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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

Internet Engineering Task Force                                  H. Chen
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                  A. Liu
Expires: September 3, 2018                                         Ciena
                                                                 T. Saad
                                                           Cisco Systems
                                                                   F. Xu
                                                                 Verizon
                                                                L. Huang
                                                            China Mobile
                                                           March 2, 2018


         Extensions to RSVP-TE for LSP Egress Local Protection
             draft-ietf-teas-rsvp-egress-protection-14.txt

Abstract

   This document describes extensions to Resource Reservation Protocol -
   Traffic Engineering (RSVP-TE) for locally protecting the egress
   node(s) of a Point-to-Point (P2P) or Point-to-Multipoint (P2MP)
   Traffic Engineered (TE) Label Switched Path (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 September 3, 2018.

Copyright Notice

   Copyright (c) 2018 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



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   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.  Egress Local Protection  . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
   3.  Terminologies  . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Protocol Extensions  . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Extensions to SERO . . . . . . . . . . . . . . . . . . . .  5
       4.1.1.  Primary Egress Subobject . . . . . . . . . . . . . . .  7
       4.1.2.  P2P LSP ID Subobject . . . . . . . . . . . . . . . . .  8
   5.  Egress Protection Behaviors  . . . . . . . . . . . . . . . . .  9
     5.1.  Ingress Behavior . . . . . . . . . . . . . . . . . . . . .  9
     5.2.  Primary Egress Behavior  . . . . . . . . . . . . . . . . . 10
     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  . . . . . . . . . . 12
       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 . . . . . . . . . . . . . . 16
     6.3.  Egress Procedures for Applications . . . . . . . . . . . . 16
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   9.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 17
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 18
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 19
     11.2. Informative References . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20












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1.  Introduction

   RFC 4090 describes two methods for locally protecting the transit
   nodes of a P2P LSP: one-to-one and facility protection.  RFC 4875
   specifies how these methods can be used to protect the transit nodes
   of a P2MP LSP.  These documents do not discuss the procedures for
   locally protecting the egress node(s) of an LSP.

   This document fills that void and specifies extensions to RSVP-TE for
   local protection of the egress node(s) of an LSP.

1.1.  Egress Local Protection

   Figure 1 shows an example of using backup LSPs to locally protect
   egresses L1 and L2 of a primary P2MP LSP from ingress R1 to two
   egresses L1 and L2.  La and Lb are the designated backup egresses for
   primary egresses L1 and L2 respectively.  The backup LSP for
   protecting L1 is from its upstream node R3 to backup egress La and
   the backup LSP for protecting L2 is from R5 to Lb.

                        *******  *******                 S Source
                     [R2]-----[R3]-----[L1]            CEx Customer Edge
                    */           &\        \            Rx Non-Egress
                   */             &\        \           Lx Egress
                  */               &\        [CE1]     *** Primary LSP
                 */                 &\      /          &&& Backup LSP
                */                   &\    /
               */                      [La]
              */
             */
            */
           */ ********  ********  *******
     [S]---[R1]------[R4]------[R5]-----[L2]
                                  &\        \
                                   &\        \
                                    &\        [CE2]
                                     &\      /
                                      &\    /
                                        [Lb]

            Figure 1: Backup LSP for Locally Protecting Egress

   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.




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   The exact mechanism by which the failure of the primary egress is
   detected by the upstream node is out of the scope of this document.

   In the beginning, the primary P2MP LSP from ingress R1 to primary
   egresses L1 and L2 is configured.  It may be used to transport the
   traffic from source S connected to R1 to destinations CE1 and CE2
   connected to L1 and L2 respectively.

   When we want to protect the primary egresses L1 and L2, we may
   configure on the ingress R1 a backup egress for L1, another backup
   egress for L2 and other options.  After the configuration, the
   ingress sends a Path message for the LSP with the information such as
   SEROs (refer to section 4.1) containing the backup egresses for
   protecting the primary egresses.

