File: rfc8828.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 8828: WebRTC IP Address Handling Requirements</title>
<meta content="Justin Uberti" name="author">
<meta content="Guo-wei Shieh" name="author">
<meta content="
       This document provides information and requirements for how IP
      addresses should be handled by Web Real-Time Communication (WebRTC) implementations. 
    " name="description">
<meta content="xml2rfc 3.5.0" name="generator">
<meta content="8828" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.5.0
    Python 3.6.10
    appdirs 1.4.4
    ConfigArgParse 1.2.3
    google-i18n-address 2.3.5
    html5lib 1.0.1
    intervaltree 3.0.2
    Jinja2 2.11.2
    kitchen 1.2.6
    lxml 4.4.2
    pycairo 1.19.0
    pycountry 19.8.18
    pyflakes 2.1.1
    PyYAML 5.3.1
    requests 2.22.0
    setuptools 40.6.2
    six 1.14.0
    WeasyPrint 51
-->
<link href="rfc8828.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 {
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}
div {
  margin: 0;
}
.alignRight.art-text {
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  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
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}
.alignRight {
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}
.alignRight > *:first-child {
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  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
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  display: block;
  border: none;
}
svg {
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}
.alignCenter.art-text {
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}
.alignCenter.art-text pre {
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}
.alignCenter {
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}
.alignCenter > *:first-child {
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     support flexbox yet.
  */
  display: table;
  margin: 0 auto;
}

/* lists */
ol, ul {
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  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
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}
li {
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}
.ulCompact li {
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}
ul.empty, .ulEmpty {
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}
ul.empty li, .ulEmpty li {
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}
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 {
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}
figure blockquote {
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}
figcaption {
  font-style: italic;
  margin: 0 0 1em 0;
}
@media screen {
  pre {
    overflow-x: auto;
    max-width: 100%;
    max-width: calc(100% - 22px);
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}

/* 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 {
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}
tr:nth-child(2n+1) > td {
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}
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;
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<table class="ears">
<thead><tr>
<td class="left">RFC 8828</td>
<td class="center">WebRTC IP Handling</td>
<td class="right">January 2021</td>
</tr></thead>
<tfoot><tr>
<td class="left">Uberti &amp; Shieh</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/rfc8828" class="eref">8828</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="2021-01" class="published">January 2021</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">J. Uberti</div>
<div class="org">Google</div>
</div>
<div class="author">
      <div class="author-name">G. Shieh</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8828</h1>
<h1 id="title">WebRTC IP Address Handling Requirements</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document provides information and requirements for how IP
      addresses should be handled by Web Real-Time Communication (WebRTC) implementations.<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/rfc8828">https://www.rfc-editor.org/info/rfc8828</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) 2021 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 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="toc compact ulEmpty">
<li class="toc compact 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><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact 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-terminology" class="xref">Terminology</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1" class="keepWithNext"><a href="#section-3" class="xref">3</a>.  <a href="#name-problem-statement" class="xref">Problem Statement</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact 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-goals" class="xref">Goals</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact 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-detailed-design" class="xref">Detailed Design</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
<ul class="toc compact ulEmpty">
<li class="toc compact ulEmpty" id="section-toc.1-1.5.2.1">
                <p id="section-toc.1-1.5.2.1.1"><a href="#section-5.1" class="xref">5.1</a>.  <a href="#name-principles" class="xref">Principles</a><a href="#section-toc.1-1.5.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc compact ulEmpty" id="section-toc.1-1.5.2.2">
                <p id="section-toc.1-1.5.2.2.1"><a href="#section-5.2" class="xref">5.2</a>.  <a href="#name-modes-and-recommendations" class="xref">Modes and Recommendations</a><a href="#section-toc.1-1.5.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc compact 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-implementation-guidance" class="xref">Implementation Guidance</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
