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rfc:rfc7276

Internet Engineering Task Force (IETF) T. Mizrahi Request for Comments: 7276 Marvell Category: Informational N. Sprecher ISSN: 2070-1721 Nokia Solutions and Networks

                                                         E. Bellagamba
                                                              Ericsson
                                                         Y. Weingarten
                                                             June 2014
                           An Overview of
      Operations, Administration, and Maintenance (OAM) Tools

Abstract

 Operations, Administration, and Maintenance (OAM) is a general term
 that refers to a toolset for fault detection and isolation, and for
 performance measurement.  Over the years, various OAM tools have been
 defined for various layers in the protocol stack.
 This document summarizes some of the OAM tools defined in the IETF in
 the context of IP unicast, MPLS, MPLS Transport Profile (MPLS-TP),
 pseudowires, and Transparent Interconnection of Lots of Links
 (TRILL).  This document focuses on tools for detecting and isolating
 failures in networks and for performance monitoring.  Control and
 management aspects of OAM are outside the scope of this document.
 Network repair functions such as Fast Reroute (FRR) and protection
 switching, which are often triggered by OAM protocols, are also out
 of the scope of this document.
 The target audience of this document includes network equipment
 vendors, network operators, and standards development organizations.
 This document can be used as an index to some of the main OAM tools
 defined in the IETF.  At the end of the document, a list of the OAM
 toolsets and a list of the OAM functions are presented as a summary.

Mizrahi, et al. Informational [Page 1] RFC 7276 Overview of OAM Tools June 2014

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/rfc7276.

Copyright Notice

 Copyright (c) 2014 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.

Mizrahi, et al. Informational [Page 2] RFC 7276 Overview of OAM Tools June 2014

Table of Contents

 1. Introduction ....................................................4
    1.1. Background .................................................5
    1.2. Target Audience ............................................6
    1.3. OAM-Related Work in the IETF ...............................6
    1.4. Focusing on the Data Plane .................................7
 2. Terminology .....................................................8
    2.1. Abbreviations ..............................................8
    2.2. Terminology Used in OAM Standards .........................10
         2.2.1. General Terms ......................................10
         2.2.2. Operations, Administration, and Maintenance ........10
         2.2.3. Functions, Tools, and Protocols ....................11
         2.2.4. Data Plane, Control Plane, and Management Plane ....11
         2.2.5. The Players ........................................12
         2.2.6. Proactive and On-Demand Activation .................13
         2.2.7. Connectivity Verification and Continuity Checks ....14
         2.2.8. Connection-Oriented vs. Connectionless
                Communication ......................................15
         2.2.9. Point-to-Point vs. Point-to-Multipoint Services ....16
         2.2.10. Failures ..........................................16
 3. OAM Functions ..................................................17
 4. OAM Tools in the IETF - A Detailed Description .................18
    4.1. IP Ping ...................................................18
    4.2. IP Traceroute .............................................19
    4.3. Bidirectional Forwarding Detection (BFD) ..................20
         4.3.1. Overview ...........................................20
         4.3.2. Terminology ........................................20
         4.3.3. BFD Control ........................................20
         4.3.4. BFD Echo ...........................................21
    4.4. MPLS OAM ..................................................21
         4.4.1. LSP Ping ...........................................21
         4.4.2. BFD for MPLS .......................................22
         4.4.3. OAM for Virtual Private Networks (VPNs) over MPLS ..23
    4.5. MPLS-TP OAM ...............................................23
         4.5.1. Overview ...........................................23
         4.5.2. Terminology ........................................24
         4.5.3. Generic Associated Channel .........................25
         4.5.4. MPLS-TP OAM Toolset ................................25
                4.5.4.1. Continuity Check and Connectivity
                         Verification ..............................26
                4.5.4.2. Route Tracing .............................26
                4.5.4.3. Lock Instruct .............................27
                4.5.4.4. Lock Reporting ............................27
                4.5.4.5. Alarm Reporting ...........................27
                4.5.4.6. Remote Defect Indication ..................27
                4.5.4.7. Client Failure Indication .................27

Mizrahi, et al. Informational [Page 3] RFC 7276 Overview of OAM Tools June 2014

                4.5.4.8. Performance Monitoring ....................28
                         4.5.4.8.1. Packet Loss Measurement (LM) ...28
                         4.5.4.8.2. Packet Delay Measurement (DM) ..28
    4.6. Pseudowire OAM ............................................29
         4.6.1. Pseudowire OAM Using Virtual Circuit
                Connectivity Verification (VCCV) ...................29
         4.6.2. Pseudowire OAM Using G-ACh .........................30
         4.6.3. Attachment Circuit - Pseudowire Mapping ............30
    4.7. OWAMP and TWAMP ...........................................31
         4.7.1. Overview ...........................................31
         4.7.2. Control and Test Protocols .........................32
         4.7.3. OWAMP ..............................................32
         4.7.4. TWAMP ..............................................33
    4.8. TRILL .....................................................33
 5. Summary ........................................................34
    5.1. Summary of OAM Tools ......................................34
    5.2. Summary of OAM Functions ..................................37
    5.3. Guidance to Network Equipment Vendors .....................38
 6. Security Considerations ........................................38
 7. Acknowledgments ................................................39
 8. References .....................................................39
    8.1. Normative References ......................................39
    8.2. Informative References ....................................39
 Appendix A. List of OAM Documents ................................ 46
    A.1. List of IETF OAM Documents ............................... 46
    A.2. List of Selected Non-IETF OAM Documents .................. 50

1. Introduction

 "OAM" is a general term that refers to a toolset for detecting,
 isolating, and reporting failures, and for monitoring network
 performance.
 There are several different interpretations of the "OAM" acronym.
 This document refers to Operations, Administration, and Maintenance,
 as recommended in Section 3 of [OAM-Def].
 This document summarizes some of the OAM tools defined in the IETF in
 the context of IP unicast, MPLS, MPLS Transport Profile (MPLS-TP),
 pseudowires, and TRILL.
 This document focuses on tools for detecting and isolating failures
 and for performance monitoring.  Hence, this document focuses on the
 tools used for monitoring and measuring the data plane; control and
 management aspects of OAM are outside the scope of this document.
 Network repair functions such as Fast Reroute (FRR) and protection
 switching, which are often triggered by OAM protocols, are also out
 of the scope of this document.

Mizrahi, et al. Informational [Page 4] RFC 7276 Overview of OAM Tools June 2014

1.1. Background

 OAM was originally used in traditional communication technologies
 such as E1 and T1, evolving into Plesiochronous Digital Hierarchy
 (PDH) and then later into Synchronous Optical Network / Synchronous
 Digital Hierarchy (SONET/SDH).  ATM was probably the first technology
 to include inherent OAM support from day one, while in other
 technologies OAM was typically defined in an ad hoc manner after the
 technology was already defined and deployed.  Packet-based networks
 were traditionally considered unreliable and best effort.  As packet-
 based networks evolved, they have become the common transport for
 both data and telephony, replacing traditional transport protocols.
 Consequently, packet-based networks were expected to provide a
 similar "carrier grade" experience, and specifically to support more
 advanced OAM functions, beyond ICMP and router hellos, that were
 traditionally used for fault detection.
 As typical networks have a multi-layer architecture, the set of OAM
 protocols similarly take a multi-layer structure; each layer has its
 own OAM protocols.  Moreover, OAM can be used at different levels of
 hierarchy in the network to form a multi-layer OAM solution, as shown
 in the example in Figure 1.
 Figure 1 illustrates a network in which IP traffic between two
 customer edges is transported over an MPLS provider network.  MPLS
 OAM is used at the provider level for monitoring the connection
 between the two provider edges, while IP OAM is used at the customer
 level for monitoring the end-to-end connection between the two
 customer edges.
         |<-------------- Customer-level OAM -------------->|
               IP OAM (Ping, Traceroute, OWAMP, TWAMP)
                      |<- Provider-level OAM ->|
                          MPLS OAM (LSP Ping)
   +-----+       +----+                        +----+       +-----+
   |     |       |    |========================|    |       |     |
   |     |-------|    |          MPLS          |    |-------|     |
   |     |  IP   |    |                        |    |  IP   |     |
   +-----+       +----+                        +----+       +-----+
   Customer     Provider                      Provider      Customer
     Edge         Edge                          Edge          Edge
                Figure 1: Example of Multi-layer OAM

Mizrahi, et al. Informational [Page 5] RFC 7276 Overview of OAM Tools June 2014

1.2. Target Audience

 The target audience of this document includes:
 o  Standards development organizations - Both IETF working groups and
    non-IETF organizations can benefit from this document when
    designing new OAM protocols, or when looking to reuse existing OAM
    tools for new technologies.
 o  Network equipment vendors and network operators can use this
    document as an index to some of the common IETF OAM tools.
 It should be noted that some background in OAM is necessary in order
 to understand and benefit from this document.  Specifically, the
 reader is assumed to be familiar with the term "OAM" [OAM-Def], the
 motivation for using OAM, and the distinction between OAM and network
 management [OAM-Mng].

1.3. OAM-Related Work in the IETF

 This memo provides an overview of the different sets of OAM tools
 defined by the IETF.  The set of OAM tools described in this memo are
 applicable to IP unicast, MPLS, pseudowires, MPLS Transport Profile
 (MPLS-TP), and TRILL.  While OAM tools that are applicable to other
 technologies exist, they are beyond the scope of this memo.
 This document focuses on IETF documents that have been published as
 RFCs, while other ongoing OAM-related work is outside the scope.
 The IETF has defined OAM protocols and tools in several different
 contexts.  We roughly categorize these efforts into a few sets of
 OAM-related RFCs, listed in Table 1.  Each set defines a logically
 coupled set of RFCs, although the sets are in some cases intertwined
 by common tools and protocols.
 The discussion in this document is ordered according to these sets
 (the acronyms and abbreviations are listed in Section 2.1).

Mizrahi, et al. Informational [Page 6] RFC 7276 Overview of OAM Tools June 2014

                      +--------------+------------+
                      | Toolset      | Transport  |
                      |              | Technology |
                      +--------------+------------+
                      |IP Ping       | IPv4/IPv6  |
                      +--------------+------------+
                      |IP Traceroute | IPv4/IPv6  |
                      +--------------+------------+
                      |BFD           | generic    |
                      +--------------+------------+
                      |MPLS OAM      | MPLS       |
                      +--------------+------------+
                      |MPLS-TP OAM   | MPLS-TP    |
                      +--------------+------------+
                      |Pseudowire OAM| Pseudowires|
                      +--------------+------------+
                      |OWAMP and     | IPv4/IPv6  |
                      |TWAMP         |            |
                      +--------------+------------+
                      |TRILL OAM     | TRILL      |
                      +--------------+------------+
              Table 1: OAM Toolset Packages in the IETF Documents
 This document focuses on OAM tools that have been developed in the
 IETF.  A short summary of some of the significant OAM standards that
 have been developed in other standard organizations is presented in
 Appendix A.2.

1.4. Focusing on the Data Plane

 OAM tools may, and quite often do, work in conjunction with a control
 plane and/or management plane.  OAM provides instrumentation tools
 for measuring and monitoring the data plane.  OAM tools often use
 control-plane functions, e.g., to initialize OAM sessions and to
 exchange various parameters.  The OAM tools communicate with the
 management plane to raise alarms, and often OAM tools may be
 activated by the management plane (as well as by the control plane),
 e.g., to locate and localize problems.
 The considerations of the control-plane maintenance tools and the
 functionality of the management plane are out of scope for this
 document, which concentrates on presenting the data-plane tools that
 are used for OAM.  Network repair functions such as Fast Reroute
 (FRR) and protection switching, which are often triggered by OAM
 protocols, are also out of the scope of this document.

