<?xml version="1.0" encoding="UTF-8"?>
  <?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?>
  <!-- generated by https://github.com/cabo/kramdown-rfc2629 version 1.2.9 -->

<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
]>

<?rfc toc="yes"?>
<?rfc sortrefs="yes"?>
<?rfc symrefs="yes"?> version='1.0' encoding='utf-8'?>
<rfc ipr="trust200902" xmlns:xi="http://www.w3.org/2001/XInclude" version="3" category="std" consensus="true" docName="draft-ietf-acme-ip-08" category="std"> indexInclude="true" ipr="trust200902" number="8738" prepTime="2020-02-28T19:14:01" scripts="Common,Latin" sortRefs="true" submissionType="IETF" symRefs="true" tocDepth="3" tocInclude="true" xml:lang="en">
  <link href="https://datatracker.ietf.org/doc/draft-ietf-acme-ip-08" rel="prev"/>
  <link href="https://dx.doi.org/10.17487/rfc8738" rel="alternate"/>
  <link href="urn:issn:2070-1721" rel="alternate"/>
  <front>
    <title abbrev="ACME-IP">ACME abbrev="ACME-IP">Automated Certificate Management Environment (ACME) IP Identifier Validation Extension</title>
    <seriesInfo name="RFC" value="8738" stream="IETF"/>
    <author initials="R.B." surname="Shoemaker" fullname="Roland Bracewell Shoemaker">
      <organization abbrev="ISRG">Internet abbrev="ISRG" showOnFrontPage="true">Internet Security Research Group</organization>
      <address>
        <email>roland@letsencrypt.org</email>
      </address>
    </author>
    <date year="2019" month="October" day="01"/>

    <area>General</area> month="02" year="2020"/>
    <area>Security</area>
    <workgroup>ACME Working Group</workgroup>

    <abstract>

<t>This
    <keyword>acme</keyword>
    <keyword>pki</keyword>
    <abstract pn="section-abstract">
      <t pn="section-abstract-1">This document specifies identifiers and challenges required to enable the Automated Certificate Management Environment (ACME) to issue certificates for IP addresses.</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 pn="section-boilerplate.1-1">
            This is an Internet Standards Track document.
        </t>
        <t 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 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/rfc8738" 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 pn="section-boilerplate.2-1">
            Copyright (c) 2020 IETF Trust and the persons identified as the
            document authors. All rights reserved.
        </t>
        <t 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 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>
          </li>
          <li pn="section-toc.1-1.2">
            <t keepWithNext="true" 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-terminology">Terminology</xref></t>
          </li>
          <li pn="section-toc.1-1.3">
            <t keepWithNext="true" 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-ip-identifier">IP Identifier</xref></t>
          </li>
          <li pn="section-toc.1-1.4">
            <t keepWithNext="true" 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-identifier-validation-chall">Identifier Validation Challenges</xref></t>
          </li>
          <li pn="section-toc.1-1.5">
            <t keepWithNext="true" 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-http-challenge">HTTP Challenge</xref></t>
          </li>
          <li pn="section-toc.1-1.6">
            <t keepWithNext="true" 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-tls-with-application-layer-">TLS with Application-Layer Protocol Negotiation (TLS ALPN) Challenge</xref></t>
          </li>
          <li pn="section-toc.1-1.7">
            <t keepWithNext="true" pn="section-toc.1-1.7.1"><xref derivedContent="7" format="counter" sectionFormat="of" target="section-7"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-dns-challenge">DNS Challenge</xref></t>
          </li>
          <li pn="section-toc.1-1.8">
            <t keepWithNext="true" pn="section-toc.1-1.8.1"><xref derivedContent="8" format="counter" sectionFormat="of" target="section-8"/>.  <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.1-1.8.2">
              <li pn="section-toc.1-1.8.2.1">
                <t keepWithNext="true" pn="section-toc.1-1.8.2.1.1"><xref derivedContent="8.1" format="counter" sectionFormat="of" target="section-8.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-identifier-types">Identifier Types</xref></t>
              </li>
              <li pn="section-toc.1-1.8.2.2">
                <t keepWithNext="true" pn="section-toc.1-1.8.2.2.1"><xref derivedContent="8.2" format="counter" sectionFormat="of" target="section-8.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-challenge-types">Challenge Types</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.9">
            <t keepWithNext="true" pn="section-toc.1-1.9.1"><xref derivedContent="9" format="counter" sectionFormat="of" target="section-9"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-security-considerations">Security Considerations</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.9.2">
              <li pn="section-toc.1-1.9.2.1">
                <t keepWithNext="true" pn="section-toc.1-1.9.2.1.1"><xref derivedContent="9.1" format="counter" sectionFormat="of" target="section-9.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-certification-authority-ca-">Certification Authority (CA) Policy Considerations</xref></t>
              </li>
            </ul>
          </li>
          <li pn="section-toc.1-1.10">
            <t keepWithNext="true" pn="section-toc.1-1.10.1"><xref derivedContent="10" format="counter" sectionFormat="of" target="section-10"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-normative-references">Normative References</xref></t>
          </li>
          <li pn="section-toc.1-1.11">
            <t keepWithNext="true" pn="section-toc.1-1.11.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.a"/><xref derivedContent="" format="title" sectionFormat="of" target="name-acknowledgments">Acknowledgments</xref></t>
          </li>
          <li pn="section-toc.1-1.12">
            <t keepWithNext="true" pn="section-toc.1-1.12.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="" format="title" sectionFormat="of" target="name-authors-address">Author's Address</xref></t>
          </li>
        </ul>
      </section>
    </toc>
  </front>
  <middle>
    <section anchor="introduction" title="Introduction">

