YANG Data Model for MPLS LDP and mLDP
draft-raza-mpls-ldp-mldp-yang-04

MPLS Working Group                                               K. Raza
Internet-Draft                                                 R. Rahman
Intended status: Standards Track                                R. Asati
Expires: April 21, 2016                              Cisco Systems, Inc.

                                                                  X. Liu
                                                             J. Tantsura
                                                                Ericsson

                                                                S. Esale
                                                        Juniper Networks

                                                                 X. Chen
                                                            L. Andersson
                                                     Huawei Technologies

                                                                 H. Shah
                                                       Ciena Corporation

                                                                M. Bocci
                                                          Alcatel-Lucent

                                                        October 19, 2015


                 YANG Data Model for MPLS LDP and mLDP
                    draft-raza-mpls-ldp-mldp-yang-02

Abstract

   This document describes a YANG data model for Multi-Protocol Label
   Switching (MPLS) Label Distribution Protocol (LDP) and Multipoint LDP
   (mLDP).

Status of This Memo

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

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   This Internet-Draft will expire on April 21, 2016.







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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   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
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   3
   3.  LDP YANG Model  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Configuration . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  Configuration Hierarchy . . . . . . . . . . . . . . .  11
       3.2.2.  All-VRFs Configuration  . . . . . . . . . . . . . . .  14
     3.3.  Operational State . . . . . . . . . . . . . . . . . . . .  14
     3.4.  Notifications . . . . . . . . . . . . . . . . . . . . . .  14
     3.5.  Actions . . . . . . . . . . . . . . . . . . . . . . . . .  15
   4.  mLDP YANG Model . . . . . . . . . . . . . . . . . . . . . . .  16
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.2.  Configuration . . . . . . . . . . . . . . . . . . . . . .  17
       4.2.1.  Configuration Hierarchy . . . . . . . . . . . . . . .  17
       4.2.2.  mldp container  . . . . . . . . . . . . . . . . . . .  19
       4.2.3.  Leveraging LDP containers . . . . . . . . . . . . . .  19
       4.2.4.  YANG tree . . . . . . . . . . . . . . . . . . . . . .  20
     4.3.  Operational State . . . . . . . . . . . . . . . . . . . .  23
     4.4.  Notifications . . . . . . . . . . . . . . . . . . . . . .  24
     4.5.  Actions . . . . . . . . . . . . . . . . . . . . . . . . .  24
   5.  YANG Specification  . . . . . . . . . . . . . . . . . . . . .  24
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  65
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  65
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  65
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  65
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  65
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  67
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  68
   Additional Contributors . . . . . . . . . . . . . . . . . . . . .  69




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1.  Introduction

   The Network Configuration Protocol (NETCONF) [RFC6241] is a network
   management protocol that defines mechanisms to manage network
   devices.  YANG [RFC6020] 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] and Multipoint LDP (mLDP)
   [RFC6388].  For LDP, it also covers LDP IPv6 [RFC7552] and LDP
   capabilities [RFC5561].

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

   o  Configuration

   o  Operational State

   o  Executables (Actions)

   o  Notifications

   Given mLDP tight coupling with LDP, mLDP model is defined under LDP
   tree.  The document is organized to first define the data model for
   the configuration, operational state, actions and notifications of
   LDP, followed by mLDP model in the same order.

2.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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

3.  LDP YANG Model

3.1.  Overview

   The LDP/mLDP Yang model is defined under "ietf-mpls-ldp" module and
   augments "mpls" list in ietf-mpls module [I-D.saad-mpls-static-yang]
   with LDP and mLDP specific parameters.

   There are four main containers in LDP module as follows:



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   o  Read-Write parameters (for configuration)

   o  Read-only parameters (for operational state)

   o  Notifications (for events)

   o  RPCs (for executing commands to perform some action)

   For the configuration and state data, this model uses follows the
   approach described in [I-D.openconfig-netmod-opstate] to represent
   the configuration (intended state) and operational (applied and
   derived) state.  This means that for each configuration leaf, there
   is an associated "state" leaf to represent the applied state.
   However, any (derived) state resulting from the configuration is kept
   under a separate "state" tree that augments MPLS routing-state tree.
   Before going into data model details, it is important to take note of
   the following points:

   o  This module aims to address only the core LDP/mLDP parameters as
      per RFC specification, as well as some widely used and deployed
      non-RFC features.  Any vendor specific feature should be defined
      in a vendor-specific augmentation of this model.

   o  Multi-topology LDP [RFC7307] and Multi-topology mLDP
      [I-D.iwijnand-mpls-mldp-multi-topology] are beyond the scope of
      this document.

   o  This module does not cover any applications running on top of LDP
      and mLDP, nor does it cover any OAM procedures for LDP and mLDP.

   o  This model is a VPN Forwarding and Routing (VRF)-centric model and
      hence falls under an MPLS routing-instance.  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.

   o  A "routing-instance" refers to a VRF instance within the scope of
      this model.

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

   o  This model assumes platform-wide label space (i.e. label space Id
      of zero).






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   o  The label and neighbor policies and filters are typically defined
      using a prefix-list.  The prefix-list is referenced from routing-
      policy model as defined in [I-D.shaikh-rtgwg-policy-model].

   o  The use of grouping (templates) for bundling and grouping the
      configuration items is not employed in current revision, and is a
      subject for consideration in future.

   A graphical representation of LDP YANG data model is presented in
   Figure 2, Figure 4, Figure 5, and Figure 6.  Whereas, the actual
   model definition in YANG is captured in Section 5.

3.2.  Configuration

   This specification defines the configuration parameters for base LDP
   as defined 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 specification supports VRF-centric configuration.  For
   implementations that support protocol-centric configuration, with
   provision for inheritance and items that apply to all vrfs, we
   recommend an augmentation of this model such that any protocol-
   centric or all-vrf configuration is defined under their designated
   containers within the standard routing-instance (please see section
   Section 3.2.2)

   This model augments MPLS configuration as defined in MPLS base
   specification [I-D.saad-mpls-static-yang].  For LDP interfaces, this
   model still uses its own container and leaf, and is subject to
   alignment in future once MPLS interface model is solidified in MPLS
   base specification.  Furthermore, as mentioned earlier, the
   configuration tree presents read-write intended configuration leave/
   items as well as read-only state of the applied configuration.  The
   former is listed under "config" container and latter under "state"
   container.

   Following is high-level configuration tree for LDP/mLDP:











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   module: ietf-mpls-ldp
      +-- routing
       +-- routing-instance [name]
        +-- mpls
             +-- mpls-ldp
                .
                .

                                 Figure 1

   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 parent.  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 on
   any child level.

   Following is a simplified graphical representation of the data model
   for LDP configuration, along with its applied state.


module: ietf-mpls-ldp
augment /rt:routing/rt:routing-instance/mpls:mpls:
   +--rw mpls-ldp!
      +--rw global
      |  +--rw config
      |  |  +--rw capability
      |  |  |  +--rw end-of-lib {capability-end-of-lib}?
      |  |  |  |  +--rw enable?   boolean
      |  |  |  +--rw typed-wildcard-fec {capability-typed-wildcard-fec}?
      |  |  |  |  +--rw enable?   boolean
      |  |  |  +--rw upstream-label-assignment {capability-upstream-label-assignment}?
      |  |  |  |  +--rw enable?   boolean
      |  |  +--rw graceful-restart
      |  |  |  +--rw enable?                boolean
      |  |  |  +--rw helper-enable?         boolean {graceful-restart-helper-mode}?
      |  |  |  +--rw reconnect-time?        uint16
      |  |  |  +--rw recovery-time?         uint16
      |  |  |  +--rw forwarding-holdtime?   uint16
      |  |  +--rw igp-synchronization-delay?   uint16
      |  |  +--rw lsr-id?                      yang:dotted-quad
      |  |  +--rw nonstop-routing?             boolean
      |  +--ro state
      |     +--ro capability
      |     |  +--ro end-of-lib {capability-end-of-lib}?
      |     |  |  +--ro enable?   boolean
      |     |  +--ro typed-wildcard-fec {capability-typed-wildcard-fec}?
      |     |  |  +--ro enable?   boolean



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      |     |  +--ro upstream-label-assignment {capability-upstream-label-assignment}?
      |     |     +--ro enable?   boolean
      |     +--ro graceful-restart
      |     |  +--ro enable?                boolean
      |     |  +--ro helper-enable?         boolean {graceful-restart-helper-mode}?
      |     |  +--ro reconnect-time?        uint16
      |     |  +--ro recovery-time?         uint16
      |     |  +--ro forwarding-holdtime?   uint16
      |     +--ro igp-synchronization-delay?   uint16
      |     +--ro lsr-id?                      yang:dotted-quad
      |     +--ro nonstop-routing?             boolean
      +--rw address-family* [af]
      |  +--rw af        address-family-type
      |  +--rw config
      |  |  +--rw enable?         boolean
      |  |  +--rw label-policy
      |  |  |  +--rw independent-mode
      |  |  |  |  +--rw assign {policy-label-assignment-config}?
      |  |  |  |  |  +--rw (prefix-option)?
      |  |  |  |  |     +--:(prefix-list)
      |  |  |  |  |     |  +--rw prefix-list?        prefix-list-ref
      |  |  |  |  |     +--:(host-routes-only)
      |  |  |  |  |        +--rw host-routes-only?   boolean
      |  |  |  |  +--rw advertise
      |  |  |  |  |  +--rw explicit-null!
      |  |  |  |  |  |  +--rw prefix-list?   prefix-list-ref
      |  |  |  |  |  +--rw prefix-list?     prefix-list-ref
      |  |  |  |  +--rw accept
      |  |  |  |     +--rw prefix-list?   prefix-list-ref
      |  |  |  +--rw ordered-mode {policy-ordered-label-config}?
      |  |  |     +--rw egress-lsr
      |  |  |     |  +--rw prefix-list?   prefix-list-ref
      |  |  |     +--rw advertise
      |  |  |     |  +--rw prefix-list?   prefix-list-ref
      |  |  |     +--rw accept
      |  |  |        +--rw prefix-list?   prefix-list-ref
      |  |  +--rw ipv4
      |  |  |  +--rw transport-address?   inet:ipv4-address
      |  |  +--rw ipv6
      |  |     +--rw transport-address?   inet:ipv6-address
      |  +--ro state
      |     +--ro enable?         boolean
      |     +--ro label-policy
      |     |  +--ro independent-mode
      |     |  |  +--ro assign {policy-label-assignment-config}?
      |     |  |  |  +--ro (prefix-option)?
      |     |  |  |     +--:(prefix-list)
      |     |  |  |     |  +--ro prefix-list?        prefix-list-ref



