BESS Working Group                                          H. Shah, Ed.
Internet-Draft                                         Ciena Corporation
Intended status: Standards Track                       P. Brissette, Ed.
Expires: January 3, 2020                             Cisco Systems, Inc.
                                                            I. Chen, Ed.
                                                   The MITRE Corporation
                                                         I. Hussain, Ed.
                                                    Infinera Corporation
                                                             B. Wen, Ed.
                                                                 Comcast
                                                    K. Tiruveedhula, Ed.
                                                        Juniper Networks
                                                           July 02, 2019


                  YANG Data Model for MPLS-based L2VPN
                   draft-ietf-bess-l2vpn-yang-10.txt

Abstract

   This document describes a YANG data model for Layer 2 VPN (L2VPN)
   services over MPLS networks.  These services include point-to-point
   Virtual Private Wire Service (VPWS) and multipoint Virtual Private
   LAN service (VPLS) that uses LDP and BGP signaled Pseudowires.  It is
   expected that this model will be used by the management tools run by
   the network operators in order to manage and monitor the network
   resources that they use to deliver L2VPN services.

   This document also describes the YANG data model for the Pseudowires.
   The independent definition of the Pseudowires facilitates its use in
   Ethernet Segment and EVPN data models defined in separate document.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 3, 2020.



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Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   4
   3.  L2VPN YANG Model  . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Latest addition . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Open issues and next steps  . . . . . . . . . . . . . . .   8
     3.4.  Pseudowire Common . . . . . . . . . . . . . . . . . . . .   8
       3.4.1.  Pseudowire  . . . . . . . . . . . . . . . . . . . . .   8
       3.4.2.  pw-templates  . . . . . . . . . . . . . . . . . . . .   8
     3.5.  L2VPN Common  . . . . . . . . . . . . . . . . . . . . . .   8
       3.5.1.  redundancy-group-templates  . . . . . . . . . . . . .   8
     3.6.  L2VPN instance  . . . . . . . . . . . . . . . . . . . . .   9
       3.6.1.  common attributes . . . . . . . . . . . . . . . . . .   9
       3.6.2.  PW list . . . . . . . . . . . . . . . . . . . . . . .   9
       3.6.3.  List of endpoints . . . . . . . . . . . . . . . . . .   9
       3.6.4.  point-to-point or multipoint service  . . . . . . . .  10
       3.6.5.  multi-segment pseudowire  . . . . . . . . . . . . . .  11
     3.7.  Operational State . . . . . . . . . . . . . . . . . . . .  11
     3.8.  Yang tree . . . . . . . . . . . . . . . . . . . . . . . .  11
   4.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  43
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  43
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  43
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  44
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  44
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  44
   Appendix A.  Example Configuration  . . . . . . . . . . . . . . .  47
   Appendix B.  Contributors . . . . . . . . . . . . . . . . . . . .  47
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  48





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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 [RFC7950] is a modular language that represents data
   structures in an XML or JSON tree format, and is used as a data
   modeling language for the NETCONF.

   This document defines a YANG data model for MPLS based Layer 2 VPN
   services (L2VPN) [RFC4664] and includes switching between the local
   attachment circuits.  The L2VPN model covers point-to-point VPWS and
   Multipoint VPLS services.  These services use signaling of
   Pseudowires across MPLS networks using LDP [RFC8077][RFC4762] or
   BGP[RFC4761].

   The data model covers Ethernet based Layer 2 services.  The Ethernet
   Attachment Circuits are not defined.  Instead, they are leveraged
   from other standards organizations such as IEEE802.1 and Metro
   Ethernet Forum (MEF).

   Other Layer 2 services, such as ATM, Frame Relay, TDM, etc are
   included in the scope but will be covered as the future work items.

   The objective of the model is to define building blocks that can
   easily be assembled in different order to realize different services.

   The data model uses following constructs for configuration and
   management:

   o  Configuration

   o  Operational State

   o  Executables (Actions)

   o  Notifications

   This document focuses on definition of configuration, state and
   notification objects.

   The L2VPN data object model uses the instance centric approach.  The
   L2VPN instance is recognized by network instance model.  The network-
   instance container is defined in network instance model [I-D.ietf-
   netmod-ni-model].

   Within this network instance, L2VPN container contains definitions of
   a set of common parameters, a list of PWs and a list of endpoints.  A




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   special constraint is added for the VPWS configuration such that only
   two endpoints are allowed in the list of endpoints.

   The Pseudowire data object model is defined independent of the L2VPN
   data object model to allow its inclusion in the Ethernet Segment and
   EVPN data objects.

   The L2VPN data object model augments Psuedowire data object for its
   definition.

   The document also includes Notifications used by the L2VPN object
   model

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].

3.  L2VPN YANG Model

3.1.  Overview

   The document defines configuration of one single container for L2VPN.
   Within the l2vpn container, common parameters and a list of endpoints
   are defined.  For the point-to-point VPWS configuration, endpoint
   list is used with the constraint that limits the number of endpoints
   to be two.  For the multipoint service, endpoint list is used.  Each
   endpoint contains the common definition that is either an attachment
   circuit, a pseudowire or a redundancy group.  The previous versions
   of this document represented VPWS service with definition of
   endpoint-a and endpoint-z while VPLS with a list of endpoints.  This
   duplicattion is removed with simplified version whereby list of
   endpoints is used for both.  When defining VPWS, the numnber of
   endpoints is constrained to two endpoints.

   The l2vpn container also includes definition of common building
   blocks for redundancy-grp templates and pseudowire-templates.

   The State objects have been consolidated with the configuration
   object as per the recommendations provided by the Guidelines for Yang
   Module Authors document.

   The IETF working group has defined the VPWS and VPLS services that
   leverages the pseudowire technologies defined by the PWE3 working
   group.  A large number of RFCs from these working groups cover this
   subject matter.  Hence, it is prudent that this document state the
   scope of the MPLS L2VPN object model definitions.



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   The following documents are within the scope.  This is not an
   exhaustive list but a representation of documents that are covered
   for this work:

   o  Requirements for Pseudo-wire Emulation Edge-to-Edge (PWE3)
      [RFC3916]

   o  Pseudo-wire Emulation Edge-to-Edge (PWE3) Architecture [RFC3985]

   o  IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)
      [RFC4446]

   o  Pseudowire Setup and Maintenance Using the Label Distribution
      Protocol (LDP) [RFC8077]

   o  Encapsulation Methods for Transport of Ethernet over MPLS Networks
      [RFC4448]

   o  Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over
      an MPLS PSN [RFC4385]

   o  Requirements for Multi-Segment Pseudowire Emulation Edge-to-Edge
      (PWE3) [RFC5254]

   o  An Architecture for Multi-Segment Pseudowire Emulation Edge-to-
      Edge [RFC5659]

   o  Segmented Pseudowire [RFC6073]

   o  Framework for Layer 2 Virtual Private Networks [RFC4664]

   o  Service Requirements for Layer 2 Provider-Provisioned Virtual
      Private Networks [RFC4665]

   o  Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery
      and Signaling [RFC4761]

   o  Virtual Private LAN Service (VPLS) Using Label Distribution
      Protocol (LDP) Signaling [RFC4762]

   o  Attachment Individual Identifier (AII) Types for Aggregation
      [RFC5003]

   o  Provisioning, Auto-Discovery, and Signaling in Layer 2 Virtual
      Private Networks (L2VPNs) [RFC6074]

   o  Flow-Aware Transport of Pseudowires over an MPLS Packet Switched
      Network [RFC6391]



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   o  Layer 2 Virtual Private Networks Using BGP for Auto-Discovery and
      Signaling [RFC6624]

   o  Extensions to the Virtual Private LAN Service (VPLS) Provider Edge
      (PE) Model for Provider Backbone Bridging [RFC7041]

   o  LDP Extensions for Optimized MAC Address Withdrawal in a
      Hierarchical Virtual Private LAN Service (H-VPLS) [RFC7361]

   o  Using the generic associated channel label for Pseudowire in the
      MPLS Transport Profile [RFC6423]

   o  Pseudowire status for static pseudowire [RFC6478]

   The specifics of pseudowire over MPLS-TP LSPs is in scope.  However,
   the initial effort addresses definitions of object models that are
   commonly deployed.