<ul class="toc compact ulEmpty">
<li class="toc compact ulEmpty" id="section-toc.1-1.6.2.1">
                <p id="section-toc.1-1.6.2.1.1"><a href="#section-6.1" class="xref">6.1</a>.  <a href="#name-ensuring-normal-routing" class="xref">Ensuring Normal Routing</a><a href="#section-toc.1-1.6.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc compact ulEmpty" id="section-toc.1-1.6.2.2">
                <p id="section-toc.1-1.6.2.2.1"><a href="#section-6.2" class="xref">6.2</a>.  <a href="#name-determining-associated-loca" class="xref">Determining Associated Local Addresses</a><a href="#section-toc.1-1.6.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc compact 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-application-guidance" class="xref">Application Guidance</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact 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-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact 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-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.9.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact ulEmpty" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#section-10" class="xref">10</a>. <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.10.1" class="pilcrow">¶</a></p>
<ul class="toc compact ulEmpty">
<li class="toc compact ulEmpty" id="section-toc.1-1.10.2.1">
                <p id="section-toc.1-1.10.2.1.1"><a href="#section-10.1" class="xref">10.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.10.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc compact ulEmpty" id="section-toc.1-1.10.2.2">
                <p id="section-toc.1-1.10.2.2.1"><a href="#section-10.2" class="xref">10.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.10.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc compact ulEmpty" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#section-appendix.a" class="xref"></a><a href="#name-acknowledgements" class="xref">Acknowledgements</a><a href="#section-toc.1-1.11.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc compact ulEmpty" id="section-toc.1-1.12">
            <p id="section-toc.1-1.12.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a><a href="#section-toc.1-1.12.1" class="pilcrow">¶</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">One of WebRTC's key features is its support of peer-to-peer
      connections. However, when establishing such a connection, which involves
       connection attempts from various IP addresses, WebRTC may allow a web
       application to learn additional information about the user compared to an
       application that only uses the Hypertext Transfer Protocol (HTTP)
       <span>[<a href="#RFC7230" class="xref">RFC7230</a>]</span>. This may be problematic in
       certain cases. This
       document summarizes the concerns and makes recommendations on how WebRTC
       implementations should best handle the trade-off between privacy and media
       performance.<a href="#section-1-1" class="pilcrow">¶</a></p>
</section>
<section id="section-2">
      <h2 id="name-terminology">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-terminology" class="section-name selfRef">Terminology</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-problem-statement">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-problem-statement" class="section-name selfRef">Problem Statement</a>
      </h2>
<p id="section-3-1">In order to establish a peer-to-peer connection, WebRTC
      implementations use Interactive Connectivity Establishment (ICE)
      <span>[<a href="#RFC8445" class="xref">RFC8445</a>]</span>. ICE attempts to discover multiple IP
      addresses using techniques such as Session Traversal Utilities for NAT
      (STUN)
      <span>[<a href="#RFC5389" class="xref">RFC5389</a>]</span> and Traversal Using Relays
      around NAT (TURN)
      <span>[<a href="#RFC5766" class="xref">RFC5766</a>]</span> and then checks the
      connectivity of each
      local-address-remote-address pair in order to select the best one. The
      addresses that are collected usually consist of an endpoint's private
      physical or virtual addresses and its public Internet addresses.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">These addresses are provided to the web application so that
      they can be communicated to the remote endpoint for its checks. This
      allows the application to learn more about the local network
      configuration than it would from a typical HTTP scenario, in which the
      web server would only see a single public Internet address, i.e., the
      address from which the HTTP request was sent.<a href="#section-3-2" class="pilcrow">¶</a></p>
<p id="section-3-3">The additional information revealed falls into three categories:<a href="#section-3-3" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-3-4">
        <li id="section-3-4.1">If the client is multihomed, additional public IP addresses for the
        client can be learned. In particular, if the client tries to hide its
        physical location through a Virtual Private Network (VPN), and the VPN
        and local OS support routing over multiple interfaces (a "split-tunnel"
        VPN), WebRTC can discover not only the public address for the VPN, but
        also the ISP public address over which the VPN is running.<a href="#section-3-4.1" class="pilcrow">¶</a>
</li>
        <li id="section-3-4.2">If the client is behind a Network Address Translator (NAT), the
        client's private IP addresses, often
        <span>[<a href="#RFC1918" class="xref">RFC1918</a>]</span> addresses, can be learned.<a href="#section-3-4.2" class="pilcrow">¶</a>
</li>
        <li id="section-3-4.3">If the client is behind a proxy (a client-configured "classical
        application proxy", as defined in
