File: rfc9308.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 9308: Applicability of the QUIC Transport Protocol</title>
<meta content="Mirja Kühlewind" name="author">
<meta content="Brian Trammell" name="author">
<meta content="
       This document discusses the applicability of the QUIC transport protocol,
focusing on caveats impacting application protocol development and deployment
over QUIC. Its intended audience is designers of application protocol mappings
to QUIC and implementors of these application protocols. 
    " name="description">
<meta content="xml2rfc 3.15.0" name="generator">
<meta content="QUIC" name="keyword">
<meta content="application protocol mapping" name="keyword">
<meta content="deployment" name="keyword">
<meta content="9308" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.15.0
    Python 3.9.13
    appdirs 1.4.4
    ConfigArgParse 1.5.3
    google-i18n-address 2.5.1
    html5lib 1.1
    intervaltree 3.1.0
    Jinja2 3.1.2
    kitchen 1.2.6
    lxml 4.9.0
    MarkupSafe 2.1.1
    pycountry 22.3.5
    PyYAML 6.0
    requests 2.28.0
    setuptools 44.1.1
    six 1.16.0
    weasyprint 56.1
-->
<link href="rfc9308.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 {
  display: table;
  border: none;
  margin: 0 auto;
}

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

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

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

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

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

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

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

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

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

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

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

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

.refInstance {
  margin-bottom: 1.25em;
}

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

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

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

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

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

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

/* pagination */
@media print {
  body {

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

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

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

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

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

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

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

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

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

}

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


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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
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<body class="xml2rfc">
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<table class="ears">
<thead><tr>
<td class="left">RFC 9308</td>
<td class="center">QUIC Applicability</td>
<td class="right">September 2022</td>
</tr></thead>
<tfoot><tr>
<td class="left">Kühlewind &amp; Trammell</td>
<td class="center">Informational</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/rfc9308" class="eref">9308</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Informational</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2022-09" class="published">September 2022</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Authors:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">M. Kühlewind</div>
<div class="org">Ericsson</div>
</div>
<div class="author">
      <div class="author-name">B. Trammell</div>
<div class="org">Google Switzerland GmbH</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9308</h1>
<h1 id="title">Applicability of the QUIC Transport Protocol</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document discusses the applicability of the QUIC transport protocol,
focusing on caveats impacting application protocol development and deployment
over QUIC. Its intended audience is designers of application protocol mappings
to QUIC and implementors of these application protocols.<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 document is not an Internet Standards Track specification; it is
            published for informational purposes.<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).  Not all documents
            approved by the IESG are candidates for any level of Internet
            Standard; see 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/rfc9308">https://www.rfc-editor.org/info/rfc9308</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2022 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Revised BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Revised BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="auto internal xref">1</a>.  <a href="#name-introduction" class="internal xref">Introduction</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="auto internal xref">2</a>.  <a href="#name-the-necessity-of-fallback" class="internal xref">The Necessity of Fallback</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="auto internal xref">3</a>.  <a href="#name-0-rtt" class="internal xref">0-RTT</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1" class="keepWithNext"><a href="#section-3.1" class="auto internal xref">3.1</a>.  <a href="#name-replay-attacks" class="internal xref">Replay Attacks</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="auto internal xref">3.2</a>.  <a href="#name-session-resumption-versus-k" class="internal xref">Session Resumption versus Keep-Alive</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="auto internal xref">4</a>.  <a href="#name-use-of-streams" class="internal xref">Use of Streams</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="auto internal xref">4.1</a>.  <a href="#name-stream-versus-flow-multiple" class="internal xref">Stream versus Flow Multiplexing</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="auto internal xref">4.2</a>.  <a href="#name-prioritization" class="internal xref">Prioritization</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.3">
                <p id="section-toc.1-1.4.2.3.1"><a href="#section-4.3" class="auto internal xref">4.3</a>.  <a href="#name-ordered-and-reliable-delive" class="internal xref">Ordered and Reliable Delivery</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.4">
                <p id="section-toc.1-1.4.2.4.1"><a href="#section-4.4" class="auto internal xref">4.4</a>.  <a href="#name-flow-control-deadlocks" class="internal xref">Flow Control Deadlocks</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.5">
                <p id="section-toc.1-1.4.2.5.1"><a href="#section-4.5" class="auto internal xref">4.5</a>.  <a href="#name-stream-limit-commitments" class="internal xref">Stream Limit Commitments</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="auto internal xref">5</a>.  <a href="#name-packetization-and-latency" class="internal xref">Packetization and Latency</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="auto internal xref">6</a>.  <a href="#name-error-handling" class="internal xref">Error Handling</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="auto internal xref">7</a>.  <a href="#name-acknowledgment-efficiency" class="internal xref">Acknowledgment Efficiency</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-8" class="auto internal xref">8</a>.  <a href="#name-port-selection-and-applicat" class="internal xref">Port Selection and Application Endpoint Discovery</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8.2.1">
