MPLS Working Group

Internet Engineering Task Force (IETF)                           T. Saad
Internet-Draft
Request for Comments: 8960                              Juniper Networks
Intended status:
Category: Standards Track                                        K. Raza
Expires: April 29, 2021
ISSN: 2070-1721                                                R. Gandhi
                                                     Cisco Systems Inc Systems, Inc.
                                                                  X. Liu
                                                          Volta Networks
                                                               V. Beeram
                                                        Juniper Networks
                                                        October 26,
                                                           December 2020

                    A YANG Data Model for MPLS Base
                      draft-ietf-mpls-base-yang-17

Abstract

   This document contains a specification of the MPLS base YANG data
   model.  The MPLS base YANG data model serves as a base framework for
   configuring and managing an MPLS switching subsystem on an MPLS-
   enabled router.  It is expected that other MPLS YANG data models
   (e.g.
   (e.g., MPLS Label Switched Path (LSP) Static, LDP static, LDP, or RSVP-TE YANG
   data models) will augment the MPLS base YANG data model.

Status of This Memo

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

   Internet-Drafts are working documents an Internet Standards Track document.

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   This Internet-Draft will expire on April 29, 2021.
   https://www.rfc-editor.org/info/rfc8960.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Acronyms and Abbreviations  . . . . . . . . . . . . . . .   3
   2.  MPLS Base Model . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Model Overview  . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Model Organization  . . . . . . . . . . . . . . . . . . .   4
     2.3.  Model Design  . . . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Model Tree Diagram  . . . . . . . . . . . . . . . . . . .   8
     2.5.  Model  MPLS Base YANG Module . . . . . . . . . . . . . . . . . . . .   9
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   5.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  21
   6.  References
     5.1.  Normative References
     5.2.  Informative References
   Appendix A.  Data Tree Instance Example  . . . . . . . . . . .  21
   7.
   Acknowledgments
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  27
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  27
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  27
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29

1.  Introduction

   A core routing YANG data model is defined in [RFC8349], and [RFC8349]; it provides a
   basis for the development of routing data models for specific Address
   Families (AFs).  Specifically, [RFC8349] defines a model for a
   generic Routing Information Base (RIB) that is Address-
   Family (AF) AF agnostic.
   [RFC8349] also defines two instances of RIBs based on the generic RIB
   model for IPv4 and IPv6 AFs.

   The MPLS base model that is defined in this document augments the generic RIB
   model defined in [RFC8349] with additional data that enables MPLS
   forwarding for the one or more specific destination prefix(es) prefixes present in the
   one or more AF RIB(s) RIBs, as described in the MPLS architecture document
   [RFC3031].

   The MPLS base model also defines a new instance of the generic RIB
   YANG data model as defined in [RFC8349] to store native MPLS routes.
   The native MPLS RIB instance stores route(s) one or more routes that are not
   associated with other AF instance RIBs (such as IPv4, IPv4 or IPv6 instance RIB(s)),
   RIBs) but are enabled for MPLS forwarding.  Examples of such native
   MPLS routes are routes programmed by RSVP on one or more transit MPLS router(s)
   routers along the path of a Label Switched Path (LSP).  Other example(s)
   examples are MPLS routes that cross-connect to specific Layer-2 Layer 2
   adjacencies, such as
   Layer-2 Layer 2 Attachment Circuit(s) (ACs)), Circuits (ACs); or Layer-3 Layer 3
   adjacencies, such as
   Segment-Routing Segment Routing (SR) Adjacency Segments (Adj-SIDs) (Adj-
   SIDs) as described in [RFC8402].

   The MPLS base YANG data model serves as a basis for future
   development of MPLS YANG data models covering more-sophisticated MPLS
   feature(s) features and sub-system(s).
   subsystems that are more sophisticated.  The main purpose is to
   provide essential building blocks for other YANG data models
   involving different control-plane protocols, protocols and MPLS functions.

   To this end, it is expected that the MPLS base data model will be
   augmented by a number of other YANG modules developed at by the IETF (e.g.
   (e.g., by the TEAS and MPLS working groups). Working Groups).

   The YANG module defined in this document conforms to the Network
   Management Datastore Architecture (NMDA) [RFC8342].

1.1.  Terminology

   The terminology for describing YANG data models is found in
   [RFC7950].

1.2.  Acronyms and Abbreviations

   MPLS:  Multiprotocol Label Switching

   RIB:  Routing Information Base

   LSP:  Label Switched Path

   LSR:  Label Switching Router

      LER: Label Edge Router

      FEC: Forwarding Equivalence Class

   NHLFE:  Next Hop Label Forwarding Entry

      ILM: Incoming Label Map

2.  MPLS Base Model

   This document describes the 'ietf-mpls' "ietf-mpls" YANG module that module, which provides
   base components of the MPLS data model.  It is expected that other
   MPLS YANG modules will augment 'ietf-mpls' the "ietf-mpls" YANG module for other
   MPLS
   extension extensions to provision Label Switched Paths (LSPs) (e.g. LSPs (e.g., MPLS
   Static, static, MPLS LDP LDP, or
   MPLS RSVP-TE LSP(s)). LSPs).

2.1.  Model Overview

   This document models MPLS labeled MPLS-labeled routes as an augmentation of the
   generic routing RIB data model as defined in [RFC8349].  For example,
   IP prefix routes (e.g. (e.g., routes stored in IPv4 or IPv6 RIBs) are
   augmented to carry additional data to enable it them for MPLS
   forwarding.

