File: rfc9279.html

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<!DOCTYPE html>
<html lang="en" class="RFC">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 9279: Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Version 2 (MLDv2) Message Extension</title>
<meta content="Mahesh Sivakumar" name="author">
<meta content="Stig Venaas" name="author">
<meta content="Zheng(Sandy) Zhang" name="author">
<meta content="Hitoshi Asaeda" name="author">
<meta content="
       This document specifies a generic mechanism to extend IGMPv3 and Multicast Listener Discovery Version 2
(MLDv2) by using a list of TLVs (Type, Length, and Value).
       
    " name="description">
<meta content="xml2rfc 3.12.10" name="generator">
<meta content="Multicast" name="keyword">
<meta content="9279" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.12.10
    Python 3.6.15
    appdirs 1.4.4
    ConfigArgParse 1.4.1
    google-i18n-address 2.4.0
    html5lib 1.0.1
    intervaltree 3.0.2
    Jinja2 2.11.3
    kitchen 1.2.6
    lxml 4.7.1
    MarkupSafe 2.0.1
    pycairo 1.15.1
    pycountry 19.8.18
    pyflakes 2.1.1
    PyYAML 5.4.1
    requests 2.24.0
    setuptools 40.5.0
    six 1.14.0
    WeasyPrint 52.5
-->
<link href="rfc9279.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

  NOTE: Changes at the bottom of this file overrides some earlier settings.

  Once the style has stabilized and has been adopted as an official RFC style,
  this can be consolidated so that style settings occur only in one place, but
  for now the contents of this file consists first of the initial CSS work as
  provided to the RFC Formatter (xml2rfc) work, followed by itemized and
  commented changes found necssary during the development of the v3
  formatters.

*/

/* fonts */
@import url('https://fonts.googleapis.com/css?family=Noto+Sans'); /* Sans-serif */
@import url('https://fonts.googleapis.com/css?family=Noto+Serif'); /* Serif (print) */
@import url('https://fonts.googleapis.com/css?family=Roboto+Mono'); /* Monospace */

@viewport {
  zoom: 1.0;
  width: extend-to-zoom;
}
@-ms-viewport {
  width: extend-to-zoom;
  zoom: 1.0;
}
/* general and mobile first */
html {
}
body {
  max-width: 90%;
  margin: 1.5em auto;
  color: #222;
  background-color: #fff;
  font-size: 14px;
  font-family: 'Noto Sans', Arial, Helvetica, sans-serif;
  line-height: 1.6;
  scroll-behavior: smooth;
}
.ears {
  display: none;
}

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
  margin: 1em 0 0.5em;
  font-weight: bold;
  line-height: 1.3;
}
#title {
  clear: both;
  border-bottom: 1px solid #ddd;
  margin: 0 0 0.5em 0;
  padding: 1em 0 0.5em;
}
.author {
  padding-bottom: 4px;
}
h1 {
  font-size: 26px;
  margin: 1em 0;
}
h2 {
  font-size: 22px;
  margin-top: -20px;  /* provide offset for in-page anchors */
  padding-top: 33px;
}
h3 {
  font-size: 18px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h4 {
  font-size: 16px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h5, h6 {
  font-size: 14px;
}
#n-copyright-notice {
  border-bottom: 1px solid #ddd;
  padding-bottom: 1em;
  margin-bottom: 1em;
}
/* general structure */
p {
  padding: 0;
  margin: 0 0 1em 0;
  text-align: left;
}
div, span {
  position: relative;
}
div {
  margin: 0;
}
.alignRight.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
  padding: 0;
}
.alignRight {
  margin: 1em 0;
}
.alignRight > *:first-child {
  border: none;
  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
  clear: both;
  display: block;
  border: none;
}
svg {
  display: block;
}
.alignCenter.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignCenter.art-text pre {
  padding: 0;
}
.alignCenter {
  margin: 1em 0;
}
.alignCenter > *:first-child {
  border: none;
  margin: 0 auto;
}

/* lists */
ol, ul {
  padding: 0;
  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
  margin-left: 1em;
}
li {
  margin: 0 0 0.25em 0;
}
.ulCompact li {
  margin: 0;
}
ul.empty, .ulEmpty {
  list-style-type: none;
}
ul.empty li, .ulEmpty li {
  margin-top: 0.5em;
}
ul.ulBare, li.ulBare {
  margin-left: 0em !important;
}
ul.compact, .ulCompact,
ol.compact, .olCompact {
  line-height: 100%;
  margin: 0 0 0 2em;
}

/* definition lists */
dl {
}
dl > dt {
  float: left;
  margin-right: 1em;
}
/* 
dl.nohang > dt {
  float: none;
}
*/
dl > dd {
  margin-bottom: .8em;
  min-height: 1.3em;
}
dl.compact > dd, .dlCompact > dd {
  margin-bottom: 0em;
}
dl > dd > dl {
  margin-top: 0.5em;
  margin-bottom: 0em;
}

/* links */
a {
  text-decoration: none;
}
a[href] {
  color: #22e; /* Arlen: WCAG 2019 */
}
a[href]:hover {
  background-color: #f2f2f2;
}
figcaption a[href],
a[href].selfRef {
  color: #222;
}
/* XXX probably not this:
a.selfRef:hover {
  background-color: transparent;
  cursor: default;
} */

/* Figures */
tt, code, pre, code {
  background-color: #f9f9f9;
  font-family: 'Roboto Mono', monospace;
}
pre {
  border: 1px solid #eee;
  margin: 0;
  padding: 1em;
}
img {
  max-width: 100%;
}
figure {
  margin: 0;
}
figure blockquote {
  margin: 0.8em 0.4em 0.4em;
}
figcaption {
  font-style: italic;
  margin: 0 0 1em 0;
}
@media screen {
  pre {
    overflow-x: auto;
    max-width: 100%;
    max-width: calc(100% - 22px);
  }
}

