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<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
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<rfc category="std" xmlns:xi="http://www.w3.org/2001/XInclude"  docName="draft-ietf-i2rs-yang-l2-network-topology-18"
     ipr="trust200902"> number="8944" ipr="trust200902" obsoletes="" updates="" submissionType="IETF" category="std" consensus="true" xml:lang="en" tocInclude="true" tocDepth="3" symRefs="true" sortRefs="true" version="3">

  <!-- xml2rfc v2v3 conversion 3.1.1 -->
  <front>
    <title abbrev="YANG Data Model for L2 Topologies">A YANG Data Model for
    Layer 2 Network Topologies</title>
    <seriesInfo name="RFC" value="8944"/>
    <author fullname="Jie Dong" initials="J." surname="Dong">
      <organization>Huawei</organization>
      <address>
        <postal>
          <street>Huawei Campus, No.
          <street>No. 156 Beiqing Rd.</street>
	  <extaddr>Huawei Campus</extaddr>
	  <city>Beijing</city>
          <code>100095</code>
          <country>China</country>
        </postal>
        <email>jie.dong@huawei.com</email>
      </address>
    </author>
    <author fullname="Xiugang Wei" initials="X." surname="Wei">
      <organization>Huawei</organization>
      <address>
        <postal>
          <street>Huawei Campus, No.
          <street>No. 156 Beiqing Rd.</street>
	  <extaddr>Huawei Campus</extaddr>
          <city>Beijing</city>
          <code>100095</code>
          <country>China</country>
        </postal>
        <email>weixiugang@huawei.com</email>
      </address>
    </author>
    <author fullname="Qin Wu" initials="Q." surname="Wu">
      <organization>Huawei</organization>
      <address>
        <postal>
          <street>101 Software Avenue, Yuhua Avenue</street>
	  <street>Yuhua District</street>
          <city>Nanjing</city>
          <code>210012</code>
          <country>China</country>
        </postal>
        <email>bill.wu@huawei.com</email>
      </address>
    </author>
    <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
      <organization>Orange</organization>
      <address>
        <postal>
          <street>Rennes 35000</street>
          <country>France</country>
        </postal>
        <email>mohamed.boucadair@orange.com</email>
      </address>
    </author>
    <author fullname="Anders Liu" initials="A." surname="Liu">
      <organization>Tecent</organization>
      <address>
        <postal>
          <street>Yinke Building 38 Haidian St,
          <street>38 Haidian St</street>
	  <extaddr>Yinke Building</extaddr>
	  <street>Haidian District</street>
          <city>Beijing</city>
          <code>100080</code>
          <country>China</country>
        </postal>
        <email>andersliu@tencent.com</email>
      </address>
    </author>
    <date year="2020"/> year="2020" month="November"/>

<keyword>VxLAN</keyword>
<keyword>VLAN</keyword>
<keyword>QinQ</keyword>
<keyword>Provider Backbone Bridging</keyword>
<keyword>Ethernet</keyword>
<keyword>VPLS</keyword>

    <abstract>
      <t>This document defines a YANG data model for Layer 2 network
      topologies. In particular, this data model augments the generic network
      and network topology data models with Layer 2 specific topology
      attributes.</t>
    </abstract>

    <note title="Editorial Note (To be removed by RFC Editor)">
      <t>Please update these statements within the document with the RFC
      number to be assigned
      attributes that are specific to this document:<list style="symbols">
          <t>"This version of this YANG module is part of RFC XXXX;"</t>

          <t>"RFC XXXX: A YANG Data Model for Layer 2 Network Topologies";</t>

          <t>reference: RFC XXXX</t>
        </list></t>

      <t>Please update the "revision" date of the YANG module.</t>
    </note> 2.</t>
    </abstract>
  </front>
  <middle>
    <section title="Introduction"> numbered="true" toc="default">
      <name>Introduction</name>
      <t><xref target="RFC8345"/> target="RFC8345" format="default"/> defines the YANG <xref target="RFC6020"/> target="RFC6020" format="default"/>
        <xref target="RFC7950"/> target="RFC7950" format="default"/> data models of the abstract (generic) network
      and network topology. Such models can be augmented with
      technology-specific details to build more specific topology models.</t>
      <t>This document defines the YANG data model for Layer 2 (L2) network
      topologies by augmenting the generic network (Section 6.1 of <xref
      target="RFC8345"/>) (<xref target="RFC8345"
      sectionFormat="of" section="6.1"/>) and network topology (Section 6.2 of <xref
      target="RFC8345"/>) (<xref
      target="RFC8345" sectionFormat="of" section="6.2"/>) data models with
      L2-specific topology attributes. An
      example is provided in <xref target="ex"/>.</t> target="ex" format="default"/>.</t>
      <t>There are multiple applications for such a data model. For example,
      within the context of Interface to the Routing System (I2RS), nodes
      within the network can use the data model to capture their understanding
      of the overall network topology and expose it to a network controller. A
      network controller can then use the instantiated topology data to
      compare and reconcile its own view of the network topology with that of
      the network elements that it controls. Alternatively, nodes within the
      network may compare and reconcile this understanding either among
      themselves or with the help of a controller. Beyond the network element
      and the immediate context of I2RS itself, a network controller might
      even use the data model to represent its view of the topology that it
      controls and expose it to external applications. Further use cases where
      the data model can be applied are described in <xref
      target="I2RS-UR"/>.</t> target="I-D.ietf-i2rs-usecase-reqs-summary" format="default"/>.</t>
      <t>This document uses the common YANG types defined in <xref
      target="RFC6991"/> target="RFC6991" format="default"/> and adopts the Network Management Datastore
      Architecture (NMDA) <xref target="RFC8342"/>.</t> target="RFC8342" format="default"/>.</t>
    </section>
    <section title="Terminology">
      <t>The numbered="true" toc="default">
      <name>Terminology</name>
        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
      "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
    NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and
      "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are
    to be interpreted as described in BCP 14 BCP&nbsp;14 <xref target="RFC2119"/>
    <xref target="RFC8174"/> when, and only when, they appear in all capitals,
    as shown here.</t> here.
        </t>

      <t>The terminology for describing YANG modules is defined in <xref
      target="RFC7950"/>. target="RFC7950" format="default"/>. The meanings of the symbols used in the tree diagram
      are defined in <xref target="RFC8340"/>.</t> target="RFC8340" format="default"/>.</t>
    </section>
    <section title="Layer numbered="true" toc="default">
      <name>Layer 2 Topology Model"> Model</name>
      <t>The Layer 2 network topology YANG module is designed to be generic
      and applicable to Layer 2 networks built with different Layer 2
      technologies. It can be used to describe both the physical and the
      logical (virtual) Layer 2 network topologies.</t>
      <t>The relationship between the Layer 2 topology module and the generic
      network and network topology module is shown in <xref target="dia"/>. target="dia" format="default"/>. In
      order to represent a Layer 2 network topology, the generic network and
      topology models are augmented with Layer 2 specific L2-specific information, such as
      the identifiers, identities (e.g., Provider Backbone Bridging <xref
      target="IEEE802.1ah"/>,
      target="IEEE802.1ah" format="default"/>, QinQ <xref target="IEEE802.1ad"/>, target="IEEE802.1ad"
      format="default"/>, or VXLAN Virtual eXtensible Local Area Network (VXLAN)
      <xref target="RFC7348"/>), target="RFC7348" format="default"/>), attributes, and states of the Layer 2
      networks, nodes, links, and termination points. Some of the information
      may be collected via Link Layer Discovery Protocol (LLDP) <xref
      target="IEEE802.1AB"/> target="IEEE802.1AB" format="default"/> or other Layer 2 protocols, and some of them may
      be locally configured.</t>

