . . . . . . . .  7
       2.1.4.  OAM and IP Capabilities  . . . . . . . . . . . . . . .  7
       2.1.5.  Interoperability and Interworking  . . . . . . . . . .  8
       2.1.6.  Configuration  . . . . . . . . . . . . . . . . . . . .  8
     2.2.  Functional Requirements  . . . . . . . . . . . . . . . . .  9
       2.2.1.  General Requirements . . . . . . . . . . . . . . . . .  9
       2.2.2.  Continuity Checks  . . . . . . . . . . . . . . . . . . 10
       2.2.3.  Connectivity Verifications . . . . . . . . . . . . . . 10
       2.2.4.  Route Tracing  . . . . . . . . . . . . . . . . . . . . 11
       2.2.5.  Diagnostic Tests . . . . . . . . . . . . . . . . . . . 11
       2.2.6.  Lock Instruct  . . . . . . . . . . . . . . . . . . . . 11
       2.2.7.  Lock Reporting . . . . . . . . . . . . . . . . . . . . 12
       2.2.8.  Alarm Reporting  . . . . . . . . . . . . . . . . . . . 12
       2.2.9.  Remote Defect Indication . . . . . . . . . . . . . . . 13
       2.2.10. Client Failure Indication  . . . . . . . . . . . . . . 13
       2.2.11. Packet Loss Measurement  . . . . . . . . . . . . . . . 13
       2.2.12. Packet Delay Measurement . . . . . . . . . . . . . . . 14
   3.  Congestion Considerations  . . . . . . . . . . . . . . . . . . 15
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 16

1.  Introduction

   In the context of MPLS Transport Profile (MPLS-TP, see [9] and [1]),
   the rationales for Operations, Administration, and Maintenance (OAM)
   are twofold as it can serve:

   o  as a network-oriented functionality, used by a transport network
      operator to monitor his network infrastructure and to implement
      internal mechanisms in order to enhance the general behavior and
      the level of performance of his network (e.g., protection
      mechanism in case of node or link failure).  As an example, fault
      localization is typically associated with this use case.

   o  as a service-oriented functionality, used by a transport service
      provider to monitor services offered to end customers in order to
      be able to react rapidly in case of a problem and to be able to
      verify some of the Service Level Agreement (SLA) parameters (e.g.,
      using performance monitoring) negotiated with the end customers.
      Note that a transport service could be provided over several
      networks or administrative domains that may not all be owned and
      managed by the same transport service provider.

   More generally, OAM is an important and fundamental functionality in
   transport networks as it contributes to:

   o  the reduction of operational complexity and costs, by allowing for
      efficient and automatic detection, localization, and handling and
      diagnosis of defects, as well as by minimizing service
      interruptions and operational repair times.

   o  the enhancement of network availability, by ensuring that defects
      (for example, those resulting in misdirected customer traffic) and
      faults are detected, diagnosed, and dealt with before a customer
      reports the problem.

   o  meeting service and performance objectives, as the OAM
      functionality allows for SLA verification in a multi-maintenance
      domain environment and allows for the determination of service
      degradation due, for example, to packet delay or packet loss.

1.1.  Scope of This Document

   This document lists architectural and functional requirements for the
   OAM functionality of MPLS-TP.  These requirements apply to
   pseudowires (PWs), Label Switched Paths (LSPs), and Sections.

   These requirements are derived from the set of requirements specified
   by ITU-T and published in the ITU-T Supplement Y.Sup4 [10].

   By covering transport specificities, these requirements complement
   those identified in RFC 4377 [11]; yet, some requirements may be
   similar.

   This document only lists architectural and functional OAM
   requirements.  It does not detail the implications of their
   applicability to the various types (e.g., point-to-point, point-to-
   multipoint, unidirectional, bidirectional, etc.) of PWs, LSPs, and
   Sections.  Furthermore, this document does not provide requirements
   on how the protocol solution(s) should behave to achieve the
   functional objectives.  Please see [12] for further information.

   Note that the OAM functions identified in this document may be used
   for fault-management, performance-monitoring, and/or protection-
   switching applications.  For example, connectivity verification can
   be used for fault management by detecting failure conditions, but may
   also be used for performance monitoring through its contribution to
   the evaluation of performance metrics (e.g., unavailability time).
   Nevertheless, it is outside the scope of this document to specify
   which function should be used for which application.

