<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<rfc category="std" docName="draft-ietf-idr-bgp-model-06" ipr="trust200902">
  <?rfc toc="yes"?>

  <front>
    <title abbrev="BGP YANG Model">BGP YANG Model for Service Provider
    Networks</title>

    <author fullname="Mahesh Jethanandani" initials="M.J."
            surname="Jethanandani">
      <organization>VMware</organization>

      <address>
        <postal>
          <street/>

          <city/>

          <region/>

          <code/>

          <country/>
        </postal>

        <phone/>

        <facsimile/>

        <email>mjethanandani@gmail.com</email>

        <uri/>
      </address>
    </author>

    <author fullname="Keyur Patel" initials="K.P." surname="Patel">
      <organization>Arrcus</organization>

      <address>
        <postal>
          <street/>

          <city/>

          <region>CA</region>

          <country>USA</country>
        </postal>

        <email>keyur@arrcus.com</email>
      </address>
    </author>

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

      <address>
        <postal>
          <street>7453 Hickory Hill</street>

          <city>Saline</city>

          <region>MI</region>

          <code>48176</code>

          <country>USA</country>
        </postal>

        <email>shares@ndzh.com</email>
      </address>
    </author>

    <date day="13" month="June" year="2019"/>

    <area>Routing</area>

    <workgroup>Interdomain Routing</workgroup>

    <keyword>bgp</keyword>

    <keyword>yang</keyword>

    <abstract>
      <t>This document defines a YANG data model for configuring and managing
      BGP, including protocol, policy, and operational aspects, such as RIB,
      based on data center, carrier and content provider operational
      requirements.</t>
    </abstract>
  </front>

  <middle>
    <section anchor="intro" title="Introduction">
      <t>This document describes a <xref target="RFC7950">YANG</xref> data
      model for the <xref target="RFC4271">BGP-4</xref> protocol, including
      various protocol extensions, policy configuration, as well as defining
      key operational state data, including Routing Information Base (RIB).
      The model is intended to be vendor-neutral, in order to allow operators
      to manage BGP configuration in heterogeneous environments with routers
      supplied by multiple vendors. The model is also intended to be readily
      mapped to existing implementations to facilitate support from as large a
      set of routing hardware and software vendors as possible. This module
      does not support previous versions of BGP, and cannot support
      establishing and maintaining state information of neighbors with
      previous versions of BGP.</t>

      <section anchor="goals" title="Goals and approach">
        <t>The model covers the base BGP features that are deployed across
        major implementations and the common BGP configurations in use across
        a number of operator network deployments. In particular, this model
        attempts to cover BGP features defined in <xref
        target="RFC4271">BGP</xref>, <xref target="RFC1997">BGP Communities
        Attribute </xref>, <xref target="RFC4456">BGP Route Reflection</xref>,
        <xref target="RFC4760">Multiprotocol Extensions for BGP-4 </xref>,
        <xref target="RFC5065">Autonomous System Confederations for BGP
        </xref>, <xref target="RFC2439">BGP Route Flap Damping </xref>, <xref
        target="RFC4724">Graceful Restart Mechanism for BGP </xref>, and <xref
        target="RFC6811">BGP Prefix Origin Validation </xref>.</t>

        <t>Along with configuration of base BGP features, this model also
        addresses policy configuration, by providing "hooks" for applying
        policies, and also defining BGP-specific policy features. The BGP
        policy features are intended to be used with the general routing
        policy model defined in <xref target="I-D.ietf-rtgwg-policy-model">A
        YANG Data Model for Routing Policy Management </xref>. The model
        conforms to the <xref target="RFC8342">NMDA</xref> architecture and
        has support for configuring <xref target="RFC5880">Bidirectional
        Forward Detection (BFD) </xref> for fast next hop liveliness
        check.</t>

        <t>For the base BGP features, the focus of the model described in this
        document is on providing configuration and operational state
        information relating to: <list style="symbols">
            <t>The global BGP instance, and neighbors whose configuration is
            specified individually, or templated with the use of
            peer-groups.</t>

            <t>The address families that are supported by peers, and the
            global configuration which relates to them.</t>

            <t>The policy configuration "hooks" and BGP-specific policy
            features that relate to a neighbor - controlling the import and
            export of NLRIs.</t>

            <t>RIB contents.</t>
          </list></t>

        <t>As mentioned earlier, any configuration items that are deemed to be
        widely available in existing major BGP implementations are included in
        the model. Additional, more esoteric, configuration items that are not
        commonly used, or only available from a single implementation, are
        omitted from the model with an expectation that they will be available
        in companion modules that augment or extend the current model. This
        allows clarity in identifying data that is part of the vendor-neutral
        base model.</t>

        <t>Where possible, naming in the model follows conventions used in
        available standards documents, and otherwise tries to be
        self-explanatory with sufficient descriptions of the intended
        behavior. Similarly, configuration data value constraints and default
        values, where used, are based on recommendations in current standards
        documentation, or those commonly used in multiple implementations.
        Since implementations can vary widely in this respect, this version of
        the model specifies only a limited set of defaults and ranges with the
        expectation of being more prescriptive in future versions based on
        actual operator use.</t>
      </section>

      <section title="Note to RFC Editor">
        <t>This document uses several placeholder values throughout the
        document. Please replace them as follows and remove this note before
        publication.</t>

        <t>RFC XXXX, where XXXX is the number assigned to this document at the
        time of publication.</t>

        <t>2019-06-13 with the actual date of the publication of this
        document.</t>

        <t>RFC ZZZZ, where ZZZZ is the number assigned to <xref
        target="I-D.ietf-rtgwg-policy-model">A YANG Data Model for Routing
        Policy Management</xref>.</t>

        <t>RFC AAAA, where AAAA is the number assigned to <xref
        target="RFC7854">BGP Monitoring Protocol </xref>.</t>

        <t>RFC BBBB, where BBBB is the number assigned to <xref
        target="I-D.ietf-bfd-yang">YANG Data Model for Bidirectional Forward
        Detection</xref>.</t>
      </section>

      <section title="Terminology">
        <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
        "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
        "OPTIONAL" in this document are to be interpreted as described in
        <xref target="RFC2119">BCP 14 </xref> <xref target="RFC8174"/> when,
        and only when, they appear in all capitals, as shown here.</t>
      </section>

      <section title="Abbreviations">
        <texttable>
          <ttcol>Abbreviation</ttcol>

          <ttcol/>

          <c>AFI</c>

          <c>Address Family Identifier</c>

          <c>BFD</c>

          <c>Bidirectional Forward Detection</c>

          <c>NLRI</c>

          <c>Network Layer Reachability Information</c>

          <c>NMDA</c>

          <c>Network Management Datastore Architecture</c>

          <c>RIB</c>

          <c>Routing Information Base</c>

          <c>SAFI</c>

          <c>Subsequent Address Family Identifier</c>
        </texttable>
      </section>
    </section>

    <section anchor="overview" title="Model overview">
      <t>The BGP model is defined across several YANG modules and submodules,
      but at a high level is organized into six elements:</t>

      <t><list style="symbols">
          <t>base protocol configuration -- configuration affecting BGP
          protocol-related operations, defined at various levels of
          hierarchy.</t>

          <t>multiprotocol configuration -- configuration affecting individual
          address-families within BGP <xref target="RFC4760">Multiprotocol
          Extensions for BGP-4 </xref>.</t>

          <t>neighbor configuration -- configuration affecting an individual
          neighbor within BGP.</t>

          <t>neighbor multiprotocol configuration -- configuration affecting
          individual address-families for a neighbor within BGP.</t>

          <t>policy configuration -- hooks for application of the policies
          defined in <xref target="I-D.ietf-rtgwg-policy-model">A YANG Data
          Model for Routing Policy Management </xref> that act on routes sent
          (received) to (from) peers or other routing protocols and
          BGP-specific policy features.</t>

          <t>operational state -- variables used for monitoring and management
          of BGP operations.</t>
        </list></t>

      <t>These modules also make use of standard Internet types, such as IP
      addresses and prefixes, autonomous system numbers, etc., defined in
      <xref target="RFC6991">Common YANG Data Types </xref>.</t>

      <section anchor="overview.protocol" title="BGP protocol configuration">
        <t>The BGP protocol configuration model is organized hierarchically,
        much like the majority of router implementations. That is,
        configuration items can be specified at multiple levels, as shown
        below.</t>

        <figure>
          <artwork><![CDATA[
module: ietf-bgp

  augment /rt:routing/rt:control-plane-protocols/rt:control-plane-proto
col:
    +--rw bgp
       +--rw global!
       |  +--rw as                         inet:as-number
       |  +--rw identifier?                yang:dotted-quad
       |  +--rw default-route-distance
       |  +--rw confederation
       |  +--rw graceful-restart
       |  +--rw use-multiple-paths
       |  +--rw route-selection-options
       |  +--rw afi-safis
       |  +--rw apply-policy
       |  +--ro total-paths?               uint32
       |  +--ro total-prefixes?            uint32
       +--rw neighbors
       |  +--rw neighbor* [remote-address]
       |  +---n established            
       |  +---n backward-transition    
       |  +--rw clear-neighbors {clear-neighbors}?
       +--rw peer-groups
       |  +--rw peer-group* [peer-group-name]
       +--rw interfaces
       |  +--rw interface* [name]
       +--ro rib
          +--ro attr-sets
          +--ro communities
          +--ro ext-communities
          +--ro afi-safis

]]></artwork>
        </figure>

        <t>Users may specify configuration at a higher level and have it apply
        to all lower-level items, or provide overriding configuration at a
        lower level of the hierarchy. Overriding configuration items are
        optional, with neighbor specific configuration being the most specific
        or lowest level, followed by peer-group, and finally global. Global
        configuration options reflect a subset of the peer-group or neighbor
        specific configuration options which are relevant to the entire BGP
        instance.</t>

        <t>The model makes the simplifying assumption that most of the
        configuration items are available at all levels of the hierarchy. That
        is, very little configuration is specific to a particular level in the
        hierarchy, other than obvious items such as "group-name" only being
        available for the peer group-level config. A notable exception is for
        sub-address family configuration where some items are only applicable
        for a given AFI-SAFI combination.</t>

        <t>In order to allow common configuration to be applied to a set of
        neighbors, all neighbor configuration options are available within a
        peer-group. A neighbor is associated to a particular peer-group
        through the use of a peer-group leaf (which provides a reference to a
        configured item in the peer-group list).</t>

        <t>Address-family configuration is made available in multiple points
        within the model - primarily within the global container, where
        instance-wide configuration can be set (for example, global protocol
        parameters, the BGP best path route selection options, or global
        policies relating to the address-family); and on a per-neighbor or
        per-peer-group basis, where address-families can be enabled or
        disabled, and policy associated with the parent entity applied. Within
        the afi-safi container, generic configuration that applies to all
        address-families (e.g., whether the AFI-SAFI is enabled) is presented
        at the top-level, with address-family specific containers made
        available for options relating to only that AFI-SAFI. Within the
        current revision of the model a generic set of address-families, and
        common configuration and state options are included - further work is
        expected to add additional parameters to this area of the model.</t>

        <t>The following address-families are currently supported by the
        model:</t>

        <figure>
          <artwork><![CDATA[
        +--rw bgp
          +--rw global!
             +--rw afi-safis
                +--rw afi-safi* [afi-safi-name]
                   +--rw afi-safi-name              identityref
                   |
                   +--rw ipv4-unicast
                   |     ...
                   +--rw ipv6-unicast
                   |     ...
                   +--rw ipv4-labeled-unicast
                   |     ...
                   +--rw ipv6-labeled-unicast
                   |     ...
                   +--rw l3vpn-ipv4-unicast
                   |     ...
                   +--rw l3vpn-ipv6-unicast
                   |     ...
                   +--rw l3vpn-ipv4-multicast
                   |     ...
                   +--rw l3vpn-ipv6-multicast
                   |     ...
                   +--rw l2vpn-vpls
                   |     ...
                   +--rw l2vpn-evpn
                   |     ...
      ]]></artwork>
        </figure>
      </section>

      <section anchor="overview.policy" title="Policy configuration overview">
        <t>The BGP policy configuration model augments the generic YANG
        routing policy model described in <xref
        target="I-D.ietf-rtgwg-policy-model">A YANG Data Model for Routing
        Policy Management </xref>, which represents a condition-action policy
        framework for routing. This model adds BGP-specific conditions (e.g.,
        matching on the community attribute), and actions (e.g., setting local
        preference) to the generic policy framework.</t>

        <t>Policies that are defined in the routing-policy model are
        referenced in multiple places within the model: <list style="symbols">
            <t>within the global instance, where a policy applies to all
            address-families for all peers.</t>

            <t>on a global AFI-SAFI basis, where policies apply to all peers
            for a particular address-family.</t>

            <t>on a per-peer-group or per-neighbor basis - where the policy
            applies to all address-families for the particular group or
            neighbor.</t>

            <t>on a per-afi-safi basis within a neighbor or peer-group
            context, where the policy is specific to the AFI-SAFI for a a
            specific neighbor or group.</t>
          </list></t>

        <figure>
          <artwork><![CDATA[

module: ietf-bgp-policy
  augment /rpol:routing-policy/rpol:defined-sets:
    +--rw bgp-defined-sets
          ...
  augment /rpol:routing-policy/rpol:policy-definitions
            /rpol:policy-definition/rpol:statements/rpol:statement
            /rpol:conditions:
    +--rw bgp-conditions
          ...
  augment /rpol:routing-policy/rpol:policy-definitions
            /rpol:policy-definition/rpol:statements/rpol:statement
            /rpol:actions:
    +--rw bgp-actions
          ...
            ]]></artwork>
        </figure>
      </section>

      <section title="BGP RIB overview">
        <t>The RIB data model represents the BGP RIB contents. The model
        supports five logical RIBs per address family.</t>

        <t>A abridged version of the tree shows the RIB portion of the tree
        diagram.</t>

        <t><figure>
            <artwork><![CDATA[

module: ietf-bgp
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol:
    +--rw bgp
       +--ro rib
          +--ro afi-safis
             +--ro afi-safi* [afi-safi-name]
                +--ro afi-safi-name    identityref
                +--ro ipv4-unicast
                |  +--ro loc-rib
                |  |  +--ro routes
                |  |     +--ro route* [prefix origin path-id]
                |  |     |     ...
                |  |     +--ro clear-routes {clear-routes}?
                |  |           ...
                |  +--ro neighbors
                |     +--ro neighbor* [neighbor-address]
                |        +--ro neighbor-address    inet:ip-address
                |        +--ro adj-rib-in-pre
                |        |     ...
                |        +--ro adj-rib-in-post
                |        |     ...
                |        +--ro adj-rib-out-pre
                |        |     ...
                |        +--ro adj-rib-out-post
                |              ...
                +--ro ipv6-unicast
                   +--ro loc-rib
                   |  +--ro routes
                   |     +--ro route* [prefix origin path-id]
                   |     |     ...
                   |     +--ro clear-routes {clear-routes}?
                   |           ...
                   +--ro neighbors
                      +--ro neighbor* [neighbor-address]
                         +--ro neighbor-address    inet:ip-address
                         +--ro adj-rib-in-pre
                         |     ...
                         +--ro adj-rib-in-post
                         |     ...
                         +--ro adj-rib-out-pre
                         |     ...
                         +--ro adj-rib-out-post
                               ...

