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rfc:rfc6669

Internet Engineering Task Force (IETF) N. Sprecher Request for Comments: 6669 Nokia Siemens Networks Category: Informational L. Fang ISSN: 2070-1721 Cisco Systems

                                                             July 2012
An Overview of the Operations, Administration, and Maintenance (OAM)
             Toolset for MPLS-Based Transport Networks

Abstract

 This document provides an overview of the Operations, Administration,
 and Maintenance (OAM) toolset for MPLS-based transport networks.  The
 toolset consists of a comprehensive set of fault management and
 performance monitoring capabilities (operating in the data plane)
 that are appropriate for transport networks as required in RFC 5860
 and support the network and services at different nested levels.
 This overview includes a brief recap of the MPLS Transport Profile
 (MPLS-TP) OAM requirements and functions and the generic mechanisms
 created in the MPLS data plane that allow the OAM packets to run
 in-band and share their fate with data packets.  The protocol
 definitions for each of the MPLS-TP OAM tools are defined in separate
 documents (RFCs or Working Group documents), which are referenced by
 this document.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 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).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see 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/rfc6669.

Sprecher & Fang Informational [Page 1] RFC 6669 OAM Toolset July 2012

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Sprecher & Fang Informational [Page 2] RFC 6669 OAM Toolset July 2012

Table of Contents

 1. Introduction ....................................................4
    1.1. Scope ......................................................4
    1.2. Acronyms ...................................................5
 2. Basic OAM Infrastructure Functionality ..........................6
 3. MPLS-TP OAM Functions ...........................................8
    3.1. Continuity Check and Connectivity Verification .............8
         3.1.1. Documents for CC-CV Tools ...........................8
    3.2. Remote Defect Indication ...................................8
         3.2.1. Documents for RDI ...................................9
    3.3. Route Tracing ..............................................9
         3.3.1. Documents for Route Tracing .........................9
    3.4. Alarm Reporting ............................................9
         3.4.1. Documents for Alarm Reporting .......................9
    3.5. Lock Instruct ..............................................9
         3.5.1. Documents for Lock Instruct ........................10
    3.6. Lock Reporting ............................................10
         3.6.1. Documents for Lock Reporting .......................10
    3.7. Diagnostic ................................................10
         3.7.1. Documents for Diagnostic Testing ...................10
    3.8. Packet Loss Measurement ...................................10
         3.8.1. Documents for Packet Loss Measurement ..............11
    3.9. Packet Delay Measurement ..................................11
         3.9.1. Documents for Delay Measurement ....................11
 4. MPLS-TP OAM Documents Guide ....................................12
 5. OAM Toolset Applicability and Utilization ......................13
    5.1. Connectivity Check and Connectivity Verification ..........14
    5.2. Diagnostic Tests and Lock Instruct ........................14
    5.3. Lock Reporting ............................................15
    5.4. Alarm Reporting and Link Down Indication ..................15
    5.5. Remote Defect Indication ..................................16
    5.6. Packet Loss and Delay Measurement .........................17
 6. Security Considerations ........................................18
 7. Acknowledgements ...............................................18
 8. References .....................................................19
    8.1. Normative References ......................................19
    8.2. Informative References ....................................20
 Contributors ......................................................21

Sprecher & Fang Informational [Page 3] RFC 6669 OAM Toolset July 2012

1. Introduction

1.1. Scope

 The MPLS Transport Profile (MPLS-TP) architectural framework is
 defined in [RFC5921], and it describes a common set of protocol
 functions that supports the operational models and capabilities
 typical of such transport networks.
 Operations, Administration, and Maintenance (OAM) plays a significant
 role in carrier networks.  It provides methods for fault management
 and performance monitoring in both the transport and service layers,
 in order to improve their ability to support services with guaranteed
 and strict Service Level Agreements (SLAs) while reducing their
 operational costs.
 [RFC5654], in general, and [RFC5860], in particular, define a set of
 requirements for the OAM functionality for MPLS-TP Label Switched
 Paths (LSPs), Pseudowires (PWs), and Sections.
 The OAM solution, developed by the joint IETF and ITU-T MPLS-TP
 project, has three objectives:
 o  The OAM toolset should be developed based on existing MPLS
    architecture, technology, and toolsets.
 o  The OAM operational experience should be similar to that in other
    transport networks.
 o  The OAM toolset developed for MPLS-based transport networks needs
    to be fully interoperable with existing MPLS OAM tools as
    documented in Section 2.1.5. of [RFC5860].
 The MPLS-TP OAM toolset is based on the following existing tools:
 o  LSP ping, as defined in [RFC4379].
 o  Bidirectional Forwarding Detection (BFD), as defined in [RFC5880]
    and refined in [RFC5884].
 o  ITU-T OAM for the Ethernet toolset, as defined in [Y.1731].  This
    has been used as functionality guidelines for the performance
    measurement tools that were not previously supported in MPLS.
 Note that certain extensions and adjustments have been specified,
 relative to the existing MPLS tools, in order to conform to the
 transport environment and the requirements of MPLS-TP.  However,
 compatibility with the existing MPLS tools has been maintained.

