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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

Internet Engineering Task Force                                  H. Chen
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                  A. Liu
Expires: September 19, 2018                                        Ciena
                                                                 T. Saad
                                                           Cisco Systems
                                                                   F. Xu
                                                                 Verizon
                                                                L. Huang
                                                            China Mobile
                                                          March 18, 2018


         Extensions to RSVP-TE for LSP Egress Local Protection
             draft-ietf-teas-rsvp-egress-protection-16.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 19, 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  . . . . . . . . . . . . . . 11
       5.4.1.  Signaling for One-to-One Protection  . . . . . . . . . 12
       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.  Application Traffic Considerations . . . . . . . . . . . . . . 14
     6.1.  A Typical Application  . . . . . . . . . . . . . . . . . . 14
     6.2.  PLR Procedure for Applications . . . . . . . . . . . . . . 16
     6.3.  Egress Procedures for Applications . . . . . . . . . . . . 17
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   9.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 18
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 19
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 19
     11.2. Informative References . . . . . . . . . . . . . . . . . . 20
   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.  Egress node and
   egress will be used exchangeably.

1.1.  Egress Local Protection

   In general, locally protecting an egress node of an LSP means that
   when the egress node fails, the traffic that the LSP carries will be
   delivered to its destination by the direct upstream node of the
   egress node to a backup egress node.  Without protecting the egress
   node of the LSP, when the egress node fails, the traffic will be lost
   (i.e., the traffic will not be delivered to its destination).

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




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            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 node La, which delivers the traffic to
   CE1.  The time for switching the traffic is within tens of
   milliseconds.

   The exact mechanism by which the failure of the primary egress node
   is detected by the upstream node R3 is out of the scope of this
   document.

   In the beginning, the primary P2MP LSP from ingress R1 to primary
   egress nodes 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.

   To protect the primary egress nodes L1 and L2, one configures on the
   ingress R1 a backup egress node for L1, another backup egress node
   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 egress nodes for protecting the
   primary egress nodes.

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


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






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   P2MP:  Point-to-MultiPoint

   P2P:  Point-to-Point

   LSR:  Label Switching Router

   RSVP:  Resource ReSerVation Protocol

   S2L:  Source-to-Leaf

   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 Section 4.2) indicates the



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   branch node that is to originate the backup LSP (to a backup egress
   node).  The branch node is typically the direct upstream node of the
   primary egress node of the primary LSP.  If the direct upstream node
   does not support local protection against the failure of the primary
   egress node, the branch node can be any (upstream) node on the
   primary LSP.  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 second subobject is an egress protection subobject, which is a
   PROTECTION object with a new C-TYPE (TBA1).  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 (TBA1) |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            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 on transmission and MUST be
   ignored on receipt.

   Four optional subobjects are defined.  They are IPv4 and IPv6 primary
   egress node, IPv4 and IPv6 P2P LSP ID subobjects.  IPv4 and IPv6
   primary egress node subobjects indicate the IPv4 and IPv6 address of
   the primary egress node respectively.  IPv4 and IPv6 P2P LSP ID
   subobjects contains the information for identifying IPv4 and IPv6
   backup point-to-point (P2P) LSP tunnels respectively.  Their contents
   are described in sections 4.1.1 through 4.1.2.2.  They have the
   following format:




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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 (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 on transmission and MUST be
   ignored on receipt.

   The third (final) subobject (refer to RFC 4873 Section 4.2) in the
   SERO contains the egress node of the backup LSP, i.e., the address of
   the backup egress node in the place of the merge node.

   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 node, 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 node, which indicates the address of the primary egress node.
   The third one contains the backup egress node.

   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:




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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    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:

      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 node 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



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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:

      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 node 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 node 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 node 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 node of
   a P2MP LSP, the ingress MUST set the "S2L Sub LSP Backup Desired"
   flag in an SERO object.

   The decision to instantiate a backup egress for protecting the
   primary egress of an LSP can be initiated by either the ingress or
   the primary egress of that LSP, but not both.

   A backup egress node MUST be configured on the ingress of an LSP to
   protect a primary egress node of the LSP if and only if the backup



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   egress node is not configured on the primary egress node (refer to
   section 5.2).

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

5.2.  Primary Egress Behavior

   To protect a primary egress node of an LSP, a backup egress node MUST
   be configured on the primary egress node of the LSP to protect the
   primary egress node if and only if the backup egress node is not
   configured on the ingress of the LSP (refer to section 5.1).

   If the backup egress node is configured on the primary egress node of
   the LSP, the primary egress node MUST send its upstream node a Resv
   message for the LSP with an SERO for protecting the primary egress
   node.  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 node sends its corresponding backup egress node 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 node to be protected is in the
   primary egress subobject in the SERO.

   When the backup egress node receives the information about a UA label
   and its related forwarding from the primary egress node, 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



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   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 node of the LSP
   as a branch node, it MUST forward them unchanged.

   If the transit node is the upstream node of a primary egress node to
   be protected as a branch node, it determines the backup egress node,
   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 node as the branch node)
   MUST extract the backup egress node 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 node, which is not the
   primary egress node but has the same IP address as the destination IP
   address of the LSP.