   Note also that it is anticipated that implementers may wish to
   implement OAM message handling in hardware.  Although not a
   requirement, this fact could be taken as a design consideration.

1.2.  Requirements Language and Terminology

   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 [2].
   Although this document is not a protocol specification, the use of
   this language clarifies the instructions to protocol designers
   producing solutions that satisfy the requirements set out in this
   document.

   In this document, we:

   o  refer to the inability of a function to perform a required action
      as a fault.  This does not include an inability due to preventive
      maintenance, lack of external resources, or planned actions.  See
      also ITU-T G.806 [3].

   o  refer to the situation in which the density of anomalies has
      reached a level where the ability to perform a required function
      has been interrupted as a defect.  See also ITU-T G.806 [3].

   o  refer to OAM actions that are carried out continuously or at least
      over long periods of time, permitting proactive reporting of fault
      and/or performance results as proactive OAM.

   o  refer to OAM actions that are initiated via manual intervention
      for a limited time to carry out troubleshooting as on-demand OAM.

   o  refer to a Label Edge Router (LER), for a given LSP or Section,
      and to a PW Terminating Provider Edge (T-PE), for a given PW, as
      an End Point.  Further, we refer to a Label Switching Router
      (LSR), for a given LSP, and to a PW Switching Provider Edge
      (S-PE), for a given PW, as an Intermediate Point.  This document
      does not make a distinction between End Points (e.g., source and
      destination) as it can be inferred from the context of the
      sentences.

   o  use the term "node" as a general reference to End Points and
      Intermediate Points.

   o  refer to both segment and concatenated segments as segments (see
      [1] for definitions relating to the term "segment" as well as for
      other definitions relating to MPLS-TP).

   o  refer to both single segment PWs and multi-segment PWs as PWs.

   o  refer to both bidirectional associated LSPs and bidirectional co-
      routed LSPs as bidirectional LSPs.

2.  OAM Requirements

   This section lists the requirements by which the OAM functionality of
   MPLS-TP should abide.

   The requirements listed below may be met by one or more OAM
   protocols; the definition or selection of these protocols is outside
   the scope of this document.

   RFC 5654 [1] states (Requirement #2) that the MPLS-TP design, SHOULD
   as far as reasonably possible, reuse existing MPLS standards.  This
   general requirement applies to MPLS-TP OAM.  MPLS-TP OAM is defined
   in this document through a set of functional requirements.  These
   requirements will be met by protocol solutions defined in other
   documents.  The way in which those protocols are operated and the way
   in which a network operator can control and use the MPLS-TP OAM
   functions SHOULD be as similar as possible to the mechanisms and
   techniques used to operate OAM in other transport technologies.

2.1.  Architectural Requirements

2.1.1.  Scope of OAM

   The protocol solution(s) developed to meet the requirements
   identified in this document MUST at least be applicable to point-to-
   point bidirectional PWs, point-to-point co-routed bidirectional LSPs,
   and point-to-point bidirectional Sections.  Section 2.2 provides
   additional information with regard to the applicability to point-to-
   point associated bidirectional LSPs, point-to-point unidirectional
   LSPs, and point-to-multipoint LSPs.

   The service emulated by a PW may span multiple domains.  An LSP may
   also span multiple domains.  The protocol solution(s) MUST be
   applicable to end-to-end and to segments.  More generally, it MUST be
   possible to operate OAM functions on a per-domain basis and across
   multiple domains.

   Since LSPs may be stacked, the protocol solution(s) MUST be
   applicable on any LSP, regardless of the label stack depth.
   Furthermore, it MUST be possible to estimate OAM fault and
   performance metrics of a single PW or LSP segment or of an aggregate
   of PW or LSP segments.

2.1.2.  Independence

   The protocol solution(s) SHOULD be independent of the underlying
   tunneling or point-to-point technology or transmission media.

   The protocol solution(s) SHOULD be independent of the service a PW
   may emulate.

   Any OAM function operated on a PW, LSP, or Section SHOULD be
   independent of the OAM function(s) operated on a different PW, LSP,
   or Section.  In other words, only the OAM functions operated on a
   given LSP (for example) should be used to achieve the OAM objectives
   for that LSP.

