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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: March 29, 2011
                                                   Rahul Aggarwal (Ed.)
                                                 Juniper Networks, Inc.

                                                 Martin Vigoureux (Ed.)
                                                         Alcatel-Lucent

                                                       Xuehui Dai (Ed.)
                                                        ZTE Corporation

                                                     September 29, 2010


        MPLS Transport Profile Lock Instruct and Loopback Functions
                      draft-ietf-mpls-tp-li-lb-00.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 March 29, 2007.



Abstract




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   This document specifies an extension to MPLS Operation,
   administration, and Maintenance (OAM) to operate an MPLS Transport
   Profile (MPLS-TP) Label Switched Path (LSP), bi-directional RSVP-TE
   tunnels, pseudowires (PW), or Multi-segment PWs in loopback mode for
   management purpose. 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 MPLS-TP LSP back to the source.

Table of Contents


   1. Introduction...................................................3
   2. Terminology....................................................4
   3. MPLS-TP Loopback/Lock Mechanism................................5
      3.1. In-band Message Identification............................5
      3.2. MPLS LI-LB Message Format.................................5
      3.3. LSP Ping Extensions.......................................8
         3.3.1. Lock Request TLV.....................................8
         3.3.2. Unlock Request TLV...................................8
         3.3.3. Loopback Request TLV.................................8
         3.3.4. Loopback Removal TLV.................................9
         3.3.5. Response TLV.........................................9
         3.3.6. Authentication TLV..................................10
   4. Loopback/Lock Operations......................................10
      4.1. Lock Request.............................................10
      4.2. Unlock Request...........................................10
      4.3. Loopback Request.........................................11
      4.4. Loopback Removal.........................................11
   5. Data packets..................................................11
   6. Operation.....................................................12
      6.1. General Procedures.......................................12
      6.2. Example Topology.........................................12
      6.3. Locking an LSP...........................................13
      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
   TBD..............................................................16
   9. References....................................................16
      9.1. Normative References.....................................16
      9.2. 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. MPLS-TP bidirectional
   LSP emulating traditional transport circuits need to provide the same
   loopback capability.  The mechanisms in this document apply to
   associated bidirectional paths as defined in [7], which include MPLS-
   TP LSPs, bi-directional RSVP-TE tunnels, pseudowires (PW), and Multi-
   segment PWs.

   To describe the loopback functionality, let us assume a bi-
   directional MPLS-TP LSP A <---> B <---> C <---> D where A, B, C, and
   D are MPLS capable nodes. Also, let us assume that the network
   operator requires C to loop, back to A, the packets sent from A. In
   this example, A and D acts as Maintenance End Points (MEPs) and C
   acts as a Maintenance Intermediate Point (MIP). The operator can
   setup the MPLS-TP LSP into loopback mode such that C loops all the
   packets (regardless of whether they are data or control packets)
   generated by node A back to A. The packets are not also forwarded
   towards D. Similarly, any traffic received by C from the reverse
   direction will be dropped.

   The operator must take the MPLS-TP LSP out of service before setting
   up the MPLS-TP LSP in loopback mode. This is accomplished by the MEP
   establishing the loopback first sending a Lock command to the remote
   MEP(s). In the case above, A sends a Lock request message along the
   MPLS-TP LSP and destined to D to lock the MPLS-TP LSP. The message
   will be intercepted by D since it is at the end of the LSP. D
   responds to the lock request with a reply message specifying whether
   it can take the LSP out of service or not.

   In order to set the MPLS-TP LSP in loopback mode, A sends a Loopback
   request message to the MIP or MEP where the loopback is to be
   enabled. In the above example, the MPLS TTL value is set so that the
   message will be intercepted by C.

   This message contains a request to instruct C to operate the
   corresponding MPLS-TP LSP in Loopback mode. C responds to the
   Loopback request with a reply message back to A to indicate whether
   or not it has successfully set the MPLS-TP LSP into the loopback
   mode. If the loopback cannot be set, the reply message would contain
   an error code. Upon receiving such a reply to the loopback request, A
   logs the event and takes further reporting actions as necessary.  If
   the MPLS-TP LSP was previously locked, A sends another request
   message to D to unlock it.