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      |     |  |  |     +--:(host-routes-only)
      |     |  |  |        +--ro host-routes-only?   boolean
      |     |  |  +--ro advertise
      |     |  |  |  +--ro explicit-null!
      |     |  |  |  |  +--ro prefix-list?   prefix-list-ref
      |     |  |  |  +--ro prefix-list?     prefix-list-ref
      |     |  |  +--ro accept
      |     |  |     +--ro prefix-list?   prefix-list-ref
      |     |  +--ro ordered-mode {policy-ordered-label-config}?
      |     |     +--ro egress-lsr
      |     |     |  +--ro prefix-list?   prefix-list-ref
      |     |     +--ro advertise
      |     |     |  +--ro prefix-list?   prefix-list-ref
      |     |     +--ro accept
      |     |        +--ro prefix-list?   prefix-list-ref
      |     +--ro ipv4
      |     |  +--ro transport-address?   inet:ipv4-address
      |     +--ro ipv6
      |        +--ro transport-address?   inet:ipv6-address
      +--rw discovery
      |  +--rw interfaces
      |  |  +--rw config
      |  |  |  +--rw hello-holdtime?   uint16
      |  |  |  +--rw hello-interval?   uint16
      |  |  +--ro state
      |  |  |  +--ro hello-holdtime?   uint16
      |  |  |  +--ro hello-interval?   uint16
      |  |  +--rw interface* [interface]
      |  |     +--rw interface         if:interface-ref
      |  |     +--rw config
      |  |     |  +--rw hello-holdtime?              uint16
      |  |     |  +--rw hello-interval?              uint16
      |  |     |  +--rw igp-synchronization-delay?   uint16 {per-interface-timer-config}?
      |  |     +--ro state
      |  |     |  +--ro hello-holdtime?              uint16
      |  |     |  +--ro hello-interval?              uint16
      |  |     |  +--ro igp-synchronization-delay?   uint16 {per-interface-timer-config}?
      |  |     +--rw address-family* [af]
      |  |        +--rw af        address-family-type
      |  |        +--rw config
      |  |        |  +--rw enable?   boolean
      |  |        |  +--rw ipv4
      |  |        |  |  +--rw transport-address?   union
      |  |        |  +--rw ipv6
      |  |        |     +--rw transport-address?   union
      |  |        +--ro state
      |  |           +--ro enable?   boolean
      |  |           +--ro ipv4



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      |  |           |  +--ro transport-address?   union
      |  |           +--ro ipv6
      |  |              +--ro transport-address?   union
      |  +--rw targeted
      |     +--rw config
      |     |  +--rw hello-holdtime?   uint16
      |     |  +--rw hello-interval?   uint16
      |     |  +--rw hello-accept {policy-extended-discovery-config}?
      |     |     +--rw enable?      boolean
      |     |     +--rw peer-list?   peer-list-ref
      |     +--ro state
      |     |  +--ro hello-holdtime?   uint16
      |     |  +--ro hello-interval?   uint16
      |     |  +--ro hello-accept {policy-extended-discovery-config}?
      |     |     +--ro enable?      boolean
      |     |     +--ro peer-list?   peer-list-ref
      |     +--rw address-family
      |        +--rw ipv4
      |        |  +--rw target* [address]
      |        |     +--rw address    inet:ipv4-address
      |        |     +--rw config
      |        |     |  +--rw enable?   boolean
      |        |     +--ro state
      |        |        +--ro enable?   boolean
      |        +--rw ipv6
      |           +--rw target* [address]
      |              +--rw address    inet:ipv6-address
      |              +--rw config
      |              |  +--rw enable?   boolean
      |              +--ro state
      |                 +--ro enable?   boolean
      +--rw forwarding-nexthop {forwarding-nexthop-config}?
      |  +--rw interfaces
      |     +--rw interface* [interface]
      |        +--rw interface         if:interface-ref
      |        +--rw address-family* [af]
      |           +--rw af        address-family-type
      |           +--rw config
      |           |  +--rw ldp-disable?    boolean
      |           +--ro state
      |              +--ro ldp-disable?    boolean
      +--rw neighbors
         +--rw config
         |  +--rw md5-password?                   string
         |  +--rw session-ka-holdtime?            uint16
         |  +--rw session-ka-interval?            uint16
         |  +--rw session-downstream-on-demand {session-downstream-on-demand-config}?
         |  |  +--rw enable?      boolean



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         |  |  +--rw peer-list?   peer-list-ref
         |  +--rw session-protection {session-protection}?
         |     +--rw enable?      boolean
         |     +--rw duration?    union
         |     +--rw peer-list?   peer-list-ref
         +--ro state
         |  +--ro md5-password?                   string
         |  +--ro session-ka-holdtime?            uint16
         |  +--ro session-ka-interval?            uint16
         |  +--ro session-downstream-on-demand {session-downstream-on-demand-config}?
         |  |  +--ro enable?      boolean
         |  |  +--ro peer-list?   peer-list-ref
         |  +--ro session-protection {session-protection}?
         |     +--ro enable?      boolean
         |     +--ro duration?    union
         |     +--ro peer-list?   peer-list-ref
         +--rw neighbor* [lsr-id]
            +--rw lsr-id    union
            +--rw config
            |  +--rw admin-down?            boolean
            |  +--rw capability
            |  +--rw md5-password?          string
            |  +--rw graceful-restart
            |  |  +--rw enable?           boolean
            |  |  +--rw reconnect-time?   uint16
            |  |  +--rw recovery-time?    uint16
            |  +--rw session-ka-holdtime?   uint16
            |  +--rw session-ka-interval?   uint16
            |  +--rw session-protection {session-protection}?
            |  |  +--rw enable?     boolean
            |  |  +--rw duration?   union
            |  +--rw address-family
            |     +--rw ipv4
            |     |  +--rw label-policy
            |     |     +--rw advertise
            |     |     |  +--rw prefix-list?   prefix-list-ref
            |     |     +--rw accept
            |     |        +--rw prefix-list?   prefix-list-ref
            |     +--rw ipv6
            |        +--rw label-policy
            |           +--rw advertise
            |           |  +--rw prefix-list?   prefix-list-ref
            |           +--rw accept
            |              +--rw prefix-list?   prefix-list-ref
            +--ro state
               +--ro admin-down?            boolean
               +--ro capability
               +--ro md5-password?          string



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               +--ro graceful-restart
               |  +--ro enable?           boolean
               |  +--ro reconnect-time?   uint16
               |  +--ro recovery-time?    uint16
               +--ro session-ka-holdtime?   uint16
               +--ro session-ka-interval?   uint16
               +--ro session-protection {session-protection}?
               |  +--ro enable?     boolean
               |  +--ro duration?   union
               +--ro address-family
                  +--ro ipv4
                  |  +--ro label-policy
                  |     +--ro advertise
                  |     |  +--ro prefix-list?   prefix-list-ref
                  |     +--ro accept
                  |        +--ro prefix-list?   prefix-list-ref
                  +--ro ipv6
                     +--ro label-policy
                        +--ro advertise
                        |  +--ro prefix-list?   prefix-list-ref
                        +--ro accept
                           +--ro prefix-list?   prefix-list-ref


                                 Figure 2

3.2.1.  Configuration Hierarchy

   The LDP configuration container is logically divided into following
   high-level config areas:





















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      Per-VRF parameters
          o Global parameters
          o Per-address-family parameters
          o LDP Capabilities parameters
          o Hello Discovery parameters
              - interfaces
                 - Per-interface:
                    Global
                    Per-address-family
              - targeted
                 - Per-target
         o Neighbor parameters
              - Global
              - Per-neighbor
                 Per-address-family
                 Capabilities parameters
         o Forwarding parameters

                                 Figure 3

   Following subsections briefly explain these configuration areas.

3.2.1.1.  Per-VRF parameters

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

3.2.1.1.1.  Per-VRF 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.

3.2.1.1.2.  Per-VRF Capabilities parameters

   This container falls under 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 neighbors
   in the given VRF instance.  There is also a per-neighbor level
   capability container that is provided to override a capability that
   is enabled/specified at VRF level.





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3.2.1.1.3.  Per-VRF 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 the AF, prefix-list based label
   policies, and LDP transport address.

3.2.1.1.4.  Per-VRF 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.

   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 former is interface hello timers, and example
   of latter is enabling hellos for a given AF under an interface.
   [TODO: Align with MPLS base interface model once MPLS base gets
   matured]

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

3.2.1.1.5.  Per-VRF Neighbor parameters

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

   Like per-interface parameters, some per-neighbor 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 former is
   per-neighbor password configuration, whereas the example of latter is
   prefix-list based label policies (inbound and outbound) that apply to
   a given neighbor.



