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Versions: 00 01 02 03 04 05 06 draft-ietf-pwe3-oam-config

MPLS Working Group                                         F. Zhang, Ed.
Internet-Draft                                                B. Wu, Ed.
Intended status: Standards Track                         ZTE Corporation
Expires: January 12, 2012                             E. Bellagamba, Ed.
                                                                Ericsson
                                                           July 11, 2011


    Label Distribution Protocol Extensions for Proactive Operations,
 Administration and Maintenance Configuration of Dynamic MPLS Transport
                           Profile Pseudowire
                  draft-zhang-mpls-tp-pw-oam-config-05

Abstract

   This document specifies extensions to the Label Distribution Protocol
   (LDP) to configure and control proactive Operations, Adminstration
   and Maintenance (OAM) functions, suitable for dynamic Single-Segment
   PseudoWire (SS-PW) and Multi-Segment PseudoWire (MS-PW).

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on January 12, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   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
   2.  Conventions used in this document  . . . . . . . . . . . . . .  3
     2.1.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Analysis of Existing PW OAM Configuration  . . . . . . . . . .  4
     3.1.  MPLS PW OAM Functions  . . . . . . . . . . . . . . . . . .  4
     3.2.  Virtual Circuit Connectivity Verification  . . . . . . . .  5
     3.3.  VCCV Bidirectional Forwarding Detection  . . . . . . . . .  5
     3.4.  PW Status  . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.5.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Analysis of PW OAM Configuration Extended by MPLS-TP . . . . .  6
     4.1.  Continuity Check, Connectivity Verification and Remote
           Defect Indication  . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Performance Monitoring Loss/Delay  . . . . . . . . . . . .  7
     4.3.  FMS  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  On-demand OAM Functions  . . . . . . . . . . . . . . . . .  7
     4.5.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  MPLS-TP PW OAM Capability Advertisement  . . . . . . . . . . .  8
   6.  PW OAM Configurationd Procedures . . . . . . . . . . . . . . .  9
     6.1.  Establishment of OAM Entities and Functions  . . . . . . .  9
     6.2.  Adjustment of OAM Parameters . . . . . . . . . . . . . . . 10
     6.3.  Deleting OAM Entities  . . . . . . . . . . . . . . . . . . 11
   7.  LDP extensions . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  MPLS-TP PW OAM Capability TLV  . . . . . . . . . . . . . . 12
       7.1.1.  Backward Compatibility . . . . . . . . . . . . . . . . 13
     7.2.  MPLS-TP PW OAM Administration TLV  . . . . . . . . . . . . 13
     7.3.  MPLS-TP PW OAM Configuration TLV . . . . . . . . . . . . . 14
       7.3.1.  BFD Configuration TLV  . . . . . . . . . . . . . . . . 15
       7.3.2.  MPLS-TP PW PM Loss TLV . . . . . . . . . . . . . . . . 15
       7.3.3.  MPLS-TP PW PM Delay TLV  . . . . . . . . . . . . . . . 16
       7.3.4.  MPLS-TP PW FMS TLV . . . . . . . . . . . . . . . . . . 16
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 17
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     11.1. Normative references . . . . . . . . . . . . . . . . . . . 17
     11.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19







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1.  Introduction

   MPLS Pseudowire (PW) is defined in [RFC3985] and [RFC5659], which
   provide for emulated services over an MPLS Packet Switched Network
   (PSN).  MPLS Transport Profile (MPLS-TP) describes a profile of MPLS
   that enables operational models typical in transport networks, while
   providing additional Operations, Administration and Maintenance
   (OAM), survivability and other maintenance functions not previously
   supported by IP/MPLS.  The corresponding requirements are defined in
   [RFC5860].

   The MPLS-TP OAM mechanisms that are operated to meet transport
   requirements are described in [I-D.ietf-mpls-tp-oam-framework],
   categorized into proactive and on-demand monitoring.  Proactive
   monitoring refers to OAM operations that are either configured to be
   carried out periodically and continuously or preconfigured to act on
   certain events such as alarm signals.  In contrast, on-demand
   monitoring is initiated manually and for a limited amount of time,
   usually for operations such as diagnostics to investigate into a
   defect condition.

   The Network Management System (NMS) or Label Switched Path (LSP) Ping
   [I-D.ietf-mpls-lsp-ping-mpls-tp-oam-conf] is used to configure these
   OAM functionalities if a control plane is not instantiated.  But if
   the control plane is used, it MUST support the configuration and
   modification of OAM maintenance points as well as the activation/
   deactivation of OAM when the transport path or transport service is
   established or modified [RFC5654].

