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MPLS Working Group                                          K. Raza, Ed.
Internet-Draft                                                  R. Asati
Intended status: Standards Track                           Cisco Systems
Expires: September 21, 2020
                                                                  X. Liu
                                                          Volta Networks

                                                                S. Esale
                                                        Juniper Networks

                                                                 X. Chen
                                                     Huawei Technologies

                                                                 H. Shah
                                                       Ciena Corporation


                                                          March 20, 2020


                      YANG Data Model for MPLS LDP
                      draft-ietf-mpls-ldp-yang-09

Abstract

   This document describes a YANG data model for Multi-Protocol Label
   Switching (MPLS) Label Distribution Protocol (LDP).  The model also
   serves as the base model to define Multipoint LDP (mLDP) model.

   The YANG modules in this document conform to the Network Management
   Datastore Architecture (NMDA).

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 September 21, 2020.

Copyright Notice

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




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Base and Extended . . . . . . . . . . . . . . . . . . . .   3
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   4
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  The Complete Tree . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Configuration . . . . . . . . . . . . . . . . . . . . . . . .  16
     5.1.  Configuration Hierarchy . . . . . . . . . . . . . . . . .  19
       5.1.1.  Global parameters . . . . . . . . . . . . . . . . . .  20
       5.1.2.  Capabilities parameters . . . . . . . . . . . . . . .  20
       5.1.3.  Per-Address-Family parameters . . . . . . . . . . . .  20
       5.1.4.  Hello Discovery parameters  . . . . . . . . . . . . .  20
       5.1.5.  Peer parameters . . . . . . . . . . . . . . . . . . .  21
       5.1.6.  Forwarding parameters . . . . . . . . . . . . . . . .  21
   6.  Operational State . . . . . . . . . . . . . . . . . . . . . .  22
     6.1.  Adjacency state . . . . . . . . . . . . . . . . . . . . .  22
     6.2.  Peer state  . . . . . . . . . . . . . . . . . . . . . . .  23
     6.3.  Bindings state  . . . . . . . . . . . . . . . . . . . . .  24
     6.4.  Capabilities state  . . . . . . . . . . . . . . . . . . .  26
   7.  Notifications . . . . . . . . . . . . . . . . . . . . . . . .  27
   8.  Action  . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
   9.  YANG Specification  . . . . . . . . . . . . . . . . . . . . .  27
     9.1.  Base  . . . . . . . . . . . . . . . . . . . . . . . . . .  27
     9.2.  Extended  . . . . . . . . . . . . . . . . . . . . . . . .  59
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  80
     10.1.  YANG model . . . . . . . . . . . . . . . . . . . . . . .  80
       10.1.1.  Writable nodes . . . . . . . . . . . . . . . . . . .  81
       10.1.2.  Readable nodes . . . . . . . . . . . . . . . . . . .  81
       10.1.3.  RPC operations . . . . . . . . . . . . . . . . . . .  82
       10.1.4.  Notifications  . . . . . . . . . . . . . . . . . . .  83
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  83
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  83
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  84
   14. Normative References  . . . . . . . . . . . . . . . . . . . .  84
   15. Informative References  . . . . . . . . . . . . . . . . . . .  87
   Appendix A.  Data Tree Example  . . . . . . . . . . . . . . . . .  88
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  92




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1.  Introduction

   The Network Configuration Protocol (NETCONF) [RFC6241] is one of the
   network management protocols that defines mechanisms to manage
   network devices.  YANG [RFC6020] [RFC7950] is a modular language that
   represents data structures in an XML tree format, and is used as a
   data modelling language for the NETCONF.

   This document introduces a YANG data model for MPLS Label
   Distribution Protocol (LDP) [RFC5036].  This model also covers LDP
   IPv6 [RFC7552] and LDP capabilities [RFC5561] specifications.

   The data model is defined for the following constructs that are used
   for managing the protocol:

   *  Configuration

   *  Operational State

   *  Executables (Actions)

   *  Notifications

   This document is organized to define the data model for each of the
   above constructs in the sequence as listed above.

1.1.  Base and Extended

   The configuration and state items are divided into the following two
   broad categories:

   *  Base

   *  Extended

   The "base" category contains the basic and fundamental features that
   are covered in LDP base specification [RFC5036] and constitute the
   minimum requirements for a typical base LDP deployment.  Whereas, the
   "extended" category contains other non-base features.  All the items
   in a base category are mandatory and hence no "if-feature" is allowed
   under the "base" category.  The base and extended categories are
   defined in their own modules as described later.

   The example of base feature includes the configuration of LDP lsr-id,
   enabling LDP interfaces, setting password for LDP session etc.,
   whereas the examples of extended feature include inbound/outbound
   label policies, igp sync [RFC5443], downstream-on-demand etc.  It is




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   worth highlighting that LDP IPv6 [RFC7552] is also categorized as an
   extended feature.

   While "base" model support will suffice for small deployments, it is
   expected that large deployments will require both the "base" and
   "extended" models support from the vendors.

2.  Specification of Requirements

   In this document, the word "IP" is used to refer to both IPv4 and
   IPv6, unless otherwise explicitly stated.  For example, "IP address
   family" should be read as "IPv4 and/or IPv6 address family".

3.  Overview

   This document defines two new modules for LDP YANG support:

   *  "ietf-mpls-ldp" module that specifies the base LDP features and
      augments /rt:routing/rt:control-plane-protocols/rt:control-plane-
      protocol defined in [RFC8349].  We define new identity 'mpls-ldp'
      for LDP and the model allows only a single instance of 'mpls-ldp'.

   *  "ietf-mpls-ldp-extended" module that specifies the extended LDP
      features and augments the base LDP module.

   It is to be noted that mLDP YANG model [I-D.ietf-mpls-mldp-yang]
   augments LDP base and extended modules to specify the mLDP specific
   base and extended features.

   There are four types of containers in our module(s):

   *  Read-Write parameters for configuration (Section 5)

   *  Read-only parameters for operational state (Section 6)

   *  Notifications for events (Section 7)

   *  RPCs for executing commands to perform some action (Section 8)

   The modules in this document conforms to the Network Management
   Datastore Architecture (NMDA) defined in [RFC8342].  The operational
   state data is combined with the associated configuration data in the
   same hierarchy [RFC8407].  When protocol states are retrieved from
   the NMDA operational state datastore, the returned states cover all
   "config true" (rw) and "config false" (ro) nodes defined in the
   schema.





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   Following diagram depicts high level LDP YANG tree organization and
   hierarchy:


            +-- rw routing
               +-- rw control-plane-protocols
                +-- rw control-plane-protocol
                 +-- rw mpls-ldp
                     +-- rw ...
                         +-- rw ...                 // base
                         |   +-- rw ...
                         |   +-- ro ...
                         |   +--
                         +-- ro ...
                         |   +-- ro ...
                         |   +-- ro ...
                         |   +--
                         +-- rw ldp-ext: ....       // extended
                         |   +-- rw ...
                         |   +-- ro ...
                         |   +--
                         +-- ro ...
                             +-- ro ...
                             +-- ro ...


       rpcs:
          +-- x mpls-ldp-some_action
          +-- x . . . . .

       notifications:
          +--- n mpls-ldp-some_event
          +--- n ...


                    Figure 1: LDP YANG tree organization

   Before going into data model details, it is important to take note of
   the following points:

   *  This model aims to address only the core LDP parameters as per RFC
      specification, as well as well-known and widely deployed
      manageability controls (such as label filtering policies to apply
      filtering rules on the assignment, advertisement, and acceptance
      for label bindings).  Any vendor specific feature should be
      defined in a vendor-specific augmentation of this model.

   *  Multi-topology LDP [RFC7307] is beyond the scope of this document.



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   *  This model does not cover any applications running on top of LDP,
      nor does it cover any OAM procedures for LDP.

   *  This model is a VPN Routing and Forwarding (VRF)-centric model.
      It is important to note that [RFC4364] defines VRF tables and
      default forwarding tables as different, however from a YANG
      modelling perspective this introduces unnecessary complications,
      hence we are treating the default forwarding table as just another
      VRF.

   *  A "network-instance", as defined in [RFC8529], refers to a VRF
      instance (both default and non-default) within the scope of this
      model.

   *  This model supports two address-families, namely "ipv4" and
      "ipv6".

   *  This model assumes platform-wide label space (i.e. label space Id
      of zero).  However, when Upstream Label assignment [RFC6389] is in
      use, an upstream assigned label is looked up in a Context-Specific
      label space as defined in [RFC5331].

   *  The label and peer policies (including filters) are defined using
      prefix-set and neighbor-set respectively as defined in routing-
      policy model [I-D.ietf-rtgwg-policy-model].

   *  This model uses the terms LDP "neighbor"/"adjacency", "session",
      and "peer" with the following semantics:

      -  Neighbor/Adjacency: An LDP enabled LSR that is discovered
         through LDP discovery mechanisms.

      -  Session: An LDP neighbor with whom a TCP connection has been
         established.

      -  Peer: An LDP session which has successfully progressed beyond
         its initialization phase and is either already exchanging the
         bindings or is ready to do so.

      It is to be noted that LDP Graceful Restart (GR) mechanisms
      defined in [RFC3478] allow keeping the exchanged bindings for some
      time after a session goes down with a peer.  We call such a state
      belonging to a "stale" peer -- i.e. keeping peer bindings from a
      peer with whom currently there is either no connection established
      or connection is established but GR session is in recovery state.
      When used in this document, the above terms will refer strictly to
      the semantics and definitions defined for them.




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   A simplified graphical tree representation of base and extended LDP
   YANG data model is presented in Figure 2.  The meaning of the symbols
   in these tree diagrams is defined in [RFC8340].

   The actual YANG specification for base and extended modules is
   captured in Section 9.

   While presenting the YANG tree view and actual specification, this
   document assumes readers' familiarity with the concepts of YANG
   modeling, its presentation and its compilation.

4.  The Complete Tree

   Following is a complete tree representation of configuration, state,
   notification, and RPC items under LDP base and extended modules.

   module: ietf-mpls-ldp
     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol:
       +--rw mpls-ldp
          +--rw global
          |  +--rw capability
          |  |  +--rw ldp-ext:end-of-lib {capability-end-of-lib}?
          |  |  |  +--rw ldp-ext:enabled?   boolean
          |  |  +--rw ldp-ext:typed-wildcard-fec
          |  |  |       {capability-typed-wildcard-fec}?
          |  |  |  +--rw ldp-ext:enabled?   boolean
          |  |  +--rw ldp-ext:upstream-label-assignment
          |  |          {capability-upstream-label-assignment}?
          |  |     +--rw ldp-ext:enabled?   boolean
          |  +--rw graceful-restart
          |  |  +--rw enabled?                  boolean
          |  |  +--rw reconnect-time?           uint16
          |  |  +--rw recovery-time?            uint16
          |  |  +--rw forwarding-holdtime?      uint16
          |  |  +--rw ldp-ext:helper-enabled?   boolean
          |  |          {graceful-restart-helper-mode}?
          |  +--rw lsr-id?
          |  |       rt-types:router-id
          |  +--rw address-families
          |  |  +--rw ipv4!
          |  |  |  +--rw enabled?                           boolean
          |  |  |  +--ro label-distribution-control-mode?   enumeration
          |  |  |  +--ro bindings
          |  |  |  |  +--ro address* [address]
          |  |  |  |  |  +--ro address               inet:ipv4-address
          |  |  |  |  |  +--ro advertisement-type?   advertised-received
          |  |  |  |  |  +--ro peer



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          |  |  |  |  |     +--ro lsr-id?           leafref
          |  |  |  |  |     +--ro label-space-id?   leafref
          |  |  |  |  +--ro fec-label* [fec]
          |  |  |  |     +--ro fec     inet:ipv4-prefix
          |  |  |  |     +--ro peer*
          |  |  |  |             [lsr-id label-space-id advertisement-type]
          |  |  |  |        +--ro lsr-id                leafref
          |  |  |  |        +--ro label-space-id        leafref
          |  |  |  |        +--ro advertisement-type
          |  |  |  |        |       advertised-received
          |  |  |  |        +--ro label?
          |  |  |  |        |       rt-types:mpls-label
          |  |  |  |        +--ro used-in-forwarding?   boolean
          |  |  |  +--rw ldp-ext:label-policy
          |  |  |  |  +--rw ldp-ext:advertise
          |  |  |  |  |  +--rw ldp-ext:egress-explicit-null
          |  |  |  |  |  |  +--rw ldp-ext:enabled?   boolean
          |  |  |  |  |  +--rw ldp-ext:prefix-list?
          |  |  |  |  |          prefix-list-ref
          |  |  |  |  +--rw ldp-ext:accept
          |  |  |  |  |  +--rw ldp-ext:prefix-list?   prefix-list-ref
          |  |  |  |  +--rw ldp-ext:assign
          |  |  |  |          {policy-label-assignment-config}?
          |  |  |  |     +--rw ldp-ext:independent-mode
          |  |  |  |     |  +--rw ldp-ext:prefix-list?   prefix-list-ref
          |  |  |  |     +--rw ldp-ext:ordered-mode
          |  |  |  |             {policy-ordered-label-config}?
          |  |  |  |        +--rw ldp-ext:egress-prefix-list?
          |  |  |  |                prefix-list-ref
          |  |  |  +--rw ldp-ext:transport-address?
          |  |  |          inet:ipv4-address
          |  |  +--rw ldp-ext:ipv6!
          |  |     +--rw ldp-ext:enabled?
          |  |     |       boolean
          |  |     +--rw ldp-ext:label-policy
          |  |     |  +--rw ldp-ext:advertise
          |  |     |  |  +--rw ldp-ext:egress-explicit-null
          |  |     |  |  |  +--rw ldp-ext:enabled?   boolean
          |  |     |  |  +--rw ldp-ext:prefix-list?
          |  |     |  |          prefix-list-ref
          |  |     |  +--rw ldp-ext:accept
          |  |     |  |  +--rw ldp-ext:prefix-list?   prefix-list-ref
          |  |     |  +--rw ldp-ext:assign
          |  |     |          {policy-label-assignment-config}?
          |  |     |     +--rw ldp-ext:independent-mode
          |  |     |     |  +--rw ldp-ext:prefix-list?   prefix-list-ref
          |  |     |     +--rw ldp-ext:ordered-mode
          |  |     |             {policy-ordered-label-config}?



