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Versions: (draft-ietf-mpls-rsvp-egress-protection) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 RFC 8400

Internet Engineering Task Force                                  H. Chen
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                  A. Liu
Expires: May 1, 2017                                            Ericsson
                                                                 T. Saad
                                                           Cisco Systems
                                                                   F. Xu
                                                                 Verizon
                                                                L. Huang
                                                            China Mobile
                                                                   N. So
                                                     Tata Communications
                                                        October 28, 2016


         Extensions to RSVP-TE for LSP Egress Local Protection
             draft-ietf-teas-rsvp-egress-protection-06.txt

Abstract

   This document describes extensions to Resource Reservation Protocol -
   Traffic Engineering (RSVP-TE) for locally protecting egress nodes of
   a Traffic Engineered (TE) Label Switched Path (LSP), which is a
   Point-to-Point (P2P) LSP or a Point-to-Multipoint (P2MP) LSP.

Status of this Memo

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

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 1, 2017.

Copyright Notice

   Copyright (c) 2016 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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  An Example of Egress Local Protection  . . . . . . . . . .  3
     1.2.  Egress Local Protection with FRR . . . . . . . . . . . . .  4
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Protocol Extensions  . . . . . . . . . . . . . . . . . . . . .  4
     4.1.  Extensions to SERO . . . . . . . . . . . . . . . . . . . .  4
       4.1.1.  Primary Egress Subobject . . . . . . . . . . . . . . .  6
       4.1.2.  P2P LSP ID Subobject . . . . . . . . . . . . . . . . .  7
       4.1.3.  Opaque Data Subobject  . . . . . . . . . . . . . . . .  8
   5.  Egress Protection Behaviors  . . . . . . . . . . . . . . . . .  8
     5.1.  Ingress Behavior . . . . . . . . . . . . . . . . . . . . .  9
     5.2.  Primary Egress Behavior  . . . . . . . . . . . . . . . . .  9
     5.3.  Backup Egress Behavior . . . . . . . . . . . . . . . . . . 10
     5.4.  Transit Node and PLR Behavior  . . . . . . . . . . . . . . 10
       5.4.1.  Signaling for One-to-One Protection  . . . . . . . . . 11
       5.4.2.  Signaling for Facility Protection  . . . . . . . . . . 11
       5.4.3.  Signaling for S2L Sub LSP Protection . . . . . . . . . 13
       5.4.4.  PLR Procedures during Local Repair . . . . . . . . . . 13
   6.  Considering Application Traffic  . . . . . . . . . . . . . . . 14
     6.1.  A Typical Application  . . . . . . . . . . . . . . . . . . 14
     6.2.  PLR Procedure for Applications . . . . . . . . . . . . . . 15
     6.3.  Egress Procedures for Applications . . . . . . . . . . . . 15
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Definition of PROTECTION Object Reserved Bits  . . . . . . 16
     8.2.  New Subobjects . . . . . . . . . . . . . . . . . . . . . . 16
   9.  Co-authors . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
   11. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 17
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     12.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18





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1.  Introduction

   RFC 4090 describes two methods for protecting the transit nodes of a
   P2P LSP: one-to-one and facility protection.  RFC 4875 specifies how
   to use them to protect the transit nodes of a P2MP LSP.  However,
   they do not mention any local protection for an egress of an LSP.

   To protect the egresses of an LSP (P2P or P2MP), an existing approach
   sets up a backup LSP from a backup ingress (or the ingress of the
   LSP) to the backup egresses, where each egress is paired with a
   backup egress and protected by the backup egress.

   This approach uses more resources and provides slow fault recovery.
   This document specifies extensions to RSVP-TE for local protection of
   an egress of an LSP, which overcomes these disadvantages.

1.1.  An Example of Egress Local Protection

   Figure 1 shows an example of using backup LSPs to locally protect
   egresses of a primary P2MP LSP from ingress R1 to two egresses: L1
   and L2.  The primary LSP is represented by star(*) lines and backup
   LSPs by hyphen(-) lines.

   La and Lb are the designated backup egresses for egresses L1 and L2
   respectively.  To distinguish an egress (e.g., L1) from a backup
   egress (e.g., La), an egress is called a primary egress if needed.

   The backup LSP for protecting L1 is from its upstream node R3 to
   backup egress La.  The one for protecting L2 is from R5 to Lb.