      <t><figure anchor="dia" title="Layer
      <figure anchor="dia">
        <name>Layer 2 Topology YANG Module Structure"> Structure</name>
        <artwork align="center"> align="center" name="" type="" alt=""><![CDATA[
+---------------------+
|    ietf-network     |
+----------^----------+
           |
           |
+---------------------+
|ietf-network-topology|
+----------^----------+
           |
           |
+----------^----------+
|   ietf-l2-topology  |
+---------------------+
</artwork>
        </figure></t>
]]></artwork>
      </figure>
      <t>The structure of the "ietf-l2-topology" YANG module is depicted in
      the following tree diagram:</t>

      <t><figure>
          <artwork>module:

      <sourcecode name="" type="yangtree" ><![CDATA[
module: ietf-l2-topology
  augment /nw:networks/nw:network/nw:network-types:
    +--rw l2-topology!
  augment /nw:networks/nw:network:
    +--rw l2-topology-attributes
       +--rw name?    string
       +--rw flags*   l2-flag-type
  augment /nw:networks/nw:network/nw:node:
    +--rw l2-node-attributes
       +--rw name?                 string
       +--rw flags*                node-flag-type
       +--rw bridge-id*            string
       +--rw management-address*   inet:ip-address
       +--rw management-mac?       yang:mac-address
       +--rw management-vlan?      string
  augment /nw:networks/nw:network/nt:link:
    +--rw l2-link-attributes
       +--rw name?        string
       +--rw flags*       link-flag-type
       +--rw rate?        uint64
       +--rw delay?       uint32
       +--rw auto-nego?   boolean
       +--rw duplex?      duplex-mode
  augment /nw:networks/nw:network/nw:node/nt:termination-point:
    +--rw l2-termination-point-attributes
       +--rw interface-name?       string
       +--rw mac-address?          yang:mac-address
       +--rw port-number*          uint32
       +--rw unnumbered-id*        uint32
       +--rw encapsulation-type?   identityref
       +--rw outer-tag?            dot1q-types:vid-range-type {VLAN}?
       +--rw outer-tpid?           dot1q-types:dot1q-tag-type {QinQ}?
       +--rw inner-tag?            dot1q-types:vid-range-type {VLAN}?
       +--rw inner-tpid?           dot1q-types:dot1q-tag-type {QinQ}?
       +--rw lag?                  boolean
       +--rw member-link-tp*       -&gt;
              -> /nw:networks/network/node/nt:termination-point/tp-id
       +--rw vxlan {VXLAN}?
          +--rw vni-id?   vni

  notifications:
    +---n l2-node-event
    |  +--ro event-type?           l2-network-event-type
    |  +--ro node-ref?             -&gt;
                      -> /nw:networks/network[nw:network-id=current()
                         /../network-ref]/node/node-id
    |  +--ro network-ref?          -&gt;          -> /nw:networks/network/network-id
    |  +--ro l2-topology!
    |  +--ro l2-node-attributes
    |     +--ro name?                 string
    |     +--ro flags*                node-flag-type
    |     +--ro bridge-id*            uint64
    |     +--ro management-address*   inet:ip-address
    |     +--ro management-mac?       yang:mac-address
    |     +--ro management-vlan?      string
    +---n l2-link-event
    |  +--ro event-type?           l2-network-event-type
    |  +--ro link-ref?             -&gt;
                      -> /nw:networks/network[nw:network-id=current()
                         /../network-ref]/nt:link/link-id
    |  +--ro network-ref?          -&gt;          -> /nw:networks/network/network-id
    |  +--ro l2-topology!
    |  +--ro l2-link-attributes
    |     +--ro name?        string
    |     +--ro flags*       link-flag-type
    |     +--ro rate?        uint64
    |     +--ro delay?       uint32
    |     +--ro auto-nego?   boolean
    |     +--ro duplex?      duplex-mode
    +---n l2-termination-point-event
       +--ro event-type?                        l2-network-event-type
       +--ro tp-ref?                            -&gt;
                      -> /nw:networks/network[nw:network-id=current()
                         /../network-ref]/node[nw:node-id=current()
                         /../node-ref]/nt:termination-point/tp-id
       +--ro node-ref?                 -&gt;
                      -> /nw:networks/network[nw:network-id=current()
                         /../network-ref]/node/node-id
       +--ro network-ref?              -&gt;          -> /nw:networks/network/network-id
       +--ro l2-topology!
       +--ro l2-termination-point-attributes
          +--ro interface-name?       string
          +--ro mac-address?          yang:mac-address
          +--ro port-number*          uint32
          +--ro unnumbered-id*        uint32
          +--ro encapsulation-type?   identityref
          +--ro outer-tag?         dot1q-types:vid-range-type {VLAN}?
          +--ro outer-tpid?        dot1q-types:dot1q-tag-type {QinQ}?
          +--ro inner-tag?         dot1q-types:vid-range-type {VLAN}?
          +--ro inner-tpid?        dot1q-types:dot1q-tag-type {QinQ}?
          +--ro lag?               boolean
          +--ro member-link-tp*       -&gt;
              -> /nw:networks/network/node/nt:termination-point/tp-id
          +--ro vxlan {VXLAN}?
             +--ro vni-id?   vni</artwork>
        </figure></t>   vni
]]></sourcecode>
      <t>The Layer 2 topology Topology YANG module augments the "ietf-network" and
      "ietf-network-topology" YANG modules as follows:</t>

      <t><list style="symbols">
          <t>A
      <ul spacing="normal">
        <li>A new network type "l2-network-type" is introduced. This is
          represented by a container object, object and is inserted under the
          "network-types" container of the generic "ietf-network" module
          defined in Section 6.1 of <xref target="RFC8345"/>.</t>

          <t>Additional target="RFC8345" sectionFormat="of" section="6.1"/>.</li>
        <li>Additional network attributes are introduced in a grouping
          "l2-network-attributes", which augments the "network" list of the
          "ietf-network" module. The attributes include the Layer 2 network name
          and a set of flags. Each type of flag is represented by a separate
          identity.</t>

          <t>Additional
          identity.</li>

        <li>Additional data objects for Layer 2 nodes are introduced by
          augmenting the "node" list of the generic "ietf-network" module.
      New objects include the Layer 2 node identifier, management address,
      management mac, mangement vlan MAC address, management VLAN, and a set of flags.</t>