   The IETF work in L2VPN and PWE3 working group relating to L2TP, OAM,
   multicast (e.g. p2mp, etree, etc) and access specific protocols such
   as G.8032, MSTP, etc is out-of-scope for this document.

   The following is the high level view of the L2VPN data model.




























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 PW // Container
         PW specific attributes

         PW template definition


 template-ref Redundancy-Group // redundancy-group
                    template
                    attributes

 Network Instance // container
    l2vpn  // containter

         common attributes


         BGP-parameters // container
                           common attributes
                           auto-discovery attributes
                           signaling attributes

         // list of PWs being used
         PW // container
                 template-ref PW
                 attribute-override

         PBB-parameters // container
                           pbb specific attributes

         VPWS-constraints // rule to limit number of endpoints to two

         // List of endpoints, where each member endpoint container is -
                 PW // reference
                 redundancy-grp // container
                         AC // eventual reference to standard AC
                         PW // reference



                                 Figure 1

3.2.  Latest addition

   Pseudowire module is extended to include,

   Multi-segment PW - a new attribute is added to pseudowire that
   identifies the pseudowire as a member of the multi-segment




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   pseudowire.  Two pseudowire members in a VPWS, configures a multi-
   segment pseudowire at the switching PE.

   Pseudowire load-balancing - The load-balancing behaviour for a
   pseudowire can be configured either using the FAT label that resides
   below the pseudowire label or Entropy label with Entropy label
   indicator above the pseudowire label.  By default, the load-balancing
   is disabled.

   FEC 129 related - AGI, SAII and TAII string configurations is added
   to faciliate FEC 129 based pseudowire configuration.

3.3.  Open issues and next steps

   This section provides updates on open issues and will be removed
   before publication.  Authors believes the document has covered the
   topics within the scope of the document.  However, there are items,
   such as PW Headend, VPLS IRB, etc that can be candidate for
   inclusion.  The authors would like to progress the document to
   publication for general availability with current content and tackle
   the other topics in a follow up document.

3.4.  Pseudowire Common

3.4.1.  Pseudowire

   Pseudowire definitions is moved to a seperate container in order to
   allow Ethernet Segment and EVPN models can refer without having to
   pull down L2VPN container.

3.4.2.  pw-templates

   The pw-templates container contains a list of pw-template.  Each pw-
   template defines a list of common pseudowire attributes such as PW
   MTU, control word support etc.

3.5.  L2VPN Common

3.5.1.  redundancy-group-templates

   The redundancy-group-template contains a list of templates.  Each
   template defines common attributes related to redundancy such as
   protection mode, reversion parameters, etc.








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3.6.  L2VPN instance

   The network instance container defined in the network instance model
   [I-D.ietf-rtgwg-ni-model] identifies the L2VPN instance.  One of the
   value defined by the ni-type used in the instance model refers to VSI
   (Virtual Switch Instance) to denote the L2VPN instance.  The name
   attribute field is used as the key to refer to specific network
   instance.  Network Instance of type VSI anchors L2VPN container with
   a list of endpoints which when limited to two entries represents
   point to point service (i.e.  VPWS) while more than two endpoints
   represent multipoint service (i.e.  VPLS).  Within a service
   instance, a set of common attributes are defined, followed by a list
   of PWs and a list of endpoints.

3.6.1.  common attributes

   The common attributes apply to entire L2VPN instance.  These
   attributes typically include attributes such as mac-aging-timer, BGP
   related parameters (if using BGP signaling), discovery-type, etc.

3.6.2.  PW list

   The PW list is the number of PWs that are being used for a given
   L2VPN instance.  Each PW entry refers to PW template to inherit
   common attributes for the PW.  The one or more attributes from the
   template can be overriden.  It further extends definitions of more PW
   specific attributes such as use of control word, mac withdraw, what
   type of signaling (i.e.  LDP or BGP), setting of the TTL, etc.

3.6.3.  List of endpoints

   The list of endpoints define the characteristics of the L2VPN
   service.  In the case of VPWS, the list is limited to two entries
   while for VPLS, there could be many.

   Each entry in the endpoint list, may hold AC, PW or redundancy-grp
   references.  The core aspect of endpoint container is its flexible
   personality based on what user decides to include in it.  It is
   future-proofed with possible extensions that can be included in the
   endpoint container such as Integrated Route Bridging (IRB), PW
   Headend, Virtual Switch Instance, etc.

   The endpoint entry also includes the split-horizon attribute which
   defines the frame forwarding restrictions between the endpoints
   belonging to same split-horizon group.  This construct permits
   multiple instances of split horizon groups with its own endpoint
   members.  The frame forwarding restrictions does not apply between
   endpoints that belong to two different split horizon groups.



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3.6.3.1.  ac

   Attachment Circuit (AC)resides within endpoint entry either as an
   independent entity or as a member of the redundancy group.  AC is not
   defined in this document but references the definitions specified by
   other working groups and standard bodies.

3.6.3.2.  pw

   The Pseudo-wire resides within endpoint entry either as an
   independent entity or as a member of the redundancy group.  The PW
   refers to one of the entry in the list of PWs defined with the L2VPN
   instance.

3.6.3.3.  redundancy-grp choice

   The redundancy-grp is a generic redundancy construct which can hold
   primary and backup members of AC and PWs.  This flexibility permits
   combinations of -

   o  primary and backup AC

   o  primary and backup PW

   o  primary AC and backup PW

   o  primary PW and backup AC

   The redundancy group also defines attributes of the type of
   redundancy, such as protection mode, reroute mode, reversion related
   parameters, etc.

3.6.4.  point-to-point or multipoint service

   The point-to-point service as defined for VPWS is represented by a
   list of endpoints and is limited to two entries by the VPWS constrain
   rules

   The multipoint service as defined for VPLS is represented by a list
   of endpoints.

   The list of endpoints with one entry is invalid.

   The augmentation of ietf-l2vpn module is TBD.  All IP addresses
   defined in this module are currently scoped under global VRF/table.






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3.6.5.  multi-segment pseudowire

   The multi-segment pseudowire is expressed as configuration of two
   pseudowire segments at the switching PEs that provides end-to-end PW
   path between two terminating PEs consisting of multiple pseudowire
   segments.

   The multi-segment pseudowire is configured at switching PE using two
   endpoints that consists of pseudowires of type "ms-pw-members".  The
   VPWS service construct is used with "vpws constraint" that restricts
   the number of endpoints to two.

   To verify consistency, a) verify that both endpoints are using ms-pw-
   member pseudowires and b) it is only used as for VPWS configuration
   at the switching PE.

3.7.  Operational State

   The operational state of L2VPN attributes has been consolidated with
   the configuration as per recommendations from the guidelines for the
   YANG author document.