                     [R2]*****[R3]*****[L1]
                    *          \ :.....:   $            **** Primary LSP
                   *            \           $           ---- Backup LSP
                  *              \           [CE1]      .... BFD Session
                 *                \         $              $ Link
                *                  \       $              $
               *                    ---[La]              $
              *
          [R1]******[R4]*******[R5]*****[L2]
         $                      \ :.....:   $
        $                        \           $
     [S]                          \           [CE2]
                                   \         $
                                    \       $
                                     ---[Lb]


            Figure 1: Backup LSP for Locally Protecting Egress



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   During normal operations, the traffic carried by the P2MP LSP is sent
   through R3 to L1, which delivers the traffic to its destination CE1.
   When R3 detects the failure of L1, R3 switches the traffic to the
   backup LSP to backup egress La, which delivers the traffic to CE1.
   The time for switching the traffic is within tens of milliseconds.

   The failure of a primary egress (e.g., L1 in the figure) may be
   detected by its upstream node (e.g., R3 in the figure) through a BFD
   between the upstream node and the egress in MPLS networks.  Exactly
   how the failure is detected is out of scope for this document.

1.2.  Egress Local Protection with FRR

   Using the egress local protection and the FRR, we can locally protect
   the egresses, the links and the transit nodes of an LSP.  The traffic
   switchover time is within tens of milliseconds whenever an egress,
   any of the links and the transit nodes of the LSP fails.

   The egress nodes of the LSP can be locally protected via the egress
   local protection.  All the links and the transit nodes of the LSP can
   be locally protected through using the FRR.


2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.


3.  Terminology

   This document uses terminologies defined in RFC 2205, RFC 3209, RFC
   4090, RFC 4873 and RFC 4875.


4.  Protocol Extensions

4.1.  Extensions to SERO

   The Secondary Explicit Route object (SERO) is defined in RFC 4873.
   The format of the SERO is re-used.

   The SERO used for protecting a primary egress node of a primary LSP
   may be added into the Path messages for the LSP and sent from the
   ingress node of the LSP to the upstream node of the egress node.  It
   contains three subobjects.




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   The first subobject indicates the branch node that is to originate
   the backup LSP (to a backup egress node).  The branch node is the
   direct upstream node of the primary egress node of the primary LSP if
   it can provide fast local protection for the primary egress node.
   The branch node can be a (upstream) node on the primary LSP, but not
   the direct upstream node if the direct upstream node does not provide
   any fast local protection against the failure of the primary egress
   node.  In this case, the backup LSP from the branch node to the
   backup egress node protects against failures on the segment of the
   primary LSP from the branch node to the primary egress node,
   including the primary egress node.

   The final (third) subobject in the SERO contains the egress node of
   the backup LSP, i.e., the address of the backup egress node.

   The second subobject is a protection subobject defined in RFC 4873,
   but with some extensions, which include a few of flags for egress
   local protection and some optional subobjects.  These new flags use a
   few of bits in the existing reserved field.  The optional subobjects
   follow the flags field.  The contents of the PROTECTION object is
   extended in the same way.

   The format of the extended protection subobject is defined as
   follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|    Type     |     Length    |    Reserved   |   C-Type      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |S|P|N|O| Reserved  | LSP Flags |     Reserved      | Link Flags|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |I|R|    Reserved   | Seg.Flags |        Reserved       |E-Flags|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Optional subobjects                       |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   E-Flags are defined for egress local protection.

   x01 (Egress local protection bit):  It is set (1) to indicate an
      egress local protection.

   x02 (Other sending UA label bit):  It is set (1) to indicate another
      protocol is desired for sending a label as a UA label from a
      primary egress to a backup egress.




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   x04 (S2L sub LSP backup desired bit):  It is set (1) to indicate S2L
      Sub LSP (ref to RFC 4875) is desired for protecting an egress of a
      P2MP LSP.

   The other flags are not valid and reset to zero when the egress local
   protection bit is set.

   After the upstream node of the primary egress node as the branch node
   receives the SERO and determines a backup egress node for the primary
   egress, it computes a path from itself to the backup egress node and
   sets up a backup LSP along the path for protecting the primary egress
   node according to the information in the FAST_REROUTE object in the
   Path message.  For example, if facility protection is desired,
   facility protection is provided for the primary egress node.