/* aside, blockquote */
aside, blockquote {
  margin-left: 0;
  padding: 1.2em 2em;
}
blockquote {
  background-color: #f9f9f9;
  color: #111; /* Arlen: WCAG 2019 */
  border: 1px solid #ddd;
  border-radius: 3px;
  margin: 1em 0;
}
cite {
  display: block;
  text-align: right;
  font-style: italic;
}

/* tables */
table {
  width: 100%;
  margin: 0 0 1em;
  border-collapse: collapse;
  border: 1px solid #eee;
}
th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.5em 0.75em;
}
th {
  text-align: left;
  background-color: #e9e9e9;
}
tr:nth-child(2n+1) > td {
  background-color: #f5f5f5;
}
table caption {
  font-style: italic;
  margin: 0;
  padding: 0;
  text-align: left;
}
table p {
  /* XXX to avoid bottom margin on table row signifiers. If paragraphs should
     be allowed within tables more generally, it would be far better to select on a class. */
  margin: 0;
}

/* pilcrow */
a.pilcrow {
  color: #666; /* Arlen: AHDJ 2019 */
  text-decoration: none;
  visibility: hidden;
  user-select: none;
  -ms-user-select: none;
  -o-user-select:none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}
@media screen {
  aside:hover > a.pilcrow,
  p:hover > a.pilcrow,
  blockquote:hover > a.pilcrow,
  div:hover > a.pilcrow,
  li:hover > a.pilcrow,
  pre:hover > a.pilcrow {
    visibility: visible;
  }
  a.pilcrow:hover {
    background-color: transparent;
  }
}

/* misc */
hr {
  border: 0;
  border-top: 1px solid #eee;
}
.bcp14 {
  font-variant: small-caps;
}

.role {
  font-variant: all-small-caps;
}

/* info block */
#identifiers {
  margin: 0;
  font-size: 0.9em;
}
#identifiers dt {
  width: 3em;
  clear: left;
}
#identifiers dd {
  float: left;
  margin-bottom: 0;
}
/* Fix PDF info block run off issue */
@media print {
  #identifiers dd {
    float: none;
  }
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

/* The prepared/rendered info at the very bottom of the page */
.docInfo {
  color: #666; /* Arlen: WCAG 2019 */
  font-size: 0.9em;
  font-style: italic;
  margin-top: 2em;
}
.docInfo .prepared {
  float: left;
}
.docInfo .prepared {
  float: right;
}

/* table of contents */
#toc  {
  padding: 0.75em 0 2em 0;
  margin-bottom: 1em;
}
nav.toc ul {
  margin: 0 0.5em 0 0;
  padding: 0;
  list-style: none;
}
nav.toc li {
  line-height: 1.3em;
  margin: 0.75em 0;
  padding-left: 1.2em;
  text-indent: -1.2em;
}
/* references */
.references dt {
  text-align: right;
  font-weight: bold;
  min-width: 7em;
}
.references dd {
  margin-left: 8em;
  overflow: auto;
}

.refInstance {
  margin-bottom: 1.25em;
}

.references .ascii {
  margin-bottom: 0.25em;
}

/* index */
.index ul {
  margin: 0 0 0 1em;
  padding: 0;
  list-style: none;
}
.index ul ul {
  margin: 0;
}
.index li {
  margin: 0;
  text-indent: -2em;
  padding-left: 2em;
  padding-bottom: 5px;
}
.indexIndex {
  margin: 0.5em 0 1em;
}
.index a {
  font-weight: 700;
}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
  .index ul {
    -moz-column-count: 2;
    -moz-column-gap: 20px;
  }
  .index ul ul {
    -moz-column-count: 1;
    -moz-column-gap: 0;
  }
}

/* authors */
address.vcard {
  font-style: normal;
  margin: 1em 0;
}

address.vcard .nameRole {
  font-weight: 700;
  margin-left: 0;
}
address.vcard .label {
  font-family: "Noto Sans",Arial,Helvetica,sans-serif;
  margin: 0.5em 0;
}
address.vcard .type {
  display: none;
}
.alternative-contact {
  margin: 1.5em 0 1em;
}
hr.addr {
  border-top: 1px dashed;
  margin: 0;
  color: #ddd;
  max-width: calc(100% - 16px);
}

/* temporary notes */
.rfcEditorRemove::before {
  position: absolute;
  top: 0.2em;
  right: 0.2em;
  padding: 0.2em;
  content: "The RFC Editor will remove this note";
  color: #9e2a00; /* Arlen: WCAG 2019 */
  background-color: #ffd; /* Arlen: WCAG 2019 */
}
.rfcEditorRemove {
  position: relative;
  padding-top: 1.8em;
  background-color: #ffd; /* Arlen: WCAG 2019 */
  border-radius: 3px;
}
.cref {
  background-color: #ffd; /* Arlen: WCAG 2019 */
  padding: 2px 4px;
}
.crefSource {
  font-style: italic;
}
/* alternative layout for smaller screens */
@media screen and (max-width: 1023px) {
  body {
    padding-top: 2em;
  }
  #title {
    padding: 1em 0;
  }
  h1 {
    font-size: 24px;
  }
  h2 {
    font-size: 20px;
    margin-top: -18px;  /* provide offset for in-page anchors */
    padding-top: 38px;
  }
  #identifiers dd {
    max-width: 60%;
  }
  #toc {
    position: fixed;
    z-index: 2;
    top: 0;
    right: 0;
    padding: 0;
    margin: 0;
    background-color: inherit;
    border-bottom: 1px solid #ccc;
  }
  #toc h2 {
    margin: -1px 0 0 0;
    padding: 4px 0 4px 6px;
    padding-right: 1em;
    min-width: 190px;
    font-size: 1.1em;
    text-align: right;
    background-color: #444;
    color: white;
    cursor: pointer;
  }
  #toc h2::before { /* css hamburger */
    float: right;
    position: relative;
    width: 1em;
    height: 1px;
    left: -164px;
    margin: 6px 0 0 0;
    background: white none repeat scroll 0 0;
    box-shadow: 0 4px 0 0 white, 0 8px 0 0 white;
    content: "";
  }
  #toc nav {
    display: none;
    padding: 0.5em 1em 1em;
    overflow: auto;
    height: calc(100vh - 48px);
    border-left: 1px solid #ddd;
  }
}

