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Dual-Homing Protection for MPLS Transport Profile (MPLS-TP) Pseudowires
draft-cheng-pwe3-mpls-tp-dual-homing-protection-00

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Weiqiang Cheng , Lei Wang , Han Li , Kai Liu , Shahram Davari , Jie Dong
Last updated 2014-07-01
Replaced by draft-ietf-pals-mpls-tp-dual-homing-protection, RFC 8184
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draft-cheng-pwe3-mpls-tp-dual-homing-protection-00
Network Working Group                                           W. Cheng
Internet-Draft                                                   L. Wang
Intended status: Standards Track                                   H. Li
Expires: December 19, 2014                                  China Mobile
                                                                  K. Liu
                                                     Huawei Technologies
                                                               S. Davari
                                                    Broadcom Corporation
                                                                 J. Dong
                                                     Huawei Technologies
                                                           July 01, 2014

Dual-Homing Protection for MPLS Transport Profile (MPLS-TP) Pseudowires
           draft-cheng-pwe3-mpls-tp-dual-homing-protection-00

Abstract

   In some scenarios, the MPLS Trasport Profile (MPLS-TP) Pseudowires
   (PWs) are provisioned through either static configuration or
   management plane, where a dynamic control plane is not available.  A
   fast protection mechanism for MPLS-TP PWs is needed to protect
   against the failure of Attachment Circuit (AC), the failure of
   Provider Edge (PE) and also the failure in the Packet Switched
   Network (PSN).  This document proposes a dual-homing protection
   mechanism for MPLS-TP PWs, which can provide fast protection for
   comprehensive failure scenarios including the failure of AC, the PE
   node or the PSN network.

Requirements Language

   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 [RFC2119].

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

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   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 December 19, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  MPLS-TP PW Dual-Homing Protection Scenarios . . . . . . . . .   3
     2.1.  One-side Dual-Homing Protection . . . . . . . . . . . . .   3
     2.2.  Two-side Dual-Homing Protection . . . . . . . . . . . . .   4
   3.  Overview of the Proposed Solution . . . . . . . . . . . . . .   5
   4.  Protocol Extensions for MPLS-TP PW Dual-Homing Protection . .   6
     4.1.  Information Exchange Between Dual-Homing PEs  . . . . . .   6
     4.2.  Protection Procedures . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   [RFC6372] and [RFC6378] describe the framework and mechanism of MPLS-
   TP Linear protection, which can provide protection for the MPLS LSP
   or PW between the edge nodes.  Such mechanism does not protect the
   failure of the Attachement Circuit (AC) or the edge node.  [RFC6718]
   [RFC6870] describe the framework and mechanism for PW redundancy to
   provide protection for AC or PE node failure.  The PW redundancy
   mechanism is based on the signaling of Label Distribution Protocol
   (LDP), which is applicable to MPLS PWs or MPLS-TP PWs with a dynamic
   control plane.  [I-D.ietf-pwe3-endpoint-fast-protection] describes a

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   fast local repair mechanism for PW egress endpoint failures, which is
   based on PW redundancy, upstream label assignment and context
   specific label switching.  Such mechanism is applicable to PWs with a
   dynamic control plane.

   In some scenarios such as mobile backhauling, the MPLS-TP PWs are
   provisioned through either static configuration or management plane,
   where a dynamic control plane is not available.  A fast protection
   mechanism is needed for these MPLS-TP PWs to protect against the
   failure of AC, the PE node or the PSN network.

   In addition, if at least one side CE node is dual-homed to two PEs,
   and a fault occurs in the primary AC, operators usually prefer to
   perform switchover only in the AC side and keeps using the working
   pseudowire if possible.  The purpose is to avoid massive PW
   switchover caused by AC failure in mobile backhaul networks and to
   achieve efficient and balanced link bandwidth utilization in the PSN
   network.

   This document proposes a dual-homing protection mechanism for static
   MPLS-TP PWs, which can provide fast protection for comprehensive
   failure scenarios including failure of AC, the PE node or the PSN
   network, and meet the requirement of avoiding PW switchover when
   possible.  The mechanism defined in this document is complementary to
   the existing protection mechanisms.

   The proposed mechanism has been deployed in several mobile backhaul
   networks which use static MPLS-TP PWs for the backhauling of mobile
   traffic from the RF sites to the core sites.