Mizrahi, et al. Informational [Page 7] RFC 7276 Overview of OAM Tools June 2014

 Since OAM protocols are used for monitoring the data plane, it is
 imperative for OAM tools to be capable of testing the actual data
 plane with as much accuracy as possible.  Thus, it is important to
 enforce fate-sharing between OAM traffic that monitors the data plane
 and the data-plane traffic it monitors.

2. Terminology

2.1. Abbreviations

 ACH      Associated Channel Header
 AIS      Alarm Indication Signal
 ATM      Asynchronous Transfer Mode
 BFD      Bidirectional Forwarding Detection
 CC       Continuity Check
 CC-V     Continuity Check and Connectivity Verification
 CV       Connectivity Verification
 DM       Delay Measurement
 ECMP     Equal-Cost Multipath
 FEC      Forwarding Equivalence Class
 FRR      Fast Reroute
 G-ACh    Generic Associated Channel
 GAL      Generic Associated Channel Label
 ICMP     Internet Control Message Protocol
 L2TP     Layer 2 Tunneling Protocol
 L2VPN    Layer 2 Virtual Private Network
 L3VPN    Layer 3 Virtual Private Network
 LCCE     L2TP Control Connection Endpoint
 LDP      Label Distribution Protocol

Mizrahi, et al. Informational [Page 8] RFC 7276 Overview of OAM Tools June 2014

 LER      Label Edge Router
 LM       Loss Measurement
 LSP      Label Switched Path
 LSR      Label Switching Router
 ME       Maintenance Entity
 MEG      Maintenance Entity Group
 MEP      MEG End Point
 MIP      MEG Intermediate Point
 MP       Maintenance Point
 MPLS     Multiprotocol Label Switching
 MPLS-TP  MPLS Transport Profile
 MTU      Maximum Transmission Unit
 OAM      Operations, Administration, and Maintenance
 OWAMP    One-Way Active Measurement Protocol
 PDH      Plesiochronous Digital Hierarchy
 PE       Provider Edge
 PSN      Public Switched Network
 PW       Pseudowire
 PWE3     Pseudowire Emulation Edge-to-Edge
 RBridge  Routing Bridge
 RDI      Remote Defect Indication
 SDH      Synchronous Digital Hierarchy
 SONET    Synchronous Optical Network
 TRILL    Transparent Interconnection of Lots of Links

Mizrahi, et al. Informational [Page 9] RFC 7276 Overview of OAM Tools June 2014

 TTL      Time To Live
 TWAMP    Two-Way Active Measurement Protocol
 VCCV     Virtual Circuit Connectivity Verification
 VPN      Virtual Private Network

2.2. Terminology Used in OAM Standards

2.2.1. General Terms

 A wide variety of terms is used in various OAM standards.  This
 section presents a comparison of the terms used in various OAM
 standards, without fully quoting the definition of each term.
 An interesting overview of the term "OAM" and its derivatives is
 presented in [OAM-Def].  A thesaurus of terminology for MPLS-TP terms
 is presented in [TP-Term], which provides a good summary of some of
 the OAM-related terminology.

2.2.2. Operations, Administration, and Maintenance

 The following definition of OAM is quoted from [OAM-Def]:
 The components of the "OAM" acronym (and provisioning) are defined as
 follows:
 o  Operations - Operation activities are undertaken to keep the
    network (and the services that the network provides) up and
    running.  It includes monitoring the network and finding problems.
    Ideally these problems should be found before users are affected.
 o  Administration - Administration activities involve keeping track
    of resources in the network and how they are used.  It includes
    all the bookkeeping that is necessary to track networking
    resources and the network under control.
 o  Maintenance - Maintenance activities are focused on facilitating
    repairs and upgrades -- for example, when equipment must be
    replaced, when a router needs a patch for an operating system
    image, or when a new switch is added to a network.  Maintenance
    also involves corrective and preventive measures to make the
    managed network run more effectively, e.g., adjusting device
    configuration and parameters.

Mizrahi, et al. Informational [Page 10] RFC 7276 Overview of OAM Tools June 2014

2.2.3. Functions, Tools, and Protocols

 OAM Function
    An OAM function is an instrumentation measurement type or
    diagnostic.
    OAM functions are the atomic building blocks of OAM, where each
    function defines an OAM capability.
    Typical examples of OAM functions are presented in Section 3.
 OAM Protocol
    An OAM protocol is a protocol used for implementing one or more
    OAM functions.
    The OWAMP-Test [OWAMP] is an example of an OAM protocol.
 OAM Tool
    An OAM tool is a specific means of applying one or more OAM
    functions.
    In some cases, an OAM protocol *is* an OAM tool, e.g., OWAMP-Test.
    In other cases, an OAM tool uses a set of protocols that are not
    strictly OAM related; for example, Traceroute (Section 4.2) can be
    implemented using UDP and ICMP messages, without using an OAM
    protocol per se.

2.2.4. Data Plane, Control Plane, and Management Plane

 Data Plane
    The data plane is the set of functions used to transfer data in
    the stratum or layer under consideration [ITU-Terms].
    The data plane is also known as the forwarding plane or the user
    plane.
 Control Plane
    The control plane is the set of protocols and mechanisms that
    enable routers to efficiently learn how to forward packets towards
    their final destination (based on [Comp]).

Mizrahi, et al. Informational [Page 11] RFC 7276 Overview of OAM Tools June 2014

 Management Plane
    The term "Management Plane", as described in [Mng], is used to
    describe the exchange of management messages through management
    protocols (often transported by IP and by IP transport protocols)
    between management applications and the managed entities such as
    network nodes.
 Data Plane vs. Control Plane vs. Management Plane
    The distinction between the planes is at times a bit vague.  For
    example, the definition of "Control Plane" above may imply that
    OAM tools such as ping, BFD, and others are in fact in the control
    plane.
    This document focuses on tools used for monitoring the data plane.
    While these tools could arguably be considered to be in the
    control plane, these tools monitor the data plane, and hence it is
    imperative to have fate-sharing between OAM traffic that monitors
    the data plane and the data-plane traffic it monitors.
    Another potentially vague distinction is between the management
    plane and control plane.  The management plane should be seen as
    separate from, but possibly overlapping with, the control plane
    (based on [Mng]).

2.2.5. The Players

 An OAM tool is used between two (or more) peers.  Various terms are
 used in IETF documents to refer to the players that take part in OAM.
 Table 2 summarizes the terms used in each of the toolsets discussed
 in this document.

Mizrahi, et al. Informational [Page 12] RFC 7276 Overview of OAM Tools June 2014

      +--------------------------+---------------------------+
      | Toolset                  | Terms                     |
      +--------------------------+---------------------------+
      | Ping / Traceroute        |- Host                     |
      | ([ICMPv4], [ICMPv6],     |- Node                     |
      |  [TCPIP-Tools])          |- Interface                |
      |                          |- Gateway                  |
      + ------------------------ + ------------------------- +
      | BFD [BFD]                |- System                   |
      + ------------------------ + ------------------------- +
      | MPLS OAM [MPLS-OAM-FW]   |- LSR                      |
      + ------------------------ + ------------------------- +
      | MPLS-TP OAM [TP-OAM-FW]  |- End Point - MEP          |
      |                          |- Intermediate Point - MIP |
      + ------------------------ + ------------------------- +
      | Pseudowire OAM [VCCV]    |- PE                       |
      |                          |- LCCE                     |
      + ------------------------ + ------------------------- +
      | OWAMP and TWAMP          |- Host                     |
      | ([OWAMP], [TWAMP])       |- End system               |
      + ------------------------ + ------------------------- +
      | TRILL OAM [TRILL-OAM]    |- RBridge                  |
      +--------------------------+---------------------------+
                Table 2: Maintenance Point Terminology

2.2.6. Proactive and On-Demand Activation

 The different OAM tools may be used in one of two basic types of
 activation:
 Proactive
    Proactive activation - indicates that the tool is activated on a
    continual basis, where messages are sent periodically, and errors
    are detected when a certain number of expected messages are not
    received.
 On-demand
    On-demand activation - indicates that the tool is activated
    "manually" to detect a specific anomaly.

Mizrahi, et al. Informational [Page 13] RFC 7276 Overview of OAM Tools June 2014

2.2.7. Connectivity Verification and Continuity Checks

 Two distinct classes of failure management functions are used in OAM
 protocols: Connectivity Verification and Continuity Checks.  The
 distinction between these terms is defined in [MPLS-TP-OAM] and is
 used similarly in this document.
 Continuity Check
    Continuity Checks are used to verify that a destination is
    reachable, and are typically sent proactively, though they can be
    invoked on-demand as well.
 Connectivity Verification
    A Connectivity Verification function allows Alice to check whether
    she is connected to Bob or not.  It is noted that while the CV
    function is performed in the data plane, the "expected path" is
    predetermined in either the control plane or the management plane.
    A Connectivity Verification (CV) protocol typically uses a CV
    message, followed by a CV reply that is sent back to the
    originator.  A CV function can be applied proactively or
    on-demand.
    Connectivity Verification tools often perform path verification as
    well, allowing Alice to verify that messages from Bob are received
    through the correct path, thereby verifying not only that the two
    MPs are connected, but also that they are connected through the
    expected path, allowing detection of unexpected topology changes.
    Connectivity Verification functions can also be used for checking
    the MTU of the path between the two peers.
    Connectivity Verification and Continuity Checks are considered
    complementary mechanisms and are often used in conjunction with
    each other.

Mizrahi, et al. Informational [Page 14] RFC 7276 Overview of OAM Tools June 2014

2.2.8. Connection-Oriented vs. Connectionless Communication

 Connection-Oriented
    In connection-oriented technologies, an end-to-end connection is
    established (by a control protocol or provisioned by a management
    system) prior to the transmission of data.
    Typically a connection identifier is used to identify the
    connection.  In connection-oriented technologies, it is often the
    case (although not always) that all packets belonging to a
    specific connection use the same route through the network.
 Connectionless
    In connectionless technologies, data is typically sent between end
    points without prior arrangement.  Packets are routed
    independently based on their destination address, and hence
    different packets may be routed in a different way across the
    network.
 Discussion
    The OAM tools described in this document include tools that
    support connection-oriented technologies, as well as tools for
    connectionless technologies.
    In connection-oriented technologies, OAM is used to monitor a
    *specific* connection; OAM packets are forwarded through the same
    route as the data traffic and receive the same treatment.  In
    connectionless technologies, OAM is used between a source and
    destination pair without defining a specific connection.
    Moreover, in some cases, the route of OAM packets may differ from
    the one of the data traffic.  For example, the connectionless IP
    Ping (Section 4.1) tests the reachability from a source to a given
    destination, while the connection-oriented LSP Ping (Section
    4.4.1) is used for monitoring a specific LSP (connection) and
    provides the capability to monitor all the available paths used by
    an LSP.
    It should be noted that in some cases connectionless protocols are
    monitored by connection-oriented OAM protocols.  For example,
    while IP is a connectionless protocol, it can be monitored by BFD
    (Section 4.3), which is connection oriented.

Mizrahi, et al. Informational [Page 15] RFC 7276 Overview of OAM Tools June 2014

2.2.9. Point-to-Point vs. Point-to-Multipoint Services

 Point-to-point (P2P)
    A P2P service delivers data from a single source to a single
    destination.
 Point-to-multipoint (P2MP)
    A P2MP service delivers data from a single source to a one or more
    destinations (based on [Signal]).
    An MP2MP service is a service that delivers data from more than
    one source to one or more receivers (based on [Signal]).
    Note: the two definitions for P2MP and MP2MP are quoted from
    [Signal].  Although [Signal] describes a specific case of P2MP and
    MP2MP that is MPLS-specific, these two definitions also apply to
    non-MPLS cases.
 Discussion
    The OAM tools described in this document include tools for P2P
    services, as well as tools for P2MP services.
    The distinction between P2P services and P2MP services affects the
    corresponding OAM tools.  A P2P service is typically simpler to
    monitor, as it consists of a single pair of endpoints.  P2MP and
    MP2MP services present several challenges.  For example, in a P2MP
    service, the OAM mechanism not only verifies that each of the
    destinations is reachable from the source but also verifies that
    the P2MP distribution tree is intact and loop-free.