   This document specifies the extensions to the LDP protocol to
   negotiate PW OAM capabilities, configure and bootstrap proactive PW
   OAM functions, suitable for Point to Point (P2P) SS-PW and MS-PW.
   The extensions to Point to Multi-Point (P2MP) PW will be studied in
   the future.


2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.1.  Acronyms








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      AC: Attachment Circuit
      AIS: Alarm indication signal
      BFD: Bidirectional Forwarding Detection
      CC: Continuity Check
      CV: Connectivity Verification
      DM: Delay Measurement
      FEC: Forwarding Equivalence Class
      FMS: Fault Management Signal
      ICMP: Internet Control Message Protocol
      LDI: Link Down Indication
      LDP: Label Distribution Protocol
      LKR: Lock Reporting
      LM: Loss Measurement
      LSP: Label Switched Path
      ME: Maintenance Entity
      MEG: Maintenance Entity Group
      MEP: Maintenance Entity Group End Point
      MIP: Maintenance Entity Group Intermediate Point
      MPLS-TP: MPLS Transport Profile
      MS-PW: Multi-Segment PseudoWire
      NMS: Network Management System
      OAM: Operations, Adminstration and Maintenance
      P2MP: Point to Multi-Point
      PE: Provider Edge
      PHB: Per-Hop Behavior
      PM: Performance Monitoring
      PSN: Packet Switched Network
      PW: PseudoWire
      S-PE: Switching Provider Edge
      SPME: Sub-Path Maintenance Entity
      SS-PW: Single-Segment Pseudo Wire
      T-PE: Terminating Provider Edge
      TLV: Type Length Value
      VCCV: Virtual Circuit Connectivity Verification


3.  Analysis of Existing PW OAM Configuration

3.1.  MPLS PW OAM Functions

   Before MPLS-TP standards, PW OAM functions have been implemented by
   [RFC5085], [RFC5885], [RFC4447] and [I-D.ietf-pwe3-static-pw-status].
   [RFC5085] defines Connectivity Verification (CV) function, which
   belongs to on-demand PW monitoring.  Poactive Continuity Check (CC),
   as well as PW and Attachemnt Circuit (AC) status notification, are
   defined in [RFC5885].  The documents [RFC4447] and
   [I-D.ietf-pwe3-static-pw-status] give some other ways of PW/AC status
   notification.



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3.2.  Virtual Circuit Connectivity Verification

   Virtual Circuit Connectivity Verification (VCCV) is used to verify
   and further diagnose PW forwarding path, and the VCCV capabilities
   negotiation is defined in [RFC5085].

3.3.  VCCV Bidirectional Forwarding Detection

   Four CV types based on Bidirectional Forwarding Detection (BFD) are
   specified in [RFC5885], which describes the VCCV BFD capabilities
   negotiation and the procedures of selecting one of them when multiple
   BFD CV types are advertised.  If the BFD parameters (such as sending
   interval) need to be modified, BFD itself will handle it.

3.4.  PW Status

   PW status codes provide a mechanism to signal the status of PW and AC
   failure.  When PW control plane exists, the PW Status TLV is carried
   in the initial Label Mapping message and Notification message to
   signal all PW status messages [RFC4447].  When an event occurs, an
   update PW status will be sent.

3.5.  Conclusion

   In summary, IP/MPLS PW OAM functions and their relationship with LDP/
   LSP Ping/NMS are described in table 1.  This document will not
   replace or deprecate these existing functions(e.g., VCCV capability
   advertisement and PW status negotiation for MPLS networks).


|----------------------------------------------------------------------|
|              |              |  LDP         | LSP Ping |     NMS      |
|----------------------------------------------------------------------|
|              |   VCCV       |  Capability  |          |  Capability  |
|              |  LSP ping    |  negotiation |          |configuration&|
|  On-demand   |              |              |          | Bootstrapping|
|     OAM      |-------------------------------------------------------|
|              |   VCCV       |  Capability  |          |  Capability  |
|              |  ICMP ping   |  negotiation |          |configuration&|
|              |              |              |          | Bootstrapping|
|----------------------------------------------------------------------|
|              |   VCCV BFD   |  Capability  |          | Capability   |
|              |              | negotiation& |          |configuration&|
|              |              | Bootstrapping|          | Bootstrapping|
|  Proactive   |-------------------------------------------------------|
|    OAM       |   PW status  | Capability   |          | Capability   |
|              |              | negotiation& |          |configuration&|
|              |              | Bootstrapping|          | Bootstrapping|



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|----------------------------------------------------------------------|


