File: rfc8815.html

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<!DOCTYPE html>
<html lang="en" class="RFC BCP">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 8815: Deprecating Any-Source Multicast (ASM) for Interdomain Multicast</title>
<meta content="Mikael Abrahamsson" name="author">
<meta content="Tim Chown" name="author">
<meta content="Lenny Giuliano" name="author">
<meta content="Toerless Eckert" name="author">
<meta content="
       
 This document recommends deprecation of the use of
 Any-Source Multicast (ASM) for interdomain multicast. 
        It recommends the use of Source-Specific Multicast (SSM) for 
 interdomain multicast applications and recommends that hosts and routers
 in these deployments fully support SSM.  The recommendations in this document do not preclude the continued use of 
ASM within a single organization or domain and are especially easy to 
adopt in existing deployments of intradomain ASM using PIM Sparse Mode 
(PIM-SM).
       
    " name="description">
<meta content="xml2rfc 2.47.0" name="generator">
<meta content="8815" name="rfc.number">
<link href="rfc8815.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;
  /* this isn't optimal, but it's an existence proof.  PrinceXML doesn't
     support flexbox yet.
  */
  display: table;
  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.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;
}
#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;
  }
  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;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
}
div#internal-metadata {
  padding: 0.5em;                       /* to match the external-metadata padding */
}
/* Styling for title RFC Number */
h1#rfcnum {
  clear: both;
  margin: 0 0 -1em;
  padding: 1em 0 0 0;
}
/* Make .olPercent look the same as <ol><li> */
dl.olPercent > dd {
  margin-bottom: 0.25em;
  min-height: initial;
}
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<link href="https://dx.doi.org/10.17487/rfc8815" rel="alternate">
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<table class="ears">
<thead><tr>
<td class="left">RFC 8815</td>
<td class="center">Deprecating Interdomain ASM</td>
<td class="right">August 2020</td>
</tr></thead>
<tfoot><tr>
<td class="left">Abrahamsson, et al.</td>
<td class="center">Best Current Practice</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/rfc8815" class="eref">8815</a></dd>
<dt class="label-bcp">BCP:</dt>
<dd class="bcp">229</dd>
<dt class="label-category">Category:</dt>
<dd class="category">Best Current Practice</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2020-08" class="published">August 2020</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. Abrahamsson</div>
</div>
<div class="author">
      <div class="author-name">T. Chown</div>
<div class="org">Jisc</div>
</div>
<div class="author">
      <div class="author-name">L. Giuliano</div>
<div class="org">Juniper Networks, Inc.</div>
</div>
<div class="author">
      <div class="author-name">T. Eckert</div>
<div class="org">Futurewei Technologies Inc.</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8815</h1>
<h1 id="title">Deprecating Any-Source Multicast (ASM) for Interdomain Multicast</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">
 This document recommends deprecation of the use of
 Any-Source Multicast (ASM) for interdomain multicast. 
        It recommends the use of Source-Specific Multicast (SSM) for 
 interdomain multicast applications and recommends that hosts and routers
 in these deployments fully support SSM.  The recommendations in this document do not preclude the continued use of 
ASM within a single organization or domain and are especially easy to 
adopt in existing deployments of intradomain ASM using PIM Sparse Mode 
(PIM-SM).<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 memo documents an Internet Best Current Practice.<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 BCPs 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/rfc8815">https://www.rfc-editor.org/info/rfc8815</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>
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            Copyright (c) 2020 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
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            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 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.<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="ulEmpty compact toc">
<li class="ulEmpty compact toc" 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><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
</li>
          <li class="ulEmpty compact toc" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-background" class="xref">Background</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.2.2.1">
                <p id="section-toc.1-1.2.2.1.1" class="keepWithNext"><a href="#section-2.1" class="xref">2.1</a>.  <a href="#name-multicast-service-models" class="xref">Multicast Service Models</a><a href="#section-toc.1-1.2.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.2.2.2">
                <p id="section-toc.1-1.2.2.2.1"><a href="#section-2.2" class="xref">2.2</a>.  <a href="#name-asm-routing-protocols" class="xref">ASM Routing Protocols</a><a href="#section-toc.1-1.2.2.2.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.2.2.2.2.1">
                    <p id="section-toc.1-1.2.2.2.2.1.1" class="keepWithNext"><a href="#section-2.2.1" class="xref">2.2.1</a>.  <a href="#name-pim-sparse-mode-pim-sm" class="xref">PIM Sparse Mode (PIM-SM)</a><a href="#section-toc.1-1.2.2.2.2.1.1" class="pilcrow">¶</a></p>
</li>
                  <li class="ulEmpty compact toc" id="section-toc.1-1.2.2.2.2.2">
                    <p id="section-toc.1-1.2.2.2.2.2.1"><a href="#section-2.2.2" class="xref">2.2.2</a>.  <a href="#name-embedded-rp" class="xref">Embedded-RP</a><a href="#section-toc.1-1.2.2.2.2.2.1" class="pilcrow">¶</a></p>
</li>
                  <li class="ulEmpty compact toc" id="section-toc.1-1.2.2.2.2.3">
                    <p id="section-toc.1-1.2.2.2.2.3.1"><a href="#section-2.2.3" class="xref">2.2.3</a>.  <a href="#name-bidir-rp" class="xref">BIDIR-RP</a><a href="#section-toc.1-1.2.2.2.2.3.1" class="pilcrow">¶</a></p>
</li>
                </ul>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.2.2.3">
                <p id="section-toc.1-1.2.2.3.1"><a href="#section-2.3" class="xref">2.3</a>.  <a href="#name-ssm-routing-protocols" class="xref">SSM Routing Protocols</a><a href="#section-toc.1-1.2.2.3.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="ulEmpty compact toc" 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-discussion" class="xref">Discussion</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-observations-on-asm-and-ssm" class="xref">Observations on ASM and SSM Deployments</a><a href="#section-toc.1-1.3.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" 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-advantages-of-ssm-for-inter" class="xref">Advantages of SSM for Interdomain Multicast</a><a href="#section-toc.1-1.3.2.2.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.3.2.2.2.1">
                    <p id="section-toc.1-1.3.2.2.2.1.1"><a href="#section-3.2.1" class="xref">3.2.1</a>.  <a href="#name-reduced-network-operations-" class="xref">Reduced Network Operations Complexity</a><a href="#section-toc.1-1.3.2.2.2.1.1" class="pilcrow">¶</a></p>
</li>
                  <li class="ulEmpty compact toc" id="section-toc.1-1.3.2.2.2.2">
                    <p id="section-toc.1-1.3.2.2.2.2.1"><a href="#section-3.2.2" class="xref">3.2.2</a>.  <a href="#name-no-network-wide-ip-multicas" class="xref">No Network-Wide IP Multicast Group-Address Management</a><a href="#section-toc.1-1.3.2.2.2.2.1" class="pilcrow">¶</a></p>
</li>
                  <li class="ulEmpty compact toc" id="section-toc.1-1.3.2.2.2.3">
                    <p id="section-toc.1-1.3.2.2.2.3.1"><a href="#section-3.2.3" class="xref">3.2.3</a>.  <a href="#name-intrinsic-source-control-se" class="xref">Intrinsic Source-Control Security</a><a href="#section-toc.1-1.3.2.2.2.3.1" class="pilcrow">¶</a></p>
</li>
                </ul>
</li>
