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Versions: (draft-boutros-mpls-tp-li-lb) 00 01 02 03 04 05 06 07 08 RFC 6435

Network Working Group                                Sami Boutros (Ed.)
Internet Draft                                     Siva Sivabalan (Ed.)
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: December 5, 2011
                                                   Rahul Aggarwal (Ed.)
                                                 Juniper Networks, Inc.

                                                 Martin Vigoureux (Ed.)
                                                         Alcatel-Lucent

                                                       Xuehui Dai (Ed.)
                                                        ZTE Corporation

                                                           June 5, 2011


        MPLS Transport Profile Lock Instruct and Loopback Functions
                      draft-ietf-mpls-tp-li-lb-02.txt


Status of this Memo

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

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   This Internet-Draft will expire on December 5, 2011.



Abstract




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   This document specifies an extension to MPLS Operation,
   administration, and Maintenance (OAM) to operate an Label Switched
   Path (LSP), bi-directional RSVP-TE tunnels, Pseudowires (PW), or
   Multi-segment PWs in loopback mode for management purpose in an MPLS
   based Transport. This extension includes mechanism to lock and
   unlock MPLS-TP Tunnels (i.e. data and control traffic) and can be
   used to loop all traffic (i.e, data and control traffic) at a
   specified LSR on the path of the LSP in an MPLS based Transport
   Network back to the source. However, the mechanisms are intended to
   be applicable to other aspects of MPLS as well.

Table of Contents


   1. Introduction...................................................3
   2. Terminology....................................................5
   3. Loopback/Lock Mechanism........................................5
      3.1. In-band Message Identification............................5
      3.2. LI-LB Message Format......................................6
      3.3. Return codes..............................................7
      3.4. Cause codes...............................................7
      3.5. Authentication TLV........................................8
      3.6. LSP Ping Extensions.......................................9
         3.6.1. LI-LB Request TLV....................................9
         3.6.2. LI-LB Response TLV...................................9
   4. Loopback/Lock Operations.......................................9
      4.1. Lock Request.............................................10
      4.2. Unlock Request...........................................10
      4.3. Loopback Request.........................................10
      4.4. Loopback Removal.........................................11
   5. Data packets..................................................11
   6. Operation.....................................................11
      6.1. General Procedures.......................................11
      6.2. Example Topology.........................................11
      6.3. Locking an LSP...........................................12
      6.4. Unlocking an LSP.........................................13
      6.5. Setting an LSP into Loopback mode........................14
      6.6. Removing an LSP from Loopback mode.......................15
   7. Security Considerations.......................................16
   8. IANA Considerations...........................................16
      8.1. Pseudowire Associated Channel Type.......................16
      8.2. New LSP Ping TLV types...................................16
   9. Acknowledgements..............................................16
   10. References...................................................16
      10.1. Normative References....................................16
      10.2. Informative References..................................17
   Author's Addresses...............................................17
   Full Copyright Statement.........................................19
   Intellectual Property Statement..................................19


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1. Introduction

   In traditional transport networks, circuits are provisioned across
   multiple nodes and service providers have the ability to operate the
   transport circuit such as T1 line in loopback mode for management
   purposes, e.g., to test or verify connectivity of the circuit up to a
   specific node on the path of the circuit, to test the circuit
   performance with respect to delay/jitter, etc. This document provides
   the same loopback capability for the bi-directional LSPs in MPLS
   based Transport Networks emulating traditional transport circuits.
   The mechanisms in this document apply to co-routed bidirectional
   paths as defined in [7], which include LSPs, bi-directional RSVP-TE
   tunnels, Pseudowires (PW), and Multi-segment PWs in MPLS based
   Transport Networks. However, the mechanisms are intended to be
   applicable to other aspects of MPLS as well.

   This document specifies how to operate the Lock and Loopback
   functions over both the Generic Associated Channel (GACh) and over
   LSP-Ping. LSP-Ping itself can run either over the GACh or using
   native IP addressing; the manner in which LSP-Ping is transported in
   an MPLS-TP network is out of the scope of this document.

