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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft-ietf-opsawg-teas-common-ac-04" category="std" consensus="true" submissionType="IETF" tocInclude="true" sortRefs="true" symRefs="true" version="3">
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  <front>
    <title abbrev="Common Attachment Circuit YANG">A Common YANG Data Model for Attachment Circuits</title>
    <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-teas-common-ac-04"/>
    <author fullname="Mohamed Boucadair" role="editor">
      <organization>Orange</organization>
      <address>
        <email>mohamed.boucadair@orange.com</email>
      </address>
    </author>
    <author fullname="Richard Roberts" role="editor">
      <organization>Juniper</organization>
      <address>
        <email>rroberts@juniper.net</email>
      </address>
    </author>
    <author fullname="Oscar Gonzalez de Dios">
      <organization>Telefonica</organization>
      <address>
        <email>oscar.gonzalezdedios@telefonica.com</email>
      </address>
    </author>
    <author fullname="Samier Barguil Giraldo">
      <organization>Nokia</organization>
      <address>
        <email>samier.barguil_giraldo@nokia.com</email>
      </address>
    </author>
    <author fullname="Bo Wu">
      <organization>Huawei Technologies</organization>
      <address>
        <email>lana.wubo@huawei.com</email>
      </address>
    </author>
    <date year="2024" month="January" day="22"/>
    <area>Operations and Management</area>
    <workgroup>OPSAWG</workgroup>
    <keyword>Slice Service</keyword>
    <keyword>L3VPN</keyword>
    <keyword>L2VPN</keyword>
    <abstract>
      <?line 92?>

<t>The document specifies a common Attachment Circuits (ACs) YANG module, which is designed with the intent to be reusable by other models. For example, this common model can be reused by service models to expose ACs as a service, service models that require binding a service to a set of ACs, network and device models to provision ACs, etc.</t>
    </abstract>
    <note removeInRFC="true">
      <name>Discussion Venues</name>
      <t>Discussion of this document takes place on the
    Operations and Management Area Working Group Working Group mailing list (opsawg@ietf.org),
    which is archived at <eref target="https://mailarchive.ietf.org/arch/browse/opsawg/"/>.</t>
      <t>Source for this draft and an issue tracker can be found at
    <eref target="https://github.com/boucadair/attachment-circuit-model"/>.</t>
    </note>
  </front>
  <middle>
    <?line 96?>

<section anchor="introduction">
      <name>Introduction</name>
      <t>Connectivity services are provided by networks to customers via dedicated terminating points (e.g., service functions, Customer Premises Equipment (CPEs), Autonomous System Border Routers (ASBRs), data centers gateways, Internet Exchange Points). A connectivity service is basically about ensuring data transfer received from (or destined to) a given terminating point to (or from) other terminating points that belong to the same customer/service, an interconnection node, or an ancillary node. A set of objectives for the connectivity service may eventually be negotiated and agreed upon between a customer a network provider. For that data transfer to take place within the provider network, it is assumed that adequate setup is provisioned over the links that connect customer terminating points and a provider network so that data can be successfully exchanged over these links. The required setup is referred to in this document as Attachment Circuits (ACs), while the underlying link is referred to as "bearer".</t>
      <t>This document adheres to the definition of an attachment circuit as provided in <xref section="1.2" sectionFormat="of" target="RFC4364"/>, especially:</t>
      <ul empty="true">
        <li>
          <t>Routers can be attached to each other, or to end systems, in a
   variety of different ways: PPP connections, ATM Virtual Circuits
   (VCs), Frame Relay VCs, ethernet interfaces, Virtual Local Area
   Networks (VLANs) on ethernet interfaces, GRE tunnels, Layer 2
   Tunneling Protocol (L2TP) tunnels, IPsec tunnels, etc.  We will use
   the term "attachment circuit" to refer generally to some such means
   of attaching to a router.  An attachment circuit may be the sort of
   connection that is usually thought of as a "data link", or it may be
   a tunnel of some sort; what matters is that it be possible for two
   devices to be network layer peers over the attachment circuit.</t>
        </li>
      </ul>
      <t>When a customer requests a new value-added service, the service can be bound to existing attachment circuits or trigger the instantiation of new attachment circuits. Whether these attachment circuits are specific to a given service or be shared to deliver a variety of services is deployment-specific.</t>
      <t>An example of attachment circuits is depicted in <xref target="uc"/>. A Customer Edge (CE) may be a physical node or a logical entity. A CE is seen by the network as a peer Service Attachment Point (SAP) <xref target="RFC9408"/>. CEs may be dedicated to one single service (e.g., Layer 3 Virtual Private Network (VPN), Layer 2 VPN) or host multiple services (e.g., Service Functions <xref target="RFC7665"/>). A single AC (as seen by a network provider) may be bound to one or multiple peer SAPs (e.g., CE#1 and CE#2). For example, and as discussed in <xref target="RFC4364"/>, multiple CEs can be attached to a PE over the same attachment circuit. This is typically implemented if the Layer 2 infrastructure between the CE and the network provides a multipoint service. The same CE may terminate multiple ACs. These ACs may be over the same or distinct bearers.</t>
      <figure anchor="uc">
        <name>Examples of ACs</name>
        <artset>
          <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/svg" version="1.1" height="224" width="528" viewBox="0 0 528 224" class="diagram" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap="round">
              <path d="M 8,112 L 8,160" fill="none" stroke="black"/>
              <path d="M 72,32 L 72,48" fill="none" stroke="black"/>
              <path d="M 72,112 L 72,160" fill="none" stroke="black"/>
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              <path d="M 304,176 L 304,208" fill="none" stroke="black"/>
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              <path d="M 520,32 L 520,80" fill="none" stroke="black"/>
              <path d="M 520,128 L 520,160" fill="none" stroke="black"/>
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              <path d="M 376,48 L 400,48" fill="none" stroke="black"/>
              <path d="M 424,48 L 456,48" fill="none" stroke="black"/>
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              <path d="M 424,64 L 456,64" fill="none" stroke="black"/>
              <path d="M 8,80 L 72,80" fill="none" stroke="black"/>
              <path d="M 456,80 L 520,80" fill="none" stroke="black"/>
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              <path d="M 176,96 L 208,96" fill="none" stroke="black"/>
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              <path d="M 376,144 L 400,144" fill="none" stroke="black"/>
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              <path d="M 416,208 L 496,208" fill="none" stroke="black"/>
              <g class="text">
                <text x="8" y="52">│</text>
                <text x="412" y="52">AC</text>
                <text x="8" y="68">│</text>
                <text x="36" y="68">CE#1</text>
                <text x="72" y="68">│</text>
                <text x="412" y="68">AC</text>
                <text x="484" y="68">CE#3</text>
                <text x="164" y="100">AC</text>
                <text x="280" y="100">Network</text>
                <text x="36" y="148">CE#2</text>
                <text x="412" y="148">AC</text>
                <text x="484" y="148">CE#4</text>
                <text x="404" y="212">AC</text>
              </g>
            </svg>
          </artwork>
          <artwork type="ascii-art" align="center"><![CDATA[
.-------.                .--------------------.         .-------.
│       +------.         |                    +---AC----+       |
│ CE#1  │      |         |                    +---AC----+ CE#3  |
'-------'      |         |                    |         '-------'
               +---AC----+     Network        |
.-------.      |         |                    |
|       |      |         |                    |         .-------.
| CE#2  +------'         |                    +---AC----+ CE#4  |
'-------'                |                    |         '----+--'
                         '-----------+--------'              |
                                     |                       |
                                     '-----------AC----------'
]]></artwork>
        </artset>
      </figure>
      <t>This document specifies a common module ("ietf-ac-common") for attachment circuits (<xref target="sec-module"/>). The model is designed with the intent to be reusable by other models and, therefore, ensure consistent AC structures among modules that manipulate ACs. For example, the common model can be reused by service models to expose AC as a service (e.g., <xref target="I-D.ietf-opsawg-teas-attachment-circuit"/>), service models that require binding a service to a set of ACs (e.g., <xref target="I-D.ietf-teas-ietf-network-slice-nbi-yang"/>)), network models to provision ACs (e.g., <xref target="I-D.ietf-opsawg-ntw-attachment-circuit"/>), device models, etc.</t>
      <t>The common AC module eases data inheritance between modules (e.g., from service to network models as per <xref target="RFC8969"/>).</t>
      <t>The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in <xref target="RFC8342"/>.</t>
    </section>
    <section anchor="conventions-and-definitions">
      <name>Conventions and Definitions</name>
      <t>The key words "<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 "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as
described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they
appear in all capitals, as shown here.</t>
      <?line -18?>

<t>The meanings of the symbols in the YANG tree diagrams are defined in <xref target="RFC8340"/>.</t>
      <t>This document uses the following terms:</t>
      <dl>
        <dt>Bearer:</dt>
        <dd>
          <t>A physical or logical link that connects a customer node (or site) to a provider network.</t>
        </dd>
        <dt/>
        <dd>
          <t>A bearer can be a wireless or wired link. One or multiple technologies can be used to build a bearer. The bearer type can be specified by a customer.</t>
        </dd>
        <dt/>
        <dd>
          <t>The operator allocates a unique bearer reference to identify a bearer within its network (e.g., customer line identifier). Such a reference can be retrieved by a customer and then used in subsequent service placement requests to unambiguously identify where a service is to be bound.</t>
        </dd>
        <dt/>
        <dd>
          <t>The concept of bearer can be generalized to refer to the required underlying connection for the provisioning of an attachment circuit.</t>
        </dd>
        <dt/>
        <dd>
          <t>One or multiple attachment circuits may be hosted over the same bearer (e.g., multiple Virtual Local Area Networks (VLANs) on the same bearer that is provided by a physical link).</t>
        </dd>
        <dt>Network controller:</dt>
        <dd>
          <t>Denotes a functional entity responsible for the management of the service provider network. One or multiple network controllers can be deployed in a service provider network.</t>
        </dd>
        <dt>Service orchestrator:</dt>
        <dd>
          <t>Refers to a functional entity that interacts with the customer of a network service.</t>
        </dd>
        <dt/>
        <dd>
          <t>A service orchestrator is typically responsible for the attachment circuits, the Provider Edge (PE) selection, and requesting the activation of the requested services to a network controller.</t>
        </dd>
        <dt/>
        <dd>
          <t>A service orchestrator may interact with one or more network controllers.</t>
        </dd>
        <dt>Service provider network:</dt>
        <dd>
          <t>A network that is able to provide network services (e.g., L2VPN, L3VPN, or Network Slice Services).</t>
        </dd>
        <dt>Service provider:</dt>
        <dd>
          <t>A service provider that offers network services (e.g., L2VPN, L3VPN, or Network Slice Services).</t>
        </dd>
      </dl>
    </section>
    <section anchor="description-of-the-ac-common-yang-module">
      <name>Description of the AC Common YANG Module</name>
      <t>The full tree diagram of the module can be generated using the
"pyang" tool <xref target="PYANG"/> with "-f tree --tree-print-groupings" command-line parameters.  That tree is not included here because it is
too long (<xref section="3.3" sectionFormat="of" target="RFC8340"/>).  Instead, subtrees are provided
for the reader's convenience.</t>
      <ul empty="true">
        <li>
          <t>The full tree of the "ietf-ac-common" module is available at <xref target="AC-Common-Tree"/>.</t>
        </li>
      </ul>
      <section anchor="identities">
        <name>Identities</name>
        <t>The module defines a set of identities, including the following:</t>
        <dl>
          <dt>'address-allocation-type':</dt>
          <dd>
            <t>Used to specify the IP address allocation type in an AC. For example, this identity can used to indicate whether the provider network provides DHCP service, DHCP relay, or static addressing. Note that for the IPv6 case, Stateless Address Autoconfiguration (SLAAC) <xref target="RFC4862"/> can be used.</t>
          </dd>
          <dt>'local-defined-next-hop':</dt>
          <dd>
            <t>Used to specify next hop actions. For example, this identity can be used to indicate an action to discard traffic for a given destination or treat traffic towards addresses within the specified next-hop prefix as though they are connected to a local link.</t>
          </dd>
          <dt>'l2-tunnel-type':</dt>
          <dd>
            <t>Uses to control the Layer 2 tunnel selection for an AC. The current version supports indicating pseudowire, Virtual Private LAN Service (VPLS), and Virtual eXtensible Local Area Network (VXLAN).</t>
          </dd>
          <dt>'precedence-type':</dt>
          <dd>
            <t>Used to indicate the redundancy type when requesting ACs. For example, this identity can be used to tag primary and secondary ACs.</t>
          </dd>
        </dl>
      </section>
      <section anchor="reusable-groupings">
        <name>Reusable Groupings</name>
        <t>The module also defines a set of reusable groupings, including the following:</t>
        <dl>
          <dt>'op-instructions' (<xref target="op-full-tree"/>):</dt>
          <dd>
            <t>Defines a set of parameters to specify scheduling instructions and report related events for a service request (e.g., AC or bearer).</t>
          </dd>
        </dl>
        <figure anchor="op-full-tree">
          <name>Operational Instructions Grouping</name>
          <artwork align="center"><![CDATA[
  grouping service-status:
    +-- status
       +-- admin-status
       |  +-- status?        identityref
       |  +--ro last-change?   yang:date-and-time
       +--ro oper-status
          +--ro status?        identityref
          +--ro last-change?   yang:date-and-time
  grouping op-instructions:
    +-- requested-start?   yang:date-and-time
    +-- requested-stop?    yang:date-and-time
    +--ro actual-start?      yang:date-and-time
    +--ro actual-stop?       yang:date-and-time