        <span>[<a href="#RFC1919" class="xref">RFC1919</a>], <a href="https://www.rfc-editor.org/rfc/rfc1919#section-3" class="relref">Section 3</a></span>), but direct access to the
        Internet is permitted, WebRTC's STUN checks will bypass the proxy and
        reveal the public IP address of the client. This concern also applies
        to the "enterprise TURN server" scenario described in
        <span>[<a href="#RFC7478" class="xref">RFC7478</a>], <a href="https://www.rfc-editor.org/rfc/rfc7478#section-2.3.5.1" class="relref">Section 2.3.5.1</a></span> if, as above, direct
        Internet access is permitted. However, when the term "proxy" is used in
        this document, it is always in reference to an
        <span>[<a href="#RFC1919" class="xref">RFC1919</a>]</span> proxy server.<a href="#section-3-4.3" class="pilcrow">¶</a>
</li>
      </ol>
<p id="section-3-5">Of these three concerns, the first is the most significant, because for some
      users, the purpose of using a VPN is for anonymity. However, different
      VPN users will have different needs, and some VPN users (e.g., corporate
      VPN users) may in fact prefer WebRTC to send media traffic directly --
      i.e., not through the VPN.<a href="#section-3-5" class="pilcrow">¶</a></p>
<p id="section-3-6">The second concern is less significant but valid nonetheless. The core
      issue is that web applications can learn about addresses that are not
      exposed to the Internet; typically, these address are IPv4, but they can
      also be IPv6, as in the case of NAT64 <span>[<a href="#RFC6146" class="xref">RFC6146</a>]</span>.
      While disclosure of the <span>[<a href="#RFC4941" class="xref">RFC4941</a>]</span> IPv6 addresses
      recommended by <span>[<a href="#RFC8835" class="xref">RFC8835</a>]</span> is fairly
      benign due to their intentionally short lifetimes, IPv4 addresses present
      some challenges. Although private IPv4 addresses often contain minimal
      entropy (e.g., 192.168.0.2, a fairly common address), in the worst case,
      they can contain 24 bits of entropy with an indefinite lifetime. As such,
      they can be a fairly significant fingerprinting surface. In addition,
      intranet web sites can be attacked more easily when their IPv4 address
      range is externally known.<a href="#section-3-6" class="pilcrow">¶</a></p>
<p id="section-3-7">Private IP addresses can also act as an identifier that allows
      web applications running in isolated browsing contexts (e.g., normal and
      private browsing) to learn that they are running on the same device. This
      could allow the application sessions to be correlated, defeating some of
      the privacy protections provided by isolation. It should be noted that
      private addresses are just one potential mechanism for this correlation
      and this is an area for further study.<a href="#section-3-7" class="pilcrow">¶</a></p>
<p id="section-3-8">The third concern is the least common, as proxy administrators can already
      control this behavior through organizational firewall policy, and
      generally, forcing WebRTC traffic through a proxy server will have
      negative effects on both the proxy and media quality.<a href="#section-3-8" class="pilcrow">¶</a></p>
<p id="section-3-9">Note also that these concerns predate WebRTC; Adobe Flash Player has
      provided similar functionality since the introduction of Real-Time
      Media Flow Protocol (RTMFP) support
      <span>[<a href="#RFC7016" class="xref">RFC7016</a>]</span> in 2008.<a href="#section-3-9" class="pilcrow">¶</a></p>
</section>
<section id="section-4">
      <h2 id="name-goals">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-goals" class="section-name selfRef">Goals</a>
      </h2>
<p id="section-4-1">WebRTC's support of secure peer-to-peer connections facilitates
      deployment of decentralized systems, which can have privacy benefits. As
      a result, blunt solutions that disable WebRTC or make it significantly
      harder to use are undesirable. This document takes a more nuanced
      approach, with the following goals:<a href="#section-4-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4-2.1">Provide a framework for understanding the problem so that controls
        might be provided to make different trade-offs regarding performance and
        privacy concerns with WebRTC.<a href="#section-4-2.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-4-2.2">Using that framework, define settings that enable peer-to-peer
        communications, each with a different balance between performance and
        privacy.<a href="#section-4-2.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-4-2.3">Finally, provide recommendations for default settings that provide
        reasonable performance without also exposing addressing information in
        a way that might violate user expectations.<a href="#section-4-2.3" class="pilcrow">¶</a>
</li>
      </ul>
</section>
<section id="section-5">
      <h2 id="name-detailed-design">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-detailed-design" class="section-name selfRef">Detailed Design</a>
      </h2>
<section id="section-5.1">
        <h3 id="name-principles">
<a href="#section-5.1" class="section-number selfRef">5.1. </a><a href="#name-principles" class="section-name selfRef">Principles</a>
        </h3>
<p id="section-5.1-1">The key principles for our framework are stated below:<a href="#section-5.1-1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-5.1-2">
          <li id="section-5.1-2.1">By default, WebRTC traffic should follow typical IP routing (i.e.,
          WebRTC should use the same interface used for HTTP traffic) and only
          the system's 'typical' public addresses (or those of an enterprise
          TURN server, if present) should be visible to the application.