            </ul>
</li>
          <li class="ulEmpty compact toc" 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-recommendations" class="xref">Recommendations</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="xref">4.1</a>.  <a href="#name-deprecating-use-of-asm-for-" class="xref">Deprecating Use of ASM for Interdomain Multicast</a><a href="#section-toc.1-1.4.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="xref">4.2</a>.  <a href="#name-including-network-support-f" class="xref">Including Network Support for IGMPv3/MLDv2</a><a href="#section-toc.1-1.4.2.2.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.3">
                <p id="section-toc.1-1.4.2.3.1"><a href="#section-4.3" class="xref">4.3</a>.  <a href="#name-building-application-suppor" class="xref">Building Application Support for SSM</a><a href="#section-toc.1-1.4.2.3.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.4">
                <p id="section-toc.1-1.4.2.4.1"><a href="#section-4.4" class="xref">4.4</a>.  <a href="#name-developing-application-guid" class="xref">Developing Application Guidance: SSM, ASM, Service Discovery</a><a href="#section-toc.1-1.4.2.4.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.5">
                <p id="section-toc.1-1.4.2.5.1"><a href="#section-4.5" class="xref">4.5</a>.  <a href="#name-preferring-ssm-applications" class="xref">Preferring SSM Applications Intradomain</a><a href="#section-toc.1-1.4.2.5.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.6">
                <p id="section-toc.1-1.4.2.6.1"><a href="#section-4.6" class="xref">4.6</a>.  <a href="#name-documenting-an-asm-ssm-prot" class="xref">Documenting an ASM/SSM Protocol Mapping Mechanism</a><a href="#section-toc.1-1.4.2.6.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.7">
                <p id="section-toc.1-1.4.2.7.1"><a href="#section-4.7" class="xref">4.7</a>.  <a href="#name-not-filtering-asm-addressin" class="xref">Not Filtering ASM Addressing between Domains</a><a href="#section-toc.1-1.4.2.7.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.8">
                <p id="section-toc.1-1.4.2.8.1"><a href="#section-4.8" class="xref">4.8</a>.  <a href="#name-not-precluding-intradomain-" class="xref">Not Precluding Intradomain ASM</a><a href="#section-toc.1-1.4.2.8.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.4.2.9">
                <p id="section-toc.1-1.4.2.9.1"><a href="#section-4.9" class="xref">4.9</a>.  <a href="#name-evolving-pim-deployments-fo" class="xref">Evolving PIM Deployments for SSM</a><a href="#section-toc.1-1.4.2.9.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="ulEmpty compact toc" 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-future-interdomain-asm-work" class="xref">Future Interdomain ASM Work</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
</li>
          <li class="ulEmpty compact toc" 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-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
</li>
          <li class="ulEmpty compact toc" 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-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
</li>
          <li class="ulEmpty compact toc" 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-references" class="xref">References</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p>
<ul class="ulEmpty compact toc">
<li class="ulEmpty compact toc" id="section-toc.1-1.8.2.1">
                <p id="section-toc.1-1.8.2.1.1"><a href="#section-8.1" class="xref">8.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.8.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="ulEmpty compact toc" id="section-toc.1-1.8.2.2">
                <p id="section-toc.1-1.8.2.2.1"><a href="#section-8.2" class="xref">8.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.8.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
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            <p id="section-toc.1-1.9.1"><a href="#section-appendix.a" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a><a href="#section-toc.1-1.9.1" class="pilcrow">¶</a></p>
</li>
          <li class="ulEmpty compact toc" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a><a href="#section-toc.1-1.10.1" class="pilcrow">¶</a></p>
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        </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">
 IP Multicast has been deployed in various forms, within
 private networks, the wider Internet, and federated networks
        such as national or regional research networks.
        While a number of service models have been published, and in many cases
 revised over time, there has been no strong recommendation
 made by the IETF on the appropriateness of those models to certain scenarios,
        even though vendors and federations have often made such recommendations.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">
 This document addresses this gap by making a BCP-level
 recommendation to deprecate the use of Any-Source Multicast (ASM) 
 for interdomain 
 multicast, leaving Source-Specific Multicast (SSM) 
 as the recommended interdomain mode of
        multicast.  
 Therefore, this document recommends that all hosts and routers that support 
 interdomain multicast applications fully support SSM.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">
 This document does not make any statement on the use of ASM
 within a single domain or organization and, therefore, does not preclude its use. Indeed, there are application contexts for
 which ASM is currently still widely considered well suited within a
 single domain.<a href="#section-1-3" class="pilcrow">¶</a></p>
<p id="section-1-4">
        The main issue in most cases with moving to SSM is application support.
        Many applications are initially deployed for intradomain use and are later
        deployed interdomain. Therefore, this document recommends that
        applications support SSM, even when they are initially intended for
        intradomain use. As explained below, SSM applications are
        readily compatible with existing intradomain ASM deployments using PIM-SM, as PIM-SSM is merely a subset of PIM-SM.<a href="#section-1-4" class="pilcrow">¶</a></p>
</section>
<section id="section-2">
      <h2 id="name-background">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-background" class="section-name selfRef">Background</a>
      </h2>
<section id="section-2.1">
        <h3 id="name-multicast-service-models">
<a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-multicast-service-models" class="section-name selfRef">Multicast Service Models</a>
        </h3>
<p id="section-2.1-1">
   Any-Source Multicast (ASM) and Source-Specific Multicast (SSM)
   are the two multicast service models in use today.  In ASM, as originally 
   described in <span>[<a href="#RFC1112" class="xref">RFC1112</a>]</span>, receivers express interest 
   in joining a multicast group address, and routers use multicast 
   routing protocols to deliver traffic from 
   the sender(s) to the receivers.  If there are multiple senders 
   for a given group, traffic from all senders will be delivered 
   to the receivers.  Since receivers specify only the group address, 
   the network -- and therefore the multicast routing protocols -- are 
   responsible for source discovery.<a href="#section-2.1-1" class="pilcrow">¶</a></p>
<p id="section-2.1-2">
   In SSM, by contrast, receivers specify both group and source when
   expressing interest in joining a multicast stream.  Source discovery
   in SSM is handled by some out-of-band mechanism (typically in the application 
   layer), which drastically simplifies the network and how the multicast 
   routing protocols operate.<a href="#section-2.1-2" class="pilcrow">¶</a></p>
<p id="section-2.1-3">
   IANA has reserved specific ranges of IPv4 and IPv6 address
   space for multicast addressing.
   Guidelines for IPv4 multicast address assignments
   can be found in <span>[<a href="#RFC5771" class="xref">RFC5771</a>]</span>, while
   guidelines for IPv6 multicast address assignments
   can be found in <span>[<a href="#RFC2375" class="xref">RFC2375</a>]</span> and
   <span>[<a href="#RFC3307" class="xref">RFC3307</a>]</span>.