]]></artwork>
        </figure>
        <dl>
          <dt>Layer 2 encapsulations (<xref target="l2-full-tree"/>):</dt>
          <dd>
            <t>Groupings for the following encapsulation schemes are supported: dot1Q, QinQ, and priority-tagged.</t>
          </dd>
          <dt>Layer 2 tunnel services  (<xref target="l2-full-tree"/>):</dt>
          <dd>
            <t>These grouping are used to define Layer 2 tunnel services that may be needed for the activation of an AC. Examples of supported Layer 2 servers are the pseudowire
(<xref section="6.1" sectionFormat="of" target="RFC8077"/>), VPLS, or VXLAN <xref target="RFC7348"/>.</t>
          </dd>
        </dl>
        <figure anchor="l2-full-tree">
          <name>Layer 2 Connection Groupings</name>
          <artwork align="center"><![CDATA[
  grouping dot1q:
    +-- tag-type?   identityref
    +-- cvlan-id?   uint16
  grouping priority-tagged:
    +-- tag-type?   identityref
  grouping qinq:
    +-- tag-type?   identityref
    +-- svlan-id    uint16
    +-- cvlan-id    uint16
  grouping pseudowire:
    +-- vcid?      uint32
    +-- far-end?   union
  grouping vpls:
    +-- vcid?      uint32
    +-- far-end*   union
  grouping vxlan:
    +-- vni-id             uint32
    +-- peer-mode?         identityref
    +-- peer-ip-address*   inet:ip-address
  grouping l2-tunnel-service:
    +-- type?         identityref
    +-- pseudowire
    |  +-- vcid?      uint32
    |  +-- far-end?   union
    +-- vpls
    |  +-- vcid?      uint32
    |  +-- far-end*   union
    +-- vxlan
       +-- vni-id             uint32
       +-- peer-mode?         identityref
       +-- peer-ip-address*   inet:ip-address
]]></artwork>
        </figure>
        <dl>
          <dt>Layer 3 address allocation (<xref target="l3-full-tree"/>):</dt>
          <dd>
            <t>Defines both IPv4 and IPv6 groupings to specify IP address allocation over an AC. Both dynamic and static address schemes are supported.</t>
          </dd>
          <dt>IP connections (<xref target="l3-full-tree"/>)::</dt>
          <dd>
            <t>Defines IPv4 and IPv6 grouping for managing Layer 3 connectivity over an AC. Both basic and more elaborated IP connection groupings are supported.</t>
          </dd>
        </dl>
        <figure anchor="l3-full-tree">
          <name>Layer 3 Connection Groupings</name>
          <artwork align="center"><![CDATA[
  grouping ipv4-allocation-type:
    +-- prefix-length?             uint8
    +-- address-allocation-type?   identityref
  grouping ipv6-allocation-type:
    +-- prefix-length?             uint8
    +-- address-allocation-type?   identityref
  grouping ipv4-connection-basic:
    +-- prefix-length?                       uint8
    +-- address-allocation-type?             identityref
    +-- (allocation-type)?
       +--:(dynamic)
          +-- (provider-dhcp)?
          |  +--:(dhcp-service-type)
          |     +-- dhcp-service-type?       enumeration
          +-- (dhcp-relay)?
             +--:(customer-dhcp-servers)
                +-- customer-dhcp-servers
                   +-- server-ip-address*   inet:ipv4-address
  grouping ipv6-connection-basic:
    +-- prefix-length?                       uint8
    +-- address-allocation-type?             identityref
    +-- (allocation-type)?
       +--:(dynamic)
          +-- (provider-dhcp)?
          |  +--:(dhcp-service-type)
          |     +-- dhcp-service-type?       enumeration
          +-- (dhcp-relay)?
             +--:(customer-dhcp-servers)
                +-- customer-dhcp-servers
                   +-- server-ip-address*   inet:ipv6-address
  grouping ipv4-connection:
    +-- local-address?                           inet:ipv4-address
    +-- virtual-address?                         inet:ipv4-address
    +-- prefix-length?                           uint8
    +-- address-allocation-type?                 identityref
    +-- (allocation-type)?
       +--:(dynamic)
       |  +-- (address-assign)?
       |  |  +--:(number)
       |  |  |  +-- number-of-dynamic-address?   uint16
       |  |  +--:(explicit)
       |  |     +-- customer-addresses
       |  |        +-- address-pool* [pool-id]
       |  |           +-- pool-id?         string
       |  |           +-- start-address    inet:ipv4-address
       |  |           +-- end-address?     inet:ipv4-address
       |  +-- (provider-dhcp)?
       |  |  +--:(dhcp-service-type)
       |  |     +-- dhcp-service-type?           enumeration
       |  +-- (dhcp-relay)?
       |     +--:(customer-dhcp-servers)
       |        +-- customer-dhcp-servers
       |           +-- server-ip-address*   inet:ipv4-address
       +--:(static-addresses)
          +-- address* [address-id]
             +-- address-id?         string
             +-- customer-address?   inet:ipv4-address
  grouping ipv6-connection:
    +-- local-address?                           inet:ipv6-address
    +-- virtual-address?                         inet:ipv6-address
    +-- prefix-length?                           uint8
    +-- address-allocation-type?                 identityref
    +-- (allocation-type)?
       +--:(dynamic)
       |  +-- (address-assign)?
       |  |  +--:(number)
       |  |  |  +-- number-of-dynamic-address?   uint16
       |  |  +--:(explicit)
       |  |     +-- customer-addresses
       |  |        +-- address-pool* [pool-id]
       |  |           +-- pool-id?         string
       |  |           +-- start-address    inet:ipv6-address
       |  |           +-- end-address?     inet:ipv6-address
       |  +-- (provider-dhcp)?
       |  |  +--:(dhcp-service-type)
       |  |     +-- dhcp-service-type?           enumeration
       |  +-- (dhcp-relay)?
       |     +--:(customer-dhcp-servers)
       |        +-- customer-dhcp-servers
       |           +-- server-ip-address*   inet:ipv6-address
       +--:(static-addresses)
          +-- address* [address-id]
             +-- address-id?         string
             +-- customer-address?   inet:ipv6-address
]]></artwork>
        </figure>
        <dl>
          <dt>Routing parameters (<xref target="rtg-full-tree"/>):</dt>
          <dd>
            <t>In addition to static routing, the module supports the following routing protocols: BGP <xref target="RFC4271"/>, OSPF <xref target="RFC4577"/> or <xref target="RFC6565"/>, IS-IS <xref target="ISO10589"/><xref target="RFC1195"/><xref target="RFC5308"/>, and RIP <xref target="RFC2453"/>. For all supported routing protocols, 'address-family' indicates whether IPv4, IPv6, or both address families are to be activated. For example, this parameter is used to determine whether RIPv2 <xref target="RFC2453"/>, RIP Next Generation (RIPng), or both are to be enabled <xref target="RFC2080"/>. More details about supported routing groupings are provided hereafter:
</t>
            <ul spacing="normal">
              <li>
                <t>Authentication: These groupings include the required information to manage the authentication of OSPF, IS-IS, BGP, and RIP. Similar to <xref target="RFC9182"/>, this version of the common AC model assumes that parameters specific to the TCP-AO are preconfigured as part of the key chain that is referenced in the model. No assumption is made about how such a key chain is preconfigured. However, the structure of the key chain should cover data nodes beyond those in <xref target="RFC8177"/>, mainly SendID and RecvID (Section 3.1 of <xref target="RFC5925"/>).</t>
              </li>
              <li>
                <t>BGP peer groups: Includes a set of parameters to identify a BGP peer group. Such a group can be defined by providing a local AS Number (ASN), a customer's ASN, and the address families to be activated for this group. BGP peer groups can be identified by a name.</t>
              </li>
              <li>
                <t>Basic parameters: These groupings include the minimal set of routing configuration that is required for the activation of OSPF, IS-IS, BGP, and RIP.</t>
              </li>
              <li>
                <t>Static routing: Parameters to configure an entry of a list of IP static routing entries.</t>
              </li>
            </ul>
          </dd>
        </dl>
        <figure anchor="rtg-full-tree">
          <name>Layer 3 Connection Groupings</name>
          <artwork align="center"><![CDATA[
  grouping bgp-authentication:
    +-- authentication
       +-- enable?            boolean
       +-- keying-material
          +-- (option)?
             +--:(ao)
             |  +-- enable-ao?          boolean
             |  +-- ao-keychain?        key-chain:key-chain-ref
             +--:(md5)
             |  +-- md5-keychain?       key-chain:key-chain-ref
             +--:(explicit)
                +-- key-id?             uint32
                +-- key?                string
                +-- crypto-algorithm?   identityref
  grouping ospf-authentication:
    +-- authentication
       +-- enable?            boolean
       +-- keying-material
          +-- (option)?
             +--:(auth-key-chain)
             |  +-- key-chain?          key-chain:key-chain-ref
             +--:(auth-key-explicit)
                +-- key-id?             uint32
                +-- key?                string
                +-- crypto-algorithm?   identityref
  grouping isis-authentication:
    +-- authentication
       +-- enable?            boolean
       +-- keying-material
          +-- (option)?
             +--:(auth-key-chain)
             |  +-- key-chain?          key-chain:key-chain-ref
             +--:(auth-key-explicit)
                +-- key-id?             uint32
                +-- key?                string
                +-- crypto-algorithm?   identityref
  grouping rip-authentication:
    +-- authentication
       +-- enable?            boolean
       +-- keying-material
          +-- (option)?
             +--:(auth-key-chain)
             |  +-- key-chain?          key-chain:key-chain-ref
             +--:(auth-key-explicit)
                +-- key?                string
                +-- crypto-algorithm?   identityref
  grouping bgp-peer-group-without-name:
    +--ro local-as?         inet:as-number
    +-- peer-as?          inet:as-number
    +-- address-family?   identityref
  grouping bgp-peer-group-with-name:
    +-- name?             string
    +--ro local-as?         inet:as-number
    +-- peer-as?          inet:as-number
    +-- address-family?   identityref
  grouping ospf-basic:
    +-- address-family?   identityref
    +-- area-id           yang:dotted-quad
    +-- metric?           uint16
  grouping isis-basic:
    +-- address-family?   identityref
    +-- area-address      area-address
  grouping ipv4-static-rtg-entry:
    +-- lan?        inet:ipv4-prefix
    +-- lan-tag?    string
    +-- next-hop?   union
    +-- metric?     uint32
  grouping ipv4-static-rtg:
    +-- ipv4-lan-prefixes* [lan next-hop] {vpn-common:ipv4}?
       +-- lan?        inet:ipv4-prefix
       +-- lan-tag?    string
       +-- next-hop?   union
       +-- metric?     uint32
       +-- status
          +-- admin-status
          |  +-- status?        identityref
          |  +--ro last-change?   yang:date-and-time
          +--ro oper-status
             +--ro status?        identityref
             +--ro last-change?   yang:date-and-time
  grouping ipv6-static-rtg-entry:
    +-- lan?        inet:ipv6-prefix
    +-- lan-tag?    string
    +-- next-hop?   union
    +-- metric?     uint32
  grouping ipv6-static-rtg:
    +-- ipv6-lan-prefixes* [lan next-hop] {vpn-common:ipv6}?
       +-- lan?        inet:ipv6-prefix
       +-- lan-tag?    string
       +-- next-hop?   union
       +-- metric?     uint32
       +-- status
          +-- admin-status
          |  +-- status?        identityref
          |  +--ro last-change?   yang:date-and-time
          +--ro oper-status
             +--ro status?        identityref
             +--ro last-change?   yang:date-and-time
  grouping bfd:
    +-- holdtime?   uint32
]]></artwork>
        </figure>
        <dl>
          <dt>Bandwidth parameters (<xref target="bw-full-tree"/>):</dt>
          <dd>
            <t>Bandwidth parameters can be represented using the Committed
Information Rate (CIR), the Excess Information Rate (EIR), or the Peak
Information Rate (PIR).</t>
          </dd>
          <dt/>
          <dd>
            <t>These parameters can be provided per bandwidth type. Type values are
taken from <xref target="RFC9181"/>, e.g.,:</t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>'bw-per-cos':</dt>
                  <dd>
                    <t>The bandwidth is per Class of Service (CoS).</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>'bw-per-site':</dt>
                  <dd>
                    <t>The bandwidth is to all ACs that belong to the same site.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </dd>
        </dl>
        <figure anchor="bw-full-tree">
          <name>Bandwidth Groupings</name>
          <artwork align="center"><![CDATA[
  grouping bandwidth-parameters:
    +-- cir?   uint64
    +-- cbs?   uint64
    +-- eir?   uint64
    +-- ebs?   uint64
    +-- pir?   uint64
    +-- pbs?   uint64
  grouping bandwidth-per-type:
    +-- bandwidth* [bw-type]
       +-- bw-type?     identityref
       +-- (type)?
          +--:(per-cos)
          |  +-- cos* [cos-id]
          |     +-- cos-id?   uint8
          |     +-- cir?      uint64
          |     +-- cbs?      uint64
          |     +-- eir?      uint64
          |     +-- ebs?      uint64
          |     +-- pir?      uint64
          |     +-- pbs?      uint64
          +--:(other)
             +-- cir?   uint64
             +-- cbs?   uint64
             +-- eir?   uint64
             +-- ebs?   uint64
             +-- pir?   uint64
             +-- pbs?   uint64
]]></artwork>
        </figure>
      </section>
    </section>
    <section anchor="sec-module">
      <name>Common Attachment Circuit YANG Module</name>
      <t>This module uses types defined in <xref target="RFC6991"/>, <xref target="RFC8177"/>, and  <xref target="RFC9181"/>.</t>
      <sourcecode markers="true" name="ietf-ac-common@2023-11-13.yang"><![CDATA[
module ietf-ac-common {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-ac-common";
  prefix ac-common;