          However, in the interest of optimal media quality, it should be
          possible to enable WebRTC to make use of all network interfaces to
          determine the ideal route.<a href="#section-5.1-2.1" class="pilcrow">¶</a>
</li>
          <li id="section-5.1-2.2">By default, WebRTC should be able to negotiate direct peer-to-peer
          connections between endpoints (i.e., without traversing a NAT or
          relay server) when such connections are possible. This ensures that
          applications that need true peer-to-peer routing for bandwidth or
          latency reasons can operate successfully.<a href="#section-5.1-2.2" class="pilcrow">¶</a>
</li>
          <li id="section-5.1-2.3">It should be possible to configure WebRTC to not disclose private
          local IP addresses, to avoid the issues associated with web
          applications learning such addresses. This document does not require
          this to be the default state, as there is no currently defined
          mechanism that can satisfy this requirement as well as the
          aforementioned requirement to allow direct peer-to-peer
          connections.<a href="#section-5.1-2.3" class="pilcrow">¶</a>
</li>
          <li id="section-5.1-2.4">By default, WebRTC traffic should not be sent through proxy
          servers, due to the media-quality problems associated with sending
          WebRTC traffic over TCP, which is almost always used when
          communicating with such proxies, as well as proxy performance issues
          that may result from proxying WebRTC's long-lived, high-bandwidth
          connections. However, it should be possible to force WebRTC to send
          its traffic through a configured proxy if desired.<a href="#section-5.1-2.4" class="pilcrow">¶</a>
</li>
        </ol>
</section>
<section id="section-5.2">
        <h3 id="name-modes-and-recommendations">
<a href="#section-5.2" class="section-number selfRef">5.2. </a><a href="#name-modes-and-recommendations" class="section-name selfRef">Modes and Recommendations</a>
        </h3>
<p id="section-5.2-1">Based on these ideas, we define four specific modes of WebRTC
        behavior, reflecting different media quality/privacy trade-offs:<a href="#section-5.2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlNewline" id="section-5.2-2">
          <dt id="section-5.2-2.1">Mode 1 - Enumerate all addresses:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.2">WebRTC <span class="bcp14">MUST</span> use all network interfaces to
          attempt communication with STUN servers, TURN servers, or peers. This
          will converge on the best media path and is ideal when media
          performance is the highest priority, but it discloses the most
          information.<a href="#section-5.2-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.3">Mode 2 - Default route + associated local addresses:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.4">WebRTC
     <span class="bcp14">MUST</span> follow the
          kernel routing table rules, which will typically cause media packets
          to take the same route as the application's HTTP traffic. If an
          enterprise TURN server is present, the preferred route <span class="bcp14">MUST</span> be
          through this TURN server. Once an interface has been chosen, the
          private IPv4 and IPv6 addresses associated with this interface <span class="bcp14">MUST</span>
          be discovered and provided to the application as host candidates.