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          |  |     |        +--rw ldp-ext:egress-prefix-list?
          |  |     |                prefix-list-ref
          |  |     +--rw ldp-ext:transport-address
          |  |     |       inet:ipv6-address
          |  |     +--ro ldp-ext:label-distribution-control-mode?
          |  |     |       enumeration
          |  |     +--ro ldp-ext:bindings
          |  |        +--ro ldp-ext:address* [address]
          |  |        |  +--ro ldp-ext:address
          |  |        |  |       inet:ipv6-address
          |  |        |  +--ro ldp-ext:advertisement-type?
          |  |        |  |       advertised-received
          |  |        |  +--ro ldp-ext:peer
          |  |        |     +--ro ldp-ext:lsr-id?           leafref
          |  |        |     +--ro ldp-ext:label-space-id?   leafref
          |  |        +--ro ldp-ext:fec-label* [fec]
          |  |           +--ro ldp-ext:fec     inet:ipv6-prefix
          |  |           +--ro ldp-ext:peer*
          |  |                   [lsr-id label-space-id advertisement-type]
          |  |              +--ro ldp-ext:lsr-id                leafref
          |  |              +--ro ldp-ext:label-space-id        leafref
          |  |              +--ro ldp-ext:advertisement-type
          |  |              |       advertised-received
          |  |              +--ro ldp-ext:label?
          |  |              |       rt-types:mpls-label
          |  |              +--ro ldp-ext:used-in-forwarding?   boolean
          |  +--rw ldp-ext:forwarding-nexthop
          |  |       {forwarding-nexthop-config}?
          |  |  +--rw ldp-ext:interfaces
          |  |     +--rw ldp-ext:interface* [name]
          |  |        +--rw ldp-ext:name              if:interface-ref
          |  |        +--rw ldp-ext:address-family* [afi]
          |  |           +--rw ldp-ext:afi            identityref
          |  |           +--rw ldp-ext:ldp-disable?   boolean
          |  +--rw ldp-ext:igp-synchronization-delay?   uint16
          +--rw discovery
          |  +--rw interfaces
          |  |  +--rw hello-holdtime?   uint16
          |  |  +--rw hello-interval?   uint16
          |  |  +--rw interface* [name]
          |  |     +--rw name
          |  |     |       if:interface-ref
          |  |     +--ro next-hello?                          uint16
          |  |     +--rw address-families
          |  |     |  +--rw ipv4!
          |  |     |  |  +--rw enabled?                     boolean
          |  |     |  |  +--ro hello-adjacencies
          |  |     |  |  |  +--ro hello-adjacency* [adjacent-address]



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          |  |     |  |  |     +--ro adjacent-address
          |  |     |  |  |     |       inet:ipv4-address
          |  |     |  |  |     +--ro flag*               identityref
          |  |     |  |  |     +--ro hello-holdtime
          |  |     |  |  |     |  +--ro adjacent?     uint16
          |  |     |  |  |     |  +--ro negotiated?   uint16
          |  |     |  |  |     |  +--ro remaining?    uint16
          |  |     |  |  |     +--ro next-hello?         uint16
          |  |     |  |  |     +--ro statistics
          |  |     |  |  |     |  +--ro discontinuity-time
          |  |     |  |  |     |  |       yang:date-and-time
          |  |     |  |  |     |  +--ro hello-received?
          |  |     |  |  |     |  |       yang:counter64
          |  |     |  |  |     |  +--ro hello-dropped?
          |  |     |  |  |     |          yang:counter64
          |  |     |  |  |     +--ro peer
          |  |     |  |  |        +--ro lsr-id?           leafref
          |  |     |  |  |        +--ro label-space-id?   leafref
          |  |     |  |  +--rw ldp-ext:transport-address?   union
          |  |     |  +--rw ldp-ext:ipv6!
          |  |     |     +--rw ldp-ext:enabled?             boolean
          |  |     |     +--ro ldp-ext:hello-adjacencies
          |  |     |     |  +--ro ldp-ext:hello-adjacency*
          |  |     |     |          [adjacent-address]
          |  |     |     |     +--ro ldp-ext:adjacent-address
          |  |     |     |     |       inet:ipv6-address
          |  |     |     |     +--ro ldp-ext:flag*
          |  |     |     |     |       identityref
          |  |     |     |     +--ro ldp-ext:hello-holdtime
          |  |     |     |     |  +--ro ldp-ext:adjacent?     uint16
          |  |     |     |     |  +--ro ldp-ext:negotiated?   uint16
          |  |     |     |     |  +--ro ldp-ext:remaining?    uint16
          |  |     |     |     +--ro ldp-ext:next-hello?         uint16
          |  |     |     |     +--ro ldp-ext:statistics
          |  |     |     |     |  +--ro ldp-ext:discontinuity-time
          |  |     |     |     |  |       yang:date-and-time
          |  |     |     |     |  +--ro ldp-ext:hello-received?
          |  |     |     |     |  |       yang:counter64
          |  |     |     |     |  +--ro ldp-ext:hello-dropped?
          |  |     |     |     |          yang:counter64
          |  |     |     |     +--ro ldp-ext:peer
          |  |     |     |        +--ro ldp-ext:lsr-id?           leafref
          |  |     |     |        +--ro ldp-ext:label-space-id?   leafref
          |  |     |     +--rw ldp-ext:transport-address?   union
          |  |     +--rw ldp-ext:hello-holdtime?              uint16
          |  |     |       {per-interface-timer-config}?
          |  |     +--rw ldp-ext:hello-interval?              uint16
          |  |     |       {per-interface-timer-config}?



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          |  |     +--rw ldp-ext:igp-synchronization-delay?   uint16
          |  |             {per-interface-timer-config}?
          |  +--rw targeted
          |     +--rw hello-holdtime?     uint16
          |     +--rw hello-interval?     uint16
          |     +--rw hello-accept
          |     |  +--rw enabled?                 boolean
          |     |  +--rw ldp-ext:neighbor-list?   neighbor-list-ref
          |     |          {policy-targeted-discovery-config}?
          |     +--rw address-families
          |        +--rw ipv4!
          |        |  +--ro hello-adjacencies
          |        |  |  +--ro hello-adjacency*
          |        |  |          [local-address adjacent-address]
          |        |  |     +--ro local-address       inet:ipv4-address
          |        |  |     +--ro adjacent-address    inet:ipv4-address
          |        |  |     +--ro flag*               identityref
          |        |  |     +--ro hello-holdtime
          |        |  |     |  +--ro adjacent?     uint16
          |        |  |     |  +--ro negotiated?   uint16
          |        |  |     |  +--ro remaining?    uint16
          |        |  |     +--ro next-hello?         uint16
          |        |  |     +--ro statistics
          |        |  |     |  +--ro discontinuity-time
          |        |  |     |  |       yang:date-and-time
          |        |  |     |  +--ro hello-received?
          |        |  |     |  |       yang:counter64
          |        |  |     |  +--ro hello-dropped?
          |        |  |     |          yang:counter64
          |        |  |     +--ro peer
          |        |  |        +--ro lsr-id?           leafref
          |        |  |        +--ro label-space-id?   leafref
          |        |  +--rw target* [adjacent-address]
          |        |     +--rw adjacent-address    inet:ipv4-address
          |        |     +--rw enabled?            boolean
          |        |     +--rw local-address?      inet:ipv4-address
          |        +--rw ldp-ext:ipv6!
          |           +--ro ldp-ext:hello-adjacencies
          |           |  +--ro ldp-ext:hello-adjacency*
          |           |          [local-address adjacent-address]
          |           |     +--ro ldp-ext:local-address
          |           |     |       inet:ipv6-address
          |           |     +--ro ldp-ext:adjacent-address
          |           |     |       inet:ipv6-address
          |           |     +--ro ldp-ext:flag*
          |           |     |       identityref
          |           |     +--ro ldp-ext:hello-holdtime
          |           |     |  +--ro ldp-ext:adjacent?     uint16



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          |           |     |  +--ro ldp-ext:negotiated?   uint16
          |           |     |  +--ro ldp-ext:remaining?    uint16
          |           |     +--ro ldp-ext:next-hello?         uint16
          |           |     +--ro ldp-ext:statistics
          |           |     |  +--ro ldp-ext:discontinuity-time
          |           |     |  |       yang:date-and-time
          |           |     |  +--ro ldp-ext:hello-received?
          |           |     |  |       yang:counter64
          |           |     |  +--ro ldp-ext:hello-dropped?
          |           |     |          yang:counter64
          |           |     +--ro ldp-ext:peer
          |           |        +--ro ldp-ext:lsr-id?           leafref
          |           |        +--ro ldp-ext:label-space-id?   leafref
          |           +--rw ldp-ext:target* [adjacent-address]
          |              +--rw ldp-ext:adjacent-address
          |              |       inet:ipv6-address
          |              +--rw ldp-ext:enabled?            boolean
          |              +--rw ldp-ext:local-address?
          |                      inet:ipv6-address
          +--rw peers
             +--rw authentication
             |  +--rw (authentication-type)?
             |     +--:(password)
             |     |  +--rw key?                 string
             |     |  +--rw crypto-algorithm?    identityref
             |     +--:(ldp-ext:key-chain) {key-chain}?
             |        +--rw ldp-ext:key-chain?   key-chain:key-chain-ref
             +--rw session-ka-holdtime?                       uint16
             +--rw session-ka-interval?                       uint16
             +--rw peer* [lsr-id label-space-id]
             |  +--rw lsr-id                         rt-types:router-id
             |  +--rw label-space-id                 uint16
             |  +--rw authentication
             |  |  +--rw (authentication-type)?
             |  |     +--:(password)
             |  |     |  +--rw key?                 string
             |  |     |  +--rw crypto-algorithm?    identityref
             |  |     +--:(ldp-ext:key-chain) {key-chain}?
             |  |        +--rw ldp-ext:key-chain?
             |  |                key-chain:key-chain-ref
             |  +--rw address-families
             |  |  +--rw ipv4!
             |  |  |  +--ro hello-adjacencies
             |  |  |  |  +--ro hello-adjacency*
             |  |  |  |          [local-address adjacent-address]
             |  |  |  |     +--ro local-address       inet:ipv4-address
             |  |  |  |     +--ro adjacent-address    inet:ipv4-address
             |  |  |  |     +--ro flag*               identityref



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             |  |  |  |     +--ro hello-holdtime
             |  |  |  |     |  +--ro adjacent?     uint16
             |  |  |  |     |  +--ro negotiated?   uint16
             |  |  |  |     |  +--ro remaining?    uint16
             |  |  |  |     +--ro next-hello?         uint16
             |  |  |  |     +--ro statistics
             |  |  |  |     |  +--ro discontinuity-time
             |  |  |  |     |  |       yang:date-and-time
             |  |  |  |     |  +--ro hello-received?
             |  |  |  |     |  |       yang:counter64
             |  |  |  |     |  +--ro hello-dropped?
             |  |  |  |     |          yang:counter64
             |  |  |  |     +--ro interface?          if:interface-ref
             |  |  |  +--rw ldp-ext:label-policy
             |  |  |     +--rw ldp-ext:advertise
             |  |  |     |  +--rw ldp-ext:prefix-list?   prefix-list-ref
             |  |  |     +--rw ldp-ext:accept
             |  |  |        +--rw ldp-ext:prefix-list?   prefix-list-ref
             |  |  +--rw ldp-ext:ipv6!
             |  |     +--ro ldp-ext:hello-adjacencies
             |  |     |  +--ro ldp-ext:hello-adjacency*
             |  |     |          [local-address adjacent-address]
             |  |     |     +--ro ldp-ext:local-address
             |  |     |     |       inet:ipv6-address
             |  |     |     +--ro ldp-ext:adjacent-address
             |  |     |     |       inet:ipv6-address
             |  |     |     +--ro ldp-ext:flag*
             |  |     |     |       identityref
             |  |     |     +--ro ldp-ext:hello-holdtime
             |  |     |     |  +--ro ldp-ext:adjacent?     uint16
             |  |     |     |  +--ro ldp-ext:negotiated?   uint16
             |  |     |     |  +--ro ldp-ext:remaining?    uint16
             |  |     |     +--ro ldp-ext:next-hello?         uint16
             |  |     |     +--ro ldp-ext:statistics
             |  |     |     |  +--ro ldp-ext:discontinuity-time
             |  |     |     |  |       yang:date-and-time
             |  |     |     |  +--ro ldp-ext:hello-received?
             |  |     |     |  |       yang:counter64
             |  |     |     |  +--ro ldp-ext:hello-dropped?
             |  |     |     |          yang:counter64
             |  |     |     +--ro ldp-ext:interface?
             |  |     |             if:interface-ref
             |  |     +--rw ldp-ext:label-policy
             |  |        +--rw ldp-ext:advertise
             |  |        |  +--rw ldp-ext:prefix-list?   prefix-list-ref
             |  |        +--rw ldp-ext:accept
             |  |           +--rw ldp-ext:prefix-list?   prefix-list-ref
             |  +--ro label-advertisement-mode



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             |  |  +--ro local?        label-adv-mode
             |  |  +--ro peer?         label-adv-mode
             |  |  +--ro negotiated?   label-adv-mode
             |  +--ro next-keep-alive?               uint16
             |  +--ro received-peer-state
             |  |  +--ro graceful-restart
             |  |  |  +--ro enabled?          boolean
             |  |  |  +--ro reconnect-time?   uint16
             |  |  |  +--ro recovery-time?    uint16
             |  |  +--ro capability
             |  |     +--ro end-of-lib
             |  |     |  +--ro enabled?   boolean
             |  |     +--ro typed-wildcard-fec
             |  |     |  +--ro enabled?   boolean
             |  |     +--ro upstream-label-assignment
             |  |        +--ro enabled?   boolean
             |  +--ro session-holdtime
             |  |  +--ro peer?         uint16
             |  |  +--ro negotiated?   uint16
             |  |  +--ro remaining?    uint16
             |  +--ro session-state?                 enumeration
             |  +--ro tcp-connection
             |  |  +--ro local-address?    inet:ip-address
             |  |  +--ro local-port?       inet:port-number
             |  |  +--ro remote-address?   inet:ip-address
             |  |  +--ro remote-port?      inet:port-number
             |  +--ro up-time?
             |  |       rt-types:timeticks64
             |  +--ro statistics
             |  |  +--ro discontinuity-time          yang:date-and-time
             |  |  +--ro received
             |  |  |  +--ro total-octets?          yang:counter64
             |  |  |  +--ro total-messages?        yang:counter64
             |  |  |  +--ro address?               yang:counter64
             |  |  |  +--ro address-withdraw?      yang:counter64
             |  |  |  +--ro initialization?        yang:counter64
             |  |  |  +--ro keepalive?             yang:counter64
             |  |  |  +--ro label-abort-request?   yang:counter64
             |  |  |  +--ro label-mapping?         yang:counter64
             |  |  |  +--ro label-release?         yang:counter64
             |  |  |  +--ro label-request?         yang:counter64
             |  |  |  +--ro label-withdraw?        yang:counter64
             |  |  |  +--ro notification?          yang:counter64
             |  |  +--ro sent
             |  |  |  +--ro total-octets?          yang:counter64
             |  |  |  +--ro total-messages?        yang:counter64
             |  |  |  +--ro address?               yang:counter64
             |  |  |  +--ro address-withdraw?      yang:counter64



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             |  |  |  +--ro initialization?        yang:counter64
             |  |  |  +--ro keepalive?             yang:counter64
             |  |  |  +--ro label-abort-request?   yang:counter64
             |  |  |  +--ro label-mapping?         yang:counter64
             |  |  |  +--ro label-release?         yang:counter64
             |  |  |  +--ro label-request?         yang:counter64
             |  |  |  +--ro label-withdraw?        yang:counter64
             |  |  |  +--ro notification?          yang:counter64
             |  |  +--ro total-addresses?            uint32
             |  |  +--ro total-labels?               uint32
             |  |  +--ro total-fec-label-bindings?   uint32
             |  +--rw ldp-ext:admin-down?            boolean
             |  |       {per-peer-admin-down}?
             |  +--rw ldp-ext:graceful-restart
             |  |       {per-peer-graceful-restart-config}?
             |  |  +--rw ldp-ext:enabled?          boolean
             |  |  +--rw ldp-ext:reconnect-time?   uint16
             |  |  +--rw ldp-ext:recovery-time?    uint16
             |  +--rw ldp-ext:session-ka-holdtime?   uint16
             |  |       {per-peer-session-attributes-config}?
             |  +--rw ldp-ext:session-ka-interval?   uint16
             |          {per-peer-session-attributes-config}?
             +--rw ldp-ext:session-downstream-on-demand
             |       {session-downstream-on-demand-config}?
             |  +--rw ldp-ext:enabled?     boolean
             |  +--rw ldp-ext:peer-list?   peer-list-ref
             +--rw ldp-ext:dual-stack-transport-preference
                     {peers-dual-stack-transport-preference}?
                +--rw ldp-ext:max-wait?      uint16
                +--rw ldp-ext:prefer-ipv4!
                   +--rw ldp-ext:peer-list?   peer-list-ref

     rpcs:
       +---x mpls-ldp-clear-peer
       |  +---w input
       |     +---w protocol-name?    leafref
       |     +---w lsr-id?           leafref
       |     +---w label-space-id?   leafref
       +---x mpls-ldp-clear-hello-adjacency
       |  +---w input
       |     +---w hello-adjacency
       |        +---w protocol-name?    leafref
       |        +---w (hello-adjacency-type)?
       |           +--:(targeted)
       |           |  +---w targeted!
       |           |     +---w target-address?   inet:ip-address
       |           +--:(link)
       |              +---w link!



