<?xml version='1.0' encoding='utf-8'?>
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" version="3" category="std" consensus="true" docName="draft-ietf-bfd-yang-17" indexInclude="true" ipr="trust200902" number="9127" prepTime="2021-10-21T17:11:46" scripts="Common,Latin" sortRefs="true" submissionType="IETF" symRefs="true" tocDepth="6" tocInclude="true" xml:lang="en">
  <link href="https://datatracker.ietf.org/doc/draft-ietf-bfd-yang-17" rel="prev"/>
  <link href="https://dx.doi.org/10.17487/rfc9127" rel="alternate"/>
  <link href="urn:issn:2070-1721" rel="alternate"/>
  <front>
    <title abbrev="BFD YANG">YANG Data Model for Bidirectional Forwarding Detection (BFD)</title>
    <seriesInfo name="RFC" value="9127" stream="IETF"/>
    <author fullname="Reshad Rahman" initials="R." role="editor" surname="Rahman">
      <organization showOnFrontPage="true"/>
      <address>
        <postal>
          <country>Canada</country>
        </postal>
        <email>reshad@yahoo.com</email>
      </address>
    </author>
    <author fullname="Lianshu Zheng" initials="L." role="editor" surname="Zheng">
      <organization showOnFrontPage="true">Huawei Technologies</organization>
      <address>
        <postal>
          <country>China</country>
        </postal>
        <email>veronique_cheng@hotmail.com</email>
      </address>
    </author>
    <author fullname="Mahesh Jethanandani" initials="M." role="editor" surname="Jethanandani">
      <organization showOnFrontPage="true">Xoriant Corporation</organization>
      <address>
        <postal>
          <street>1248 Reamwood Ave</street>
          <city>Sunnyvale</city>
          <region>California</region>
          <code>94089</code>
          <country>United States of America</country>
        </postal>
        <email>mjethanandani@gmail.com</email>
      </address>
    </author>
    <author fullname="Santosh Pallagatti" initials="S." surname="Pallagatti">
      <organization showOnFrontPage="true">VMware</organization>
      <address>
        <postal>
          <country>India</country>
        </postal>
        <email>santosh.pallagatti@gmail.com</email>
      </address>
    </author>
    <author fullname="Greg Mirsky" initials="G." surname="Mirsky">
      <organization showOnFrontPage="true">Ericsson</organization>
      <address>
        <email>gregimirsky@gmail.com</email>
      </address>
    </author>
    <date month="10" year="2021"/>
    <keyword>Liveliness check</keyword>
    <keyword>BGP</keyword>
    <keyword>OSPF</keyword>
    <keyword>IS-IS</keyword>
    <keyword>TCP-AO</keyword>
    <keyword>MD5</keyword>
    <abstract pn="section-abstract">
      <t indent="0" pn="section-abstract-1">This document defines a YANG data model that can be used to configure
      and manage Bidirectional Forwarding Detection (BFD).</t>
      <t indent="0" pn="section-abstract-2">The YANG modules in this document conform to the Network Management
      Datastore Architecture (NMDA) (RFC 8342).</t>
    </abstract>
    <boilerplate>
      <section anchor="status-of-memo" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.1">
        <name slugifiedName="name-status-of-this-memo">Status of This Memo</name>
        <t indent="0" pn="section-boilerplate.1-1">
            This is an Internet Standards Track document.
        </t>
        <t indent="0" pn="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.
        </t>
        <t indent="0" pn="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <eref target="https://www.rfc-editor.org/info/rfc9127" brackets="none"/>.
        </t>
      </section>
      <section anchor="copyright" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.2">
        <name slugifiedName="name-copyright-notice">Copyright Notice</name>
        <t indent="0" pn="section-boilerplate.2-1">
            Copyright (c) 2021 IETF Trust and the persons identified as the
            document authors. All rights reserved.
        </t>
        <t indent="0" pn="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<eref target="https://trustee.ietf.org/license-info" brackets="none"/>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.
        </t>
      </section>
    </boilerplate>
    <toc>
      <section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" pn="section-toc.1">
        <name slugifiedName="name-table-of-contents">Table of Contents</name>
        <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1">
          <li pn="section-toc.1-1.1">
            <t indent="0" keepWithNext="true" pn="section-toc.1-1.1.1"><xref derivedContent="1" format="counter" sectionFormat="of" target="section-1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-introduction">Introduction</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.1.2">
              <li pn="section-toc.1-1.1.2.1">
                <t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.1.1"><xref derivedContent="1.1" format="counter" sectionFormat="of" target="section-1.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-tree-diagrams">Tree Diagrams</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.2">
            <t indent="0" pn="section-toc.1-1.2.1"><xref derivedContent="2" format="counter" sectionFormat="of" target="section-2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-design-of-the-data-model">Design of the Data Model</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.2.2">
              <li pn="section-toc.1-1.2.2.1">
                <t indent="0" pn="section-toc.1-1.2.2.1.1"><xref derivedContent="2.1" format="counter" sectionFormat="of" target="section-2.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-design-of-the-configuration">Design of the Configuration Model</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.2.2.1.2">
                  <li pn="section-toc.1-1.2.2.1.2.1">
                    <t indent="0" keepWithNext="true" pn="section-toc.1-1.2.2.1.2.1.1"><xref derivedContent="2.1.1" format="counter" sectionFormat="of" target="section-2.1.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-common-bfd-configuration-pa">Common BFD Configuration Parameters</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.1.2.2">
                    <t indent="0" pn="section-toc.1-1.2.2.1.2.2.1"><xref derivedContent="2.1.2" format="counter" sectionFormat="of" target="section-2.1.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-single-hop-ip">Single-Hop IP</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.1.2.3">
                    <t indent="0" pn="section-toc.1-1.2.2.1.2.3.1"><xref derivedContent="2.1.3" format="counter" sectionFormat="of" target="section-2.1.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-multihop-ip">Multihop IP</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.1.2.4">
                    <t indent="0" pn="section-toc.1-1.2.2.1.2.4.1"><xref derivedContent="2.1.4" format="counter" sectionFormat="of" target="section-2.1.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-mpls-label-switched-paths">MPLS Label Switched Paths</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.1.2.5">
                    <t indent="0" pn="section-toc.1-1.2.2.1.2.5.1"><xref derivedContent="2.1.5" format="counter" sectionFormat="of" target="section-2.1.5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-link-aggregation-groups">Link Aggregation Groups</xref></t>
                  </li>
                </ul>
              </li>
              <li pn="section-toc.1-1.2.2.2">
                <t indent="0" pn="section-toc.1-1.2.2.2.1"><xref derivedContent="2.2" format="counter" sectionFormat="of" target="section-2.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-design-of-the-operational-s">Design of the Operational State Model</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.3">
                <t indent="0" pn="section-toc.1-1.2.2.3.1"><xref derivedContent="2.3" format="counter" sectionFormat="of" target="section-2.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-notifications">Notifications</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.4">
                <t indent="0" pn="section-toc.1-1.2.2.4.1"><xref derivedContent="2.4" format="counter" sectionFormat="of" target="section-2.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-rpc-operations">RPC Operations</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.5">
                <t indent="0" pn="section-toc.1-1.2.2.5.1"><xref derivedContent="2.5" format="counter" sectionFormat="of" target="section-2.5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-top-level-hierarchy">BFD Top-Level Hierarchy</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.6">
                <t indent="0" pn="section-toc.1-1.2.2.6.1"><xref derivedContent="2.6" format="counter" sectionFormat="of" target="section-2.6"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-ip-single-hop-hierarchy">BFD IP Single-Hop Hierarchy</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.7">
                <t indent="0" pn="section-toc.1-1.2.2.7.1"><xref derivedContent="2.7" format="counter" sectionFormat="of" target="section-2.7"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-ip-multihop-hierarchy">BFD IP Multihop Hierarchy</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.8">
                <t indent="0" pn="section-toc.1-1.2.2.8.1"><xref derivedContent="2.8" format="counter" sectionFormat="of" target="section-2.8"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-over-lag-hierarchy">BFD-over-LAG Hierarchy</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.9">
                <t indent="0" pn="section-toc.1-1.2.2.9.1"><xref derivedContent="2.9" format="counter" sectionFormat="of" target="section-2.9"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-over-mpls-lsps-hierarch">BFD-over-MPLS-LSPs Hierarchy</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.10">
                <t indent="0" pn="section-toc.1-1.2.2.10.1"><xref derivedContent="2.10" format="counter" sectionFormat="of" target="section-2.10"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-interaction-with-other-yang">Interaction with Other YANG Modules</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.2.2.10.2">
                  <li pn="section-toc.1-1.2.2.10.2.1">
                    <t indent="0" pn="section-toc.1-1.2.2.10.2.1.1"><xref derivedContent="2.10.1" format="counter" sectionFormat="of" target="section-2.10.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ietf-interfaces-module">"ietf-interfaces" Module</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.10.2.2">
                    <t indent="0" pn="section-toc.1-1.2.2.10.2.2.1"><xref derivedContent="2.10.2" format="counter" sectionFormat="of" target="section-2.10.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ietf-ip-module">"ietf-ip" Module</xref></t>
                  </li>
                  <li pn="section-toc.1-1.2.2.10.2.3">
                    <t indent="0" pn="section-toc.1-1.2.2.10.2.3.1"><xref derivedContent="2.10.3" format="counter" sectionFormat="of" target="section-2.10.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ietf-mpls-module">"ietf-mpls" Module</xref></t>
                  </li>
                </ul>
              </li>
              <li pn="section-toc.1-1.2.2.11">
                <t indent="0" pn="section-toc.1-1.2.2.11.1"><xref derivedContent="2.11" format="counter" sectionFormat="of" target="section-2.11"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-iana-bfd-yang-module">IANA BFD YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.12">
                <t indent="0" pn="section-toc.1-1.2.2.12.1"><xref derivedContent="2.12" format="counter" sectionFormat="of" target="section-2.12"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-types-yang-module">BFD Types YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.13">
                <t indent="0" pn="section-toc.1-1.2.2.13.1"><xref derivedContent="2.13" format="counter" sectionFormat="of" target="section-2.13"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-top-level-yang-module">BFD Top-Level YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.14">
                <t indent="0" pn="section-toc.1-1.2.2.14.1"><xref derivedContent="2.14" format="counter" sectionFormat="of" target="section-2.14"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-ip-single-hop-yang-modu">BFD IP Single-Hop YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.15">
                <t indent="0" pn="section-toc.1-1.2.2.15.1"><xref derivedContent="2.15" format="counter" sectionFormat="of" target="section-2.15"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-ip-multihop-yang-module">BFD IP Multihop YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.16">
                <t indent="0" pn="section-toc.1-1.2.2.16.1"><xref derivedContent="2.16" format="counter" sectionFormat="of" target="section-2.16"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-over-lag-yang-module">BFD-over-LAG YANG Module</xref></t>
              </li>
              <li pn="section-toc.1-1.2.2.17">
                <t indent="0" pn="section-toc.1-1.2.2.17.1"><xref derivedContent="2.17" format="counter" sectionFormat="of" target="section-2.17"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-bfd-over-mpls-yang-module">BFD-over-MPLS YANG Module</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.3">
            <t indent="0" pn="section-toc.1-1.3.1"><xref derivedContent="3" format="counter" sectionFormat="of" target="section-3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-data-model-examples">Data Model Examples</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.3.2">
              <li pn="section-toc.1-1.3.2.1">
                <t indent="0" pn="section-toc.1-1.3.2.1.1"><xref derivedContent="3.1" format="counter" sectionFormat="of" target="section-3.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ip-single-hop">IP Single-Hop</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.2">
                <t indent="0" pn="section-toc.1-1.3.2.2.1"><xref derivedContent="3.2" format="counter" sectionFormat="of" target="section-3.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ip-multihop">IP Multihop</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.3">
                <t indent="0" pn="section-toc.1-1.3.2.3.1"><xref derivedContent="3.3" format="counter" sectionFormat="of" target="section-3.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-lag">LAG</xref></t>
              </li>
              <li pn="section-toc.1-1.3.2.4">
                <t indent="0" pn="section-toc.1-1.3.2.4.1"><xref derivedContent="3.4" format="counter" sectionFormat="of" target="section-3.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-mpls">MPLS</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.4">
            <t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" format="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-security-considerations">Security Considerations</xref></t>
          </li>
          <li pn="section-toc.1-1.5">
            <t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" format="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-iana-considerations">IANA Considerations</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.5.2">
              <li pn="section-toc.1-1.5.2.1">
                <t indent="0" pn="section-toc.1-1.5.2.1.1"><xref derivedContent="5.1" format="counter" sectionFormat="of" target="section-5.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-iana-maintained-iana-bfd-ty">IANA-Maintained "iana-bfd-types" Module</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.6">
            <t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" format="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-references">References</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.6.2">
              <li pn="section-toc.1-1.6.2.1">
                <t indent="0" pn="section-toc.1-1.6.2.1.1"><xref derivedContent="6.1" format="counter" sectionFormat="of" target="section-6.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-normative-references">Normative References</xref></t>
              </li>
              <li pn="section-toc.1-1.6.2.2">
                <t indent="0" pn="section-toc.1-1.6.2.2.1"><xref derivedContent="6.2" format="counter" sectionFormat="of" target="section-6.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-informative-references">Informative References</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.7">
            <t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="Appendix A" format="default" sectionFormat="of" target="section-appendix.a"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-echo-function-configuration">Echo Function Configuration Example</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.7.2">
              <li pn="section-toc.1-1.7.2.1">
                <t indent="0" pn="section-toc.1-1.7.2.1.1"><xref derivedContent="A.1" format="counter" sectionFormat="of" target="section-appendix.a.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-example-yang-module-for-bfd">Example YANG Module for BFD Echo Function Configuration</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.8">
            <t indent="0" pn="section-toc.1-1.8.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="" format="title" sectionFormat="of" target="name-acknowledgments">Acknowledgments</xref></t>
          </li>
          <li pn="section-toc.1-1.9">
            <t indent="0" pn="section-toc.1-1.9.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.c"/><xref derivedContent="" format="title" sectionFormat="of" target="name-authors-addresses">Authors' Addresses</xref></t>
          </li>
        </ul>
      </section>
    </toc>
  </front>
  <middle>
    <section numbered="true" toc="include" removeInRFC="false" pn="section-1">
      <name slugifiedName="name-introduction">Introduction</name>
      <t indent="0" pn="section-1-1">This document defines a YANG data model that can be used to configure 
      and manage Bidirectional Forwarding Detection (BFD) <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/>. BFD is a network protocol that is used
      for liveness detection of arbitrary paths between systems. Some examples
      of different types of paths over which we have BFD are as follows:</t>
      <ol spacing="normal" type="1" indent="adaptive" start="1" pn="section-1-2">
      <li pn="section-1-2.1" derivedCounter="1.">Two systems directly connected via IP. This is known as BFD over
      single-hop IP, a.k.a. <xref target="RFC5881" format="default" sectionFormat="of" derivedContent="RFC5881">BFD for
      IPv4 and IPv6</xref>.</li>
        <li pn="section-1-2.2" derivedCounter="2.">Two systems connected via multiple hops as described in <xref target="RFC5883" format="default" sectionFormat="of" derivedContent="RFC5883">"Bidirectional Forwarding Detection
      (BFD) for Multihop Paths"</xref>.</li>
        <li pn="section-1-2.3" derivedCounter="3.">Two systems connected via MPLS Label Switched Paths (LSPs) as
      described in <xref target="RFC5884" format="default" sectionFormat="of" derivedContent="RFC5884">"Bidirectional
      Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)"</xref>.</li>
        <li pn="section-1-2.4" derivedCounter="4.">Two systems connected via a Link Aggregation Group (LAG) interface
      as described in <xref target="RFC7130" format="default" sectionFormat="of" derivedContent="RFC7130">"Bidirectional
      Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces"</xref>.</li>
        <li pn="section-1-2.5" derivedCounter="5.">Two systems connected via pseudowires (PWs). This is known as
      Virtual Circuit Connectivity Verification (VCCV), as described in <xref target="RFC5885" format="default" sectionFormat="of" derivedContent="RFC5885">"Bidirectional
      Forwarding Detection (BFD) for the Pseudowire Virtual
      Circuit Connectivity Verification (VCCV)"</xref>. This scenario is not
      addressed in this document.</li>
      </ol>
      <t indent="0" pn="section-1-3">BFD typically does not operate on its own. Various control protocols,
      also known as BFD clients, use the services provided by BFD for their
      own operation, as described in <xref target="RFC5882" format="default" sectionFormat="of" derivedContent="RFC5882">"Generic Application of Bidirectional Forwarding
      Detection (BFD)"</xref>. The obvious
      candidates that use BFD are those that do not have "hellos" to detect
      failures, e.g., static routes, and routing protocols whose "hellos" do
      not support sub-second failure detection, e.g., OSPF and IS-IS.</t>
      <t indent="0" pn="section-1-4">The YANG modules in this document conform to the <xref target="RFC8342" format="default" sectionFormat="of" derivedContent="RFC8342">Network Management Datastore
      Architecture (NMDA)</xref>. This means that the data models do not have
      separate top-level or sibling containers for configuration data and
      operational state data.</t>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-1.1">
        <name slugifiedName="name-tree-diagrams">Tree Diagrams</name>
        <t indent="0" pn="section-1.1-1">This document uses the graphical representation of data models, as defined in
            <xref target="RFC8340" format="default" sectionFormat="of" derivedContent="RFC8340"/>.</t>
      </section>
    </section>
    <section anchor="DESIGN-DATA" numbered="true" toc="include" removeInRFC="false" pn="section-2">
      <name slugifiedName="name-design-of-the-data-model">Design of the Data Model</name>
      <t indent="0" pn="section-2-1">Since BFD is used for liveness detection of various forwarding
      paths, there is no uniform key to identify a BFD session, and so the BFD
      data model is split into multiple YANG modules where each module
      corresponds to one type of forwarding path. For example, BFD for IP
      single-hop is in one YANG module, and BFD for MPLS is in another YANG
      module. The main difference between these modules is how a BFD session
      is uniquely identified, i.e., the key for the list containing the BFD
      sessions for that forwarding path. To avoid duplication of BFD
      definitions, we have common types and groupings that are used by all
      the modules.</t>
      <t indent="0" pn="section-2-2">A new control-plane protocol, "bfdv1", is defined, and a "bfd" container
      is created under "control-plane-protocol" as specified in <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349">"A YANG Data Model for Routing
      Management (NMDA Version)"</xref>. This new "bfd" container is augmented
      by the following YANG modules for their respective specific information:
      </t>
      <ol spacing="normal" type="1" indent="adaptive" start="1" pn="section-2-3">
        <li pn="section-2-3.1" derivedCounter="1.">The "ietf-bfd-ip-sh" module (<xref target="bfd-ip-single-hop-module" format="default" sectionFormat="of" derivedContent="Section 2.14"/>) augments
          "/routing/control-plane-protocols/control-plane-protocol/bfd/" with
          the "ip-sh" container for BFD sessions over IP single-hop.</li>
        <li pn="section-2-3.2" derivedCounter="2.">The "ietf-bfd-ip-mh" module (<xref target="bfd-ip-multihop-module" format="default" sectionFormat="of" derivedContent="Section 2.15"/>) augments
          "/routing/control-plane-protocols/control-plane-protocol/bfd/" with
          the "ip-mh" container for BFD sessions over IP multihop.</li>
        <li pn="section-2-3.3" derivedCounter="3.">The "ietf-bfd-lag" module (<xref target="bfd-over-lag-module" format="default" sectionFormat="of" derivedContent="Section 2.16"/>) augments
          "/routing/control-plane-protocols/control-plane-protocol/bfd/" with
          the "lag" container for BFD sessions over a LAG.</li>
        <li pn="section-2-3.4" derivedCounter="4.">The "ietf-bfd-mpls" module (<xref target="bfd-over-mpls-module" format="default" sectionFormat="of" derivedContent="Section 2.17"/>) augments
          "/routing/control-plane-protocols/control-plane-protocol/bfd/" with
          the "mpls" container for BFD-over-MPLS LSPs.</li>
      </ol>
      <t indent="0" pn="section-2-4">BFD can operate in the following contexts:</t>
      <ol spacing="normal" type="1" indent="adaptive" start="1" pn="section-2-5">
        <li pn="section-2-5.1" derivedCounter="1.">At the network device level.</li>
        <li pn="section-2-5.2" derivedCounter="2.">In logical network elements (LNEs) as described in <xref target="RFC8530" format="default" sectionFormat="of" derivedContent="RFC8530">"YANG Model for Logical Network Elements"</xref>.</li>
        <li pn="section-2-5.3" derivedCounter="3.">In network instances as described in <xref target="RFC8529" format="default" sectionFormat="of" derivedContent="RFC8529">"YANG Data Model for Network Instances"</xref>.</li>
      </ol>
      <t indent="0" pn="section-2-6"> When used at the network device level, the BFD YANG data model is
        used "as is". When the BFD YANG data model is used in an LNE or network instance, the BFD YANG data model augments
        the mounted routing model for the LNE or network instance.</t>
      <section anchor="CFG-MODEL" numbered="true" toc="include" removeInRFC="false" pn="section-2.1">
        <name slugifiedName="name-design-of-the-configuration">Design of the Configuration Model</name>
        <t indent="0" pn="section-2.1-1">The configuration model consists mainly of the parameters specified
        in <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD</xref> -- for example, desired
        minimum transmit interval, required minimum receive interval, and
        detection multiplier.</t>
        <t indent="0" pn="section-2.1-2">BFD clients are applications that use BFD for fast detection of
        failures. Some implementations have BFD session configuration under
        the BFD clients -- for example, BFD session configuration under routing
        applications such as OSPF, IS-IS, or BGP. Other implementations have
        BFD session configuration centralized under BFD, i.e., outside the
        multiple BFD clients.</t>
        <t indent="0" pn="section-2.1-3">The main BFD parameters of interest to a BFD client are those
        related to the
        multiplier and interval(s), since those parameters impact the
        convergence time of the BFD clients when a failure occurs. Other
        parameters, such as BFD authentication, are not specific to the
        requirements of the BFD client. Configuration of BFD for all
        clients should be centralized. However, this is a problem for BFD clients
        that auto-discover their peers. For example, IGPs do not have the
        peer address configured; instead, the IGP is enabled on an interface,
        and the IGP peers are auto-discovered. So, for an operator to configure
        BFD to an IGP peer, the operator would first have to determine the
        peer addresses. And when a new peer is discovered, BFD configuration
        would need to be added. To avoid this issue, we define the grouping
        "client-cfg-parms" in <xref target="BFD-TYPES" format="default" sectionFormat="of" derivedContent="Section 2.12"/> for BFD clients to
        configure BFD: this allows BFD clients, such as the IGPs, to have
        configuration (multiplier and intervals) for the BFD sessions they
        need. For example, when a new IGP peer is discovered, the IGP would
        create a BFD session to the newly discovered peer; similarly, when
        an IGP peer goes away, the IGP would remove the BFD session to that
        peer. The mechanism for how the BFD sessions are created and removed by
        the BFD clients is outside the scope of this document, but
        this would typically be done by using an API implemented by the BFD module on
        the system. In the case of BFD clients that create BFD sessions via their own
        configuration, authentication parameters (if required) are still
        specified in BFD.</t>
        <section anchor="BFD-COMMON-CFG" numbered="true" toc="include" removeInRFC="false" pn="section-2.1.1">
          <name slugifiedName="name-common-bfd-configuration-pa">Common BFD Configuration Parameters</name>
          <t indent="0" pn="section-2.1.1-1">The basic BFD configuration parameters are as follows:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.1.1-2">
            <dt pn="section-2.1.1-2.1">local-multiplier</dt>
            <dd pn="section-2.1.1-2.2">This is the detection time multiplier as defined in <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD</xref>.</dd>
            <dt pn="section-2.1.1-2.3">desired-min-tx-interval</dt>
            <dd pn="section-2.1.1-2.4">This is the Desired Min TX Interval as defined in <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD</xref>.</dd>
            <dt pn="section-2.1.1-2.5">required-min-rx-interval</dt>
            <dd pn="section-2.1.1-2.6">This is the Required Min RX Interval as defined in <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD</xref>.</dd>
          </dl>
          <t indent="0" pn="section-2.1.1-3">Although <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD</xref>
          allows for different values for transmit and receive intervals, some 
          implementations allow users to specify just one interval that is
          used for both transmit and receive intervals, or separate values for
          transmit and receive intervals. The BFD YANG data model supports this:
          there is a choice between "min-interval", used for both transmit and
          receive intervals, and "desired-min-tx-interval" and
          "required-min-rx-interval". This is supported via the
          "base-cfg-parms" grouping (<xref target="BFD-TYPES" format="default" sectionFormat="of" derivedContent="Section 2.12"/>), which
          is used by the YANG modules for the various forwarding paths.</t>
          <t indent="0" pn="section-2.1.1-4">For BFD authentication, we have the following:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.1.1-5">
            <dt pn="section-2.1.1-5.1">key-chain</dt>
            <dd pn="section-2.1.1-5.2">This is a reference to "key-chain" as defined in <xref target="RFC8177" format="default" sectionFormat="of" derivedContent="RFC8177">"YANG Data Model for Key
            Chains"</xref>. The keys, cryptographic algorithms, key lifetime,
            etc. are all defined in the "key-chain" model.</dd>
            <dt pn="section-2.1.1-5.3">meticulous</dt>
            <dd pn="section-2.1.1-5.4">This enables a meticulous mode as per <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880">BFD </xref>.</dd>
          </dl>
        </section>
        <section anchor="IP-SH-CFG" numbered="true" toc="include" removeInRFC="false" pn="section-2.1.2">
          <name slugifiedName="name-single-hop-ip">Single-Hop IP</name>
          <t indent="0" pn="section-2.1.2-1">For single-hop IP, there is an augment of the "bfd" data node, as
          described in 
          <xref target="DESIGN-DATA" format="default" sectionFormat="of" derivedContent="Section 2"/>. The "ip-sh" node
          contains a list of IP single-hop sessions where each session is
          uniquely identified by the interface and destination address
          pair. We use the configuration parameters defined in
          <xref target="BFD-COMMON-CFG" format="default" sectionFormat="of" derivedContent="Section 2.1.1"/>. The "ip-sh" node
          also contains a list of interfaces and is used to specify
          authentication parameters for BFD sessions that are created by BFD
          clients. See <xref target="CFG-MODEL" format="default" sectionFormat="of" derivedContent="Section 2.1"/>.</t>
          <t indent="0" pn="section-2.1.2-2"><xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> and <xref target="RFC5881" format="default" sectionFormat="of" derivedContent="RFC5881"/> do not specify whether
          the Echo function operates continuously or on demand. Therefore, the mechanism used to
          start and stop the Echo function is implementation specific and should
          be done by augmentation:</t>
          <ol spacing="normal" type="1" indent="adaptive" start="1" pn="section-2.1.2-3">
            <li pn="section-2.1.2-3.1" derivedCounter="1.">Configuration. This is suitable for an Echo function that
            operates continuously. An example is provided in <xref target="ECHO-CONFIG" format="default" sectionFormat="of" derivedContent="Appendix A"/>.</li>
            <li pn="section-2.1.2-3.2" derivedCounter="2.">RPC. This is suitable for an Echo function that operates 
            on demand.</li>
          </ol>
        </section>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.1.3">
          <name slugifiedName="name-multihop-ip">Multihop IP</name>
          <t indent="0" pn="section-2.1.3-1">For multihop IP, there is an augment of the "bfd" data node, as described in
          <xref target="DESIGN-DATA" format="default" sectionFormat="of" derivedContent="Section 2"/>.</t>
          <t indent="0" pn="section-2.1.3-2">Because of multiple paths, there could be multiple multihop IP
          sessions between a source and a destination address. We identify
          this set of sessions as a "session-group". The key for each "session-group" consists
          of the following:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.1.3-3">
            <dt pn="section-2.1.3-3.1">Source address</dt>
            <dd pn="section-2.1.3-3.2">Address belonging to the local system as per <xref target="RFC5883" format="default" sectionFormat="of" derivedContent="RFC5883">"Bidirectional Forwarding
            Detection (BFD) for Multihop Paths"</xref>.</dd>
            <dt pn="section-2.1.3-3.3">Destination address</dt>
            <dd pn="section-2.1.3-3.4">Address belonging to the remote system as per <xref target="RFC5883" format="default" sectionFormat="of" derivedContent="RFC5883"/>.</dd>
          </dl>
          <t indent="0" pn="section-2.1.3-4">We use the configuration parameters defined in <xref target="BFD-COMMON-CFG" format="default" sectionFormat="of" derivedContent="Section 2.1.1"/>.</t>
          <t indent="0" pn="section-2.1.3-5">This document also provides the following parameters:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.1.3-6">
            <dt pn="section-2.1.3-6.1">tx-ttl</dt>
            <dd pn="section-2.1.3-6.2">TTL of outgoing BFD control packets.</dd>
            <dt pn="section-2.1.3-6.3">rx-ttl</dt>
            <dd pn="section-2.1.3-6.4">Minimum TTL of incoming BFD control packets.</dd>
          </dl>
        </section>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.1.4">
          <name slugifiedName="name-mpls-label-switched-paths">MPLS Label Switched Paths</name>
          <t indent="0" pn="section-2.1.4-1">Here, we address MPLS LSPs whose 
          Forwarding Equivalence Class (FEC) <xref target="RFC3031" format="default" sectionFormat="of" derivedContent="RFC3031"/> is an IP
          address. The "bfd"
          node (<xref target="DESIGN-DATA" format="default" sectionFormat="of" derivedContent="Section 2"/>) is augmented
          with "mpls", which contains a list of sessions uniquely identified by
          an IP prefix. Because of multiple paths, there could be multiple
          MPLS sessions to an MPLS FEC. We identify this set of sessions as a
          "session-group".</t>
          <t indent="0" pn="section-2.1.4-2">Since these LSPs are unidirectional, there is no LSP
          configuration on the egress node.</t>
          <t indent="0" pn="section-2.1.4-3">The BFD parameters for the egress node are added under
          "mpls".</t>
        </section>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.1.5">
          <name slugifiedName="name-link-aggregation-groups">Link Aggregation Groups</name>
          <t indent="0" pn="section-2.1.5-1">Per <xref target="RFC7130" format="default" sectionFormat="of" derivedContent="RFC7130">"Bidirectional
          Forwarding Detection (BFD) on Link Aggregation Group (LAG)
          Interfaces"</xref>, configuring BFD on a LAG consists of having micro-BFD
          sessions on each LAG member link. Since the BFD parameters are an
          attribute of the LAG, they should be under the LAG. However, there is
          no LAG YANG data model that we can augment. So, a "lag" data node is
          added to the "bfd" node; see <xref target="DESIGN-DATA" format="default" sectionFormat="of" derivedContent="Section 2"/>. The configuration is per LAG: we have a list of
          LAGs. The destination IP address of the micro-BFD sessions is
          configured per LAG and per address family (IPv4 and IPv6).</t>
        </section>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.2">
        <name slugifiedName="name-design-of-the-operational-s">Design of the Operational State Model</name>
        <t indent="0" pn="section-2.2-1">The operational state model contains both the overall statistics for
        the BFD sessions running on the device and the per-session operational
        information.</t>
        <t indent="0" pn="section-2.2-2">The overall statistics for the BFD sessions consist of the number of BFD
        sessions, the number of BFD sessions that are up, etc. This information is available
        globally (i.e., for all BFD sessions) under the "bfd" node 
        (<xref target="DESIGN-DATA" format="default" sectionFormat="of" derivedContent="Section 2"/>) and also per type of
        forwarding path.</t>
        <t indent="0" pn="section-2.2-3">For each BFD session, three main categories of operational state
        data are shown.</t>
        <ol spacing="normal" type="1" indent="adaptive" start="1" pn="section-2.2-4">
       <li pn="section-2.2-4.1" derivedCounter="1.">The first category includes fundamental information regarding a BFD session, such as
        the local discriminator, the remote discriminator, and the ability to
        support Demand mode.</li>
          <li pn="section-2.2-4.2" derivedCounter="2.">The
        second category includes BFD "session-running" information, e.g., the
        remote BFD state and the diagnostic code received. Another example is
        the actual transmit interval between the control packets, which may be
        different from the configured desired minimum transmit
        interval. Similar examples include the actual receive interval
        between the control packets and the actual transmit interval between
        the Echo packets.</li>
          <li pn="section-2.2-4.3" derivedCounter="3."> The third category contains the detailed statistics
        for the session, e.g., when the session transitioned up/down and how
        long it has been in that state.</li>
        </ol>
        <t indent="0" pn="section-2.2-5">For some path types, there may be more than one session on the
        virtual path to the destination. For example, with IP multihop and
        MPLS LSPs, there could be multiple BFD sessions from the source to the
        same destination to test the various paths (ECMP) to the destination.
        This is represented by having multiple "sessions" under each
        "session-group".</t>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.3">
        <name slugifiedName="name-notifications">Notifications</name>
        <t indent="0" pn="section-2.3-1">This YANG data model defines notifications to inform end users of
        important events detected during the protocol operation. The
        local discriminator identifies the corresponding BFD session on the
        local system, and the remote discriminator identifies the BFD session
        on the remote system.
        Notifications also give more important details about BFD sessions,
        e.g., new state, time in previous state, network instance, and the
        reason that the BFD session state changed. The notifications are
        defined for each type of forwarding path but use groupings for common
        information.</t>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.4">
        <name slugifiedName="name-rpc-operations">RPC Operations</name>
        <t indent="0" pn="section-2.4-1">None.</t>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.5">
        <name slugifiedName="name-bfd-top-level-hierarchy">BFD Top-Level Hierarchy</name>
        <t indent="0" pn="section-2.5-1">At the "bfd" node under "control-plane-protocol", there is no
        configuration data -- only operational state data. The operational state 
        data consists of overall BFD session statistics, i.e., for BFD on all
        types of forwarding paths.</t>
        <sourcecode type="yangtree" markers="false" pn="section-2.5-2">
module: ietf-bfd
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol:
    +--rw bfd
       +--ro summary
          +--ro number-of-sessions?              yang:gauge32
          +--ro number-of-sessions-up?           yang:gauge32
          +--ro number-of-sessions-down?         yang:gauge32
          +--ro number-of-sessions-admin-down?   yang:gauge32
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.6">
        <name slugifiedName="name-bfd-ip-single-hop-hierarchy">BFD IP Single-Hop Hierarchy</name>
        <t indent="0" pn="section-2.6-1">An "ip-sh" node is added under the "bfd" node in
        "control-plane-protocol". The configuration data and operational state data
        for each BFD IP single-hop session are under this "ip-sh" node.</t>
        <sourcecode type="yangtree" markers="false" pn="section-2.6-2">
module: ietf-bfd-ip-sh
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/bfd:bfd:
    +--rw ip-sh
       +--ro summary
       |  +--ro number-of-sessions?              yang:gauge32
       |  +--ro number-of-sessions-up?           yang:gauge32
       |  +--ro number-of-sessions-down?         yang:gauge32
       |  +--ro number-of-sessions-admin-down?   yang:gauge32
       +--rw sessions
       |  +--rw session* [interface dest-addr]
       |     +--rw interface                         if:interface-ref
       |     +--rw dest-addr                         inet:ip-address
       |     +--rw source-addr?                      inet:ip-address
       |     +--rw local-multiplier?                 multiplier
       |     +--rw (interval-config-type)?
       |     |  +--:(tx-rx-intervals)
       |     |  |  +--rw desired-min-tx-interval?    uint32
       |     |  |  +--rw required-min-rx-interval?   uint32
       |     |  +--:(single-interval) {single-minimum-interval}?
       |     |     +--rw min-interval?               uint32
       |     +--rw demand-enabled?                   boolean
       |     |       {demand-mode}?
       |     +--rw admin-down?                       boolean
       |     +--rw authentication! {authentication}?
       |     |  +--rw key-chain?    key-chain:key-chain-ref
       |     |  +--rw meticulous?   boolean
       |     +--ro path-type?                        identityref
       |     +--ro ip-encapsulation?                 boolean
       |     +--ro local-discriminator?              discriminator
       |     +--ro remote-discriminator?             discriminator
       |     +--ro remote-multiplier?                multiplier
       |     +--ro demand-capability?                boolean
       |     |       {demand-mode}?
       |     +--ro source-port?                      inet:port-number
       |     +--ro dest-port?                        inet:port-number
       |     +--ro session-running
       |     |  +--ro session-index?                uint32
       |     |  +--ro local-state?                  state
       |     |  +--ro remote-state?                 state
       |     |  +--ro local-diagnostic?
       |     |  |       iana-bfd-types:diagnostic
       |     |  +--ro remote-diagnostic?
       |     |  |       iana-bfd-types:diagnostic
       |     |  +--ro remote-authenticated?         boolean
       |     |  +--ro remote-authentication-type?
       |     |  |       iana-bfd-types:auth-type {authentication}?
       |     |  +--ro detection-mode?               enumeration
       |     |  +--ro negotiated-tx-interval?       uint32
       |     |  +--ro negotiated-rx-interval?       uint32
       |     |  +--ro detection-time?               uint32
       |     |  +--ro echo-tx-interval-in-use?      uint32
       |     |          {echo-mode}?
       |     +--ro session-statistics
       |        +--ro create-time?
       |        |       yang:date-and-time
       |        +--ro last-down-time?
       |        |       yang:date-and-time
       |        +--ro last-up-time?
       |        |       yang:date-and-time
       |        +--ro down-count?                     yang:counter32
       |        +--ro admin-down-count?               yang:counter32
       |        +--ro receive-packet-count?           yang:counter64
       |        +--ro send-packet-count?              yang:counter64
       |        +--ro receive-invalid-packet-count?   yang:counter64
       |        +--ro send-failed-packet-count?       yang:counter64
       +--rw interfaces* [interface]
          +--rw interface         if:interface-ref
          +--rw authentication! {authentication}?
             +--rw key-chain?    key-chain:key-chain-ref
             +--rw meticulous?   boolean