2.2.10. Failures

 The terms "Failure", "Fault", and "Defect" are used interchangeably
 in the standards, referring to a malfunction that can be detected by
 a Connectivity Verification or a Continuity Check.  In some
 standards, such as 802.1ag [IEEE802.1Q], there is no distinction
 between these terms, while in other standards each of these terms
 refers to a different type of malfunction.

Mizrahi, et al. Informational [Page 16] RFC 7276 Overview of OAM Tools June 2014

 The terminology used in IETF MPLS-TP OAM is based on the ITU-T
 terminology, which distinguishes between these three terms in
 [ITU-T-G.806] as follows:
 Fault
 The term "Fault" refers to an inability to perform a required action,
 e.g., an unsuccessful attempt to deliver a packet.
 Defect
 The term "Defect" refers to an interruption in the normal operation,
 such as a consecutive period of time where no packets are delivered
 successfully.
 Failure
 The term "Failure" refers to the termination of the required
 function.  While a Defect typically refers to a limited period of
 time, a failure refers to a long period of time.

3. OAM Functions

 This subsection provides a brief summary of the common OAM functions
 used in OAM-related standards.  These functions are used as building
 blocks in the OAM standards described in this document.
 o  Connectivity Verification (CV), Path Verification, and Continuity
    Check (CC):
    As defined in Section 2.2.7.
 o  Path Discovery / Fault Localization:
    This function can be used to trace the route to a destination,
    i.e., to identify the nodes along the route to the destination.
    When more than one route is available to a specific destination,
    this function traces one of the available routes.  When a failure
    occurs, this function attempts to detect the location of the
    failure.
    Note that the term "route tracing" (or "Traceroute"), which is
    used in the context of IP and MPLS, is sometimes referred to as
    "path tracing" in the context of other protocols, such as TRILL.

Mizrahi, et al. Informational [Page 17] RFC 7276 Overview of OAM Tools June 2014

 o  Performance Monitoring:
    Typically refers to:
  • Loss Measurement (LM) - monitors the packet loss rate.
  • Delay Measurement (DM) - monitors the delay and delay variation

(jitter).

4. OAM Tools in the IETF - A Detailed Description

 This section presents a detailed description of the sets of OAM-
 related tools in each of the toolsets in Table 1.

4.1. IP Ping

 Ping is a common network diagnostic application for IP networks that
 use ICMP.  According to [NetTerms], 'Ping' is an abbreviation for
 Packet internet groper, although the term has been so commonly used
 that it stands on its own.  As defined in [NetTerms], it is a program
 used to test reachability of destinations by sending them an ICMP
 Echo request and waiting for a reply.
 The ICMP Echo request/reply exchange in Ping is used as a Continuity
 Check function for the Internet Protocol.  The originator transmits
 an ICMP Echo request packet, and the receiver replies with an Echo
 reply.  ICMP Ping is defined in two variants: [ICMPv4] is used for
 IPv4, and [ICMPv6] is used for IPv6.
 Ping can be invoked to either a unicast destination or a multicast
 destination.  In the latter case, all members of the multicast group
 send an Echo reply back to the originator.
 Ping implementations typically use ICMP messages.  UDP Ping is a
 variant that uses UDP messages instead of ICMP Echo messages.
 Ping is a single-ended Continuity Check, i.e., it allows the
 *initiator* of the Echo request to test the reachability.  If it is
 desirable for both ends to test the reachability, both ends have to
 invoke Ping independently.
 Note that since ICMP filtering is deployed in some routers and
 firewalls, the usefulness of Ping is sometimes limited in the wider
 Internet.  This limitation is equally relevant to Traceroute.

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4.2. IP Traceroute

 Traceroute ([TCPIP-Tools], [NetTools]) is an application that allows
 users to discover a path between an IP source and an IP destination.
 The most common way to implement Traceroute [TCPIP-Tools] is
 described as follows.  Traceroute sends a sequence of UDP packets to
 UDP port 33434 at the destination.  By default, Traceroute begins by
 sending three packets (the number of packets is configurable in most
 Traceroute implementations), each with an IP Time-To-Live (or Hop
 Limit in IPv6) value of one, to the destination.  These packets
 expire as soon as they reach the first router in the path.
 Consequently, that router sends three ICMP Time Exceeded Messages
 back to the Traceroute application.  Traceroute now sends another
 three UDP packets, each with the TTL value of 2.  These messages
 cause the second router to return ICMP messages.  This process
 continues, with ever-increasing values for the TTL field, until the
 packets actually reach the destination.  Because no application
 listens to port 33434 at the destination, the destination returns
 ICMP Destination Unreachable Messages indicating an unreachable port.
 This event indicates to the Traceroute application that it is
 finished.  The Traceroute program displays the round-trip delay
 associated with each of the attempts.
 While Traceroute is a tool that finds *a* path from A to B, it should
 be noted that traffic from A to B is often forwarded through Equal-
 Cost Multipaths (ECMPs).  Paris Traceroute [PARIS] is an extension to
 Traceroute that attempts to discovers all the available paths from A
 to B by scanning different values of header fields (such as UDP
 ports) in the probe packets.
 It is noted that Traceroute is an application, and not a protocol.
 As such, it has various different implementations.  One of the most
 common ones uses UDP probe packets, as described above.  Other
 implementations exist that use other types of probe messages, such as
 ICMP or TCP.
 Note that IP routing may be asymmetric.  While Traceroute discovers a
 path between a source and destination, it does not reveal the reverse
 path.
 A few ICMP extensions ([ICMP-MP], [ICMP-Int]) have been defined in
 the context of Traceroute.  These documents define several
 extensions, including extensions to the ICMP Destination Unreachable
 message, that can be used by Traceroute applications.

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 Traceroute allows path discovery to *unicast* destination addresses.
 A similar tool [mtrace] was defined for multicast destination
 addresses; it allows tracing the route that a multicast IP packet
 takes from a source to a particular receiver.

4.3. Bidirectional Forwarding Detection (BFD)

4.3.1. Overview

 While multiple OAM tools have been defined for various protocols in
 the protocol stack, Bidirectional Forwarding Detection [BFD], defined
 by the IETF BFD working group, is a generic OAM tool that can be
 deployed over various encapsulating protocols, and in various medium
 types.  The IETF has defined variants of the protocol for IP
 ([BFD-IP], [BFD-Multi]), for MPLS LSPs [BFD-LSP], and for pseudowires
 [BFD-VCCV].  The usage of BFD in MPLS-TP is defined in [TP-CC-CV].
 BFD includes two main OAM functions, using two types of BFD packets:
 BFD Control packets and BFD Echo packets.

4.3.2. Terminology

 BFD operates between *systems*.  The BFD protocol is run between two
 or more systems after establishing a *session*.

4.3.3. BFD Control

 BFD supports a bidirectional Continuity Check, using BFD Control
 packets that are exchanged within a BFD session.  BFD sessions
 operate in one of two modes:
 o  Asynchronous mode (i.e., proactive): in this mode, BFD Control
    packets are sent periodically.  When the receiver detects that no
    BFD Control packets have been received during a predetermined
    period of time, a failure is reported.
 o  Demand mode: in this mode, BFD Control packets are sent on demand.
    Upon need, a system initiates a series of BFD Control packets to
    check the continuity of the session.  BFD Control packets are sent
    independently in each direction.
 Each of the endpoints (referred to as systems) of the monitored path
 maintains its own session identification, called a Discriminator;
 both Discriminators are included in the BFD Control Packets that are
 exchanged between the endpoints.  At the time of session
 establishment, the Discriminators are exchanged between the two
 endpoints.  In addition, the transmission (and reception) rate is

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 negotiated between the two endpoints, based on information included
 in the control packets.  These transmission rates may be renegotiated
 during the session.
 During normal operation of the session, i.e., when no failures have
 been detected, the BFD session is in the Up state.  If no BFD Control
 packets are received during a period of time called the Detection
 Time, the session is declared to be Down.  The detection time is a
 function of the pre-configured or negotiated transmission rate and a
 parameter called Detect Mult.  Detect Mult determines the number of
 missing BFD Control packets that cause the session to be declared as
 Down.  This parameter is included in the BFD Control packet.

4.3.4. BFD Echo

 A BFD Echo packet is sent to a peer system and is looped back to the
 originator.  The echo function can be used proactively or on demand.
 The BFD Echo function has been defined in BFD for IPv4 and IPv6
 ([BFD-IP]), but it is not used in BFD for MPLS LSPs or PWs, or in BFD
 for MPLS-TP.

4.4. MPLS OAM

 The IETF MPLS working group has defined OAM for MPLS LSPs.  The
 requirements and framework of this effort are defined in
 [MPLS-OAM-FW] and [MPLS-OAM], respectively.  The corresponding OAM
 tool defined, in this context, is LSP Ping [LSP-Ping].  OAM for P2MP
 services is defined in [MPLS-P2MP].
 BFD for MPLS [BFD-LSP] is an alternative means for detecting data-
 plane failures, as described below.

4.4.1. LSP Ping

 LSP Ping is modeled after the Ping/Traceroute paradigm, and thus it
 may be used in one of two modes:
 o  "Ping" mode: In this mode, LSP Ping is used for end-to-end
    Connectivity Verification between two LERs.
 o  "Traceroute" mode: This mode is used for hop-by-hop fault
    isolation.

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 LSP Ping is based on the ICMP Ping operation (of data-plane
 Connectivity Verification) with additional functionality to verify
 data-plane vs. control-plane consistency for a Forwarding Equivalence
 Class (FEC) and also to identify Maximum Transmission Unit (MTU)
 problems.
 The Traceroute functionality may be used to isolate and localize MPLS
 faults, using the Time-To-Live (TTL) indicator to incrementally
 identify the sub-path of the LSP that is successfully traversed
 before the faulty link or node.
 The challenge in MPLS networks is that the traffic of a given LSP may
 be load-balanced across Equal-Cost Multipaths (ECMPs).  LSP Ping
 monitors all the available paths of an LSP by monitoring its
 different FECs.  Note that MPLS-TP does not use ECMP, and thus does
 not require OAM over multiple paths.
 Another challenge is that an MPLS LSP does not necessarily have a
 return path; traffic that is sent back from the egress LSR to the
 ingress LSR is not necessarily sent over an MPLS LSP, but it can be
 sent through a different route, such as an IP route.  Thus,
 responding to an LSP Ping message is not necessarily as trivial as in
 IP Ping, where the responder just swaps the source and destination IP
 addresses.  Note that this challenge is not applicable to MPLS-TP,
 where a return path is always available.
 It should be noted that LSP Ping supports unique identification of
 the LSP within an addressing domain.  The identification is checked
 using the full FEC identification.  LSP Ping is extensible to include
 additional information needed to support new functionality, by use of
 Type-Length-Value (TLV) constructs.  The usage of TLVs is typically
 handled by the control plane, as it is not easy to implement in
 hardware.
 LSP Ping supports both asynchronous and on-demand activation.

4.4.2. BFD for MPLS

 BFD [BFD-LSP] can be used to detect MPLS LSP data-plane failures.
 A BFD session is established for each MPLS LSP that is being
 monitored.  BFD Control packets must be sent along the same path as
 the monitored LSP.  If the LSP is associated with multiple FECs, a
 BFD session is established for each FEC.

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 While LSP Ping can be used for detecting MPLS data-plane failures and
 for verifying the MPLS LSP data plane against the control plane, BFD
 can only be used for the former.  BFD can be used in conjunction with
 LSP Ping, as is the case in MPLS-TP (see Section 4.5.4).