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       |                 +---w next-hop-interface?   leafref
       |                 +---w next-hop-address?     inet:ip-address
       +---x mpls-ldp-clear-peer-statistics
          +---w input
             +---w protocol-name?    leafref
             +---w lsr-id?           leafref
             +---w label-space-id?   leafref

     notifications:
       +---n mpls-ldp-peer-event
       |  +--ro event-type?   oper-status-event-type
       |  +--ro peer
       |     +--ro protocol-name?    leafref
       |     +--ro lsr-id?           leafref
       |     +--ro label-space-id?   leafref
       +---n mpls-ldp-hello-adjacency-event
       |  +--ro event-type?       oper-status-event-type
       |  +--ro protocol-name?    leafref
       |  +--ro (hello-adjacency-type)?
       |     +--:(targeted)
       |     |  +--ro targeted
       |     |     +--ro target-address?   inet:ip-address
       |     +--:(link)
       |        +--ro link
       |           +--ro next-hop-interface?   if:interface-ref
       |           +--ro next-hop-address?     inet:ip-address
       +---n mpls-ldp-fec-event
          +--ro event-type?      oper-status-event-type
          +--ro protocol-name?   leafref
          +--ro fec?             inet:ip-prefix


                          Figure 2: Complete Tree

5.  Configuration

   This specification defines the configuration parameters for base LDP
   as specified in [RFC5036] and LDP IPv6 [RFC7552].  Moreover, it
   incorporates provisions to enable LDP Capabilities [RFC5561], and
   defines some of the most significant and commonly used capabilities
   such as Typed Wildcard FEC [RFC5918], End-of-LIB [RFC5919], and LDP
   Upstream Label Assignment [RFC6389].

   This model augments /rt:routing/rt:control-plane-protocols/
   rt:control-plane-protocol that is defined in [RFC8349] and follows
   NMDA as mentioned earlier.





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   Following is the high-level configuration organization for base LDP
   module:

           augment /rt:routing/rt:control-plane-protocols:
                     /rt:control-plane-protocol:
                 +-- mpls-ldp
                     +-- global
                     |    +-- ...
                     |    +-- ...
                     |    +-- address-families
                     |    |   +-- ipv4
                     |    |     +-- . . .
                     |    |     +-- . . .
                     |    +-- capability
                     |        +-- ...
                     |        +-- ...
                     +-- discovery
                     |    +-- interfaces
                     |    |   +-- ...
                     |    |   +-- ...
                     |    |   +-- interface* [interface]
                     |    |     +-- ...
                     |    |     +-- address-families
                     |    |       +-- ipv4
                     |    |         +-- ...
                     |    |         +-- ...
                     |    +-- targeted
                     |        +-- ...
                     |        +-- address-families
                     |            +-- ipv4
                     |                +- target* [adjacent-address]
                     |                  +- ...
                     |                  +- ...
                     +-- peers
                          +-- ...
                          +-- ...
                          +-- peer* [lsr-id label-space-id]
                              +-- ...
                              +-- ...


                 Figure 3: Base Configuration organization

   Following is the high-level configuration organization for extended
   LDP:






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           augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol
                 +-- mpls-ldp
                     +-- global
                     |    +-- ...
                     |    +-- ...
                     |    +-- address-families
                     |    |   +-- ipv4
                     |    |   | +-- . . .
                     |    |   | +-- . . .
                     |    |   | +-- label-policy
                     |    |   |   +-- ...
                     |    |   |   +-- ...
                     |    |   +-- ipv6
                     |    |     +-- . . .
                     |    |     +-- . . .
                     |    |     +-- label-policy
                     |    |       +-- ...
                     |    |       +-- ...
                     |    +-- capability
                     |    |   +-- ...
                     |    |   +-- ...
                     |    +-- discovery
                     |        +-- interfaces
                     |        |   +-- ...
                     |        |   +-- ...
                     |        |   +-- interface* [interface]
                     |        |     +-- ...
                     |        |     +-- address-families
                     |        |       +-- ipv4
                     |        |       | +-- ...
                     |        |       | +-- ...
                     |        |       +-- ipv6
                     |        |         +-- ...
                     |        |         +-- ...
                     |        +-- targeteted
                     |            +-- ...
                     |            +-- address-families
                     |              +-- ipv6
                     |                +- target* [adjacent-address]
                     |                  +- ...
                     |                  +- ...
                     +-- forwarding-nexthop
                     |   +-- ...
                     |   +-- ...
                     +-- peers
                          +-- ...
                          +-- ...
                          +-- peer*



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                              +-- ...
                              +-- ...
                              +-- label-policy
                              |   +-- ..
                              +-- address-families
                                 +-- ipv4
                                 |   +-- ...
                                 +-- ipv6
                                     +-- ...



               Figure 4: Extended Configuration organization

   Given the configuration hierarchy, the model allows inheritance such
   that an item in a child tree is able to derive value from a similar
   or related item in one of the parents.  For instance, hello holdtime
   can be configured per-VRF or per-VRF-interface, thus allowing
   inheritance as well flexibility to override with a different value at
   any child level.

5.1.  Configuration Hierarchy

   LDP module resides under a network-instance and the scope of any LDP
   configuration defined under this tree is per network-instance (per-
   VRF).  This configuration is further divided into sub categories as
   follows.

   *  Global parameters

   *  Per-address-family parameters

   *  LDP Capabilities parameters

   *  Hello Discovery parameters

      -  interfaces

         o  Global

         o  Per-interface: Global

         o  Per-interface: Per-address-family

      -  targeted

         o  Global




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         o  Per-address-family: Per-target

   *  Peer parameters

      -  Global

      -  Per-peer: Global

      -  Per-peer: Per-address-family

   *  Forwarding parameters

   Following subsections briefly explain these configuration areas.

5.1.1.  Global parameters

   There are configuration items that are available directly under a VRF
   instance and do not fall under any other sub tree.  Example of such a
   parameter is LDP LSR Id that is typically configured per VRF.  To
   keep legacy LDP features and applications working in an LDP IPv4
   networks with this model, this document recommends an operator to
   pick a routable IPv4 unicast address (within a routing domain) as an
   LSR Id.

5.1.2.  Capabilities parameters

   This container falls under the global tree and holds the LDP
   capabilities that are to be enabled for certain features.  By
   default, an LDP capability is disabled unless explicitly enabled.
   These capabilities are typically used to negotiate with LDP peer(s)
   the support/non-support related to a feature and its parameters.  The
   scope of a capability enabled under this container applies to all LDP
   peers in the given VRF instance.  There is also a peer level
   capability container that is provided to override a capability that
   is enabled/specified at VRF level.

5.1.3.  Per-Address-Family parameters

   Any LDP configuration parameter related to IP address family (AF)
   whose scope is VRF wide is configured under this tree.  The examples
   of per-AF parameters include enabling LDP for an address family,
   prefix-list based label policies, and LDP transport address.

5.1.4.  Hello Discovery parameters

   This container is used to hold LDP configuration related to Hello and
   discovery process for both basic (link) and extended (targeted)
   discovery.



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   The "interfaces" is a container to configure parameters related to
   VRF interfaces.  There are parameters that apply to all interfaces
   (such as hello timers), as well as parameters that can be configured
   per-interface.  Hence, an interface list is defined under
   "interfaces" container.  The model defines parameters to configure
   per-interface non AF related items, as well as per-interface per-AF
   items.  The example of the former is interface hello timers, and
   example of the latter is enabling hellos for a given AF under an
   interface.

   The "targeted" container under a VRF instance allows to configure LDP
   targeted discovery related parameters.  Within this container, the
   "target" list provides a means to configure multiple target addresses
   to perform extended discovery to a specific destination target, as
   well as to fine-tune the per-target parameters.

5.1.5.  Peer parameters

   This container is used to hold LDP configuration related to LDP
   sessions and peers under a VRF instance.  This container allows to
   configure parameters that either apply on VRF's all peers or a subset
   (peer-list) of VRF peers.  The example of such parameters include
   authentication password, session KA timers etc.  Moreover, the model
   also allows per-peer parameter tuning by specifying a "peer" list
   under the "peers" container.  A peer is uniquely identified by its
   LSR Id.

   Like per-interface parameters, some per-peer parameters are AF-
   agnostic (i.e. either non AF related or apply to both IP address
   families), and some that belong to an AF.  The example of the former
   is per-peer session password configuration, whereas the example of
   the latter is prefix-list based label policies (inbound and outbound)
   that apply to a given peer.

5.1.6.  Forwarding parameters

   This container is used to hold configuration used to control LDP
   forwarding behavior under a VRF instance.  One example of a
   configuration under this container is when a user wishes to enable
   neighbor discovery on an interface but wishes to disable use of the
   same interface as forwarding nexthop.  This example configuration
   makes sense only when there are more than one LDP enabled interfaces
   towards the neighbor.








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6.  Operational State

   Operational state of LDP can be queried and obtained from read-only
   state containers that fall under the same tree (/rt:routing/
   rt:control-plane-protocols/rt:control-plane-protocol) as the
   configuration.

   Following are main areas for which LDP operational state is defined:

   *  Neighbor Adjacencies

   *  Peer

   *  Bindings (FEC-label and address)

   *  Capabilities

6.1.  Adjacency state

   Neighbor adjacencies are per address-family hello adjacencies that
   are formed with neighbors as result of LDP basic or extended
   discovery.  In terms of organization, there is a source of discovery
   (e.g. interface or target address) along with its associated
   parameters and one or more discovered neighbors along with neighbor
   discovery related parameters.  For the basic discovery, there could
   be more than one discovered neighbor for a given source (interface),
   whereas there is at most one discovered neighbor for an extended
   discovery source (local-address and target-address).  It is also to
   be noted that the reason for a targeted neighbor adjacency could be
   either an active source (locally configured targeted) or passive
   source (to allow any incoming extended/targeted hellos).  A neighbor/
   adjacency record also contains session-state that helps highlight
   whether a given adjacency has progressed to subsequent session level
   or to eventual peer level.

   Following captures high level tree hierarchy for neighbor adjacency
   state.  The tree is shown for ipv4 address-family only; a similar
   tree exists for ipv6 address-family as well.













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      +--rw mpls-ldp!
         +--rw discovery
            +--rw interfaces
            |  +--rw interface* [interface]
            |     +--rw address-families
            |        +--rw ipv4
            |           +--ro hello-adjacencies
            |              +--ro hello-adjacencies* [adjacent-address]
            |                 +--ro adjacent-address
            |                    . . . .
            |                    . . . .
            +--rw targeted
               +--rw address-families
                  +--rw ipv4
                     +--ro hello-adjacencies
                        +--ro hello-adjacencies*
                        |                  [local-address adjacent-address]
                        +--ro local-address
                           +--ro adjacent-address
                              . . . .
                              . . . .


                         Figure 5: Adjacency state

6.2.  Peer state

   Peer related state is presented under peers tree.  This is one of the
   core state that provides info on the session related parameters
   (mode, authentication, KA timeout etc.), TCP connection info, hello
   adjacencies for the peer, statistics related to messages and
   bindings, and capabilities exchange info.

   Following captures high level tree hierarchy for peer state.  The
   peer's hello adjacencies tree is shown for ipv4 address-family only;
   a similar tree exists for ipv6 address-family as well.















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       +--rw mpls-ldp!
           +--rw peers
              +--rw peer* [lsr-id label-space-id]
                  +--rw lsr-id
                  +--rw label-space-id
                  +--ro label-advertisement-mode
                  +--ro session-state
                  +--ro tcp-connection
                  +--ro session-holdtime?
                  +--ro up-time
                  +-- . . . .
                  +--ro address-families
                  |  +--ro ipv4
                  |     +--ro hello-adjacencies
                  |        +--ro hello-adjacencies*
                  |                        [local-address adjacent-address]
                  |           . . . .
                  |           . . . .
                  +--ro received-peer-state
                  |  +--ro . . . .
                  |  +--ro capability
                  |     +--ro . . . .
                  +--ro statistics
                     +-- . . . .
                     +-- received
                     |   +-- ...
                     +-- sent
                         +-- ...


                            Figure 6: Peer state

6.3.  Bindings state

   Binding state provides information on LDP FEC-label bindings as well
   as address binding for both inbound (received) as well as outbound
   (advertised) direction.  FEC-label bindings are presented as a FEC-
   centric view, and address bindings are presented as an address-
   centric view:












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        FEC-Label bindings:
            FEC 203.0.113.1/32:
              advertised: local-label 16000
                peer 192.0.2.1:0
                peer 192.0.2.2:0
                peer 192.0.2.3:0
              received:
                peer 192.0.2.1:0, label 16002, used-in-forwarding=Yes
                peer 192.0.2.2:0, label 17002, used-in-forwarding=No
            FEC 203.0.113.2/32:
               . . . .
            FEC 198.51.100.0/24:
               . . . .
            FEC 2001:db8:0:2::
               . . . .
            FEC 2001:db8:0:3::
               . . . .

        Address bindings:
            Addr 192.0.2.10:
               advertised
            Addr 2001:db8:0:10::
               advertised

            Addr 192.0.2.1:
              received, peer 192.0.2.1:0
            Addr 192.0.2.2:
              received, peer 192.0.2.2:0
            Addr 192.0.2.3:
              received, peer 192.0.2.3:0
            Addr 2001:db8:0:2::
              received, peer 192.0.2.2:0
            Addr 2001:db8:0:3::
              received, peer 192.0.2.3:0


                         Figure 7: Example Bindings

   Note that all local addresses are advertised to all peers and hence
   no need to provide per-peer information for local address
   advertisement.  Furthermore, note that it is easy to derive a peer-
   centric view for the bindings from the information already provided
   in this model.