   The protocol solution(s) MUST support the capability to be
   concurrently and independently operated end-to-end and on segments.
   Therefore, any OAM function applied to segment(s) of a PW or LSP
   SHOULD be independent of the OAM function(s) operated on the end-to-
   end PW or LSP.  It SHOULD also be possible to distinguish an OAM
   packet running over a segment of a PW or LSP from another OAM packet
   running on the end-to-end PW or LSP.

   Furthermore, any OAM function applied to segment(s) of a PW or LSP
   SHOULD be independent of the OAM function(s) applied to other
   segment(s) of the same PW or LSP.

      Note: Independence should not be understood in terms of isolation
      as there can be interactions between OAM functions operated, for
      example, on two different LSPs.

2.1.3.  Data Plane

   OAM functions operate in the data plane.  OAM packets MUST run in-
   band; that is, OAM packets for a specific PW, LSP, or Section MUST
   follow the exact same data path as user traffic of that PW, LSP, or
   Section.  This is often referred to as fate sharing.

   It MUST be possible to discriminate user traffic from OAM packets.
   This includes a means to differentiate OAM packets from user traffic
   as well as the capability to apply specific treatment to OAM packets,
   at the nodes processing these OAM packets.

   As part of the design of OAM protocol solution(s) for MPLS-TP, a
   mechanism for enabling the encapsulation and differentiation of OAM
   messages on a PW, LSP, or Section, MUST be provided.  Such mechanism
   SHOULD also support the encapsulation and differentiation of existing
   IP/MPLS and PW OAM messages.

2.1.4.  OAM and IP Capabilities

   There are environments where IP capabilities are present in the data
   plane.  IP/MPLS environments are examples of such environments.
   There are also environments where IP capabilities may not be present
   in the data plane.  MPLS-TP environments are examples of environments
   where IP capabilities might or might not be present.

      Note: Presence or absence of IP capabilities is deployment
      scenario dependent.

   It MUST be possible to deploy the OAM functionality in any of these
   environments.  As a result, it MUST be possible to operate OAM
   functions with or without relying on IP capabilities, and it MUST be
   possible to choose to make use of IP capabilities when these are
   present.

   Furthermore, the mechanism required for enabling the encapsulation
   and differentiation of OAM messages (see Section 2.1.3) MUST support
   the capability to differentiate OAM messages of an OAM function

   operated by relying on IP capabilities (e.g., using encapsulation in
   an IP header) from OAM messages of an OAM function operated without
   relying on any IP capability.

   Note that IP capabilities include the capability to form a standard
   IP header, to encapsulate a payload in an IP header, to parse and
   analyze the fields of an IP header, and to take actions based on the
   content of these fields.

   For certain functions, OAM messages need to incorporate
   identification information (e.g., of source and/or destination
   nodes).  The protocol solution(s) MUST at least support
   identification information in the form of an IP addressing structure
   and MUST also be extensible to support additional identification
   schemes.

2.1.5.  Interoperability and Interworking

   It is REQUIRED that OAM interoperability is achieved between distinct
   domains materializing the environments described in Section 2.1.4.
   It is also REQUIRED that the first two requirements of Section 2.1.4
   still hold and MUST still be met when interoperability is achieved.

   When MPLS-TP is run with IP routing and forwarding capabilities, it
   MUST be possible to operate any of the existing IP/MPLS and PW OAM
   protocols (e.g., LSP-Ping [4], MPLS-BFD [13], VCCV [5], and VCCV-BFD
   [14]).

2.1.6.  Configuration

   OAM functions MUST operate and be configurable even in the absence of
   a control plane.  Conversely, it SHOULD be possible to configure as
   well as enable/disable the capability to operate OAM functions as
   part of connectivity management, and it SHOULD also be possible to
   configure as well as enable/disable the capability to operate OAM
   functions after connectivity has been established.

   In the latter case, the customer MUST NOT perceive service
   degradation as a result of OAM enabling/disabling.  Ideally, OAM
   enabling/disabling should take place without introducing any customer
   impairments (e.g., no customer packet losses).  Procedures aimed to
   prevent any traffic impairment MUST be defined for the enabling/
   disabling of OAM functions.

   Means for configuring OAM functions and for connectivity management
   are outside the scope of this document.

2.2.  Functional Requirements

   Hereafter are listed the required functionalities composing the
   MPLS-TP OAM toolset.  The list may not be exhaustive and as such the
   OAM mechanisms developed in support of the identified requirements
   SHALL be extensible and thus SHALL NOT preclude the definition of
   additional OAM functionalities, in the future.