/* alternative layout for wide screens */
@media screen and (min-width: 1024px) {
  body {
    max-width: 724px;
    margin: 42px auto;
    padding-left: 1.5em;
    padding-right: 29em;
  }
  #toc {
    position: fixed;
    top: 42px;
    right: 42px;
    width: 25%;
    margin: 0;
    padding: 0 1em;
    z-index: 1;
  }
  #toc h2 {
    border-top: none;
    border-bottom: 1px solid #ddd;
    font-size: 1em;
    font-weight: normal;
    margin: 0;
    padding: 0.25em 1em 1em 0;
  }
  #toc nav {
    display: block;
    height: calc(90vh - 84px);
    bottom: 0;
    padding: 0.5em 0 0;
    overflow: auto;
  }
  img { /* future proofing */
    max-width: 100%;
    height: auto;
  }
}

/* pagination */
@media print {
  body {

    width: 100%;
  }
  p {
    orphans: 3;
    widows: 3;
  }
  #n-copyright-notice {
    border-bottom: none;
  }
  #toc, #n-introduction {
    page-break-before: always;
  }
  #toc {
    border-top: none;
    padding-top: 0;
  }
  figure, pre {
    page-break-inside: avoid;
  }
  figure {
    overflow: scroll;
  }
  pre.breakable {
    break-inside: auto;
  }
  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }
  h2+*, h3+*, h4+*, h5+*, h6+* {
    page-break-before: avoid;
  }
  pre {
    white-space: pre-wrap;
    word-wrap: break-word;
    font-size: 10pt;
  }
  table {
    border: 1px solid #ddd;
  }
  td {
    border-top: 1px solid #ddd;
  }
}

/* This is commented out here, as the string-set: doesn't
   pass W3C validation currently */
/*
.ears thead .left {
  string-set: ears-top-left content();
}

.ears thead .center {
  string-set: ears-top-center content();
}

.ears thead .right {
  string-set: ears-top-right content();
}

.ears tfoot .left {
  string-set: ears-bottom-left content();
}

.ears tfoot .center {
  string-set: ears-bottom-center content();
}

.ears tfoot .right {
  string-set: ears-bottom-right content();
}
*/

@page :first {
  padding-top: 0;
  @top-left {
    content: normal;
    border: none;
  }
  @top-center {
    content: normal;
    border: none;
  }
  @top-right {
    content: normal;
    border: none;
  }
}

@page {
  size: A4;
  margin-bottom: 45mm;
  padding-top: 20px;
  /* The follwing is commented out here, but set appropriately by in code, as
     the content depends on the document */
  /*
  @top-left {
    content: 'Internet-Draft';
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-left {
    content: string(ears-top-left);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-center {
    content: string(ears-top-center);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-right {
    content: string(ears-top-right);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @bottom-left {
    content: string(ears-bottom-left);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-center {
    content: string(ears-bottom-center);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-right {
      content: '[Page ' counter(page) ']';
      vertical-align: top;
      border-top: solid 1px #ccc;
  }
  */

}

/* Changes introduced to fix issues found during implementation */
/* Make sure links are clickable even if overlapped by following H* */
a {
  z-index: 2;
}
/* Separate body from document info even without intervening H1 */
section {
  clear: both;
}


/* Top align author divs, to avoid names without organization dropping level with org names */
.author {
  vertical-align: top;
}

/* Leave room in document info to show Internet-Draft on one line */
#identifiers dt {
  width: 8em;
}

/* Don't waste quite as much whitespace between label and value in doc info */
#identifiers dd {
  margin-left: 1em;
}

/* Give floating toc a background color (needed when it's a div inside section */
#toc {
  background-color: white;
}

/* Make the collapsed ToC header render white on gray also when it's a link */
@media screen and (max-width: 1023px) {
  #toc h2 a,
  #toc h2 a:link,
  #toc h2 a:focus,
  #toc h2 a:hover,
  #toc a.toplink,
  #toc a.toplink:hover {
    color: white;
    background-color: #444;
    text-decoration: none;
  }
}

/* Give the bottom of the ToC some whitespace */
@media screen and (min-width: 1024px) {
  #toc {
    padding: 0 0 1em 1em;
  }
}

/* Style section numbers with more space between number and title */
.section-number {
  padding-right: 0.5em;
}

/* prevent monospace from becoming overly large */
tt, code, pre, code {
  font-size: 95%;
}

/* Fix the height/width aspect for ascii art*/
pre.sourcecode,
.art-text pre {
  line-height: 1.12;
}


/* Add styling for a link in the ToC that points to the top of the document */
a.toplink {
  float: right;
  margin-right: 0.5em;
}

/* Fix the dl styling to match the RFC 7992 attributes */
dl > dt,
dl.dlParallel > dt {
  float: left;
  margin-right: 1em;
}
dl.dlNewline > dt {
  float: none;
}

/* Provide styling for table cell text alignment */
table td.text-left,
table th.text-left {
  text-align: left;
}
table td.text-center,
table th.text-center {
  text-align: center;
}
table td.text-right,
table th.text-right {
  text-align: right;
}