2.  MPLS-TP PW Dual-Homing Protection Scenarios

   The following sections describe the typical topology and application
   scenarios of MPLS-TP PW dual-homing protection.  The scenarios can be
   classified into two categories: one-side dual-homing and two-side
   dual-homing.

2.1.  One-side Dual-Homing Protection

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           |<--------------- Emulated Service --------------->|
           |                                                  |
           |          |<------- Pseudo Wire ------>|          |
           |          |                            |          |
           |          |    |<-- PSN Tunnels-->|    |          |
           |          V    V                  V    V          |
           V    AC    +----+                  +----+          V
     +-----+    |     | PE1|                  |    |          +-----+
     |     |----------|........PW1.(working).......|          |     |
     |     |          |    |                  |    |          |     |
     |     |          +----+                  |    |     AC   |     |
     |     |            ||                    |    |     |    |     |
     | CE1 |           DNI PW                 |PE3 |----------| CE2 |
     |     |            ||                    |    |          |     |
     |     |          +----+                  |    |          |     |
     |     |          |    |                  |    |          |     |
     |     |----------|......PW2.(protection)......|          |     |
     +-----+    |     | PE2|                  |    |          +-----+
                AC    +----+                  +----+
                Figure 1. One-side PW dual-homing protection

   Figure 1 illustrates the network scenario of one-side CE dual-homing
   protection.  CE1 is dual-homed to PE1 and PE2, while CE2 is single-
   homed to PE3.  This topology protects the node failures of PE1 and
   PE2 and the AC link failures between CE1 and PE1, PE2.  This scheme
   can be used in mobile backhauling application scenarios.  For
   example, NodeB serves as CE2 while RNC serves as CE1.  PE3 works as
   an access side MPLS-TP device while PE1 and PE2 works as a core side
   MPLS-TP device.

2.2.  Two-side Dual-Homing Protection

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           |<---------------- Emulated Service -------------->|
           |                                                  |
           |          |<-------- Pseudowire ------>|          |
           |          |                            |          |
           |          |    |<-- PSN Tunnels-->|    |          |
           |          V    V                  V    V          |
           V    AC    +----+                  +----+     AC   V
     +-----+    |     |....|.......PW1........|....|     |    +-----+
     |     |----------| PE1|                  | PE3|----------|     |
     |     |          +----+                  +----+          |     |
     |     |            ||                      ||            |     |
     | CE1 |          DNI PW                  DNI PW          | CE2 |
     |     |            ||                      ||            |     |
     |     |          +----+                  +----+          |     |
     |     |          |    |                  |    |          |     |
     |     |----------| PE2|                  | PE4|--------- |     |
     +-----+    |     |....|.......PW2........|....|     |    +-----+
                AC    +----+                  +----+     AC

               Figure 2. Two-side PW dual-homing protection

   Figure 2 illustrates the network scenario of two-side CE dual-homing.
   CE1 is dual-homed to PE1 and PE2, and CE2 is dual-homed to PE3 and
   PE4.  This topology can protect the node failure of the dual-homing
   PEs on both sides, and also protects the AC link failures between the
   CEs and their dual-homing PEs.  Meanwhile, dual-homing PW protection
   can protect the failure occured in the PSN network.  This scenario is
   mainly used for services providing for important business customers.
   In this case, CE1 and CE2 can be regarded as service access points.

3.  Overview of the Proposed Solution

   The linear protection mechanisms for MPLS-TP network are defined in
   [RFC6378] [I-D.ietf-mpls-tp-psc-itu].  When such mechanisms are
   applied to PW linear protection, both the working PW and the
   protection PW need to terminate on the same PE nodes.  This section
   extends these mechanisms to provide dual-homing protection for MPLS-
   TP PWs.

   With MPLS-TP PW dual-homing protection mechanism, the linear
   protection mechanisms on the Single-homing PE (e.g.  PE3 in figure 3)
   are not changed, while on the dual-homing side the working PW and
   protection PW are terminated on two dual-homing PEs (e.g.  PE1 and
   PE2 in figure 3) respectively, to provide protection for the dual-
   homing PEs and the connected ACs.  A dedicated Dual-Node
   Interconnection (DNI) PW is established between the two dual-homing
   PE nodes, which is used to bridge the PW traffic when failure happens
   in the working PW or the primary AC.  In order to make the linear

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   protection mechanism work under the dual-homing PEs scenario, some
   coordination between the dual-homing PE nodes is necessary.  The
   protection switching mechanism is detailed in following sections.