Sprecher & Fang Informational [Page 4] RFC 6669 OAM Toolset July 2012

 This document provides an overview of the MPLS-TP OAM toolset, which
 consists of tools for MPLS-TP fault management and performance
 monitoring.  This overview includes a brief recap of MPLS-TP OAM
 requirements, their functions, and the generic mechanisms used to
 support the MPLS-TP OAM operation.
 The protocol definitions for individual MPLS-TP OAM tools are
 specified in separate RFCs (or Working Group documents), which are
 referenced by this document.
 In addition, this document includes a table that cross-references the
 solution documents of the OAM functionality supported.  Finally, the
 document presents the applicability and utilization of each tool in
 the MPLS-TP OAM toolset.

1.2. Acronyms

 This document uses the following acronyms:
 ACH     Associated Channel Header
 AIS     Alarm Indication Signal
 BFD     Bidirectional Forwarding Detection
 CC-CV   Continuity Check and Connectivity Verification
 DM      Delay Measurement
 FM      Fault Management
 G-ACh   Generic Associated Channel
 GAL     G-ACh Label
 GMPLS   Generalized Multiprotocol Label Switching
 IANA    Internet Assigned Numbers Authority
 LDI     Link Down Indication
 LKR     Lock Report
 LM      Loss Measurement
 LOC     Loss of Continuity
 LSP     Label Switched Path
 MEP     Maintenance Entity Group End Point
 MEG     Maintenance Entity Group
 MIP     Maintenance Entity Group Intermediate Point
 MPLS    Multiprotocol Label Switching
 MPLS-TP Transport Profile for MPLS
 OAM     Operations, Administration, and Maintenance
 PM      Performance Monitoring
 PW      Pseudowire
 RDI     Remote Defect Indication
 SLA     Service Level Agreement
 TLV     Type, Length, Value
 VCCV    Virtual Circuit Connectivity Verification

Sprecher & Fang Informational [Page 5] RFC 6669 OAM Toolset July 2012

2. Basic OAM Infrastructure Functionality

 [RFC5860] defines a set of requirements for OAM architecture and
 general principles of operations, which are evaluated below:
 [RFC5860] requires that --
 o  OAM mechanisms in MPLS-TP are independent of the transmission
    media and the client service being emulated by the PW ([RFC5860],
    Section 2.1.2).
 o  MPLS-TP OAM must be able to support both an IP-based and non-IP-
    based environment.  If the network is IP based, i.e., IP routing
    and forwarding are available, then it must be possible to choose
    to make use of IP capabilities.  On the other hand, in
    environments where IP functionality is not available, the OAM
    tools must still be able to operate independent of IP forwarding
    and routing ([RFC5860], Section 2.1.4).  It is required to have
    OAM interoperability between distinct domains materializing the
    environments ([RFC5860], Section 2.1.5).
 o  All OAM protocols support identification information, at least in
    the form of IP addressing structure, and are extensible to support
    additional identification schemes ([RFC5860], Section 2.1.4).
 o  OAM packets and the user traffic are congruent (i.e., OAM packets
    are transmitted in-band) and there is a need to differentiate OAM
    packets from user-plane packets [RFC5860], Section 2.1.3.
    Inherent in this requirement is the principle that full operation
    of the MPLS-TP OAM must be possible independently of the control
    or management plane used to operate the network [RFC5860], Section
    2.1.3.
 o  MPLS-TP OAM supports point-to-point bidirectional PWs, point-to-
    point co-routed bidirectional LSPs, and point-to-point
    bidirectional Sections ([RFC5860], Section 2.1.1).  The
    applicability of particular MPLS-TP OAM functions to point-to-
    point associated bidirectional LSPs, point-to-point unidirectional
    LSPs, and point-to-multipoint LSPs, is described in [RFC5860],
    Section 2.2.  In addition, MPLS-TP OAM supports these LSPs and PWs
    when they span either single or multiple domains ([RFC5860],
    Section 2.1.1).
 o  OAM packets may be directed to an intermediate point of an LSP/PW
    ([RFC5860], Sections 2.2.3, 2.2.4, and 2.2.5).