/* Make the alternative author contact informatio look less like just another
   author, and group it closer with the primary author contact information */
.alternative-contact {
  margin: 0.5em 0 0.25em 0;
}
address .non-ascii {
  margin: 0 0 0 2em;
}

/* With it being possible to set tables with alignment
  left, center, and right, { width: 100%; } does not make sense */
table {
  width: auto;
}

/* Avoid reference text that sits in a block with very wide left margin,
   because of a long floating dt label.*/
.references dd {
  overflow: visible;
}

/* Control caption placement */
caption {
  caption-side: bottom;
}

/* Limit the width of the author address vcard, so names in right-to-left
   script don't end up on the other side of the page. */

address.vcard {
  max-width: 30em;
  margin-right: auto;
}

/* For address alignment dependent on LTR or RTL scripts */
address div.left {
  text-align: left;
}
address div.right {
  text-align: right;
}

/* Provide table alignment support.  We can't use the alignX classes above
   since they do unwanted things with caption and other styling. */
table.right {
 margin-left: auto;
 margin-right: 0;
}
table.center {
 margin-left: auto;
 margin-right: auto;
}
table.left {
 margin-left: 0;
 margin-right: auto;
}

/* Give the table caption label the same styling as the figcaption */
caption a[href] {
  color: #222;
}

@media print {
  .toplink {
    display: none;
  }

  /* avoid overwriting the top border line with the ToC header */
  #toc {
    padding-top: 1px;
  }

  /* Avoid page breaks inside dl and author address entries */
  .vcard {
    page-break-inside: avoid;
  }