]]></artwork>
          </figure></t>

        <section title="Local Routing">
          <t>The loc-rib is the main BGP routing table for the local routing
          instance, containing best-path selections for each prefix. The
          loc-rib table may contain multiple routes for a given prefix, with
          an attribute to indicate which was selected as the best path. Note
          that multiple paths may be used or advertised even if only one path
          is marked as best, e.g., when using BGP add-paths. An implementation
          may choose to mark multiple paths in the RIB as best path by setting
          the flag to true for multiple entries.</t>
        </section>

        <section title="Pre updates per-neighbor">
          <t>The adj-rib-in-pre table is a per-neighbor table containing the
          NLRI updates received from the neighbor before any local input
          policy rules or filters have been applied. This can be considered
          the 'raw' updates from a given neighbor.</t>
        </section>

        <section title="Post updates per-neighbor">
          <t>The adj-rib-in-post table is a per-neighbor table containing the
          routes received from the neighbor that are eligible for best-path
          selection after local input policy rules have been applied.</t>
        </section>

        <section title="Pre route advertisements per-neighbor">
          <t>The adj-rib-out-pre table is a per-neighbor table containing
          routes eligible for sending (advertising) to the neighbor before
          output policy rules have been applied.</t>
        </section>

        <section title="Post route advertisements per-neighbor">
          <t>The adj-rib-out-post table is a per-neighbor table containing
          routes eligible for sending (advertising) to the neighbor after
          output policy rules have been applied</t>
        </section>
      </section>
    </section>

    <section title="Relation to other YANG data models">
      <t>The BGP model augments the Routing Management model <xref
      target="RFC8349">A YANG Data Model for Routing Management </xref> which
      defines the notion of routing, routing protocols, routing instances, or
      VRFs, and RIBs.</t>
    </section>

    <section title="Security Considerations">
      <t>The YANG module specified in this document defines a schema for data
      that is designed to be accessed via network management protocols such as
      <xref target="RFC6241">NETCONF</xref> or <xref
      target="RFC8040">RESTCONF</xref>. The lowest NETCONF layer is the secure
      transport layer, and the mandatory-to-implement secure transport is
      <xref target="RFC6242">Secure Shell (SSH)</xref>. The lowest RESTCONF
      layer is HTTPS, and the mandatory-to-implement secure transport is <xref
      target="RFC8446">TLS</xref>. The <xref target="RFC8341">NETCONF Access
      Control Model (NACM) </xref> 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>There are a number of data nodes defined in this YANG module that are
      writable/creatable/deletable (i.e., config true, which is the default).
      These data nodes may be considered sensitive or vulnerable in some
      network environments. Write operations (e.g., edit-config) to these data
      nodes without proper protection can have a negative effect on network
      operations. These are the subtrees and data nodes and their
      sensitivity/vulnerability:</t>

      <t>Some of the readable data nodes in this YANG module may be considered
      sensitive or vulnerable in some network environments. It is thus
      important to control read access (e.g., via get, get-config, or
      notification) to these data nodes. These are the subtrees and data nodes
      and their sensitivity/vulnerability:</t>

      <t>Some of the RPC operations in this YANG module may be considered
      sensitive or vulnerable in some network environments. It is thus
      important to control access to these operations. These are the
      operations and their sensitivity/vulnerability:</t>
    </section>

    <section title="IANA Considerations">
      <t>This document registers three URIs and three YANG modules.</t>

      <section title="URI Registration">
        <t>in the <xref target="RFC3688">IETF XML registry</xref> [RFC3688].
        Following the format in RFC 3688, the following registration is
        requested to be made: <figure>
            <artwork><![CDATA[URI: urn:ietf:params:xml:ns:yang:ietf-bgp
URI: urn:ietf:params:xml:ns:yang:ietf-bgp-policy
URI: urn:ietf:params:xml:ns:yang:ietf-bgp-types
]]></artwork>
          </figure></t>

        <t>Registrant Contact: The IESG. XML: N/A, the requested URI is an XML
        namespace.</t>
      </section>

      <section title="YANG Module Name Registration">
        <t>This document registers three YANG module in the YANG Module Names
        registry <xref target="RFC6020">YANG</xref>.</t>

        <t><figure>
            <artwork><![CDATA[name: ietf-bgp
namespace: urn:ietf:params:xml:ns:yang:ietf-bgp
prefix: bgp
reference: RFC XXXX

name: ietf-bgp-policy
namespace: urn:ietf:params:xml:ns:yang:ietf-bgp-policy
prefix: bp
reference: RFC XXXX

name: ietf-bgp-types
namespace: urn:ietf:params:xml:ns:yang:ietf-bgp-types
prefix: bt
reference: RFC XXXX
]]></artwork>
          </figure></t>
      </section>
    </section>

    <section anchor="models" title="YANG modules">
      <t>The modules comprising the BGP configuration and operational model
      are described by the YANG modules and submodules in the sections
      below.</t>

      <t>The main module, ietf-bgp.yang, includes the following submodules:
      <list style="symbols">
          <t>ietf-bgp-common - defines the groupings that are common across
          more than one context (where contexts are neighbor, group,
          global)</t>

          <t>ietf-bgp-common-multiprotocol - defines the groupings that are
          common across more than one context, and relate to multiprotocol
          BGP</t>

          <t>ietf-bgp-common-structure - defines groupings that are shared by
          multiple contexts, but are used only to create structural elements,
          i.e., containers (leaf nodes are defined in separate groupings)</t>

          <t>ietf-bgp-global - groupings with data specific to the global
          context</t>

          <t>ietf-bgp-peer-group - groupings with data specific to the peer
          group context</t>

          <t>ietf-bgp-neighbor - groupings with data specific to the neighbor
          context</t>

          <t>ietf-bgp-rib - grouping for representing BGP RIB.</t>
        </list></t>

      <t>Additionally, modules include: <list style="symbols">
          <t>ietf-bgp-types - common type and identity definitions for BGP,
          including BGP policy</t>

          <t>ietf-bgp-policy - BGP-specific policy data definitions for use
          with <xref target="I-D.ietf-rtgwg-policy-model"/> (described in more
          detail <xref target="overview.policy"/>)</t>
        </list></t>
    </section>

    <section title="Structure of the YANG modules">
      <t>The YANG model can be subdivided between the main module for base
      items, types, policy data, and the RIB module.</t>

      <section title="Main module and submodules for base items">
        <t><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp@2019-06-13.yang"
module ietf-bgp {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp";
  prefix bgp;

  /*
   * Import and Include
   */

  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349, A YANG Data Model for Routing Management
       (NMDA Version)";
  }
  import ietf-routing-policy {
    prefix rpol;
    reference
      "RFC ZZZZ, A YANG Data Model for Routing Policy Management";
  }
  import ietf-interfaces {
    prefix if;
    reference
      "RFC 8343, A YANG Data Model for Interface Management.";
  }
  import ietf-bgp-types {
    prefix bt;
    reference
      "RFC XXXX, BGP YANG Model for Service Provider Network.";
  }
  import ietf-bfd-types {
    prefix bfd;
    reference
      "RFC BBBB, YANG Data Model for Bidirectional Forward Detection.";
  }
  import ietf-inet-types { 
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types.";
  }
  import ietf-yang-types { 
    prefix yang; 
    reference
      "RFC 6991: Common YANG Data Types.";
  }


  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-common-structure;
  include ietf-bgp-neighbor;
  include ietf-bgp-peer-group;
  include ietf-bgp-rib-types;
  include ietf-bgp-rib;
  include ietf-bgp-rib-ext;
  include ietf-bgp-rib-attributes;
  include ietf-bgp-rib-table-attributes;
  include ietf-bgp-rib-tables;

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

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com";
  description
    "This module describes a YANG model for BGP protocol
     configuration. It is a limited subset of all of the configuration
     parameters available in the variety of vendor implementations,
     hence it is expected that it would be augmented with vendor-
     specific configuration data as needed. Additional modules or
     submodules to handle other aspects of BGP configuration,
     including policy, VRFs, VPNs, and additional address families
     are also expected.

     This model supports the following BGP configuration level
     hierarchy:

      BGP
        |
        +-> [ global BGP configuration ]
          +-> AFI / SAFI global
        +-> peer group
          +-> [ peer group config ]
          +-> AFI / SAFI [ per-AFI overrides ]
        +-> neighbor
          +-> [ neighbor config ]
          +-> [ optional pointer to peer-group ]
          +-> AFI / SAFI [ per-AFI overrides ]";

  revision 2019-06-13 {
    description
      "Initial Version";
    reference
      "RFC XXXX, BGP Model for Service Provider Network ";
  }

  /*
   * Identity
   */

  identity bgp {
    base rt:routing-protocol;
    description
      "BGP protocol.";
  }

  /*
   * Feature(s)
   */
  feature clear-routes {
    description
      "Clearing of BGP routes is supported.";
  }

  feature clear-neighbors {
    description
      "Clearing of BGP neighbors is supported.";
  }

  feature clear-statistics {
    description
      "Clearing of BGP statistics is supported.";
  }

  /*
   * Containers
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol" {
    when "derived-from-or-self(rt:type, 'bgp')" {
      description
        "This augmentation is valid for a routing protocol
         instance of BGP.";
    }
    description
      "BGP protocol augmentation of ietf-routing module
       control-plane-protocol.";

    container bgp {
      description
        "Top-level configuration for the BGP router";
      container global {
        presence "Enables global configuration of BGP";
        description
          "Global configuration for the BGP router";

        leaf as {
          type inet:as-number;
          mandatory true;
          description
            "Local autonomous system number of the router.  Uses
             the 32-bit as-number type from the model in RFC 6991.";
        }

        leaf identifier {
          type yang:dotted-quad;
          description
            "BGP Identifier of the router - an unsigned 32-bit,
             non-zero integer that should be unique within an AS.
             The value of the BGP Identifier for a BGP speaker is
             determined upon startup and is the same for every local
             interface and BGP peer.";
          reference
            "RFC 6286: AS-Wide Unique BGP ID for BGP-4. Section 2.1";
        }

        container default-route-distance {
          description
            "Administrative distance (or preference) assigned to
             routes received from different sources
             (external, internal, and local).";

          leaf external-route-distance {
            type uint8 {
              range "1..255";
            }
            description
              "Administrative distance for routes learned from
               external BGP (eBGP).";
          }
          leaf internal-route-distance {
            type uint8 {
              range "1..255";
            }
            description
              "Administrative distance for routes learned from
               internal BGP (iBGP).";
          }
        }

        container confederation {
          description
            "Configuration options specifying parameters when the
             local router is within an autonomous system which is
             part of a BGP confederation.";

          leaf enabled {
            type boolean;
            description
              "When this leaf is set to true it indicates that
               the local-AS is part of a BGP confederation";
          }

          leaf identifier {
            type inet:as-number;
            description
              "Confederation identifier for the autonomous system.";
          }

          leaf-list member-as {
            type inet:as-number;
            description
              "Remote autonomous systems that are to be treated
               as part of the local confederation.";
          }
        }

        container graceful-restart {
          description
            "Parameters relating the graceful restart mechanism for
             BGP";
          uses graceful-restart-config;
        }

        uses global-group-use-multiple-paths;
        uses route-selection-options;

        container afi-safis {
          description
	    "List of address-families associated with the BGP
             instance";
          list afi-safi {
            key "afi-safi-name";

            description
              "AFI,SAFI configuration available for the
               neighbour or group";

            uses mp-afi-safi-config;
            uses state;

            container graceful-restart {
              description
                "Parameters relating to BGP graceful-restart";

              uses mp-afi-safi-graceful-restart-config;
            }

            uses route-selection-options;
            uses global-group-use-multiple-paths;
            uses mp-all-afi-safi-list-contents;
          }
        }
        uses rpol:apply-policy-group;
        uses state;
      }

      container neighbors {
        description
          "Configuration for BGP neighbors";

        list neighbor {
          key "remote-address";
	  
          description
            "List of BGP neighbors configured on the local system,
             uniquely identified by remote IPv[46] address";

	  leaf local-address {
	    type inet:ip-address;
	    config false;
	    description 
	      "The local IP address of this entry's BGP connection.";
	  }

	  leaf local-port {
	    type inet:port-number {
	      range "0..65535";
	    }
	    config false;
	    description 
	      "The local port for the TCP connection between
               the BGP peers.";
	  }

          leaf peer-group {
            type leafref {
              path "../../../peer-groups/peer-group/peer-group-name";
            }
            description
              "The peer-group with which this neighbor is associated";
          }

          leaf identifier {
            type yang:dotted-quad;
            config false;
            description 
              "The BGP Identifier of this entry's BGP peer.
               This entry MUST be 0.0.0.0 unless the
               sessionstate is in the openconfirm or the
               established state.";
            reference   
              "RFC 4271, Section 4.2, 'BGP Identifier'.";
          }

          leaf remote-address {
            type inet:ip-address;
            description
	      "The remote IP address of this entry's BGP peer.";
          }

	  leaf remote-port {
	    type inet:port-number {
	      range "0..65535";
	    }
	    config false;
	    description 
	      "The remote port for the TCP connection
               between the BGP peers.  Note that the
               objects local-addr, local-port, remote-addr, and
               reemote-port provide the appropriate
               reference to the standard MIB TCP
               connection table.";
	  }

	  leaf remote-as {
	    type inet:as-number;
	    config false;
	    description 
	      "The remote autonomous system number received in
               the BGP OPEN message.";
	    reference   
	      "RFC 4271, Section 4.2.";
	  }

          leaf enabled {
            type boolean;
            default "true";
            description
              "Whether the BGP peer is enabled. In cases where the
               enabled leaf is set to false, the local system should
               not initiate connections to the neighbor, and should
               not respond to TCP connections attempts from the
               neighbor. If the state of the BGP session is
               ESTABLISHED at the time that this leaf is set to false,
               the BGP session should be ceased.

               A transition from 'false' to 'true' will cause
               the BGP Manual Start Event to be generated.
               A transition from 'true' to 'false' will cause
               the BGP Manual Stop Event to be generated.
               This parameter can be used to restart BGP peer
               connections. Care should be used in providing
               write access to this object without adequate
               authentication.";
            reference
              "RFC 4271, Section 8.1.2.";
          }

          uses neighbor-group-config;

          leaf session-state {
            type enumeration {
              enum idle {
                description
                  "Neighbor is down, and in the Idle state of the FSM";
              }
              enum connect {
                description
                  "Neighbor is down, and the session is waiting for the
                   underlying transport session to be established";
              }
              enum active {
                description
                  "Neighbor is down, and the local system is awaiting a
                   connection from the remote peer";
              }
              enum opensent {
                description
                  "Neighbor is in the process of being established.  The
                   local system has sent an OPEN message";
              }
              enum openconfirm {
                description
                  "Neighbor is in the process of being established.
                   The local system is awaiting a NOTIFICATION or
                   KEEPALIVE message";
              }
              enum established {
                description
                  "Neighbor is up - the BGP session with the peer is
                   established";
              }
            }
	    //  notification does not like a non-config statement.
	    //  config false;
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.1.2.";
          }

          leaf last-established {
            type uint64;
            config false;
            description
              "This timestamp indicates the time that the BGP session
               last transitioned in or out of the Established state.
               The value is the timestamp in seconds relative to the
               Unix Epoch (Jan 1, 1970 00:00:00 UTC).