   The design of OAM mechanisms for MPLS-TP, MUST allow for the ability
   to support experimental OAM functions.  These functions MUST be
   disabled by default.

   The use of any OAM function MUST be optional and it MUST be possible
   to select the set of OAM function(s) to use on any PW, LSP, or
   Section.

   It is RECOMMENDED that any protocol solution, meeting one or more
   functional requirement(s), be the same for PWs, LSPs, and Sections.

   It is RECOMMENDED that any protocol solution, meeting one or more
   functional requirement(s), effectively provides a fully featured
   function; that is, a function that is applicable to all the cases
   identified for that functionality.  In that context, protocol
   solution(s) MUST state their applicability.

   Unless otherwise stated, the OAM functionalities MUST NOT rely on
   user traffic; that is, only OAM messages MUST be used to achieve the
   objectives.

   For the on-demand OAM functions, the result of which may vary
   depending on packet size, it SHOULD be possible to perform these
   functions using different packet sizes.

2.2.1.  General Requirements

   If a defect or fault occurs on a PW, LSP, or Section, mechanisms MUST
   be provided to detect it, diagnose it, localize it, and notify the
   appropriate nodes.  Mechanisms SHOULD exist such that corrective
   actions can be taken.

   Furthermore, mechanisms MUST be available for a service provider to
   be aware of a fault or defect affecting the service(s) he provides,
   even if the fault or defect is located outside of his domain.

   Protocol solution(s) developed to meet these requirements may rely on
   information exchange.  Information exchange between various nodes
   involved in the operation of an OAM function SHOULD be reliable such
   that, for example, defects or faults are properly detected or that
   state changes are effectively known by the appropriate nodes.

2.2.2.  Continuity Checks

   The MPLS-TP OAM toolset MUST provide a function to enable an End
   Point to monitor the liveness of a PW, LSP, or Section.

   This function SHOULD be performed between End Points of PWs, LSPs,
   and Sections.

   This function SHOULD be performed proactively.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.3.  Connectivity Verifications

   The MPLS-TP OAM toolset MUST provide a function to enable an End
   Point to determine whether or not it is connected to specific End
   Point(s) by means of the expected PW, LSP, or Section.

   This function SHOULD be performed proactively between End Points of
   PWs, LSPs, and Sections.

   This function SHOULD be performed on-demand between End Points and
   Intermediate Points of PWs and LSPs, and between End Points of PWs,
   LSPs, and Sections.

   The protocol solution(s) developed to perform this function
   proactively MUST also apply to point-to-point associated
   bidirectional LSPs, point-to-point unidirectional LSPs, and point-to-
   multipoint LSPs.

   The protocol solution(s) developed to perform this function on-demand
   MAY also apply to point-to-point associated bidirectional LSPs, to
   point-to-point unidirectional LSPs, and point-to-multipoint LSPs in
   case a return path exists.

2.2.4.  Route Tracing

   The MPLS-TP OAM toolset MUST provide functionality to enable an End
   Point to discover the Intermediate (if any) and End Point(s) along a
   PW, LSP, or Section, and more generally to trace the route of a PW,
   LSP, or Section.  The information collected MUST include identifiers
   related to the nodes and interfaces composing that route.

   This function SHOULD be performed on-demand.

   This function SHOULD be performed between End Points and Intermediate
   Points of PWs and LSPs, and between End Points of PWs, LSPs, and
   Sections.

   The protocol solution(s) developed to perform this function MAY also
   apply to point-to-point associated bidirectional LSPs, to point-to-
   point unidirectional LSPs, and point-to-multipoint LSPs in case a
   return path exists.

2.2.5.  Diagnostic Tests

   The MPLS-TP OAM toolset MUST provide a function to enable conducting
   diagnostic tests on a PW, LSP, or Section.  An example of such a
   diagnostic test consists of performing a loop-back function at a node
   such that all OAM and data traffic are looped back to the originating
   End Point.  Another example of such diagnostic test consists in
   estimating the bandwidth of, e.g., an LSP.

   This function SHOULD be performed on-demand.

   This function SHOULD be performed between End Points and Intermediate
   Points of PWs and LSPs, and between End Points of PWs, LSPs, and
   Sections.