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3.2.1.1.6.  Per-VRF 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.

3.2.2.  All-VRFs Configuration

   TODO.

3.3.  Operational State

   Operational state of LDP can be queried and obtained from this read-
   only container "mpls-ldp" which is augmented from "routing-state" of
   MPLS tree (/rt:routing-state/rt:routing-instance/mpls:mpls).

   Please note that "applied" state of a configuration item is already
   captured under configuration tree.  This state tree only refers to
   the "derived" state related to the protocol.

   Following is a simplified graphical representation of the data model
   for LDP derived operational state.


   module: ietf-mpls-ldp
   augment /rt:routing-state/rt:routing-instance/mpls:mpls:
      +--ro mpls-ldp
         +-- ...
         +-- ...

   [Ed note: TODO (later revision)]

                                 Figure 4

3.4.  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 neighbor, 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 with outgoing label.





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   Following is a simplified graphical representation of the data model
   for LDP notifications.


   module: ietf-mpls-ldp
   notifications:
      +---n mpls-ldp-neighbor-event
      |  +--ro event-type?             oper-status-event-type
      |  +--ro routing-instance-ref?   rt:routing-instance-ref
      |  +--ro neighbor-ref?           leafref
      +---n mpls-ldp-adjacency-event
      |  +--ro event-type?             oper-status-event-type
      |  +--ro routing-instance-ref?   rt:routing-instance-ref
      |  +--ro (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 routing-instance-ref?   rt:routing-instance-ref
         +--ro prefix?                 inet:ip-prefix


                                 Figure 5

3.5.  Actions

   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 neighbors, 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 of a given type, or clear a
   specific entity.

   Following is a simplified graphical representation of the data model
   for LDP actions.











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   module: ietf-mpls-ldp
   rpcs:
      +---x mpls-ldp-clear-neighbor
      |  +---w input
      |     +---w routing-instance-ref?   rt:routing-instance-ref
      |     +---w lsr-id?                 union
      +---x mpls-ldp-clear-adjacency
      |  +---w input
      |     +---w routing-instance-ref?   rt:routing-instance-ref
      |     +---w adjacency
      |        +---w (adjacency-type)?
      |           +--:(targeted)
      |           |  +---w targeted!
      |           |     +---w target-address?   inet:ip-address
      |           +--:(link)
      |              +---w link!
      |                 +---w next-hop-interface?   if:interface-ref
      |                 +---w next-hop-address?     inet:ip-address
      +---x mpls-ldp-clear-neighbor-statistics
         +---w input
            +---w routing-instance-ref?   rt:routing-instance-ref
            +---w lsr-id?                 union


                                 Figure 6

4.  mLDP YANG Model

4.1.  Overview

   Due to tight dependency of mLDP on LDP, mLDP model builds on top of
   LDP model defined earlier in the document.  Following are the main
   mLDP areas and documents that are within the scope of this model:

   o  mLDP Base Specification [RFC6388]

   o  mLDP Recursive FEC [RFC6512]

   o  Targeted mLDP [RFC7060]

   o  mLDP Fast-Reroute (FRR)

      *  Node Protection [I-D.ietf-mpls-mldp-node-protection]

      *  Multicast-only

   o  Hub-and-Spoke Multipoint LSPs [RFC7140]




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   o  mLDP Inband Signaling [RFC6826] (future revision)

   o  mLDP Inband Signaling with Wildcards [RFC7438] (future revision)

   o  Configured Leaf LSPs (manually provisioned)

   [Ed Note: Some of the topics in the above list are to be addressed/
   added in later revision of this document].

4.2.  Configuration

4.2.1.  Configuration Hierarchy

   In terms of overall configuration layout, following figure highlights
   extensions to LDP configuration model to incorporate mLDP:




































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      +-- mpls-ldp
         +-- ...
         +-- ...
         +-- mldp
         |  +-- ...
         |  +-- ...
         |  +-- address-family* [af]
         |     +-- af
         |        +-- ...
         |        +-- ...
         +-- global
         |  +-- ...
         |  +-- capability
         |     +-- ...
         |     +-- ...
         |     +-- mldp
         |        +-- ...
         |        +-- ...
         +-- discovery
         |  +-- ...
         |  +-- ...
         +-- forwarding-nexthop
         |  +-- interfaces
         |     +-- interface* [interface]
         |        +-- interface
         |        +-- address-family* [af]
         |           +-- af
         |           +-- ...
         |           +-- mldp-disable
         +-- neighbors
            +-- ...
            +-- ...
            +-- neighbor* [lsr-id]
                +-- ...
                +-- ...
                +-- capability
                    +-- ...
                    +-- ...
                    +-- mldp
                        +-- ...
                        +-- ...

                                 Figure 7

   From above hierarchy, we can categorize mLDP configuration parameters
   into two types:

   o  Parameters that leverage/extend LDP containers and parameters



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   o  Parameters that are mLDP specific

   Following subsections first describe mLDP specific configuration
   parameters, followed by those leveraging LDP.

4.2.2.  mldp container

   mldp container resides directly under "mpls-ldp" and holds the
   configuration related to items that are mLDP specific.  The main
   items under this container are:

   o  mLDP enabling: To enable mLDP under a (VRF) routing instance, mldp
      container is enabled under LDP.  Given that mLDP requires LDP
      signalling, it is not sensible to allow disabling LDP control
      plane under a (VRF) routing-instance while requiring mLDP to be
      enabled for the same.  However, if a user wishes only to allow
      signalling for multipoint FECs on an LDP/mLDP enabled VRF
      instance, he/she can use LDP label-policies to disable unicast
      FECs under the VRF.

   o  mLDP per-AF features: mLDP manages its own list of IP address-
      families and the features enabled underneath.  The per-AF mLDP
      configuration items include:

      *  Multicast-only FRR: This enables Multicast-only FRR
         functionality for a given AF under mLDP.  The feature allows
         route-policy to be configured for finer control/applicability
         of the feature.

      *  Recursive FEC: The recursive-fec feature [RFC6512] can be
         enabled per AF with a route-policy.

      *  Configured Leaf LSPs: To provision multipoint leaf LSP
         manually, a container is provided per-AF under LDP.  The
         configuration is flexible and allows a user to specify MP LSPs
         of type p2mp or mp2mp with IPv4 or IPv6 root address(es) by
         using either LSP-Id or (S,G).

   Targeted mLDP feature specification [RFC7060] do not require any mLDP
   specific configuration.  It, however, requires LDP upstream-label-
   assignment capability to be enabled.

4.2.3.  Leveraging LDP containers

   mLDP configuration model leverages following configuration areas and
   containers that are already defined for LDP:





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   o  Capabilities: A new container "mldp" is defined under Capabilities
      container.  This new container specifies any mLDP specific
      capabilities and their parameters.  Moreover, a new "mldp"
      container is also added under per-neighbor capability container to
      override/control mLDP specific capabilities on a neighbor level.
      In the scope of this document, the most important capabilities
      related to mLDP are p2mp, mp2mp, make-before-break, hub-and-spoke,
      and node-protection.

   o  Discovery and Neighbor: mLDP requires LDP discovery and neighbor
      procedures to form mLDP peering.  A neighbor is treated as mLDP
      neighbor only when either P2MP or MP2MP capabilities have been
      successfully exchanged with the peer.  If a user wish to
      selectively enable or disable mLDP with a mLDP-enabled peer, he/
      she may use per-neighbor mLDP capabilities configuration.  [Ed
      Note: The option to control mLDP enabling/disabling on a neighbor-
      list is being explored for future ].  In most common deployments,
      it is desirable to disable mLDP (capabilities announcements) on a
      targeted-only LDP session, where targeted-only session is the one
      whose discovery sources are targeted only.  In future revision, a
      configuration option for this support will also be provided.

   o  Forwarding: By default, mLDP is allowed to select any of the LDP
      enabled interface as a downstream interface towards a nexthop
      (LDP/mLDP peer) for MP LSP programming.  However, a configuration
      option is provided to allow mLDP to exclude a given interface from
      such a selection.  Note that such a configuration option will be
      useful only when there are more than one interfaces available for
      the downstream selection.

   This goes without saying that mLDP configuration tree follows the
   same approach as LDP, where the tree comprise leafs for intended
   configuration as well their applied state.

4.2.4.  YANG tree

   The following figure captures the YANG tree for mLDP configuration.
   The figure has been simplified to display only mLDP items and not LDP
   items to keep the focus.


module: ietf-mpls-ldp
augment /rt:routing/rt:routing-instance/mpls:mpls:
   +--rw mpls-ldp!
      +--rw global
      |  +--rw config
      |  |  +--rw capability
      |  |     +--rw mldp {mldp}?



