Re: [OPSAWG] Last Call: <draft-ietf-opsawg-oam-overview-08.txt> (An Overview of Operations, Administration, and Maintenance (OAM) Mechanisms) to Informational RFC

[Thomas Nadeau <[e-mail]>]

	The changes look ok except for one minor one:

	One of the changes in 4.4.2 BFD for MPLS states the following:

The advantage of BFD is that it can	
 	   provide faster failure detection, and scales better to a large number	
 	   of LSPs



	That is a popular misconception. When I at a previous gig we were able to actually figure out how to make them both perform
equally well for CV operations, but we just decided to not implement it that way. I'd suggest removing that sentence altogether.
They are two tools with different implementations, some more optimal than others. 

	

> Hi Tom,
>  
> Thanks again for your comments.
> A link to the updated draft:
> http://tools.ietf.org/html/draft-ietf-opsawg-oam-overview-13
>  
> We believe the current draft addresses all the comments below.
> We have replied to every single comment below (search for [TM]).
>  
> Please let us know if you believe something is still amiss.
>  
> Thanks,
> Tal.
>  
> From: Thomas Nadeau [mailto:[e-mail]] 
> Sent: Monday, January 20, 2014 5:29 PM
> To: Benoit Claise
> Cc: [e-mail]; [e-mail]; IETF Disgust
> Subject: Re: Last Call: <draft-ietf-opsawg-oam-overview-08.txt> (An Overview of Operations, Administration, and Maintenance (OAM) Mechanisms) to Informational RFC
>  
>  
>             Reviewing the current version of the draft (12), many of the comments below are still not addressed.
>  
>             --Tom
>  
>  
>  
> Here is Tom Nadeau's feedback, forwarded with permission:
> 
> Regards, Benoit
> 
> ==============
> 
> Some general comments:
>  
> I did not find any discussion around use of configuration within OAM mechanisms. This is clearly something that is happening in groups like PWE3 and CCAMP. The motivation for this should be explained and documented to at least guide these efforts.
> [TM] The current draft includes a significantly clearer explanation, up front  in the abstract and introduction, that this document focuses on OAM tools, i.e., on the data plane of OAM. That is why, for example we do not discuss configuration contexts such as CCAMP.
> 2. There is no real discussion around the security aspects of these tools. Should there be?
>  
> [TM] We received a similar comment from other reviewers, as well as the SecDir review in the previous IETF last call. After some discussion between our AD at the time (Ron Bonica) and the Sec AD (Sean Turner), the current phrasing of the "Security Considerations" section was agreed. It is mainly an issue of where you draw the line between which content to include and which content not to include in the draft, and security is currently out of scope.
>  
> 3. While the document provides a nice taxonomy of various OAM tools, it does not really discuss the techniques for using them. I do not expect anything in detail, but it is not obvious that many of these tools can be orchestrated to form a "toolset" that can be used to do multi-layer OAM functions for services such as carrier Ethernet over VPLS over MPLS, for example.
>  
> [TM] Following your comment, we added quite a bit of text to the introduction to explain this multi-layer orchestration. You can take full credit for the fact that this doll IETF draft now includes an ASCII art figure (Figure 1). :)
>  
>  
> 4. It might be useful to at least mention in the performance metrics section, a discussion around the accuracy of these tools and how it depends on scale, implementation and network configurations.
> [TM] Following your comment we added a note about this in section 4.7.1. See the paragraphs beginning with “It should be noted that while [OWAMP]…”.
>  
>  
> My detailed comments inline starting with TOM:
>  
> --Tom
>  
>  
>  
>  
>  
>  
> Expires: July 2013                                Nokia Siemens Networks
>                                                            E. Bellagamba
>                                                                 Ericsson
>                                                            Y. Weingarten
>  
>                                                          January 9, 2013
>  
>                               An Overview of
>         Operations, Administration, and Maintenance (OAM) Mechanisms
>                    draft-ietf-opsawg-oam-overview-08.txt
>  
>  
> Abstract
>  
>    Operations, Administration, and Maintenance (OAM) is a general term
>    that refers to a toolset that can be used for fault detection and
>    isolation, and for performance measurement. OAM mechanisms have been
>    defined for various layers in the protocol stack, and are used with a
>    variety of protocols.
>  
>    This document presents an overview of the OAM mechanisms that have
>    been defined and are currently being defined by the IETF.
>  
> Status of this Memo
>  
>    This Internet-Draft is submitted to IETF in full conformance with the
>    provisions of BCP 78 and BCP 79.
>  
>    Internet-Drafts are working documents of the Internet Engineering
>    Task Force (IETF), its areas, and its working groups.  Note that
>    other groups may also distribute working documents as Internet-
>    Drafts.
>  
>    Internet-Drafts are draft documents valid for a maximum of six months
>    and may be updated, replaced, or obsoleted by other documents at any
>    time.  It is inappropriate to use Internet-Drafts as reference
>    material or to cite them other than as "work in progress."
>  
>    The list of current Internet-Drafts can be accessed at
>    http://www.ietf.org/ietf/1id-abstracts.txt.
>  
>    The list of Internet-Draft Shadow Directories can be accessed at
>    http://www.ietf.org/shadow.html.
>  
>    This Internet-Draft will expire on July 9, 2013.
>  
>  
>  
> Mizrahi, et al.         Expires July 9, 2013                  [Page 1]
> Internet-Draft       Overview of OAM Mechanisms           January 2013
>  
>  
> Copyright Notice
>  
>    Copyright (c) 2013 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.
>  
> Table of Contents
>  
>  
>    1. Introduction ................................................. 3
>       1.1. The Building Blocks of OAM .............................. 3
>       1.2. Forwarding Plane vs. Management Plane ................... 4
>       1.3. The OAM toolsets ........................................ 4
>       1.4. IETF OAM Documents ...................................... 6
>       1.5. Non-IETF OAM Documents ................................. 10
>    2. Basic Terminology ........................................... 12
>       2.1. Abbreviations .......................................... 12
>       2.2. Terminology used in OAM Standards ...................... 13
>          2.2.1. General Terms ..................................... 13
>          2.2.2. OAM Maintenance Entities .......................... 13
>          2.2.3. OAM Maintenance Points ............................ 14
>          2.2.4. Proactive and On-demand activation ................ 15
>          2.2.5. Connectivity Verification and Continuity Checks ... 15
>          2.2.6. Failures .......................................... 15
>    3. OAM Tools ................................................... 16
>       3.1. IP Ping and Traceroute ................................. 16
>          3.1.1. Ping .............................................. 16
>          3.1.2. Traceroute......................................... 16
>       3.2. Bidirectional Forwarding Detection (BFD) ............... 17
>          3.2.1. Overview .......................................... 17
>          3.2.2. BFD Control ....................................... 17
>          3.2.3. BFD Echo .......................................... 18
>       3.3. MPLS OAM ............................................... 18
>       3.4. MPLS-TP OAM ............................................ 19
>          3.4.1. Overview .......................................... 19
>          3.4.2. Generic Associated Channel ........................ 19
>          3.4.3. MPLS-TP OAM Toolset ............................... 20
>             3.4.3.1. Continuity Check and Connectivity Verification 20
>  
>  
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>  
>  
>             3.4.3.2. Route Tracing ................................ 21
>             3.4.3.3. Lock Instruct ................................ 21
>             3.4.3.4. Lock Reporting ............................... 21
>             3.4.3.5. Alarm Reporting .............................. 21
>             3.4.3.6. Remote Defect Indication ..................... 22
>             3.4.3.7. Client Failure Indication .................... 22
>             3.4.3.8. Packet Loss Measurement (LM) ................. 22
>             3.4.3.9. Packet Delay Measurement (DM) ................ 22
>       3.5. PWE3 OAM ............................................... 23
>          3.5.1. PWE3 OAM using Virtual Circuit Connectivity Verification
>          (VCCV) ................................................... 23
>          3.5.2. PWE3 OAM using G-ACh .............................. 24
>       3.6. OWAMP and TWAMP......................................... 24
>          3.6.1. Overview .......................................... 24
>          3.6.2. Control and Test Protocols ........................ 24
>          3.6.3. OWAMP ............................................. 25
>          3.6.4. TWAMP ............................................. 26
>       3.7. Summary of OAM Functions ............................... 26
>    4. Security Considerations ..................................... 27
>    5. IANA Considerations ......................................... 27
>    6. Acknowledgments ............................................. 27
>    7. References .................................................. 28
>       7.1. Normative References ................................... 28
>       7.2. Informative References ................................. 31
>  
> 1. Introduction
>  
>    OAM is a general term that refers to a toolset for detecting,
>    isolating and reporting connection failures and performance
>    degradation.