<t>The numbered="true" toc="include" removeInRFC="false" pn="section-1">
      <name slugifiedName="name-introduction">Introduction</name>
      <t pn="section-1-1">The Automatic Certificate Management Environment (ACME) <xref target="RFC8555"/> target="RFC8555" format="default" sectionFormat="of" derivedContent="RFC8555"/> only defines challenges for validating control of DNS host name identifiers, which limits its use to being used for issuing certificates for DNS identifiers. In order to allow validation of IPv4 and IPv6 identifiers for inclusion in X.509 certificates, this document specifies how challenges defined in the original ACME specification and the TLS-ALPN extension specification <xref target="I-D.ietf-acme-tls-alpn"/> target="RFC8737" format="default" sectionFormat="of" derivedContent="RFC8737"/> can be used to validate IP identifiers.</t>
    </section>
    <section anchor="terminology" title="Terminology">

<t>The numbered="true" toc="include" removeInRFC="false" pn="section-2">
      <name slugifiedName="name-terminology">Terminology</name>
      <t pn="section-2-1">
    The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and “OPTIONAL” "<bcp14>OPTIONAL</bcp14>" in this document are
    to be interpreted as described in BCP 14 BCP 14 <xref target="RFC2119"/> target="RFC2119" format="default" sectionFormat="of" derivedContent="RFC2119"/>
        <xref target="RFC8174"/> target="RFC8174" format="default" sectionFormat="of" derivedContent="RFC8174"/> when, and only when, they appear in all capitals,
    as shown here.</t> here.
      </t>
    </section>
    <section anchor="ip-identifier" title="IP Identifier">