   The IPv6 multicast address format is described
   in <span>[<a href="#RFC4291" class="xref">RFC4291</a>]</span>.<a href="#section-2.1-3" class="pilcrow">¶</a></p>
</section>
<section id="section-2.2">
        <h3 id="name-asm-routing-protocols">
<a href="#section-2.2" class="section-number selfRef">2.2. </a><a href="#name-asm-routing-protocols" class="section-name selfRef">ASM Routing Protocols</a>
        </h3>
<section id="section-2.2.1">
          <h4 id="name-pim-sparse-mode-pim-sm">
<a href="#section-2.2.1" class="section-number selfRef">2.2.1. </a><a href="#name-pim-sparse-mode-pim-sm" class="section-name selfRef">PIM Sparse Mode (PIM-SM)</a>
          </h4>
<p id="section-2.2.1-1">
           The most commonly deployed ASM routing protocol is Protocol Independent
     Multicast - Sparse Mode (PIM-SM), as 
     detailed in <span>[<a href="#RFC7761" class="xref">RFC7761</a>]</span>.
     PIM-SM, as the name suggests, was designed to be used in scenarios
     where the subnets with receivers are sparsely distributed throughout 
     the network. 
     Because receivers do not indicate sender addresses in ASM (but only group addresses), 
     PIM-SM uses the concept of a Rendezvous Point (RP) as a "meeting point" 
     for sources and receivers, and all routers in a PIM-SM domain are 
     configured to use a specific RP(s), either explicitly or through
            dynamic RP-discovery protocols.<a href="#section-2.2.1-1" class="pilcrow">¶</a></p>
<p id="section-2.2.1-2">
     To enable PIM-SM to work between multiple
     domains, an interdomain, inter-RP signaling protocol known
     as Multicast Source Discovery Protocol (MSDP)
     <span>[<a href="#RFC3618" class="xref">RFC3618</a>]</span> is used to allow an RP in one 
     domain to learn of the existence of a source in another domain.
     Deployment scenarios for MSDP are given in <span>[<a href="#RFC4611" class="xref">RFC4611</a>]</span>.
     MSDP floods information
            about all active sources for all multicast streams to all RPs in all 
     the domains -- even if there is no receiver for a given application in a domain.
     As a result of this key scalability and security issue, along with
     other deployment challenges with the protocol,
     MSDP was never extended to support IPv6 and remains an Experimental protocol.<a href="#section-2.2.1-2" class="pilcrow">¶</a></p>
<p id="section-2.2.1-3">At the time of writing, there is no IETF
          interdomain solution at the level of
          Proposed Standard for IPv4 ASM
          multicast, because MSDP was the de facto mechanism for the
          interdomain source discovery problem, and it is
          Experimental. Other protocol options were investigated at
          the same time but were never implemented or deployed and are
          now historic (e.g., <span>[<a href="#RFC3913" class="xref">RFC3913</a>]</span>).<a href="#section-2.2.1-3" class="pilcrow">¶</a></p>
</section>
<section id="section-2.2.2">
          <h4 id="name-embedded-rp">
<a href="#section-2.2.2" class="section-number selfRef">2.2.2. </a><a href="#name-embedded-rp" class="section-name selfRef">Embedded-RP</a>
          </h4>
<p id="section-2.2.2-1">Due to the availability of more bits in an IPv6 address than in IPv4,
            an IPv6-specific mechanism was designed in support of interdomain 
     ASM, with PIM-SM leveraging those bits.
     Embedded-RP <span>[<a href="#RFC3956" class="xref">RFC3956</a>]</span> allows routers supporting the protocol
     to determine the RP for the group without any
     prior configuration or discovery protocols, simply by observing the unicast RP
            address that is embedded (included) in the IPv6 multicast group address.
     Embedded-RP allows PIM-SM operation across any IPv6 network 
     in which there is an end-to-end path of routers
            supporting this mechanism, including interdomain deployment.<a href="#section-2.2.2-1" class="pilcrow">¶</a></p>
</section>
<section id="section-2.2.3">
          <h4 id="name-bidir-rp">
<a href="#section-2.2.3" class="section-number selfRef">2.2.3. </a><a href="#name-bidir-rp" class="section-name selfRef">BIDIR-RP</a>
          </h4>
<p id="section-2.2.3-1">BIDIR-PIM <span>[<a href="#RFC5015" class="xref">RFC5015</a>]</span> is
   another protocol to support ASM.
            There is no standardized option to operate BIDIR-PIM interdomain. It is
            deployed intradomain for applications where many sources send traffic
            to the same IP multicast groups because, unlike PIM-SM, it does not
            create per-source state. BIDIR-PIM is one of the important reasons for this
            document to not deprecate intradomain ASM.<a href="#section-2.2.3-1" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-2.3">
        <h3 id="name-ssm-routing-protocols">
<a href="#section-2.3" class="section-number selfRef">2.3. </a><a href="#name-ssm-routing-protocols" class="section-name selfRef">SSM Routing Protocols</a>
        </h3>
<p id="section-2.3-1">
         SSM is detailed in <span>[<a href="#RFC4607" class="xref">RFC4607</a>]</span>. It mandates the use of 
          PIM-SSM for routing of SSM.  PIM-SSM is merely a subset of PIM-SM
   <span>[<a href="#RFC7761" class="xref">RFC7761</a>]</span>.<a href="#section-2.3-1" class="pilcrow">¶</a></p>
<p id="section-2.3-2">
   PIM-SSM expects the sender's source address(es)
   to be known in advance by receivers through some out-of-band mechanism (typically 
   in the application layer); thus, the 
   receiver's designated router can send a PIM Join message directly towards the 
   source without needing to use an RP.<a href="#section-2.3-2" class="pilcrow">¶</a></p>
<p id="section-2.3-3">
   IPv4 addresses in the 232/8 (232.0.0.0 to
      232.255.255.255) range are designated as Source-Specific Multicast
      (SSM) destination addresses and are reserved for use by 
   source-specific applications and protocols. 
   For IPv6, the address prefix 
   ff3x::/32 is reserved for source-specific multicast use.  See <span>[<a href="#RFC4607" class="xref">RFC4607</a>]</span>.<a href="#section-2.3-3" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-3">
      <h2 id="name-discussion">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-discussion" class="section-name selfRef">Discussion</a>
      </h2>
<section id="section-3.1">
        <h3 id="name-observations-on-asm-and-ssm">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-observations-on-asm-and-ssm" class="section-name selfRef">Observations on ASM and SSM Deployments</a>
        </h3>
<p id="section-3.1-1">
 In enterprise and campus scenarios, ASM in the form of PIM-SM is 
 likely the most commonly deployed 
 multicast protocol.  The configuration and
 management of an RP (including RP redundancy) within a single 
 domain is a well-understood operational practice.  However, if interworking
 with external PIM domains is needed in IPv4 multicast deployments,
 interdomain MSDP is required to 
 exchange information about sources between domain RPs. 
 Deployment experience has shown MSDP to be a complex and fragile protocol 
 to manage and troubleshoot.  Some of these issues include complex 
 Reverse Path Forwarding (RPF) 
 rules, state attack protection, and filtering of undesired sources.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<p id="section-3.1-2">
 PIM-SM is a general-purpose protocol that can handle all
 use cases. In particular, it was designed for cases such as
 videoconferencing where multiple sources may come and go 
 during a multicast
 session. But for cases where a single, persistent source for a group
        is used, and receivers can be configured to know of that source,
 PIM-SM has unnecessary complexity. Therefore, SSM removes the need for 
 many of the most 
 complex components of PIM-SM.<a href="#section-3.1-2" class="pilcrow">¶</a></p>
<p id="section-3.1-3">
 As explained above, MSDP was not extended to support IPv6. Instead,
        the proposed interdomain ASM solution for PIM-SM with IPv6
 is Embedded-RP, which allows the RP address 
 for a multicast group to be embedded in the group address, 
 making RP discovery automatic for all routers on the path
 between a receiver and a sender.