                     Table 1: IP/MPLS PW OAM Functions


4.  Analysis of PW OAM Configuration Extended by MPLS-TP

4.1.  Continuity Check, Connectivity Verification and Remote Defect
      Indication

   The Proactive CC, CV and Remote Defect Indication (RDI) functions of
   MPLS-TP are based on the extensions to BFD
   [I-D.ietf-mpls-tp-cc-cv-rdi], which addresses the proactive CV gap
   that VCCV BFD does not support.  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 PW, so local
   discriminator values are not exchanged
   [I-D.ietf-mpls-tp-oam-analysis].  However, in order to identify
   certain extreme cases of mis-connectivity and fulfill the
   requirements that the BFD mechanism MUST be the same for LSP, Single
   Segment Pseudowire (SS-PW), Multi Segment Pseudowire (MS-PW) and
   Section as well as for Sub-path Maintenance Element (SPME), BFD might
   still need to use discriminator values to identify the connection
   being verified at both ends of the PW.  The discriminator values can
   be statically configured, or signaled via LSP Ping or LDP extensions
   defined in this document.

   Timer negotiation, such as Transmitter (TX)/Receiver (RX) interval is
   performed in subsequent BFD control messages [RFC5880], but it also
   can be gotten by control plane signaling
   [I-D.ietf-mpls-tp-oam-framework].

   The source Maintenance Entity Group End Point Identifier (MEP-ID)
   does not need to be carried, for they can be deduced from the
   advertised FEC (129) TLV, as described in
   [I-D.ietf-mpls-tp-identifiers].

   Per-hop Behavior (PHB), which identifies the per-hop behavior of BFD
   packet, SHOULD be configured as well.  This permits the verification
   of correct operation of Quality of Serivce (QoS) queuing as well as
   connectivity.

   If BFD Authentication using a shared key / password is desired (i.e.
   actual authentication not only error detection) the "BFD
   Authentication sub-TLV" MUST be included in the "BFD Configuration
   sub-TLV".  The "BFD Authentication sub-TLV" is used to specify which
   authentication method that should be used and which shared key /



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   password that should be used for this particular session.  How the
   key exchange is performed is out of scope of this document.

   In conclusion, the configuration of CC-CV-RDI by control plane is not
   necessary, but for consistent operation of transport path and
   section, it SHOULD be an option.

4.2.  Performance Monitoring Loss/Delay

   Performance monitoring (PM) of PWs, especially for packet Loss
   Measurement (LM) and packet Delay Measurement (DM), are specified in
   [I-D.ietf-mpls-loss-delay], [I-D.ietf-mpls-tp-loss-delay-profile].

   For proactive LM, the transmission rate and PHB associated with the
   LM OAM packets originating from a MEP need to be negotiated with the
   other MEP.  LM OAM packets should be transmitted with the same PHB
   class that the LM is intended to measure.

   Just like LM, Both one way and two way mode of proactive DM need the
   two MEPs nodes of PW to negotiate the measure interval and PHB value
   of OAM packets.

4.3.  FMS

   Fault Management Signals (FMS) are specified in
   [I-D.ietf-mpls-tp-fault], with which a server PW can notify client
   PWs about various fault conditions to suppress alarms or to be used
   as triggers for actions in the client PWs.  The following signals are
   defined: Alarm Indication Signal (AIS), Link Down Indication (LDI)
   and Lock Reporting (LKR).

   For each MEP of each Maintenance Entity Group (MEG), enabling/
   disabling the generation of FMS packets, the transmitted period and
   PHB SHOULD be configured.  This can be done independently, and the
   values of configured parameters can be different, but for easy
   maintenance, these setting SHOULD be consistent.

   In conclusion, the configuration of FMS by control plane is not
   necessary, but for easy maintenance, it SHOULD be an option also.

4.4.  On-demand OAM Functions

   The extended on-demand OAM functions MAY need capability negotiation
   in the LDP Initialization message [RFC5561].  However, On-demand PW
   OAM functions are expected to be carried out by directly accessing
   network nodes via a management interface; hence configuration and
   control of on-demand PW OAM functions are out-of-scope for this
   document.



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4.5.  Conclusion

   According to the analysis above, LDP needs to be extended to
   negotiate PW OAM capabilities, configure and bootstrap proactive PW
   OAM functions, such as, CC-CV-RDI, PM Loss/Delay, FMS.  In this way,
   OAM configuration is bound to PW signaling, avoiding two separate
   management/configuration steps (PW establishment followed by OAM
   configuration) which would increases delay, processing and more
   importantly may be prune to mis-configuration errors.