  import ietf-vpn-common {
    prefix vpn-common;
    reference
      "RFC 9181: A Common YANG Data Model for Layer 2 and Layer 3
                 VPNs";
  }
  import ietf-netconf-acm {
    prefix nacm;
    reference
      "RFC 8341: Network Configuration Access Control Model";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types, Section 4";
  }
  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Data Types, Section 3";
  }
  import ietf-key-chain {
    prefix key-chain;
    reference
      "RFC 8177: YANG Data Model for Key Chains";
  }

  organization
    "IETF OPSAWG (Operations and Management Area Working Group)";
  contact
    "WG Web:   <https://datatracker.ietf.org/wg/opsawg/>
     WG List:  <mailto:opsawg@ietf.org>

     Editor:   Mohamed Boucadair
               <mailto:mohamed.boucadair@orange.com>
     Author:   Richard Roberts
               <mailto:rroberts@juniper.net>
     Author:   Oscar Gonzalez de Dios
               <mailto:oscar.gonzalezdedios@telefonica.com>
     Author:   Samier Barguil
               <mailto:ssamier.barguil_giraldo@nokia.com>
     Author:   Bo Wu
               <mailto:lana.wubo@huawei.com>";
  description
    "This YANG module defines a common attachment circuit (AC)
     YANG model.

     Copyright (c) 2024 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 Revised BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

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

  revision 2023-11-13 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: A Common YANG Data Model for Attachment Circuits";
  }

  /****************************Identities************************/
  // IP address allocation types

  identity address-allocation-type {
    description
      "Base identity for address allocation type in the AC.";
  }

  identity provider-dhcp {
    base address-allocation-type;
    description
      "The provider's network provides a DHCP service to the
       customer.";
  }

  identity provider-dhcp-relay {
    base address-allocation-type;
    description
      "The provider's network provides a DHCP relay service to the
       customer.";
  }

  identity provider-dhcp-slaac {
    if-feature "vpn-common:ipv6";
    base address-allocation-type;
    description
      "The provider's network provides a DHCP service to the customer
       as well as IPv6 Stateless Address Autoconfiguration (SLAAC).";
    reference
      "RFC 4862: IPv6 Stateless Address Autoconfiguration";
  }

  identity static-address {
    base address-allocation-type;
    description
      "The provider's network provides static IP addressing to the
       customer.";
  }

  identity slaac {
    if-feature "vpn-common:ipv6";
    base address-allocation-type;
    description
      "The provider's network uses IPv6 SLAAC to provide addressing
       to the customer.";
    reference
      "RFC 4862: IPv6 Stateless Address Autoconfiguration";
  }

  identity dynamic-infra {
    base address-allocation-type;
    description
      "The IP address is dynamically allocated by the hosting
       infrastrcture.";
  }

  // next-hop actions 

  identity local-defined-next-hop {
    description
      "Base identity of local defined next hops.";
  }

  identity discard {
    base local-defined-next-hop;
    description
      "Indicates an action to discard traffic for the corresponding
       destination. For example, this can be used to black-hole
       traffic.";
  }

  identity local-link {
    base local-defined-next-hop;
    description
      "Treat traffic towards addresses within the specified next-hop
       prefix as though they are connected to a local link.";
  }

  // Layer 2 tunnel types

  identity l2-tunnel-type {
    description
      "Base identity for Layer 2 tunnel selection for an AC.";
  }

  identity pseudowire {
    base l2-tunnel-type;
    description
      "Pseudowire tunnel termination for the AC.";
  }

  identity vpls {
    base l2-tunnel-type;
    description
      "Virtual Private LAN Service (VPLS) tunnel termination for
       the AC.";
  }

  identity vxlan {
    base l2-tunnel-type;
    description
      "Virtual eXtensible Local Area Network (VXLAN) tunnel
       termination for the AC.";
  }

  // Tagging precedence

  identity precedence-type {
    description
      "Redundancy type. The service can be created with primary and
       secondary tagging.";
  }

  identity primary {
    base precedence-type;
    description
      "Identifies the main attachment circuit.";
  }

  identity secondary {
    base precedence-type;
    description
      "Identifies the secondary attachment circuit.";
  }

  /****************************Typedefs************************/

  typedef predefined-next-hop {
    type identityref {
      base local-defined-next-hop;
    }
    description
      "Predefined next-hop designation for locally generated
       routes.";
  }

  typedef area-address {
    type string {
      pattern '[0-9A-Fa-f]{2}(\.[0-9A-Fa-f]{4}){0,6}';
    }
    description
      "This type defines the area address format.";
  }

  /************************Reusable groupings********************/
  /**** Service Status ****/

  grouping service-status {
    description
      "Service status grouping.";
    container status {
      description
        "Service status.";
      container admin-status {
        description
          "Administrative service status.";
        leaf status {
          type identityref {
            base vpn-common:administrative-status;
          }
          description
            "Administrative service status.";
        }
        leaf last-change {
          type yang:date-and-time;
          config false;
          description
            "Indicates the actual date and time of the service
             status change.";
        }
      }
      container oper-status {
        config false;
        description
          "Operational service status.";
        uses vpn-common:oper-status-timestamp;
      }
    }
  }


  /**** A set of profiles ****/

  grouping ac-profile-cfg {
    description
      "Grouping for AC profile configuration.";
    container valid-provider-identifiers {
      description
        "Container for valid provider profile identifiers.
         The profiles only have significance within the service
         provider's administrative domain.";
      list encryption-profile-identifier {
        key "id";
        description
          "List of encryption profile identifiers.";
        leaf id {
          type string;
          description
            "Identification of the encryption profile to be used.";
        }
      }
      list qos-profile-identifier {
        key "id";
        description
          "List of QoS profile identifiers.";
        leaf id {
          type string;
          description
            "Identification of the QoS profile to be used.";
        }
      }
      list bfd-profile-identifier {
        key "id";
        description
          "List of BFD profile identifiers.";
        leaf id {
          type string;
          description
            "Identification of the BFD profile to be used.";
        }
      }
      list forwarding-profile-identifier {
        key "id";
        description
          "List of forwarding profile identifiers.";
        leaf id {
          type string;
          description
            "Identification of the forwarding profile to be used.";
        }
      }
      list routing-profile-identifier {
        key "id";
        description
          "List of routing profile identifiers.";
        leaf id {
          type string;
          description
            "Identification of the routing profile to be used by
             the routing protocols over an AC.";
        }
      }
      nacm:default-deny-write;
    }
  }

  /**** Operational instructions ****/

  grouping op-instructions {
    description
      "Scheduling instructions.";
    leaf requested-start {
      type yang:date-and-time;
      description
        "Indicates the requested date and time when the service is
         expected to be active.";
    }
    leaf requested-stop {
      type yang:date-and-time;
      description
        "Indicates the requested date and time when the service is
         expected to be disabled.";
    }
    leaf actual-start {
      type yang:date-and-time;
      config false;
      description
        "Indicates the actual date and time when the service
         actually was enabled.";
    }
    leaf actual-stop {
      type yang:date-and-time;
      config false;
      description
        "Indicates the actual date and time when the service
         actually was disabled.";
    }
  }

  /**** Layer 2 encapsulations ****/
  // Dot1q

  grouping dot1q {
    description
      "Defines a grouping for tagged interfaces.";
    leaf tag-type {
      type identityref {
        base vpn-common:tag-type;
      }
      description
        "Tag type.";
    }
    leaf cvlan-id {
      type uint16 {
        range "1..4094";
      }
      description
        "VLAN identifier.";
    }
  }