3.8.  Yang tree


module: ietf-pseudowires
  +--rw pseudowires
     +--rw pseudowire* [name]
     |  +--rw name                    string
     |  +--ro state?                  pseudowire-status-type
     |  +--rw template?               pw-template-ref
     |  +--rw mtu?                    uint16
     |  +--rw mac-withdraw?           boolean
     |  +--rw pw-loadbalance?         enumeration
     |  +--rw ms-pw-member?           boolean
     |  +--rw cw-negotiation?         cw-negotiation-type
     |  +--rw tunnel-policy?          string
     |  +--rw (pw-type)?
     |     +--:(configured-pw)
     |     |  +--rw peer-ip?          inet:ip-address
     |     |  +--rw pw-id?            uint32
     |     |  +--rw group-id?         uint32
     |     |  +--rw icb?              boolean
     |     |  +--rw transmit-label?   rt-types:mpls-label
     |     |  +--rw receive-label?    rt-types:mpls-label
     |     |  +--rw generalized?      boolean
     |     |  +--rw agi?              string
     |     |  +--rw saii?             string



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     |     |  +--rw taii?             string
     |     +--:(bgp-pw)
     |     |  +--rw remote-pe-id?     inet:ip-address
     |     +--:(bgp-ad-pw)
     |        +--rw remote-ve-id?     uint16
     +--rw pw-templates
        +--rw pw-template* [name]
           +--rw name              string
           +--rw mtu?              uint16
           +--rw cw-negotiation?   cw-negotiation-type
           +--rw tunnel-policy?    string

module: ietf-l2vpn
  +--rw l2vpn
     +--rw redundancy-group-templates
        +--rw redundancy-group-template* [name]
           +--rw name               string
           +--rw protection-mode?   enumeration
           +--rw reroute-mode?      enumeration
           +--rw dual-receive?      boolean
           +--rw revert?            boolean
           +--rw reroute-delay?     uint16
           +--rw revert-delay?      uint16

  augment /ni:network-instances/ni:network-instance/ni:ni-type:
    +--:(l2vpn)
       +--rw type?               identityref
       +--rw mtu?                uint16
       +--rw mac-aging-timer?    uint32
       +--rw service-type?       l2vpn-service-type
       +--rw discovery-type?     l2vpn-discovery-type
       +--rw signaling-type      l2vpn-signaling-type
       +--rw bgp-parameters
       |  +--rw vpn-id?   string
       |  +--rw rd-rt
       |     +--rw route-distinguisher?   rt-types:route-distinguisher
       |     +--rw vpn-target* [route-target]
       |        +--rw route-target         rt-types:route-target
       |        +--rw route-target-type    rt-types:route-target-type
       +--rw bgp-signaling
       |  +--rw site-id?      uint16
       |  +--rw site-range?   uint16
       +--rw endpoint* [name]
       |  +--rw name                      string
       |  +--rw (ac-or-pw-or-redundancy-grp)?
       |  |  +--:(ac)
       |  |  |  +--rw ac* [name]
       |  |  |     +--rw name     if:interface-ref



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       |  |  |     +--ro state?   operational-state-type
       |  |  +--:(pw)
       |  |  |  +--rw pw* [name]
       |  |  |     +--rw name     pw:pseudowire-ref
       |  |  |     +--ro state?   -> /pw:pseudowires/pseudowire[pw:name=current()/../name]/state
       |  |  +--:(redundancy-grp)
       |  |     +--rw (primary)
       |  |     |  +--:(primary-ac)
       |  |     |  |  +--rw primary-ac
       |  |     |  |     +--rw name?    if:interface-ref
       |  |     |  |     +--ro state?   operational-state-type
       |  |     |  +--:(primary-pw)
       |  |     |     +--rw primary-pw* [name]
       |  |     |        +--rw name     pw:pseudowire-ref
       |  |     |        +--ro state?   -> /pw:pseudowires/pseudowire[pw:name=current()/../name]/state
       |  |     +--rw (backup)?
       |  |     |  +--:(backup-ac)
       |  |     |  |  +--rw backup-ac
       |  |     |  |     +--rw name?    if:interface-ref
       |  |     |  |     +--ro state?   operational-state-type
       |  |     |  +--:(backup-pw)
       |  |     |     +--rw backup-pw* [name]
       |  |     |        +--rw name          pw:pseudowire-ref
       |  |     |        +--ro state?        -> /pw:pseudowires/pseudowire[pw:name=current()/../name]/state
       |  |     |        +--rw precedence?   uint32
       |  |     +--rw template?           redundancy-group-template-ref
       |  |     +--rw protection-mode?    enumeration
       |  |     +--rw reroute-mode?       enumeration
       |  |     +--rw dual-receive?       boolean
       |  |     +--rw revert?             boolean
       |  |     +--rw reroute-delay?      uint16
       |  |     +--rw revert-delay?       uint16
       |  +--rw split-horizon-group?      string
       +--rw vpws-constraints
       +--rw pbb-parameters
          +--rw (component-type)?
             +--:(i-component)
             |  +--rw i-sid?                   i-sid-type
             |  +--rw backbone-src-mac?        yang:mac-address
             +--:(b-component)
                +--rw bind-b-component-name?   l2vpn-instance-name-ref
                +--ro bind-b-component-type?   identityref
  augment /pw:pseudowires/pw:pseudowire:
    +--rw vccv-ability?     boolean
    +--rw request-vlanid?   uint16
    +--rw vlan-tpid?        string
    +--rw ttl?              uint8
  augment /pw:pseudowires/pw:pseudowire/pw:pw-type:



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    +--:(bgp-pw)
    |  +--rw bgp-pw
    |     +--rw remote-pe-id?   inet:ip-address
    +--:(bgp-ad-pw)
       +--rw bgp-ad-pw
          +--rw remote-ve-id?   uint16

  notifications:
    +---n l2vpn-state-change-notification
       +--ro l2vpn-instance-name?      l2vpn-instance-name-ref
       +--ro l2vpn-instance-type?      -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:type
       +--ro endpoint?                 -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint/name
       +--ro (ac-or-pw-or-redundancy-grp)?
       |  +--:(ac)
       |  |  +--ro ac?                 -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/ac/name
       |  +--:(pw)
       |  |  +--ro pw?                 -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/pw/name
       |  +--:(redundancy-grp)
       |     +--ro (primary)
       |     |  +--:(primary-ac)
       |     |  |  +--ro primary-ac?   -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/primary-ac/name
       |     |  +--:(primary-pw)
       |     |     +--ro primary-pw?   -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/primary-pw/name
       |     +--ro (backup)?
       |        +--:(backup-ac)
       |        |  +--ro backup-ac?    -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/backup-ac/name
       |        +--:(backup-pw)
       |           +--ro backup-pw?    -> /ni:network-instances/network-instance[ni:name=current()/../l2vpn-instance-name]/l2vpn:endpoint[l2vpn:name=current()/../endpoint]/backup-pw/name
       +--ro state?                    identityref



                                 Figure 2

4.  YANG Module

   The L2VPN configuration container is logically divided into following
   high level config areas:



<CODE BEGINS> file "ietf-pseudowires@2018-10-17.yang"
 module ietf-pseudowires {
  namespace "urn:ietf:params:xml:ns:yang:ietf-pseudowires";
  prefix "pw";

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



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  }

  import ietf-routing-types {
    prefix "rt-types";
  }

  organization  "ietf";
  contact       "ietf";
  description   "Pseudowire YANG model";

  revision "2018-10-17" {
    description "Second revision " +
                "  - Added group-id and attachment identifiers " +
                "";
    reference   "";
  }

  revision "2017-06-26" {
    description "Initial revision " +
                "  - Created a new model for pseudowires, which used " +
                "    to be defined within the L2VPN model " +
                "";
    reference   "";
  }

  /* Typedefs */

  typedef pseudowire-ref {
    type leafref {
      path "/pw:pseudowires/pw:pseudowire/pw:name";
    }
    description "A type that is a reference to a pseudowire";
  }

  typedef pw-template-ref {
    type leafref {
      path "/pw:pseudowires/pw:pw-templates/pw:pw-template/pw:name";
    }
    description "A type that is a reference to a pw-template";
  }

  typedef cw-negotiation-type {
    type enumeration {
      enum "non-preferred" {
        description "No preference for control-word";
      }
      enum "preferred" {
        description "Prefer to have control-word negotiation";