Sprecher & Fang Informational [Page 6] RFC 6669 OAM Toolset July 2012

 [RFC5860], Section 2.2 recommends that any protocol solution meeting
 one or more functional requirement(s) be the same for PWs, LSPs, and
 Sections.
 The following document set addresses the basic requirements listed
 above:
 o  [RFC6371] describes the architectural framework for conformance to
    the basic requirements listed above.  It also defines the basic
    relationships between the MPLS structures, e.g., LSP, PW, and the
    structures necessary for OAM functionality, i.e., the Maintenance
    Entity Group (MEG), its end points, and intermediate points.
 o  [RFC5586] specifies the use of the MPLS-TP in-band control
    channels.  It generalizes the applicability of the PW ACH to MPLS
    LSPs and Sections by defining a Generic Associated Channel
    (G-ACh).  The G-ACh allows control packets to be multiplexed
    transparently over LSPs and Sections similar to that of PW VCCV
    [RFC5085].  The Generic Association Label (GAL) is defined by
    assigning a reserved MPLS label value and is used to identify the
    OAM control packets.  The value of the ACH Channel Type field
    indicates the specific protocol carried on the associated control
    channel.  Each MPLS-TP OAM protocol has an IANA-assigned channel
    type allocated to it.
 [RFC5085] defines an Associated Channel Header (ACH) that provides a
 PW associated control channel between a PW's end points, over which
 OAM and other control messages can be exchanged.  [RFC5586]
 generalizes the PW Associated Channel Header (ACH) to provide common
 in-band control channels also at the LSP and MPLS-TP link levels.
 The G-ACh allows control packets to be multiplexed transparently over
 the same LSP or MPLS-TP link as in PW VCCV.  Multiple control
 channels can exist between end points.
 [RFC5085] also defines a label-based exception mechanism that helps a
 Label Switching Router (LSR) to identify the control packets and
 direct them to the appropriate entity for processing.  The use of
 G-ACh and GAL provides the necessary mechanisms to allow OAM packets
 to run in-band and share their fate with data packets.  It is
 expected that all of the OAM protocols will be used in conjunction
 with this Generic Associated Channel.
 o  [RFC6370] provides an IP-based identifier set for MPLS-TP that can
    be used to identify the transport entities in the network and
    referenced by the different OAM protocols.

Sprecher & Fang Informational [Page 7] RFC 6669 OAM Toolset July 2012

       Note: [MPLS-TP-ITU-Idents] augments that set of identifiers to
       include identifier information in a format used by the ITU-T.
       Other identifier sets may be defined as well.

3. MPLS-TP OAM Functions

 The following sections discuss the OAM functions that are required in
 [RFC5860] and expanded upon in [RFC6371].

3.1. Continuity Check and Connectivity Verification

 Continuity Check and Connectivity Verification (CC-CV) are OAM
 operations generally used in tandem and complement each other.  These
 functions are generally run proactively, but may also be used
 on-demand for diagnoses of a specific condition.  [RFC5860] states
 that the function should allow the MEPs to proactively monitor the
 liveliness and connectivity of a transport path (LSP, PW, or a
 Section) between them.  In on-demand mode, this function should
 support monitoring between the MEPs and between a MEP and MIP.  Note
 that as specified in [RFC6371], Sections 3.3 and 3.4, a MEP and a MIP
 can reside in an unspecified location within a node, or in a
 particular interface on a specific side of the forwarding engine.
 [RFC6371] highlights the need for the CC-CV messages to include
 unique identification of the MEG that is being monitored and the MEP
 that originated the message.  The function, both proactively and in
 on-demand mode, needs to be transmitted at regular transmission rates
 pre-configured by the operator.

3.1.1. Documents for CC-CV Tools

 [RFC6428] defines BFD extensions to support proactive CC-CV
 applications.
 [RFC6426] provides LSP ping extensions that are used to implement
 on-demand connectivity verification.
 Both of these tools will be used within the basic functionality
 framework described in Section 2.

3.2. Remote Defect Indication

 Remote Defect Indication (RDI) is used by a path end point to report
 that a defect is detected on a bidirectional connection to its peer
 end point.  [RFC5860] points out that this function may be applied to
 a unidirectional LSP only if a return path exists.  [RFC6371] points
 out that this function is associated with the proactive CC-CV
 function.

Sprecher & Fang Informational [Page 8] RFC 6669 OAM Toolset July 2012

3.2.1. Documents for RDI

 [RFC6428] provides an extension for BFD that includes the RDI
 indication in the BFD format and a specification of how this
 indication is to be used.

3.3. Route Tracing

 [RFC5860] defines the need for functionality that would allow a path
 end point to identify the intermediate points (if any) and end
 point(s) along the path (LSP, PW, or a Section).  This function would
 be used in on-demand mode.  Normally, this path will be used for
 bidirectional PW, LSP, and Sections; however, unidirectional paths
 may be supported only if a return path exists.