  // priority-tagged

  grouping priority-tagged {
    description
      "Priority tagged.";
    leaf tag-type {
      type identityref {
        base vpn-common:tag-type;
      }
      description
        "Tag type.";
    }
  }

  // QinQ

  grouping qinq {
    description
      "Includes QinQ parameters.";
    leaf tag-type {
      type identityref {
        base vpn-common:tag-type;
      }
      description
        "Tag type.";
    }
    leaf svlan-id {
      type uint16 {
        range "1..4094";
      }
      mandatory true;
      description
        "Service VLAN (S-VLAN) identifier.";
    }
    leaf cvlan-id {
      type uint16 {
        range "1..4094";
      }
      mandatory true;
      description
        "Customer VLAN (C-VLAN) identifier.";
    }
  }

  /**** Layer 2 tunnel services ****/
  // pseudowire (PW)

  grouping pseudowire {
    description
      "Includes pseudowire termination parameters.";
    leaf vcid {
      type uint32;
      description
        "Indicates a PW or virtual circuit (VC) identifier.";
    }
    leaf far-end {
      type union {
        type uint32;
        type inet:ip-address;
      }
      description
        "Neighbor reference.";
      reference
        "RFC 8077: Pseudowire Setup and Maintenance Using the Label
                   Distribution Protocol (LDP), Section 6.1";
    }
  }

  // VPLS

  grouping vpls {
    description
      "VPLS termination parameters.";
    leaf vcid {
      type uint32;
      description
        "VC identifier.";
    }
    leaf-list far-end {
      type union {
        type uint32;
        type inet:ip-address;
      }
      description
        "Neighbor reference.";
    }
  }

  // VXLAN

  grouping vxlan {
    description
      "VXLAN termination parameters.";
    leaf vni-id {
      type uint32;
      mandatory true;
      description
        "VXLAN Network Identifier (VNI).";
    }
    leaf peer-mode {
      type identityref {
        base vpn-common:vxlan-peer-mode;
      }
      description
        "Specifies the VXLAN access mode. By default,
         the peer mode is set to 'static-mode'.";
    }
    leaf-list peer-ip-address {
      type inet:ip-address;
      description
        "List of a peer's IP addresses.";
    }
  }

  // Layer 2 Tunnel service

  grouping l2-tunnel-service {
    description
      "Defines a Layer 2 tunnel termination.";
    leaf type {
      type identityref {
        base l2-tunnel-type;
      }
      description
        "Selects the tunnel termination type for an AC.";
    }
    container pseudowire {
      when "derived-from-or-self(../type, 'ac-common:pseudowire')" {
        description
          "Only applies when the Layer 2 service type is
           'pseudowire'.";
      }
      description
        "Includes pseudowire termination parameters.";
      uses pseudowire;
    }
    container vpls {
      when "derived-from-or-self(../type, 'ac-common:vpls')" {
        description
          "Only applies when the Layer 2 service type is 'vpls'.";
      }
      description
        "VPLS termination parameters.";
      uses vpls;
    }
    container vxlan {
      when "derived-from-or-self(../type, 'ac-common:vxlan')" {
        description
          "Only applies when the Layer 2 service type is 'vxlan'.";
      }
      description
        "VXLAN termination parameters.";
      uses vxlan;
    }
  }

  /**** Layer 3 connection *****/
  // IPv4 allocation type

  grouping ipv4-allocation-type {
    description
      "IPv4-specific parameters.";
    leaf prefix-length {
      type uint8 {
        range "0..32";
      }
      description
        "Subnet prefix length expressed in bits. It is applied to
         both local and customer addresses.";
    }
    leaf address-allocation-type {
      type identityref {
        base address-allocation-type;
      }
      must "not(derived-from-or-self(current(), 'ac-common:slaac') "
         + "or derived-from-or-self(current(), "
         + "'ac-common:provider-dhcp-slaac'))" {
        error-message "SLAAC is only applicable to IPv6.";
      }
      description
        "Defines how IPv4 addresses are allocated to the peer site.";
    }
  }

  // IPv6 allocation type

  grouping ipv6-allocation-type {
    description
      "IPv6-specific parameters.";
    leaf prefix-length {
      type uint8 {
        range "0..128";
      }
      description
        "Subnet prefix length expressed in bits. It is applied to
          both local and customer addresses.";
    }
    leaf address-allocation-type {
      type identityref {
        base address-allocation-type;
      }
      description
        "Defines how IPv6 addresses are allocated to the peer site.";
    }
  }

  // Basic parameters for IPv4 connection 

  grouping ipv4-connection-basic {
    description
      "Basic set fof IPv4-specific parameters for the connection.";
    uses ipv4-allocation-type;
    choice allocation-type {
      description
        "Choice of the IPv4 address allocation.";
      case dynamic {
        description
          "When the addresses are allocated by DHCP or other dynamic
           means local to the infrastructure.";
        choice provider-dhcp {
          description
            "Parameters related to DHCP-allocated addresses. IP
             addresses are allocated by DHCP, that is provided by
             the operator.";
          leaf dhcp-service-type {
            type enumeration {
              enum server {
                description
                  "Local DHCP server.";
              }
              enum relay {
                description
                  "Local DHCP relay.  DHCP requests are relayed to
                   a provider's server.";
              }
            }
            description
              "Indicates the type of DHCP service to be enabled on
               an AC.";
          }
        }
        choice dhcp-relay {
          description
            "The DHCP relay is provided by the operator.";
          container customer-dhcp-servers {
            description
              "Container for a list of the customer's DHCP servers.";
            leaf-list server-ip-address {
              type inet:ipv4-address;
              description
                "IPv4 addresses of the customer's DHCP server.";
            }
          }
        }
      }
    }
  }

  // Basic parameters for IPv6 connection

  grouping ipv6-connection-basic {
    description
      "Basic set fof IPv6-specific parameters for the connection.";
    uses ipv6-allocation-type;
    choice allocation-type {
      description
        "Choice of the IPv6 address allocation.";
      case dynamic {
        description
          "When the addresses are allocated by DHCP or other dynamic
           means local to the infrastructure.";
        choice provider-dhcp {
          description
            "Parameters related to DHCP-allocated addresses.
             IP addresses are allocated by DHCP, that is provided
             by the operator.";
          leaf dhcp-service-type {
            type enumeration {
              enum server {
                description
                  "Local DHCP server.";
              }
              enum relay {
                description
                  "Local DHCP relay.  DHCP requests are relayed to a
                   provider's server.";
              }
            }
            description
              "Indicates the type of DHCP service to be enabled on
               the AC.";
          }
        }
        choice dhcp-relay {
          description
            "The DHCP relay is provided by the operator.";
          container customer-dhcp-servers {
            description
              "Container for a list of the customer's DHCP servers.";
            leaf-list server-ip-address {
              type inet:ipv6-address;
              description
                "IPv6 addresses of the customer's DHCP server.";
            }
          }
        }
      }
    }
  }

  // Full parameters for the IPv4 connection

  grouping ipv4-connection {
    description
      "IPv4-specific parameters.";
    leaf local-address {
      type inet:ipv4-address;
      description
        "The IP address used at the provider's interface.";
    }
    leaf virtual-address {
      type inet:ipv4-address;
      description
        "This addresss may be used for redundancy purposes.";
    }
    uses ipv4-allocation-type;
    choice allocation-type {
      description
        "Choice of the IPv4 address allocation.";
      case dynamic {
        description
          "When the addresses are allocated by DHCP or other
           dynamic means local to the infrastructure.";
        choice address-assign {
          description
            "A choice for how IPv4 addresses are assigned.";
          case number {
            leaf number-of-dynamic-address {
              type uint16;
              description
                "Specifies the number of IP addresses to be assigned
                 to the customer on the AC.";
            }
          }
          case explicit {
            container customer-addresses {
              description
                "Container for customer addresses to be allocated
                 using DHCP.";
              list address-pool {
                key "pool-id";
                description
                  "Describes IP addresses to be dyncamically
                   allocated.

                   When only 'start-address' is present, it
                   represents a single address.

                   When both 'start-address' and 'end-address' are
                   specified, it implies a range inclusive of both
                   addresses.";
                leaf pool-id {
                  type string;
                  description
                    "A pool identifier for the address range from
                     'start-address' to 'end-address'.";
                }
                leaf start-address {
                  type inet:ipv4-address;
                  mandatory true;
                  description
                    "Indicates the first address in the pool.";
                }
                leaf end-address {
                  type inet:ipv4-address;
                  description
                    "Indicates the last address in the pool.";
                }
              }
            }
          }
        }
        choice provider-dhcp {
          description
            "Parameters related to DHCP-allocated addresses. IP
             addresses are allocated by DHCP, which is provided by
             the operator.";
          leaf dhcp-service-type {
            type enumeration {
              enum server {
                description
                  "Local DHCP server.";
              }
              enum relay {
                description
                  "Local DHCP relay.  DHCP requests are relayed to
                   a provider's server.";
              }
            }
            description
              "Indicates the type of DHCP service to be enabled on
               this AC.";
          }
        }
        choice dhcp-relay {
          description
            "The DHCP relay is provided by the operator.";
          container customer-dhcp-servers {
            description
              "Container for a list of the customer's DHCP servers.";
            leaf-list server-ip-address {
              type inet:ipv4-address;
              description
                "IPv4 addresses of the customer's DHCP server.";
            }
          }
        }
      }
      case static-addresses {
        description
          "Lists the IPv4 addresses that are used.";
        list address {
          key "address-id";
          ordered-by user;
          description
            "Lists the IPv4 addresses that are used. The first
             address of the list is the primary address of the
             connection.";
          leaf address-id {
            type string;
            description
              "An identifier of the static IPv4 address.";
          }
          leaf customer-address {
            type inet:ipv4-address;
            description
              "An IPv4 address of the customer side.";
          }
        }
      }
    }
  }

  // Full parameters for the IPv6 connection

  grouping ipv6-connection {
    description
      "IPv6-specific parameters.";
    leaf local-address {
      type inet:ipv6-address;
      description
        "IPv6 address of the provider side.";
    }
    leaf virtual-address {
      type inet:ipv6-address;
      description
        "This addresss may be used for redundancy purposes.";
    }
    uses ipv6-allocation-type;
    choice allocation-type {
      description
        "Choice of the IPv6 address allocation.";
      case dynamic {
        description
          "When the addresses are allocated by DHCP or other
           dynamic means local to the infrastructure.";
        choice address-assign {
          description
            "A choice for how IPv6 addresses are assigned.";
          case number {
            leaf number-of-dynamic-address {
              type uint16;
              description
                "Specifies the number of IP addresses to be
                 assigned to the customer on this access.";
            }
          }
          case explicit {
            container customer-addresses {
              description
                "Container for customer addresses to be allocated
                 using DHCP.";
              list address-pool {
                key "pool-id";
                description
                  "Describes IP addresses to be dyncamically
                   allocated.

                   When only 'start-address' is present, it
                   represents a single address.