                <p id="section-toc.1-1.8.2.1.1"><a href="#section-8.1" class="auto internal xref">8.1</a>.  <a href="#name-source-port-selection" class="internal xref">Source Port Selection</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-9" class="auto internal xref">9</a>.  <a href="#name-connection-migration" class="internal xref">Connection Migration</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#section-10" class="auto internal xref">10</a>. <a href="#name-connection-termination" class="internal xref">Connection Termination</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#section-11" class="auto internal xref">11</a>. <a href="#name-information-exposure-and-th" class="internal xref">Information Exposure and the Connection ID</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11.2.1">
                <p id="section-toc.1-1.11.2.1.1"><a href="#section-11.1" class="auto internal xref">11.1</a>.  <a href="#name-server-generated-connection" class="internal xref">Server-Generated Connection ID</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11.2.2">
                <p id="section-toc.1-1.11.2.2.1"><a href="#section-11.2" class="auto internal xref">11.2</a>.  <a href="#name-mitigating-timing-linkabili" class="internal xref">Mitigating Timing Linkability with Connection ID Migration</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11.2.3">
                <p id="section-toc.1-1.11.2.3.1"><a href="#section-11.3" class="auto internal xref">11.3</a>.  <a href="#name-using-server-retry-for-redi" class="internal xref">Using Server Retry for Redirection</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.12">
            <p id="section-toc.1-1.12.1"><a href="#section-12" class="auto internal xref">12</a>. <a href="#name-quality-of-service-qos-and-" class="internal xref">Quality of Service (QoS) and Diffserv Code Point (DSCP)</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.13">
            <p id="section-toc.1-1.13.1"><a href="#section-13" class="auto internal xref">13</a>. <a href="#name-use-of-versions-and-cryptog" class="internal xref">Use of Versions and Cryptographic Handshake</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.14">
            <p id="section-toc.1-1.14.1"><a href="#section-14" class="auto internal xref">14</a>. <a href="#name-enabling-deployment-of-new-" class="internal xref">Enabling Deployment of New Versions</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.15">
            <p id="section-toc.1-1.15.1"><a href="#section-15" class="auto internal xref">15</a>. <a href="#name-unreliable-datagram-service" class="internal xref">Unreliable Datagram Service over QUIC</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.16">
            <p id="section-toc.1-1.16.1"><a href="#section-16" class="auto internal xref">16</a>. <a href="#name-iana-considerations" class="internal xref">IANA Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.17">
            <p id="section-toc.1-1.17.1"><a href="#section-17" class="auto internal xref">17</a>. <a href="#name-security-considerations" class="internal xref">Security Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.18">
            <p id="section-toc.1-1.18.1"><a href="#section-18" class="auto internal xref">18</a>. <a href="#name-references" class="internal xref">References</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.18.2.1">
                <p id="section-toc.1-1.18.2.1.1"><a href="#section-18.1" class="auto internal xref">18.1</a>.  <a href="#name-normative-references" class="internal xref">Normative References</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.18.2.2">
                <p id="section-toc.1-1.18.2.2.1"><a href="#section-18.2" class="auto internal xref">18.2</a>.  <a href="#name-informative-references" class="internal xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.19">
            <p id="section-toc.1-1.19.1"><a href="#appendix-A" class="auto internal xref"></a><a href="#name-acknowledgments" class="internal xref">Acknowledgments</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.20">
            <p id="section-toc.1-1.20.1"><a href="#appendix-B" class="auto internal xref"></a><a href="#name-contributors" class="internal xref">Contributors</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.21">
            <p id="section-toc.1-1.21.1"><a href="#appendix-C" class="auto internal xref"></a><a href="#name-authors-addresses" class="internal xref">Authors' Addresses</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<div id="introduction">
<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">QUIC <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span> is a new transport protocol providing a number of
advanced features. While initially designed for the HTTP use case, it provides
capabilities that can be used with a much wider variety of applications. QUIC is
encapsulated in UDP. QUIC version 1 integrates TLS 1.3 <span>[<a href="#RFC8446" class="cite xref">TLS13</a>]</span> to
encrypt all payload data and most control information. The version of HTTP that
uses QUIC is known as HTTP/3 <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">This document provides guidance for application developers who want to use
the QUIC protocol without implementing it on their own. This includes general
guidance for applications operating over HTTP/3 or directly over QUIC.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">In the following sections, we discuss specific caveats to QUIC's applicability
and issues that application developers must consider when using QUIC as a
transport for their applications.<a href="#section-1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="fallback">
<section id="section-2">
      <h2 id="name-the-necessity-of-fallback">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-the-necessity-of-fallback" class="section-name selfRef">The Necessity of Fallback</a>
      </h2>
<p id="section-2-1">QUIC uses UDP as a substrate. This enables userspace implementation and permits
traversal of network middleboxes (including NAT) without requiring updates to
existing network infrastructure.<a href="#section-2-1" class="pilcrow">¶</a></p>
<p id="section-2-2">Measurement studies have shown between 3% <span>[<a href="#Trammell16" class="cite xref">Trammell16</a>]</span> and
5% <span>[<a href="#Swett16" class="cite xref">Swett16</a>]</span> of networks block all UDP traffic, though there
is little evidence of other forms of systematic disadvantage to UDP traffic
compared to TCP <span>[<a href="#Edeline16" class="cite xref">Edeline16</a>]</span>. This blocking implies that all applications
running on top of QUIC must either be prepared to accept connectivity failure
on such networks or be engineered to fall back to some other transport
protocol. In the case of HTTP, this fallback is TLS over TCP.<a href="#section-2-2" class="pilcrow">¶</a></p>
<p id="section-2-3">The IETF Transport Services (TAPS) specifications <span>[<a href="#I-D.ietf-taps-arch" class="cite xref">TAPS-ARCH</a>]</span> describe a system with a
common API for multiple protocols. This is particularly relevant for QUIC as
it addresses the implications of fallback among multiple protocols.<a href="#section-2-3" class="pilcrow">¶</a></p>
<p id="section-2-4">Specifically, fallback to insecure protocols or to weaker versions of secure
protocols needs to be avoided. In general, an application that implements
fallback needs to consider the security consequences. A fallback to TCP and
TLS exposes control information to modification and manipulation in the
network. Additionally, downgrades to TLS versions older than 1.3, which is
used in QUIC version 1, might result in significantly weaker
cryptographic protection. For example, the results of protocol negotiation
<span>[<a href="#RFC7301" class="cite xref">RFC7301</a>]</span> only have confidentiality protection if TLS 1.3 is used.<a href="#section-2-4" class="pilcrow">¶</a></p>
<p id="section-2-5">These applications must operate, perhaps with impaired functionality, in the
absence of features provided by QUIC not present in the fallback protocol. For
fallback to TLS over TCP, the most obvious difference is that TCP does not