<t><xref target="RFC8555"/> numbered="true" toc="include" removeInRFC="false" pn="section-3">
      <name slugifiedName="name-ip-identifier">IP Identifier</name>
      <t pn="section-3-1"><xref target="RFC8555" format="default" sectionFormat="of" derivedContent="RFC8555"/> only defines the identifier
      type “dns”, "dns", which is used to refer to fully qualified domain names. If
      an ACME server wishes to request proof that a user controls a an IPv4 or
      IPv6 address, it MUST <bcp14>MUST</bcp14> create an authorization with the
      identifier type “ip”. "ip". The value field of the identifier MUST
      <bcp14>MUST</bcp14> contain the textual form of the address as defined
      in <xref target="RFC1123"/> Section 2.1 target="RFC1123" sectionFormat="of" section="2.1" format="default" derivedLink="https://rfc-editor.org/rfc/rfc1123#section-2.1" derivedContent="RFC1123"/> for IPv4 and in
      <xref target="RFC5952"/> Section 4 target="RFC5952" sectionFormat="of" section="4" format="default" derivedLink="https://rfc-editor.org/rfc/rfc5952#section-4" derivedContent="RFC5952"/> for IPv6.</t>

<t>An
      <t pn="section-3-2">An identifier for the IPv6 address 2001:db8::1 would be formatted
      like so:</t>

<figure><artwork><![CDATA[
      <sourcecode type="json" markers="false" pn="section-3-3">
{"type": "ip", "value": "2001:db8::1"}
]]></artwork></figure>
</sourcecode>
    </section>
    <section anchor="identifier-validation-challenges" title="Identifier numbered="true" toc="include" removeInRFC="false" pn="section-4">
      <name slugifiedName="name-identifier-validation-chall">Identifier Validation Challenges">

<t>IP Challenges</name>
      <t pn="section-4-1">IP identifiers MAY <bcp14>MAY</bcp14> be used with the existing “http-01” "http-01"
      (see Section 8.3 of <xref target="RFC8555"/>) target="RFC8555" sectionFormat="of" section="8.3" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8555#section-8.3" derivedContent="RFC8555"/>) and “tls-alpn-01”
      "tls-alpn-01" (see Section 3 of <xref target="I-D.ietf-acme-tls-alpn"/>). target="RFC8737" sectionFormat="of" section="3" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8737#section-3" derivedContent="RFC8737"/>). To use IP identifiers with these challenges, their
      initial DNS resolution step MUST <bcp14>MUST</bcp14> be skipped, and the IP
      address used for validation MUST <bcp14>MUST</bcp14> be the value of the
      identifier.</t>
    </section>
    <section anchor="http-challenge" title="HTTP Challenge">

<t>For numbered="true" toc="include" removeInRFC="false" pn="section-5">
      <name slugifiedName="name-http-challenge">HTTP Challenge</name>
      <t pn="section-5-1">For the “http-01” "http-01" challenge, the Host header field MUST
      <bcp14>MUST</bcp14> be set to the IP address being used for validation
      per <xref target="RFC7230"/>. target="RFC7230" format="default" sectionFormat="of" derivedContent="RFC7230"/>. The textual form of this
      address MUST <bcp14>MUST</bcp14> be as defined in <xref target="RFC1123"/> Section 2.1 target="RFC1123" sectionFormat="of" section="2.1" format="default" derivedLink="https://rfc-editor.org/rfc/rfc1123#section-2.1" derivedContent="RFC1123"/> for IPv4 and in <xref target="RFC5952"/> Section 4 target="RFC5952" sectionFormat="of" section="4" format="default" derivedLink="https://rfc-editor.org/rfc/rfc5952#section-4" derivedContent="RFC5952"/> for IPv6.</t>
    </section>
    <section anchor="tls-with-application-level-protocol-negotiation-tls-alpn-challenge" title="TLS numbered="true" toc="include" removeInRFC="false" pn="section-6">
      <name slugifiedName="name-tls-with-application-layer-">TLS with Application Level Application-Layer Protocol Negotiation (TLS ALPN) Challenge">