4.4.3. OAM for Virtual Private Networks (VPNs) over MPLS

 The IETF has defined two classes of VPNs: Layer 2 VPNs (L2VPNs) and
 Layer 3 VPNs (L3VPNs).  [L2VPN-OAM] provides the requirements and
 framework for OAM in the context of L2VPNs, and specifically it also
 defines the OAM layering of L2VPNs over MPLS.  [L3VPN-OAM] provides a
 framework for the operation and management of L3VPNs.

4.5. MPLS-TP OAM

4.5.1. Overview

 The MPLS working group has defined the OAM toolset that fulfills the
 requirements for MPLS-TP OAM.  The full set of requirements for
 MPLS-TP OAM are defined in [MPLS-TP-OAM] and include both general
 requirements for the behavior of the OAM tools and a set of
 operations that should be supported by the OAM toolset.  The set of
 mechanisms required are further elaborated in [TP-OAM-FW], which
 describes the general architecture of the OAM system and also gives
 overviews of the functionality of the OAM toolset.
 Some of the basic requirements for the OAM toolset for MPLS-TP are:
 o  MPLS-TP OAM must be able to support both an IP-based environment
    and a non-IP-based environment.  If the network is IP based, i.e.,
    IP routing and forwarding are available, then the MPLS-TP OAM
    toolset should rely on the IP routing and forwarding capabilities.
    On the other hand, in environments where IP functionality is not
    available, the OAM tools must still be able to operate without
    dependence on IP forwarding and routing.
 o  OAM packets and the user traffic are required to be congruent
    (i.e., OAM packets are transmitted in-band), and there is a need
    to differentiate OAM packets from ordinary user packets in the
    data plane.  Inherent in this requirement is the principle that
    MPLS-TP OAM be independent of any existing control plane, although
    it should not preclude use of the control-plane functionality.
    OAM packets are identified by the Generic Associated Channel Label
    (GAL), which is a reserved MPLS label value (13).

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4.5.2. Terminology

 Maintenance Entity (ME)
    The MPLS-TP OAM tools are designed to monitor and manage a
    Maintenance Entity (ME).  An ME, as defined in [TP-OAM-FW],
    defines a relationship between two points of a transport path to
    which maintenance and monitoring operations apply.
    The term "Maintenance Entity (ME)" is used in ITU-T
    Recommendations (e.g., [ITU-T-Y1731]), as well as in the MPLS-TP
    terminology ([TP-OAM-FW]).
 Maintenance Entity Group (MEG)
    The collection of one or more MEs that belong to the same
    transport path and that are maintained and monitored as a group
    are known as a Maintenance Entity Group (based on [TP-OAM-FW]).
 Maintenance Point (MP)
    A Maintenance Point (MP) is a functional entity that is defined at
    a node in the network and can initiate and/or react to OAM
    messages.  This document focuses on the data-plane functionality
    of MPs, while MPs interact with the control plane and with the
    management plane as well.
    The term "MP" is used in IEEE 802.1ag and was similarly adopted in
    MPLS-TP ([TP-OAM-FW]).
 MEG End Point (MEP)
    A MEG End Point (MEP) is one of the endpoints of an ME, and can
    initiate OAM messages and respond to them (based on [TP-OAM-FW]).
 MEG Intermediate Point (MIP)
    In between MEPs, there are zero or more intermediate points,
    called MEG Intermediate Points  (based on [TP-OAM-FW]).
    A MEG Intermediate Point (MIP) is an intermediate point that does
    not generally initiate OAM frames (one exception to this is the
    use of AIS notifications) but is able to respond to OAM frames
    that are destined to it.  A MIP in MPLS-TP identifies OAM packets
    destined to it by the expiration of the TTL field in the OAM
    packet.  The term "Maintenance Point" is a general term for MEPs
    and MIPs.

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 Up and Down MEPs
    IEEE 802.1ag [IEEE802.1Q] defines a distinction between Up MEPs
    and Down MEPs.  A MEP monitors traffic in either the direction
    facing the network or the direction facing the bridge.  A Down MEP
    is a MEP that receives OAM packets from and transmits them to the
    direction of the network.  An Up MEP receives OAM packets from and
    transmits them to the direction of the bridging entity.  MPLS-TP
    ([TP-OAM-FW]) uses a similar distinction on the placement of the
    MEP -- at either the ingress, egress, or forwarding function of
    the node (Down / Up MEPs).  This placement is important for
    localization of a failure.
    Note that the terms "Up MEP" and "Down MEP" are entirely unrelated
    to the conventional "Up"/"Down" terminology, where "Down" means
    faulty and "Up" means not faulty.
    The distinction between Up and Down MEPs was defined in
    [TP-OAM-FW], but has not been used in other MPLS-TP RFCs, as of
    the writing of this document.

4.5.3. Generic Associated Channel

 In order to address the requirement for in-band transmission of
 MPLS-TP OAM traffic, MPLS-TP uses a Generic Associated Channel
 (G-ACh), defined in [G-ACh] for LSP-based OAM traffic.  This
 mechanism is based on the same concepts as the PWE3 ACH [PW-ACH] and
 VCCV [VCCV] mechanisms.  However, to address the needs of LSPs as
 differentiated from PW, the following concepts were defined for
 [G-ACh]:
 o  An Associated Channel Header (ACH), which uses a format similar to
    the PW Control Word [PW-ACH], is a 4-byte header that is prepended
    to OAM packets.
 o  A Generic Associated Channel Label (GAL).  The GAL is a reserved
    MPLS label value (13) that indicates that the packet is an ACH
    packet and the payload follows immediately after the label stack.
 It should be noted that while the G-ACh was defined as part of the
 MPLS-TP definition effort, the G-ACh is a generic tool that can be
 used in MPLS in general, and not only in MPLS-TP.

4.5.4. MPLS-TP OAM Toolset

 To address the functionality that is required of the OAM toolset, the
 MPLS WG conducted an analysis of the existing IETF and ITU-T OAM
 tools and their ability to fulfill the required functionality.  The

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 conclusions of this analysis are documented in [OAM-Analys].  MPLS-TP
 uses a mixture of OAM tools that are based on previous standards and
 adapted to the requirements of [MPLS-TP-OAM].  Some of the main
 building blocks of this solution are based on:
 o  Bidirectional Forwarding Detection ([BFD], [BFD-LSP]) for
    proactive Continuity Check and Connectivity Verification.
 o  LSP Ping as defined in [LSP-Ping] for on-demand Connectivity
    Verification.
 o  New protocol packets, using G-ACH, to address different
    functionality.
 o  Performance measurement protocols.
 The following subsections describe the OAM tools defined for MPLS-TP
 as described in [TP-OAM-FW].

4.5.4.1. Continuity Check and Connectivity Verification

 Continuity Checks and Connectivity Verification are presented in
 Section 2.2.7 of this document.  As presented there, these tools may
 be used either proactively or on demand.  When using these tools
 proactively, they are generally used in tandem.
 For MPLS-TP there are two distinct tools: the proactive tool is
 defined in [TP-CC-CV], while the on-demand tool is defined in
 [OnDemand-CV].  In on-demand mode, this function should support
 monitoring between the MEPs and, in addition, between a MEP and MIP.
 [TP-OAM-FW] highlights, when performing Connectivity Verification,
 the need for the CC-V messages to include unique identification of
 the MEG that is being monitored and the MEP that originated the
 message.
 The proactive tool [TP-CC-CV] is based on extensions to BFD (see
 Section 4.3) with the additional limitation that the transmission and
 receiving rates are based on configuration by the operator.  The
 on-demand tool [OnDemand-CV] is an adaptation of LSP Ping (see
 Section 4.4.1) for the required behavior of MPLS-TP.

4.5.4.2. Route Tracing

 [MPLS-TP-OAM] defines that there is a need for functionality that
 would allow a path endpoint to identify the intermediate and
 endpoints of the path.  This function would be used in on-demand
 mode.  Normally, this path will be used for bidirectional PW, LSP,

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 and Sections; however, unidirectional paths may be supported only if
 a return path exists.  The tool for this is based on the LSP Ping
 (see Section 4.4.1) functionality and is described in [OnDemand-CV].

4.5.4.3. Lock Instruct

 The Lock Instruct function [Lock-Loop] is used to notify a transport-
 path endpoint of an administrative need to disable the transport
 path.  This functionality will generally be used in conjunction with
 some intrusive OAM function, e.g., performance measurement or
 diagnostic testing, to minimize the side-effect on user data traffic.

4.5.4.4. Lock Reporting

 Lock Reporting is a function used by an endpoint of a path to report
 to its far-end endpoint that a lock condition has been affected on
 the path.

4.5.4.5. Alarm Reporting

 Alarm reporting [TP-Fault] provides the means to suppress alarms
 following detection of defect conditions at the server sub-layer.
 Alarm reporting is used by an intermediate point of a path, that
 becomes aware of a fault on the path, to report to the endpoints of
 the path.  [TP-OAM-FW] states that this may occur as a result of a
 defect condition discovered at a server sub-layer.  This generates an
 Alarm Indication Signal (AIS) that continues until the fault is
 cleared.  The consequent action of this function is detailed in
 [TP-OAM-FW].

4.5.4.6. Remote Defect Indication

 Remote Defect Indication (RDI) is used proactively by a path endpoint
 to report to its peer endpoint that a defect is detected on a
 bidirectional connection between them.  [MPLS-TP-OAM] points out that
 this function may be applied to a unidirectional LSP only if a return
 path exists.  [TP-OAM-FW] points out that this function is associated
 with the proactive CC-V function.

4.5.4.7. Client Failure Indication

 Client Failure Indication (CFI) is defined in [MPLS-TP-OAM] to allow
 the propagation information from one edge of the network to the
 other.  The information concerns a defect to a client, in the case
 that the client does not support alarm notification.

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4.5.4.8. Performance Monitoring

 The definition of MPLS performance monitoring was motivated by the
 MPLS-TP requirements [MPLS-TP-OAM] but was defined generically for
 MPLS in [MPLS-LM-DM].  An additional document [TP-LM-DM] defines a
 performance monitoring profile for MPLS-TP.

4.5.4.8.1. Packet Loss Measurement (LM)

 Packet Loss Measurement is a function used to verify the quality of
 the service.  Packet loss, as defined in [IPPM-1LM] and
 [MPLS-TP-OAM], indicates the ratio of the number of user packets lost
 to the total number of user packets sent during a defined time
 interval.
 There are two possible ways of determining this measurement:
 o  Using OAM packets, it is possible to compute the statistics based
    on a series of OAM packets.  This, however, has the disadvantage
    of being artificial and may not be representative since part of
    the packet loss may be dependent upon packet sizes and upon the
    implementation of the MEPs that take part in the protocol.
 o  Delimiting messages can be sent at the start and end of a
    measurement period during which the source and sink of the path
    count the packets transmitted and received.  After the end
    delimiter, the ratio would be calculated by the path OAM entity.

4.5.4.8.2. Packet Delay Measurement (DM)

 Packet Delay Measurement is a function that is used to measure one-
 way or two-way delay of a packet transmission between a pair of the
 endpoints of a path (PW, LSP, or Section).  Where:
 o  One-way packet delay, as defined in [IPPM-1DM], 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.  Note that one-way delay
    measurement requires the clocks of the two endpoints to be
    synchronized.
 o  Two-way packet delay, as defined in [IPPM-2DM], 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
    looped-back packet by the same source node, when the loopback is
    performed at the packet's destination node.  Note that due to
    possible path asymmetry, the one-way packet delay from one
    endpoint to another is not necessarily equal to half of the

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    two-way packet delay.  As opposed to one-way delay measurement,
    two-way delay measurement does not require the two endpoints to be
    synchronized.
    For each of these two metrics, the DM function allows the MEP to
    measure the delay, as well as the delay variation.  Delay
    measurement is performed by exchanging timestamped OAM packets
    between the participating MEPs.