                   When both 'start-address' and 'end-address' are
                   specified, it implies a range inclusive of both
                   addresses.";
                leaf pool-id {
                  type string;
                  description
                    "A pool identifier for the address range from
                     'start-address' to 'end-address'.";
                }
                leaf start-address {
                  type inet:ipv6-address;
                  mandatory true;
                  description
                    "Indicates the first address in the pool.";
                }
                leaf end-address {
                  type inet:ipv6-address;
                  description
                    "Indicates the last address in the pool.";
                }
              }
            }
          }
        }
        choice provider-dhcp {
          description
            "Parameters related to DHCP-allocated addresses.
             IP addresses are allocated by DHCP, which is provided
             by the operator.";
          leaf dhcp-service-type {
            type enumeration {
              enum server {
                description
                  "Local DHCP server.";
              }
              enum relay {
                description
                  "Local DHCP relay.  DHCP requests are relayed
                   to a provider's server.";
              }
            }
            description
              "Indicates the type of DHCP service to
               be enabled on this access.";
          }
        }
        choice dhcp-relay {
          description
            "The DHCP relay is provided by the operator.";
          container customer-dhcp-servers {
            description
              "Container for a list of the customer's DHCP servers.";
            leaf-list server-ip-address {
              type inet:ipv6-address;
              description
                "IPv6 addresses of the customer's DHCP server.";
            }
          }
        }
      }
      case static-addresses {
        description
          "Lists the IPv6 addresses that are used.";
        list address {
          key "address-id";
          ordered-by user;
          description
            "Lists the IPv6 addresses that are used. The first
             address of the list is the primary IP address of
             the connection.";
          leaf address-id {
            type string;
            description
              "An identifier of the static IPv6 address.";
          }
          leaf customer-address {
            type inet:ipv6-address;
            description
              "An IPv6 address of the customer side.";
          }
        }
      }
    }
  }

  /**** Routing ****/
  // Routing authentication

  grouping bgp-authentication {
    description
      "Grouping for BGP authentication parameters.";
    container authentication {
      description
        "Container for BGP authentication  parameters.";
      leaf enable {
        type boolean;
        description
          "Enables or disables authentication.";
      }
      container keying-material {
        when "../enable = 'true'";
        description
          "Container for describing how a BGP routing session is to
           be secured on an AC.";
        choice option {
          description
            "Choice of authentication options.";
          case ao {
            description
              "Uses the TCP Authentication Option (TCP-AO).";
            reference
              "RFC 5925: The TCP Authentication Option";
            leaf enable-ao {
              type boolean;
              description
                "Enables the TCP-AO.";
            }
            leaf ao-keychain {
              type key-chain:key-chain-ref;
              description
                "Reference to the TCP-AO key chain.";
              reference
                "RFC 8177: YANG Data Model for Key Chains";
            }
          }
          case md5 {
            description
              "Uses MD5 to secure the session.";
            reference
              "RFC 4364: BGP/MPLS IP Virtual Private Networks
                         (VPNs), Section 13.2";
            leaf md5-keychain {
              type key-chain:key-chain-ref;
              description
                "Reference to the MD5 key chain.";
              reference
                "RFC 8177: YANG Data Model for Key Chains";
            }
          }
          case explicit {
            leaf key-id {
              type uint32;
              description
                "Key identifier.";
            }
            leaf key {
              type string;
              description
                "BGP authentication key.

                 This model only supports the subset of keys that
                 are representable as ASCII strings.";
            }
            leaf crypto-algorithm {
              type identityref {
                base key-chain:crypto-algorithm;
              }
              description
                "Indicates the cryptographic algorithm associated
                 with the key.";
            }
          }
        }
      }
    }
  }

  grouping ospf-authentication {
    description
      "Authentication configuration.";
    container authentication {
      description
        "Container for OSPF authentication  parameters.";
      leaf enable {
        type boolean;
        description
          "Enables or disables authentication.";
      }
      container keying-material {
        when "../enable = 'true'";
        description
          "Container for describing how an OSPF session is to be
           secured for this AC.";
        choice option {
          description
            "Options for OSPF authentication.";
          case auth-key-chain {
            leaf key-chain {
              type key-chain:key-chain-ref;
              description
                "Name of the key chain.";
            }
          }
          case auth-key-explicit {
            leaf key-id {
              type uint32;
              description
                "Key identifier.";
            }
            leaf key {
              type string;
              description
                "OSPF authentication key.

                 This model only supports the subset of keys that
                 are representable as ASCII strings.";
            }
            leaf crypto-algorithm {
              type identityref {
                base key-chain:crypto-algorithm;
              }
              description
                "Indicates the cryptographic algorithm associated
                 with the key.";
            }
          }
        }
      }
    }
  }

  grouping isis-authentication {
    description
      "IS-IS authentication configuration.";
    container authentication {
      description
        "Container for IS-IS authentication  parameters.";
      leaf enable {
        type boolean;
        description
          "Enables or disables authentication.";
      }
      container keying-material {
        when "../enable = 'true'";
        description
          "Container for describing how an IS-IS session is secured
           over an AC.";
        choice option {
          description
            "Options for IS-IS authentication.";
          case auth-key-chain {
            leaf key-chain {
              type key-chain:key-chain-ref;
              description
                "Name of the key chain.";
            }
          }
          case auth-key-explicit {
            leaf key-id {
              type uint32;
              description
                "Key identifier.";
            }
            leaf key {
              type string;
              description
                "IS-IS authentication key.

                 This model only supports the subset of keys that
                 are representable as ASCII strings.";
            }
            leaf crypto-algorithm {
              type identityref {
                base key-chain:crypto-algorithm;
              }
              description
                "Indicates the cryptographic algorithm associated
                 with the key.";
            }
          }
        }
      }
    }
  }

  grouping rip-authentication {
    description
      "RIP authentication configuration.";
    container authentication {
      description
        "Container for RIP authentication  parameters.";
      leaf enable {
        type boolean;
        description
          "Enables or disables authentication.";
      }
      container keying-material {
        when "../enable = 'true'";
        description
          "Container for describing how a RIP session is to be
           secured on this AC.";
        choice option {
          description
            "Specifies the authentication
             scheme.";
          case auth-key-chain {
            leaf key-chain {
              type key-chain:key-chain-ref;
              description
                "Name of the key chain.";
            }
          }
          case auth-key-explicit {
            leaf key {
              type string;
              description
                "RIP authentication key.

                 This model only supports the subset of keys that
                 are representable as ASCII strings.";
            }
            leaf crypto-algorithm {
              type identityref {
                base key-chain:crypto-algorithm;
              }
              description
                "Indicates the cryptographic algorithm associated
                 with the key.";
            }
          }
        }
      }
    }
  }

  // Basic routing parameters

  grouping bgp-peer-group-without-name {
    description
      "Identifies a BGP peer-group configured on the local system.";
    leaf local-as {
      type inet:as-number;
      config false;
      description
        "Indicates a local AS Number (ASN). This ASN is exposed
         to a customer so that it knows which ASN to use
         to set up a BGP session.";
    }
    leaf peer-as {
      type inet:as-number;
      description
        "Indicates the customer's ASN when the customer
         requests BGP routing.";
    }
    leaf address-family {
      type identityref {
        base vpn-common:address-family;
      }
      description
        "This node contains the address families to be activated.
         'dual-stack' means that both IPv4 and IPv6 will be
         activated.";
    }
  }

  grouping bgp-peer-group-with-name {
    description
      "Identifies a BGP peer-group configured on the local system -
       identified by a peer-group name.";
    leaf name {
      type string;
      description
        "Name of the BGP peer-group.";
    }
    uses bgp-peer-group-without-name;
  }

  grouping ospf-basic {
    description
      "Configuration specific to OSPF.";
    leaf address-family {
      type identityref {
        base vpn-common:address-family;
      }
      description
        "Indicates whether IPv4, IPv6, or both are to be activated.";
    }
    leaf area-id {
      type yang:dotted-quad;
      mandatory true;
      description
        "Area ID.";
      reference
        "RFC 4577: OSPF as the Provider/Customer Edge Protocol
                   for BGP/MPLS IP Virtual Private Networks
                   (VPNs), Section 4.2.3
         RFC 6565: OSPFv3 as a Provider Edge to Customer Edge
                   (PE-CE) Routing Protocol, Section 4.2";
    }
    leaf metric {
      type uint16;
      description
        "Metric of the AC.  It is used in the routing state
         calculation and path selection.";
    }
  }

  grouping isis-basic {
    description
      "Basic configuration specific to IS-IS.";
    leaf address-family {
      type identityref {
        base vpn-common:address-family;
      }
      description
        "Indicates whether IPv4, IPv6, or both are to be activated.";
    }
    leaf area-address {
      type area-address;
      mandatory true;
      description
        "Area address.";
    }
  }

  // Static routing 

  grouping ipv4-static-rtg-entry {
    description
      "Paramters to configure a specific IPv4 static routing entry.";
    leaf lan {
      type inet:ipv4-prefix;
      description
        "LAN prefix.";
    }
    leaf lan-tag {
      type string;
      description
        "Internal tag to be used in service policies.";
    }
    leaf next-hop {
      type union {
        type inet:ip-address;
        type predefined-next-hop;
      }
      description
        "The next hop that is to be used for the static route.
         This may be specified as an IP address or a
         predefined next-hop type (e.g., 'discard' or
         'local-link').";
    }
    leaf metric {
      type uint32;
      description
        "Indicates the metric associated with the static route.";
    }
  }

  grouping ipv4-static-rtg {
    description
      "Configuration specific to IPv4 static routing.";
    list ipv4-lan-prefixes {
      if-feature "vpn-common:ipv4";
      key "lan next-hop";
      description
        "List of LAN prefixes for the site.";
      uses ipv4-static-rtg-entry;
      uses ac-common:service-status;
    }
  }

  grouping ipv6-static-rtg-entry {
    description
      "Paramters to configure a specific IPv6 static routing entry.";
    leaf lan {
      type inet:ipv6-prefix;
      description
        "LAN prefixes.";
    }
    leaf lan-tag {
      type string;
      description
        "Internal tag to be used in service (e.g., VPN) policies.";
    }
    leaf next-hop {
      type union {
        type inet:ip-address;
        type predefined-next-hop;
      }
      description
        "The next hop that is to be used for the static route.
         This may be specified as an IP address or a predefined
         next-hop type (e.g., 'discard' or 'local-link').";
    }
    leaf metric {
      type uint32;
      description
        "Indicates the metric associated with the static route.";
    }
  }

  grouping ipv6-static-rtg {
    description
      "Configuration specific to IPv6 static routing.";
    list ipv6-lan-prefixes {
      if-feature "vpn-common:ipv6";
      key "lan next-hop";
      description
        "List of LAN prefixes for the site.";
      uses ipv6-static-rtg-entry;
      uses ac-common:service-status;
    }
  }

  // OAM

  grouping bfd {
    description
      "Container for BFD.";
    leaf holdtime {
      type uint32;
      units "milliseconds";
      description
        "Expected BFD holdtime.
         The customer may impose some fixed values
         for the holdtime period if the provider allows
         the customer to use this function.
         If the provider doesn't allow the customer to
         use this function, fixed values will not be set.";
      reference
        "RFC 5880: Bidirectional Forwarding Detection (BFD),
                   Section 6.8.18";
    }
  }