               The BGP session uptime can be computed by clients as
               the difference between this value and the current time
               in UTC (assuming the session is in the ESTABLISHED
               state, per the session-state leaf).";
          }

          leaf-list supported-capabilities {
            type identityref {
              base bt:bgp-capability;
            }
            config false;
            description
              "BGP capabilities negotiated as supported with the peer";
          }

          leaf negotiated-hold-time {
            type decimal64 {
              fraction-digits 2;
            }
            config false;
            description
              "The negotiated hold-time for the BGP session";
          }
      
          leaf last-error {
            type binary {
              length "2";
            }
	    // notification does not like non-config statement.
	    // config false;
            description 
              "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
            reference   
              "RFC 4271, Section 4.5.";
          }

          leaf fsm-established-time {
            type yang:gauge32;
            units "seconds";
            config false;
            description 
              "This timer indicates how long (in
               seconds) this peer has been in the
               established state or how long
               since this peer was last in the
               established state.  It is set to zero when
               a new peer is configured or when the router is
               booted.";
            reference   
              "RFC 4271, Section 8.";
          }

          container timers {
            description
              "Timers related to a BGP neighbor";

            uses neighbor-group-timers-config;

          }

          container transport {
            description
              "Transport session parameters for the BGP neighbor";

            uses neighbor-group-transport-config;
          }

	  leaf erroneous-update-messages {
            type uint32;
            config false;
            description
              "The number of BGP UPDATE messages for which the
               treat-as-withdraw mechanism has been applied based on
               erroneous message contents";
          }

          container graceful-restart {
            description
              "Parameters relating the graceful restart mechanism for
               BGP";

            uses graceful-restart-config;

            leaf peer-restart-time {
              type uint16 {
                range "0..4096";
              }
              config false;
              description
                "The period of time (advertised by the peer) that the
                 peer expects a restart of a BGP session to take";
            }

            leaf peer-restarting {
              type boolean;
              config false;
              description
                "This flag indicates whether the remote neighbor is
                 currently in the process of restarting, and hence
                 received routes are currently stale";
            }

            leaf local-restarting {
              type boolean;
              config false;
              description
                "This flag indicates whether the local neighbor is
                 currently restarting. The flag is unset after all NLRI
                 have been advertised to the peer, and the End-of-RIB
                 (EOR) marker has been unset";
            }

            leaf mode {
              type enumeration {
                enum HELPER_ONLY {
                  description
                    "The local router is operating in helper-only
                     mode, and hence will not retain forwarding state
                     during a local session restart, but will do so
                     during a restart of the remote peer";
                }
                enum BILATERAL {
                  description
                    "The local router is operating in both helper
                     mode, and hence retains forwarding state during
                     a remote restart, and also maintains forwarding
                     state during local session restart";
                }
                enum REMOTE_HELPER {
                  description
                    "The local system is able to retain routes during
                     restart but the remote system is only able to
                     act as a helper";
                }
              }
              config false;
              description
                "This leaf indicates the mode of operation of BGP
                 graceful restart with the peer";
            }
          }

          uses structure-neighbor-group-ebgp-multihop;
          uses structure-neighbor-group-route-reflector;
          uses structure-neighbor-group-as-path-options;
          uses structure-neighbor-group-add-paths;
          uses bgp-neighbor-use-multiple-paths;
          uses rpol:apply-policy-group;

          container afi-safis {
            description
              "Per-address-family configuration parameters associated
               with the neighbor";
            uses bgp-neighbor-afi-safi-list;
          }

	  container statistics {

            leaf established-transitions {
              type yang:counter64;
              config false;
              description
                "Number of transitions to the Established state for the
               neighbor session.  This value is analogous to the
               bgpPeerFsmEstablishedTransitions object from the standard
               BGP-4 MIB";
              reference
                "RFC 4273 - Definitions of Managed Objects for BGP-4";
            }

            leaf fsm-established-transitions {
              type yang:counter32;
              config false;
              description
                "The total number of times the BGP FSM
               transitioned into the established state
               for this peer.";
              reference
                "RFC 4271, Section 8.";
            }

            container messages {
              config false;
              description
                "Counters for BGP messages sent and received from the
               neighbor";

              leaf in-total-messages {
                type yang:counter32;
                config false;
                description
                  "The total number of messages received
                 from the remote peer on this connection.";
                reference
                  "RFC 4271, Section 4.";
              }

              leaf out-total-messages {
                type yang:counter32;
                config false;
                description
                  "The total number of messages transmitted to
                 the remote peer on this connection.";
                reference
                  "RFC 4271, Section 4.";
              }

              leaf in-update-elapsed-time {
                type yang:gauge32;
                units "seconds";
                config false;
                description
                  "Elapsed time (in seconds) since the last BGP
                 UPDATE message was received from the peer.
                 Each time in-updates is incremented,
                 the value of this object is set to zero (0).";
                reference
                  "RFC 4271, Section 4.3.
                 RFC 4271, Section 8.2.2, Established state.";
              }

              container sent {
                description
                  "Counters relating to BGP messages sent to the
                 neighbor";
                uses bgp-neighbor-counters-message-types-state;
              }

              container received {
                description
                  "Counters for BGP messages received from the
                   neighbor";
                uses bgp-neighbor-counters-message-types-state;
              }
            }

            container queues {
              config false;
              description
                "Counters related to queued messages associated with
                 the BGP neighbor";

              leaf input {
                type uint32;
                description
                  "The number of messages received from the peer
                   currently queued";
              }

              leaf output {
                type uint32;
                description
                  "The number of messages queued to be sent to the
                   peer";
              }
            }

	    container clear-statistics {
	      if-feature "clear-statistics";

	      action clear {
		input {
		  leaf clear-at {
		    type yang:date-and-time;
		    description
		      "Time when the clear action needs to be
                       executed.";
		  }
		}

		output {
		  leaf clear-finished-at {
		    type yang:date-and-time;
		    description
		      "Time when the clear action command completed.";
		  }
		}
	      }
	      description
		"Clear statistics action command.";
	    }
	    description
	      "Statistics per neighbor.";
	  }
        }

	notification established {
          description
            "The established event is generated
             when the BGP FSM enters the established state.";

          leaf remote-address {
            type leafref {
              path "../../neighbor/remote-address";
            }
            description
              "IP address of the neighbor that went into established
               state.";
          }

          leaf last-error {
            type leafref {
	      path "../../neighbor/last-error";
            }
            description
              "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
            reference
              "RFC 4271, Section 4.5.";
          }

          leaf session-state {
	    type leafref {
	      path "../../neighbor/session-state";
            }
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.2.2.";
          }
        }

        notification backward-transition {
          description
            "The backward-transition event is
             generated when the BGP FSM moves from a higher
             numbered state to a lower numbered state.";

	  leaf remote-addr {
	    type leafref {
              path "../../neighbor/remote-address";
	    }
	    description
              "IP address of the neighbor that went away from
               established state.";
          }

	  leaf last-error {
            type leafref {
	      path "../../neighbor/last-error";
            }
	    description
	      "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
	    reference
	      "RFC 4271, Section 4.5.";
	  }

	  leaf session-state {
	    type leafref {
	      path "../../neighbor/session-state";
            }
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.2.2.";
	  }
        }

        container clear-neighbors {
          if-feature "clear-neighbors";

          action clear {
            input {
              leaf clear-at {
                type yang:date-and-time;
		description
		  "Time when the clear action command needs to be
                   executed.";
              }
            }

            output {
              leaf clear-finished-at {
                type yang:date-and-time;
		description
		  "Time when the clear action command completed.";
              }
            }
          }
	  description
	    "Clear neighbors action.";
        }
      }

      container peer-groups {
        description
          "Configuration for BGP peer-groups";
        uses bgp-peer-group-list;
      }

      container interfaces {
        list interface {
          key "name";

          leaf name {
            type if:interface-ref;
            description
              "Reference to the interface within the routing instance.";
          }

          container bfd {
            if-feature "bt:bfd";

            uses bfd:client-cfg-parms;
            description
              "BFD client configuration.";
            reference
              "RFC BBBB - YANG Data Model for Bidirectional Forwarding
               Detection.";
          }
          description
            "List of interfaces within the routing instance.";
        }
        description
          "Interface specific parameters.";
      }
      uses rib;
    }
  }
}
<CODE ENDS>


]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-common@2019-06-13.yang"
submodule ietf-bgp-common {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  import ietf-bgp-types { 
    prefix bt; 
  }
  import ietf-inet-types { 
    prefix inet; 
  }

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com";

  description
    "This sub-module contains common groupings that are common across
     multiple contexts within the BGP module. That is to say that
     they may be application to a subset of global, peer-group or
     neighbor contexts.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXXX, BGP Model for Service Provider Network.";
  }

  grouping neighbor-group-timers-config {
    description
      "Config parameters related to timers associated with the BGP
       peer";

    leaf connect-retry-interval {
      type uint32 {
	range "1..65535";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the
         ConnectRetryTimer.  The suggested value
         for this timer is 120 seconds.";
      reference
        "RFC 4271, Section 8.2.2.  This is the value used
         to initialize the 'ConnectRetryTimer'.";
    }

    leaf hold-time {
      type uint32 {
        range "0 | 3..65535";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the HoldTimer
         established with the peer.  The
         value of this object is calculated by this
         BGP speaker, using the smaller of the
         values in hold-time-configured and the
         Hold Time received in the OPEN message.

         This value must be at least three seconds
         if it is not zero (0).

         If the Hold Timer has not been established
         with the peer this object MUST have a value
         of zero (0).

         If the hold-time-configured object has
         a value of (0), then this object MUST have a
         value of (0).";
      reference
        "RFC 4271, Section 4.2.";
    }

    leaf keepalive-interval {
      type uint32 {
        range "0..21845";
      }
      units "seconds";
      default 30;
      description
        "Time interval (in seconds) for the KeepAlive
         timer established with the peer.  The value
         of this object is calculated by this BGP
         speaker such that, when compared with
         hold-time, it has the same proportion
         that keep-alive-configured has,
         compared with hold-time-configured.

         If the KeepAlive timer has not been established
         with the peer, this object MUST have a value
         of zero (0).

         If the of keep-alive-configured object
         has a value of (0), then this object MUST have
         a value of (0).";
      reference
        "RFC 4271, Section 4.4.";
    }

    leaf hold-time-configured {
      type uint32 {
        range "0 | 3..65535";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the Hold Time
         configured for this BGP speaker with this
         peer.  This value is placed in an OPEN
         message sent to this peer by this BGP
         speaker, and is compared with the Hold
         Time field in an OPEN message received
         from the peer when determining the Hold
         Time (hold-time) with the peer.
         This value must not be less than three
         seconds if it is not zero (0).  If it is
         zero (0), the Hold Time is NOT to be
         established with the peer.  The suggested
         value for this timer is 90 seconds.";
      reference
        "RFC 4271, Section 4.2.
         RFC 4271, Section 10.";
    }

    leaf keep-alive-configured {
      type uint32 {
        range "0..21845";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the
         KeepAlive timer configured for this BGP
         speaker with this peer.  The value of this
         object will only determine the
         KEEPALIVE messages' frequency relative to
         the value specified in
         hold-time-configured; the actual
         time interval for the KEEPALIVE messages is
         indicated by keep-alive.  A
         reasonable maximum value for this timer
         would be one third of that of
         hold-time-configured.
         If the value of this object is zero (0),
         no periodical KEEPALIVE messages are sent
         to the peer after the BGP connection has
         been established.  The suggested value for
         this timer is 30 seconds.";
      reference
        "RFC 4271, Section 4.4.
         RFC 4271, Section 10.";
    }

    leaf min-as-origination-interval {
      type uint32 {
        range "0..65535";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the
         MinASOriginationInterval timer.
         The suggested value for this timer is 15
         seconds.";
      reference
        "RFC 4271, Section 9.2.1.2.
         RFC 4271, Section 10.";
    }

    leaf min-route-advertisement-interval {
      type uint32 {
        range "0..65535";
      }
      units "seconds";
      description
        "Time interval (in seconds) for the
         MinRouteAdvertisementInterval timer.
         The suggested value for this timer is 30
         seconds for EBGP connections and 5
         seconds for IBGP connections.";
      reference
        "RFC 4271, Section 9.2.1.1.
         RFC 4271, Section 10.";
    }
  }

  grouping neighbor-group-config {
    description
      "Neighbor level configuration items.";

    leaf peer-as {
      type inet:as-number;
      description
        "AS number of the peer.";
    }

    leaf local-as {
      type inet:as-number;
      description
        "The local autonomous system number that is to be used when
         establishing sessions with the remote peer or peer group, if
         this differs from the global BGP router autonomous system
         number.";
    }

    leaf peer-type {
        type bt:peer-type;
        description
          "Explicitly designate the peer or peer group as internal
           (iBGP) or external (eBGP).";
    }

    leaf auth-password {
      type string;
      description
        "Configures an MD5 authentication password for use with
         neighboring devices.";
    }

    leaf remove-private-as {
      // could also make this a container with a flag to enable
      // remove-private and separate option.  here, option implies
      // remove-private is enabled.
      type bt:remove-private-as-option;
      description
        "Remove private AS numbers from updates sent to peers - when
         this leaf is not specified, the AS_PATH attribute should be
         sent to the peer unchanged";
    }

    leaf description {
      type string;
      description
        "An optional textual description (intended primarily for use
         with a peer or group";
    }
  }

  grouping neighbor-group-transport-config {
    description
      "Configuration parameters relating to the transport protocol
       used by the BGP session to the peer";

    leaf tcp-mss {
      type uint16;
      description
        "Sets the max segment size for BGP TCP sessions.";
    }

    leaf mtu-discovery {
      type boolean;
      default false;
      description
        "Turns path mtu discovery for BGP TCP sessions on (true) or
         off (false)";
    }

    leaf passive-mode {
      type boolean;
      default false;
      description
        "Wait for peers to issue requests to open a BGP session,
         rather than initiating sessions from the local router.";
    }

    leaf local-address {
      type union {
        type inet:ip-address;
        type leafref {
          path "../../../../interfaces/interface/name";
        }
      }
      description
        "Set the local IP (either IPv4 or IPv6) address to use for
         the session when sending BGP update messages.  This may be
         expressed as either an IP address or reference to the name
         of an interface.";
    }
  }

  grouping graceful-restart-config {
    description
      "Configuration parameters relating to BGP graceful restart.";

    leaf enabled {
      type boolean;
      description
        "Enable or disable the graceful-restart capability.";
    }

    leaf restart-time {
      type uint16 {
        range 0..4096;
      }
      description
        "Estimated time (in seconds) for the local BGP speaker to
         restart a session. This value is advertise in the graceful
         restart BGP capability.  This is a 12-bit value, referred to
         as Restart Time in RFC4724.  Per RFC4724, the suggested
         default value is <= the hold-time value.";
    }

    leaf stale-routes-time {
      type uint32;
      description
        "An upper-bound on the time that stale routes will be
         retained by a router after a session is restarted. If an
         End-of-RIB (EOR) marker is received prior to this timer
         expiring stale-routes will be flushed upon its receipt - if
         no EOR is received, then when this timer expires stale paths
         will be purged. This timer is referred to as the
         Selection_Deferral_Timer in RFC4724";
    }

    leaf helper-only {
      type boolean;
      default true;
      description
        "Enable graceful-restart in helper mode only. When this leaf
         is set, the local system does not retain forwarding its own
         state during a restart, but supports procedures for the
         receiving speaker, as defined in RFC4724.";
    }
  }

  grouping use-multiple-paths-config {
    description
      "Generic configuration options relating to use of multiple
       paths for a referenced AFI-SAFI, group or neighbor";

    leaf enabled {
      type boolean;
      default false;
      description
        "Whether the use of multiple paths for the same NLRI is
         enabled for the neighbor. This value is overridden by any
         more specific configuration value.";
    }
  }

  grouping use-multiple-paths-ebgp-as-options-config {
    description
      "Configuration parameters specific to eBGP multi-path applicable
       to all contexts";

    leaf allow-multiple-as {
     type boolean;
     default "false";
     description
      "Allow multi-path to use paths from different neighboring ASes.
       The default is to only consider multiple paths from the same
       neighboring AS.";
    }
  }

  grouping global-group-use-multiple-paths {
    description
      "Common grouping used for both global and groups which provides
       configuration and state parameters relating to use of multiple
       paths";

    container use-multiple-paths {
      description
        "Parameters related to the use of multiple paths for the
        same NLRI";

      uses use-multiple-paths-config;

      container ebgp {
        description
          "Multi-Path parameters for eBGP";

        leaf allow-multiple-as {
          type boolean;
          default "false";
          description
            "Allow multi-path to use paths from different neighboring
             ASes.  The default is to only consider multiple paths
             from the same neighboring AS.";
        }

        leaf maximum-paths {
          type uint32;
          default 1;
          description
            "Maximum number of parallel paths to consider when using
             BGP multi-path. The default is use a single path.";
        }
      }

      container ibgp {
        description
          "Multi-Path parameters for iBGP";

        leaf maximum-paths {
          type uint32;
          default 1;
          description
            "Maximum number of parallel paths to consider when using
             iBGP multi-path. The default is to use a single path";
        }
      }
    }
  }

  grouping route-selection-options {
    description
      "Configuration and state relating to route selection options";

    container route-selection-options {
      description
        "Parameters relating to options for route selection";

      leaf enable-aigp {
        type boolean;
        default false;
        description
          "Flag to enable sending / receiving accumulated IGP
           attribute in routing updates";
      }
    }
  }

  grouping state {
    description
      "Grouping containing common counters relating to prefixes and
       paths";

    leaf total-paths {
      type uint32;
      config false;
      description
        "Total number of BGP paths within the context";
    }

    leaf total-prefixes {
      type uint32;
      config false;
      description
        "Total number of BGP prefixes received within the context";
    }
  }
}
<CODE ENDS>
 