   Furthermore, LSP ping can be used to configure the proactive PW OAM
   function extended by MPLS-TP also, suitable for dynamic and static
   PW.  For reference, the following table 2 describes the different
   scope of different proactive OAM bootstrapping schemes of dynamic PW.



  |--------------------------------------------------------------------|
  |           |           |  LDP         | LSP Ping     |   NMS        |
  |--------------------------------------------------------------------|
  |           |           |Capability    |              | Capability   |
  |           |           |negotiation&  |              |configuration&|
  |           | CC/CV/RDI |Function      | Function     | Function     |
  |           |           |configuration&|configuration&|configuration&|
  |           |           |Bootstrapping |Bootstrapping | Bootstrapping|
  |           |--------------------------------------------------------|
  | Proactive |           |Capability    |              |  Capability  |
  |    OAM    |           |negotiation&  |              |configuration&|
  |           |   FMS     |Function      | Function     | Function     |
  |           |           |configuration&|configuration&|configuration&|
  |           |           |Bootstrapping |Bootstrapping | Bootstrapping|
  |           |--------------------------------------------------------|
  |           |           |Capability    |              |  Capability  |
  |           |           |negotiation&  |              |configuration&|
  |           | PM Loss/  |Function      | Function     | Function     |
  |           |   Delay   |configuration&|configuration&|configuration&|
  |           |           |Bootstrapping |Bootstrapping | Bootstrapping|
  |-----------|--------------------------------------------------------|


                     Table 2: MPLS-TP PW OAM Functions


5.  MPLS-TP PW OAM Capability Advertisement

   When a PW is first set up, the PEs MUST attempt to negotiate the
   usage of OAM functions.  At the time of writing this specification,
   there are PW status negotiation and VCCV capability advertisement.



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   For the proactive OAM functions extended by MPLS-TP, such as CC-CV-
   RDI, PM loss/delay and FMS, the capability negotiation MAY be also
   needed, so a PE that supports the MPLS-TP PW OAM capability MUST
   include MPLS-TP PW OAM Capability TLV in the LDP Initialization
   message.  And if the peer has not advertised this capability, the
   corresponding PW OAM configuration information will not be sent to
   the peer.


6.  PW OAM Configurationd Procedures

   A PE may play an active or passive role in the signaling of the PW.
   There exist two situations:

   a) Active/active: both PEs of a PW are active (SS-PW), they select PW
   OAM configuration parameters and send with the Label Mapping message
   to each other independently.

   b) Active/passive: one PE is active and the others are passive
   (MS-PW).  The active/passive role election is defined in Section
   7.2.1 of [RFC6073] and applies here, this document does not define
   any new role election procedures.

   The general rules of OAM configuration procedures are mostly
   identical between MS-PW and SS-PW, except that SS-PW does not need to
   configure MIP function and the Mapping message are sent out
   independently.  This section takes MS-PW as an example to describe
   the general OAM configuration procedures.  As for SS-PW, there may be
   some collisions of PW OAM configuration parameters, and these
   specific differences would be addressed in section 6.

6.1.  Establishment of OAM Entities and Functions

   Assuming there is one PW that needs to be setup between T-PE1 and
   T-PE2, across S-PE1 and S-PE2.  OAM functions must be setup and
   enabled in the appropriate order so that spurious alarms can be
   avoided.

       +-------+        +-------+        +-------+        +-------+
       |       |        |       |        |       |        |       |
       |      A|--------|B     C|--------|D     E|--------|F      |
       |       |        |       |        |       |        |       |
       +-------+        +-------+        +-------+        +-------+
         T-PE1            S-PE1            S-PE2            T-PE2


                 Figure 1: MS-PW OAM Configuration Scheme




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   Fist of all, T-PE1 MUST setup the OAM sink function to be prepared to
   receive OAM messages but MUST suppress any OAM alarms (e.g., due to
   missing or unidentified OAM messages).  The Mapping message MUST be
   sent with the "OAM Alarms Enabled" cleared, "OAM MEP Entities
   desired" set and "OAM MIP Entities desired" set in the MPLS-TP PW OAM
   Administation TLV.

   When the Mapping message arrives at the downstream receivers, such as
   S-PE1, S-PE2 and T-PE2, they MUST establish and configure OAM
   entities according to the OAM information provided in Mapping
   message.  If this is not possible, a Notification message SHOULD be
   sent and neither the OAM entities nor the PW SHOULD be established.
   If OAM entities are established successfully, the middle points
   (S-PE1 and S-PE2) MUST forward the Mapping message downstream, the
   endpoint (T-PE2) MUST set the OAM Source function and MUST be
   prepared to Send OAM messages.

   The same rules are applied to the reverse direction (from T-PE2 to
   T-PE1), that is to say, T-PE2 needs to setup the OAM sink function to
   be prepared to receive OAM messages but MUST suppress any OAM alarms
   (e.g., due to missing or unidentified OAM messages).  The Mapping
   message MUST be sent with the "OAM Alarms Enabled" cleared, "OAM MEP
   Entities desired" set, "OAM MIP Entities desired" set in the MPLS-TP
   PW OAM Administration TLV.  When T-PE1 receives the Mapping message,
   it completes any pending OAM configuration and enables the OAM source
   function to send OAM messages.