   This document also defines a new instance of the generic RIB model
   defined in [RFC8349] to store one or more native MPLS route(s) routes
   (described further in Section 2.3) by extending the identity 'address-family'
   "address-family" defined in [RFC8349] with a new "mpls" identity as suggested in identity; see
   Section 3 of [RFC8349].

2.2.  Model Organization

     Routing          +---------------+    v: import
     YANG module      | ietf-routing  |    o: augment
                      +---------------+
                          o
                          |
                          v
     MPLS base        +-----------+    v: import
     YANG module      | ietf-mpls |    o: augment
                      +-----------+
                         o      o------+
                         |              \
                         v               v
                 +-------------------+ +---------------------+
     MPLS Static static | ietf-mpls-static@ | | ietf-mpls-ldp.yang@ | . .
     LSP YANG    +-------------------+ +---------------------+
     module

           @: not in this document, document; shown for illustration only

                Figure 1: Relationship between MPLS modules Modules

   The 'ietf-mpls' "ietf-mpls" YANG module defines the following identities:

   mpls:

      This identity
      Identity that extends the 'address-family' "address-family" identity for of RIB
      instance(s) identity
      instances, as defined in [RFC8349] [RFC8349], to represent the native MPLS
      RIB instance.

   label-block-alloc-mode:
      A base YANG identity for one or more supported label block label-block
      allocation mode(s). modes.

   The 'ietf-mpls' "ietf-mpls" YANG module contains the following high-level types
   and groupings:

   mpls-operations-type:
      An enumeration type that represents support for possible MPLS
      operation types (impose-and-forward, pop-and-forward, pop-impose-
      and-forward, and pop-and-lookup) pop-and-lookup).

   nhlfe-role:
      An enumeration type that represents the role of the NHLFE entry. Next Hop Label
      Forwarding Entry (NHLFE).

   nhlfe-single-contents:
      A YANG grouping that describes a single Next Hop Label Forwarding
      Entry (NHLFE) NHLFE and its associated
      parameters as described in the MPLS architecture document
      [RFC3031].  This grouping is specific to the case when a single next-hop
      next hop is associated with the route.

   The NHLFE is used when forwarding a labeled packet.  It contains the
   following information:

   1.  the  The packet's next hop.  For 'nhlfe-single-contents' "nhlfe-single-contents", only a
       single next hop is expected, while for 'nhlfe-multiple-contents' "nhlfe-multiple-contents",
       multiple next hops are possible.

   2.  the  The operation to perform on the packet's label stack; this stack.  This can
       be one of the following operations: a) replace

       a.  Replace the label at the top of the label stack with one or
           more specified new label b) pop labels.

       b.  Pop the label stack c) replace stack.

       c.  Replace the label at the top of the label stack with a
           specified new label, and then push one or more specified new
           labels onto the label stack.  d) push

       d.  Push one or more
       label(s) on labels onto an unlabeled packet

   It packet.

   The NHLFE may also contain:

     d) the data link

   1.  The data-link encapsulation to use when transmitting the packet

     e) the packet.

   2.  The way to encode the label stack when transmitting the packet

     f) any packet.

   3.  Any other information needed in order to properly dispose of the
       packet.

   nhlfe-multiple-contents:
      A YANG grouping that describes a set of NHLFE(s) NHLFEs and their
      associated parameters as described in the MPLS architecture
      document [RFC3031].  This grouping is used when multiple next-hops next hops
      are associated with the route.

   interfaces-mpls:
      A YANG grouping that describes the list of MPLS enabled MPLS-enabled interfaces
      on a device.

   label-blocks:
      A YANG grouping that describes the list of assigned MPLS label
      blocks and their properties.

   rib-mpls-properties:
      A YANG grouping for the augmentation of the generic RIB with MPLS
      label forwarding data as defined in [RFC3031].

   rib-active-route-mpls-input:
      A YANG grouping for the augmentation to the 'active-route' "active-route" RPC
      that is specific to the MPLS RIB instance.

2.3.  Model Design

   The MPLS routing model is based on the core routing data model
   defined in [RFC8349].  Figure 2 shows the extensions introduced by
   the MPLS base model on defined RIB(s). RIBs.

                                +-----------------+
                                | MPLS base model |
                                +-----------------+
                              ____/  |  |_____  |________
                             /       |        \          \
                            /        |         \          \
                           o         o          o          +
                    +---------+  +---------+  +--------+ +-----------+
                    | RIB(v4) |  | RIB(v6) |  | RIB(x) | | RIB(mpls) |
                    +---------+  +---------+  +--------+ +-----------+

           +: created by the MPLS base model
           o: augmented by the MPLS base model

        Figure 2: Relationship between MPLS model Model and RIB instances Instances

   As shown in Figure 2, the MPLS base YANG data model augments defined
   instance(s)
   instances of AF RIB(s) RIBs with additional data that enables MPLS
   forwarding for destination prefix(es) store prefixes stored in such RIB(s). RIBs.  For
   example, an IPv4 prefix stored in RIB(v4) is augmented to carry a an
   MPLS local label and per next-hop one or more per-next-hop remote label(s) labels to enable
   MPLS forwarding for such a prefix.