   Note that if a backup egress node is not configured explicitly for
   protecting a primary egress node, the primary egress node and the
   backup egress node SHOULD have a same local address configured, and
   the cost to the local address on the backup egress node SHOULD be
   much bigger than the cost to the local address on the primary egress
   node.  Thus primary egress node and backup egress node is considered
   as a virtual node.  Note that the backup egress node is different
   from this local address (e.g., from the primary egress node' view).
   In other words, it is identified by an address different from this
   local address.

   After obtaining the backup egress node, the PLR computes a backup
   path from itself to the backup egress node and sets up a backup LSP
   along the path.  It excludes the segment including the primary egress
   node to be protected when computing the path.  The PLR sends the
   primary egress node a Path message with an SERO for the primary LSP,
   which indicates the backup egress node 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 node.

   The PLR MUST provide one-to-one backup protection for the primary
   egress node if the "One-to-One Backup Desired" flag is set in the



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   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 node in the Resv message according to the status of
   the primary egress node and the backup LSP protecting the primary
   egress node.  For example, it sets the "local protection available"
   and the "node protection" flag indicating that the primary egress
   node is protected when the backup LSP is up and ready for protecting
   the primary egress node.

5.4.1.  Signaling for One-to-One Protection

   The behavior of the upstream node of a primary egress node 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 node in a session different
   from the primary LSP.

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

   When the PLR detects the failure of the primary egress node, it
   switches the packets from the primary LSP to the backup LSP to the
   backup egress node.  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 node 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 node, the primary egress node of these LSPs MAY
   be protected by one backup LSP from the PLR to the backup egress node
   designated for protecting the primary egress node.

   The PLR selects or creates a backup LSP from itself to the backup
   egress node.  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 node is created.

   After getting the backup LSP, the PLR associates the backup LSP with
   a primary LSP for protecting its primary egress node.  The PLR



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   records that the backup LSP is used to protect the primary LSP
   against its primary egress node 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 node
   MUST send the backup egress node 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 node, it
   redirects the packets from the primary LSP into the backup LSP to
   backup egress node and keeps the primary LSP label from the primary
   egress node in the label stack if the label is not implicit null.
   The backup egress node delivers the packets to the same destinations
   as the primary egress node using the backup LSP label as context
   label and the labels under as UA labels.

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 node of a P2MP LSP.  The PLR
   MUST determine to protect a primary egress node 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 node,
   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 node, 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 node, 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 node of an LSP as a PLR
   detects the failure of the primary egress node, it follows the



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   procedures defined in section 6.5 of RFC 4090.  It SHOULD notify the
   ingress about the failure of the primary egress node 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 node 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 node
   SHOULD be removed.  When a bypass LSP from the PLR to a backup egress
   node protects the primary egress node, the PLR MUST NOT send any Path
   message for the primary LSP through the bypass LSP to the backup
   egress node.

   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.

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


6.  Application Traffic Considerations

   This section focuses on an example with 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 the primary LSP.  R1
   is the ingress of the LSP and L1 is the (primary) egress node 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 node L1 of the LSP, L1 pops the LSP label and uses
   the VPN label to deliver the traffic to CE2.

   In previous solutions based on ingress protection to protect the VPN
   traffic against failure of the egress node L1 of the LSP, when the
   egress node fails, the ingress R1 of the LSP does the reroute (refer



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   to Figure 2).  This solution entailed:

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

   2.  A backup LSP from ingress R1 to backup egress node 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.


                       *****    *****
     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.

   The solution defined in this document using egress local protection
   for protecting L3VPN traffic entails (refer to Figure 3):

   1.  A BFD session between R3 (i.e., upstream of L1) and egress node
       L1 of the primary LSP.  This is different from the BFD session in
       Figure 2, which is multi-hop between ingress R1 and egress node
       L1.  The PLR R3 is closer to L1 than the ingress R1.  It may
       detect the failure of the egress node L1 faster and more
       reliably.  Therefore, this solution can provide faster protection
       for failure of an egress node.





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

   3.  Primary egress node L1 sends backup egress node La the VPN label
       as UA label and related information.  The backup egress node 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 node 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.


                        *****    *****
      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 node 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 node
   for protecting a primary egress node 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 node sends the backup egress node the application
   traffic label (e.g., the VPN label) as UA label when needed.



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6.3.  Egress Procedures for Applications

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

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


7.  Security Considerations

   This document builds upon existing work, specifically the security
   considerations of RFCs 4090, 4875, 3209 and 2205 continue to apply.
   Additionally, protecting a primary egress node of a P2P LSP carrying
   service traffic through a backup egress node requires an out-of-band
   communication between the primary egress node and the backup egress
   node, in order for the primary egress node to convey a service label
   as UA label and its related forwarding information to the backup
   egress node.  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 requested to assign a new C-Type under PROTECTION object
   class, Class Number 37:

     Value                      Description          Definition
     -----                      -----------          ----------
     TBA1(suggested value 3)    Egress Protection    Section 4.1

   IANA is requested to create and maintain a new registry under
   PROTECTION object class (Class Number 37) and Egress Protection
   (C-Type TBA1).  Initial values for the registry are given below.  The
   future assignments are to be made through IETF Review (RFC 8216).




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     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


      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





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      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

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>.



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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-
              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






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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


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

   Email: huanglu@chinamobile.com





























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