   After this round, OAM entities are established and configured for the
   PW and OAM messages MAY already be exchanged, and OAM alarms can now
   be enabled.  The T-PE nodes(T-PE1 and T-PE2), while still keeping OAM
   alarms disabled send a Notification message with "OAM Alarms Enabled"
   PW status flag set, and enable the OAM alarms after processing the
   Notification message.  At this point, data-plane OAM is fully
   functional, and the MPLS-TP OAM PW configuration TLV MAY be omitted
   in subsequent Notification messages

   The PW MAY be setup with OAM entities right away with the first
   signaling, as described above, but a PW MAY be signaled and
   established without OAM configuration first, and OAM entities may be
   added later.  This can be done by sending a Notification message with
   the related configuration parameters subsequently.

6.2.  Adjustment of OAM Parameters

   There may be a need to change the parameters of an already
   established and configured OAM function during the lifetime of the
   PW.  To do so the T-PE nodes need to send a Notification message with
   the updated parameters.  OAM parameters that influence the content



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   and timing of OAM messages and identify the way OAM defects and
   alarms are derived and generated.  Hence, to avoid spurious alarms,
   it is important that both sides, OAM sink and source, are updated in
   a synchronized way.  Firstly, the alarms of the OAM sink function
   should be suppressed and only then should expected OAM parameters be
   adjusted.  Subsequently, the parameters of the OAM source function
   can be updated.  Finally, the alarms of the OAM sink side can be
   enabled again.

   In accordance with the above operation, T-PE1 MUST send a
   Notification message with "OAM Alarms Enabled" cleared and including
   the updated MPLS-TP PW OAM Configuration TLV corresponding to the new
   parameter settings.  The initiator (T-PE1) MUST keep its OAM sink and
   source functions running unmodified, but it MUST suppress OAM alarms
   after the updated Notification message is sent.  The receiver (T-PE2)
   MUST firstly disable all OAM alarms, then update the OAM parameters
   according to the information in the Notification message and reply
   with a Notification message acknowledging the changes by including
   the MPLS-TP PW OAM Configuration TLV.  Note that the receiving side
   has the possibility to adjust the requested OAM configuration
   parameters and reply with and updated MPLS-TP PW OAM Configuration
   TLV in the Notification message, reflecting the actually configured
   values.  However, in order to avoid an extensive negotiation phase,
   in the case of adjusting already configured OAM functions, the
   receiving side SHOULD NOT update the parameters requested in the
   Notification message to an extent that would provide lower
   performance than what has been configured previously.

   The initiator (T-PE1) MUST only update its OAM sink and source
   functions when it has received the Notification message from the
   peer.  After the OAM parameters are updated and OAM is running
   according the new parameter settings, OAM alarms are still disabled,
   so a subsequent Notification messages exchanges with "OAM Alarms
   Enabled" flag set are needed to enable OAM alarms again.

6.3.  Deleting OAM Entities

   In some cases it may be useful to remove some or all OAM entities and
   functions from one PW without actually tearing down the connection.
   To avoid any spurious alarm, the following procedure should be
   followed:

   The T-PE nodes disable OAM alarms and SHOULD send Notification
   message to each other with "OAM Alarms Enabled" cleared but unchanged
   OAM configuration and without the MPLS-TP PW OAM Configuration TLV.
   After that, T-PE1 (T-PE2) SHOULD delete OAM source functions, then
   send a Notification message with "OAM MEP Entities desired" and "OAM
   MIP Entities desired" cleared.  While T-PE2 (T-PE1) deletes OAM sink



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   function when it receives the Notification message with "OAM MEP
   Entities desired" cleared, S-PE1 and S-PE2 delete MIP configuration
   when they receive the Notification message with "OAM MIP Entities
   desired" cleared.

   Alternatively, if only some OAM functions need to be removed, the
   T-PE node sends the Notification message with the updated OAM
   Configuration TLV.  Changes between the contents of the previously
   signaled OAM Configuration TLV and the currently received TLV
   represent which functions SHOULD be removed/added.


7.  LDP extensions

   Below, LDP extensions to configure proactive MPLS-TP PW OAM functions
   are defined.

