<?xml version='1.0' encoding='utf-8'?>
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" version="3" category="info" consensus="true" docName="draft-ietf-mboned-ieee802-mcast-problems-15" indexInclude="true" ipr="trust200902" number="9119" prepTime="2021-10-08T15:24:28" 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-mboned-ieee802-mcast-problems-15" rel="prev"/>
  <link href="https://dx.doi.org/10.17487/rfc9119" rel="alternate"/>
  <link href="urn:issn:2070-1721" rel="alternate"/>
  <front>
    <title abbrev="Multicast Over IEEE 802 Wireless">Multicast Considerations over IEEE 802 Wireless Media</title>
    <seriesInfo name="RFC" value="9119" stream="IETF"/>
    <author fullname="Charles E. Perkins" initials="C." surname="Perkins">
      <organization showOnFrontPage="true">Lupin Lodge</organization>
      <address>
        <phone>+1 408 255 9223</phone>
        <email>charliep@lupinlodge.com</email>
      </address>
    </author>
    <author fullname="Mike McBride" initials="M." surname="McBride">
      <organization abbrev="Futurewei" showOnFrontPage="true">Futurewei Technologies Inc.</organization>
      <address>
        <postal>
          <street>2330 Central Expressway</street>
          <city>Santa Clara</city>
          <code>95055</code>
          <region>CA</region>
          <country>United States of America</country>
        </postal>
        <email>michael.mcbride@futurewei.com</email>
      </address>
    </author>
    <author fullname="Dorothy Stanley" initials="D" surname="Stanley">
      <organization abbrev="HPE" showOnFrontPage="true">Hewlett Packard Enterprise</organization>
      <address>
        <postal>
          <street>6280 America Center Dr.</street>
          <city>San Jose</city>
          <code>95002</code>
          <region>CA</region>
          <country>United States of America</country>
        </postal>
        <phone>+1 630 363 1389</phone>
        <email>dorothy.stanley@hpe.com</email>
      </address>
    </author>
    <author fullname="Warren Kumari" initials="W" surname="Kumari">
      <organization abbrev="Google" showOnFrontPage="true">Google</organization>
      <address>
        <postal>
          <street>1600 Amphitheatre Parkway</street>
          <city>Mountain View</city>
          <code>94043</code>
          <region>CA</region>
          <country>United States of America</country>
        </postal>
        <email>warren@kumari.net</email>
      </address>
    </author>
    <author fullname="Juan Carlos Zúñiga" initials="JC" surname="Zúñiga">
      <organization abbrev="SIGFOX" showOnFrontPage="true">SIGFOX</organization>
      <address>
        <postal>
          <street/>
          <city>Montreal</city>
          <code/>
          <country>Canada</country>
        </postal>
        <email>j.c.zuniga@ieee.org</email>
      </address>
    </author>
    <date month="10" year="2021"/>
    <area>Internet</area>
    <workgroup>Internet Area</workgroup>
    <keyword>Multicast</keyword>
    <keyword>Broadcast</keyword>
    <keyword>BUM</keyword>
    <keyword>wifi</keyword>
    <keyword>wireless</keyword>
    <keyword>IEEE 802 Wireless Multicast</keyword>
    <abstract pn="section-abstract">
      <t indent="0" pn="section-abstract-1">
	 Well-known issues with multicast have prevented the deployment of
	 multicast in 802.11 (Wi-Fi) and other local-area wireless environments.
	 This document describes the known limitations
	 of wireless (primarily 802.11) Layer 2 multicast.  Also described are certain multicast
	 enhancement features that have been specified by the IETF
	 and by IEEE 802 for wireless media, as well as some operational choices that can be made to improve the performance of the network.  Finally,
	 some recommendations are provided about the usage and combination of
	 these features and operational choices.
      </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 document is not an Internet Standards Track specification; it is
            published for informational purposes.  
        </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).  Not all documents
            approved by the IESG are candidates for any level of Internet
            Standard; see 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/rfc9119" 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>
          </li>
          <li pn="section-toc.1-1.2">
            <t indent="0" 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 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-identified-multicast-issues">Identified Multicast Issues</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-issues-at-layer-2-and-below">Issues at Layer 2 and Below</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.3.2.1.2">
                  <li pn="section-toc.1-1.3.2.1.2.1">
                    <t indent="0" keepWithNext="true" pn="section-toc.1-1.3.2.1.2.1.1"><xref derivedContent="3.1.1" format="counter" sectionFormat="of" target="section-3.1.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-multicast-reliability">Multicast Reliability</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.1.2.2">
                    <t indent="0" pn="section-toc.1-1.3.2.1.2.2.1"><xref derivedContent="3.1.2" format="counter" sectionFormat="of" target="section-3.1.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-lower-and-variable-data-rat">Lower and Variable Data Rate</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.1.2.3">
                    <t indent="0" pn="section-toc.1-1.3.2.1.2.3.1"><xref derivedContent="3.1.3" format="counter" sectionFormat="of" target="section-3.1.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-capacity-and-impact-on-inte">Capacity and Impact on Interference</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.1.2.4">
                    <t indent="0" pn="section-toc.1-1.3.2.1.2.4.1"><xref derivedContent="3.1.4" format="counter" sectionFormat="of" target="section-3.1.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-power-save-effects-on-multi">Power-Save Effects on Multicast</xref></t>
                  </li>
                </ul>
              </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-issues-at-layer-3-and-above">Issues at Layer 3 and Above</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.3.2.2.2">
                  <li pn="section-toc.1-1.3.2.2.2.1">
                    <t indent="0" pn="section-toc.1-1.3.2.2.2.1.1"><xref derivedContent="3.2.1" format="counter" sectionFormat="of" target="section-3.2.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ipv4-issues">IPv4 Issues</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.2.2.2">
                    <t indent="0" pn="section-toc.1-1.3.2.2.2.2.1"><xref derivedContent="3.2.2" format="counter" sectionFormat="of" target="section-3.2.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ipv6-issues">IPv6 Issues</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.2.2.3">
                    <t indent="0" pn="section-toc.1-1.3.2.2.2.3.1"><xref derivedContent="3.2.3" format="counter" sectionFormat="of" target="section-3.2.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-mld-issues">MLD Issues</xref></t>
                  </li>
                  <li pn="section-toc.1-1.3.2.2.2.4">
                    <t indent="0" pn="section-toc.1-1.3.2.2.2.4.1"><xref derivedContent="3.2.4" format="counter" sectionFormat="of" target="section-3.2.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-spurious-neighbor-discovery">Spurious Neighbor Discovery</xref></t>
                  </li>
                </ul>
              </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-multicast-protocol-optimiza">Multicast Protocol Optimizations</xref></t>
            <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.4.2">
              <li pn="section-toc.1-1.4.2.1">
                <t indent="0" pn="section-toc.1-1.4.2.1.1"><xref derivedContent="4.1" format="counter" sectionFormat="of" target="section-4.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-proxy-arp-in-80211-2012">Proxy ARP in 802.11-2012</xref></t>
              </li>
              <li pn="section-toc.1-1.4.2.2">
                <t indent="0" pn="section-toc.1-1.4.2.2.1"><xref derivedContent="4.2" format="counter" sectionFormat="of" target="section-4.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ipv6-address-registration-a">IPv6 Address Registration and Proxy Neighbor Discovery</xref></t>
              </li>
              <li pn="section-toc.1-1.4.2.3">
                <t indent="0" pn="section-toc.1-1.4.2.3.1"><xref derivedContent="4.3" format="counter" sectionFormat="of" target="section-4.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-buffering-to-improve-batter">Buffering to Improve Battery Life</xref></t>
              </li>
              <li pn="section-toc.1-1.4.2.4">
                <t indent="0" pn="section-toc.1-1.4.2.4.1"><xref derivedContent="4.4" format="counter" sectionFormat="of" target="section-4.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-limiting-multicast-buffer-h">Limiting Multicast Buffer Hardware Queue Depth</xref></t>
              </li>
              <li pn="section-toc.1-1.4.2.5">
                <t indent="0" pn="section-toc.1-1.4.2.5.1"><xref derivedContent="4.5" format="counter" sectionFormat="of" target="section-4.5"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-ipv6-support-in-80211-2012">IPv6 Support in 802.11-2012</xref></t>
              </li>
              <li pn="section-toc.1-1.4.2.6">
                <t indent="0" pn="section-toc.1-1.4.2.6.1"><xref derivedContent="4.6" format="counter" sectionFormat="of" target="section-4.6"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-using-unicast-instead-of-mu">Using Unicast Instead of Multicast</xref></t>
                <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.4.2.6.2">
                  <li pn="section-toc.1-1.4.2.6.2.1">
                    <t indent="0" pn="section-toc.1-1.4.2.6.2.1.1"><xref derivedContent="4.6.1" format="counter" sectionFormat="of" target="section-4.6.1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-overview">Overview</xref></t>
                  </li>
                  <li pn="section-toc.1-1.4.2.6.2.2">
                    <t indent="0" pn="section-toc.1-1.4.2.6.2.2.1"><xref derivedContent="4.6.2" format="counter" sectionFormat="of" target="section-4.6.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-layer-2-conversion-to-unica">Layer 2 Conversion to Unicast</xref></t>
                  </li>
                  <li pn="section-toc.1-1.4.2.6.2.3">
                    <t indent="0" pn="section-toc.1-1.4.2.6.2.3.1"><xref derivedContent="4.6.3" format="counter" sectionFormat="of" target="section-4.6.3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-directed-multicast-service-">Directed Multicast Service (DMS)</xref></t>
                  </li>
                  <li pn="section-toc.1-1.4.2.6.2.4">
                    <t indent="0" pn="section-toc.1-1.4.2.6.2.4.1"><xref derivedContent="4.6.4" format="counter" sectionFormat="of" target="section-4.6.4"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-automatic-multicast-tunneli">Automatic Multicast Tunneling (AMT)</xref></t>
                  </li>
                </ul>
              </li>
              <li pn="section-toc.1-1.4.2.7">
                <t indent="0" pn="section-toc.1-1.4.2.7.1"><xref derivedContent="4.7" format="counter" sectionFormat="of" target="section-4.7"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-groupcast-with-retries-gcr">GroupCast with Retries (GCR)</xref></t>
              </li>
            </ul>
          </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-operational-optimizations">Operational Optimizations</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-mitigating-problems-from-sp">Mitigating Problems from Spurious Neighbor Discovery</xref></t>
              </li>
              <li pn="section-toc.1-1.5.2.2">
                <t indent="0" pn="section-toc.1-1.5.2.2.1"><xref derivedContent="5.2" format="counter" sectionFormat="of" target="section-5.2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-mitigating-spurious-service">Mitigating Spurious Service Discovery Messages</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-multicast-considerations-fo">Multicast Considerations for Other Wireless Media</xref></t>
          </li>
          <li pn="section-toc.1-1.7">
            <t indent="0" 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-recommendations">Recommendations</xref></t>
          </li>
          <li pn="section-toc.1-1.8">
            <t indent="0" 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-ongoing-discussion-items">Ongoing Discussion Items</xref></t>
          </li>
          <li pn="section-toc.1-1.9">
            <t indent="0" 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>
          </li>
          <li pn="section-toc.1-1.10">
            <t indent="0" 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-iana-considerations">IANA Considerations</xref></t>
          </li>
          <li pn="section-toc.1-1.11">
            <t indent="0" pn="section-toc.1-1.11.1"><xref derivedContent="11" format="counter" sectionFormat="of" target="section-11"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-informative-references">Informative References</xref></t>
          </li>
          <li pn="section-toc.1-1.12">
            <t indent="0" pn="section-toc.1-1.12.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.a"/><xref derivedContent="" format="title" sectionFormat="of" target="name-acknowledgements">Acknowledgements</xref></t>
          </li>
          <li pn="section-toc.1-1.13">
            <t indent="0" pn="section-toc.1-1.13.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="" format="title" sectionFormat="of" target="name-authors-addresses">Authors' Addresses</xref></t>
          </li>
        </ul>
      </section>
    </toc>
  </front>
  <middle>
    <section anchor="intro" numbered="true" toc="include" removeInRFC="false" pn="section-1">
      <name slugifiedName="name-introduction">Introduction</name>
      <t indent="0" pn="section-1-1">
	 Well-known issues with multicast have prevented the deployment of
	 multicast in 802.11 <xref target="dot11" format="default" sectionFormat="of" derivedContent="dot11"/> and other local-area
	 wireless environments, as described in <xref target="mc-props" format="default" sectionFormat="of" derivedContent="mc-props"/> and <xref target="mc-prob-stmt" format="default" sectionFormat="of" derivedContent="mc-prob-stmt"/>.  Performance issues have been observed
	 when multicast
	 packet transmissions of IETF protocols are used over IEEE 802 wireless
	 media.  Even though enhancements for multicast transmissions have been
	 designed at both IETF and IEEE 802, incompatibilities still exist
	 between specifications, implementations, and configuration choices.
