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Versions: (draft-sprecher-mpls-tp-oam-analysis) 00 01 02 03 04 05 06 07 08 09 RFC 6669

Network Working Group                                   N. Sprecher, Ed.
Internet-Draft                                    Nokia Siemens Networks
Intended status: Informational                      H. van Helvoort, Ed.
Expires: May 13, 2010                                             Huawei
                                                           E. Bellagamba
                                                                Ericsson
                                                           Y. Weingarten
                                                  Nokia Siemens Networks
                                                            Nov 09, 2009


                          MPLS-TP OAM Analysis
                 draft-ietf-mpls-tp-oam-analysis-00.txt

Abstract

   This document analyzes the set of requirements for Operations,
   Administration, and Maintenance (OAM) for the Transport Profile of
   MPLS(MPLS-TP) as defined in [MPLS-TP OAM Reqs], to evaluate whether
   existing OAM tools (either from the current MPLS toolset or from the
   ITU-T documents) can be applied to these requirements.  Eventually,
   the purpose of the document is to recommend which of the existing
   tools should be extended and what new tools should be defined to
   support the set of OAM requirements for MPLS-TP.  This document
   reports the conclusions of the MPLS-TP design team discussions
   concerning the MPLS-TP OAM tools at IETF75.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on May 13, 2010.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Organization of the document . . . . . . . . . . . . . . .  4
     1.3.  LSP Ping . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.4.  MPLS BFD . . . . . . . . . . . . . . . . . . . . . . . . .  6
     1.5.  PW VCCV  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     1.6.  ITU Recommendation Y.1731  . . . . . . . . . . . . . . . .  8
     1.7.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  9
   2.  Architectural requirements and general principles of
       operation  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     2.1.  Architectural and Principles of Operation -
           Recommendations and Guidelines . . . . . . . . . . . . . . 12
   3.  MPLS-TP OAM Functions  . . . . . . . . . . . . . . . . . . . . 13
     3.1.  Continuity Check and Connectivity Verification . . . . . . 13
       3.1.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 13
       3.1.2.  Gap analysis . . . . . . . . . . . . . . . . . . . . . 14
       3.1.3.  Recommendations and Guidelines . . . . . . . . . . . . 15
     3.2.  Alarm Reporting  . . . . . . . . . . . . . . . . . . . . . 15
       3.2.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 15
       3.2.2.  Recommendations and Guidelines . . . . . . . . . . . . 15
     3.3.  Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . 15
       3.3.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 16
       3.3.2.  Recommendations and Guidelines . . . . . . . . . . . . 16
     3.4.  Route Tracing  . . . . . . . . . . . . . . . . . . . . . . 16
       3.4.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 16
       3.4.2.  Recommendations and Guidelines . . . . . . . . . . . . 16
     3.5.  Lock Instruct  . . . . . . . . . . . . . . . . . . . . . . 16
       3.5.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 16
       3.5.2.  Recommendations and Guidelines . . . . . . . . . . . . 17
     3.6.  Lock Reporting . . . . . . . . . . . . . . . . . . . . . . 17
       3.6.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 17
       3.6.2.  Recommendations and Guidelines . . . . . . . . . . . . 17
     3.7.  Remote Defect Indication . . . . . . . . . . . . . . . . . 17
       3.7.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 17
       3.7.2.  Recommendations and Guidelines . . . . . . . . . . . . 18
     3.8.  Client Failure Indication  . . . . . . . . . . . . . . . . 18
       3.8.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 18
       3.8.2.  Recommendations and Guidelines . . . . . . . . . . . . 18
     3.9.  Packet Loss Measurement  . . . . . . . . . . . . . . . . . 18
       3.9.1.  Existing tools . . . . . . . . . . . . . . . . . . . . 19
       3.9.2.  Recommendations and Guidelines . . . . . . . . . . . . 19
     3.10. Packet Delay Measurement . . . . . . . . . . . . . . . . . 19
       3.10.1. Existing tools . . . . . . . . . . . . . . . . . . . . 20
       3.10.2. Recommendations and Guidelines . . . . . . . . . . . . 20
   4.  Recommendations  . . . . . . . . . . . . . . . . . . . . . . . 20
   5.  MPLS-TP OAM Documents Organization . . . . . . . . . . . . . . 22



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     5.1.  Document 1: "Encapsulation of BFD and LspPing in ACH"  . . 22
     5.2.  Document 2: "Extended BFD" . . . . . . . . . . . . . . . . 23
     5.3.  Document 3: "Extended LSP Ping"  . . . . . . . . . . . . . 23
     5.4.  Document 4: "Extensions for Lock Instruct" . . . . . . . . 24
     5.5.  Document 5: "AIS and Lock Reporting" . . . . . . . . . . . 24
     5.6.  Document 6: "Client Fault Indication"  . . . . . . . . . . 24
     5.7.  Document 7: "Packet Loss"  . . . . . . . . . . . . . . . . 25
     5.8.  Document 8: "Packet Delay" . . . . . . . . . . . . . . . . 25
     5.9.  Document 9: "Diagnostic Tests" . . . . . . . . . . . . . . 25
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   9.  Informative References . . . . . . . . . . . . . . . . . . . . 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27





































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1.  Introduction

1.1.  Scope

   OAM (Operations, Administration, and Maintenance) plays a significant
   role in carrier networks, providing methods for fault management and
   performance monitoring in both the transport and the service layers
   in order to improve their ability to support services with guaranteed
   and strict Service Level Agreements (SLAs) while reducing their
   operational costs.

   [MPLS-TP Reqs] in general, and [MPLS-TP OAM Reqs] in particular
   define a set of requirements for OAM functionality in MPLS-Transport
   Profile (MPLS-TP) for MPLS-TP Label Switched Paths (LSPs) (network
   infrastructure) and Pseudowires (PWs) (services).