>  
>    This document summarizes the OAM tools and mechanisms defined in the
>    IETF.
>  
>    The term OAM in this document refers to Operations, Administration
>    and Maintenance [OAM-Def], focusing on the forwarding plane of OAM.
>    Hence, management aspects are outside the scope of this document.
>  
> TOM: This is a curious sentence to me since to me, OAM is management, or a subset of it.   Also, if you look at the referenced documents, there are many indirect references to MIBs, Netconf, etc… making this sentence further confusing. It might be helpful to explain more clearly that the authors here intended to not cover those things explicitly rather than grouping them arbitrarily under the definition of "management aspects"  Further, to clarify, it might be useful to expand on what "forwarding plane" is here just to be clear.   That is, is this "in band" or "out-of band" or both? Some of the tools referred to here also are part of the control AND data planes. 
> [TM] We significantly improved the distinction between the different planes: data plane, control plane, management plane. We added a definition of each of the terms, and we now explicitly explain that the draft focuses on the data plane. We also explain in the current draft that we adopt the OAM acronym as recommended in RFC 6291: Operations, Administration and Maintenance (without Management...). Please let us know if you think something is still missing here.
>  
>  
> 1.1. The Building Blocks of OAM
>  
>    An OAM protocol is run in the context of a Maintenance Domain,
>    consisting of two or more nodes that run the OAM protocol, referred
>    to as Maintenance Points (MP).
>  
>    This subsection provides a brief summary of the common tools used by
>    OAM protocols. An OAM protocol typically supports one or more of the
>    tools described below.
>  
>  
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>  
>  
>    o Continuity Checking (CC):
>       Used for verifying the liveness of a connection between two MPs.
>  
>    o Connectivity Verification (CV):
>       Allows an MP to check whether it is connected to a peer MP, and to
>       verify that messages from the peer MP are received through the
>       expected path.
>  
>    o Path Discovery / Fault Localization:
>       An MP uses this mechanism to trace the route to a peer MP, i.e.,
>       to identify the nodes along the path to the peer MP. When a
>       connection fails, this mechanism also allows the MP to detect the
>       location of the failure.
>  
> TOM: The definition calls this "path discovery" but then talks about tracing routes. A better way of describing this in the paragraph would be that there I a use of path tracing in order to discover (or re-discover) paths that have been changed, created or destroyed.  
> [TM] We rephrased this paragraph, and hopefully it is clearer and more accurate now.
>  
>  
>    o Performance Monitoring:
>       Consists of 3 main functions
>  
>         o Loss Measurement (LM) - monitors the packet loss rate of a
>           connection.
>  
>         o Delay Measurement (DM) - monitors the delay and delay
>           variation between MPs.
>  
>         o Throughput measurement - monitors the throughput of a
>           connection.
>  
> TOM: Along with the discussion above around path trace/discovery, it is imperative that paths be discovered (one way or another) in order to successfully d performance monitoring on those paths.
> [TM] True. However this section presents a short list of typical OAM functions, and we would rather stick with succinct descriptions in this section.
>  
>  
> 1.2. Forwarding Plane vs. Management Plane
>  
>    While the OAM tools may, and quite often do, work in conjunction with
>    a control-plane or management plane, they are usually defined to be
>    independent of the control-plane.  The OAM tools communicate with the
>    management plane to raise alarms, and often the on-demand tools may
>    be activated by the management, e.g. to locate and localize problems.
>  
>    The considerations of the control-plane maintenance tools or the
>    functionality of the management-plane are out of scope for this
>    document, which will concentrate on presenting the forwarding-plane
>    tools that are used for OAM.
>  
> TOM: What about the data plane? For example, the GACH OAM type is such an example. VCCV also operates within the data plane after its configuration capabilities have been signaled.  It should also be mentioned that it is imperative that when required, OAM tools are capable of testing the actual data plane in as much accuracy as possible, but that they all should note how accurate.   Not all OAM tools are created equal.
> [TM] We rephrased this subsection, and now have a much clearer definition of each plane in “2.2.4. Data Plane, Control Plane and Management Plane”. We also added specific text about the importance of fate-sharing (see section 1.4), which addresses the second part of your comment.
>  
>  
> 1.3. The OAM toolsets
>  
>    This memo provides an overview of the different sets of OAM
>    mechanisms defined by the IETF. It is intended for those with little
>    or no familiarity with the described mechanisms. The set of OAM
>    mechanisms described in this memo are applicable to IP unicast, MPLS,
>    pseudowires, and MPLS for the transport environment (MPLS-TP). While
>    OAM mechanisms that are applicable to other technologies exist, they
>  
>  
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>  
>  
>    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 mechanisms in several
>    different fronts:
>  
>    o IP Ping and Traceroute:
>       Ping is a very simple and common application for failure diagnosis
>  
> TOM: I am not sure the term "common" is necessary.
> [TM] Removed.
>  
>       that uses ICMP Echo requests, as defined in [ICMPv4], and
>       [ICMPv6].
>       Traceroute ([TCPIP-Tools], [NetTools]) is 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.
>  
>    o BFD:
>       Bidirectional Forwarding Detection (BFD) is defined in [BFD] as a
>       framework for a lightweight generic OAM mechanism.  The intention
>       is to define a base mechanism that can be used with various
>       encapsulation types, network environments, and in various medium
>       types.
>  
>    o MPLS OAM:
>       MPLS LSP Ping, as defined in [MPLS-OAM], [MPLS-OAM-FW] and [LSP-
>       Ping], is an OAM mechanism for point to point MPLS LSPs. It
>       includes two main functions: Ping and Traceroute.
>  
>    o MPLS-TP OAM:
>       MPLS-TP OAM is defined in a set of RFCs. 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 Section 1.4.
>  
>    o PWE3 OAM:
>       The PWE3 OAM architecture defines control channels that support
>       the use of existing IETF OAM tools to be used for a pseudowire
>       (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.
>  
>    o OWAMP and TWAMP:
>       The One Way Active Measurement Protocol (OWAMP) and the Two Way
>       Active Measurement Protocols (TWAMP) are two protocols defined in
>       the IP Performance Metrics (IPPM) working group in the IETF. These
>       protocols allow delay and packet loss measurement in IP networks.
>  
>  
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>  
>  
>    This document summarizes the OAM mechanisms defined by the IETF. We
>    first present a comparison of the terminology used in various OAM
>    standards, and then summarize the OAM functions that each OAM
>    standard provides.
>  
> 1.4. IETF OAM Documents
>  
>    Table 1 summarizes the IETF OAM related RFCs discussed in this
>    document.
>  
>    The table includes a "Type" column, specifying the nature of each of
>    the listed documents:
>  
>    o Tool: documents that define an OAM tool or mechanism.
>  
>    o Prof.: documents that define a profile or a variant for an OAM
>       tool that is defined in other documents.
>  
>    o Inf.: documents that define an infrastructure that is used by OAM
>       tools.
>  
>    o Misc.: other OAM related documents, e.g., OAM requirement and
>       framework documents.