      </t>
      <t indent="0" pn="section-1-2"> Many IETF protocols depend on multicast/broadcast for delivery of
	 control messages to multiple receivers. Multicast allows data to be sent to 
	 multiple interested recipients without the source needing to send duplicate
	 data to each recipient. With broadcast traffic, data is sent to every device 
	 regardless of their expressed interest in the data. Multicast is used for various
	 purposes such as Neighbor Discovery, network flooding, and address
	 resolution, as well as minimizing media occupancy for the
	 transmission of data that is intended for multiple receivers.
	 In addition to protocol use of broadcast/multicast for
	 control messages, more applications, such as Push To Talk in
	 hospitals or video in enterprises, universities, and homes, are
	 sending multicast IP to end-user devices, which are increasingly
	 using Wi-Fi for their connectivity. </t>
      <t indent="0" pn="section-1-3"> IETF protocols typically rely on network protocol layering in order
	 to reduce or eliminate any dependence of higher-level protocols on
	 the specific nature of the MAC-layer protocols or the physical media.
	 In the case of multicast transmissions, higher-level protocols have
	 traditionally been designed as if transmitting a packet to an IP
	 address had the same cost in interference and network media access,
	 regardless of whether the destination IP address is a unicast address
	 or a multicast or broadcast address. This model was reasonable for
	 networks where the physical medium was wired, like Ethernet.
	 Unfortunately, for many wireless media, the costs to access the
	 medium can be quite different.  Multicast over Wi-Fi has often been
	 plagued by such poor performance that it is disallowed.
	 Some enhancements have been designed
	 in IETF protocols that are assumed to work primarily over wireless
	 media.  However, these enhancements are usually implemented in limited
	 deployments and are not widespread on most wireless networks.</t>
      <t indent="0" pn="section-1-4"> IEEE 802 wireless protocols have been designed with certain features
	 to support multicast traffic. For instance, lower modulations are
	 used to transmit multicast frames so that these can be received by
	 all stations in the cell, regardless of the distance or path
	 attenuation from the base station or Access Point (AP).  

 However, these
	 lower modulation transmissions occupy the medium longer;
	 they hamper efficient transmission of traffic using
	 higher-order modulations to nearby stations.
	 For these and other reasons, IEEE 802 Working Groups such as 802.11
	 have designed features to improve the performance of multicast
	 transmissions at Layer 2 <xref target="ietf_802-11" format="default" sectionFormat="of" derivedContent="ietf_802-11"/>.
	 In addition to protocol design features, certain operational and
	 configuration enhancements can ameliorate the network
	 performance issues created by multicast traffic,
	 as described in <xref target="optim3" format="default" sectionFormat="of" derivedContent="Section 5"/>.</t>
      <t indent="0" pn="section-1-5"> There seems to be general agreement that these problems will not
	 be fixed anytime soon, primarily because it's expensive to do so
	 and because of the unreliability of multicast.  Compared to unicast over Wi-Fi,
	 multicast is often treated as somewhat of a second-class citizen even
	 though there are many protocols using multicast.  Something needs to
	 be provided in order to make them more reliable.  IPv6
	 Neighbor Discovery saturating the Wi-Fi link is only part of the
	 problem.  Wi-Fi traffic classes may help.  This document is intended
	 to help make the determination about
	 what problems should be solved by the IETF and what problems
	 should be solved by the IEEE (see <xref target="discussion" format="default" sectionFormat="of" derivedContent="Section 8"/>).
      </t>
      <t indent="0" pn="section-1-6"> This document details various problems caused by multicast transmission
	 over wireless networks, including high packet error rates, no
	 acknowledgements, and low data rate.  It also explains some
	 enhancements that have been designed at the IETF and IEEE 802.11 to ameliorate
	 the effects of the radio medium on multicast traffic.  Recommendations are also provided
	 to implementors about how to use and combine these enhancements.
	 Some advice about the operational choices that can be made is also
	 included.  It is likely that this document will also be considered
	 relevant to designers of future IEEE wireless specifications. </t>
    </section>
    <section anchor="def" numbered="true" toc="include" removeInRFC="false" pn="section-2">
      <name slugifiedName="name-terminology">Terminology</name>
      <t indent="0" pn="section-2-1">This document uses the following definitions:
      </t>
      <dl newline="true" indent="3" spacing="normal" pn="section-2-2">
        <dt pn="section-2-2.1">ACK</dt>
        <dd pn="section-2-2.2"> The 802.11 Layer 2 acknowledgement.</dd>
        <dt pn="section-2-2.3">AES-CCMP</dt>
        <dd pn="section-2-2.4">AES-Counter Mode CBC-MAC Protocol</dd>
        <dt pn="section-2-2.5">AP</dt>
        <dd pn="section-2-2.6"> IEEE 802.11 Access Point.</dd>
        <dt pn="section-2-2.7">Basic rate</dt>
        <dd pn="section-2-2.8"> The slowest rate of all the
	   connected devices at which multicast and broadcast traffic is
	   generally transmitted.</dd>
        <dt pn="section-2-2.9">DVB-H</dt>
        <dd pn="section-2-2.10">Digital Video Broadcasting - Handheld</dd>
        <dt pn="section-2-2.11">DVB-IPDC</dt>
        <dd pn="section-2-2.12">Digital Video Broadcasting - Internet Protocol Datacasting</dd>
        <dt pn="section-2-2.13">DTIM</dt>
        <dd pn="section-2-2.14">Delivery Traffic Indication Map; an information element that advertises whether or not any associated
	   stations have buffered multicast or broadcast frames.</dd>
        <dt pn="section-2-2.15">MCS</dt>
        <dd pn="section-2-2.16"> Modulation and Coding Scheme.</dd>
        <dt pn="section-2-2.17">NOC</dt>
        <dd pn="section-2-2.18"> Network Operations Center.</dd>
        <dt pn="section-2-2.19">PER</dt>
        <dd pn="section-2-2.20"> Packet Error Rate.</dd>
        <dt pn="section-2-2.21">STA</dt>
        <dd pn="section-2-2.22"> 802.11 station (e.g., handheld device).</dd>
        <dt pn="section-2-2.23">TIM</dt>
        <dd pn="section-2-2.24">Traffic Indication Map; an
	   information element that advertises whether or not any associated
	   stations have buffered unicast frames.</dd>
        <dt pn="section-2-2.25">TKIP</dt>
        <dd pn="section-2-2.26">Temporal Key Integrity Protocol</dd>
        <dt pn="section-2-2.27">WiMAX</dt>
        <dd pn="section-2-2.28">Worldwide Interoperability for Microwave Access</dd>
        <dt pn="section-2-2.29">WPA</dt>
        <dd pn="section-2-2.30">Wi-Fi Protected Access</dd>
      </dl>
    </section>
    <section anchor="multicast_issues" numbered="true" toc="include" removeInRFC="false" pn="section-3">
      <name slugifiedName="name-identified-multicast-issues">Identified Multicast Issues</name>
      <section anchor="l2_issues" numbered="true" toc="include" removeInRFC="false" pn="section-3.1">
        <name slugifiedName="name-issues-at-layer-2-and-below">Issues at Layer 2 and Below</name>
        <t indent="0" pn="section-3.1-1"> In this section, some of the issues related to the use of multicast
	   transmissions over IEEE 802 wireless technologies are described.</t>
        <section anchor="reliability" numbered="true" toc="include" removeInRFC="false" pn="section-3.1.1">
          <name slugifiedName="name-multicast-reliability">Multicast Reliability</name>
          <t indent="0" pn="section-3.1.1-1"> Multicast traffic is typically much less reliable than unicast
	    traffic. Since multicast makes point-to-multipoint communications,
	    multiple acknowledgements would be needed to guarantee reception
	    at all recipients. However, since there are no ACKs for multicast
	    packets, it is not possible for the AP to
	    know whether or not a retransmission is needed.  Even in the wired
	    Internet, this characteristic often causes undesirably high error
	    rates.  This has contributed to the relatively slow uptake of
	    multicast applications even though the protocols have long been
	    available.  The situation for wireless links is much worse and is
	    quite sensitive to the presence of background traffic.
	    Consequently, there can be a high packet error rate (PER)
	    due to lack of retransmission and because the sender never backs
	    off.  PER is the ratio, in percent, of the number of packets not successfully 
	    received by the device. It is not uncommon for there to be a packet loss rate of 5%
	    or more, which is particularly troublesome for video and other
	    environments where high data rates and high reliability are
	    required.  </t>
        </section>
        <section anchor="lower_rate" numbered="true" toc="include" removeInRFC="false" pn="section-3.1.2">
          <name slugifiedName="name-lower-and-variable-data-rat">Lower and Variable Data Rate</name>
          <t indent="0" pn="section-3.1.2-1"> Multicast over wired differs from multicast over wireless because
	    transmission over wired links often occurs at
	    a fixed rate.  Wi-Fi, on the other hand, has a transmission rate
	    that varies depending upon the STA's proximity to the AP.
	    The throughput of video flows and the capacity of the broader
	    Wi-Fi network will change with device movement. This impacts the ability for QoS
	    solutions to effectively reserve bandwidth and provide admission
	    control. </t>
          <t indent="0" pn="section-3.1.2-2"> For wireless stations authenticated and linked with an AP, the power
	    necessary for good reception can vary from station to station.  For
	    unicast, the goal is to minimize power requirements while maximizing
	    the data rate to the destination.  For multicast, the goal is simply
	    to maximize the number of receivers that will correctly receive the
	    multicast packet; generally, the AP has
	    to use a much lower data rate at a power level high enough for even
	    the farthest station to receive the packet, for example, as briefly


	    mentioned in <xref target="RFC5757" sectionFormat="of" section="4" format="default" derivedLink="https://rfc-editor.org/rfc/rfc5757#section-4" derivedContent="RFC5757"/>.  Consequently, the data
	    rate of a video stream, for instance, would be constrained by the
	    environmental considerations of the least-reliable receiver
	    associated with the AP. </t>
          <t indent="0" pn="section-3.1.2-3"> Because more robust modulation and coding schemes (MCSs)
	    have a longer range but also a lower data rate, multicast/broadcast
	    traffic is generally transmitted at the slowest rate of all the
	    connected devices. This is also known as the basic rate.
	    The amount of additional interference depends on the
	    specific wireless technology.  In fact, backward compatibility and
	    multi-stream implementations mean that the maximum unicast rates
	    are currently up to a few Gbps, so there can be more than
	    3 orders of magnitude difference in the transmission rate between
	    multicast/broadcast versus optimal unicast forwarding.  Some
	    techniques employed to increase spectral efficiency, such as spatial
	    multiplexing in Multiple Input Multiple Output (MIMO) systems, are not available with more than
	    one intended receiver; it is not the case that backwards
	    compatibility is the only factor responsible for lower multicast
	    transmission rates. </t>
          <t indent="0" pn="section-3.1.2-4"> Wired multicast also affects wireless LANs when the AP extends
	    the wired segment; in that case, multicast/broadcast frames
	    on the wired LAN side are copied to the Wireless Local Area Network (WLAN).  Since broadcast
	    messages are transmitted at the most robust MCS,
	    many large frames are sent at a slow rate over the air. </t>
        </section>
        <section anchor="interference" numbered="true" toc="include" removeInRFC="false" pn="section-3.1.3">
          <name slugifiedName="name-capacity-and-impact-on-inte">Capacity and Impact on Interference</name>
          <t indent="0" pn="section-3.1.3-1"> Transmissions at a lower
	    rate require longer occupancy of the wireless medium and thus
	    take away from the airtime of other communications and
	    degrade the overall capacity.  Furthermore, transmission at higher
	    power, as is required to reach all multicast STAs associated
	    with the AP, proportionately increases the area of interference with other 
	    consumers of the radio spectrum. </t>
        </section>
        <section anchor="power_save" numbered="true" toc="include" removeInRFC="false" pn="section-3.1.4">
          <name slugifiedName="name-power-save-effects-on-multi">Power-Save Effects on Multicast</name>
          <t indent="0" pn="section-3.1.4-1"> One of the characteristics of multicast transmission over Wi-Fi is that every
	    station has to be configured to wake up to receive the multicast frame,
	    even though the received packet may ultimately be discarded.  This
	    process can have a large effect on the power consumption by
	    the multicast receiver station. For this reason, there are workarounds,
	    such as Directed Multicast Service (DMS) described in <xref target="optim2" format="default" sectionFormat="of" derivedContent="Section 4"/>, to
	    prevent unnecessarily waking up stations.</t>
          <t indent="0" pn="section-3.1.4-2"> Multicast (and unicast) can work poorly with the power-save mechanisms defined in
	    IEEE 802.11e for the following reasons.