          <t>Additional flags.</li>
        <li>Additional data objects for Layer 2 termination points are
          introduced by augmenting the "termination-point" list of the
          "ietf-network-topology" module defined in Section 6.2 of <xref
          target="RFC8345"/>. target="RFC8345"
	  sectionFormat="of" section="6.2"/>.
      New objects include the interface name, encapsulation type,
      lag support indication, and attributes that are specific to
      the Layer 2 termination point type
          specific attributes.</t>

          <t>Links type.</li>
        <li>Links in the "ietf-network-topology" module are augmented as well
          with a set of Layer 2 parameters, allowing to associate a link with
          a name, a set of Layer 2 link attributes, and flags.</t>

          <t>Some flags.</li>
        <li>Some optional Layer 2 technology specific technology-specific attributes are
          introduced in this module as Layer 2 features because these
          attributes may be useful to expose to above services/applications.
          Note that learning or configuring advanced
	  Layer 2 technology-specific attributes is not within the scope of
	  the Layer
          2 Topology YANG module; dedicated YANG modules should be used
          instead (e.g., <xref target="I-D.ietf-trill-yang"/>).</t>
        </list></t> target="I-D.ietf-trill-yang" format="default"/>).</li>
      </ul>
    </section>
    <section anchor="L2YANG" title="Layer numbered="true" toc="default">
      <name>Layer 2 Topology YANG Module"> Module</name>

      <t>This module uses types defined in <xref target="RFC6991"/>, target="RFC6991"
      format="default"/>, <xref
      target="RFC7224"/>, target="RFC7224" format="default"/>, <xref target="IEEE802.1Qcp"/>,
      target="IEEE802.1Qcp" format="default"/>, and <xref
      target="RFC8345"/>. target="RFC8345"
      format="default"/>. It also references <xref target="RFC4761"/><xref
      target="RFC4762">, </xref>, target="IEEE802.1Q-2014"
      format="default"/>, <xref target="IEEE802.1ad" format="default"/>, <xref
      target="RFC7348" format="default"/>, and
      <xref target="RFC4202"/>.</t>

      <t><figure>
          <artwork>&lt;CODE BEGINS&gt; file "ietf-l2-topology@2020-06-29.yang" target="RFC7727" format="default"/>.</t>

      <sourcecode name="ietf-l2-topology@2020-11-02.yang" type="yang" markers="true"><![CDATA[
module ietf-l2-topology {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-l2-topology";
  prefix l2t;

  import ietf-network {
    prefix nw;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }
  import ietf-network-topology {
    prefix nt;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991:Common YANG Data Types";
  }
  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991:Common YANG Data Types";
  }
  import iana-if-type {
    prefix ianaift;
    reference
      "RFC 7224: IANA Interface Type YANG Module";
  }
  import ieee802-dot1q-types {
    prefix dot1q-types;
    reference
      "IEEE Std 802.1Qcp-2018: Bridges and Bridged
       Networks - Amendment: YANG Data Model";
  }

  organization
    "IETF I2RS (Interface to the Routing System) Working Group";
  contact
    "WG Web:   &lt;http://tools.ietf.org/wg/i2rs/&gt;   <http://tools.ietf.org/wg/i2rs/>
     WG List:  &lt;mailto:i2rs@ietf.org&gt;  <mailto:i2rs@ietf.org>

     Editor:    Jie Dong
               &lt;mailto:jie.dong@huawei.com&gt;
               <mailto:jie.dong@huawei.com>

     Editor:    Xiugang Wei
               &lt;mailto:weixiugang@huawei.com&gt;
               <mailto:weixiugang@huawei.com>

     Editor:    Qin Wu
               &lt;mailto:bill.wu@huawei.com&gt;
               <mailto:bill.wu@huawei.com>

     Editor:    Mohamed Boucadair
               &lt;mailto:mohamed.boucadair@orange.com&gt;
               <mailto:mohamed.boucadair@orange.com>

     Editor:    Anders Liu
               &lt;andersliu@tencent.com&gt;";
               <mailto:andersliu@tencent.com>";
  description
    "This module defines a basic model for the Layer 2 topology
     of a network.

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

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

     This version of this YANG module is part of RFC XXXX; 8944; see
     the RFC itself for full legal notices.";

  revision 2020-06-29 2020-11-02 {
    description
      "Initial revision"; revision.";
    reference
      "RFC XXXX: 8944: A YANG Data Model for Layer 2 Network Topologies";
  }

  feature VLAN {
    description
      "Enables VLAN tag support as defined in IEEE 802.1Q.";
    reference
      "IEEE Std 802.1Q-2014: Bridges and Bridged Networks";
  }

  feature QinQ {
    description
      "Enables QinQ double tag support as defined in IEEE 802.1ad.";
    reference
      "IEEE Std 802.1ad: Provider Bridges";
  }

  feature VXLAN {
    description
      "Enables VXLAN support as defined in RFC7348."; RFC 7348.";
    reference
      "RFC 7348: Virtual eXtensible Local Area Network (VXLAN):
                 A Framework for Overlaying Virtualized Layer 2
                 Networks over Layer 3 Networks";
  }

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

  identity eth-encapsulation-type {
    base ianaift:iana-interface-type;
    description
      "Base identity from which specific Ethernet
       encapsulation types are derived.";
    reference
      "RFC 7224: IANA Interface Type YANG Module";
  }

  identity ethernet {
    base eth-encapsulation-type;
    description
      "Native Ethernet encapsulation.";
  }

  identity vlan {
    base eth-encapsulation-type;
    description
      "VLAN encapsulation.";
  }

  identity qinq {
    base eth-encapsulation-type;
    description
      "QinQ encapsulation.";
  }

  identity pbb {
    base eth-encapsulation-type;
    description
      "Provider-backbone-bridging
      "Provider Backbone Bridging (PBB) encapsulation.
       The PBB functions are developed in IEEE 802.1ah.";
  }

  identity trill {
    base eth-encapsulation-type;
    description
      "TRILL
      "Transparent Interconnection of Lots of Links (TRILL)
       encapsulation.";
  }

  identity vpls {
    base eth-encapsulation-type;
    description
      "Ethernet VPLS Virtual Private LAN Service (VPLS)
       interface encapsulation.";
  }

  identity vxlan {
    base eth-encapsulation-type;
    description
      "VXLAN MAC Media Access Control (MAC) in UDP encapsulation.";
    reference
      "RFC 7348: Virtual eXtensible Local Area  Network (VXLAN):
                 A Framework for Overlaying Virtualized Layer 2
                 Networks over Layer 3 Networks";
  }

  typedef vni {
    type uint32 {
      range "0..16777215";
    }
    description
      "VXLAN Network Identifier or VXLAN Segment ID.
       It allows up to 16 M VXLAN segments to coexist
       within the same administrative domain.