          This ensures that direct connections can still be established in this
          mode.<a href="#section-5.2-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.5">Mode 3 - Default route only: </dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.6">This is the same as Mode 2, except that
          the associated private addresses <span class="bcp14">MUST NOT</span> be provided; the only IP
          addresses gathered are those discovered via mechanisms like STUN and
          TURN (on the default route). This may cause traffic to hairpin
          through a NAT, fall back to an application TURN server, or fail
          altogether, with resulting quality implications.<a href="#section-5.2-2.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-5.2-2.7">Mode 4 - Force proxy:</dt>
          <dd style="margin-left: 1.5em" id="section-5.2-2.8">This is the same as Mode 3, but when the
          application's HTTP traffic is sent through a proxy, WebRTC media
          traffic <span class="bcp14">MUST</span> also be proxied. If the proxy does not support UDP (as
          is the case for all HTTP and most SOCKS
          <span>[<a href="#RFC1928" class="xref">RFC1928</a>]</span> proxies), or the WebRTC implementation does
          not support UDP proxying, the use of UDP will be disabled, and TCP
          will be used to send and receive media through the proxy. Use of TCP
          will result in reduced media quality, in addition to any performance
          considerations associated with sending all WebRTC media through the
          proxy server.<a href="#section-5.2-2.8" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
<p id="section-5.2-3">Mode 1 <span class="bcp14">MUST NOT</span> be used unless user consent has been provided. The
        details of this consent are left to the implementation; one potential
        mechanism is to tie this consent to getUserMedia (device permissions)
        consent, described in <span>[<a href="#RFC8827" class="xref">RFC8827</a>], <a href="https://www.rfc-editor.org/rfc/rfc8827#section-6.2" class="relref">Section 6.2</a></span>.
        Alternatively, implementations can provide a specific
        mechanism to obtain user consent.<a href="#section-5.2-3" class="pilcrow">¶</a></p>
<p id="section-5.2-4">In cases where user consent has not been obtained, Mode 2 <span class="bcp14">SHOULD</span> be
        used.<a href="#section-5.2-4" class="pilcrow">¶</a></p>
<p id="section-5.2-5">These defaults provide a reasonable trade-off that permits trusted
        WebRTC applications to achieve optimal network performance but gives
        applications without consent (e.g., 1-way streaming or data-channel
        applications) only the minimum information needed to achieve direct
        connections, as defined in Mode 2. However, implementations <span class="bcp14">MAY</span> choose
        stricter modes if desired, e.g., if a user indicates they want all
        WebRTC traffic to follow the default route.<a href="#section-5.2-5" class="pilcrow">¶</a></p>
<p id="section-5.2-6">Future documents may define additional modes and/or update the
        recommended default modes.<a href="#section-5.2-6" class="pilcrow">¶</a></p>
<p id="section-5.2-7">Note that the suggested defaults can still be used even for
        organizations that want all external WebRTC traffic to traverse a proxy
        or enterprise TURN server, simply by setting an organizational firewall
        policy that allows WebRTC traffic to only leave through the proxy or
        TURN server. This provides a way to ensure the proxy or TURN server is
        used for any external traffic but still allows direct connections
        (and, in the proxy case, avoids the performance issues associated with
        forcing media through said proxy) for intra-organization traffic.<a href="#section-5.2-7" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-6">
      <h2 id="name-implementation-guidance">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-implementation-guidance" class="section-name selfRef">Implementation Guidance</a>
      </h2>
<p id="section-6-1">This section provides guidance to WebRTC implementations on how to
      implement the policies described above.<a href="#section-6-1" class="pilcrow">¶</a></p>
<section id="section-6.1">
        <h3 id="name-ensuring-normal-routing">
<a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-ensuring-normal-routing" class="section-name selfRef">Ensuring Normal Routing</a>
        </h3>
<p id="section-6.1-1">When trying to follow typical IP routing, as required by Modes 2
        and 3, the simplest approach is
        to bind() the sockets used for peer-to-peer connections to the wildcard
        addresses (0.0.0.0 for IPv4, :: for IPv6), which allows the OS to route