   The purpose of this document is to analyze the OAM requirements and
   evaluate whether existing OAM tools defined for MPLS can be used to
   meet the requirements, identify which tools need to be extended to
   comply with the requirements, and which new tools need to be defined.
   We also take the ITU-T OAM toolset, as defined in [Y.1731], as a
   candidate to base these new tools upon.  The existing tools that are
   evaluated include LSP Ping (defined in [LSP Ping]), MPLS Bi-
   directional Forwarding Detection (BFD) (defined in [BASE BFD]) and
   Virtual Circuit Connectivity Verification (VCCV) (defined in [PW
   VCCV] and [VCCV BFD]), and the ITU-T OAM toolset defined in [Y.1731].

   This document reports the conclusions of the MPLS-TP design team
   discussions on the MPLS-TP OAM tools at IETF75 and the guidelines
   that were agreed.  The guidelines refer to a set of existing OAM
   tools that need to be enhanced to fully support the MPLS-TP OAM
   requirements and identify new tools that need to be defined.  The
   organizational structure of the documents on MPLS-TP OAM tools was
   also discussed and agreed at IETF75 and is described later in this
   document.

1.2.  Organization of the document

   Sections 1.3 - 1.6 provide an overview of the existing MPLS tools.

   Section 2 of the document analyzes the requirements that are
   documented in [MPLS-TP OAM Reqs] and provides basic principles of
   operation for the OAM functionality that is required.

   Section 3 evaluates which existing tools can provide coverage for the
   different OAM functions that are required to support MPLS-TP.

   The recommendations are summarized in section 4, and reflect the



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   guidelines which were agreed by the MPLS-TP design team during the
   meetings at IETF 75.  These guidelines relate to the functionality
   could be covered by the existing toolset and what extensions or new
   tools would be needed in order to provide full coverage of the OAM
   functionality for MPLS-TP.

   The OAM tools for MPLS-TP OAM will be defined in a set of documents.
   Section 5 describes the organization of this set of documents as
   agreed by the MPLS-TP design team at IETF75.

1.3.  LSP Ping

   LSP Ping is a variation of ICMP Ping and traceroute [ICMP] adapted to
   the needs of MPLS LSP.  Forwarding, of the LSP Ping packets, is based
   upon the LSP Label and label stack, in order to guarantee that the
   echo messages are switched in-band (i.e. over the same data route) of
   the LSP.  However, it should be noted that the messages are
   transmitted using IP/UDP encapsulation and IP addresses in the 127/8
   (loopback) range.  The use of the loopback range guarantees that the
   LSP Ping messages will be terminated, by a loss of connectivity or
   inability to continue on the path, without being transmitted beyond
   the LSP.  For a bi-directional LSP (either associated or co-routed)
   the return message of the LSP Ping could be sent on the return LSP.
   For unidirectional LSPs and in some case for bi-directional LSPs, the
   return message may be sent using IP forwarding to the IP address of
   the LSP ingress node.

   LSP Ping extends the basic ICMP Ping operation (of data-plane
   connectivity and continuity check) 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.

   As mentioned above, LSP Ping requires the presenece of the MPLS
   control plane when verifying the consistency of the data-plane
   against the control-plane.  However, LSP Ping is not dependent on the
   MPLS control-plane for its operation, i.e. even though the
   propagation of the LSP label may be performed over the control-plane
   via the Label Distribution Protocol (LDP).

   It should be noted that LSP Ping does support 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.



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   LSP Ping can be activated both in on-demand and pro-active
   (asynchronous) modes, as defined in [MPLS-TP OAM Reqs].

   [P2MP LSP Ping] clarifies the applicability of LSP Ping to MPLS P2MP
   LSPs, and extends the techniques and mechanisms of LSP Ping to the
   MPLS P2MP environment.

   [MPLS LSP Ping] extends LSP Ping to operate over MPLS tunnels or for
   a stitched LSP.

   As pointed out above, TTL exhaust is the method used to terminate
   flows at intermediate LSRs.  This is used as part of the traceroute
   of a path and to locate a problem that was discovered previously.

   Some of the drawbacks identified with LSP Ping include - LSP Ping is
   considered to be computational intensive as pointed out in [MPLS
   BFD].  The applicability for a pro-active mode of operation is
   analyzed in the sections below.  Use of the loopback address range
   (to protect against leakage outside the LSP) assumes that all of the
   intermediate nodes support some IP functionality.  Note that ECMP is
   not supported in MPLS-TP, therefore its implication on OAM
   capabilities is not analyzed in this document.

1.4.  MPLS BFD

   BFD (Bidirectional Forwarding Detection) [BASE BFD] is a mechanism
   that is defined for fast fault detection for point-to-point
   connections.  BFD defines a simple packet that may be transmitted
   over any protocol, dependent on the application that is employing the
   mechanism.  BFD is dependent upon creation of a session that is
   agreed upon by both ends of the link (which may be a single link,
   LSP, etc.) that is being checked.  The session is assigned a separate
   identifier by each end of the path being monitored.  This session
   identifier is by nature only unique within the context of node that
   assigned it.  As part of the session creation, the end-points
   negotiate an agreed transmission rate for the BFD packets.  BFD
   supports an echo function to check the continuity, and verify the
   reachability of the desired destination.  BFD does not support
   neither a discovery mechanism nor a traceroute capability for fault
   localization, these must be provided by use of other mechanisms.  The
   BFD packets support authentication between the routers being checked.

   BFD can be used in pro-active (asynchronous) and on-demand modes, as
   defined in [MPLS-TP OAM Reqs], of operation.

   [MPLS BFD] defines the use of BFD for P2P LSP end-points and is used
   to verify data-plane continuity.  It uses a simple hello protocol
   which can be easily implemented in hardware.  The end-points of the



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   LSP exchange hello packets at negotiated regular intervals and an
   end-point is declared down when expected hello packets do not show
   up.  Failures in each direction can be monitored independently using
   the same BFD session.  The use of the BFD echo function and on-demand
   activation are outside the scope of the MPLS BFD specification.