          </t>
          <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3.1.4-3">
            <li pn="section-3.1.4-3.1"> Clients may be unable to stay in sleep mode due to
		multicast control packets frequently waking them up.</li>
            <li pn="section-3.1.4-3.2"> A unicast packet is delayed until an STA wakes up and requests
		it.  Unicast traffic may also be delayed to improve power
		save and efficiency and to increase the probability of aggregation.</li>
            <li pn="section-3.1.4-3.3"> Multicast traffic is delayed in a wireless network if any of
		the STAs in that network are power savers.
		All STAs associated with the AP have to be
		awake at a known time to receive multicast traffic.</li>
            <li pn="section-3.1.4-3.4"> Packets can also be discarded due to buffer limitations in
		the AP and non-AP STA.</li>
          </ul>
        </section>
      </section>
      <section anchor="l3_issues" numbered="true" toc="include" removeInRFC="false" pn="section-3.2">
        <name slugifiedName="name-issues-at-layer-3-and-above">Issues at Layer 3 and Above</name>
        <t indent="0" pn="section-3.2-1"> This section identifies some representative IETF protocols and
	  describes possible negative effects due to performance degradation
	  when using multicast transmissions for control messages.
	  Common uses of multicast include:
        </t>
        <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3.2-2">
          <li pn="section-3.2-2.1"> Control plane signaling </li>
          <li pn="section-3.2-2.2"> Neighbor Discovery </li>
          <li pn="section-3.2-2.3"> Address resolution </li>
          <li pn="section-3.2-2.4"> Service Discovery </li>
          <li pn="section-3.2-2.5"> Applications (video delivery, stock data, etc.) </li>
          <li pn="section-3.2-2.6"> On-demand routing </li>
          <li pn="section-3.2-2.7"> Backbone construction </li>
          <li pn="section-3.2-2.8"> Other Layer 3 protocols (non-IP) </li>
        </ul>
        <t indent="0" pn="section-3.2-3">
	User Datagram Protocol (UDP) is the most common transport-layer
	protocol for multicast applications.
	By itself, UDP is not reliable -- messages may be lost or
	delivered out of order.
        </t>
        <section anchor="IPv4" numbered="true" toc="include" removeInRFC="false" pn="section-3.2.1">
          <name slugifiedName="name-ipv4-issues">IPv4 Issues</name>
          <t indent="0" pn="section-3.2.1-1"> The following list contains some representative
	    discovery protocols that utilize broadcast/multicast and are used with IPv4.
          </t>
          <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3.2.1-2">
            <li pn="section-3.2.1-2.1">ARP <xref target="RFC0826" format="default" sectionFormat="of" derivedContent="RFC0826"/></li>
            <li pn="section-3.2.1-2.2">DHCP <xref target="RFC2131" format="default" sectionFormat="of" derivedContent="RFC2131"/></li>
            <li pn="section-3.2.1-2.3">Multicast DNS (mDNS) <xref target="RFC6762" format="default" sectionFormat="of" derivedContent="RFC6762"/></li>
            <li pn="section-3.2.1-2.4">Universal Plug and Play (uPnP) <xref target="RFC6970" format="default" sectionFormat="of" derivedContent="RFC6970"/></li>
          </ul>
          <t indent="0" pn="section-3.2.1-3"> After initial configuration, ARP (described in more detail later), DHCP, and uPnP occur much less
	    commonly, but service discovery can occur at any time.  Some
	    widely deployed service discovery protocols (e.g., for finding a
	    printer) utilize mDNS (i.e., multicast), which is often dropped by operators.  Even if multicast 
	    snooping <xref target="RFC4541" format="default" sectionFormat="of" derivedContent="RFC4541"/> (which provides the benefit of conserving 
	    bandwidth on those segments of the network where no node has expressed interest in receiving 
	    packets addressed to the group address) is utilized, many devices can register at once and cause serious
	    network degradation.</t>
        </section>
        <section anchor="IPv6" numbered="true" toc="include" removeInRFC="false" pn="section-3.2.2">
          <name slugifiedName="name-ipv6-issues">IPv6 Issues</name>
          <t indent="0" pn="section-3.2.2-1"> IPv6 makes extensive use of multicast, including the following:
          </t>
          <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-3.2.2-2">
            <li pn="section-3.2.2-2.1"> DHCPv6 <xref target="RFC8415" format="default" sectionFormat="of" derivedContent="RFC8415"/></li>
            <li pn="section-3.2.2-2.2"> Protocol Independent Multicast (PIM) <xref target="RFC7761" format="default" sectionFormat="of" derivedContent="RFC7761"/></li>
            <li pn="section-3.2.2-2.3"> IPv6 Neighbor Discovery Protocol (NDP) <xref target="RFC4861" format="default" sectionFormat="of" derivedContent="RFC4861"/></li>
            <li pn="section-3.2.2-2.4"> Multicast DNS (mDNS) <xref target="RFC6762" format="default" sectionFormat="of" derivedContent="RFC6762"/></li>
            <li pn="section-3.2.2-2.5"> Router Discovery <xref target="RFC4286" format="default" sectionFormat="of" derivedContent="RFC4286"/></li>
          </ul>
          <t indent="0" pn="section-3.2.2-3"> IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate Address 
	    Detection (DAD) and address lookup make use of link-scope multicast.  In
	    contrast to IPv4, an IPv6 node will typically use multiple
	    addresses and may change them often for privacy reasons.  This
	    intensifies the impact of multicast messages that are associated
	    with the mobility of a node.  Router advertisement (RA) messages
	    are also periodically multicast over the link.
          </t>
          <t indent="0" pn="section-3.2.2-4"> Neighbors may be considered lost if several consecutive
	    Neighbor Discovery packets fail.
          </t>
        </section>
        <section anchor="mld" numbered="true" toc="include" removeInRFC="false" pn="section-3.2.3">
          <name slugifiedName="name-mld-issues">MLD Issues</name>
          <t indent="0" pn="section-3.2.3-1"> Multicast Listener Discovery (MLD) <xref target="RFC4541" format="default" sectionFormat="of" derivedContent="RFC4541"/> is
	    used to identify members of a multicast group that are connected to
	    the ports of a switch.  Forwarding multicast frames into a
	    Wi-Fi-enabled area can use switch support for hardware
	    forwarding state information. However, since IPv6 makes heavy use
	    of multicast, each STA with an IPv6 address will require state on
	    the switch for several and possibly many solicited-node multicast
	    addresses. A solicited-node multicast address is an IPv6 multicast 
	    address used by NDP to verify whether an IPv6 address is already 
	    used by the local link. Multicast addresses that do not have forwarding state
	    installed (perhaps due to hardware memory limitations on the
	    switch) cause frames to be flooded on all ports of the switch. Some 
	    switch vendors do not support MLD for link-scope multicast due to
	    the increase it can cause in state. </t>
        </section>
        <section anchor="spurious" numbered="true" toc="include" removeInRFC="false" pn="section-3.2.4">
          <name slugifiedName="name-spurious-neighbor-discovery">Spurious Neighbor Discovery</name>
          <t indent="0" pn="section-3.2.4-1"> On the Internet, there is a "background radiation" of scanning
	    traffic (people scanning for vulnerable machines) and backscatter
	    (responses from spoofed traffic, etc.). This means that routers
	    very often receive packets destined for IPv4 addresses regardless of
	    whether those IP addresses are in use. In the cases where the IP
	    is assigned to a host, the router broadcasts an ARP request, receives an ARP
	    reply, and caches it; then, traffic can be delivered to the host.
	    When the IP address is not in use, the router broadcasts one (or
	    more) ARP requests and never gets a reply. This means that it does
	    not populate the ARP cache, and the next time there is traffic for
	    that IP address, the router will rebroadcast the ARP requests.
          </t>
          <t indent="0" pn="section-3.2.4-2"> The rate of these ARP requests is proportional to the size of the
	    subnets, the rate of scanning and backscatter, and how long the
	    router keeps state on non-responding ARPs. As it turns out, this
	    rate is inversely proportional to how occupied the subnet is
	    (valid ARPs end up in a cache, stopping the broadcasting; unused
	    IPs never respond, and so cause more broadcasts).  Depending on
	    the address space in use, the time of day, how occupied the
	    subnet is, and other unknown factors, thousands of broadcasts per second 
	    have been observed. Around 2,000 broadcasts per second have been observed at
	    the IETF NOC during face-to-face meetings. </t>
          <t indent="0" pn="section-3.2.4-3"> With Neighbor Discovery for IPv6 <xref target="RFC4861" format="default" sectionFormat="of" derivedContent="RFC4861"/>, nodes 
      accomplish address resolution by multicasting a Neighbor Solicitation 
      that asks the target node to return its link-layer address.  Neighbor 
      Solicitation messages are multicast to the solicited-node multicast 
      address of the target address.  The target returns its link-layer address 
      in a unicast Neighbor Advertisement message.  A single request-response 
      pair of packets is sufficient for both the initiator and the target to resolve 
      each other's link-layer addresses; the initiator includes its link-layer 
      address in the Neighbor Solicitation.</t>
          <t indent="0" pn="section-3.2.4-4"> On a wired network, there is not a huge difference between unicast,
	    multicast, and broadcast traffic.  Due to hardware filtering
	    (see, e.g., <xref target="Deri-2010" format="default" sectionFormat="of" derivedContent="Deri-2010"/>), inadvertently flooded
	    traffic (or excessive Ethernet multicast) on wired networks
	    can be quite a bit less costly compared to wireless cases where sleeping 
	    devices have to wake up to process packets.  Wired Ethernets tend to be switched
	    networks, further reducing interference from multicast.  There is
	    effectively no collision / scheduling problem except at extremely
	    high port utilizations. </t>
          <t indent="0" pn="section-3.2.4-5"> This is not true in the wireless realm; wireless equipment is
	    often unable to send high volumes of broadcast and multicast
	    traffic, causing numerous broadcast and multicast packets to be
	    dropped.  Consequently, when a host connects, it is often not
	    able to complete DHCP, and IPv6 RAs get dropped, leading to
	    users being unable to use the network.</t>
        </section>
      </section>
    </section>
    <section anchor="optim2" numbered="true" toc="include" removeInRFC="false" pn="section-4">
      <name slugifiedName="name-multicast-protocol-optimiza">Multicast Protocol Optimizations</name>
      <t indent="0" pn="section-4-1"> This section lists some optimizations that have been specified in
	IEEE 802 and IETF that are aimed at reducing or eliminating the
	issues discussed in <xref target="multicast_issues" format="default" sectionFormat="of" derivedContent="Section 3"/>.</t>
      <section anchor="proxy-arp" numbered="true" toc="include" removeInRFC="false" pn="section-4.1">
        <name slugifiedName="name-proxy-arp-in-80211-2012">Proxy ARP in 802.11-2012</name>
        <t indent="0" pn="section-4.1-1"> The AP knows the Medium Access Control (MAC) address and IP address for all associated
	    STAs.  In this way, the AP acts as the central "manager" for all
	    the 802.11 STAs in its Basic Service Set (BSS). Proxy ARP is easy to implement at the
	    AP and offers the following advantages:
        </t>
        <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.1-2">
          <li pn="section-4.1-2.1"> Reduced broadcast traffic (transmitted at low MCS) on the
	       wireless medium.</li>
          <li pn="section-4.1-2.2"> STA benefits from extended power save in sleep mode, as ARP
	    requests for STA's IP address are handled instead by the AP.</li>
          <li pn="section-4.1-2.3"> ARP frames are kept off the wireless medium.</li>
          <li pn="section-4.1-2.4"> No changes are needed to STA implementation.</li>
        </ul>
        <t indent="0" pn="section-4.1-3"> Here is the specification language as
	    described in clause 10.23.13 of <xref target="dot11-proxyarp" format="default" sectionFormat="of" derivedContent="dot11-proxyarp"/>:
        </t>
        <blockquote pn="section-4.1-4">
          <t indent="0" pn="section-4.1-4.1">When the AP supports Proxy ARP "[...] the AP shall maintain a
		Hardware Address to Internet Address mapping for each
		associated station, and shall update the mapping when the
		Internet Address of the associated station changes. When the
		IPv4 address being resolved in the ARP request packet is used
		by a non-AP STA currently associated to the BSS, the proxy ARP
		service shall respond on behalf of the STA to an ARP request or an ARP Probe.
          </t>
        </blockquote>
      </section>
      <section anchor="proxy-ND" numbered="true" toc="include" removeInRFC="false" pn="section-4.2">
        <name slugifiedName="name-ipv6-address-registration-a">IPv6 Address Registration and Proxy Neighbor Discovery</name>
        <t indent="0" pn="section-4.2-1">
	As used in this section,
	a Low-Power Wireless Personal Area Network (6LoWPAN) denotes a Low-Power and Lossy Network (LLN) that supports
	<xref target="RFC6282" format="default" sectionFormat="of" derivedContent="RFC6282"> 6LoWPAN Header Compression (HC)</xref>.
	A <xref target="RFC9030" format="default" sectionFormat="of" derivedContent="RFC9030">6TiSCH network</xref>
	is an example of a 6LoWPAN.