   After receiving the Path message with the information, the upstream
   node of a primary egress sets up a backup LSP to the corresponding
   backup egress for protecting the primary egress.


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.  Terminologies

   The following terminologies are used in this document.

   LSP:  Label Switched Path

   TE:  Traffic Engineering

   P2MP:  Point-to-MultiPoint

   P2P:  Point-to-Point

   LSR:  Label Switching Router

   RSVP:  Resource ReSerVation Protocol

   S2L:  Source-to-Leaf







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   SERO:  Secondary Explicit Route Object

   RRO:  Record Route Object

   BFD:  Bidirectional Forwarding Detection

   VPN:  Virtual Private Network

   L3VPN:  Layer 3 VPN

   VRF:  Virtual Routing and Forwarding

   LFIB:  Label Forwarding Information Base

   UA:  Upstream Assigned

   PLR:  Point of Local Repair

   BGP:  Border Gateway Protocol

   CE:  Customer Edge

   PE:  Provider Edge


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.

   The first subobject (refer to RFC 4873) 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.



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   The second subobject is an egress protection subobject, which is a
   PROTECTION object with a new C-TYPE (3).  The format of the egress
   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 (3)  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Reserved                   |E-Flags|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Optional subobjects                       |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   E-Flags are defined for egress local protection.

   Bit 31 (Egress local protection flag):  It is the least significant
      bit of the 32-bit word and is set to 1 indicating an egress local
      protection.

   Bit 30 (S2L sub LSP backup desired flag):  It is the second least
      significant bit of the 32-bit word and is set to 1 indicating S2L
      sub LSP (ref to RFC 4875) is desired for protecting an egress of a
      P2MP LSP.

   The Reserved parts MUST be set to zero.

   Four optional subobjects are defined.  They are IPv4 and IPv6 primary
   egress, IPv4 and IPv6 P2P LSP ID subobjects.  They have the following
   format:

      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 (zero)       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Contents/Body of subobject                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where Type is the type of a subobject, Length is the total size of
   the subobject in bytes, including Type, Length and Contents fields.
   The Reserved field MUST be set to zero.

   The third (final) subobject (refer to RFC 4873) in the SERO contains
   the egress node of the backup LSP, i.e., the address of the backup
   egress node.




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   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 new SERO based on the SERO received
   and adds the new SERO into the Path message for the backup LSP.  The
   new SERO also contains three subobjects as the SERO for the primary
   LSP.  The first subobject in the new SERO indicates the upstream
   node, which may be copied from the first subobject in the SERO
   received.  The second subobject in the new SERO includes a primary
   egress, which indicates the address of the primary egress node.  The
   third one contains the backup egress.

   The upstream node updates the SERO in the Path message for the
   primary LSP.  The egress 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 Type of an IPv4 primary egress subobject is 1, and the body of
   the subobject is given 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 address (4 bytes)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      o IPv4 address: IPv4 address of the primary egress node

   The Type of an IPv6 primary egress subobject is 2, and the body of
   the 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv6 address (16 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 Type of an IPv4 P2P LSP ID subobject is 3, and the body of the
   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               P2P LSP Tunnel Egress IPv4 Address              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Reserved (MUST be zero)    |           Tunnel ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Extended Tunnel ID                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     o P2P LSP Tunnel Egress IPv4 Address:
         IPv4 address of the egress of the tunnel
     o Tunnel ID (ref to RFC 4875 and RFC 3209):
         A 16-bit identifier being constant over the life of the tunnel
         occupies the least significant 16 bits of the 32 bit word.
     o Extended Tunnel ID (ref to RFC 4875 and RFC 3209):
         A 4-byte identifier being constant over the life of the tunnel

4.1.2.2.  IPv6 P2P LSP ID Subobject

   The Type of an IPv6 P2P LSP ID subobject is 4, and the body of the
   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~         P2P LSP Tunnel Egress IPv6 Address (16 bytes)         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Reserved (MUST be zero)    |           Tunnel ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 Extended Tunnel ID (16 bytes)                 ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     o P2P LSP Tunnel Egress IPv6 Address:
         IPv6 address of the egress of the tunnel
     o Tunnel ID (ref to RFC 4875 and RFC 3209):
         A 16-bit identifier being constant over the life of the tunnel
         occupies the least significant 16 bits of the 32 bit word.
     o Extended Tunnel ID (ref to RFC 4875 and RFC 3209):
         A 16-byte identifier being constant over the life of the tunnel


5.  Egress Protection Behaviors

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.