                +----------------+
               /                |                +--------+
          AC1 /|   PE1          |  Working PW    |        |
             / |        ++-----------------------|        |
            /  |        ||      | Service PW1    |        |
       +---/+  +--------||------+                |        |   +----+
       |    |         DNI PW                     |  PE3   |   |    |
       | CE1|           ||                       |        |---| CE2|
       +---\+  +--------||------+                |        |   +----+
            \  |        ||      | Protection PW  |        |
             \ |        ++-----------------------|        |
          AC2 \|                | Service PW2    |        |
               \   PE2          |                +--------+
               +----------------+

                Figure 3. Dual-homing Proctection with DNI PW

   The following failure scenarios can be protected by MPLS-TP PW dual-
   homing protection:

   o  Failure of the working PW (PW1)

   o  Failure of the working AC (AC1)

   o  Failure of the working PE (PE1)

4.  Protocol Extensions for MPLS-TP PW Dual-Homing Protection

   In order to achieve the MPLS-TP PW dual-homing protection,
   coordination is needed between the dual-homing PE nodes to
   communicate the service PW status and protection coordination
   requests.  The forwarding state of dual-homing PEs is also specified.

4.1.  Information Exchange Between Dual-Homing PEs

   A new Channel Type is defined for the coordination between the dual-
   homing PEs of MPLS-TP PWs.  Such channel type can be used for the
   exchange of different kinds of information.  This document uses this
   channel type for the PW status exchange and protection coordination
   between the dual-homing PEs.  Other use cases of this channel type
   are for further study and are out of the scope of this document.

   The MPLS-TP Dual-Homing Coordination (DHC) message is sent on the DNI
   PW between the dual-homing PEs.

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   The format of an MPLS-TP DHC 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 1|Version|     Flags     |         DHC Code Point        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Dual-Homing Group ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         TLV  Length           |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                              TLVs                             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Figure 4. MPLS-TP Dual-Homing Coordination Message

   The Dual-Homing Group ID is a 4-octet unsigned integer to identify
   the dual-homing PEs in the same dual-homing group.

   2 TLVs are defined in MPLS-TP Dual-Homing Coordination message for
   MPLS-TP PW dual-homing protection:

   Type        Description               Length
    1          PW Status                 20 Bytes
    2        Dual-Node Switching         16 Bytes

   The PW Status TLV is used by a dual-homing PE to report its Service
   PW status to the other dual-homing PE in the same dual-homing group.

      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=1 (PW Status)        |          Length               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Destination Node_ID                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Source Node_ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         DNI PW-ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Reserved                            |P|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Service PW Request                   |D|F|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 5. PW Status TLV

   - The Destination Node_ID is the 32-bit Node_ID of the receiving PE.

   - The Source Node_ID is the 32-bit Node_ID of the sending PE.

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   - The DNI PW-ID field contains PW-ID of the DNI PW.

   - The P (Protection) bit indicates whether the message is sent by the
   working PE (P=0) or by the protection PE (P=1).

   - The Service PW Request field indicates the protection request
   generated on the Service PW between the sending PE and the remote PE.
   Two bits are defined in the Service PW Request field:

   o  F bit: Indicates Signal Fail (SF) request is generated on the
      service PW.  It can be either a local request or a remote request
      received from the remote PE.

   o  D bit: Indicates Signal Degrade (SD) request is generated on the
      service PW.  It can be either a local request or a remote request
      received from the remote PE.

   o  Other bits are reserved and MUST be set to 0 and SHOULD be ignored
      upon receipt.

   The Dual-Node Switching TLV is used by the protection dual-homing PE
   to send protection state coordination to the working dual-homing PE.

      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=2 (Dual-Node Switching) |          Length               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Destination Node_ID                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Source Node_ID                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         DNI PW-ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Reserved                         |S|P|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 6. Dual-node Switching TLV

   - The Destination Node_ID is the 32-bit Node_ID of the receiving PE.

   - The Source Node_ID is the 32-bit Node_ID of the sending PE.