3.3.1. Documents for Route Tracing

 [RFC6426] specifies that the LSP ping enhancements for MPLS-TP on-
 demand connectivity verification include information on the use of
 LSP ping for route tracing of an MPLS-TP path.

3.4. Alarm Reporting

 Alarm Reporting is a function used by an intermediate point of a path
 (LSP or PW) to report to the end points of the path that a fault
 exists on the path.  [RFC6371] states that this may occur as a result
 of a defect condition discovered at a server layer.  The intermediate
 point generates an Alarm Indication Signal (AIS) that continues until
 the fault is cleared.  The consequent action of this function is
 detailed in [RFC6371].

3.4.1. Documents for Alarm Reporting

 MPLS-TP defines a new protocol to address this functionality that is
 documented in [RFC6427].  This protocol uses all of the basic
 mechanisms detailed in Section 2.

3.5. Lock Instruct

 The Lock Instruct function is an administrative control tool that
 allows a path end point to instruct its peer end point to lock the
 path (LSP, PW, or Section).  The tool is necessary to support single-
 side provisioning for administrative locking, according to [RFC6371].
 This function is used on-demand.

Sprecher & Fang Informational [Page 9] RFC 6669 OAM Toolset July 2012

3.5.1. Documents for Lock Instruct

 [RFC6435] describes the details of a new ACH-based protocol format
 for this functionality.

3.6. Lock Reporting

 Lock Reporting, defined in [RFC5860], is similar to the Alarm
 Reporting function described above.  It is used by an intermediate
 point to notify the end points of a transport path (LSP or PW) that
 an administrative lock condition exists for the transport path.

3.6.1. Documents for Lock Reporting

 MPLS-TP defines a new protocol to address this functionality that is
 documented in [RFC6427].  This protocol uses all the basic mechanisms
 detailed in Section 2.

3.7. Diagnostic

 [RFC5860] indicates a need to provide an OAM function that would
 enable conducting different diagnostic tests on a PW, LSP, or
 Section.  [RFC6371] provides two types of specific tests to be used
 through this functionality:
 o  Throughput estimation - allowing the provider to verify the
    bandwidth/throughput of a transport path.  This is an out-of-
    service tool that uses special packets of varying sizes to test
    the actual bandwidth and/or throughput of the path.
 o  Data-plane loopback - this out-of-service tool causes all traffic
    that reaches the target node, either a MEP or MIP, to be looped
    back to the originating MEP.  For targeting MIPs, a co-routed
    bidirectional path is required.

3.7.1. Documents for Diagnostic Testing

 [RFC6435] describes the details of a new ACH-based protocol format
 for the data-plane loopback functionality.
 The tool for throughput estimation is under study.

3.8. Packet Loss Measurement

 Packet Loss Measurement is required by [RFC5860] to provide a
 quantification of the packet loss ratio on a transport path.  This is
 the ratio of the number of user packets lost to the total number of
 user packets during a defined time interval.  To employ this

Sprecher & Fang Informational [Page 10] RFC 6669 OAM Toolset July 2012

 function, [RFC6371] defines that the two end points of the transport
 path should exchange counters of messages transmitted and received
 within a time period bounded by loss-measurement messages.  The
 framework warns that there may be small errors in the computation,
 which result from various issues.

3.8.1. Documents for Packet Loss Measurement

 [RFC6374] describes the protocol formats and procedures for using the
 tool and enabling efficient and accurate measurement of packet loss,
 delay, and throughput in MPLS networks.  [RFC6375] describes a
 profile of the general MPLS loss, delay, and throughput measurement
 techniques that suffice to meet the specific requirements of MPLS-TP.
 Note that the tool logic is based on the behavior of the parallel
 function described in [Y.1731].

3.9. Packet Delay Measurement

 Packet Delay Measurement is a function that is used to measure the
 one-way or two-way delay of packet transmission between a pair of the
 end points of a path (PW, LSP, or Section), as described in
 [RFC5860], where:
 o  One-way packet delay is the time elapsed from the start of
    transmission of the first bit of the packet by a source node until
    the reception of the last bit of that packet by the destination
    node.
 o  Two-way packet delay is the time elapsed from the start of
    transmission of the first bit of the packet by a source node until
    the reception of the last bit of the loop-backed packet by the
    same source node, when the loopback is performed at the packet's
    destination node.
 [RFC6371] describes how the tool could be used (both in proactive and
 on-demand modes) for either one-way or two-way measurement.  However,
 it warns that the one-way delay option requires precise time
 synchronization between the end points.