   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 configured on the primary egress (refer to section 5.2).

   The ingress MUST send a Path message for the LSP with the objects
   above and the SEROs for protecting egresses of the LSP if protection
   of the egresses is desired.  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 contains it; otherwise
   the address in the final subobject is zero.



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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 configured on the
   ingress of the LSP (refer to section 5.1).

   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.

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 SERO with egress protection subobject in the
   message.  If there is an egress protection subobject 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 SERO.

   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



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   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
   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 an
   SERO into the Path messages for the backup LSP, which 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 in a session different from the



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   primary LSP.

   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
   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.  How UA label is sent is out of scope for this
   document.

   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
   alive 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.
   When a bypass LSP from the PLR to a backup egress protects the
   primary egress, the PLR MUST NOT send any Path message for the
   primary LSP through the bypass LSP to the backup egress.

   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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   Note that the procedure for protecting the primary egress is
   triggered on the PLR if the primary egress failure is determined.  If
   link (from PLR to primary egress) failure and primary egress alive
   are determined, then link protection procedure is triggered on the
   PLR.  How to determine these is out of scope for this document.


6.  Considering Application Traffic

   This section focuses on the application traffic carried by P2P LSPs.

6.1.  A Typical Application

   L3VPN is a typical application.  Figure 2 below shows a simple VPN,
   which consists of two CEs CE1 and CE2 connected to two PEs R1 and L1
   respectively.  There is a P2P LSP from R1 to L1, which is represented
   by stars (****).  This LSP is called primary LSP.  R1 is the ingress
   of the LSP and L1 is the (primary) egress of the LSP.  R1 sends the
   VPN traffic received from CE1 through the P2P LSP to L1, which
   delivers the traffic to CE2.  R1 sends the VPN traffic with a LSP
   label and a VPN label via the LSP.  When the traffic reaches the
   egress L1 of the LSP, L1 pops the LSP label and uses the VPN label to
   deliver the traffic to CE2.

   To protect the VPN traffic against the failure of the egress L1 of
   the LSP, an existing solution (refer to Figure 2) includes:

   1.  A multi-hop BFD session between ingress R1 and egress L1 of
       primary LSP.  The BFD session is represented by dots (....).

   2.  A backup LSP from ingress R1 to backup egress La, which is
       indicated by ands (&&&&).

   3.  La sends R1 a VPN backup label and related information via BGP.

   4.  R1 has a VRF with two sets of routes for CE2: one set uses the
       primary LSP and L1 as next hop; the other uses the backup LSP and
       La as next hop.













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

                Figure 2: Protect Egress for L3VPN Traffic

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

   When R1 detects the failure of L1, R1 sends the traffic from CE1 via
   the backup LSP with the VPN backup label received from La as inner
   label to La, which delivers the traffic to CE2 using the 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 (i.e., upstream of L1) and egress L1 of
       the primary LSP.  This is different from the BFD session in
       Figure 2, which is multi-hop between ingress R1 and egress L1.
       The PLR R3 is closer to L1 than the ingress R1.  It may detect
       the failure of the egress L1 faster and more reliable.  Thus we
       can have faster protection for egress.

   2.  A backup LSP from R3 to backup egress La.  This is different from
       the backup LSP in Figure 2, which is an end to end LSP from
       ingress R1 to backup egress La.

   3.  Primary egress L1 sends backup egress La the VPN label as UA
       label and related information.  The backup egress La uses the
       backup LSP label as a context label and creates a forwarding
       entry using the VPN label in a LFIB for the primary egress L1.