 Embedded-RP can support lightweight ad hoc deployments.
 However, it relies
 on a single RP for an entire group that could only be made resilient
        within one domain. While this approach solves the MSDP issues, it does
        not solve the problem of unauthorized sources sending traffic to ASM
        multicast groups; this security issue 
 is one of biggest problems of interdomain multicast.<a href="#section-3.1-3" class="pilcrow">¶</a></p>
<p id="section-3.1-4">
 As stated in RFC 4607, SSM is particularly well suited to either
 dissemination-style applications with one or more senders 
 whose identities are known (by some out-of-band mechanism) before the 
 application starts running or applications that utilize some
        signaling to indicate the source address of the 
 multicast stream (e.g., an electronic programming guide
 in IPTV applications).
        Therefore, SSM through PIM-SSM is very well suited
 to applications such as classic linear-broadcast TV over IP.<a href="#section-3.1-4" class="pilcrow">¶</a></p>
<p id="section-3.1-5">
 SSM requires applications, host operating systems, and the 
 designated routers connected to receiving hosts 
 to support Internet Group Management Protocol, Version 3 (IGMPv3) 
 <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and 
 Multicast Listener Discovery, Version 2 (MLDv2) 
 <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span>.  While support for 
 IGMPv3 and MLDv2 has been commonplace in routing platforms for
 a long time, it has also now become widespread in common operating
 systems for several years (Windows, Mac OS,
        Linux/Android) and is no longer an impediment to SSM deployment.<a href="#section-3.1-5" class="pilcrow">¶</a></p>
</section>
<div id="advantages">
<section id="section-3.2">
        <h3 id="name-advantages-of-ssm-for-inter">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-advantages-of-ssm-for-inter" class="section-name selfRef">Advantages of SSM for Interdomain Multicast</a>
        </h3>
<p id="section-3.2-1">This section describes the three key benefits that SSM
        with PIM-SSM has over ASM. These benefits also apply 
        to intradomain deployment but are even more important in
        interdomain deployments. See <span>[<a href="#RFC4607" class="xref">RFC4607</a>]</span> for
        more details.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<section id="section-3.2.1">
          <h4 id="name-reduced-network-operations-">
<a href="#section-3.2.1" class="section-number selfRef">3.2.1. </a><a href="#name-reduced-network-operations-" class="section-name selfRef">Reduced Network Operations Complexity</a>
          </h4>
<p id="section-3.2.1-1">
   A significant benefit of SSM is the reduced complexity that comes through
   eliminating the network-based source discovery required in ASM with PIM-SM. 

   Specifically, SSM eliminates the need for RPs,
   shared trees, Shortest Path Tree (SPT) switchovers, PIM registers, 
   MSDP, dynamic RP-discovery mechanisms (Bootstrap Router
   (BSR) / AutoRP), and data-driven 
   state creation.  SSM simply utilizes a small 
   subset of PIM-SM, alongside the integration with IGMPv3/MLDv2, where the
          source address signaled from the receiver is immediately used to
          create (S,G) state. 
   Eliminating network-based source discovery for interdomain 
   multicast means the vast majority of the complexity of multicast goes away.<a href="#section-3.2.1-1" class="pilcrow">¶</a></p>
<p id="section-3.2.1-2">
   This reduced complexity makes SSM radically simpler to manage, 
   troubleshoot, and operate, particularly for backbone network
   operators.  This is the main operator motivation for the recommendation
   to deprecate the use of ASM in interdomain scenarios.<a href="#section-3.2.1-2" class="pilcrow">¶</a></p>
<p id="section-3.2.1-3">Note that this discussion does not apply to BIDIR-PIM, and there is
          (as mentioned above) no standardized interdomain solution for BIDIR-PIM.
   In BIDIR-PIM, traffic is forwarded to the RP instead of building state as in PIM-SM.  This occurs even in the absence of receivers.
   Therefore, BIDIR-PIM offers a trade-off of state complexity at the cost of 
creating unnecessary traffic (potentially a large amount).<a href="#section-3.2.1-3" class="pilcrow">¶</a></p>
</section>
<section id="section-3.2.2">
          <h4 id="name-no-network-wide-ip-multicas">
<a href="#section-3.2.2" class="section-number selfRef">3.2.2. </a><a href="#name-no-network-wide-ip-multicas" class="section-name selfRef">No Network-Wide IP Multicast Group-Address Management</a>
          </h4>
<p id="section-3.2.2-1">
          In ASM, IP multicast group addresses need to be assigned to applications
          and instances thereof, so that two simultaneously active application instances
          will not share the same group address and receive IP multicast traffic from
   each other.<a href="#section-3.2.2-1" class="pilcrow">¶</a></p>
<p id="section-3.2.2-2">
          In SSM, no such IP multicast group management is necessary. Instead, the IP multicast
          group address simply needs to be assigned locally on a source like a unicast transport
          protocol port number: the only coordination required is to ensure that
    different applications running on the same host don't send to the same group
    address.  This does not require any network-operator involvement.<a href="#section-3.2.2-2" class="pilcrow">¶</a></p>
</section>
<div id="source-security">
<section id="section-3.2.3">
          <h4 id="name-intrinsic-source-control-se">
<a href="#section-3.2.3" class="section-number selfRef">3.2.3. </a><a href="#name-intrinsic-source-control-se" class="section-name selfRef">Intrinsic Source-Control Security</a>
          </h4>
<p id="section-3.2.3-1">
   SSM is implicitly secure against off-path unauthorized/undesired sources.
   Receivers only receive packets from the sources they explicitly specify
          in their IGMPv3/MLDv2 membership messages, as opposed to ASM, where any host
          can send traffic to a group address and have it transmitted to all receivers. 
          With PIM-SSM, traffic from sources not requested by any receiver will
          be discarded by the First-Hop Router (FHR) of that source, minimizing source
          attacks against shared network bandwidth and receivers.<a href="#section-3.2.3-1" class="pilcrow">¶</a></p>
<p id="section-3.2.3-2">
          This benefit is particularly important in interdomain deployments
  because there are no standardized solutions for ASM control of
  sources and the most common intradomain operational practices such as
  Access Control Lists (ACLs) on the sender's FHR are not feasible for
  interdomain deployments.<a href="#section-3.2.3-2" class="pilcrow">¶</a></p>
<p id="section-3.2.3-3">
   This topic is expanded upon in <span>[<a href="#RFC4609" class="xref">RFC4609</a>]</span>.<a href="#section-3.2.3-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
</section>
<div id="recommendations">
<section id="section-4">
      <h2 id="name-recommendations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-recommendations" class="section-name selfRef">Recommendations</a>
      </h2>
<p id="section-4-1">
 This section provides recommendations for a variety of stakeholders in
 SSM deployment, including vendors, operators, and application developers.