   Following captures high level tree hierarchy for bindings state.  The
   tree shown below is for ipv4 address-family only; a similar tree
   exists for ipv6 address-family as well.




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        +--rw mpls-ldp!
           +--rw global
              +--rw address-families
                 +--rw ipv4
                     +--ro bindings
                        +--ro address* [address]
                        |  +--ro address (ipv4-address or ipv6-address)
                        |  +--ro advertisement-type?   advertised-received
                        |  +--ro peer?        leafref
                        +--ro fec-label* [fec]
                           +--ro fec     (ipv4-prefix or ipv6-prefix)
                           +--ro peer* [peer advertisement-type]
                              +--ro peer                  leafref
                              +--ro advertisement-type? advertised-received
                              +--ro label?                mpls:mpls-label
                              +--ro used-in-forwarding?   boolean


                          Figure 8: Bindings state

6.4.  Capabilities state

   LDP capabilities state comprise two types of information - global
   information (such as timer etc.), and per-peer information.

   Following captures high level tree hierarchy for LDP capabilities
   state.


      +--rw mpls-ldp!
         +--rw peers
            +--rw peer* [lsr-id label-space-id]
               +--rw lsr-id    yang:dotted-quad
               +--rw label-space-id
               +--ro received-peer-state
                  +--ro capability
                     +--ro . . . .
                     +--ro . . . .


                        Figure 9: Capabilities state










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7.  Notifications

   This model defines a list of notifications to inform client of
   important events detected during the protocol operation.  These
   events include events related to changes in the operational state of
   an LDP peer, hello adjacency, and FEC etc.  It is to be noted that an
   LDP FEC is treated as operational (up) as long as it has at least 1
   NHLFE (Next Hop Label Forwarding Entry) with outgoing label.

   A simplified graphical representation of the data model for LDP
   notifications is shown in Figure 2.

8.  Action

   This model defines a list of rpcs that allow performing an action or
   executing a command on the protocol.  For example, it allows to clear
   (reset) LDP peers, hello-adjacencies, and statistics.  The model
   makes an effort to provide different level of control so that a user
   is able to either clear all, or clear all for a given type, or clear
   a specific entity.

   A simplified graphical representation of the data model for LDP
   actions is shown in Figure 2.

9.  YANG Specification

   Following sections specify the actual YANG (module) specification for
   LDP constructs defined earlier in the document.

9.1.  Base

   This YANG module imports types defined in [RFC6991], [RFC8349],
   [RFC8294], [RFC8343], and [RFC8344].



   <CODE BEGINS> file "ietf-mpls-ldp@2020-02-25.yang"

   // RFC Editor: replace the above date 2020-02-25 with the date of
   // publication and remove this note.

   module ietf-mpls-ldp {
     yang-version 1.1;

     namespace "urn:ietf:params:xml:ns:yang:ietf-mpls-ldp";
     prefix "ldp";

     import ietf-inet-types {



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       prefix "inet";
       reference "RFC 6991: Common YANG Data Types";
     }

     import ietf-yang-types {
       prefix "yang";
       reference "RFC 6991: Common YANG Data Types";
     }

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8349: A YANG Data Model for Routing Management (NMDA
          version)";
     }

     import ietf-routing-types {
       prefix "rt-types";
       reference
         "RFC 8294: Common YANG Data Types for the Routing Area";
     }

     import ietf-interfaces {
       prefix "if";
       reference "RFC 8343: A YANG Data Model for Interface Management";
     }

     import ietf-ip {
       prefix "ip";
       reference "RFC 7277: A YANG Data Model for IP Management";
     }

     import ietf-key-chain {
       prefix "key-chain";
       reference "RFC 8177: YANG Data Model for Key Chains";
     }

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

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

        Editor:   Rajiv Asati
                  <mailto:rajiva@cisco.com>



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

        Editor:   Santosh Esale
                  <mailto:sesale@juniper.net>

        Editor:   Xia Chen
                  <mailto:jescia.chenxia@huawei.com>

        Editor:   Himanshu Shah
                  <mailto:hshah@ciena.com>";

     description
       "This YANG module defines the essential components for the
        management of Multi-Protocol Label Switching (MPLS) Label
        Distribution Protocol (LDP). It is also the base model to
        be augmented for Multipoint LDP (mLDP).

        Copyright (c) 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
        (http://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 Editor: replace XXXX with actual RFC number and remove
        // this note

     revision 2020-02-25 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Data Model for MPLS LDP.";
         // RFC Editor: replace XXXX with actual RFC number and remove
         // this note
     }

     /*
      * Typedefs
      */
     typedef advertised-received {
       type enumeration {



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         enum advertised {
           description "Advertised information.";
         }
         enum received {
           description "Received information.";
         }
       }
       description
         "Received or advertised.";
     }

     typedef downstream-upstream {
       type enumeration {
         enum downstream {
           description "Downstream information.";
         }
         enum upstream {
           description "Upstream information.";
         }
       }
       description
         "Downstream or upstream.";
     }

     typedef label-adv-mode {
       type enumeration {
         enum downstream-unsolicited {
           description "Downstream Unsolicited.";
         }
         enum downstream-on-demand {
           description "Downstream on Demand.";
         }
       }
       description
         "Label Advertisement Mode.";
     }

     typedef oper-status-event-type {
       type enumeration {
         enum up {
           value 1;
           description
             "Operational status changed to up.";
         }
         enum down {
           value 2;
           description
             "Operational status changed to down.";



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         }
       }
       description "Operational status event type for notifications.";
     }

     /*
      * Identities
      */
     identity mpls-ldp {
       base rt:control-plane-protocol;
       description
         "LDP protocol.";
       reference
         "RFC 5036: LDP Specification";
     }

     identity adjacency-flag-base {
       description "Base type for adjacency flags.";
     }

     identity adjacency-flag-active {
       base adjacency-flag-base;
       description
         "This adjacency is configured and actively created.";
     }

     identity adjacency-flag-passive {
       base adjacency-flag-base;
       description
         "This adjacency is not configured and passively accepted.";
     }

     /*
      * Groupings
      */

     grouping adjacency-state-attributes {
       description
         "The operational state attributes of an LDP Hello adjacency,
          which can used for basic and extended discoveris, in IPv4 and
          IPv6 address families.";

       leaf-list flag {
         type identityref {
           base adjacency-flag-base;
         }
         description
           "On or more flags to indicate whether the adjacency is



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            actively created, passively accepted, or both.";
       }
       container hello-holdtime {
         description
           "Containing Hello holdtime state information.";
         leaf adjacent {
           type uint16;
           units seconds;
           description
             "The holdtime value learned from the adjacent LSR.";
         }
         leaf negotiated {
           type uint16;
           units seconds;
           description
             "The holdtime negotiated between this LSR and the adjacent
              LSR.";
         }
         leaf remaining {
           type uint16;
           units seconds;
           description
             "The time remaining until the holdtime timer expires.";
         }
       }

       leaf next-hello {
         type uint16;
         units seconds;
         description
           "The time when the next Hello message will be sent.";
       }

       container statistics {
         description
           "Statistics objects.";

         leaf discontinuity-time {
           type yang:date-and-time;
           mandatory true;
           description
             "The time on the most recent occasion at which any one or
              more of this interface's counters suffered a
              discontinuity.  If no such discontinuities have occurred
              since the last re-initialization of the local management
              subsystem, then this node contains the time the local
              management subsystem re-initialized itself.";
         }



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         leaf hello-received {
           type yang:counter64;
           description
             "The number of Hello messages received.";
         }
         leaf hello-dropped {
           type yang:counter64;
           description
             "The number of Hello messages dropped.";
         }
       } // statistics
     } // adjacency-state-attributes

     grouping basic-discovery-timers {
       description
         "The timer attributes for basic discovery, used in the
          per-interface setting and in the all-interface setting.";

       leaf hello-holdtime {
         type uint16 {
           range 15..3600;
         }
         units seconds;
         description
           "The time interval for which a LDP link Hello adjacency
            is maintained in the absence of link Hello messages from
            the LDP neighbor.
            This leaf may be configured at the per-interface level or
            the global level, with precedence given to the value at the
            per-interface level.  If the leaf is not configured at
            either level, the default value at the global level is
            used.";
       }
       leaf hello-interval {
         type uint16 {
           range 5..1200;
         }
         units seconds;
         description
           "The interval between consecutive LDP link Hello messages
            used in basic LDP discovery.
            This leaf may be configured at the per-interface level or
            the global level, with precedence given to the value at the
            per-interface level.  If the leaf is not configured at
            either level, the default value at the global level is
            used.";
       }
     } // basic-discovery-timers



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     grouping binding-address-state-attributes {
       description
         "Operational state attributes of an address binding, used in
          IPv4 and IPv6 address families.";

       leaf advertisement-type {
         type advertised-received;
         description
           "Received or advertised.";
       }
       container peer {
         when "../advertisement-type = 'received'" {
           description
             "Applicable for received address.";
         }
         description
           "LDP peer from which this address is received.";
         uses ldp-peer-ref-from-binding;
       }
     } // binding-address-state-attributes

     grouping binding-label-state-attributes {
       description
         "Operational state attributes for a FEC-label binding, used in
          IPv4 and IPv6 address families.";

       list peer {
         key "lsr-id label-space-id advertisement-type";
         description
           "List of advertised and received peers.";
         uses ldp-peer-ref-from-binding {
           description
             "The LDP peer from which this binding is received, or to
              which this binding is advertised.
              The peer is identified by its LDP ID, which consists of
              the LSR ID and the Label Space ID.";
         }
         leaf advertisement-type {
           type advertised-received;
           description
             "Received or advertised.";
         }
         leaf label {
           type rt-types:mpls-label;
           description
             "Advertised (outbound) or received (inbound)
              label.";
         }



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         leaf used-in-forwarding {
           type boolean;
           description
             "'true' if the label is used in forwarding.";
         }
       } // peer
     } // binding-label-state-attributes

     grouping graceful-restart-attributes-per-peer {
       description
         "Per peer graceful restart attributes.
          On the local side, these attributes are configuration and
          operational state data. One the peer side, these attributes
          are operational state data received from the peer.";

       container graceful-restart {
         description
           "Attributes for graceful restart.";
         leaf enabled {
           type boolean;
           description
             "Enable or disable graceful restart.
              This leaf may be configured at the per-peer level or the
              global level, with precedence given to the value at the
              per-peer level.  If the leaf is not configured at either
              level, the default value at the global level is used.";
         }
         leaf reconnect-time {
           type uint16 {
             range 10..1800;
           }
           units seconds;
           description
             "Specifies the time interval that the remote LDP peer
              must wait for the local LDP peer to reconnect after the
              remote peer detects the LDP communication failure.
              This leaf may be configured at the per-peer level or the
              global level, with precedence given to the value at the
              per-peer level.  If the leaf is not configured at either
              level, the default value at the global level is used.";
         }
         leaf recovery-time {
           type uint16 {
             range 30..3600;
           }
           units seconds;
           description
             "Specifies the time interval, in seconds, that the remote



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              LDP peer preserves its MPLS forwarding state after
              receiving the Initialization message from the restarted
              local LDP peer.
              This leaf may be configured at the per-peer level or the
              global level, with precedence given to the value at the
              per-peer level.  If the leaf is not configured at either
              level, the default value at the global level is used.";
         }
       } // graceful-restart
     } // graceful-restart-attributes-per-peer

     grouping ldp-interface-ref {
       description
         "Defining a reference to LDP interface.";

       leaf name {
         type if:interface-ref;
         must "(/if:interfaces/if:interface[if:name=current()]/ip:ipv4)"
           + " or "
           + "(/if:interfaces/if:interface[if:name=current()]/ip:ipv6)"
         {
           description "Interface is IPv4 or IPv6.";
         }
         description
           "The name of an LDP interface.";
       }
     }

     grouping ldp-peer-ref-absolute {
       description
         "An absolute reference to an LDP peer, by the LDP ID, which
          consists of the LSR ID and the Label Space ID.";

       leaf protocol-name {
         type leafref {
           path "/rt:routing/rt:control-plane-protocols/"
             + "rt:control-plane-protocol/rt:name";
         }
         description
           "The name of the LDP protocol instance.";
       }
       leaf lsr-id {
         type leafref {
           path "/rt:routing/rt:control-plane-protocols/"
             + "rt:control-plane-protocol"
             + "[rt:name=current()/../protocol-name]/"
             + "ldp:mpls-ldp/ldp:peers/ldp:peer/ldp:lsr-id";
         }



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         description
           "The LSR ID of the peer, as a portion of the peer LDP ID.";
       }
       leaf label-space-id {
         type leafref {
           path "/rt:routing/rt:control-plane-protocols/"
             + "rt:control-plane-protocol"
             + "[rt:name=current()/../protocol-name]/"
             + "ldp:mpls-ldp/ldp:peers/"
             + "ldp:peer[ldp:lsr-id=current()/../lsr-id]/"
             + "ldp:label-space-id";
         }
         description
           "The Label Space ID of the peer, as a portion of the peer
            LDP ID.";
       }
     } // ldp-peer-ref-absolute

     grouping ldp-peer-ref-from-binding {
       description
         "A relative reference to an LDP peer, by the LDP ID, which
          consists of the LSR ID and the Label Space ID.";

       leaf lsr-id {
         type leafref {
           path "../../../../../../../ldp:peers/ldp:peer/ldp:lsr-id";
         }
         description
           "The LSR ID of the peer, as a portion of the peer LDP ID.";
       }
       leaf label-space-id {
         type leafref {
           path "../../../../../../../ldp:peers/"
             + "ldp:peer[ldp:lsr-id=current()/../lsr-id]/"
             + "ldp:label-space-id";
         }
         description
           "The Label Space ID of the peer, as a portion of the peer
              LDP ID.";
       }
     } // ldp-peer-ref-from-binding

     grouping ldp-peer-ref-from-interface {
       description
         "A relative reference to an LDP peer, by the LDP ID, which
          consists of the LSR ID and the Label Space ID.";

       container peer {



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         description
           "Reference to an LDP peer, by the LDP ID, which consists of
            the LSR ID and the Label Space ID.";
         leaf lsr-id {
           type leafref {
             path "../../../../../../../../../ldp:peers/ldp:peer/"
               + "ldp:lsr-id";
           }
           description
             "The LSR ID of the peer, as a portion of the peer LDP ID.";
         }
         leaf label-space-id {
           type leafref {
             path "../../../../../../../../../ldp:peers/"
               + "ldp:peer[ldp:lsr-id=current()/../lsr-id]/"
               + "ldp:label-space-id";
           }
           description
             "The Label Space ID of the peer, as a portion of the peer
              LDP ID.";
         }
       } // peer
     } // ldp-peer-ref-from-interface

     grouping ldp-peer-ref-from-target {
       description
         "A relative reference to an LDP peer, by the LDP ID, which
          consists of the LSR ID and the Label Space ID.";

       container peer {
         description
           "Reference to an LDP peer, by the LDP ID, which consists of
            the LSR ID and the Label Space ID.";
         leaf lsr-id {
           type leafref {
             path "../../../../../../../../ldp:peers/ldp:peer/"
               + "ldp:lsr-id";
           }
           description
             "The LSR ID of the peer, as a portion of the peer LDP ID.";
         }
         leaf label-space-id {
           type leafref {
             path "../../../../../../../../ldp:peers/"
               + "ldp:peer[ldp:lsr-id=current()/../lsr-id]/"
               + "ldp:label-space-id";
           }
           description