}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
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<table class="ears">
<thead><tr>
<td class="left">RFC 9279</td>
<td class="center">IGMPv3/MLDv2 Message Extension</td>
<td class="right">August 2022</td>
</tr></thead>
<tfoot><tr>
<td class="left">Sivakumar, et al.</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc9279" class="eref">9279</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2022-08" class="published">August 2022</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Authors:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">M. Sivakumar</div>
<div class="org">Juniper Networks</div>
</div>
<div class="author">
      <div class="author-name">S. Venaas</div>
<div class="org">Cisco Systems, Inc.</div>
</div>
<div class="author">
      <div class="author-name">Z. Zhang</div>
<div class="org">ZTE Corporation</div>
</div>
<div class="author">
      <div class="author-name">H. Asaeda</div>
<div class="org">NICT</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9279</h1>
<h1 id="title">Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Version 2 (MLDv2) Message Extension</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document specifies a generic mechanism to extend IGMPv3 and Multicast Listener Discovery Version 2
(MLDv2) by using a list of TLVs (Type, Length, and Value).<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="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
            <span><a href="https://www.rfc-editor.org/info/rfc9279">https://www.rfc-editor.org/info/rfc9279</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2022 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) 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 Revised BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Revised BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="xref">2</a>.  <a href="#name-conventions-used-in-this-do" class="xref">Conventions Used in This Document</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-extension-format" class="xref">Extension Format</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1" class="keepWithNext"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-multicast-listener-query-ex" class="xref">Multicast Listener Query Extension</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="xref">3.2</a>.  <a href="#name-version-2-multicast-listene" class="xref">Version 2 Multicast Listener Report Extension</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.3">
                <p id="section-toc.1-1.3.2.3.1"><a href="#section-3.3" class="xref">3.3</a>.  <a href="#name-igmp-membership-query-exten" class="xref">IGMP Membership Query Extension</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.4">
                <p id="section-toc.1-1.3.2.4.1"><a href="#section-3.4" class="xref">3.4</a>.  <a href="#name-igmp-version-3-membership-r" class="xref">IGMP Version 3 Membership Report Extension</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-no-op-tlv" class="xref">No-op TLV</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-processing-the-extension" class="xref">Processing the Extension</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-applicability-and-backwards" class="xref">Applicability and Backwards Compatibility</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-8" class="xref">8</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-9" class="xref">9</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9.2.1">
                <p id="section-toc.1-1.9.2.1.1"><a href="#section-9.1" class="xref">9.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9.2.2">
                <p id="section-toc.1-1.9.2.2.1"><a href="#section-9.2" class="xref">9.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#appendix-A" class="xref"></a><a href="#name-acknowledgements" class="xref">Acknowledgements</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#appendix-B" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">This document defines a generic method to extend IGMPv3 <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and MLDv2 <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span> messages to accommodate information other than what
      is contained in the current message formats. This is done by allowing a
      list of TLVs to be used in the Additional Data
      section of IGMPv3 and MLDv2 messages.  This document defines a registry
      for such TLVs.  Other documents will define their specific types, and
      their values and semantics. The extension would only be used when
      at least one TLV is to be added to the message. This extension also
      applies to the lightweight versions of IGMPv3 and MLDv2 as defined in
      <span>[<a href="#RFC5790" class="xref">RFC5790</a>]</span>.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">
      When this extension mechanism is used, it replaces the Additional Data
      section defined in IGMPv3/MLDv2 with TLVs.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">
      Additional Data is defined for Query messages in IGMPv3 (<span><a href="https://www.rfc-editor.org/rfc/rfc3376#section-4.1.10" class="relref">Section 4.1.10</a> of [<a href="#RFC3376" class="xref">RFC3376</a>]</span>)
      and MLDv2 (<span><a href="https://www.rfc-editor.org/rfc/rfc3810#section-5.1.12" class="relref">Section 5.1.12</a> of [<a href="#RFC3810" class="xref">RFC3810</a>]</span>), and for Report
      messages in IGMPv3 (<span><a href="https://www.rfc-editor.org/rfc/rfc3376#section-4.2.11" class="relref">Section 4.2.11</a> of [<a href="#RFC3376" class="xref">RFC3376</a>]</span>) and  MLDv2 (<span><a href="https://www.rfc-editor.org/rfc/rfc3810#section-5.2.11" class="relref">Section 5.2.11</a> of [<a href="#RFC3810" class="xref">RFC3810</a>]</span>).<a href="#section-1-3" class="pilcrow">¶</a></p>
</section>
<section id="section-2">
      <h2 id="name-conventions-used-in-this-do">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-conventions-used-in-this-do" class="section-name selfRef">Conventions Used in This Document</a>
      </h2>
<p id="section-2-1">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> 
    when, and only when, they appear in all capitals, as shown here.<a href="#section-2-1" class="pilcrow">¶</a></p>
</section>
<section id="section-3">
      <h2 id="name-extension-format">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-extension-format" class="section-name selfRef">Extension Format</a>
      </h2>
<p id="section-3-1">
      For each of the IGMPv3 and MLDv2 headers, a previously reserved bit
      is used to indicate the presence of this extension.
      When this extension is used,
      the Additional Data of IGMPv3 and MLDv2 messages is formatted as
      follows. Note that this format contains a variable number of TLVs.
      It <span class="bcp14">MUST</span> contain at least one TLV.<a href="#section-3-1" class="pilcrow">¶</a></p>
<span id="name-extension-format-2"></span><figure id="figure-1">
        <div class="alignLeft art-text artwork" id="section-3-2.1">
<pre>
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Extension Type 1       |       Extension Length 1      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Extension Value 1                       |
.                               .                               .
.                               .                               .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Extension Type 2       |       Extension Length 2      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Extension Value 2                       |
.                               .                               .
.                               .                               .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Extension Type n       |       Extension Length n      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Extension Value n                       |
.                               .                               .
.                               .                               .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a>:
<a href="#name-extension-format-2" class="selfRef">Extension Format</a>
        </figcaption></figure>
<span class="break"></span><dl class="dlParallel" id="section-3-3">
        <dt id="section-3-3.1">Extension Type:</dt>
        <dd style="margin-left: 1.5em" id="section-3-3.2">2 octets. This identifies a particular Extension Type as defined in the "IGMP/MLD Extension Types" registry. If this is not the first TLV, it will follow immediately after the end of the previous one.  There is no alignment or padding.<a href="#section-3-3.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-3-3.3">Extension Length:</dt>