  // QoS

  grouping bandwidth-parameters {
    description
      "A grouping for bandwidth parameters.";
    leaf cir {
      type uint64;
      units "bps";
      description
        "Committed Information Rate (CIR). The maximum number of bits
         that a port can receive or send during one second over
         an interface.";
    }
    leaf cbs {
      type uint64;
      units "bytes";
      description
        "Committed Burst Size (CBS). CBS controls the bursty nature
         of the traffic.  Traffic that does not use the configured
         CIR accumulates credits until the credits reach the
         configured CBS.";
    }
    leaf eir {
      type uint64;
      units "bps";
      description
        "Excess Information Rate (EIR), i.e., excess frame delivery
         allowed not subject to a Service Level Agreement (SLA).
         The traffic rate can be limited by EIR.";
    }
    leaf ebs {
      type uint64;
      units "bytes";
      description
        "Excess Burst Size (EBS).  The bandwidth available for burst
         traffic from the EBS is subject to the amount of bandwidth
         that is accumulated during periods when traffic allocated
         by the EIR policy is not used.";
    }
    leaf pir {
      type uint64;
      units "bps";
      description
        "Peak Information Rate (PIR), i.e., maximum frame delivery
         allowed. It is equal to or less than sum of CIR and EIR.";
    }
    leaf pbs {
      type uint64;
      units "bytes";
      description
        "Peak Burst Size (PBS).";
    }
  }