        ]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-common-multiprotocol@2019-06-13.yang"
submodule ietf-bgp-common-multiprotocol {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  import ietf-bgp-types { 
    prefix bt; 
  }
  import ietf-routing-policy { 
    prefix rpol; 
  }

  include ietf-bgp-common;

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This sub-module contains groupings that are related to support
     for multiple protocols in BGP. The groupings are common across
     multiple contexts.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping mp-afi-safi-graceful-restart-config {
    description
      "BGP graceful restart parameters that apply on a per-AFI-SAFI
       basis";

    leaf enabled {
      type boolean;
      default false;
      description
        "This leaf indicates whether graceful-restart is enabled for
         this AFI-SAFI";
    }
  }

  grouping mp-afi-safi-config {
    description
      "Configuration parameters used for all BGP AFI-SAFIs";

    leaf afi-safi-name {
      type identityref {
        base "bt:afi-safi-type";
      }
      description "AFI,SAFI";
    }

    leaf enabled {
      type boolean;
      default false;
      description
        "This leaf indicates whether the IPv4 Unicast AFI,SAFI is
        enabled for the neighbour or group";
    }
  }

  grouping mp-all-afi-safi-list-contents {
    description
      "A common grouping used for contents of the list that is used
       for AFI-SAFI entries";

    // import and export policy included for the afi/safi
    uses rpol:apply-policy-group;

    container ipv4-unicast {
      when "../afi-safi-name = 'bt:ipv4-unicast'" {
        description
          "Include this container for IPv4 Unicast specific
           configuration";
      }

      description
        "IPv4 unicast configuration options";

      // include common IPv[46] unicast options
      uses mp-ipv4-ipv6-unicast-common;

      // placeholder for IPv4 unicast  specific configuration
    }

    container ipv6-unicast {
      when "../afi-safi-name = 'bt:ipv6-unicast'" {
        description
          "Include this container for IPv6 Unicast specific
           configuration";
      }

      description
        "IPv6 unicast configuration options";

      // include common IPv[46] unicast options
      uses mp-ipv4-ipv6-unicast-common;

      // placeholder for IPv6 unicast specific configuration
      // options
    }

    container ipv4-labeled-unicast {
      when "../afi-safi-name = 'bt:ipv4-labeled-unicast'" {
        description
          "Include this container for IPv4 Labeled Unicast specific
           configuration";
      }

      description
        "IPv4 Labeled Unicast configuration options";

      uses mp-all-afi-safi-common;

      // placeholder for IPv4 Labeled Unicast specific config
      // options
    }

    container ipv6-labeled-unicast {
      when "../afi-safi-name = 'bt:ipv6-labeled-unicast'" {
        description
          "Include this container for IPv6 Labeled Unicast specific
           configuration";
      }

      description
        "IPv6 Labeled Unicast configuration options";

      uses mp-all-afi-safi-common;

      // placeholder for IPv6 Labeled Unicast specific config
      // options.
    }

    container l3vpn-ipv4-unicast {
      when "../afi-safi-name = 'bt:l3vpn-ipv4-unicast'" {
        description
          "Include this container for IPv4 Unicast L3VPN specific
           configuration";
      }

      description
        "Unicast IPv4 L3VPN configuration options";

      // include common L3VPN configuration options
      uses mp-l3vpn-ipv4-ipv6-unicast-common;

      // placeholder for IPv4 Unicast L3VPN specific config options.
    }

    container l3vpn-ipv6-unicast {
      when "../afi-safi-name = 'bt:l3vpn-ipv6-unicast'" {
        description
          "Include this container for unicast IPv6 L3VPN specific
           configuration";
      }

      description
        "Unicast IPv6 L3VPN configuration options";

      // include common L3VPN configuration options
      uses mp-l3vpn-ipv4-ipv6-unicast-common;

      // placeholder for IPv6 Unicast L3VPN specific configuration
      // options
    }

    container l3vpn-ipv4-multicast {
      when "../afi-safi-name = 'bt:l3vpn-ipv4-multicast'" {
        description
          "Include this container for multicast IPv6 L3VPN specific
           configuration";
      }

      description
        "Multicast IPv4 L3VPN configuration options";

      // include common L3VPN multicast options
      uses mp-l3vpn-ipv4-ipv6-multicast-common;

      // placeholder for IPv4 Multicast L3VPN specific configuration
      // options
    }

    container l3vpn-ipv6-multicast {
      when "../afi-safi-name = 'bt:l3vpn-ipv6-multicast'" {
        description
          "Include this container for multicast IPv6 L3VPN specific
           configuration";
      }
      description
        "Multicast IPv6 L3VPN configuration options";

      // include common L3VPN multicast options
      uses mp-l3vpn-ipv4-ipv6-multicast-common;

      // placeholder for IPv6 Multicast L3VPN specific configuration
      // options
    }

    container l2vpn-vpls {
      when "../afi-safi-name = 'bt:l2vpn-vpls'" {
        description
          "Include this container for BGP-signalled VPLS specific
           configuration";
      }

      description
        "BGP-signalled VPLS configuration options";

      // include common L2VPN options
      uses mp-l2vpn-common;

      // placeholder for BGP-signalled VPLS specific configuration
      // options
    }

    container l2vpn-evpn {
      when "../afi-safi-name = 'bt:l2vpn-evpn'" {
        description
          "Include this container for BGP EVPN specific
           configuration";
      }

      description
        "BGP EVPN configuration options";

      // include common L2VPN options
      uses mp-l2vpn-common;

      // placeholder for BGP EVPN specific configuration options
    }
  }

  // Common groupings across multiple AFI,SAFIs
  grouping mp-all-afi-safi-common {
    description
      "Grouping for configuration common to all AFI,SAFI";

    container prefix-limit {
      description
        "Parameters relating to the prefix limit for the AFI-SAFI";
      leaf max-prefixes {
        type uint32;
        description
          "Maximum number of prefixes that will be accepted from the
           neighbour";
      }
      leaf shutdown-threshold-pct {
        type bt:percentage;
        description
          "Threshold on number of prefixes that can be received from
           a neighbour before generation of warning messages or log
           entries. Expressed as a percentage of max-prefixes";
      }
        
      leaf restart-timer {
        type decimal64 {
          fraction-digits 2;
        }
        units "seconds";
        description
          "Time interval in seconds after which the BGP session is
           re-established after being torn down due to exceeding the
           max-prefix limit.";
      }
    }
  }

  grouping mp-ipv4-ipv6-unicast-common {
    description
      "Common configuration that is applicable for IPv4 and IPv6
      unicast";

    // include common afi-safi options.
    uses mp-all-afi-safi-common;

    // configuration options that are specific to IPv[46] unicast
    leaf send-default-route {
      type boolean;
      default "false";
      description
        "If set to true, send the default-route to the neighbour(s)";
    }
  }

  grouping mp-l3vpn-ipv4-ipv6-unicast-common {
    description
      "Common configuration applied across L3VPN for IPv4
       and IPv6";

    // placeholder -- specific configuration options that are generic
    // across IPv[46] unicast address families.
    uses mp-all-afi-safi-common;
  }

  grouping mp-l3vpn-ipv4-ipv6-multicast-common {
    description
      "Common configuration applied across L3VPN for IPv4
      and IPv6";

    // placeholder -- specific configuration options that are
    // generic across IPv[46] multicast address families.
    uses mp-all-afi-safi-common;
  }

  grouping mp-l2vpn-common {
    description
      "Common configuration applied across L2VPN address
      families";

    // placeholder -- specific configuration options that are
    // generic across L2VPN address families
    uses mp-all-afi-safi-common;
  }

  // Config groupings for common groups
  grouping mp-all-afi-safi-common-prefix-limit-config {
    description
      "Configuration parameters relating to prefix-limits for an
      AFI-SAFI";

  }
}
<CODE ENDS>
 
        ]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-common-structure@2019-06-13.yang"
submodule ietf-bgp-common-structure {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  import ietf-bgp-types { prefix bt; }
  import ietf-routing-policy { prefix rpol; }
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-common;

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This sub-module contains groupings that are common across
     multiple BGP contexts and provide structure around other
     primitive groupings.";


  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping structure-neighbor-group-ebgp-multihop {
    description
      "Structural grouping used to include eBGP multi-hop
       configuration and state for both BGP neighbors and peer
       groups";

    container ebgp-multihop {
      description
        "eBGP multi-hop parameters for the BGPgroup";

      leaf enabled {
        type boolean;
        default "false";
        description
          "When enabled the referenced group or neighbors are
           permitted to be indirectly connected - including cases
           where the TTL can be decremented between the BGP peers";
      }

      leaf multihop-ttl {
        type uint8;
        description
          "Time-to-live value to use when packets are sent to the
           referenced group or neighbors and ebgp-multihop is
           enabled";
      }
    }
  }

  grouping structure-neighbor-group-route-reflector {
    description
      "Structural grouping used to include route reflector
       configuration and state for both BGP neighbors and peer
       groups";

    container route-reflector {
      description
        "Route reflector parameters for the BGPgroup";
      reference
	"RFC 4456: BGP Route Reflection.";

      leaf route-reflector-cluster-id {
        type bt:rr-cluster-id-type;
        description
          "route-reflector cluster id to use when local router is
           configured as a route reflector.  Commonly set at the
           group level, but allows a different cluster id to be set
           for each neighbor.";
      }

      leaf route-reflector-client {
        type boolean;
        default "false";
        description
          "Configure the neighbor as a route reflector client.";
      }
    }
  }

  grouping structure-neighbor-group-as-path-options {
    description
      "Structural grouping used to include AS_PATH manipulation
       configuration and state for both BGP neighbors and peer
       groups";

    container as-path-options {
      description
        "AS_PATH manipulation parameters for the BGP neighbor or
        group";
      leaf allow-own-as {
        type uint8;
        default 0;
        description
          "Specify the number of occurrences of the local BGP
           speaker's AS that can occur within the AS_PATH before it
           is rejected.";
      }

      leaf replace-peer-as {
        type boolean;
        default "false";
        description
          "Replace occurrences of the peer's AS in the AS_PATH with
           the local autonomous system number";
      }
    }
  }

  grouping structure-neighbor-group-add-paths {
    description
      "Structural grouping used to include ADD-PATHs configuration
       and state for both BGP neighbors and peer groups";

    container add-paths {
      description
        "Parameters relating to the advertisement and receipt of
         multiple paths for a single NLRI (add-paths)";

      leaf receive {
        type boolean;
        default false;
        description
          "Enable ability to receive multiple path advertisements for
           an NLRI from the neighbor or group";
      }

      leaf send-max {
        type uint8;
        description
          "The maximum number of paths to advertise to neighbors for
           a single NLRI";
      }
      leaf eligible-prefix-policy {
        type leafref {
          path "/rpol:routing-policy/rpol:policy-definitions/" +
               "rpol:policy-definition/rpol:name";
        }
        description
          "A reference to a routing policy which can be used to
           restrict the prefixes for which add-paths is enabled";
      }
    }
  }
}
<CODE ENDS>
 
        ]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-peer-group@2019-06-13.yang"
submodule ietf-bgp-peer-group {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  import ietf-routing-policy { 
    prefix rpol; 
  }

  // Include the common submodule
  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-common-structure;

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This sub-module contains groupings that are specific to the
     peer-group context of the OpenConfig BGP module.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping bgp-peer-group-config {
    description
      "Configuration parameters relating to a base BGP peer group
       that are not also applicable to any other context (e.g.,
       neighbor)";

    leaf peer-group-name {
      type string;
      description
        "Name of the BGP peer-group";
    }
  }

  grouping bgp-peer-group-afi-safi-list {
    description
      "List of address-families associated with the BGP peer-group";

    list afi-safi {
      key "afi-safi-name";

      description
        "AFI, SAFI configuration available for the
         neighbour or group";

      uses mp-afi-safi-config;

      container graceful-restart {
        description
          "Parameters relating to BGP graceful-restart";

        uses mp-afi-safi-graceful-restart-config;
      }

      uses route-selection-options;
      uses global-group-use-multiple-paths;
      uses mp-all-afi-safi-list-contents;
    }
  }

  grouping bgp-peer-group-base {
    description
      "Parameters related to a BGP group.";

    uses bgp-peer-group-config;
    uses neighbor-group-config;
    uses state;

    container timers {
      description
        "Timers related to a BGP peer-group.";

      uses neighbor-group-timers-config;
    }

    container transport {
      description
        "Transport session parameters for the BGP peer-group.";

      uses neighbor-group-transport-config;
    }

    container graceful-restart {
      description
        "Parameters relating the graceful restart mechanism for BGP.";

      uses graceful-restart-config;
    }

    uses structure-neighbor-group-ebgp-multihop;
    uses structure-neighbor-group-route-reflector;
    uses structure-neighbor-group-as-path-options;
    uses structure-neighbor-group-add-paths;
    uses global-group-use-multiple-paths;
    uses rpol:apply-policy-group;

    container afi-safis {
      description
        "Per-address-family configuration parameters associated with
         the group.";
      uses bgp-peer-group-afi-safi-list;
    }
  }

  grouping bgp-peer-group-list {
    description
      "The list of BGP peer groups";

    list peer-group {
      key "peer-group-name";
      description
        "List of BGP peer-groups configured on the local system -
         uniquely identified by peer-group name";
      
      uses bgp-peer-group-base;
    }
  }
}
<CODE ENDS>
 
        ]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-neighbor@2019-06-13.yang"
submodule ietf-bgp-neighbor {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  // Include the common submodule
  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-peer-group;
  include ietf-bgp-common-structure;