        <dd style="margin-left: 1.5em" id="section-3-3.4">2 octets. This specifies the length in octets of the following Extension Value field. The length may be zero if no value is needed.<a href="#section-3-3.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-3-3.5">Extension Value:</dt>
        <dd style="margin-left: 1.5em" id="section-3-3.6">This field contains the value. The specification defining the Extension Type describes the length and contents of this field.<a href="#section-3-3.6" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-3-4">
      IGMPv3 and MLDv2 messages are defined so they can fit within the
      network MTU in order to avoid fragmentation. An IGMPv3/MLDv2 Report
      message contains a number of records. The records are called
      Group Records for IGMPv3 and Address Records for MLDv2.
      When this extension
      mechanism is used, the number of records in each Report message
      <span class="bcp14">SHOULD</span> be kept small enough so that the entire message, including any
      extension TLVs, can fit within the network MTU.<a href="#section-3-4" class="pilcrow">¶</a></p>
<section id="section-3.1">
        <h3 id="name-multicast-listener-query-ex">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-multicast-listener-query-ex" class="section-name selfRef">Multicast Listener Query Extension</a>
        </h3>
<p id="section-3.1-1">The MLDv2 Query message format <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span> with extension
      is shown below. The E-bit <span class="bcp14">MUST</span> be set to 1 to indicate that the extension
      is present. Otherwise, it <span class="bcp14">MUST</span> be 0.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<span id="name-mld-query-extension"></span><figure id="figure-2">
          <div class="alignLeft art-text artwork" id="section-3.1-2.1">
<pre>
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Type = 130   |      Code     |           Checksum            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Maximum Response Code      |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    *                                                               *
    |                                                               |
    *                       Multicast Address                       *
    |                                                               |
    *                                                               *
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |E| Resv|S| QRV |     QQIC      |     Number of Sources (N)     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    *                                                               *
    |                                                               |
    *                       Source Address [1]                      *
    |                                                               |
    *                                                               *
    |                                                               |
    +-                                                             -+
    |                                                               |
    *                                                               *
    |                                                               |
    *                       Source Address [2]                      *
    |                                                               |
    *                                                               *
    |                                                               |
    +-                              .                              -+
    .                               .                               .
    .                               .                               .
    +-                                                             -+
    |                                                               |
    *                                                               *
    |                                                               |
    *                       Source Address [N]                      *
    |                                                               |
    *                                                               *
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Extension                          |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a>:
<a href="#name-mld-query-extension" class="selfRef">MLD Query Extension</a>
          </figcaption></figure>
</section>
<section id="section-3.2">
        <h3 id="name-version-2-multicast-listene">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-version-2-multicast-listene" class="section-name selfRef">Version 2 Multicast Listener Report Extension</a>
        </h3>
<p id="section-3.2-1">The MLDv2 Report message format <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span> with
      extension is shown below. The E-bit <span class="bcp14">MUST</span> be set to 1 to indicate that
      the extension is present. Otherwise, it <span class="bcp14">MUST</span> be 0.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<span id="name-mld-report-extension"></span><figure id="figure-3">
          <div class="alignLeft art-text artwork" id="section-3.2-2.1">
<pre>
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Type = 143   |    Reserved   |           Checksum            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |E|         Reserved            |Nr of Mcast Address Records (M)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                  Multicast Address Record [1]                 .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                  Multicast Address Record [2]                 .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               .                               |
    .                               .                               .
    |                               .                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                  Multicast Address Record [M]                 .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Extension                          |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-3" class="selfRef">Figure 3</a>:
<a href="#name-mld-report-extension" class="selfRef">MLD Report Extension</a>
          </figcaption></figure>
</section>
<section id="section-3.3">
        <h3 id="name-igmp-membership-query-exten">
<a href="#section-3.3" class="section-number selfRef">3.3. </a><a href="#name-igmp-membership-query-exten" class="section-name selfRef">IGMP Membership Query Extension</a>
        </h3>
<p id="section-3.3-1">The IGMPv3 Query message format <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> with the
      extension is shown below. The E-bit <span class="bcp14">MUST</span> be set to 1 to indicate that
      the extension is present. Otherwise, it <span class="bcp14">MUST</span> be 0.<a href="#section-3.3-1" class="pilcrow">¶</a></p>
<span id="name-igmp-query-extension"></span><figure id="figure-4">
          <div class="alignLeft art-text artwork" id="section-3.3-2.1">
<pre>
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Type = 0x11  | Max Resp Code |           Checksum            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Group Address                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |E| Resv|S| QRV |     QQIC      |     Number of Sources (N)     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Source Address [1]                      |
    +-                                                             -+
    |                       Source Address [2]                      |
    +-                              .                              -+
    .                               .                               .
    .                               .                               .
    +-                                                             -+
    |                       Source Address [N]                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Extension                          |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-4" class="selfRef">Figure 4</a>:
<a href="#name-igmp-query-extension" class="selfRef">IGMP Query Extension</a>
          </figcaption></figure>
</section>
<section id="section-3.4">
        <h3 id="name-igmp-version-3-membership-r">
<a href="#section-3.4" class="section-number selfRef">3.4. </a><a href="#name-igmp-version-3-membership-r" class="section-name selfRef">IGMP Version 3 Membership Report Extension</a>
        </h3>
<p id="section-3.4-1">The IGMPv3 Report message format <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> with the
      extension is shown below. The E-bit <span class="bcp14">MUST</span> be set to 1 to indicate that
      the extension is present. Otherwise, it <span class="bcp14">MUST</span> be 0.<a href="#section-3.4-1" class="pilcrow">¶</a></p>