   The MPLS base model also creates a separate instance of the generic
   RIB model defined in [RFC8349] to store one or more MPLS native route(s)
   routes that are enabled for MPLS forwarding, forwarding but are not stored in one
   or more other AF RIB(s). RIBs.

   Some examples of such native MPLS routes are:

   o  routes

   *  Routes programmed by RSVP on Label Switched Router(s) Switching Routers (LSRs) along
      the path of a Label Switched Path (LSP),

   o  routes an LSP,

   *  Routes that cross-connect an MPLS local label to a Layer-2, Layer 2 or
      Layer-3 VRF,

   o  routes
      Layer 3 Virtual Routing and Forwarding (VRF) entity,

   *  Routes that cross-connect an MPLS local label to a specific
      Layer-2 Layer
      2 adjacency or interface, such as Layer-2 Layer 2 Attachment
      Circuit(s) Circuits
      (ACs), or

   o  routes

   *  Routes that cross-connect an MPLS local label to a Layer-3 Layer 3
      adjacency or interface - interface, such as MPLS Segment-Routing Segment Routing (SR)
      Adjacency Segments (Adj-SIDs), (Adj-SIDs) or SR MPLS Binding SIDs, etc. SIDs as defined
      in [RFC8402].

2.4.  Model Tree Diagram

   The MPLS base tree diagram that diagram, which follows the notation defined in
   [RFC8340]
   [RFC8340], is shown in Figure 3.

   module: ietf-mpls
     augment /rt:routing:
       +--rw mpls
          +--rw ttl-propagate?       boolean
          +--rw mpls-label-blocks
          |  +--rw mpls-label-block* [index]
          |     +--rw index                    string
          |     +--rw start-label?             rt-types:mpls-label
          |     +--rw end-label?               rt-types:mpls-label
          |     +--rw block-allocation-mode?   identityref
          |     +--ro inuse-labels-count?      yang:gauge32
          +--rw interfaces
             +--rw interface* [name]
                +--rw name                      if:interface-ref
                +--rw mpls-enabled?             boolean
                +--rw maximum-labeled-packet?   uint32
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route:
       +--ro mpls-enabled?         boolean
       +--ro mpls-local-label?     rt-types:mpls-label
       +--ro destination-prefix?   -> ../mpls-local-label
       +--ro route-context?        string
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop
               /rt:next-hop-options/rt:simple-next-hop:
       +--ro mpls-label-stack
          +--ro entry* [id]
             +--ro id               uint8
             +--ro label?           rt-types:mpls-label
             +--ro ttl?             uint8
             +--ro traffic-class?   uint8
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop
               /rt:next-hop-options/rt:next-hop-list/rt:next-hop-list
               /rt:next-hop:
       +--ro index?              string
       +--ro backup-index?       string
       +--ro loadshare?          uint16
       +--ro role?               nhlfe-role
       +--ro mpls-label-stack
          +--ro entry* [id]
             +--ro id               uint8
             +--ro label?           rt-types:mpls-label
             +--ro ttl?             uint8
             +--ro traffic-class?   uint8
     augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input:
       +---w destination-address?   -> ../mpls-local-label
       +---w mpls-local-label?      rt-types:mpls-label
     augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output
               /rt:route/rt:next-hop/rt:next-hop-options
               /rt:simple-next-hop:
       +-- mpls-label-stack
          +-- entry* [id]
             +-- id               uint8
             +-- label?           rt-types:mpls-label
             +-- ttl?             uint8
             +-- traffic-class?   uint8
     augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output
               /rt:route/rt:next-hop/rt:next-hop-options
               /rt:next-hop-list/rt:next-hop-list/rt:next-hop:
       +-- index?              string
       +-- backup-index?       string
       +-- loadshare?          uint16
       +-- role?               nhlfe-role
       +-- mpls-label-stack
          +-- entry* [id]
             +-- id               uint8
             +-- label?           rt-types:mpls-label
             +-- ttl?             uint8
             +-- traffic-class?   uint8

                      Figure 3: MPLS Base tree diagram Tree Diagram

2.5.  Model  MPLS Base YANG Module

   This section describes the 'ietf-mpls' "ietf-mpls" YANG module that module, which provides
   base components of the MPLS data model.  Other YANG module(s) modules may
   import and augment the base MPLS base module to add feature specific feature-specific data.

   The ietf-mpls "ietf-mpls" YANG module imports the following YANG modules:

   o  ietf-routing

   *  "ietf-routing" as defined in [RFC8349]

   o  ietf-routing-types

   *  "ietf-routing-types" as defined in [RFC8294]

   o  ietf-interfaces

   *  "ietf-yang-types" as defined in [RFC6991]

   *  "ietf-interfaces" as defined in [RFC8343]

   This YANG module also references the following RFCs in defining the
   types and
   types, YANG grouping groupings, and other features of the YANG module: [RFC3032],
   [RFC3031], [RFC3032], [RFC4090], [RFC5714], and [RFC7424].