<t>For Challenge</name>
      <t pn="section-6-1">For the “tls-alpn-01” "tls-alpn-01" challenge, the subjectAltName extension in the
      validation certificate MUST <bcp14>MUST</bcp14> contain a single iPAddress
      that matches the address being validated. As <xref target="RFC6066"/> target="RFC6066" format="default" sectionFormat="of" derivedContent="RFC6066"/> does not permit IP addresses to be used in the SNI Server
      Name Indication (SNI) extension HostName field, the server MUST
      <bcp14>MUST</bcp14> instead use the IN-ADDR.ARPA <xref target="RFC1034"/> target="RFC1034" format="default" sectionFormat="of" derivedContent="RFC1034"/> or IP6.ARPA <xref target="RFC3596"/> target="RFC3596" format="default" sectionFormat="of" derivedContent="RFC3596"/>
      reverse mapping of the IP address as the HostName field value instead of
      the IP address string representation itself. For example, if the IP
      address being validated is 2001:db8::1, the SNI HostName field should
      contain “1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa”.</t>
"1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa".</t>
    </section>
    <section anchor="dns-challenge" title="DNS Challenge">

<t>The numbered="true" toc="include" removeInRFC="false" pn="section-7">
      <name slugifiedName="name-dns-challenge">DNS Challenge</name>
      <t pn="section-7-1">The existing “dns-01” "dns-01" challenge MUST NOT <bcp14>MUST NOT</bcp14> be used to validate IP identifiers.</t>
    </section>
    <section anchor="iana-considerations" title="IANA Considerations"> numbered="true" toc="include" removeInRFC="false" pn="section-8">
      <name slugifiedName="name-iana-considerations">IANA Considerations</name>
      <section anchor="identifier-types" title="Identifier Types">

<t>Adds numbered="true" toc="include" removeInRFC="false" pn="section-8.1">
        <name slugifiedName="name-identifier-types">Identifier Types</name>
        <t pn="section-8.1-1">Per this document, a new type has been added to the “ACME "ACME Identifier Types” Types"
	registry defined in Section 9.7.7 of <xref target="RFC8555"/> target="RFC8555" sectionFormat="of" section="9.7.7" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8555#section-9.7.7" derivedContent="RFC8555"/> with Label “ip” "ip" and Reference “I-D.ietf-acme-ip”.</t>
	"RFC 8738".</t>
      </section>
      <section anchor="challenge-types" title="Challenge Types">

<t>Adds numbered="true" toc="include" removeInRFC="false" pn="section-8.2">
        <name slugifiedName="name-challenge-types">Challenge Types</name>
        <t pn="section-8.2-1">Per this document, two new entries have been added to the “ACME "ACME Validation Methods” Methods"
	registry defined in Section 9.7.8 of <xref target="RFC8555"/>. target="RFC8555" sectionFormat="of" section="9.7.8" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8555#section-9.7.8" derivedContent="RFC8555"/>. These entries are defined below:</t>

<texttable>
      <ttcol align='left'>Label</ttcol>
      <ttcol align='left'>Identifier Type</ttcol>
      <ttcol align='left'>ACME</ttcol>
      <ttcol align='left'>Reference</ttcol>
      <c>http-01</c>
      <c>ip</c>
      <c>Y</c>
      <c>I-D.ietf-acme-ip</c>
      <c>tls-alpn-01</c>
      <c>ip</c>
      <c>Y</c>
      <c>I-D.ietf-acme-ip</c>
</texttable>
        <table align="center" pn="table-1">
          <thead>
            <tr>
              <th align="left" colspan="1" rowspan="1">Label</th>
              <th align="left" colspan="1" rowspan="1">Identifier Type</th>
              <th align="left" colspan="1" rowspan="1">ACME</th>
              <th align="left" colspan="1" rowspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="left" colspan="1" rowspan="1">http-01</td>
              <td align="left" colspan="1" rowspan="1">ip</td>
              <td align="left" colspan="1" rowspan="1">Y</td>
              <td align="left" colspan="1" rowspan="1">RFC 8738</td>
            </tr>
            <tr>
              <td align="left" colspan="1" rowspan="1">tls-alpn-01</td>
              <td align="left" colspan="1" rowspan="1">ip</td>
              <td align="left" colspan="1" rowspan="1">Y</td>
              <td align="left" colspan="1" rowspan="1">RFC 8738</td>
            </tr>
          </tbody>
        </table>
      </section>
    </section>
    <section anchor="security-considerations" title="Security Considerations">