   The BFD session mechanism requires an additional (external) mechanism
   to bootstrap and bind the session to a particular LSP or FEC.  LSP
   Ping is designated by [MPLS BFD] as the bootstrap mechanism for the
   BFD session in an MPLS environment.  The implication is that the
   session establishment BFD messages for MPLS are transmitted using a
   IP/UDP encapsulation.

   In order to be able to identify certain extreme cases of mis-
   connectivity, it is necessary that each managed connection have its
   own unique identifiers.  BFD uses Discriminator values to identify
   the connection being verified, at both ends of the path.  These
   discriminator values are set by each end-node to be unique only in
   the context of that node.  This limited scope of uniqueness would not
   identify a misconnection of crossing paths that could assign the same
   discriminators to the different sessions.

1.5.  PW VCCV

   [PW VCCV] provides end-to-end fault detection and diagnostics 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 sending 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 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



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   PW, it is the responsibility of the operator to set consistent
   options at both ends.

1.6.  ITU Recommendation Y.1731

   [Y.1731] specifies a set of OAM procedures and related packet data
   unit (PDU) formats that meet the transport network requirements for
   OAM.  These PDU and procedures address similar requirements to those
   outlined in [MPLS-TP OAM Reqs].

   The PDU and procedures defined in [Y.1731] are described for an
   Ethernet environment, with the appropriate encapsulation for that
   environment.  However, the actual PDU formats are technology agnostic
   and could be carried over different encapsulations, e.g.  VCCV
   control channel.  The OAM procedures, likewise, could be supported by
   MPLS-TP nodes just as they are supported by Ethernet nodes.

   [Y.1731] describes procedures to support the following OAM functions:

   o  Connectivity and Continuity Monitoring - for pro-active mode end-
      to-end checking

   o  Loopback functionality - to verify connectivity to intermediate
      nodes in an on-demand mode

   o  Link Trace - provides information on the intermediate nodes of the
      path being monitored, may be used for fault localization.  This is
      activated in an on-demand mode.

   o  Alarm Indication Signaling - for alarm suppression in case of
      faults that are detected at the server layer, activated pro-
      actively.

   o  Remote Defect Indication - as part of the Connectivity and
      Continuity Monitoring packets, performed pro-actively

   o  Locked Signal - for alarm suppression in case of administrative
      locking at the server layer.  This function is performed pro-
      actively.

   o  Performance monitoring - including measurement of packet delays
      both uni and bi-directional (on-demand), measurement of the ratio
      of lost packets (pro-active), the effective bandwidth that is
      supported without packet loss, and throughput measurement.

   The PDU defined in [Y.1731] includes various information elements
   (fields) including information on the MEG-Level, etc.  Addressing of
   the PDU as defined in [Y.1731] is based on the MAC Address of the



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   nodes, which would need to be adjusted to support other addressing
   schemes.  The addressing information is carried in <Type, Length,
   Value> (TLV) fields that follow the actual PDU.  In the LBM PDU the
   MAC address is used to identify the MIP to which the message is
   intended

1.7.  Acronyms

                  This draft uses the following acronyms:

       +---------+------------------------------------------------+
       | AC      | Attachment Circuit                             |
       | ACH     | Associated Channel Header                      |
       | BFD     | Bidirectional Forwarding Detection             |
       | CC-V    | Continuity Check and Connectivity Verification |
       | FEC     | Forwarding Equivalence Class                   |
       | G-ACH   | Generic Associated Channel Header              |
       | LDP     | Label Distribution Protocol                    |
       | LSP     | Label Switched Path                            |
       | MPLS-TP | Transport Profile for MPLS                     |
       | OAM     | Operations, Administration, and Maintenance    |
       | PDU     | Packet Data Unit                               |
       | PW      | Pseudowire                                     |
       | RDI     | Remote Defect Indication                       |
       | SLA     | Service Level Agreement                        |
       | TLV     | Type, Length, Value                            |
       | TTL     | Time-to-live                                   |
       | VCCV    | Virtual Circuit Connectivity Verification      |
       +---------+------------------------------------------------+


2.  Architectural requirements and general principles of operation

   [MPLS-TP OAM Reqs] defines a set of requirements on OAM architecture
   and general principles of operations which are evaluated below:

   o  [MPLS-TP OAM Reqs] requires that OAM mechanisms in MPLS-TP are
      independent of the transmission media and of the client service
      being emulated by the PW.  The existing tools comply with this
      requirement.

   o  [MPLS-TP OAM Reqs] requires that the 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 MUST be able to operate by
      relying on the IP routing and forwarding capabilities.  All of the
      existing MPLS tools (i.e.  LSP Ping, VCCV Ping, MPLS BFD, and VCCV
      BFD) can support this functionality.  The Y.1731 toolset does not



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      specifically support this functionality, but rather relies on
      underlying technologies for forwarding this could also be over IP,
      e.g. by using a VCCV extension.  Note that some of the MPLS-TP
      tools such as Alarm Report are very transport oriented and may not
      support IP functionality.

   o  [MPLS-TP OAM Reqs] requires that MPLS-TP OAM MUST be able to
      operate without IP functionality and without relying on control
      and/or management planes.  It is required that OAM functionality
      MUST NOT be dependent on IP routing and forwarding capabilities.
      Except for the LSP Ping operation of verifying the data-plane vs.
      the control-plane, the existing tools do not rely on control
      and/or management plane, however the following should be observed
      regarding the reliance on IP functionality:

      *  LSP Ping, VCCV Ping, and MPLS BFD makes use of IP header
         (UDP/IP) and do not completely comply with the requirement.  In
         the on-demand mode, LSP Ping also may use IP forwarding to
         reply back to the source router.  This dependence on IP, has
         further implications concerning the use of LSP Ping as the
         bootstrap mechanism for BFD for MPLS.  There are extensions to
         LSP-Ping that are under discussion that allow LSP-Ping to
         restrict replies to the backside of a bidirectional LSP.

      *  VCCV BFD supports the use of PW-ACH encapsulated BFD sessions
         for PWs and can comply with the requirement.