   4.  L1 and La is virtualized as one node (or address).  R1 has a VRF
       with one set of routes for CE2, using the primary LSP from R1 to
       L1 and virtualized node as next hop.  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 the VPN traffic.
       The cost to L1 is configured to be less than the cost to La.





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

            Figure 3: Locally Protect Egress for L3VPN Traffic

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

   When the primary egress L1 fails, its upstream node R3 detects it and
   switches the VPN traffic from the primary LSP to the backup LSP to
   La, which delivers the traffic to CE2 using the backup LSP label as a
   context label to get the LFIB for L1 and the VPN label as UA label to
   find the forwarding entry in the LFIB to forward the traffic to CE2.

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.,
   the 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 label, 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

   This document builds upon existing work, so in particular the



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   security considerations of RFCs 4090, 4875, 3209 and 2205 continue to
   apply.  Additionally, protecting a primary egress of a P2P LSP
   carrying service traffic through a backup egress requires an out-of-
   band communication between the primary egress and the backup egress,
   in order for the primary egress to convey a service label as UA label
   and its related forwarding information to the backup egress.  It is
   important to confirm that the identifiers used to identify the
   primary and backup egress nodes in the LSP are verified to match with
   the identifiers used in the out-of-band protocol (such as BGP).


8.  IANA Considerations

   IANA maintains a registry called "Class Names, Class Numbers, and
   Class Types" under "Resource Reservation Protocol (RSVP) Parameters".
   IANA is to assign a new C-Type under PROTECTION object class, Class
   Number 37:

     Value      Description               Definition
     -----      -----------               ----------
      3         Egress Protection         Section 4.1.1

   IANA is to create and maintain a new registry under PROTECTION object
   class (Class Number 37) and Egress Protection (C-Type 3).  Initial
   values for the registry are given below.  The future assignments are
   to be made through IETF Review (RFC 8216).


     Value      Name                     Definition
     -----      ----                     ----------
      0         Reserved
      1         IPv4_PRIMARY_EGRESS      Section 4.1.1
      2         IPv6_PRIMARY_EGRESS      Section 4.1.1
      3         IPv4_P2P_LSP_ID          Section 4.1.2
      4         IPv6_P2P_LSP_ID          Section 4.1.2
      5-127     Unassigned
      128-255   Reserved


9.  Co-authors and Contributors

   1.  Co-authors


      Ning So
      Tata
      E-mail: ningso01@gmail.com




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      Mehmet Toy
      Verizon
      E-mail: mehmet.toy@verizon.com


      Lei Liu
      Fujitsu
      E-mail: lliu@us.fujitsu.com


      Zhenbin Li
      Huawei Technologies
      Email: lizhenbin@huawei.com

   2.  Contributors


      Boris Zhang
      Telus Communications
      Email: Boris.Zhang@telus.com


      Nan Meng
      Huawei Technologies
      Email: mengnan@huawei.com


      Prejeeth Kaladharan
      Huawei Technologies
      Email: prejeeth@gmail.com


      Vic Liu
      China Mobile
      Email: liu.cmri@gmail.com


10.  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 and Quintin Zhao for their
   valuable comments and suggestions on this draft.


11.  References




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11.1.  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,
              <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc4875>.

   [RFC4873]  Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
              "GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
              May 2007, <https://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,
              <https://www.rfc-editor.org/info/rfc2119>.

11.2.  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, <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc4872>.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-



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              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              DOI 10.17487/RFC3473, January 2003,
              <https://www.rfc-editor.org/info/rfc3473>.

   [FRAMEWK]  Shen, Y., Jeyananth, M., Decraene, B., and H. Gredler,
              "MPLS Egress Protection Framework",
              draft-shen-mpls-egress-protection-framework ,
              October 2016.


Authors' Addresses

   Huaimo Chen
   Huawei Technologies
   Boston, MA
   USA

   Email: huaimo.chen@huawei.com


   Autumn Liu
   Ciena
   USA

   Email: hliu@ciena.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











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

   Email: huanglu@chinamobile.com












































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