       The use of value '0' is implementation-specific."; implementation specific.";
    reference
      "RFC 7348: Virtual eXtensible Local Area  Network (VXLAN):
                 A Framework for Overlaying Virtualized Layer 2
                 Networks over Layer 3 Networks";
  }

  typedef l2-flag-type {
    type identityref {
      base flag-identity;
    }
    description
      "Base type for L2 flags. One example of L2 flag
       type is trill trill, which represents the trill topology
       type.";
  }

  typedef node-flag-type {
    type identityref {
      base flag-identity;
    }
    description
      "Node flag attributes.  The physical node can be
       one example of a node flag attribute.";
  }

  typedef link-flag-type {
    type identityref {
      base flag-identity;
    }
    description
      "Link flag attributes.  One example of a link flag
       attribute is the pseudowire.";
  }

  typedef l2-network-event-type {
    type enumeration {
      enum addition {
        value 0;
        description
          "A Layer 2 node or link or termination-point
           has been added.";
      }
      enum removal {
        value 1;
        description
          "A Layer 2 node or link or termination-point
           has been removed.";
      }
      enum update {
        value 2;
        description
          "A Layer 2 node or link or termination-point
           has been updated.";
      }
    }
    description
      "Layer 2 network event type for notifications.";
  }

  typedef duplex-mode {
    type enumeration {
      enum full-duplex {
        description
          "Indicates full-duplex mode.";
      }
      enum half-duplex {
        description
          "Indicates half-duplex mode.";
      }
    }
    description
      "Indicates the type of the duplex mode.";
  }

  grouping l2-network-type {
    description
      "Indicates the topology type to be L2.";
    container l2-topology {
      presence "Indicates L2 Network Topology.";
      description
        "The presence of the container node indicates
         L2 Network Topology.";
    }
  }

  grouping l2-topology-attributes {
    description
      "L2 Topology topology scope attributes.";
    container l2-topology-attributes {
      description
        "Contains L2 topology attributes.";
      leaf name {
        type string;
        description
          "Name of the topology.";
      }
      leaf-list flags {
        type l2-flag-type;
        description
          "Topology flags.";
      }
    }
  }

  grouping l2-node-attributes {
    description
      "L2 node attributes"; attributes.";
    container l2-node-attributes {
      description
        "Contains L2 node attributes.";
      leaf name {
        type string;
        description
          "Node name.";
      }
      leaf-list flags {
        type node-flag-type;
        description
          "Node flags.  It can be used to indicates indicate
           node flag attributes.";
      }
      leaf-list bridge-id {
        type string {
          pattern '[0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){7}';
        }
        description
          "This is the bridge identifier represented as a
           hexadecimal 8 octet 8-octet string.  It has 4 bits of
           priority, 12 bits of MSTI-ID Multiple Spanning Tree
           Instance Identifier (MSTI-ID), and the base bridge
           identifier.  There may be multiple one for each
           spanning tree instance.";
        reference
          "RFC 7727: Spanning Tree Protocol (STP) Application of
                     the Inter-Chassis Communication Protocol
                     (ICCP)";
      }
      leaf-list management-address {
        type inet:ip-address;
        description
          "IP address used for management purpose.";
      }
      leaf management-mac {
        type yang:mac-address;
        description
          "This is a MAC address used for the bridge management.
           It can be the Bridge Base VID, VLAN ID (VID), interface
           MAC address address, or other. ";
      }
      leaf management-vlan {
        type string;
        description
          "This is a VLAN that supports the Management management address.
           The actual VLAN ID type and value would be a member of
           this VLAN.";
      }
    }
  }

  grouping l2-link-attributes {
    description
      "L2 link attributes"; attributes.";
    container l2-link-attributes {
      description
        "Contains L2 link attributes.";
      leaf name {
        type string;
        description
          "Link name.";
      }
      leaf-list flags {
        type link-flag-type;
        description
          "Link flags.  It can be used to indicate
           link flag attributes.";
      }
      leaf rate {
        type uint64;
        units "Kbps";
        description
          "Link rate.  It specifies bandwidth requirements
           associated with the specific link.  The link
           contains a source and a destination.";
      }
      leaf delay {
        type uint32;
        units "microseconds";
        description
          "Unidirectional Link link delay in
           microseconds.";
      }
      leaf auto-nego {
        type boolean;
        default "true";
        description
          "Set to true if auto negotiation auto-negotiation is supported.
           Set to false if auto negotiation auto-negotiation is not supported.";
      }
      leaf duplex {
        type duplex-mode;
        description
          "Expose
          "Exposes the duplex mode, full duplex full-duplex or half-duplex.";
      }
    }
  }

  grouping l2-termination-point-attributes {
    description
      "L2 termination point attributes"; attributes.";
    container l2-termination-point-attributes {
      description
        "Containing L2 termination point attributes.";
      leaf interface-name {
        type string;
        description
          "Name of the interface.  The name can (but does not
           have to) correspond to an interface reference of a
           containing node's interface, i.e., the path name of a
           corresponding interface data node on the containing
           node is reminiscent of data type interface-ref defined
           in RFC 8343.  It should be noted that data type
           interface-ref of RFC 8343 cannot be used directly,
           as this data type is used to reference an interface
           in a datastore of a single node in the network, not
           to uniquely reference interfaces across a network.";
      }
      leaf mac-address {
        type yang:mac-address;
        description
          "Interface MAC address for logical link control.";
      }
      leaf-list port-number {
        type uint32;
        description
          " List of port numbers of the Bridge bridge ports for which each
            entry contains Bridge bridge management information.";
      }
      leaf-list unnumbered-id {
        type uint32;
        description
          "List of unnumbered interface identifiers.
           The unnumbered interface identifier will correspond to
           the ifIndex value of the interface, i.e., the ifIndex
           value of the ifEntry that represents the interface in
           implementations where the Interfaces Group MIB
           (RFC 2863) is supported.";
      }
      leaf encapsulation-type {
        type identityref {
          base eth-encapsulation-type;
        }
        description
          "Encapsulation type of this
                 termination point.";
      }
      leaf outer-tag {
        if-feature "VLAN";
        type dot1q-types:vid-range-type;
        description
          "The outermost VLAN tag.  It may include a list of VLAN
           Ids,
           Ids or non overlapping nonoverlapping VLAN ranges.";
      }
      leaf outer-tpid {
        if-feature "QinQ";
        type dot1q-types:dot1q-tag-type;
        description
          "Identifies a specific 802.1Q tag type of outermost VLAN
           tag.";
      }
      leaf inner-tag {
        if-feature "VLAN";
        type dot1q-types:vid-range-type;
        description
          "The inner VLAN tag.  It may include a list of VLAN
           Ids,
           Ids or non overlapping nonoverlapping VLAN ranges.";
      }
      leaf inner-tpid {
        if-feature "QinQ";
        type dot1q-types:dot1q-tag-type;
        description
          "Identifies a specific 802.1Q tag type of inner VLAN tag.";
      }
      leaf lag {
        type boolean;
        default "false";
        description
          "Defines whether lag is supported or not.
           When it is set to true, the lag is supported.";
      }
      leaf-list member-link-tp {
        when "../lag = 'true'" {
          description
            "Relevant only when the lag interface is supported.";
        }
        type leafref {
          path "/nw:networks/nw:network/nw:node/nt:termination-point/nt:tp-id"; "/nw:networks/nw:network/nw:node"
             + "/nt:termination-point/nt:tp-id";
        }
        description
          "List of member link termination points associated with
           specific l2 L2 termination point.";
      }
      container vxlan {
        when "derived-from-or-self(../encapsulation-type, 'l2t:vxlan')" "
           + "'l2t:vxlan')" {
          description
            "Only applies when the type of the Ethernet
             encapsulation is 'vxlan'.";
        }
        if-feature "VXLAN";
        leaf vni-id {
          type vni;
          description
            "VXLAN Network Identifier (VNI).";
        }
        description
          "Vxlan encapsulation type.";
      }
    }
  }