provide stream multiplexing, and therefore stream multiplexing would need to be
implemented in the application layer if needed. Further, TCP implementations
and network paths often do not support the TCP Fast Open (TFO) option <span>[<a href="#RFC7413" class="cite xref">RFC7413</a>]</span>, which
enables sending of payload data together with the first control packet of a new
connection as also provided by 0-RTT session resumption in QUIC. Note that
there is some evidence of middleboxes blocking SYN data even if TFO was
successfully negotiated (see <span>[<a href="#PaaschNanog" class="cite xref">PaaschNanog</a>]</span>). And even if Fast Open
successfully operates end to end, it is limited to a single packet of TLS
handshake and application data, unlike QUIC 0-RTT.<a href="#section-2-5" class="pilcrow">¶</a></p>
<p id="section-2-6">Moreover, while encryption (in this case TLS) is inseparably integrated with
QUIC, TLS negotiation over TCP can be blocked. If TLS over TCP cannot be
supported, the connection should be aborted, and the application then ought
to present a suitable prompt to the user that secure communication is
unavailable.<a href="#section-2-6" class="pilcrow">¶</a></p>
<p id="section-2-7">In summary, any fallback mechanism is likely to impose a degradation of
performance and can degrade security; however, fallback must not silently
violate the application's expectation of confidentiality or integrity of its
payload data.<a href="#section-2-7" class="pilcrow">¶</a></p>
</section>
</div>
<div id="zero-rtt">
<section id="section-3">
      <h2 id="name-0-rtt">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-0-rtt" class="section-name selfRef">0-RTT</a>
      </h2>
<p id="section-3-1">QUIC provides for 0-RTT connection establishment. Though the same facility
exists in TLS 1.3 with TCP, 0-RTT presents opportunities and challenges for
applications using QUIC.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">A transport protocol that provides 0-RTT connection establishment is
qualitatively different from one that does not provide 0-RTT from the point of view of the
application using it. Relative trade-offs between the cost of closing and
reopening a connection and trying to keep it open are different; see
<a href="#resumption-v-keepalive" class="auto internal xref">Section 3.2</a>.<a href="#section-3-2" class="pilcrow">¶</a></p>
<p id="section-3-3">An application needs to deliberately choose to use 0-RTT, as 0-RTT carries a
risk of replay attack.  Application protocols that use 0-RTT require a profile
that describes the types of information that can be safely sent. For HTTP, this
profile is described in <span>[<a href="#RFC8470" class="cite xref">HTTP-REPLAY</a>]</span>.<a href="#section-3-3" class="pilcrow">¶</a></p>
<div id="replay-attacks">
<section id="section-3.1">
        <h3 id="name-replay-attacks">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-replay-attacks" class="section-name selfRef">Replay Attacks</a>
        </h3>
<p id="section-3.1-1">Retransmission or malicious replay of data contained in 0-RTT packets could
cause the server side to receive multiple copies of the same data.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<p id="section-3.1-2">Application data sent by the client in 0-RTT packets could be processed more
than once if it is replayed. Applications need to be aware of what is safe to
send in 0-RTT. Application protocols that seek to enable the use of 0-RTT need
a careful analysis and a description of what can be sent in 0-RTT; see
<span><a href="https://www.rfc-editor.org/rfc/rfc9001#section-5.6" class="relref">Section 5.6</a> of [<a href="#RFC9001" class="cite xref">QUIC-TLS</a>]</span>.<a href="#section-3.1-2" class="pilcrow">¶</a></p>
<p id="section-3.1-3">In some cases, it might be sufficient to limit application data sent in 0-RTT
to data that does not cause actions with lasting effects at a 
server. Initiating data retrieval or establishing configuration are
examples of actions that could be safe. Idempotent operations -- those for which
repetition has the same net effect as a single operation -- might be safe.
However, it is also possible to combine individually idempotent operations into
a non-idempotent sequence of operations.<a href="#section-3.1-3" class="pilcrow">¶</a></p>
<p id="section-3.1-4">Once a server accepts 0-RTT data, there is no means of selectively discarding
data that is received. However, protocols can define ways to reject individual
actions that might be unsafe if replayed.<a href="#section-3.1-4" class="pilcrow">¶</a></p>
<p id="section-3.1-5">Some TLS implementations and deployments might be able to provide partial or
even complete replay protection, which could be used to manage replay risk.<a href="#section-3.1-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="resumption-v-keepalive">
<section id="section-3.2">
        <h3 id="name-session-resumption-versus-k">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-session-resumption-versus-k" class="section-name selfRef">Session Resumption versus Keep-Alive</a>
        </h3>
<p id="section-3.2-1">Because QUIC is encapsulated in UDP, applications using QUIC must deal with
short network idle timeouts. Deployed stateful middleboxes will generally
establish state for UDP flows on the first packet sent and keep state for
much shorter idle periods than for TCP. <span>[<a href="#RFC5382" class="cite xref">RFC5382</a>]</span> suggests a TCP idle
period of at least 124 minutes, though there is no evidence of widespread
implementation of this guideline in the literature. However, short network timeout for
UDP is well-documented. According to a 2010 study
(<span>[<a href="#Hatonen10" class="cite xref">Hatonen10</a>]</span>), UDP applications can assume that any NAT binding or other
state entry can expire after just thirty seconds of inactivity.  <span><a href="https://www.rfc-editor.org/rfc/rfc8085#section-3.5" class="relref">Section 3.5</a> of [<a href="#RFC8085" class="cite xref">RFC8085</a>]</span> further discusses keep-alive intervals for UDP: it
requires that there is a minimum value of 15 seconds, but recommends larger values, or that keep-alive is omitted entirely.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<p id="section-3.2-2">By using a connection ID, QUIC is designed to be robust to NAT 
rebinding after a timeout. However, this only helps if one endpoint maintains
availability at the address its peer uses and the peer is the one to send
after the timeout occurs.<a href="#section-3.2-2" class="pilcrow">¶</a></p>
<p id="section-3.2-3">Some QUIC connections might not be robust to NAT rebinding because the routing
infrastructure (in particular, load balancers) uses the address/port 4-tuple
to direct traffic. Furthermore, middleboxes with functions other than address
translation could still affect the path. In particular, some firewalls do not
admit server traffic for which the firewall has no recent state for a
corresponding packet sent from the client.<a href="#section-3.2-3" class="pilcrow">¶</a></p>
<p id="section-3.2-4">QUIC applications can adjust idle periods to manage the risk of timeout. Idle
periods and the network idle timeout are distinct from the connection idle
timeout, which is defined as the minimum of either endpoint's idle timeout
parameter; see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-10.1" class="relref">Section 10.1</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>. There are three options:<a href="#section-3.2-4" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-3.2-5.1">Ignore the issue if the application-layer protocol consists only of
interactions with no or very short idle periods or if the protocol's resistance
to NAT rebinding is sufficient.<a href="#section-3.2-5.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-3.2-5.2">Ensure there are no long idle periods.<a href="#section-3.2-5.2" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-3.2-5.3">Resume the session after a long idle period, using 0-RTT resumption when