   The upstream node constructs a PROTECTION object based on the
   protection subobject in the SERO and adds the object into the Path
   message for the backup LSP.  The object contains a subobject called a
   primary egress subobject, which indicates the address of the primary
   egress node.

   The upstream node updates the SERO in the Path message for the
   primary LSP.  The protection subobject in the SERO contains a
   subobject called a P2P LSP ID subobject, which contains the
   information for identifying the backup LSP.  The final subobject in
   the SERO indicates the address of the backup egress node.

4.1.1.  Primary Egress Subobject

   There are two primary egress subobjects.  One is IPv4 primary egress
   subobject and the other is IPv6 primary egress subobject.

   The format of IPv4 primary egress subobject 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Length    |            Reserved           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 address (4 bytes)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     o Type:         0x01 for IPv4 primary egress
     o Length:       The total length of the subobject, which is 8 bytes
     o IPv4 address: IPv4 address of the primary egress node

   The format of IPv6 primary egress subobject is shown below:




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     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      |     Length    |            Reserved           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    IPv6 address (16 bytes)                    |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    o Type:         0x02 for IPv6 primary egress
    o Length:       The total length of the subobject, which is 20 bytes
    o IPv6 address: The IPv6 address of the primary egress node

4.1.2.  P2P LSP ID Subobject

   A P2P LSP ID subobject contains the information for identifying a
   backup point-to-point (P2P) LSP tunnel.

4.1.2.1.  IPv4 P2P LSP ID Subobject

   The format of IPv4 P2P LSP ID subobject 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Length    |           Tunnel ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               P2P LSP Tunnel Egress IPv4 Address              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Extended Tunnel ID                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     o Type:   0x03 for IPv4 P2P LSP ID
     o Length: The total length of the subobject in bytes, which is 12
     o Tunnel ID:
         A 16-bit identifier being constant over the life of the tunnel
     o P2P LSP Tunnel Egress IPv4 Address:
         IPv4 address of the egress of the tunnel
     o Extended Tunnel ID:
         A 4-byte identifier being constant over the life of the tunnel

4.1.2.2.  IPv6 P2P LSP ID Subobject

   The format of IPv6 P2P LSP ID subobject is illustrated below:







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      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      |     Length    |           Tunnel ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~         P2P LSP Tunnel Egress IPv6 Address (16 bytes)         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 Extended Tunnel ID (16 bytes)                 ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     o Type:     0x04 for IPv6 P2P LSP ID
     o Length:   The total length of the subobject in bytes, which is 36
     o Tunnel ID:
         A 16-bit identifier being constant over the life of the tunnel
     o P2P LSP Tunnel Egress IPv6 Address:
         IPv6 address of the egress of the tunnel
     o Extended Tunnel ID:
         A 16-byte identifier being constant over the life of the tunnel

4.1.3.  Opaque Data Subobject

   A opaque data subobject contains a piece of opaque data.  The format
   of opaque data subobject 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Length    |           Reserved            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Opaque Data                           |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     o Type:   0x05 for opaque data
     o Length: The total length of the subobject in bytes

   This subobject may be used by a primary egress node (e.g., L1) to
   send its corresponding backup egress node (e.g., La) the information
   about forwarding the traffic to a receiver (e.g., CE1) through its
   upstream node (e.g., R3).  It may contain a label as a UA label and a
   receiver such as CE1.  The exact format and meanings of the opaque
   data are out of scope for this document.


5.  Egress Protection Behaviors






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5.1.  Ingress Behavior

   To protect a primary egress of an LSP, the ingress MUST set the
   "label recording desired" flag and the "node protection desired" flag
   in the SESSION_ATTRIBUTE object.

   If one-to-one backup or facility backup is desired to protect a
   primary egress of an LSP, the ingress MUST include a FAST_REROUTE
   object and set the "One-to-One Backup Desired" or "Facility Backup
   Desired" flag respectively.

   If S2L Sub LSP backup is desired to protect a primary egress of a
   P2MP LSP, the ingress MUST set the "S2L Sub LSP Backup Desired" flag
   in an SERO object.

   If another protocol is desired for sending a label as a upstream
   assigned label to a backup egress, the ingress MUST set the "Other
   Sending UA Label" flag.

   A backup egress MUST be configured on the ingress of an LSP to
   protect a primary egress of the LSP if and only if the backup egress
   is not indicated in another place.