4.6. Pseudowire OAM

4.6.1. Pseudowire OAM Using Virtual Circuit Connectivity Verification

      (VCCV)
 VCCV, as defined in [VCCV], provides a means for end-to-end fault
 detection and diagnostic tools to be used for PWs (regardless of the
 underlying tunneling technology).  The VCCV switching function
 provides a Control Channel associated with each PW.  [VCCV] defines
 three Control Channel (CC) types, i.e., three possible methods for
 transmitting and identifying OAM messages:
 o  Control Channel Type 1: In-band VCCV, as described in [VCCV], is
    also referred to as "PWE3 Control Word with 0001b as first
    nibble".  It uses the PW Associated Channel Header [PW-ACH].
 o  Control Channel Type 2: Out-of-band VCCV, as described in [VCCV],
    is also referred to as "MPLS Router Alert Label".  In this case,
    the Control Channel is created by using the MPLS router alert
    label [MPLS-ENCAPS] immediately above the PW label.
 o  Control Channel Type 3: TTL expiry VCCV, as described in [VCCV],
    is also referred to as "MPLS PW Label with TTL == 1", i.e., the
    Control Channel is identified when the value of the TTL field in
    the PW label is set to 1.
 VCCV currently supports the following OAM tools: ICMP Ping, LSP Ping,
 and BFD.  ICMP and LSP Ping are IP encapsulated before being sent
 over the PW ACH.  BFD for VCCV [BFD-VCCV] supports two modes of
 encapsulation -- either IP/UDP encapsulated (with IP/UDP header) or
 PW-ACH encapsulated (with no IP/UDP header) -- and provides support
 to signal the AC status.  The use of the VCCV Control Channel
 provides the context, based on the MPLS-PW label, required to bind
 and bootstrap the BFD session to a particular pseudowire (FEC),
 eliminating the need to exchange Discriminator values.

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 VCCV consists of two components: (1) the signaled component to
 communicate VCCV capabilities as part of the VC label, and (2) the
 switching component to cause the PW payload to be treated as a
 control packet.
 VCCV is not directly dependent upon the presence of a control plane.
 The VCCV capability advertisement may be performed as part of the PW
 signaling when LDP is used.  In case of manual configuration of the
 PW, it is the responsibility of the operator to set consistent
 options at both ends.  The manual option was created specifically to
 handle MPLS-TP use cases where no control plane was a requirement.
 However, new use cases such as pure mobile backhaul find this
 functionality useful too.
 The PWE3 working group has conducted an implementation survey of VCCV
 [VCCV-SURVEY] that analyzes which VCCV mechanisms are used in
 practice.

4.6.2. Pseudowire OAM Using G-ACh

 As mentioned above, VCCV enables OAM for PWs by using a Control
 Channel for OAM packets.  When PWs are used in MPLS-TP networks,
 rather than the Control Channels defined in VCCV, the G-ACh can be
 used as an alternative Control Channel.  The usage of the G-ACh for
 PWs is defined in [PW-G-ACh].

4.6.3. Attachment Circuit - Pseudowire Mapping

 The PWE3 working group has defined a mapping and notification of
 defect states between a pseudowire (PW) and the Attachment Circuits
 (ACs) of the end-to-end emulated service.  This mapping is of key
 importance to the end-to-end functionality.  Specifically, the
 mapping is provided by [PW-MAP], by [L2TP-EC] for L2TPv3 pseudowires,
 and by Section 5.3 of [ATM-L2] for ATM.
 [L2VPN-OAM] provides the requirements and framework for OAM in the
 context of Layer 2 Virtual Private Networks (L2VPNs), and
 specifically it also defines the OAM layering of L2VPNs over
 pseudowires.
 The mapping defined in [Eth-Int] allows an end-to-end emulated
 Ethernet service over pseudowires.

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4.7. OWAMP and TWAMP

4.7.1. Overview

 The IPPM working group in the IETF defines common criteria and
 metrics for measuring performance of IP traffic ([IPPM-FW]).  Some of
 the key RFCs published by this working group have defined metrics for
 measuring connectivity [IPPM-Con], delay ([IPPM-1DM], [IPPM-2DM]),
 and packet loss [IPPM-1LM].  It should be noted that the work of the
 IETF in the context of performance metrics is not limited to IP
 networks; [PM-CONS] presents general guidelines for considering new
 performance metrics.
 The IPPM working group has defined not only metrics for performance
 measurement but also protocols that define how the measurement is
 carried out.  The One-Way Active Measurement Protocol [OWAMP] and the
 Two-Way Active Measurement Protocol [TWAMP] each define a method and
 protocol for measuring performance metrics in IP networks.
 OWAMP [OWAMP] enables measurement of one-way characteristics of IP
 networks, such as one-way packet loss and one-way delay.  For its
 proper operation, OWAMP requires accurate time-of-day setting at its
 endpoints.
 TWAMP [TWAMP] is a similar protocol that enables measurement of both
 one-way and two-way (round-trip) characteristics.
 OWAMP and TWAMP are each comprised of two separate protocols:
 o  OWAMP-Control/TWAMP-Control: used to initiate, start, and stop
    test sessions and to fetch their results.  Continuity Check and
    Connectivity Verification are tested and confirmed by establishing
    the OWAMP/TWAMP Control Protocol TCP connection.
 o  OWAMP-Test/TWAMP-Test: used to exchange test packets between two
    measurement nodes.  Enables the loss and delay measurement
    functions, as well as detection of other anomalies, such as packet
    duplication and packet reordering.
 It should be noted that while [OWAMP] and [TWAMP] define tools for
 performance measurement, they do not define the accuracy of these
 tools.  The accuracy depends on scale, implementation, and network
 configurations.
 Alternative protocols for performance monitoring are defined, for
 example, in MPLS-TP OAM ([MPLS-LM-DM], [TP-LM-DM]) and in Ethernet
 OAM [ITU-T-Y1731].

Mizrahi, et al. Informational [Page 31] RFC 7276 Overview of OAM Tools June 2014

4.7.2. Control and Test Protocols

 OWAMP and TWAMP control protocols run over TCP, while the test
 protocols run over UDP.  The purpose of the control protocols is to
 initiate, start, and stop test sessions, and for OWAMP to fetch
 results.  The test protocols introduce test packets (which contain
 sequence numbers and timestamps) along the IP path under test
 according to a schedule, and they record statistics of packet
 arrival.  Multiple sessions may be simultaneously defined, each with
 a session identifier, and defining the number of packets to be sent,
 the amount of padding to be added (and thus the packet size), the
 start time, and the send schedule (which can be either a constant
 time between test packets or exponentially distributed
 pseudorandomly).  Statistics recorded conform to the relevant IPPM
 RFCs.
 From a security perspective, OWAMP and TWAMP test packets are hard to
 detect because they are simply UDP streams between negotiated port
 numbers, with potentially nothing static in the packets.  OWAMP and
 TWAMP also include optional authentication and encryption for both
 control and test packets.

4.7.3. OWAMP

 OWAMP defines the following logical roles: Session-Sender,
 Session-Receiver, Server, Control-Client, and Fetch-Client.  The
 Session-Sender originates test traffic that is received by the
 Session-Receiver.  The Server configures and manages the session, as
 well as returning the results.  The Control-Client initiates requests
 for test sessions, triggers their start, and may trigger their
 termination.  The Fetch-Client requests the results of a completed
 session.  Multiple roles may be combined in a single host -- for
 example, one host may play the roles of Control-Client, Fetch-Client,
 and Session-Sender, and a second may play the roles of Server and
 Session-Receiver.
 In a typical OWAMP session, the Control-Client establishes a TCP
 connection to port 861 of the Server, which responds with a Server
 greeting message indicating supported security/integrity modes.  The
 Control-Client responds with the chosen communications mode, and the
 Server accepts the mode.  The Control-Client then requests and fully
 describes a test session to which the Server responds with its
 acceptance and supporting information.  More than one test session
 may be requested with additional messages.  The Control-Client then
 starts a test session; the Server acknowledges and then instructs the
 Session-Sender to start the test.  The Session-Sender then sends test
 packets with pseudorandom padding to the Session-Receiver until the
 session is complete or until the Control-Client stops the session.

Mizrahi, et al. Informational [Page 32] RFC 7276 Overview of OAM Tools June 2014

 Once finished, the Session-Sender reports to the Server, which
 recovers data from the Session-Receiver.  The Fetch-Client can then
 send a fetch request to the Server, which responds with an
 acknowledgement and, immediately thereafter, the result data.

4.7.4. TWAMP

 TWAMP defines the following logical roles: Session-Sender,
 Session-Reflector, Server, and Control-Client.  These are similar to
 the OWAMP roles, except that the Session-Reflector does not collect
 any packet information, and there is no need for a Fetch-Client.
 In a typical TWAMP session, the Control-Client establishes a TCP
 connection to port 862 of the Server, and the mode is negotiated as
 in OWAMP.  The Control-Client then requests sessions and starts them.
 The Session-Sender sends test packets with pseudorandom padding to
 the Session-Reflector, which returns them with timestamps inserted.

4.8. TRILL

 The requirements of OAM in TRILL are defined in [TRILL-OAM].  The
 challenge in TRILL OAM, much like in MPLS networks, is that traffic
 between RBridges RB1 and RB2 may be forwarded through more than one
 path.  Thus, an OAM protocol between RBridges RB1 and RB2 must be
 able to monitor all the available paths between the two RBridges.
 During the writing of this document, the detailed definition of the
 TRILL OAM tools is still work in progress.  This subsection presents
 the main requirements of TRILL OAM.
 The main requirements defined in [TRILL-OAM] are:
 o  Continuity Checking (CC) - the TRILL OAM protocol must support a
    function for CC between any two RBridges RB1 and RB2.
 o  Connectivity Verification (CV) - connectivity between two RBridges
    RB1 and RB2 can be verified on a per-flow basis.
 o  Path Tracing - allows an RBridge to trace all the available paths
    to a peer RBridge.
 o  Performance monitoring - allows an RBridge to monitor the packet
    loss and packet delay to a peer RBridge.

Mizrahi, et al. Informational [Page 33] RFC 7276 Overview of OAM Tools June 2014

5. Summary

 This section summarizes the OAM tools and functions presented in this
 document.  This summary is an index to some of the main OAM tools
 defined in the IETF.  This compact index can be useful to all readers
 from network operators to standards development organizations.  The
 summary includes a short subsection that presents some guidance to
 network equipment vendors.

5.1. Summary of OAM Tools

 This subsection provides a short summary of each of the OAM toolsets
 described in this document.
 A detailed list of the RFCs related to each toolset is given in
 Appendix A.1.

Mizrahi, et al. Informational [Page 34] RFC 7276 Overview of OAM Tools June 2014

+———–+——————————————+————+

Toolset Description Transport
Technology

+———–+——————————————+————+

IP Ping Ping ([IntHost], [NetTerms]) is a simple IPv4/IPv6
application for testing reachability that
uses ICMP Echo messages ([ICMPv4],
[ICMPv6]).

+———–+——————————————+————+

IP Traceroute ([TCPIP-Tools], [NetTools]) is IPv4/IPv6
Traceroute an application that allows users to trace
the path between an IP source and an IP
destination, i.e., to identify the nodes
along the path. If more than one path
exists between the source and
destination, Traceroute traces *a* path.
The most common implementation of
Traceroute uses UDP probe messages,
although there are other implementations
that use different probes, such as ICMP
or TCP. Paris Traceroute [PARIS] is an
extension that attempts to discover all
the available paths from A to B by
scanning different values of header
fields.

+———–+——————————————+————+

BFD Bidirectional Forwarding Detection (BFD) generic
is defined in [BFD] as a framework for a
lightweight generic OAM tool. The
intention is to define a base tool
that can be used with various
encapsulation types, network
environments, and various medium
types.