        WebRTC traffic the same way as it would HTTP traffic. STUN and TURN
        will work as usual, and host candidates can still be determined as
        mentioned below.<a href="#section-6.1-1" class="pilcrow">¶</a></p>
</section>
<section id="section-6.2">
        <h3 id="name-determining-associated-loca">
<a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-determining-associated-loca" class="section-name selfRef">Determining Associated Local Addresses</a>
        </h3>
<p id="section-6.2-1">When binding to a wildcard address, some extra work is needed to
        determine the associated local address required by Mode 2, which we
        define as the source
        address that would be used for any packets sent to the web application
        host (assuming that UDP and TCP get the same routing treatment). Use of
        the web-application host as a destination ensures the right source
        address is selected, regardless of where the application resides (e.g.,
        on an intranet).<a href="#section-6.2-1" class="pilcrow">¶</a></p>
<p id="section-6.2-2">First, the appropriate remote IPv4/IPv6 address is obtained by
        resolving the host component of the web application URI
        <span>[<a href="#RFC3986" class="xref">RFC3986</a>]</span>. If the client is behind a proxy and cannot
        resolve these IPs via DNS, the address of the proxy can be used
        instead. Or, if the web application was loaded from a file:// URI
        <span>[<a href="#RFC8089" class="xref">RFC8089</a>]</span> rather than over the network, the
        implementation can fall back to a well-known DNS name or IP
        address.<a href="#section-6.2-2" class="pilcrow">¶</a></p>
<p id="section-6.2-3">Once a suitable remote IP has been determined, the implementation
        can create a UDP socket, bind() it to the appropriate wildcard address,
        and then connect() to the remote IP. Generally, this results in
        the socket being assigned a local address based on the kernel routing
        table, without sending any packets over the network.<a href="#section-6.2-3" class="pilcrow">¶</a></p>
<p id="section-6.2-4">Finally, the socket can be queried using getsockname() or the
        equivalent to determine the appropriate local address.<a href="#section-6.2-4" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-7">
      <h2 id="name-application-guidance">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-application-guidance" class="section-name selfRef">Application Guidance</a>
      </h2>
<p id="section-7-1">The recommendations mentioned in this document may cause certain
      WebRTC applications to malfunction. In order to be robust in all
      scenarios, the following guidelines are provided for applications:<a href="#section-7-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-7-2.1">Applications <span class="bcp14">SHOULD</span> deploy a TURN server with support for both UDP
        and TCP connections to the server. This ensures that connectivity can
        still be established, even when Mode 3 or 4 is in use, assuming the
        TURN server can be reached.<a href="#section-7-2.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-7-2.2">Applications <span class="bcp14">SHOULD</span> detect when they don't have access to the full
        set of ICE candidates by checking for the presence of host candidates.
        If no host candidates are present, Mode 3 or 4 is in use; this
        knowledge can be useful for diagnostic purposes.<a href="#section-7-2.2" class="pilcrow">¶</a>
</li>
      </ul>
</section>
<section id="section-8">
      <h2 id="name-security-considerations">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-8-1">This document describes several potential privacy and security concerns
      associated with WebRTC peer-to-peer connections and provides mechanisms
      and recommendations for WebRTC implementations to address these concerns.<a href="#section-8-1" class="pilcrow">¶</a></p>
</section>
<section id="section-9">
      <h2 id="name-iana-considerations">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-9-1">This document has no IANA actions.<a href="#section-9-1" class="pilcrow">¶</a></p>
</section>
<section id="section-10">
      <h2 id="name-references">
<a href="#section-10" class="section-number selfRef">10. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-10.1">
        <h3 id="name-normative-references">
<a href="#section-10.1" class="section-number selfRef">10.1. </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="RFC3986">[RFC3986]</dt>
        <dd>