   <CODE BEGINS> file "ietf-mpls@2020-10-26.yang" "ietf-mpls@2020-11-19.yang"
   module ietf-mpls {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-mpls";

  /* Replace with IANA when assigned */

     prefix mpls;

     import ietf-routing {
       prefix rt;
       reference
      "RFC8349:
         "RFC 8349: A YANG Data Model for Routing Management"; Management
          (NMDA Version)";
     }
     import ietf-routing-types {
       prefix rt-types;
       reference
      "RFC8294:Common
         "RFC 8294: Common YANG Data Types for the Routing Area";
     }
     import ietf-yang-types {
       prefix yang;
       reference
      "RFC6991:
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-interfaces {
       prefix if;
       reference
      "RFC8343:
         "RFC 8343: A YANG Data Model for Interface Management";
     }

     organization
       "IETF MPLS Working Group";
     contact
       "WG Web:   <http://tools.ietf.org/wg/mpls/>   <https://datatracker.ietf.org/wg/mpls/>
        WG List:  <mailto:mpls@ietf.org>

        Editor:   Tarek Saad
                  <mailto:tsaad@juniper.net>

        Editor:   Kamran Raza
                  <mailto:skraza@cisco.com>

        Editor:   Rakesh Gandhi
                  <mailto:rgandhi@cisco.com>

        Editor:   Xufeng Liu
               <mailto: xufeng.liu.ietf@gmail.com>
                  <mailto:xufeng.liu.ietf@gmail.com>

        Editor:   Vishnu Pavan Beeram
                  <mailto:vbeeram@juniper.net>";
     description
       "This YANG module defines the essential components for the
        management of the MPLS subsystem.  The model fully conforms
        to the Network Management Datastore Architecture (NMDA).

        Copyright (c) 2018 2020 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; 8960; see the
        RFC itself for full legal notices.";

  // RFC Ed.: replace XXXX with actual RFC number and remove this
  // note.
  // RFC Ed.: update the date below with the date of RFC publication
  // and remove this note.

     revision 2020-10-26 2020-11-19 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: 8960: A YANG Data Model for base MPLS"; MPLS Base";
     }

     /* Identities */

     identity mpls {
       base rt:address-family;
       description
         "This identity represents the MPLS address family.";
     }

     identity mpls-unicast {
       base mpls:mpls;
       description
         "This identity represents the MPLS unicast address family.";
     }

     identity label-block-alloc-mode {
       description
         "Base identity for label-block allocation mode.";
     }

     identity label-block-alloc-mode-manager {
       base label-block-alloc-mode;
       description
      "Label block
         "Label-block allocation on the reserved block
          is managed by the label manager.";
     }

     identity label-block-alloc-mode-application {
       base label-block-alloc-mode;
       description
      "Label block
         "Label-block allocation on the reserved block
          is managed by the application.";
     }

     /**
      * Typedefs
      */

     typedef mpls-operations-type {
       type enumeration {
         enum impose-and-forward {
           description
             "Operation to impose one or more outgoing label(s) labels and
              forward to
           next-hop."; the next hop.";
         }
         enum pop-and-forward {
           description
             "Operation to pop the incoming label and forward to next-hop."; the
              next hop.";
         }
         enum pop-impose-and-forward {
           description
             "Operation to pop the incoming label, impose one or more
              outgoing label(s) labels, and forward to next-hop."; the next hop.";
         }
         enum swap-and-forward {
           description
             "Operation to swap the incoming label, label with the outgoing
              label and forward to next-hop."; the next hop.";
         }
         enum pop-and-lookup {
           description
             "Operation to pop the incoming label and perform
              a lookup.";
         }
       }
       description
      "MPLS operations types.";
         "Types of MPLS operations.";
     }

     typedef nhlfe-role {
       type enumeration {
         enum primary {
           description
          "Next-hop
             "The next hop acts as the primary for carrying traffic.";
         }
         enum backup {
           description
          "Next-hop
             "The next hop acts as the backup.";
         }
         enum primary-and-backup {
           description
          "Next-hop
             "The next hop simultaneously acts as both the primary and
              the backup simultaneously for carry carrying traffic.";
         }
       }
       description
      "The next-hop role.";
         "Role of the next hop.";
     }

     grouping nhlfe-single-contents {
       description
         "A grouping that describes a single Next Hop Label Forwarding
          Entry (NHLFE) and its associated parameters as described in
          the MPLS architecture.  This grouping is specific to the case
          when a single next-hop next hop is associated with the route.";
       uses rt-types:mpls-label-stack;
     }

     grouping nhlfe-multiple-contents {
       description
         "A grouping that describes a set of NHLFE(s) NHLFEs and their
          associated parameters as described in the MPLS
          architecture.  This grouping is used when multiple next-hops next hops
          are associated with the route.";
       leaf index {
         type string;
         description
           "A user-specified identifier utilised utilized to uniquely
            reference the next-hop entry in the next-hop list.
            The value of this index has no semantic meaning
            other than for referencing the entry.";
       }
       leaf backup-index {
         type string;
         description
           "A user-specified identifier utilised utilized to uniquely
            reference the backup next-hop entry in the NHLFE list.
            The value of this index has no semantic meaning
            other than for referencing the entry.";
         reference
        "RFC4090 and RFC5714";
           "RFC 4090: Fast Reroute Extensions to RSVP-TE for LSP Tunnels
            RFC 5714: IP Fast Reroute Framework";
       }
       leaf loadshare {
         type uint16;
         default "1";
         description
           "This value is used to compute a loadshare load share to perform un-equal
            unequal load balancing when multiple outgoing next-hop(s) next hops are
            specified.  A share is computed as a ratio of this number to
            the total under all next-hops(s)."; next hops.";
         reference
        "RFC7424, section 5.4,
         RFC3031, section
           "RFC 3031: Multiprotocol Label Switching Architecture,
            Sections 3.11 and 3.12."; 3.12
            RFC 7424: Mechanisms for Optimizing Link Aggregation Group
            (LAG) and Equal-Cost Multipath (ECMP) Component Link
            Utilization in Networks, Section 5.4";
       }
       leaf role {
         type nhlfe-role;
         description
        "NHLFE role.";
           "Role of the NHLFE.";
       }
       uses nhlfe-single-contents;
     }