   The ingress MUST send a Path message for the LSP with the objects
   above and the SEROs for protecting egresses of the LSP.  For each
   primary egress of the LSP to be protected, the ingress MUST add an
   SERO object into the Path message if the backup egress or some
   options are given.  If the backup egress is given, then the final
   subobject in the SERO containts it; otherwise the address in the
   final subobject is zero.

5.2.  Primary Egress Behavior

   To protect a primary egress of an LSP, a backup egress MUST be
   configured on the primary egress of the LSP to protect the primary
   egress if and only if the backup egress is not indicated in another
   place.

   If the backup egress is configured on the primary egress of the LSP,
   the primary egress MUST send its upstream node a Resv message for the
   LSP with an SERO for protecting the primary egress.  It sets the
   flags in the SERO in the same way as an ingress.

   If the LSP carries the service traffic with a service label, the
   primary egress sends its corresponding backup egress the information
   about the service label as a UA label and the related forwarding.





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5.3.  Backup Egress Behavior

   When a backup egress node receives a Path message for an LSP, it
   determines whether the LSP is used for egress local protection
   through checking the PROTECTION object in the message.  If there is a
   PROTECTION object in the Path message for the LSP and the Egress
   local protection flag in the object is set to one, the LSP is the
   backup LSP for egress local protection.  The primary egress to be
   protected is in the primary egress subobject in the PROTECTION
   object.

   When the backup egress receives the information about a UA label and
   its related forwarding from the primary egress, it uses the backup
   LSP label as a context label and creates a forwarding entry using the
   information about the UA label and the related forwarding.  This
   forwarding entry is in a forwarding table for the primary egress
   node.

   When the primary egress node fails, its upstream node switches the
   traffic from the primary LSP to the backup LSP to the backup egress
   node, which delivers the traffic to its receiver such as CE using the
   backup LSP label as a context label to get the forwarding table for
   the primary egress node and the service label as UA label to find the
   forwarding entry in the table to forward the traffic to the receiver.

5.4.  Transit Node and PLR Behavior

   If a transit node of an LSP receives the Path message with the SEROs
   and it is not an upstream node of any primary egress of the LSP as a
   branch node, it MUST forward them unchanged.

   If the transit node is the upstream node of a primary egress to be
   protected as a branch node, it determines the backup egress, obtains
   a path for the backup LSP and sets up the backup LSP along the path.
   If the upstream node receives the Resv message with an SERO object,
   it MUST sends its upstream node the Resv message without the object.

   The PLR (upstream node of the primary egress as the branch node) MUST
   extract the backup egress from the respective SERO object in either a
   Path or a Resv message.  If no matching SERO object is found, the PLR
   tries to find the backup egress, which is not the primary egress but
   has the same IP address as the destination IP address of the LSP.

   Note that if a backup egress is not configured explicitly for
   protecting a primary egress, the primary egress and the backup egress
   SHOULD have a same local address configured, and the cost to the
   local address on the backup egress SHOULD be much bigger than the
   cost to the local address on the primary egress.  Thus primary egress



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   and backup egress is considered as a virtual node.  Note that the
   backup egress is different from this local address (e.g., from the
   primary egress' view).  In other words, it is identified by an
   address different from this local address.

   After obtaining the backup egress, the PLR computes a backup path
   from itself to the backup egress and sets up a backup LSP along the
   path.  It excludes the segment including the primary egress to be
   protected when computing the path.  The PLR sends the primary egress
   a Path message with an SERO for the primary LSP, which indicates the
   backup egress by the final subobject in the SERO.  The PLR puts a
   PROTECTION object into the Path messages for the backup LSP.  The
   object indicates the primary egress.

   The PLR MUST provide one-to-one backup protection for the primary
   egress if the "One-to-One Backup Desired" flag is set in the message;
   otherwise, it MUST provide facility backup protection if the
   "Facility Backup Desired flag" is set.

   The PLR MUST set the protection flags in the RRO Sub-object for the
   primary egress in the Resv message according to the status of the
   primary egress and the backup LSP protecting the primary egress.  For
   example, it sets the "local protection available" and the "node
   protection" flag indicating that the primary egress is protected when
   the backup LSP is up and ready for protecting the primary egress.

5.4.1.  Signaling for One-to-One Protection

   The behavior of the upstream node of a primary egress of an LSP as a
   PLR is the same as that of a PLR for one-to-one backup described in
   RFC 4090 except for that the upstream node as a PLR creates a backup
   LSP from itself to a backup egress.