<t>The numbered="true" toc="include" removeInRFC="false" pn="section-9">
      <name slugifiedName="name-security-considerations">Security Considerations</name>
      <t pn="section-9-1">The extensions to ACME described in this document do not deviate from
      the broader threat model described in <xref target="RFC8555"/> Section 10.1.</t> target="RFC8555" sectionFormat="of" section="10.1" format="default" derivedLink="https://rfc-editor.org/rfc/rfc8555#section-10.1" derivedContent="RFC8555"/>.</t>
      <section anchor="ca-policy-considerations" title="CA numbered="true" toc="include" removeInRFC="false" pn="section-9.1">
        <name slugifiedName="name-certification-authority-ca-">Certification Authority (CA) Policy Considerations">

<t>This Considerations</name>
        <t pn="section-9.1-1">This document only specifies how a an ACME server may validate that a
	certificate applicant controls a an IP identifier at the time of
	validation. The CA may wish to perform additional checks not specified
	in this document. For example, if the CA believes an IP identifier
	belongs to a an ISP or cloud service provider with short delegation
	periods, they may wish to impose additional restrictions on
	certificates requested for that identifier.</t>
      </section>
    </section>
<section anchor="acknowledgments" title="Acknowledgments">

<t>The author would like to thank those who contributed to this document and offered editorial and technical input, especially Jacob Hoffman-Andrews and Daniel McCarney.</t>