  notifications:
    +---n singlehop-notification
       +--ro local-discr?                 discriminator
       +--ro remote-discr?                discriminator
       +--ro new-state?                   state
       +--ro state-change-reason?         iana-bfd-types:diagnostic
       +--ro time-of-last-state-change?   yang:date-and-time
       +--ro dest-addr?                   inet:ip-address
       +--ro source-addr?                 inet:ip-address
       +--ro session-index?               uint32
       +--ro path-type?                   identityref
       +--ro interface?                   if:interface-ref
       +--ro echo-enabled?                boolean
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.7">
        <name slugifiedName="name-bfd-ip-multihop-hierarchy">BFD IP Multihop Hierarchy</name>
        <t indent="0" pn="section-2.7-1">An "ip-mh" node is added under the "bfd" node in
        "control-plane-protocol". The configuration data and operational state data
        for each BFD IP multihop session are under this "ip-mh" node. In the
        operational state model, we support multiple BFD multihop sessions per
        remote address (ECMP); the local discriminator is used as the key.</t>
        <sourcecode type="yangtree" markers="false" pn="section-2.7-2">
module: ietf-bfd-ip-mh
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/bfd:bfd:
    +--rw ip-mh
       +--ro summary
       |  +--ro number-of-sessions?              yang:gauge32
       |  +--ro number-of-sessions-up?           yang:gauge32
       |  +--ro number-of-sessions-down?         yang:gauge32
       |  +--ro number-of-sessions-admin-down?   yang:gauge32
       +--rw session-groups
          +--rw session-group* [source-addr dest-addr]
             +--rw source-addr                       inet:ip-address
             +--rw dest-addr                         inet:ip-address
             +--rw local-multiplier?                 multiplier
             +--rw (interval-config-type)?
             |  +--:(tx-rx-intervals)
             |  |  +--rw desired-min-tx-interval?    uint32
             |  |  +--rw required-min-rx-interval?   uint32
             |  +--:(single-interval) {single-minimum-interval}?
             |     +--rw min-interval?               uint32
             +--rw demand-enabled?                   boolean
             |       {demand-mode}?
             +--rw admin-down?                       boolean
             +--rw authentication! {authentication}?
             |  +--rw key-chain?    key-chain:key-chain-ref
             |  +--rw meticulous?   boolean
             +--rw tx-ttl?                           bfd-types:hops
             +--rw rx-ttl                            bfd-types:hops
             +--ro sessions* []
                +--ro path-type?              identityref
                +--ro ip-encapsulation?       boolean
                +--ro local-discriminator?    discriminator
                +--ro remote-discriminator?   discriminator
                +--ro remote-multiplier?      multiplier
                +--ro demand-capability?      boolean {demand-mode}?
                +--ro source-port?            inet:port-number
                +--ro dest-port?              inet:port-number
                +--ro session-running
                |  +--ro session-index?                uint32
                |  +--ro local-state?                  state
                |  +--ro remote-state?                 state
                |  +--ro local-diagnostic?
                |  |       iana-bfd-types:diagnostic
                |  +--ro remote-diagnostic?
                |  |       iana-bfd-types:diagnostic
                |  +--ro remote-authenticated?         boolean
                |  +--ro remote-authentication-type?
                |  |       iana-bfd-types:auth-type {authentication}?
                |  +--ro detection-mode?               enumeration
                |  +--ro negotiated-tx-interval?       uint32
                |  +--ro negotiated-rx-interval?       uint32
                |  +--ro detection-time?               uint32
                |  +--ro echo-tx-interval-in-use?      uint32
                |          {echo-mode}?
                +--ro session-statistics
                   +--ro create-time?
                   |       yang:date-and-time
                   +--ro last-down-time?
                   |       yang:date-and-time
                   +--ro last-up-time?
                   |       yang:date-and-time
                   +--ro down-count?
                   |       yang:counter32
                   +--ro admin-down-count?
                   |       yang:counter32
                   +--ro receive-packet-count?
                   |       yang:counter64
                   +--ro send-packet-count?
                   |       yang:counter64
                   +--ro receive-invalid-packet-count?
                   |       yang:counter64
                   +--ro send-failed-packet-count?
                           yang:counter64