appropriate.<a href="#section-3.2-5.3" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-3.2-6">The first strategy is the easiest, but it only applies to certain applications.<a href="#section-3.2-6" class="pilcrow">¶</a></p>
<p id="section-3.2-7">Either the server or the client in a QUIC application can send PING frames as
keep-alives to prevent the connection and any on-path state from timing out.
Recommendations for the use of keep-alives are application specific, mainly
depending on the latency requirements and message frequency of the application.
In this case, the application mapping must specify whether the client or server
is responsible for keeping the application alive.  While <span>[<a href="#Hatonen10" class="cite xref">Hatonen10</a>]</span> suggests
that 30 seconds might be a suitable value for the public Internet when a NAT
is on path, larger values are preferable if the deployment can consistently
survive NAT rebinding or is known to be in a controlled environment (e.g.,
data centers) in order to lower network and computational load.<a href="#section-3.2-7" class="pilcrow">¶</a></p>
<p id="section-3.2-8">Sending PING frames more frequently than every 30 seconds over long idle
periods may result in excessive unproductive traffic in some situations and
unacceptable power usage for power-constrained (mobile) devices. Additionally,
timeouts shorter than 30 seconds can make it harder to handle transient network
interruptions, such as Virtual Machine (VM) migration or coverage loss during mobility.
See <span>[<a href="#RFC8085" class="cite xref">RFC8085</a>]</span>, especially Section <a href="https://www.rfc-editor.org/rfc/rfc8085#section-3.5" class="relref">3.5</a>.<a href="#section-3.2-8" class="pilcrow">¶</a></p>
<p id="section-3.2-9">Alternatively, the client (but not the server) can use session resumption
instead of sending keep-alive traffic. In this case, a client that wants to send
data to a server over a connection that has been idle longer than the server's
idle timeout (available from the idle_timeout transport parameter) can simply
reconnect. When possible, this reconnection can use 0-RTT session resumption,
reducing the latency involved with restarting the connection. Of course, this
approach is only valid in cases in which it is safe to use 0-RTT and when the
client is the restarting peer.<a href="#section-3.2-9" class="pilcrow">¶</a></p>
<p id="section-3.2-10">The trade-offs between resumption and keep-alives need to be evaluated on a
per-application basis. In general, applications should use keep-alives only in
circumstances where continued communication is highly likely; <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>, for
instance, recommends using keep-alives only when a request is outstanding.<a href="#section-3.2-10" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="use-of-streams">
<section id="section-4">
      <h2 id="name-use-of-streams">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-use-of-streams" class="section-name selfRef">Use of Streams</a>
      </h2>
<p id="section-4-1">QUIC's stream multiplexing feature allows applications to run multiple streams
over a single connection without head-of-line blocking between streams.  Stream
data is carried within frames where one QUIC packet on the wire can carry one
or multiple stream frames.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">Streams can be unidirectional or bidirectional, and a stream may be initiated
either by client or server. Only the initiator of a unidirectional stream can
send data on it.<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">Streams and connections can each carry a maximum of
 2<sup>62</sup>-1 bytes in each direction due to encoding limitations on
stream offsets and connection flow control limits. In the presently unlikely
event that this limit is reached by an application, a new connection would
need to be established.<a href="#section-4-3" class="pilcrow">¶</a></p>
<p id="section-4-4">Streams can be independently opened and closed, gracefully or abruptly. An
application can gracefully close the egress direction of a stream by instructing
QUIC to send a FIN bit in a STREAM frame. It cannot gracefully close the ingress
direction without a peer-generated FIN, much like in TCP. However, an endpoint
can abruptly close the egress direction or request that its peer abruptly close
the ingress direction; these actions are fully independent of each other.<a href="#section-4-4" class="pilcrow">¶</a></p>
<p id="section-4-5">QUIC does not provide an interface for exceptional handling of any stream.
If a stream that is critical for an application is closed, the application can
generate error messages on the application layer to inform the other end and/or
the higher layer, which can eventually terminate the QUIC connection.<a href="#section-4-5" class="pilcrow">¶</a></p>
<p id="section-4-6">Mapping of application data to streams is application specific and described for
HTTP/3 in <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>. There are a few general principles to apply when
designing an application's use of streams:<a href="#section-4-6" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4-7.1">A single stream provides ordering. If the application requires certain data to
be received in order, that data should be sent on the same stream. There is
no guarantee of transmission, reception, or delivery order across streams.<a href="#section-4-7.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-4-7.2">Multiple streams provide concurrency. Data that can be processed
independently, and therefore would suffer from head-of-line blocking if forced
to be received in order, should be transmitted over separate streams.<a href="#section-4-7.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-4-7.3">Streams can provide message orientation and allow messages to be canceled.
If one message is mapped to a single stream, resetting the stream to expire an
unacknowledged message can be used to emulate partial reliability
for that message.<a href="#section-4-7.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-4-8">If a QUIC receiver has opened the maximum allowed concurrent
streams, and the sender indicates that more streams are needed, it
does not automatically lead to an increase of the maximum number of
streams by the receiver. Therefore, an application should consider the
maximum number of allowed, currently open, and currently used streams when
determining how to map data to streams.<a href="#section-4-8" class="pilcrow">¶</a></p>
<p id="section-4-9">QUIC assigns a numerical identifier, called the stream ID, to each stream.  While
the relationship between these identifiers and stream types is clearly defined
in version 1 of QUIC, future versions might change this relationship for various
reasons. QUIC implementations should expose the properties of each stream
(which endpoint initiated the stream, whether the stream is unidirectional or
bidirectional, the stream ID used for the stream); applications should query for
these properties rather than attempting to infer them from the stream ID.<a href="#section-4-9" class="pilcrow">¶</a></p>
<p id="section-4-10">The method of allocating stream identifiers to streams opened by the application
might vary between transport implementations. Therefore, an application should
not assume a particular stream ID will be assigned to a stream that has not yet
been allocated.  For example, HTTP/3 uses stream IDs to refer to streams that
have already been opened but makes no assumptions about future stream IDs or
the way in which they are assigned (see <span><a href="https://www.rfc-editor.org/rfc/rfc9114#section-6" class="relref">Section 6</a> of [<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>).<a href="#section-4-10" class="pilcrow">¶</a></p>
<div id="stream-versus-flow-multiplexing">
<section id="section-4.1">
        <h3 id="name-stream-versus-flow-multiple">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-stream-versus-flow-multiple" class="section-name selfRef">Stream versus Flow Multiplexing</a>