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      |  |        +--rw p2mp
      |  |        |  +--rw enable?   boolean
      |  |        +--rw mp2mp
      |  |        |  +--rw enable?   boolean
      |  |        +--rw make-before-break
      |  |        |  +--rw enable?             boolean
      |  |        |  +--rw switchover-delay?   uint16
      |  |        |  +--rw timeout?            uint16
      |  |        +--rw hub-and-spoke {capability-mldp-hsmp}?
      |  |        |  +--rw enable?   boolean
      |  |        +--rw node-protection {capability-mldp-node-protection}?
      |  |           +--rw plr?           boolean
      |  |           +--rw merge-point
      |  |              +--rw enable?                            boolean
      |  |              +--rw targeted-session-teardown-delay?   uint16
      |  +--ro state
      |     +--ro capability
      |        +--ro mldp {mldp}?
      |           +--ro p2mp
      |           |  +--ro enable?   boolean
      |           +--ro mp2mp
      |           |  +--ro enable?   boolean
      |           +--ro make-before-break
      |           |  +--ro enable?             boolean
      |           |  +--ro switchover-delay?   uint16
      |           |  +--ro timeout?            uint16
      |           +--ro hub-and-spoke {capability-mldp-hsmp}?
      |           |  +--ro enable?   boolean
      |           +--ro node-protection {capability-mldp-node-protection}?
      |              +--ro plr?           boolean
      |              +--ro merge-point
      |                 +--ro enable?                            boolean
      |                 +--ro targeted-session-teardown-delay?   uint16
      +--rw mldp {mldp}?
      |  +--rw config
      |  |  +--rw enable?   boolean
      |  +--ro state
      |  |  +--ro enable?   boolean
      |  +--rw address-family* [af]
      |     +--rw af                      address-family-type
      |     +--rw config
      |     |  +--rw multicast-only-frr {mldp-mofrr}?
      |     |  |  +--rw prefix-list?   prefix-list-ref
      |     |  +--rw recursive-fec
      |     |     +--rw prefix-list?   prefix-list-ref
      |     +--ro state
      |     |  +--ro multicast-only-frr {mldp-mofrr}?
      |     |  |  +--ro prefix-list?   prefix-list-ref



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      |     |  +--ro recursive-fec
      |     |     +--ro prefix-list?   prefix-list-ref
      |     +--rw configured-leaf-lsps
      |        +--rw p2mp
      |        |  +--rw roots-ipv4
      |        |  |  +--rw root* [root-addr]
      |        |  |     +--rw root-addr    inet:ipv4-address
      |        |  |     +--rw lsp* [lsp-id source-addr group-addr]
      |        |  |        +--rw lsp-id         uint16
      |        |  |        +--rw source-addr    inet:ipv4-address-no-zone
      |        |  |        +--rw group-addr     inet:ipv4-address-no-zone
      |        |  +--rw roots-ipv6
      |        |     +--rw root* [root-addr]
      |        |        +--rw root-addr    inet:ipv6-address
      |        |        +--rw lsp* [lsp-id source-addr group-addr]
      |        |           +--rw lsp-id         uint16
      |        |           +--rw source-addr    inet:ipv6-address-no-zone
      |        |           +--rw group-addr     inet:ipv6-address-no-zone
      |        +--rw mp2mp
      |           +--rw roots-ipv4
      |           |  +--rw root* [root-addr]
      |           |     +--rw root-addr    inet:ipv4-address
      |           |     +--rw lsp* [lsp-id source-addr group-addr]
      |           |        +--rw lsp-id         uint16
      |           |        +--rw source-addr    inet:ipv4-address-no-zone
      |           |        +--rw group-addr     inet:ipv4-address-no-zone
      |           +--rw roots-ipv6
      |              +--rw root* [root-addr]
      |                 +--rw root-addr    inet:ipv6-address
      |                 +--rw lsp* [lsp-id source-addr group-addr]
      |                    +--rw lsp-id         uint16
      |                    +--rw source-addr    inet:ipv6-address-no-zone
      |                    +--rw group-addr     inet:ipv6-address-no-zone
      +--rw forwarding-nexthop {forwarding-nexthop-config}?
      |  +--rw interfaces
      |     +--rw interface* [interface]
      |        +--rw interface         if:interface-ref
      |        +--rw address-family* [af]
      |           +--rw af        address-family-type
      |           +--rw config
      |           |  +--rw mldp-disable?   boolean {mldp}?
      |           +--ro state
      |              +--ro mldp-disable?   boolean {mldp}?
      +--rw neighbors
         +--rw neighbor* [lsr-id]
            +--rw lsr-id    union
            +--rw config
            |  +--rw capability



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            |     +--rw mldp {mldp}?
            |        +--rw p2mp
            |        |  +--rw enable?   boolean
            |        +--rw mp2mp
            |        |  +--rw enable?   boolean
            |        +--rw make-before-break
            |        |  +--rw enable?             boolean
            |        |  +--rw switchover-delay?   uint16
            |        |  +--rw timeout?            uint16
            |        +--rw hub-and-spoke {capability-mldp-hsmp}?
            |        |  +--rw enable?   boolean
            |        +--rw node-protection {capability-mldp-node-protection}?
            |           +--rw plr?           boolean
            |           +--rw merge-point
            |              +--rw enable?                            boolean
            |              +--rw targeted-session-teardown-delay?   uint16
            +--ro state
               +--ro capability
                  +--ro mldp {mldp}?
                     +--ro p2mp
                     |  +--ro enable?   boolean
                     +--ro mp2mp
                     |  +--ro enable?   boolean
                     +--ro make-before-break
                     |  +--ro enable?             boolean
                     |  +--ro switchover-delay?   uint16
                     |  +--ro timeout?            uint16
                     +--ro hub-and-spoke {capability-mldp-hsmp}?
                     |  +--ro enable?   boolean
                     +--ro node-protection {capability-mldp-node-protection}?
                        +--ro plr?           boolean
                        +--ro merge-point
                           +--ro enable?                            boolean
                           +--ro targeted-session-teardown-delay?   uint16


                                 Figure 8

4.3.  Operational State

   Operational state of mLDP can be queried and obtained from this read-
   only container "mldp" which resides under mpls-ldp container.  Please
   note that "applied" state of an mLDP configuration item is already
   captured under mldp configuration tree.  This mldp state tree only
   refers to the "derived" state related to mLDP protocol.

   Following is a simplified graphical representation of the data model
   for mLDP derived operational state.



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   module: ietf-mpls-ldp
   augment /rt:routing-state/rt:routing-instance/mpls:mpls:
      +--ro mpls-ldp
         +-- ro mldp
             +-- ...

             [Ed note: TODO (later revision)]



                                 Figure 9

4.4.  Notifications

   mLDP notification module consists of notification related to changes
   in the operational state of an mLDP FEC.  Following is a simplified
   graphical representation of the data model for mLDP notifications:


   module: ietf-mpls-ldp
   notifications:
      +---n mpls-mldp-fec-event
         +--ro event-type?             oper-status-event-type
         +--ro routing-instance-ref?   rt:routing-instance-ref
         +--ro tree-type?              multipoint-type
         +--ro root?                   inet:ip-address
         +--ro (lsp-key-type)?
            +--:(lsp-id-based)
            |  +--ro lsp-id?                 uint16
            +--:(source-group-based)
               +--ro source-addr?            inet:ip-address
               +--ro group-addr?             inet:ip-address


                                 Figure 10

4.5.  Actions

   Currently, no RPCs/actions are defined for mLDP.

5.  YANG Specification

   Following are actual YANG definition for LDP and mLDP constructs
   defined earlier in the document.



   <CODE BEGINS> file "ietf-mpls-ldp@2015-10-19.yang" -->



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   module ietf-mpls-ldp {
     namespace "urn:ietf:params:xml:ns:yang:ietf-mpls-ldp";
     // replace with IANA namespace when assigned
     prefix ldp;

     import ietf-inet-types {
       prefix "inet";
     }

     import ietf-yang-types {
       prefix "yang";
     }

     import ietf-interfaces {
       prefix "if";
     }

     import ietf-ip {
       prefix "ip";
     }

     import ietf-routing {
       prefix "rt";
     }

     import ietf-mpls {
       prefix "mpls";
     }

     import routing-policy {
       prefix "rpl";
     }

     organization "TBD";
     contact "TBD";
     description
       "";

     revision 2015-10-19 {
       description
         "Initial revision.";
       reference
         "";
     }

     /*
      * Features
      */



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     feature admin-down-config {
       description
         "This feature indicates that the system allows to configure
          administrative down on a VRF instance and a neighbor.";
     }

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

     feature capability-mldp-hsmp {
       description
         "This feature indicates that the system allows to configure
          mLDP hub-and-spoke-multipoint capability.";
     }

     feature capability-mldp-node-protection {
       description
         "This feature indicates that the system allows to configure
          mLDP node-protection 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 global-session-authentication {
       description
         "This feature indicates that the system allows to configure
          authentication at global level.";
     }




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     feature graceful-restart-helper-mode {
       description
         "This feature indicates that the system supports graceful
          restart helper mode.";
     }

     feature mldp {
       description
         "This feature indicates that the system supports Multicast
          LDP (mLDP).";
     }

     feature mldp-mofrr {
       description
         "This feature indicates that the system supports mLDP
          Multicast only FRR (MoFRR).";
     }

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

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

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

     feature policy-label-assignment-config {
       description
         "This feature indicates that the system allows to configure
          policies to assign labels according to certain prefixes.";
     }



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

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

     feature session-protection {
       description
         "This feature indicates that the system supports session
          protection";
     }

     /*
      * Typedefs
      */
     typedef address-family-type {
       type enumeration {
         enum ipv4 {
           description "IPv4";
         }
         enum ipv6 {
           description "IPv6";
         }
       }
       description
         "Address family type.";
     }

     typedef multipoint-type {
       type enumeration {
         enum p2mp {
           description "Point to multipoint.";
         }
         enum mp2mp {
           description "Multipoint to multipoint.";
         }
       }
       description
         "p2mp or mp2mp.";
     }

     typedef peer-list-ref {



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       type leafref {
         path "/rpl:routing-policy/rpl:defined-sets/rpl:neighbor-sets/"
           + "rpl:neighbor-set/rpl:neighbor-set-name";
       }
       description
         "A type for a reference to a peer list.";
     }

     typedef prefix-list-ref {
       type leafref {
         path "/rpl:routing-policy/rpl:defined-sets/rpl:prefix-sets/"
           + "rpl:prefix-set/rpl:prefix-set-name";
       }
       description
         "A type for a reference to a prefix list.";
     }

