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

Versions: (draft-saad-mpls-base-yang)   00 01 02         Standards Track
          03 04 05 06 07 08 09 10 11 12 13 14 15                        
          16 17                                                         
MPLS Working Group                                               T. Saad
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                                 K. Raza
Expires: February 18, 2021                                     R. Gandhi
                                                       Cisco Systems Inc
                                                                  X. Liu
                                                          Volta Networks
                                                               V. Beeram
                                                        Juniper Networks
                                                         August 17, 2020


                    A YANG Data Model for MPLS Base
                      draft-ietf-mpls-base-yang-15

Abstract

   This document contains a specification of the MPLS base YANG model.
   The MPLS base YANG 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 models (e.g.  MPLS Label Switched
   Path (LSP) Static, LDP or RSVP-TE YANG models) will augment the MPLS
   base YANG 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 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 https://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 February 18, 2021.

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
   Provisions Relating to IETF Documents



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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   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  . . . . . . . . . . . . . . . . . . .   7
     2.5.  Model YANG Module . . . . . . . . . . . . . . . . . . . .   8
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   5.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  19
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  19
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  20
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   A core routing data model is defined in [RFC8349], and 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)
   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 specific destination prefix(es)
   present in the AF RIB(s) as described in the MPLS architecture
   document [RFC3031].

   The MPLS base model also defines a new instance of the generic RIB
   model as defined in {!RFC8349}} to store native MPLS routes.  The
   native MPLS RIB instance stores route(s) that are not associated with
   other AF instance RIBs (such as IPv4, or IPv6 instance RIB(s)), but
   are enabled for MPLS forwarding.  Examples of such native MPLS routes



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   are routes programmed by RSVP on transit MPLS router(s) along the
   path of a Label Switched Path (LSP).  Other example(s) are MPLS
   routes that cross-connect to specific Layer-2 adjacencies, such as
   Layer-2 Attachment Circuit(s) (ACs)), or Layer-3 adjacencies, such as
   Segment-Routing (SR) Adjacency Segments (Adj-SIDs) described in
   [RFC8402].

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

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

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

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   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



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2.  MPLS Base Model

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

2.1.  Model Overview

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

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

2.2.  Model Organization

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

           @: not in this document, shown for illustration only

                Figure 1: Relationship between MPLS modules

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

   mpls:





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

   label-block-alloc-mode:

      A base YANG identity for supported label block allocation mode(s).

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

   mpls-operations-type:

      An enumeration type that represents support possible MPLS
      operation types (impose-and-forward, pop-and-forward, pop-impose-
      and-forward, and pop-and-lookup)

   nhlfe-role:

      An enumeration type that represents the role of the NHLFE entry.

   nhlfe-single-contents:

      A YANG grouping that describes single NHLFE and its associated
      parameters as described in the MPLS architecture document
      [RFC3031].

   nhlfe-multiple-contents:

      A YANG grouping that describes a set of NHLFE(s) and their
      associated parameters as described in the MPLS architecture
      document [RFC3031].

   interfaces-mpls:

      A YANG grouping that describes the list of 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 MPLS label forwarding data
      to the generic RIB as defined in [RFC3031].




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   rib-active-route-mpls-input:

      A YANG grouping for the augmentation to the '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).

                                +-----------------+
                                | 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 and RIB instances

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

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

   Some examples of such native MPLS routes are:

   o  routes programmed by RSVP on Label Switched Router(s) (LSRs) along
      the path of a Label Switched Path (LSP),

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





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

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

2.4.  Model Tree Diagram

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

   module: ietf-mpls
     augment /rt:routing:
       +--rw mpls {mpls}?
          +--rw ttl-propagate?   boolean
          +--rw label-blocks
          |  +--rw 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 free-labels-count?       yang:counter32
          |     +--ro inuse-labels-count?      yang:counter32
          +--rw interface* [name]
             +--rw name                      if:interface-ref
             +--rw enabled?                  boolean
             +--rw maximum-labeled-packet?   uint32
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route:
       +--ro mpls-enabled?         boolean {mpls}?
       +--ro local-label?          rt-types:mpls-label {mpls}?
       +--ro destination-prefix?   -> ../local-label {mpls}?
       +--ro route-context?        string {mpls}?
     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



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       +--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?   -> ../local-label
       +---w 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

2.5.  Model YANG Module

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

   The ietf-mpls module imports the following modules:

   o  ietf-routing defined in [RFC8349]

   o  ietf-routing-types defined in [RFC8294]




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   o  ietf-interfaces defined in [RFC8343]

   This model also references the following RFCs in defining the types
   and YANG grouping of the YANG module: [RFC3032], [RFC3031], and
   [RFC7424].

