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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                                   N. So
Expires: June 21, 2016                               Tata Communications
                                                                  A. Liu
                                                                Ericsson
                                                                 T. Saad
                                                           Cisco Systems
                                                                   F. Xu
                                                                 Verizon
                                                       December 19, 2015


         Extensions to RSVP-TE for LSP Egress Local Protection
             draft-ietf-teas-rsvp-egress-protection-03.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 June 21, 2016.

Copyright Notice

   Copyright (c) 2015 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.  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.  EGRESS_BACKUP Object . . . . . . . . . . . . . . . . . . .  4
       4.1.1.  EGRESS_BACKUP IPv4 Object  . . . . . . . . . . . . . .  5
       4.1.2.  EGRESS_BACKUP IPv6 Object  . . . . . . . . . . . . . .  5
       4.1.3.  P2P LSP ID Subobject . . . . . . . . . . . . . . . . .  6
       4.1.4.  Label Subobject  . . . . . . . . . . . . . . . . . . .  7
     4.2.  Path Message . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Egress Protection Behaviors  . . . . . . . . . . . . . . . . .  8
     5.1.  Ingress Behavior . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Transit Node and PLR Behavior  . . . . . . . . . . . . . .  9
       5.2.1.  Signaling for One-to-One Protection  . . . . . . . . .  9
       5.2.2.  Signaling for Facility Protection  . . . . . . . . . . 10
       5.2.3.  Signaling for S2L Sub LSP Protection . . . . . . . . . 11
       5.2.4.  PLR Procedures during Local Repair . . . . . . . . . . 11
   6.  Considering Application Traffic  . . . . . . . . . . . . . . . 12
     6.1.  A Typical Application  . . . . . . . . . . . . . . . . . . 12
     6.2.  PLR Procedure for Applications . . . . . . . . . . . . . . 13
     6.3.  Egress Procedures for Applications . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  A New Class Number . . . . . . . . . . . . . . . . . . . . 14
   9.  Co-authors . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
   11. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 15
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     12.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16








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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.

   The egress local protection may be generalized and used with the
   segment protection defined in RFC 4873.  How it is generalized and
   used is out of scope for this document.


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 and RFC 4875.


4.  Protocol Extensions

   This section presents new RSVP objects.

4.1.  EGRESS_BACKUP Object

   A new object EGRESS_BACKUP is defined for egress local protection.
   It contains a backup egress for a primary egress.



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4.1.1.  EGRESS_BACKUP IPv4 Object


     Class = EGRESS_BACKUP, EGRESS_BACKUP_IPv4 C-Type = 1

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Backup Egress IPv4 address                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Primary Egress IPv4 address                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Reserved (must be zero)              |     Flags     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                         (Subobjects)                          ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      o Backup Egress IPv4 address:
         IPv4 address of the backup egress node
      o Primary Egress IPv4 address:
         IPv4 address of the primary egress node
      o Flags
         0x01    S2L Sub LSP Backup Desired
         0x02    Other Sending UA Label

   Flag "S2L Sub LSP Backup Desired" is used to indicate if S2L Sub LSP
   (ref to RFC 4875) is desired for protecting an egress of a P2MP LSP.

   Flag "Other Sending UA Label" is used to indicate if another protocol
   is desired for sending a label as a UA label from a primary egress to
   a backup egress.

   The Subobjects are TLVs.  One of them is P2P LSP ID IPv4 subobject.
   Another is Label subobject.

4.1.2.  EGRESS_BACKUP IPv6 Object















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     Class = EGRESS_BACKUP, EGRESS_BACKUP_IPv6 C-Type = 2

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~             Backup Egress IPv6 address (16 bytes)             ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~             Primary Egress IPv6 address (16 bytes)            ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Reserved (must be zero)              |     Flags     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                         (Subobjects)                          ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      o Backup Egress IPv6 address:
         IPv6 address of the backup egress node
      o Primary Egress IPv6 address:
         IPv6 address of the primary egress node
      o Flags
         0x01    S2L Sub LSP Backup Desired
         0x02    Other Sending UA Label

4.1.3.  P2P LSP ID Subobject

   A P2P LSP ID subobject contains the information for identifying a
   backup LSP tunnel.

4.1.3.1.  P2P LSP ID IPv4 Subobject


     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: 0x01 for P2P LSP ID IPv4
    o Length: The total length of the subobject in bytes, which is 12.
    o Tunnel ID:
        A 16-bit identifier that is 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



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4.1.3.2.  P2P LSP ID IPv6 Subobject


     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: 0x02 for P2P LSP ID IPv6
    o Length: The total length of the subobject in bytes, which is 36.
    o Tunnel ID:
        A 16-bit identifier that is 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

4.1.4.  Label Subobject


      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    |     Flags     |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              Label                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                           (sub-TLVs )                         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     o Type: 0x03 for Label
     o Length: The total length of the subobject in bytes.
     o Flags: 0x01 = Global Label
     o Label: Value of Label

4.2.  Path Message

   A Path message is enhanced to carry the information about a backup
   egress for a primary egress of an LSP by including an egress backup
   descriptor list.  The format of the message is illustrated below.