      *  Y.1731 PDU are technology agnostic and thereby not dependent on
         IP functionality.  These PDU could be carried by VCCV or G-ACH
         control channels.

   o  [MPLS-TP OAM Reqs] requires that OAM tools for fault management do
      not rely on user traffic, and the existing MPLS OAM tools and
      Y.1731 already comply with this requirement.

   o  It is also required that OAM packets and the user traffic are
      congruent (i.e.  OAM packets are transmitted in-band) and there is
      a need to differentiate OAM packets from user-plane ones.

      *  For PWs, VCCV provides a control channel that can be associated
         with each PW which allows sending OAM packets in band of PWs
         and allow the receiving end-point to intercept, interpret, and
         process them locally as OAM messages.  VCCV defines different
         VCCV Connectivity Verification Types for MPLS (like ICMP Ping,
         LSP Ping and IP/UDP encapsulated BFD and PW-ACH encapsulated
         BFD).





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      *  Currently there is no distinct OAM payload identifier in MPLS
         shim.  BFD and LSP Ping packets for LSPs are carried over
         UDP/IP and are addressed to the loopback address range.  The
         router at the end-point intercepts, interprets, and processes
         the packets.  [MPLS G-ACH] generalizes the use of the PW ACH
         and enables provision of control channels at the MPLS LSP and
         sections levels.  This new mechanism would support carrying the
         existing MPLS OAM messages or the Y.1731 messages at the LSP
         and the section levels to be transmitted over the G-ACH.

   o  [MPLS-TP OAM Reqs] requires that the MPLS-TP OAM mechanism allows
      the propagation of AC (Attachment Circuit) failures and their
      clearance across a MPLS-TP domain

      *  BFD for VCCV supports a mechanism for "Fault detection and
         AC/PW Fault status signaling."  This can be used for both IP/
         UDP encapsulated or PW-ACH encapsulated BFD sessions, i.e. by
         setting the appropriate VCCV Connectivity Verification
         Type.This mechanism could support this requirement.  Note that
         in the PWE3 WG there are two proposals regarding how to
         transmit the AC failures over an ACH that may be applicable to
         this requirement.

   o  [MPLS-TP OAM Reqs] requires a single OAM technology and consistent
      OAM capabilities for LSPs, PWs, and Sections.  The existing set of
      tools defines a different way of operating the OAM functions (e.g.
      LSP Ping to bootstrap MPLS BFD vs. VCCV).  Currently, the Y.1731
      functionality is defined for Ethernet paths, and the procedures
      could readily be redefined for the various MPLS-TP path concepts.

   o  [MPLS-TP OAM Reqs] requires allowing OAM packets to be directed to
      an intermediate point of a LSP/PW.  Technically, this could be
      supported by the proper setting of the TTL value.  It is also
      recommended to include the identifier of the intermediate point
      within the OAM message to allow the intermediate point to validate
      that the message is really intended for it.  The information can
      be included in an ACH-TLV according to the definitions in [MPLS-TP
      ACH TLV].  The applicability of such a solution needs to be
      examined per OAM function.  For details, see below.

   o  [MPLS-TP OAM Reqs] suggests that OAM messages MAY be
      authenticated.  BFD defines support for optional authentication
      fields using different authentication methods as defined in [BASE
      BFD].  Other tools should support this capability as well.  Y.1731
      functionality uses the identification of the path for
      authentication.  Authentication information could be included in
      an optional TLV field according to the definitions in [MPLS-TP ACH
      TLV] when not available in the OAM PDU.



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2.1.  Architectural and Principles of Operation - Recommendations and
      Guidelines

   Based on the requirements analysis above, the following guidelines
   should be followed to create an OAM environment that could more fully
   support the requirements cited:

   o  Define a generalized addressing scheme that can also support
      unique identification of the monitored paths (or connections).

   o  Use G-ACH for LSP and section levels.

   o  Define architectural element that is based on LSP hierarchy to
      apply the mechanisms to segments and concatenated segments.

   o  Apply BFD to these new mechanisms using the control channel
      encapsulation, as defined above - allowing use of BFD for MPLS-TP
      independent of IP functionality.  This could be used to address
      the CC-V functionality, described below.

   o  Similarly, LSP Ping could be extended to use only the LSP path (in
      both directions) without IP Forwarding.  Addressing for PW can be
      included by using the VCCV mechanism.  LSP Ping could be used to
      address the CC-V, Route Tracing, RDI, and Lock/Alarm Reporting
      functionality cited in the requirements.

   o  The Y.1731 PDU set could be used as a basis for defining the
      information units to be transmitted over the G-ACH.  The actual
      procedures and addressing schemes would need to be adjusted for
      the MPLS-TP environment.

   o  Define a mechanism that could be used to idnetify an intermediate
      point of a path in a unique way, to support the maintenance
      functions.  This addressing should be flexible to allow support
      for different addressing schemes, and would supplement the TTL
      exception mechanism to allow an OAM packet to be intercepted by
      intermediate nodes.

   Creating these extensions/mechanisms would fulfill the following
   architectural requirements, mentioned above:

   o  Independence of IP forwarding and routing, when needed.

   o  OAM packets should be transmitted in-band.

   o  Support a single OAM technology for LSP, PW, and Sections.

   In addition, the following additional requirements can be satisfied:



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   o  Provide the ability to carry other types of communications (e.g.,
      APS, Management Control Channel (MCC), Signaling Control Channel
      (SCC)), by defining new types of communication channels for PWs,
      Sections, and LSPs.

   o  The design of the OAM mechanisms for MPLS-TP MUST allow the
      ability to support vendor specific and experimental OAM functions.


3.  MPLS-TP OAM Functions

   The following sections discuss the required OAM functions that were
   identified in [MPLS-TP OAM Reqs].

3.1.  Continuity Check and Connectivity Verification

   Continuity Check and Connectivity Verification (CC-V) are OAM
   operations generally used in tandem, and compliment each other.
   These functions may be split into separate mechanisms.  Together they
   are used to detect loss of traffic continuity and misconnections
   between path end-points and are useful for applications like Fault
   Management, Performance Monitoring and Protection Switching, etc.  To
   guarantee that CC-V can identify misconnections from cross-
   connections it is necessary that the tool use network-wide unique
   identifiers for the path that is being checked in the session.