3.9.1. Documents for Delay Measurement

 [RFC6374] describes the protocol formats and procedures for using the
 tool and enabling efficient and accurate measurement of packet loss,
 delay, and throughput in MPLS networks.  [RFC6375] describes a
 profile of the general MPLS loss, delay, and throughput measurement
 techniques that suffices to meet the specific requirements of MPLS-
 TP.  Note that the tool logic is based on the behavior of the
 parallel function described in [Y.1731].

Sprecher & Fang Informational [Page 11] RFC 6669 OAM Toolset July 2012

4. MPLS-TP OAM Documents Guide

 The complete MPLS-TP OAM protocol suite is covered by a small set of
 existing IETF documents.  This set of documents may be expanded in
 the future to cover additional OAM functionality.  In order to allow
 the reader to understand this set of documents, a cross-reference of
 the existing documents (RFCs or Working Group documents) for the
 initial phase of the specification of MPLS-based transport networks
 is provided below.
 [RFC5586] provides a specification of the basic structure of protocol
 messages for in-band data-plane OAM in an MPLS environment.
 [RFC6370] provides definitions of different formats that may be used
 within OAM protocol messages to identify the network elements of an
 MPLS-based transport network.
 The following table (Table 1) provides the summary of proactive MPLS-
 TP OAM Fault Management toolset functions, the associated
 tool/protocol, and the corresponding RFCs in which they are defined.
+--------------------------+-------------------------------+---------+
| OAM Functions            | OAM Tools/Protocols           | RFCs    |
+--------------------------+-------------------------------+---------+
| Continuity Check and     | Bidirectional Forwarding      |[RFC6428]|
| Connectivity             | Detection (BFD)               |         |
| Verification             |                               |         |
+--------------------------+-------------------------------+---------+
| Remote Defect Indication | Flag in Bidirectional         |[RFC6428]|
| (RDI)                    | Forwarding Detection (BFD)    |         |
|                          | message                       |         |
+--------------------------+-------------------------------+---------+
| Alarm Indication Signal  | G-ACh-based AIS message       |[RFC6427]|
| (AIS)                    |                               |         |
+--------------------------+-------------------------------+---------+
| Link Down Indication     | Flag in AIS message           |[RFC6427]|
| (LDI)                    |                               |         |
+--------------------------+-------------------------------+---------+
| Lock Reporting (LKR)     | G-ACh-based LKR message       |[RFC6427]|
|                          |                               |         |
+--------------------------+-------------------------------+---------+
           Table 1.  Proactive Fault Management OAM Toolset

Sprecher & Fang Informational [Page 12] RFC 6669 OAM Toolset July 2012

 The following table (Table 2) provides an overview of the on-demand
 MPLS-TP OAM Fault Management toolset functions, the associated
 tool/protocol, and the corresponding RFCs in which they are defined.
+------------------------+---------------------------------+---------+
| OAM Functions          | OAM Tools/Protocols             |  RFCs   |
+------------------------+---------------------------------+---------+
| Connectivity           | LSP Ping                        |[RFC6426]|
| Verification           |                                 |         |
+------------------------+---------------------------------+---------+
| Lock Instruct (LI)     | (1) G-ACh-based Loopback,       |[RFC6426]|
|                        | (2) Lock Instruct (LI)          |         |
+------------------------+---------------------------------+---------+
| Lock Report (LKR)      | Flag in AIS message             |[RFC6426]|
|                        |                                 |         |
+------------------------+---------------------------------+---------+
           Table 2.  On Demand Fault Management OAM Toolset
 The following table (Table 3) provides the Performance Monitoring
 Functions, the associated tool/protocol definitions, and the
 corresponding RFCs in which they are defined.
 +----------------------+--------------------------+-----------------+
 | OAM Functions        | OAM Tools/Protocols      | RFCs            |
 +----------------------+--------------------------+-----------------+
 | Packet Loss          | G-ACh-based LM & DM      | [RFC6374]       |
 | Measurement (LM)     | query messages           | [RFC6375]       |
 +----------------------+--------------------------+-----------------+
 | Packet Delay         | G-ACh-based LM & DM      | [RFC6374]       |
 | Measurement (DM)     | query messages           | [RFC6375]       |
 +----------------------+--------------------------+-----------------+
 | Throughput           | derived from Loss        | [RFC6374]       |
 | Measurement          | Measurement              | [RFC6375]       |
 +----------------------+--------------------------+-----------------+
 | Delay Variation      | derived from Delay       | [RFC6374]       |
 | Measurement          | Measurement              | [RFC6375]       |
 +----------------------+--------------------------+-----------------+
             Table 3.  Performance Monitoring OAM Toolset

5. OAM Toolset Applicability and Utilization

 The following subsections present the MPLS-TP OAM toolset from the
 perspective of the specified protocols and identifies the required
 functionality that is supported by the particular protocol.