  notifications:
    +---n multihop-notification
       +--ro local-discr?                 discriminator
       +--ro remote-discr?                discriminator
       +--ro new-state?                   state
       +--ro state-change-reason?         iana-bfd-types:diagnostic
       +--ro time-of-last-state-change?   yang:date-and-time
       +--ro dest-addr?                   inet:ip-address
       +--ro source-addr?                 inet:ip-address
       +--ro session-index?               uint32
       +--ro path-type?                   identityref
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.8">
        <name slugifiedName="name-bfd-over-lag-hierarchy">BFD-over-LAG Hierarchy</name>
        <t indent="0" pn="section-2.8-1">A "lag" node is added under the "bfd" node in
        "control-plane-protocol". The configuration data and operational state data
        for each BFD LAG session are under this "lag" node.</t>
        <sourcecode type="yangtree" markers="false" pn="section-2.8-2">
module: ietf-bfd-lag
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/bfd:bfd:
    +--rw lag
       +--rw micro-bfd-ipv4-session-statistics
       |  +--ro summary
       |     +--ro number-of-sessions?              yang:gauge32
       |     +--ro number-of-sessions-up?           yang:gauge32
       |     +--ro number-of-sessions-down?         yang:gauge32
       |     +--ro number-of-sessions-admin-down?   yang:gauge32
       +--rw micro-bfd-ipv6-session-statistics
       |  +--ro summary
       |     +--ro number-of-sessions?              yang:gauge32
       |     +--ro number-of-sessions-up?           yang:gauge32
       |     +--ro number-of-sessions-down?         yang:gauge32
       |     +--ro number-of-sessions-admin-down?   yang:gauge32
       +--rw sessions
          +--rw session* [lag-name]
             +--rw lag-name                          if:interface-ref
             +--rw ipv4-dest-addr?
             |       inet:ipv4-address
             +--rw ipv6-dest-addr?
             |       inet:ipv6-address
             +--rw local-multiplier?                 multiplier
             +--rw (interval-config-type)?
             |  +--:(tx-rx-intervals)
             |  |  +--rw desired-min-tx-interval?    uint32
             |  |  +--rw required-min-rx-interval?   uint32
             |  +--:(single-interval) {single-minimum-interval}?
             |     +--rw min-interval?               uint32
             +--rw demand-enabled?                   boolean
             |       {demand-mode}?
             +--rw admin-down?                       boolean
             +--rw authentication! {authentication}?
             |  +--rw key-chain?    key-chain:key-chain-ref
             |  +--rw meticulous?   boolean
             +--rw use-ipv4?                         boolean
             +--rw use-ipv6?                         boolean
             +--ro member-links* [member-link]
                +--ro member-link       if:interface-ref
                +--ro micro-bfd-ipv4
                |  +--ro path-type?              identityref
                |  +--ro ip-encapsulation?       boolean
                |  +--ro local-discriminator?    discriminator
                |  +--ro remote-discriminator?   discriminator
                |  +--ro remote-multiplier?      multiplier
                |  +--ro demand-capability?      boolean
                |  |       {demand-mode}?
                |  +--ro source-port?            inet:port-number
                |  +--ro dest-port?              inet:port-number
                |  +--ro session-running
                |  |  +--ro session-index?                uint32
                |  |  +--ro local-state?                  state
                |  |  +--ro remote-state?                 state
                |  |  +--ro local-diagnostic?
                |  |  |       iana-bfd-types:diagnostic
                |  |  +--ro remote-diagnostic?
                |  |  |       iana-bfd-types:diagnostic
                |  |  +--ro remote-authenticated?         boolean
                |  |  +--ro remote-authentication-type?
                |  |  |       iana-bfd-types:auth-type
                |  |  |       {authentication}?
                |  |  +--ro detection-mode?               enumeration
                |  |  +--ro negotiated-tx-interval?       uint32
                |  |  +--ro negotiated-rx-interval?       uint32
                |  |  +--ro detection-time?               uint32
                |  |  +--ro echo-tx-interval-in-use?      uint32
                |  |          {echo-mode}?
                |  +--ro session-statistics
                |     +--ro create-time?
                |     |       yang:date-and-time
                |     +--ro last-down-time?
                |     |       yang:date-and-time
                |     +--ro last-up-time?
                |     |       yang:date-and-time
                |     +--ro down-count?
                |     |       yang:counter32
                |     +--ro admin-down-count?
                |     |       yang:counter32
                |     +--ro receive-packet-count?
                |     |       yang:counter64
                |     +--ro send-packet-count?
                |     |       yang:counter64
                |     +--ro receive-invalid-packet-count?
                |     |       yang:counter64
                |     +--ro send-failed-packet-count?
                |             yang:counter64
                +--ro micro-bfd-ipv6
                   +--ro path-type?              identityref
                   +--ro ip-encapsulation?       boolean
                   +--ro local-discriminator?    discriminator
                   +--ro remote-discriminator?   discriminator
                   +--ro remote-multiplier?      multiplier
                   +--ro demand-capability?      boolean
                   |       {demand-mode}?
                   +--ro source-port?            inet:port-number
                   +--ro dest-port?              inet:port-number
                   +--ro session-running
                   |  +--ro session-index?                uint32
                   |  +--ro local-state?                  state
                   |  +--ro remote-state?                 state
                   |  +--ro local-diagnostic?
                   |  |       iana-bfd-types:diagnostic
                   |  +--ro remote-diagnostic?
                   |  |       iana-bfd-types:diagnostic
                   |  +--ro remote-authenticated?         boolean
                   |  +--ro remote-authentication-type?
                   |  |       iana-bfd-types:auth-type
                   |  |       {authentication}?
                   |  +--ro detection-mode?               enumeration
                   |  +--ro negotiated-tx-interval?       uint32
                   |  +--ro negotiated-rx-interval?       uint32
                   |  +--ro detection-time?               uint32
                   |  +--ro echo-tx-interval-in-use?      uint32
                   |          {echo-mode}?
                   +--ro session-statistics
                      +--ro create-time?
                      |       yang:date-and-time
                      +--ro last-down-time?
                      |       yang:date-and-time
                      +--ro last-up-time?
                      |       yang:date-and-time
                      +--ro down-count?
                      |       yang:counter32
                      +--ro admin-down-count?
                      |       yang:counter32
                      +--ro receive-packet-count?
                      |       yang:counter64
                      +--ro send-packet-count?
                      |       yang:counter64
                      +--ro receive-invalid-packet-count?
                      |       yang:counter64
                      +--ro send-failed-packet-count?
                              yang:counter64

  notifications:
    +---n lag-notification
       +--ro local-discr?                 discriminator
       +--ro remote-discr?                discriminator
       +--ro new-state?                   state
       +--ro state-change-reason?         iana-bfd-types:diagnostic
       +--ro time-of-last-state-change?   yang:date-and-time
       +--ro dest-addr?                   inet:ip-address
       +--ro source-addr?                 inet:ip-address
       +--ro session-index?               uint32
       +--ro path-type?                   identityref
       +--ro lag-name?                    if:interface-ref
       +--ro member-link?                 if:interface-ref
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.9">
        <name slugifiedName="name-bfd-over-mpls-lsps-hierarch">BFD-over-MPLS-LSPs Hierarchy</name>
        <t indent="0" pn="section-2.9-1">An "mpls" node is added under the "bfd" node in
        "control-plane-protocol". The configuration is per MPLS FEC under this
        "mpls" node. In the operational state model, we support multiple BFD
        sessions per MPLS FEC (ECMP); the local discriminator is used as the key.
        The "mpls" node can be used in a network device (top level) or can be
        mounted in an LNE or network instance.</t>
        <sourcecode type="yangtree" markers="false" pn="section-2.9-2">
module: ietf-bfd-mpls
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/bfd:bfd:
    +--rw mpls
       +--ro summary
       |  +--ro number-of-sessions?              yang:gauge32
       |  +--ro number-of-sessions-up?           yang:gauge32
       |  +--ro number-of-sessions-down?         yang:gauge32
       |  +--ro number-of-sessions-admin-down?   yang:gauge32
       +--rw egress
       |  +--rw enabled?                          boolean
       |  +--rw local-multiplier?                 multiplier
       |  +--rw (interval-config-type)?
       |  |  +--:(tx-rx-intervals)
       |  |  |  +--rw desired-min-tx-interval?    uint32
       |  |  |  +--rw required-min-rx-interval?   uint32
       |  |  +--:(single-interval) {single-minimum-interval}?
       |  |     +--rw min-interval?               uint32
       |  +--rw authentication! {authentication}?
       |     +--rw key-chain?    key-chain:key-chain-ref
       |     +--rw meticulous?   boolean
       +--rw session-groups
          +--rw session-group* [mpls-fec]
             +--rw mpls-fec                          inet:ip-prefix
             +--rw local-multiplier?                 multiplier
             +--rw (interval-config-type)?
             |  +--:(tx-rx-intervals)
             |  |  +--rw desired-min-tx-interval?    uint32
             |  |  +--rw required-min-rx-interval?   uint32
             |  +--:(single-interval) {single-minimum-interval}?
             |     +--rw min-interval?               uint32
             +--rw demand-enabled?                   boolean
             |       {demand-mode}?
             +--rw admin-down?                       boolean
             +--rw authentication! {authentication}?
             |  +--rw key-chain?    key-chain:key-chain-ref
             |  +--rw meticulous?   boolean
             +--ro sessions* []
                +--ro path-type?              identityref
                +--ro ip-encapsulation?       boolean
                +--ro local-discriminator?    discriminator
                +--ro remote-discriminator?   discriminator
                +--ro remote-multiplier?      multiplier
                +--ro demand-capability?      boolean {demand-mode}?
                +--ro source-port?            inet:port-number
                +--ro dest-port?              inet:port-number
                +--ro session-running
                |  +--ro session-index?                uint32
                |  +--ro local-state?                  state
                |  +--ro remote-state?                 state
                |  +--ro local-diagnostic?
                |  |       iana-bfd-types:diagnostic
                |  +--ro remote-diagnostic?
                |  |       iana-bfd-types:diagnostic
                |  +--ro remote-authenticated?         boolean
                |  +--ro remote-authentication-type?
                |  |       iana-bfd-types:auth-type {authentication}?
                |  +--ro detection-mode?               enumeration
                |  +--ro negotiated-tx-interval?       uint32
                |  +--ro negotiated-rx-interval?       uint32
                |  +--ro detection-time?               uint32
                |  +--ro echo-tx-interval-in-use?      uint32
                |          {echo-mode}?
                +--ro session-statistics
                |  +--ro create-time?
                |  |       yang:date-and-time
                |  +--ro last-down-time?
                |  |       yang:date-and-time
                |  +--ro last-up-time?
                |  |       yang:date-and-time
                |  +--ro down-count?
                |  |       yang:counter32
                |  +--ro admin-down-count?
                |  |       yang:counter32
                |  +--ro receive-packet-count?
                |  |       yang:counter64
                |  +--ro send-packet-count?
                |  |       yang:counter64
                |  +--ro receive-invalid-packet-count?
                |  |       yang:counter64
                |  +--ro send-failed-packet-count?
                |          yang:counter64
                +--ro mpls-dest-address?      inet:ip-address