	In order to control the use of IPv6 multicast over 6LoWPANs, the
	<xref target="RFC6775" format="default" sectionFormat="of" derivedContent="RFC6775">6LoWPAN Neighbor Discovery (6LoWPAN ND)</xref>
	standard defines an address registration mechanism that relies on a
	central registry to assess address uniqueness as a substitute to the
	inefficient DAD mechanism found in the mainstream IPv6 Neighbor Discovery Protocol (NDP)
	<xref target="RFC4861" format="default" sectionFormat="of" derivedContent="RFC4861"/> <xref target="RFC4862" format="default" sectionFormat="of" derivedContent="RFC4862"/>.
        </t>
        <t indent="0" pn="section-4.2-2">
	The 6lo Working Group has specified an
	<xref target="RFC8505" format="none" sectionFormat="of" derivedContent="">update</xref> to <xref target="RFC6775" format="default" sectionFormat="of" derivedContent="RFC6775"/>.
	Wireless devices can register their address to a
	<xref target="RFC8929" format="default" sectionFormat="of" derivedContent="RFC8929">Backbone Router</xref>,
	which proxies for the registered addresses with the IPv6
	NDP running on a high-speed aggregating backbone. The update also
	enables a proxy registration mechanism on behalf of the Registered
	Node, e.g., by a 6LoWPAN router to which the mobile node is attached.
        </t>
        <t indent="0" pn="section-4.2-3">
	The general idea behind the Backbone Router concept is that broadcast
	and multicast messaging should be tightly controlled in a variety
	of  WLANs and Wireless Personal Area
	Networks (WPANs).
	Connectivity to a particular link that provides the subnet should
	be left to Layer 3. The model for the Backbone Router operation is
	represented in <xref target="figBackbone" format="default" sectionFormat="of" derivedContent="Figure 1"/>.
        </t>
        <figure anchor="figBackbone" align="left" suppress-title="false" pn="figure-1">
          <name slugifiedName="name-backbone-link-and-backbone-">Backbone Link and Backbone Routers</name>
          <artwork name="" type="" align="left" alt="" pn="section-4.2-4.1">
              |
            +-----+
            |     | Gateway (default) router
            |     |
            +-----+
               |
               |      Backbone Link
         +--------------------+------------------+
         |                    |                  |
      +-----+             +-----+             +-----+
      |     | Backbone    |     | Backbone    |     | Backbone
      |     | router 1    |     | router 2    |     | router 3
      +-----+             +-----+             +-----+
         o                o   o  o              o o
     o o   o  o       o o   o  o  o         o  o  o  o o
    o  o o  o o       o   o  o  o  o        o  o  o o o
    o   o  o  o          o    o  o           o  o   o
      o   o o               o  o                 o o

        LLN 1              LLN 2                LLN 3
</artwork>
        </figure>
        <t indent="0" pn="section-4.2-5">
      LLN nodes can move freely from an LLN anchored at one IPv6 Backbone Router
      to an LLN anchored at another Backbone Router on the same backbone,
      keeping any of the IPv6 addresses they have configured.
      The Backbone Routers maintain a Binding Table of their
      Registered Nodes, which serves as a distributed database of all the LLN
      nodes. An extension to the Neighbor Discovery Protocol is introduced to
      exchange Binding Table information across the Backbone Link as needed
      for the operation of IPv6 Neighbor Discovery.
        </t>
        <t indent="0" pn="section-4.2-6">
	<xref target="RFC6775" format="default" sectionFormat="of" derivedContent="RFC6775"/> and follow-on work <xref target="RFC8505" format="default" sectionFormat="of" derivedContent="RFC8505"/>
	address the needs of LLNs, and similar techniques are likely to be
	valuable on any type of
	link where sleeping devices are attached or where the use of
	broadcast and multicast operations should be limited. </t>
      </section>
      <section anchor="buffer" numbered="true" toc="include" removeInRFC="false" pn="section-4.3">
        <name slugifiedName="name-buffering-to-improve-batter">Buffering to Improve Battery Life</name>
        <t indent="0" pn="section-4.3-1"> Methods have been developed to help save battery life; for example,
	a device might not wake up when the AP receives a multicast packet.
	The AP acts on behalf of STAs in various ways.  To enable use of
	the power-saving feature for STAs in its BSS, the AP buffers frames
	for delivery to the STA at the time when the STA is scheduled for
	reception.  If an AP, for instance, expresses a Delivery Traffic
	Indication Message (DTIM) of 3, then
	the AP will send a multicast packet every 3 packets.  In fact,
	when any single wireless STA associated with an AP has
	802.11 power-save mode enabled, the AP buffers all multicast
	frames and sends them only after the next DTIM beacon.  </t>
        <t indent="0" pn="section-4.3-2"> In practice, most APs will send a multicast every 30 packets.
	For unicast, the AP could send a Traffic Indication Message (TIM),
	but, for multicast, the AP sends a broadcast to everyone.  DTIM does
	power management, but STAs can choose whether to wake up 
	and whether to drop the packet.  Unfortunately, without proper administrative
	control, such STAs may be unable to determine why their
	multicast operations do not work. </t>
      </section>
      <section numbered="true" toc="include" removeInRFC="false" pn="section-4.4">
        <name slugifiedName="name-limiting-multicast-buffer-h">Limiting Multicast Buffer Hardware Queue Depth</name>
        <t indent="0" pn="section-4.4-1">The Content after Beacon (CAB) queue is used for beacon-triggered 
    transmission of buffered multicast frames. If lots of multicast frames were 
    buffered and this queue fills up, it drowns out all regular traffic. To limit the 
    damage that buffered traffic can do, some drivers limit the amount of 
    queued multicast data to a fraction of the beacon_interval. An example of 
    this is <xref target="CAB" format="default" sectionFormat="of" derivedContent="CAB"/>. </t>
      </section>
      <section anchor="ipv6" numbered="true" toc="include" removeInRFC="false" pn="section-4.5">
        <name slugifiedName="name-ipv6-support-in-80211-2012">IPv6 Support in 802.11-2012</name>
        <t indent="0" pn="section-4.5-1"> IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a special 
    multicast address for this purpose.
        </t>
        <t indent="0" pn="section-4.5-2"> Here is the specification language from clause 10.23.13
	    of <xref target="dot11-proxyarp" format="default" sectionFormat="of" derivedContent="dot11-proxyarp"/>:
        </t>
        <blockquote pn="section-4.5-3">
          <t indent="0" pn="section-4.5-3.1">When an IPv6 address is being resolved, the Proxy Neighbor
	    Discovery service shall respond with a Neighbor Advertisement
	    message [...] on behalf of an associated STA to an [ICMPv6]
	    Neighbor Solicitation message [...]. When MAC address mappings
	    change, the AP may send unsolicited Neighbor Advertisement
	    Messages on behalf of a STA.</t>
        </blockquote>
        <t indent="0" pn="section-4.5-4">NDP may be used to request additional information using the following methods, among others:
        </t>
        <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.5-5">
          <li pn="section-4.5-5.1">Maximum Transmission Unit</li>
          <li pn="section-4.5-5.2">Router Solicitation</li>
          <li pn="section-4.5-5.3">Router Advertisement</li>
        </ul>
        <t indent="0" pn="section-4.5-6">
	NDP messages are sent as group-addressed (broadcast) frames
	in 802.11. Using the proxy operation helps to keep NDP messages off
	the wireless medium.</t>
      </section>
      <section anchor="convert" numbered="true" toc="include" removeInRFC="false" pn="section-4.6">
        <name slugifiedName="name-using-unicast-instead-of-mu">Using Unicast Instead of Multicast</name>
        <t indent="0" pn="section-4.6-1"> It is often possible to transmit multicast control and data messages
	  by using unicast transmissions to each station individually.</t>
        <section anchor="convert-over" numbered="true" toc="include" removeInRFC="false" pn="section-4.6.1">
          <name slugifiedName="name-overview">Overview</name>
          <t indent="0" pn="section-4.6.1-1">
	   In many situations, it's a good choice to use unicast instead of
	   multicast over the Wi-Fi link.  This avoids most of the
	   problems specific to multicast over Wi-Fi, since the individual
	   frames are then acknowledged and buffered for power-save clients
	   in the way that unicast traffic normally operates.
          </t>
          <t indent="0" pn="section-4.6.1-2">
	   This approach comes with the trade-off of sometimes sending
	   the same packet multiple times over the Wi-Fi link.  However,
	   in many cases, such as video into a residential home network,
	   this can be a good trade-off since the Wi-Fi link may have enough
	   capacity for the unicast traffic to be transmitted to each
	   subscribed STA, even though multicast addressing may have been
	   necessary for the upstream access network.
          </t>
          <t indent="0" pn="section-4.6.1-3">
	   Several technologies exist that can be used to arrange unicast
	   transport over the Wi-Fi link, outlined in the subsections below.
          </t>
        </section>
        <section anchor="convert-l2" numbered="true" toc="include" removeInRFC="false" pn="section-4.6.2">
          <name slugifiedName="name-layer-2-conversion-to-unica">Layer 2 Conversion to Unicast</name>
          <t indent="0" pn="section-4.6.2-1">
	    It is often possible to transmit multicast control and data messages
	    by using unicast transmissions to each station individually.
          </t>
          <t indent="0" pn="section-4.6.2-2">
	    Although there is not yet a standardized method of conversion, at
	    least one widely available implementation exists in the Linux
	    bridging code <xref target="bridge-mc-2-uc" format="default" sectionFormat="of" derivedContent="bridge-mc-2-uc"/>.  Other proprietary
	    implementations are available from various vendors.
	    In general, these implementations perform a straightforward
	    mapping for groups or channels, discovered by IGMP or MLD
	    snooping, to the corresponding unicast MAC addresses.
          </t>
        </section>
        <section anchor="convert-DMS" numbered="true" toc="include" removeInRFC="false" pn="section-4.6.3">
          <name slugifiedName="name-directed-multicast-service-">Directed Multicast Service (DMS)</name>
          <t indent="0" pn="section-4.6.3-1">
	    DMS enables an STA to request that the AP
	    transmit multicast group-addressed frames destined to the
	    requesting STAs as individually addressed frames (i.e., convert
	    multicast to unicast).  Here are some characteristics of DMS:
          </t>
          <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.6.3-2">
            <li pn="section-4.6.3-2.1">	Requires 802.11n Aggregate MAC Service Data Units (A-MSDUs).</li>
            <li pn="section-4.6.3-2.2">	Individually addressed frames are acknowledged and are
		buffered for power-save STAs.</li>
            <li pn="section-4.6.3-2.3">	The requesting STA may specify traffic characteristics for
		DMS traffic.</li>
            <li pn="section-4.6.3-2.4">	DMS was defined in IEEE Std 802.11v-2011 <xref target="v2011" format="default" sectionFormat="of" derivedContent="v2011"/>.</li>
            <li pn="section-4.6.3-2.5"> DMS requires changes to both AP and STA implementation.</li>
          </ul>
          <t indent="0" pn="section-4.6.3-3">
	    DMS is not currently implemented in products.
	    See <xref target="Tramarin2017" format="default" sectionFormat="of" derivedContent="Tramarin2017"/> and <xref target="Oliva2013" format="default" sectionFormat="of" derivedContent="Oliva2013"/>
	    for more information. </t>
        </section>
        <section anchor="convert-amt" numbered="true" toc="include" removeInRFC="false" pn="section-4.6.4">
          <name slugifiedName="name-automatic-multicast-tunneli">Automatic Multicast Tunneling (AMT)</name>
          <t indent="0" pn="section-4.6.4-1">
	    AMT <xref target="RFC7450" format="default" sectionFormat="of" derivedContent="RFC7450"/> provides a method to tunnel multicast
	    IP packets inside unicast IP packets over network links that only
	    support unicast.  When an operating system or application running
	    on an STA has an AMT gateway capability integrated, it's possible
	    to use unicast to traverse the Wi-Fi link by deploying an AMT
	    relay in the non-Wi-Fi portion of the network connected to the AP.
          </t>
          <t indent="0" pn="section-4.6.4-2">
	    It is recommended that multicast-enabled networks deploying AMT
	    relays for this purpose make the relays locally discoverable with
	    the following methods, as described in
			<xref target="RFC8777" format="default" sectionFormat="of" derivedContent="RFC8777"/>:
          </t>
          <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.6.4-3">
            <li pn="section-4.6.4-3.1">DNS-based Service Discovery (DNS-SD) <xref target="RFC6763" format="default" sectionFormat="of" derivedContent="RFC6763"/></li>
            <li pn="section-4.6.4-3.2">The well-known IP addresses from <xref target="RFC7450" sectionFormat="of" section="7" format="default" derivedLink="https://rfc-editor.org/rfc/rfc7450#section-7" derivedContent="RFC7450"/></li>
          </ul>
          <t indent="0" pn="section-4.6.4-4">
	   An AMT gateway that implements multiple standard discovery methods
	   is more likely to discover the local multicast-capable network
	   instead of forming a connection to a nonlocal AMT relay further upstream.