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

     /*
      * Identities
      */

     /*
      * Groupings
      */
     grouping ldp-instance-ref {
       description
         "An absolute reference to an LDP instance.";
       leaf routing-instance-ref {
         type rt:routing-instance-ref;
         description
           "Reference to the routing instance.";
       }



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     } // ldp-instance-ref

     grouping ldp-neighbor-ref {
       description
         "An absolute reference to an LDP neighbor.";
       uses ldp-instance-ref;
       leaf neighbor-ref {
         type leafref {
           path "/rt:routing/rt:routing-instance"
             + "[rt:name = current()/../routing-instance-ref]/"
             + "mpls:mpls/mpls-ldp/"
             + "neighbors/neighbor/lsr-id";
         }
         description
           "Reference to an LDP neighbor.";
       }
     } // ldp-neighbor-ref

     grouping ldp-adjacency-ref {
       description
         "An absolute reference to an LDP adjacency.";
       uses ldp-instance-ref;
       choice adjacency-type {
         description
           "Interface or targeted adjacency.";
         case targeted {
           container targeted {
             description "Targeted adjacency.";
             leaf target-address {
               type inet:ip-address;
               description
                 "The target address.";
             }
           } // targeted
         }
         case link {
           container link {
             description "Link adjacency.";
             leaf next-hop-interface {
               type if:interface-ref;
               description
                 "Interface connecting to next-hop.";
             }
             leaf next-hop-address {
               type inet:ip-address;
               must "../next-hop-interface" {
                 description
                   "Applicable when interface is specified.";



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               }
               description
                 "IP address of next-hop.";
             }
           } // link
         }
       }
     } // ldp-adjacency-ref

     grouping ldp-fec-event {
       description
         "A LDP FEC event.";
       uses ldp-instance-ref;
       leaf prefix {
         type inet:ip-prefix;
         description
           "FEC.";
       }
     } // ldp-fec-event

     grouping mldp-fec-event {
       description
         "A mLDP FEC event.";
       uses ldp-instance-ref;
       leaf tree-type {
         type multipoint-type;
         description
           "p2mp or mp2mp.";
       }
       leaf root {
         type inet:ip-address;
         description
           "Root address.";
       }
       choice lsp-key-type {
         description
           "LSP ID based or source-group based .";
         case lsp-id-based {
           leaf lsp-id {
             type uint16;
             description
               "ID to identify the LSP.";
           }
         }
         case source-group-based {
           leaf source-addr {
             type inet:ip-address;
             description



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               "LSP source address.";
           }
           leaf group-addr {
             type inet:ip-address;
             description
               "Multicast group address.";
           }
         } // case source-group-based
       }
     } // mldp-fec-event

     grouping basic-discovery-timers {
       description
         "Basic discovery timer attributes.";
       leaf hello-holdtime {
         type uint16 {
           range 15..3600;
         }
         units seconds;
         default 15;
         description
           "The time interval for which a LDP link Hello adjacency
            is maintained in the absence of link Hello messages from
            the LDP neighbor";
       }
       leaf hello-interval {
         type uint16 {
           range 5..1200;
         }
         units seconds;
         default 5;
         description
           "The interval between consecutive LDP link Hello messages
            used in basic LDP discovery";
       }
     } // basic-discovery-timers

     grouping extended-discovery-timers {
       description
         "Extended discovery timer attributes.";
       leaf hello-holdtime {
         type uint16 {
           range 15..3600;
         }
         units seconds;
         default 45;
         description
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            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.";
       }
     } // extended-discovery-timers

     grouping graceful-restart-attributes {
       description
         "Graceful restart configuration attributes.";
       container graceful-restart {
         description
           "Attributes for graceful restart.";
         leaf enable {
           type boolean;
           description
             "Enable or disable graceful restart.";
         }
         leaf helper-enable {
           if-feature graceful-restart-helper-mode;
           type boolean;
           description
             "Enable or disable graceful restart helper mode.";
         }
         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.";
         }
         leaf recovery-time {
           type uint16 {
             range 30..3600;
           }
           units seconds;
           description



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             "";
         }
         leaf forwarding-holdtime {
           type uint16 {
             range 30..3600;
           }
           units seconds;
           description
             "";
         }
       } // graceful-restart
     } // graceful-restart-attributes

     grouping graceful-restart-attributes-per-neighbor {
       description
         "Per neighbor graceful restart configuration attributes.";
       container graceful-restart {
         description
           "Attributes for graceful restart.";
         leaf enable {
           type boolean;
           description
             "Enable or disable graceful restart.";
         }
         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.";
         }
         leaf recovery-time {
           type uint16 {
             range 30..3600;
           }
           units seconds;
           description
             "";
         }
       } // graceful-restart
     } // graceful-restart-attributes-per-neighbor

     grouping neighbor-attributes {
       description "Neighbor configuration attributes.";




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       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
            neighbor.";
       }
       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.";
       }
     } // neighbor-attributes

     grouping session-protection-per-vrf {
       description "Session protection attributes.";
       container session-protection {
         if-feature session-protection;
         description
           "Session protection attributes.";
         leaf enable {
           type boolean;
           description
             "'true' if session protection is enabled.";
         }
         leaf duration {
           type union {
             type uint32;
             type enumeration {
               enum "infinite" {
                 description "The duration is infinite.";
               }
             }
           }
           units seconds;
           description
             "Session protection duration.";
         }
         leaf peer-list {



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           type peer-list-ref;
           description
             "The name of a peer ACL.";
         }
       } // session-protection
     } // session-protection-per-vrf

     grouping session-protection-per-neighbor {
       description "Session protection attributes.";
       container session-protection {
         if-feature session-protection;
         description
           "Session protection attributes.";
         leaf enable {
           type boolean;
           description
             "'true' if session protection is enabled.";
         }
         leaf duration {
           type union {
             type uint32;
             type enumeration {
               enum "infinite" {
                 description "The duration is infinite.";
               }
             }
           }
           units seconds;
           description
             "Session protection duration.";
         }
       } // session-protection
     } // session-protection-per-neighbor

     grouping neighbor-authentication {
       description
         "Neighbor authentication attributes.";
       leaf md5-password {
         type string {
           length "1..80";
         }
         description
           "Assigns an encrypted MD5 password to an LDP
            neighbor";
       } // md5-password
     } // neighbor-authentication

     grouping neighbor-attributes-container {



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       description "Container of neighbor configuration attributes.";
       container neighbors {
         description
           "Container of neighbor configuration attributes.";
         uses neighbor-authentication {
           if-feature global-session-authentication;
         }
         uses neighbor-attributes;
       }
     } // neighbor-attributes-container

     grouping instance-attributes {
       description "Configuration attributes at instance level.";

       container capability {
         description "Configure capability.";
         container end-of-lib {
           if-feature capability-end-of-lib;
           description
             "Configure upstream label assignment capability.";
           leaf enable {
             type boolean;
             description
               "Enable end-of-lib capability.";
           }
         }
         container typed-wildcard-fec {
           if-feature capability-typed-wildcard-fec;
           description
             "Configure typed-wildcard-fec capability.";
           leaf enable {
             type boolean;
             description
               "Enable typed-wildcard-fec capability.";
           }
         }
         container upstream-label-assignment {
           if-feature capability-upstream-label-assignment;
           description
             "Configure upstream label assignment capability.";
           leaf enable {
             type boolean;
             description
               "Enable upstream label assignment.";
           }
         }
         container mldp {
           if-feature mldp;



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           description
             "Multipoint capabilities.";
           uses mldp-capabilities;
         }
       } // capability

       uses graceful-restart-attributes;

       leaf igp-synchronization-delay {
         type uint16 {
           range 3..60;
         }
         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.";
       }
       leaf lsr-id {
         type yang:dotted-quad;
         description "Router ID.";
       }
     } // instance-attributes

     grouping global-attributes {
       description "Configuration attributes at global level.";

       uses instance-attributes;

       leaf nonstop-routing {
         type boolean;
         default false;
         description
           "Enables Nonstop Routing (NSR)";
       }
     } // global-attributes

     grouping policy-attributes {
       description
         "LDP policy attributes.";
       container label-policy {
         description
           "Label policy attributes.";
         container independent-mode {
           description
             "Independent label policy attributes.";
           container assign {



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             if-feature policy-label-assignment-config;
             description
               "Label assignment policies";
             choice prefix-option {
               description
                 "Use either prefix-list or host-routes-only.";
               case prefix-list {
                 leaf prefix-list {
                   type prefix-list-ref;
                   description
                     "Assign labels according to certain prefixes.";
                 }
               }
               case host-routes-only {
                 leaf host-routes-only {
                   type boolean;
                   description
                     "'true' to apply host routes only.";
                 }
               }
             } // prefix-option
           }
           container advertise {
             description
               "Label advertising policies.";
             container explicit-null {
               presence "Present to enable 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 prefix-list {
                 type prefix-list-ref;
                 description
                   "Prefix list name. Applies the filters in the
                    specified prefix list to label
                    advertisements.
                    If the prefix list is not specified, explicit
                    null label advertisement is enabled for all
                    directly connected prefixes.";
               }
             }
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Applies the prefix list to outgoing label
                  advertisements.";



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             }
           }
           container accept {
             description
               "Label advertisement acceptance policies.";
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Applies the prefix list to incoming label
                  advertisements.";
             }
           }
         } // independent-mode
         container ordered-mode {
           if-feature policy-ordered-label-config;
           description
             "Ordered label policy attributes.";
           container egress-lsr {
             description
               "Egress LSR label assignment policies";
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Assign labels according to certain prefixes.";
             }
           }
           container advertise {
             description
               "Label advertising policies.";
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Applies the prefix list to outgoing label
                  advertisements.";
             }
           }
           container accept {
             description
               "Label advertisement acceptance policies.";
             leaf prefix-list {
               type prefix-list-ref;
               description
                 "Applies the prefix list to incoming label
                  advertisements.";
             }
           }
         } // ordered-mode
       } // label-policy