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This sub-module contains groupings that are specific to the
     neighbor context of the BGP module.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping bgp-neighbor-use-multiple-paths {
    description
      "Multi-path configuration and state applicable to a BGP
       neighbor";

    container use-multiple-paths {
      description
        "Parameters related to the use of multiple-paths for the same
         NLRI when they are received only from this neighbor";

      uses use-multiple-paths-config;

      container ebgp {
        description
          "Multi-path configuration for eBGP";
        uses use-multiple-paths-ebgp-as-options-config;
      }
    }
  }

  grouping bgp-neighbor-counters-message-types-state {
    description
      "Grouping of BGP message types, included for re-use across
       counters";

    leaf updates-received {
      type uint64;
      description
        "Number of BGP UPDATE messages received from this neighbor.";
      reference
	"RFC 4273: bgpPeerInUpdates.";
    }

    leaf updates-sent {
      type uint64;
      description
        "Number of BGP UPDATE messages sent to this neighbor";
      reference
        "RFC 4273 - bgpPeerOutUpdates";
    }

    leaf messages-received {
      type uint64;
      description
        "Number of BGP messages received from thsi neighbor";
      reference
        "RFC 4273 - bgpPeerInTotalMessages";
    }

    leaf messages-sent {
      type uint64;
      description
        "Number of BGP messages received from thsi neighbor";
      reference
        "RFC 4273 - bgpPeerOutTotalMessages";
    }

    leaf notification {
      type uint64;
      description
        "Number of BGP NOTIFICATION messages indicating an error
         condition has occurred exchanged.";
    }
  }

  grouping bgp-neighbor-afi-safi-list {
    description
      "List of address-families associated with the BGP neighbor";

    list afi-safi {
      key "afi-safi-name";

      description
        "AFI, SAFI configuration available for the neighbor or
         group";

      uses mp-afi-safi-config;

      leaf active {
        type boolean;
        config false;
        description
          "This value indicates whether a particular AFI-SAFI has
           been successfully negotiated with the peer. An AFI-SAFI may
           be enabled in the current running configuration, but a
           session restart may be required in order to negotiate the
           new capability.";
      }

      container prefixes {
        config false;
        description
          "Prefix counters for the BGP session";

        leaf received {
          type uint32;
          description
            "The number of prefixes received from the neighbor";
        }

        leaf sent {
          type uint32;
          description
            "The number of prefixes advertised to the neighbor";
        }

        leaf installed {
          type uint32;
          description
            "The number of advertised prefixes installed in the
             Loc-RIB";
        }
      }

      container graceful-restart {
        description
          "Parameters relating to BGP graceful-restart";

        uses mp-afi-safi-graceful-restart-config;

        leaf received {
          type boolean;
          config false;
          description
            "This leaf indicates whether the neighbor advertised the
             ability to support graceful-restart for this AFI-SAFI";
        }

        leaf advertised {
          type boolean;
          config false;
          description
            "This leaf indicates whether the ability to support
             graceful-restart has been advertised to the peer";
        }
      }

      uses mp-all-afi-safi-list-contents;
      uses bgp-neighbor-use-multiple-paths;
    }
  }
}
<CODE ENDS>
 

]]></artwork>
          </figure></t>
      </section>

      <section title="BGP types">
        <t><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-types@2019-06-13.yang"
module ietf-bgp-types {
  yang-version "1.1";
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-types";

  prefix "bt";

  import ietf-inet-types { 
    prefix inet; 
  }

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This module contains general data definitions for use in BGP
     policy. It can be imported by modules that make use of BGP
     attributes";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  identity bgp-capability {
    description "Base identity for a BGP capability";
  }

  identity mp-bgp {
    base bgp-capability;
    description
      "Multi-protocol extensions to BGP";
    reference
      "RFC 4760";
  }

  identity route-refresh {
    base bgp-capability;
    description
      "The BGP route-refresh functionality";
    reference
      "RFC2918";
  }

  identity asn32 {
    base bgp-capability;
    description
      "4-byte (32-bit) AS number functionality";
    reference
      "RFC6793";
  }

  identity graceful-restart {
    base bgp-capability;
    description
      "Graceful restart functionality";
    reference
      "RFC4724";
  }

  identity add-paths {
    base bgp-capability;
    description
      "BGP add-paths";
    reference
      "RFC 7911.";
  }

  identity afi-safi-type {
    description
      "Base identity type for AFI,SAFI tuples for BGP-4";
    reference
      "RFC4760 - multi-protocol extensions for BGP-4";
  }

  identity ipv4-unicast {
    base afi-safi-type;
    description
      "IPv4 unicast (AFI,SAFI = 1,1)";
    reference
      "RFC4760";
  }

  identity ipv6-unicast {
    base afi-safi-type;
    description
      "IPv6 unicast (AFI,SAFI = 2,1)";
    reference
      "RFC4760";
  }

  identity ipv4-labeled-unicast {
    base afi-safi-type;
    description
      "Labeled IPv4 unicast (AFI,SAFI = 1,4)";
    reference
      "RFC3107";
  }

  identity ipv6-labeled-unicast {
    base afi-safi-type;
    description
      "Labeled IPv6 unicast (AFI,SAFI = 2,4)";
    reference
      "RFC3107";
  }

  identity l3vpn-ipv4-unicast {
    base afi-safi-type;
    description
      "Unicast IPv4 MPLS L3VPN (AFI,SAFI = 1,128)";
    reference
      "RFC4364";
  }

  identity l3vpn-ipv6-unicast {
    base afi-safi-type;
    description
      "Unicast IPv6 MPLS L3VPN (AFI,SAFI = 2,128)";
    reference
      "RFC4659";
  }

  identity l3vpn-ipv4-multicast {
    base afi-safi-type;
    description
      "Multicast IPv4 MPLS L3VPN (AFI,SAFI = 1,129)";
    reference
      "RFC6514";
  }

  identity l3vpn-ipv6-multicast {
    base afi-safi-type;
    description
      "Multicast IPv6 MPLS L3VPN (AFI,SAFI = 2,129)";
    reference
      "RFC6514";
  }

  identity l2vpn-vpls {
    base afi-safi-type;
    description
      "BGP-signalled VPLS (AFI,SAFI = 25,65)";
    reference
      "RFC4761";
  }

  identity l2vpn-evpn {
    base afi-safi-type;
    description
      "BGP MPLS Based Ethernet VPN (AFI,SAFI = 25,70)";
  }

  identity BGP_WELL_KNOWN_STD_COMMUNITY {
    description
      "Reserved communities within the standard community space
       defined by RFC1997. These communities must fall within the
       range 0xFFFF0000 to 0xFFFFFFFF";
    reference
      "RFC 1997";
  }

  identity NO_EXPORT {
    base BGP_WELL_KNOWN_STD_COMMUNITY;
    description
      "Do not export NLRI received carrying this community outside
       the bounds of this autonomous system, or this confederation if
       the local autonomous system is a confederation member AS. This
       community has a value of 0xFFFFFF01.";
    reference
      "RFC1997";
  }

  identity NO_ADVERTISE {
    base BGP_WELL_KNOWN_STD_COMMUNITY;
    description
      "All NLRI received carrying this community must not be
       advertised to other BGP peers. This community has a value of
       0xFFFFFF02.";
    reference
      "RFC1997";
  }

  identity NO_EXPORT_SUBCONFED {
    base BGP_WELL_KNOWN_STD_COMMUNITY;
    description
      "All NLRI received carrying this community must not be
       advertised to external BGP peers - including over confederation
       sub-AS boundaries. This community has a value of 0xFFFFFF03.";
    reference
      "RFC1997";
  }

  identity NOPEER {
    base BGP_WELL_KNOWN_STD_COMMUNITY;
    description
      "An autonomous system receiving NLRI tagged with this community
       is advised not to re-advertise the NLRI to external bi-lateral
       peer autonomous systems. An AS may also filter received NLRI
       from bilateral peer sessions when they are tagged with this
       community value";
    reference
      "RFC3765";
  }

  identity as-path-segment-type {
    description
      "Base AS Path Segment Type. In [BGP-4], the path segment type
       is a 1-octet field with the following values defined.";
    reference
      "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
  }

  identity as-set {
    base as-path-segment-type;
    description
      "Unordered set of autonomous systems that a route in the UPDATE
       message has traversed.";
    reference
      "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
  }

  identity as-sequence {
    base as-path-segment-type;
    description
      "Ordered set of autonomous systems that a route in the UPDATE
       message has traversed.";
    reference
      "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
  }

  identity as-confed-sequence {
    base as-path-segment-type;
    description
      "Ordered set of Member Autonomous Systems in the local
       confederation that the UPDATE message has traversed.";
    reference
      "RFC 5065, Autonomous System Configuration for BGP.";
  }

  identity as-confed-set {
    base as-path-segment-type;
    description
      "Unordered set of Member Autonomous Systems in the local
       confederation that the UPDATE message has traversed.";
    reference
      "RFC 5065, Autonomous System Configuration for BGP.";
  }

  /*
   * Features.
   */
  feature ttl-security {
    description
      "BGP Time To Live (TTL) security check support.";
    reference
      "RFC 5082, The Generalized TTL Security Mechanism (GTSM)";
  }

  feature bfd {
    description
      "Support for BFD detection of BGP neighbor reachability.";
    reference
      "RFC 5880, Bidirectional Forward Detection (BFD),
       RFC 5881, Bidirectional Forward Detection for IPv4 and IPv6
                 (Single Hop).
       RFC 5883, Bidirectional Forwarding Detection (BFD) for Multihop 
		 Paths";
  }

  typedef bgp-session-direction {
    type enumeration {
      enum INBOUND {
        description
          "Refers to all NLRI received from the BGP peer";
      }
      enum OUTBOUND {
        description
          "Refers to all NLRI advertised to the BGP peer";
      }
    }
    description
      "Type to describe the direction of NLRI transmission";
  }

  typedef bgp-well-known-community-type {
    type identityref {
      base BGP_WELL_KNOWN_STD_COMMUNITY;
    }
    description
      "Type definition for well-known IETF community attribute
       values";
    reference
      "IANA Border Gateway Protocol (BGP) Well Known Communities";
  }


  typedef bgp-std-community-type {
    // TODO: further refine restrictions and allowed patterns
    // 4-octet value:
    //  <as number> 2 octets
    //  <community value> 2 octets
    type union {
      type uint32 {
      // per RFC 1997, 0x00000000 - 0x0000FFFF and 0xFFFF0000 -
      // 0xFFFFFFFF are reserved
        range "65536..4294901759"; // 0x00010000..0xFFFEFFFF
      }
      type string {
        pattern '([0-9]+:[0-9]+)';
      }
    }
    description
      "Type definition for standard community attributes";
    reference
      "RFC 1997 - BGP Communities Attribute";
  }

  typedef bgp-ext-community-type {
    // TODO: needs more work to make this more precise given the
    // variability of extended community attribute specifications
    // 8-octet value:
    //  <type> 2 octects
    //  <value> 6 octets

    type union {
      type string {
        // Type 1: 2-octet global and 4-octet local
        //         (AS number)        (Integer)
        pattern '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                '[1-9][0-9]{1,4}|[0-9]):'                          +
                '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
      }
      type string {
        // Type 2: 4-octet global and 2-octet local
        //         (ipv4-address)     (integer)
        pattern '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                '2[0-4][0-9]|25[0-5]):'                            +
                '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                '[1-9][0-9]{1,4}|[0-9])';
      }
      type string {
        // route-target with Type 1
        // route-target:(ASN):(local-part)
        pattern 'route\-target:(6[0-5][0-5][0-3][0-5]|'            +
                '[1-5][0-9]{4}|[1-9][0-9]{1,4}|[0-9]):'            +
                '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
      }
      type string {
        // route-target with Type 2
        // route-target:(IPv4):(local-part)
        pattern 'route\-target:' +
                '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                '2[0-4][0-9]|25[0-5]):'                            +
                '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                '[1-9][0-9]{1,4}|[0-9])';
      }
      type string {
        // route-origin with Type 1
        pattern 'route\-origin:(6[0-5][0-5][0-3][0-5]|'            +
                '[1-5][0-9]{4}|[1-9][0-9]{1,4}|[0-9]):'            +
                '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
      }
      type string {
        // route-origin with Type 2
        pattern 'route\-origin:' +
                '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                '2[0-4][0-9]|25[0-5]):'                            +
                '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                '[1-9][0-9]{1,4}|[0-9])';
      }
    }
    description
      "Type definition for extended community attributes";
    reference
      "RFC 4360 - BGP Extended Communities Attribute";
  }

  typedef bgp-community-regexp-type {
    // TODO: needs more work to decide what format these regexps can
    // take.
    type string;
    description
      "Type definition for communities specified as regular
       expression patterns";
  }

  typedef bgp-origin-attr-type {
    type enumeration {
      enum IGP {
        description "Origin of the NLRI is internal";
      }
      enum EGP {
        description "Origin of the NLRI is EGP";
      }
      enum INCOMPLETE {
        description "Origin of the NLRI is neither IGP or EGP";
      }
    }
    description
      "Type definition for standard BGP origin attribute";
    reference
      "RFC 4271 - A Border Gateway Protocol 4 (BGP-4), Sec 4.3";
  }

  typedef peer-type {
    type enumeration {
      enum INTERNAL {
        description "internal (iBGP) peer";
      }
      enum EXTERNAL {
        description "external (eBGP) peer";
      }
    }
    description
      "Labels a peer or peer group as explicitly internal or
       external";
  }

  identity REMOVE_PRIVATE_AS_OPTION {
    description
      "Base identity for options for removing private autonomous
       system numbers from the AS_PATH attribute";
  }

  identity PRIVATE_AS_REMOVE_ALL {
    base REMOVE_PRIVATE_AS_OPTION;
    description
      "Strip all private autonomous system numbers from the AS_PATH.
       This action is performed regardless of the other content of the
       AS_PATH attribute, and for all instances of private AS numbers
       within that attribute.";
  }

  identity PRIVATE_AS_REPLACE_ALL {
    base REMOVE_PRIVATE_AS_OPTION;
    description
      "Replace all instances of private autonomous system numbers in
       the AS_PATH with the local BGP speaker's autonomous system
       number. This action is performed regardless of the other
       content of the AS_PATH attribute, and for all instances of
       private AS number within that attribute.";
  }

  typedef remove-private-as-option {
    type identityref {
      base REMOVE_PRIVATE_AS_OPTION;
    }
    description
      "Set of options for configuring how private AS path numbers
       are removed from advertisements";
  }

  typedef percentage {
    type uint8 {
      range "0..100";
    }
    description
      "Integer indicating a percentage value";
  }

  typedef rr-cluster-id-type {
    type union {
      type uint32;
      type inet:ipv4-address;
    }
    description
      "Union type for route reflector cluster ids:
       option 1: 4-byte number
       option 2: IP address";
  }

  typedef community-type {
    type enumeration {
      enum STANDARD {
        description
	"Send only standard communities";
      }
      enum EXTENDED {
        description
	"Send only extended communities";
      }
      enum BOTH {
        description
	"Send both standard and extended communities";
      }
      enum NONE {
        description
	"Do not send any community attribute";
      }
    }
    description
      "Type describing variations of community attributes:
       STANDARD: standard BGP community [rfc1997]
       EXTENDED: extended BGP community [rfc4360]
       BOTH: both standard and extended community";
  }
}
<CODE ENDS>
       
        ]]></artwork>
          </figure></t>
      </section>

      <section title="BGP policy data">
        <t><figure>
            <artwork><![CDATA[
    <CODE BEGINS> file "ietf-bgp-policy@2019-06-13.yang"
module ietf-bgp-policy {
  yang-version "1.1";
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-policy";
  prefix "bp";