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             "The Label Space ID of the peer, as a portion of the peer
              LDP ID.";
         }
       } // peer
     } // ldp-peer-ref-from-target

     grouping peer-attributes {
       description
         "Peer configuration attributes, used in the per-peer setting
          can in the all-peer setting.";

       leaf session-ka-holdtime {
         type uint16 {
           range 45..3600;
         }
         units seconds;
         description
           "The time interval after which an inactive LDP session
            terminates and the corresponding TCP session closes.
            Inactivity is defined as not receiving LDP packets from the
            peer.
            This leaf may be configured at the per-peer level or the
            global level, with precedence given to the value at the
            per-peer level.  If the leaf is not configured at either
            level, the default value at the global level is used.";
       }
       leaf session-ka-interval {
         type uint16 {
           range 15..1200;
         }
         units seconds;
         description
           "The interval between successive transmissions of keepalive
            packets. Keepalive packets are only sent in the absence of
            other LDP packets transmitted over the LDP session.
            This leaf may be configured at the per-peer level or the
            global level, with precedence given to the value at the
            per-peer level.  If the leaf is not configured at either
            level, the default value at the global level is used.";
       }
     } // peer-attributes

     grouping peer-authentication {
       description
         "Peer authentication container, used in the per-peer setting
          can in the all-peer setting.";

       container authentication {



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         description
           "Containing authentication information.";
         choice authentication-type {
           description
             "Choice of authentication.";
           case password {
             leaf key {
               type string;
               description
                 "This leaf specifies the authentication key. The length
                  of the key may be dependent on the cryptographic
                  algorithm.";
             }
             leaf crypto-algorithm {
               type identityref {
                 base key-chain:crypto-algorithm;
               }
               description
                 "Cryptographic algorithm associated with key.";
              }
           }
         }
       }
     } // peer-authentication

     grouping peer-state-derived {
       description
         "The peer state information derived from the LDP protocol
          operations.";

       container label-advertisement-mode {
         config false;
         description "Label advertisement mode state.";
         leaf local {
           type label-adv-mode;
           description
             "Local Label Advertisement Mode.";
         }
         leaf peer {
           type label-adv-mode;
           description
             "Peer Label Advertisement Mode.";
         }
         leaf negotiated {
           type label-adv-mode;
           description
             "Negotiated Label Advertisement Mode.";
         }



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       }
       leaf next-keep-alive {
         type uint16;
         units seconds;
         config false;
         description
           "Time duration from now until sending the next KeepAlive
            message.";
       }

       container received-peer-state {
         config false;
         description
           "Operational state information learned from the peer.";

         uses graceful-restart-attributes-per-peer;

         container capability {
           description "Peer capability information.";
           container end-of-lib {
             description
               "Peer's end-of-lib capability.";
             leaf enabled {
               type boolean;
               description
                 "'true' if peer's end-of-lib capability is enabled.";
             }
           }
           container typed-wildcard-fec {
             description
               "Peer's typed-wildcard-fec capability.";
             leaf enabled {
               type boolean;
               description
                 "'true' if peer's typed-wildcard-fec capability is
                   enabled.";
             }
           }
           container upstream-label-assignment {
             description
               "Peer's upstream label assignment capability.";
             leaf enabled {
               type boolean;
               description
                 "'true' if peer's upstream label assignment is
                  enabled.";
             }
           }



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         } // capability
       } // received-peer-state

       container session-holdtime {
         config false;
         description "Session holdtime state.";
         leaf peer {
           type uint16;
           units seconds;
           description "Peer holdtime.";
         }
         leaf negotiated {
           type uint16;
           units seconds;
           description "Negotiated holdtime.";
         }
         leaf remaining {
           type uint16;
           units seconds;
           description "Remaining holdtime.";
         }
       } // session-holdtime

       leaf session-state {
         type enumeration {
           enum non-existent {
             description "NON EXISTENT state. Transport disconnected.";
           }
           enum initialized {
             description "INITIALIZED state.";
           }
           enum openrec {
             description "OPENREC state.";
           }
           enum opensent {
             description "OPENSENT state.";
           }
           enum operational {
             description "OPERATIONAL state.";
           }
         }
         config false;
         description
           "Representing the operational status of the LDP session.";
         reference
           "RFC5036, Sec. 2.5.4.";
       }




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       container tcp-connection {
         config false;
         description "TCP connection state.";
         leaf local-address {
           type inet:ip-address;
           description "Local address.";
         }
         leaf local-port {
           type inet:port-number;
           description "Local port number.";
         }
         leaf remote-address {
           type inet:ip-address;
           description "Remote address.";
         }
         leaf remote-port {
           type inet:port-number;
           description "Remote port number.";
         }
       } // tcp-connection

       leaf up-time {
         type rt-types:timeticks64;
         config false;
         description
           "The number of time ticks (hundredths of a second) since the
            the state of the session with the peer changed to
            OPERATIONAL.";
       }

       container statistics {
         config false;
         description
           "Statistics objects.";

         leaf discontinuity-time {
           type yang:date-and-time;
           mandatory true;
           description
             "The time on the most recent occasion at which any one or
              more of this interface's counters suffered a
              discontinuity.  If no such discontinuities have occurred
              since the last re-initialization of the local management
              subsystem, then this node contains the time the local
              management subsystem re-initialized itself.";
         }

         container received {



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           description "Inbound statistics.";
           uses statistics-peer-received-sent;
         }
         container sent {
           description "Outbound statistics.";
           uses statistics-peer-received-sent;
         }

         leaf total-addresses {
           type uint32;
           description
             "The number of learned addresses.";
         }
         leaf total-labels {
           type uint32;
           description
             "The number of learned labels.";
         }
         leaf total-fec-label-bindings {
           type uint32;
           description
             "The number of learned label-address bindings.";
         }
       } // statistics
     } // peer-state-derived

     grouping statistics-peer-received-sent {
       description
         "Inbound and outbound statistic counters.";
       leaf total-octets {
         type yang:counter64;
         description
           "The total number of octets sent or received.";
       }
       leaf total-messages {
         type yang:counter64;
         description
           "The number of messages sent or received.";
       }
       leaf address {
         type yang:counter64;
         description
           "The number of address messages sent or received.";
       }
       leaf address-withdraw {
         type yang:counter64;
         description
           "The number of address-withdraw messages sent or received.";



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       }
       leaf initialization {
         type yang:counter64;
         description
           "The number of initialization messages sent or received.";
       }
       leaf keepalive {
         type yang:counter64;
         description
           "The number of keepalive messages sent or received.";
       }
       leaf label-abort-request {
         type yang:counter64;
         description
           "The number of label-abort-request messages sent or
            received.";
       }
       leaf label-mapping {
         type yang:counter64;
         description
           "The number of label-mapping messages sent or received.";
       }
       leaf label-release {
         type yang:counter64;
         description
           "The number of label-release messages sent or received.";
       }
       leaf label-request {
         type yang:counter64;
         description
           "The number of label-request messages sent or received.";
       }
       leaf label-withdraw {
         type yang:counter64;
         description
           "The number of label-withdraw messages sent or received.";
       }
       leaf notification {
         type yang:counter64;
         description
           "The number of notification messages sent or received.";
       }
     } // statistics-peer-received-sent

     /*
      * Configuration data and operational state data nodes
      */




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     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol" {
       when "derived-from-or-self(rt:type, 'ldp:mpls-ldp')" {
         description
           "This augmentation is only valid for a control-plane
            protocol instance of LDP (type 'mpls-ldp').";
       }
       description
         "LDP augmentation to routing control-plane protocol
          configuration and state.";

       container mpls-ldp {
         must "not (../../rt:control-plane-protocol"
           + "[derived-from-or-self(rt:type, 'ldp:mpls-ldp')]"
           + "[rt:name!=current()/../rt:name])"
         {
           description "Only one LDP instance is allowed.";
         }

         description
           "Containing configuration and operational data for the LDP
            protocol.";

         container global {
           description
             "Global attributes for LDP.";

           container capability {
             description
               "Containing the LDP capability data. The container is
                used for augmentations.";
             reference
               "RFC5036: Sec. 1.5.";
           }

           container graceful-restart {
             description
               "Attributes for graceful restart.";
             leaf enabled {
               type boolean;
               default false;
               description
                 "Enable or disable graceful restart.";
             }
             leaf reconnect-time {
               type uint16 {
                 range 10..1800;
               }



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               units seconds;
               default 120;
               description
                 "Specifies the time interval that the remote LDP peer
                  must wait for the local LDP peer to reconnect after
                  the remote peer detects the LDP communication
                  failure.";
             }
             leaf recovery-time {
               type uint16 {
                 range 30..3600;
               }
               units seconds;
               default 120;
               description
                 "Specifies the time interval, in seconds, that the
                  remote LDP peer preserves its MPLS forwarding state
                  after receiving the Initialization message from the
                  restarted local LDP peer.";
             }
             leaf forwarding-holdtime {
               type uint16 {
                 range 30..3600;
               }
               units seconds;
               default 180;
               description
                 "Specifies the time interval, in seconds, before the
                  termination of the recovery phase.";
             }
           } // graceful-restart

           leaf lsr-id {
             type rt-types:router-id;
             description
               "Specify the value to act as the LDP LSR ID.
                If this attribute is not specified, LDP uses the router
                ID as determined by the system.";
           }

           container address-families {
             description
               "Per address family confgiration and operational state.
                The address family can be either IPv4 or IPv6.";
             container ipv4 {
               presence
                 "Present if IPv4 is enabled, unless the 'enabled'
                  leaf is set to 'false'";



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               description
                 "Containing data related to the IPv4 address family.";

               leaf enabled {
                 type boolean;
                 default true;
                 description
                 "'false' to disable the address family.";
               }

               leaf label-distribution-control-mode {
                 type enumeration {
                   enum independent {
                     description
                     "Independent label distribution control.";
                   }
                   enum ordered {
                     description
                     "Ordered label distribution control.";
                   }
                 }
                 config false;
                 description
                   "Label distribution control mode.";
                 reference
                   "RFC5036: LDP Specification. Sec 2.6.";
               }

               // ipv4 bindings
               container bindings {
                 config false;
                 description
                   "LDP address and label binding information.";
                 list address {
                   key "address";
                   description
                     "List of address bindings learned by LDP.";
                   leaf address {
                     type inet:ipv4-address;
                     description
                       "The IPv4 address learned from an Address
                        message received from or advertised to a peer.";
                   }
                   uses binding-address-state-attributes;
                 }

                 list fec-label {
                   key "fec";



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                   description
                     "List of FEC-label bindings learned by LDP.";
                   leaf fec {
                     type inet:ipv4-prefix;
                     description
                       "The prefix FEC value in the FEC-label binding,
                        learned in a Label Mapping message received from
                        or advertised to a peer.";
                   }
                   uses binding-label-state-attributes;
                 }
               } // bindings
             } // ipv4
           } // address-families
         } // global

         container discovery {
           description
             "Neighbor discovery configuration and operational state.";

           container interfaces {
             description
               "A list of interfaces for LDP Basic Discovery.";
             reference
               "RFC5036: LDP Specification. Sec 2.4.1.";

             uses basic-discovery-timers {
               refine "hello-holdtime" {
                 default 15;
               }
               refine "hello-interval" {
                 default 5;
               }
             }

             list interface {
               key "name";
               description
                 "List of LDP interfaces used for LDP Basic Discovery.";
               uses ldp-interface-ref;
               leaf next-hello {
                 type uint16;
                 units seconds;
                 config false;
                 description "Time to send the next Hello message.";
               }

               container address-families {



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                 description
                   "Container for address families.";
                 container ipv4 {
                   presence
                     "Present if IPv4 is enabled, unless the 'enabled'
                      leaf is set to 'false'";
                   description
                     "IPv4 address family.";

                   leaf enabled {
                     type boolean;
                     default true;
                     description
                     "Set to false to disable the address family on
                      the interface.";
                   }

                   container hello-adjacencies {
                     config false;
                     description
                       "Containing a list of Hello adjacencies.";

                     list hello-adjacency {
                       key "adjacent-address";
                       config false;
                       description "List of Hello adjacencies.";

                       leaf adjacent-address {
                         type inet:ipv4-address;
                         description
                           "Neighbor address of the Hello adjacency.";
                       }

                       uses adjacency-state-attributes;
                       uses ldp-peer-ref-from-interface;
                     }
                   }
                 } // ipv4
               } // address-families
             } // interface
           } // interfaces

           container targeted
           {
             description
               "A list of targeted neighbors for extended discovery.";

             leaf hello-holdtime {



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               type uint16 {
                 range 15..3600;
               }
               units seconds;
               default 45;
               description
                 "The time interval for which LDP targeted Hello
                  adjacency is maintained in the absence of targeted
                  Hello messages from an LDP neighbor.";
             }
             leaf hello-interval {
               type uint16 {
                 range 5..3600;
               }
               units seconds;
               default 15;
               description
                 "The interval between consecutive LDP targeted Hello
                  messages used in extended LDP discovery.";
             }

             container hello-accept {
               description
                 "LDP policy to control the acceptance of extended
                  neighbor discovery Hello messages.";

               leaf enabled {
                 type boolean;
                 default false;
                 description
                   "'true' to accept; 'false' to deny.";
               }
             }

             container address-families {
               description
                 "Container for address families.";
               container ipv4 {
                 presence
                   "Present if IPv4 is enabled.";
                 description
                   "IPv4 address family.";

                 container hello-adjacencies {
                   config false;
                   description
                     "Containing a list of Hello adjacencies.";




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                   list hello-adjacency {
                     key "local-address adjacent-address";
                     description "List of Hello adjacencies.";

                     leaf local-address {
                       type inet:ipv4-address;
                       description
                         "Local address of the Hello adjacency.";
                     }
                     leaf adjacent-address {
                       type inet:ipv4-address;
                       description
                         "Neighbor address of the Hello adjacency.";
                     }

                     uses adjacency-state-attributes;
                     uses ldp-peer-ref-from-target;
                   }
                 }

                 list target {
                   key "adjacent-address";
                   description
                     "Targeted discovery params.";

                   leaf adjacent-address {
                     type inet:ipv4-address;
                     description
                       "Configures a remote LDP neighbor for the
                        extended LDP discovery.";
                   }

                   leaf enabled {
                     type boolean;
                     default true;
                     description
                       "'true' to enable the target.";
                   }
                   leaf local-address {
                     type inet:ipv4-address;
                     description
                       "The local address used as the source address to
                        send targeted Hello messages.
                        If the value is not specified, the
                        transport-address is used as the source
                        address.";
                   }
                 } // target