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     } // policy-attributes

     grouping neighbor-af-policy-attributes {
       description
         "LDP policy attributes under neighbor 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 outgoing label
                  advertisements.";
           }
         }
         container accept {
           description
             "Label advertisement acceptance policies.";
           leaf prefix-list {
             type prefix-list-ref;
             description
               "Applies the prefix list to incoming label
                advertisements.";
           }
         } // accept
       } // label-policy
     } // neighbor-af-policy-attributes

     grouping extended-discovery-policy-attributes {
       description
         "LDP policy to control the acceptance of extended neighbor
          discovery hello messages.";
       container hello-accept {
         if-feature policy-extended-discovery-config;
         description
           "Extended discovery acceptance policies.";

         leaf enable {
           type boolean;
           description
             "'true' to accept; 'false' to deny.";
         }
         leaf peer-list {
           type peer-list-ref;
           description



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             "The name of a peer ACL.";
         }
       } // hello-accept
     } // extended-discovery-policy-attributes

     grouping mldp-capabilities {
       description
         "mLDP capabilities.";
       container p2mp {
         description
           "Configure point-to-multipoint capability.";
         leaf enable {
           type boolean;
           description
             "Enable point-to-multipoint.";
         }
       }
       container mp2mp {
         description
           "Configure multipoint-to-multipoint capability.";
         leaf enable {
           type boolean;
           description
             "Enable multipoint-to-multipoint.";
         }
       }
       container make-before-break {
         description
           "Configure make-before-break capability.";
         leaf enable {
           type boolean;
           description
             "Enable make-before-break.";
         }
         leaf switchover-delay {
           type uint16;
           units seconds;
           description
             "Switchover delay in seconds.";
         }
         leaf timeout {
           type uint16;
           units seconds;
           description
             "Timeout in seconds.";
         }
       }
       container hub-and-spoke {



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         if-feature capability-mldp-hsmp;
         description
           "Configure hub-and-spoke-multipoint capability.";
         reference
           "RFC7140: LDP Extensions for Hub and Spoke Multipoint
            Label Switched Path";
         leaf enable {
           type boolean;
           description
             "Enable hub-and-spoke-multipoint.";
         }
       }
       container node-protection {
         if-feature capability-mldp-node-protection;
         description
           "Configure node-protection capability.";
         reference
           "draft-ietf-mpls-mldp-node-protection: mLDP Node
            Protection.";
         leaf plr {
           type boolean;
           description
             "Point of Local Repair capable for MP LSP node
              protection.";
         }
         container merge-point {
           description
             "Merge Point capable for MP LSP node protection.";
           leaf enable {
             type boolean;
             description
               "Enable merge point capability.";
           }
           leaf targeted-session-teardown-delay {
             type uint16;
             units seconds;
             description
               "Targeted session teardown delay.";
           }
         } // merge-point
       }
     } // mldp-capabilities

     grouping  mldp-configured-lsp-roots {
       description
         "mLDP roots containers.";

       container roots-ipv4 {



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         when "../../../af = 'ipv4'" {
           description
             "Only for IPv4.";
         }
         description
           "Configured IPv4 multicast LSPs.";
         list root {
           key "root-addr";
           description
             "List of roots for configured multicast LSPs.";

           leaf root-addr {
             type inet:ipv4-address;
             description
               "Root address.";
           }

           list lsp {
             must "(lsp-id = 0 and source-addr != '0.0.0.0' and "
               + "group-addr != '0.0.0.0') or "
               + "(lsp-id != 0 and source-addr = '0.0.0.0' and "
               + "group-addr = '0.0.0.0')" {
               description
                 "A LSP can be identified by either <lsp-id> or
                  <source-addr, group-addr>.";
             }
             key "lsp-id source-addr group-addr";
             description
               "List of LSPs.";
             leaf lsp-id {
               type uint16;
               description "ID to identify the LSP.";
             }
             leaf source-addr {
               type inet:ipv4-address-no-zone;
               description
                 "Source address.";
             }
             leaf group-addr {
               type inet:ipv4-address-no-zone;
               description
                 "Group address.";
             }
           } // list lsp
         } // list root
       } // roots-ipv4

       container roots-ipv6 {



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         when "../../../af = 'ipv6'" {
           description
             "Only for IPv6.";
         }
         description
           "Configured IPv6 multicast LSPs.";

         list root {
           key "root-addr";
           description
             "List of roots for configured multicast LSPs.";

           leaf root-addr {
             type inet:ipv6-address;
             description
               "Root address.";
           }

           list lsp {
             must "(lsp-id = 0 and source-addr != '::' and "
               + "group-addr != '::') or "
               + "(lsp-id != 0 and source-addr = '::' and "
               + "group-addr = '::')" {
               description
                 "A LSP can be identified by either <lsp-id> or
                  <source-addr, group-addr>.";
             }
             key "lsp-id source-addr group-addr";
             description
               "List of LSPs.";
             leaf lsp-id {
               type uint16;
               description "ID to identify the LSP.";
             }
             leaf source-addr {
               type inet:ipv6-address-no-zone;
               description
                 "Source address.";
             }
             leaf group-addr {
               type inet:ipv6-address-no-zone;
               description
                 "Group address.";
             }
           } // list lsp
         } // list root
       } // roots-ipv6
     } // mldp-configured-lsp-roots



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     /*
      * Configuration data nodes
      */

     augment "/rt:routing/rt:routing-instance/mpls:mpls" {
       description "LDP augmentation.";

       container mpls-ldp {
         presence "Container for LDP protocol.";
         description
           "Container for LDP protocol.";

         container global {
           description
             "Global attributes for LDP.";
           container config {
             description
               "Configuration data.";
             uses global-attributes;
           }
           container state {
             config false;
             description
               "Operational state data.";
             uses global-attributes;
           }
         }

         container mldp {
           if-feature mldp;
           description
             "mLDP attributes at per instance level. Defining attributes
              here does not enable any MP capabilities. MP capabilities
              need to be explicitly enabled under container
              capability.";

           container config {
             description
               "Configuration data.";
             leaf enable {
               type boolean;
               description
                 "Enable mLDP.";
             }
           }
           container state {
             config false;
             description



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               "Operational state data.";
             leaf enable {
               type boolean;
               description
                 "Enable mLDP.";
             }
           }

           list address-family {
             key "af";
             description
               "Per-af params.";
             leaf af {
               type address-family-type;
               description
                 "Address family type value.";
             }

             container config {
               description
                 "Configuration data.";
               container multicast-only-frr {
                 if-feature mldp-mofrr;
                 description
                   "Multicast only FRR (MoFRR) policy.";
                 leaf prefix-list {
                   type prefix-list-ref;
                   description
                     "Enables MoFRR for the specified access list.";
                 }
               } // multicast-only-frr
               container recursive-fec {
                 description
                   "Recursive FEC policy.";
                 leaf prefix-list {
                   type prefix-list-ref;
                   description
                     "Enables recursive FEC for the specified access
                      list.";
                 }
               } // recursive-for
             }
             container state {
               config false;
               description
                 "Operational state data.";
               container multicast-only-frr {
                 if-feature mldp-mofrr;



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                 description
                   "Multicast only FRR (MoFRR) policy.";
                 leaf prefix-list {
                   type prefix-list-ref;
                   description
                     "Enables MoFRR for the specified access list.";
                 }
               } // multicast-only-frr
               container recursive-fec {
                 description
                   "Recursive FEC policy.";
                 leaf prefix-list {
                   type prefix-list-ref;
                   description
                     "Enables recursive FEC for the specified access
                      list.";
                 }
               } // recursive-for
             }

             container configured-leaf-lsps {
               description
                 "Configured multicast LSPs.";

               container p2mp {
                 description
                   "Configured point-to-multipoint LSPs.";
                 uses mldp-configured-lsp-roots;
               }
               container mp2mp {
                 description
                   "Configured multipoint-to-multipoint LSPs.";
                 uses mldp-configured-lsp-roots;
               }
             } // configured-leaf-lsps
           } // list address-family
         } // mldp

         list address-family {
           key "af";
           description
             "Per-vrf per-af params.";
           leaf af {
             type address-family-type;
             description
               "Address family type value.";
           }




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           container config {
             description
               "Configuration data.";
             leaf enable {
               type boolean;
               description
                 "'true' to enable the address family.";
             }
             uses policy-attributes;

             container ipv4 {
               when "../../af = 'ipv4'" {
                 description
                   "Only for IPv4.";
               }
               description
                 "IPv4 address family.";
               leaf transport-address {
                 type inet:ipv4-address;
                 description
                   "The transport address advertised in LDP Hello
                    messages.";
               }
             } // ipv4
             container ipv6 {
               when "../../af = 'ipv6'" {
                 description
                   "Only for IPv6.";
               }
               description
                 "IPv6 address family.";
               leaf transport-address {
                 type inet:ipv6-address;
                 description
                   "The transport address advertised in LDP Hello
                    messages.";
               }
             } // ipv6
           }
           container state {
             config false;
             description
               "Operational state data.";
             leaf enable {
               type boolean;
               description
                 "'true' to enable the address family.";
             }