   - The DNI PW-ID field contains PW-ID of the DNI PW.

   - The P (Protection) bit indicates whether the message is sent by the
   working PE (P=0) or by the protection PE (P=1).  With the mechanism
   described in this document, only the protection PE could send out the
   DHC message with the Dual-node Switching TLV.

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   - The S (PW Switching) bit indicates which service PW is used for
   transporting user traffic.  It is set to 0 when traffic is
   transported on the working PW, and is set to 1 if traffic will be
   transported on the protection PW.  The value of the S bit is
   determined by the protection coordination mechanism between the dual-
   homing protection PE and the remote PE.

4.2.  Protection Procedures

   MPLS-TP PW dual-homing protection mechanism can work with the
   existing AC side redundancy mechanisms, e.g.  MC-LAG.  On PSN network
   side, PSN tunnel protection mechanism is not required, as the dual-
   homing PW protection can also protect the failure happened in the PSN
   network.

   For the single-homing PE, it just treats the working PW and
   protection PW as if they terminate on the same remote PE node, thus
   normal protection coordination mechanisms still apply to the single-
   homing PE.

   The protection behavior of the dual-homing PEs is determined by the
   components shown in the figure below:

              +------------+             +------------------+
              |   PE3      |             |      PE1         |
              |       +---+| service PW1 |+---+        +---+|
              |       |PW1|---------------|PW1|        |AC1|\
              |       +---+| working PW  |+---+        +---+|\
              |            |             |     +------+     | \
              |            |             |     |DNI PW|     |  \  AC1
              |            |             |     +------+     |   \(active)
              |            |             +--------||--------+    \
 +-----+  AC3 |            |                      ||           +--\---+
 | CE2 |------|            |                      || DNI PW    |  CE1 |
 +-----|      |            |                      ||           +--/---+
              |            |             +--------||--------+    /
              |            |             |     +------+     |   /
              |            |             |     |DNI PW|     |  / AC2
              |            |             |     +------+     | /(standby)
              |            |             |                  |/
              |       +---+| service PW2 |+---+        +---+/
              |       |PW2|---------------|PW2|        |AC2||
              |       +---+|protection PW|+---+  PE2   +---+|
              +------------+             +------------------+
            Figure 7. Components of PW Dual-Homing protection

   In figure 7, for a dual-homing PE, Service PW is the PW which carries
   service between dual-homing PE and the remote PE.  The status of

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   Service PW is determined by the OAM and protection switching
   coordination mechanisms between the dual-homing PEs and the remote
   PE.

   DNI PW is the PW between the two dual-homing PE nodes.  It is used to
   bridge traffic when failure occurs in PSN network or in the AC side.
   The status of DNI PW is determined by OAM protocol running between
   the dual-homing PEs.

   AC is the link which connects the dual-homing PEs to the dual-homed
   CE.  The AC status is determined by MC-LAG or other AC redundancy
   mechanisms.

   The PW status and protection coordination requests are exchanged
   between the dual-homing PEs using the DHC message defined in section
   4.1.

   After the exchange of PW status information using the MPLS-TP DHC
   Message, both dual-homing PEs obtain the status of working and
   protection service PWs, the AC and the DNI PW.  The forwarding
   behavoir of dual-homing PE nodes are determined by the forwarding
   state machine shown in the following table:

          +-----------+---------+--------+---------------------+
          |Service PW |   AC    | DNI PW | Forwarding Behavior |
          +-----------+---------+--------+---------------------+
          |  Active   | Active  |   Up   |Service PW <-> AC    |
          +-----------+---------+--------+---------------------+
          |  Active   | Standby |   Up   |Service PW <-> DNI PW|
          +-----------+---------+--------+---------------------+
          |  Standby  | Active  |   Up   |    DNI PW <-> AC    |
          +-----------+---------+--------+---------------------+
          |  Standby  | Standby |   Up   |  Drop all packets   |
          +-----------+---------+--------+---------------------+
             Table 1. Dual-homing PE Forwarding State Machine

   In normal state, the working PW is in active state, and the primary
   AC is active state, according to Table 1, PW traffic will be
   forwarded between the working service PW and the primary AC (AC1).
   No traffic will go through the protection PE or the DNI PW, as both
   the protection service PW and the AC connecting to the protection PE
   are in standby state.