Sprecher & Fang Informational [Page 13] RFC 6669 OAM Toolset July 2012

5.1. Connectivity Check and Connectivity Verification

 Proactive Continuity Check and Connectivity Verification (CC-CV)
 functions are used to detect loss of continuity (LOC) and unintended
 connectivity between two MEPs.  Loss of connectivity, mis-merging,
 mis-connectivity, or unexpected Maintenance Entity Group End Points
 (MEPs) can be detected using the CC-CV tools.  See Sections 3.1, 3.2,
 3.3 in this document for CC-CV protocol references.
 The CC-CV tools are used to support MPLS-TP fault management,
 performance management, and protection switching.  Proactive CC-CV
 control packets are sent by the source MEP to the sink MEP.  The
 sink-MEP monitors the arrival of the CC-CV control packets and
 detects the defect.  For bidirectional transport paths, the CC-CV
 protocol is usually transmitted simultaneously in both directions.
 The transmission interval of the CC-CV control packets can be
 configured.  For example:
 o  3.3 ms is the default interval for protection switching.
 o  100 ms is the default interval for performance monitoring.
 o  1 s is the default interval for fault management.

5.2. Diagnostic Tests and Lock Instruct

 [RFC6435] describes a protocol that provides a mechanism to Lock and
 Unlock traffic (e.g., data and control traffic or specific OAM
 traffic) at a specific LSR on the path of the MPLS-TP LSP to allow
 loopback of the traffic to the source.
 These diagnostic functions apply to associated bidirectional MPLS-TP
 LSPs, including MPLS-TP LSPs, bidirectional RSVP-Traffic Engineering
 (RSVP-TE) tunnels (which is relevant for the MPLS-TP dynamic control-
 plane option with GMPLS), and single-segment and multi-segment
 Pseudowires.  [RFC6435] provides the protocol definition for
 diagnostic tests functions.
 [RFC6435] defines a mechanism where a lock instruction is sent by a
 management application to both ends of a point-to-point LSP,
 requesting them to take the LSP out-of-service.  When an end point
 gets the management request, it locks the LSP and sends a Lock
 Instruct message to the other end of the LSP.  The Lock Instruct
 message is carried in a Generic ACH message and is sent periodically.
 The time between successive messages is no longer than the value set
 in the Refresh Timer field of the Lock Instruct message.  An LSP end
 point keeps the LSP locked while it is either receiving the periodic

Sprecher & Fang Informational [Page 14] RFC 6669 OAM Toolset July 2012

 Lock Instruct messages or has an in-force lock instruction from the
 management application.
 Note that since the management application will receive a management
 plane response from both ends of the LSP confirming that the LSP has
 been locked, there is no requirement for the Lock Instruct message to
 have a response.  Therefore, [RFC6435] does not define a Lock
 Instruct response message.
 The loopback operations include:
 o  Lock: take an LSP out of service for maintenance.
 o  Unlock: Restore a previously locked LSP to service.
 o  Set_Full_Loopback and Set_OAM_Loopback.
 o  Unset_Full_Loopback and Set_OAM_Loopback.
 Operators can use the loopback mode to test the connectivity or
 performance (loss, delay, delay variation, and throughput) of a given
 LSP up to a specific node on the path of the LSP.

5.3. Lock Reporting

 The Lock Report (LKR) function is used to communicate to the MEPS of
 the client (sub-)layer MEPs the administrative locking of a server
 (sub-)layer MEP, and consequential interruption of data traffic
 forwarding in the client layer.  See Section 3.6 in this document for
 Lock Reporting protocol references.
 When an operator is taking the LSP out of service for maintenance or
 another operational reason, using the LKR function can help to
 distinguish the condition as administrative locking from a defect
 condition.
 The Lock Report function may also serve the purpose of alarm
 suppression in the MPLS-TP network above the level at which the Lock
 has occurred.  The receipt of an LKR message may be treated as the
 equivalent of the loss of continuity at the client layer.

5.4. Alarm Reporting and Link Down Indication

 Alarm Indication Signal (AIS) message is used to suppress alarms
 following detection of defect conditions at the server (sub-)layer.
 When the Link Down Indication (LDI) is set, the AIS message may be
 used to trigger recovery mechanisms.