   This document uses a sample topology to describe the lock instruct
   and loopback functions.  This sample topology comprises four MPLS-TP
   nodes [A---B---C---D].  There is an LSP from A to D, and thus A and D
   are MEPs and B and C are MIPs.  Unless otherwise specified, the
   operator desires to lock the LSP (this is done on A and D, by
   definition) and loop the LSP at C.

   That is, the desired behavior is that all packets transmitted by A on
   this locked and looped LSP arrive at C from B and are encapsulated in
   the D->A direction by C such that these packets reach A.

   Locking and looping an LSP is a two-step process.  The first step is
   to lock the LSP so that it is not made available to carry user
   traffic. The locking of an LSP is managed by the two MEPs of an LSP -
   in this example, A and D.  Locking is controlled by one of the MEPs;
   this example uses A.  A sends a Lock request message to D along the
   LSP, either in the GACh or in LSP-Ping.  This message will be
   received by D as it is the far-end MEP for that LSP.  D responds to
   the lock request with an ACK or NACK; the ACK indicates that D has
   taken the LSP out of service (i.e. Locked the LSP) and the NACK
   indicates that D cannot comply with the Lock request.  In general, if
   a message (e.g. Lock request, Loopback request) cannot be complied
   with, the node which received the request replies with a NACK and a
   cause code; the details of error message processing are discussed
   later in this document.


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   Once A has received the ACK to its Lock request, A is then allowed to
   put the LSP in Loopback mode.  In order to set the LSP in Loopback
   mode, A sends a Loopback request message to the MIP or MEP where A
   desired the loopback to be enabled.  In this example, A desires to
   set the loopback at C, although note that it is possible to A to set
   the loopback at any node downstream of A (e.g. B, C, D).  The TTL on
   the Loopback request message is set by A such that the TTL expires
   when it reaches the node where A wants the loopback to be set (in
   this case, C).  C responds to the Loopback request with a reply
   message (ACK/NACK) back to A to indicate whether it has successfully
   set the LSP into the Loopback mode.

   If A receives an ACK from its Loopback request, the LSP is now in
   Loopback mode.  A is free to send any test packets down this LSP as
   it sees fit.  These packets MUST NOT be forwared towards D.  As the
   LSP is locked, D MUST NOT transmit any traffic on the LSP in the
   reverse direction (that is, D->A).  Any traffic received by C from
   the reverse direction MUST be dropped and MAY be logged, as the
   receipt of traffic by C in the D->A direction indicates an error.

   When A desires to remove the LSP from Loopback state, it begins to
   reverse the Loopback and Lock.  This is a two-step process; first A
   removes the Loopback from C, then A removes the Lock from D. This
   process is similar to the process of establishing Lock and Loopback
   in the first place.  A sends a Loopback Remove message to C using the
   TTL method described above, and C ACKs or NACKs the Loopback Remove.
   Once A receives the Loopback Remove ACK from C, A sends a Lock Remove
   message to D. D must ACK or NACK this message.  Once A receives the
   Lock Remove ACK from D, the LSP is brought back into normal
   operation.

   The proposed mechanism is based on a new set of messages and TLVs
   which can be transported using one of the following methods:

   (1) An in-band MPLS message transported using a new ACH code point,
   the message will have different types to perform the loopback
   request/remove and Lock/unlock functions, and may carry new set of
   TLVs.

   (2) A new set of TLVs which can be transported using LSP-Ping
   extensions defined in [4], and in compliance to specifications [5].

   Method (1) and (2) are referred to as "in-band option" and "LSP-Ping
   option" respectively in the rest of the document.

   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 RFC-2119 [3].

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2. Terminology

   ACH: Associated Channel Header

   LSR: Label Switching Router

   MEP: Maintenance Entity Group End Point

   MIP: Maintenance Entity Group Intermediate Point.