        </h3>
<p id="section-4.1-1">Streams are meaningful only to the application; since stream information is
carried inside QUIC's encryption boundary, a given packet exposes
no information about which
stream(s) are carried within the packet.
Therefore, stream multiplexing is not intended to be used for differentiating
streams in terms of network treatment. Application traffic requiring different
network treatment should therefore be carried over different 5-tuples (i.e.,
multiple QUIC connections). Given QUIC's ability to send application data in
the first RTT of a connection (if a previous connection to the same host has
been successfully established to provide the necessary credentials), the cost
of establishing another connection is extremely low.<a href="#section-4.1-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="prioritization">
<section id="section-4.2">
        <h3 id="name-prioritization">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-prioritization" class="section-name selfRef">Prioritization</a>
        </h3>
<p id="section-4.2-1">Stream prioritization is not exposed to either the network or the receiver.
Prioritization is managed by the sender, and the QUIC transport should
provide an interface for applications to prioritize streams <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span>.
Applications can implement their own prioritization scheme on top of QUIC: an
application protocol that runs on top of QUIC can define explicit messages
for signaling priority, such as those defined in
<span>[<a href="#RFC9218" class="cite xref">RFC9218</a>]</span> for HTTP. An application protocol can define rules
that allow an endpoint to determine priority based on context or can
provide a higher-level interface and leave the determination to the
application on top.<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<p id="section-4.2-2">Priority handling of retransmissions can be implemented by the sender in the
transport layer. <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span> recommends retransmitting lost data before new data,
unless indicated differently by the application. When a QUIC endpoint uses
fully reliable streams for transmission, prioritization of retransmissions will
be beneficial in most cases, filling in gaps and freeing up the flow
control window. For partially reliable or unreliable streams,
priority scheduling of retransmissions over data of higher-priority streams
might not be desirable. For such streams, QUIC could either provide an
explicit interface to control prioritization or derive the prioritization
decision from the reliability level of the stream.<a href="#section-4.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="ordered-and-reliable-delivery">
<section id="section-4.3">
        <h3 id="name-ordered-and-reliable-delive">
<a href="#section-4.3" class="section-number selfRef">4.3. </a><a href="#name-ordered-and-reliable-delive" class="section-name selfRef">Ordered and Reliable Delivery</a>
        </h3>
<p id="section-4.3-1">QUIC streams enable ordered and reliable delivery.  Though it is possible for an
implementation to provide options that use streams for partial reliability
or out-of-order delivery, most implementations will assume that data is
reliably delivered in order.<a href="#section-4.3-1" class="pilcrow">¶</a></p>
<p id="section-4.3-2">Under this assumption, an endpoint that receives stream data might not make
forward progress until data that is contiguous with the start of a stream is
available.  In particular, a receiver might withhold flow control credit until
contiguous data is delivered to the application; see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-2.2" class="relref">Section 2.2</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>.
To support this receive logic, an endpoint will send stream data until it is
acknowledged, ensuring that data at the start of the stream is sent and
acknowledged first.<a href="#section-4.3-2" class="pilcrow">¶</a></p>
<p id="section-4.3-3">An endpoint that uses a different sending behavior and does not negotiate that
change with its peer might encounter performance issues or deadlocks.<a href="#section-4.3-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="flow-control-deadlocks">
<section id="section-4.4">
        <h3 id="name-flow-control-deadlocks">
<a href="#section-4.4" class="section-number selfRef">4.4. </a><a href="#name-flow-control-deadlocks" class="section-name selfRef">Flow Control Deadlocks</a>
        </h3>
<p id="section-4.4-1">QUIC flow control (<span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-4" class="relref">Section 4</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>) provides a means of managing access
to the limited buffers that endpoints have for incoming data.  This mechanism limits
the amount of data that can be in buffers in endpoints or in transit on the
network.  However, there are several ways in which limits can produce conditions
that can cause a connection to either perform suboptimally or become deadlocked.<a href="#section-4.4-1" class="pilcrow">¶</a></p>
<p id="section-4.4-2">Deadlocks in flow control are possible for any protocol that uses QUIC, though
whether they become a problem depends on how implementations consume data and
provide flow control credit.  Understanding what causes deadlocking might help
implementations avoid deadlocks.<a href="#section-4.4-2" class="pilcrow">¶</a></p>
<p id="section-4.4-3">The size and rate of updates to flow control credit can affect
performance. Applications that use QUIC often have a data consumer that reads
data from transport buffers. Some implementations might have independent
receive buffers at the transport layer and application layer. Consuming data does not
always imply it is immediately processed. However, a common 
implementation technique is to extend flow control credit to the sender by emitting MAX_DATA
and/or MAX_STREAM_DATA frames as data is consumed. Delivery of these frames
is affected by the latency of the back channel from the receiver to the data
sender. If credit is not extended in a timely manner, the
sending application can be blocked, effectively throttling the sender.<a href="#section-4.4-3" class="pilcrow">¶</a></p>
<p id="section-4.4-4">Large application messages can produce deadlocking if the recipient does not
read data from the transport incrementally. If the message is larger than the
flow control credit available and the recipient does not release additional flow
control credit until the entire message is received and delivered, a deadlock
can occur. This is possible even where stream flow control limits are not
reached because connection flow control limits can be consumed by other streams.<a href="#section-4.4-4" class="pilcrow">¶</a></p>
<p id="section-4.4-5">A length-prefixed message format makes it easier for a data consumer to leave
data unread in the transport buffer and thereby withhold flow control credit. If
flow control limits prevent the remainder of a message from being sent, a
deadlock will result.  A length prefix might also enable the detection of this
sort of deadlock.  Where application protocols have messages that might be
processed as a single unit, reserving flow control credit for the entire message
atomically makes this style of deadlock less likely.<a href="#section-4.4-5" class="pilcrow">¶</a></p>
<p id="section-4.4-6">A data consumer can eagerly read all data as it becomes available in order to
make the receiver extend flow control credit and reduce the chances of a
deadlock.  However, such a data consumer might need other means for holding a
peer accountable for the additional state it keeps for partially processed
messages.<a href="#section-4.4-6" class="pilcrow">¶</a></p>
<p id="section-4.4-7">Deadlocking can also occur if data on different streams is interdependent.
Suppose that data on one stream arrives before the data on a second stream on
which it depends.  A deadlock can occur if the first stream is left unread,
preventing the receiver from extending flow control credit for the second