>  
>    +-----------+--------------------------------------+-----+----------+
>    |           | Title                                |Type | RFC      |
>    +-----------+--------------------------------------+-----+----------+
>    |IP Ping and| Internet Control Message Protocol    |Tool | RFC 792  |
>    |Traceroute | [ICMPv4]                             |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Internet Control Message Protocol    |Tool | RFC 4443 |
>    |           | (ICMPv6) for the Internet Protocol   |     |          |
>    |           | Version 6 (IPv6) Specification       |     |          |
>    |           | [ICMPv6]                             |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A Primer On Internet and TCP/IP      |Tool | RFC 2151 |
>    |           | Tools and Utilities [TCPIP-Tools]    |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | FYI on a Network Management Tool     |Tool | RFC 1147 |
>    |           | Catalog: Tools for Monitoring and    |     |          |
>    |           | Debugging TCP/IP Internets and       |     |          |
>    |           | Interconnected Devices [NetTools]    |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Extended ICMP to Support Multi-Part  |Tool | RFC 4884 |
>  
>  
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>  
>    |           | Messages [ICMP-MP]                   |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | ICMP Extensions for Multiprotocol    |Tool | RFC 4950 |
>    |           | Label Switching [ICMP-Ext]           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Extending ICMP for Interface and     |Tool | RFC 5837 |
>    |           | Next-Hop Identification [ICMP-Int]   |     |          |
>    +-----------+--------------------------------------+-----+----------+
>    |BFD        | Bidirectional Forwarding Detection   |Tool | RFC 5880 |
>    |           | [BFD]                                |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Bidirectional Forwarding Detection   |Prof.| RFC 5881 |
>    |           | (BFD) for IPv4 and IPv6 (Single Hop) |     |          |
>    |           | [BFD-IP]                             |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Generic Application of Bidirectional |Misc.| RFC 5882 |
>    |           | Forwarding Detection [BFD-Gen]       |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Bidirectional Forwarding Detection   |Prof.| RFC 5883 |
>    |           | (BFD) for Multihop Paths [BFD-Multi] |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Bidirectional Forwarding Detection   |Prof.| RFC 5884 |
>    |           | for MPLS Label Switched Paths (LSPs) |     |          |
>    |           | [BFD-LSP]                            |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Bidirectional Forwarding Detection   |Prof.| RFC 5885 |
>    |           | for the Pseudowire Virtual Circuit   |     |          |
>    |           | Connectivity Verification (VCCV)     |     |          |
>    |           | [BFD-VCCV]                           |     |          |
>    +-----------+--------------------------------------+-----+----------+
>    |MPLS OAM   | Operations and Management (OAM)      |Misc.| RFC 4377 |
>    |           | Requirements for Multi-Protocol Label|     |          |
>    |           | Switched (MPLS) Networks [MPLS-OAM]  |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A Framework for Multi-Protocol       |Misc.| RFC 4378 |
>    |           | Label Switching (MPLS) Operations    |     |          |
>    |           | and Management (OAM) [MPLS-OAM-FW]   |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Detecting Multi-Protocol Label       |Tool | RFC 4379 |
>    |           | Switched (MPLS) Data Plane Failures  |     |          |
>    |           | [LSP-Ping]                           |     |          |
>  
>  
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>  
>    |           +--------------------------------------+-----+----------+
>    |           | Operations and Management (OAM)      |Misc.| RFC 4687 |
>    |           | Requirements for Point-to-Multipoint |     |          |
>    |           | MPLS Networks [MPLS-P2MP]            |     |          |
>    +-----------+--------------------------------------+-----+----------+
>    |MPLS-TP    | Requirements for OAM in MPLS-TP      |Misc.| RFC 5860 |
>    |OAM        | [MPLS-TP-OAM]                        |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | MPLS Generic Associated Channel      |Inf. | RFC 5586 |
>    |           | [G-ACh]                              |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | MPLS-TP OAM Framework                |Misc.| RFC 6371 |
>    |           | [TP-OAM-FW]                          |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Proactive Connectivity Verification, |Tool | RFC 6428 |
>    |           | Continuity Check, and Remote Defect  |     |          |
>    |           | Indication for the MPLS Transport    |     |          |
>    |           | Profile [TP-CC-CV]                   |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | MPLS On-Demand Connectivity          |Tool | RFC 6426 |
>    |           | Verification and Route Tracing       |     |          |
>    |           | [OnDemand-CV]                        |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | MPLS Fault Management Operations,    |Tool | RFC 6427 |
>    |           | Administration, and Maintenance (OAM)|     |          |
>    |           | [TP-Fault]                           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | MPLS Transport Profile Lock Instruct |Tool | RFC 6435 |
>    |           | and Loopback Functions [Lock-Loop]   |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Packet Loss and Delay Measurement for|Tool | RFC 6374 |
>    |           | MPLS Networks [MPLS-LM-DM]           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A Packet Loss and Delay Measurement  |Prof.| RFC 6375 |
>    |           | Profile for MPLS-Based Transport     |     |          |
>    |           | Networks [TP-LM-DM]                  |     |          |
>    +-----------+--------------------------------------+-----+----------+
>    |PWE3 OAM   | Pseudowire Virtual Circuit           |Inf. | RFC 5085 |
>    |           | Connectivity Verification (VCCV):    |     |          |
>    |           | A Control Channel for Pseudowires    |     |          |
>    |           | [VCCV]                               |     |          |
>  
>  
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>  
>  
>    |           +--------------------------------------+-----+----------+
>    |           | Bidirectional Forwarding Detection   |Prof.| RFC 5885 |
>    |           | for the Pseudowire Virtual Circuit   |     |          |
>    |           | Connectivity Verification (VCCV)     |     |          |
>    |           | [BFD-VCCV]                           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Using the Generic Associated Channel |Inf. | RFC 6423 |
>    |           | Label for Pseudowire in the MPLS     |     |          |
>    |           | Transport Profile (MPLS-TP)          |     |          |
>    |           | [PW-G-ACh]                           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Pseudowire (PW) Operations,          |Misc.| RFC 6310 |
>    |           | Administration, and Maintenance (OAM)|     |          |
>    |           | Message Mapping [PW-Map]             |     |          |
>    +-----------+--------------------------------------+-----+----------+
>    |OWAMP and  | A One-way Active Measurement Protocol|Tool | RFC 4656 |
>    |TWAMP      | [OWAMP]                              |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A Two-Way Active Measurement Protocol|Tool | RFC 5357 |
>    |           | [TWAMP]                              |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | Framework for IP Performance Metrics |Misc.| RFC 2330 |
>    |           | [IPPM-FW]                            |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | IPPM Metrics for Measuring           |Misc.| RFC 2678 |
>    |           | Connectivity [IPPM-Con]              |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A One-way Delay Metric for IPPM      |Misc.| RFC 2679 |
>    |           | [IPPM-1DM]                           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A One-way Packet Loss Metric for IPPM|Misc.| RFC 2680 |
>    |           | [IPPM-1LM]                           |     |          |
>    |           +--------------------------------------+-----+----------+
>    |           | A Round-trip Delay Metric for IPPM   |Misc.| RFC 2681 |
>    |           | [IPPM-2DM]                           |     |          |
>    +-----------+--------------------------------------+-----+----------+
>                  Table 1 Summary of IETF OAM Related RFCs
>  
>  
>  
>  
>  
>  
>  
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>  
>  
> 1.5. Non-IETF OAM Documents
>  
>    In addition to the OAM mechanisms defined by the IETF, the IEEE and
>    ITU-T have also defined various OAM mechanisms that focus on
>    Ethernet, and various other transport network environments. These
>    various mechanisms, 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 mechanisms 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 IETF OAM mechanisms listed
>    above and are mentioned here only as reference material:
>  
>    o OAM mechanisms for Ethernet based networks have been defined by
>       both the ITU-T in [ITU-T-Y1731], and by the IEEE in [IEEE802.1ag].
>       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
>       MPLS-TP OAM in [ITU-G8113.1] and [ITU-G8113.2].
>  
>    Table 2 summarizes the OAM standards mentioned in this document. This
>    document focuses on IETF OAM standards, but these non-IETF standards
>    are referenced where relevant.