<span class="refAuthor">Berners-Lee, T.</span><span class="refAuthor">, Fielding, R.</span><span class="refAuthor">, and L. Masinter</span>, <span class="refTitle">"Uniform Resource Identifier (URI): Generic Syntax"</span>, <span class="seriesInfo">STD 66</span>, <span class="seriesInfo">RFC 3986</span>, <span class="seriesInfo">DOI 10.17487/RFC3986</span>, <time datetime="2005-01" class="refDate">January 2005</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3986">https://www.rfc-editor.org/info/rfc3986</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5389">[RFC5389]</dt>
        <dd>
<span class="refAuthor">Rosenberg, J.</span><span class="refAuthor">, Mahy, R.</span><span class="refAuthor">, Matthews, P.</span><span class="refAuthor">, and D. Wing</span>, <span class="refTitle">"Session Traversal Utilities for NAT (STUN)"</span>, <span class="seriesInfo">RFC 5389</span>, <span class="seriesInfo">DOI 10.17487/RFC5389</span>, <time datetime="2008-10" class="refDate">October 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5389">https://www.rfc-editor.org/info/rfc5389</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5766">[RFC5766]</dt>
        <dd>
<span class="refAuthor">Mahy, R.</span><span class="refAuthor">, Matthews, P.</span><span class="refAuthor">, and J. Rosenberg</span>, <span class="refTitle">"Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)"</span>, <span class="seriesInfo">RFC 5766</span>, <span class="seriesInfo">DOI 10.17487/RFC5766</span>, <time datetime="2010-04" class="refDate">April 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5766">https://www.rfc-editor.org/info/rfc5766</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8089">[RFC8089]</dt>
        <dd>
<span class="refAuthor">Kerwin, M.</span>, <span class="refTitle">"The "file" URI Scheme"</span>, <span class="seriesInfo">RFC 8089</span>, <span class="seriesInfo">DOI 10.17487/RFC8089</span>, <time datetime="2017-02" class="refDate">February 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8089">https://www.rfc-editor.org/info/rfc8089</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>
<dt id="RFC8445">[RFC8445]</dt>
      <dd>
<span class="refAuthor">Keranen, A.</span><span class="refAuthor">, Holmberg, C.</span><span class="refAuthor">, and J. Rosenberg</span>, <span class="refTitle">"Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal"</span>, <span class="seriesInfo">RFC 8445</span>, <span class="seriesInfo">DOI 10.17487/RFC8445</span>, <time datetime="2018-07" class="refDate">July 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8445">https://www.rfc-editor.org/info/rfc8445</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-10.2">
        <h3 id="name-informative-references">
<a href="#section-10.2" class="section-number selfRef">10.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC1918">[RFC1918]</dt>
        <dd>
<span class="refAuthor">Rekhter, Y.</span><span class="refAuthor">, Moskowitz, B.</span><span class="refAuthor">, Karrenberg, D.</span><span class="refAuthor">, de Groot, G. J.</span><span class="refAuthor">, and E. Lear</span>, <span class="refTitle">"Address Allocation for Private Internets"</span>, <span class="seriesInfo">BCP 5</span>, <span class="seriesInfo">RFC 1918</span>, <span class="seriesInfo">DOI 10.17487/RFC1918</span>, <time datetime="1996-02" class="refDate">February 1996</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1918">https://www.rfc-editor.org/info/rfc1918</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC1919">[RFC1919]</dt>
        <dd>
<span class="refAuthor">Chatel, M.</span>, <span class="refTitle">"Classical versus Transparent IP Proxies"</span>, <span class="seriesInfo">RFC 1919</span>, <span class="seriesInfo">DOI 10.17487/RFC1919</span>, <time datetime="1996-03" class="refDate">March 1996</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1919">https://www.rfc-editor.org/info/rfc1919</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC1928">[RFC1928]</dt>
        <dd>
<span class="refAuthor">Leech, M.</span><span class="refAuthor">, Ganis, M.</span><span class="refAuthor">, Lee, Y.</span><span class="refAuthor">, Kuris, R.</span><span class="refAuthor">, Koblas, D.</span><span class="refAuthor">, and L. Jones</span>, <span class="refTitle">"SOCKS Protocol Version 5"</span>, <span class="seriesInfo">RFC 1928</span>, <span class="seriesInfo">DOI 10.17487/RFC1928</span>, <time datetime="1996-03" class="refDate">March 1996</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1928">https://www.rfc-editor.org/info/rfc1928</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4941">[RFC4941]</dt>
        <dd>
<span class="refAuthor">Narten, T.</span><span class="refAuthor">, Draves, R.</span><span class="refAuthor">, and S. Krishnan</span>, <span class="refTitle">"Privacy Extensions for Stateless Address Autoconfiguration in IPv6"</span>, <span class="seriesInfo">RFC 4941</span>, <span class="seriesInfo">DOI 10.17487/RFC4941</span>, <time datetime="2007-09" class="refDate">September 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4941">https://www.rfc-editor.org/info/rfc4941</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6146">[RFC6146]</dt>