     grouping interfaces-mpls {
       description
         "List of MPLS interfaces.";
       container interfaces {
         description
           "List of MPLS enabled interaces."; MPLS-enabled interfaces.";
         list interface {
           key "name";
           description
          "MPLS enabled
             "MPLS-enabled interface entry.";
           leaf name {
             type if:interface-ref;
             description
               "A reference to the name of a an interface in the system
                that is to be enabled for MPLS.";
           }
           leaf mpls-enabled {
             type boolean;
             default "false";
             description
               "'true' if mpls MPLS encapsulation is enabled on the
                interface.
                'false' if mpls MPLS encapsulation is disabled on the
                interface.";
           }
           leaf maximum-labeled-packet {
             type uint32;
             units "octets";
             description
               "Maximum labeled packet size.";
             reference
            "RFC3032, section 3.2.";
               "RFC 3032: MPLS Label Stack Encoding, Section 3.2";
           }
         }
       }
     }

     grouping globals {
       description
         "MPLS global configuration grouping.";
       leaf ttl-propagate {
         type boolean;
         default "true";
         description
           "Propagate TTL between IP and MPLS.";
       }
     }

     grouping label-blocks {
       description
         "Label-block allocation grouping.";
       container mpls-label-blocks {
         description
           "Label-block allocation container.";
         list mpls-label-block {
           key "index";
           description
             "List of MPLS label-blocks."; label blocks.";
           leaf index {
             type string;
             description
               "A user-specified identifier utilised utilized to uniquely
                reference an MPLS label block.";
           }
           leaf start-label {
             type rt-types:mpls-label;
             must '. <= ../end-label' {
               error-message
              "The start-label "'start-label' must be less than or equal "
                           + "to end-label"; 'end-label'";
             }
             description
               "Label-block start.";
           }
           leaf end-label {
             type rt-types:mpls-label;
             must '. >= ../start-label' {
               error-message
              "The end-label "'end-label' must be greater than or equal "
                           + "to start-label"; "equal to 'start-label'";
             }
             description
               "Label-block end.";
           }
           leaf block-allocation-mode {
             type identityref {
               base label-block-alloc-mode;
             }
             description
               "Label-block allocation mode.";
           }
           leaf inuse-labels-count {
             when "derived-from-or-self(../block-allocation-mode, "
                + "'mpls:label-block-alloc-mode-manager')";
             type yang:gauge32;
             config false;
             description
            "Label-block inuse
               "Number of labels count."; in use in the label block.";
           }
         }
       }
     }

     grouping rib-mpls-properties {
       description
         "A grouping of native MPLS RIB properties.";
       leaf destination-prefix {
         type leafref {
           path "../mpls-local-label";
         }
         description
           "MPLS destination prefix.";
       }
       leaf route-context {
         type string;
         description
           "A context associated with the native MPLS route.";
       }
     }

     grouping rib-active-route-mpls-input {
       description
         "A grouping applicable to native MPLS RIB 'active-route'
          RPC input augmentation.";
       leaf destination-address {
         type leafref {
           path "../mpls-local-label";
         }
         description
           "MPLS native active route 'active-route' destination.";
       }
       leaf mpls-local-label {
         type rt-types:mpls-label;
         description
           "MPLS local label.";
       }
     }

     augment "/rt:routing" {
       description
         "MPLS augmentation.";
       container mpls {
         description
           "MPLS container, container to be used as an augmentation target node
            for the configuration of other MPLS sub-features config, e.g. sub-features, e.g.,
            MPLS static LSP, Label Switched Paths (LSPs), MPLS LDP LSPs,
            and Trafic Traffic Engineering MPLS LSP Tunnels, etc."; Tunnels.";
         uses globals;
         uses label-blocks;
         uses interfaces-mpls;
       }
     }

     /* Augmentation of MPLS routes augmentation */

     augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route" {
       description
         "This augmentation is applicable to all MPLS routes.";
       leaf mpls-enabled {
         type boolean;
         default "false";
         description
           "Indicates whether MPLS is enabled for this route.";
       }
       leaf mpls-local-label {
         when "../mpls-enabled = 'true'";
         type rt-types:mpls-label;
         description
           "MPLS local label associated with the route.";
       }
       uses rib-mpls-properties {
         /* MPLS AF Address Family (AF) augmentation to the
            native MPLS RIB */
         when "derived-from-or-self(../../rt:address-family, "
            + "'mpls:mpls')" {
           description
             "This augment is valid only for routes of the native MPLS
              RIB.";
         }
       }
     }

     /* MPLS simple-next-hop augmentation */

     augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
           + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
       description
      "Augment
         "Augments the 'simple-next-hop' case in IP unicast routes.";
       uses nhlfe-single-contents {
         when "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route"
            + "/mpls:mpls-enabled = 'true'";
       }
     }