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      }
    }
    description "control-word negotiation preference type";
  }

  typedef pseudowire-status-type {
    type bits {
      bit pseudowire-forwarding {
        position 0;
        description "Pseudowire is forwarding";
      }
      bit pseudowire-not-forwarding {
        position 1;
        description "Pseudowire is not forwarding";
      }
      bit local-attachment-circuit-receive-fault {
        position 2;
        description "Local attachment circuit (ingress) receive " +
                    "fault";
      }
      bit local-attachment-circuit-transmit-fault {
        position 3;
        description "Local attachment circuit (egress) transmit " +
                    "fault";
      }
      bit local-PSN-facing-PW-receive-fault {
        position 4;
        description "Local PSN-facing PW (ingress) receive fault";
      }
      bit local-PSN-facing-PW-transmit-fault {
        position 5;
        description "Local PSN-facing PW (egress) transmit fault";
      }
      bit PW-preferential-forwarding-status {
        position 6;
        description "Pseudowire preferential forwarding status";
      }
      bit PW-request-switchover-status {
        position 7;
        description "Pseudowire request switchover status";
      }
    }
    description
      "Pseudowire status type, as registered in the IANA " +
      "Pseudowire Status Code Registry";
  }

  /* Data */



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  container pseudowires {
    description "Configuration management of pseudowires";
    list pseudowire {
      key "name";
      description "A pseudowire";
      leaf name {
        type string;
        description "pseudowire name";
      }
      leaf state {
        type pseudowire-status-type;
        config false;
        description "pseudowire operation status";
        reference "RFC 4446 and IANA Pseudowire Status Codes " +
                  "Registery";
      }
      leaf template {
        type pw-template-ref;
        description "pseudowire template";
      }
      leaf mtu {
        type uint16;
        description "PW MTU";
      }
      leaf mac-withdraw {
        type boolean;
        default false;
        description "Enable (true) or disable (false) MAC withdraw";
      }
      leaf pw-loadbalance {
        type enumeration {
          enum "disabled" {
            value 0;
            description "load-balancing disabled";
          }
          enum "fat-pw" {
            value 1;
            description "load-balance using FAT label below PW label";
          }
          enum "entropy" {
            value 2;
            description "load-balance using ELI/EL above PW label";
          }
        }
        description "PW load-balancing";
      }
      leaf ms-pw-member {
        type boolean;



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        default false;
        description "Enable (true) or disable (false) not a member of MS-PW";
      }
      leaf cw-negotiation {
        type cw-negotiation-type;
        description "cw-negotiation";
      }
      leaf tunnel-policy {
        type string;
        description "tunnel policy name";
      }
      choice pw-type {
        description "A choice of pseudowire type";
        case configured-pw {
          leaf peer-ip {
            type inet:ip-address;
            description "peer IP address";
          }
          leaf pw-id {
            type uint32;
            description "pseudowire id";
          }
          leaf group-id {
            type uint32;
            description "group id";
          }
          leaf icb {
            type boolean;
            description "inter-chassis backup";
          }
          leaf transmit-label {
            type rt-types:mpls-label;
            description "transmit lable";
          }
          leaf receive-label {
            type rt-types:mpls-label;
            description "receive label";
          }
          leaf generalized {
            type boolean;
            description "generalized pseudowire id FEC element";
          }
          leaf agi {
            type string;
            description "attachment group identifier";
          }
          leaf saii {
            type string;



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            description "source attachment individual identifier";
          }
          leaf taii {
            type string;
            description "target attachment individual identifier";
          }
        }
        case bgp-pw {
          leaf remote-pe-id {
            type inet:ip-address;
            description "remote pe id";
          }
        }
        case bgp-ad-pw {
          leaf remote-ve-id {
            type uint16;
            description "remote ve id";
          }
        }
      }
    }
    container pw-templates {
      description "pw-templates";
      list pw-template {
        key "name";
        description "pw-template";
        leaf name {
          type string;
          description "name";
        }
        leaf mtu {
          type uint16;
          description "pseudowire mtu";
        }
        leaf cw-negotiation {
          type cw-negotiation-type;
          default "preferred";
          description
            "control-word negotiation preference";
        }
        leaf tunnel-policy {
          type string;
          description "tunnel policy name";
        }
      }
    }
  }
}



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<CODE ENDS>
<CODE BEGINS> file "ietf-l2vpn@2019-05-28.yang"
module ietf-l2vpn {
  namespace "urn:ietf:params:xml:ns:yang:ietf-l2vpn";
  prefix "l2vpn";

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

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

  import ietf-routing-types {
    prefix "rt-types";
  }

  import ietf-interfaces {
    prefix "if";
  }

  import ietf-network-instance {
    prefix "ni";
  }

  import ietf-pseudowires {
    prefix "pw";
  }

  organization  "ietf";
  contact       "ietf";
  description   "l2vpn";

  revision "2019-05-28" {
    description "Nineth revision " +
                "  - Used bgp parameters hierarchy common to L2VPN and EVPN " +
                "";
    reference   "";
  }

  revision "2018-02-06" {
    description "Eighth revision " +
                "  - Incorporated ietf-network-instance model " +
                "  - change the type of attachment circuit to " +
                "    if:interface-ref " +
                "";
    reference   "";



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  }

  revision "2017-09-21" {
    description "Seventh revision " +
                "  - Fixed yangdump errors " +
                "";
    reference   "";
  }
  revision "2017-06-26" {
    description "Sixth revision " +
                "  - Removed unused module mpls " +
                "  - Renamed l2vpn-instances-state to l2vpn-instances " +
                "  - Added pseudowire status as defined in RFC4446 and " +
                "    IANA Pseudowire Status Codes Register " +
                "  - Added notifications " +
                "  - Moved PW definition out of L2VPN " +
                "  - Moved model to NMDA style specified in " +
                "    draft-dsdt-nmda-guidelines-01.txt " +
                "  - Renamed l2vpn-instances and l2vpn-instance to " +
                "    instances and instance to shorten xpaths " +
                "";
    reference   "";
  }

  revision "2017-03-06" {
    description "Sixth revision " +
                "  - Removed the 'common' container and move pw-templates " +
                "    and redundancy-group-templates up a level " +
                "  - Consolidated the endpoint configuration such that " +
                "    all L2VPN instances has a list of endpoint.  For " +
                "    certain types of L2VPN instances such as VPWS where " +
                "    each L2VPN instance is limited to at most two " +
                "    endpoint, additional augment statements were included " +
                "    to add necessary constraints " +
                "  - Removed discovery-type and signaling-type operational " +
                "    state from VPLS pseudowires, as these two parameters " +
                "    are configured as L2VPN parameters rather than " +
                "    pseudowire paramteres " +
                "  - Renamed l2vpn-instances to l2vpn-instances-state " +
                "    in the operational state branch " +
                "  - Removed BGP parameter groupings and reused " +
                "    ietf-routing-types.yang module instead " +
                "";
    reference "";
  }

  revision "2016-10-24" {
    description "Fifth revision " +



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                "  - Edits based on Giles's comments " +
                "    5) Remove relative leafrefs in groupings, " +
                "       and the resulting new groupings are: " +
                "       (a) bgp-auto-discovery-parameters-grp " +
                "       (b) bgp-signaling-parameters-grp " +
                "       (c) endpoint-grp " +
                "    11) Merge VPLS and VPWS into one single list " +
                "       and use augment statements to handle " +
                "       differences between VPLS and VPWS " +
                "  - Add a new grouping l2vpn-common-parameters-grp " +
                "    to make VPLS and VPWS more consistent";
    reference "";
  }

  revision "2016-05-31" {
    description "Fourth revision " +
                "  - Edits based on Giles's comments " +
                "    1) Change enumeration to identityref type for: " +
                "       (a) l2vpn-service-type " +
                "       (b) l2vpn-discovery-type " +
                "       (c) l2vpn-signaling-type " +
                "       bgp-rt-type, cw-negotiation, and " +
                "       pbb-component remain enumerations " +
                "    2) Define i-sid-type for leaf 'i-sid' " +
                "       (which is renamed from 'i-tag') " +
                "    3) Rename 'vpn-targets' to 'vpn-target' " +
                "    4) Import ietf-mpls.yang and reuse the " +
                "       'mpls-label' type defined in ietf-mpls.yang " +
                "       transmit-label and receive-label " +
                "    8) Change endpoint list's key to name " +
                "    9) Changed MTU to type uint16 " +
                "";
    reference "";
  }

  revision "2016-03-07" {
    description "Third revision " +
                "  - Changed the module name to ietf-l2vpn " +
                "  - Merged EVPN into L2VPN " +
                "  - Eliminated the definitions of attachment " +
                "    circuit with the intention to reuse other " +
                "    layer-2 definitions " +
                "  - Added state branch";
    reference "";
  }

  revision "2015-10-08" {
    description "Second revision " +



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                "  - Added container vpls-instances " +
                "  - Rearranged groupings and typedefs to be " +
                "    reused across vpls-instance and vpws-instances";
    reference "";
  }

  revision "2015-06-30" {
    description "Initial revision";
    reference   "";
  }