   MPLS-TP: MPLS Transport Profile

   MPLS-OAM: MPLS Operations, Administration and Maintenance

   MPLS-TP LSP: Bidirectional Label Switch Path representing a circuit

   NMS: Network Management System

   TLV: Type Length Value

   TTL: Time To Live

   LI-LB: Lock instruct-Loopback

3. Loopback/Lock Mechanism

   For the in-band option, the proposed mechanism uses a new code point
   in the Associated Channel Header (ACH) described in [6].

3.1. In-band Message Identification

  In the in-band option, the LI-LB channel is identified by the ACH as
  defined in RFC 5586 [6] with the Channel Type set to the LI-LB code
  point = 0xHH.  [HH to be assigned by IANA from the PW Associated
  Channel Type registry]  The LI-LB Channel does not use ACH TLVs and
  MUST not include the ACH TLV header. The LI-LB ACH
   Channel is shown below.

    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 0 1|Version|Reserved       |    0xHH ( LI-LB)       |      +-+-
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1: ACH Indication of LI-LB

   The LI-LB Channel is 0xHH (to be assigned by IANA)



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3.2. LI-LB Message Format

   The format of an LI-LB Message is shown below.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Version       | Message Type  | Operation     | Reserved      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Return Code   | Cause Code    | Message Length                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sender's Handle                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             TLV's                             |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 2: MPLS LI-LB Message Format

   Version: The Version Number is currently 1.  (Note: the version
   number is to be incremented whenever a change is made that affects
   the ability of an implementation to correctly parse or process the
   request/response message. These changes include any syntactic or
   semantic changes made to any of the fixed fields, or to any Type-
   Length-Value (TLV) or sub-TLV assignment or format that is defined at
   a certain version number.  The version number may not need to be
   changed if an optional TLV or sub-TLV is added.)

   Message Type

   Two message types are defined as shown below.

                Message Type          Description
                ------------          -------------
                         0x0          LI-LB request
                         0x1          LI-LB response


   Operation

   Four operations are defined as shown below. The operations can appear
   in a Request or Response message.

                   Operation          Description
                   ---------          -------------
                         0x1          Lock
                         0x2          Unlock
                         0x3          Set_Loopback

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                         0x4          Unset_Loopback


   Message Length

   The total length of any included TLVs.

   Sender's Handle

   The Sender's Handle is filled in by the sender, and MUST be copied
   unchanged by the receiver in the MPLS response message (if any).
   There are no semantics associated with this handle, although a sender
   may find this useful for matching up requests with replies.

   Message ID

   The Message ID is set by the sender of an MPLS request message. It
   MUST be copied unchanged by the receiver in the MPLS response message
   (if any).  A sender SHOULD increment this value on each new message.
   A retransmitted message SHOULD leave the value unchanged.

   The Return code and Cause code only have meaning in a Response
   message. In a request message the Return code and Cause code must be
   set to zero and ignored on receipt. Return codes and cause codes are
   described in the following Sections.

3.3. Return codes

         Value   Meaning
         -----   -------
            0    Informational
            1    Success
            2    Failure



3.4.   Cause codes

   Value   Meaning
   -----   -------
       0    Success
       1    Fail to match target MIP/MEP ID
       2    Malformed LI-LB request received
       3    One or more of the TLVs is/are unknown
       4    Authentication failed
       5    LSP/PW already locked
       6    LSP/PW already unlocked
       7    Fail to lock LSP/PW

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       8    Fail to unlock LSP/PW
       9    LSP/PW already in loopback mode
      10    LSP/PW is not in loopback mode
      11    Fail to set LSP/PW in loopback mode
      12    Fail to remove LSP/PW from loopback mode
      13    No label binding for received message
      14    Authentication required but not received.

Note that in the case of cause code 3, the unknown TLV can also be
optionally included in the response. For failure responses with multiple
causes only the first cause code can be included.

3.5. Authentication 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           type = TBD          |       Length = 0xx            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Variable Length Value                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The PPP CHAP described in [9] will be used to authenticate the LI-LB
   request.

   The variable length value carried in the optional authentication TLV,
   will include the Packet Format described in section 3.2 of [9].

   The optional authentication TLV can be included in the MPLS OAM LSP
   Ping echo messages containing a LI-LB request TLV or in the inband
   LI-LB Message. When an authentication TLV is present in the Request
   message the CHAP procedures described in section 3.2 of [9] MUST be
   followed.