          </t>
        </section>
      </section>
      <section anchor="GCR" numbered="true" toc="include" removeInRFC="false" pn="section-4.7">
        <name slugifiedName="name-groupcast-with-retries-gcr">GroupCast with Retries (GCR)</name>
        <t indent="0" pn="section-4.7-1"> GCR (defined in <xref target="dot11aa" format="default" sectionFormat="of" derivedContent="dot11aa"/>) provides greater
	reliability by using either unsolicited retries or a block
	acknowledgement mechanism. GCR increases the probability of broadcast
	frame reception success but still does not guarantee success.</t>
        <t indent="0" pn="section-4.7-2"> For the block acknowledgement mechanism, the AP transmits each
	group-addressed frame as a conventional group-addressed transmission.
	Retransmissions are group addressed but hidden from non-11aa STAs.
	A directed block acknowledgement scheme is used to harvest reception
	status from receivers; retransmissions are based upon these
	responses.</t>
        <t indent="0" pn="section-4.7-3"> GCR is suitable for all group sizes including medium to large
	groups. As the number of devices in the group increases, GCR can send
	block acknowledgement requests to only a small subset of the group.
	GCR does require changes to both AP and STA implementations.</t>
        <t indent="0" pn="section-4.7-4"> GCR may introduce unacceptable latency. After sending a group of
	data frames to the group, the AP has to do the following:

        </t>
        <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.7-5">
          <li pn="section-4.7-5.1">Unicast a Block Ack Request (BAR) to a subset of members.</li>
          <li pn="section-4.7-5.2">Wait for the corresponding Block Ack (BA).</li>
          <li pn="section-4.7-5.3">Retransmit any missed frames.</li>
          <li pn="section-4.7-5.4">Resume other operations that may have been delayed.</li>
        </ul>
        <t indent="0" pn="section-4.7-6"> This latency may not be acceptable for some traffic.</t>
        <t indent="0" pn="section-4.7-7"> There are ongoing extensions in 802.11 to improve GCR performance.
        </t>
        <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-4.7-8">
          <li pn="section-4.7-8.1"> BAR is sent using downlink Multi-User MIMO.</li>
          <li pn="section-4.7-8.2"> BA is sent using uplink MU-MIMO (uplink MU-MIMO is an IEEE 801.11ax-2021 feature).</li>
          <li pn="section-4.7-8.3"> Latency may also be reduced by simultaneously receiving BA
		information from multiple STAs.</li>
        </ul>
      </section>
    </section>
    <section anchor="optim3" numbered="true" toc="include" removeInRFC="false" pn="section-5">
      <name slugifiedName="name-operational-optimizations">Operational Optimizations</name>
      <t indent="0" pn="section-5-1">	This section lists some operational optimizations that can be
	implemented when deploying wireless IEEE 802 networks to mitigate
	some of the issues discussed in <xref target="multicast_issues" format="default" sectionFormat="of" derivedContent="Section 3"/>.</t>
      <section anchor="mitigate-spurious" numbered="true" toc="include" removeInRFC="false" pn="section-5.1">
        <name slugifiedName="name-mitigating-problems-from-sp">Mitigating Problems from Spurious Neighbor Discovery</name>
        <dl newline="true" indent="6" spacing="normal" pn="section-5.1-1">
          <dt pn="section-5.1-1.1">ARP Sponges</dt>
          <dd pn="section-5.1-1.2">
            <t indent="0" pn="section-5.1-1.2.1"> An ARP Sponge
	    sits on a network and learns which IP addresses are actually in
	    use. It also listens for ARP requests, and, if it sees an ARP for
	    an IP address that it believes is not used, it will reply with
	    its own MAC address. This means that the router now has an IP-to-MAC mapping, which it caches. If that IP is later assigned to a
	    machine (e.g., using DHCP), the ARP Sponge will see this and will
	    stop replying for that address. Gratuitous ARPs (or the machine
	    ARPing for its gateway) will replace the sponged address in the
	    router ARP table. This technique is quite effective; unfortunately, the ARP Sponge daemons were not really designed for
	    this use (one of the most widely deployed ARP Sponges
	    <xref target="arpsponge" format="default" sectionFormat="of" derivedContent="arpsponge"/> was
	    designed to deal with the disappearance of participants from an
	    Internet Exchange Point (IXP)) and so are not optimized for this purpose.  

One daemon is
	    needed per subnet; the tuning is tricky (the scanning rate versus
	    the population rate versus retries, etc.), and sometimes daemons just stop, 
	    requiring a restart of the daemon that causes disruption. </t>
          </dd>
          <dt pn="section-5.1-1.3">Router mitigations</dt>
          <dd pn="section-5.1-1.4">
            <t indent="0" pn="section-5.1-1.4.1"> Some
	    routers (often those based on Linux) implement a "negative ARP
	    cache" daemon. If the router does not see a reply to
	    an ARP, it can be configured to cache this information for some
	    interval. Unfortunately, the core routers in use often do
	    not support this. Instead, when a host connects to a network and gets an IP
	    address, it will ARP for its default gateway (the router). The
	    router will update its cache with the IP to host MAC mapping
	    learned from the request (passive ARP learning). </t>
          </dd>
          <dt pn="section-5.1-1.5">Firewall unused space</dt>
          <dd pn="section-5.1-1.6">
            <t indent="0" pn="section-5.1-1.6.1"> The
	    distribution of users on wireless networks / subnets may change in various
	    use cases, such as conference venues (e.g., Service Set Identifiers (SSIDs) are renamed, some SSIDs
	    lose favor, etc.).  This makes utilization for particular SSIDs
	    difficult to predict ahead of time, but usage can be monitored
	    as attendees use the different networks. Configuring multiple
	    DHCP pools per subnet and enabling them sequentially can create
	    a large subnet from which only addresses in the lower portions
	    are assigned. Therefore, input IP access lists can be applied,
	    which deny traffic to the upper, unused portions. Then the
	    router does not attempt to forward packets to the unused portions
	    of the subnets and so does not ARP for it. This method has proven
	    to be very effective but is somewhat of a blunt axe, is fairly
	    labor intensive, and requires coordination. </t>
          </dd>
          <dt pn="section-5.1-1.7">Disabling/Filtering ARP requests</dt>
          <dd pn="section-5.1-1.8">
            <t indent="0" pn="section-5.1-1.8.1"> In general, the router does not need to ARP for
	    hosts; when a host connects, the router can learn the IP-to-MAC
	    mapping from the ARP request sent by that host.  Consequently, it
	    should be possible to disable and/or filter ARP requests from the
	    router.  Unfortunately, ARP is a very low-level/fundamental part
	    of the IP stack and is often offloaded from the normal control
	    plane. While many routers can filter Layer 2 traffic, this is
	    usually implemented as an input filter and/or has limited
	    ability to filter output broadcast traffic. 

This means that the seemingly simple and obvious solution to "just disable ARP or filter it outbound" is made difficult or awkward in practice by implementations and/or architectural issues.
            </t>
          </dd>
          <dt pn="section-5.1-1.9">NAT</dt>
          <dd pn="section-5.1-1.10">
            <t indent="0" pn="section-5.1-1.10.1"> Broadcasts can often be 
	    caused by outside Wi-Fi scanning / backscatter traffic. In order to reduce the impact of
	    broadcasts, NAT can be used on the entire (or a large portion) of a network. This would
	    eliminate NAT translation entries for unused addresses, and the router would never ARP 
	    for them. There are, however, many reasons to avoid using NAT in such a blanket fashion.
            </t>
          </dd>
          <dt pn="section-5.1-1.11">Stateful firewalls</dt>
          <dd pn="section-5.1-1.12"> Another
	    obvious solution would be to put a stateful firewall between the
	    wireless network and the Internet. This firewall would block
	    incoming traffic not associated with an outbound request.
	    But this conflicts with the need and desire of some
	    organizations to have the network as open as possible and to
	    honor the end-to-end principle. An attendee on a meeting network
	    should be an Internet host and should be able to receive
	    unsolicited requests. Unfortunately, keeping the network working
	    and stable is the first priority, and a stateful firewall may be
	    required in order to achieve this.</dd>
        </dl>
      </section>
      <section anchor="mitigate-spurious-sd" numbered="true" toc="include" removeInRFC="false" pn="section-5.2">
        <name slugifiedName="name-mitigating-spurious-service">Mitigating Spurious Service Discovery Messages</name>
        <t indent="0" pn="section-5.2-1">
		In networks that must support hundreds of STAs, operators have
		observed network degradation due to many devices simultaneously
		registering with mDNS. In a network with many clients, it is
		recommended to ensure that mDNS packets designed to discover
		services in smaller home networks be constrained to avoid
		disrupting other traffic.
        </t>
      </section>
    </section>
    <section anchor="other-media" numbered="true" toc="include" removeInRFC="false" pn="section-6">
      <name slugifiedName="name-multicast-considerations-fo">Multicast Considerations for Other Wireless Media</name>
      <t indent="0" pn="section-6-1"> Many of the causes of performance degradation described in earlier
	sections are also observable for wireless media other than 802.11.</t>
      <t indent="0" pn="section-6-2"> For instance, problems with power save, excess media occupancy, and
	poor reliability will also affect 802.15.3 and 802.15.4. Unfortunately,
	802.15 media specifications do not yet include mechanisms similar to
	those developed for 802.11. In fact, the design philosophy for 802.15
	is oriented towards minimality, with the result that many such
	functions are relegated to operation within higher-layer protocols.
	This leads to a patchwork of non-interoperable and vendor-specific
	solutions.  See <xref target="uli" format="default" sectionFormat="of" derivedContent="uli"/> for additional discussion
	and a proposal for a task group to resolve similar issues, in which
	the multicast problems might be considered for mitigation. </t>
      <t indent="0" pn="section-6-3"> Similar considerations hold for most other wireless media.  A brief
	introduction is provided in <xref target="RFC5757" format="default" sectionFormat="of" derivedContent="RFC5757"/> for the following:
      </t>
      <ul bare="false" empty="false" indent="3" spacing="normal" pn="section-6-4">
        <li pn="section-6-4.1"> 802.16 WiMAX </li>
        <li pn="section-6-4.2"> 3GPP/3GPP2 </li>
        <li pn="section-6-4.3"> DVB-H/DVB-IPDC </li>
        <li pn="section-6-4.4"> TV Broadcast and Satellite Networks </li>
      </ul>
    </section>
    <section anchor="recommendations" numbered="true" toc="include" removeInRFC="false" pn="section-7">
      <name slugifiedName="name-recommendations">Recommendations</name>
      <t indent="0" pn="section-7-1">	This section provides some recommendations about the usage and
	combinations of some of the multicast enhancements described in Sections
	<xref target="optim2" format="counter" sectionFormat="of" derivedContent="4"/> and <xref target="optim3" format="counter" sectionFormat="of" derivedContent="5"/>.</t>
      <t indent="0" pn="section-7-2"> Future protocol documents utilizing multicast signaling should
	be carefully scrutinized if the protocol is likely to be used over
	wireless media. </t>
      <t indent="0" pn="section-7-3"> The use of proxy methods should be encouraged to conserve network bandwidth
	and power utilization by low-power devices.  

The device can send a unicast message to its proxy, and then the proxy can take care
	of any needed multicast operations.  </t>
      <t indent="0" pn="section-7-4"> Multicast signaling for wireless devices should be done in a way that is
	compatible with low duty-cycle operation. </t>
    </section>
    <section anchor="discussion" numbered="true" toc="include" removeInRFC="false" pn="section-8">
      <name slugifiedName="name-ongoing-discussion-items">Ongoing Discussion Items</name>
      <t indent="0" pn="section-8-1">	This section suggests two discussion items for further resolution. </t>
      <t indent="0" pn="section-8-2"> First, standards (and private) organizations should develop guidelines to help clarify when
	multicast packets would be better served by being sent wired rather than wireless.  
For example, 802.1ak <xref target="IEEE802.1ak" format="default" sectionFormat="of" derivedContent="IEEE802.1ak"/> works on
	both Ethernet and Wi-Fi, and organizations could help with deployment decision making
	by developing guidelines for multicast over Wi-Fi, including options for when traffic should be sent wired.
      </t>
      <t indent="0" pn="section-8-3">
	Second, reliable registration to Layer 2 multicast groups and a reliable
	multicast operation at Layer 2 might provide a good multicast over Wi-Fi solution.
	There shouldn't be a need to support 2<sup>24</sup> groups to get solicited node
	multicast working: it is possible to simply select a number of
	bits that make sense for a given network size to limit the
	number of unwanted deliveries to reasonable levels.  
The IEEE 802.1,
	802.11, and 802.15 Working Groups should be encouraged to revisit Layer 2 multicast issues and provide
	workable solutions.