 It also suggests further work that could be undertaken within the IETF.<a href="#section-4-1" class="pilcrow">¶</a></p>
<section id="section-4.1">
        <h3 id="name-deprecating-use-of-asm-for-">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-deprecating-use-of-asm-for-" class="section-name selfRef">Deprecating Use of ASM for Interdomain Multicast</a>
        </h3>
<p id="section-4.1-1">
 This document recommends that the use of ASM be deprecated
 for interdomain multicast; thus, implicitly, it recommends that hosts and
 routers that support such interdomain applications
 fully support SSM and its associated protocols.
 Best current practices for deploying interdomain multicast using SSM
 are documented in <span>[<a href="#RFC8313" class="xref">RFC8313</a>]</span>.<a href="#section-4.1-1" class="pilcrow">¶</a></p>
<p id="section-4.1-2">
 The recommendation applies to the use of ASM between domains where 
 either MSDP (IPv4) or Embedded-RP (IPv6) is used.<a href="#section-4.1-2" class="pilcrow">¶</a></p>
<p id="section-4.1-3">
 An interdomain use of ASM multicast in the context of this document
        is one where PIM-SM with RPs/MSDP/Embedded-RP
        is run on routers operated by two or more separate administrative entities.<a href="#section-4.1-3" class="pilcrow">¶</a></p>
<p id="section-4.1-4">
 The focus of this document is deprecation of interdomain ASM multicast,
 and while encouraging the use of SSM within domains,
 it leaves operators free to choose to use ASM within their own domains.
 A more inclusive interpretation of this recommendation is that it  
 also extends to deprecating use of ASM in the case where PIM is 
 operated in a single operator domain, but where
 user hosts or non-PIM network edge devices are under
        different operator control. A typical example of this case is a 
 service provider  offering
        IPTV (single operator domain for PIM) to subscribers operating an
        IGMP proxy home gateway and IGMPv3/MLDv2 hosts (computer, tablets, set-top boxes).<a href="#section-4.1-4" class="pilcrow">¶</a></p>
</section>
<section id="section-4.2">
        <h3 id="name-including-network-support-f">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-including-network-support-f" class="section-name selfRef">Including Network Support for IGMPv3/MLDv2</a>
        </h3>
<p id="section-4.2-1">
 This document recommends that all hosts, router platforms, and 
 security appliances used for deploying multicast
 support the components of IGMPv3 <span>[<a href="#RFC3376" class="xref">RFC3376</a>]</span> and MLDv2 
 <span>[<a href="#RFC3810" class="xref">RFC3810</a>]</span> necessary to support SSM (i.e., explicitly sending 
 source-specific reports).
 "IPv6 Node Requirements" <span>[<a href="#RFC8504" class="xref">RFC8504</a>]</span>
 states that MLDv2 must be supported in all implementations.
 Such support is already widespread in common host and router platforms.<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<p id="section-4.2-2">
 Further guidance on IGMPv3 and MLDv2 is given in
 <span>[<a href="#RFC4604" class="xref">RFC4604</a>]</span>.<a href="#section-4.2-2" class="pilcrow">¶</a></p>
<p id="section-4.2-3">
        Multicast snooping is often used to limit the flooding of multicast traffic
        in a Layer 2 network.  With snooping, an L2 switch will monitor IGMP/MLD
 messages and only forward multicast traffic out on host ports that have 
 interested receivers connected.
 Such snooping capability should therefore support IGMPv3 and MLDv2.
        There is further discussion in <span>[<a href="#RFC4541" class="xref">RFC4541</a>]</span>.<a href="#section-4.2-3" class="pilcrow">¶</a></p>
</section>
<section id="section-4.3">
        <h3 id="name-building-application-suppor">
<a href="#section-4.3" class="section-number selfRef">4.3. </a><a href="#name-building-application-suppor" class="section-name selfRef">Building Application Support for SSM</a>
        </h3>
<p id="section-4.3-1">
 The recommendation to use SSM for interdomain multicast means that 
 applications should properly trigger the sending of IGMPv3/MLDv2 
 source-specific report messages.
 It should be noted, however, that there is a wide range of applications today 
 that only support ASM.  In many cases, this is due to application developers
 being unaware of the operational concerns of networks and the implications of
 using ASM versus SSM.  This document serves to 
 provide clear direction for application developers who might currently only
 consider using ASM to instead support SSM, which only requires relatively minor
 changes for many applications, particularly those with single sources.<a href="#section-4.3-1" class="pilcrow">¶</a></p>
<p id="section-4.3-2">
 It is often thought that ASM is required for multicast applications
 where there are multiple sources. However,
 RFC 4607 also describes how SSM can be used instead of PIM-SM
 for multi-party applications:<a href="#section-4.3-2" class="pilcrow">¶</a></p>
<blockquote id="section-4.3-3">SSM can be used to
    build multi-source applications where all participants' identities
    are not known in advance, but the multi-source "rendezvous"
    functionality does not occur in the network layer in this case.  Just
    like in an application that uses unicast as the underlying transport,
    this functionality can be implemented by the application or by an
    application-layer library.<a href="#section-4.3-3" class="pilcrow">¶</a>
</blockquote>
<p id="section-4.3-4">
 Some useful considerations for multicast applications can be found
 in  <span>[<a href="#RFC3170" class="xref">RFC3170</a>]</span>.<a href="#section-4.3-4" class="pilcrow">¶</a></p>
</section>
<div id="guidance">
<section id="section-4.4">
        <h3 id="name-developing-application-guid">
<a href="#section-4.4" class="section-number selfRef">4.4. </a><a href="#name-developing-application-guid" class="section-name selfRef">Developing Application Guidance: SSM, ASM, Service Discovery</a>
        </h3>
<p id="section-4.4-1">
        Applications with many-to-many communication patterns can create more
        (S,G) state than is feasible for networks to manage, whether the source discovery is
        done by ASM with PIM-SM or at the application level and SSM/PIM-SSM.
        These applications are not best supported by either SSM/PIM-SSM or ASM/PIM-SM.<a href="#section-4.4-1" class="pilcrow">¶</a></p>
<p id="section-4.4-2">
   Instead, these applications are better served by routing protocols
   that do not create (S,G), such as BIDIR-PIM.  
   Unfortunately, many applications today use ASM solely for service
   discovery. One example is where clients send IP multicast packets to
   elicit unicast replies from server(s).  Deploying any form of IP
   multicast solely in support of such service discovery is, in general,
   not recommended.   Dedicated
   service discovery via DNS-based Service
   Discovery (DNS-SD) <span>[<a href="#RFC6763" class="xref">RFC6763</a>]</span> should be used
   for this instead.<a href="#section-4.4-2" class="pilcrow">¶</a></p>
<p id="section-4.4-3">
 This document describes best practices to explain when to use SSM in
 applications -- e.g., when ASM without (S,G) state in the network is
 better, or when dedicated service-discovery 
 mechanisms should be used. However, specifying how applications
 can support these practices is
 outside the scope of this document.