   The CHAP packets will be transmitted by the authenticator using LI-LB
   Request or response messages, responses to the authentication
   protocol messages will be transmitted using LI-LB request or response
   messages.

   If the CHAP negotiation results in a failure, the authenticator or
   the sender of the request message MUST stop requesting the LI-LB
   function.

   A receiver of an LI-LB request, MAY send an error "Authentication
   required but not received", if the optional authentication TLV is not
   included in the LI-LB request.




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3.6. LSP Ping Extensions

3.6.1. LI-LB Request 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           type = TBD          | length = 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Operation  |
   +-+-+-+-+-+-+

                   Operation          Description
                   ---------          -------------
                         0x1          Lock
                         0x2          Unlock
                         0x3          Set_Loopback
                         0x4          Unset_Loopback


   A MEP includes a LI-LB Request TLV in the MPLS LSP Ping echo request
   message to request the MEP on the other side of the LSP toperform
   Lock/Unlock and Set/Unset Loopback operations. Only one LI-LB request
   TLV can be present in an LSP Ping Echo request message.

3.6.2. LI-LB Response 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           type = TBD         |        Length = 0x3            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Operation    | ReturnCode     |  CauseCode   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Only one LI-LB response TLV can be present in an LSP Ping Echo
   request message.

4. Loopback/Lock Operations

   When performing a Lock or Loopback function, the reply to a message
   MUST use the same method as the original message. That is, if a node
   requests lock or loopback using LSP Ping then any replies to that
   request must also use LSP Ping; if a node requests lock or loopback
   using in-band, any replies to that request must use in-band. It is
   permissible to use different methods for the lock and the loopback
   functions on a given LSP. For example, a node can lock an LSP using
   the LSP Ping method and then can loop the LSP using the in-band
   method, or vice versa.


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   An ACK response of a request will be a response message with return
   code 1 (success) and cause code 0, while a NACK response will have a
   return code 2 (failure) and the corresponding cause code.



4.1. Lock Request

   Lock Request is used to request a MEP to take an LSP out of service
   so that some form of maintenance can be done.

   The receiver MEP MUST send either an ACK or a NAK response to the
   sender MEP. Until the sender MEP receives an ACK, it MUST NOT assume
   that the receiver MEP has taken the LSP out of service. A receiver
   MEP sends an ACK only if it can successfully lock the LSP. Otherwise,
   it sends a NAK.

   The receiver MEP once locked, MUST discard all received traffic.



4.2. Unlock Request

   The Unlock Request is sent from the MEP which has previously sent
   lock request. Upon receiving the unlock request message, the receiver
   MEP brings the LSP back in service.

   The receiver MEP MUST send either an ACK or a NAK response to the
   sender MEP. Until the sender MEP receives an ACK, it MUST NOT assume
   that the LSP has been put back in service. A receiver MEP sends an
   ACK only if the LSP has been unlocked, and unlock operation is
   successful. Otherwise, it sends a NAK.



4.3. Loopback Request


   When a MEP wants to put an LSP in loopback mode, it sends a Loopback
   request message. The message can be intercepted by either a MIP or a
   MEP depending on the MPLS TTL value. The receiver puts in
   corresponding LSP in loopback mode.

   The receiver MEP or MIP MUST send either an ACK or NAK response to
   the sender MEP. An ACK response is sent if the LSP is successfully
   put in loopback mode. Otherwise, a NAK response is sent. Until an ACK
   response is received, the sender MEP MUST NOT assume that the LSP can
   operate in loopback mode.



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4.4. Loopback Removal


   When loopback mode operation of an LSP is no longer required, the MEP
   that previously sent the Loopback request message sends another
   Loopback Removal message. The receiver MEP changes the LSP from
   loopback mode to normal mode of operation.