      </t>
    </section>
    <section anchor="sec" numbered="true" toc="include" removeInRFC="false" pn="section-9">
      <name slugifiedName="name-security-considerations">Security Considerations</name>
      <t indent="0" pn="section-9-1">
	This document does not introduce or modify any security mechanisms. 
	Multicast deployed on wired or wireless networks as discussed in this document can be 
	made more secure in a variety of ways. 
<xref target="RFC4601" format="default" sectionFormat="of" derivedContent="RFC4601"/>, for instance,
  specifies the use of IPsec to ensure authentication of the link-local messages 
  in the Protocol Independent Multicast - Sparse Mode (PIM-SM) routing protocol.  
  <xref target="RFC5796" format="default" sectionFormat="of" derivedContent="RFC5796"/> specifies mechanisms to authenticate the PIM-SM link-local messages 
  using the IP security (IPsec) Encapsulating Security Payload (ESP) or (optionally) the
   Authentication Header (AH).
      </t>
      <t indent="0" pn="section-9-2">When using mechanisms that convert multicast traffic to unicast traffic for traversing radio links, 
    the AP (or other entity) is forced to explicitly track which subscribers care about certain multicast traffic.  
    This is generally a reasonable trade-off but does result in another entity that is tracking what entities 
    subscribe to which multicast traffic.  While such information is already (by necessity) tracked elsewhere, 
    this does present an expansion of the attack surface for that potentially privacy-sensitive information.</t>
      <t indent="0" pn="section-9-3">
	As noted in <xref target="group_key" format="default" sectionFormat="of" derivedContent="group_key"/>, the unreliable nature of
	multicast transmission over wireless media can cause subtle problems
	with multicast group key management and updates. 

<xref target="group_key" format="default" sectionFormat="of" derivedContent="group_key"/> states that when TKIP (WPA, now deprecated) or AES-CCMP (WPA2/WPA3) encryption is in use, AP-to-client (FromDS) multicasts have to be encrypted with a separate encryption key that 
	is known to all of the clients (this is called the Group Key). Quoting further from that
	website, "... most clients are able to get connected and surf the web,
	check email, etc. even when FromDS multicasts are broken. So a lot of
	people don't realize they have multicast problems on their network..."
      </t>
      <t indent="0" pn="section-9-4">This document encourages the use of proxy methods to conserve network bandwidth and
        power utilization by low-power devices. Such proxy methods in general have security considerations that 
        require the proxy to be trusted to not misbehave. One such proxy method listed is an ARP Sponge that listens for ARP requests, and, if it sees an ARP for an IP address that it believes is not used, it will reply 
        with its own MAC address. ARP poisoning and false advertising could potentially undermine (e.g., DoS) 
        this and other proxy approaches.</t>
    </section>
    <section anchor="iana" numbered="true" toc="include" removeInRFC="false" pn="section-10">
      <name slugifiedName="name-iana-considerations">IANA Considerations</name>
      <t indent="0" pn="section-10-1"> This document has no IANA actions.</t>
    </section>
  </middle>
  <back>
    <references pn="section-11">
      <name slugifiedName="name-informative-references">Informative References</name>
      <reference anchor="arpsponge" target="http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.182.4692" quoteTitle="true" derivedAnchor="arpsponge">
        <front>
          <title>Effects of IPv4 and IPv6 address resolution on AMS-IX and the ARP Sponge</title>
          <author fullname="Marco Wessel">
            <organization showOnFrontPage="true">"Universiteit van Amsterdam"</organization>
          </author>
          <author fullname="Niels Sijm">
            <organization showOnFrontPage="true">"Universiteit van Amsterdam"</organization>
          </author>
          <date month="July" year="2009"/>
        </front>
      </reference>
      <reference anchor="bridge-mc-2-uc" target="https://github.com/torvalds/linux/commit/6db6f0e" quoteTitle="true" derivedAnchor="bridge-mc-2-uc">
        <front>
          <title>bridge: multicast to unicast</title>
          <author/>
          <date month="January" year="2017"/>
        </front>
        <refcontent>commit 6db6f0e</refcontent>
      </reference>
      <reference anchor="CAB" target="https://patchwork.kernel.org/patch/2687951/" quoteTitle="true" derivedAnchor="CAB">
        <front>
          <title>limit multicast buffer hardware queue depth</title>
          <author/>
          <date year="2013" month="June"/>
        </front>
        <refcontent>commit 2687951</refcontent>
      </reference>
      <reference anchor="Deri-2010" target="http://ripe61.ripe.net/presentations/138-Deri_RIPE_61.pdf" quoteTitle="true" derivedAnchor="Deri-2010">
        <front>
          <title abbrev="Deri-2010">10 Gbit Hardware Packet Filtering Using Commodity Network Adapters</title>
          <author fullname="Luca Deri" initials="L." surname="Deri">
            <organization showOnFrontPage="true">NTOP</organization>
          </author>
          <author fullname="Joseph Gasparakis" initials="J." surname="Gasparakis">
            <organization showOnFrontPage="true">Intel</organization>
          </author>
          <date month="November" year="2010"/>
        </front>
        <refcontent>RIPE 61</refcontent>
      </reference>
      <reference anchor="dot11" target="https://standards.ieee.org/standard/802_11-2020.html" quoteTitle="true" derivedAnchor="dot11">
        <front>
          <title>Information Technology--Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks--Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications (includes 802.11v amendment)</title>
          <author>
            <organization showOnFrontPage="true">IEEE</organization>
          </author>
          <date month="December" year="2020"/>
        </front>
        <seriesInfo name="DOI" value="10.1109/IEEESTD.2021.9363693"/>
        <seriesInfo name="IEEE Std" value="802.11-2020"/>
      </reference>
      <reference anchor="dot11-proxyarp" target="https://mentor.ieee.org/802.11/dcn/15/11-15-1015-01-00ax-proxy-arp-in-802-11ax.pptx" quoteTitle="true" derivedAnchor="dot11-proxyarp">
        <front>
          <title>Proxy ARP in 802.11ax</title>
          <author fullname="Guido R. Hiertz" initials="G." surname="Hiertz"/>
          <author fullname="Filip Mestanov" initials="F." surname="Mestanov"/>
          <author fullname="Brian Hart" initials="B." surname="Hart"/>
          <date month="September" year="2015"/>
        </front>
      </reference>
      <reference anchor="dot11aa" target="https://standards.ieee.org/standard/802_11aa-2012.html" quoteTitle="true" derivedAnchor="dot11aa">
        <front>
          <title>Information technology--Telecommunications and information exchange between systems Local and metropolitan area networks--Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 2: MAC Enhancements for Robust Audio Video Streaming</title>
          <author>
            <organization showOnFrontPage="true">IEEE</organization>
          </author>
          <date month="March" year="2012"/>
        </front>
        <seriesInfo name="DOI" value="10.1109/IEEESTD.2012.6204193"/>
        <seriesInfo name="IEEE Std" value="802.11aa-2012"/>
      </reference>
      <reference anchor="group_key" target="https://superuser.com/questions/730288/why-do-some-wifi-routers-block-multicast-packets-going-from-wired-to-wireless" quoteTitle="true" derivedAnchor="group_key">
        <front>
          <title>Subject: Why do some WiFi routers block multicast packets going from wired to wireless?</title>
          <author/>
          <date month="January" year="2017"/>
        </front>
        <refcontent>message to the Super User Q &amp; A community</refcontent>
      </reference>
      <reference anchor="IEEE802.1ak" target="https://www.ieee802.org/1/pages/802.1ak.html" quoteTitle="true" derivedAnchor="IEEE802.1ak">
        <front>
          <title>Local and Metropolitan Area Networks Virtual Bridged Local Area Networks - Amendment 07: Multiple Registration Protocol</title>
          <author>
            <organization showOnFrontPage="true">IEEE</organization>
          </author>
          <date month="June" year="2007"/>
        </front>
        <seriesInfo name="DOI" value="10.1109/IEEESTD.2007.380667"/>
        <seriesInfo name="IEEE Std" value="802.1ak-2007"/>
      </reference>
      <reference anchor="ietf_802-11" target="https://mentor.ieee.org/802.11/dcn/15/11-15-1261-03-0arc-multicast-performance-optimization-features-overview-for-ietf-nov-2015.ppt" quoteTitle="true" derivedAnchor="ietf_802-11">
        <front>
          <title>IEEE 802.11 multicast capabilities</title>
          <author fullname="Dorothy Stanley" initials="D." surname="Stanley"/>
          <date month="November" year="2015"/>
        </front>
      </reference>
      <reference anchor="mc-prob-stmt" target="https://www.iab.org/wp-content/IAB-uploads/2013/01/multicast-problem-statement.pptx" quoteTitle="true" derivedAnchor="mc-prob-stmt">
        <front>
          <title>Multicast on 802.11</title>
          <author fullname="Mikael Abrahamsson">
            <organization showOnFrontPage="true">Deutsche Telekom</organization>
          </author>
          <author fullname="Adrian Stephens">
            <organization showOnFrontPage="true">Intel Corporation</organization>
          </author>
          <date year="2013"/>
        </front>
      </reference>
      <reference anchor="mc-props" target="https://mentor.ieee.org/802.11/dcn/15/11-15-1161-02-0arc-802-11-multicast-properties.ppt" quoteTitle="true" derivedAnchor="mc-props">
        <front>
          <title>IEEE 802.11 multicast properties</title>
          <author fullname="Adrian Stephens">
            <organization showOnFrontPage="true">Intel Corporation</organization>
          </author>
          <date month="September" year="2015"/>
        </front>
      </reference>
      <reference anchor="Oliva2013" quoteTitle="true" target="https://doi.org/10.1109/WoWMoM.2013.6583394" derivedAnchor="Oliva2013">
        <front>
          <title>Performance evaluation of the IEEE 802.11aa multicast mechanisms for video streaming</title>
          <author fullname="Antonio de la Oliva" initials="A." surname="de la Oliva">
            <organization showOnFrontPage="true">Universidad Carlos III de Madrid</organization>
            <address>
              <postal>
                <street>Avda. Universidad, 30, 28911 Leganes, Spain</street>
              </postal>
            </address>
          </author>
          <author fullname="Pablo Serrano" initials="P." surname="Serrano">
            <organization showOnFrontPage="true">Universidad Carlos III de Madrid</organization>
            <address>
              <postal>
                <street>Avda. Universidad, 30, 28911 Leganes, Spain</street>
              </postal>
            </address>
          </author>
          <author fullname="Pablo Salvador" initials="P." surname="Salvador">
            <organization showOnFrontPage="true">Institute IMDEA Networks,</organization>
            <address>
              <postal>
                <street>Avda. del Mar Mediterraneo, 22, 28911 Leganes, Spain</street>
              </postal>
            </address>
          </author>
          <author fullname="Albert Banchs" initials="A." surname="Banchs">
            <organization showOnFrontPage="true">Institute IMDEA Networks,</organization>
            <address>
              <postal>
                <street>Avda. del Mar Mediterraneo, 22, 28911 Leganes, Spain</street>
              </postal>
            </address>
          </author>
          <date month="June" year="2013"/>
        </front>
        <seriesInfo name="DOI" value="10.1109/WoWMoM.2013.6583394"/>
        <refcontent>2013 IEEE 14th International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM), pp. 1-9 </refcontent>
      </reference>
      <reference anchor="RFC0826" target="https://www.rfc-editor.org/info/rfc826" quoteTitle="true" derivedAnchor="RFC0826">
        <front>
          <title>An Ethernet Address Resolution Protocol: Or Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware</title>
          <author initials="D." surname="Plummer" fullname="D. Plummer">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="1982" month="November"/>
          <abstract>
            <t indent="0">The purpose of this RFC is to present a method of Converting Protocol Addresses (e.g., IP addresses) to Local Network Addresses (e.g., Ethernet addresses).  This is an issue of general concern in the ARPA Internet Community at this time.  The method proposed here is presented for your consideration and comment.  This is not the specification of an Internet Standard.</t>
          </abstract>
        </front>
        <seriesInfo name="STD" value="37"/>
        <seriesInfo name="RFC" value="826"/>
        <seriesInfo name="DOI" value="10.17487/RFC0826"/>
      </reference>
      <reference anchor="RFC2131" target="https://www.rfc-editor.org/info/rfc2131" quoteTitle="true" derivedAnchor="RFC2131">
        <front>
          <title>Dynamic Host Configuration Protocol</title>
          <author initials="R." surname="Droms" fullname="R. Droms">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="1997" month="March"/>
          <abstract>
            <t indent="0">The Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configuration information to hosts on a TCPIP network.  DHCP is based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allocation of reusable network addresses and additional configuration options.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="2131"/>
        <seriesInfo name="DOI" value="10.17487/RFC2131"/>
      </reference>
      <reference anchor="RFC4286" target="https://www.rfc-editor.org/info/rfc4286" quoteTitle="true" derivedAnchor="RFC4286">
        <front>
          <title>Multicast Router Discovery</title>
          <author initials="B." surname="Haberman" fullname="B. Haberman">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="J." surname="Martin" fullname="J. Martin">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2005" month="December"/>
          <abstract>
            <t indent="0">The concept of Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) snooping requires the ability to identify the location of multicast routers.  Since snooping is not standardized, there are many mechanisms in use to identify the multicast routers.  However, this can lead to interoperability issues between multicast routers and snooping switches from different vendors.</t>
            <t indent="0">This document introduces a general mechanism that allows for the discovery of multicast routers.  This new mechanism, Multicast Router Discovery (MRD), introduces a standardized means of identifying multicast routers without a dependency on particular multicast routing protocols.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="4286"/>
        <seriesInfo name="DOI" value="10.17487/RFC4286"/>
      </reference>