7.1.  MPLS-TP PW OAM Capability TLV

   A new Capability Parameter TLV called the MPLS-TP PW OAM Capability
   TLV is defined, and the format is as follows:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |1|0|              Type (TBD)   |     Length (= 4)              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |1| Reserved    |               Capability Data       |F|D|L|V|C|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       MPLS-TP PW OAM Capability TLV

   The value of the U-bit for the MPLS-TP PW OAM Capability TLV MUST be
   set to 1 so that a receiver MUST silently ignore this TLV if unknown
   to it, and continue processing the rest of the message[RFC5036].
   Currently defined specific OAM Capability Flags in the "Capability
   Data" field from right to left are:


   One bit "C" (31, IANA to assign)             CC mode supported
   One bit "V" (30, IANA to assign)             CV mode supported
   One bit "L" (29, IANA to assign)             PM Loss supported
   One bit "D" (28, IANA to assign)             PM Delay supported
   One bit "F" (27, IANA to assign)             FMS supported


   The above bits can be set individually to indicate more than one kind
   of OAM capabilities at once, and the other reserved bits MUST be set



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   to zero on transmission and MUST be ignored on receipt.

   The MPLS-TP PW OAM Capability TLV MAY be included by a PE in an
   Initialization message to signal its peer that it supports the
   MPLS-TP PW OAM Capability.  If the remote peer does not support the
   MPLS-TP PW OAM Capability TLV or the Initialization message sent by
   the remote peer does not include the MPLS-TP PW OAM Capability TLV,
   the resulting negotiation does not support MPLS-TP PW OAM capability.
   If instead the negotiation supports the MPLS-TP PW OAM capability,
   then the subsequent LDP Mapping message will carry the information of
   the MPLS-TP PW OAM configuration.

7.1.1.  Backward Compatibility

   If both the two T-PEs can recognize the MPLS-TP PW OAM Capability
   TLV,and CC or CV mode is supported, the BFD configuration procedure
   described in this document is adopted.  Otherwise, if at least one of
   the two T-PEs do not support the CC or CV mode, the old VCCV BFD
   [RFC5885] will be performed.  In this situation, the procedure
   described in [RFC5885] MUST be followed: the C and V flags of MPLS-TP
   PW OAM Configuration TLV MUST NOT be set and the BFD Configuration
   sub-TLV MUST NOT be carried as a sub-TLV of MPLS-TP PW OAM
   Configuration TLV also.

   The described behavior ensures full compatibility with the existing
   implementations.

7.2.  MPLS-TP PW OAM Administration TLV

   The format of the MPLS-TP PW OAM Administration TLV is as follows:

         0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0|0|          Type (TBD)     |            Length               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E|I|A|         Reserved                                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     MPLS-TP PW OAM Administration TLV

   One bit "E" (0, IANA to assign): "OAM MEP entities desired" is
   allocated.  If the "OAM MEP entities desired" bit is set it is
   indicating that the establishment of OAM MEP entities are required at
   the endpoints of the signaled PW.  If the establishment of MEPs is
   not supported, a Notification message MUST be sent.  If the "OAM MEP
   entities desired" bit is set and additional parameters are needed to
   be configured on the OAM entities, an "MPLS-TP PW OAM Configuration



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   TLV" may be included in the Mapping or Notification message.

   One bit "I" (1, IANA to assign): "OAM MIP entities desired" is
   allocated.  This bit can only be set if the "OAM MEP entities
   desired" bit is set.  If the "OAM MIP entities desired" bit is set,
   it is indicating that the establishment of OAM MIP entities is
   required at every transit node of the signaled PW.  If the
   establishment of a MIP is not supported, a Notification message MUST
   be sent.

   One bit "A" (2, IANA to assign): "OAM Alarms Enabled" is allocated.
   This bit can only be set if the "OAM MEP entities desired" bit is
   set.  If the "OAM Alarms Enabled" bit is set, it is indicating that
   the T-PE needs to enable OAM alarms.  If the establishment of a MIP
   is not supported, a Notification message MUST be sent.

   Reserved (29bits): This field MUST be set to zero on transmission and
   MUST be ignored on receipt.

7.3.  MPLS-TP PW OAM Configuration TLV

   The "MPLS-TP PW OAM Configuration TLV" is depicted in the following
   figure.  It may be carried in the Mapping and Notification messages,
   just following the PW Status TLV.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|0|       Type (TBD)          |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |C|V|L|D|F|             OAM Function Flags                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                           sub-TLVs                            ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     MPLS-TP PW OAM Configuration TLV

   Type: indicates a new type: the MPLS-TP PW OAM Configuration TLV
   (IANA to assign).  If this type is not supported, a Notification
   message MUST be sent.

   OAM Function Flags: a bitmap numbered from left to right as shown in
   the figure.

   These flags are defined in this document:




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      OAM Function Flag bit#             Description
      ---------------------      ---------------------------
               0 (C)             Continuity Check (CC)
               1 (V)             Connectivity Verification (CV)
               2 (L)             Performance Monitoring/Loss (PM/Loss)
               3 (D)             Performance Monitoring/Delay (PM/Delay)
               4 (F)             Fault Management Signals (FMS)
               5-31              Reserved (set all to 0s)

   Sub-TLVs corresponding to the different flags are defined in section
   3.2 of [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext].