<span id="name-igmp-report-extension"></span><figure id="figure-5">
          <div class="alignLeft art-text artwork" id="section-3.4-2.1">
<pre>
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Type = 0x22  |    Reserved   |           Checksum            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |E|         Reserved            |  Number of Group Records (M)  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                        Group Record [1]                       .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                        Group Record [2]                       .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               .                               |
    .                               .                               .
    |                               .                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                        Group Record [M]                       .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            Extension                          |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-5" class="selfRef">Figure 5</a>:
<a href="#name-igmp-report-extension" class="selfRef">IGMP Report Extension</a>
          </figcaption></figure>
</section>
</section>
<section id="section-4">
      <h2 id="name-no-op-tlv">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-no-op-tlv" class="section-name selfRef">No-op TLV</a>
      </h2>
<p id="section-4-1">
      The No-op TLV is a No-Operation TLV that <span class="bcp14">MUST</span> be ignored during
      processing. This TLV may be used to verify that the extension mechanism has been implemented correctly. Note that there is
      no alignment requirement, so there is no need to use this Extension Type
      to provide alignment.<a href="#section-4-1" class="pilcrow">¶</a></p>
<span id="name-no-op-tlv-format"></span><figure id="figure-6">
        <div class="alignLeft art-text artwork" id="section-4-2.1">
<pre>
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        No-op Type = 0         |          No-op Length         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                             Value                             |
    .                               .                               .
    .                               .                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
</div>
<figcaption><a href="#figure-6" class="selfRef">Figure 6</a>:
<a href="#name-no-op-tlv-format" class="selfRef">No-op TLV Format</a>
        </figcaption></figure>
<span class="break"></span><dl class="dlParallel" id="section-4-3">
        <dt id="section-4-3.1">No-op Type:</dt>
        <dd style="margin-left: 1.5em" id="section-4-3.2">2 octets. The type of the No-op TLV extension is 0.<a href="#section-4-3.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-4-3.3">Extension Length:</dt>
        <dd style="margin-left: 1.5em" id="section-4-3.4">2 octets. This specifies the length in octets of the following Value field. The length may be zero if no value is needed.<a href="#section-4-3.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-4-3.5"> Value:</dt>
        <dd style="margin-left: 1.5em" id="section-4-3.6">This field contains the value. As this Extension Type is always ignored, the value can be arbitrary data. The number of octets used <span class="bcp14">MUST</span> match the specified length.<a href="#section-4-3.6" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
</section>
<section id="section-5">
      <h2 id="name-processing-the-extension">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-processing-the-extension" class="section-name selfRef">Processing the Extension</a>
      </h2>
<p id="section-5-1">
      The procedure specified in this document only applies when the E-bit
      is set.<a href="#section-5-1" class="pilcrow">¶</a></p>
<p id="section-5-2">
      If the validation of the TLVs fails, the entire Additional Data field
      <span class="bcp14">MUST</span> be ignored as specified in IGMPv3 <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and MLDv2 <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span>.
      The following checks must pass for the validation of the TLVs not to
      fail:<a href="#section-5-2" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-5-3.1">
        At least one TLV <span class="bcp14">MUST</span> be present.<a href="#section-5-3.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-5-3.2">
 There <span class="bcp14">MUST NOT</span> be any data in the IP payload after the last TLV.
 To check this, the parser needs to walk through each of the TLVs until
 there are less than four octets left in the IP payload.  If there are
 any octets left, validation fails.<a href="#section-5-3.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-5-3.3">
 The total length of the Extension <span class="bcp14">MUST NOT</span> exceed the remainder of
 the IP payload length.  For this validation, only the
 content of the Extension Length fields is examined.<a href="#section-5-3.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-5-4">
      Future documents defining a new Extension Type <span class="bcp14">MUST</span> specify any
      additional processing and validation.  These rules, if any, will
      be examined only after the general validation succeeds.<a href="#section-5-4" class="pilcrow">¶</a></p>
<p id="section-5-5">
      TLVs with unsupported Extension Types <span class="bcp14">MUST</span> be ignored.<a href="#section-5-5" class="pilcrow">¶</a></p>
</section>
<section id="section-6">
      <h2 id="name-applicability-and-backwards">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-applicability-and-backwards" class="section-name selfRef">Applicability and Backwards Compatibility</a>
      </h2>
<p id="section-6-1">IGMP and MLD implementations, particularly implementations on hosts,
    rarely change. The adoption process of this extension mechanism is
    expected to be slow. As new extension TLVs are defined, it may
    take a long time for them to be supported. Due to this, defining
    new extension TLVs should not be taken lightly, and it is crucial
    to consider backwards compatibility.<a href="#section-6-1" class="pilcrow">¶</a></p>
<p id="section-6-2">Implementations that do not support this extension mechanism will
    ignore it, as specified in <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span>. As mentioned
    in the previous section, unsupported extension TLVs are ignored.<a href="#section-6-2" class="pilcrow">¶</a></p>
<p id="section-6-3">It is possible that a new extension TLV will only apply to queries or
    only to reports, or that there may be other specific conditions for when it is to
    be used. A document defining a new Extension Type <span class="bcp14">MUST</span> specify the
    conditions under which the new Extension Type should be used, including which
    message types.
    It <span class="bcp14">MUST</span> also be specified what the behavior should be if a message is not
    used in the defined manner, e.g., if it is present in a Query message,
    when it was only expected to be used in reports.<a href="#section-6-3" class="pilcrow">¶</a></p>
<p id="section-6-4">When defining new Extension Types, the effect of partial support for the new TLV, by either the hosts or routers, on the same link should be carefully considered. Further, whether there are any
    dependencies or restrictions on combinations between the new Extension
    Types and any preexisting Extension Types must be considered.<a href="#section-6-4" class="pilcrow">¶</a></p>
<p id="section-6-5">This document defines an extension mechanism only for IGMPv3 and MLDv2.
    Hence, this mechanism does not apply if hosts or routers send older version
    messages.<a href="#section-6-5" class="pilcrow">¶</a></p>
</section>
<section id="section-7">
      <h2 id="name-security-considerations">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-7-1">The Security Considerations of <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span> also apply here.<a href="#section-7-1" class="pilcrow">¶</a></p>
<p id="section-7-2">This document extends the IGMP and MLD message formats, allowing for a
    variable number of TLVs. Implementations must take care not to exceed the packet boundary when parsing
    the TLVs, because an attacker could
    intentionally specify a TLV with a length exceeding the boundary.<a href="#section-7-2" class="pilcrow">¶</a></p>
<p id="section-7-3">An implementation could add a large number of minimal TLVs in a
    message to increase the cost of processing the message. This would magnify
    a denial-of-service attack.<a href="#section-7-3" class="pilcrow">¶</a></p>
</section>
<div id="IANA">
<section id="section-8">
      <h2 id="name-iana-considerations">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-8-1">IANA has created a new registry called "IGMP/MLD Extension Types"