   The protocol solution(s) developed to perform this function MAY also
   apply to point-to-point associated bidirectional LSPs, to point-to-
   point unidirectional LSPs and point-to-multipoint LSPs, in case a
   return path exists.

2.2.6.  Lock Instruct

   The MPLS-TP OAM toolset MUST provide functionality to enable an End
   Point of a PW, LSP, or Section to instruct its associated End
   Point(s) to lock the PW, LSP, or Section.  Note that lock corresponds
   to an administrative status in which it is expected that only test
   traffic, if any, and OAM (dedicated to the PW, LSP, or Section) can
   be mapped on that PW, LSP, or Section.

   This function SHOULD be performed on-demand.

   This function SHOULD be performed between End Points of PWs, LSPs,
   and Sections.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.7.  Lock Reporting

   Based on the tunneling capabilities of MPLS, there are cases where
   Intermediate Point(s) of a PW or of an LSP coincide with End Point(s)
   of another LSP on which the former is mapped/tunneled.  Further, it
   may happen that the tunnel LSP is out of service as a result of a
   lock action on that tunnel LSP.  By means outside of the scope of
   this document, the Intermediate Point(s) of the PW or LSP may be
   aware of this condition.  The MPLS-TP OAM toolset MUST provide a
   function to enable an Intermediate Point of a PW or LSP to report, to
   an End Point of that same PW or LSP, a lock condition indirectly
   affecting that PW or LSP.

   This function SHOULD be performed proactively.

   This function SHOULD be performed between Intermediate Points and End
   Points of PWs and LSPs.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.8.  Alarm Reporting

   Based on the tunneling capabilities of MPLS, there are cases where
   Intermediate Point(s) of a PW or of an LSP coincide with End Point(s)
   of another LSP on which the former is mapped/tunneled.  Further, it
   may happen that the tunnel LSP be out of service as a result of a
   fault on that tunnel LSP.  By means outside of the scope of this
   document, the Intermediate Point(s) of the PW or LSP may be aware of
   this condition.  The MPLS-TP OAM toolset MUST provide functionality
   to enable an Intermediate Point of a PW or LSP to report, to an End
   Point of that same PW or LSP, a fault or defect condition indirectly
   affecting that PW or LSP.

   This function SHOULD be performed proactively.

   This function SHOULD be performed between Intermediate Points and End
   Points of PWs and LSPs.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.9.  Remote Defect Indication

   The MPLS-TP OAM toolset MUST provide a function to enable an End
   Point to report, to its associated End Point, a fault or defect
   condition that it detects on a PW, LSP, or Section for which they are
   the End Points.

   This function SHOULD be performed proactively.

   This function SHOULD be performed between End Points of PWs, LSPs,
   and Sections.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs and MAY also
   apply to point-to-point unidirectional LSPs and point-to-multipoint
   LSPs in case a return path exists.

2.2.10.  Client Failure Indication

   The MPLS-TP OAM toolset MUST provide a function to enable the
   propagation, from edge to edge of an MPLS-TP network, of information
   pertaining to a client (i.e., external to the MPLS-TP network) defect
   or fault condition detected at an End Point of a PW or LSP, if the
   client layer OAM functionality does not provide an alarm
   notification/propagation functionality.

   This function SHOULD be performed proactively.

   This function SHOULD be performed between End Points of PWs and LSPs.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.11.  Packet Loss Measurement

   The MPLS-TP OAM toolset MUST provide a function to enable the
   quantification of packet loss ratio over a PW, LSP, or Section.

   The loss of a packet is defined in RFC2680 [6] (see Section 2.4).
   This definition is used here.

   Packet-loss ratio is defined here to be the ratio of the number of
   user packets lost to the total number of user packets sent during a
   defined time interval.

   This function MAY either be performed proactively or on-demand.

   This function SHOULD be performed between End Points of PWs, LSPs,
   and Sections.

   It SHOULD be possible to rely on user traffic to perform this
   functionality.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs.

2.2.12.  Packet Delay Measurement

   The MPLS-TP OAM toolset MUST provide a function to enable the
   quantification of the one-way, and if appropriate, the two-way, delay
   of a PW, LSP, or Section.

   o  The one-way delay is defined in [7] to be the time elapsed from
      the start of transmission of the first bit of a packet by an End
      Point until the reception of the last bit of that packet by the
      other End Point.

   o  The two-way delay is defined in [8] to be the time elapsed from
      the start of transmission of the first bit of a packet by an End
      Point until the reception of the last bit of that packet by the
      same End Point.