+———–+——————————————+————+

MPLS OAM MPLS LSP Ping, as defined in [MPLS-OAM], MPLS
[MPLS-OAM-FW], and [LSP-Ping], is an OAM
tool for point-to-point and
point-to-multipoint MPLS LSPs.
It includes two main functions: Ping and
Traceroute.
BFD [BFD-LSP] is an alternative means for
detecting MPLS LSP data-plane failures.

Mizrahi, et al. Informational [Page 35] RFC 7276 Overview of OAM Tools June 2014

+———–+——————————————+————+

MPLS-TP OAM MPLS-TP OAM is defined in a set of RFCs. MPLS-TP
The OAM requirements for MPLS Transport
Profile (MPLS-TP) are defined in
[MPLS-TP-OAM]. Each of the tools in the
OAM toolset is defined in its own RFC, as
specified in Appendix A.1.

+———–+——————————————+————+

Pseudowire The PWE3 OAM architecture defines Control Pseudowire
OAM Channels that support the use of existing
IETF OAM tools to be used for a pseudo-
wire (PW). The Control Channels that are
defined in [VCCV] and [PW-G-ACh] may be
used in conjunction with ICMP Ping, LSP
Ping, and BFD to perform CC and CV
functionality. In addition, the channels
support use of any of the MPLS-TP-based
OAM tools for completing their respective
OAM functionality for a PW.

+———–+——————————————+————+

OWAMP and The One-Way Active Measurement Protocol IPv4/IPv6
TWAMP [OWAMP] and the Two-Way Active Measure-
ment Protocol [TWAMP] are two protocols
defined in the IP Performance Metrics
(IPPM) working group in the IETF. These
protocols allow various performance
metrics to be measured, such as packet
loss, delay, delay variation,
duplication, and reordering.

+———–+——————————————+————+

TRILL OAM The requirements of OAM in TRILL are TRILL
defined in [TRILL-OAM]. These
requirements include Continuity Checking,
Connectivity Verification, path tracing,
and performance monitoring. During the
writing of this document, the detailed
definition of the TRILL OAM tools
is work in progress.

+———–+——————————————+————+

           Table 3: Summary of OAM-Related IETF Tools

Mizrahi, et al. Informational [Page 36] RFC 7276 Overview of OAM Tools June 2014

5.2. Summary of OAM Functions

 Table 4 summarizes the OAM functions that are supported in each of
 the toolsets that were analyzed in this section.  The columns of this
 table are the typical OAM functions described in Section 1.3.

+———–+———-+————-+———-+———-+———–+

ContinuityConnectivity Path Perf. Other
Toolset Check Verification Discovery MonitoringFunctions

+———–+———-+————-+———-+———-+———–+

IP Ping Echo

+———–+———-+————-+———-+———-+———–+

IP Traceroute
Traceroute

+———–+———-+————-+———-+———-+———–+

BFD BFD BFD Control RDI using
Control/ BFD Control
Echo

+———–+———-+————-+———-+———-+———–+

MPLS OAM "Ping" mode "Trace-
(LSP Ping) route"
mode

+———–+———-+————-+———-+———-+———–+

MPLS-TP CC CV/proactive Route -LM -Diagnostic
OAM or on demand Tracing -DM Test
-Lock
-Alarm
Reporting
-Client
Failure
Indication
-RDI

+———–+———-+————-+———-+———-+———–+

Pseudowire BFD -BFD LSP Ping
OAM -ICMP Ping
-LSP Ping

+———–+———-+————-+———-+———-+———–+

OWAMP and - control -DM
TWAMP protocol -LM

+———–+———-+————-+———-+———-+———–+

TRILL OAM CC CV Path -DM
tracing -LM

+———–+———-+————-+———-+———-+———–+

     Table 4: Summary of the OAM Functionality in IETF OAM Tools

Mizrahi, et al. Informational [Page 37] RFC 7276 Overview of OAM Tools June 2014

5.3. Guidance to Network Equipment Vendors

 As mentioned in Section 1.4, it is imperative for OAM tools to be
 capable of testing the actual data plane with as much accuracy as
 possible.  While this guideline may appear obvious, it is worthwhile
 to emphasize the key importance of enforcing fate-sharing between OAM
 traffic that monitors the data plane and the data-plane traffic it
 monitors.

6. Security Considerations

 OAM is tightly coupled with the stability of the network.  A
 successful attack on an OAM protocol can create a false illusion of
 nonexistent failures or prevent the detection of actual ones.  In
 both cases, the attack may result in denial of service.
 Some of the OAM tools presented in this document include security
 mechanisms that provide integrity protection, thereby preventing
 attackers from forging or tampering with OAM packets.  For example,
 [BFD] includes an optional authentication mechanism for BFD Control
 packets, using either SHA1, MD5, or a simple password.  [OWAMP] and
 [TWAMP] have three modes of security: unauthenticated, authenticated,
 and encrypted.  The authentication uses SHA1 as the HMAC algorithm,
 and the encrypted mode uses AES encryption.
 Confidentiality is typically not considered a requirement for OAM
 protocols.  However, the use of encryption (e.g., [OWAMP] and
 [TWAMP]) can make it difficult for attackers to identify OAM packets,
 thus making it more difficult to attack the OAM protocol.
 OAM can also be used as a means for network reconnaissance;
 information about addresses, port numbers, and the network topology
 and performance can be gathered by either passively eavesdropping on
 OAM packets or actively sending OAM packets and gathering information
 from the respective responses.  This information can then be used
 maliciously to attack the network.  Note that some of this
 information, e.g., addresses and port numbers, can be gathered even
 when encryption is used ([OWAMP], [TWAMP]).
 For further details about the security considerations of each OAM
 protocol, the reader is encouraged to review the Security
 Considerations section of each document referenced by this memo.

Mizrahi, et al. Informational [Page 38] RFC 7276 Overview of OAM Tools June 2014

7. Acknowledgments

 The authors gratefully acknowledge Sasha Vainshtein, Carlos
 Pignataro, David Harrington, Dan Romascanu, Ron Bonica, Benoit
 Claise, Stewart Bryant, Tom Nadeau, Elwyn Davies, Al Morton, Sam
 Aldrin, Thomas Narten, and other members of the OPSA WG for their
 helpful comments on the mailing list.
 This document was originally prepared using 2-Word-v2.0.template.dot.

8. References

8.1. Normative References

 [OAM-Def]     Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
               D., and S. Mansfield, "Guidelines for the Use of the
               "OAM" Acronym in the IETF", BCP 161, RFC 6291, June
               2011.

8.2. Informative References

 [ATM-L2]      Singh, S., Townsley, M., and C. Pignataro,
               "Asynchronous Transfer Mode (ATM) over Layer 2
               Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May
               2006.
 [BFD]         Katz, D. and D. Ward, "Bidirectional Forwarding
               Detection (BFD)", RFC 5880, June 2010.
 [BFD-Gen]     Katz, D. and D. Ward, "Generic Application of
               Bidirectional Forwarding Detection (BFD)", RFC 5882,
               June 2010.
 [BFD-IP]      Katz, D. and D. Ward, "Bidirectional Forwarding
               Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC
               5881, June 2010.
 [BFD-LSP]     Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
               "Bidirectional Forwarding Detection (BFD) for MPLS
               Label Switched Paths (LSPs)", RFC 5884, June 2010.
 [BFD-Multi]   Katz, D. and D. Ward, "Bidirectional Forwarding
               Detection (BFD) for Multihop Paths", RFC 5883, June
               2010.

Mizrahi, et al. Informational [Page 39] RFC 7276 Overview of OAM Tools June 2014

 [BFD-VCCV]    Nadeau, T., Ed., and C. Pignataro, Ed., "Bidirectional
               Forwarding Detection (BFD) for the Pseudowire Virtual
               Circuit Connectivity Verification (VCCV)", RFC 5885,
               June 2010.
 [Comp]        Bonaventure, O., "Computer Networking: Principles,
               Protocols and Practice", 2008.
 [Dup]         Uijterwaal, H., "A One-Way Packet Duplication Metric",
               RFC 5560, May 2009.
 [Eth-Int]     Mohan, D., Ed., Bitar, N., Ed., Sajassi, A., Ed.,
               DeLord, S., Niger, P., and R. Qiu, "MPLS and Ethernet
               Operations, Administration, and Maintenance (OAM)
               Interworking", RFC 7023, October 2013.
 [G-ACh]       Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
               "MPLS Generic Associated Channel", RFC 5586, June 2009.
 [ICMP-Ext]    Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
               "ICMP Extensions for Multiprotocol Label Switching",
               RFC 4950, August 2007.
 [ICMP-Int]    Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed.,
               Shen, N., and JR. Rivers, "Extending ICMP for Interface
               and Next-Hop Identification", RFC 5837, April 2010.
 [ICMP-MP]     Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
               "Extended ICMP to Support Multi-Part Messages", RFC
               4884, April 2007.
 [ICMPv4]      Postel, J., "Internet Control Message Protocol", STD 5,
               RFC 792, September 1981.
 [ICMPv6]      Conta, A., Deering, S., and M. Gupta, Ed., "Internet
               Control Message Protocol (ICMPv6) for the Internet
               Protocol Version 6 (IPv6) Specification", RFC 4443,
               March 2006.
 [IEEE802.1Q]  IEEE, "IEEE Standard for Local and metropolitan area
               networks - Media Access Control (MAC) Bridges and
               Virtual Bridged Local Area Networks", IEEE 802.1Q,
               October 2012.

Mizrahi, et al. Informational [Page 40] RFC 7276 Overview of OAM Tools June 2014

 [IEEE802.3ah] IEEE, "IEEE Standard for Information technology - Local
               and metropolitan area networks - Carrier sense multiple
               access with collision detection (CSMA/CD) access method
               and physical layer specifications", IEEE 802.3ah,
               clause 57, December 2008.
 [IntHost]     Braden, R., Ed., "Requirements for Internet Hosts -
               Communication Layers", STD 3, RFC 1122, October 1989.
 [IPPM-1DM]    Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
               Delay Metric for IPPM", RFC 2679, September 1999.
 [IPPM-1LM]    Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
               Packet Loss Metric for IPPM", RFC 2680, September 1999.
 [IPPM-2DM]    Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-
               trip Delay Metric for IPPM", RFC 2681, September 1999.
 [IPPM-Con]    Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
               Connectivity", RFC 2678, September 1999.
 [IPPM-FW]     Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
               "Framework for IP Performance Metrics", RFC 2330, May
               1998.
 [ITU-G8113.1] ITU-T, "Operations, Administration and Maintenance
               mechanism for MPLS-TP in Packet Transport Network
               (PTN)",  ITU-T Recommendation G.8113.1/Y.1372.1,
               November 2012.
 [ITU-G8113.2] ITU-T, "Operations, administration and maintenance
               mechanisms for MPLS-TP networks using the tools defined
               for MPLS", ITU-T Recommendation G.8113.2/Y.1372.2,
               November 2012.
 [ITU-T-CT]    Betts, M., "Allocation of a Generic Associated Channel
               Type for ITU-T MPLS Transport Profile Operation,
               Maintenance, and Administration (MPLS-TP OAM)", RFC
               6671, November 2012.
 [ITU-T-G.806] ITU-T, "Characteristics of transport equipment -
               Description methodology and generic functionality",
               ITU-T Recommendation G.806, January 2009.
 [ITU-T-Y1711] ITU-T, "Operation & Maintenance mechanism for MPLS
               networks", ITU-T Recommendation Y.1711, February 2004.