  /* identities */

  identity l2vpn-instance-type {
    description "Base identity from which identities of " +
                "l2vpn service instance types are derived";
  }

  identity vpws-instance-type {
    base l2vpn-instance-type;
    description "This identity represents VPWS instance type";
  }

  identity vpls-instance-type {
    base l2vpn-instance-type;
    description "This identity represents VPLS instance type";
  }

  identity link-discovery-protocol {
    description "Base identiy from which identities describing " +
                "link discovery protocols are derived";
  }

  identity lacp {
    base "link-discovery-protocol";
    description "This identity represents LACP";
  }

  identity lldp {
    base "link-discovery-protocol";
    description "This identity represents LLDP";
  }

  identity bpdu {
    base "link-discovery-protocol";
    description "This identity represens BPDU";
  }




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  identity cpd {
    base "link-discovery-protocol";
    description "This identity represents CPD";
  }

  identity udld {
    base "link-discovery-protocol";
    description "This identity represens UDLD";
  }

  identity l2vpn-service {
    description "Base identity from which identities describing " +
                "L2VPN services are derived";
  }

  identity Ethernet {
    base "l2vpn-service";
    description "This identity represents Ethernet service";
  }

  identity ATM {
    base "l2vpn-service";
    description "This identity represents Asynchronous Transfer " +
                "Mode service";
  }

  identity FR {
    base "l2vpn-service";
    description "This identity represent Frame-Relay service";
  }

  identity TDM {
    base "l2vpn-service";
    description "This identity represent Time Devision " +
                "Multiplexing service";
  }
  identity l2vpn-discovery {
    description "Base identity from which identities describing " +
                "L2VPN discovery protocols are derived";
  }

  identity manual-discovery {
    base "l2vpn-discovery";
    description "Manual configuration of l2vpn service";
  }

  identity bgp-auto-discovery {
    base "l2vpn-discovery";



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    description "Border Gateway Protocol (BGP) auto-discovery of " +
                "l2vpn service";
  }

  identity ldp-discovery {
    base "l2vpn-discovery";
    description "Label Distribution Protocol (LDP) discovery of " +
                "l2vpn service";
  }

  identity mixed-discovery {
    base "l2vpn-discovery";
    description "Mixed discovery methods of l2vpn service";
  }

  identity l2vpn-signaling {
    description "Base identity from which identities describing " +
                "L2VPN signaling protocols are derived";
  }

  identity static-configuration {
    base "l2vpn-signaling";
    description "Static configuration of labels (no signaling)";
  }

  identity ldp-signaling {
    base "l2vpn-signaling";
    description "Label Distribution Protocol (LDP) signaling";
  }

  identity bgp-signaling {
    base "l2vpn-signaling";
    description "Border Gateway Protocol (BGP) signaling";
  }

  identity mixed-signaling {
    base "l2vpn-signaling";
    description "Mixed signaling methods";
  }

  identity l2vpn-notification-state {
    description "The base identity on which notification states " +
                "are based";
  }

  identity MAC-limit-reached {
    base "l2vpn-notification-state";
    description "MAC limit is reached";



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  }
  identity MAC-limit-cleared {
    base "l2vpn-notification-state";
    description "MAC limit is cleared";
  }

  identity MTU-mismatched {
    base "l2vpn-notification-state";
    description "MAC is mismatched";
  }

  identity MTU-mismatched-cleared {
    base "l2vpn-notification-state";
    description "MAC is mismatch is cleared";
  }

  identity state-changed-to-up {
    base "l2vpn-notification-state";
    description "State is changed to UP";
  }

  identity state-changed-to-down {
    base "l2vpn-notification-state";
    description "State is changed to down";
  }

  identity MAC-move-limit-exceeded {
    base "l2vpn-notification-state";
    description "MAC move limit is exceeded";
  }

  identity MAC-move-limit-exceeded-cleared {
    base "l2vpn-notification-state";
    description "MAC move limit exceeded is cleared";
  }

  identity MAC-flap-detected {
    base "l2vpn-notification-state";
    description "MAC flap detected";
  }

  identity port-disabled-due-to-MAC-flap {
    base "l2vpn-notification-state";
    description "Port disabled due to MAC flap";
  }

  /* typedefs */




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  typedef l2vpn-service-type {
    type identityref {
      base "l2vpn-service";
    }
    description "L2VPN service type";
  }

  typedef l2vpn-discovery-type {
    type identityref {
      base "l2vpn-discovery";
    }
    description "L2VPN discovery type";
  }

  typedef l2vpn-signaling-type {
    type identityref {
      base "l2vpn-signaling";
    }
    description "L2VPN signaling type";
  }

  typedef link-discovery-protocol-type {
    type identityref {
      base "link-discovery-protocol";
    }
    description "This type is used to identify " +
                "link discovery protocol";
  }

  typedef pbb-component-type {
    type enumeration {
      enum "b-component" {
        description "Identifies as a b-component";
      }
      enum "i-component" {
        description "Identifies as an i-component";
      }
    }
    description "This type is used to identify " +
                "the type of PBB component";
  }

  typedef redundancy-group-template-ref {
    type leafref {
      path "/l2vpn:l2vpn/l2vpn:redundancy-group-templates" +
           "/l2vpn:redundancy-group-template/l2vpn:name";
    }
    description "redundancy-group-template-ref";



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  }
  typedef l2vpn-instance-name-ref {
    type leafref {
      path "/ni:network-instances/ni:network-instance" +
           "/ni:name";
    }
    description "l2vpn-instance-name-ref";
  }

  typedef l2vpn-instance-type-ref {
    type leafref {
      path "/ni:network-instances/ni:network-instance" +
           "/l2vpn:type";
    }
    description "l2vpn-instance-type-ref";
  }

  typedef operational-state-type {
    type enumeration {
      enum 'up' {
        description "Operational state is up";
      }
      enum 'down' {
        description "Operational state is down";
      }
    }
    description "operational-state-type";
  }

  typedef i-sid-type {
    type uint32 {
      range "0..16777216";
    }
    description "I-SID type that is 24-bits. " +
                "This should be moved to ieee-types.yang at " +
                "http://www.ieee802.org/1/files/public/docs2015" +
                "/new-mholness-ieee-types-yang-v01.yang";
  }

  /* groupings */

  grouping pbb-parameters-grp {
    description "PBB parameters grouping";
    container pbb-parameters {
      description "pbb-parameters";
      choice component-type {
        description "PBB component type";
        case i-component {