   Two-way delay may be quantified using data traffic loopback at the
   remote End Point of the PW, LSP, or Section (see Section 2.2.5).

   Accurate quantification of one-way delay may require clock
   synchronization, the means for which are outside the scope of this
   document.

   This function SHOULD be performed on-demand and MAY be performed
   proactively.

   This function SHOULD be performed between End Points of PWs, LSPs,
   and Sections.

   The protocol solution(s) developed to perform this function MUST also
   apply to point-to-point associated bidirectional LSPs, point-to-point
   unidirectional LSPs, and point-to-multipoint LSPs, but only to enable
   the quantification of the one-way delay.

3.  Congestion Considerations

   A mechanism (e.g., rate limiting) MUST be provided to prevent OAM
   packets from causing congestion in the Packet Switched Network.

4.  Security Considerations

   This document, in itself, does not imply any security consideration
   but OAM, as such, is subject to several security considerations.  OAM
   messages can reveal sensitive information such as passwords,
   performance data and details about, e.g., the network topology.

   The nature of OAM therefore suggests having some form of
   authentication, authorization, and encryption in place.  This will
   prevent unauthorized access to MPLS-TP equipment and it will prevent
   third parties from learning about sensitive information about the
   transport network.

   OAM systems (network management stations) SHOULD be designed such
   that OAM functions cannot be accessed without authorization.

   OAM protocol solutions MUST include the facility for OAM messages to
   authenticated to prove their origin and to make sure that they are
   destined for the receiving node.  The use of such facilities MUST be
   configurable.

   An OAM packet received over a PW, LSP, or Section MUST NOT be
   forwarded beyond the End Point of that PW, LSP, or Section, so as to
   avoid that the OAM packet leaves the current administrative domain.

5.  Acknowledgements

   The editors gratefully acknowledge the contributions of Matthew
   Bocci, Italo Busi, Thomas Dietz, Annamaria Fulignoli, Huub van
   Helvoort, Enrique Hernandez-Valencia, Wataru Imajuku, Kam Lam, Marc
   Lasserre, Lieven Levrau, Han Li, Julien Meuric, Philippe Niger,
   Benjamin Niven-Jenkins, Jing Ruiquan, Nurit Sprecher, Yuji Tochio,
   Satoshi Ueno, and Yaacov Weingarten.

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

6.  References

6.1.  Normative References

   [1]   Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
         S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654,
         September 2009.

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

   [3]   ITU-T Recommendation G.806, "Characteristics of transport
         equipment - Description methodology and generic functionality",
         2009.

   [4]   Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
         Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.

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

   [6]   Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Packet
         Loss Metric for IPPM", RFC 2680, September 1999.

   [7]   Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Delay
         Metric for IPPM", RFC 2679, September 1999.

   [8]   Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay
         Metric for IPPM", RFC 2681, September 1999.

6.2.  Informative References

   [9]   Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, L.,
         and L. Berger, "A Framework for MPLS in Transport Networks",
         Work in Progress, May 2010.

   [10]  ITU-T Supplement Y.Sup4, "ITU-T Y.1300-series: Supplement on
         transport requirements for T-MPLS OAM and considerations for
         the application of IETF MPLS technology", 2008.

   [11]  Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
         Matsushima, "Operations and Management (OAM) Requirements for
         Multi-Protocol Label Switched (MPLS) Networks", RFC 4377,
         February 2006.

   [12]  Busi, I., Ed., Niven-Jenkins, B., Ed., and D. Allan, Ed.,
         "MPLS-TP OAM Framework", Work in Progress, April 2010.

   [13]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
         For MPLS LSPs", Work in Progress, June 2008.

   [14]  Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
         Forwarding Detection (BFD) for the Pseudowire Virtual Circuit
         Connectivity Verification (VCCV)", Work in Progress, July 2009.

Authors' Addresses

   Martin Vigoureux (editor)
   Alcatel-Lucent
   Route de Villejust
   Nozay  91620
   France

   EMail: martin.vigoureux@alcatel-lucent.com


   David Ward (editor)
   Juniper Networks

   EMail: dward@juniper.net


   Malcolm Betts (editor)
   M. C. Betts Consulting Ltd.

   EMail: malcolm.betts@rogers.com