   The receiver MEP or MIP MUST send either an ACK or NAK response to
   the sender MEP. An ACK response is sent if the LSP is already in
   loopback mode, and if the LSP is successfully put back in normal
   operation mode. Otherwise, a NAK response is sent. Until an ACK
   response is received, the sender MEP MUST NOT assume that the LSP is
   put back in normal operation mode.

5. Data packets

   Data packets sent from the sender MEP will be looped back to that
   sender MEP. OAM packets not intercepted by TTL expiry will as well be
   looped back. The use of data packets to measure packet loss, delay
   and delay variation is outside the scope of this document.

6. Operation

6.1. General Procedures

   When placing an LSP into Loopback mode, the operation MUST first be
   preceded by a Lock operation.

   When sending Loopback Request/Removal using LSP Ping or in-Band
   messages the TTL of the topmost label is set as follows:-

   If the target node is a MIP, the TTL MUST be set to the exact number
   of hops required to reach that MIP.

   If the target node is a MEP, the value MUST be set to at least the
   number of hops required to reach that MEP. For most operations where
   the target is a MEP, the TTL MAY be set to 255.

   However, to remove a MEP from Loopback mode, the sending MEP MUST set
   the TTL to the exact number of hops required to reach the MEP (if the
   TTL were set higher, the Loopback removal message would be looped
   back toward the sender).

6.2. Example Topology

   The next four sections discuss the procedures for Locking, Unlocking,
   setting an LSP into loopback, and removing the loopback.  The
   description is worded using an example. Assume an LSP traverses nodes
   A <--> B <--> C <--> D.  We will refer to the Maintenance Entities

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   involved as MEP-A, MIP-B, MIP-C, and MEP-D respectively.  Suppose a
   maintenance operation invoked at MEP-A requires a loopback be set at
   MIP-C. To invoke Loopack mode at MIP-C, A would first need to lock
   the LSP. Then it may proceed to set the loopback at C. Following the
   loopback operation, A would need to remove the loopback at C and
   finally unlock the LSP.

   The following sections describe MEP-A setting and unsetting a lock at
   MEP-D and then setting and removing a loopback at MIP-C.

6.3. Locking an LSP

   1. MEP-A sends an MPLS LSP Ping Echo request message with the Lock
   TLV or an in-Band Lock request Message. Optionally, an authentication
   TLV MAY be included.

   2. Upon receiving the request message, D uses the received label
   stack and the Target Stack FEC TLV as per [5]/source MEP-ID to
   identify the LSP. If no label binding exists or there is no
   associated LSP back to the originator, the event is logged.
   Processing ceases.  Otherwise the message is delivered to the target
   MEP.

   a. if the source MEP-ID does not match, the event is logged and
   processing ceases.

   b. if the target MEP-ID does not match, MEP-D sends a failure
   response with cause code 1.

   MEP-D then examines the message, and:

   c. if the message is malformed, it sends a failure response with
   cause code 2 back to MEP-A.

   d. if message authentication fails, it MAY send a failure response
   with cause code 4 back to MEP-A.

   e. if any of the TLVs is not known, it sends a failure response with
   cause code 3 back to MEP-A. It may also include the unknown TLVs.

   f. if the LSP is already locked, it sends a response with
   cause code 5 back to MEP-A.

   g. if the LSP is not already locked and cannot be locked, it sends a
   failure response with cause code 7 back to A.

   h. if the LSP is successfully locked, it sends a success response
   with cause code 0 (Success) back to MEP-A.



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   The response is sent using an MPLS LSP Ping echo reply with a
   response TLV or an in-Band Lock response message. An authentication
   TLV MAY be included.

   MEP-D will lock the LSP, resulting in that all traffic from D to A,
   including all OAM traffic, stops.

     a. MEP-A will detect a discontinuation in the OAM traffic, e.g. cv
        and cc packets, but since it has been informed that the LSP will
        be locked it will take no action(s).

     b. When MEP-A receives the LI ACK, MEP-A discontinues sending
        other OAM traffic, e.g. cv and cc packets. MEP-D will detect
        this, but since it is in Locked state it will take no action.

6.4. Unlocking an LSP

   1. MEP-A sends an MPLS Echo request message with the unLock TLV or an
   in-Band unLock request Message. Optionally, an authentication TLV MAY
   be included.