Sprecher & Fang Informational [Page 15] RFC 6669 OAM Toolset July 2012

 When a server MEP detects the failure, it asserts LOC or signal fail,
 which sets the flag up to generate an OAM packet with the AIS
 message.  The AIS message is forwarded to the downstream sink MEP in
 the client layer.  This enables the client layer to suppress the
 generation of secondary alarms.
 An LDI flag is defined in the AIS message.  The LDI flag is set in
 the AIS message in response to detecting a fatal failure in the
 server layer.  Receipt of an AIS message with this flag set may be
 interpreted by a MEP as an indication of signal fail at the client
 layer.
 The protocols for AIS and LDI are defined in [RFC6427].
 Fault OAM messages are generated by intermediate nodes where an LSP
 is switched and propagated to the end points (MEPs).
 From a practical point of view, when both proactive Continuity Check
 functions and LDI are used, one may consider running the proactive
 Continuity Check functions at a slower rate (e.g., longer BFD hello
 intervals), and reply on LDI to trigger fast protection switch over
 upon failure detection in a given LSP.

5.5. Remote Defect Indication

 The Remote Defect Indication (RDI) function enables an end point to
 report to its peer end point that a fault or defect condition is
 detected on the PW, LSP, or Section.
 The RDI OAM function is supported by the use of BFD control packets
 [RFC6428].  RDI is only used for bidirectional connections and is
 associated with proactive CC-CV activation.
 When an end point (MEP) detects a signal failure condition, it sets
 the flag up by setting the diagnostic field of the BFD control packet
 to a particular value to indicate the failure condition on the
 associated PW, LSP, or Section.  Additionally, the BFD control packet
 is transmitted with the failure flag up to the other end point (its
 peer MEP).
 The RDI function can be used to facilitate protection switching by
 synchronizing the two end points when unidirectional failure occurs
 and is detected by one end.

Sprecher & Fang Informational [Page 16] RFC 6669 OAM Toolset July 2012

5.6. Packet Loss and Delay Measurement

 The packet loss and delay measurement toolset enables operators to
 measure the quality of the packet transmission over a PW, LSP, or
 Section.  Section 3.8 in this document defines the protocols for
 packet loss measurement, and Section 3.9 defines the protocols for
 packet delay measurement.
 The loss and delay protocols have the following characteristics and
 capabilities:
 o  They support the measurement of packet loss, delay, and throughput
    over Label Switched Paths (LSPs), Pseudowires, and MPLS Sections.
 o  The same LM and DM protocols can be used for both
    continuous/proactive and selective/on-demand measurements.
 o  The LM and DM protocols use a simple query/response model for
    bidirectional measurement that allows a single node -- the querier
    -- to measure the loss or delay in both directions.
 o  The LM and DM protocols use query messages for unidirectional loss
    and delay measurement.  The measurement can either be carried out
    at the downstream node(s), or at the querier if an out-of-band
    return path is available.
 o  The LM and DM protocols do not require that the transmit-and-
    receive interfaces be the same when performing bidirectional
    measurement.
 o  The LM supports test-message-based measurement (i.e., inferred
    mode) as well as measurement based on data-plane counters (i.e.,
    direct mode).
 o  The LM protocol supports both 32-bit and 64-bit counters.
 o  The LM protocol supports measurement in terms of both packet
    counts and octet counts; although for simplicity, only packet
    counters are currently included in the MPLS-TP profile.
 o  The LM protocol can be used to measure channel throughput as well
    as packet loss.
 o  The DM protocol supports varying the measurement message size in
    order to measure delays associated with different packet sizes.
 o  The DM protocol uses IEEE 1588 timestamps [IEEE1588] by default
    but also supports other timestamp formats, such as NTP.

Sprecher & Fang Informational [Page 17] RFC 6669 OAM Toolset July 2012

6. Security Considerations

 This document, as an overview of MPLS OAM tools, does not by itself
 raise any particular security considerations.
 The general security considerations are provided in [RFC5920] and
 [MPLS-TP-SEC].  Security considerations for each function within the
 OAM toolset have been recorded in each document that specifies a
 particular functionality.
 In general, OAM is always an area where the security risk is high.
 For example, confidential information may be intercepted by attackers
 to gain access to networks; therefore, authentication, authorization,
 and encryption must be enforced to prevent security breaches.
 It is also important to strictly follow operational security
 procedures.  For example, in the case of MPLS-TP static provisioning,
 the operator interacts directly with the Network Management System
 (NMS) and devices, and it is critical in order to prevent human
 errors and malicious attacks.
 Since MPLS-TP OAM uses G-ACh, the security risks and mitigations
 described in [RFC5085] also apply here.  In short, messages on the
 G-ACh could be intercepted, or false G-ACh packets could be inserted.
 Additionally, DoS attacks can be mounted by flooding G-ACh messages
 to peer devices.  To mitigate this type of attack, throttling
 mechanisms or rate limits can be used.  For more details, please see
 [RFC5085].

7. Acknowledgements

 The authors would like to thank the MPLS-TP experts from both the
 IETF and ITU-T for their helpful comments.  In particular, we would
 like to thank Loa Andersson and the Area Directors for their
 suggestions and enhancements to the text.
 Thanks to Tom Petch for useful comments and discussions.
 Thanks to Rui Costa for his review and comments, which helped improve
 this document.