  // import some basic types
  import ietf-inet-types { 
    prefix inet; 
  }
  import ietf-routing-policy {
    prefix rpol; 
  }
  import ietf-bgp-types { 
    prefix bt; 
  }
  
  import ietf-routing-types {
    prefix rt-types;
  }

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This module contains data definitions for BGP routing policy.
     It augments the base routing-policy module with BGP-specific
     options for conditions and actions.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  // typedef statements

  typedef bgp-set-community-option-type {
    type enumeration {
      enum ADD {
        description
          "Add the specified communities to the existing
           community attribute";
      }
      enum REMOVE {
        description
          "Remove the specified communities from the
           existing community attribute";
      }
      enum REPLACE {
        description
          "Replace the existing community attribute with
           the specified communities. If an empty set is
           specified, this removes the community attribute
           from the route.";
      }
    }
    description
      "Type definition for options when setting the community
       attribute in a policy action";
  }

  typedef bgp-next-hop-type {
    type union {
      type inet:ip-address-no-zone;
      type enumeration {
        enum SELF {
          description
            "Special designation for local router's own
             address, i.e., next-hop-self";
        }
      }
    }
    description
      "Type definition for specifying next-hop in policy actions";
  }

  typedef bgp-set-med-type {
    type union {
      type uint32;
      type string {
        pattern "^[+-][0-9]+";
      }
      type enumeration {
        enum IGP {
          description
            "Set the MED value to the IGP cost toward the
             next hop for the route";
        }
      }
    }
    description
      "Type definition for specifying how the BGP MED can
       be set in BGP policy actions. The three choices are to set
       the MED directly, increment/decrement using +/- notation,
       and setting it to the IGP cost (predefined value).";
  }

  // augment statements

  augment "/rpol:routing-policy/rpol:defined-sets" {
    description
      "Adds BGP defined sets container to routing policy model.";

    container bgp-defined-sets {
      description
        "BGP-related set definitions for policy match conditions";

      container community-sets {
        description
          "Enclosing container for list of defined BGP community sets";

        list community-set {
          key "community-set-name";
          description
            "List of defined BGP community sets";

          leaf community-set-name {
            type string;
            mandatory true;
            description
              "Name / label of the community set -- this is used to
               reference the set in match conditions";
          }

          leaf-list community-member {
            type union {
              type bt:bgp-std-community-type;
              type bt:bgp-community-regexp-type;
              type bt:bgp-well-known-community-type;
            }
            description
              "Members of the community set";
          }
        }
      }

      container ext-community-sets {
        description
          "Enclosing container for list of extended BGP community
           sets";
        list ext-community-set {
          key "ext-community-set-name";
          description
            "List of defined extended BGP community sets";

          leaf ext-community-set-name {
            type string;
            description
              "Name / label of the extended community set -- this is
               used to reference the set in match conditions";
          }

          leaf-list ext-community-member {
            type union {
              type rt-types:route-target;
              type bt:bgp-community-regexp-type;
            }
            description
              "Members of the extended community set";
          }
        }
      }

      container as-path-sets {
        description
          "Enclosing container for list of define AS path sets";

        list as-path-set {
          key "as-path-set-name";
          description
            "List of defined AS path sets";

          leaf as-path-set-name {
            type string;
            description
              "Name of the AS path set -- this is used to reference the
               set in match conditions";
          }

          leaf-list as-path-set-member {
            // TODO: need to refine typedef for AS path expressions
            type string;
            description
              "AS path expression -- list of ASes in the set";
          }
        }
      }
    }
  }

  grouping set-community-action-common {
    description
      "Common leaves for set-community and set-ext-community
       actions";

    leaf method {
      type enumeration {
        enum INLINE {
          description
            "The extended communities are specified inline as a
             list";
        }
        enum REFERENCE {
          description
            "The extended communities are specified by referencing a
             defined ext-community set";
        }
      }
      description
        "Indicates the method used to specify the extended
         communities for the set-ext-community action";
    }

    leaf options {
      type bgp-set-community-option-type;
      description
        "Options for modifying the community attribute with
         the specified values.  These options apply to both
         methods of setting the community attribute.";
    }
  }

  augment "/rpol:routing-policy/rpol:policy-definitions/" +
    "rpol:policy-definition/rpol:statements/rpol:statement/" +
    "rpol:conditions" {
    description
      "BGP policy conditions added to routing policy module";

    container bgp-conditions {
      description
        "Top-level container for BGP specific policy conditions ";

      leaf med-eq {
        type uint32;
        description
          "Condition to check if the received MED value is equal to
           the specified value";
      }

      leaf origin-eq {
        type bt:bgp-origin-attr-type;
        description
          "Condition to check if the route origin is equal to the
           specified value";
      }
      
      leaf-list next-hop-in {
        type inet:ip-address-no-zone;
        description
          "List of next hop addresses to check for in the route
           update";
      }

      leaf-list afi-safi-in {
        type identityref {
          base bt:afi-safi-type;
        }
        description
          "List of address families which the NLRI may be within";
      }

      leaf local-pref-eq {
        type uint32;
        // TODO: add support for other comparisons if needed
        description
          "Condition to check if the local pref attribute is equal to
           the specified value";
      }

      leaf route-type {
        // TODO: verify extent of vendor support for this comparison
        type enumeration {
          enum INTERNAL {
            description "route type is internal";
          }
          enum EXTERNAL {
            description "route type is external";
          }
        }
        description
          "Condition to check the route type in the route update";
      }

      container community-count {
        description
          "Value and comparison operations for conditions based on the
           number of communities in the route update";
      }

      container as-path-length {
        description
          "Value and comparison operations for conditions based on the
           length of the AS path in the route update";
      }

      container match-community-set {
        description
          "Top-level container for match conditions on communities.
           Match a referenced community-set according to the logic
           defined in the match-set-options leaf";

        leaf community-set {
          type leafref {
            path 
              "/rpol:routing-policy/rpol:defined-sets/" +
              "bp:bgp-defined-sets/bp:community-sets/" +
              "bp:community-set/bp:community-set-name";
          }
          description
            "References a defined community set";
        }

        uses rpol:match-set-options-group;
      }

      container match-ext-community-set {
        description
          "Match a referenced extended community-set according to the
           logic defined in the match-set-options leaf";

        leaf ext-community-set {
          type leafref {
            path 
              "/rpol:routing-policy/rpol:defined-sets/" +
              "bp:bgp-defined-sets/bp:ext-community-sets/" +
              "bp:ext-community-set/" +
              "bp:ext-community-set-name";
          }
          description "References a defined extended community set";
        }

        uses rpol:match-set-options-group;
      }

      container match-as-path-set {
        description
          "Match a referenced as-path set according to the logic
           defined in the match-set-options leaf";

        leaf as-path-set {
          type leafref {
            path "/rpol:routing-policy/rpol:defined-sets/" +
              "bp:bgp-defined-sets/bp:as-path-sets/" +
              "bp:as-path-set/bp:as-path-set-name";
          }
          description
            "References a defined AS path set";
        }
        uses rpol:match-set-options-group;
      }
    }
  }

  augment "/rpol:routing-policy/rpol:policy-definitions/" +
    "rpol:policy-definition/rpol:statements/rpol:statement/" +
    "rpol:actions" {
    description
      "BGP policy actions added to routing policy module.";

    container bgp-actions {
      description
        "Top-level container for BGP-specific actions";

      leaf set-route-origin {
        type bt:bgp-origin-attr-type;
        description
          "Set the origin attribute to the specified value";
      }

      leaf set-local-pref {
        type uint32;
        description
          "Set the local pref attribute on the route update";
      }

      leaf set-next-hop {
        type bgp-next-hop-type;
        description
          "Set the next-hop attribute in the route update";
      }

      leaf set-med {
        type bgp-set-med-type;
        description
          "Set the med metric attribute in the route update";
      }

      container set-as-path-prepend {
        description
          "Action to prepend local AS number to the AS-path a
           specified number of times";

        leaf repeat-n {
          type uint8 {
            range 1..max;
          }
          description
            "Number of times to prepend the local AS number to the AS
             path.  The value should be between 1 and the maximum
             supported by the implementation.";
        }
      }

      container set-community {
        description
          "Action to set the community attributes of the route, along
           with options to modify how the community is modified.
           Communities may be set using an inline list OR
           reference to an existing defined set (not both).";

        uses set-community-action-common;
        container inline {
          when "../method = 'INLINE'" {
            description
              "Active only when the set-community method is INLINE";
          }
          description
            "Set the community values for the action inline with
             a list.";

          leaf-list communities {
            type union {
              type bt:bgp-std-community-type;
              type bt:bgp-well-known-community-type;
            }
            description
              "Set the community values for the update inline with a
               list.";
          }
        }

        container reference {
          when "../method = 'REFERENCE'" {
            description
              "Active only when the set-community method is REFERENCE";
          }
          description
            "Provide a reference to a defined community set for the
             set-community action";

          leaf community-set-ref {
            type leafref {
              path "/rpol:routing-policy/rpol:defined-sets/" +
                "bp:bgp-defined-sets/" +
                "bp:community-sets/bp:community-set/" +
                "bp:community-set-name";
            }
            description
              "References a defined community set by name";
          }
        }
      }

      container set-ext-community {
        description
          "Action to set the extended community attributes of the
           route, along with options to modify how the community is
           modified. Extended communities may be set using an inline
           list OR a reference to an existing defined set (but not
           both).";

        uses set-community-action-common;
        container inline {
          when "../method = 'INLINE'" {
            description
              "Active only when the set-community method is INLINE";
          }
          description
            "Set the extended community values for the action inline
             with a list.";

          leaf-list communities {
            type union {
              type rt-types:route-target;
              type bt:bgp-well-known-community-type;
            }
            description
              "Set the extended community values for the update inline
               with a list.";
          }
        }

        container reference {
          when "../method = 'REFERENCE'" {
            description
              "Active only when the set-community method is REFERENCE";
          }
          description
            "Provide a reference to an extended community set for the
             set-ext-community action";

          leaf ext-community-set-ref {
            type leafref {
              path 
                "/rpol:routing-policy/rpol:defined-sets/" +
                "bp:bgp-defined-sets/bp:ext-community-sets/" +
                "bp:ext-community-set/" +
                "bp:ext-community-set-name";
            }
            description
              "References a defined extended community set by name";
          }
        }
      }
    }
  }

  // rpc statements

  // notification statements
}
    <CODE ENDS>
    ]]></artwork>
          </figure></t>
      </section>

      <section title="RIB modules">
        <t><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib@2019-06-13.yang"
submodule ietf-bgp-rib {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  /*
   * Import and Include
   */
  import ietf-bgp-types {
    prefix "bt";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Networks.";
  }

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

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

  import ietf-routing-types {
    prefix "rt";
    reference
      "RFC 8294: Routing Area YANG Types.";
  }
  

  include ietf-bgp-rib-types;
  include ietf-bgp-rib-tables;

  // groupings of attributes in three categories:
  //  - shared across multiple routes
  //  - common to LOC-RIB and Adj-RIB, but not shared across routes
  //  - specific to LOC-RIB or Adj-RIB
  include ietf-bgp-rib-attributes;

  // groupings of annotations for each route or table
  include ietf-bgp-rib-table-attributes;

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "Defines a submodule for representing BGP routing table (RIB)
     contents.  The submodule supports 5 logical RIBs per address
     family:

     loc-rib: This is the main BGP routing table for the local routing
     instance, containing best-path selections for each prefix. The
     loc-rib table may contain multiple routes for a given prefix,
     with an attribute to indicate which was selected as the best
     path.  Note that multiple paths may be used or advertised even if
     only one path is marked as best, e.g., when using BGP
     add-paths.  An implementation may choose to mark multiple
     paths in the RIB as best path by setting the flag to true for
     multiple entries.

     adj-rib-in-pre: This is a per-neighbor table containing the NLRI
     updates received from the neighbor before any local input policy
     rules or filters have been applied.  This can be considered the
     'raw' updates from a given neighbor.

     adj-rib-in-post: This is a per-neighbor table containing the
     routes received from the neighbor that are eligible for
     best-path selection after local input policy rules have been
     applied.

     adj-rib-out-pre: This is a per-neighbor table containing routes
     eligible for sending (advertising) to the neighbor before output
     policy rules have been applied.

     adj-rib-out-post: This is a per-neighbor table containing routes
     eligible for sending (advertising) to the neighbor after output
     policy rules have been applied.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXXX, BGP YANG Model for Service Provider Network.";
  }

  grouping rib {
    description
      "Grouping for rib.";

    container rib {
      config false;

      container attr-sets {
        description
          "Enclosing container for the list of path attribute sets";

        list attr-set {
          key "index";

          description
            "List of path attributes that may be in use by multiple
             routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
               index is used to reference an attribute set from a
               specific path.  Multiple paths may reference the same
               attribute set.";
          }

          leaf origin {
            type bt:bgp-origin-attr-type;
            description
              "BGP attribute defining the origin of the path
               information.";
          }

          leaf atomic-aggregate {
            type boolean;
            description
              "BGP attribute indicating that the prefix is an atomic
               aggregate; i.e., the peer selected a less specific
               route without selecting a more specific route that is
               included in it.";
            reference
	      "RFC 4271: Section 5.1.6.";
          }

          leaf next-hop {
            type inet:ip-address;
            description
              "BGP next hop attribute defining the IP address of the
               router that should be used as the next hop to the
               destination";
            reference
	      "RFC 4271: Section 5.1.3.";
          }

          leaf med {
            type uint32;
            description
              "BGP multi-exit discriminator attribute used in BGP route
               selection process";
            reference
	      "RFC 4271: Section 5.1.4.";
          }

          leaf local-pref {
            type uint32;
            description
              "BGP local preference attribute sent to internal peers to
               indicate the degree of preference for externally learned
               routes.  The route with the highest local preference
               value is preferred.";
            reference
	      "RFC 4271: Section 5.1.5.";
          }

          leaf originator-id {
            type yang:dotted-quad;
            description
              "BGP attribute that provides the id as an IPv4 address
               of the originator of the announcement.";
            reference
              "RFC 4456 - BGP Route Reflection: An Alternative to Full
               Mesh Internal BGP (IBGP)";
          }

          leaf-list cluster-list {
            type yang:dotted-quad;
            description
              "Represents the reflection path that the route has
               passed.";
            reference
              "RFC 4456 - BGP Route Reflection: An Alternative to Full
               Mesh Internal BGP (IBGP)";
          }

          leaf aigp-metric {
            type uint64;
            description
              "BGP path attribute representing the accumulated IGP
               metric for the path";
            reference
              "RFC 7311 - The Accumulated IGP Metric Attribute for BGP";
          }
          container aggregator {
            config false;
            description
              "BGP attribute indicating the prefix has been
               aggregated by the specified AS and router.";
            reference
	      "RFC 4271: Section 5.1.7.";

            leaf as {
              type inet:as-number;
              description
                "AS number of the autonomous system that performed the
                 aggregation.";
            }

            leaf as4 {
              type inet:as-number;
              description
                "AS number of the autonomous system that performed the
                 aggregation (4-octet representation).  This value is
                 populated if an upstream router is not 4-octet capable.
                 Its semantics are similar to the AS4_PATH optional
                 transitive attribute";
              reference
                "RFC 6793 - BGP Support for Four-octet AS Number Space";
            }

            leaf address {
              type inet:ipv4-address;
              description
                "IP address of the router that performed the
                 aggregation.";
            }
          }
          container as-path {
            description
              "Enclosing container for the list of AS path segments.

               In the Adj-RIB-In or Adj-RIB-Out, this list should show
               the received or sent AS_PATH, respectively.  For
               example, if the local router is not 4-byte capable, this
               value should consist of 2-octet ASNs or the AS_TRANS
               (AS 23456) values received or sent in route updates.