>  
>    +-----------+--------------------------------------+---------------+
>    |           | Title                                |Standard/Draft |
>    +-----------+--------------------------------------+---------------+
>    |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   |               |
>  
>  
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>  
>  
>    |           | 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)       |               |
>    |           +--------------------------------------+---------------+
>    |           | 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-Y1731]  |
>    |Ethernet   | Ethernet-based Networks              |               |
>    |OAM        |                                      |               |
>    +-----------+--------------------------------------+---------------+
>    |IEEE       | Connectivity Fault Management        | IEEE 802.1ag  |
>    |CFM        | [IEEE802.1ag]                        |               |
>    |           |                                      |               |
>    |           |  Note: CFM was originally published  |               |
>    |           |  as IEEE 802.1ag, 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]               |               |
>    |           |                                      |               |
>  
>  
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>  
>  
>    |           |  Note: link level OAM was originally |               |
>    |           |  defined in IEEE 802.3ah, and is now |               |
>    |           |  incorporated in the 802.3 standard. |               |
>    +-----------+--------------------------------------+---------------+
>          Table 2 Non-IETF OAM Standards Mentioned in this Document
>  
> 2. Basic Terminology
>  
> 2.1. Abbreviations
>  
>    ACH    Associated Channel Header
>  
>    AIS    Alarm Indication Signal
>  
>    BFD    Bidirectional Forwarding Detection
>  
>    CC     Continuity Check
>  
>    CV     Connectivity Verification
>  
>    DM     Delay Measurement
>  
>    FEC    Forwarding Equivalence Class
>  
>    GAL    Generic Associated Label
>  
>    ICMP   Internet Control Message Protocol
>  
>    LDP    Label Distribution Protocol
>  
>    LM     Loss Measurement
>  
>    LSP    Label Switched Path
>  
>    ME     Maintenance Entity
>  
>    MEG    Maintenance Entity Group
>  
>    MEP    MEG End Point
>  
>    MIP    MEG Intermediate Point
>  
>    MP     Maintenance Point
>  
>    MPLS   Multiprotocol Label Switching
>  
>  
>  
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>  
>  
>    MPLS-TP MPLS Transport Profile
>  
>    MTU    Maximum Transmission Unit
>  
>    OAM    Operations, Administration, and Maintenance
>  
>    PW     Pseudowire
>  
>    PWE3   Pseudowire Emulation Edge-to-Edge
>  
>    RDI    Remote Defect Indication
>  
>    TTL    Time To Live
>  
>    VCCV   Virtual Circuit Connectivity Verification
>  
>  
> TOM: Why is this section not at the top of this document, as is customary for RFCs?  
> [TM] The introduction is now significantly shorter than it was when you sent this comment, which means that the terminology section is now much closer to the beginning of the document.
>  
>  
> 2.2. Terminology used in OAM Standards
>  
> 2.2.1. General Terms
>  
>    A wide variety of terms is used in various OAM standards. Each of the
>    OAM standards listed in the reference section includes a section that
>    defines terms relevant to that tool. A thesaurus of terminology for
>    MPLS-TP terms is presented in [TP-Term], and provides a good summary
>    of some of the OAM related terminology.
>  
>    This section presents a comparison of the terms used in various OAM
>    standards, without fully quoting the definition of each term. For a
>    formal definition of each term, refer to the references at the end of
>    this document.
>  
> 2.2.2. OAM Maintenance Entities
>  
>    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 following related terms are also quoted from [TP-OAM-FW]:
>  
>    o MEP: The two points that define a maintenance entity.
>  
>    o MEG: The collection of one or more MEs that belongs to the same
>       transport path and that are maintained and monitored as a group
>       are known as a Maintenance Entity Group (MEG).
>  
>  
>  
>  
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>  
>  
>    o MIP: In between MEPs, there are zero or more intermediate points,
>       called Maintenance Entity Group Intermediate Points (MIPs).
>  
>    A pair of MEPs engaged in an ME are connected by a communication
>    link, which may be one of several types of connection, e.g. a single
>    physical connection, a set of physical connections, or a virtual link
>    such as an MPLS LSP.
>  
>    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]). Various terms are used to refer to an ME. For example, BFD does
>    not explicitly use a term that is equivalent to ME, but rather uses
>    the term "session", referring to the relationship between two nodes
>    using a BFD protocol. The MPLS LSP Ping ([LSP-Ping]) terminology
>    simply uses the term "LSP" in this context.
>  
>    MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG)
>    in [TP-OAM-FW], similar to the terms defined by ITU-T.  A MEG allows
>    the monitoring of a compound set of MEs, for example when monitoring
>    a p2mp MEG that is considered to be the set of MEs between the root
>    and each individual destination MEP.
>  
> 2.2.3. OAM Maintenance Points
>  
>    A Maintenance Point (MP) is a functional entity that is defined at a
>    node in the network, and either initiates or reacts to OAM messages.
>    A Maintenance End Point (MEP) is one of the end points of an ME, and
>    can initiate OAM messages and respond to them. A Maintenance
>    Intermediate Point (MIP) is an intermediate point between two MEPs,
>    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 value of the TTL field in the OAM packet. The
>    term Maintenance Point is a general term for MEPs and MIPs.
>  
>    The 802.1ag defines a finer distinction between Up MPs and Down MPs.
>    An MP is a bridge interface, that is monitored by an OAM protocol
>    either in the direction facing the network, or in the direction
>    facing the bridge. A Down MP is an MP that receives OAM packets from,
>    and transmits them to the direction of the network. An Up MP receives
>    OAM packets from, and transmits them to the direction of the bridging
>    entity.
>  
>    MPLS-TP ([TP-OAM-FW]) uses a similar distinction on the placement of
>    the MP - either at the ingress, egress, or forwarding function of the
>    node (Down / Up MPs).  This placement is important for localization
>    of a connection failure.
>  
>  
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>  
>  
> 2.2.4. Proactive and On-demand activation
>  
>    The different OAM tools may be used in one of two basic types of
>    activation:
>  
>    o Proactive activation - indicates that the tool is activated on a
>       continual basis periodically, where messages are sent between the
>       two MEPs, and errors are detected when a certain number of
>       expected messages are not received.
>  
>    o On-demand activation - indicates that the tool is activated
>       "manually" to detect a specific anomaly.  In this activation a
>       small number of OAM messages are sent by a MEP and the reply
>       message is received.
>  
> 2.2.5. 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 checks are used to verify the liveness of a connection or
>    a path between two MPs, and are typically sent proactively, though
>    they can be invoked on-demand as well.
>  
>    A connectivity verification function allows an MP to check whether it
>    is connected to a peer MP or not. This function also allows the MP to
>    verify that messages from the peer MP 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. This allows detection of unexpected topology changes. 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 and continuity checks are considered
>    complementary mechanisms, and are often used in conjunction with each
>    other.
>  
> 2.2.6. Failures
>  
>    The terms Failure, Fault, and Defect are used interchangeably in the
>    standards, referring to a malfunction that can be detected by a
>    connectivity or a continuity check. In some standards, such as
>    [IEEE802.1ag], there is no distinction between these terms, while in
>  
>  
>  
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>  
>  
>    other standards each of these terms refers to a different type of
>    malfunction.
>  
>    The terminology used in IETF MPLS-TP OAM takes after the ITU-T, which
>    distinguishes between these terms in [ITU-T-G.806]; The term Fault
>    refers to an inability to perform a required action, e.g., an
>    unsuccessful attempt to deliver a packet. The term Defect refers to
>    an interruption in the normal operation, such as a consecutive period
>    of time where no packets are delivered successfully. The term Failure
>    refers to the termination of the required function. While a Defect
>    typically refers to a limited period of time, a failure refers to a
>    long period of time.
>  
> 3. OAM Tools
>  
> 3.1. IP Ping and Traceroute
>  
> 3.1.1. Ping
>  
>    Ping is a common network diagnosis application for IP networks that
>    uses ICMP. The ICMP Echo request/reply exchange is a connectivity
>    verification 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.
>  
> 3.1.2. Traceroute
>  
>    Traceroute ([TCPIP-Tools], [NetTools]) is an application that allows
>    users to discover the path between an IP source and an IP
>    destination. 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 (TTL) value
>    of one to the destination. These packets expire as soon as they reach
>    the first router in the path. That router responds by sending three
>    ICMP Time Exceeded Messages 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.