3.1.1.  Existing tools

   LSP Ping provides much of the functionality required for co-routed
   bidirectional LSPs.  As observed above, LSP Ping may be operated in
   both asynchronous and on-demand mode.  Addressing is based on the
   full FEC identification that provides a unique identifier, and the
   basic functionality only requires support for the loopback address
   range in each node on the LSP path.

   BFD defines functionality that can be used to support the pro-active
   OAM CC-V function when operated in the asynchronous mode.  However,
   the current definition of basic BFD is dependent on use of LSP Ping
   to bootstrap the BFD session.  Regarding the connectivity functional
   aspects, basic BFD has a limitation that it uses only locally unique
   (to each node) session identifiers.

   VCCV can be used to carry either LSP Ping or BFD packets that are not
   IP/UDP encapsulated for CC-V on a PW.  Note that PW termination/
   switching points use only locally unique (to each node) labels.  The
   PW label identifies the path uniquely only at the LSP level.

   Y.1731 provides functionality for all aspects of CC-V for an Ethernet



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   environment, this could be translated for the MPLS-TP environment.
   The CCM PDU defined in [Y.1731] includes the ability to set the
   frequency of the messages that are transmitted, and provides for
   attaching the address of the path (in the Ethernet case - the MEG
   Level) and a sequencing number to verify that CCM messages were not
   dropped.

3.1.2.  Gap analysis

   LSP Ping could be used to cover the cases of co-routed bidirectional
   LSPs.  However, there is a certain amount of computational overhead
   involved with use of LSP Ping (as was observed in sec 1.1), the
   verification of the control-plane, and the need to support the
   loopback functionality at each intermediate node.  LSP Ping uses a
   fully qualified LSP identifier, and when used in conjunction with
   VCCV would use the PW label to identify the transport path.  LSP Ping
   can be extended to bypass the verification of the control plane

   BFD could be extended to fill the gaps indicated above.  The
   extension would include:

   o  A mechanism should be defined to carry BFD packets over LSP
      without reliance on IP functionality.

   o  A mechanism should be defined to bootstrap BFD sessions for MPLS
      that is not dependent on UDP.

   o  BFD needs to be used in conjunction with "globally" unique
      identifiers for the path or ME being checked to allow connectivity
      verfication support.  There are two possibilities, to allow BFD to
      support this new type of identifier -

      *  Change the semantics of the two Discriminator fields that exist
         in BFD and have each node select the ME unique identifier.
         This may have backward compatibility implications.

      *  Create a new optional field in the packet carrying the BFD that
         would identify the path being checked, in addition to the
         existing session identifiers.

   o  Extensions to BFD would be needed to cover P2MP connections.

   Use of the Y.1731 functionality is another option that could be
   considered.  The basic PDU for CCM includes (in the flags field) an
   indication of the frequency of the packets [eliminating the need to
   "negotiate" the frequency between the end-points], and also a flag
   used for RDI.  The procedure itself would need adaptation to comply
   with the MPLS environment.



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   An additional option would be to create a new tool that would give
   coverage for both aspects of CC-V according to the requirements and
   the principles of operation (see section 2.1).  This option is less
   preferable.

3.1.3.  Recommendations and Guidelines

   Extend LSP Ping to fully support the on-demand Connectivity
   Verification function resolving the gaps described above.  Extend BFD
   to support proactive Continuity Check & Connectivity Verification
   (CC-V) resolving the gaps described above.

   Note that [MPLS BFD] defines a method for using BFD to provide
   verification of multipoint or multicast connectivity.

3.2.  Alarm Reporting

   Alarm Reporting is a function that is used by an intermediate point
   in a path to notify the end-points of the path of a fault or defect
   condition indirectly affecting that path.  Such information may be
   used by the endpoints, for example, to suppress alarms that may be
   generated by maintenance end-points of the path.  This function
   should also have the capability to differentiate an administrative
   lock from a failure condition at a different execution level.

3.2.1.  Existing tools

   There is no mechanism defined in the IETF to support this function.
   Y.1731 does define a PDU and procedure for this functionality.

3.2.2.  Recommendations and Guidelines

   Define a new tool and PDU to support Alarm Reporting.  The PDU should
   be transmitted over a G-ACH.  The frequency of transmision after the
   alarm is raised and the continued frequency until it is cleared
   should be indicated in the definition.

   Describe also how the Alarm Reporting functionality may be supported
   in the control-plane and management-plane.

3.3.  Diagnostic

   A diagnostic test is a function that is used between path end-points
   to verify bandwidth throughput, packet loss, bit errors, etc.  This
   is usually performed by sending packets of varying sizes at
   increasing rates (until the limits of the service level) to measure
   the actual utilization.




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3.3.1.  Existing tools

   There is no mechanism defined in the IETF to support this function.
   [Y.1731] describes a function that is dependent on sending a series
   of TST packets (this is a PDU whose size can be varied) at differing
   frequencies.

3.3.2.  Recommendations and Guidelines

   Define a new tool and PDU to support Diagnostic.

3.4.  Route Tracing

   Functionality of route determination is used to determine the route
   of a connection across the MPLS transport network.  [MPLS-TP OAM
   Reqs] defines that this functionality MUST allow a path end-point to
   identify the intermediate and end-points of the path.  This
   functionality MUST support co-routed bidirectional paths, and MAY
   support associated bidirectional and unidirectional p2p paths, as
   well as p2mp unidirectional paths.  Unidirectional path support is
   dependent on the existence of a return path to allow the original
   end-point to receive the trace information.

3.4.1.  Existing tools

   LSP Ping supports a trace route function that could be used for
   bidirectional paths.  Support of unidirectional paths would be
   dependent on the ability of identifying a return path.

3.4.2.  Recommendations and Guidelines

   Extend LSP Ping to support the Route Trace functionality and to
   address additional options, i.e.  PW and p2mp unidirectional LSP.