   For active/active signaling, if the flags in the "MPLS-TP PW OAM
   Function Flags sub-TLV" are different in the two Mapping message, the
   two PEs nodes can compare the node IDs.  Label Withdraw message MUST
   be sent by the PE with lower ID, then it sends the Label Mapping
   message again with the same flags carried in the received Label
   Mapping message.

7.3.1.  BFD Configuration TLV

   BFD Configuration TLV follows the same TLV structure defined for
   Resource ReSerVation Protocol Traffic Engineering (RSVP-TE) in
   section 3.3 of [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext].

   For active/active signaling, if the flags of "BFD Configuration TLV"
   are different in the two Mapping message, similarly Label Withdraw
   message MUST be sent by the PE with lower identifier.  Then it sends
   the Label Mapping message again with the same flags carried in the
   "BFD configuration TLV" of the received Label Mapping message.  If
   the flags of "BFD Configuration TLV" are the same, but the values of
   "Negotiation Timer parameters sub-TLV" are different, both the PE
   nodes MUST adopt the bigger interval and detection time multiplier.

7.3.2.  MPLS-TP PW PM Loss TLV

   MPLS-TP PW PM Loss TLV follows the same TLV structure defined for
   RSVP-TE in section 3.4 of [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext].

   For active/active signaling, if the flags of "MPLS-TP PW OAM PM Loss
   TLV" are different in the two Mapping message, similarly Label
   Withdraw message MUST be sent by the PE with lower ID.  Then it sends
   the Label Mapping message again with the same flags carried in the
   "MPLS-TP PW OAM PM Loss TLV" of the received Label Mapping message.
   If the flags of "MPLS-TP PW OAM PM Loss TLV" are the same, but the
   Measurement Interval and Loss Threshold are different, both the PE
   nodes MUST adopt the bigger values.




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7.3.3.  MPLS-TP PW PM Delay TLV

   MPLS-TP PW PM Delay TLV follows the same TLV structure defined for
   RSVP-TE in section 3.5 of [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext].

   For active/active signaling, if the flags of "MPLS-TP PW OAM PM Delay
   TLV" are different in the two Mapping message, similarly Label
   Withdraw message MUST be sent by the PE with lower ID.  Then it sends
   the Label Mapping message again with the same flags carried in the
   "MPLS-TP PW OAM PM Delay TLV" of the received Label Mapping message.
   If the flags of "MPLS-TP PW OAM PM Delay TLV" are the same, but the
   Measurement Interval and Delay Threshold are different, both the PE
   nodes MUST adopt the bigger values.

7.3.4.  MPLS-TP PW FMS TLV

   MPLS-TP PW FMS TLV follows the same TLV structure defined for RSVP-TE
   in section 3.6 of [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext].

   For active/active signaling, if the flags of "MPLS-TP PW OAM FMS TLV"
   are different in the two Mapping message, similarly Label Withdraw
   message MUST be sent by the PE with lower ID.  Then it sends the
   Label Mapping message again with the same flags carried in the
   "MPLS-TP PW OAM FMS TLV" of the received Label Mapping message.

   Notes: Client Signal Fail (CSF) dees not need to be supported.


8.  IANA Considerations

   This document specifies the following new LDP TLV types:
   o  MPLS-TP PW OAM Capability TLV;
   o  MPLS-TP PW OAM Administration TLV;
   o  MPLS-TP PW OAM Configuration TLV;

   Sub-TLV types to be carried in the "MPLS-TP PW OAM Configuration
   TLV":
   o  BFD Configuration sub-TLV;
   o  MPLS-TP PW PM Loss sub-TLV;
   o  MPLS-TP PW PM Delay sub-TLV;
   o  MPLS-TP PW FMS sub-TLV;

   Sub-TLV types to be carried in the "BFD Configuration sub-TLV":
   o  Local Discriminator sub-TLV;
   o  Negotiation Timer Parameters sub-TLV.
   o  BFD Authentication sub-TLV





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9.  Security Considerations

   Security considerations relating to LDP are described in section 5 of
   [RFC5036] and section 11 of [RFC5561].  Security considerations
   relating to use of LDP in setting up PWs is described in section 8 of
   [RFC4447].

   This document defines new TLV/sub-TLV types, and OAM configuration
   procedures intended for use with MPLS-TP, which do not raise any
   additional security issues.


10.  Acknowledgement

   The authors would like to thank Andew Malis, Greg Mirsky, Luca
   Martini, Matthew Bocci, Thomas Nadeau for their valuable comments and
   discussions, especially would like to thank Eric Gray for his review
   of this document.