      <reference anchor="RFC4541" target="https://www.rfc-editor.org/info/rfc4541" quoteTitle="true" derivedAnchor="RFC4541">
        <front>
          <title>Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches</title>
          <author initials="M." surname="Christensen" fullname="M. Christensen">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="K." surname="Kimball" fullname="K. Kimball">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="F." surname="Solensky" fullname="F. Solensky">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2006" month="May"/>
          <abstract>
            <t indent="0">This memo describes the recommendations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) snooping switches.  These are based on best current practices for IGMPv2, with further considerations for IGMPv3- and MLDv2-snooping.  Additional areas of relevance, such as link layer topology changes and Ethernet-specific encapsulation issues, are also considered.  This memo provides information for the Internet community.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="4541"/>
        <seriesInfo name="DOI" value="10.17487/RFC4541"/>
      </reference>
      <reference anchor="RFC4601" target="https://www.rfc-editor.org/info/rfc4601" quoteTitle="true" derivedAnchor="RFC4601">
        <front>
          <title>Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)</title>
          <author initials="B." surname="Fenner" fullname="B. Fenner">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Handley" fullname="M. Handley">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="H." surname="Holbrook" fullname="H. Holbrook">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="I." surname="Kouvelas" fullname="I. Kouvelas">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2006" month="August"/>
          <abstract>
            <t indent="0">This document specifies Protocol Independent Multicast - Sparse Mode (PIM-SM).  PIM-SM is a multicast routing protocol that can use the underlying unicast routing information base or a separate multicast-capable routing information base.  It builds unidirectional shared trees rooted at a Rendezvous Point (RP) per group, and optionally creates shortest-path trees per source.</t>
            <t indent="0">This document obsoletes RFC 2362, an Experimental version of PIM-SM.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="4601"/>
        <seriesInfo name="DOI" value="10.17487/RFC4601"/>
      </reference>
      <reference anchor="RFC4861" target="https://www.rfc-editor.org/info/rfc4861" quoteTitle="true" derivedAnchor="RFC4861">
        <front>
          <title>Neighbor Discovery for IP version 6 (IPv6)</title>
          <author initials="T." surname="Narten" fullname="T. Narten">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="E." surname="Nordmark" fullname="E. Nordmark">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="W." surname="Simpson" fullname="W. Simpson">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="H." surname="Soliman" fullname="H. Soliman">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2007" month="September"/>
          <abstract>
            <t indent="0">This document specifies the Neighbor Discovery protocol for IP Version 6.  IPv6 nodes on the same link use Neighbor Discovery to discover each other's presence, to determine each other's link-layer addresses, to find routers, and to maintain reachability information about the paths to active neighbors.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="4861"/>
        <seriesInfo name="DOI" value="10.17487/RFC4861"/>
      </reference>
      <reference anchor="RFC4862" target="https://www.rfc-editor.org/info/rfc4862" quoteTitle="true" derivedAnchor="RFC4862">
        <front>
          <title>IPv6 Stateless Address Autoconfiguration</title>
          <author initials="S." surname="Thomson" fullname="S. Thomson">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="T." surname="Narten" fullname="T. Narten">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="T." surname="Jinmei" fullname="T. Jinmei">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2007" month="September"/>
          <abstract>
            <t indent="0">This document specifies the steps a host takes in deciding how to autoconfigure its interfaces in IP version 6.  The autoconfiguration process includes generating a link-local address, generating global addresses via stateless address autoconfiguration, and the Duplicate Address Detection procedure to verify the uniqueness of the addresses on a link.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="4862"/>
        <seriesInfo name="DOI" value="10.17487/RFC4862"/>
      </reference>
      <reference anchor="RFC5757" target="https://www.rfc-editor.org/info/rfc5757" quoteTitle="true" derivedAnchor="RFC5757">
        <front>
          <title>Multicast Mobility in Mobile IP Version 6 (MIPv6): Problem Statement and Brief Survey</title>
          <author initials="T." surname="Schmidt" fullname="T. Schmidt">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Waehlisch" fullname="M. Waehlisch">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="G." surname="Fairhurst" fullname="G. Fairhurst">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2010" month="February"/>
          <abstract>
            <t indent="0">This document discusses current mobility extensions to IP-layer multicast.  It describes problems arising from mobile group communication in general, the case of multicast listener mobility, and problems for mobile senders using Any Source Multicast and  Source-Specific Multicast.  Characteristic aspects of multicast  routing and deployment issues for fixed IPv6 networks are summarized. Specific properties and interplays with the underlying network access are  surveyed with respect to the relevant technologies in the wireless  domain.  It outlines the principal approaches to multicast mobility,  together with a comprehensive exploration of the mobile multicast  problem and solution space.  This document concludes with a conceptual  road map for initial steps in standardization for use by future mobile multicast protocol designers.  This document is a product of the IP Mobility Optimizations (MobOpts) Research Group.  This document is not an  Internet Standards Track specification; it is published for informational  purposes.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="5757"/>
        <seriesInfo name="DOI" value="10.17487/RFC5757"/>
      </reference>
      <reference anchor="RFC5796" target="https://www.rfc-editor.org/info/rfc5796" quoteTitle="true" derivedAnchor="RFC5796">
        <front>
          <title>Authentication and Confidentiality in Protocol Independent Multicast Sparse Mode (PIM-SM) Link-Local Messages</title>
          <author initials="W." surname="Atwood" fullname="W. Atwood">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="S." surname="Islam" fullname="S. Islam">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Siami" fullname="M. Siami">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2010" month="March"/>
          <abstract>
            <t indent="0">RFC 4601 mandates the use of IPsec to ensure authentication of the link-local messages in the Protocol Independent Multicast - Sparse Mode (PIM-SM) routing protocol.  This document specifies mechanisms to authenticate the PIM-SM link-local messages using the IP security (IPsec) Encapsulating Security Payload (ESP) or (optionally) the Authentication Header (AH).  It specifies optional mechanisms to provide confidentiality using the ESP.  Manual keying is specified as the mandatory and default group key management solution.  To deal with issues of scalability and security that exist with manual keying, optional support for an automated group key management mechanism is provided.  However, the procedures for implementing automated group key management are left to other documents.  This document updates RFC 4601.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="5796"/>
        <seriesInfo name="DOI" value="10.17487/RFC5796"/>
      </reference>
      <reference anchor="RFC6282" target="https://www.rfc-editor.org/info/rfc6282" quoteTitle="true" derivedAnchor="RFC6282">
        <front>
          <title>Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks</title>
          <author initials="J." surname="Hui" fullname="J. Hui" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="P." surname="Thubert" fullname="P. Thubert">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2011" month="September"/>
          <abstract>
            <t indent="0">This document updates RFC 4944, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks".  This document specifies an IPv6 header compression format for IPv6 packet delivery in Low Power Wireless Personal Area Networks (6LoWPANs).  The compression format relies on shared context to allow compression of arbitrary prefixes.  How the information is maintained in that shared context is out of scope. This document specifies compression of multicast addresses and a framework for compressing next headers.  UDP header compression is specified within this framework.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="6282"/>
        <seriesInfo name="DOI" value="10.17487/RFC6282"/>
      </reference>
      <reference anchor="RFC6762" target="https://www.rfc-editor.org/info/rfc6762" quoteTitle="true" derivedAnchor="RFC6762">
        <front>
          <title>Multicast DNS</title>
          <author initials="S." surname="Cheshire" fullname="S. Cheshire">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Krochmal" fullname="M. Krochmal">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2013" month="February"/>
          <abstract>
            <t indent="0">As networked devices become smaller, more portable, and more ubiquitous, the ability to operate with less configured infrastructure is increasingly important.  In particular, the ability to look up DNS resource record data types (including, but not limited to, host names) in the absence of a conventional managed DNS server is useful.</t>
            <t indent="0">Multicast DNS (mDNS) provides the ability to perform DNS-like operations on the local link in the absence of any conventional Unicast DNS server.  In addition, Multicast DNS designates a portion of the DNS namespace to be free for local use, without the need to pay any annual fee, and without the need to set up delegations or otherwise configure a conventional DNS server to answer for those names.</t>
            <t indent="0">The primary benefits of Multicast DNS names are that (i) they require little or no administration or configuration to set them up, (ii) they work when no infrastructure is present, and (iii) they work during infrastructure failures.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="6762"/>
        <seriesInfo name="DOI" value="10.17487/RFC6762"/>
      </reference>
      <reference anchor="RFC6763" target="https://www.rfc-editor.org/info/rfc6763" quoteTitle="true" derivedAnchor="RFC6763">
        <front>
          <title>DNS-Based Service Discovery</title>
          <author initials="S." surname="Cheshire" fullname="S. Cheshire">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Krochmal" fullname="M. Krochmal">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2013" month="February"/>
          <abstract>
            <t indent="0">This document specifies how DNS resource records are named and structured to facilitate service discovery.  Given a type of service that a client is looking for, and a domain in which the client is looking for that service, this mechanism allows clients to discover a list of named instances of that desired service, using standard DNS queries. This mechanism is referred to as DNS-based Service Discovery, or DNS-SD.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="6763"/>
        <seriesInfo name="DOI" value="10.17487/RFC6763"/>
      </reference>
      <reference anchor="RFC6775" target="https://www.rfc-editor.org/info/rfc6775" quoteTitle="true" derivedAnchor="RFC6775">
        <front>
          <title>Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)</title>
          <author initials="Z." surname="Shelby" fullname="Z. Shelby" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="S." surname="Chakrabarti" fullname="S. Chakrabarti">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="E." surname="Nordmark" fullname="E. Nordmark">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="C." surname="Bormann" fullname="C. Bormann">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2012" month="November"/>
          <abstract>
            <t indent="0">The IETF work in IPv6 over Low-power Wireless Personal Area Network (6LoWPAN) defines 6LoWPANs such as IEEE 802.15.4.  This and other similar link technologies have limited or no usage of multicast signaling due to energy conservation.  In addition, the wireless network may not strictly follow the traditional concept of IP subnets and IP links.  IPv6 Neighbor Discovery was not designed for non- transitive wireless links, as its reliance on the traditional IPv6 link concept and its heavy use of multicast make it inefficient and sometimes impractical in a low-power and lossy network.  This document describes simple optimizations to IPv6 Neighbor Discovery, its addressing mechanisms, and duplicate address detection for Low- power Wireless Personal Area Networks and similar networks.  The document thus updates RFC 4944 to specify the use of the optimizations defined here.  [STANDARDS-TRACK]</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="6775"/>
        <seriesInfo name="DOI" value="10.17487/RFC6775"/>
      </reference>
      <reference anchor="RFC6970" target="https://www.rfc-editor.org/info/rfc6970" quoteTitle="true" derivedAnchor="RFC6970">
        <front>
          <title>Universal Plug and Play (UPnP) Internet Gateway Device - Port Control Protocol Interworking Function (IGD-PCP IWF)</title>
          <author initials="M." surname="Boucadair" fullname="M. Boucadair">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="R." surname="Penno" fullname="R. Penno">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="D." surname="Wing" fullname="D. Wing">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2013" month="July"/>
          <abstract>
            <t indent="0">This document specifies the behavior of the Universal Plug and Play (UPnP) Internet Gateway Device - Port Control Protocol Interworking Function (IGD-PCP IWF).  A UPnP IGD-PCP IWF is required to be embedded in Customer Premises (CP) routers to allow for transparent NAT control in environments where a UPnP IGD is used on the LAN side and PCP is used on the external side of the CP router.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="6970"/>
        <seriesInfo name="DOI" value="10.17487/RFC6970"/>
      </reference>
      <reference anchor="RFC7450" target="https://www.rfc-editor.org/info/rfc7450" quoteTitle="true" derivedAnchor="RFC7450">
        <front>
          <title>Automatic Multicast Tunneling</title>
          <author initials="G." surname="Bumgardner" fullname="G. Bumgardner">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2015" month="February"/>
          <abstract>