>  
>  
>  
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>  
>  
>    Note that IP routing may be asymmetric. While Traceroute reveals the
>    path between a source and destination, it may not reveal the reverse
>    path.
>  
>    A few ICMP extensions ([ICMP-Ext], [ICMP-MP], [ICMP-Int]) have been
>    defined in the context of Traceroute. These extensions augment the
>    ICMP Destination Unreachable message, and can be used by Traceroute
>    applications.
>  
> 3.2. Bidirectional Forwarding Detection (BFD)
>  
> 3.2.1. Overview
>  
>    While multiple OAM mechanisms 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 mechanism
>    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 PWE3
>    [BFD-VCCV]. The usage of BFD in MPLS-TP is defined in [MPLS-TP-CC-
>    CV].
>  
>    BFD includes two main OAM functions, using two types of BFD packets:
>    BFD Control packets, and BFD Echo packets.
>  
> 3.2.2. 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 packet have been received during a predetermined
>       period of time, a failure is detected.
>  
>    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
>       verify the liveness of the session. BFD control packets are sent
>       independently in each direction.
>  
>    Each of the end-points of the monitored path maintains its own
>    session identification, called a Discriminator, both of which are
>    included in the BFD Control Packets that are exchanged between the
>    end-points.  At the time of session establishment, the Discriminators
>    are exchanged between the two-end points.  In addition, the
>    transmission (and reception) rate is negotiated between the two end-
>  
>  
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>  
>  
>    points, 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. no failures are
>    detected, the BFD session is in the Up state.  If no BFD Control
>    packets are received during a fixed period of time, called the
>  
> TOM: Fixed, pre-configured or negotiated period of time (i.e.: BFD interval)
> [TM] We rephrased this sentence.
>  
>    Detection Time, the session is declared to be Down. The detection
>    time is a function of the negotiated transmission time, 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.
>  
> 3.2.3. 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 is not used in BFD for MPLS LSPs, PWs, or in BFD for
>    MPLS-TP.
>  
> 3.3. 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 mechanism
>    defined, in this context, is LSP Ping [LSP-Ping].
>  
>    LSP Ping is based on ICMP Ping and just like its predecessor 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.
>  
>    LSP Ping extends the basic ICMP Ping operation (of data-plane
>    connectivity verification) with functionality to verify data-plane
>    vs. control-plane consistency for a Forwarding Equivalence Class
>    (FEC) and also Maximum Transmission Unit (MTU) problems. The
>    traceroute functionality may be used to isolate and localize the 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.
>  
>  
>  
>  
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>  
>  
>    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 easily extensible to
>    include additional information needed to support new functionality,
>    by use of Type-Length-Value (TLV) constructs. The usage of TLVs is
>    typically not easy to perform in hardware, and is thus typically
>    handled by the control plane.
>  
>    LSP Ping supports both asynchronous, as well as, on-demand
>    activation.
>  
> 3.4. MPLS-TP OAM
>  
> 3.4.1. Overview
>  
>    The MPLS working group is currently working on defining 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
>    mechanisms 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 as well as giving 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 and 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 user-plane ones. 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.
>  
> 3.4.2. 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
>  
>  
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>  
>  
>    on the same concepts as the PWE3 ACH and 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), that uses a format similar to
>       the PW Control Word, is a 4-byte header that is prepended to OAM
>       packets.
>  
>    o A Generic Associated 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.
>  
> 3.4.3. 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
>    mechanisms and their ability to fulfill the required functionality.
>    The conclusions of this analysis are documented in [OAM-Analys]. The
>    MPLS working group currently plans to use a mixture of OAM mechanisms
>    that are based on various existing standards, and adapt them 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 that are based on the
>       functionality that is described in [ITU-T-Y1731].
>  
>    The following sub-sections describe the OAM tools defined for MPLS-TP
>    as described in [TP-OAM-FW].
>  
> 3.4.3.1. Continuity Check and Connectivity Verification
>  
>    Continuity Check and Connectivity Verification are presented in
>    Section 2.2.5. 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
>  
>  
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>  
>  
>    [OnDemand-CV].Proactively [MPLS-TP-OAM] states that the function
>    should allow the MEPs to monitor the liveness and connectivity of a
>    transport path. 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 3.2. ) 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 3.3. ) for the required behavior of MPLS-TP.
>  
> 3.4.3.2. Route Tracing
>  
>    [MPLS-TP-OAM] defines that there is a need for functionality that
>    would allow a path end-point to identify the intermediate and end-
>    points of the path. This function would be used in on-demand mode.
>    Normally, this path will be used for bidirectional PW, LSP, and
>    sections, however, unidirectional paths may be supported only if a
>    return path exists.  The tool for this is based on the LSP Ping (see
>    Section 3.3. ) functionality and is described in [OnDemand-CV].
>  
> 3.4.3.3. Lock Instruct
>  
>    The Lock Instruct function [Lock-Loop] is used to notify a transport
>    path end-point 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, Diagnostic
>    testing, to minimize the side-effect on user data traffic.
>  
> 3.4.3.4. Lock Reporting
>  
>    Lock Reporting is a function used by an end-point of a path to report
>    to its far-end end-point that a lock condition has been affected on
>    the path.
>  
> 3.4.3.5. Alarm Reporting
>  
>    Alarm Reporting is a function used by an intermediate point of a
>    path, that becomes aware of a fault on the path, to report to the
>    end-points 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
>  
>  
>  
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>  
>  
>    fault is cleared. The consequent action of this function is detailed
>    in [TP-OAM-FW].
>  
> 3.4.3.6. Remote Defect Indication
>  
>    Remote Defect Indication (RDI) is used proactively by a path end-
>    point to report to its peer end-point 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 there a
>    return path exists.  [TP-OAM-FW] points out that this function is
>    associated with the proactive CC-V function.
>  
> 3.4.3.7. 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.
>  
> 3.4.3.8. Packet Loss Measurement (LM)
>  
>    Packet Loss Measurement is a function used to verify the quality of
>    the service. This function indicates the ratio of packets that are
>    not delivered out of all packets that are transmitted by the path
>    source.
>  
>    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.
>  
> TOM: Not just packet sizes. Things like implementation (as I mentioned above with the comment about the accuracy or truthfulness of the data plane processing of OAM packets).  Doing very accurate RTT as a simple example, with just IP Pings, is a tricky thing to make work.  Also, it is important to mention that the scale in terms of number of packets, number of tests, etc… can and will impact these parameters too.
> [TM] Following your comment we rephrased this sentence.
>  
>  
>  
>    o Sending delimiting messages for 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.
>  
> 3.4.3.9. 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
>    end-points of a path (PW, LSP, or Section). Where:
>  
>  
>  
>  
>  
>  
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>  
>  
>    o One-way packet delay is the time elapsed from the start of
>       transmission of the first bit of the packet by a source node until
>       the reception of the last bit of that packet by the destination
>       node.
>  
>    o Two-way packet delay is the time elapsed from the start of
>       transmission of the first bit of the packet by a source node until
>       the reception of the last bit of the loop-backed packet by the
>       same source node, when the loopback is performed at the packet's
>       destination node.
>  
>    Similarly to the packet loss measurement this could be performed in
>    either of the two ways outlined above.
>  
> 3.5. PWE3 OAM
>  
> 3.5.1. PWE3 OAM using Virtual Circuit Connectivity Verification (VCCV)
>  
>    VCCV, as defined in [VCCV], provides a means for end-to-end fault
>    detection and diagnostics tools to be extended for PWs (regardless of
>    the underlying tunneling technology). The VCCV switching function
>    provides a control channel associated with each PW (based on the PW
>    Associated Channel Header (ACH) which is defined in [PW-ACH]), and
>    allows transmitting the OAM packets in-band with PW data (using CC
>    Type 1: In-band VCCV).
>  
>    VCCV currently supports the following OAM mechanisms: 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 pseudo wire (FEC),
>    eliminating the need to exchange Discriminator values.
>  
>    VCCV consists of two components: (1) signaled component to
>    communicate VCCV capabilities as part of VC label, and (2) 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 negotiation 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.