               In the Loc-RIB, this list should reflect the effective
               AS path for the route, e.g., a 4-octet value if the
               local router is 4-octet capable.";
            reference
              "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)
               RFC 6793 - BGP Support for Four-octet AS Number Space
               RFC 5065 - Autonomous System Confederations for BGP";

            list segment {
              key "type";

              config false;
              uses bgp-as-path-attr;
              description
                "List of AS PATH segments";
            }
          }
          container as4-path {
            description
              "This is the path encoded with 4-octet
               AS numbers in the optional transitive AS4_PATH attribute.
               This value is populated with the received or sent
               attribute in Adj-RIB-In or Adj-RIB-Out, respectively.
               It should not be populated in Loc-RIB since the Loc-RIB
               is expected to store the effective AS-Path in the
               as-path leaf regardless of being 4-octet or 2-octet.";
            reference
              "RFC 6793 - BGP Support for Four-octet AS Number Space";

            list segment {
              key "type";

              config false;
              uses bgp-as-path-attr;
              description
                "List of AS PATH segments";
            }
          }
        }
      }

      container communities {
        description
          "Enclosing container for the list of community attribute
        sets";

        list community {
          key "index";

          config false;
          description
            "List of path attributes that may be in use by multiple
          routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
              index is used to reference an attribute set from a
              specific path.  Multiple paths may reference the same
              attribute set.";
          }

          uses bgp-community-attr-state;
        }
      }

      container ext-communities {
        description
          "Enclosing container for the list of extended community
           attribute sets";

        list ext-community {
          key "index";

          config false;
          description
            "List of path attributes that may be in use by multiple
             routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
               index is used to reference an attribute set from a
               specific path.  Multiple paths may reference the same
               attribute set.";
          }

          leaf-list ext-community {
            type rt:route-target;
            description
              "List of BGP extended community attributes. The received
               extended community may be an explicitly modeled
               type or unknown, represented by an 8-octet value
               formatted according to RFC 4360.";
            reference
              "RFC 4360 - BGP Extended Communities Attribute";
          }
        }
      }

      container afi-safis {
	config false;
	description
	  "Enclosing container for address family list";

	list afi-safi {
	  key "afi-safi-name";
	  description
	    "List of afi-safi types.";

	  leaf afi-safi-name {
	    type identityref {
	      base bt:afi-safi-type;
	    }
	    description "AFI,SAFI name.";
	  }

	  container ipv4-unicast {
	    when "../afi-safi-name = 'bt:ipv4-unicast'" {
	      description
		"Include this container for IPv4 unicast RIB";
	    }
	    description
	      "Routing tables for IPv4 unicast -- active when the
              afi-safi name is ipv4-unicast";

	    uses ipv4-loc-rib;
	    uses ipv4-adj-rib;
	  }

	  container ipv6-unicast {
	    when "../afi-safi-name = 'bt:ipv6-unicast'" {
	      description
		"Include this container for IPv6 unicast RIB";
	    }
	    description
	      "Routing tables for IPv6 unicast -- active when the
               afi-safi name is ipv6-unicast";

	    uses ipv6-loc-rib;
	    uses ipv6-adj-rib;
	  }
	}
      }
      description
	"Top level container for BGP RIB";
    }
  }
}
<CODE ENDS>

]]></artwork>
          </figure><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-ext@2019-06-13.yang"
submodule ietf-bgp-rib-ext {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bre";
  }

  include ietf-bgp-rib-types;
  
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";
  
  description
    "Defines additional data nodes for the OpenConfig BGP RIB model.
     These items reflect extensions that are desirable features but
     are not currently supported in a majority of BGP
     implementations.";

  revision "2019-06-13" {
    description
      "Initial Revision.";
    reference
      "RFC XXXX: BGP YANG Model for Service Providers.";
  }

  grouping rib-ext-route-annotations {
    description
      "Extended annotations for routes in the routing tables";

    leaf reject-reason {
      type union {
        type identityref {
          base bgp-not-selected-bestpath;
        }
        type identityref {
          base bgp-not-selected-policy;
        }
      }
      description
        "Indicates the reason the route is not used, either due to
         policy filtering or bestpath selection";
    }
  }
}
<CODE ENDS>

]]></artwork>
          </figure></t>

        <figure>
          <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-types@2019-06-13.yang"
submodule ietf-bgp-rib-types {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "Defines identity and type definitions associated with
     the BGP RIB modules";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXXX, BGP Model for Service Provider Network.";
  }

  identity invalid-route-reason {
    description
      "Base identity for reason code for routes that are rejected as
       invalid.  Some derived entities are based on BMP v3";
    reference
      "BGP Monitoring Protocol (draft-ietf-grow-bmp-07)";
  }

  identity invalid-cluster-loop {
    base invalid-route-reason;
    description
      "Route was invalid due to CLUSTER_LIST loop";
  }

  identity invalid-as-loop {
    base invalid-route-reason;
    description
      "Route was invalid due to AS_PATH loop";
  }

  identity invalid-originator {
    base invalid-route-reason;
    description
      "Route was invalid due to ORIGINATOR_ID, e.g., update has
       local router as originator";
  }

  identity bgp-not-selected-bestpath {
    description
      "Base identity for indicating reason a route was was not
       selected by BGP route selection algorithm";
    reference
      "RFC 4271 - Section 9.1";
  }

  identity local-pref-lower {
    base bgp-not-selected-bestpath;
    description
      "Route has a lower localpref attribute than current best path";
    reference
      "RFC 4271 - Section 9.1.2";
  }

  identity as-path-longer {
    base bgp-not-selected-bestpath;
    description
      "Route has a longer AS path attribute than current best path";
    reference
      "RFC 4271 - Section 9.1.2.2 (a)";
  }

  identity origin-type-higher {
    base bgp-not-selected-bestpath;
    description
      "Route has a higher origin type, i.e., IGP origin is preferred
       over EGP or incomplete";
    reference
      "RFC 4271 - Section 9.1.2.2 (b)";
  }

  identity med-higher {
    base bgp-not-selected-bestpath;
    description
      "Route has a higher MED, or metric, attribute than the current
       best path";
    reference
      "RFC 4271 - Section 9.1.2.2 (c)";
  }

  identity prefer-external {
    base bgp-not-selected-bestpath;
    description
      "Route source is via IGP, rather than EGP.";
    reference
      "RFC 4271 - Section 9.1.2.2 (d)";
  }

  identity nexthop-cost-higher {
    base bgp-not-selected-bestpath;
    description
      "Route has a higher interior cost to the next hop.";
    reference
      "RFC 4271 - Section 9.1.2.2 (e)";
  }

  identity higher-router-id {
    base bgp-not-selected-bestpath;
    description
      "Route was sent by a peer with a higher BGP Identifier value,
       or router id";
    reference
      "RFC 4271 - Section 9.1.2.2 (f)";
  }

  identity higher-peer-address {
    base bgp-not-selected-bestpath;
    description
      "Route was sent by a peer with a higher IP address";
    reference
      "RFC 4271 - Section 9.1.2.2 (g)";
  }

  identity bgp-not-selected-policy {
    description
      "Base identity for reason code for routes that are rejected
       due to policy";
  }

  identity rejected-import-policy {
    base bgp-not-selected-policy;
    description
      "Route was rejected after apply import policies";
  }
}
<CODE ENDS>

]]></artwork>
        </figure>

        <figure>
          <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-attributes@2019-06-13.yang"
submodule ietf-bgp-rib-attributes {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  // import some basic types
  import ietf-bgp-types {
    prefix bgpt;
  }

  import ietf-inet-types {
    prefix inet;
  }

  include ietf-bgp-rib-types;
  
  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This submodule contains common data definitions for BGP
     attributes for use in BGP RIB tables.";


  revision "2019-06-13" {
    description
      "Initial version";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Network";
  }

  grouping bgp-as-path-attr {
    description
      "Data for representing BGP AS-PATH attribute";

    leaf type {
      type identityref {
	base bgpt:as-path-segment-type;
      }
      description
        "The type of AS-PATH segment";
    }

    leaf-list member {
      type inet:as-number;
      description
        "List of the AS numbers in the AS-PATH segment";
    }
  }

  grouping bgp-community-attr-state {
    description
      "Common definition of BGP community attributes";

    leaf-list community {
      type union {
        type bgpt:bgp-well-known-community-type;
        type bgpt:bgp-std-community-type;
      }
      description
        "List of standard or well-known BGP community
         attributes.";
    }
  }

  grouping bgp-unknown-attr-flags-state {
    description
      "Operational state data for path attribute flags";

    leaf optional {
      type boolean;
      description
        "Defines whether the attribute is optional (if
         set to true) or well-known (if set to false).
         Set in the high-order bit of the BGP attribute
         flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf transitive {
      type boolean;
      description
        "Defines whether an optional attribute is transitive
         (if set to true) or non-transitive (if set to false).  For
         well-known attributes, the transitive flag must be set to
         true.  Set in the second high-order bit of the BGP attribute
         flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf partial {
      type boolean;
      description
        "Defines whether the information contained in the optional
         transitive attribute is partial (if set to true) or complete
         (if set to false).  For well-known attributes and for
         optional non-transitive attributes, the partial flag
         must be set to false.  Set in the third high-order bit of
         the BGP attribute flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf extended {
      type boolean;
      description
        "Defines whether the attribute length is one octet
         (if set to false) or two octets (if set to true).  Set in
         the fourth high-order bit of the BGP attribute flags
         octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }
  }

  grouping bgp-unknown-attr-state {
    description
      "Operational state data for path attributes not shared
       across route entries, common to LOC-RIB and Adj-RIB";

    leaf attr-type {
      type uint8;
      description
        "1-octet value encoding the attribute type code";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf attr-len {
      type uint16;
      description
        "One or two octet attribute length field indicating the
         length of the attribute data in octets.  If the Extended
         Length attribute flag is set, the length field is 2 octets,
         otherwise it is 1 octet";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf attr-value {
      type binary {
        length 0..65535;
      }
      description
        "Raw attribute value, not including the attribute
         flags, type, or length.  The maximum length
         of the attribute value data is 2^16-1 per the max value
         of the attr-len field (2 octets).";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }
  }

  grouping bgp-unknown-attr-top {
    description
      "Unknown path attributes that are not expected to be shared
       across route entries, common to LOC-RIB and Adj-RIB";

    container unknown-attributes {
      description
        "Unknown path attributes that were received in the UPDATE
         message which contained the prefix.";

      list unknown-attribute {
        key "attr-type";
        description
          "This list contains received attributes that are unrecognized
           or unsupported by the local router.  The list may be empty.";

	uses bgp-unknown-attr-flags-state;
	uses bgp-unknown-attr-state;
      }
    }
  }

  grouping bgp-loc-rib-attr-state {
    description
      "Path attributes that are not expected to be shared across
       route entries, specific to LOC-RIB";

  }

  grouping bgp-adj-rib-attr-state {
    description
      "Path attributes that are not expected to be shared across
       route entries, specific to Adj-RIB";

    leaf path-id {
      type uint32;
      description
        "When the BGP speaker supports advertisement of multiple
         paths for a prefix, the path identifier is used to
         uniquely identify a route based on the combination of the
         prefix and path id.  In the Adj-RIB-In, the path-id value is
         the value received in the update message.   In the Loc-RIB,
         if used, it should represent a locally generated path-id
         value for the corresponding route.  In Adj-RIB-Out, it
         should be the value sent to a neighbor when add-paths is
         used, i.e., the capability has been negotiated.";
      reference
        "RFC 7911: Advertisement of Multiple Paths in BGP";
    }
  }
}
<CODE ENDS>

]]></artwork>
        </figure>

        <figure>
          <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-table-attributes@2019-06-13.yang"
submodule ietf-bgp-rib-table-attributes {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  // import some basic types
  import ietf-yang-types {
    prefix types;
    reference
      "RFC 6991, Common YANG Data Types.";
  }

  include ietf-bgp-rib-types;
  
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com";

  description
    "This submodule contains common data definitions for data
     related to a RIB entry, or RIB table.";


  revision "2019-06-13" {
    description
      "Initial version.";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Network.";
  }

  grouping bgp-common-route-annotations-state {
    description
      "Data definitions for flags and other information attached
       to routes in both LOC-RIB and Adj-RIB";

    leaf last-modified {
      type types:timeticks;
      description
        "Timestamp when this path was last modified.

         The value is the timestamp in seconds relative to
         the Unix Epoch (Jan 1, 1970 00:00:00 UTC).";
    }

    leaf valid-route {
      type boolean;
      description
        "Indicates that the route is considered valid by the
         local router";
    }

    leaf invalid-reason {
      type identityref {
        base invalid-route-reason;
      }
      description
        "If the route is rejected as invalid, this indicates the
         reason.";
    }
  }

  grouping bgp-loc-rib-route-annotations-state {
    description
      "Data definitions for information attached to routes in the
       LOC-RIB";

       // placeholder for route metadata specific to the LOC-RIB
  }

  grouping bgp-adj-rib-in-post-route-annotations-state {
    description
      "Data definitions for information attached to routes in the
       Adj-RIB-in post-policy table";

    leaf best-path {
      type boolean;
      description
        "Current path was selected as the best path.";
    }
  }

  grouping bgp-common-table-attrs-state {
    description
      "Common attributes attached to all routing tables";

      // placeholder for metadata associated with all tables
  }

  grouping bgp-common-table-attrs-top {
    // no enclosing container as this data will fit under an
    // existing LOC-RIB container

    uses bgp-common-table-attrs-state;
    description
      "Operational state data for data related to the entire
       LOC-RIB";
  }
}
<CODE ENDS>

]]></artwork>
        </figure>

        <t><figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-tables@2019-06-13.yang"
submodule ietf-bgp-rib-tables {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

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

  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Data Types.";
  }
  
  import ietf-routing {
    prefix "rt";
    reference
      "RFC 8022: A YANG Data Model for Routing Management";
  }

  include ietf-bgp-rib-ext;
  include ietf-bgp-rib-attributes;
  include ietf-bgp-rib-table-attributes;