     /* MPLS next-hop-list augmentation */

     augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
           + "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
           + "rt:next-hop-list/rt:next-hop" {
       description
         "This leaf augments the 'next-hop-list' case of IP unicast
          routes.";
       uses nhlfe-multiple-contents {
         when "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route"
            + "/mpls:mpls-enabled = 'true'";
       }
     }

     /* MPLS RPC input augmentation */

     augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input" {
       description
         "Input MPLS augmentation for the 'active-route' action
          statement.";
       uses rib-active-route-mpls-input {
         /* MPLS AF augmentation to the native MPLS RIB */
         when "derived-from-or-self(../rt:address-family, "
            + "'mpls:mpls')" {
           description
             "This augment is valid only for routes of the native MPLS
              RIB.";
         }
       }
     }

     /* MPLS RPC output augmentation */

     augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/"
           + "rt:output/rt:route/"
           + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
       description
         "Output MPLS augmentation for the 'active-route' action
          statement.";
       uses nhlfe-single-contents;
     }

     augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/"
           + "rt:output/rt:route/"
           + "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
           + "rt:next-hop-list/rt:next-hop" {
       description
         "Output MPLS augmentation for the 'active-route' action
          statement.";
       uses nhlfe-multiple-contents;
     }
   }
   <CODE ENDS>

                      Figure 4: MPLS base Base YANG module. Module

3.  IANA Considerations

   This document registers the following URIs URI in the 'ns' sub-registry "ns" subregistry of
   the IETF "IETF XML registry Registry" [RFC3688].  Following the format in
   [RFC3688], the following registration is requested to be made.

   URI:  urn:ietf:params:xml:ns:yang:ietf-mpls
   Registrant Contact:  The MPLS WG of the IETF.
   XML: N/A,  N/A; the requested URI is an XML namespace.

   This document registers a the following YANG module in the YANG "YANG Module Names
   Names" registry [RFC6020].

      name:

   Name:  ietf-mpls
      namespace:
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-mpls
      prefix:
   Prefix:  mpls
      // RFC Ed.: replace XXXX with
   Reference:  RFC number and remove this note
      reference:  RFCXXXX 8960

4.  Security Considerations

   The YANG module specified in this document define defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The NETCONF access control model Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   "/rt:routing/mpls:mpls/mpls:label-blocks": there
      There are data nodes under this path that are writeable writable, such as 'start-label'
      "start-label" and 'end-label'. "end-label".  Write operations to those data npdes
      nodes may cause disruptive action result in disruption to existing traffic.

   Some of the readable data nodes in these this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop/rt:next-
   hop-options/rt:next-hop-list/rt:next-hop-list/rt:next-hop"

   "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop/
   rt:next-hop-options/rt:next-hop-list/rt:next-hop-list/rt:next-hop"
   and
   "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output/rt:route/
   rt:next-hop/rt:next-hop-options/rt:simple-next-hop": these "/rt:routing/rt:ribs/rt:rib/rt:active-
   route/rt:output/rt:route/rt:next-hop/rt:next-hop-options/
   rt:simple-next-hop":
      These two paths are augmented by additional MPLS leaf(s) leafs defined in
      this model.  Access to this information may disclose the next-hop or path per
      information for the prefix route and/or other information.

   Some of the RPC operations in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  These are the
   operations and their sensitivity/vulnerability:

   "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input" and
   "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output/rt:route":
   these
      These two paths are augmented by additional MPLS data node(s) nodes that
      are defined in this model.  Access to those path(s) may paths may disclose
      information about per prefix route per-prefix routes and/or other information and that information; such
      disclosure may be further used for further attack(s). attacks.

   The security considerations spelled out in [RFC3031] and [RFC3032]
   apply for this document as well.

5.  Acknowledgement

   The authors would like to thank Xia Chen for her contributions to the
   early revisions of this document.

6.  Appendix A.  Data Tree Instance Example

   A simple network setup is shown in Figure 5.  R1 runs  References

5.1.  Normative References

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the ISIS
   routing protocol, Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and learns reachability about two IPv4 prefixes:
   P1: 198.51.100.1/32 A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and P2: 198.51.100.1/32, K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8294]  Liu, X., Qu, Y., Lindem, A., Hopps, C., and two IPv6 prefixes
   P3: 2001:db8:0:10::1/64 L. Berger,
              "Common YANG Data Types for the Routing Area", RFC 8294,
              DOI 10.17487/RFC8294, December 2017,
              <https://www.rfc-editor.org/info/rfc8294>.

   [RFC8340]  Bjorklund, M. and P4: 2001:db8:0:10::1/64.  We also assume
   that R1 learns about local L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8341]  Bierman, A. and remote MPLS label bindings for each
   prefix using ISIS (e.g. using Segment-Routing (SR) extensions).

   State on R1:
   ============
       IPv4 Prefix         MPLS Label
   P1: 198.51.100.1/32     16001
   P2: 198.51.100.2/32     16002 M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

5.2.  Informative References

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [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>.

   [RFC5714]  Shand, M. and S. Bryant, "IP Fast Reroute Framework",
              RFC 5714, DOI 10.17487/RFC5714, January 2010,
              <https://www.rfc-editor.org/info/rfc5714>.