>  
> TOM: Might be helpful to note that the static mode was created specifically to handle the MPLS-TP cases where no control plane was a requirement. However, new use cases such as pure mobile backhaul, etc… find this functionality useful too.
> [TM] Following your comment we added some text to explain this.
>  
>  
>  
>  
>  
>  
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>  
>  
> 3.5.2. PWE3 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].
>  
> 3.6. OWAMP and TWAMP
>  
> 3.6.1. 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].
>  
>    Alternative protocols for performance measurement are defined, for
>    example, in MPLS-TP OAM ([MPLS-LM-DM], [TP-LM-DM]), and in Ethernet
>    OAM [ITU-T-Y1731].
>  
>    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] define a method and
>    protocol for measuring delay and packet loss 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
>    end points.
>  
>    TWAMP [TWAMP] is a similar protocol that enables measurement of two-
>    way (round trip) characteristics.  TWAMP does not require accurate
>    time of day, and, furthermore, allows the use of a simple session
>    reflector, making it an attractive alternative to OWAMP.
>  
>    OWAMP and TWAMP use two separate protocols: a Control plane protocol,
>    and a Test plane protocol.
>  
> 3.6.2. 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
>  
>  
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>  
>  
>    sequence numbers and timestamps) along the IP path under test
>    according to a schedule, and 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 pseudo-random). Statistics
>    recorded conform to the relevant IPPM RFCs.
>  
>    OWAMP and TWAMP test traffic is designed with security in mind.  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.
>  
> 3.6.3. 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 playing 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 modes.  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 and the Server acknowledges.  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.  Once finished, the Fetch-Client sends a
>    fetch request to the server, which responds with an acknowledgement
>    and immediately thereafter the result data.
>  
>  
>  
>  
>  
>  
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>  
>  
> 3.6.4. 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 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 insertion of
>    timestamps.
>  
> 3.7. Summary of OAM Functions
>  
>    Table 3 summarizes the OAM functions that are supported in each of
>    the categories that were analyzed in this section.
>  
>    +-----------+-------+--------+--------+-----------+-------+--------+
>    | Standard  |Continu|Connecti|Path    |Defect     |Perform|Other   |
>    |           |ity    |vity    |Discover|Indications|ance   |Function|
>    |           |Check  |Verifica|y       |           |Monitor|s       |
>    |           |       |tion    |        |           |ing    |        |
>    +-----------+-------+--------+--------+-----------+-------+--------+
>    |IP Ping    |       |Echo    |        |           |       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |IP         |       |        |Tracerou|           |       |        |
>    |Traceroute |       |        |te      |           |       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |BFD        |BFD    |BFD     |        |           |       |        |
>    |           |Control|Echo    |        |           |       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |MPLS OAM   |       |"Ping"  |"Tracero|           |       |        |
>    |(LSP Ping) |       |mode    |ute"    |           |       |        |
>    |           |       |        |mode    |           |       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |MPLS-TP    |CC     |CV/pro- |Route   |-Alarm     |-LM    |-Diagnos|
>    |OAM        |       |active  |Tracing | Reporting |-DM    | tic Tes|
>    |           |       |or on-  |        |-Client    |       | t      |
>    |           |       |demand  |        | Failure   |       |-Lock   |
>    |           |       |        |        | Indication|       |        |
>    |           |       |        |        |-Remote    |       |        |
>  
>  
>  
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>  
>  
>    |           |       |        |        | Defect    |       |        |
>    |           |       |        |        | Indication|       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |PWE3 OAM   |BFD    |-BFD    |LSP-Ping|           |       |        |
>    |           |       |-ICMP   |        |           |       |        |
>    |           |       | Ping   |        |           |       |        |
>    |           |       |-LSP-   |        |           |       |        |
>    |           |       | Ping   |        |           |       |        |
>    + --------- + ----- + ------ + ------ + --------- + ----- + ------ +
>    |OWAMP and  |       |        |        |           |-Delay |        |
>    |TWAMP      |       |        |        |           | measur|        |
>    |           |       |        |        |           | ement |        |
>    |           |       |        |        |           |-Packet|        |
>    |           |       |        |        |           | loss  |        |
>    |           |       |        |        |           | measur|        |
>    |           |       |        |        |           | ement |        |
>    +-----------+-------+--------+--------+-----------+-------+--------+
>                      Table 3 Summary of OAM Functions
>  
> 4. Security Considerations
>  
>    This memo presents an overview of existing OAM mechanisms, and
>    proposes no new OAM mechanisms. Therefore, this document introduces
>    no security considerations. However, the OAM mechanism reviewed in
>    this document can and do present security issues. The reader is
>    encouraged to review the Security Considerations section of each
>    document reference by this memo.
>  
> 5. IANA Considerations
>  
>    There are no new IANA considerations implied by this document.
>  
> 6. Acknowledgments
>  
>    The authors gratefully acknowledge Sasha Vainshtein, Carlos
>    Pignataro, David Harrington, Dan Romascanu, Ron Bonica and other
>    members of the OPSAWG mailing list for their helpful comments.
>  
>    This document was prepared using 2-Word-v2.0.template.dot.
>  
>  
>  
>  
>  
>  
>  
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>  
>  
> 7. References
>  
> 7.1. Normative References
>  
>    [LSP-Ping]    Kompella, K., Swallow, G., "Detecting Multi-Protocol
>                  Label Switched (MPLS) Data Plane Failures", RFC 4379,
>                  February 2006.
>  
>    [MPLS-OAM]    Nadeau, T., Morrow, M., Swallow, G., Allan, D.,
>                  Matsushima, S., "Operations and Management (OAM)
>                  Requirements for Multi-Protocol Label Switched (MPLS)
>                  Networks", RFC 4377, February 2006.
>  
>    [MPLS-OAM-FW] Allan, D., Nadeau, T., "A Framework for Multi-Protocol
>                  Label Switching (MPLS) Operations and Management
>                  (OAM)", RFC 4378, February 2006.
>  
>    [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.
>  
>    [MPLS-TP-OAM] Vigoureux, M., Ward, D., Betts, M., "Requirements for
>                  OAM in MPLS Transport Networks", RFC 5860, May 2010.
>  
>    [G-ACh]       Bocci, M., Vigoureux, M., Bryant, S., "MPLS Generic
>                  Associated Channel", RFC 5586, June 2009.
>  
>    [VCCV]        Nadeau, T., Pignataro, C., "Pseudowire Virtual Circuit
>                  Connectivity Verification (VCCV): A Control Channel
>                  for Pseudowires", RFC 5085, December 2007.
>  
>    [PW-ACH]      Bryant, S., Swallow, G., Martini, L., McPherson, D.,
>                  "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word
>                  for Use over an MPLS PSN", RFC 4385, February 2006.
>  
>    [ICMPv4]      Postel, J., "Internet Control Message Protocol", STD 5,
>                  RFC 792, September 1981.
>  
>    [ICMPv6]      Conta, A., Deering, S., and M. Gupta, "Internet Control
>                  Message Protocol (ICMPv6) for the Internet Protocol
>                  Version 6 (IPv6) Specification", RFC 4443, March 2006.
>  
>    [MPLS-P2MP]   Yasukawa, S., Farrel, A., King, D., Nadeau, T.,
>                  "Operations and Management (OAM) Requirements for
>                  Point-to-Multipoint MPLS Networks", RFC 4687,
>                  September 2006.
>  
>  
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>  
>  
>    [ICMP-Ext]    Bonica, R., Gan, D., Tappan, D., Pignataro, C., "ICMP
>                  Extensions for Multiprotocol Label Switching", RFC
>                  4950, August 2007.
>  
>    [ICMP-MP]     Bonica, R., Gan, D., Tappan, D., Pignataro, C.,
>                  "Extended ICMP to Support Multi-Part Messages", RFC
>                  4884, April 2007.
>  
>    [ICMP-Int]    Atlas, A., Bonica, R., Pignataro, C., Shen, N., Rivers,
>                  JR., "Extending ICMP for Interface and Next-Hop
>                  Identification", RFC 5837, April 2010.