   If the LSP is a P2MP LSP and a primary egress of the LSP is also a
   transit node (i.e., bud node), the upstream node of the primary
   egress as a PLR creates a backup LSP from itself to each of the next
   hops of the primary egress.

   When the PLR detects the failure of the primary egress, it switches
   the packets from the primary LSP to the backup LSP to the backup
   egress.  For the failure of the bud node of a P2MP LSP, the PLR also
   switches the packets to the backup LSPs to the bud node's next hops,
   where the packets are merged into the primary LSP.

5.4.2.  Signaling for Facility Protection

   Except for backup LSP and downstream label, the behavior of the
   upstream node of the primary egress of a primary LSP as a PLR follows



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   the PLR behavior for facility backup described in RFC 4090.

   For a number of primary P2P LSPs going through the same PLR to the
   same primary egress, the primary egress of these LSPs MAY be
   protected by one backup LSP from the PLR to the backup egress
   designated for protecting the primary egress.

   The PLR selects or creates a backup LSP from itself to the backup
   egress.  If there is a backup LSP that satisfies the constraints
   given in the Path message, then this one is selected; otherwise, a
   new backup LSP to the backup egress is created.

   After getting the backup LSP, the PLR associates the backup LSP with
   a primary LSP for protecting its primary egress.  The PLR records
   that the backup LSP is used to protect the primary LSP against its
   primary egress failure and MUST include an SERO object in the Path
   message for the primary LSP.  The object MUST contain the backup LSP
   ID.  It indicates that the primary egress MUST send the backup egress
   the service label as UA label and the information about forwarding
   the traffic to its destination using the label if there is a service
   carried by the LSP and the primary LSP label as UA label if the label
   is not implicit null.

   A UA label MAY be sent via another protocol (e.g., BGP).  If "Other
   Sending UA Label" flag is one, the primary egress MUST send the
   backup egress the UA labels and the information about forwarding the
   traffic to its destination using the labels through another protocol.

   After receiving the Path message with the PROTECTION subobject in an
   SERO, the primary egress MUST include the information about the UA
   labels in the Resv message with an SERO having a PROTECTION subobject
   containing an opaque data subobject if "Other Sending UA Label" flag
   is zero.  When the PLR receives the Resv message with the information
   about the UA labels, it MUST include the information in the Path
   message with a PROTECTION object containing the opaque data subobject
   for the backup LSP to the backup egress.  Thus the UA labels are sent
   to the backup egress from the primary egress via RSVP.

   When the PLR detects the failure of the primary egress, it redirects
   the packets from the primary LSP into the backup LSP to backup egress
   and keeps the primary LSP label from the primary egress in the label
   stack if the label is not implicit null.  The backup egress delivers
   the packets to the same destinations as the primary egress using the
   backup LSP label as context label and the labels under as UA labels.







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5.4.3.  Signaling for S2L Sub LSP Protection

   The S2L Sub LSP Protection uses a S2L Sub LSP (ref to RFC 4875) as a
   backup LSP to protect a primary egress of a P2MP LSP.  The PLR MUST
   determine to protect a primary egress of a P2MP LSP via S2L sub LSP
   protection when it receives a Path message with flag "S2L Sub LSP
   Backup Desired" set.

   The PLR MUST set up the backup S2L sub LSP to the backup egress,
   create and maintain its state in the same way as of setting up a
   source to leaf (S2L) sub LSP defined in RFC 4875 from the signaling's
   point of view.  It computes a path for the backup LSP from itself to
   the backup egress, constructs and sends a Path message along the
   path, receives and processes a Resv message responding to the Path
   message.

   After receiving the Resv message for the backup LSP, the PLR creates
   a forwarding entry with an inactive state or flag called inactive
   forwarding entry.  This inactive forwarding entry is not used to
   forward any data traffic during normal operations.

   When the PLR detects the failure of the primary egress, it changes
   the forwarding entry for the backup LSP to active.  Thus, the PLR
   forwards the traffic to the backup egress through the backup LSP,
   which sends the traffic to its destination.

5.4.4.  PLR Procedures during Local Repair

   When the upstream node of a primary egress of an LSP as a PLR detects
   the failure of the primary egress, it follows the procedures defined
   in section 6.5 of RFC 4090.  It SHOULD notify the ingress about the
   failure of the primary egress in the same way as a PLR notifies the
   ingress about the failure of a transit node.