  notifications:
    +---n mpls-notification
       +--ro local-discr?                 discriminator
       +--ro remote-discr?                discriminator
       +--ro new-state?                   state
       +--ro state-change-reason?         iana-bfd-types:diagnostic
       +--ro time-of-last-state-change?   yang:date-and-time
       +--ro dest-addr?                   inet:ip-address
       +--ro source-addr?                 inet:ip-address
       +--ro session-index?               uint32
       +--ro path-type?                   identityref
       +--ro mpls-dest-address?           inet:ip-address
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.10">
        <name slugifiedName="name-interaction-with-other-yang">Interaction with Other YANG Modules</name>
        <t indent="0" pn="section-2.10-1"><xref target="RFC8532" format="default" sectionFormat="of" derivedContent="RFC8532">"Generic YANG Data Model for the Management
        of Operations, Administration, and Maintenance (OAM) Protocols That
        Use Connectionless Communications"</xref> describes how the 
        Layer-Independent OAM Management in the Multi-Layer Environment (LIME)
        connectionless OAM model could be extended to support BFD.</t>
        <t indent="0" pn="section-2.10-2">Also, the operation of the BFD data model depends on configuration
        parameters that are defined in other YANG modules.</t>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.10.1">
          <name slugifiedName="name-ietf-interfaces-module">"ietf-interfaces" Module</name>
          <t indent="0" pn="section-2.10.1-1">The following boolean configuration is defined in <xref target="RFC8343" format="default" sectionFormat="of" derivedContent="RFC8343">"A YANG Data Model for Interface Management"</xref>:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.10.1-2">
            <dt pn="section-2.10.1-2.1">/if:interfaces/if:interface/if:enabled</dt>
            <dd pn="section-2.10.1-2.2">If this configuration is set to "false", no BFD packets can be
            transmitted or received on that interface.</dd>
          </dl>
        </section>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.10.2">
          <name slugifiedName="name-ietf-ip-module">"ietf-ip" Module</name>
          <t indent="0" pn="section-2.10.2-1">The following boolean configuration is defined in <xref target="RFC8344" format="default" sectionFormat="of" derivedContent="RFC8344">"A YANG Data Model for IP Management"</xref>:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.10.2-2">
            <dt pn="section-2.10.2-2.1">/if:interfaces/if:interface/ip:ipv4/ip:enabled</dt>
            <dd pn="section-2.10.2-2.2">If this configuration is set to "false", no BFD IPv4 packets
            can be transmitted or received on that interface.</dd>
            <dt pn="section-2.10.2-2.3">/if:interfaces/if:interface/ip:ipv4/ip:forwarding</dt>
            <dd pn="section-2.10.2-2.4">If this configuration is set to "false", no BFD IPv4 packets
            can be transmitted or received on that interface.</dd>
            <dt pn="section-2.10.2-2.5">/if:interfaces/if:interface/ip:ipv6/ip:enabled</dt>
            <dd pn="section-2.10.2-2.6">If this configuration is set to "false", no BFD IPv6 packets
            can be transmitted or received on that interface.</dd>
            <dt pn="section-2.10.2-2.7">/if:interfaces/if:interface/ip:ipv6/ip:forwarding</dt>
            <dd pn="section-2.10.2-2.8">If this configuration is set to "false", no BFD IPv6 packets
            can be transmitted or received on that interface.</dd>
          </dl>
        </section>
        <section numbered="true" toc="include" removeInRFC="false" pn="section-2.10.3">
          <name slugifiedName="name-ietf-mpls-module">"ietf-mpls" Module</name>
          <t indent="0" pn="section-2.10.3-1">The following boolean configuration is defined in <xref target="RFC8960" format="default" sectionFormat="of" derivedContent="RFC8960">"A YANG Data Model for MPLS Base"</xref>:</t>
          <dl newline="true" spacing="normal" indent="3" pn="section-2.10.3-2">
            <dt pn="section-2.10.3-2.1">/rt:routing/mpls:mpls/mpls:interfaces/mpls:interface/mpls:mpls‑enabled</dt>
            <dd pn="section-2.10.3-2.2">If this configuration is set to "false", no BFD MPLS packets
            can be transmitted or received on that interface.</dd>
          </dl>
        </section>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.11">
        <name slugifiedName="name-iana-bfd-yang-module">IANA BFD YANG Module</name>
        <t indent="0" pn="section-2.11-1">This YANG module imports definitions from <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/>.  It
      references <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> and <xref target="RFC6428" format="default" sectionFormat="of" derivedContent="RFC6428"/>.</t>
        <sourcecode name="iana-bfd-types@2021-10-21.yang" type="yang" markers="true" pn="section-2.11-2">
module iana-bfd-types {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:iana-bfd-types";
  prefix iana-bfd-types;

  organization
    "IANA";
  contact
    "Internet Assigned Numbers Authority

     Postal: ICANN
             12025 Waterfront Drive, Suite 300
             Los Angeles, CA 90094-2536
             United States of America
     Tel:    +1 310 301 5800
     &lt;mailto:iana@iana.org&gt;";
  description
    "This module defines YANG data types for IANA-registered
     BFD parameters.

     This YANG module is maintained by IANA and reflects the
     'BFD Diagnostic Codes' and 'BFD Authentication Types'
     registries.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Type definitions
   */

  typedef diagnostic {
    type enumeration {
      enum none {
        value 0;
        description
          "No Diagnostic.";
      }
      enum control-expiry {
        value 1;
        description
          "Control Detection Time Expired.";
      }
      enum echo-failed {
        value 2;
        description
          "Echo Function Failed.";
      }
      enum neighbor-down {
        value 3;
        description
          "Neighbor Signaled Session Down.";
      }
      enum forwarding-reset {
        value 4;
        description
          "Forwarding Plane Reset.";
      }
      enum path-down {
        value 5;
        description
          "Path Down.";
      }
      enum concatenated-path-down {
        value 6;
        description
          "Concatenated Path Down.";
      }
      enum admin-down {
        value 7;
        description
          "Administratively Down.";
      }
      enum reverse-concatenated-path-down {
        value 8;
        description
          "Reverse Concatenated Path Down.";
      }
      enum mis-connectivity-defect {
        value 9;
        description
          "Mis-connectivity defect.";
        reference
          "RFC 5880: Bidirectional Forwarding Detection (BFD)
           RFC 6428: Proactive Connectivity Verification, Continuity
           Check, and Remote Defect Indication for the MPLS Transport
           Profile";
      }
    }
    description
      "BFD diagnostic codes as defined in RFC 5880.  Values are
       maintained in the 'BFD Diagnostic Codes' IANA registry.
       Range is 0 to 31.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD)";
  }

  typedef auth-type {
    type enumeration {
      enum reserved {
        value 0;
        description
          "Reserved.";
      }
      enum simple-password {
        value 1;
        description
          "Simple Password.";
      }
      enum keyed-md5 {
        value 2;
        description
          "Keyed MD5.";
      }
      enum meticulous-keyed-md5 {
        value 3;
        description
          "Meticulous Keyed MD5.";
      }
      enum keyed-sha1 {
        value 4;
        description
          "Keyed SHA1.";
      }
      enum meticulous-keyed-sha1 {
        value 5;
        description
          "Meticulous Keyed SHA1.";
      }
    }
    description
      "BFD authentication type as defined in RFC 5880.  Values are
       maintained in the 'BFD Authentication Types' IANA registry.
       Range is 0 to 255.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD)";
  }
}
</sourcecode>
      </section>
      <section anchor="BFD-TYPES" numbered="true" toc="include" removeInRFC="false" pn="section-2.12">
        <name slugifiedName="name-bfd-types-yang-module">BFD Types YANG Module</name>
        <t indent="0" pn="section-2.12-1">This YANG module imports typedefs from <xref target="RFC6991" format="default" sectionFormat="of" derivedContent="RFC6991"/> and <xref target="RFC8177" format="default" sectionFormat="of" derivedContent="RFC8177"/>.
        It also imports definitions from
        <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/>, <xref target="RFC5881" format="default" sectionFormat="of" derivedContent="RFC5881"/>,
        <xref target="RFC5883" format="default" sectionFormat="of" derivedContent="RFC5883"/>, <xref target="RFC5884" format="default" sectionFormat="of" derivedContent="RFC5884"/>, and
        <xref target="RFC7130" format="default" sectionFormat="of" derivedContent="RFC7130"/>, as well as the
        "control-plane-protocol" identity from
        <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>.

</t>
        <sourcecode name="ietf-bfd-types@2021-10-21.yang" type="yang" markers="true" pn="section-2.12-2">
module ietf-bfd-types {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-types";
  prefix bfd-types;

  import iana-bfd-types {
    prefix iana-bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  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 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }
  import ietf-key-chain {
    prefix key-chain;
    reference
      "RFC 8177: YANG Data Model for Key Chains";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains a collection of BFD-specific YANG data type
     definitions, as per RFC 5880, and also groupings that are common
     to other BFD YANG modules.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 5880: Bidirectional Forwarding Detection (BFD)
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Feature definitions
   */

  feature single-minimum-interval {
    description
      "This feature indicates that the server supports configuration
       of one minimum interval value that is used for both transmit
       and receive minimum intervals.";
  }

  feature authentication {
    description
      "This feature indicates that the server supports BFD
       authentication.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD),
       Section 6.7";
  }

  feature demand-mode {
    description
      "This feature indicates that the server supports BFD Demand
       mode.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD),
       Section 6.6";
  }

  feature echo-mode {
    description
      "This feature indicates that the server supports BFD Echo
       mode.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD),
       Section 6.4";
  }

  /*
   * Identity definitions
   */

  identity bfdv1 {
    base rt:control-plane-protocol;
    description
      "BFD protocol version 1.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD)";
  }

  identity path-type {
    description
      "Base identity for the BFD path type.  The path type indicates
       the type of path on which BFD is running.";
  }

  identity path-ip-sh {
    base path-type;
    description
      "BFD on IP single-hop.";
    reference
      "RFC 5881: Bidirectional Forwarding Detection (BFD)
       for IPv4 and IPv6 (Single Hop)";
  }

  identity path-ip-mh {
    base path-type;
    description
      "BFD on IP multihop paths.";
    reference
      "RFC 5883: Bidirectional Forwarding Detection (BFD) for
       Multihop Paths";
  }

  identity path-mpls-te {
    base path-type;
    description
      "BFD on MPLS Traffic Engineering.";
    reference
      "RFC 5884: Bidirectional Forwarding Detection (BFD)
       for MPLS Label Switched Paths (LSPs)";
  }

  identity path-mpls-lsp {
    base path-type;
    description
      "BFD on an MPLS Label Switched Path.";
    reference
      "RFC 5884: Bidirectional Forwarding Detection (BFD)
       for MPLS Label Switched Paths (LSPs)";
  }

  identity path-lag {
    base path-type;
    description
      "Micro-BFD on LAG member links.";
    reference
      "RFC 7130: Bidirectional Forwarding Detection (BFD) on
       Link Aggregation Group (LAG) Interfaces";
  }

  identity encap-type {
    description
      "Base identity for BFD encapsulation type.";
  }

  identity encap-ip {
    base encap-type;
    description
      "BFD with IP encapsulation.";
  }

  /*
   * Type definitions
   */

  typedef discriminator {
    type uint32;
    description
      "BFD Discriminator as described in RFC 5880.";
    reference
      "RFC 5880: Bidirectional Forwarding Detection (BFD)";
  }

  typedef state {
    type enumeration {
      enum adminDown {
        value 0;
        description
          "'adminDown' state.";
      }
      enum down {
        value 1;
        description
          "'Down' state.";
      }
      enum init {
        value 2;
        description
          "'Init' state.";
      }
      enum up {
        value 3;
        description
          "'Up' state.";
      }
    }
    description
      "BFD states as defined in RFC 5880.";
  }

  typedef multiplier {
    type uint8 {
      range "1..255";
    }
    description
      "BFD multiplier as described in RFC 5880.";
  }

  typedef hops {
    type uint8 {
      range "1..255";
    }
    description
      "This corresponds to Time To Live for IPv4 and corresponds to
       the hop limit for IPv6.";
  }

  /*
   * Groupings
   */

  grouping auth-parms {
    description
      "Grouping for BFD authentication parameters
       (see Section 6.7 of RFC 5880).";
    container authentication {
      if-feature "authentication";
      presence "Enables BFD authentication (see Section 6.7
                of RFC 5880).";
      description
        "Parameters for BFD authentication.";
      reference
        "RFC 5880: Bidirectional Forwarding Detection (BFD),
         Section 6.7";
      leaf key-chain {
        type key-chain:key-chain-ref;
        description
          "Name of the 'key-chain' as per RFC 8177.";
      }
      leaf meticulous {
        type boolean;
        description
          "Enables a meticulous mode as per Section 6.7 of
           RFC 5880.";
      }
    }
  }

  grouping base-cfg-parms {
    description
      "BFD grouping for base configuration parameters.";
    leaf local-multiplier {
      type multiplier;
      default "3";
      description
        "Multiplier transmitted by the local system.";
    }
    choice interval-config-type {
      default "tx-rx-intervals";
      description
        "Two interval values or one value used for both transmit and
         receive.";
      case tx-rx-intervals {
        leaf desired-min-tx-interval {
          type uint32;
          units "microseconds";
          default "1000000";
          description
            "Desired minimum transmit interval of control packets.";
        }
        leaf required-min-rx-interval {
          type uint32;
          units "microseconds";
          default "1000000";
          description
            "Required minimum receive interval of control packets.";
        }
      }
      case single-interval {
        if-feature "single-minimum-interval";
        leaf min-interval {
          type uint32;
          units "microseconds";
          default "1000000";
          description
            "Desired minimum transmit interval and required
             minimum receive interval of control packets.";
        }
      }
    }
  }

  grouping client-cfg-parms {
    description
      "BFD grouping for configuration parameters
       used by BFD clients, e.g., IGP or MPLS.";
    leaf enabled {
      type boolean;
      default "false";
      description
        "Indicates whether BFD is enabled.";
    }
    uses base-cfg-parms;
  }

  grouping common-cfg-parms {
    description
      "BFD grouping for common configuration parameters.";
    uses base-cfg-parms;
    leaf demand-enabled {
      if-feature "demand-mode";
      type boolean;
      default "false";
      description
        "To enable Demand mode.";
    }
    leaf admin-down {
      type boolean;
      default "false";
      description
        "Indicates whether the BFD session is administratively
         down.";
    }
    uses auth-parms;
  }

  grouping all-session {
    description
      "BFD session operational information.";
    leaf path-type {
      type identityref {
        base path-type;
      }
      config false;
      description
        "BFD path type.  This indicates the path type that BFD is
         running on.";
    }
    leaf ip-encapsulation {
      type boolean;
      config false;
      description
        "Indicates whether BFD encapsulation uses IP.";
    }
    leaf local-discriminator {
      type discriminator;
      config false;
      description
        "Local discriminator.";
    }
    leaf remote-discriminator {
      type discriminator;
      config false;
      description
        "Remote discriminator.";
    }
    leaf remote-multiplier {
      type multiplier;
      config false;
      description
        "Remote multiplier.";
    }
    leaf demand-capability {
      if-feature "demand-mode";
      type boolean;
      config false;
      description
        "Local Demand mode capability.";
    }
    leaf source-port {
      when "../ip-encapsulation = 'true'" {
        description
          "Source port valid only when IP encapsulation is used.";
      }
      type inet:port-number;
      config false;
      description
        "Source UDP port.";
    }
    leaf dest-port {
      when "../ip-encapsulation = 'true'" {
        description
          "Destination port valid only when IP encapsulation
           is used.";
      }
      type inet:port-number;
      config false;
      description
        "Destination UDP port.";
    }
    container session-running {
      config false;
      description
        "BFD 'session-running' information.";
      leaf session-index {
        type uint32;
        description
          "An index used to uniquely identify BFD sessions.";
      }
      leaf local-state {
        type state;
        description
          "Local state.";
      }
      leaf remote-state {
        type state;
        description
          "Remote state.";
      }
      leaf local-diagnostic {
        type iana-bfd-types:diagnostic;
        description
          "Local diagnostic.";
      }
      leaf remote-diagnostic {
        type iana-bfd-types:diagnostic;
        description
          "Remote diagnostic.";
      }
      leaf remote-authenticated {
        type boolean;
        description
          "Indicates whether incoming BFD control packets are
           authenticated.";
      }
      leaf remote-authentication-type {
        when "../remote-authenticated = 'true'" {
          description
            "Only valid when incoming BFD control packets are
             authenticated.";
        }
        if-feature "authentication";
        type iana-bfd-types:auth-type;
        description
          "Authentication type of incoming BFD control packets.";
      }
      leaf detection-mode {
        type enumeration {
          enum async-with-echo {
            value 1;
            description
              "Async with echo.";
          }
          enum async-without-echo {
            value 2;
            description
              "Async without echo.";
          }
          enum demand-with-echo {
            value 3;
            description
              "Demand with echo.";
          }
          enum demand-without-echo {
            value 4;
            description
              "Demand without echo.";
          }
        }
        description
          "Detection mode.";
      }
      leaf negotiated-tx-interval {
        type uint32;
        units "microseconds";
        description
          "Negotiated transmit interval.";
      }
      leaf negotiated-rx-interval {
        type uint32;
        units "microseconds";
        description
          "Negotiated receive interval.";
      }
      leaf detection-time {
        type uint32;
        units "microseconds";
        description
          "Detection time.";
      }
      leaf echo-tx-interval-in-use {
        when "../../path-type = 'bfd-types:path-ip-sh'" {
          description
            "Echo is supported for IP single-hop only.";
        }
        if-feature "echo-mode";
        type uint32;
        units "microseconds";
        description
          "Echo transmit interval in use.";
      }
    }
    container session-statistics {
      config false;
      description
        "BFD per-session statistics.";
      leaf create-time {
        type yang:date-and-time;
        description
          "Time and date when this session was created.";
      }
      leaf last-down-time {
        type yang:date-and-time;
        description
          "Time and date of the last time this session went down.";
      }
      leaf last-up-time {
        type yang:date-and-time;
        description
          "Time and date of the last time this session went up.";
      }
      leaf down-count {
        type yang:counter32;
        description
          "The number of times this session has transitioned to the
           'down' state.";
      }
      leaf admin-down-count {
        type yang:counter32;
        description
          "The number of times this session has transitioned to the
           'admin-down' state.";
      }
      leaf receive-packet-count {
        type yang:counter64;
        description
          "Count of received packets in this session.  This includes
           valid and invalid received packets.";
      }
      leaf send-packet-count {
        type yang:counter64;
        description
          "Count of sent packets in this session.";
      }
      leaf receive-invalid-packet-count {
        type yang:counter64;
        description
          "Count of invalid received packets in this session.";
      }
      leaf send-failed-packet-count {
        type yang:counter64;
        description
          "Count of packets that failed to be sent in this session.";
      }
    }
  }