>  
>    [TCPIP-Tools] Kessler, G., Shepard, S., "A Primer On Internet and
>                  TCP/IP Tools and Utilities", RFC 2151, June 1997.
>  
>    [NetTools]    Stine, R., "FYI on a Network Management Tool Catalog:
>                  Tools for Monitoring and Debugging TCP/IP Internets
>                  and Interconnected Devices", RFC 1147, April 1990.
>  
>    [IPPM-FW]     Paxson, V., Almes, G., Mahdavi, J., and Mathis, M.,
>                  "Framework for IP Performance Metrics", RFC 2330, May
>                  1998.
>  
>    [IPPM-Con]    Mahdavi, J., Paxson, V., "IPPM Metrics for Measuring
>                  Connectivity", RFC 2678, September 1999.
>  
>    [IPPM-1DM]    Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
>                  Delay Metric for IPPM", RFC 2679, September 1999.
>  
>    [IPPM-1LM]    Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
>                  Packet Loss Metric for IPPM", RFC 2680, September
>                  1999.
>  
>    [IPPM-2DM]    Almes, G., Kalidindi, S., Zekauskas, M., "A Round-trip
>                  Delay Metric for IPPM", RFC 2681, September 1999.
>  
>    [OWAMP]       Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and
>                  Zekauskas, M., "A One-way Active Measurement Protocol
>                  (OWAMP)", RFC 4656, September 2006.
>  
>    [TWAMP]       Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and
>                  Babiarz, J., "A Two-Way Active Measurement Protocol
>                  (TWAMP)", RFC 5357, October 2008.
>  
>    [BFD]         Katz, D., Ward, D., "Bidirectional Forwarding Detection
>                  (BFD)", RFC 5880, June 2010.
>  
>  
>  
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>  
>  
>    [BFD-IP]      Katz, D., Ward, D., "Bidirectional Forwarding Detection
>                  (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June
>                  2010.
>  
>    [BFD-Gen]     Katz, D., Ward, D., "Generic Application of
>                  Bidirectional Forwarding Detection (BFD)", RFC 5882,
>                  June 2010.
>  
>    [BFD-Multi]   Katz, D., Ward, D., "Bidirectional Forwarding Detection
>                  (BFD) for Multihop Paths", RFC 5883, June 2010.
>  
>    [BFD-LSP]     Aggarwal, R., Kompella, K., Nadeau, T., and Swallow,
>                  G., "Bidirectional Forwarding Detection (BFD) for MPLS
>                  Label Switched Paths (LSPs)", RFC 5884, June 2010.
>  
>    [BFD-VCCV]    Nadeau, T., Pignataro, C., "Bidirectional Forwarding
>                  Detection (BFD) for the Pseudowire Virtual Circuit
>                  Connectivity Verification (VCCV)", RFC 5885, June
>                  2010.
>  
>    [TP-OAM-FW]   Busi, I., Allan, D., "Operations, Administration and
>                  Maintenance Framework for MPLS-based Transport
>                  Networks ", RFC 6371, September 2011.
>  
>    [TP-CC-CV]    Allan, D., Swallow, G., Drake, J., "Proactive
>                  Connectivity Verification, Continuity Check and Remote
>                  Defect indication for MPLS Transport Profile", RFC
>                  6428, November 2011.
>  
>    [OnDemand-CV] Gray, E., Bahadur, N., Boutros, S., Aggarwal, R. "MPLS
>                  On-Demand Connectivity Verification and Route
>                  Tracing", RFC 6426, November 2011.
>  
>    [MPLS-LM-DM]  Frost, D., Bryant, S., "Packet Loss and Delay
>                  Measurement for MPLS Networks", RFC 6374, September
>                  2011.
>  
>    [TP-LM-DM]    Frost, D., Bryant, S., "A Packet Loss and Delay
>                  Measurement Profile for MPLS-Based Transport
>                  Networks", RFC 6375, September 2011.
>  
>    [TP-Fault]    Swallow, G., Fulignoli, A., Vigoureux, M., Boutros, S.,
>                  "MPLS Fault Management Operations, Administration, and
>                  Maintenance (OAM)", RFC 6427, November 2011.
>  
>  
>  
>  
>  
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>  
>  
>    [Lock-Loop]   Boutros, S., Sivabalan, S., Aggarwal, R., Vigoureux,
>                  M., Dai, X., "MPLS Transport Profile Lock Instruct and
>                  Loopback Functions", RFC 6435, November 2011.
>  
>    [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.
>  
>    [PW-Map]      M. Aissaoui, P. Busschbach, L. Martini, M. Morrow, T.
>                  Nadeau, "Pseudowire (PW) Operations, Administration,
>                  and Maintenance (OAM) Message Mapping", RFC 6310, July
>                  2011.
>  
>    [PW-G-ACh]    Li, H., Martini, L., He, J., Huang, F., "Using the
>                  Generic Associated Channel Label for Pseudowire in the
>                  MPLS Transport Profile (MPLS-TP)", RFC 6423, November
>                  2011.
>  
> 7.2. Informative References
>  
>    [OAM-Def]     Andersson, L., Van Helvoort, H., Bonica, R., Romascanu,
>                  D., Mansfield, S., "Guidelines for the use of the OAM
>                  acronym in the IETF ", RFC 6291, June 2011.
>  
>    [OAM-Analys]  Sprecher, N., Fang, L., "An Overview of the OAM Tool
>                  Set for  MPLS based Transport Networks", RFC 6669,
>                  July 2012.
>  
>    [TP-Term]     Van Helvoort, H., Andersson, L., Sprecher, N., "A
>                  Thesaurus for the Terminology used in Multiprotocol
>                  Label Switching Transport Profile (MPLS-TP)
>                  drafts/RFCs and ITU-T's Transport Network
>                  Recommendations", work-in-progress, draft-ietf-mpls-
>                  tp-rosetta-stone, July 2012.
>  
>    [IEEE802.1ag] IEEE 802.1Q, "IEEE Standard for Local and metropolitan
>                  area networks - Media Access Control (MAC) Bridges and
>                  Virtual Bridged Local Area Networks", October 2012.
>  
>    [ITU-T-Y1731] ITU-T Recommendation G.8013/Y.1731, "OAM Functions and
>                  Mechanisms for Ethernet-based Networks", July 2011.
>  
>    [ITU-T-Y1711] ITU-T Recommendation Y.1711, "Operation & Maintenance
>                  mechanism for MPLS networks", February 2004.
>  
>  
>  
>  
> Mizrahi, et al.         Expires July 9, 2013                 [Page 31]
> Internet-Draft       Overview of OAM Mechanisms           January 2013
>  
>  
>    [IEEE802.3ah] IEEE 802.3, "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",
>                  clause 57, December 2008.
>  
>    [ITU-T-G.806] ITU-T Recommendation G.806, "Characteristics of
>                  transport equipment - Description methodology and
>                  generic functionality", January 2009.
>  
>    [ITU-G8113.2] ITU-T Recommendation G.8113.2/Y.1372.2, "Operations,
>                  administration and maintenance mechanisms for MPLS-TP
>                  networks using the tools defined for MPLS", November
>                  2012.
>  
>    [ITU-G8113.1] ITU-T Recommendation G.8113.1/Y.1372.1, "Operations,
>                  Administration and Maintenance mechanism for MPLS-TP
>                  in Packet Transport Network (PTN)", November 2012.
>  
>  
>  
> Authors' Addresses
>  
>    Tal Mizrahi
>    Marvell
>    6 Hamada St.
>    Yokneam, 20692
>    Israel
>  
>    Email: [e-mail]
>  
>  
>    Nurit Sprecher
>    Nokia Siemens Networks
>    3 Hanagar St. Neve Ne'eman B
>    Hod Hasharon,   45241
>    Israel
>  
>    Email: [e-mail]
>  
>  
>    Elisa Bellagamba
>    Ericsson
>    6 Farogatan St.
>    Stockholm,   164 40
>    Sweden
>  
>  
>  
> Mizrahi, et al.         Expires July 9, 2013                 [Page 32]
> Internet-Draft       Overview of OAM Mechanisms           January 2013
>  
>  
>    Phone: [phone]
>    Email: [e-mail]
>  
>  
>    Yaacov Weingarten
>    34 Hagefen St.