 Further work on this subject may be expected within the IETF.<a href="#section-4.4-3" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-4.5">
        <h3 id="name-preferring-ssm-applications">
<a href="#section-4.5" class="section-number selfRef">4.5. </a><a href="#name-preferring-ssm-applications" class="section-name selfRef">Preferring SSM Applications Intradomain</a>
        </h3>
<p id="section-4.5-1">
        If feasible, it is recommended for applications to use SSM even if they
        are initially only meant to be used in intradomain environments supporting ASM. 
 Because PIM-SSM is a subset of PIM-SM, existing intradomain PIM-SM networks
 are automatically compatible with SSM applications. Thus, SSM applications  
 can operate alongside existing ASM applications.
        SSM's benefits of simplified address management and significantly reduced
 operational complexity apply equally to intradomain use.<a href="#section-4.5-1" class="pilcrow">¶</a></p>
<p id="section-4.5-2">However, for some applications, it may be prohibitively difficult to
        add support for source discovery, so intradomain ASM may still be appropriate.<a href="#section-4.5-2" class="pilcrow">¶</a></p>
</section>
<section id="section-4.6">
        <h3 id="name-documenting-an-asm-ssm-prot">
<a href="#section-4.6" class="section-number selfRef">4.6. </a><a href="#name-documenting-an-asm-ssm-prot" class="section-name selfRef">Documenting an ASM/SSM Protocol Mapping Mechanism</a>
        </h3>
<p id="section-4.6-1">
 In the case of existing ASM applications that cannot readily be ported to SSM,
 it may be possible to use some form of protocol mapping -- i.e., to have a 
 mechanism to translate a (*,G) join or leave to a (S,G) join or leave for 
 a specific source S.  The general challenge in performing such mapping is 
 determining where the configured source address, S, comes from.<a href="#section-4.6-1" class="pilcrow">¶</a></p>
<p id="section-4.6-2">
 There are existing vendor-specific mechanisms deployed that achieve this function,
 but none are documented in IETF documents.  This may be a useful 
 area for the IETF to work on as an interim
 transition mechanism. However, these mechanisms would introduce additional 
 administrative burdens, along with the need for some form of address management, 
 neither of which are required in SSM.  Hence, this should not be considered a
 long-term solution.<a href="#section-4.6-2" class="pilcrow">¶</a></p>
</section>
<section id="section-4.7">
        <h3 id="name-not-filtering-asm-addressin">
<a href="#section-4.7" class="section-number selfRef">4.7. </a><a href="#name-not-filtering-asm-addressin" class="section-name selfRef">Not Filtering ASM Addressing between Domains</a>
        </h3>
<p id="section-4.7-1">
 A key benefit of SSM is that the receiver specifies the source-group tuple 
 when signaling interest in a multicast stream.  Hence, the group address need 
 not be globally unique, so there is no need for multicast address allocation
 as long the reserved SSM range is used.<a href="#section-4.7-1" class="pilcrow">¶</a></p>
<p id="section-4.7-2">
 Despite the deprecation of interdomain ASM, it is recommended that operators 
 not filter ASM group ranges at domain boundaries, as some form of 
 ASM-SSM mappings may continue to be used for some time.<a href="#section-4.7-2" class="pilcrow">¶</a></p>
</section>
<div id="precluding">
<section id="section-4.8">
        <h3 id="name-not-precluding-intradomain-">
<a href="#section-4.8" class="section-number selfRef">4.8. </a><a href="#name-not-precluding-intradomain-" class="section-name selfRef">Not Precluding Intradomain ASM</a>
        </h3>
<p id="section-4.8-1">
 The use of ASM within a single multicast domain such as a campus or
 enterprise is still relatively common today. There are even global
        enterprise networks that have successfully been using
        PIM-SM for many years. The operators of such networks most often
        use Anycast-RP <span>[<a href="#RFC4610" class="xref">RFC4610</a>]</span> or MSDP (with IPv4) for RP 
 resilience, at the expense of the extra operational complexity. 
 These existing practices are unaffected by this document.<a href="#section-4.8-1" class="pilcrow">¶</a></p>
<p id="section-4.8-2">In the past decade, some BIDIR-PIM deployments have scaled
 interdomain ASM deployments beyond the capabilities of PIM-SM. This, too,
        is unaffected by this document; instead, it is encouraged where
        necessary due to application requirements (see <a href="#guidance" class="xref">Section 4.4</a>).<a href="#section-4.8-2" class="pilcrow">¶</a></p>
<p id="section-4.8-3">
 This document also does not preclude continued use of ASM with multiple
        PIM-SM domains inside organizations, such as with IPv4 MSDP or IPv6 Embedded-RP.
 This includes organizations that are federations and have appropriate, nonstandardized
        mechanisms to deal with the interdomain ASM issues explained in <a href="#advantages" class="xref">Section 3.2</a>.<a href="#section-4.8-3" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-4.9">
        <h3 id="name-evolving-pim-deployments-fo">
<a href="#section-4.9" class="section-number selfRef">4.9. </a><a href="#name-evolving-pim-deployments-fo" class="section-name selfRef">Evolving PIM Deployments for SSM</a>
        </h3>
<p id="section-4.9-1">
  Existing PIM-SM deployments can usually be used to run SSM
 applications with few-to-no changes.  In some widely available
 router implementations of PIM-SM, PIM-SSM is simply enabled by default
 in the designated SSM address spaces whenever PIM-SM is
 enabled.  In other implementations, simple configuration options
 exist to enable it.  This allows migration of ASM applications
 to SSM/PIM-SSM solely through application-side development
 to handle source-signaling via
 IGMPv3/MLDv2 and using SSM addresses.  No network actions are
 required for this transition; unchanged ASM applications can
 continue to coexist without issues.<a href="#section-4.9-1" class="pilcrow">¶</a></p>
<p id="section-4.9-2">When running PIM-SM, IGMPv3/MLDv2 (S,G) membership reports may also result in
        the desired PIM-SSM (S,G) operations and bypass any RP procedures. This is not
        standardized but depends on implementation and may require additional configuration
        in available products.  In general, it is recommended to always use SSM address space
        for SSM applications. For example, the interaction of IGMPv3/MLDv2 (S,G) membership
        reports and BIDIR-PIM is undefined and may not result in forwarding of any traffic.<a href="#section-4.9-2" class="pilcrow">¶</a></p>
<p id="section-4.9-3">
        Note that these migration recommendations do not include considerations on when
        or how to evolve those intradomain applications best served by ASM/BIDIR-PIM from PIM-SM
        to BIDIR-PIM. This may also be important but is outside the scope of this document.<a href="#section-4.9-3" class="pilcrow">¶</a></p>
</section>
</section>
</div>
<section id="section-5">
      <h2 id="name-future-interdomain-asm-work">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-future-interdomain-asm-work" class="section-name selfRef">Future Interdomain ASM Work</a>
      </h2>
<p id="section-5-1">
      Future work may attempt to overcome current limitations of ASM solutions,
      such as interdomain deployment solutions for BIDIR-PIM or source-access-control
      mechanisms for IPv6 PIM-SM with embedded-RP. Such work could modify or amend the
      recommendations of this document (like any future IETF Standards
      Track / BCP work).<a href="#section-5-1" class="pilcrow">¶</a></p>
<p id="section-5-2">
 Nevertheless, it is very unlikely that any ASM solution, even with such 
 future work, can ever provide the same intrinsic security and network- and 
 address-management simplicity as SSM (see <a href="#advantages" class="xref">Section 3.2</a>).  Accordingly, this 
 document recommends that future work for general-purpose interdomain IP 
 multicast focus on SSM items listed in <a href="#recommendations" class="xref">Section 4</a>.<a href="#section-5-2" class="pilcrow">¶</a></p>
</section>
<section id="section-6">
      <h2 id="name-security-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-6-1">
 This document adds no new security considerations. It instead
        removes security issues incurred by interdomain ASM with PIM-SM/MSDP, such as
        infrastructure control-plane attacks and application and bandwidth/congestion
        attacks from unauthorized sources sending to ASM multicast groups.