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          leaf i-sid {
            type i-sid-type;
            description "I-SID";
          }
          leaf backbone-src-mac {
            type yang:mac-address;
            description "backbone-src-mac";
          }
        }
        case b-component {
          leaf bind-b-component-name {
            type l2vpn-instance-name-ref;
            must "/ni:network-instances" +
                 "/ni:network-instance[ni:name=current()]" +
                 "/l2vpn:type = 'l2vpn:vpls-instance-type'" {
              description "A b-component must be an L2VPN instance " +
                          "of type vpls-instance-type";
            }
            description "Reference to the associated b-component";
          }
          leaf bind-b-component-type {
            type identityref {
              base l2vpn-instance-type;
            }
            must ". = 'l2vpn:vpls-instance-type'" {
              description "The associated b-component must have " +
                          "type vpls-instance-type";
            }
            config false;
            description "Type of the associated b-component";
          }
        }
      }
    }
  }

  grouping pbb-parameters-state-grp {
    description "PBB parameters grouping";
    container pbb-parameters {
      description "pbb-parameters";
      choice component-type {
        description "PBB component type";
        case i-component {
          leaf i-sid {
            type i-sid-type;
            description "I-SID";
          }
          leaf backbone-src-mac {



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            type yang:mac-address;
            description "backbone-src-mac";
          }
        }
        case b-component {
          leaf bind-b-component-name {
            type string;
            description "Name of the associated b-component";
          }
          leaf bind-b-component-type {
            type identityref {
              base l2vpn-instance-type;
            }
            must ". = 'l2vpn:vpls-instance-type'" {
              description "The associated b-component must have " +
                          "type vpls-instance-type";
            }
            description "Type of the associated b-component";
          }
        }
      }
    }
  }

  grouping l2vpn-common-parameters-grp {
    description "L2VPN common parameters";
    leaf type {
      type identityref {
        base l2vpn-instance-type;
      }
      description "Type of L2VPN service instance";
    }
    leaf mtu {
      type uint16;
      description "MTU of L2VPN service";
    }
    leaf mac-aging-timer {
      type uint32;
      description "mac-aging-timer, the duration after which" +
                  "a MAC entry is considered aged out";
    }
    leaf service-type {
      type l2vpn-service-type;
      default Ethernet;
      description "L2VPN service type";
    }
    leaf discovery-type {
      type l2vpn-discovery-type;



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      default manual-discovery;
      description "L2VPN service discovery type";
    }
    leaf signaling-type {
      type l2vpn-signaling-type;
      mandatory true;
      description "L2VPN signaling type";
    }
  }
  grouping bgp-signaling-parameters-grp {
    description "BGP parameters for signaling";
    leaf site-id {
      type uint16;
      description "Site ID";
    }
    leaf site-range {
      type uint16;
      description "Site Range";
    }
  }

  grouping redundancy-group-properties-grp {
    description "redundancy-group-properties-grp";
    leaf protection-mode {
      type enumeration {
        enum "frr" {
          value 0;
          description "fast reroute";
        }
        enum "master-slave" {
          value 1;
          description "master-slave";
        }
        enum "independent" {
          value 2;
          description "independent";
        }
      }
      description "protection-mode";
    }
    leaf reroute-mode {
      type enumeration {
        enum "immediate" {
          value 0;
          description "immediate reroute";
        }
        enum "delayed" {
          value 1;



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          description "delayed reroute";
        }
        enum "never" {
          value 2;
          description "never reroute";
        }
      }
      description "reroute-mode";
    }
    leaf dual-receive {
      type boolean;
      description
      "allow extra traffic to be carried by backup";
    }
    leaf revert {
      type boolean;
      description "allow forwarding to revert to primary " +
                  "after restoring primary";
    }
    leaf reroute-delay {
      when "../reroute-mode = 'delayed'" {
        description "Specify amount of time to " +
                    "delay reroute only when " +
                    "delayed route is configured";
      }
      type uint16;
      description "amount of time to delay reroute";
    }
    leaf revert-delay {
      when "../revert = 'true'" {
        description "Specify the amount of time to " +
                    "wait to revert to primary " +
                    "only if reversion is configured";
      }
      type uint16;
      description "amount ot time to wait to revert to primary";
    }
  }

  grouping endpoint-grp {
    description "A grouping that defines the structure of " +
                "an endpoint";
    choice ac-or-pw-or-redundancy-grp {
      description "A choice ofattachment circuit or " +
                  "pseudowire or redundancy group";
      case ac {
        description "Attachment circuit(s) as an endpoint";
      }



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      case pw {
        description "Pseudowire(s) as an endpoint";
      }
      case redundancy-grp {
        description "Redundancy group as an endpoint";
        choice primary {
          mandatory true;
          description "primary options";
          case primary-ac {
            description "primary-ac";
          }
          case primary-pw {
            description "primary-pw";
          }
        }
        choice backup {
          description "backup options";
          case backup-ac {
            description "backup-ac";
          }
          case backup-pw {
            description "backup-pw";
          }
        }
      }
    }
  }

  /* L2VPN YANG Model */

  container l2vpn {
    description "L2VPN specific data";

    container redundancy-group-templates {
      description "redundancy group templates";
      list redundancy-group-template {
        key "name";
        description "redundancy-group-template";
        leaf name {
          type string;
          description "name";
        }
        uses redundancy-group-properties-grp;
      }
    }
  }

  /* augments */



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  augment "/ni:network-instances/ni:network-instance/ni:ni-type" {
    description
      "Augmentation for L2VPN instance";
    case l2vpn {
      description "An L2VPN service instance";
      uses l2vpn-common-parameters-grp;
      container bgp-parameters {
        when "../discovery-type = 'l2vpn:bgp-auto-discovery'" {
          description "Parameters used when discovery type is " +
                      "bgp-auto-discovery";
        }
        description "BGP auto-discovery parameters";
        leaf vpn-id {
          type string;
          description "VPN ID";
        }
        container rd-rt {
          leaf route-distinguisher {
            type rt-types:route-distinguisher;
            description "BGP route distinguisher";
          }
          uses rt-types:vpn-route-targets;
          description "Route distiguisher and " +
                      "corresponding VPN route targets";
        }
      }
      container bgp-signaling {
        when "../signaling-type = 'l2vpn:bgp-signaling'" {
          description "Check signaling type: " +
                      "Can only configure BGP signaling if " +
                      "signaling type is BGP";
        }
        description "BGP signaling parameters";
        uses bgp-signaling-parameters-grp;
      }
      list endpoint {
        key "name";
        description "An endpoint";
        leaf name {
          type string;
          description "endpoint name";
        }
        uses endpoint-grp {
          augment "ac-or-pw-or-redundancy-grp/ac" {
            description "Augment for attachment circuit(s) " +
                        "as an endpoint";
            list ac {
              key "name";



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              leaf name {
                type if:interface-ref;
                description "Name of attachment circuit";
              }
              leaf state {
                type operational-state-type;
                config false;
                description "attachment circuit up/down state";
              }
              description "An L2VPN instance's " +
                          "attachment circuit list";
            }
          }
          augment "ac-or-pw-or-redundancy-grp/pw" {
            description "Augment for pseudowire(s) as an endpoint";
            list pw {
              key "name";
              leaf name {
                type pw:pseudowire-ref;
                must "(../../../type = " +
                       " 'l2vpn:vpws-instance-type') or " +
                       "(not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vccv-ability)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /request-vlanid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vlan-tpid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /ttl)))" {
                    description "Only a VPWS PW has parameters " +
                                "vccv-ability, request-vlanid, " +
                                "vlan-tpid, and ttl";
                  }
                description "Pseudowire name";
              }
              leaf state {
                type leafref {
                  path "/pw:pseudowires" +
                       "/pw:pseudowire[pw:name=current()/../name]" +
                       "/pw:state";
                }
                config false;
                description "Pseudowire state";
              }