  grouping session-statistics-summary {
    description
      "Grouping for session statistics summary.";
    container summary {
      config false;
      description
        "BFD session statistics summary.";
      leaf number-of-sessions {
        type yang:gauge32;
        description
          "Number of BFD sessions.";
      }
      leaf number-of-sessions-up {
        type yang:gauge32;
        description
          "Number of BFD sessions currently in the 'Up' state
           (as defined in RFC 5880).";
      }
      leaf number-of-sessions-down {
        type yang:gauge32;
        description
          "Number of BFD sessions currently in the 'Down' or 'Init'
           state but not 'adminDown' (as defined in RFC 5880).";
      }
      leaf number-of-sessions-admin-down {
        type yang:gauge32;
        description
          "Number of BFD sessions currently in the 'adminDown' state
           (as defined in RFC 5880).";
      }
    }
  }

  grouping notification-parms {
    description
      "This group describes common parameters that will be sent
       as part of BFD notifications.";
    leaf local-discr {
      type discriminator;
      description
        "BFD local discriminator.";
    }
    leaf remote-discr {
      type discriminator;
      description
        "BFD remote discriminator.";
    }
    leaf new-state {
      type state;
      description
        "Current BFD state.";
    }
    leaf state-change-reason {
      type iana-bfd-types:diagnostic;
      description
        "Reason for the BFD state change.";
    }
    leaf time-of-last-state-change {
      type yang:date-and-time;
      description
        "Calendar time of the most recent previous state change.";
    }
    leaf dest-addr {
      type inet:ip-address;
      description
        "BFD peer address.";
    }
    leaf source-addr {
      type inet:ip-address;
      description
        "BFD local address.";
    }
    leaf session-index {
      type uint32;
      description
        "An index used to uniquely identify BFD sessions.";
    }
    leaf path-type {
      type identityref {
        base path-type;
      }
      description
        "BFD path type.";
    }
  }
}
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-2.13">
        <name slugifiedName="name-bfd-top-level-yang-module">BFD Top-Level YANG Module</name>
        <t indent="0" pn="section-2.13-1">This YANG module imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>. It also references
        <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/>.</t>
        <sourcecode name="ietf-bfd@2021-10-21.yang" type="yang" markers="true" pn="section-2.13-2">
module ietf-bfd {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd";
  prefix bfd;

  import ietf-bfd-types {
    prefix bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains the YANG definition for BFD parameters as
     per RFC 5880.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 5880: Bidirectional Forwarding Detection (BFD)
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol" {
    when "derived-from-or-self(rt:type, 'bfd-types:bfdv1')" {
      description
        "This augmentation is only valid for a control-plane protocol
         instance of BFD (type 'bfdv1').";
    }
    description
      "BFD augmentation.";
    container bfd {
      description
        "BFD top-level container.";
      uses bfd-types:session-statistics-summary;
    }
  }
}
</sourcecode>
      </section>
      <section anchor="bfd-ip-single-hop-module" numbered="true" toc="include" removeInRFC="false" pn="section-2.14">
        <name slugifiedName="name-bfd-ip-single-hop-yang-modu">BFD IP Single-Hop YANG Module</name>
        <t indent="0" pn="section-2.14-1">This YANG module imports "interface-ref" from <xref target="RFC8343" format="default" sectionFormat="of" derivedContent="RFC8343"/> and typedefs from <xref target="RFC6991" format="default" sectionFormat="of" derivedContent="RFC6991"/>.  It also imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>, and it references
        <xref target="RFC5881" format="default" sectionFormat="of" derivedContent="RFC5881"/>.</t>
        <sourcecode name="ietf-bfd-ip-sh@2021-10-21.yang" type="yang" markers="true" pn="section-2.14-2">
module ietf-bfd-ip-sh {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh";
  prefix bfd-ip-sh;

  import ietf-bfd-types {
    prefix bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-bfd {
    prefix bfd;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-interfaces {
    prefix if;
    reference
      "RFC 8343: A YANG Data Model for Interface Management";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains the YANG definition for BFD IP single-hop
     as per RFC 5881.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 5881: Bidirectional Forwarding Detection (BFD)
     for IPv4 and IPv6 (Single Hop)
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Augments
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/bfd:bfd" {
    description
      "BFD augmentation for IP single-hop.";
    container ip-sh {
      description
        "BFD IP single-hop top-level container.";
      uses bfd-types:session-statistics-summary;
      container sessions {
        description
          "BFD IP single-hop sessions.";
        list session {
          key "interface dest-addr";
          description
            "List of IP single-hop sessions.";
          leaf interface {
            type if:interface-ref;
            description
              "Interface on which the BFD session is running.";
          }
          leaf dest-addr {
            type inet:ip-address;
            description
              "IP address of the peer.";
          }
          leaf source-addr {
            type inet:ip-address;
            description
              "Local IP address.";
          }
          uses bfd-types:common-cfg-parms;
          uses bfd-types:all-session;
        }
      }
      list interfaces {
        key "interface";
        description
          "List of interfaces.";
        leaf interface {
          type if:interface-ref;
          description
            "BFD information for this interface.";
        }
        uses bfd-types:auth-parms;
      }
    }
  }

  /*
   * Notifications
   */

  notification singlehop-notification {
    description
      "Notification for BFD single-hop session state change.  An
       implementation may rate-limit notifications, e.g., when a
       session is continuously changing state.";
    uses bfd-types:notification-parms;
    leaf interface {
      type if:interface-ref;
      description
        "Interface to which this BFD session belongs.";
    }
    leaf echo-enabled {
      type boolean;
      description
        "Indicates whether Echo was enabled for BFD.";
    }
  }
}
</sourcecode>
      </section>
      <section anchor="bfd-ip-multihop-module" numbered="true" toc="include" removeInRFC="false" pn="section-2.15">
        <name slugifiedName="name-bfd-ip-multihop-yang-module">BFD IP Multihop YANG Module</name>
        <t indent="0" pn="section-2.15-1">This YANG module imports typedefs from
        <xref target="RFC6991" format="default" sectionFormat="of" derivedContent="RFC6991"/>. It also imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>, and it references
        <xref target="RFC5883" format="default" sectionFormat="of" derivedContent="RFC5883"/>.</t>
        <sourcecode name="ietf-bfd-ip-mh@2021-10-21.yang" type="yang" markers="true" pn="section-2.15-2">
module ietf-bfd-ip-mh {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh";
  prefix bfd-ip-mh;

  import ietf-bfd-types {
    prefix bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-bfd {
    prefix bfd;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains the YANG definition for BFD IP multihop
     as per RFC 5883.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 5883: Bidirectional Forwarding Detection (BFD) for
     Multihop Paths
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Augments
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/bfd:bfd" {
    description
      "BFD augmentation for IP multihop.";
    container ip-mh {
      description
        "BFD IP multihop top-level container.";
      uses bfd-types:session-statistics-summary;
      container session-groups {
        description
          "BFD IP multihop session groups.";
        list session-group {
          key "source-addr dest-addr";
          description
            "Group of BFD IP multihop sessions (for ECMP).  A
             group of sessions is between one source and one
             destination.  Each session has a different field
             in the UDP/IP header for ECMP.";
          leaf source-addr {
            type inet:ip-address;
            description
              "Local IP address.";
          }
          leaf dest-addr {
            type inet:ip-address;
            description
              "IP address of the peer.";
          }
          uses bfd-types:common-cfg-parms;
          leaf tx-ttl {
            type bfd-types:hops;
            default "255";
            description
              "Hop count of outgoing BFD control packets.";
          }
          leaf rx-ttl {
            type bfd-types:hops;
            mandatory true;
            description
              "Minimum allowed hop count value for incoming BFD
               control packets.  Control packets whose hop count is
               lower than this value are dropped.";
          }
          list sessions {
            config false;
            description
              "The multiple BFD sessions between a source and a
               destination.";
            uses bfd-types:all-session;
          }
        }
      }
    }
  }

  /*
   * Notifications
   */

  notification multihop-notification {
    description
      "Notification for BFD multihop session state change.  An
       implementation may rate-limit notifications, e.g., when a
       session is continuously changing state.";
    uses bfd-types:notification-parms;
  }
}
</sourcecode>
      </section>
      <section anchor="bfd-over-lag-module" numbered="true" toc="include" removeInRFC="false" pn="section-2.16">
        <name slugifiedName="name-bfd-over-lag-yang-module">BFD-over-LAG YANG Module</name>
        <t indent="0" pn="section-2.16-1">This YANG module imports "interface-ref" from <xref target="RFC8343" format="default" sectionFormat="of" derivedContent="RFC8343"/> and typedefs from <xref target="RFC6991" format="default" sectionFormat="of" derivedContent="RFC6991"/>.  It also imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>. Additionally, it references
        <xref target="RFC7130" format="default" sectionFormat="of" derivedContent="RFC7130"/>.</t>
        <sourcecode name="ietf-bfd-lag@2021-10-21.yang" type="yang" markers="true" pn="section-2.16-2">
module ietf-bfd-lag {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-lag";
  prefix bfd-lag;

  import ietf-bfd-types {
    prefix bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-bfd {
    prefix bfd;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-interfaces {
    prefix if;
    reference
      "RFC 8343: A YANG Data Model for Interface Management";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains the YANG definition for BFD-over-LAG
     interfaces as per RFC 7130.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 7130: Bidirectional Forwarding Detection (BFD) on
     Link Aggregation Group (LAG) Interfaces
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Augments
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/bfd:bfd" {
    description
      "BFD augmentation for a LAG.";
    container lag {
      description
        "BFD-over-LAG top-level container.";
      container micro-bfd-ipv4-session-statistics {
        description
          "Micro-BFD IPv4 session counters.";
        uses bfd-types:session-statistics-summary;
      }
      container micro-bfd-ipv6-session-statistics {
        description
          "Micro-BFD IPv6 session counters.";
        uses bfd-types:session-statistics-summary;
      }
      container sessions {
        description
          "BFD-over-LAG sessions.";
        list session {
          key "lag-name";
          description
            "List of BFD-over-LAG sessions.";
          leaf lag-name {
            type if:interface-ref;
            description
              "Name of the LAG.";
          }
          leaf ipv4-dest-addr {
            type inet:ipv4-address;
            description
              "IPv4 address of the peer, for IPv4 micro-BFD.";
          }
          leaf ipv6-dest-addr {
            type inet:ipv6-address;
            description
              "IPv6 address of the peer, for IPv6 micro-BFD.";
          }
          uses bfd-types:common-cfg-parms;
          leaf use-ipv4 {
            type boolean;
            description
              "Using IPv4 micro-BFD.";
          }
          leaf use-ipv6 {
            type boolean;
            description
              "Using IPv6 micro-BFD.";
          }
          list member-links {
            key "member-link";
            config false;
            description
              "Micro-BFD over a LAG.  This represents one
               member link.";
            leaf member-link {
              type if:interface-ref;
              description
                "Member link on which micro-BFD is running.";
            }
            container micro-bfd-ipv4 {
              when "../../use-ipv4 = 'true'" {
                description
                  "Needed only if IPv4 is used.";
              }
              description
                "Micro-BFD IPv4 session state on a member link.";
              uses bfd-types:all-session;
            }
            container micro-bfd-ipv6 {
              when "../../use-ipv6 = 'true'" {
                description
                  "Needed only if IPv6 is used.";
              }
              description
                "Micro-BFD IPv6 session state on a member link.";
              uses bfd-types:all-session;
            }
          }
        }
      }
    }
  }

  /*
   * Notifications
   */

  notification lag-notification {
    description
      "Notification for BFD-over-LAG session state change.
       An implementation may rate-limit notifications, e.g., when a
       session is continuously changing state.";
    uses bfd-types:notification-parms;
    leaf lag-name {
      type if:interface-ref;
      description
        "LAG interface name.";
    }
    leaf member-link {
      type if:interface-ref;
      description
        "Member link on which BFD is running.";
    }
  }
}
</sourcecode>
      </section>
      <section anchor="bfd-over-mpls-module" numbered="true" toc="include" removeInRFC="false" pn="section-2.17">
        <name slugifiedName="name-bfd-over-mpls-yang-module">BFD-over-MPLS YANG Module</name>
        <t indent="0" pn="section-2.17-1">This YANG module imports typedefs from <xref target="RFC6991" format="default" sectionFormat="of" derivedContent="RFC6991"/>. It also imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>.
        Additionally, it references <xref target="RFC5586" format="default" sectionFormat="of" derivedContent="RFC5586"/> and
        <xref target="RFC5884" format="default" sectionFormat="of" derivedContent="RFC5884"/>.</t>
        <sourcecode name="ietf-bfd-mpls@2021-10-21.yang" type="yang" markers="true" pn="section-2.17-2">
module ietf-bfd-mpls {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-mpls";
  prefix bfd-mpls;

  import ietf-bfd-types {
    prefix bfd-types;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-bfd {
    prefix bfd;
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349: A YANG Data Model for Routing Management
       (NMDA Version)";
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains the YANG definition for BFD parameters for
     MPLS LSPs as per RFC 5884.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";
  reference
    "RFC 5884: Bidirectional Forwarding Detection (BFD)
     for MPLS Label Switched Paths (LSPs)
     RFC 9127: YANG Data Model for Bidirectional Forwarding
     Detection (BFD)";

  revision 2021-10-21 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Identity definitions
   */

  identity encap-gach {
    base bfd-types:encap-type;
    description
      "BFD with G-ACh encapsulation as per RFC 5586.";
    reference
      "RFC 5586: MPLS Generic Associated Channel";
  }

  identity encap-ip-gach {
    base bfd-types:encap-type;
    description
      "BFD with IP and G-ACh encapsulation as per RFC 5586.";
  }

  /*
   * Groupings
   */

  grouping encap-cfg {
    description
      "Configuration for BFD encapsulation.";
    leaf encap {
      type identityref {
        base bfd-types:encap-type;
      }
      default "bfd-types:encap-ip";
      description
        "BFD encapsulation.";
    }
  }

  grouping mpls-dest-address {
    description
      "Destination address as per RFC 5884.";
    reference
      "RFC 5884: Bidirectional Forwarding Detection (BFD)
       for MPLS Label Switched Paths (LSPs)";
    leaf mpls-dest-address {
      type inet:ip-address;
      config false;
      description
        "Destination address as per RFC 5884.
         Needed if IP encapsulation is used.";
    }
  }

  /*
   * Augments
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/bfd:bfd" {
    description
      "BFD augmentation for MPLS.";
    container mpls {
      description
        "BFD MPLS top-level container.";
      uses bfd-types:session-statistics-summary;
      container egress {
        description
          "Egress configuration.";
        uses bfd-types:client-cfg-parms;
        uses bfd-types:auth-parms;
      }
      container session-groups {
        description
          "BFD-over-MPLS session groups.";
        list session-group {
          key "mpls-fec";
          description
            "Group of BFD MPLS sessions (for ECMP).  A group of
             sessions is for one FEC.  Each session has a different
             field in the UDP/IP header for ECMP.";
          leaf mpls-fec {
            type inet:ip-prefix;
            description
              "MPLS FEC.";
          }
          uses bfd-types:common-cfg-parms;
          list sessions {
            config false;
            description
              "The BFD sessions for an MPLS FEC.  The local
               discriminator is unique for each session in the
               group.";
            uses bfd-types:all-session;
            uses bfd-mpls:mpls-dest-address;
          }
        }
      }
    }
  }