 RFC 4609 describes the additional security benefits of using
 SSM instead of ASM.<a href="#section-6-1" class="pilcrow">¶</a></p>
</section>
<section id="section-7">
      <h2 id="name-iana-considerations">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-7-1">This document has no IANA actions.<a href="#section-7-1" class="pilcrow">¶</a></p>
</section>
<section id="section-8">
      <h2 id="name-references">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-8.1">
        <h3 id="name-normative-references">
<a href="#section-8.1" class="section-number selfRef">8.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC1112">[RFC1112]</dt>
        <dd>
<span class="refAuthor">Deering, S.</span>, <span class="refTitle">"Host extensions for IP multicasting"</span>, <span class="seriesInfo">STD 5</span>, <span class="seriesInfo">RFC 1112</span>, <span class="seriesInfo">DOI 10.17487/RFC1112</span>, <time datetime="1989-08" class="refDate">August 1989</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1112">https://www.rfc-editor.org/info/rfc1112</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3307">[RFC3307]</dt>
        <dd>
<span class="refAuthor">Haberman, B.</span>, <span class="refTitle">"Allocation Guidelines for IPv6 Multicast Addresses"</span>, <span class="seriesInfo">RFC 3307</span>, <span class="seriesInfo">DOI 10.17487/RFC3307</span>, <time datetime="2002-08" class="refDate">August 2002</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3307">https://www.rfc-editor.org/info/rfc3307</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><span class="refAuthor">, and 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><span class="refAuthor"> and 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="RFC3956">[RFC3956]</dt>
        <dd>
<span class="refAuthor">Savola, P.</span><span class="refAuthor"> and B. Haberman</span>, <span class="refTitle">"Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address"</span>, <span class="seriesInfo">RFC 3956</span>, <span class="seriesInfo">DOI 10.17487/RFC3956</span>, <time datetime="2004-11" class="refDate">November 2004</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3956">https://www.rfc-editor.org/info/rfc3956</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4291">[RFC4291]</dt>
        <dd>
<span class="refAuthor">Hinden, R.</span><span class="refAuthor"> and S. Deering</span>, <span class="refTitle">"IP Version 6 Addressing Architecture"</span>, <span class="seriesInfo">RFC 4291</span>, <span class="seriesInfo">DOI 10.17487/RFC4291</span>, <time datetime="2006-02" class="refDate">February 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4291">https://www.rfc-editor.org/info/rfc4291</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4607">[RFC4607]</dt>
        <dd>
<span class="refAuthor">Holbrook, H.</span><span class="refAuthor"> and B. Cain</span>, <span class="refTitle">"Source-Specific Multicast for IP"</span>, <span class="seriesInfo">RFC 4607</span>, <span class="seriesInfo">DOI 10.17487/RFC4607</span>, <time datetime="2006-08" class="refDate">August 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4607">https://www.rfc-editor.org/info/rfc4607</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5771">[RFC5771]</dt>
        <dd>
<span class="refAuthor">Cotton, M.</span><span class="refAuthor">, Vegoda, L.</span><span class="refAuthor">, and D. Meyer</span>, <span class="refTitle">"IANA Guidelines for IPv4 Multicast Address Assignments"</span>, <span class="seriesInfo">BCP 51</span>, <span class="seriesInfo">RFC 5771</span>, <span class="seriesInfo">DOI 10.17487/RFC5771</span>, <time datetime="2010-03" class="refDate">March 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5771">https://www.rfc-editor.org/info/rfc5771</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7761">[RFC7761]</dt>
        <dd>
<span class="refAuthor">Fenner, B.</span><span class="refAuthor">, Handley, M.</span><span class="refAuthor">, Holbrook, H.</span><span class="refAuthor">, Kouvelas, I.</span><span class="refAuthor">, Parekh, R.</span><span class="refAuthor">, Zhang, Z.</span><span class="refAuthor">, and L. Zheng</span>, <span class="refTitle">"Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)"</span>, <span class="seriesInfo">STD 83</span>, <span class="seriesInfo">RFC 7761</span>, <span class="seriesInfo">DOI 10.17487/RFC7761</span>, <time datetime="2016-03" class="refDate">March 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7761">https://www.rfc-editor.org/info/rfc7761</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8313">[RFC8313]</dt>
      <dd>
<span class="refAuthor">Tarapore, P., Ed.</span><span class="refAuthor">, Sayko, R.</span><span class="refAuthor">, Shepherd, G.</span><span class="refAuthor">, Eckert, T., Ed.</span><span class="refAuthor">, and R. Krishnan</span>, <span class="refTitle">"Use of Multicast across Inter-domain Peering Points"</span>, <span class="seriesInfo">BCP 213</span>, <span class="seriesInfo">RFC 8313</span>, <span class="seriesInfo">DOI 10.17487/RFC8313</span>, <time datetime="2018-01" class="refDate">January 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8313">https://www.rfc-editor.org/info/rfc8313</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-8.2">
        <h3 id="name-informative-references">
<a href="#section-8.2" class="section-number selfRef">8.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC2375">[RFC2375]</dt>
        <dd>
<span class="refAuthor">Hinden, R.</span><span class="refAuthor"> and S. Deering</span>, <span class="refTitle">"IPv6 Multicast Address Assignments"</span>, <span class="seriesInfo">RFC 2375</span>, <span class="seriesInfo">DOI 10.17487/RFC2375</span>, <time datetime="1998-07" class="refDate">July 1998</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2375">https://www.rfc-editor.org/info/rfc2375</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3170">[RFC3170]</dt>
        <dd>
<span class="refAuthor">Quinn, B.</span><span class="refAuthor"> and K. Almeroth</span>, <span class="refTitle">"IP Multicast Applications: Challenges and Solutions"</span>, <span class="seriesInfo">RFC 3170</span>, <span class="seriesInfo">DOI 10.17487/RFC3170</span>, <time datetime="2001-09" class="refDate">September 2001</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3170">https://www.rfc-editor.org/info/rfc3170</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3618">[RFC3618]</dt>
        <dd>
<span class="refAuthor">Fenner, B., Ed.</span><span class="refAuthor"> and D. Meyer, Ed.</span>, <span class="refTitle">"Multicast Source Discovery Protocol (MSDP)"</span>, <span class="seriesInfo">RFC 3618</span>, <span class="seriesInfo">DOI 10.17487/RFC3618</span>, <time datetime="2003-10" class="refDate">October 2003</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3618">https://www.rfc-editor.org/info/rfc3618</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3913">[RFC3913]</dt>
        <dd>
<span class="refAuthor">Thaler, D.</span>, <span class="refTitle">"Border Gateway Multicast Protocol (BGMP): Protocol Specification"</span>, <span class="seriesInfo">RFC 3913</span>, <span class="seriesInfo">DOI 10.17487/RFC3913</span>, <time datetime="2004-09" class="refDate">September 2004</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3913">https://www.rfc-editor.org/info/rfc3913</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4541">[RFC4541]</dt>
        <dd>