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   If the loopback request can be performed, the input LSP from the
   direction of A is directly cross-connected to the output LSP towards
   A. All the packets generated by node A (data and control) are looped
   back at C, excepting the case of TTL expiration.

   When the loopback operation is no longer required, A sends a request
   message to remove the loopback and thus restore the LSP to its
   original forwarding state. In this example the MPLS TTL is set such
   that this message is intercepted by C. It is expected that C sends a
   reply back to A to with a return code either ACKing or NAK the
   loopback removal request. Upon getting an ACK response to loopback
   mode removal request, A sends another request message to unlock the
   MPLS-TP LSP. The packet is intercepted by D as it is at the end of
   the MPLS-TP LSP.

   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

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.

   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].

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


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   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. MPLS-TP 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 MPLS-TP LI-LB channel is identified by the
  ACH as defined in RFC 5586 [6] with the Channel Type set to the MPLS-
  TP 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 (MPLS-TP LI-LB)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1: ACH Indication of MPLS-TP LI-LB

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

3.2. MPLS LI-LB Message Format

   The format of an MPLS-TP 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                        |


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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           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
                         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 returned
   unchanged by the receiver in the MPLS response message (if any).


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   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.

   Return code

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


   Cause code

         Value   Meaning
         -----   -------
            0    No cause code
            1    Fail to match target MIP/MEP ID
            2    Malformed request received
            3    One or more of the TLVs is/are unknown
            4    Authentication failed
            5    MPLS-TP LSP/PW already locked
            6    MPLS-TP LSP/PW already unlocked
            7    Fail to lock MPLS-TP LSP/PW
            8    Fail to unlock MPLS-TP LSP/PW
            9    MPLS-TP LSP/PW already in loopback mode
           10    MPLS-TP LSP/PW is not in loopback mode
           11    Fail to set MPLS-TP LSP/PW in loopback mode
           12    Fail to remove MPLS-TP/PW from loopback mode
           13    No label binding for received message


   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.









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3.3. LSP Ping Extensions

3.3.1. Lock 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 = 0                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   A MEP includes a Lock Request TLV in the MPLS LSP Ping echo request
   message to request the MEP on the other side of the MPLS-TP LSP to
   take the LSP out of service.

3.3.2. Unlock 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 = 0                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Unlock Request TLV is sent from the MEP which has previously sent
   lock request. Upon receiving the LSP Ping Echo request message with
   the unlock request TLV, the receiver MEP brings the MPLS-TP LSP back
   in service.

3.3.3. Loopback 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 = 0                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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










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3.3.4. Loopback Removal 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 = 0                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   When loopback mode operation of an MPLS-TP LSP is no longer required,
   the MEP that previously sent the MPLS LSP Ping echo request message
   with a loopback TLV, sends another MPLS LSP Ping echo request message
   with a Loopback Removal TLV. The receiver MEP changes the MPLS-TP LSP
   from loopback mode to normal mode of operation.

3.3.5. 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 = 0x1            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |ReturnCode   |
   +-+-+-+-+-+-+-+

      Return code
   Value   Meaning
   -----   -------
       0    Success
       1    Fail to match target MIP/MEP ID
       2    Malformed loopback request received
       3    One or more of the TLVs is/are unknown
       4    Authentication failed
       5    MPLS-TP LSP/PW already locked
       6    MPLS-TP LSP/PW already unlocked
       7    Fail to lock MPLS-TP LSP/PW
       8    Fail to unlock MPLS-TP LSP/PW
       9    MPLS-TP LSP/PW already in loopback mode
      10    MPLS-TP LSP/PW is not in loopback mode
      11    Fail to set MPLS-TP LSP/PW in loopback mode
      12    Fail to remove MPLS-TP LSP/PW from loopback mode
      13    No label binding for received message

Note that in the case of error code 3, the unknown TLV can also be
optionally included in the response TLV.