            <t indent="0">This document describes Automatic Multicast Tunneling (AMT), a protocol for delivering multicast traffic from sources in a multicast-enabled network to receivers that lack multicast connectivity to the source network.  The protocol uses UDP encapsulation and unicast replication to provide this functionality.</t>
            <t indent="0">The AMT protocol is specifically designed to support rapid deployment by requiring minimal changes to existing network infrastructure.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="7450"/>
        <seriesInfo name="DOI" value="10.17487/RFC7450"/>
      </reference>
      <reference anchor="RFC7761" target="https://www.rfc-editor.org/info/rfc7761" quoteTitle="true" derivedAnchor="RFC7761">
        <front>
          <title>Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)</title>
          <author initials="B." surname="Fenner" fullname="B. Fenner">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Handley" fullname="M. Handley">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="H." surname="Holbrook" fullname="H. Holbrook">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="I." surname="Kouvelas" fullname="I. Kouvelas">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="R." surname="Parekh" fullname="R. Parekh">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="Z." surname="Zhang" fullname="Z. Zhang">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="L." surname="Zheng" fullname="L. Zheng">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2016" month="March"/>
          <abstract>
            <t indent="0">This document specifies Protocol Independent Multicast - Sparse Mode (PIM-SM).  PIM-SM is a multicast routing protocol that can use the underlying unicast routing information base or a separate multicast-capable routing information base.  It builds unidirectional shared trees rooted at a Rendezvous Point (RP) per group, and it optionally creates shortest-path trees per source.</t>
            <t indent="0">This document obsoletes RFC 4601 by replacing it, addresses the errata filed against it, removes the optional (*,*,RP), PIM Multicast Border Router features and authentication using IPsec that lack sufficient deployment experience (see Appendix A), and moves the PIM specification to Internet Standard.</t>
          </abstract>
        </front>
        <seriesInfo name="STD" value="83"/>
        <seriesInfo name="RFC" value="7761"/>
        <seriesInfo name="DOI" value="10.17487/RFC7761"/>
      </reference>
      <reference anchor="RFC8415" target="https://www.rfc-editor.org/info/rfc8415" quoteTitle="true" derivedAnchor="RFC8415">
        <front>
          <title>Dynamic Host Configuration Protocol for IPv6 (DHCPv6)</title>
          <author initials="T." surname="Mrugalski" fullname="T. Mrugalski">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Siodelski" fullname="M. Siodelski">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="B." surname="Volz" fullname="B. Volz">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="A." surname="Yourtchenko" fullname="A. Yourtchenko">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="M." surname="Richardson" fullname="M. Richardson">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="S." surname="Jiang" fullname="S. Jiang">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="T." surname="Lemon" fullname="T. Lemon">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="T." surname="Winters" fullname="T. Winters">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2018" month="November"/>
          <abstract>
            <t indent="0">This document describes the Dynamic Host Configuration Protocol for IPv6 (DHCPv6): an extensible mechanism for configuring nodes with network configuration parameters, IP addresses, and prefixes. Parameters can be provided statelessly, or in combination with stateful assignment of one or more IPv6 addresses and/or IPv6 prefixes.  DHCPv6 can operate either in place of or in addition to stateless address autoconfiguration (SLAAC).</t>
            <t indent="0">This document updates the text from RFC 3315 (the original DHCPv6 specification) and incorporates prefix delegation (RFC 3633), stateless DHCPv6 (RFC 3736), an option to specify an upper bound for how long a client should wait before refreshing information (RFC 4242), a mechanism for throttling DHCPv6 clients when DHCPv6 service is not available (RFC 7083), and relay agent handling of unknown messages (RFC 7283).  In addition, this document clarifies the interactions between models of operation (RFC 7550).  As such, this document obsoletes RFC 3315, RFC 3633, RFC 3736, RFC 4242, RFC 7083, RFC 7283, and RFC 7550.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="8415"/>
        <seriesInfo name="DOI" value="10.17487/RFC8415"/>
      </reference>
      <reference anchor="RFC8505" target="https://www.rfc-editor.org/info/rfc8505" quoteTitle="true" derivedAnchor="RFC8505">
        <front>
          <title>Registration Extensions for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery</title>
          <author initials="P." surname="Thubert" fullname="P. Thubert" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="E." surname="Nordmark" fullname="E. Nordmark">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="S." surname="Chakrabarti" fullname="S. Chakrabarti">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="C." surname="Perkins" fullname="C. Perkins">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2018" month="November"/>
          <abstract>
            <t indent="0">This specification updates RFC 6775 -- the Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery specification -- to clarify the role of the protocol as a registration technique and simplify the registration operation in 6LoWPAN routers, as well as to provide enhancements to the registration capabilities and mobility detection for different network topologies, including the Routing Registrars performing routing for host routes and/or proxy Neighbor Discovery in a low-power network.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="8505"/>
        <seriesInfo name="DOI" value="10.17487/RFC8505"/>
      </reference>
      <reference anchor="RFC8777" target="https://www.rfc-editor.org/info/rfc8777" quoteTitle="true" derivedAnchor="RFC8777">
        <front>
          <title>DNS Reverse IP Automatic Multicast Tunneling (AMT) Discovery</title>
          <author initials="J." surname="Holland" fullname="J. Holland">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2020" month="April"/>
          <abstract>
            <t indent="0">This document updates RFC 7450, "Automatic Multicast Tunneling" (or AMT), by modifying the relay discovery process.  A new DNS resource record named AMTRELAY is defined for publishing AMT relays for source-specific multicast channels.  The reverse IP DNS zone for a multicast sender's IP address is configured to use AMTRELAY resource records to advertise a set of AMT relays that can receive and forward multicast traffic from that sender over an AMT tunnel.  Other extensions and clarifications to the relay discovery process are also defined.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="8777"/>
        <seriesInfo name="DOI" value="10.17487/RFC8777"/>
      </reference>
      <reference anchor="RFC8929" target="https://www.rfc-editor.org/info/rfc8929" quoteTitle="true" derivedAnchor="RFC8929">
        <front>
          <title>IPv6 Backbone Router</title>
          <author initials="P." surname="Thubert" fullname="P. Thubert" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="C.E." surname="Perkins" fullname="C.E. Perkins">
            <organization showOnFrontPage="true"/>
          </author>
          <author initials="E." surname="Levy-Abegnoli" fullname="E. Levy-Abegnoli">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2020" month="November"/>
          <abstract>
            <t indent="0">This document updates RFCs 6775 and 8505 in order to enable proxy services for IPv6 Neighbor Discovery by Routing Registrars called "Backbone Routers". Backbone Routers are placed along the wireless edge of a backbone and federate multiple wireless links to form a single Multi-Link Subnet (MLSN).</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="8929"/>
        <seriesInfo name="DOI" value="10.17487/RFC8929"/>
      </reference>
      <reference anchor="RFC9030" target="https://www.rfc-editor.org/info/rfc9030" quoteTitle="true" derivedAnchor="RFC9030">
        <front>
          <title>An Architecture for IPv6 over the Time-Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)</title>
          <author initials="P." surname="Thubert" fullname="P. Thubert" role="editor">
            <organization showOnFrontPage="true"/>
          </author>
          <date year="2021" month="May"/>
          <abstract>
            <t indent="0">This document describes a network architecture that provides low-latency, low-jitter, and high-reliability packet delivery.  It combines a high-speed powered backbone and subnetworks using IEEE 802.15.4 time-slotted channel hopping (TSCH) to meet the requirements of low-power wireless deterministic applications.</t>
          </abstract>
        </front>
        <seriesInfo name="RFC" value="9030"/>
        <seriesInfo name="DOI" value="10.17487/RFC9030"/>
      </reference>
      <reference anchor="Tramarin2017" quoteTitle="true" derivedAnchor="Tramarin2017">
        <front>
          <title>IEEE 802.11n for Distributed Measurement Systems</title>
          <author fullname="Federico Tramarin" initials="F." surname="Tramarin">
            <organization showOnFrontPage="true">National Research Council of Italy, CNR-IEIIT</organization>
            <address>
              <postal>
                <street>Via Gradenigo 6/B, 35131 Padova, Italy</street>
              </postal>
            </address>
          </author>
          <author fullname="Stefano Vitturi" initials="S." surname="Vitturi">
            <organization showOnFrontPage="true">National Research Council of Italy, CNR-IEIIT</organization>
            <address>
              <postal>
                <street>Via Gradenigo 6/B, 35131 Padova, Italy</street>
              </postal>
            </address>
          </author>
          <author fullname="Michele Luvisotto" initials="M." surname="Luvisotto">
            <organization showOnFrontPage="true">Dept. of Information Engineering, University of Padova</organization>
            <address>
              <postal>
                <street>Via Gradenigo 6/B, 35131 Padova, Italy</street>
              </postal>
            </address>
          </author>
          <date month="May" year="2017"/>
        </front>
        <refcontent>2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), pp. 1-6</refcontent>
      </reference>
      <reference anchor="uli" target="https://mentor.ieee.org/802.15/dcn/15/15-15-0521-01-wng0-llc-proposal-for-802-15-4.pptx" quoteTitle="true" derivedAnchor="uli">
        <front>
          <title>LLC Proposal for 802.15.4</title>
          <author fullname="Pat Kinney" initials="P." surname="Kinney">
          </author>
          <date month="September" year="2015"/>
        </front>
      </reference>
      <reference anchor="v2011" target="https://ieeexplore.ieee.org/document/5716530" quoteTitle="true" derivedAnchor="v2011">
        <front>
          <title>Information technology -- Local and metropolitan area networks -- Specific requirements -- Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 8: IEEE 802.11 Wireless Network Management</title>
          <author>
            <organization showOnFrontPage="true">IEEE</organization>
          </author>
          <date month="February" year="2011"/>
        </front>
        <seriesInfo name="DOI" value="10.1109/IEEESTD.2011.5716530"/>
        <seriesInfo name="IEEE Std" value="802.11v-2011"/>
      </reference>
    </references>
    <section anchor="acknowledgements" numbered="false" toc="include" removeInRFC="false" pn="section-appendix.a">
      <name slugifiedName="name-acknowledgements">Acknowledgements</name>
      <t indent="0" pn="section-appendix.a-1">
	This document has benefitted from discussions with the following
	people, in alphabetical order:
	   <contact fullname="Mikael Abrahamsson"/>,
	    <contact fullname="Bill Atwood"/>,
	    <contact fullname="Stuart Cheshire"/>,
	    <contact fullname="Donald Eastlake 3rd"/>,
	    <contact fullname="Toerless Eckert"/>,
	    <contact fullname="Jake Holland"/>,
	    <contact fullname="Joel Jaeggli"/>,
	    <contact fullname="Jan Komissar"/>,
	    <contact fullname="David Lamparter"/>,
	    <contact fullname="Morten Pedersen"/>,
	    <contact fullname="Pascal Thubert"/>, and
	    <contact fullname="Jeffrey (Zhaohui) Zhang"/>.
      </t>
    </section>
    <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.b">
      <name slugifiedName="name-authors-addresses">Authors' Addresses</name>
      <author fullname="Charles E. Perkins" initials="C." surname="Perkins">
        <organization showOnFrontPage="true">Lupin Lodge</organization>
        <address>
          <phone>+1 408 255 9223</phone>
          <email>charliep@lupinlodge.com</email>
        </address>
      </author>
      <author fullname="Mike McBride" initials="M." surname="McBride">
        <organization abbrev="Futurewei" showOnFrontPage="true">Futurewei Technologies Inc.</organization>
        <address>
          <postal>
            <street>2330 Central Expressway</street>
            <city>Santa Clara</city>
            <code>95055</code>
            <region>CA</region>
            <country>United States of America</country>
          </postal>
          <email>michael.mcbride@futurewei.com</email>
        </address>
      </author>
      <author fullname="Dorothy Stanley" initials="D" surname="Stanley">
        <organization abbrev="HPE" showOnFrontPage="true">Hewlett Packard Enterprise</organization>
        <address>
          <postal>
            <street>6280 America Center Dr.</street>
            <city>San Jose</city>
            <code>95002</code>
            <region>CA</region>
            <country>United States of America</country>
          </postal>
          <phone>+1 630 363 1389</phone>
          <email>dorothy.stanley@hpe.com</email>
        </address>
      </author>
      <author fullname="Warren Kumari" initials="W" surname="Kumari">
        <organization abbrev="Google" showOnFrontPage="true">Google</organization>
        <address>
          <postal>
            <street>1600 Amphitheatre Parkway</street>
            <city>Mountain View</city>
            <code>94043</code>
            <region>CA</region>
            <country>United States of America</country>
          </postal>
          <email>warren@kumari.net</email>
        </address>
      </author>
      <author fullname="Juan Carlos Zúñiga" initials="JC" surname="Zúñiga">
        <organization abbrev="SIGFOX" showOnFrontPage="true">SIGFOX</organization>
        <address>
          <postal>
            <street/>
            <city>Montreal</city>
            <code/>
            <country>Canada</country>
          </postal>
          <email>j.c.zuniga@ieee.org</email>
        </address>
      </author>
    </section>
  </back>
</rfc>