</section>
  </middle>
  <back>
    <references title='Normative References'> pn="section-10">
      <name slugifiedName="name-normative-references">Normative References</name>
      <reference anchor="RFC1034" target='https://www.rfc-editor.org/info/rfc1034'> target="https://www.rfc-editor.org/info/rfc1034" quoteTitle="true" derivedAnchor="RFC1034">
        <front>
          <title>Domain names - concepts and facilities</title>
          <author initials='P.V.' surname='Mockapetris' fullname='P.V. Mockapetris'><organization /></author> initials="P.V." surname="Mockapetris" fullname="P.V. Mockapetris">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='1987' month='November' />
<abstract><t>This year="1987" month="November"/>
          <abstract>
            <t>This RFC is the revised basic definition of The Domain Name System.  It obsoletes RFC-882.  This memo describes the domain style names and their used for host address look up and electronic mail forwarding.  It discusses the clients and servers in the domain name system and the protocol used between them.</t></abstract> them.</t>
          </abstract>
        </front>
        <seriesInfo name='STD' value='13'/> name="STD" value="13"/>
        <seriesInfo name='RFC' value='1034'/> name="RFC" value="1034"/>
        <seriesInfo name='DOI' value='10.17487/RFC1034'/> name="DOI" value="10.17487/RFC1034"/>
      </reference>
      <reference anchor="RFC1123" target='https://www.rfc-editor.org/info/rfc1123'> target="https://www.rfc-editor.org/info/rfc1123" quoteTitle="true" derivedAnchor="RFC1123">
        <front>
          <title>Requirements for Internet Hosts - Application and Support</title>
          <author initials='R.' surname='Braden' fullname='R. Braden' role='editor'><organization /></author> initials="R." surname="Braden" fullname="R. Braden" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='1989' month='October' />
<abstract><t>This year="1989" month="October"/>
          <abstract>
            <t>This RFC is an official specification for the Internet community.  It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents relating to hosts.  [STANDARDS-TRACK]</t></abstract>  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name='STD' value='3'/> name="STD" value="3"/>
        <seriesInfo name='RFC' value='1123'/> name="RFC" value="1123"/>
        <seriesInfo name='DOI' value='10.17487/RFC1123'/> name="DOI" value="10.17487/RFC1123"/>
      </reference>
      <reference anchor="RFC2119" target='https://www.rfc-editor.org/info/rfc2119'> target="https://www.rfc-editor.org/info/rfc2119" quoteTitle="true" derivedAnchor="RFC2119">
        <front>
          <title>Key words for use in RFCs to Indicate Requirement Levels</title>
          <author initials='S.' surname='Bradner' fullname='S. Bradner'><organization /></author> initials="S." surname="Bradner" fullname="S. Bradner">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='1997' month='March' />
<abstract><t>In year="1997" month="March"/>
          <abstract>
            <t>In many standards track documents several words are used to signify the requirements in the specification.  These words are often capitalized. This document defines these words as they should be interpreted in IETF documents.  This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t></abstract> improvements.</t>
          </abstract>
        </front>
        <seriesInfo name='BCP' value='14'/> name="BCP" value="14"/>
        <seriesInfo name='RFC' value='2119'/> name="RFC" value="2119"/>
        <seriesInfo name='DOI' value='10.17487/RFC2119'/> name="DOI" value="10.17487/RFC2119"/>
      </reference>
      <reference anchor="RFC3596" target='https://www.rfc-editor.org/info/rfc3596'> target="https://www.rfc-editor.org/info/rfc3596" quoteTitle="true" derivedAnchor="RFC3596">
        <front>
          <title>DNS Extensions to Support IP Version 6</title>
          <author initials='S.' surname='Thomson' fullname='S. Thomson'><organization /></author> initials="S." surname="Thomson" fullname="S. Thomson">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='C.' surname='Huitema' fullname='C. Huitema'><organization /></author> initials="C." surname="Huitema" fullname="C. Huitema">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='V.' surname='Ksinant' fullname='V. Ksinant'><organization /></author> initials="V." surname="Ksinant" fullname="V. Ksinant">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='M.' surname='Souissi' fullname='M. Souissi'><organization /></author> initials="M." surname="Souissi" fullname="M. Souissi">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2003' month='October' />
<abstract><t>This year="2003" month="October"/>
          <abstract>
            <t>This document defines the changes that need to be made to the Domain Name System (DNS) to support hosts running IP version 6 (IPv6).  The changes include a resource record type to store an IPv6 address, a domain to support lookups based on an IPv6 address, and updated definitions of existing query types that return Internet addresses as part of additional section processing.  The extensions are designed to be compatible with existing applications and, in particular, DNS implementations themselves.  [STANDARDS-TRACK]</t></abstract>  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name='STD' value='88'/> name="STD" value="88"/>
        <seriesInfo name='RFC' value='3596'/> name="RFC" value="3596"/>
        <seriesInfo name='DOI' value='10.17487/RFC3596'/> name="DOI" value="10.17487/RFC3596"/>
      </reference>
      <reference anchor="RFC5952" target='https://www.rfc-editor.org/info/rfc5952'> target="https://www.rfc-editor.org/info/rfc5952" quoteTitle="true" derivedAnchor="RFC5952">
        <front>
          <title>A Recommendation for IPv6 Address Text Representation</title>
          <author initials='S.' surname='Kawamura' fullname='S. Kawamura'><organization /></author> initials="S." surname="Kawamura" fullname="S. Kawamura">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='M.' surname='Kawashima' fullname='M. Kawashima'><organization /></author> initials="M." surname="Kawashima" fullname="M. Kawashima">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2010' month='August' />
<abstract><t>As year="2010" month="August"/>
          <abstract>
            <t>As IPv6 deployment increases, there will be a dramatic increase in the need to use IPv6 addresses in text.  While the IPv6 address architecture in Section 2.2 of RFC 4291 describes a flexible model for text representation of an IPv6 address, this flexibility has been causing problems for operators, system engineers, and users.  This document defines a canonical textual representation format.  It does not define a format for internal storage, such as within an application or database.  It is expected that the canonical format will be followed by humans and systems when representing IPv6 addresses as text, but all implementations must accept and be able to handle any legitimate RFC 4291 format.  [STANDARDS-TRACK]</t></abstract>  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name='RFC' value='5952'/> name="RFC" value="5952"/>