  grouping bandwidth-per-type {
    description
      "Grouping for bandwidth per type.";
    list bandwidth {
      key "bw-type";
      description
        "List for bandwidth per type data nodes.";
      leaf bw-type {
        type identityref {
          base vpn-common:bw-type;
        }
        description
          "Indicates the bandwidth type.";
      }
      choice type {
        description
          "Choice based upon bandwidth type.";
        case per-cos {
          description
            "Bandwidth per CoS.";
          list cos {
            key "cos-id";
            description
              "List of Class of Services.";
            leaf cos-id {
              type uint8;
              description
                "Identifier of the CoS, indicated by a Differentiated
                 Services Code Point (DSCP) or a CE-CLAN CoS (802.1p)
                 value in the service frame.";
              reference
                "IEEE Std 802.1Q: Bridges and Bridged Networks";
            }
            uses bandwidth-parameters;
          }
        }
        case other {
          description
            "Other bandwidth types.";
          uses bandwidth-parameters;
        }
      }
    }
  }
}
]]></sourcecode>
    </section>
    <section anchor="security-considerations">
      <name>Security Considerations</name>
      <t>The YANG module specified in this document defines schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF <xref target="RFC6241"/> or RESTCONF <xref target="RFC8040"/>.  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) <xref target="RFC6242"/>.  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   <xref target="RFC8446"/>.</t>
      <t>The Network Configuration Access Control Model (NACM) <xref target="RFC8341"/>
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.</t>
      <t>The "ietf-ac-common" module defines a set of identities, types, and
   groupings.  These nodes are intended to be reused by other YANG
   modules.  The module by itself does not expose any data nodes that
   are writable, data nodes that contain read-only state, or RPCs.</t>
      <t>YANG modules that use the groupings that are defined in this document
   should identify the corresponding security considerations.  For
   example, reusing some of these groupings will expose privacy-related
   information (e.g., 'ipv6-lan-prefixes' or 'ipv4-lan-prefixes').  Disclosing such information may
   be considered a violation of the customer-provider trust
   relationship.</t>
      <t>Several groupings ('bgp-authentication', 'ospf-authentication', 'isis-authentication', and 'rip-authentication') rely
   upon <xref target="RFC8177"/> for authentication purposes.  As such, modules that will reuse these groupings
   will inherit the security considerations discussed in Section 5 of
   <xref target="RFC8177"/>.  Also, these groupings support supplying explicit keys as
   strings in ASCII format.  The use of keys in hexadecimal string
   format would afford greater key entropy with the same number of key-
   string octets.  However, such a format is not included in this
   version of the common AC model, because it is not supported by the underlying
   device modules (e.g., <xref target="RFC8695"/>).</t>
    </section>
    <section anchor="iana-considerations">
      <name>IANA Considerations</name>
      <t>IANA is requested to register the following URI in the "ns" subregistry within
   the "IETF XML Registry" <xref target="RFC3688"/>:</t>
      <artwork><![CDATA[
   URI:  urn:ietf:params:xml:ns:yang:ietf-ac-common
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.
]]></artwork>
      <t>IANA is requested to register the following YANG module in the "YANG Module
   Names" subregistry <xref target="RFC6020"/> within the "YANG Parameters" registry:</t>
      <artwork><![CDATA[
   Name:  ietf-ac-common
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-ac-common
   Prefix:  ac-common
   Maintained by IANA?  N
   Reference:  RFC XXXX
]]></artwork>
    </section>
  </middle>
  <back>
    <references>
      <name>References</name>
      <references anchor="sec-normative-references">
        <name>Normative References</name>
        <reference anchor="ISO10589" target="https://www.iso.org/standard/30932.html">
          <front>
            <title>Information technology - Telecommunications and information exchange between systems - Intermediate System to Intermediate System intra-domain routeing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode network service (ISO8473)</title>
            <author>
              <organization>ISO</organization>
            </author>
            <date year="2002"/>
          </front>
        </reference>
        <reference anchor="RFC8342">
          <front>
            <title>Network Management Datastore Architecture (NMDA)</title>
            <author fullname="M. Bjorklund" initials="M." surname="Bjorklund"/>
            <author fullname="J. Schoenwaelder" initials="J." surname="Schoenwaelder"/>
            <author fullname="P. Shafer" initials="P." surname="Shafer"/>
            <author fullname="K. Watsen" initials="K." surname="Watsen"/>
            <author fullname="R. Wilton" initials="R." surname="Wilton"/>
            <date month="March" year="2018"/>
            <abstract>
              <t>Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8342"/>
          <seriesInfo name="DOI" value="10.17487/RFC8342"/>
        </reference>
        <reference anchor="RFC2119">
          <front>
            <title>Key words for use in RFCs to Indicate Requirement Levels</title>
            <author fullname="S. Bradner" initials="S." surname="Bradner"/>
            <date month="March" year="1997"/>
            <abstract>
              <t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="2119"/>
          <seriesInfo name="DOI" value="10.17487/RFC2119"/>
        </reference>
        <reference anchor="RFC8174">
          <front>
            <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
            <author fullname="B. Leiba" initials="B." surname="Leiba"/>
            <date month="May" year="2017"/>
            <abstract>
              <t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="8174"/>
          <seriesInfo name="DOI" value="10.17487/RFC8174"/>
        </reference>
        <reference anchor="RFC8077">
          <front>
            <title>Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)</title>
            <author fullname="L. Martini" initials="L." role="editor" surname="Martini"/>
            <author fullname="G. Heron" initials="G." role="editor" surname="Heron"/>
            <date month="February" year="2017"/>
            <abstract>
              <t>Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode, and Ethernet) can be emulated over an MPLS backbone by encapsulating the Layer 2 Protocol Data Units (PDUs) and then transmitting them over pseudowires (PWs). It is also possible to use pseudowires to provide low-rate Time-Division Multiplexed and Synchronous Optical NETworking circuit emulation over an MPLS-enabled network. This document specifies a protocol for establishing and maintaining the pseudowires, using extensions to the Label Distribution Protocol (LDP). Procedures for encapsulating Layer 2 PDUs are specified in other documents.</t>
              <t>This document is a rewrite of RFC 4447 for publication as an Internet Standard.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="84"/>
          <seriesInfo name="RFC" value="8077"/>
          <seriesInfo name="DOI" value="10.17487/RFC8077"/>
        </reference>
        <reference anchor="RFC7348">
          <front>
            <title>Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks</title>
            <author fullname="M. Mahalingam" initials="M." surname="Mahalingam"/>
            <author fullname="D. Dutt" initials="D." surname="Dutt"/>
            <author fullname="K. Duda" initials="K." surname="Duda"/>
            <author fullname="P. Agarwal" initials="P." surname="Agarwal"/>
            <author fullname="L. Kreeger" initials="L." surname="Kreeger"/>
            <author fullname="T. Sridhar" initials="T." surname="Sridhar"/>
            <author fullname="M. Bursell" initials="M." surname="Bursell"/>
            <author fullname="C. Wright" initials="C." surname="Wright"/>
            <date month="August" year="2014"/>
            <abstract>
              <t>This document describes Virtual eXtensible Local Area Network (VXLAN), which is used to address the need for overlay networks within virtualized data centers accommodating multiple tenants. The scheme and the related protocols can be used in networks for cloud service providers and enterprise data centers. This memo documents the deployed VXLAN protocol for the benefit of the Internet community.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7348"/>
          <seriesInfo name="DOI" value="10.17487/RFC7348"/>
        </reference>
        <reference anchor="RFC4271">
          <front>
            <title>A Border Gateway Protocol 4 (BGP-4)</title>
            <author fullname="Y. Rekhter" initials="Y." role="editor" surname="Rekhter"/>
            <author fullname="T. Li" initials="T." role="editor" surname="Li"/>
            <author fullname="S. Hares" initials="S." role="editor" surname="Hares"/>
            <date month="January" year="2006"/>
            <abstract>
              <t>This document discusses the Border Gateway Protocol (BGP), which is an inter-Autonomous System routing protocol.</t>
              <t>The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems (ASes) that reachability information traverses. This information is sufficient for constructing a graph of AS connectivity for this reachability from which routing loops may be pruned, and, at the AS level, some policy decisions may be enforced.</t>
              <t>BGP-4 provides a set of mechanisms for supporting Classless Inter-Domain Routing (CIDR). These mechanisms include support for advertising a set of destinations as an IP prefix, and eliminating the concept of network "class" within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including aggregation of AS paths.</t>
              <t>This document obsoletes RFC 1771. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="4271"/>
          <seriesInfo name="DOI" value="10.17487/RFC4271"/>
        </reference>
        <reference anchor="RFC4577">
          <front>
            <title>OSPF as the Provider/Customer Edge Protocol for BGP/MPLS IP Virtual Private Networks (VPNs)</title>
            <author fullname="E. Rosen" initials="E." surname="Rosen"/>
            <author fullname="P. Psenak" initials="P." surname="Psenak"/>
            <author fullname="P. Pillay-Esnault" initials="P." surname="Pillay-Esnault"/>
            <date month="June" year="2006"/>
            <abstract>
              <t>Many Service Providers offer Virtual Private Network (VPN) services to their customers, using a technique in which customer edge routers (CE routers) are routing peers of provider edge routers (PE routers). The Border Gateway Protocol (BGP) is used to distribute the customer's routes across the provider's IP backbone network, and Multiprotocol Label Switching (MPLS) is used to tunnel customer packets across the provider's backbone. This is known as a "BGP/MPLS IP VPN". The base specification for BGP/MPLS IP VPNs presumes that the routing protocol on the interface between a PE router and a CE router is BGP. This document extends that specification by allowing the routing protocol on the PE/CE interface to be the Open Shortest Path First (OSPF) protocol.</t>
              <t>This document updates RFC 4364. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="4577"/>
          <seriesInfo name="DOI" value="10.17487/RFC4577"/>
        </reference>
        <reference anchor="RFC6565">
          <front>
            <title>OSPFv3 as a Provider Edge to Customer Edge (PE-CE) Routing Protocol</title>
            <author fullname="P. Pillay-Esnault" initials="P." surname="Pillay-Esnault"/>
            <author fullname="P. Moyer" initials="P." surname="Moyer"/>
            <author fullname="J. Doyle" initials="J." surname="Doyle"/>
            <author fullname="E. Ertekin" initials="E." surname="Ertekin"/>
            <author fullname="M. Lundberg" initials="M." surname="Lundberg"/>
            <date month="June" year="2012"/>
            <abstract>
              <t>Many Service Providers (SPs) offer Virtual Private Network (VPN) services to their customers using a technique in which Customer Edge (CE) routers are routing peers of Provider Edge (PE) routers. The Border Gateway Protocol (BGP) is used to distribute the customer's routes across the provider's IP backbone network, and Multiprotocol Label Switching (MPLS) is used to tunnel customer packets across the provider's backbone. Support currently exists for both IPv4 and IPv6 VPNs; however, only Open Shortest Path First version 2 (OSPFv2) as PE-CE protocol is specified. This document extends those specifications to support OSPF version 3 (OSPFv3) as a PE-CE routing protocol. The OSPFv3 PE-CE functionality is identical to that of OSPFv2 except for the differences described in this document. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6565"/>
          <seriesInfo name="DOI" value="10.17487/RFC6565"/>
        </reference>
        <reference anchor="RFC1195">
          <front>
            <title>Use of OSI IS-IS for routing in TCP/IP and dual environments</title>
            <author fullname="R. Callon" initials="R." surname="Callon"/>
            <date month="December" year="1990"/>
            <abstract>
              <t>This memo specifies an integrated routing protocol, based on the OSI Intra-Domain IS-IS Routing Protocol, which may be used as an interior gateway protocol (IGP) to support TCP/IP as well as OSI. This allows a single routing protocol to be used to support pure IP environments, pure OSI environments, and dual environments. This specification was developed by the IS-IS working group of the Internet Engineering Task Force. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="1195"/>
          <seriesInfo name="DOI" value="10.17487/RFC1195"/>
        </reference>
        <reference anchor="RFC5308">
          <front>
            <title>Routing IPv6 with IS-IS</title>
            <author fullname="C. Hopps" initials="C." surname="Hopps"/>
            <date month="October" year="2008"/>
            <abstract>
              <t>This document specifies a method for exchanging IPv6 routing information using the IS-IS routing protocol. The described method utilizes two new TLVs: a reachability TLV and an interface address TLV to distribute the necessary IPv6 information throughout a routing domain. Using this method, one can route IPv6 along with IPv4 and OSI using a single intra-domain routing protocol. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5308"/>
          <seriesInfo name="DOI" value="10.17487/RFC5308"/>
        </reference>
        <reference anchor="RFC2453">
          <front>
            <title>RIP Version 2</title>
            <author fullname="G. Malkin" initials="G." surname="Malkin"/>
            <date month="November" year="1998"/>
            <abstract>
              <t>This document specifies an extension of the Routing Information Protocol (RIP) to expand the amount of useful information carried in RIP messages and to add a measure of security. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="56"/>
          <seriesInfo name="RFC" value="2453"/>
          <seriesInfo name="DOI" value="10.17487/RFC2453"/>
        </reference>
        <reference anchor="RFC2080">
          <front>
            <title>RIPng for IPv6</title>
            <author fullname="G. Malkin" initials="G." surname="Malkin"/>
            <author fullname="R. Minnear" initials="R." surname="Minnear"/>
            <date month="January" year="1997"/>
            <abstract>
              <t>This document specifies a routing protocol for an IPv6 internet. It is based on protocols and algorithms currently in wide use in the IPv4 Internet [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="2080"/>
          <seriesInfo name="DOI" value="10.17487/RFC2080"/>
        </reference>
        <reference anchor="RFC8177">
          <front>
            <title>YANG Data Model for Key Chains</title>
            <author fullname="A. Lindem" initials="A." role="editor" surname="Lindem"/>
            <author fullname="Y. Qu" initials="Y." surname="Qu"/>
            <author fullname="D. Yeung" initials="D." surname="Yeung"/>
            <author fullname="I. Chen" initials="I." surname="Chen"/>
            <author fullname="J. Zhang" initials="J." surname="Zhang"/>
            <date month="June" year="2017"/>
            <abstract>
              <t>This document describes the key chain YANG data model. Key chains are commonly used for routing protocol authentication and other applications requiring symmetric keys. A key chain is a list containing one or more elements containing a Key ID, key string, send/accept lifetimes, and the associated authentication or encryption algorithm. By properly overlapping the send and accept lifetimes of multiple key chain elements, key strings and algorithms may be gracefully updated. By representing them in a YANG data model, key distribution can be automated.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8177"/>
          <seriesInfo name="DOI" value="10.17487/RFC8177"/>
        </reference>
        <reference anchor="RFC5925">
          <front>
            <title>The TCP Authentication Option</title>
            <author fullname="J. Touch" initials="J." surname="Touch"/>
            <author fullname="A. Mankin" initials="A." surname="Mankin"/>
            <author fullname="R. Bonica" initials="R." surname="Bonica"/>
            <date month="June" year="2010"/>
            <abstract>
              <t>This document specifies the TCP Authentication Option (TCP-AO), which obsoletes the TCP MD5 Signature option of RFC 2385 (TCP MD5). TCP-AO specifies the use of stronger Message Authentication Codes (MACs), protects against replays even for long-lived TCP connections, and provides more details on the association of security with TCP connections than TCP MD5. TCP-AO is compatible with either a static Master Key Tuple (MKT) configuration or an external, out-of-band MKT management mechanism; in either case, TCP-AO also protects connections when using the same MKT across repeated instances of a connection, using traffic keys derived from the MKT, and coordinates MKT changes between endpoints. The result is intended to support current infrastructure uses of TCP MD5, such as to protect long-lived connections (as used, e.g., in BGP and LDP), and to support a larger set of MACs with minimal other system and operational changes. TCP-AO uses a different option identifier than TCP MD5, even though TCP-AO and TCP MD5 are never permitted to be used simultaneously. TCP-AO supports IPv6, and is fully compatible with the proposed requirements for the replacement of TCP MD5. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5925"/>
          <seriesInfo name="DOI" value="10.17487/RFC5925"/>
        </reference>
        <reference anchor="RFC9181">
          <front>
            <title>A Common YANG Data Model for Layer 2 and Layer 3 VPNs</title>
            <author fullname="S. Barguil" initials="S." surname="Barguil"/>
            <author fullname="O. Gonzalez de Dios" initials="O." role="editor" surname="Gonzalez de Dios"/>
            <author fullname="M. Boucadair" initials="M." role="editor" surname="Boucadair"/>
            <author fullname="Q. Wu" initials="Q." surname="Wu"/>
            <date month="February" year="2022"/>
            <abstract>
              <t>This document defines a common YANG module that is meant to be reused by various VPN-related modules such as Layer 3 VPN and Layer 2 VPN network models.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="9181"/>
          <seriesInfo name="DOI" value="10.17487/RFC9181"/>
        </reference>
        <reference anchor="RFC6991">
          <front>
            <title>Common YANG Data Types</title>
            <author fullname="J. Schoenwaelder" initials="J." role="editor" surname="Schoenwaelder"/>
            <date month="July" year="2013"/>
            <abstract>
              <t>This document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6991"/>
          <seriesInfo name="DOI" value="10.17487/RFC6991"/>
        </reference>
        <reference anchor="RFC6241">
          <front>
            <title>Network Configuration Protocol (NETCONF)</title>
            <author fullname="R. Enns" initials="R." role="editor" surname="Enns"/>
            <author fullname="M. Bjorklund" initials="M." role="editor" surname="Bjorklund"/>
            <author fullname="J. Schoenwaelder" initials="J." role="editor" surname="Schoenwaelder"/>
            <author fullname="A. Bierman" initials="A." role="editor" surname="Bierman"/>
            <date month="June" year="2011"/>
            <abstract>
              <t>The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6241"/>
          <seriesInfo name="DOI" value="10.17487/RFC6241"/>
        </reference>
        <reference anchor="RFC8040">
          <front>
            <title>RESTCONF Protocol</title>
            <author fullname="A. Bierman" initials="A." surname="Bierman"/>
            <author fullname="M. Bjorklund" initials="M." surname="Bjorklund"/>
            <author fullname="K. Watsen" initials="K." surname="Watsen"/>
            <date month="January" year="2017"/>
            <abstract>
              <t>This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF).</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8040"/>
          <seriesInfo name="DOI" value="10.17487/RFC8040"/>
        </reference>
        <reference anchor="RFC6242">
          <front>
            <title>Using the NETCONF Protocol over Secure Shell (SSH)</title>
            <author fullname="M. Wasserman" initials="M." surname="Wasserman"/>
            <date month="June" year="2011"/>
            <abstract>
              <t>This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6242"/>
          <seriesInfo name="DOI" value="10.17487/RFC6242"/>
        </reference>
        <reference anchor="RFC8446">
          <front>
            <title>The Transport Layer Security (TLS) Protocol Version 1.3</title>
            <author fullname="E. Rescorla" initials="E." surname="Rescorla"/>
            <date month="August" year="2018"/>
            <abstract>
              <t>This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.</t>
              <t>This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8446"/>
          <seriesInfo name="DOI" value="10.17487/RFC8446"/>
        </reference>
        <reference anchor="RFC8341">
          <front>
            <title>Network Configuration Access Control Model</title>
            <author fullname="A. Bierman" initials="A." surname="Bierman"/>
            <author fullname="M. Bjorklund" initials="M." surname="Bjorklund"/>
            <date month="March" year="2018"/>
            <abstract>
              <t>The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model.</t>
              <t>This document obsoletes RFC 6536.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="91"/>
          <seriesInfo name="RFC" value="8341"/>
          <seriesInfo name="DOI" value="10.17487/RFC8341"/>
        </reference>
        <reference anchor="RFC3688">
          <front>
            <title>The IETF XML Registry</title>
            <author fullname="M. Mealling" initials="M." surname="Mealling"/>
            <date month="January" year="2004"/>
            <abstract>
              <t>This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="81"/>
          <seriesInfo name="RFC" value="3688"/>
          <seriesInfo name="DOI" value="10.17487/RFC3688"/>
        </reference>
        <reference anchor="RFC6020">
          <front>
            <title>YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)</title>
            <author fullname="M. Bjorklund" initials="M." role="editor" surname="Bjorklund"/>
            <date month="October" year="2010"/>
            <abstract>
              <t>YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6020"/>
          <seriesInfo name="DOI" value="10.17487/RFC6020"/>
        </reference>
      </references>
      <references anchor="sec-informative-references">
        <name>Informative References</name>
        <reference anchor="AC-Common-Tree" target="https://github.com/boucadair/attachment-circuit-model/blob/main/yang/full-trees/ac-common-with-groupings.txt">
          <front>
            <title>Full Common Attachment Circuit Tree Structure</title>
            <author>
              <organization/>
            </author>
            <date year="2023"/>
          </front>
        </reference>
        <reference anchor="PYANG" target="https://github.com/mbj4668/pyang">
          <front>
            <title>pyang</title>
            <author>
              <organization/>
            </author>
            <date year="2023"/>
          </front>
        </reference>
        <reference anchor="RFC4364">
          <front>
            <title>BGP/MPLS IP Virtual Private Networks (VPNs)</title>
            <author fullname="E. Rosen" initials="E." surname="Rosen"/>
            <author fullname="Y. Rekhter" initials="Y." surname="Rekhter"/>
            <date month="February" year="2006"/>
            <abstract>
              <t>This document describes a method by which a Service Provider may use an IP backbone to provide IP Virtual Private Networks (VPNs) for its customers. This method uses a "peer model", in which the customers' edge routers (CE routers) send their routes to the Service Provider's edge routers (PE routers); there is no "overlay" visible to the customer's routing algorithm, and CE routers at different sites do not peer with each other. Data packets are tunneled through the backbone, so that the core routers do not need to know the VPN routes. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="4364"/>
          <seriesInfo name="DOI" value="10.17487/RFC4364"/>
        </reference>
        <reference anchor="RFC9408">
          <front>
            <title>A YANG Network Data Model for Service Attachment Points (SAPs)</title>
            <author fullname="M. Boucadair" initials="M." role="editor" surname="Boucadair"/>
            <author fullname="O. Gonzalez de Dios" initials="O." surname="Gonzalez de Dios"/>
            <author fullname="S. Barguil" initials="S." surname="Barguil"/>
            <author fullname="Q. Wu" initials="Q." surname="Wu"/>
            <author fullname="V. Lopez" initials="V." surname="Lopez"/>
            <date month="June" year="2023"/>
            <abstract>
              <t>This document defines a YANG data model for representing an abstract view of the provider network topology that contains the points from which its services can be attached (e.g., basic connectivity, VPN, network slices). Also, the model can be used to retrieve the points where the services are actually being delivered to customers (including peer networks).</t>
              <t>This document augments the 'ietf-network' data model defined in RFC 8345 by adding the concept of Service Attachment Points (SAPs). The SAPs are the network reference points to which network services, such as Layer 3 Virtual Private Network (L3VPN) or Layer 2 Virtual Private Network (L2VPN), can be attached. One or multiple services can be bound to the same SAP. Both User-to-Network Interface (UNI) and Network-to-Network Interface (NNI) are supported in the SAP data model.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="9408"/>
          <seriesInfo name="DOI" value="10.17487/RFC9408"/>
        </reference>
        <reference anchor="RFC7665">
          <front>
            <title>Service Function Chaining (SFC) Architecture</title>
            <author fullname="J. Halpern" initials="J." role="editor" surname="Halpern"/>
            <author fullname="C. Pignataro" initials="C." role="editor" surname="Pignataro"/>
            <date month="October" year="2015"/>
            <abstract>
              <t>This document describes an architecture for the specification, creation, and ongoing maintenance of Service Function Chains (SFCs) in a network. It includes architectural concepts, principles, and components used in the construction of composite services through deployment of SFCs, with a focus on those to be standardized in the IETF. This document does not propose solutions, protocols, or extensions to existing protocols.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7665"/>
          <seriesInfo name="DOI" value="10.17487/RFC7665"/>
        </reference>
        <reference anchor="I-D.ietf-opsawg-teas-attachment-circuit">
          <front>
            <title>YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service (ACaaS)</title>
            <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
              <organization>Orange</organization>
            </author>
            <author fullname="Richard Roberts" initials="R." surname="Roberts">
              <organization>Juniper</organization>
            </author>
            <author fullname="Oscar Gonzalez de Dios" initials="O. G." surname="de Dios">
              <organization>Telefonica</organization>
            </author>
            <author fullname="Samier Barguil" initials="S." surname="Barguil">
              <organization>Nokia</organization>
            </author>
            <author fullname="Bo Wu" initials="B." surname="Wu">
              <organization>Huawei Technologies</organization>
            </author>
            <date day="14" month="January" year="2024"/>
            <abstract>
              <t>   This document specifies a YANG service data model for Attachment
   Circuits (ACs).  This model can be used for the provisioning of ACs
   before or during service provisioning (e.g., Network Slice Service).
   The document also specifies a service model for managing bearers over
   which ACs are established.