        <dd>
<span class="refAuthor">Bagnulo, M.</span><span class="refAuthor">, Matthews, P.</span><span class="refAuthor">, and I. van Beijnum</span>, <span class="refTitle">"Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers"</span>, <span class="seriesInfo">RFC 6146</span>, <span class="seriesInfo">DOI 10.17487/RFC6146</span>, <time datetime="2011-04" class="refDate">April 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6146">https://www.rfc-editor.org/info/rfc6146</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7016">[RFC7016]</dt>
        <dd>
<span class="refAuthor">Thornburgh, M.</span>, <span class="refTitle">"Adobe's Secure Real-Time Media Flow Protocol"</span>, <span class="seriesInfo">RFC 7016</span>, <span class="seriesInfo">DOI 10.17487/RFC7016</span>, <time datetime="2013-11" class="refDate">November 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7016">https://www.rfc-editor.org/info/rfc7016</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7230">[RFC7230]</dt>
        <dd>
<span class="refAuthor">Fielding, R., Ed.</span><span class="refAuthor"> and J. Reschke, Ed.</span>, <span class="refTitle">"Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing"</span>, <span class="seriesInfo">RFC 7230</span>, <span class="seriesInfo">DOI 10.17487/RFC7230</span>, <time datetime="2014-06" class="refDate">June 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7230">https://www.rfc-editor.org/info/rfc7230</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7478">[RFC7478]</dt>
        <dd>
<span class="refAuthor">Holmberg, C.</span><span class="refAuthor">, Hakansson, S.</span><span class="refAuthor">, and G. Eriksson</span>, <span class="refTitle">"Web Real-Time Communication Use Cases and Requirements"</span>, <span class="seriesInfo">RFC 7478</span>, <span class="seriesInfo">DOI 10.17487/RFC7478</span>, <time datetime="2015-03" class="refDate">March 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7478">https://www.rfc-editor.org/info/rfc7478</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8827">[RFC8827]</dt>
        <dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refTitle">"WebRTC Security Architecture"</span>, <span class="seriesInfo">RFC 8827</span>, <span class="seriesInfo">DOI 10.17487/RFC8827</span>, <time datetime="2021-01" class="refDate">January 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8827">https://www.rfc-editor.org/info/rfc8827</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8835">[RFC8835]</dt>
      <dd>
<span class="refAuthor">Alvestrand, H.</span>, <span class="refTitle">"Transports for WebRTC"</span>, <span class="seriesInfo">RFC 8835</span>, <span class="seriesInfo">DOI 10.17487/RFC8835</span>, <time datetime="2021-01" class="refDate">January 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8835">https://www.rfc-editor.org/info/rfc8835</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<section id="section-appendix.a">
      <h2 id="name-acknowledgements">
<a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a>
      </h2>
<p id="section-appendix.a-1">Several people provided input into this document, including <span class="contact-name">Bernard       Aboba</span>, <span class="contact-name">Harald Alvestrand</span>, <span class="contact-name">Youenn       Fablet</span>, <span class="contact-name">Ted Hardie</span>, <span class="contact-name">Matthew Kaufmann</span>,
      <span class="contact-name">Eric Rescorla</span>, <span class="contact-name">Adam Roach</span>, and
 <span class="contact-name">Martin Thomson</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">Justin Uberti</span></div>
<div dir="auto" class="left"><span class="org">Google</span></div>
<div dir="auto" class="left"><span class="street-address">747 6th St S</span></div>
<div dir="auto" class="left">
<span class="locality">Kirkland</span>, <span class="region">WA</span> <span class="postal-code">98033</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:justin@uberti.name" class="email">justin@uberti.name</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Guo-wei Shieh</span></div>
<div dir="auto" class="left"><span class="street-address">333 Elliott Ave W #500</span></div>
<div dir="auto" class="left">
<span class="locality">Seattle</span>, <span class="region">WA</span> <span class="postal-code">98119</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:guoweis@gmail.com" class="email">guoweis@gmail.com</a>
</div>
</address>
</section>
</div>
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