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             uses policy-attributes;

             container ipv4 {
               when "../../af = 'ipv4'" {
                 description
                   "Only for IPv4.";
               }
               description
                 "IPv4 address family.";
               leaf transport-address {
                 type inet:ipv4-address;
                 description
                   "The transport address advertised in LDP Hello
                    messages.";
               }
             } // ipv4
             container ipv6 {
               when "../../af = 'ipv6'" {
                 description
                   "Only for IPv6.";
               }
               description
                 "IPv6 address family.";
               leaf transport-address {
                 type inet:ipv6-address;
                 description
                   "The transport address advertised in LDP Hello
                    messages.";
               }
             } // ipv6
           }
         }

         container discovery {
           description
             "Neibgbor discovery configuration.";

           container interfaces {
             description
               "A list of interfaces for basic descovery.";
             container config {
               description
                 "Configuration data.";
               uses basic-discovery-timers;
             }
             container state {
               config false;
               description



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                 "Operational state data.";
               uses basic-discovery-timers;
             }

             list interface {
               key "interface";
               description
                 "List of LDP interfaces.";
               leaf interface {
                 type if:interface-ref;
                 description
                   "Interface.";
               }
               container config {
                 description
                   "Configuration data.";
                 uses basic-discovery-timers {
                   if-feature per-interface-timer-config;
                 }
                 leaf igp-synchronization-delay {
                   if-feature per-interface-timer-config;
                   type uint16 {
                     range 3..60;
                   }
                   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.";
                 }
               }
               container state {
                 config false;
                 description
                   "Operational state data.";
                 uses basic-discovery-timers {
                   if-feature per-interface-timer-config;
                 }
                 leaf igp-synchronization-delay {
                   if-feature per-interface-timer-config;
                   type uint16 {
                     range 3..60;
                   }
                   units seconds;
                   description
                     "Sets the interval that the LDP waits before
                      notifying the Interior Gateway Protocol (IGP) that



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                      label exchange is completed so that IGP can start
                      advertising the normal metric for the link.";
                 }
               }

               list address-family {
                 key "af";
                 description
                   "Per-vrf per-af params.";
                 leaf af {
                   type address-family-type;
                   description
                     "Address family type value.";
                 }
                 container config {
                   description
                     "Configuration data.";
                   leaf enable {
                     type boolean;
                     description
                       "Enable the address family on the interface.";
                   }

                   container ipv4 {
                     must "/if:interfaces/if:interface"
                       + "[name = current()/../../../interface]/"
                       + "ip:ipv4" {
                       description
                         "Only if IPv4 is enabled on the interface.";
                     }
                     description
                       "IPv4 address family.";
                     leaf transport-address {
                       type union {
                         type enumeration {
                           enum "use-interface-address" {
                             description
                             "Use interface address as the transport
                              address.";
                           }
                         }
                         type inet:ipv4-address;
                       }
                       description
                         "IP address to be advertised as the LDP
                           transport address.";
                     }
                   }



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                   container ipv6 {
                     must "/if:interfaces/if:interface"
                       + "[name = current()/../../../interface]/"
                       + "ip:ipv6" {
                       description
                         "Only if IPv6 is enabled on the interface.";
                     }
                     description
                       "IPv6 address family.";
                     leaf transport-address {
                       type union {
                         type enumeration {
                           enum "use-interface-address" {
                             description
                             "Use interface address as the transport
                              address.";
                           }
                         }
                         type inet:ipv4-address;
                       }
                       description
                         "IP address to be advertised as the LDP
                          transport address.";
                     }
                   } // ipv6
                 }
                 container state {
                   config false;
                   description
                     "Operational state data.";
                   leaf enable {
                     type boolean;
                     description
                       "Enable the address family on the interface.";
                   }

                   container ipv4 {
                     must "/if:interfaces/if:interface"
                       + "[name = current()/../../../interface]/"
                       + "ip:ipv4" {
                       description
                         "Only if IPv4 is enabled on the interface.";
                     }
                     description
                       "IPv4 address family.";
                     leaf transport-address {
                       type union {
                         type enumeration {



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                           enum "use-interface-address" {
                             description
                             "Use interface address as the transport
                              address.";
                           }
                         }
                         type inet:ipv4-address;
                       }
                       description
                         "IP address to be advertised as the LDP
                          transport address.";
                     }
                   }
                   container ipv6 {
                     must "/if:interfaces/if:interface"
                       + "[name = current()/../../../interface]/"
                       + "ip:ipv6" {
                       description
                         "Only if IPv6 is enabled on the interface.";
                     }
                     description
                       "IPv6 address family.";
                     leaf transport-address {
                       type union {
                         type enumeration {
                           enum "use-interface-address" {
                             description
                             "Use interface address as the transport
                              address.";
                           }
                         }
                         type inet:ipv4-address;
                       }
                       description
                         "IP address to be advertised as the LDP
                          transport address.";
                     }
                   } // ipv6
                 }
               } // address-family
             } // list interface
           } // interfaces

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



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               description
                 "Configuration data.";
               uses extended-discovery-timers;
               uses extended-discovery-policy-attributes;
             }
             container state {
               config false;
               description
                 "Operational state data.";
               uses extended-discovery-timers;
               uses extended-discovery-policy-attributes;
             }

             container address-family {
               description
                 "Per-vrf per-af params.";
               container ipv4 {
                 description
                   "IPv4 address family.";
                 list target {
                   key "address";
                   description
                     "Targeted discovery params.";

                   leaf address {
                     type inet:ipv4-address;
                     description
                       "Configures a remote LDP neighbor and enables
                        extended LDP discovery of the specified
                        neighbor.";
                   }
                   container config {
                     description
                       "Configuration data.";
                     leaf enable {
                       type boolean;
                       description
                         "Enable the target.";
                     }
                   }
                   container state {
                     config false;
                     description
                       "Operational state data.";
                     leaf enable {
                       type boolean;
                       description
                         "Enable the target.";



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                     }
                   }
                 }
               } // ipv4
               container ipv6 {
                 description
                   "IPv6 address family.";
                 list target {
                   key "address";
                   description
                     "Targeted discovery params.";

                   leaf address {
                     type inet:ipv6-address;
                     description
                       "Configures a remote LDP neighbor and enables
                        extended LDP discovery of the specified
                        neighbor.";
                   }
                   container config {
                     description
                       "Configuration data.";
                     leaf enable {
                       type boolean;
                       description
                         "Enable the target.";
                     }
                   }
                   container state {
                     config false;
                     description
                       "Operational state data.";
                     leaf enable {
                       type boolean;
                       description
                         "Enable the target.";
                     }
                   }
                 }
               } // ipv6
             } // address-family
           } // targeted
         } // discovery

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



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           container interfaces {
             description
               "A list of interfaces on which forwarding is disabled.";

             list interface {
               key "interface";
               description
                 "List of LDP interfaces.";
               leaf interface {
                 type if:interface-ref;
                 description
                   "Interface.";
               }
               list address-family {
                 key "af";
                 description
                   "Per-vrf per-af params.";
                 leaf af {
                   type address-family-type;
                   description
                     "Address family type value.";
                 }
                 container config {
                   description
                     "Configuration data.";
                   leaf ldp-disable {
                     type boolean;
                     description
                       "Disable LDP forwarding on the interface.";
                   }
                   leaf mldp-disable {
                     if-feature mldp;
                     type boolean;
                     description
                       "Disable mLDP forwarding on the interface.";
                   }
                 }
                 container state {
                   config false;
                   description
                     "Operational state data.";
                   leaf ldp-disable {
                     type boolean;
                     description
                       "Disable LDP forwarding on the interface.";
                   }
                   leaf mldp-disable {
                     if-feature mldp;



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                     type boolean;
                     description
                       "Disable mLDP forwarding on the interface.";
                   }
                 }
               } // address-family
             } // list interface
           } // interfaces
         } // forwarding-nexthop

         container neighbors {
           description
             "Neighbors configuration attributes.";

           container config {
             description
               "Configuration data.";
             uses neighbor-authentication {
               if-feature global-session-authentication;
             }
             uses neighbor-attributes;

             container session-downstream-on-demand {
               if-feature session-downstream-on-demand-config;
               description
                 "Session downstream-on-demand attributes.";
               leaf enable {
                 type boolean;
                 description
                   "'true' if session downstream-on-demand is enabled.";
               }
               leaf peer-list {
                 type peer-list-ref;
                 description
                   "The name of a peer ACL.";
               }
             }

             uses session-protection-per-vrf;
           }
           container state {
             config false;
             description
               "Operational state data.";
             uses neighbor-authentication {
               if-feature global-session-authentication;
             }
             uses neighbor-attributes;



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             container session-downstream-on-demand {
               if-feature session-downstream-on-demand-config;
               description
                 "Session downstream-on-demand attributes.";
               leaf enable {
                 type boolean;
                 description
                   "'true' if session downstream-on-demand is enabled.";
               }
               leaf peer-list {
                 type peer-list-ref;
                 description
                   "The name of a peer ACL.";
               }
             }

             uses session-protection-per-vrf;
           }

           list neighbor {
             key "lsr-id";
             description
               "List of neighbors.";

             leaf lsr-id {
               type union {
                 type yang:dotted-quad;
                 type uint32;
               }
               description "LSR ID.";
             }

             container config {
               description
                 "Configuration data.";
               leaf admin-down {
                 type boolean;
                 default false;
                 description
                   "'true' to disable the neighbor.";
               }

               container capability {
                 description
                   "Per neighbor capability";
                 container mldp {
                   if-feature mldp;
                   description



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                     "mLDP capabilities.";
                   uses mldp-capabilities;
                 }
               }

               uses neighbor-authentication;

               uses graceful-restart-attributes-per-neighbor {
                 if-feature per-neighbor-graceful-restart-config;
               }

               uses neighbor-attributes {
                 if-feature per-neighbor-session-attributes-config;
               }
               uses session-protection-per-neighbor;

               container address-family {
                 description
                   "Per-vrf per-af params.";
                 container ipv4 {
                   description
                     "IPv4 address family.";
                   uses neighbor-af-policy-attributes;
                 }
                 container ipv6 {
                   description
                     "IPv6 address family.";
                   uses neighbor-af-policy-attributes;
                 } // ipv6
               } // address-family
             }
             container state {
               config false;
               description
                 "Operational state data.";
               leaf admin-down {
                 type boolean;
                 default false;
                 description
                   "'true' to disable the neighbor.";
               }

               container capability {
                 description
                   "Per neighbor capability";
                 container mldp {
                   if-feature mldp;
                   description