3.5.  Lock Instruct

   The Lock instruct function allows the system to block off
   transmission of data along a LSP.  When a path end-point receives a
   command, e.g. from the management system, that the path is blocked,
   the end-point informs the far-end that the path has been locked and
   that no data should be transmitted.  This function is used on-demand.

3.5.1.  Existing tools

   There is no mechanism defined in the IETF to support this function,
   but LSP Ping could be extended to support this functionality between
   the path endpoints.  Y.1731 does define a PDU and procedure for this
   functionality.



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3.5.2.  Recommendations and Guidelines

   Extend LSP Ping to support Lock instruct.  The frequency at which
   these messages are transmitted until the lock situation is cleared,
   should be clearly indicated.

3.6.  Lock Reporting

   Lock reporting is used by an intermediate point to notify the end
   points of a transport path (that the intermediate point is a member
   of) that an external lock condition exits for this transport path.
   This function is used proactively.

3.6.1.  Existing tools

   There is no mechanism defined in neither the IETF nor in Y.1731 to
   support this function.

3.6.2.  Recommendations and Guidelines

   Define a new tool and PDU to support Lock reporting.  This tool could
   be designed similarly to the Alarm Reporting tool (described above),
   but would need to be initiated by an intermediate point of the
   transport path.

3.7.  Remote Defect Indication

   Remote Defect Indication (RDI) is used by a path end-point to notify
   its peer end-point that a defect, usually a unidirectional defect, is
   detected on a bi-directional connection between them.

   This function should be supported in pro-active mode.

3.7.1.  Existing tools

   There is no mechanism defined in the IETF to fully support this
   functionality, however BFD supports a mechanism of informing the far-
   end that the session has gone down, and the Diagnostic field
   indicates the reason.  Similarly, when LSP Ping is used for a co-
   routed bidirectional LSP the far-end LER could notify that there was
   a misconnectivity.

   In [Y.1731] this functionality is defined as part of the CC-V
   function as a flag in the PDU.







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3.7.2.  Recommendations and Guidelines

   Extend BFD (which is recommended to be used for proactive CC-V) to
   transmit the signal of Remote Defect Indication without disrupting
   the CC-V functionality.  Such an extension could be similar to that
   suggested by the ITU recommendation.

3.8.  Client Failure Indication

   Client Failure Indication (CFI) function is used to propagate an
   indication of a failure to the far-end sink when alarm suppression in
   the client layer is not supported.

3.8.1.  Existing tools

   There is a possibility of using the BFD over VCCV mechanism for
   "Fault detection and AC/PW Fault status signaling".  However, there
   is a need to differentiate between faults on the AC and the PW.  In
   the PWE3 WG there are some proposals regarding how to transmit the
   CFI over an ACH.

3.8.2.  Recommendations and Guidelines

   Use PWE3 tool to propagate Client Fail Indication via an ACH.

3.9.  Packet Loss Measurement

   Packet Loss Measurement is a function that is 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.

   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.








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3.9.1.  Existing tools

   There is no mechanism defined in the IETF to support this function.
   [Y.1731] describes a function that is based on sending the CCM
   packets [used for CC-V support (see sec 3.1)] for proactive support
   and specialized loss-measurement packets for on-demand measurement.
   These packets include information (in the additional TLV fields) of
   packet counters that are maintained by each of the end-points of a
   path.  These counters maintain a count of packets transmitted by the
   ingress end-point and the count of packets received from the far-end
   of the path by the egress end-point.

3.9.2.  Recommendations and Guidelines

   One possibility is to define a mechanism to support Packet Loss
   Measurement, based on the delimiting messages.  This would include a
   way for delimiting the periods for monitoring the packet
   transmissions to measure the loss ratios, and computation of the
   ratio between received and transmitted packets.

   A second possibility would be to define a functionality based on the
   description of the loss-measurement function defined in [Y.1731] that
   is dependent on the counters maintained, by the MPLS LSR (as
   described in [RFC3813], of received and transmitted octets.  Define a
   new PDU for the message that utilizes G-ACH.  This option appears
   more suitable for performance monitoring statistics, which in
   transport applications are based on the continuous monitoring of the
   traffic interested (100 ms gating).

3.10.  Packet Delay Measurement

   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:

   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
   one of two ways -



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   o  Using OAM packets - checking delay (either one-way or two-way) in
      transmission of OAM packets.  May not fully reflect delay of
      larger packets, however, gives feedback on general service level.

   o  Using delimited periods of transmission - may be too intrusive on
      the client traffic.

3.10.1.  Existing tools

   There is no mechanism defined in the IETF toolset that fulfills all
   of the MPLS-TP OAM requirements.

   [Y.1731] describes a function in which specific OAM packets are sent
   with a transmission time-stamp from one end of the managed path to
   the other end (these are transparent to the intermediate nodes).  The
   delay measurement is supported for both one-way and two-way
   measurement of the delay.  It should be noted that the functionality
   on the one-way delay measurement is dependent upon a certain degree
   of synchronization between the time clocks of the two-ends of the
   transport path.

3.10.2.  Recommendations and Guidelines

   Define a mechanism that would support Packe Delay Measurement, based
   on the procedures defined in [Y.1731].  The mechanism should be based
   on measurement of the delay in transmission and reception of OAM
   packets, transmitted in-band with normal traffic.  Define an
   appropriate PDU that would utilize the G-ACH.


4.  Recommendations

   As indicated above, LSP-Ping could easily be extended to support some
   of the functionality between the path end-points and between an end-
   point of a path and an intermediate point.  BFD could also be
   extended to support some of the functions between the end-points of a
   path.  Some of the OAM functions defined in [Y.1731] (especially for
   performance monitoring) could also be adapted.

   The guidelines that are used in this document are as follows:

   o  Re-use/extend existing IETF protocols wherever applicable.

   o  Define new message format for each of the rest of the OAM
      functions, which are aligned with the ACH and ACH-TLV definitions,
      and includes only relevant information.





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   o  Adapt Y.1731 functionality where applicable (mainly for
      performance monitoring).