stream.  To reduce the likelihood of deadlock for interdependent data, the
sender should ensure that dependent data is not sent until the data
it depends on has been accounted for in both stream- and connection-level flow
control credit.<a href="#section-4.4-7" class="pilcrow">¶</a></p>
<p id="section-4.4-8">Some deadlocking scenarios might be resolved by canceling affected streams with
STOP_SENDING or RESET_STREAM.  Canceling some streams results in the connection
being terminated in some protocols.<a href="#section-4.4-8" class="pilcrow">¶</a></p>
</section>
</div>
<div id="stream-limit-commitments">
<section id="section-4.5">
        <h3 id="name-stream-limit-commitments">
<a href="#section-4.5" class="section-number selfRef">4.5. </a><a href="#name-stream-limit-commitments" class="section-name selfRef">Stream Limit Commitments</a>
        </h3>
<p id="section-4.5-1">QUIC endpoints are responsible for communicating the cumulative limit of streams
they would allow to be opened by their peer. Initial limits are advertised using
the initial_max_streams_bidi and initial_max_streams_uni transport parameters.
As streams are opened and closed, they are consumed, and the cumulative total is
incremented. Limits can be increased using the MAX_STREAMS frame, but there is no
mechanism to reduce limits. Once stream limits are reached, no more streams can
be opened, which prevents applications using QUIC from making further progress.
At this stage, connections can be terminated via idle timeout or explicit close;
see <a href="#sec-termination" class="auto internal xref">Section 10</a>.<a href="#section-4.5-1" class="pilcrow">¶</a></p>
<p id="section-4.5-2">An application that uses QUIC and communicates a cumulative stream limit might
require the connection to be closed before the limit is reached, e.g.,
to stop the server in order to perform scheduled maintenance. Immediate connection close
causes abrupt closure of actively used streams. Depending on how an application
uses QUIC streams, this could be undesirable or detrimental to behavior or
performance.<a href="#section-4.5-2" class="pilcrow">¶</a></p>
<p id="section-4.5-3">A more graceful closure technique is to stop sending increases to
stream limits and allow the connection to naturally terminate once remaining
streams are consumed. However, the period of time it takes to do so is dependent
on the peer, and an unpredictable closing period might not fit application or
operational needs. Applications using QUIC can be conservative with open stream
limits in order to reduce the commitment and indeterminism. However, being
overly conservative with stream limits affects stream concurrency. Balancing
these aspects can be specific to applications and their deployments.<a href="#section-4.5-3" class="pilcrow">¶</a></p>
<p id="section-4.5-4">Instead of
relying on stream limits to avoid abrupt closure, an application layer's graceful
close mechanism can be used to communicate the intention to explicitly close the
connection at some future point. HTTP/3 provides such a mechanism using the
GOAWAY frame. In HTTP/3, when the GOAWAY frame is received by a client, it
stops opening new streams even if the cumulative stream limit would allow.
Instead, the client would create a new connection on which to open further
streams.  Once all streams are closed on the old connection, it can be
terminated safely by a connection close or after expiration of the idle timeout
(see <a href="#sec-termination" class="auto internal xref">Section 10</a>).<a href="#section-4.5-4" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="packetization-and-latency">
<section id="section-5">
      <h2 id="name-packetization-and-latency">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-packetization-and-latency" class="section-name selfRef">Packetization and Latency</a>
      </h2>
<p id="section-5-1">QUIC exposes an interface that provides multiple streams to the application;
however, the application usually cannot control how data transmitted over those
streams is mapped into frames or how those frames are bundled into packets.<a href="#section-5-1" class="pilcrow">¶</a></p>
<p id="section-5-2">By default, many implementations will try to pack STREAM frames 
from one or more streams into each QUIC packet, in order to minimize
bandwidth consumption and computational costs (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-13" class="relref">Section 13</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>). If there is not enough data
available to fill a packet, an implementation might wait for a short time to
optimize bandwidth efficiency instead of latency. This delay can either be
preconfigured or dynamically adjusted based on the observed sending pattern of
the application.<a href="#section-5-2" class="pilcrow">¶</a></p>
<p id="section-5-3">If the application requires low latency, with only small chunks of data to
send, it may be valuable to indicate to QUIC that all data should be sent out
immediately. Alternatively, if the application expects to use a specific
sending pattern, it can also provide a suggested delay to QUIC for how long to
wait before bundling frames into a packet.<a href="#section-5-3" class="pilcrow">¶</a></p>
<p id="section-5-4">Similarly, an application usually has no control over the length of a QUIC
packet on the wire. QUIC provides the ability to add a PADDING frame to
arbitrarily increase the size of packets. Padding is used by QUIC to ensure that
the path is capable of transferring datagrams of at least a certain size during
the handshake (see Sections <a href="https://www.rfc-editor.org/rfc/rfc9000#section-8.1" class="relref">8.1</a> and <a href="https://www.rfc-editor.org/rfc/rfc9000#section-14.1" class="relref">14.1</a> of <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span>) and for path validation
after connection migration (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-8.2" class="relref">Section 8.2</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>) as well as for Datagram
Packetization Layer PMTU Discovery (DPLPMTUD) (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-14.3" class="relref">Section 14.3</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>).<a href="#section-5-4" class="pilcrow">¶</a></p>
<p id="section-5-5">Padding can also be used by an application to reduce leakage of
information about the data that is sent. A QUIC implementation can expose an
interface that allows an application layer to specify how to apply padding.<a href="#section-5-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="error-handling">
<section id="section-6">
      <h2 id="name-error-handling">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-error-handling" class="section-name selfRef">Error Handling</a>
      </h2>
<p id="section-6-1">QUIC recommends that endpoints signal any detected errors to
the peer. Errors can occur at the transport layer and the application layer.
Transport errors, such as a protocol violation, affect the entire connection.
Applications that use QUIC can define their own error detection and signaling
(see, for example, <span><a href="https://www.rfc-editor.org/rfc/rfc9114#section-8" class="relref">Section 8</a> of [<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>). Application errors can affect an
entire connection or a single stream.<a href="#section-6-1" class="pilcrow">¶</a></p>
<p id="section-6-2">QUIC defines an error code space that is used for error handling at the
transport layer. QUIC encourages endpoints to use the most specific code,
although any applicable code is permitted, including generic ones.<a href="#section-6-2" class="pilcrow">¶</a></p>
<p id="section-6-3">Applications using QUIC define an error
code space that is independent of QUIC or other applications (see, for
example, <span><a href="https://www.rfc-editor.org/rfc/rfc9114#section-8.1" class="relref">Section 8.1</a> of [<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>). The values in an application error code