   Moreover, the PLR MUST let the upstream part of the primary LSP stay
   after the primary egress fails through sending Resv message to its
   upstream node along the primary LSP.  The downstream part of the
   primary LSP from the PLR to the primary egress SHOULD be removed.

   In the local revertive mode, the PLR will re-signal each of the
   primary LSPs that were routed over the restored resource once it
   detects that the resource is restored.  Every primary LSP
   successfully re-signaled along the restored resource will be switched
   back.







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6.  Considering Application Traffic

   This section focuses on the application traffic carried by P2P LSPs.
   When a primary egress of a P2MP LSP fails, the application traffic
   carried by the P2MP LSP is delivered to the same destination by the
   backup egress since the inner label if any for the traffic is a
   upstream assigned label for every egress of the P2MP LSP.

6.1.  A Typical Application

   L3VPN is a typical application.  An existing solution (refer to
   Figure 2) for protecting L3VPN traffic against egress failure
   includes: 1) A multi-hop BFD session between ingress R1 and egress L1
   of primary LSP; 2) A backup LSP from ingress R1 to backup egress La;
   3) La sends R1 VPN backup label and related information via BGP; 4)
   R1 has a VRF with two sets of routes: one uses primary LSP and L1 as
   next hop; the other uses backup LSP and La as next hop.

     CE1,CE2 in    [R2]*****[R3]*****[L1]             **** Primary LSP
     one VPN      *                  :   $            ---- Backup LSP
                 *  .................:    $           .... BFD Session
             [R1] ..:                      [CE2]         $ Link
            $    \                        $             $
           $      \                      $
      [CE1]        [R4]-----[R5]-----[La](BGP sends R1 VPN backup label)


                Figure 2: Protect Egress for L3VPN Traffic

   In normal operations, R1 sends the traffic from CE1 through primary
   LSP with VPN label received from L1 as inner label to L1, which
   delivers the traffic to CE2 using VPN label.

   When R1 detects the failure of L1, R1 sends the traffic from CE1 via
   backup LSP with VPN backup label received from La as inner label to
   La, which delivers the traffic to CE2 using VPN backup label.

   A new solution (refer to Figure 3) with egress local protection for
   protecting L3VPN traffic includes: 1) A BFD session between R3 and
   egress L1 of primary LSP; 2) A backup LSP from R3 to backup egress
   La; 3) L1 sends La VPN label as UA label and related information; 4)
   L1 and La is virtualized as one.  This can be achieved by configuring
   a same local address on L1 and La, using the address as a destination
   of the LSP and BGP next hop for VPN traffic.







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     CE1,CE2 in    [R2]*****[R3]*****[L1]             **** Primary LSP
     one VPN      *          \ :.....:   $            ---- Backup LSP
                 *            \           $           .... BFD Session
             [R1]               \          [CE2]         $ Link
            $                     \       $             $
           $                        \    $
      [CE1]                          [La](VPN label from L1 as UA label)


            Figure 3: Locally Protect Egress for L3VPN Traffic

   When R3 detects L1's failure, R3 sends the traffic from primary LSP
   via backup LSP to La, which delivers the traffic to CE2 using VPN
   label as UA label under the backup LSP label as a context label.

6.2.  PLR Procedure for Applications

   When the PLR gets a backup LSP from itself to a backup egress for
   protecting a primary egress of a primary LSP, it includes an SERO
   object in the Path message for the primary LSP.  The object contains
   the ID information of the backup LSP and indicates that the primary
   egress sends the backup egress the application traffic label (e.g.,
   VPN label) as UA label when needed.

6.3.  Egress Procedures for Applications

   When a primary egress of an LSP sends the ingress of the LSP a label
   for an application such as a VPN, it sends the backup egress for
   protecting the primary egress the label as a UA label.  Exactly how
   the label is sent is out of scope for this document.

   When the backup egress receives a UA label from the primary egress,
   it adds a forwarding entry with the label into the LFIB for the
   primary egress.  When the backup egress receives a packet from the
   backup LSP, it uses the top label as a context label to find the LFIB
   for the primary egress and the inner label to deliver the packet to
   the same destination as the primary egress according to the LFIB.


7.  Security Considerations

   In principle this document does not introduce new security issues.
   The security considerations pertaining to RFC 4090, RFC 4875 and
   other RSVP protocols remain relevant.