  augment "/nw:networks/nw:network/nw:network-types" {
    description
      "Introduces new network type for L2 topology.";
    uses l2-network-type;
  }
  augment "/nw:networks/nw:network" {
    when '/nw:networks/nw:network/nw:network-types/l2t:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Configuration parameters for the L2 network
       as a whole.";
    uses l2-topology-attributes;
  }
  augment "/nw:networks/nw:network/nw:node" {
    when '/nw:networks/nw:network/nw:network-types/l2t:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Configuration parameters for L2 at the node
       level.";
    uses l2-node-attributes;
  }
  augment "/nw:networks/nw:network/nt:link" {
    when '/nw:networks/nw:network/nw:network-types/l2t:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Augments L2 topology link information.";
    uses l2-link-attributes;
  }
  augment "/nw:networks/nw:network/nw:node/nt:termination-point" {
    when '/nw:networks/nw:network/nw:network-types/l2t:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Augments L2 topology termination point information.";
    uses l2-termination-point-attributes;
  }

  notification l2-node-event {
    description
      "Notification event for L2 node.";
    leaf event-type {
      type l2-network-event-type;
      description
        "Event type.";
    }
    uses nw:node-ref;
    uses l2-network-type;
    uses l2-node-attributes;
  }

  notification l2-link-event {
    description
      "Notification event for L2 link.";
    leaf event-type {
      type l2-network-event-type;
      description
        "Event type.";
    }
    uses nt:link-ref;
    uses l2-network-type;
    uses l2-link-attributes;
  }

  notification l2-termination-point-event {
    description
      "Notification event for L2 termination point.";
    leaf event-type {
      type l2-network-event-type;
      description
        "Event type.";
    }
    uses nt:tp-ref;
    uses l2-network-type;
    uses l2-termination-point-attributes;
  }
}
&lt;CODE ENDS&gt;</artwork>
        </figure></t>
]]></sourcecode>
    </section>
    <section anchor="IANA" title="IANA Considerations">
      <t>This document requests IANA to register numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>IANA has registered the following URIs in the
      "ns" subregistry within the "IETF "The IETF XML Registry" <xref
      target="RFC3688"/>:</t>

      <t><figure>
          <artwork>   URI: urn:ietf:params:xml:ns:yang:ietf-l2-topology
   Registrant Contact: The IESG.
   XML: N/A; target="RFC3688" format="default"/>:</t>
<dl newline="false" spacing="compact">
   <dt>URI:</dt>
   <dd>urn:ietf:params:xml:ns:yang:ietf-l2-topology</dd>
   <dt>Registrant Contact:</dt>
   <dd>The IESG.</dd>
   <dt>XML:</dt>
   <dd>N/A; the requested URI is an XML namespace.

   URI: urn:ietf:params:xml:ns:yang:ietf-l2-topology-state
   Registrant Contact: The IESG.
   XML: N/A; namespace.</dd>
</dl>
<dl newline="false" spacing="compact">
   <dt>URI:</dt>
   <dd>urn:ietf:params:xml:ns:yang:ietf-l2-topology-state</dd>
   <dt>Registrant Contact:</dt>
   <dd>The IESG.</dd>
   <dt>XML:</dt>
   <dd>N/A; the requested URI is an XML namespace.
</artwork>
        </figure></t>

      <t>This document requests IANA to register namespace.</dd>
</dl>
      <t>IANA has registered the following YANG modules in
      the "YANG Module Names" subregistry <xref target="RFC6020"/> target="RFC6020" format="default"/> within the
      "YANG Parameters" registry.</t>

      <figure>
        <artwork>  name: ietf-l2-topology
  namespace: urn:ietf:params:xml:ns:yang:ietf-l2-topology
  prefix: l2t
  reference: RFC XXXX

  name: ietf-l2-topology-state
  namespace: urn:ietf:params:xml:ns:yang:ietf-l2-topology-state
  prefix: l2t-s
  reference: RFC XXXX</artwork>
      </figure>

      <t/>
<dl newline="false" spacing="compact">
  <dt>Name:</dt>
  <dd>ietf-l2-topology</dd>
  <dt>Namespace:</dt>
  <dd>urn:ietf:params:xml:ns:yang:ietf-l2-topology</dd>
  <dt>Prefix:</dt>
  <dd>l2t</dd>
  <dt>Reference:</dt>
  <dd>RFC 8944</dd>
</dl>
<dl newline="false" spacing="compact">
  <dt>Name:</dt>
  <dd>ietf-l2-topology-state</dd>
  <dt>Namespace:</dt>
  <dd>urn:ietf:params:xml:ns:yang:ietf-l2-topology-state</dd>
  <dt>Prefix:</dt>
  <dd>l2t-s</dd>
  <dt>Reference:</dt>
  <dd>RFC 8944</dd>
</dl>

      <t>These modules are not maintained by IANA.</t>
    </section>
    <section anchor="Security" title="Security Considerations"> numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>The YANG module modules specified in this document defines define a schema for data
      that is designed to be accessed via network management protocols protocols, such as
      NETCONF
      Network Configuration Protocol (NETCONF) <xref target="RFC6241"/> target="RFC6241"
      format="default"/> or RESTCONF <xref target="RFC8040"/>. target="RFC8040"
      format="default"/>.
      The lowest NETCONF layer is the secure transport layer, and the
      mandatory-to-implement secure transport is Secure Shell (SSH) <xref
      target="RFC6242"/>. target="RFC6242" format="default"/>. The lowest RESTCONF layer is HTTPS, and the
      mandatory-to-implement secure transport is TLS <xref
      target="RFC8446"/>.</t> target="RFC8446" format="default"/>.</t>
      <t>The Network Configuration Access Control Model (NACM) <xref
      target="RFC8341"/> target="RFC8341" format="default"/> provides the means to restrict access for particular
      NETCONF or RESTCONF users to a preconfigured subset of all available
      NETCONF or RESTCONF protocol operations and content.</t>
      <t>The Layer 2 topology module defines information that can be
      configurable in certain instances, for example example, in the case of virtual
      topologies that can be created by client applications. In such cases, a
      malicious client could introduce topologies that are undesired.
      Specifically, a malicious client could attempt to remove or add a node,
      a link, or a termination point, point by creating or deleting corresponding
      elements in the node, link, and termination point lists, respectively.
      In the case of a topology that is learned, the server will automatically
      prohibit such misconfiguration attempts. In the case of a topology that
      is configured, i.e. i.e., whose origin is "intended", the undesired
      configuration could become effective and be reflected in the operational
      state datastore [RFC8342], <xref target="RFC8342" format="default"/>, leading to
      disruption of services provided
      via this topology. For those reasons, it is important that the NACM is
      vigorously applied to prevent topology misconfiguration by unauthorized
      clients.</t>
      <t>There are a number of data nodes defined in this YANG module that are
      writable/creatable/deletable (i.e., config true, which is the default).
      These data nodes may be considered sensitive or vulnerable in some
      network environments. Write operations (e.g., edit-config) to these data
      nodes without proper protection can have a negative effect on network
      operations. These are the subtrees and data nodes and their
      sensitivity/vulnerability:<list style="symbols">
          <t>l2-network-attributes: A
      sensitivity/vulnerability:</t>
      <dl newline="true" spacing="normal">
        <dt>l2-network-attributes:</dt>
	<dd>A malicious client could attempt to
          sabotage the configuration of any of the contained attributes, such
          as the name or the flag data nodes.</t>