  /*
   * Notifications
   */

  notification mpls-notification {
    description
      "Notification for BFD-over-MPLS FEC session state change.
       An implementation may rate-limit notifications, e.g., when a
       session is continuously changing state.";
    uses bfd-types:notification-parms;
    leaf mpls-dest-address {
      type inet:ip-address;
      description
        "Destination address as per RFC 5884.
         Needed if IP encapsulation is used.";
    }
  }
}
</sourcecode>
      </section>
    </section>
    <section numbered="true" toc="include" removeInRFC="false" pn="section-3">
      <name slugifiedName="name-data-model-examples">Data Model Examples</name>
      <t indent="0" pn="section-3-1">This section presents some simple and illustrative examples of how to
      configure BFD.</t>
      <t indent="0" pn="section-3-2">The examples are represented in XML <xref target="W3C.REC-xml-20081126" format="default" sectionFormat="of" derivedContent="W3C.REC-xml-20081126"/>.</t>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-3.1">
        <name slugifiedName="name-ip-single-hop">IP Single-Hop</name>
        <t indent="0" pn="section-3.1-1">The following is an example configuration for a BFD IP single-hop
        session. The desired transmit interval and the required receive
        interval are both set to 10 ms.</t>
        <sourcecode type="xml" markers="false" pn="section-3.1-2">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"&gt;
  &lt;interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"&gt;
    &lt;interface&gt;
      &lt;name&gt;eth0&lt;/name&gt;
      &lt;type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"&gt;
        ianaift:ethernetCsmacd
      &lt;/type&gt;
    &lt;/interface&gt;
  &lt;/interfaces&gt;
  &lt;routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing"&gt;
    &lt;control-plane-protocols&gt;
      &lt;control-plane-protocol&gt;
        &lt;type xmlns:bfd-types=
            "urn:ietf:params:xml:ns:yang:ietf-bfd-types"&gt;
          bfd-types:bfdv1
        &lt;/type&gt;
        &lt;name&gt;name:BFD&lt;/name&gt;
        &lt;bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd"&gt;
          &lt;ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh"&gt;
            &lt;sessions&gt;
              &lt;session&gt;
                &lt;interface&gt;eth0&lt;/interface&gt;
                &lt;dest-addr&gt;2001:db8:0:113::101&lt;/dest-addr&gt;
                &lt;desired-min-tx-interval&gt;
                  10000
                &lt;/desired-min-tx-interval&gt;
                &lt;required-min-rx-interval&gt;
                  10000
                &lt;/required-min-rx-interval&gt;
              &lt;/session&gt;
            &lt;/sessions&gt;
          &lt;/ip-sh&gt;
        &lt;/bfd&gt;
      &lt;/control-plane-protocol&gt;
    &lt;/control-plane-protocols&gt;
  &lt;/routing&gt;
&lt;/config&gt;
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-3.2">
        <name slugifiedName="name-ip-multihop">IP Multihop</name>
        <t indent="0" pn="section-3.2-1">The following is an example configuration for a BFD IP multihop
        session group. The desired transmit interval and the required receive
        interval are both set to 150 ms.</t>
        <sourcecode type="xml" markers="false" pn="section-3.2-2">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"&gt;
  &lt;routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing"&gt;
    &lt;control-plane-protocols&gt;
      &lt;control-plane-protocol&gt;
        &lt;type xmlns:bfd-types=
            "urn:ietf:params:xml:ns:yang:ietf-bfd-types"&gt;
          bfd-types:bfdv1
        &lt;/type&gt;
        &lt;name&gt;name:BFD&lt;/name&gt;
        &lt;bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd"&gt;
          &lt;ip-mh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh"&gt;
            &lt;session-groups&gt;
              &lt;session-group&gt;
                &lt;source-addr&gt;2001:db8:0:113::103&lt;/source-addr&gt;
                &lt;dest-addr&gt;2001:db8:0:114::100&lt;/dest-addr&gt;
                &lt;desired-min-tx-interval&gt;
                  150000
                &lt;/desired-min-tx-interval&gt;
                &lt;required-min-rx-interval&gt;
                  150000
                &lt;/required-min-rx-interval&gt;
                &lt;rx-ttl&gt;240&lt;/rx-ttl&gt;
              &lt;/session-group&gt;
            &lt;/session-groups&gt;
          &lt;/ip-mh&gt;
        &lt;/bfd&gt;
      &lt;/control-plane-protocol&gt;
    &lt;/control-plane-protocols&gt;
  &lt;/routing&gt;
&lt;/config&gt;
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-3.3">
        <name slugifiedName="name-lag">LAG</name>
        <t indent="0" pn="section-3.3-1">The following is an example of BFD configuration for a LAG session.
        In this case, an interface named "Bundle-Ether1" of interface type
        "ieee8023adLag" has a desired transmit interval and required receive interval
        set to 10 ms.</t>
        <sourcecode type="xml" markers="false" pn="section-3.3-2">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"&gt;
  &lt;interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"&gt;
    &lt;interface&gt;
      &lt;name&gt;Bundle-Ether1&lt;/name&gt;
      &lt;type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"&gt;
        ianaift:ieee8023adLag
      &lt;/type&gt;
    &lt;/interface&gt;
  &lt;/interfaces&gt;
  &lt;routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing"&gt;
    &lt;control-plane-protocols&gt;
      &lt;control-plane-protocol&gt;
        &lt;type xmlns:bfd-types=
            "urn:ietf:params:xml:ns:yang:ietf-bfd-types"&gt;
          bfd-types:bfdv1
        &lt;/type&gt;
        &lt;name&gt;name:BFD&lt;/name&gt;
        &lt;bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd"&gt;
          &lt;lag xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-lag"&gt;
            &lt;sessions&gt;
              &lt;session&gt;
                &lt;lag-name&gt;Bundle-Ether1&lt;/lag-name&gt;
                &lt;ipv6-dest-addr&gt;2001:db8:112::16&lt;/ipv6-dest-addr&gt;
                &lt;desired-min-tx-interval&gt;
                  100000
                &lt;/desired-min-tx-interval&gt;
                &lt;required-min-rx-interval&gt;
                  100000
                &lt;/required-min-rx-interval&gt;
                &lt;use-ipv6&gt;true&lt;/use-ipv6&gt;
              &lt;/session&gt;
            &lt;/sessions&gt;
          &lt;/lag&gt;
        &lt;/bfd&gt;
      &lt;/control-plane-protocol&gt;
    &lt;/control-plane-protocols&gt;
  &lt;/routing&gt;
&lt;/config&gt;
</sourcecode>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-3.4">
        <name slugifiedName="name-mpls">MPLS</name>
        <t indent="0" pn="section-3.4-1">The following is an example of BFD configured for an MPLS LSP. In
        this case, the desired transmit interval and required receive interval
        are both set to 250 ms.</t>
        <sourcecode type="xml" markers="false" pn="section-3.4-2">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"&gt;
  &lt;routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing"&gt;
    &lt;control-plane-protocols&gt;
      &lt;control-plane-protocol&gt;
        &lt;type xmlns:bfd-types=
            "urn:ietf:params:xml:ns:yang:ietf-bfd-types"&gt;
          bfd-types:bfdv1
        &lt;/type&gt;
        &lt;name&gt;name:BFD&lt;/name&gt;
        &lt;bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd"&gt;
          &lt;mpls xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-mpls"&gt;
            &lt;session-groups&gt;
              &lt;session-group&gt;
                &lt;mpls-fec&gt;2001:db8:114::/116&lt;/mpls-fec&gt;
                &lt;desired-min-tx-interval&gt;
                  250000
                &lt;/desired-min-tx-interval&gt;
                &lt;required-min-rx-interval&gt;
                  250000
                &lt;/required-min-rx-interval&gt;
              &lt;/session-group&gt;
            &lt;/session-groups&gt;
          &lt;/mpls&gt;
        &lt;/bfd&gt;
      &lt;/control-plane-protocol&gt;
    &lt;/control-plane-protocols&gt;
  &lt;/routing&gt;
&lt;/config&gt;
</sourcecode>
      </section>
    </section>
    <section numbered="true" toc="include" removeInRFC="false" pn="section-4">
      <name slugifiedName="name-security-considerations">Security Considerations</name>
      <t indent="0" pn="section-4-1">The YANG modules specified in this document define a schema for data
that is designed to be accessed via network management protocols such
as NETCONF <xref target="RFC6241" format="default" sectionFormat="of" derivedContent="RFC6241"/> or RESTCONF <xref target="RFC8040" format="default" sectionFormat="of" derivedContent="RFC8040"/>.
The lowest NETCONF layer is the secure transport layer, and the
mandatory-to-implement secure transport is Secure Shell (SSH)
<xref target="RFC6242" format="default" sectionFormat="of" derivedContent="RFC6242"/>. The lowest RESTCONF layer is HTTPS, and the
mandatory-to-implement secure transport is TLS <xref target="RFC8446" format="default" sectionFormat="of" derivedContent="RFC8446"/>.</t>
      <t indent="0" pn="section-4-2">The Network Configuration Access Control Model (NACM) <xref target="RFC8341" format="default" sectionFormat="of" derivedContent="RFC8341"/>
provides the means to restrict access for particular NETCONF or RESTCONF users
to a preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.</t>
      <t indent="0" pn="section-4-3">There are a number of data nodes defined in these YANG modules 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 from a write access perspective:</t>
      <dl newline="true" spacing="normal" indent="3" pn="section-4-4">
        <dt pn="section-4-4.1">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh/sessions:</dt>
        <dd pn="section-4-4.2">
          <t indent="0" pn="section-4-4.2.1">This list specifies the IP single-hop BFD sessions.</t>
          <t indent="0" pn="section-4-4.2.2">Data nodes "local-multiplier", "desired-min-tx-interval",
      "required-min-rx-interval", and "min-interval" all impact the
      BFD IP single-hop session. The "source-addr" and "dest-addr" data nodes can be used to
      send BFD packets to unwitting recipients. <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> describes how BFD mitigates such
      threats. Authentication data nodes "key-chain" and "meticulous" impact the
      security of the BFD IP single-hop session.</t>
        </dd>
        <dt pn="section-4-4.3">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/session-group:</dt>
        <dd pn="section-4-4.4">
          <t indent="0" pn="section-4-4.4.1">This list specifies the IP multihop BFD session groups.</t>
          <t indent="0" pn="section-4-4.4.2">Data nodes "local-multiplier", "desired-min-tx-interval",
      "required-min-rx-interval", and "min-interval" all impact the
      BFD IP multihop session. The "source-addr" and "dest-addr" data nodes can be used to
      send BFD packets to unwitting recipients. <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> describes how BFD mitigates such
      threats. Authentication data nodes "key-chain" and "meticulous" impact the
      security of the BFD IP multihop session.</t>
        </dd>
        <dt pn="section-4-4.5">/routing/control-plane-protocols/control-plane-protocol/bfd/lag/sessions:</dt>
        <dd pn="section-4-4.6">
          <t indent="0" pn="section-4-4.6.1">This list specifies the BFD sessions over a LAG.</t>
          <t indent="0" pn="section-4-4.6.2">Data nodes "local-multiplier", "desired-min-tx-interval",
      "required-min-rx-interval", and "min-interval" all impact the BFD-over-LAG
      session. The "ipv4-dest-addr" and "ipv6-dest-addr" data nodes can be used to
      send BFD packets to unwitting recipients. <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> describes how BFD mitigates such
      threats. Authentication data nodes "key-chain" and "meticulous" impact the
      security of the BFD-over-LAG session.</t>
        </dd>
        <dt pn="section-4-4.7">/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/session-group:</dt>
        <dd pn="section-4-4.8">
          <t indent="0" pn="section-4-4.8.1">This list specifies the session groups for BFD over MPLS.</t>
          <t indent="0" pn="section-4-4.8.2">Data nodes "local-multiplier", "desired-min-tx-interval",
      "required-min-rx-interval", and "min-interval" all impact the
      BFD-over-MPLS-LSPs session. Authentication data nodes "key-chain" and "meticulous" impact
      the security of the BFD-over-MPLS-LSPs session.</t>
        </dd>
        <dt pn="section-4-4.9">/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/egress:</dt>
        <dd pn="section-4-4.10">Data nodes "local-multiplier", "desired-min-tx-interval",
      "required-min-rx-interval", and "min-interval" all impact the
      BFD-over-MPLS-LSPs sessions for which this device is an MPLS LSP egress
      node. Authentication data nodes "key-chain" and "meticulous" impact the
      security of the BFD-over-MPLS-LSPs sessions for which this device is an
      MPLS LSP egress node.</dd>
      </dl>
      <t indent="0" pn="section-4-5">The YANG modules have writable data nodes that can be used for the
      creation of BFD sessions and the modification of BFD session parameters. The
      system should "police" the creation of BFD sessions to prevent new sessions
      from causing existing BFD sessions to fail. In the case of BFD session
      modification, the BFD protocol has mechanisms in place that allow for
      in-service modification.</t>
      <t indent="0" pn="section-4-6">When BFD clients are used to modify BFD configuration (as described
      in <xref target="CFG-MODEL" format="default" sectionFormat="of" derivedContent="Section 2.1"/>), the BFD clients need to
      be included in an analysis of the security properties of the system that
      uses BFD (e.g., when considering the authentication and authorization of
      control actions). In many cases, BFD is not the most vulnerable portion
      of such a composite system, since BFD is limited to generating
      well-defined traffic at a fixed rate on a given path; in the case of an
      IGP acting as a BFD client, attacking the IGP could cause more broad-scale
      disruption than would (de)configuring a BFD session.</t>
      <t indent="0" pn="section-4-7">Some of the readable data nodes in these YANG modules 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 from a read access perspective:</t>
      <dl newline="true" spacing="normal" indent="3" pn="section-4-8">
        <dt pn="section-4-8.1">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh/summary:</dt>
        <dd pn="section-4-8.2">Access to this information discloses the number of BFD IP single-hop
      sessions that are in the "up", "down", or "admin-down" state. The counters include BFD
      sessions for which the user does not have read access.</dd>
        <dt pn="section-4-8.3">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh/sessions/session/:</dt>
        <dd pn="section-4-8.4">Access to data nodes "local-discriminator" and "remote-discriminator"
      (combined with the data nodes in the authentication container) provides the
      ability to spoof BFD IP single-hop packets.</dd>
        <dt pn="section-4-8.5">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/summary:</dt>
        <dd pn="section-4-8.6">Access to this information discloses the number of BFD IP multihop
      sessions that are in the "up", "down", or "admin-down" state. The counters include BFD
      sessions for which the user does not have read access.</dd>
        <dt pn="section-4-8.7">/routing/control-plane-protocols/control-plane-protocol/bfd/ip-mh/session-groups/session-group/sessions:</dt>
        <dd pn="section-4-8.8">Access to data nodes "local-discriminator" and "remote-discriminator"
      (combined with the data nodes in the session group's authentication container) provides the
      ability to spoof BFD IP multihop packets.</dd>
        <dt pn="section-4-8.9">/routing/control-plane-protocols/control-plane-protocol/bfd/lag/micro-bfd-ipv4-session-statistics/summary:</dt>
        <dd pn="section-4-8.10">Access to this information discloses the number of micro-BFD IPv4 LAG
      sessions that are in the "up", "down", or "admin-down" state. The counters include BFD
      sessions for which the user does not have read access.</dd>
        <dt pn="section-4-8.11">/routing/control-plane-protocols/control-plane-protocol/bfd/lag/sessions/session/member-links/member-link/micro-bfd-ipv4:</dt>
        <dd pn="section-4-8.12">Access to data nodes "local-discriminator" and "remote-discriminator"
      (combined with the data nodes in the session's authentication container) provides the
      ability to spoof BFD IPv4 LAG packets.</dd>
        <dt pn="section-4-8.13">/routing/control-plane-protocols/control-plane-protocol/bfd/lag/micro-bfd-ipv6-session-statistics/summary:</dt>
        <dd pn="section-4-8.14">Access to this information discloses the number of micro-BFD IPv6 LAG
      sessions that are in the "up", "down", or "admin-down" state. The counters include BFD
      sessions for which the user does not have read access.</dd>
        <dt pn="section-4-8.15">/routing/control-plane-protocols/control-plane-protocol/bfd/lag/sessions/session/member-links/member-link/micro-bfd-ipv6:</dt>
        <dd pn="section-4-8.16">Access to data nodes "local-discriminator" and "remote-discriminator"
      (combined with the data nodes in the session's authentication container) provides the
      ability to spoof BFD IPv6 LAG packets.</dd>
        <dt pn="section-4-8.17">/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/summary:</dt>
        <dd pn="section-4-8.18">Access to this information discloses the number of BFD sessions over
      MPLS LSPs that are in the "up", "down", or "admin-down" state. The counters include BFD
      sessions for which the user does not have read access.</dd>
        <dt pn="section-4-8.19">/routing/control-plane-protocols/control-plane-protocol/bfd/mpls/session-groups/session-group/sessions:</dt>
        <dd pn="section-4-8.20">Access to data nodes "local-discriminator" and "remote-discriminator"
      (combined with the data nodes in the session group's authentication container) provides the
      ability to spoof BFD-over-MPLS-LSPs packets.</dd>
      </dl>
      <t indent="0" pn="section-4-9">This document does not define any RPC operations.</t>
    </section>
    <section numbered="true" toc="include" removeInRFC="false" pn="section-5">
      <name slugifiedName="name-iana-considerations">IANA Considerations</name>
      <t indent="0" pn="section-5-1">IANA has registered the following namespace URIs in the "IETF XML
      Registry" <xref target="RFC3688" format="default" sectionFormat="of" derivedContent="RFC3688"/>:</t>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-2">
        <dt pn="section-5-2.1">URI:</dt>
        <dd pn="section-5-2.2">urn:ietf:params:xml:ns:yang:iana-bfd-types</dd>
        <dt pn="section-5-2.3">Registrant Contact:</dt>
        <dd pn="section-5-2.4">The IESG.</dd>
        <dt pn="section-5-2.5">XML:</dt>
        <dd pn="section-5-2.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-3">
        <dt pn="section-5-3.1">URI:</dt>
        <dd pn="section-5-3.2">urn:ietf:params:xml:ns:yang:ietf-bfd-types</dd>
        <dt pn="section-5-3.3">Registrant Contact:</dt>
        <dd pn="section-5-3.4">The IESG.</dd>
        <dt pn="section-5-3.5">XML:</dt>
        <dd pn="section-5-3.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-4">
        <dt pn="section-5-4.1">URI:</dt>
        <dd pn="section-5-4.2">urn:ietf:params:xml:ns:yang:ietf-bfd</dd>
        <dt pn="section-5-4.3">Registrant Contact:</dt>
        <dd pn="section-5-4.4">The IESG.</dd>
        <dt pn="section-5-4.5">XML:</dt>
        <dd pn="section-5-4.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-5">
        <dt pn="section-5-5.1">URI:</dt>
        <dd pn="section-5-5.2">urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh</dd>
        <dt pn="section-5-5.3">Registrant Contact:</dt>
        <dd pn="section-5-5.4">The IESG.</dd>
        <dt pn="section-5-5.5">XML:</dt>
        <dd pn="section-5-5.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-6">
        <dt pn="section-5-6.1">URI:</dt>
        <dd pn="section-5-6.2">urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh</dd>
        <dt pn="section-5-6.3">Registrant Contact:</dt>
        <dd pn="section-5-6.4">The IESG.</dd>
        <dt pn="section-5-6.5">XML:</dt>
        <dd pn="section-5-6.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-7">
        <dt pn="section-5-7.1">URI:</dt>
        <dd pn="section-5-7.2">urn:ietf:params:xml:ns:yang:ietf-bfd-lag</dd>
        <dt pn="section-5-7.3">Registrant Contact:</dt>
        <dd pn="section-5-7.4">The IESG.</dd>
        <dt pn="section-5-7.5">XML:</dt>
        <dd pn="section-5-7.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-8">
        <dt pn="section-5-8.1">URI:</dt>
        <dd pn="section-5-8.2">urn:ietf:params:xml:ns:yang:ietf-bfd-mpls</dd>
        <dt pn="section-5-8.3">Registrant Contact:</dt>
        <dd pn="section-5-8.4">The IESG.</dd>
        <dt pn="section-5-8.5">XML:</dt>
        <dd pn="section-5-8.6">N/A; the requested URI is an XML namespace.</dd>
      </dl>
      <t indent="0" pn="section-5-9">IANA has registered the following YANG modules in the "YANG Module Names"
      registry <xref target="RFC6020" format="default" sectionFormat="of" derivedContent="RFC6020"/>:</t>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-10">
        <dt pn="section-5-10.1">Name:</dt>
        <dd pn="section-5-10.2">iana-bfd-types</dd>
        <dt pn="section-5-10.3">Namespace:</dt>
        <dd pn="section-5-10.4">urn:ietf:params:xml:ns:yang:iana-bfd-types</dd>
        <dt pn="section-5-10.5">Prefix:</dt>
        <dd pn="section-5-10.6">iana-bfd-types</dd>
        <dt pn="section-5-10.7">Reference:</dt>
        <dd pn="section-5-10.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-11">
        <dt pn="section-5-11.1">Name:</dt>
        <dd pn="section-5-11.2">ietf-bfd-types</dd>
        <dt pn="section-5-11.3">Namespace:</dt>
        <dd pn="section-5-11.4">urn:ietf:params:xml:ns:yang:ietf-bfd-types</dd>
        <dt pn="section-5-11.5">Prefix:</dt>
        <dd pn="section-5-11.6">bfd-types</dd>
        <dt pn="section-5-11.7">Reference:</dt>
        <dd pn="section-5-11.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-12">
        <dt pn="section-5-12.1">Name:</dt>
        <dd pn="section-5-12.2">ietf-bfd</dd>
        <dt pn="section-5-12.3">Namespace:</dt>
        <dd pn="section-5-12.4">urn:ietf:params:xml:ns:yang:ietf-bfd</dd>
        <dt pn="section-5-12.5">Prefix:</dt>
        <dd pn="section-5-12.6">bfd</dd>
        <dt pn="section-5-12.7">Reference:</dt>
        <dd pn="section-5-12.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-13">
        <dt pn="section-5-13.1">Name:</dt>
        <dd pn="section-5-13.2">ietf-bfd-ip-sh</dd>
        <dt pn="section-5-13.3">Namespace:</dt>
        <dd pn="section-5-13.4">urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh</dd>
        <dt pn="section-5-13.5">Prefix:</dt>
        <dd pn="section-5-13.6">bfd-ip-sh</dd>
        <dt pn="section-5-13.7">Reference:</dt>
        <dd pn="section-5-13.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-14">
        <dt pn="section-5-14.1">Name:</dt>
        <dd pn="section-5-14.2">ietf-bfd-ip-mh</dd>
        <dt pn="section-5-14.3">Namespace:</dt>
        <dd pn="section-5-14.4">urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh</dd>
        <dt pn="section-5-14.5">Prefix:</dt>
        <dd pn="section-5-14.6">bfd-ip-mh</dd>
        <dt pn="section-5-14.7">Reference:</dt>
        <dd pn="section-5-14.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-15">
        <dt pn="section-5-15.1">Name:</dt>
        <dd pn="section-5-15.2">ietf-bfd-lag</dd>
        <dt pn="section-5-15.3">Namespace:</dt>
        <dd pn="section-5-15.4">urn:ietf:params:xml:ns:yang:ietf-bfd-lag</dd>
        <dt pn="section-5-15.5">Prefix:</dt>
        <dd pn="section-5-15.6">bfd-lag</dd>
        <dt pn="section-5-15.7">Reference:</dt>
        <dd pn="section-5-15.8">RFC 9127</dd>
      </dl>
      <dl newline="false" spacing="compact" indent="3" pn="section-5-16">
        <dt pn="section-5-16.1">Name:</dt>
        <dd pn="section-5-16.2">ietf-bfd-mpls</dd>
        <dt pn="section-5-16.3">Namespace:</dt>
        <dd pn="section-5-16.4">urn:ietf:params:xml:ns:yang:ietf-bfd-mpls</dd>
        <dt pn="section-5-16.5">Prefix:</dt>
        <dd pn="section-5-16.6">bfd-mpls</dd>
        <dt pn="section-5-16.7">Reference:</dt>
        <dd pn="section-5-16.8">RFC 9127</dd>
      </dl>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-5.1">
        <name slugifiedName="name-iana-maintained-iana-bfd-ty">IANA-Maintained "iana-bfd-types" Module</name>
        <t indent="0" pn="section-5.1-1">This document defines the initial version of the IANA-maintained
        "iana-bfd-types" YANG module.</t>
        <t indent="0" pn="section-5.1-2">The "iana-bfd-types" YANG module mirrors the "BFD Diagnostic Codes"
        and "BFD Authentication Types" registries at
        <eref target="https://www.iana.org/assignments/bfd-parameters/" brackets="angle"/>. Whenever
        these registries change, IANA must update the "iana-bfd-types" YANG
        module.</t>
      </section>
    </section>
  </middle>
  <back>
    <references pn="section-6">
      <name slugifiedName="name-references">References</name>
      <references pn="section-6.1">
        <name slugifiedName="name-normative-references">Normative References</name>
        <reference anchor="RFC3688" target="https://www.rfc-editor.org/info/rfc3688" quoteTitle="true" derivedAnchor="RFC3688">
          <front>
            <title>The IETF XML Registry</title>
            <author initials="M." surname="Mealling" fullname="M. Mealling">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2004" month="January"/>
            <abstract>
              <t indent="0">This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="81"/>
          <seriesInfo name="RFC" value="3688"/>
          <seriesInfo name="DOI" value="10.17487/RFC3688"/>
        </reference>
        <reference anchor="RFC5586" target="https://www.rfc-editor.org/info/rfc5586" quoteTitle="true" derivedAnchor="RFC5586">
          <front>
            <title>MPLS Generic Associated Channel</title>
            <author initials="M." surname="Bocci" fullname="M. Bocci" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Vigoureux" fullname="M. Vigoureux" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="S." surname="Bryant" fullname="S. Bryant" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2009" month="June"/>
            <abstract>
              <t indent="0">This document generalizes the applicability of the pseudowire (PW) Associated Channel Header (ACH), enabling the realization of a control channel associated to MPLS Label Switched Paths (LSPs) and MPLS Sections in addition to MPLS pseudowires.  In order to identify the presence of this Associated Channel Header in the label stack, this document also assigns one of the reserved MPLS label values to the Generic Associated Channel Label (GAL), to be used as a label based exception mechanism.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5586"/>
          <seriesInfo name="DOI" value="10.17487/RFC5586"/>
        </reference>
        <reference anchor="RFC5880" target="https://www.rfc-editor.org/info/rfc5880" quoteTitle="true" derivedAnchor="RFC5880">
          <front>
            <title>Bidirectional Forwarding Detection (BFD)</title>
            <author initials="D." surname="Katz" fullname="D. Katz">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Ward" fullname="D. Ward">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">This document describes a protocol intended to detect faults in the bidirectional path between two forwarding engines, including interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency.  It operates independently of media, data protocols, and routing protocols. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5880"/>
          <seriesInfo name="DOI" value="10.17487/RFC5880"/>
        </reference>
        <reference anchor="RFC5881" target="https://www.rfc-editor.org/info/rfc5881" quoteTitle="true" derivedAnchor="RFC5881">
          <front>
            <title>Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)</title>