<CODE BEGINS> file "ietf-mpls@2020-08-17.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: A YANG Data Model for Routing Management";
  }
  import ietf-routing-types {
    prefix rt-types;
    reference
      "RFC8294:Common YANG Data Types for the Routing Area";
  }
  import ietf-yang-types {
    prefix yang;
    reference
      "RFC6991: Common YANG Data Types";
  }
  import ietf-interfaces {
    prefix if;
    reference
      "RFC8343: A YANG Data Model for Interface Management";
  }

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

     WG List:  <mailto:mpls@ietf.org>

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

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



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

     Editor:   Xufeng Liu
               <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 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; 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 2020-08-17 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: A YANG Data Model for base MPLS";
  }

  feature mpls {
    description
      "Indicates support for MPLS switching.";
    reference
      "RFC3031";
  }

  /* Identities */

  identity mpls {
    base rt:address-family;



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    description
      "This identity represents the MPLS address family.";
  }

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

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

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

  /**
   * Typedefs
   */

  typedef mpls-operations-type {
    type enumeration {
      enum impose-and-forward {
        description
          "Operation impose outgoing label(s) and forward to
           next-hop.";
      }
      enum pop-and-forward {
        description
          "Operation pop incoming label and forward to next-hop.";
      }
      enum pop-impose-and-forward {
        description
          "Operation pop incoming label, impose one or more
           outgoing label(s) and forward to next-hop.";
      }
      enum swap-and-forward {
        description
          "Operation swap incoming label, with outgoing label and
           forward to next-hop.";
      }



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      enum pop-and-lookup {
        description
          "Operation pop incoming label and perform a lookup.";
      }
    }
    description
      "MPLS operations types.";
  }

  typedef nhlfe-role {
    type enumeration {
      enum PRIMARY {
        description
          "Next-hop acts as primary traffic carrying.";
      }
      enum BACKUP {
        description
          "Next-hop acts as backup.";
      }
      enum PRIMARY_AND_BACKUP {
        description
          "Next-hop acts as primary and backup simultaneously.";
      }
    }
    description
      "The next-hop role.";
  }

  grouping nhlfe-single-contents {
    description
      "MPLS simple NHLFE contents.";
    uses rt-types:mpls-label-stack;
  }

  grouping nhlfe-multiple-contents {
    description
      "MPLS NHLFE contents.";
    leaf index {
      type string;
      description
        "A user-specified identifier utilised 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



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        "A user-specified identifier utilised 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.";
    }
    leaf loadshare {
      type uint16;
      description
        "This value is used to compute a loadshare to perform un-equal
         load balancing when multiple outgoing next-hop(s) are
         specified. A share is computed as a ratio of this number to the
         total under all next-hops(s).";
      reference
        "RFC7424, section 5.4,
         RFC3031, section 3.11 and 3.12.";
    }
    leaf role {
      type nhlfe-role;
      description
        "NHLFE role.";
    }
    uses nhlfe-single-contents;
  }

  grouping interfaces-mpls {
    description
      "List of MPLS interfaces.";
    list interface {
      key "name";
      description
        "List of MPLS interfaces.";
      leaf name {
        type if:interface-ref;
        description
          "The name of a configured MPLS interface.";
      }
      leaf enabled {
        type boolean;
        description
          "'true' if mpls encapsulation is enabled on the interface.
           'false' if mpls encapsulation is disabled on the interface.";
      }
      leaf maximum-labeled-packet {
        type uint32;
        units "octets";
        description
          "Maximum labeled packet size.";
        reference