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Editor:  Mahesh Jethanandani (mjethanandani@gmail.com)
     Authors: Keyur Patel,
              Mahesh Jethanandani,
              Susan Hares";

  description
    "This submodule contains structural data definitions for
     BGP routing tables.";

  revision "2019-06-13" {
    description
      "Initial Version";
    reference 
      "RFC XXXX, BGP YANG Model for Service Provider Network.";
  }


  grouping bgp-adj-rib-common-attr-refs {
    description
      "Definitions of common references to attribute sets for
      multiple AFI-SAFIs for Adj-RIB tables";

    leaf attr-index {
      type leafref {
        path "../../../../../../../../../attr-sets/" +
	     "attr-set/index";
      }
      description
        "Reference to the common attribute group for the
        route";
    }

    leaf community-index {
      type leafref {
        path "../../../../../../../../../communities/community/" +
          "index";
      }
      description
        "Reference to the community attribute for the route";
    }

    leaf ext-community-index {
      type leafref {
        path "../../../../../../../../../ext-communities/" +
          "ext-community/index";
      }
      description
        "Reference to the extended community attribute for the
        route";
    }
  }

  grouping bgp-loc-rib-common-attr-refs {
    description
      "Definitions of common references to attribute sets for
      multiple AFI-SAFIs for LOC-RIB tables";

    leaf attr-index {
      type leafref {
        path "../../../../../../../attr-sets/attr-set/" +
          "index";
      }
      description
        "Reference to the common attribute group for the
        route";
    }

    leaf community-index {
      type leafref {
        path "../../../../../../../communities/community/" +
          "index";
      }
      description
        "Reference to the community attribute for the route";
    }

    leaf ext-community-index {
      type leafref {
        path "../../../../../../../ext-communities/" +
          "ext-community/index";
      }
      description
        "Reference to the extended community attribute for the
        route";
    }
  }

  grouping bgp-loc-rib-common-keys {
    description
      "Common references used in keys for IPv4 and IPv6
      LOC-RIB entries";

    leaf origin {
      type union {
        type inet:ip-address;
        type identityref {
          base rt:routing-protocol;
        }
      }
      description
        "Indicates the origin of the route.  If the route is learned
        from a neighbor, this value is the neighbor address.  If
        the route was injected or redistributed from another
        protocol, the origin indicates the source protocol for the
        route.";
    }

    leaf path-id {
      type uint32;
      // TODO: YANG does not allow default values for key
      // default 0;
      description
        "If the route is learned from a neighbor, the path-id
        corresponds to the path-id for the route in the
        corresponding adj-rib-in-post table.  If the route is
        injected from another protocol, or the neighbor does not
        support BGP add-paths, the path-id should be set
        to zero, also the default value.";
    }
  }

  grouping clear-routes {
    description
      "Action to clear BGP routes.";

    container clear-routes {
      if-feature "clear-routes";

      action clear {
        input {
          leaf clear-at {
            type yang:date-and-time;
	    description
	      "The time, in the future when the clear operation will
               be initiated.";
          }
        }

        output {
          leaf clear-finished-at {
            type yang:date-and-time;
	    description
	      "The time when the clear operation finished.";
          }
        }
      }
      description
	"Action commands to clear routes governed by a if-feature.";
    }
  }

  grouping ipv4-loc-rib {
    description
      "Top-level grouping for IPv4 routing tables";

    container loc-rib {
      config false;
      description
        "Container for the IPv4 BGP LOC-RIB data";

      uses bgp-common-table-attrs-top;

      container routes {
        description
          "Enclosing container for list of routes in the routing
          table.";

        list route {
          key "prefix origin path-id";

          description
            "List of routes in the table, keyed by the route
            prefix, the route origin, and path-id.  The route
            origin can be either the neighbor address from which
            the route was learned, or the source protocol that
            injected the route.  The path-id distinguishes routes
            for the same prefix received from a neighbor (e.g.,
            if add-paths is eanbled).";

	  leaf prefix {
	    type inet:ipv4-prefix;
	    description
	      "The IPv4 prefix corresponding to the route";
	  }

          uses bgp-loc-rib-common-keys;
          uses bgp-loc-rib-common-attr-refs;
          uses bgp-loc-rib-attr-state;
          uses bgp-common-route-annotations-state;
          uses bgp-loc-rib-route-annotations-state;
          uses bgp-unknown-attr-top;
          uses rib-ext-route-annotations;
        }

	uses clear-routes;
      }
    }
  }

  grouping ipv6-loc-rib {
    description
      "Top-level grouping for IPv6 routing tables";

    container loc-rib {
      config false;
      description
        "Container for the IPv6 BGP LOC-RIB data";

      uses bgp-common-table-attrs-top;

      container routes {
        description
          "Enclosing container for list of routes in the routing
          table.";

        list route {
          key "prefix origin path-id";

          description
            "List of routes in the table, keyed by the route
            prefix, the route origin, and path-id.  The route
            origin can be either the neighbor address from which
            the route was learned, or the source protocol that
            injected the route.  The path-id distinguishes routes
            for the same prefix received from a neighbor (e.g.,
            if add-paths is eanbled).";

	  leaf prefix {
	    type inet:ipv6-prefix;
	    description
	      "The IPv6 prefix corresponding to the route";
	  }

          uses bgp-loc-rib-common-keys;
          uses bgp-loc-rib-common-attr-refs;
          uses bgp-loc-rib-attr-state;
          uses bgp-common-route-annotations-state;
          uses bgp-loc-rib-route-annotations-state;
          uses bgp-unknown-attr-top;
          uses rib-ext-route-annotations;
        }

	uses clear-routes;
      }
    }
  }

  grouping ipv4-adj-rib-common {
    description
      "Common structural grouping for each IPv4 adj-RIB table";

    uses bgp-common-table-attrs-top;

    container routes {
      config false;
      description
        "Enclosing container for list of routes in the routing
        table.";

      list route {
        key "prefix path-id";

        description
          "List of routes in the table, keyed by a combination of
          the route prefix and path-id to distinguish multiple
          routes received from a neighbor for the same prefix,
          e.g., when BGP add-paths is enabled.";

	leaf prefix {
	  type inet:ipv4-prefix;
	  description
	    "Prefix for the route";
	}

        uses bgp-adj-rib-attr-state;
        uses bgp-adj-rib-common-attr-refs;
        uses bgp-common-route-annotations-state;
        uses bgp-unknown-attr-top;
	uses rib-ext-route-annotations;
      }

      uses clear-routes;
    }
  }

  grouping ipv4-adj-rib-in-post {
    description
      "Common structural grouping for the IPv4 adj-rib-in
      post-policy table";

    uses bgp-common-table-attrs-top;

    container routes {
      config false;
      description
        "Enclosing container for list of routes in the routing
        table.";

      list route {
        key "prefix path-id";

        description
          "List of routes in the table, keyed by a combination of
          the route prefix and path-id to distinguish multiple
          routes received from a neighbor for the same prefix,
          e.g., when BGP add-paths is enabled.";

	leaf prefix {
	  type inet:ipv4-prefix;
	  description
	    "Prefix for the route";
	}

        uses bgp-adj-rib-attr-state;
        uses bgp-adj-rib-common-attr-refs;
        uses bgp-common-route-annotations-state;
        uses bgp-adj-rib-in-post-route-annotations-state;
        uses bgp-unknown-attr-top;
	uses rib-ext-route-annotations;
      }
    }
  }


  grouping ipv4-adj-rib {
    description
      "Top-level grouping for Adj-RIB table";

    container neighbors {
      config false;
      description
        "Enclosing container for neighbor list";

      list neighbor {
        key "neighbor-address";
        description
          "List of neighbors (peers) of the local BGP speaker";

	leaf neighbor-address {
	  type inet:ip-address;
	  description
	    "IP address of the BGP neighbor or peer";
	}

        container adj-rib-in-pre {
          description
            "Per-neighbor table containing the NLRI updates
            received from the neighbor before any local input
            policy rules or filters have been applied.  This can
            be considered the 'raw' updates from the neighbor.";

          uses ipv4-adj-rib-common;

        }

        container adj-rib-in-post {
          description
            "Per-neighbor table containing the paths received from
            the neighbor that are eligible for best-path selection
            after local input policy rules have been applied.";

          uses ipv4-adj-rib-in-post;
        }

        container adj-rib-out-pre {
          description
            "Per-neighbor table containing paths eligble for
            sending (advertising) to the neighbor before output
            policy rules have been applied";

          uses ipv4-adj-rib-common;

        }

        container adj-rib-out-post {
          description
            "Per-neighbor table containing paths eligble for
            sending (advertising) to the neighbor after output
            policy rules have been applied";

          uses ipv4-adj-rib-common;

        }
      }
    }
  }

  grouping ipv6-adj-rib-common {
    description
      "Common structural grouping for each IPv6 adj-RIB table";

    uses bgp-common-table-attrs-state;

    container routes {
      config false;
      description
        "Enclosing container for list of routes in the routing
        table.";

      list route {
        key "prefix path-id";

        description
          "List of routes in the table";

	leaf prefix {
	  type inet:ipv6-prefix;
	  description
	    "Prefix for the route";
	}

        uses bgp-adj-rib-attr-state;
        uses bgp-adj-rib-common-attr-refs;
        uses bgp-common-route-annotations-state;
        uses bgp-unknown-attr-top;
	uses rib-ext-route-annotations;
      }

      uses clear-routes;
    }
  }

  grouping ipv6-adj-rib-in-post {
    description
      "Common structural grouping for the IPv6 adj-rib-in
      post-policy table";

    uses bgp-common-table-attrs-state;

    container routes {
      config false;
      description
        "Enclosing container for list of routes in the routing
        table.";

      list route {
        key "prefix path-id";

        description
          "List of routes in the table";

	leaf prefix {
	  type inet:ipv6-prefix;
	  description
	    "Prefix for the route";
	}

        uses bgp-adj-rib-attr-state;
        uses bgp-adj-rib-common-attr-refs;
        uses bgp-common-route-annotations-state;
        uses bgp-adj-rib-in-post-route-annotations-state;
        uses bgp-unknown-attr-top;
	uses rib-ext-route-annotations;
      }
    }
  }

  grouping ipv6-adj-rib {
    description
      "Top-level grouping for Adj-RIB table";

    container neighbors {
      config false;
      description
        "Enclosing container for neighbor list";

      list neighbor {
        key "neighbor-address";
        description
          "List of neighbors (peers) of the local BGP speaker";

	leaf neighbor-address {
	  type inet:ip-address;
	  description
	    "IP address of the BGP neighbor or peer";
	}

        container adj-rib-in-pre {
          description
            "Per-neighbor table containing the NLRI updates
            received from the neighbor before any local input
            policy rules or filters have been applied.  This can
            be considered the 'raw' updates from the neighbor.";

          uses ipv6-adj-rib-common;

        }

        container adj-rib-in-post {
          description
            "Per-neighbor table containing the paths received from
            the neighbor that are eligible for best-path selection
            after local input policy rules have been applied.";

          uses ipv6-adj-rib-in-post;
        }

        container adj-rib-out-pre {
          description
            "Per-neighbor table containing paths eligble for
            sending (advertising) to the neighbor before output
            policy rules have been applied";

          uses ipv6-adj-rib-common;

        }

        container adj-rib-out-post {
          description
            "Per-neighbor table containing paths eligble for
            sending (advertising) to the neighbor after output
            policy rules have been applied";

          uses ipv6-adj-rib-common;

        }
      }
    }
  }
}
<CODE ENDS>

]]></artwork>
          </figure></t>

        <figure>
          <artwork><![CDATA[
<CODE BEGINS> file "ietf-bgp-rib-table-attributes@2019-06-13.yang"
submodule ietf-bgp-rib-table-attributes {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  // import some basic types
  import ietf-yang-types {
    prefix types;
    reference
      "RFC 6991, Common YANG Data Types.";
  }

  include ietf-bgp-rib-types;
  
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com";

  description
    "This submodule contains common data definitions for data
     related to a RIB entry, or RIB table.";


  revision "2019-06-13" {
    description
      "Initial version.";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Network.";
  }

  grouping bgp-common-route-annotations-state {
    description
      "Data definitions for flags and other information attached
       to routes in both LOC-RIB and Adj-RIB";

    leaf last-modified {
      type types:timeticks;
      description
        "Timestamp when this path was last modified.

         The value is the timestamp in seconds relative to
         the Unix Epoch (Jan 1, 1970 00:00:00 UTC).";
    }

    leaf valid-route {
      type boolean;
      description
        "Indicates that the route is considered valid by the
         local router";
    }

    leaf invalid-reason {
      type identityref {
        base invalid-route-reason;
      }
      description
        "If the route is rejected as invalid, this indicates the
         reason.";
    }
  }

  grouping bgp-loc-rib-route-annotations-state {
    description
      "Data definitions for information attached to routes in the
       LOC-RIB";

       // placeholder for route metadata specific to the LOC-RIB
  }

  grouping bgp-adj-rib-in-post-route-annotations-state {
    description
      "Data definitions for information attached to routes in the
       Adj-RIB-in post-policy table";

    leaf best-path {
      type boolean;
      description
        "Current path was selected as the best path.";
    }
  }

  grouping bgp-common-table-attrs-state {
    description
      "Common attributes attached to all routing tables";

      // placeholder for metadata associated with all tables
  }

  grouping bgp-common-table-attrs-top {
    // no enclosing container as this data will fit under an
    // existing LOC-RIB container

    uses bgp-common-table-attrs-state;
    description
      "Operational state data for data related to the entire
       LOC-RIB";
  }
}
<CODE ENDS>

]]></artwork>
        </figure>
      </section>
    </section>

    <section title="Examples">
      <t>This section tries to show some examples in how the model can be
      used.</t>

      <section title="Creating BGP Instance">
        <t>This example shows how to enable BGP with the IPv4 unicast address
        family, while adding one network to advertise.</t>

        <t><figure>
            <artwork><![CDATA[
[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing
      xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <control-plane-protocols>
      <control-plane-protocol>
	<type
	    xmlns:bgpm="urn:ietf:params:xml:ns:yang:ietf-bgp">bgpm:bgp
	</type>
	<name>BGP</name>
	<bgp
	    xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
	  <global>
	    <as>64496</as>
	    <afi-safis>
	      <afi-safi>
		<afi-safi-name
		    xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-\
unicast
		</afi-safi-name>
	      </afi-safi>
	    </afi-safis>
	  </global>
	</bgp>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>

]]></artwork>
          </figure></t>
      </section>

      <section title="Neighbor Address Family Configuration">
        <t>This example shows how to configure a BGP peer, where the remote
        address is 192.0.2.1, the remote AS number is 64497, and the address
        family of the peer is IPv4 unicast.</t>

        <t><figure>
            <artwork><![CDATA[
[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing
      xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <control-plane-protocols>
      <control-plane-protocol>
	<type
	    xmlns:bgp="urn:ietf:params:xml:ns:yang:ietf-bgp">bgp:bgp
	</type>
	<name>name:BGP</name>
	<bgp
	    xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
	  <global>
	    <as>64496</as>
	    <afi-safis>
	      <afi-safi>
		<afi-safi-name
		    xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-\
unicast
		</afi-safi-name>
	      </afi-safi>
	    </afi-safis>
	  </global>
	  <neighbors>
	    <neighbor>
	      <remote-address>192.0.2.1</remote-address>
	      <peer-as>64497</peer-as>
	      <description>"Peer Router B"</description>
	      <afi-safis>
		<afi-safi>
		  <afi-safi-name
		      xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv\
4-unicast
		  </afi-safi-name>
		</afi-safi>
	      </afi-safis>
	    </neighbor>
	  </neighbors>
	</bgp>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>

]]></artwork>
          </figure></t>
      </section>
    </section>

    <section title="Contributors">
      <t>Previous versions of this document saw contributions from Anees
      Shaikh, Rob Shakir, Kevin D'Souza, Alexander Clemm, Aleksandr Zhadkin,
      and Xyfeng Liu.</t>
    </section>

    <section title="Acknowledgements">
      <t>The authors are grateful for valuable contributions to this document
      and the associated models from: Ebben Aires, Pavan Beeram, Chris Chase,
      Ed Crabbe, Luyuan Fang, Bill Fenner, Akshay Gattani, Josh George, Vijay
      Gill, Matt John, Jeff Haas, Dhanendra Jain, Acee Lindem, Ina Minei, Carl
      Moberg, Ashok Narayanan, Einar Nilsen-Nygaard, Adam Simpson, Puneet
      Sood, Jason Sterne, Jeff Tantsura, Jim Uttaro, and Gunter
      Vandevelde.</t>

      <t>Credit is also due to authors of the OpenConfig, whose model was
      relied upon to come up with this model.</t>

      <t>Special thanks to Robert Wilton who helped convert the YANG models to
      a NMDA compatible model.</t>
    </section>
  </middle>

  <back>
    <references title="Normative references">
      <?rfc include='reference.RFC.1997'?>

      <?rfc include='reference.RFC.2119'?>

      <?rfc include='reference.RFC.2439'?>

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

      <?rfc include='reference.RFC.4271'?>

      <?rfc include='reference.RFC.4456'?>

      <?rfc include='reference.RFC.4724'?>

      <?rfc include='reference.RFC.4760'?>

      <?rfc include='reference.RFC.5065'?>

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

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

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

      <?rfc include='reference.RFC.6811'?>

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

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

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

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

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

      <?rfc include='reference.RFC.8349'?>

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

    <references title="Informative references">
      <?rfc include='reference.RFC.5880'?>

      <?rfc include='reference.RFC.7854'?>

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

      <?rfc include='reference.RFC.8349?>

      <?rfc include='reference.I-D.ietf-rtgwg-policy-model'?>

      <?rfc include='reference.I-D.ietf-bfd-yang'?>
    </references>
  </back>
</rfc>