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               } // ipv4
             } // address-families
           } // targeted
         } // discovery

         container peers {
           description
             "Peers configuration attributes.";

           uses peer-authentication;
           uses peer-attributes {
             refine session-ka-holdtime {
               default 180;
             }
             refine session-ka-interval {
               default 60;
             }
           }

           list peer {
             key "lsr-id label-space-id";
             description
               "List of peers.";

             leaf lsr-id {
               type rt-types:router-id;
               description
                 "The LSR ID of the peer, to identify the globally
                  unique LSR. This is the first four octets of the LDP
                  ID. This leaf is used together with the leaf
                  'label-space-id' to form the LDP ID.";
               reference
                 "RFC5036. Sec 2.2.2.";
             }
             leaf label-space-id {
               type uint16;
               description
                 "The Label Space ID of the peer, to identify a specific
                  label space within the LSR. This is the last two
                  octets of the LDP ID. This leaf is used together with
                  the leaf 'lsr-id' to form the LDP ID.";
               reference
                 "RFC5036. Sec 2.2.2.";
             }

             uses peer-authentication;

             container address-families {



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               description
                 "Per-vrf per-af params.";
               container ipv4 {
                 presence
                   "Present if IPv4 is enabled.";
                 description
                   "IPv4 address family.";

                 container hello-adjacencies {
                   config false;
                   description
                     "Containing a list of Hello adjacencies.";

                   list hello-adjacency {
                     key "local-address adjacent-address";
                     description "List of Hello adjacencies.";

                     leaf local-address {
                       type inet:ipv4-address;
                       description
                         "Local address of the Hello adjacency.";
                     }
                     leaf adjacent-address {
                       type inet:ipv4-address;
                       description
                         "Neighbor address of the Hello adjacency.";
                     }

                     uses adjacency-state-attributes;

                     leaf interface {
                       type if:interface-ref;
                       description "Interface for this adjacency.";
                     }
                   }
                 }
               } // ipv4
             } // address-families

             uses peer-state-derived;
           } // list peer
         } // peers
       } // container mpls-ldp
     }

     /*
      * RPCs
      */



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     rpc mpls-ldp-clear-peer {
       description
         "Clears the session to the peer.";
       input {
         uses ldp-peer-ref-absolute {
           description
             "The LDP peer to be cleared. If this is not provided
              then all peers are cleared.
              The peer is identified by its LDP ID, which consists of
              the LSR ID and the Label Space ID.";
         }
       }
     }

     rpc mpls-ldp-clear-hello-adjacency {
       description
         "Clears the hello adjacency";
       input {
         container hello-adjacency {
           description
             "Link adjacency or targettted adjacency. If this is not
              provided then all Hello adjacencies are cleared";
           leaf protocol-name {
             type leafref {
               path "/rt:routing/rt:control-plane-protocols/"
                 + "rt:control-plane-protocol/rt:name";
             }
             description
               "The name of the LDP protocol instance.";
           }
           choice hello-adjacency-type {
             description "Adjacency type.";
             case targeted {
               container targeted {
                 presence "Present to clear targeted adjacencies.";
                 description
                   "Clear targeted adjacencies.";
                 leaf target-address {
                   type inet:ip-address;
                   description
                     "The target address. If this is not provided then
                      all targeted adjacencies are cleared";
                 }
               }
             }
             case link {
               container link {
                 presence "Present to clear link adjacencies.";



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                 description
                   "Clear link adjacencies.";
                 leaf next-hop-interface {
                   type leafref {
                     path "/rt:routing/rt:control-plane-protocols/"
                       + "rt:control-plane-protocol/mpls-ldp/discovery/"
                       + "interfaces/interface/name";
                   }
                   description
                     "Interface connecting to next-hop. If this is not
                      provided then all link adjacencies are cleared.";
                 }
                 leaf next-hop-address {
                   type inet:ip-address;
                   must "../next-hop-interface" {
                     description
                       "Applicable when interface is specified.";
                   }
                   description
                     "IP address of next-hop. If this is not provided
                      then adjacencies to all next-hops on the given
                      interface are cleared.";
                 }
               }
             }
           } // hello-adjacency-type
         } // hello-adjacency
       } // input
     } // mpls-ldp-clear-hello-adjacency

     rpc mpls-ldp-clear-peer-statistics {
       description
         "Clears protocol statistics (e.g. sent and received
          counters).";
       input {
         uses ldp-peer-ref-absolute {
           description
             "The LDP peer whose statistics are to be cleared.
              If this is not provided then all peers' statistics are
              cleared.
              The peer is identified by its LDP ID, which consists of
              the LSR ID and the Label Space ID.";
         }
       }
     }

     /*
      * Notifications



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      */
     notification mpls-ldp-peer-event {

       description
         "Notification event for a change of LDP peer operational
          status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       container peer {
         description
           "Reference to an LDP peer, by the LDP ID, which consists of
            the LSR ID and the Label Space ID.";
         uses ldp-peer-ref-absolute;
       }
     }

     notification mpls-ldp-hello-adjacency-event {
       description
         "Notification event for a change of LDP adjacency operational
          status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       leaf protocol-name {
         type leafref {
           path "/rt:routing/rt:control-plane-protocols/"
             + "rt:control-plane-protocol/rt:name";
         }
         description
           "The name of the LDP protocol instance.";
       }
       choice hello-adjacency-type {
         description
           "Interface or targeted adjacency.";
         case targeted {
           container targeted {
             description
               "Targeted adjacency through LDP extended discovery.";
             leaf target-address {
               type inet:ip-address;
               description
                 "The target adjacent address learned.";
             }
           }
         }



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         case link {
           container link {
             description
               "Link adjacency through LDP basic discovery.";
             leaf next-hop-interface {
               type if:interface-ref;
               description
                 "The interface connecting to the adjacent next hop.";
             }
             leaf next-hop-address {
               type inet:ip-address;
               must "../next-hop-interface" {
                 description
                   "Applicable when interface is specified.";

               }
               description
                 "IP address of the next hop. This can be IPv4 or IPv6
                  address.";
             }
           }
         }
       } // hello-adjacency-type
     } // mpls-ldp-hello-adjacency-event

     notification mpls-ldp-fec-event {
       description
         "Notification event for a change of FEC status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       leaf protocol-name {
         type leafref {
           path "/rt:routing/rt:control-plane-protocols/"
             + "rt:control-plane-protocol/rt:name";
         }
         description
           "The name of the LDP protocol instance.";
       }
       leaf fec {
         type inet:ip-prefix;
         description
           "The address prefix element of the FEC whose status
            has changed.";
       }
     }
   }



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   <CODE ENDS>



                         Figure 10: LDP base module

9.2.  Extended

   This YANG module imports types defined in [RFC6991], [RFC8349],
   [RFC8177], and [RFC8343].



   <CODE BEGINS> file "ietf-mpls-ldp-extended@2020-02-25.yang"

   // RFC Editor: replace the above date 2020-02-25  with the date of
   // publication and remove this note.

   module ietf-mpls-ldp-extended {
     yang-version 1.1;

     namespace "urn:ietf:params:xml:ns:yang:ietf-mpls-ldp-extended";
     prefix "ldp-ext";

     import ietf-inet-types {
       prefix "inet";
       reference "RFC 6991: Common YANG Data Types";
     }

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8349: A YANG Data Model for Routing Management (NMDA
          version)";
     }

     import ietf-key-chain {
       prefix "key-chain";
       reference "RFC 8177: YANG Data Model for Key Chains";
     }

     import ietf-mpls-ldp {
       prefix "ldp";
       reference "RFC XXXX: YANG Data Model for MPLS LDP";
       // RFC Editor: replace XXXX with actual RFC number and remove
       // this note
     }




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     import ietf-interfaces {
       prefix "if";
       reference "RFC 8343: A YANG Data Model for Interface Management";
     }

     import ietf-routing-policy {
       prefix rt-pol;
       reference
         "I-D.ietf-rtgwg-policy-model: A YANG Data Model for Routing
          Policy Management";
     }

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

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

        Editor:   Rajiv Asati
                  <mailto:rajiva@cisco.com>

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

        Editor:   Santosh Esale
                  <mailto:sesale@juniper.net>

        Editor:   Xia Chen
                  <mailto:jescia.chenxia@huawei.com>

        Editor:   Himanshu Shah
                  <mailto:hshah@ciena.com>";

     description
       "This YANG module defines the extended components for the
        management of Multi-Protocol Label Switching (MPLS) Label
        Distribution Protocol (LDP). It is also the model to
        be augmented for extended Multipoint LDP (mLDP).

        Copyright (c) 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



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        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://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 Editor: replace XXXX with actual RFC number and remove
        // this note

     revision 2020-02-25 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Data Model for MPLS LDP.";

         // RFC Editor: replace XXXX with actual RFC number and remove
         // this note
     }

     /*
      * Features
      */
     feature capability-end-of-lib {
       description
         "This feature indicates that the system allows to configure
          LDP end-of-lib capability.";
     }

     feature capability-typed-wildcard-fec {
       description
         "This feature indicates that the system allows to configure
          LDP typed-wildcard-fec capability.";
     }

     feature capability-upstream-label-assignment {
       description
         "This feature indicates that the system allows to configure
          LDP upstream label assignment capability.";
     }

     feature forwarding-nexthop-config {
       description
         "This feature indicates that the system allows to configure
          forwarding nexthop on interfaces.";
     }

     feature graceful-restart-helper-mode {



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       description
         "This feature indicates that the system supports graceful
          restart helper mode. We call an LSR to be operating in GR
          helper mode when it advertises 0 as its FT Reconnect Timeout
          in the FT Session TLV.
          Please refer RFC3478 section 2 for details.";
     }

     feature key-chain {
       description
         "This feature indicates that the system supports keychain for
          authentication.";
     }

     feature peers-dual-stack-transport-preference {
       description
         "This feature indicates that the system allows to configure
          the transport connection preference in a dual-stack setup
          for peers.";
     }

     feature per-interface-timer-config {
       description
         "This feature indicates that the system allows to configure
          interface Hello timers at the per-interface level.";
     }

     feature per-peer-admin-down {
       description
         "This feature indicates that the system allows to
          administratively disable a peer.";
     }

     feature per-peer-graceful-restart-config {
       description
         "This feature indicates that the system allows to configure
          graceful restart at the per-peer level.";
     }

     feature per-peer-session-attributes-config {
       description
         "This feature indicates that the system allows to configure
          session attributes at the per-peer level.";
     }

     feature policy-label-assignment-config {
       description
         "This feature indicates that the system allows to configure



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          policies to assign labels according to certain prefixes.";
     }

     feature policy-ordered-label-config {
       description
         "This feature indicates that the system allows to configure
          ordered label policies.";
     }

     feature policy-targeted-discovery-config {
       description
         "This feature indicates that the system allows to configure
          policies to control the acceptance of targeted neighbor
          discovery Hello messages.";
     }

     feature session-downstream-on-demand-config {
       description
         "This feature indicates that the system allows to configure
          session downstream-on-demand";
     }

     /*
      * Typedefs
      */
     typedef neighbor-list-ref {
       type leafref {
         path "/rt-pol:routing-policy/rt-pol:defined-sets/"
           + "rt-pol:neighbor-sets/rt-pol:neighbor-set/rt-pol:name";
       }
       description
         "A type for a reference to a neighbor address list.
          The string value is the name identifier for uniquely
          identifying the referenced address list, which contains a list
          of addresses that a routing policy can applied.";
       reference
         "I-D.ietf-rtgwg-policy-model: A YANG Data Model for Routing
          Policy Management";
     }

     typedef prefix-list-ref {
       type leafref {
         path "/rt-pol:routing-policy/rt-pol:defined-sets/"
           + "rt-pol:prefix-sets/rt-pol:prefix-set/rt-pol:name";
       }
       description
         "A type for a reference to a prefix list.
          The string value is the name identifier for uniquely



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          identifying the referenced prefix set, which contains a list
          of prefixes that a routing policy can applied.";
       reference
         "I-D.ietf-rtgwg-policy-model: A YANG Data Model for Routing
          Policy Management";
     }

     typedef peer-list-ref {
       type leafref {
         path "/rt-pol:routing-policy/rt-pol:defined-sets/"
           + "rt-pol:neighbor-sets/rt-pol:neighbor-set/rt-pol:name";
       }
       description
         "A type for a reference to a peer address list.
          The string value is the name identifier for uniquely
          identifying the referenced address list, which contains a list
          of addresses that a routing policy can applied.";
       reference
         "I-D.ietf-rtgwg-policy-model: A YANG Data Model for Routing
          Policy Management";
     }

     /*
      * Identities
      */

     /*
      * Groupings
      */
     grouping address-family-ipv4-augment {
       description "Augmentation to address family IPv4.";

       uses policy-container;

       leaf transport-address {
         type inet:ipv4-address;
         description
           "The transport address advertised in LDP Hello messages.
            If this value is not specified, the LDP LSR ID is used as
            the transport address.";
         reference
           "RFC5036. Sec. 3.5.2.";
       }
     }

     grouping authentication-keychain-augment {
       description "Augmentation to authentication to add keychain.";




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       leaf key-chain {
         type key-chain:key-chain-ref;
         description
           "key-chain name.
            If not specified, no key chain is used.";
       }
     }

     grouping capability-augment {
       description "Augmentation to capability.";

       container end-of-lib {
         if-feature capability-end-of-lib;
         description
           "Configure end-of-lib capability.";
         leaf enabled {
           type boolean;
           default false;
           description
             "'true' to enable end-of-lib capability.";
         }
       }
       container typed-wildcard-fec {
         if-feature capability-typed-wildcard-fec;
         description
           "Configure typed-wildcard-fec capability.";
         leaf enabled {
           type boolean;
           default false;
           description
             "'true' to enable typed-wildcard-fec capability.";
         }
       }
       container upstream-label-assignment {
         if-feature capability-upstream-label-assignment;
         description
           "Configure upstream label assignment capability.";
         leaf enabled {
           type boolean;
           default false;
           description
             "'true' to enable upstream label assignment.";
         }
       }
     } // capability-augment

     grouping global-augment {
       description "Augmentation to global attributes.";



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       leaf igp-synchronization-delay {
         type uint16 {
           range "0 | 3..300";
         }
         units seconds;
         default 0;
         description
           "Sets the interval that the LDP waits before notifying the
            Interior Gateway Protocol (IGP) that label exchange is
            completed so that IGP can start advertising the normal
            metric for the link.
            If the value is not specified, there is no delay.";
       }
     }

     grouping global-forwarding-nexthop-augment {
       description
         "Augmentation to global forwarding nexthop interfaces.";

       container forwarding-nexthop {
         if-feature forwarding-nexthop-config;
         description
           "Configuration for forwarding nexthop.";

         container interfaces {
           description
             "Containing a list of interfaces on which forwarding can be
              disabled.";

           list interface {
             key "name";
             description
               "List of LDP interfaces on which forwarding can be
                disabled.";
             uses ldp:ldp-interface-ref;
             list address-family {
               key "afi";
               description
                 "Per-vrf per-af params.";
               leaf afi {
                 type identityref {
                   base rt:address-family;
                 }
                 description
                   "Address family type value.";
               }
               leaf ldp-disable {
                 type boolean;