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          "RFC3032, 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 label-blocks {
      description
        "Label-block allocation container.";
      list label-block {
        key "index";
        unique "start-label end-label";
        description
          "List of MPLS label-blocks.";
        leaf index {
          type string;
          description
            "A user-specified identifier utilised to uniquely
             reference an MPLS label block.";
        }
        leaf start-label {
          type rt-types:mpls-label;
          must '. >= ../end-label' {
            error-message "The start-label must be less than or equal "
                        + "to end-label";
          }
          description
            "Label-block start.";
        }
        leaf end-label {
          type rt-types:mpls-label;
          must '. <= ../start-label' {
            error-message "The end-label must be greater than or equal "
                        + "to start-label";
          }



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          description
            "Label-block end.";
        }
        leaf block-allocation-mode {
          type identityref {
            base label-block-alloc-mode;
          }
          description
            "Label-block allocation mode.";
        }
        leaf free-labels-count {
          when "derived-from-or-self(../block-allocation-mode, "
             + "'mpls:label-block-alloc-mode-manager')";
          type yang:counter32;
          config false;
          description
            "Label-block free labels count.";
        }
        leaf inuse-labels-count {
          when "derived-from-or-self(../block-allocation-mode, "
             + "'mpls:label-block-alloc-mode-manager')";
          type yang:counter32;
          config false;
          description
            "Label-block inuse labels count.";
        }
      }
    }
  }

  grouping rib-mpls-properties {
    description
      "A grouping of native MPLS RIB properties.";
    leaf destination-prefix {
      type leafref {
        path "../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 {



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

  augment "/rt:routing" {
    if-feature "mpls";
    description
      "MPLS augmentation.";
    container mpls {
      description
        "MPLS container, to be used as an augmentation target node
         other MPLS sub-features config, e.g. MPLS static LSP, MPLS
         LDP LSPs, and Trafic Engineering MPLS LSP Tunnels, etc.";
      uses globals;
      uses label-blocks;
      uses interfaces-mpls;
    }
  }

  /* MPLS routes augmentation */

  augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route" {
    if-feature "mpls";
    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 local-label {
      when "../mpls-enabled = 'true'";
      type rt-types:mpls-label;
      description



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        "MPLS local label associated with the route.";
    }
    uses rib-mpls-properties {
      /* MPLS AF aaugmentation to native MPLS RIB */
      when "derived-from-or-self(../../rt:address-family, "
         + "'mpls:mpls')" {
        description
          "This augment is valid only for routes of 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 '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 aaugmentation to native MPLS RIB */
      when "derived-from-or-self(../rt:address-family, "



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         + "'mpls:mpls')" {
        description
          "This augment is valid only for routes of 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 YANG module

3.  IANA Considerations

   This document registers the following URIs in the IETF XML 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, the requested URI is an XML namespace.

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






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

4.  Security Considerations

   The YANG modules specified in this document define 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 [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.

   Some of the readable data nodes in these YANG modules 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:active-route/rt:output/rt:route: this
   path is augmented by additional MPLS leaf(s) defined in this model.
   Access to this information may disclose the per prefix and/or other
   information.

   /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output/rt:route/
   rt:next-hop/rt:next-hop-options/rt:simple-next-hop: this path is
   augmented by additional MPLS leaf(s) defined in this model.  Access
   to this information may disclose the next-hop or path per prefix and/
   or other information.

5.  Acknowledgement

   The authors would like to thank the members of the multi-vendor YANG
   design team who are involved in the definition of this model.

6.  Contributors







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      Igor Bryskin
      Huawei Technologies
      email: Igor.Bryskin@huawei.com


      Himanshu Shah
      Ciena
      email: hshah@ciena.com


7.  References

7.1.  Normative References

   [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>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.



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   [RFC8294]  Liu, X., Qu, Y., Lindem, A., Hopps, C., and 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 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>.

7.2.  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>.

   [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>.



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   [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>.

Authors' Addresses

   Tarek Saad
   Juniper Networks

   Email: tsaad@juniper.net


   Kamran Raza
   Cisco Systems Inc

   Email: skraza@cisco.com


   Rakesh Gandhi
   Cisco 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















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