        <seriesInfo name='DOI' value='10.17487/RFC5952'/> name="DOI" value="10.17487/RFC5952"/>
      </reference>
      <reference anchor="RFC6066" target='https://www.rfc-editor.org/info/rfc6066'> target="https://www.rfc-editor.org/info/rfc6066" quoteTitle="true" derivedAnchor="RFC6066">
        <front>
          <title>Transport Layer Security (TLS) Extensions: Extension Definitions</title>
          <author initials='D.' surname='Eastlake 3rd' fullname='D. initials="D." surname="Eastlake 3rd" fullname="D. Eastlake 3rd'><organization /></author> 3rd">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2011' month='January' />
<abstract><t>This year="2011" month="January"/>
          <abstract>
            <t>This document provides specifications for existing TLS extensions.  It is a companion document for RFC 5246, &quot;The "The Transport Layer Security (TLS) Protocol Version 1.2&quot;. 1.2".  The extensions specified are server_name, max_fragment_length, client_certificate_url, trusted_ca_keys, truncated_hmac, and status_request.  [STANDARDS-TRACK]</t></abstract>  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name='RFC' value='6066'/> name="RFC" value="6066"/>
        <seriesInfo name='DOI' value='10.17487/RFC6066'/> name="DOI" value="10.17487/RFC6066"/>
      </reference>
      <reference anchor="RFC7230" target='https://www.rfc-editor.org/info/rfc7230'> target="https://www.rfc-editor.org/info/rfc7230" quoteTitle="true" derivedAnchor="RFC7230">
        <front>
          <title>Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing</title>
          <author initials='R.' surname='Fielding' fullname='R. Fielding' role='editor'><organization /></author> initials="R." surname="Fielding" fullname="R. Fielding" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='J.' surname='Reschke' fullname='J. Reschke' role='editor'><organization /></author> initials="J." surname="Reschke" fullname="J. Reschke" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2014' month='June' />
<abstract><t>The year="2014" month="June"/>
          <abstract>
            <t>The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems.  This document provides an overview of HTTP architecture and its associated terminology, defines the &quot;http&quot; "http" and &quot;https&quot; "https" Uniform Resource Identifier (URI) schemes, defines the HTTP/1.1 message syntax and parsing requirements, and describes related security concerns for implementations.</t></abstract> implementations.</t>
          </abstract>
        </front>
        <seriesInfo name='RFC' value='7230'/> name="RFC" value="7230"/>
        <seriesInfo name='DOI' value='10.17487/RFC7230'/> name="DOI" value="10.17487/RFC7230"/>
      </reference>
      <reference anchor="RFC8174" target='https://www.rfc-editor.org/info/rfc8174'> target="https://www.rfc-editor.org/info/rfc8174" quoteTitle="true" derivedAnchor="RFC8174">
        <front>
          <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
          <author initials='B.' surname='Leiba' fullname='B. Leiba'><organization /></author> initials="B." surname="Leiba" fullname="B. Leiba">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2017' month='May' />
<abstract><t>RFC year="2017" month="May"/>
          <abstract>
            <t>RFC 2119 specifies common key words that may be used in protocol  specifications.  This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the  defined special meanings.</t></abstract> meanings.</t>
          </abstract>
        </front>
        <seriesInfo name='BCP' value='14'/> name="BCP" value="14"/>
        <seriesInfo name='RFC' value='8174'/> name="RFC" value="8174"/>
        <seriesInfo name='DOI' value='10.17487/RFC8174'/> name="DOI" value="10.17487/RFC8174"/>
      </reference>
      <reference anchor="RFC8555" target='https://www.rfc-editor.org/info/rfc8555'> target="https://www.rfc-editor.org/info/rfc8555" quoteTitle="true" derivedAnchor="RFC8555">
        <front>
          <title>Automatic Certificate Management Environment (ACME)</title>
          <author initials='R.' surname='Barnes' fullname='R. Barnes'><organization /></author> initials="R." surname="Barnes" fullname="R. Barnes">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='J.' surname='Hoffman-Andrews' fullname='J. Hoffman-Andrews'><organization /></author> initials="J." surname="Hoffman-Andrews" fullname="J. Hoffman-Andrews">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='D.' surname='McCarney' fullname='D. McCarney'><organization /></author> initials="D." surname="McCarney" fullname="D. McCarney">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials='J.' surname='Kasten' fullname='J. Kasten'><organization /></author> initials="J." surname="Kasten" fullname="J. Kasten">
            <organization showOnFrontPage="true"/>
          </author>
          <date year='2019' month='March' />
<abstract><t>Public year="2019" month="March"/>
          <abstract>
            <t>Public Key Infrastructure using X.509 (PKIX) certificates are used for a number of purposes, the most significant of which is the authentication of domain names.  Thus, certification authorities (CAs) in the Web PKI are trusted to verify that an applicant for a certificate legitimately represents the domain name(s) in the certificate.  As of this writing, this verification is done through a collection of ad hoc mechanisms.  This document describes a protocol that a CA and an applicant can use to automate the process of verification and certificate issuance.  The protocol also provides facilities for other certificate management functions, such as certificate revocation.</t></abstract> revocation.</t>
          </abstract>
        </front>
        <seriesInfo name='RFC' value='8555'/> name="RFC" value="8555"/>
        <seriesInfo name='DOI' value='10.17487/RFC8555'/> name="DOI" value="10.17487/RFC8555"/>
      </reference>
      <reference anchor="I-D.ietf-acme-tls-alpn"> anchor="RFC8737" target="https://www.rfc-editor.org/info/rfc8737" quoteTitle="true" derivedAnchor="RFC8737">
        <front>
<title>ACME
          <title>Automated Certificate Management Environment (ACME) TLS ALPN Application-Layer Protocol Negotiation (ALPN) Challenge Extension</title>
          <author initials='R' surname='Shoemaker' fullname='Roland Shoemaker'> initials="R.B." surname="Shoemaker" fullname="Roland Bracewell Shoemaker">
            <organization /> showOnFrontPage="true"/>
          </author>
          <date month='September' day='5' year='2019' />