<span class="refAuthor">Christensen, M.</span><span class="refAuthor">, Kimball, K.</span><span class="refAuthor">, and F. Solensky</span>, <span class="refTitle">"Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches"</span>, <span class="seriesInfo">RFC 4541</span>, <span class="seriesInfo">DOI 10.17487/RFC4541</span>, <time datetime="2006-05" class="refDate">May 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4541">https://www.rfc-editor.org/info/rfc4541</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4604">[RFC4604]</dt>
        <dd>
<span class="refAuthor">Holbrook, H.</span><span class="refAuthor">, Cain, B.</span><span class="refAuthor">, and B. Haberman</span>, <span class="refTitle">"Using Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Protocol Version 2 (MLDv2) for Source-Specific Multicast"</span>, <span class="seriesInfo">RFC 4604</span>, <span class="seriesInfo">DOI 10.17487/RFC4604</span>, <time datetime="2006-08" class="refDate">August 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4604">https://www.rfc-editor.org/info/rfc4604</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4609">[RFC4609]</dt>
        <dd>
<span class="refAuthor">Savola, P.</span><span class="refAuthor">, Lehtonen, R.</span><span class="refAuthor">, and D. Meyer</span>, <span class="refTitle">"Protocol Independent Multicast - Sparse Mode (PIM-SM) Multicast Routing Security Issues and Enhancements"</span>, <span class="seriesInfo">RFC 4609</span>, <span class="seriesInfo">DOI 10.17487/RFC4609</span>, <time datetime="2006-10" class="refDate">October 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4609">https://www.rfc-editor.org/info/rfc4609</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4610">[RFC4610]</dt>
        <dd>
<span class="refAuthor">Farinacci, D.</span><span class="refAuthor"> and Y. Cai</span>, <span class="refTitle">"Anycast-RP Using Protocol Independent Multicast (PIM)"</span>, <span class="seriesInfo">RFC 4610</span>, <span class="seriesInfo">DOI 10.17487/RFC4610</span>, <time datetime="2006-08" class="refDate">August 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4610">https://www.rfc-editor.org/info/rfc4610</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4611">[RFC4611]</dt>
        <dd>
<span class="refAuthor">McBride, M.</span><span class="refAuthor">, Meylor, J.</span><span class="refAuthor">, and D. Meyer</span>, <span class="refTitle">"Multicast Source Discovery Protocol (MSDP) Deployment Scenarios"</span>, <span class="seriesInfo">BCP 121</span>, <span class="seriesInfo">RFC 4611</span>, <span class="seriesInfo">DOI 10.17487/RFC4611</span>, <time datetime="2006-08" class="refDate">August 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4611">https://www.rfc-editor.org/info/rfc4611</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5015">[RFC5015]</dt>
        <dd>
<span class="refAuthor">Handley, M.</span><span class="refAuthor">, Kouvelas, I.</span><span class="refAuthor">, Speakman, T.</span><span class="refAuthor">, and L. Vicisano</span>, <span class="refTitle">"Bidirectional Protocol Independent Multicast (BIDIR-PIM)"</span>, <span class="seriesInfo">RFC 5015</span>, <span class="seriesInfo">DOI 10.17487/RFC5015</span>, <time datetime="2007-10" class="refDate">October 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5015">https://www.rfc-editor.org/info/rfc5015</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6763">[RFC6763]</dt>
        <dd>
<span class="refAuthor">Cheshire, S.</span><span class="refAuthor"> and M. Krochmal</span>, <span class="refTitle">"DNS-Based Service Discovery"</span>, <span class="seriesInfo">RFC 6763</span>, <span class="seriesInfo">DOI 10.17487/RFC6763</span>, <time datetime="2013-02" class="refDate">February 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6763">https://www.rfc-editor.org/info/rfc6763</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8504">[RFC8504]</dt>
      <dd>
<span class="refAuthor">Chown, T.</span><span class="refAuthor">, Loughney, J.</span><span class="refAuthor">, and T. Winters</span>, <span class="refTitle">"IPv6 Node Requirements"</span>, <span class="seriesInfo">BCP 220</span>, <span class="seriesInfo">RFC 8504</span>, <span class="seriesInfo">DOI 10.17487/RFC8504</span>, <time datetime="2019-01" class="refDate">January 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8504">https://www.rfc-editor.org/info/rfc8504</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<section id="section-appendix.a">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<p id="section-appendix.a-1">
 The authors would like to thank members of the IETF MBONE Deployment
 Working Group for discussions on the
 content of this document, with specific thanks to the following people for their 
 contributions to the document:
 <span class="contact-name">Hitoshi Asaeda</span>,
 <span class="contact-name">Dale Carder</span>,
 <span class="contact-name">Jake Holland</span>,
 <span class="contact-name">Albert Manfredi</span>,
 <span class="contact-name">Mike McBride</span>,
 <span class="contact-name">Per Nihlen</span>,
 <span class="contact-name">Greg Shepherd</span>,
 <span class="contact-name">James Stevens</span>,
 <span class="contact-name">Stig Venaas</span>,
 <span class="contact-name">Nils Warnke</span>,
 and
 <span class="contact-name">Sandy Zhang</span>.<a href="#section-appendix.a-1" class="pilcrow">¶</a></p>
</section>
<div id="authors-addresses">
<section id="section-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">Mikael Abrahamsson</span></div>
<div dir="auto" class="left"><span class="locality">Stockholm</span></div>
<div dir="auto" class="left"><span class="country-name">Sweden</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:swmike@swm.pp.se" class="email">swmike@swm.pp.se</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Tim Chown</span></div>
<div dir="auto" class="left"><span class="org">Jisc</span></div>
<div dir="auto" class="left"><span class="extended-address">Harwell Oxford</span></div>
<div dir="auto" class="left"><span class="street-address">Lumen House, Library Avenue</span></div>
<div dir="auto" class="left"><span class="locality">Didcot</span></div>
<div dir="auto" class="left"><span class="postal-code">OX11 0SG</span></div>
<div dir="auto" class="left"><span class="country-name">United Kingdom</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:tim.chown@jisc.ac.uk" class="email">tim.chown@jisc.ac.uk</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Lenny Giuliano</span></div>
<div dir="auto" class="left"><span class="org">Juniper Networks, Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">2251 Corporate Park Drive</span></div>
<div dir="auto" class="left">
<span class="locality">Herndon</span>, <span class="region">Virginia</span> <span class="postal-code">20171</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:lenny@juniper.net" class="email">lenny@juniper.net</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Toerless Eckert</span></div>
<div dir="auto" class="left"><span class="org">Futurewei Technologies Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">2330 Central Expy</span></div>
<div dir="auto" class="left">
<span class="locality">Santa Clara</span>, <span class="region">California</span> <span class="postal-code">95050</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:tte@cs.fau.de" class="email">tte@cs.fau.de</a>
</div>
</address>
</section>
</div>
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