   If AC1 goes down due to some fault, the AC side redundancy mechanism
   would switchover to the backup AC (AC2), the state of AC2 changes to
   active.  There is no change in the status of working and protection
   PW.  According to Table 1, PE1 starts to forward traffic between the
   working PW and the DNI PW, while PE2 starts to forward traffic

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   between DNI PW and AC2.  Note that in this case only AC switchover
   takes place, in PSN network traffic keeps transporting on the working
   PW and PW switchover is no needed.

   If the working PW is down due to some fault in the PSN network, both
   the remote PE (PE3) and the working PE (PE1) would detect the failure
   using MPLS-TP OAM mechanisms, then PE3 would send a normal protection
   coordination message on the protection path to inform its peer node
   (PE2) to switchover to the protection PW.  PE1 would also inform PE2
   the working PW status (down) using the MPLS-TP DHC message.  Then
   according to Table 1, PE2 starts to forward traffic between the
   protection PW and the DNI PW, and PE1 starts to forward traffic
   between the DNI PW and AC1.

   If the working PE (PE1) goes down, both the remote PE(PE3) and the
   protection PE(PE2) would detect the failure using MPLS-TP OAM
   mechanisms, the state of AC1 would change to down, and the state of
   AC2 will change to active according to AC side redundancy mechansim.
   Then PE3 would send a normal protection coordination message on the
   protection path to inform its peer node (PE2) to switchover to the
   protection PW.  Then according to table 1, PE2 starts to forward
   traffic between the protection PW and AC2.

5.  IANA Considerations

   IANA needs to assign one new channel type for "MPLS-TP Dual-Homing
   Coordination messgae" from the "Pseudowire Associated Channel Types"
   registry.

   This document creates a new registry called "MPLS-TP DHC TLVs"
   registry. 2 new TLVs are defined in this document:

   Type        Description               Length
    1          PW Status                 20 Bytes
    2        Dual-Node Switching         16 Bytes

6.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the security model of MPLS-TP linear protection as defined in
   [RFC6378].  Please refer to [RFC5920] for MPLS security issues and
   generic methods for securing traffic privacy and integrity.

7.  References

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7.1.  Normative References

   [I-D.ietf-mpls-tp-psc-itu]
              Ryoo, J., Gray, E., Helvoort, H., D'Alessandro, A.,
              Cheung, T., and E. Osborne, "MPLS Transport Profile (MPLS-
              TP) Linear Protection to Match the Operational
              Expectations of SDH, OTN and Ethernet Transport Network
              Operators", draft-ietf-mpls-tp-psc-itu-04 (work in
              progress), March 2014.

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

   [RFC6372]  Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS-
              TP) Survivability Framework", RFC 6372, September 2011.

   [RFC6378]  Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
              A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
              Protection", RFC 6378, October 2011.

7.2.  Informative References

   [I-D.ietf-pwe3-endpoint-fast-protection]
              Shen, Y., Aggarwal, R., Henderickx, W., and Y. Jiang, "PW
              Endpoint Fast Failure Protection", draft-ietf-pwe3-
              endpoint-fast-protection-00 (work in progress), December
              2013.

   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [RFC6718]  Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire
              Redundancy", RFC 6718, August 2012.

   [RFC6870]  Muley, P. and M. Aissaoui, "Pseudowire Preferential
              Forwarding Status Bit", RFC 6870, February 2013.

Authors' Addresses

   Weiqiang Cheng
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  100053
   China

   Email: chengweiqiang@chinamobile.com

Cheng, et al.           Expires December 19, 2014              [Page 12]
Internet-Draft    Dual-Homing Protection for MPLS-TP PW        June 2014

   Lei Wang
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  100053
   China

   Email: Wangleiyj@chinamobile.com

   Han Li
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  100053
   China

   Email: Lihan@chinamobile.com

   Kai Liu
   Huawei Technologies
   Huawei Base, Bantian, Longgang District
   Shenzhen  518129
   China

   Email: alex.liukai@huawei.com

   Shahram Davari
   Broadcom Corporation
   3151 Zanker Road
   San Jose  95134-1933
   United States

   Email: davari@broadcom.com

   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: jie.dong@huawei.com

Cheng, et al.           Expires December 19, 2014              [Page 13]