Mizrahi, et al. Informational [Page 41] RFC 7276 Overview of OAM Tools June 2014

 [ITU-T-Y1731] ITU-T, "OAM Functions and Mechanisms for Ethernet-based
               Networks", ITU-T Recommendation G.8013/Y.1731, July
               2011.
 [ITU-Terms]   ITU-R/ITU-T, "ITU-R/ITU-T Terms and Definitions", 2013,
               <http://www.itu.int/pub/R-TER-DB>.
 [L2TP-EC]     McGill, N. and C. Pignataro, "Layer 2 Tunneling
               Protocol Version 3 (L2TPv3) Extended Circuit Status
               Values", RFC 5641, August 2009.
 [L2VPN-OAM]   Sajassi, A., Ed., and D. Mohan, Ed., "Layer 2 Virtual
               Private Network (L2VPN) Operations, Administration, and
               Maintenance (OAM) Requirements and Framework", RFC
               6136, March 2011.
 [L3VPN-OAM]   El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan,
               K., and A. Gonguet, "Framework for Layer 3 Virtual
               Private Networks (L3VPN) Operations and Management",
               RFC 4176, October 2005.
 [Lock-Loop]   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.
 [LSP-Ping]    Kompella, K. and G. Swallow, "Detecting Multi-Protocol
               Label Switched (MPLS) Data Plane Failures", RFC 4379,
               February 2006.
 [Mng]         Farrel, A., "Inclusion of Manageability Sections in
               Path Computation Element (PCE) Working Group Drafts",
               RFC 6123, February 2011.
 [MPLS-ENCAPS] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
               Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
               Encoding", RFC 3032, January 2001.
 [MPLS-LM-DM]  Frost, D. and S. Bryant, "Packet Loss and Delay
               Measurement for MPLS Networks", RFC 6374, September
               2011.
 [MPLS-OAM]    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.

Mizrahi, et al. Informational [Page 42] RFC 7276 Overview of OAM Tools June 2014

 [MPLS-OAM-FW] Allan, D., Ed., and T. Nadeau, Ed., "A Framework for
               Multi-Protocol Label Switching (MPLS) Operations and
               Management (OAM)", RFC 4378, February 2006.
 [MPLS-P2MP]   Yasukawa, S., Farrel, A., King, D., and T. Nadeau,
               "Operations and Management (OAM) Requirements for
               Point-to-Multipoint MPLS Networks", RFC 4687, September
               2006.
 [MPLS-TP-OAM] 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.
 [mtrace]      Fenner, W. and S. Casner, "A "traceroute" facility for
               IP Multicast", Work in Progress, July 2000.
 [NetTerms]    Jacobsen, O. and D. Lynch, "A Glossary of Networking
               Terms", RFC 1208, March 1991.
 [NetTools]    Enger, R. and J. Reynolds, "FYI on a Network Management
               Tool Catalog: Tools for Monitoring and Debugging TCP/IP
               Internets and Interconnected Devices", FYI 2, RFC 1470,
               June 1993.
 [OAM-Analys]  Sprecher, N. and L. Fang, "An Overview of the
               Operations, Administration, and Maintenance (OAM)
               Toolset for MPLS-Based Transport Networks", RFC 6669,
               July 2012.
 [OAM-Label]   Ohta, H., "Assignment of the 'OAM Alert Label' for
               Multiprotocol Label Switching Architecture (MPLS)
               Operation and Maintenance (OAM) Functions", RFC 3429,
               November 2002.
 [OAM-Mng]     Ersue, M., Ed., and B. Claise, "An Overview of the IETF
               Network Management Standards", RFC 6632, June 2012.
 [OnDemand-CV] Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal,
               "MPLS On-Demand Connectivity Verification and Route
               Tracing", RFC 6426, November 2011.
 [OWAMP]       Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and
               M. Zekauskas, "A One-way Active Measurement Protocol
               (OWAMP)", RFC 4656, September 2006.

Mizrahi, et al. Informational [Page 43] RFC 7276 Overview of OAM Tools June 2014

 [PARIS]       Augustin, B., Friedman, T., and R. Teixeira, "Measuring
               Load-balanced Paths in the Internet", IMC '07
               Proceedings of the 7th ACM SIGCOMM conference on
               Internet measurement, 2007.
 [PM-CONS]     Clark, A. and B. Claise, "Guidelines for Considering
               New Performance Metric Development", BCP 170, RFC 6390,
               October 2011.
 [PW-ACH]      Bryant, S., Swallow, G., Martini, L., and D. McPherson,
               "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word
               for Use over an MPLS PSN", RFC 4385, February 2006.
 [PW-G-ACh]    Li, H., Martini, L., He, J., and F. Huang, "Using the
               Generic Associated Channel Label for Pseudowire in the
               MPLS Transport Profile (MPLS-TP)", RFC 6423, November
               2011.
 [PW-MAP]      Aissaoui, M., Busschbach, P., Martini, L., Morrow, M.,
               Nadeau, T., and Y(J). Stein, "Pseudowire (PW)
               Operations, Administration, and Maintenance (OAM)
               Message Mapping", RFC 6310, July 2011.
 [Reorder]     Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
               S., and J. Perser, "Packet Reordering Metrics", RFC
               4737, November 2006.
 [Signal]      Yasukawa, S., Ed., "Signaling Requirements for Point-
               to-Multipoint Traffic-Engineered MPLS Label Switched
               Paths (LSPs)", RFC 4461, April 2006.
 [TCPIP-Tools] Kessler, G. and S. Shepard, "A Primer On Internet and
               TCP/IP Tools and Utilities", FYI 30, RFC 2151, June
               1997.
 [TP-CC-CV]    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.
 [TP-Fault]    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.
 [TP-LM-DM]    Frost, D., Ed., and S. Bryant, Ed., "A Packet Loss and
               Delay Measurement Profile for MPLS-Based Transport
               Networks", RFC 6375, September 2011.

Mizrahi, et al. Informational [Page 44] RFC 7276 Overview of OAM Tools June 2014

 [TP-OAM-FW]   Busi, I., Ed., and D. Allan, Ed., "Operations,
               Administration, and Maintenance Framework for MPLS-
               Based Transport Networks", RFC 6371, September 2011.
 [TP-Term]     van Helvoort, H., Ed., Andersson, L., Ed., and N.
               Sprecher, Ed., "A Thesaurus for the Interpretation of
               Terminology Used in MPLS Transport Profile (MPLS-TP)
               Internet-Drafts and RFCs in the Context of the ITU-T's
               Transport Network Recommendations", RFC 7087, December
               2013.
 [TRILL-OAM]   Senevirathne, T., Bond, D., Aldrin, S., Li, Y., and R.
               Watve, "Requirements for Operations, Administration,
               and Maintenance (OAM) in Transparent Interconnection of
               Lots of Links (TRILL)", RFC 6905, March 2013.
 [TWAMP]       Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and
               J. Babiarz, "A Two-Way Active Measurement Protocol
               (TWAMP)", RFC 5357, October 2008.
 [VCCV]        Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire
               Virtual Circuit Connectivity Verification (VCCV): A
               Control Channel for Pseudowires", RFC 5085, December
               2007.
 [VCCV-SURVEY] Del Regno, N., Ed., and A. Malis, Ed., "The Pseudowire
               (PW) and Virtual Circuit Connectivity Verification
               (VCCV) Implementation Survey Results", RFC 7079,
               November 2013.

Mizrahi, et al. Informational [Page 45] RFC 7276 Overview of OAM Tools June 2014

Appendix A. List of OAM Documents

A.1. List of IETF OAM Documents

 Table 5 summarizes the OAM-related RFCs produced by the IETF.
 It is important to note that the table lists various RFCs that are
 different by nature.  For example, some of these documents define OAM
 tools or OAM protocols (or both), while others define protocols that
 are not strictly OAM related, but are used by OAM tools.  The table
 also includes RFCs that define the requirements or the framework of
 OAM in a specific context (e.g., MPLS-TP).
 The RFCs in the table are categorized in a few sets as defined in
 Section 1.3.
 +-----------+--------------------------------------+----------+
 | Toolset   | Title                                | RFC      |
 +-----------+--------------------------------------+----------+
 |IP Ping    | Requirements for Internet Hosts --   | RFC 1122 |
 |           | Communication Layers [IntHost]       |          |
 |           +--------------------------------------+----------+
 |           | A Glossary of Networking Terms       | RFC 1208 |
 |           | [NetTerms]                           |          |
 |           +--------------------------------------+----------+
 |           | Internet Control Message Protocol    | RFC 792  |
 |           | [ICMPv4]                             |          |
 |           +--------------------------------------+----------+
 |           | Internet Control Message Protocol    | RFC 4443 |
 |           | (ICMPv6) for the Internet Protocol   |          |
 |           | Version 6 (IPv6) Specification       |          |
 |           | [ICMPv6]                             |          |
 +-----------+--------------------------------------+----------+
 |IP         | A Primer On Internet and TCP/IP      | RFC 2151 |
 |Traceroute | Tools and Utilities [TCPIP-Tools]    |          |
 |           +--------------------------------------+----------+
 |           | FYI on a Network Management Tool     | RFC 1470 |
 |           | Catalog: Tools for Monitoring and    |          |
 |           | Debugging TCP/IP Internets and       |          |
 |           | Interconnected Devices [NetTools]    |          |
 |           +--------------------------------------+----------+
 |           | Internet Control Message Protocol    | RFC 792  |
 |           | [ICMPv4]                             |          |
 |           +--------------------------------------+----------+
 |           | Internet Control Message Protocol    | RFC 4443 |
 |           | (ICMPv6) for the Internet Protocol   |          |
 |           | Version 6 (IPv6) Specification       |          |
 |           | [ICMPv6]                             |          |

Mizrahi, et al. Informational [Page 46] RFC 7276 Overview of OAM Tools June 2014

 |           +--------------------------------------+----------+
 |           | Extended ICMP to Support Multi-Part  | RFC 4884 |
 |           | Messages [ICMP-MP]                   |          |
 |           +--------------------------------------+----------+
 |           | Extending ICMP for Interface and     | RFC 5837 |
 |           | Next-Hop Identification [ICMP-Int]   |          |
 +-----------+--------------------------------------+----------+
 |BFD        | Bidirectional Forwarding Detection   | RFC 5880 |
 |           | (BFD) [BFD]                          |          |
 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5881 |
 |           | (BFD) for IPv4 and IPv6 (Single Hop) |          |
 |           | [BFD-IP]                             |          |
 |           +--------------------------------------+----------+
 |           | Generic Application of Bidirectional | RFC 5882 |
 |           | Forwarding Detection (BFD)[BFD-Gen]  |          |
 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5883 |
 |           | (BFD) for Multihop Paths [BFD-Multi] |          |
 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5884 |
 |           | (BFD) for MPLS Label Switched Paths  |          |
 |           | (LSPs) [BFD-LSP]                     |          |
 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5885 |
 |           | for the Pseudowire Virtual Circuit   |          |
 |           | Connectivity Verification (VCCV)     |          |
 |           | [BFD-VCCV]                           |          |
 +-----------+--------------------------------------+----------+
 |MPLS OAM   | Operations and Management (OAM)      | RFC 4377 |
 |           | Requirements for Multi-Protocol Label|          |
 |           | Switched (MPLS) Networks [MPLS-OAM]  |          |
 |           +--------------------------------------+----------+
 |           | A Framework for Multi-Protocol       | RFC 4378 |
 |           | Label Switching (MPLS) Operations    |          |
 |           | and Management (OAM) [MPLS-OAM-FW]   |          |
 |           +--------------------------------------+----------+
 |           | Detecting Multi-Protocol Label       | RFC 4379 |
 |           | Switched (MPLS) Data Plane Failures  |          |
 |           | [LSP-Ping]                           |          |
 |           +--------------------------------------+----------+
 |           | Operations and Management (OAM)      | RFC 4687 |
 |           | Requirements for Point-to-Multipoint |          |
 |           | MPLS Networks [MPLS-P2MP]            |          |
 |           +--------------------------------------+----------+
 |           | ICMP Extensions for Multiprotocol    | RFC 4950 |
 |           | Label Switching [ICMP-Ext]           |          |