>    Karnei Shomron,   4485500
>    Israel
>  
>    Email: [e-mail]
>  
>  
>  
>  
>  
>  
>  
>  
>  
> draft-ietf-opsawg-oam-overview authors,
> 
> Here is my feedback on this document.
> 
> 1.
> Is this document in line with http://tools.ietf.org/html/draft-ietf-trill-oam-req-04? 
> * For example, the following definitions could be reused.
>    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 that over a period of time no packets are delivered
>    successfully.
>  
>    Failure: The term Failure refers to the termination of the required
>    function over a longer period of time. Persistence of a defect for a
>    period of time is interpreted as a failure.
>  
> * For example, on the basic abstract 
> Abstract
>  
>    Operations, Administration, and Maintenance (OAM) is a general term
>    that refers to a toolset that can be used for fault detection and
>    isolation, and for performance measurement. OAM mechanisms have been
>    defined for various layers in the protocol stack, and are used with a
>    variety of protocols.
>  
> Abstract (draft-ietf-trill-oam-req-04)
>  
>    OAM (Operations, Administration and Maintenance) is a general term
>    used to identify functions and toolsets to troubleshoot and monitor
>    networks. This document presents, OAM Requirements applicable to
>    TRILL. 
>  
> So, as an example: does OAM include function? 
> I advice to review draft-ietf-trill-oam-req-04
>  
> 2. 
> draft-ietf-trill-oam is not mentioned, while the abstract mentions:
>    This document presents an overview of the OAM mechanisms that have
>    been defined and are currently being defined by the IETF.
> Search for OAM in the current draft names (https://datatracker.ietf.org/), and you will find many references.
> Ok, I see later on:       
>    This document focuses on IETF
>    documents that have been published as RFCs, while other ongoing OAM-
>    related work is outside the scope.
> Ok, fine then: we don't need a reference to all the drafts. 
> However, draft-ietf-trill-oam is closed to be a RFC, and should be mentioned.
>  
>  
> 3.
> Section 1
>    The term OAM in this document refers to Operations, Administration
>    and Maintenance [OAM-Def], focusing on the forwarding plane of OAM.
> What does it mean "focusing on the forwarding plane of OAM"?
> Do you take a subset of the definition for this document?
> Btw, I don't see a definition in the terminology section.
> In section 2.2.3
>    A Maintenance Point (MP) is a functional entity that is defined at a
>    node in the network, and either initiates or reacts to OAM messages.
> Which plane is MP?
>  
> 4.
> Section 1, Introduction
> "Hence, management aspects are outside the scope of this document."
> I don't understand which management aspects we speak about here.
> 5.
> Clarifying question regarding 1.2
> If speak about OWAMP or TWAMP 'synthetic traffic), is that data plane, control plane, or management plane?
> Note that I found later on in the draft:
>    OWAMP and TWAMP use two separate protocols: a Control plane protocol,
>    and a Test plane protocol.
> Interestingly enough, after reading the document, I reviewed http://datatracker.ietf.org/doc/draft-ietf-opsawg-oam-overview/ballot/, and saw the same feedback from Stewart Bryant:
> Provide a clear view of OAM functionality and its relationship
> to various “planes” of networking (data plane, control plane,
> management plane). In particular, the importance of
> fate-sharing of OAM and user traffic flows in packet networks
> should be explained.
> 6.
> I see a multiplication of "plane" terms in the IETF document, and in this document in particular.
> I could find: forwarding plane, management plane, control plane, data plane, user plane, and test plane.
> Way too many.
> Please be consistent
> 7.
>    Table 1 summarizes the IETF OAM related RFCs discussed in this
>    document.
>  
>    Table 2 summarizes the OAM standards mentioned in this document. 
>  
> You need to change the Table 2 description. Do you want to say something along the lines of:
>    Table 2 summarizes the OAM standards specified by other Standard Development Organization 
>    (SDO) than the IETF, along with IETF references where applicable.
>  
>  
> 8.
> Section 2.2.1
>    For a formal definition of each term, refer to the references at the end of
>    this document.
> Without a reference to a specific RFC, this is the type of statement which is not useful: you have 5 pages of references.
> You position this document as "An Overview of Operations, Administration, and Maintenance (OAM) Mechanisms", but you tell the reader: "if you want to know about the terms,
> just read first all references!"
>  
> 9.
> You specify some terms and some OAM categories, 
>    2.2.2. OAM Maintenance Entities .......................... 13
>          2.2.3. OAM Maintenance Points ............................ 14
>          2.2.4. Proactive and On-demand activation ................ 15
>          2.2.5. Connectivity Verification and Continuity Checks ... 15
>          2.2.6. Failures .......................................... 15
> ... but you don't use them in the section 3
>  
> Just one example with section 3.2.2
> -
>    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
>       verify the liveness of the session
> Instead of liveness, you have defined Connectivity Verification and Continuity Checks in section 2.2.5
> - OLD:
>    Each of the end-points of the monitored path maintains its own
>    session identification
> NEW:
>    Each of the MEP maintains its own session identification
> OR NEW (actually I don't know)
>    Each of the MP maintains its own session identification
> - OLD
>    A BFD echo packet is sent to a peer system
> Peer system = MEP, MP, or something else?
> - etc... 
>  
> 10. 
> This document is composed of a list of OAM content and references, but I'm really missing the document "scope and target audience".
> When we did RFC 6632, which is the companion document, we had http://tools.ietf.org/html/rfc6632#section-1.1
>  
>    The target audience of the document is, on the one hand, IETF working
>    groups, which aim to select appropriate standard management protocols
>    and data models to address their needs concerning network management.
>    On the other hand, the document can be used as an overview and
>    guideline by non-IETF Standards Development Organizations (SDOs)
>    planning to use IETF management technologies and data models for the
>    realization of management applications.  The document can also be
>    used to initiate a discussion between the bodies with the goal to
>    gather new requirements and to detect possible gaps.  Finally, this
>    document is directed to all interested parties that seek to get an
>    overview of the current set of the IETF network management protocols
>    such as network administrators or newcomers to the IETF.
>  
> You should have something similar.
>  
>  
> 11.
> Section 3.6.1, put the paragraph 2 at the end of the section. The "alternative" in the following sentence would then make sense
>    Alternative protocols for performance measurement are defined, for
>    example, in MPLS-TP OAM ([MPLS-LM-DM], [TP-LM-DM]), and in Ethernet
>    OAM [ITU-T-Y1731].
>  
>  
> My conclusions: this document still needs some work
>  
> Regards, Benoit
>  
> The IESG has received a request from the Operations and Management Area
> Working Group WG (opsawg) to consider the following document:
> - 'An Overview of Operations, Administration, and Maintenance (OAM)
>    Mechanisms'
>   <draft-ietf-opsawg-oam-overview-08.txt> as Informational RFC
>  
> The IESG plans to make a decision in the next few weeks, and solicits
> final comments on this action. Please send substantive comments to the
> [e-mail] mailing lists by 2013-01-25. Exceptionally, comments may be
> sent to [e-mail] instead. In either case, please retain the
> beginning of the Subject line to allow automated sorting.
>  
> Abstract
>  
>  
>    Operations, Administration, and Maintenance (OAM) is a general term
>    that refers to a toolset that can be used for fault detection and
>    isolation, and for performance measurement. OAM mechanisms have been
>    defined for various layers in the protocol stack, and are used with a
>    variety of protocols.
>  
>    This document presents an overview of the OAM mechanisms that have
>    been defined and are currently being defined by the IETF.
>  
>  
>  
>  
> The file can be obtained via
> http://datatracker.ietf.org/doc/draft-ietf-opsawg-oam-overview/
>  
> IESG discussion can be tracked via
> http://datatracker.ietf.org/doc/draft-ietf-opsawg-oam-overview/ballot/
>  
>  
> No IPR declarations have been submitted directly on this I-D.
>  
>  
>  
>  
>  
>