            <author initials="D." surname="Katz" fullname="D. Katz">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Ward" fullname="D. Ward">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol over IPv4 and IPv6 for single IP hops. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5881"/>
          <seriesInfo name="DOI" value="10.17487/RFC5881"/>
        </reference>
        <reference anchor="RFC5882" target="https://www.rfc-editor.org/info/rfc5882" quoteTitle="true" derivedAnchor="RFC5882">
          <front>
            <title>Generic Application of Bidirectional Forwarding Detection (BFD)</title>
            <author initials="D." surname="Katz" fullname="D. Katz">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Ward" fullname="D. Ward">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">This document describes the generic application of the Bidirectional Forwarding Detection (BFD) protocol.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5882"/>
          <seriesInfo name="DOI" value="10.17487/RFC5882"/>
        </reference>
        <reference anchor="RFC5883" target="https://www.rfc-editor.org/info/rfc5883" quoteTitle="true" derivedAnchor="RFC5883">
          <front>
            <title>Bidirectional Forwarding Detection (BFD) for Multihop Paths</title>
            <author initials="D." surname="Katz" fullname="D. Katz">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Ward" fullname="D. Ward">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol over multihop paths, including unidirectional links.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5883"/>
          <seriesInfo name="DOI" value="10.17487/RFC5883"/>
        </reference>
        <reference anchor="RFC5884" target="https://www.rfc-editor.org/info/rfc5884" quoteTitle="true" derivedAnchor="RFC5884">
          <front>
            <title>Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)</title>
            <author initials="R." surname="Aggarwal" fullname="R. Aggarwal">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="K." surname="Kompella" fullname="K. Kompella">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="T." surname="Nadeau" fullname="T. Nadeau">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="G." surname="Swallow" fullname="G. Swallow">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">One desirable application of Bidirectional Forwarding Detection (BFD) is to detect a Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) data plane failure.  LSP Ping is an existing mechanism for detecting MPLS data plane failures and for verifying the MPLS LSP data plane against the control plane.  BFD can be used for the former, but not for the latter.  However, the control plane processing required for BFD Control packets is relatively smaller than the processing required for LSP Ping messages.  A combination of LSP Ping and BFD can be used to provide faster data plane failure detection and/or make it possible to provide such detection on a greater number of LSPs.  This document describes the applicability of BFD in relation to LSP Ping for this application.  It also describes procedures for using BFD in this environment.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5884"/>
          <seriesInfo name="DOI" value="10.17487/RFC5884"/>
        </reference>
        <reference anchor="RFC5885" target="https://www.rfc-editor.org/info/rfc5885" quoteTitle="true" derivedAnchor="RFC5885">
          <front>
            <title>Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)</title>
            <author initials="T." surname="Nadeau" fullname="T. Nadeau" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="C." surname="Pignataro" fullname="C. Pignataro" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="June"/>
            <abstract>
              <t indent="0">This document describes Connectivity Verification (CV) Types using Bidirectional Forwarding Detection (BFD) with Virtual Circuit Connectivity Verification (VCCV).  VCCV provides a control channel that is associated with a pseudowire (PW), as well as the corresponding operations and management functions such as connectivity verification to be used over that control channel. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5885"/>
          <seriesInfo name="DOI" value="10.17487/RFC5885"/>
        </reference>
        <reference anchor="RFC6020" target="https://www.rfc-editor.org/info/rfc6020" quoteTitle="true" derivedAnchor="RFC6020">
          <front>
            <title>YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)</title>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2010" month="October"/>
            <abstract>
              <t indent="0">YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6020"/>
          <seriesInfo name="DOI" value="10.17487/RFC6020"/>
        </reference>
        <reference anchor="RFC6241" target="https://www.rfc-editor.org/info/rfc6241" quoteTitle="true" derivedAnchor="RFC6241">
          <front>
            <title>Network Configuration Protocol (NETCONF)</title>
            <author initials="R." surname="Enns" fullname="R. Enns" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Schoenwaelder" fullname="J. Schoenwaelder" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="A." surname="Bierman" fullname="A. Bierman" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2011" month="June"/>
            <abstract>
              <t indent="0">The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices.  It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages.  The NETCONF protocol operations are realized as remote procedure calls (RPCs).  This document obsoletes RFC 4741.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6241"/>
          <seriesInfo name="DOI" value="10.17487/RFC6241"/>
        </reference>
        <reference anchor="RFC6242" target="https://www.rfc-editor.org/info/rfc6242" quoteTitle="true" derivedAnchor="RFC6242">
          <front>
            <title>Using the NETCONF Protocol over Secure Shell (SSH)</title>
            <author initials="M." surname="Wasserman" fullname="M. Wasserman">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2011" month="June"/>
            <abstract>
              <t indent="0">This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem.  This document obsoletes RFC 4742.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6242"/>
          <seriesInfo name="DOI" value="10.17487/RFC6242"/>
        </reference>
        <reference anchor="RFC6991" target="https://www.rfc-editor.org/info/rfc6991" quoteTitle="true" derivedAnchor="RFC6991">
          <front>
            <title>Common YANG Data Types</title>
            <author initials="J." surname="Schoenwaelder" fullname="J. Schoenwaelder" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2013" month="July"/>
            <abstract>
              <t indent="0">This document introduces a collection of common data types to be used with the YANG data modeling language.  This document obsoletes RFC 6021.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6991"/>
          <seriesInfo name="DOI" value="10.17487/RFC6991"/>
        </reference>
        <reference anchor="RFC7130" target="https://www.rfc-editor.org/info/rfc7130" quoteTitle="true" derivedAnchor="RFC7130">
          <front>
            <title>Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces</title>
            <author initials="M." surname="Bhatia" fullname="M. Bhatia" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Chen" fullname="M. Chen" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="S." surname="Boutros" fullname="S. Boutros" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Binderberger" fullname="M. Binderberger" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Haas" fullname="J. Haas" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2014" month="February"/>
            <abstract>
              <t indent="0">This document defines a mechanism to run Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) interfaces.  It does so by running an independent Asynchronous mode BFD session on every LAG member link.</t>
              <t indent="0">This mechanism allows the verification of member link continuity, either in combination with, or in absence of, Link Aggregation Control Protocol (LACP).  It provides a shorter detection time than what LACP offers.  The continuity check can also cover elements of Layer 3 (L3) bidirectional forwarding.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7130"/>
          <seriesInfo name="DOI" value="10.17487/RFC7130"/>
        </reference>
        <reference anchor="RFC8040" target="https://www.rfc-editor.org/info/rfc8040" quoteTitle="true" derivedAnchor="RFC8040">
          <front>
            <title>RESTCONF Protocol</title>
            <author initials="A." surname="Bierman" fullname="A. Bierman">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="K." surname="Watsen" fullname="K. Watsen">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2017" month="January"/>
            <abstract>
              <t indent="0">This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF).</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8040"/>
          <seriesInfo name="DOI" value="10.17487/RFC8040"/>
        </reference>
        <reference anchor="RFC8177" target="https://www.rfc-editor.org/info/rfc8177" quoteTitle="true" derivedAnchor="RFC8177">
          <front>
            <title>YANG Data Model for Key Chains</title>
            <author initials="A." surname="Lindem" fullname="A. Lindem" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="Y." surname="Qu" fullname="Y. Qu">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Yeung" fullname="D. Yeung">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="I." surname="Chen" fullname="I. Chen">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Zhang" fullname="J. Zhang">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2017" month="June"/>
            <abstract>
              <t indent="0">This document describes the key chain YANG data model.  Key chains are commonly used for routing protocol authentication and other applications requiring symmetric keys.  A key chain is a list containing one or more elements containing a Key ID, key string, send/accept lifetimes, and the associated authentication or encryption algorithm.  By properly overlapping the send and accept lifetimes of multiple key chain elements, key strings and algorithms may be gracefully updated.  By representing them in a YANG data model, key distribution can be automated.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8177"/>
          <seriesInfo name="DOI" value="10.17487/RFC8177"/>
        </reference>
        <reference anchor="RFC8340" target="https://www.rfc-editor.org/info/rfc8340" quoteTitle="true" derivedAnchor="RFC8340">
          <front>
            <title>YANG Tree Diagrams</title>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="L." surname="Berger" fullname="L. Berger" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">This document captures the current syntax used in YANG module tree diagrams.  The purpose of this document is to provide a single location for this definition.  This syntax may be updated from time to time based on the evolution of the YANG language.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="215"/>
          <seriesInfo name="RFC" value="8340"/>
          <seriesInfo name="DOI" value="10.17487/RFC8340"/>
        </reference>
        <reference anchor="RFC8341" target="https://www.rfc-editor.org/info/rfc8341" quoteTitle="true" derivedAnchor="RFC8341">
          <front>
            <title>Network Configuration Access Control Model</title>
            <author initials="A." surname="Bierman" fullname="A. Bierman">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability.  There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.  This document defines such an access control model.</t>
              <t indent="0">This document obsoletes RFC 6536.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="91"/>
          <seriesInfo name="RFC" value="8341"/>
          <seriesInfo name="DOI" value="10.17487/RFC8341"/>
        </reference>
        <reference anchor="RFC8343" target="https://www.rfc-editor.org/info/rfc8343" quoteTitle="true" derivedAnchor="RFC8343">
          <front>
            <title>A YANG Data Model for Interface Management</title>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">This document defines a YANG data model for the management of network interfaces.  It is expected that interface-type-specific data models augment the generic interfaces data model defined in this document. The data model includes definitions for configuration and system state (status information and counters for the collection of statistics).</t>
              <t indent="0">The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342.</t>
              <t indent="0">This document obsoletes RFC 7223.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8343"/>
          <seriesInfo name="DOI" value="10.17487/RFC8343"/>
        </reference>
        <reference anchor="RFC8344" target="https://www.rfc-editor.org/info/rfc8344" quoteTitle="true" derivedAnchor="RFC8344">
          <front>
            <title>A YANG Data Model for IP Management</title>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">This document defines a YANG data model for management of IP implementations.  The data model includes configuration and system state.</t>
              <t indent="0">The YANG data model in this document conforms to the Network Management Datastore Architecture defined in RFC 8342.</t>
              <t indent="0">This document obsoletes RFC 7277.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8344"/>
          <seriesInfo name="DOI" value="10.17487/RFC8344"/>
        </reference>
        <reference anchor="RFC8349" target="https://www.rfc-editor.org/info/rfc8349" quoteTitle="true" derivedAnchor="RFC8349">
          <front>
            <title>A YANG Data Model for Routing Management (NMDA Version)</title>
            <author initials="L." surname="Lhotka" fullname="L. Lhotka">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="A." surname="Lindem" fullname="A. Lindem">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="Y." surname="Qu" fullname="Y. Qu">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">This document specifies three YANG modules and one submodule. Together, they form the core routing data model that serves as a framework for configuring and managing a routing subsystem.  It is expected that these modules will be augmented by additional YANG modules defining data models for control-plane protocols, route filters, and other functions.  The core routing data model provides common building blocks for such extensions -- routes, Routing Information Bases (RIBs), and control-plane protocols.</t>
              <t indent="0">The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA).  This document obsoletes RFC 8022.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8349"/>
          <seriesInfo name="DOI" value="10.17487/RFC8349"/>
        </reference>
        <reference anchor="RFC8446" target="https://www.rfc-editor.org/info/rfc8446" quoteTitle="true" derivedAnchor="RFC8446">
          <front>
            <title>The Transport Layer Security (TLS) Protocol Version 1.3</title>
            <author initials="E." surname="Rescorla" fullname="E. Rescorla">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="August"/>
            <abstract>
              <t indent="0">This document specifies version 1.3 of the Transport Layer Security (TLS) protocol.  TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.</t>
              <t indent="0">This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961.  This document also specifies new requirements for TLS 1.2 implementations.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8446"/>
          <seriesInfo name="DOI" value="10.17487/RFC8446"/>
        </reference>
        <reference anchor="RFC8960" target="https://www.rfc-editor.org/info/rfc8960" quoteTitle="true" derivedAnchor="RFC8960">
          <front>
            <title>A YANG Data Model for MPLS Base</title>
            <author initials="T." surname="Saad" fullname="T. Saad">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="K." surname="Raza" fullname="K. Raza">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="R." surname="Gandhi" fullname="R. Gandhi">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="X." surname="Liu" fullname="X. Liu">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="V." surname="Beeram" fullname="V. Beeram">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2020" month="December"/>
            <abstract>
              <t indent="0">This document contains a specification of the MPLS base YANG data model. The MPLS base YANG data model serves as a base framework for configuring and managing an MPLS switching subsystem on an MPLS-enabled router.  It is expected that other MPLS YANG data models (e.g., MPLS Label Switched Path (LSP) static, LDP, or RSVP-TE YANG data models) will augment the MPLS base YANG data model.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8960"/>
          <seriesInfo name="DOI" value="10.17487/RFC8960"/>
        </reference>
      </references>
      <references pn="section-6.2">
        <name slugifiedName="name-informative-references">Informative References</name>
        <reference anchor="RFC3031" target="https://www.rfc-editor.org/info/rfc3031" quoteTitle="true" derivedAnchor="RFC3031">
          <front>
            <title>Multiprotocol Label Switching Architecture</title>
            <author initials="E." surname="Rosen" fullname="E. Rosen">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="A." surname="Viswanathan" fullname="A. Viswanathan">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="R." surname="Callon" fullname="R. Callon">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2001" month="January"/>
            <abstract>
              <t indent="0">This document specifies the architecture for Multiprotocol Label Switching (MPLS).  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3031"/>
          <seriesInfo name="DOI" value="10.17487/RFC3031"/>
        </reference>
        <reference anchor="RFC6428" target="https://www.rfc-editor.org/info/rfc6428" quoteTitle="true" derivedAnchor="RFC6428">
          <front>
            <title>Proactive Connectivity Verification, Continuity Check, and Remote Defect Indication for the MPLS Transport Profile</title>
            <author initials="D." surname="Allan" fullname="D. Allan" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="G." surname="Swallow" fullname="G. Swallow" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Drake" fullname="J. Drake" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2011" month="November"/>
            <abstract>
              <t indent="0">Continuity Check, Proactive Connectivity Verification, and Remote Defect Indication functionalities are required for MPLS Transport Profile (MPLS-TP) Operations, Administration, and Maintenance (OAM).</t>
              <t indent="0">Continuity Check monitors a Label Switched Path for any loss of continuity defect.  Connectivity Verification augments Continuity Check in order to provide confirmation that the desired source is connected to the desired sink.  Remote Defect Indication enables an end point to report, to its associated end point, a fault or defect condition that it detects on a pseudowire, Label Switched Path, or Section.</t>
              <t indent="0">This document specifies specific extensions to Bidirectional Forwarding Detection (BFD) and methods for proactive Continuity Check, Continuity Verification, and Remote Defect Indication for MPLS-TP pseudowires, Label Switched Paths, and Sections using BFD as extended by this memo.  [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6428"/>
          <seriesInfo name="DOI" value="10.17487/RFC6428"/>
        </reference>
        <reference anchor="RFC8342" target="https://www.rfc-editor.org/info/rfc8342" quoteTitle="true" derivedAnchor="RFC8342">
          <front>
            <title>Network Management Datastore Architecture (NMDA)</title>
            <author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Schoenwaelder" fullname="J. Schoenwaelder">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="P." surname="Shafer" fullname="P. Shafer">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="K." surname="Watsen" fullname="K. Watsen">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="R." surname="Wilton" fullname="R. Wilton">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2018" month="March"/>
            <abstract>
              <t indent="0">Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model.  This document updates RFC 7950.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8342"/>
          <seriesInfo name="DOI" value="10.17487/RFC8342"/>
        </reference>
        <reference anchor="RFC8529" target="https://www.rfc-editor.org/info/rfc8529" quoteTitle="true" derivedAnchor="RFC8529">
          <front>
            <title>YANG Data Model for Network Instances</title>
            <author initials="L." surname="Berger" fullname="L. Berger">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="C." surname="Hopps" fullname="C. Hopps">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="A." surname="Lindem" fullname="A. Lindem">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Bogdanovic" fullname="D. Bogdanovic">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="X." surname="Liu" fullname="X. Liu">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2019" month="March"/>
            <abstract>
              <t indent="0">This document defines a network instance module.  This module can be used to manage the virtual resource partitioning that may be present on a network device.  Examples of common industry terms for virtual resource partitioning are VPN Routing and Forwarding (VRF) instances and Virtual Switch Instances (VSIs).</t>
              <t indent="0">The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8529"/>
          <seriesInfo name="DOI" value="10.17487/RFC8529"/>
        </reference>
        <reference anchor="RFC8530" target="https://www.rfc-editor.org/info/rfc8530" quoteTitle="true" derivedAnchor="RFC8530">
          <front>
            <title>YANG Model for Logical Network Elements</title>
            <author initials="L." surname="Berger" fullname="L. Berger">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="C." surname="Hopps" fullname="C. Hopps">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="A." surname="Lindem" fullname="A. Lindem">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="D." surname="Bogdanovic" fullname="D. Bogdanovic">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="X." surname="Liu" fullname="X. Liu">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2019" month="March"/>
            <abstract>
              <t indent="0">This document defines a logical network element (LNE) YANG module that is compliant with the Network Management Datastore Architecture (NMDA).  This module can be used to manage the logical resource partitioning that may be present on a network device.  Examples of common industry terms for logical resource partitioning are logical systems or logical routers.  The YANG model in this document conforms with NMDA as defined in RFC 8342.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8530"/>
          <seriesInfo name="DOI" value="10.17487/RFC8530"/>
        </reference>
        <reference anchor="RFC8532" target="https://www.rfc-editor.org/info/rfc8532" quoteTitle="true" derivedAnchor="RFC8532">
          <front>
            <title>Generic YANG Data Model for the Management of Operations, Administration, and Maintenance (OAM) Protocols That Use Connectionless Communications</title>
            <author initials="D." surname="Kumar" fullname="D. Kumar">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="Z." surname="Wang" fullname="Z. Wang">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="Q." surname="Wu" fullname="Q. Wu" role="editor">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="R." surname="Rahman" fullname="R. Rahman">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="S." surname="Raghavan" fullname="S. Raghavan">
              <organization showOnFrontPage="true"/>
            </author>
            <date year="2019" month="April"/>
            <abstract>
              <t indent="0">This document presents a base YANG Data model for the management of Operations, Administration, and Maintenance (OAM) protocols that use connectionless communications.  The data model is defined using the YANG data modeling language, as specified in RFC 7950.  It provides a technology-independent abstraction of key OAM constructs for OAM protocols that use connectionless communication.  The base model presented here can be extended to include technology-specific details.</t>
              <t indent="0">There are two key benefits of this approach: First, it leads to uniformity between OAM protocols.  Second, it supports both nested OAM workflows (i.e., performing OAM functions at the same level or different levels through a unified interface) as well as interactive OAM workflows (i.e., performing OAM functions at the same level through a unified interface).</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8532"/>
          <seriesInfo name="DOI" value="10.17487/RFC8532"/>
        </reference>
        <reference anchor="W3C.REC-xml-20081126" target="https://www.w3.org/TR/2008/REC-xml-20081126" quoteTitle="true" derivedAnchor="W3C.REC-xml-20081126">
          <front>
            <title>Extensible Markup Language (XML) 1.0 (Fifth Edition)</title>
            <author initials="T." surname="Bray" fullname="Tim Bray">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="J." surname="Paoli" fullname="Jean Paoli">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="M." surname="Sperberg-McQueen" fullname="Michael Sperberg-McQueen">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="E." surname="Maler" fullname="Eve Maler">
              <organization showOnFrontPage="true"/>
            </author>
            <author initials="F." surname="Yergeau" fullname="Francois Yergeau">
              <organization showOnFrontPage="true"/>
            </author>
            <date month="November" year="2008"/>
          </front>
          <refcontent>World Wide Web Consortium Recommendation REC-xml-20081126</refcontent>
        </reference>
      </references>
    </references>
    <section anchor="ECHO-CONFIG" numbered="true" toc="include" removeInRFC="false" pn="section-appendix.a">
      <name slugifiedName="name-echo-function-configuration">Echo Function Configuration Example</name>
      <t indent="0" pn="section-appendix.a-1">As mentioned in <xref target="IP-SH-CFG" format="default" sectionFormat="of" derivedContent="Section 2.1.2"/>, the mechanism to start
      and stop the Echo function, as defined in <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/> and discussed in 
      <xref target="RFC5881" format="default" sectionFormat="of" derivedContent="RFC5881"/>, is implementation specific. In this appendix, we
      provide an example of how the Echo function can be implemented via
      configuration.</t>
      <sourcecode type="yangtree" markers="false" pn="section-appendix.a-2">
module: example-bfd-echo
  augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
            /bfd-ip-sh:sessions:
    +--rw echo {bfd-types:echo-mode}?
       +--rw desired-min-echo-tx-interval?    uint32
       +--rw required-min-echo-rx-interval?   uint32
</sourcecode>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-appendix.a.1">
        <name slugifiedName="name-example-yang-module-for-bfd">Example YANG Module for BFD Echo Function Configuration</name>
        <t indent="0" pn="section-appendix.a.1-1">This appendix provides an example YANG module for
        configuration of the BFD Echo function.  It imports and augments
        "/routing/control-plane-protocols/control-plane-protocol" from
        <xref target="RFC8349" format="default" sectionFormat="of" derivedContent="RFC8349"/>, and it references <xref target="RFC5880" format="default" sectionFormat="of" derivedContent="RFC5880"/>.
        </t>
        <sourcecode type="yang" markers="false" pn="section-appendix.a.1-2">
module example-bfd-echo {
  namespace "tag:example.com,2021:example-bfd-echo";
  prefix example-bfd-echo;