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              description "An L2VPN instance's pseudowire list";
            }
          }
          augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
                  "primary/primary-ac" {
            description "Augment for primary-ac";
            container primary-ac {
              description "Primary AC";
              leaf name {
                type if:interface-ref;
                description "Name of attachment circuit";
              }
              leaf state {
                type operational-state-type;
                config false;
                description "attachment circuit up/down state";
              }
            }
          }
          augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
                  "primary/primary-pw" {
            description "Augment for primary-pw";
            list primary-pw {
              key "name";
              leaf name {
                type pw:pseudowire-ref;
                must "(../../../type = " +
                       " 'l2vpn:vpws-instance-type') or " +
                       "(not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vccv-ability)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /request-vlanid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vlan-tpid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /ttl)))" {
                    description "Only a VPWS PW has parameters " +
                                "vccv-ability, request-vlanid, " +
                                "vlan-tpid, and ttl";
                  }
                description "Pseudowire name";
              }
              leaf state {
                type leafref {



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                  path "/pw:pseudowires" +
                       "/pw:pseudowire[pw:name=current()/../name]" +
                       "/pw:state";
                }
                config false;
                description "Pseudowire state";
              }
              description "An L2VPN instance's pseudowire list";
            }
          }
          augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
                  "backup/backup-ac" {
            description "Augment for backup-ac";
            container backup-ac {
              description "Backup AC";
              leaf name {
                type if:interface-ref;
                description "Name of attachment circuit";
              }
              leaf state {
                type operational-state-type;
                config false;
                description "attachment circuit up/down state";
              }
            }
          }
          augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
                  "backup/backup-pw" {
            description "Augment for backup-pw";
            list backup-pw {
              key "name";
              leaf name {
                type pw:pseudowire-ref;
                must "(../../../type = " +
                       " 'l2vpn:vpws-instance-type') or " +
                       "(not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vccv-ability)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /request-vlanid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /vlan-tpid)) and " +
                       " not(boolean(/pw:pseudowires" +
                       "     /pw:pseudowire[pw:name = current()]" +
                       "     /ttl)))" {
                    description "Only a VPWS PW has parameters " +



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                                "vccv-ability, request-vlanid, " +
                                "vlan-tpid, and ttl";
                  }
                description "Pseudowire name";
              }
              leaf state {
                type leafref {
                  path "/pw:pseudowires" +
                       "/pw:pseudowire[pw:name=current()/../name]" +
                       "/pw:state";
                }
                config false;
                description "Pseudowire state";
              }
              description "A list of backup pseudowires";
            }
          }
          augment "ac-or-pw-or-redundancy-grp/redundancy-grp" {
            description "Augment for redundancy group properties";
            leaf template {
              type redundancy-group-template-ref;
              description "Reference a redundancy group " +
                          "properties template";
            }
            uses redundancy-group-properties-grp;
          }
        }
      }
    }
  }

  augment "/pw:pseudowires/pw:pseudowire" {
    description "Augment for peudowire parameters for " +
                "VPWS pseudowires";
    leaf vccv-ability {
      type boolean;
      description "vccvability";
    }
    leaf request-vlanid {
      type uint16;
      description "request vlanid";
    }
    leaf vlan-tpid {
      type string;
      description "vlan tpid";
    }
    leaf ttl {
      type uint8;



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      description "time-to-live";
    }
  }

  augment "/pw:pseudowires/pw:pseudowire/pw:pw-type" {
    description "Additional pseudowire types";
    case bgp-pw {
      container bgp-pw {
        description "BGP pseudowire";
        leaf remote-pe-id {
          type inet:ip-address;
          description "remote pe id";
        }
      }
    }
    case bgp-ad-pw {
      container bgp-ad-pw {
        description "BGP auto-discovery pseudowire";
        leaf remote-ve-id {
          type uint16;
          description "remote ve id";
        }
      }
    }
  }

  augment "/ni:network-instances/ni:network-instance/ni:ni-type" +
          "/l2vpn:l2vpn" {
    when "l2vpn:type = 'l2vpn:vpws-instance-type'" {
      description "Constraints only for VPWS pseudowires";
    }
    description "Augment for VPWS instance";
    container vpws-constraints {
      must "(count(../endpoint) <= 2) and " +
           "(count(../endpoint/pw) <= 1) and " +
           "(count(../endpoint/ac)  <= 1) and " +
           "(count(../endpoint/primary-pw)  <= 1) and " +
           "(count(../endpoint/backup-pw)  <= 1) " {
        description "A VPWS L2VPN instance has at most 2 endpoints " +
                    "and each endpoint has at most 1 pseudowire or " +
                    "1 attachment circuit";
      }
      description "VPWS constraints";
    }
  }

  augment "/ni:network-instances/ni:network-instance/ni:ni-type" +
          "/l2vpn:l2vpn" {



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    when "l2vpn:type = 'l2vpn:vpls-instance-type'" {
      description "Parameters specifically for a VPLS instance";
    }
    description "Augment for parameters for a VPLS instance";
    uses pbb-parameters-grp;
  }

  augment "/ni:network-instances/ni:network-instance/ni:ni-type" +
          "/l2vpn:l2vpn/l2vpn:endpoint" {
    when "../l2vpn:type = 'l2vpn:vpls-instance-type'" {
      description "Endpoint parameter specifically for " +
                  "a VPLS instance";
    }
    description "Augment for endpoint parameters for a VPLS instance";
    leaf split-horizon-group {
      type string;
      description "Identify a split horizon group";
    }
  }

  augment "/ni:network-instances/ni:network-instance/ni:ni-type" +
          "/l2vpn:l2vpn/l2vpn:endpoint" +
          "/l2vpn:ac-or-pw-or-redundancy-grp" +
          "/l2vpn:redundancy-grp/l2vpn:backup" +
          "/l2vpn:backup-pw/l2vpn:backup-pw" {
    when "../../l2vpn:type = 'l2vpn:vpls-instance-type'" {
      description "Backup pseudowire parameter specifically for " +
                  "a VPLS instance";
    }
    description "Augment for backup pseudowire paramters for " +
                "a VPLS instance";
    leaf precedence {
      type uint32;
      description "precedence of the pseudowire";
    }
  }

  /* Notifications */

  notification l2vpn-state-change-notification {
    description "L2VPN and constituents state change notification";
    leaf l2vpn-instance-name {
      type l2vpn-instance-name-ref;
      description "The L2VPN instance name";
    }
    leaf l2vpn-instance-type {
      type leafref {
        path "/ni:network-instances" +



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             "/ni:network-instance" +
                  "[ni:name=current()/../l2vpn-instance-name]" +
             "/l2vpn:type";
      }
      description "The L2VPN instance type";
    }
    leaf endpoint {
      type leafref {
        path "/ni:network-instances" +
             "/ni:network-instance" +
                  "[ni:name=current()/../l2vpn-instance-name]" +
             "/l2vpn:endpoint/l2vpn:name";
      }
      description "The endpoint";
    }
    uses endpoint-grp {
      augment "ac-or-pw-or-redundancy-grp/ac" {
        description "Augment for attachment circuit(s) " +
                    "as an endpoint";
        leaf ac {
          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +
                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint" +
                    "[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:ac/l2vpn:name";
          }
          description "Related attachment circuit";
        }
      }
      augment "ac-or-pw-or-redundancy-grp/pw" {
        description "Augment for pseudowire(s) as an endpoint";
        leaf pw {
          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +
                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:pw/l2vpn:name";
          }
          description "Related pseudowire";
        }
      }
      augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
              "primary/primary-ac" {
        description "Augment for primary-ac";
        leaf primary-ac {



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          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +
                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint" +
                    "[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:primary-ac/l2vpn:name";
          }
          description "Related primary attachment circuit";
        }
      }
      augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
              "primary/primary-pw" {
        description "Augment for primary-pw";
        leaf primary-pw {
          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +
                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint" +
                    "[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:primary-pw/l2vpn:name";
          }
          description "Related primary pseudowire";
        }
      }
      augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
              "backup/backup-ac" {
        description "Augment for backup-ac";
        leaf backup-ac {
          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +
                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint" +
                    "[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:backup-ac/l2vpn:name";
          }
          description "Related backup attachment circuit";
        }
      }
      augment "ac-or-pw-or-redundancy-grp/redundancy-grp/" +
              "backup/backup-pw" {
        description "Augment for backup-pw";
        leaf backup-pw {
          type leafref {
            path "/ni:network-instances" +
                 "/ni:network-instance" +



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                    "[ni:name=current()/../l2vpn-instance-name]" +
                 "/l2vpn:endpoint" +
                    "[l2vpn:name=current()/../endpoint]" +
                 "/l2vpn:backup-pw/l2vpn:name";
          }
          description "Related backup pseudowire";
        }
      }
    }
    leaf state {
      type identityref {
        base l2vpn-notification-state;
      }
      description "State change notification";
    }
  }
}

<CODE ENDS>


                                 Figure 3

5.  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.