   [RFC7424]  Krishnan, R., Yong, L., Ghanwani, A., So, N., and B.
              Khasnabish, "Mechanisms for Optimizing Link Aggregation
              Group (LAG) and Equal-Cost Multipath (ECMP) Component Link
              Utilization in Networks", RFC 7424, DOI 10.17487/RFC7424,
              January 2015, <https://www.rfc-editor.org/info/rfc7424>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

Appendix A.  Data Tree Instance Example

   A simple network setup is shown in Figure 5.  R1 runs the IS-IS
   routing protocol and learns about the reachability of two IPv4
   prefixes (P1: 198.51.100.1/32 and P2: 198.51.100.2/32) and two IPv6
   prefixes (P3: 2001:db8:0:10::1/128 and P4: 2001:db8:0:10::2/128).  We
   also assume that R1 learns about local and remote MPLS label bindings
   for each prefix using IS-IS (e.g., using Segment Routing (SR)
   extensions).

   State on R1:
   ============
       IPv4 Prefix           MPLS Label
   P1: 198.51.100.1/32       16001
   P2: 198.51.100.2/32       16002

       IPv6 Prefix           MPLS Label
   P3: 2001:db8:0:10::1/64 2001:db8:0:10::1/128  16003
   P4: 2001:db8:0:10::2/64 2001:db8:0:10::2/128  16004

   RSVP MPLS LSPv4-Tunnel:
    Source:        198.51.100.3
    Destination:   198.51.100.4
    Tunnel-ID:     10
    LSP-ID:        1
                                  192.0.2.5/30
                                  2001:db8:0:1::1/64
                                 eth0
                                 +---
                                /
                           +-----+
                           | R1  |
                           +-----+
                                \
                                 +---
                                 eth1
                                  192.0.2.13/30
                                  2001:db8:0:2::1/64

                 Figure 5: Example of network configuration. Network Configuration

   The instance data tree could then be illustrated as follows: shown in
   Figure 6, using JSON format [RFC7951]:

   {
     "ietf-routing:routing":{
       "ribs":{
         "rib":[
           {
             "name":"RIB-V4",
             "address-family":
             "ietf-ipv4-unicast-routing:v4ur:ipv4-unicast",
             "routes":{
               "route":[
                 {
                   "next-hop":{
                     "outgoing-interface":"eth0",
                     "ietf-mpls:mpls-label-stack":{
                       "entry":[
                         {
                           "id":1,
                           "label":16001,
                           "ttl":255
                         }
                       ]
                     },
                     "ietf-ipv4-unicast-routing:next-hop-address":
                     "192.0.2.5"
                   },
                "source-protocol":"isis:isis",
                   "source-protocol":"ietf-isis:isis",
                   "ietf-mpls:mpls-enabled":true,
                   "ietf-mpls:mpls-local-label":16001,
                   "ietf-ipv4-unicast-routing:destination-prefix":
                   "198.51.100.1/32",
                   "ietf-mpls:route-context":"SID-IDX:1"
                 },
                 {
                   "next-hop":{
                     "next-hop-list":{
                       "next-hop":[
                         {
                           "outgoing-interface":"eth0",
                           "ietf-mpls:index":"1",
                           "ietf-mpls:backup-index":"2",
                           "ietf-mpls:role":"primary-and-backup",
                           "ietf-mpls:mpls-label-stack":{
                             "entry":[
                               {
                                 "id":1,
                                 "label":16002,
                                 "ttl":255
                               }
                             ]
                           },
                        "ietf-ipv4-unicast-routing:address":"192.0.2.5"
                           "ietf-ipv4-unicast-routing:address":
                           "192.0.2.5"
                         },
                         {
                           "outgoing-interface":"eth1",
                           "ietf-mpls:index":"2",
                           "ietf-mpls:backup-index":"1",
                           "ietf-mpls:role":"primary-and-backup",
                           "ietf-mpls:mpls-label-stack":{
                             "entry":[
                               {
                                 "id":1,
                                 "label":16002,
                                 "ttl":255
                               }
                             ]
                           },
                        "ietf-ipv4-unicast-routing:address":"192.0.2.13"
                           "ietf-ipv4-unicast-routing:address":
                           "192.0.2.13"
                         }
                       ]
                     }
                   },
                "source-protocol":"isis:isis",
                   "source-protocol":"ietf-isis:isis",
                   "ietf-mpls:mpls-enabled":true,
                   "ietf-mpls:mpls-local-label":16002,
                   "ietf-ipv4-unicast-routing:destination-prefix":
                   "198.51.100.2/32",
                   "ietf-mpls:route-context":"SID-IDX:2"
                 }
               ]
             }
           },
           {
             "name":"RIB-V6",
             "address-family":
             "ietf-ipv6-unicast-routing:v6ur:ipv6-unicast",
             "routes":{
               "route":[
                 {
                   "next-hop":{
                     "outgoing-interface":"eth0",
                     "ietf-mpls:mpls-label-stack":{
                       "entry":[
                         {
                           "id":1,
                           "label":16003,
                           "ttl":255
                         }
                       ]
                     },
                     "ietf-ipv6-unicast-routing:next-hop-address":
                     "2001:db8:0:1::1"
                   },
                "source-protocol":"isis:isis",
                   "source-protocol":"ietf-isis:isis",
                   "ietf-mpls:mpls-enabled":true,
                "ietf-mpls:mpls-local-label":16001,
                   "ietf-mpls:mpls-local-label":16003,
                   "ietf-ipv6-unicast-routing:destination-prefix":
                "2001:db8:0:10::1/6",
                "ietf-mpls:route-context":"SID-IDX:1"
                   "2001:db8:0:10::1/128",
                   "ietf-mpls:route-context":"SID-IDX:3"
                 },
                 {
                   "next-hop":{
                     "next-hop-list":{
                       "next-hop":[
                         {
                           "outgoing-interface":"eth0",
                           "ietf-mpls:index":"1",
                           "ietf-mpls:backup-index":"2",
                           "ietf-mpls:role":"primary-and-backup",
                           "ietf-mpls:mpls-label-stack":{
                             "entry":[
                               {
                                 "id":1,
                                 "label":16004,
                                 "ttl":255
                               }
                             ]
                           },
                           "ietf-ipv6-unicast-routing:address":
                           "2001:db8:0:1::1"
                         },
                         {
                           "outgoing-interface":"eth1",
                           "ietf-mpls:index":"2",
                           "ietf-mpls:backup-index":"1",
                           "ietf-mpls:role":"primary-and-backup",
                           "ietf-mpls:mpls-label-stack":{
                             "entry":[
                               {
                                 "id":1,
                                 "label":16004,
                                 "ttl":255
                               }
                             ]
                           },
                           "ietf-ipv6-unicast-routing:address":
                           "2001:db8:0:2::1"
                         }
                       ]
                     }
                   },
                "source-protocol":"isis:isis",
                   "source-protocol":"ietf-isis:isis",
                   "ietf-mpls:mpls-enabled":true,
                   "ietf-mpls:mpls-local-label":16004,
                   "ietf-ipv6-unicast-routing:destination-prefix":
                "2001:db8:0:10::2/64",
                "ietf-mpls:route-context":"SID-IDX:2"
                   "2001:db8:0:10::2/128",
                   "ietf-mpls:route-context":"SID-IDX:4"
                 }
               ]
             }
           },
           {
             "name":"RIB-MPLS",
             "address-family":"ietf-mpls:mpls:mpls",
             "routes":{
               "route":[
                 {
                   "next-hop":{
                     "outgoing-interface":"eth0",
                     "ietf-mpls:mpls-label-stack":{
                       "entry":[
                         {
                           "id":1,
                           "label":24002,
                           "ttl":255
                         }
                       ]
                     },
                     "ietf-ipv4-unicast-routing:next-hop-address":
                     "192.0.2.5"
                   },
                "source-protocol":"rsvp:rsvp",
                   "source-protocol":"ietf-rsvp:rsvp",
                   "ietf-mpls:mpls-enabled":true,
                   "ietf-mpls:mpls-local-label":24001,
                   "ietf-mpls:destination-prefix":"24001",
                   "ietf-mpls:route-context":
                   "RSVP Src:198.51.100.3,Dst:198.51.100.4,T:10,L:1"
                 }
            }
               ]
             }
           }
         ]
       },
       "ietf-mpls:mpls":{
         "mpls-label-blocks":{
           "mpls-label-block":[
             {
              "index":"mpls-srgb-label-block",
              "start-label":16000,
              "end-label":16500,
           "block-allocation-mode":"mpls:label-block-alloc-mode-manager"
              "block-allocation-mode":
              "ietf-mpls:label-block-alloc-mode-manager"
             }
           ]
         },
         "interfaces":{
           "interface":[
             {
               "name":"eth0",
               "mpls-enabled":true,
               "maximum-labeled-packet":1488
             },
             {
               "name":"eth1",
            "mpls-enabled":true,
            "maximum-labeled-packet":1488
          }
        ]
      }
    }
  }
}