  import ietf-bfd-types {
    prefix bfd-types;
  }
  import ietf-bfd {
    prefix bfd;
  }
  import ietf-bfd-ip-sh {
    prefix bfd-ip-sh;
  }
  import ietf-routing {
    prefix rt;
  }

  organization
    "IETF BFD Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/bfd/&gt;
     WG List:  &lt;mailto:rtg-bfd@ietf.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:reshad@yahoo.com&gt;

     Editor:   Lianshu Zheng
               &lt;mailto:veronique_cheng@hotmail.com&gt;

     Editor:   Mahesh Jethanandani
               &lt;mailto:mjethanandani@gmail.com&gt;";
  description
    "This module contains an example YANG augmentation for
     configuration of the BFD Echo function.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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

     This version of this YANG module is part of RFC 9127; see the
     RFC itself for full legal notices.";

  revision 2021-09-03 {
    description
      "Initial revision.";
    reference
      "RFC 9127: YANG Data Model for Bidirectional Forwarding
       Detection (BFD)";
  }

  /*
   * Groupings
   */

  grouping echo-cfg-parms {
    description
      "BFD grouping for Echo configuration parameters.";
    leaf desired-min-echo-tx-interval {
      type uint32;
      units "microseconds";
      default "0";
      description
        "This is the minimum interval that the local system would
         like to use when transmitting BFD Echo packets.  If 0,
         the Echo function as defined in BFD (RFC 5880) is
         disabled.";
    }
    leaf required-min-echo-rx-interval {
      type uint32;
      units "microseconds";
      default "0";
      description
        "This is the Required Min Echo RX Interval as defined in BFD
         (RFC 5880).";
    }
  }

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
        + "bfd-ip-sh:sessions" {
    description
      "Augmentation for the BFD Echo function.";
    container echo {
      if-feature "bfd-types:echo-mode";
      description
        "BFD Echo function container.";
      uses echo-cfg-parms;
    }
  }
}
</sourcecode>
      </section>
    </section>
    <section numbered="false" toc="include" removeInRFC="false" pn="section-appendix.b">
      <name slugifiedName="name-acknowledgments">Acknowledgments</name>
      <t indent="0" pn="section-appendix.b-1">We would like to thank <contact fullname="Nobo Akiya"/> and
      <contact fullname="Jeff Haas"/> for their encouragement on this work.
      We would also like to thank <contact fullname="Tom Petch"/> for his
      comments on the document. We would also like to thank
      <contact fullname="Acee Lindem"/> for his guidance. Thanks also to
      <contact fullname="Jürgen Schönwälder"/>, who was instrumental in improving the YANG
      modules.</t>
    </section>
    <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.c">
      <name slugifiedName="name-authors-addresses">Authors' Addresses</name>
      <author fullname="Reshad Rahman" initials="R." role="editor" surname="Rahman">
        <organization showOnFrontPage="true"/>
        <address>
          <postal>
            <country>Canada</country>
          </postal>
          <email>reshad@yahoo.com</email>
        </address>
      </author>
      <author fullname="Lianshu Zheng" initials="L." role="editor" surname="Zheng">
        <organization showOnFrontPage="true">Huawei Technologies</organization>
        <address>
          <postal>
            <country>China</country>
          </postal>
          <email>veronique_cheng@hotmail.com</email>
        </address>
      </author>
      <author fullname="Mahesh Jethanandani" initials="M." role="editor" surname="Jethanandani">
        <organization showOnFrontPage="true">Xoriant Corporation</organization>
        <address>
          <postal>
            <street>1248 Reamwood Ave</street>
            <city>Sunnyvale</city>
            <region>California</region>
            <code>94089</code>
            <country>United States of America</country>
          </postal>
          <email>mjethanandani@gmail.com</email>
        </address>
      </author>
      <author fullname="Santosh Pallagatti" initials="S." surname="Pallagatti">
        <organization showOnFrontPage="true">VMware</organization>
        <address>
          <postal>
            <country>India</country>
          </postal>
          <email>santosh.pallagatti@gmail.com</email>
        </address>
      </author>
      <author fullname="Greg Mirsky" initials="G." surname="Mirsky">
        <organization showOnFrontPage="true">Ericsson</organization>
        <address>
          <email>gregimirsky@gmail.com</email>
        </address>
      </author>
    </section>
  </back>
</rfc>