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                     "mLDP capabilities.";
                   uses mldp-capabilities;
                 }
               }

               uses neighbor-authentication;

               uses graceful-restart-attributes-per-neighbor {
                 if-feature per-neighbor-graceful-restart-config;
               }

               uses neighbor-attributes {
                 if-feature per-neighbor-session-attributes-config;
               }
               uses session-protection-per-neighbor;

               container address-family {
                 description
                   "Per-vrf per-af params.";
                 container ipv4 {
                   description
                     "IPv4 address family.";
                   uses neighbor-af-policy-attributes;
                 }
                 container ipv6 {
                   description
                     "IPv6 address family.";
                   uses neighbor-af-policy-attributes;
                 } // ipv6
               } // address-family
             }
           } // list neighbor
         } // neighbors
       } // container mpls-ldp
     }

     /*
      * RPCs
      */
     rpc mpls-ldp-clear-neighbor {
       description
         "Clears the session to the neighbor.";
       input {
         uses ldp-instance-ref {
           description
             "VRF instance name. If this is not provided
              then all instances are cleared.";
         }



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         leaf lsr-id {
           type union {
             type yang:dotted-quad;
             type uint32;
           }
           description
             "LSR ID of neighbor to be cleared. If this is not provided
              then all neighbors are cleared";
         }
       }
     }

     rpc mpls-ldp-clear-adjacency {
       description
         "Clears the hello adjacency";
       input {
         uses ldp-instance-ref {
           description
             "VRF instance name. If this is not provided
              then all instances are cleared.";
         }
         container adjacency {
           description
             "Link adjacency or targettted adjacency. If this is not
              provided then all hello adjacencies are cleared";
           choice 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";
                 }
               } // targeted
             }
             case link {
               container link {
                 presence "Present to clear link adjacencies.";
                 description
                   "Clear link adjacencies.";
                 leaf next-hop-interface {
                   type if:interface-ref;
                   description



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                     "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.";
                 } // next-hop-address
               } // link
             }
           }
         }
       }
     }

     rpc mpls-ldp-clear-neighbor-statistics {
       description
         "Clears protocol statistics (e.g. sent and received
          counters).";
       input {
         uses ldp-instance-ref {
           description
             "VRF instance name. If this is not provided
             then all instances are cleared.";
         }
         leaf lsr-id {
           type union {
             type yang:dotted-quad;
             type uint32;
           }
           description
             "LSR ID of neighbor whose statistic are to be cleared.
              If this is not provided then all neighbors statistics are
              cleared";
         }
       }
     }

     /*
      * Notifications
      */
     notification mpls-ldp-neighbor-event {



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       description
         "Notification event for a change of LDP neighbor operational
          status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       uses ldp-neighbor-ref;
     }

     notification mpls-ldp-adjacency-event {
       description
         "Notification event for a change of LDP adjacency operational
          status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       uses ldp-adjacency-ref;
     }

     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.";
       }
       uses ldp-fec-event;
     }

     notification mpls-mldp-fec-event {
       description
         "Notification event for a change of FEC status.";
       leaf event-type {
         type oper-status-event-type;
         description "Event type.";
       }
       uses mldp-fec-event;
     }
   }

   <CODE ENDS>



                                 Figure 11




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6.  Security Considerations

   The configuration, state, action and notification data defined in
   this document are designed to be accessed via the NETCONF protocol
   [RFC6241].  The lowest NETCONF layer is the secure transport layer
   and the mandatory-to-implement secure transport is SSH [RFC6242].
   The NETCONF access control model [RFC6536] provides means to restrict
   access for particular NETCONF users to a pre-configured subset of all
   available NETCONF protocol operations and content.

   LDP is a MPLS protocol that is used to establish MPLS transport LSPs.
   So it is critical to ensure security of the protocol to avoid
   disruption of the services that depend on these transport LSPs.

   There are a number of data nodes defined in the LDP and mLDP 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.

   The security concerns listed above are, however, no different than
   faced by other routing protocols.  Hence, this draft does not change
   any underlying security issues inherent in [I-D.ietf-netmod-routing-
   cfg]

7.  IANA Considerations

   None.

8.  Acknowledgments

   The authors would like to acknowledge Danial Johari, Eddie Chami,
   Nagendra Kumar, Mannan Venkatesan, Pavan Beeram for their
   contribution to this document.  We also acknowledge Ladislav Lhotka
   for his useful comments as the YANG Doctor.

9.  References

9.1.  Normative References

   [I-D.ietf-mpls-mldp-node-protection]
              Wijnands, I., Raza, K., Atlas, A., Tantsura, J., and Q.
              Zhao, "mLDP Node Protection", draft-ietf-mpls-mldp-node-
              protection-08 (work in progress), September 2015.






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   [I-D.ietf-netmod-routing-cfg]
              Lhotka, L. and A. Lindem, "A YANG Data Model for Routing
              Management", draft-ietf-netmod-routing-cfg-20 (work in
              progress), October 2015.

   [I-D.openconfig-netmod-opstate]
              Shakir, R., Shaikh, A., and M. Hines, "Consistent Modeling
              of Operational State Data in YANG", draft-openconfig-
              netmod-opstate-01 (work in progress), July 2015.

   [I-D.saad-mpls-static-yang]
              Raza, K., Gandhi, R., Liu, X., Beeram, V., Saad, T., Chen,
              X., Jones, R., and B. Wen, "A YANG Data Model for MPLS
              Base and Static LSPs", draft-saad-mpls-static-yang-00
              (work in progress), October 2015.

   [I-D.shaikh-rtgwg-policy-model]
              Shaikh, A., Shakir, R., D'Souza, K., and C. Chase,
              "Routing Policy Configuration Model for Service Provider
              Networks", draft-shaikh-rtgwg-policy-model-01 (work in
              progress), July 2015.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

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

   [RFC5561]  Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
              Le Roux, "LDP Capabilities", RFC 5561,
              DOI 10.17487/RFC5561, July 2009,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc5919>.






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   [RFC6388]  Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
              Thomas, "Label Distribution Protocol Extensions for Point-
              to-Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
              <http://www.rfc-editor.org/info/rfc6388>.

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

   [RFC6512]  Wijnands, IJ., Rosen, E., Napierala, M., and N. Leymann,
              "Using Multipoint LDP When the Backbone Has No Route to
              the Root", RFC 6512, DOI 10.17487/RFC6512, February 2012,
              <http://www.rfc-editor.org/info/rfc6512>.

   [RFC6826]  Wijnands, IJ., Ed., Eckert, T., Leymann, N., and M.
              Napierala, "Multipoint LDP In-Band Signaling for Point-to-
              Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6826, DOI 10.17487/RFC6826, January 2013,
              <http://www.rfc-editor.org/info/rfc6826>.

   [RFC7060]  Napierala, M., Rosen, E., and IJ. Wijnands, "Using LDP
              Multipoint Extensions on Targeted LDP Sessions", RFC 7060,
              DOI 10.17487/RFC7060, November 2013,
              <http://www.rfc-editor.org/info/rfc7060>.

   [RFC7140]  Jin, L., Jounay, F., Wijnands, IJ., and N. Leymann, "LDP
              Extensions for Hub and Spoke Multipoint Label Switched
              Path", RFC 7140, DOI 10.17487/RFC7140, March 2014,
              <http://www.rfc-editor.org/info/rfc7140>.

   [RFC7438]  Wijnands, IJ., Ed., Rosen, E., Gulko, A., Joorde, U., and
              J. Tantsura, "Multipoint LDP (mLDP) In-Band Signaling with
              Wildcards", RFC 7438, DOI 10.17487/RFC7438, January 2015,
              <http://www.rfc-editor.org/info/rfc7438>.

   [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,
              <http://www.rfc-editor.org/info/rfc7552>.

9.2.  Informative References

   [I-D.iwijnand-mpls-mldp-multi-topology]
              Wijnands, I. and K. Raza, "mLDP Extensions for Multi
              Topology Routing", draft-iwijnand-mpls-mldp-multi-
              topology-03 (work in progress), June 2013.




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

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6242>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <http://www.rfc-editor.org/info/rfc6536>.

   [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,
              <http://www.rfc-editor.org/info/rfc7307>.


Authors' Addresses

   Kamran Raza
   Cisco Systems, Inc.
   Email: skraza@cisco.com

   Reshad Rahman
   Cisco Systems, Inc.
   Email: rrahman@cisco.com

   Rajiv Asati
   Cisco Systems, Inc.
   Email: rajiva@cisco.com



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   Xufeng Liu
   Ericsson
   Email: xufeng.liu@ericsson.com

   Jeff Tantsura
   Ericsson
   Email: jeff.tantsura@ericsson.com

   Santosh Esale
   Juniper Networks
   Email: sesale@juniper.net

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

   Loa Andersson
   Huawei Technologies
   Email: loa@pi.nu

   Himanshu Shah
   Ciena Corporation
   Email: hshah@ciena.com

   Matthew Bocci
   Alcatel-Lucent
   Email: matthew.bocci@alcatel-lucent.com


Additional Contributors

   Stephane Litkowski
   Orange.
   Email: stephane.litkowski@orange.com

   Sowmya Krishnaswamy
   Cisco Systems Inc.
   Email: sowkrish@cisco.com


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