   Note that protecting a primary egress of a P2P LSP carrying service
   traffic through a backup egress requires that the backup egress trust
   the primary egress for the information received for a service label



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   as UA label.


8.  IANA Considerations

   IANA is requested to administer the assignment of the new subobject
   types defined under the PROTECTION object in this document and
   summarized in this section.

8.1.  Definition of PROTECTION Object Reserved Bits

   This document defines bits carried in the Reserved field of the
   PROTECTION object defined in RFC 4873.  As no IANA registry for these
   bits is requested in RFC 4873, no IANA action is required related to
   this definition.

8.2.  New Subobjects

   Under PROTECTION object class, Class Number 37, C-Type 2, the
   following additional subobjects are defined:

     +========+=================================+
     |  Type  |        Name                     |
     +========+=================================+
     |    1   |   IPv4 primary egress           |
     +--------+---------------------------------+
     |    2   |   IPv6 primary egress           |
     +--------+---------------------------------+
     |    3   |   IPv4 P2P LSP ID               |
     +--------+---------------------------------+
     |    4   |   IPv6 P2P LSP ID               |
     +--------+---------------------------------+
     |    5   |   Opaque Data                   |
     +========+=================================+


9.  Co-authors

   Mehmet Toy, Lei Liu and Zhenbin Li


10.  Contributors

      Boris Zhang
      Telus Communications
      200 Consilium Pl Floor 15
      Toronto, ON  M1H 3J3
      Canada



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      Email: Boris.Zhang@telus.com


      Nan Meng
      Huawei Technologies
      Huawei Bld., No.156 Beiqing Rd.
      Beijing  100095
      China
      Email: mengnan@huawei.com


      Vic Liu
      China Mobile
      No.32 Xuanwumen West Street, Xicheng District
      Beijing, 100053
      China
      Email: liuzhiheng@chinamobile.com


11.  Acknowledgement

   The authors would like to thank Richard Li, Nobo Akiya, Lou Berger,
   Jeffrey Zhang, Lizhong Jin, Ravi Torvi, Eric Gray, Olufemi Komolafe,
   Michael Yue, Daniel King, Rob Rennison, Neil Harrison, Kannan
   Sampath, Yimin Shen, Ronhazli Adam, Prejeeth Kaladharan and Quintin
   Zhao for their valuable comments and suggestions on this draft.


12.  References

12.1.  Normative References

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              DOI 10.17487/RFC4090, May 2005,
              <http://www.rfc-editor.org/info/rfc4090>.

   [RFC4875]  Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
              Yasukawa, Ed., "Extensions to Resource Reservation
              Protocol - Traffic Engineering (RSVP-TE) for Point-to-
              Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
              DOI 10.17487/RFC4875, May 2007,
              <http://www.rfc-editor.org/info/rfc4875>.



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   [RFC4873]  Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
              "GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
              May 2007, <http://www.rfc-editor.org/info/rfc4873>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

12.2.  Informative References

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <http://www.rfc-editor.org/info/rfc2205>.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space",
              RFC 5331, DOI 10.17487/RFC5331, August 2008,
              <http://www.rfc-editor.org/info/rfc5331>.

   [RFC4872]  Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
              Ed., "RSVP-TE Extensions in Support of End-to-End
              Generalized Multi-Protocol Label Switching (GMPLS)
              Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
              <http://www.rfc-editor.org/info/rfc4872>.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              DOI 10.17487/RFC3473, January 2003,
              <http://www.rfc-editor.org/info/rfc3473>.


Authors' Addresses

   Huaimo Chen
   Huawei Technologies
   Boston, MA
   USA

   Email: huaimo.chen@huawei.com









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   Autumn Liu
   Ericsson
   CA
   USA

   Email: autumn.liu@ericsson.com


   Tarek Saad
   Cisco Systems

   Email: tsaad@cisco.com


   Fengman Xu
   Verizon
   2400 N. Glenville Dr
   Richardson, TX  75082
   USA

   Email: fengman.xu@verizon.com


   Lu Huang
   China Mobile
   No.32 Xuanwumen West Street, Xicheng District
   Beijing,   100053
   China

   Email: huanglu@chinamobile.com


   Ning So
   Tata Communications
   2613 Fairbourne Cir.
   Plano, TX  75082
   USA

   Email: ningso01@gmail.com












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