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                 default false;
                 description
                   "'true' to disable LDP forwarding on the interface.";
               }
             }
           } // interface
         } // interfaces
       } // forwarding-nexthop
     } // global-forwarding-nexthop-augment

     grouping graceful-restart-augment {
       description "Augmentation to graceful restart.";

       leaf helper-enabled {
         if-feature graceful-restart-helper-mode;
         type boolean;
         default false;
         description
           "Enable or disable graceful restart helper mode.";
       }
     }

     grouping interface-address-family-ipv4-augment {
       description "Augmentation to interface address family IPv4.";

       leaf transport-address {
         type union {
           type enumeration {
             enum "use-global-transport-address" {
               description
                 "Use the transport address set at the global level
                  common for all interfaces for this address family.";
             }
             enum "use-interface-address" {
               description
                 "Use interface address as the transport address.";
             }
           }
           type inet:ipv4-address;
         }
         default "use-global-transport-address";
         description
           "IP address to be advertised as the LDP transport address.";
       }
     }

     grouping interface-address-family-ipv6-augment {
       description "Augmentation to interface address family IPv6.";



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       leaf transport-address {
         type union {
           type enumeration {
             enum "use-global-transport-address" {
               description
                 "Use the transport address set at the global level
                  common for all interfaces for this address family.";
             }
             enum "use-interface-address" {
               description
                 "Use interface address as the transport address.";
             }
           }
           type inet:ipv6-address;
         }
         default "use-global-transport-address";
         description
           "IP address to be advertised as the LDP transport address.";
       }
     }

     grouping interface-augment {
       description "Augmentation to interface.";

       uses ldp:basic-discovery-timers {
         if-feature per-interface-timer-config;
       }
       leaf igp-synchronization-delay {
         if-feature per-interface-timer-config;
         type uint16 {
           range "0 | 3..300";
         }
         units seconds;
         description
           "Sets the interval that the LDP waits before notifying the
            Interior Gateway Protocol (IGP) that label exchange is
            completed so that IGP can start advertising the normal
            metric for the link.
            This leaf may be configured at the per-interface level or
            the global level, with precedence given to the value at the
            per-interface level.  If the leaf is not configured at
            either level, the default value at the global level is
            used.";
       }
     }

     grouping peer-af-policy-container {
       description



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         "LDP policy attribute container under peer address-family.";
       container label-policy {
         description
           "Label policy attributes.";
         container advertise {
           description
             "Label advertising policies.";
           leaf prefix-list {
             type prefix-list-ref;
               description
                 "Applies the prefix list to filter outgoing label
                  advertisements.
                  If the value is not specified, no prefix filter
                  is applied.";
           }
         }
         container accept {
           description
             "Label advertisement acceptance policies.";
           leaf prefix-list {
             type prefix-list-ref;
             description
               "Applies the prefix list to filer incoming label
                advertisements.
                If the value is not specified, no prefix filter
                is applied.";
           }
         }
       }
     } // peer-af-policy-container

     grouping peer-augment {
       description "Augmentation to each peer list entry.";

       leaf admin-down {
         if-feature per-peer-admin-down;
         type boolean;
         default false;
         description
           "'true' to disable the peer.";
       }

       uses ldp:graceful-restart-attributes-per-peer {
         if-feature per-peer-graceful-restart-config;
       }

       uses ldp:peer-attributes {
         if-feature per-peer-session-attributes-config;



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       }
     }

     grouping peers-augment {
       description "Augmentation to peers container.";

       container session-downstream-on-demand {
         if-feature session-downstream-on-demand-config;
         description
           "Session downstream-on-demand attributes.";
         leaf enabled {
           type boolean;
           default false;
           description
             "'true' if session downstream-on-demand is enabled.";
         }
         leaf peer-list {
           type peer-list-ref;
           description
             "The name of a peer ACL, to be applied to the
              downstream-on-demand sessions.
              If this value is not specified, no filter is applied to
              any downstream-on-demand sessions.";
         }
       }
       container dual-stack-transport-preference {
         if-feature peers-dual-stack-transport-preference;
         description
           "The settings of peers to establish TCP connection in a
            dual-stack setup.";
         leaf max-wait {
             type uint16 {
               range "0..60";
             }
             default 30;
             description
               "The maximum wait time in seconds for preferred transport
                connection establishment. 0 indicates no preference.";
         }
         container prefer-ipv4 {
           presence
             "Present if IPv4 is prefered for transport connection
              establishment, subject to the 'peer-list' in this
              container.";
           description
             "Uses IPv4 as the prefered address family for transport
              connection establishment, subject to the 'peer-list' in
              this container.



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              If this container is not present, as a default, IPv6 is
              the prefered address family for transport connection
              establishment.";
           leaf peer-list {
             type peer-list-ref;
             description
               "The name of a peer ACL, to be applied to the IPv4
                transport connections.
                If this value is not specified, no filter is applied,
                and the IPv4 is prefered for all peers.";
           }
         }
       }
     } // peers-augment

     grouping policy-container {
       description
         "LDP policy attributes.";
       container label-policy {
         description
           "Label policy attributes.";
         container advertise {
           description
             "Label advertising policies.";
           container egress-explicit-null {
             description
               "Enables an egress router to advertise an
                explicit null label (value 0) in place of an
                implicit null label (value 3) to the
                penultimate hop router.";
             leaf enabled {
               type boolean;
               default false;
               description
                 "'true' to enable explicit null.";
             }
           }
           leaf prefix-list {
             type prefix-list-ref;
             description
               "Applies the prefix list to filter outgoing label
                advertisements.
                If the value is not specified, no prefix filter
                is applied.";
           }
         }
         container accept {
           description



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             "Label advertisement acceptance policies.";
           leaf prefix-list {
             type prefix-list-ref;
             description
               "Applies the prefix list to filter incoming label
                advertisements.
                If the value is not specified, no prefix filter
                is applied.";
           }
         }
         container assign {
           if-feature policy-label-assignment-config;
           description
             "Label assignment policies";
           container independent-mode {
             description
               "Independent label policy attributes.";
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Assign labels according to certain prefixes.
                  If the value is not specified, no prefix filter
                  is applied (labels are assigned to all learned
                  routes).";

             }
           }
           container ordered-mode {
             if-feature policy-ordered-label-config;
             description
               "Ordered label policy attributes.";
             leaf egress-prefix-list {
               type prefix-list-ref;
               description
                 "Assign labels according to certain prefixes for
                  egress LSR.";
             }
           }
         } // assign
       } // label-policy
     } // policy-container

     /*
      * Configuration and state data nodes
      */
     // Forwarding nexthop augmentation to the global tree
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global" {



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       description "Forwarding nexthop augmentation.";
       uses global-forwarding-nexthop-augment;
     }

     // global/address-families/ipv6
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global/"
       + "ldp:address-families" {
       description "Global IPv6 augmentation.";

       container ipv6 {
         presence
           "Present if IPv6 is enabled, unless the 'enabled'
            leaf is set to 'false'";
         description
           "Containing data related to the IPv6 address family.";

         leaf enabled {
           type boolean;
           default true;
           description
             "'false' to disable the address family.";
         }

         uses policy-container;

         leaf transport-address {
           type inet:ipv6-address;
           mandatory true;
           description
             "The transport address advertised in LDP Hello messages.";
         }

         leaf label-distribution-control-mode {
           type enumeration {
             enum independent {
               description
               "Independent label distribution control.";
             }
             enum ordered {
               description
               "Ordered label distribution control.";
             }
           }
           config false;
           description
             "Label distribution control mode.";
           reference



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             "RFC5036: LDP Specification. Sec 2.6.";
         }

         // ipv6 bindings
         container bindings {
           config false;
           description
             "LDP address and label binding information.";
           list address {
             key "address";
             description
               "List of address bindings learned by LDP.";
             leaf address {
               type inet:ipv6-address;
               description
                 "The IPv6 address learned from an Address
                  message received from or advertised to a peer.";
             }
             uses ldp:binding-address-state-attributes;
           }

           list fec-label {
             key "fec";
             description
               "List of FEC-label bindings learned by LDP.";
             leaf fec {
               type inet:ipv6-prefix;
               description
                 "The prefix FEC value in the FEC-label binding,
                  learned in a Label Mapping message received from
                  or advertised to a peer.";
             }
             uses ldp:binding-label-state-attributes;
           }
         } // bindings
       } // ipv6
     }

     // discovery/interfaces/interface/address-families/ipv6
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:interfaces/ldp:interface/"
       + "ldp:address-families" {
       description "Interface IPv6 augmentation.";

       container ipv6 {
         presence
           "Present if IPv6 is enabled, unless the 'enabled'



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            leaf is set to 'false'";
         description
           "IPv6 address family.";

         leaf enabled {
           type boolean;
           default true;
           description
             "'false' to disable the address family on the interface.";
         }

         container hello-adjacencies {
           config false;
           description
             "Containing a list of Hello adjacencies.";

           list hello-adjacency {
             key "adjacent-address";
             config false;
             description "List of Hello adjacencies.";

             leaf adjacent-address {
               type inet:ipv6-address;
               description
                 "Neighbor address of the Hello adjacency.";
             }

             uses ldp:adjacency-state-attributes;
             uses ldp:ldp-peer-ref-from-interface;
           }
         }
       } // ipv6
     }

     // discovery/targeted/address-families/ipv6
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:targeted/ldp:address-families" {
       description "Targeted discovery IPv6 augmentation.";

       container ipv6 {
         presence
           "Present if IPv6 is enabled.";
         description
           "IPv6 address family.";

         container hello-adjacencies {
           config false;



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           description
             "Containing a list of Hello adjacencies.";

           list hello-adjacency {
             key "local-address adjacent-address";
             config false;
             description "List of Hello adjacencies.";

             leaf local-address {
               type inet:ipv6-address;
               description
                 "Local address of the Hello adjacency.";
             }
             leaf adjacent-address {
               type inet:ipv6-address;
               description
                 "Neighbor address of the Hello adjacency.";
             }

             uses ldp:adjacency-state-attributes;
             uses ldp:ldp-peer-ref-from-target;
           }
         }

         list target {
           key "adjacent-address";
           description
             "Targeted discovery params.";

           leaf adjacent-address {
             type inet:ipv6-address;
             description
               "Configures a remote LDP neighbor for the
                extended LDP discovery.";
           }
           leaf enabled {
             type boolean;
             default true;
             description
               "'true' to enable the target.";
           }
           leaf local-address {
             type inet:ipv6-address;
             description
               "The local address used as the source address to send
                targeted Hello messages.
                If the value is not specified, the transport-address
                is used as the source address.";



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           }
         } // target
       } // ipv6
     }

     // /peers/peer/state/address-families/ipv6
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/"
       + "ldp:peer/ldp:address-families" {
       description "Peer state IPv6 augmentation.";

       container ipv6 {
         presence
           "Present if IPv6 is enabled.";
         description
           "IPv6 address family.";

         container hello-adjacencies {
           config false;
           description
             "Containing a list of Hello adjacencies.";

           list hello-adjacency {
             key "local-address adjacent-address";
             description "List of Hello adjacencies.";

             leaf local-address {
               type inet:ipv6-address;
               description
                 "Local address of the Hello adjacency.";
             }
             leaf adjacent-address {
               type inet:ipv6-address;
               description
                 "Neighbor address of the Hello adjacency.";
             }

             uses ldp:adjacency-state-attributes;

             leaf interface {
               type if:interface-ref;
               description "Interface for this adjacency.";
             }
           }
         }
       } // ipv6
     }




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     /*
      * Configuration data and operational state data nodes
      */
     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global" {
       description "Graceful restart augmentation.";
       uses global-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global/"
       + "ldp:capability" {
       description "Capability augmentation.";
       uses capability-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global/"
       + "ldp:graceful-restart" {
       description "Graceful restart augmentation.";
       uses graceful-restart-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:global/"
       + "ldp:address-families/ldp:ipv4" {
       description "Address family IPv4 augmentation.";
       uses address-family-ipv4-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:interfaces/ldp:interface" {
       description "Interface augmentation.";
       uses interface-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:interfaces/ldp:interface/ldp:address-families/"
       + "ldp:ipv4" {
       description "Interface address family IPv4 augmentation.";
       uses interface-address-family-ipv4-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:interfaces/ldp:interface/ldp:address-families/"



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       + "ldp-ext:ipv6" {
       description "Interface address family IPv6 augmentation.";
       uses interface-address-family-ipv6-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:discovery/"
       + "ldp:targeted/ldp:hello-accept" {
       description "Targeted discovery augmentation.";
       leaf neighbor-list {
         if-feature policy-targeted-discovery-config;
         type neighbor-list-ref;
         description
           "The name of a neighbor ACL, to accept Hello messages from
            LDP peers as permitted by the neighbor-list policy.
            If this value is not specified, targeted Hello messages from
            any source are accepted.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers" {
       description "Peers augmentation.";
       uses peers-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/"
       + "ldp:authentication/ldp:authentication-type" {
       if-feature key-chain;
       description "Peers authentication augmentation.";
       case key-chain {
         uses authentication-keychain-augment;
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/ldp:peer" {
       description "Peer list entry augmentation.";
       uses peer-augment;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/ldp:peer/"
       + "ldp:authentication/ldp:authentication-type" {
       if-feature key-chain;
       description "Peer list entry authentication augmentation.";
       case key-chain {



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         uses authentication-keychain-augment;
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/ldp:peer/"
       + "ldp:address-families/ldp:ipv4" {
       description
         "Peer list entry IPv4 augmentation.";
       uses peer-af-policy-container;
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ldp:mpls-ldp/ldp:peers/ldp:peer/"
       + "ldp:address-families/ldp-ext:ipv6" {
       description
         "Peer list entry IPv6 augmentation.";
       uses peer-af-policy-container;
     }
   }

   <CODE ENDS>



                       Figure 11: LDP extended module

10.  Security Considerations

   This specification inherits the security considerations captured in
   [RFC5920] and the LDP protocol specification documents, namely base
   LDP [RFC5036], LDP IPv6 [RFC7552], LDP Capabilities [RFC5561], Typed
   Wildcard FEC [RFC5918], LDP End-of-LIB [RFC5919], and LDP Upstream
   Label Assignment [RFC6389].

10.1.  YANG model

   The YANG modules specified in this document 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 Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or




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   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

10.1.1.  Writable nodes

   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.

   For LDP, the ability to modify MPLS LDP configuration may allow the
   entire MPLS LDP domain to be compromised including forming LDP
   adjacencies and/or peer sessions with unauthorized routers to mount a
   massive Denial-of-Service (DoS) attack.  In particular, folling are
   the subtrees and data nodes that are sensitivite and vulnerable:

   *  /mpls-ldp/discovery/interfaces/interface: Adding LDP on any
      unprotected interface could allow an LDP hello adjacency to be
      formed with an unauthorized and malicious neighbor.  Once an hello
      adjacency is formed, a peer session could progress with this
      neighbor.

   *  /mpls-ldp/discovery/targeted/hello-accept: Allowing acceptance of
      targeted-hellos could open LDP to DoS attacks related to incoming
      targeted hellos from malicious sources.