11.  References

11.1.  Normative references

   [I-D.ietf-ccamp-rsvp-te-mpls-tp-oam-ext]
              Bellagamba, E., Andersson, L., Skoldstrom, P., Ward, D.,
              and A. Takacs, "Configuration of pro-active MPLS-TP
              Operations, Administration, and Maintenance (OAM)
              Functions Using RSVP-TE",
              draft-ietf-ccamp-rsvp-te-mpls-tp-oam-ext-05 (work in
              progress), March 2011.

   [I-D.ietf-mpls-lsp-ping-mpls-tp-oam-conf]
              Bellagamba, E., Andersson, L., Skoldstrom, P., Ward, D.,
              and J. Drake, "Configuration of pro-active MPLS-TP
              Operations, Administration, and Maintenance (OAM)
              Functions Using LSP Ping",
              draft-ietf-mpls-lsp-ping-mpls-tp-oam-conf-01 (work in
              progress), March 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit



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              Connectivity Verification (VCCV): A Control Channel for
              Pseudowires", RFC 5085, December 2007.

   [RFC5860]  Vigoureux, M., Ward, D., and M. Betts, "Requirements for
              Operations, Administration, and Maintenance (OAM) in MPLS
              Transport Networks", RFC 5860, May 2010.

11.2.  Informative References

   [I-D.ietf-mpls-loss-delay]
              Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks",
              draft-ietf-mpls-loss-delay-03 (work in progress),
              June 2011.

   [I-D.ietf-mpls-tp-cc-cv-rdi]
              Allan, D., Swallow, G., and J. Drake, "Proactive
              Connectivity Verification, Continuity Check and Remote
              Defect indication for MPLS Transport Profile",
              draft-ietf-mpls-tp-cc-cv-rdi-05 (work in progress),
              June 2011.

   [I-D.ietf-mpls-tp-fault]
              Swallow, G., Fulignoli, A., Vigoureux, M., Boutros, S.,
              and D. Ward, "MPLS Fault Management OAM",
              draft-ietf-mpls-tp-fault-04 (work in progress),
              April 2011.

   [I-D.ietf-mpls-tp-identifiers]
              Bocci, M., Swallow, G., and E. Gray, "MPLS-TP
              Identifiers", draft-ietf-mpls-tp-identifiers-06 (work in
              progress), June 2011.

   [I-D.ietf-mpls-tp-loss-delay-profile]
              Frost, D. and S. Bryant, "A Packet Loss and Delay
              Measurement Profile for MPLS-based Transport Networks",
              draft-ietf-mpls-tp-loss-delay-profile-03 (work in
              progress), April 2011.

   [I-D.ietf-mpls-tp-oam-analysis]
              Sprecher, N. and L. Fang, "An Overview of the OAM Tool Set
              for MPLS based Transport Networks",
              draft-ietf-mpls-tp-oam-analysis-04 (work in progress),
              June 2011.

   [I-D.ietf-mpls-tp-oam-framework]
              Allan, D., Busi, I., Niven-Jenkins, B., Fulignoli, A.,
              Hernandez-Valencia, E., Levrau, L., Sestito, V., Sprecher,



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              N., Helvoort, H., Vigoureux, M., Weingarten, Y., and R.
              Winter, "Operations, Administration and Maintenance
              Framework for MPLS-based Transport Networks",
              draft-ietf-mpls-tp-oam-framework-11 (work in progress),
              February 2011.

   [I-D.ietf-pwe3-static-pw-status]
              Martini, L., Swallow, G., Heron, G., and M. Bocci,
              "Pseudowire Status for Static Pseudowires",
              draft-ietf-pwe3-static-pw-status-06 (work in progress),
              July 2011.

   [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
              Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

   [RFC5561]  Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
              Le Roux, "LDP Capabilities", RFC 5561, July 2009.

   [RFC5654]  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
              and S. Ueno, "Requirements of an MPLS Transport Profile",
              RFC 5654, September 2009.

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              October 2009.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, June 2010.

   [RFC5885]  Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
              Detection (BFD) for the Pseudowire Virtual Circuit
              Connectivity Verification (VCCV)", RFC 5885, June 2010.

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011.













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Authors' Addresses

   Fei Zhang (editor)
   ZTE Corporation

   Email: zhang.fei3@zte.com.cn


   Bo Wu (editor)
   ZTE Corporation

   Email: wu.bo@zte.com.cn


   Elisa Bellagamba (editor)
   Ericsson
   Farogatan 6
   Kista, 164 40
   Sweden

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


   Attila Takacs
   Ericsson
   Laborc u. 1.
   Budapest, 1037
   Hungary

   Email: attila.takacs@ericsson.com


   Xuehui Dai
   ZTE Corporation

   Email: dai.xuehui@zte.com.cn


   Min Xiao
   ZTE Corporation

   Email: xiao.min2@zte.com.cn








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