   The recommendations on the MPLS-TP OAM tools are as follows:

   o  Define a maintenance entity that could be applied both to LSPs and
      PWs that would support management of a sub-path.  This entity
      should allow for transmission of traffic by means of label
      stacking and proper TTL setting.

   o  Extend the control and the management planes to support the
      configuration of the OAM maintenance entities and the set of
      functions to be supported by these entities.

   o  Define a mechanism that would allow the unique addressing of the
      elements that need to be monitored, e.g., the connections, end-
      points, and intermediate points of a path.  This mechanism needs
      to be flexible enough to support different addressing schemes,
      e.g.  IP addresses, NSAP, connection names.  As pointed out above,
      LSP Ping uses the full FEC identifier for the LSP - this could
      easily be applied to Section OAM since this would be considered as
      a stacked LSP.

   o  The appropriate assignment of network-wide unique identifiers for
      transport paths, needed to support connectivity verification,
      should be considered.

   o  Extend existing MPLS tools to disengage from IP forwarding
      mechanisms.

   o  Extend BFD to support the proactive CC-V functionalities.  The
      extensions should address the gaps described above.

   o  Extend LSP Ping to support the on-demand Connectivity Verification
      functionality.  The extensions should address the gaps described
      above.

   o  Define a new PDU which will be transmitted over G-ACH to support
      the Alarm Reporting functionality for data-plane implementations.
      Describe how Alarm Reporting can be supported by a control-plane
      and by a management-plane.

   o  Define a new PDU which will be transmitted over G-ACH to support
      the Lock Reporting functionality.  Use the same procedures as for
      Alarm Reporting.

   o  Extend BFD to support the Remote Defect Indication (RDI)
      functionality.  The extensions should address the gaps described



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      above.

   o  Extend LSP-Ping to support the Route tracing functionality.  The
      extensions should address the gaps described above.

   o  Extend LSP-Ping to support the Lock Instruct functionality between
      end-points of a path.  The extensions should address the gaps
      described above.

   o  Use PWE3 tool to transmit Client Fault Indication (CFI) via ACH.
      There are already some proposals in the PWE3 WG.

   o  Define a new PDU which will be transmitted over G-ACH to support
      the Packet Loss Measurement functionality.  Base the functionality
      on the procedures defined in Y.1731.

   o  Define a new PDU which be transmitted over G-ACH to support the
      Packet Delay Measurement functionality.  Base the functionality on
      the procedures defined in Y.1731.  For one-way delay measurement
      define mechanisms to ensure a certain degree of synchronization
      between the time clocks of the two-ends of the transport path.

   o  Define a new PDU which be transmitted over G-ACH to support the
      Diagnostic functionality.

   o  The tools may have the capability to authenticate the messages.
      The information may be carried in a G-ACH TLV.


5.  MPLS-TP OAM Documents Organization

   The following paragraphs list the set of documents necessary to cover
   the OAM functionalities analyzed above.  This compilation of
   documents is one of the outcomes of the MEAD team discussions that
   took place during IETF75 in Stockholm.

   It should be noted that the various document titles listed here may
   not reflect the draft titles that will be chosen at the time that the
   drafts are written, but they serve just as a topic pointer from the
   current analysis.

5.1.  Document 1: "Encapsulation of BFD and LspPing in ACH"

   The scope of the document is to define the usage of LSP Ping and BFD
   in both IP and IP-less environments.  As described in the following
   paragraphs, BFD and Lsp Ping need to be extended in order to be
   compliant with [MPLS-TP OAM Reqs].  However, this document should be
   focused on the existing Lsp Ping and BFD, without necessarily



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   referring to their extended versions.

   The draft "nitinb-mpls-tp-lsp-ping-bfd-procedures" will be considered
   as the starting point for this definition.

   In particular, the following sections will be taken into account for
   the scope:

   o  nitinb-mpls-tp-lsp-ping-bfd-procedures section 2 ("LSP-Ping
      extensions") for addressing the "Lsp Ping encapsulation in ACH"

   o  nitinb-mpls-tp-lsp-ping-bfd-procedures section 5 ("Running BFD
      over MPLS-TP LSPs") for addressing the "BFD encapsulation in ACH"

5.2.  Document 2: "Extended BFD"

   The scope of the document is to define the BFD extension and behavior
   to meet the requirements for MPLS-TP proactive Continuity Check and
   Connectivity Verification functionality and the RDI functionality as
   defined in [MPLS-TP OAM Reqs].

   The document will likely take the name
   "draft-asm-mpls-tp-bfd-cc-cv-00" and will be formed by the merging of
   the following two drafts:

   o  draft-fulignoli-mpls-tp-bfd-cv-proactive-and-rd

   o  draft-boutros-mpls-tp-cc-cv-01.txt

5.3.  Document 3: "Extended LSP Ping"

   The scope of the document is to define:

   o  A place holder for On Demand Connectivity Verification if LSP Ping
      needs to be enhanced over and above the encapsulations changes
      (defined in Document 1 "Encapsulation of BFD and LSP Ping in
      ACH").

   o  Usage of LSP Ping with MIPs and MEPs, which is partially covered
      in nitinb-mpls-tp-lsp-ping-bfd-procedures.

   o  Route Trace.  This topic has already been partially covered in
      "draft-boutros-mpls-tp-path-trace-00" and "nitinb-mpls-tp-lsp-
      ping-bfd-procedures", which will be considered as starting point
      for the Route Trace functionality included in Document 3.  The
      Route Trace section should also cover these aspects:





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      *  LSP Ping Loose ends.  This section will describe what to do
         when receiving an LSP Ping with MIP and MEP ids.

      *  In an IP-Less environment Route Trace works only in co-routed
         bidirectional LSP.

      *  In Y.1731 the CV function is separate from the Route Trace
         function, it should be captured how LSP Ping works for Route
         Trace using TTL.

5.4.  Document 4: "Extensions for Lock Instruct"

   A new document describing the LSP Ping extensions to accomplish the
   Lock Instruct desired behavior is needed.  Some material useful for
   this scope can be found in "draft-boutros-mpls-tp-loopback-02".