   2. Upon receiving the unLock request message, D uses the received
   label stack and target FEC/source MEP-ID as per [5] to identify the
   LSP. If no label binding exists or there is no associated LSP back to
   the originator, the event is logged. Processing ceases. Otherwise the
   message is delivered to the target MEP.

   a. if the source MEP-ID does not match, the event is logged and
   processing ceases.

   b. if the target MEP-ID does not match, MEP-D sends a failure
   response with cause code 1.

   MEP-D then examines the message, and:

   c. if the message is malformed, it sends a failure response with
   cause code 2 back to MEP-A.

   d. if message authentication fails, it MAY send a failure response
   with cause code 4 back to MEP-A.

   e. if any of the TLVs is not known, it sends a failure response with
   cause code 3 back to MEP-A. It may also include the unknown TLVs.

   f. if the LSP is already unlocked, it sends a response with
   cause code 6 back to MEP-A.

   g. if the LSP is locked and cannot be unlocked, it sends a response
   with cause code 8 back to MEP-A.


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   h. if the LSP is successfully unlocked, it sends a success response
   with cause code 0 (Success) back to MEP-A.

   The response is sent using an MPLS LSP Ping echo reply with a
   response TLV or an in-Band unlock response message. An authentication
   TLV MAY be included.

6.5. Setting an LSP into Loopback mode

   1. MEP-A sends an MPLS LSP Ping Echo request message with the
   loopback TLV or an in-Band Loopback request message. Optionally, an
   authentication TLV MAY be included.

   2. Upon intercepting the MPLS Loopback message via TTL expiration, C
   uses the received label stack and target FEC/source MEP-ID as per [5]
   to identify the LSP.

   If no label binding exists or there is no associated LSP back to the
   originator, the event is logged. Processing ceases.

   Otherwise the message is delivered to the target MIP/MEP - in this
   case MIP-C.

   a. if the source MEP-ID does not match, the event is logged and
   processing ceases.

   b. if the target MIP-ID does not match, MIP-C sends a failure
   response with cause code 1.

   MIP-C then examines the message, and:

   c. if the message is malformed, it sends a failure response with
   cause code 2 back to MEP-A.

   d. if the message authentication fails, it sends a failure response
   with cause code 4 back to MEP-A.

   e. if any of the TLV is not known, C sends a failure response with
   cause code 3 back to MEP-A. It may also include the unknown TLVs.

   f. if the LSP is already in the requested loopback mode, it sends a
   failure response with cause code 9 back to MEP-A.

   g. if the LSP is not already in the requested loopback mode and that
   loopback mode cannot be set, it sends a failure response with cause
   code 11 back to MEP-A.

   h. if the LSP is successfully programmed into the requested  loopback
   mode, it sends a success response with cause code 0 (Success) back to
   MEP-A.

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   The response is sent using an MPLS LSP Ping echo reply with a
   response TLV or an in-Band Loopback response message. An
   authentication TLV MAY be included.

6.6. Removing an LSP from Loopback mode

   1. MEP-A sends a MPLS LSP Ping Echo request message with the Loopback
   removal TLV or an in-Band Loopback removal request message.
   Optionally, an authentication TLV MAY be included.

   2. Upon intercepting the MPLS Loopback removal message via TTL
   expiration, C uses the received label stack and the target FEC/source
   MEP-ID as per [5] to identify the LSP.

   If no label binding exists or there is no associated LSP back to
   the originator, the event is logged. Processing ceases.

   Otherwise the message is delivered to the target MIP/MEP - in this
   case MIP-C.

   a. if the source MEP-ID does not match, the event is logged and
   processing ceases.

   b. if the target MIP-ID does not match, MIP-C sends a failure
   response with cause code 1 back to MEP-A.