   *  /mpls-ldp/peers/authentication: Allowing a peer session
      establishement is typically controlled via LDP authentication
      where a proper and secure authentication password/key management
      is warranted.

   *  /mpls-ldp/peers/peer/authentication: Same as above.

10.1.2.  Readable nodes

   Some of the readable data nodes in 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:

   The exposure of LDP databases (such as hello adjacencies, peers,
   address bindings, and fec-label bindings) beyond the scope of the LDP
   admin domain may be undesirable.  The relevant subtrees and data
   nodes are as follows:




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   *  /mpls-ldp/global/address-families/ipv4/bindings/address

   *  /mpls-ldp/global/address-families/ipv6/bindings/address

   *  /mpls-ldp/global/address-families/ipv4/bindings/fec-label

   *  /mpls-ldp/global/address-families/ipv6/bindings/fec-label

   *  /mpls-ldp/discovery/interfaces/interface/address-families/ipv4/
      hello-adjacencies

   *  /mpls-ldp/discovery/interfaces/interface/address-families/ipv6/
      hello-adjacencies

   *  /mpls-ldp/discovery/targeted/address-families/ipv4/hello-
      adjacencies

   *  /mpls-ldp/discovery/targeted/address-families/ipv6/hello-
      adjacencies

   *  /mpls-ldp/peers

   The configuration for LDP peer authentication is supported via the
   specification of key-chain [RFC8040], or via direct specification of
   a key associated with a crypto algorithm (such as MD5).  The relevant
   subtrees and data nodes are as follows:

   *  /mpls-ldp/peers/authentication

   *  /mpls-ldp/peers/peer/authentication

   The actual authentication key data (whether locally specified or part
   of a key-chain) is sensitive and needs to be kept secret from
   unauthorized parties.  For key-chain based authentication, this model
   inherits the security considerations of [RFC8040] (that includes the
   considerations with respect to the local storage and handling of
   authentication keys).  A similar procedure for storage and access to
   direct key is warranted.

10.1.3.  RPC operations

   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 otherwise control
   plane flaps, network outages, and DoS attacks are possible.  The RPC
   operations are:

   *  mpls-ldp-clear-peer



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   *  mpls-ldp-clear-hello-adjacency

10.1.4.  Notifications

   The model describes several notifications.  The implementations must
   rate-limit the generation of these notifications to avoid creating
   significant notification load and possible side effects on the system
   stability.

11.  IANA Considerations

   This document requests the registration of the following URIs in the
   IETF "XML registry" [RFC3688]:

   +----------------------------------------------------+----------+---+
   | URI                                                |Registrant|XML|
   +====================================================+==========+===+
   | urn:ietf:params:xml:ns:yang:ietf-mpls-ldp          | The IESG |N/A|
   +----------------------------------------------------+----------+---+
   | urn:ietf:params:xml:ns:yang:ietf-mpls-ldp-extended | The IESG |N/A|
   +----------------------------------------------------+----------+---+

                               Table 1: URIs

   This document requests the registration of the following YANG modules
   in the "YANG Module Names" registry [RFC6020]:

   +----------------------+---------------------------+------+---------+
   | Name                 | Namespace                 |Prefix|Reference|
   +======================+===========================+======+=========+
   |ietf-mpls-ldp         |urn:ietf:params:xml:ns:yang| ldp  | This    |
   |                      |:ietf-mpls-ldp             |      | document|
   +----------------------+---------------------------+------+---------+
   |ietf-mpls-ldp-extended|urn:ietf:params:xml:ns:yang| ldp- | This    |
   |                      |:ietf-mpls-ldp-extended    | ext  | document|
   +----------------------+---------------------------+------+---------+

                           Table 2: YANG Modules

   -- RFC Editor: Replace "this document" with the document RFC number
   at time of publication, and remove this note.

12.  Acknowledgments

   The authors would like to acknowledge Eddie Chami, Nagendra Kumar,
   Mannan Venkatesan, and Pavan Beeram for their contribution to this
   document.




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   We also acknowledge Ladislav Lhotka, Jan Lindblad, Tom Petch,
   Yingzhen Qu, and Benjamin Kaduk for their detailed review of the
   model during WG and IESG.

13.  Contributors


   Danial Johari
   Cisco Systems
   Email: dajohari@cisco.com

   Loa Andersson
   Huawei Technologies
   Email: loa@pi.nu

   Jeff Tantsura
   Apstra
   Email: jefftant.ietf@gmail.com

   Matthew Bocci
   Nokia
   Email: matthew.bocci@nokia.com

   Reshad Rahman
   Cisco Systems
   Email: rrahman@cisco.com

   Stephane Litkowski
   Cisco Systems
   Email: slitkows@cisco.com


14.  Normative References

   [I-D.ietf-rtgwg-policy-model]
              Qu, Y., Tantsura, J., Lindem, A., and X. Liu, "A YANG Data
              Model for Routing Policy Management", Work in Progress,
              Internet-Draft, draft-ietf-rtgwg-policy-model-09, 4 March
              2020, <https://tools.ietf.org/html/draft-ietf-rtgwg-
              policy-model-09>.

   [RFC3478]  Leelanivas, M., Rekhter, Y., and R. Aggarwal, "Graceful
              Restart Mechanism for Label Distribution Protocol",
              RFC 3478, DOI 10.17487/RFC3478, February 2003,
              <https://www.rfc-editor.org/info/rfc3478>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,




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              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC5036]  Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
              "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
              October 2007, <https://www.rfc-editor.org/info/rfc5036>.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space",
              RFC 5331, DOI 10.17487/RFC5331, August 2008,
              <https://www.rfc-editor.org/info/rfc5331>.

   [RFC5443]  Jork, M., Atlas, A., and L. Fang, "LDP IGP
              Synchronization", RFC 5443, DOI 10.17487/RFC5443, March
              2009, <https://www.rfc-editor.org/info/rfc5443>.

   [RFC5561]  Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
              Le Roux, "LDP Capabilities", RFC 5561,
              DOI 10.17487/RFC5561, July 2009,
              <https://www.rfc-editor.org/info/rfc5561>.

   [RFC5918]  Asati, R., Minei, I., and B. Thomas, "Label Distribution
              Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class
              (FEC)", RFC 5918, DOI 10.17487/RFC5918, August 2010,
              <https://www.rfc-editor.org/info/rfc5918>.

   [RFC5919]  Asati, R., Mohapatra, P., Chen, E., and B. Thomas,
              "Signaling LDP Label Advertisement Completion", RFC 5919,
              DOI 10.17487/RFC5919, August 2010,
              <https://www.rfc-editor.org/info/rfc5919>.

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
              <https://www.rfc-editor.org/info/rfc5920>.

   [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>.



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   [RFC6389]  Aggarwal, R. and JL. Le Roux, "MPLS Upstream Label
              Assignment for LDP", RFC 6389, DOI 10.17487/RFC6389,
              November 2011, <https://www.rfc-editor.org/info/rfc6389>.

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

   [RFC7277]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 7277, DOI 10.17487/RFC7277, June 2014,
              <https://www.rfc-editor.org/info/rfc7277>.

   [RFC7552]  Asati, R., Pignataro, C., Raza, K., Manral, V., and R.
              Papneja, "Updates to LDP for IPv6", RFC 7552,
              DOI 10.17487/RFC7552, June 2015,
              <https://www.rfc-editor.org/info/rfc7552>.

   [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>.

   [RFC8177]  Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
              Zhang, "YANG Data Model for Key Chains", RFC 8177,
              DOI 10.17487/RFC8177, June 2017,
              <https://www.rfc-editor.org/info/rfc8177>.

   [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>.

   [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>.



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   [RFC8344]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 8344, DOI 10.17487/RFC8344, March 2018,
              <https://www.rfc-editor.org/info/rfc8344>.

   [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>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [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>.

   [RFC8529]  Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
              Liu, "YANG Data Model for Network Instances", RFC 8529,
              DOI 10.17487/RFC8529, March 2019,
              <https://www.rfc-editor.org/info/rfc8529>.

15.  Informative References

   [I-D.ietf-mpls-mldp-yang]
              Raza, K., Liu, X., Esale, S., Andersson, L., Tantsura, J.,
              and S. Krishnaswamy, "YANG Data Model for MPLS mLDP", Work
              in Progress, Internet-Draft, draft-ietf-mpls-mldp-yang-06,
              31 May 2019, <https://tools.ietf.org/html/draft-ietf-mpls-
              mldp-yang-06>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC7307]  Zhao, Q., Raza, K., Zhou, C., Fang, L., Li, L., and D.
              King, "LDP Extensions for Multi-Topology", RFC 7307,
              DOI 10.17487/RFC7307, July 2014,
              <https://www.rfc-editor.org/info/rfc7307>.

   [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>.

   [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>.



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Appendix A.  Data Tree Example

   This section contains an example of an instance data tree in the JSON
   encoding [RFC7951], containing both configuration and state data.

                     +---------------------+
                     |                     |
                     | Router 203.0.113.1  |
                     |                     |
                     +----------+----------+
                                |eth1
                                |2001:db8:0:1::1/64
                                |
                                |
                                |2001:db8:0:1::2/64
                     +----------+----------+
                     |                     |         |
                     |   Another Router    +---------| 2001:db8:0:2::/64
                     |                     |         |
                     +---------------------+

                        Figure 12: Example topology

   The configuration instance data tree for Router 203.0.113.1 in the
   above figure could be as follows:

   {
     "ietf-interfaces:interfaces": {
       "interface": [
         {
           "name": "eth1",
           "description": "An interface with LDP enabled.",
           "type": "iana-if-type:ethernetCsmacd",
           "ietf-ip:ipv6": {
             "address": [
               {
                 "ip": "2001:db8:0:1::1",
                 "prefix-length": 64
               }
             ],
             "forwarding": true
           }
         }
       ]
     },
     "ietf-routing:routing": {
       "router-id": "203.0.113.1",
       "control-plane-protocols": {



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         "control-plane-protocol": [
           {
             "type": "ietf-mpls-ldp:mpls-ldp",
             "name": "ldp-1",
             "ietf-mpls-ldp:mpls-ldp": {
               "global": {
                 "address-families": {
                   "ietf-mpls-ldp-extended:ipv6": {
                     "enabled": true,
                     "transport-address": "2001:db8:0:1::1"
                   }
                 }
               },
               "discovery": {
                 "interfaces": {
                   "interface": [
                     {
                       "name": "eth1",
                       "address-families": {
                         "ietf-mpls-ldp-extended:ipv6": {
                           "enabled": true
                         }
                       }
                     }
                   ]
                 }
               }
             }
           }
         ]
       }
     }
   }


               Figure 13: Example Configuration data in JSON

   The corresponding operational state data for Router 203.0.113.1 could
   be as follows:

   {
     "ietf-interfaces:interfaces": {
       "interface": [
         {
           "name": "eth1",
           "description": "An interface with LDP enabled.",
           "type": "iana-if-type:ethernetCsmacd",
           "phys-address": "00:00:5e:00:53:01",



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           "oper-status": "up",
           "statistics": {
             "discontinuity-time": "2018-09-10T15:16:27-05:00"
           },
           "ietf-ip:ipv6": {
             "forwarding": true,
             "mtu": 1500,
             "address": [
               {
                 "ip": "2001:db8:0:1::1",
                 "prefix-length": 64,
                 "origin": "static",
                 "status": "preferred"
               },
               {
                 "ip": "fe80::200:5eff:fe00:5301",
                 "prefix-length": 64,
                 "origin": "link-layer",
                 "status": "preferred"
               }
             ],
             "neighbor": [
               {
                 "ip": "2001:db8:0:1::2",
                 "link-layer-address": "00:00:5e:00:53:02",
                 "origin": "dynamic",
                 "is-router": [null],
                 "state": "reachable"
               },
               {
                 "ip": "fe80::200:5eff:fe00:5302",
                 "link-layer-address": "00:00:5e:00:53:02",
                 "origin": "dynamic",
                 "is-router": [null],
                 "state": "reachable"
               }
             ]
           }
         }
       ]
     },
     "ietf-routing:routing": {
       "router-id": "203.0.113.1",
       "interfaces": {
         "interface": [
           "eth1"
         ]
       },



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       "control-plane-protocols": {
         "control-plane-protocol": [
           {
             "type": "ietf-mpls-ldp:mpls-ldp",
             "name": "ldp-1",
             "ietf-mpls-ldp:mpls-ldp": {
               "global": {
                 "address-families": {
                   "ietf-mpls-ldp-extended:ipv6": {
                     "enabled": true,
                     "transport-address": "2001:db8:0:1::1"
                   }
                 }
               },
               "discovery": {
                 "interfaces": {
                   "interface": [
                     {
                       "name": "eth1",
                       "address-families": {
                         "ietf-mpls-ldp-extended:ipv6": {
                           "enabled": true,
                           "hello-adjacencies": {
                             "hello-adjacency": [
                               {
                                 "adjacent-address":
                                 "fe80::200:5eff:fe00:5302",
                                 "flag": ["adjacency-flag-active"],
                                 "hello-holdtime": {
                                   "adjacent": 15,
                                   "negotiated": 15,
                                   "remaining": 9
                                 },
                                 "next-hello": 3,
                                 "statistics": {
                                   "discontinuity-time":
                                   "2018-09-10T15:16:27-05:00"
                                 },
                                 "peer": {
                                   "lsr-id": "203.0.113.2",
                                   "label-space-id": 0
                                 }
                               }
                             ]
                           }
                         }
                       }
                     }



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                   ]
                 }
               },
               "peers": {
                 "peer": [
                   {
                     "lsr-id": "203.0.113.2",
                     "label-space-id": 0,
                     "label-advertisement-mode": {
                       "local": "downstream-unsolicited",
                       "peer": "downstream-unsolicited",
                       "negotiated": "downstream-unsolicited"
                     },
                     "next-keep-alive": 5,
                     "session-holdtime": {
                       "peer": 180,
                       "negotiated": 180,
                       "remaining": 78
                     },
                     "session-state": "operational",
                     "tcp-connection": {
                       "local-address": "fe80::200:5eff:fe00:5301",
                       "local-port": 646,
                       "remote-address": "fe80::200:5eff:fe00:5302",
                       "remote-port": 646
                     },
                     "up-time": 3438100,
                     "statistics": {
                       "discontinuity-time": "2018-09-10T15:16:27-05:00"
                     }
                   }
                 ]
               }
             }
           }
         ]
       }
     }
   }


                Figure 14: Example Operational data in JSON

Authors' Addresses

   Kamran Raza (editor)
   Cisco Systems




Raza, et al.            Expires September 21, 2020             [Page 92]


Internet-Draft        YANG Data Model for MPLS LDP            March 2020


   Canada
   Email: skraza@cisco.com


   Rajiv Asati
   Cisco Systems
   United States of America
   Email: rajiva@cisco.com


   Xufeng Liu
   Volta Networks
   United States of America
   Email: xufeng.liu.ietf@gmail.com


   Santosh Esale
   Juniper Networks
   United States of America
   Email: sesale@juniper.net


   Xia Chen
   Huawei Technologies
   China
   Email: jescia.chenxia@huawei.com


   Himanshu Shah
   Ciena Corporation
   United States of America
   Email: hshah@ciena.com













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