          <t>l2-node-attributes: A nodes.</dd>
        <dt>l2-node-attributes:</dt>
	<dd>A malicious client could attempt to sabotage
          the configuration of important node attributes, such as the name or
          the management-address.</t>

          <t>l2-link-attributes: A management-address.</dd>
        <dt>l2-link-attributes:</dt>
	<dd>A malicious client could attempt to sabotage
          the configuration of important link attributes, such as the rate or
          the delay data nodes.</t>

          <t>l2-termination-point-attributes: A nodes.</dd>
        <dt>l2-termination-point-attributes:</dt>
	<dd>A malicious client could attempt
          to sabotage the configuration of important termination point
          attributes (e.g., 'maximum-frame-size').</t>
        </list></t> 'maximum-frame-size').</dd>
      </dl>
      <t>Some of the readable data nodes in this YANG module may be considered
      sensitive or vulnerable in some network environments. It is thus
      important to control read access (e.g., via get, get-config, or
      notification) to these data nodes. In particular, the YANG model module for
      layer
      Layer 2 topology may expose sensitive information, for example example, the MAC
      addresses of devices, devices or VLAN/VXLAN identifiers. Unrestricted use of such
      information can lead to privacy violations. For example, listing MAC
      addresses in a network allows monitoring of devices and their movements.
      Location information can be derived from MAC addresses of network
      devices, bypassing protection of location information by the Operating
      System.</t>
    </section>

    <section title="Acknowledgements">
      <t>The authors would like to acknowledge the comments and suggestions
      received from Susan Hares, Alia Atlas, Juergen Schoenwaelder, Mach Chen,
      Alexander Clemm, Sriganesh Kini, Oscar Gonz&aacute;lez de Dios, Stig
      Venaas, Christian Huitema, and Meral Shirazipour,Benjamin Kaduk,Don
      Fedyk.</t>

      <t>Many thanks to Ladislav Lhotka for the yang-doctors review.</t>
    </section>
  </middle>
  <back>
    <references title="Normative References">
      <?rfc include="reference.RFC.2119"?>

      <?rfc include='reference.RFC.3688'?>

      <?rfc include='reference.RFC.4202'?>

      <?rfc include='reference.RFC.4761'?>

      <?rfc include='reference.RFC.4762'?>

      <?rfc include='reference.RFC.6020'?>

      <?rfc include='reference.RFC.6991'?>

      <?rfc include='reference.RFC.7224'?>

      <?rfc include='reference.RFC.7348'?>

      <?rfc include='reference.RFC.7950'?>

      <?rfc include='reference.RFC.8345'?>

      <?rfc include='reference.RFC.8446'?>

      <?rfc include='reference.RFC.8341'?>

      <?rfc include='reference.RFC.8174'?>

    <displayreference target="I-D.ietf-trill-yang" to="TRILL-YANG"/>
    <displayreference target="I-D.ietf-i2rs-usecase-reqs-summary" to="I2RS-UR"/>

    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3688.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6020.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6991.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7224.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7348.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7950.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8345.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8446.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8341.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6241.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6242.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8040.xml"/>
      </references>

    <references title="Informative References">
      <?rfc include='reference.RFC.7951'?>

      <?rfc include='reference.RFC.8340'?>

      <?rfc include='reference.RFC.8342'?>

      <?rfc include='reference.RFC.6241'?>

      <?rfc include='reference.RFC.6242'?>

      <?rfc include='reference.RFC.8040'?>

      <?rfc include="reference.I-D.ietf-trill-yang"?>
      <references>
        <name>Informative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7951.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8340.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8342.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7727.xml"/>

<!-- [I-D.ietf-trill-yang] IESG state Expired -->

        <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.ietf-trill-yang.xml"/>

<!-- [I-D.ietf-i2rs-usecase-reqs-summary] IESG state Expired  -->

	<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.ietf-i2rs-usecase-reqs-summary.xml"/>

        <reference anchor="IEEE802.1AB">
          <front>
          <title>Station
            <title>IEEE Standard for Local and metropolitan area networks -
	    Station and Media Access Control Connectivity Discovery</title>
            <author>
            <organization/>
              <organization>IEEE</organization>
            </author>
            <date day="11" month="March" year="2016"/>
          </front>
          <seriesInfo name="IEEE" value="Std 802.1AB-2016"/>
	  <seriesInfo name="DOI" value="10.1109/IEEESTD.2016.7433915"/>
        </reference>

        <reference anchor="IEEE802.1Qcp">
          <front>
          <title>Bridges
            <title>IEEE Standard for Local and metropolitan area
	    networks--Bridges and Bridged Networks - Amendment: Networks--Amendment 30: YANG Data
	    Model</title>
            <author>
            <organization/>
              <organization>IEEE</organization>
            </author>
            <date day="14" month="September" year="2018"/>
          </front>
          <seriesInfo name="IEEE" value="Std 802.1Qcp-2018"/>
	  <seriesInfo name="DOI" value=" 10.1109/IEEESTD.2018.8467507"/>
        </reference>

        <reference anchor="IEEE802.1ad">
          <front>
          <title>Virtual
            <title>IEEE Standard for Local and Metropolitan Area
	    Networks--Virtual Bridged Local Area Networks Amendment Networks--Amendment 4:
	    Provider Bridges</title>
            <author>
            <organization/>
              <organization>IEEE</organization>
            </author>
            <date month="May" year="2006"/>
          </front>
          <seriesInfo name="IEEE" value="Std 802.1ad-2005"/>
	  <seriesInfo name="DOI" value="10.1109/IEEESTD.2006.6044678"/>
        </reference>

        <reference anchor="IEEE802.1ah">
          <front>
          <title>Virtual
            <title>IEEE Standard for Local and metropolitan area networks --
	    Virtual Bridged Local Area Networks Amendment 4: 7: Provider Backbone
	    Bridges</title>
            <author>
            <organization/>
              <organization>IEEE</organization>
            </author>
            <date day="14" month="August" year="2008"/>
          </front>
          <seriesInfo name="IEEE" value="Std 802.1ah-2008"/>
	  <seriesInfo name="DOI" value=" 10.1109/IEEESTD.2008.4602826"/>
        </reference>