   Also, the document specifies a set of reusable groupings.  Whether
   other service models reuse structures defined in the AC models or
   simply include an AC reference is a design choice of these service
   models.  Utilizing the AC service model to manage ACs over which a
   service is delivered has the advantage of decoupling service
   management from upgrading AC components to incorporate recent AC
   technologies or features.

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-teas-attachment-circuit-04"/>
        </reference>
        <reference anchor="I-D.ietf-teas-ietf-network-slice-nbi-yang">
          <front>
            <title>A YANG Data Model for the IETF Network Slice Service</title>
            <author fullname="Bo Wu" initials="B." surname="Wu">
              <organization>Huawei Technologies</organization>
            </author>
            <author fullname="Dhruv Dhody" initials="D." surname="Dhody">
              <organization>Huawei Technologies</organization>
            </author>
            <author fullname="Reza Rokui" initials="R." surname="Rokui">
              <organization>Ciena</organization>
            </author>
            <author fullname="Tarek Saad" initials="T." surname="Saad">
              <organization>Cisco Systems, Inc</organization>
            </author>
            <author fullname="John Mullooly" initials="J." surname="Mullooly">
              <organization>Cisco Systems, Inc</organization>
            </author>
            <date day="23" month="October" year="2023"/>
            <abstract>
              <t>   This document defines a YANG data model for the IETF Network Slice
   Service.  The model can be used in the IETF Network Slice Service
   interface between a customer and a provider that offers IETF Network
   Slice Services.

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-teas-ietf-network-slice-nbi-yang-08"/>
        </reference>
        <reference anchor="I-D.ietf-opsawg-ntw-attachment-circuit">
          <front>
            <title>A Network YANG Data Model for Attachment Circuits</title>
            <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
              <organization>Orange</organization>
            </author>
            <author fullname="Richard Roberts" initials="R." surname="Roberts">
              <organization>Juniper</organization>
            </author>
            <author fullname="Oscar Gonzalez de Dios" initials="O. G." surname="de Dios">
              <organization>Telefonica</organization>
            </author>
            <author fullname="Samier Barguil" initials="S." surname="Barguil">
              <organization>Nokia</organization>
            </author>
            <author fullname="Bo Wu" initials="B." surname="Wu">
              <organization>Huawei Technologies</organization>
            </author>
            <date day="14" month="December" year="2023"/>
            <abstract>
              <t>   This document specifies a network model for attachment circuits.  The
   model can be used for the provisioning of attachment circuits prior
   or during service provisioning (e.g., Network Slice Service).  A
   companion service model is specified in I-D.ietf-opsawg-teas-
   attachment-circuit.

   The module augments the Service Attachment Point (SAP) model with the
   detailed information for the provisioning of attachment circuits in
   Provider Edges (PEs).

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-ntw-attachment-circuit-04"/>
        </reference>
        <reference anchor="RFC8969">
          <front>
            <title>A Framework for Automating Service and Network Management with YANG</title>
            <author fullname="Q. Wu" initials="Q." role="editor" surname="Wu"/>
            <author fullname="M. Boucadair" initials="M." role="editor" surname="Boucadair"/>
            <author fullname="D. Lopez" initials="D." surname="Lopez"/>
            <author fullname="C. Xie" initials="C." surname="Xie"/>
            <author fullname="L. Geng" initials="L." surname="Geng"/>
            <date month="January" year="2021"/>
            <abstract>
              <t>Data models provide a programmatic approach to represent services and networks. Concretely, they can be used to derive configuration information for network and service components, and state information that will be monitored and tracked. Data models can be used during the service and network management life cycle (e.g., service instantiation, service provisioning, service optimization, service monitoring, service diagnosing, and service assurance). Data models are also instrumental in the automation of network management, and they can provide closed-loop control for adaptive and deterministic service creation, delivery, and maintenance.</t>
              <t>This document describes a framework for service and network management automation that takes advantage of YANG modeling technologies. This framework is drawn from a network operator perspective irrespective of the origin of a data model; thus, it can accommodate YANG modules that are developed outside the IETF.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8969"/>
          <seriesInfo name="DOI" value="10.17487/RFC8969"/>
        </reference>
        <reference anchor="RFC8340">
          <front>
            <title>YANG Tree Diagrams</title>
            <author fullname="M. Bjorklund" initials="M." surname="Bjorklund"/>
            <author fullname="L. Berger" initials="L." role="editor" surname="Berger"/>
            <date month="March" year="2018"/>
            <abstract>
              <t>This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="215"/>
          <seriesInfo name="RFC" value="8340"/>
          <seriesInfo name="DOI" value="10.17487/RFC8340"/>
        </reference>
        <reference anchor="RFC4862">
          <front>
            <title>IPv6 Stateless Address Autoconfiguration</title>
            <author fullname="S. Thomson" initials="S." surname="Thomson"/>
            <author fullname="T. Narten" initials="T." surname="Narten"/>
            <author fullname="T. Jinmei" initials="T." surname="Jinmei"/>
            <date month="September" year="2007"/>
            <abstract>
              <t>This document specifies the steps a host takes in deciding how to autoconfigure its interfaces in IP version 6. The autoconfiguration process includes generating a link-local address, generating global addresses via stateless address autoconfiguration, and the Duplicate Address Detection procedure to verify the uniqueness of the addresses on a link. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="4862"/>
          <seriesInfo name="DOI" value="10.17487/RFC4862"/>
        </reference>
        <reference anchor="RFC9182">
          <front>
            <title>A YANG Network Data Model for Layer 3 VPNs</title>
            <author fullname="S. Barguil" initials="S." surname="Barguil"/>
            <author fullname="O. Gonzalez de Dios" initials="O." role="editor" surname="Gonzalez de Dios"/>
            <author fullname="M. Boucadair" initials="M." role="editor" surname="Boucadair"/>
            <author fullname="L. Munoz" initials="L." surname="Munoz"/>
            <author fullname="A. Aguado" initials="A." surname="Aguado"/>
            <date month="February" year="2022"/>
            <abstract>
              <t>As a complement to the Layer 3 Virtual Private Network Service Model (L3SM), which is used for communication between customers and service providers, this document defines an L3VPN Network Model (L3NM) that can be used for the provisioning of Layer 3 Virtual Private Network (L3VPN) services within a service provider network. The model provides a network-centric view of L3VPN services.</t>
              <t>The L3NM is meant to be used by a network controller to derive the configuration information that will be sent to relevant network devices. The model can also facilitate communication between a service orchestrator and a network controller/orchestrator.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="9182"/>
          <seriesInfo name="DOI" value="10.17487/RFC9182"/>
        </reference>
        <reference anchor="RFC8695">
          <front>
            <title>A YANG Data Model for the Routing Information Protocol (RIP)</title>
            <author fullname="X. Liu" initials="X." surname="Liu"/>
            <author fullname="P. Sarda" initials="P." surname="Sarda"/>
            <author fullname="V. Choudhary" initials="V." surname="Choudhary"/>
            <date month="February" year="2020"/>
            <abstract>
              <t>This document describes a data model for the management of the Routing Information Protocol (RIP). Both RIP version 2 and RIPng are covered. The data model includes definitions for configuration, operational state, and Remote Procedure Calls (RPCs).</t>
              <t>The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA).</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8695"/>
          <seriesInfo name="DOI" value="10.17487/RFC8695"/>
        </reference>
      </references>
    </references>
    <?line 2089?>

<section numbered="false" anchor="acknowledgments">
      <name>Acknowledgments</name>
      <t>The document reuses many of the structures that were defined
in <xref target="RFC9181"/> and <xref target="RFC9182"/>.</t>
      <t>Thanks to Ebben Aries for the YANG Doctors review.</t>
    </section>
    <section anchor="contributors" numbered="false" toc="include" removeInRFC="false">
      <name>Contributors</name>
      <contact initials="V." surname="Lopez" fullname="Victor Lopez">
        <organization>Nokia</organization>
        <address>
          <email>victor.lopez@nokia.com</email>
        </address>
      </contact>
      <contact initials="I." surname="Bykov" fullname="Ivan Bykov">
        <organization>Ribbon Communications</organization>
        <address>
          <email>Ivan.Bykov@rbbn.com</email>
        </address>
      </contact>
      <contact initials="Q." surname="Wu" fullname="Qin Wu">
        <organization>Huawei</organization>
        <address>
          <email>bill.wu@huawei.com</email>
        </address>
      </contact>
      <contact initials="K." surname="Ogaki" fullname="Kenichi Ogaki">
        <organization>KDDI</organization>
        <address>
          <email>ke-oogaki@kddi.com</email>
        </address>
      </contact>
      <contact initials="L. A." surname="Munoz" fullname="Luis Angel Munoz">
        <organization>Vodafone</organization>
        <address>
          <email>luis-angel.munoz@vodafone.com</email>
        </address>
      </contact>
    </section>
  </back>
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</rfc>