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3.3.6. 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                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Mechanisms similar to PPP Chap can be used to authenticate the
   Loopback request. A variable length key can be carried in an optional
   authentication TLV which can be included in the MPLS OAM LSP Ping
   echo request message containing a loopback request TLV or the LI-LB
   Message. The use of authentication key is outside the scope of the
   document.



4. Loopback/Lock Operations

4.1. Lock Request

   Lock Request is used to request a MEP to take an MPLS-TP 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 MPLS-TP LSP out of service. A
   receiver MEP sends an ACK only if it can successfully lock the MPLS-
   TP LSP. Otherwise, it sends a NAK.



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 MPLS-TP 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 MPLS-TP LSP has been put back in service. A receiver MEP
   sends an ACK only if the MPLS-TP LSP has been unlocked, and unlock
   operation is successful. Otherwise, it sends a NAK.






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4.3. Loopback Request


   When a MEP wants to put an MPLS-TP 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 MPLS-TP 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 MPLS-TP 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 MPLS-TP LSP can operate in loopback mode.

4.4. Loopback Removal


   When loopback mode operation of an MPLS-TP LSP is no longer required,
   the MEP that previously sent the Loopback request message sends
   another Loopback Removal message. The receiver MEP changes the MPLS-
   TP 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 MPLS-TP LSP is already
   in loopback mode, and if the MPLS-TP 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
   MPLS-TP 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. In order for the sender MEP node to make sure that no
   data packets are dropped, each data MPLS packets may contain a
   sequence-id right after the label stack.  A time-stamp fields in the
   data packets can help calculate the Round trip delay of datapackets.
   The Local Time-Stamp is set by the sender, and can be used to
   calculate the round trip delay after the message is looped back.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Label with EOS bit set                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Length                        | Reserved                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Sequence-Number                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Time-Stamp                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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    |                         Time-Stamp                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Arbitrary Padding                                            |
    :                                                               :
    |  Arbitrary Padding                                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


6. Operation

6.1. General Procedures

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

   Sending LSP Ping Echo Request message with Loopback Request/Removal
   or in-Band Loopback Request/Removal Message

   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). It is RECOMMENDED that the TTL be set to the
   exact number of hops required to reach the MEP.

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 MPLS-TP LSP
   traverses nodes A <--> B <--> C <--> D.  We will refer to the
   Maintenance Entities involved as MEP-A, MIP-B, MIP-C, and MEP-D
   respectively.  Suppose a maintenance operation invoked at node A
   requires a loopback be set at node C. To invoke Loopack mode at node
   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.



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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 FEC/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 response with
   error code 1.

   MEP-D then examines the message, and:

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

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

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

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

   g. if the MPLS-TP LSP is not already locked and cannot be locked, it
   sends a response with error code 7 back to A.

   h. if the MPLS-TP LSP is successfully locked, it sends a response
   with error 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 Lock response message. An authentication
   TLV MAY be included.

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 to identify the LSP. If no

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   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 response with
   error code 1.

   MEP-D then examines the message, and:

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

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

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

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

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

   h. if the LSP is successfully unlocked, it sends a response with
   error 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 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.


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   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 response with
   error code 1.

   MIP-C then examines the message, and:

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

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

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

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

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

   h. if the MPLS-TP LSP is successfully programmed into the requested
   loopback mode, it sends a response with error 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 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 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.

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

   MIP-C then examines the message, and:

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

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

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

   f. if the MPLS-TP is not in loopback mode, it sends a response with
   error code 10 back to MEP-A.

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

   h. if the MPLS-TP is successfully changed from loopback mode to
   normal mode of operation, it sends a reply with error 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.



7. Security Considerations

   The security considerations for the authentication TLV need further
   study.

8. IANA Considerations

TBD

9. References

9.1. 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.

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

   [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-nitinb-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.

9.2. Informative References

   [9]   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

   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

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



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