    in the "Internet Group Management Protocol (IGMP) Type Numbers" section and lists this document as the reference.  
    The registration procedure is "IETF Review" <span>[<a href="#RFC8126" class="xref">RFC8126</a>]</span>.
    The registry is common for IGMP and MLD.<a href="#section-8-1" class="pilcrow">¶</a></p>
<p id="section-8-2">
    Two Extension Types (65534 and 65535) are provided for "Experimental Use"
    <span>[<a href="#RFC8126" class="xref">RFC8126</a>]</span>. Any experiments should be confined to closed
    environments where it is unlikely that they may conflict with other
    experiments; see <span>[<a href="#RFC3692" class="xref">RFC3692</a>]</span>.<a href="#section-8-2" class="pilcrow">¶</a></p>
<p id="section-8-3">
    IANA has initially populated the registry as shown in <a href="#extension_type_table" class="xref">Table 1</a><a href="#section-8-3" class="pilcrow">¶</a></p>
<span id="name-igmp-mld-extension-types"></span><div id="extension_type_table">
<table class="center" id="table-1">
        <caption>
<a href="#table-1" class="selfRef">Table 1</a>:
<a href="#name-igmp-mld-extension-types" class="selfRef">IGMP/MLD Extension Types</a>
        </caption>
<thead>
          <tr>
            <th class="text-left" rowspan="1" colspan="1">Extension Type</th>
            <th class="text-left" rowspan="1" colspan="1">Length</th>
            <th class="text-left" rowspan="1" colspan="1">Name</th>
            <th class="text-left" rowspan="1" colspan="1">Reference</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">0</td>
            <td class="text-left" rowspan="1" colspan="1">variable</td>
            <td class="text-left" rowspan="1" colspan="1">No-op</td>
            <td class="text-left" rowspan="1" colspan="1">RFC 9279</td>
          </tr>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">1-65533</td>
            <td class="text-left" rowspan="1" colspan="1"></td>
            <td class="text-left" rowspan="1" colspan="1">Unassigned</td>
            <td class="text-left" rowspan="1" colspan="1"></td>
          </tr>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">65534-65535</td>
            <td class="text-left" rowspan="1" colspan="1">variable</td>
            <td class="text-left" rowspan="1" colspan="1">Reserved for Experimental Use</td>
            <td class="text-left" rowspan="1" colspan="1"></td>
          </tr>
        </tbody>
      </table>
</div>
</section>
</div>
<section id="section-9">
      <h2 id="name-references">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-9.1">
        <h3 id="name-normative-references">
<a href="#section-9.1" class="section-number selfRef">9.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3376">[RFC3376]</dt>
        <dd>
<span class="refAuthor">Cain, B.</span>, <span class="refAuthor">Deering, S.</span>, <span class="refAuthor">Kouvelas, I.</span>, <span class="refAuthor">Fenner, B.</span>, and <span class="refAuthor">A. Thyagarajan</span>, <span class="refTitle">"Internet Group Management Protocol, Version 3"</span>, <span class="seriesInfo">RFC 3376</span>, <span class="seriesInfo">DOI 10.17487/RFC3376</span>, <time datetime="2002-10" class="refDate">October 2002</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3376">https://www.rfc-editor.org/info/rfc3376</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3810">[RFC3810]</dt>
        <dd>
<span class="refAuthor">Vida, R., Ed.</span> and <span class="refAuthor">L. Costa, Ed.</span>, <span class="refTitle">"Multicast Listener Discovery Version 2 (MLDv2) for IPv6"</span>, <span class="seriesInfo">RFC 3810</span>, <span class="seriesInfo">DOI 10.17487/RFC3810</span>, <time datetime="2004-06" class="refDate">June 2004</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3810">https://www.rfc-editor.org/info/rfc3810</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8126">[RFC8126]</dt>
        <dd>
<span class="refAuthor">Cotton, M.</span>, <span class="refAuthor">Leiba, B.</span>, and <span class="refAuthor">T. Narten</span>, <span class="refTitle">"Guidelines for Writing an IANA Considerations Section in RFCs"</span>, <span class="seriesInfo">BCP 26</span>, <span class="seriesInfo">RFC 8126</span>, <span class="seriesInfo">DOI 10.17487/RFC8126</span>, <time datetime="2017-06" class="refDate">June 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8126">https://www.rfc-editor.org/info/rfc8126</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8174">[RFC8174]</dt>
      <dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-9.2">
        <h3 id="name-informative-references">
<a href="#section-9.2" class="section-number selfRef">9.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC3692">[RFC3692]</dt>
        <dd>
<span class="refAuthor">Narten, T.</span>, <span class="refTitle">"Assigning Experimental and Testing Numbers Considered Useful"</span>, <span class="seriesInfo">BCP 82</span>, <span class="seriesInfo">RFC 3692</span>, <span class="seriesInfo">DOI 10.17487/RFC3692</span>, <time datetime="2004-01" class="refDate">January 2004</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3692">https://www.rfc-editor.org/info/rfc3692</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5790">[RFC5790]</dt>
      <dd>
<span class="refAuthor">Liu, H.</span>, <span class="refAuthor">Cao, W.</span>, and <span class="refAuthor">H. Asaeda</span>, <span class="refTitle">"Lightweight Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Version 2 (MLDv2) Protocols"</span>, <span class="seriesInfo">RFC 5790</span>, <span class="seriesInfo">DOI 10.17487/RFC5790</span>, <time datetime="2010-02" class="refDate">February 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5790">https://www.rfc-editor.org/info/rfc5790</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="ack">
<section id="appendix-A">
      <h2 id="name-acknowledgements">
<a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a>
      </h2>
<p id="appendix-A-1">The authors thank <span class="contact-name">Ron Bonica</span>, <span class="contact-name">Ian Duncan</span>, <span class="contact-name">Wesley Eddy</span>, <span class="contact-name">Leonard Giuliano</span>, <span class="contact-name">Jake Holland</span>, <span class="contact-name">Tommy Pauly</span>, <span class="contact-name">Pete Resnick</span>, <span class="contact-name">Alvaro Retana</span>, and <span class="contact-name">Zhaohui Zhang</span>   
for reviewing the document and providing valuable feedback.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authors-addresses">
<section id="appendix-B">
      <h2 id="name-authors-addresses">
<a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Mahesh Sivakumar</span></div>
<div dir="auto" class="left"><span class="org">Juniper Networks</span></div>
<div dir="auto" class="left"><span class="street-address">64 Butler St</span></div>
<div dir="auto" class="left">
<span class="locality">Milpitas</span>, <span class="region">CA</span> <span class="postal-code">95035</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:sivakumar.mahesh@gmail.com" class="email">sivakumar.mahesh@gmail.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Stig Venaas</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems, Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">Tasman Drive</span></div>
<div dir="auto" class="left">
<span class="locality">San Jose</span>, <span class="region">CA</span> <span class="postal-code">95134</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:stig@cisco.com" class="email">stig@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Zheng(Sandy) Zhang</span></div>
<div dir="auto" class="left"><span class="org">ZTE Corporation</span></div>
<div dir="auto" class="left"><span class="street-address">No. 50 Software Ave, Yuhuatai District</span></div>
<div dir="auto" class="left"><span class="locality">Nanjing</span></div>
<div dir="auto" class="left"><span class="postal-code">210000</span></div>
<div dir="auto" class="left"><span class="country-name">China</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:zhang.zheng@zte.com.cn" class="email">zhang.zheng@zte.com.cn</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Hitoshi Asaeda</span></div>
<div dir="auto" class="left"><span class="org">National Institute of Information and Communications Technology</span></div>
<div dir="auto" class="left">
<span class="street-address">4-2-1 Nukui-Kitamachi, Koganei</span>, <span class="region">Tokyo</span>
</div>
<div dir="auto" class="left"><span class="postal-code">184-8795</span></div>
<div dir="auto" class="left"><span class="country-name">Japan</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:asaeda@nict.go.jp" class="email">asaeda@nict.go.jp</a>
</div>
</address>
</section>
</div>
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