<abstract><t>This document specifies a new challenge for the Automated Certificate Management Environment (ACME) protocol which allows for domain control validation using TLS.</t></abstract> month="February" year="2020"/>
        </front>
        <seriesInfo name='Internet-Draft' value='draft-ietf-acme-tls-alpn-06' />
<format type='TXT'
        target='http://www.ietf.org/internet-drafts/draft-ietf-acme-tls-alpn-06.txt' /> name="RFC" value="8737"/>
        <seriesInfo name="DOI" value="10.17487/RFC8737"/>
      </reference>
    </references>
    <section anchor="acknowledgments" numbered="false" toc="include" removeInRFC="false" pn="section-appendix.a">
      <name slugifiedName="name-acknowledgments">Acknowledgments</name>
      <t pn="section-appendix.a-1">The author would like to thank those who contributed to this document
      and offered editorial and technical input, especially
<contact fullname="Jacob Hoffman-Andrews"/> and <contact fullname="Daniel McCarney"/>.</t>
    </section>
    <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.b">
      <name slugifiedName="name-authors-address">Author's Address</name>
      <author initials="R.B." surname="Shoemaker" fullname="Roland Bracewell Shoemaker">
        <organization abbrev="ISRG" showOnFrontPage="true">Internet Security Research Group</organization>
        <address>
          <email>roland@letsencrypt.org</email>
        </address>
      </author>
    </section>
  </back>

<!-- ##markdown-source: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-->
</rfc>

mirror server hosted at Truenetwork, Russian Federation.