                            Figure 6: Foo bar.

7.  Contributors

      Igor Bryskin
      Huawei Technologies
      email: i_bryskin@yahoo.com

      Himanshu Shah
      Ciena
      email: hshah@ciena.com

8.  References

8.1.  Normative References

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8294]  Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
              "Common YANG
               "mpls-enabled":true,
               "maximum-labeled-packet":1488
             }
           ]
         }
       }
     }
   }

                    Figure 6: Instance Data Types for the Routing Area", RFC 8294,
              DOI 10.17487/RFC8294, December 2017,
              <https://www.rfc-editor.org/info/rfc8294>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

8.2.  Informative References

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [RFC7424]  Krishnan, R., Yong, L., Ghanwani, A., So, N., and B.
              Khasnabish, "Mechanisms Example

Acknowledgments

   The authors would like to thank Xia Chen for Optimizing Link Aggregation
              Group (LAG) and Equal-Cost Multipath (ECMP) Component Link
              Utilization in Networks", RFC 7424, DOI 10.17487/RFC7424,
              January 2015, <https://www.rfc-editor.org/info/rfc7424>. her contributions to the
   early draft revisions of this document.

Contributors

   Igor Bryskin
   Huawei Technologies

   Email: i_bryskin@yahoo.com

   Himanshu Shah
   Ciena

   Email: hshah@ciena.com

Authors' Addresses

   Tarek Saad
   Juniper Networks

   Email: tsaad@juniper.net

   Kamran Raza
   Cisco Systems Inc Systems, Inc.

   Email: skraza@cisco.com

   Rakesh Gandhi
   Cisco Systems Inc Systems, Inc.

   Email: rgandhi@cisco.com

   Xufeng Liu
   Volta Networks

   Email: xufeng.liu.ietf@gmail.com

   Vishnu Pavan Beeram
   Juniper Networks

   Email: vbeeram@juniper.net