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  <Path Message> ::= <Common Header> [ <INTEGRITY> ]
                     [ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ...]
                     [ <MESSAGE_ID> ]<SESSION> <RSVP_HOP> <TIME_VALUES>
                     [ <EXPLICIT_ROUTE> ]
                     <LABEL_REQUEST> [ <PROTECTION> ] [ <LABEL_SET> ...]
                     [ <SESSION_ATTRIBUTE> ] [ <NOTIFY_REQUEST> ]
                     [ <ADMIN_STATUS> ] [ <POLICY_DATA> ... ]
                     <sender descriptor> [<S2L sub-LSP descriptor list>]
                     [<egress backup descriptor list>]


   The egress backup descriptor list in the message is defined below.
   It is a sequence of EGRESS_BACKUP objects, each of which describes a
   pair of a primary egress and a backup egress.

      <egress backup descriptor list> ::=
                        <egress backup descriptor>
                        [ <egress backup descriptor list> ]

      <egress backup descriptor> ::= <EGRESS_BACKUP>



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 include an EGRESS_BACKUP object and set
   the "S2L Sub LSP Backup Desired" flag.

   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 SHOULD be configured on the ingress of an LSP to
   protect a primary egress of the LSP.

   The ingress MUST send a Path message for the LSP with the objects



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   above and an optional egress backup descriptor list for protecting
   egresses of the LSP.  For each primary egress of the LSP to be
   protected, the ingress MUST add an EGRESS_BACKUP object into the list
   if the backup egress is given.  The object MUST contain the primary
   egress and the backup egress for protecting the primary egress.

5.2.  Transit Node and PLR Behavior

   If a transit node of an LSP receives the Path message with an egress
   backup descriptor list and it is not an upstream node of any primary
   egress of the LSP, it MUST forward the list unchanged.

   If the transit node is the upstream node of a primary egress to be
   protected, it determines the backup egress, obtains a path for the
   backup LSP and sets up the backup LSP along the path.

   The PLR (upstream node of the primary egress) MUST extract the backup
   egress from the respective EGRESS_BACKUP object in the egress backup
   descriptor list.  If no matching EGRESS_BACKUP object is found or the
   list is empty, the PLR applies a local policy to determine the backup
   egress and MUST add an EGRESS_BACKUP object with the backup egress
   and primary egress into a Path message to the primary egress.

   After obtaining the backup egress, the PLR computes a backup path
   from itself to the backup egress.  It excludes the primary egress to
   be protected when computing the path.  Thus the PLR will not select
   any path via 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.

5.2.1.  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



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   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.

5.2.2.  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 EGRESS_BACKUP object in
   the Path message to the primary egress.  The object MUST contain the
   backup egress and the backup LSP ID.  It indicates that the primary
   egress MUST send the backup egress the service label as UA 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 RSVP or another protocol (e.g., BGP).  If
   "Other Sending UA Label" flag is one, the primary egress MUST send
   the UA labels to the backup egress through another protocol;
   otherwise, UA labels MUST be sent via RSVP.

   After receiving the Path message with the EGRESS_BACKUP, the primary
   egress MUST include the information about the UA labels in the Resv
   message with an EGRESS_BACKUP object.  When the PLR receives the Resv
   message with the information about the UA labels, it MUST include the
   information in the Path message for the backup LSP to the backup
   egress.  Thus the UA labels are sent to the backup egress from the
   primary egress via RSVP.



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   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 MUST keep the primary LSP label from the primary egress in the
   label stack if the label is not implicit null.  The backup egress
   MUST deliver 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.

5.2.3.  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.

5.2.4.  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 SHOULD re-signal each of the



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   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 SHOULD be
   switched back.


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



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   a same local address on L1 and La, using the address as a destination
   of the LSP and BGP next hop for VPN traffic.

     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
   EGRESS_BACKUP 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.




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   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
   as UA label.


8.  IANA Considerations

   IANA is requested to administer the assignment of new values defined
   in this document and summarized in this section.

8.1.  A New Class Number

   IANA maintains a registry called "Class Names, Class Numbers, and
   Class Types" under "Resource Reservation Protocol-Traffic Engineering
   (RSVP-TE) Parameters".  IANA is requested to assign a new Class
   Number for new object EGRESS_BACKUP as follows:

     +===============+===============+=======================+
     |  Class Names  | Class Numbers |  Class Types          |
     +===============+===============+=======================+
     | EGRESS_BACKUP |  TBD1 (>192)  | 1: EGRESS_BACKUP_IPv4 |
     |               |               +-----------------------+
     |               |               | 2: EGRESS_BACKUP_IPv6 |
     +---------------+---------------+-----------------------+

   IANA is requested to assign Types for new TLVs in the new objects as
   follows:

      Type          Name                  Allowed in
       1      P2P_LSP_ID_IPv4 TLV      EGRESS_BACKUP_IPv4
       2      P2P_LSP_ID_IPv6 TLV      EGRESS_BACKUP_IPv6
       3      Label TLV                EGRESS_BACKUP


9.  Co-authors

   Lu Huang, Mehmet Toy, Lei Liu, Zhenbin Li


10.  Contributors

      Boris Zhang
      Telus Communications
      200 Consilium Pl Floor 15
      Toronto, ON  M1H 3J3
      Canada
      Email: Boris.Zhang@telus.com



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


12.  References

12.1.  Normative 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>.

   [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,



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              DOI 10.17487/RFC4875, May 2007,
              <http://www.rfc-editor.org/info/rfc4875>.

   [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>.

   [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

   [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>.


Authors' Addresses

   Huaimo Chen
   Huawei Technologies
   Boston, MA
   USA

   Email: huaimo.chen@huawei.com


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

   Email: ningso01@gmail.com


   Autumn Liu
   Ericsson
   CA
   USA

   Email: autumn.liu@ericsson.com






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   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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