Mizrahi, et al. Informational [Page 47] RFC 7276 Overview of OAM Tools June 2014

 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5884 |
 |           | for MPLS Label Switched Paths (LSPs) |          |
 |           | [BFD-LSP]                            |          |
 +-----------+--------------------------------------+----------+
 |MPLS-TP    | Requirements for Operations,         | RFC 5860 |
 |OAM        | Administration, and Maintenance (OAM)|          |
 |           | in MPLS Transport Networks           |          |
 |           | [MPLS-TP-OAM]                        |          |
 |           +--------------------------------------+----------+
 |           | MPLS Generic Associated Channel      | RFC 5586 |
 |           | [G-ACh]                              |          |
 |           +--------------------------------------+----------+
 |           | Operations, Administration, and      | RFC 6371 |
 |           | Maintenance Framework for MPLS-Based |          |
 |           | Transport Networks [TP-OAM-FW]       |          |
 |           +--------------------------------------+----------+
 |           | Proactive Connectivity Verification, | RFC 6428 |
 |           | Continuity Check, and Remote Defect  |          |
 |           | Indication for the MPLS Transport    |          |
 |           | Profile [TP-CC-CV]                   |          |
 |           +--------------------------------------+----------+
 |           | MPLS On-Demand Connectivity          | RFC 6426 |
 |           | Verification and Route Tracing       |          |
 |           | [OnDemand-CV]                        |          |
 |           +--------------------------------------+----------+
 |           | MPLS Fault Management Operations,    | RFC 6427 |
 |           | Administration, and Maintenance (OAM)|          |
 |           | [TP-Fault]                           |          |
 |           +--------------------------------------+----------+
 |           | MPLS Transport Profile Lock Instruct | RFC 6435 |
 |           | and Loopback Functions [Lock-Loop]   |          |
 |           +--------------------------------------+----------+
 |           | Packet Loss and Delay Measurement for| RFC 6374 |
 |           | MPLS Networks [MPLS-LM-DM]           |          |
 |           +--------------------------------------+----------+
 |           | A Packet Loss and Delay Measurement  | RFC 6375 |
 |           | Profile for MPLS-Based Transport     |          |
 |           | Networks [TP-LM-DM]                  |          |
 +-----------+--------------------------------------+----------+
 |Pseudowire | Pseudowire Virtual Circuit           | RFC 5085 |
 |OAM        | Connectivity Verification (VCCV):    |          |
 |           | A Control Channel for Pseudowires    |          |
 |           | [VCCV]                               |          |

Mizrahi, et al. Informational [Page 48] RFC 7276 Overview of OAM Tools June 2014

 |           +--------------------------------------+----------+
 |           | Bidirectional Forwarding Detection   | RFC 5885 |
 |           | for the Pseudowire Virtual Circuit   |          |
 |           | Connectivity Verification (VCCV)     |          |
 |           | [BFD-VCCV]                           |          |
 |           +--------------------------------------+----------+
 |           | Using the Generic Associated Channel | RFC 6423 |
 |           | Label for Pseudowire in the MPLS     |          |
 |           | Transport Profile (MPLS-TP)          |          |
 |           | [PW-G-ACh]                           |          |
 |           +--------------------------------------+----------+
 |           | Pseudowire (PW) Operations,          | RFC 6310 |
 |           | Administration, and Maintenance (OAM)|          |
 |           | Message Mapping [PW-MAP]             |          |
 |           +--------------------------------------+----------+
 |           | MPLS and Ethernet Operations,        | RFC 7023 |
 |           | Administration, and Maintenance (OAM)|          |
 |           | Interworking [Eth-Int]               |          |
 +-----------+--------------------------------------+----------+
 |OWAMP and  | A One-way Active Measurement Protocol| RFC 4656 |
 |TWAMP      | (OWAMP) [OWAMP]                      |          |
 |           +--------------------------------------+----------+
 |           | A Two-Way Active Measurement Protocol| RFC 5357 |
 |           | (TWAMP) [TWAMP]                      |          |
 |           +--------------------------------------+----------+
 |           | Framework for IP Performance Metrics | RFC 2330 |
 |           | [IPPM-FW]                            |          |
 |           +--------------------------------------+----------+
 |           | IPPM Metrics for Measuring           | RFC 2678 |
 |           | Connectivity [IPPM-Con]              |          |
 |           +--------------------------------------+----------+
 |           | A One-way Delay Metric for IPPM      | RFC 2679 |
 |           | [IPPM-1DM]                           |          |
 |           +--------------------------------------+----------+
 |           | A One-way Packet Loss Metric for IPPM| RFC 2680 |
 |           | [IPPM-1LM]                           |          |
 |           +--------------------------------------+----------+
 |           | A Round-trip Delay Metric for IPPM   | RFC 2681 |
 |           | [IPPM-2DM]                           |          |
 |           +--------------------------------------+----------+
 |           | Packet Reordering Metrics            | RFC 4737 |
 |           | [Reorder]                            |          |
 |           +--------------------------------------+----------+
 |           | A One-Way Packet Duplication Metric  | RFC 5560 |
 |           | [Dup]                                |          |

Mizrahi, et al. Informational [Page 49] RFC 7276 Overview of OAM Tools June 2014

 +-----------+--------------------------------------+----------+
 |TRILL OAM  | Requirements for Operations,         | RFC 6905 |
 |           | Administration, and Maintenance (OAM)|          |
 |           | in Transparent Interconnection of    |          |
 |           | Lots of Links (TRILL)                |          |
 +-----------+--------------------------------------+----------+
             Table 5: Summary of IETF OAM-Related RFCs

A.2. List of Selected Non-IETF OAM Documents

 In addition to the OAM tools defined by the IETF, the IEEE and ITU-T
 have also defined various OAM tools that focus on Ethernet and
 various other transport-network environments.  These various tools,
 defined by the three standard organizations, are often tightly
 coupled and have had a mutual effect on each other.  The ITU-T and
 IETF have both defined OAM tools for MPLS LSPs, [ITU-T-Y1711], and
 [LSP-Ping].  The following OAM standards by the IEEE and ITU-T are to
 some extent linked to the IETF OAM tools listed above and are
 mentioned here only as reference material.
 o  OAM tools for Layer 2 have been defined by the ITU-T in
    [ITU-T-Y1731] and by the IEEE in 802.1ag [IEEE802.1Q].  The IEEE
    802.3 standard defines OAM for one-hop Ethernet links
    [IEEE802.3ah].
 o  The ITU-T has defined OAM for MPLS LSPs in [ITU-T-Y1711] and for
    MPLS-TP OAM in [ITU-G8113.1] and [ITU-G8113.2].
 It should be noted that these non-IETF documents deal in many cases
 with OAM functions below the IP layer (Layer 2, Layer 2.5) and that
 in some cases operators use a multi-layered OAM approach, which is a
 function of the way their networks are designed.

Mizrahi, et al. Informational [Page 50] RFC 7276 Overview of OAM Tools June 2014

 Table 6 summarizes some of the main OAM standards published by
 non-IETF standard organizations.  This document focuses on IETF OAM
 standards, but these non-IETF standards are referenced in this
 document where relevant.
 +-----------+--------------------------------------+---------------+
 |           | Title                                | Document      |
 +-----------+--------------------------------------+---------------+
 |ITU-T      | Operation & Maintenance mechanism    | ITU-T Y.1711  |
 |MPLS OAM   | for MPLS networks [ITU-T-Y1711]      |               |
 |           +--------------------------------------+---------------+
 |           | Assignment of the 'OAM Alert Label'  | RFC 3429      |
 |           | for Multiprotocol Label Switching    |               |
 |           | Architecture (MPLS) Operation and    |               |
 |           | Maintenance (OAM) Functions          |               |
 |           | [OAM-Label]                          |               |
 |           |                                      |               |
 |           |  Note: although this is an IETF      |               |
 |           |  document, it is listed as one of the|               |
 |           |  non-IETF OAM standards, since it    |               |
 |           |  was defined as a complementary part |               |
 |           |  of ITU-T Y.1711.                    |               |
 +-----------+--------------------------------------+---------------+
 |ITU-T      | Operations, administration and       |ITU-T G.8113.2 |
 |MPLS-TP OAM| Maintenance mechanisms for MPLS-TP   |               |
 |           | networks using the tools defined for |               |
 |           | MPLS [ITU-G8113.2]                   |               |
 |           |                                      |               |
 |           |  Note: this document describes the   |               |
 |           |  OAM toolset defined by the IETF for |               |
 |           |  MPLS-TP, whereas ITU-T G.8113.1     |               |
 |           |  describes the OAM toolset defined   |               |
 |           |  by the ITU-T.                       |               |
 |           +--------------------------------------+---------------+
 |           | Operations, Administration and       |ITU-T G.8113.1 |
 |           | Maintenance mechanism for MPLS-TP in |               |
 |           | Packet Transport Network (PTN)       |               |

Mizrahi, et al. Informational [Page 51] RFC 7276 Overview of OAM Tools June 2014

 |           +--------------------------------------+---------------+
 |           | Allocation of a Generic Associated   | RFC 6671      |
 |           | Channel Type for ITU-T MPLS Transport|               |
 |           | Profile Operation, Maintenance, and  |               |
 |           | Administration (MPLS-TP OAM)         |               |
 |           | [ITU-T-CT]                           |               |
 |           |                                      |               |
 |           |  Note: although this is an IETF      |               |
 |           |  document, it is listed as one of the|               |
 |           |  non-IETF OAM standards, since it    |               |
 |           |  was defined as a complementary part |               |
 |           |  of ITU-T G.8113.1.                  |               |
 +-----------+--------------------------------------+---------------+
 |ITU-T      | OAM Functions and Mechanisms for     | ITU-T Y.1731  |
 |Ethernet   | Ethernet-based Networks              |               |
 |OAM        | [ITU-T-Y1731]                        |               |
 +-----------+--------------------------------------+---------------+
 |IEEE       | Connectivity Fault Management        | IEEE 802.1ag  |
 |CFM        | [IEEE802.1Q]                         |               |
 |           |                                      |               |
 |           |  Note: CFM was originally published  |               |
 |           |  as IEEE 802.1ag but is now          |               |
 |           |  incorporated in the 802.1Q standard.|               |
 +-----------+--------------------------------------+---------------+
 |IEEE       | Management of Data Driven and Data   | IEEE 802.1ag  |
 |DDCFM      | Dependent Connectivity Faults        |               |
 |           | [IEEE802.1Q]                         |               |
 |           |                                      |               |
 |           |  Note: DDCFM was originally published|               |
 |           |  as IEEE 802.1Qaw but is now         |               |
 |           |  incorporated in the 802.1Q standard.|               |
 +-----------+--------------------------------------+---------------+
 |IEEE       | Media Access Control Parameters,     | IEEE 802.3ah  |
 |802.3      | Physical Layers, and Management      |               |
 |link level | Parameters for Subscriber Access     |               |
 |OAM        | Networks [IEEE802.3ah]               |               |
 |           |                                      |               |
 |           |  Note: link level OAM was originally |               |
 |           |  defined in IEEE 802.3ah and is now  |               |
 |           |  incorporated in the 802.3 standard. |               |
 +-----------+--------------------------------------+---------------+
       Table 6: Non-IETF OAM Standards Mentioned in This Document

Mizrahi, et al. Informational [Page 52] RFC 7276 Overview of OAM Tools June 2014

Authors' Addresses

 Tal Mizrahi
 Marvell
 6 Hamada St.
 Yokneam  20692
 Israel
 EMail: talmi@marvell.com
 Nurit Sprecher
 Nokia Solutions and Networks
 3 Hanagar St. Neve Ne'eman B
 Hod Hasharon  45241
 Israel
 EMail: nurit.sprecher@nsn.com
 Elisa Bellagamba
 Ericsson
 6 Farogatan St.
 Stockholm  164 40
 Sweden
 Phone: +46 761440785
 EMail: elisa.bellagamba@ericsson.com
 Yaacov Weingarten
 34 Hagefen St.
 Karnei Shomron  4485500
 Israel
 EMail: wyaacov@gmail.com

Mizrahi, et al. Informational [Page 53]

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