space can be reused across connection-level and stream-level errors.<a href="#section-6-3" class="pilcrow">¶</a></p>
<p id="section-6-4">Connection errors lead to connection termination. They are signaled using a
CONNECTION_CLOSE frame, which contains an error code and a reason field that can
be zero length. Different types of CONNECTION_CLOSE frames are used to
signal transport and application errors.<a href="#section-6-4" class="pilcrow">¶</a></p>
<p id="section-6-5">Stream errors lead to stream termination. These are signaled using
STOP_SENDING or
RESET_STREAM frames, which contain only an error code.<a href="#section-6-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="acknowledgment-efficiency">
<section id="section-7">
      <h2 id="name-acknowledgment-efficiency">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-acknowledgment-efficiency" class="section-name selfRef">Acknowledgment Efficiency</a>
      </h2>
<p id="section-7-1">QUIC version 1 without extensions uses an acknowledgment strategy
adopted from TCP (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-13.2" class="relref">Section 13.2</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>).
That is, it recommends that every other packet is acknowledged.
However, generating and processing QUIC acknowledgments consumes resources
at a sender and receiver.  Acknowledgments also incur forwarding costs and
contribute to link utilization, which can impact performance over some
types of network.
Applications might be able to improve overall performance
by using alternative strategies that reduce the rate of acknowledgments.
<span>[<a href="#I-D.ietf-quic-ack-frequency" class="cite xref">QUIC-ACK-FREQUENCY</a>]</span> describes an extension to signal the desired
delay of acknowledgments and discusses use cases as well as implications for
congestion control and recovery.<a href="#section-7-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="ports">
<section id="section-8">
      <h2 id="name-port-selection-and-applicat">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-port-selection-and-applicat" class="section-name selfRef">Port Selection and Application Endpoint Discovery</a>
      </h2>
<p id="section-8-1">In general, port numbers serve two purposes: "first, they provide a
demultiplexing identifier to differentiate transport sessions between the same
pair of endpoints, and second, they may also identify the application protocol
and associated service to which processes connect" (<span><a href="https://www.rfc-editor.org/rfc/rfc6335#section-3" class="relref">Section 3</a> of [<a href="#RFC6335" class="cite xref">RFC6335</a>]</span>). The assumption
that an application can be identified in the network based on the port number
is less true today due to encapsulation and mechanisms for dynamic port
assignments, as noted in <span>[<a href="#RFC6335" class="cite xref">RFC6335</a>]</span>.<a href="#section-8-1" class="pilcrow">¶</a></p>
<p id="section-8-2">As QUIC is a general-purpose transport protocol, there are no requirements that
servers use a particular UDP port for QUIC. For an application with a fallback to 
TCP that does not already have an alternate mapping to UDP, it is usually 
appropriate to register (if necessary) and use the UDP port number corresponding to the TCP
port already registered for the application. For example,
the default port for HTTP/3 <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span> is UDP port 443, analogous to HTTP/1.1
or HTTP/2 over TLS over TCP.<a href="#section-8-2" class="pilcrow">¶</a></p>
<p id="section-8-3">Given the prevalence of the assumption in network management
practice that a port number maps unambiguously to an application, the
use of ports that cannot easily be mapped to a registered service name
might lead to blocking or other changes to the forwarding behavior by network
elements such as firewalls that use the port number for application
identification.<a href="#section-8-3" class="pilcrow">¶</a></p>
<p id="section-8-4">Applications could define an alternate endpoint discovery mechanism to allow
the usage of ports other than the default. For example, HTTP/3 (Sections <a href="https://www.rfc-editor.org/rfc/rfc9114#section-3.2" class="relref">3.2</a> and <a href="https://www.rfc-editor.org/rfc/rfc9114#section-3.3" class="relref">3.3</a> of <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>) specifies the use of HTTP Alternative Services
<span>[<a href="#RFC7838" class="cite xref">RFC7838</a>]</span> for an HTTP origin to advertise the availability of an equivalent
HTTP/3 endpoint on a certain UDP port by using "h3" as the Application-Layer
Protocol Negotiation (ALPN) <span>[<a href="#RFC7301" class="cite xref">RFC7301</a>]</span> token.<a href="#section-8-4" class="pilcrow">¶</a></p>
<p id="section-8-5">ALPN permits the
client and server to negotiate which of several protocols will be used on a
given connection.  Therefore, multiple applications might be supported on a
single UDP port based on the ALPN token offered.  Applications using QUIC
are required to register an ALPN token for use in the TLS handshake.<a href="#section-8-5" class="pilcrow">¶</a></p>
<p id="section-8-6">As QUIC version 1 deferred defining a complete version negotiation mechanism,
HTTP/3 requires QUIC version 1 and defines the
ALPN token ("h3") to only apply to that version.
So far, no single approach has been selected for
managing the use of different QUIC versions, neither in HTTP/3 nor in general.
Application protocols that use QUIC need to
consider how the protocol will manage different QUIC versions.
Decisions for those protocols might be informed by choices made by other
protocols, like HTTP/3.<a href="#section-8-6" class="pilcrow">¶</a></p>
<div id="source-port-selection">
<section id="section-8.1">
        <h3 id="name-source-port-selection">
<a href="#section-8.1" class="section-number selfRef">8.1. </a><a href="#name-source-port-selection" class="section-name selfRef">Source Port Selection</a>
        </h3>
<p id="section-8.1-1">Some UDP protocols are vulnerable to reflection attacks, where an attacker is
able to direct traffic to a third party as a denial of service. For example,
these source ports are associated with applications known to be vulnerable to
reflection attacks, often due to server misconfiguration:<a href="#section-8.1-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-8.1-2.1">port 53 - DNS <span>[<a href="#RFC1034" class="cite xref">RFC1034</a>]</span><a href="#section-8.1-2.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-8.1-2.2">port 123 - NTP <span>[<a href="#RFC5905" class="cite xref">RFC5905</a>]</span><a href="#section-8.1-2.2" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-8.1-2.3">port 1900 - SSDP <span>[<a href="#SSDP" class="cite xref">SSDP</a>]</span><a href="#section-8.1-2.3" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-8.1-2.4">port 5353 - mDNS <span>[<a href="#RFC6762" class="cite xref">RFC6762</a>]</span><a href="#section-8.1-2.4" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-8.1-2.5">port 11211 - memcache<a href="#section-8.1-2.5" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-8.1-3">Services might block source ports associated with protocols known to be
vulnerable to reflection attacks to avoid the overhead of processing large
numbers of packets. However, this practice has negative effects on
clients -- not only does it require establishment of a new connection but in
some instances might cause the client to avoid using QUIC for that service for
a period of time and downgrade to a non-UDP protocol (see <a href="#fallback" class="auto internal xref">Section 2</a>).<a href="#section-8.1-3" class="pilcrow">¶</a></p>
<p id="section-8.1-4">As a result, client implementations are encouraged to avoid using source ports
associated with protocols known to be vulnerable to reflection attacks. Note
that following the general guidance for client implementations given in
<span>[<a href="#RFC6335" class="cite xref">RFC6335</a>]</span>, to use ephemeral ports in the range 49152-65535, has the