Sprecher & Fang Informational [Page 18] RFC 6669 OAM Toolset July 2012

8. References

8.1. Normative References

 [RFC4379]  Kompella, K. and G. Swallow, "Detecting Multi-Protocol
            Label Switched (MPLS) Data Plane Failures", RFC 4379,
            February 2006.
 [RFC5085]  Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire
            Virtual Circuit Connectivity Verification (VCCV): A
            Control Channel for Pseudowires", RFC 5085, December 2007.
 [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
            "MPLS Generic Associated Channel", RFC 5586, June 2009.
 [RFC5654]  Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
            Sprecher, N., and S. Ueno, "Requirements of an MPLS
            Transport Profile", RFC 5654, September 2009.
 [RFC5860]  Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,
            "Requirements for Operations, Administration, and
            Maintenance (OAM) in MPLS Transport Networks", RFC 5860,
            May 2010.
 [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
            (BFD)", RFC 5880, June 2010.
 [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
            "Bidirectional Forwarding Detection (BFD) for MPLS Label
            Switched Paths (LSPs)", RFC 5884, June 2010.
 [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
            L., and L. Berger, "A Framework for MPLS in Transport
            Networks", RFC 5921, July 2010.
 [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
            Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.
 [RFC6371]  Busi, I., Ed., and D. Allan, Ed., "Operations,
            Administration, and Maintenance Framework for MPLS-Based
            Transport Networks", RFC 6371, September 2011.
 [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
            Measurement for MPLS Networks", RFC 6374, September 2011.
 [RFC6375]  Frost, D., Ed., and S. Bryant, Ed., "A Packet Loss and
            Delay Measurement Profile for MPLS-Based Transport
            Networks", RFC 6375, September 2011.

Sprecher & Fang Informational [Page 19] RFC 6669 OAM Toolset July 2012

 [RFC6426]  Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
            On-Demand Connectivity Verification and Route Tracing",
            RFC 6426, November 2011.
 [RFC6427]  Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed.,
            Boutros, S., and D. Ward, "MPLS Fault Management
            Operations, Administration, and Maintenance (OAM)", RFC
            6427, November 2011.
 [RFC6428]  Allan, D., Ed., Swallow Ed., G., and J. Drake Ed.,
            "Proactive Connectivity Verification, Continuity Check,
            and Remote Defect Indication for the MPLS Transport
            Profile", RFC 6428, November 2011.
 [RFC6435]  Boutros, S., Ed., Sivabalan, S., Ed., Aggarwal, R., Ed.,
            Vigoureux, M., Ed., and X. Dai, Ed., "MPLS Transport
            Profile Lock Instruct and Loopback Functions", RFC 6435,
            November 2011.

8.2. Informative References

 [IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
            Synchronization Protocol for Networked Measurement and
            Control Systems", March 2008.
 [MPLS-TP-ITU-Idents]
            Winter, R., van Helvoort, H., and M. Betts, "MPLS-TP
            Identifiers Following ITU-T Conventions", Work in
            Progress, March 2012.
 [MPLS-TP-SEC]
            Fang, L., Niven-Jenkins, B., and S. Mansfield, "MPLS-TP
            Security Framework", Work in Progress, March 2012.
 [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
            Networks", RFC 5920, July 2010.
 [Y.1731]   International Telecommunications Union - Standardization,
            "OAM functions and mechanisms for Ethernet based
            networks", ITU Y.1731, May 2006.

Sprecher & Fang Informational [Page 20] RFC 6669 OAM Toolset July 2012

Contributors

 Elisa Bellagamba   Ericsson
 Yaacov Weingarten  Nokia Siemens Networks
 Dan Frost          Cisco
 Nabil Bitar        Verizon
 Raymond Zhang      Alcatel Lucent
 Lei Wang           Telenor
 Kam Lee Yap        XO Communications
 John Drake         Juniper
 Yaakov Stein       RAD
 Anamaria Fulignoli Ericsson
 Italo Busi         Alcatel Lucent
 Huub van Helvoort  Huawei
 Thomas Nadeau      Computer Associate
 Henry Yu           TW Telecom
 Mach Chen          Huawei
 Manuel Paul        Deutsche Telekom

Authors' Addresses

 Nurit Sprecher
 Nokia Siemens Networks
 3 Hanagar St. Neve Ne'eman B
 Hod Hasharon, 45241
 Israel
 EMail: nurit.sprecher@nsn.com
 Luyuan Fang
 Cisco Systems
 111 Wood Avenue South
 Iselin, NJ 08830
 USA
 EMail: lufang@cisco.com

Sprecher & Fang Informational [Page 21]

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