	<reference anchor="I2RS-UR"> anchor="IEEE802.1Q-2014">
	  <front>
          <title>Summary of I2RS Use Case Requirements</title>

          <author fullname="Susan Hares" initials="S." surname="Hares">
            <organization/>
          </author>

          <author fullname="Mach Chen" initials="M." surname="Chen">
            <organization/>
	    <title>IEEE Standard for Local and metropolitan area
	    networks--Bridges and Bridged Networks</title>
	    <author>
	      <organization>IEEE</organization>
	    </author>
	    <date month="November" year="2016"/> month="December" year="2014"/>
	  </front>
	  <seriesInfo name="Internet-Draft"
                    value="draft-ietf-i2rs-usecase-reqs-summary-03"/> name="IEEE" value="802.1Q-2014"/>
	  <seriesInfo name="DOI" value="10.1109/IEEESTD.2014.6991462"/>
	</reference>
      </references>
    </references>
    <section title="Companion numbered="true" toc="default">
      <name>Companion YANG Module for Non-NMDA Compliant Implementations"> Non-NMDA-Compliant Implementations</name>
      <t>The YANG module ietf-l2-topology defined in this document augments
      two modules, "ietf-network" and "ietf-network-topology", that are
      designed to be used in conjunction with implementations that support the
      Network Management Datastore Architecture (NMDA) defined in <xref
      target="RFC8342"/>.
      target="RFC8342" format="default"/>. In order to allow implementations
      to use the model
      even in cases when NMDA is not supported, a set of companion modules
      have been defined that represent a state model of networks and network
      topologies, "ietf-network-state" and "ietf-network-topology-state",
      respectively.</t>
      <t>In order to be able to use the model for layer Layer 2 topologies defined
      in this document in conjunction with non-NMDA compliant non-NMDA-compliant implementations,
      a corresponding companion module is defined that represents the
      operational state of layer Layer 2 network topologies. The module
      "ietf-l2-topology-state" mirrors the module "ietf-l2-topology" defined
      in <xref target="L2YANG"/>. target="L2YANG" format="default"/>. However, it augments "ietf-network-state"
      and "ietf-network-topology-state" (instead of "ietf-network" and
      "ietf-network-topology") and all its data nodes are
      non-configurable.</t>
      nonconfigurable.</t>
      <t>The companion module "ietf-l2-topology" SHOULD NOT <bcp14>SHOULD NOT</bcp14> be supported by
      implementations that support NMDA. It is for this reason that this
      module is defined in the informative Appendix.</t> appendix.</t>
      <t>As the structure of this modules module mirrors that of its underlying
      modules, the YANG tree is not depicted separately.</t>

      <t><figure>
          <artwork>&lt;CODE BEGINS&gt; file "ietf-l2-topology-state@2020-06-29.yang"
      <sourcecode name="ietf-l2-topology-state@2020-11-02.yang" type="yang" markers="true"><![CDATA[
module ietf-l2-topology-state {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-l2-topology-state";
  prefix l2t-s;

  import ietf-network-state {
    prefix nw-s;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }
  import ietf-network-topology-state {
    prefix nt-s;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }
  import ietf-l2-topology {
    prefix l2t;
    reference
      "RFC XXXX: 8944: A YANG Data Model for Layer 2 Network Topologies";
  }

  organization
    "IETF I2RS (Interface to the Routing System) Working Group";
  contact
    "WG Web:   &lt;http://tools.ietf.org/wg/i2rs/&gt;   <http://tools.ietf.org/wg/i2rs/>
     WG List:  &lt;mailto:i2rs@ietf.org&gt;  <mailto:i2rs@ietf.org>

     Editor:    Jie Dong
               &lt;mailto:jie.dong@huawei.com&gt;
               <mailto:jie.dong@huawei.com>
     Editor:    Xiugang Wei
               &lt;mailto:weixiugang@huawei.com&gt;
               <mailto:weixiugang@huawei.com>
     Editor:    Qin Wu
               &lt;mailto:bill.wu@huawei.com&gt;
               <mailto:bill.wu@huawei.com>
     Editor:    Mohamed Boucadair
               &lt;mailto:mohamed.boucadair@orange.com&gt;
               <mailto:mohamed.boucadair@orange.com>
     Editor:   Anders Liu
               &lt;andersliu@tencent.com&gt;";
               <andersliu@tencent.com>";
  description
    "This module defines a model for Layer 2 Network Topology
     state, representing topology that either is learned or
     results from applying topology that has been configured per
     the 'ietf-l2-topology' model, mirroring the
     corresponding data nodes in this model.

     This model mirrors 'ietf-l2-topology' but contains only
     read-only state data.  The model is not needed when the
     underlying implementation infrastructure supports the
     Network Management Datastore Architecture (NMDA).

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

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

     This version of this YANG module is part of RFC XXXX; 8944; see
     the RFC itself for full legal notices.";

  revision 2020-06-29 2020-11-02 {
    description
      "Initial revision"; revision.";
    reference
      "RFC XXXX: 8944: A YANG Data Model for Layer 2 Network Topologies";
  }

  /*
   * Data nodes
   */

  augment "/nw-s:networks/nw-s:network/nw-s:network-types" {
    description
      "Introduces a new network type for L2 topology.";
    uses l2t:l2-network-type;
  }

  augment "/nw-s:networks/nw-s:network" {
    when 'nw-s:network-types/l2t-s:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Configuration parameters for the L2 network
       as a whole.";
    uses l2t:l2-topology-attributes;
  }

  augment "/nw-s:networks/nw-s:network/nw-s:node" {
    when '../nw-s:network-types/l2t-s:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Configuration parameters for L2 at the node
       level.";
    uses l2t:l2-node-attributes;
  }

  augment "/nw-s:networks/nw-s:network/nt-s:link" {
    when '../nw-s:network-types/l2t-s:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Augments L2 topology link information.";
    uses l2t:l2-link-attributes;
  }

  augment "/nw-s:networks/nw-s:network/nw-s:node/"
        + "nt-s:termination-point" {
    when '../../nw-s:network-types/l2t-s:l2-topology' {
      description
        "Augmentation parameters apply only for networks
         with L2 topology.";
    }
    description
      "Augments L2 topology termination point information.";
    uses l2t:l2-termination-point-attributes;
  }