   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]

6.  IANA Considerations

   None.

7.  Acknowledgments

   The authors would like to acknowledge Giles Heron and others for
   their useful comments.





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   MITRE has approved this document for Public Release, Distribution
   Unlimited, with Public Release Case Number 19-0683.

8.  References

8.1.  Normative References

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

8.2.  Informative References

   [RFC3916]  Xiao, X., Ed., McPherson, D., Ed., and P. Pate, Ed.,
              "Requirements for Pseudo-Wire Emulation Edge-to-Edge
              (PWE3)", RFC 3916, DOI 10.17487/RFC3916, September 2004,
              <https://www.rfc-editor.org/info/rfc3916>.

   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,
              <https://www.rfc-editor.org/info/rfc3985>.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
              February 2006, <https://www.rfc-editor.org/info/rfc4385>.

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446,
              DOI 10.17487/RFC4446, April 2006,
              <https://www.rfc-editor.org/info/rfc4446>.

   [RFC4448]  Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
              "Encapsulation Methods for Transport of Ethernet over MPLS
              Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
              <https://www.rfc-editor.org/info/rfc4448>.

   [RFC4664]  Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
              2 Virtual Private Networks (L2VPNs)", RFC 4664,
              DOI 10.17487/RFC4664, September 2006,
              <https://www.rfc-editor.org/info/rfc4664>.

   [RFC4665]  Augustyn, W., Ed. and Y. Serbest, Ed., "Service
              Requirements for Layer 2 Provider-Provisioned Virtual
              Private Networks", RFC 4665, DOI 10.17487/RFC4665,
              September 2006, <https://www.rfc-editor.org/info/rfc4665>.



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   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC4762]  Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
              <https://www.rfc-editor.org/info/rfc4762>.

   [RFC5003]  Metz, C., Martini, L., Balus, F., and J. Sugimoto,
              "Attachment Individual Identifier (AII) Types for
              Aggregation", RFC 5003, DOI 10.17487/RFC5003, September
              2007, <https://www.rfc-editor.org/info/rfc5003>.

   [RFC5254]  Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed.,
              "Requirements for Multi-Segment Pseudowire Emulation Edge-
              to-Edge (PWE3)", RFC 5254, DOI 10.17487/RFC5254, October
              2008, <https://www.rfc-editor.org/info/rfc5254>.

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              DOI 10.17487/RFC5659, October 2009,
              <https://www.rfc-editor.org/info/rfc5659>.

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073,
              DOI 10.17487/RFC6073, January 2011,
              <https://www.rfc-editor.org/info/rfc6073>.

   [RFC6074]  Rosen, E., Davie, B., Radoaca, V., and W. Luo,
              "Provisioning, Auto-Discovery, and Signaling in Layer 2
              Virtual Private Networks (L2VPNs)", RFC 6074,
              DOI 10.17487/RFC6074, January 2011,
              <https://www.rfc-editor.org/info/rfc6074>.

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

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







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   [RFC6391]  Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V.,
              Regan, J., and S. Amante, "Flow-Aware Transport of
              Pseudowires over an MPLS Packet Switched Network",
              RFC 6391, DOI 10.17487/RFC6391, November 2011,
              <https://www.rfc-editor.org/info/rfc6391>.

   [RFC6423]  Li, H., Martini, L., He, J., and F. Huang, "Using the
              Generic Associated Channel Label for Pseudowire in the
              MPLS Transport Profile (MPLS-TP)", RFC 6423,
              DOI 10.17487/RFC6423, November 2011,
              <https://www.rfc-editor.org/info/rfc6423>.

   [RFC6478]  Martini, L., Swallow, G., Heron, G., and M. Bocci,
              "Pseudowire Status for Static Pseudowires", RFC 6478,
              DOI 10.17487/RFC6478, May 2012,
              <https://www.rfc-editor.org/info/rfc6478>.

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

   [RFC6624]  Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
              Virtual Private Networks Using BGP for Auto-Discovery and
              Signaling", RFC 6624, DOI 10.17487/RFC6624, May 2012,
              <https://www.rfc-editor.org/info/rfc6624>.

   [RFC7041]  Balus, F., Ed., Sajassi, A., Ed., and N. Bitar, Ed.,
              "Extensions to the Virtual Private LAN Service (VPLS)
              Provider Edge (PE) Model for Provider Backbone Bridging",
              RFC 7041, DOI 10.17487/RFC7041, November 2013,
              <https://www.rfc-editor.org/info/rfc7041>.

   [RFC7361]  Dutta, P., Balus, F., Stokes, O., Calvignac, G., and D.
              Fedyk, "LDP Extensions for Optimized MAC Address
              Withdrawal in a Hierarchical Virtual Private LAN Service
              (H-VPLS)", RFC 7361, DOI 10.17487/RFC7361, September 2014,
              <https://www.rfc-editor.org/info/rfc7361>.

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

   [RFC8077]  Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
              Maintenance Using the Label Distribution Protocol (LDP)",
              STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
              <https://www.rfc-editor.org/info/rfc8077>.




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Appendix A.  Example Configuration

   This section shows an example configuration using the YANG data model
   defined in the document.

Appendix B.  Contributors

   The editors gratefully acknowledge the following people for their
   contributions to this document.

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

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

                  Giles Heron
                  Cisco Systems, Inc.
                  Email: giheron@cisco.com

                 Tapraj Singh
                 Cisco Systems, Inc.
                 Email: tsingh@cisco.com

                 Zhenbin Li
                 Huawei Technologies
                 Email: lizhenbin@huawei.com

                 Zhuang Shunwan
                 Huawei Technologies
                 Email: Zhuangshunwan@huawei.com

                 Wang Haibo
                 Huawei Technologies
                 Email: rainsword.wang@huawei.com

                 Sajjad Ahmed
                 Ericsson
                 Email: sajjad.ahmed@ericsson.com

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

                 Jorge Rabadan
                 Nokia



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                 Email: jorge.rabadan@nokia.com

                 Jonathan Hardwick
                 Metaswitch
                 Email: jonathan.hardwick@metaswitch.com

                 Santosh Esale
                 Juniper Networks
                 Email: sesale@juniper.net

                 Nick Delregno
                 Verizon
                 Email: nick.deregno@verizon.com

                 Luay Jalil
                 Verizon
                 Email: luay.jalil@verizon.com

                 Maria Joecylyn
                 Verizon
                 Email: joecylyn.malit@verizon.com

                                 Figure 4

Authors' Addresses

   Himanshu Shah
   Ciena Corporation

   Email: hshah@ciena.com


   Patrice Brissette
   Cisco Systems, Inc.

   Email: pbrisset@cisco.com


   Ing-When Chen
   The MITRE Corporation

   Email: ingwherchen@mitre.org


   Iftekar Hussain
   Infinera Corporation

   Email: ihussain@infinera.com



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   Bin Wen
   Comcast

   Email: Bin_Wen@cable.comcast.com


   Kishore Tiruveedhula
   Juniper Networks

   Email: kishoret@juniper.net









































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