5.5.  Document 5: "AIS and Lock Reporting"

   A new document is need for the definition of the AIS and Lock
   Reporting, however the document definition has been temporarily
   deferred by the MEAD team.  Therefore this paragraph will be updated
   in future versions.

5.6.  Document 6: "Client Fault Indication"

   A new document describing Client Fault Indication procedure needs to
   be defined.

   The following two drafts indicating a client fault indication
   transported across MPLS-TP network will be compared and merged in the
   new document:

   o  "draft-he-mpls-tp-csf", which describes a tool to propagate a
      client failure indication across an MPLS-TP network in case the
      propagation of failure status in the client layer is not
      supported.

   o  "draft-martini-pwe3-static-pw-status", which describes the usage
      of PW associated channel to signal PW status messages in case a
      static PW is used without a control plane

   It is worth noting that a Client Failure Indication is used if the
   client does not support its own OAM (IP and MPLS as clients use their
   own).  It has been also agreed that CFI is used on PW and not on
   client directly mapped on LSP MPLS-TP.






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5.7.  Document 7: "Packet Loss"

   A new document needs to be defined in order to describe a stand alone
   tool for Packet Loss measurements that can work both proactively and
   on demand.  The tool will be functionally based on Y.1731.

5.8.  Document 8: "Packet Delay"

   A new document needs to be defined about the Packet Delay measurement
   which will be based on Y.1731 from the functionality point of view.
   Moreover, [MPLS-TP OAM Frwk] needs to be updated in order to clarify
   the functionality behavior expected from this tool.

5.9.  Document 9: "Diagnostic Tests"

   One or more new documents are needed for the tools definition for
   Diagnostic Tests.  However, the documents definition has been
   temporarily deferred by the MEAD team until a clearer definition of
   "diagnostic test" in [MPLS-TP OAM Reqs].


6.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.


7.  Security Considerations

   This document does not by itself raise any particular security
   considerations.


8.  Acknowledgements

   The authors wish to thank the MEAD team for their review and proposed
   enhancements to the text.


9.  Informative References

   [RFC 2119]
              Bradner, S., "Internet Control Message Protocol", BCP 14,
              RFC 2119, March 1997.

   [ICMP]     Postel, J., "Internet Control Message Protocol", STD 5,



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              RFC 792, Sept 1981.

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

   [PW ACH]   Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

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

   [BASE BFD]
              Katz, D. and D. Ward, "Bidirectional Forwarding
              Detection", ID draft-ietf-bfd-base-09.txt, February 2009.

   [MPLS BFD]
              Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "BFD For MPLS LSPs", ID draft-ietf-bfd-mpls-07.txt,
              June 2008.

   [VCCV BFD]
              Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
              Detection (BFD) for the Pseudowire Virtual Circuit
              Connectivity Verification (VCCV)",
              ID draft-ietf-pwe3-vccv-bfd-07.txt, February 2008.

   [P2MP LSP Ping]
              Nadeau, T. and A. Farrel, "Detecting Data Plane Failures
              in Point-to-Multipoint Multiprotocol Label Switching
              (MPLS) - Extensions to LSP Ping",
              ID draft-ietf-mpls-p2mp-lsp-ping-06.txt, June 2008.

   [MPLS LSP Ping]
              Bahadur, N. and K. Kompella, "Mechanism for performing
              LSP-Ping over MPLS tunnels",
              ID draft-ietf-mpls-lsp-ping-enhanced-dsmap-00, June 2008.

   [MPLS-TP OAM Reqs]
              Vigoureux, M., Betts, M., and D. Ward, "Requirements for
              OAM in MPLS Transport Networks",
              ID draft-ietf-mpls-tp-oam-requirements-01, April 2009.

   [MPLS-TP OAM Frwk]
              Busi, I. and B. Niven-Jenkins, "MPLS-TP OAM Framework and



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              Overview", ID draft-ietf-mpls-tp-oam-requirements-01,
              March 2009.

   [MPLS-TP Reqs]
              Niven-Jenkins, B., Nadeau, T., and C. Pignataro,
              "Requirements for the Trasport Profile of MPLS",
              ID draft-ietf-mpls-tp-requirements-06, April 2009.

   [MPLS G-ACH]
              Bocci, M., Bryant, S., and M. Vigoureux, "MPLS Generic
              Associated Channel", RFC 5586, June 2009.

   [MPLS-TP ACH TLV]
              Boutros, S., Bryant, S., Sivabalan, S., Swallow, G., and
              D. Ward, "Definition of ACH TLV Structure",
              ID draft-ietf-mpls-tp-ach-tlv-00, June 2009.

   [RFC3813]  Srinivasan, C., Viswanathan, A., and T. Nadeau,
              "Multiprotocol Label Switching (MPLS) Label Switching
              Router (LSR) Management  Information Base (MIB)",
              RFC 3813, June 2004.

   [Y.1731]   International Telecommunications Union - Standardization,
              "OAM functions and mechanisms for Ethernet based
              networks", ITU Y.1731, May 2006.


Authors' Addresses

   Nurit Sprecher (editor)
   Nokia Siemens Networks
   3 Hanagar St. Neve Ne'eman B
   Hod Hasharon,   45241
   Israel

   Email: nurit.sprecher@nsn.com


   Huub van Helvoort (editor)
   Huawei
   Kolkgriend 38, 1356 BC Almere
   Netherlands

   Phone: +31 36 5316076
   Email: hhelvoort@huawei.com






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   Elisa Bellagamba
   Ericsson
   6 Farogatan St
   Stockholm,   164 40
   Sweden

   Phone: +46 761440785
   Email: elisa.bellagamba@ericsson.com


   Yaacov Weingarten
   Nokia Siemens Networks
   3 Hanagar St. Neve Ne'eman B
   Hod Hasharon,   45241
   Israel

   Phone: +972-9-775 1827
   Email: yaacov.weingarten@nsn.com

































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