   MIP-C then examines the message, and:

   c. if the message is malformed, it sends a failure response with
   cause code 2 back to MEP-A.

   d. if the message authentication fails, it sends a failure response
   with cause code 4 back to MEP-A.

   e. if any of the TLV is not known, C sends a failure response with
   cause code 3 back to MEP-A. It may also include the unknown TLVs.

   f. if the LSP is not in loopback mode, it sends a failure response
   with cause code 10 back to MEP-A.

   g. if the LSP loopback cannot be removed, it sends a failure response
   with cause code 12 back to MEP-A.

   h. if the LSP is successfully changed from loopback mode to normal
   mode of operation, it sends a reply with cause code 0 (Success ) back
   to MEP-A.

   The response is sent using an MPLS LSP Ping echo reply with a
   response TLV or an in-Band Loopback removal response message. An
   authentication TLV MAY be included.

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7. Security Considerations

   Security is addressed through the use of authentication TLV and the
   the Challenge-Handshake Authentication protocol procedures described
   in section [9].

8. IANA Considerations

8.1. Pseudowire Associated Channel Type

   LI-LB OAM requires a unique Associated Channel Type which is assigned
   by IANA from the Pseudowire Associated Channel Types Registry.

   Registry:
      Value        Description              TLV Follows  Reference
      -----------  -----------------------  -----------  ---------
      0xHHHH       LI-LB                    No           (Section 3.1)


8.2. New LSP Ping TLV types

   IANA is requested to assign TLV type values to the following TLVs
   from the "Multiprotocol Label Switching Architecture (MPLS) Label
   Switched Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-
   TLVs" sub-registry.

     1. LI-LB Request TLV (See section 3.3.1)
     2. LI-LB Response TLV (See section 3.3.2)
     3. Authentication TLV (See section 3.3.3)
9. Acknowledgements

   The authors would like to thank Loa Andersson for his valuable
   comments.

10. References

10.1. Normative References

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

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

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

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

   [5]   N. Bahadur, et. al., "MPLS on-demand Connectivity Verification,
         Route Tracing and Adjacency Verification", draft-ietf-mpls-tp-
         on-demand-cv-00, work in progress, June 2010

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

   [7]   Bocci, M. and G. Swallow, "MPLS-TP Identifiers", draft-ietf-
         mpls-tp-identifiers-01 (work in progress), June 2010.

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

   [9]   B. Lloyd, L&A, and W. Simpson, "PPP Authentication Protocols",
         October 1992.

10.2. Informative References

   [10]  Nabil Bitar, et. al, "Requirements for Multi-Segment Pseudowire
         Emulation Edge-to-Edge (PWE3) ", RFC5254, October 2008.

Author's Addresses

    Sami Boutros
   Cisco Systems, Inc.
   Email: sboutros@cisco.com

   Siva Sivabalan
   Cisco Systems, Inc.
   Email: msiva@cisco.com

   Rahul Aggarwal
   Juniper Networks.
   EMail: rahul@juniper.net

   Martin Vigoureux
   Alcatel-Lucent.
   Email: martin.vigoureux@alcatel-lucent.com

   Xuehui Dai
   ZTE Corporation.
   Email: dai.xuehui@zte.com.cn

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   George Swallow
   Cisco Systems, Inc.
   Email: swallow@cisco.com

   David Ward
   Juniper Networks.
   Email: dward@juniper.net

   Stewart Bryant
   Cisco Systems, Inc.
   Email: stbryant@cisco.com

   Carlos Pignataro
   Cisco Systems, Inc.
   Email: cpignata@cisco.com

   Eric Osborne
   Cisco Systems, Inc.
   Email: eosborne@cisco.com

   Nabil Bitar
   Verizon.
   Email: nabil.bitar@verizon.com

   Italo Busi
   Alcatel-Lucent.
   Email: italo.busi@alcatel-lucent.it

   Lieven Levrau
   Alcatel-Lucent.
   Email: llevrau@alcatel-lucent.com

   Laurent Ciavaglia
   Alcatel-Lucent.
   Email: laurent.ciavaglia@alcatel-lucent.com

   Bo Wu
   ZTE Corporation.
   Email: wu.bo@zte.com.cn



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   Jian Yang
   ZTE Corporation.
   Email: yang_jian@zte.com.cn

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