  /*
   * Notifications
   */

  notification l2-node-event {
    description
      "Notification event for L2 node.";
    leaf event-type {
      type l2t:l2-network-event-type;
      description
        "Event type.";
    }
    uses nw-s:node-ref;
    uses l2t:l2-network-type;
    uses l2t:l2-node-attributes;
  }

  notification l2-link-event {
    description
      "Notification event for a an L2 link.";
    leaf event-type {
      type l2t:l2-network-event-type;
      description
        "Event type.";
    }
    uses nt-s:link-ref;
    uses l2t:l2-network-type;
    uses l2t:l2-link-attributes;
  }

  notification l2-termination-point-event {
    description
      "Notification event for L2 termination point.";
    leaf event-type {
      type l2t:l2-network-event-type;
      description
        "Event type.";
    }
    uses nt-s:tp-ref;
    uses l2t:l2-network-type;
    uses l2t:l2-termination-point-attributes;
  }
}
&lt;CODE ENDS&gt;</artwork>
        </figure></t>
]]></sourcecode>
    </section>
    <section anchor="ex" title="An Example"> numbered="true" toc="default">
      <name>An Example</name>
      <t>This section contains an example of an instance data tree in JSON
      encoding <xref target="RFC7951"/>. target="RFC7951" format="default"/>. The example instantiates
      "ietf-l2-topology" for the topology that is depicted in the following
      diagram. There are three nodes: D1, D2, and D3. D1 has three termination
      points: 1-0-1, 1-2-1, and 1-3-1. D2 has three termination points as
      well: 2-1-1, 2-0-1, and 2-3-1. D3 has two termination points: 3-1-1 and
      3-2-1. For termination point 1-0-1, it provides lag support and has two
      member link termination points: 1-0-1-1,1-0-1-2. 1-0-1-1 and 1-0-1-2. In addition, there are
      six links, two between each pair of nodes, nodes with one going in each
      direction.</t>

      <t><figure>
          <artwork>
<figure>
  <name>A Network Topology Example</name>
      <artwork name="" type="" align="left" alt=""><![CDATA[
                +------------+                   +------------+
                |     D1     |                   |     D2     |
       1-0-1-1 /-\          /-\                 /-\          /-\
    &lt;---------&gt;|
    <--------->| | 1-0-1    | |----------------&gt;| |---------------->| | 2-1-1    | |
       1-0-1-2 | |    1-2-1 | |&lt;----------------| |<----------------| |    2-0-1 | |
    &lt;--------&gt;
    <--------> \-/  1-3-1   \-/                 \-/  2-3-1   \-/
                |   /----\   |                   |   /----\   |
                +---|    |---+                   +---|    |---+
                    \----/                           \----/
                     A  |                             A  |
                     |  |                             |  |
                     |  |                             |  |
                     |  |       +------------+        |  |
                     |  |       |     D3     |        |  |
                     |  |      /-\          /-\       |  |
                     |  +-----&gt;|  +----->| | 3-1-1    | |-------+  |
                     +---------| |    3-2-1 | |&lt;---------+ |<---------+
                               \-/          \-/
                                |            |
                                +------------+

                   Figure 2. A Network Topology Example</artwork>
        </figure></t>
]]></artwork>
</figure>
      <t>The corresponding instance data tree is depicted below:</t>

      <t><figure>
          <artwork>{
<sourcecode type="json"><![CDATA[
{
  "ietf-network:networks": {
    "network": [
      {
        "network-id": "l2-topo-example",
        "node": [
          {
            "node-id": "D1",
            "ietf-network-topology:termination-point": [
              {
                "tp-id": "1-0-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:d0",
                  "lag": true,
                  "member-link-tp": [
                    "1-0-1-1",
                    "1-0-1-2"
                  ]
                }
              },
              {
                "tp-id": "1-0-1-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:d3"
                }
              },
              {
                "tp-id": "1-0-1-2",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:d4"
                }
              },
              {
                "tp-id": "1-2-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:d1"
                }
              },
              {
                "tp-id": "1-3-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:d2"
                }
              }
            ],
            "ietf-l2-topology:l2-node-attributes": {
              "management-address": [
                "192.0.2.1",
                "2001:db8:0:1::"
              ]
            }
          },
          {
            "node-id": "D2",
            "ietf-network-topology:termination-point": [
              {
                "tp-id": "2-0-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:e0"
                }
              },
              {
                "tp-id": "2-1-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:e1"
                }
              },
              {
                "tp-id": "2-3-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:e2"
                }
              }
            ],
            "ietf-l2-topology:l2-node-attributes": {
              "management-address": [
                "192.0.2.2",
                "2001:db8:0:2::"
              ]
            }
          },
          {
            "node-id": "D3",
            "ietf-network-topology:termination-point": [
              {
                "tp-id": "3-1-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:f0"
                }
              },
              {
                "tp-id": "3-2-1",
                "ietf-l2-topology:l2-termination-point-attributes": {
                  "mac-address": "00:00:5e:00:53:f1"
                }
              }
            ],
            "ietf-l2-topology:l2-node-attributes": {
              "management-address": [
                "192.0.2.3",
                "2001:db8:0:3::"
              ]
            }
          }
        ],
        "ietf-network-topology:link": [
          {
            "link-id": "D1,1-2-1,D2,2-1-1",
            "source": {
              "source-node": "D1",
              "source-tp": "1-2-1"
            },
            "destination": {
              "dest-node": "D2",
              "dest-tp": "2-1-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          },
          {
            "link-id": "D2,2-1-1,D1,1-2-1",
            "source": {
              "source-node": "D2",
              "source-tp": "2-1-1"
            },
            "destination": {
              "dest-node": "D1",
              "dest-tp": "1-2-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          },
          {
            "link-id": "D1,1-3-1,D3,3-1-1",
            "source": {
              "source-node": "D1",
              "source-tp": "1-3-1"
            },
            "destination": {
              "dest-node": "D3",
              "dest-tp": "3-1-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          },
          {
            "link-id": "D3,3-1-1,D1,1-3-1",
            "source": {
              "source-node": "D3",
              "source-tp": "3-1-1"
            },
            "destination": {
              "dest-node": "D1",
              "dest-tp": "1-3-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          },
          {
            "link-id": "D2,2-3-1,D3,3-2-1",
            "source": {
              "source-node": "D2",
              "source-tp": "2-3-1"
            },
            "destination": {
              "dest-node": "D3",
              "dest-tp": "3-2-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          },
          {
            "link-id": "D3,3-2-1,D2,2-3-1",
            "source": {
              "source-node": "D3",
              "source-tp": "3-2-1"
            },
            "destination": {
              "dest-node": "D2",
              "dest-tp": "2-3-1"
            },
            "ietf-l2-topology:l2-link-attributes": {
              "rate": "1000"
            }
          }
        ]
      }
    ]
  }
}</artwork>
        </figure></t>
}
]]></sourcecode>
    </section>
    <section numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>The authors would like to acknowledge the comments and suggestions
      received from <contact fullname="Susan Hares"/>, <contact fullname="Alia
      Atlas"/>, <contact fullname="Juergen Schoenwaelder"/>, <contact
      fullname="Mach Chen"/>, <contact fullname="Alexander Clemm"/>, <contact
      fullname="Sriganesh Kini"/>, <contact fullname="Oscar Gonzalez de
      Dios"/>, <contact fullname="Stig Venaas"/>, <contact fullname="Christian
      Huitema"/>, <contact fullname="Meral Shirazipour"/>, <contact
      fullname="Benjamin Kaduk"/>, and <contact fullname="Don Fedyk"/>.</t>
      <t>Many thanks to <contact fullname="Ladislav Lhotka"/> for the
      yang-doctors review.</t>
    </section>
  </back>
</rfc>