effect of avoiding these ports. Note that other source ports might be
reflection vectors as well.<a href="#section-8.1-4" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="connection-migration">
<section id="section-9">
      <h2 id="name-connection-migration">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-connection-migration" class="section-name selfRef">Connection Migration</a>
      </h2>
<p id="section-9-1">QUIC supports connection migration by the client. If the client's IP address
changes, a QUIC endpoint can still associate packets
with an existing transport connection using the Destination Connection ID
field (see <a href="#connid" class="auto internal xref">Section 11</a>) in the QUIC header.
This supports cases where the address information changes, such as NAT rebinding, the
intentional change of the local interface, the expiration of a temporary
IPv6 address <span>[<a href="#RFC8981" class="cite xref">RFC8981</a>]</span>, or the indication from the server of a preferred
address (<span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-9.6" class="relref">Section 9.6</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>).<a href="#section-9-1" class="pilcrow">¶</a></p>
<p id="section-9-2">Use of a non-zero-length connection ID for the server is strongly recommended if
any clients are or could be behind a NAT. A non-zero-length connection ID is
also strongly recommended when active migration is supported. If a connection
is intentionally migrated to a new path, a new connection ID is used to minimize
linkability by network observers. The other QUIC endpoint uses the
connection ID to link different addresses to the same connection
and entity if a non-zero-length connection ID is provided.<a href="#section-9-2" class="pilcrow">¶</a></p>
<p id="section-9-3">The base specification of QUIC version 1 only supports the use of a single
network path at a time, which
enables failover use cases.  Path validation is required so that endpoints
validate paths before use to avoid address spoofing attacks.  Path validation
takes at least one RTT, and congestion control will also be reset after path
migration. Therefore, migration usually has a performance impact.<a href="#section-9-3" class="pilcrow">¶</a></p>
<p id="section-9-4">QUIC probing packets, which can be sent on multiple paths at once, are used to
perform address validation as well as measure path characteristics.  Probing
packets cannot carry application data but likely contain padding frames.
Endpoints can use information about their receipt as input to congestion control
for that path. Applications could use information learned from probing to inform
a decision to switch paths.<a href="#section-9-4" class="pilcrow">¶</a></p>
<p id="section-9-5">Only the client can actively migrate in version 1 of QUIC. However, servers can
indicate during the handshake that they prefer to transfer the connection to a
different address after the handshake. For instance, this could be used to move
from an address that is shared by multiple servers to an address that is unique
to the server instance. The server can provide an IPv4 and an IPv6 address in a
transport parameter during the TLS handshake, and the client can select between
the two if both are provided. See <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-9.6" class="relref">Section 9.6</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>.<a href="#section-9-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="sec-termination">
<section id="section-10">
      <h2 id="name-connection-termination">
<a href="#section-10" class="section-number selfRef">10. </a><a href="#name-connection-termination" class="section-name selfRef">Connection Termination</a>
      </h2>
<p id="section-10-1">QUIC connections are terminated in one of three ways: implicit idle timeout,
explicit immediate close, or explicit stateless reset.<a href="#section-10-1" class="pilcrow">¶</a></p>
<p id="section-10-2">QUIC does not provide any mechanism for graceful connection termination;
applications using QUIC can define their own graceful termination process (see,
for example, <span><a href="https://www.rfc-editor.org/rfc/rfc9114#section-5.2" class="relref">Section 5.2</a> of [<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span>).<a href="#section-10-2" class="pilcrow">¶</a></p>
<p id="section-10-3">QUIC idle timeout is enabled via transport parameters. The client and server
announce a timeout period, and the effective value for the connection is the
minimum of the two values. After the timeout period elapses, the connection is
silently closed. An application therefore should be able to configure its own
maximum value, as well as have access to the computed minimum value for this
connection. An application may adjust the maximum idle timeout for new
connections based on the number of open or expected connections since shorter
timeout values may free up resources more quickly.<a href="#section-10-3" class="pilcrow">¶</a></p>
<p id="section-10-4">Application data exchanged on streams or in datagrams defers the QUIC idle
timeout. Applications that provide their own keep-alive mechanisms will
therefore keep a QUIC connection alive. Applications that do not provide their
own keep-alive can use transport-layer mechanisms (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-10.1.2" class="relref">Section 10.1.2</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span> and <a href="#resumption-v-keepalive" class="auto internal xref">Section 3.2</a>). However, QUIC implementation
interfaces for controlling such transport behavior can vary, affecting the
robustness of such approaches.<a href="#section-10-4" class="pilcrow">¶</a></p>
<p id="section-10-5">An immediate close is signaled by a CONNECTION_CLOSE frame (see
<a href="#error-handling" class="auto internal xref">Section 6</a>). Immediate close causes all streams to become immediately
closed, which may affect applications; see <a href="#stream-limit-commitments" class="auto internal xref">Section 4.5</a>.<a href="#section-10-5" class="pilcrow">¶</a></p>
<p id="section-10-6">A stateless reset is an option of last resort for an endpoint that does not have
access to connection state. Receiving a stateless reset is an indication of an
unrecoverable error distinct from connection errors in that there is no
application-layer information provided.<a href="#section-10-6" class="pilcrow">¶</a></p>
</section>
</div>
<div id="connid">
<section id="section-11">
      <h2 id="name-information-exposure-and-th">
<a href="#section-11" class="section-number selfRef">11. </a><a href="#name-information-exposure-and-th" class="section-name selfRef">Information Exposure and the Connection ID</a>
      </h2>
<p id="section-11-1">QUIC exposes some information to the network in the unencrypted part of the
header either before the encryption context is established or because the
information is intended to be used by the network. For more information on
manageability of QUIC, see <span>[<a href="#RFC9312" class="cite xref">QUIC-MANAGEABILITY</a>]</span>.
QUIC has a long header that
exposes some additional information (the version and the source connection ID),
while the short header exposes only the destination connection ID.
In QUIC version 1, the long header is used during connection establishment,
while the short header is used for data transmission in an established
connection.<a href="#section-11-1" class="pilcrow">¶</a></p>
<p id="section-11-2">The connection ID can be zero length. Zero-length connection IDs can be
chosen on each endpoint individually and on any packet except the first packets
sent by clients during connection establishment.<a href="#section-11-2" class="pilcrow">¶</a></p>
<p id="section-11-3">An endpoint that selects a zero-length connection ID will receive packets with a
zero-length destination connection ID. The endpoint needs to use other
information, such as the source and destination IP address and port number to
identify which connection is referred to. This could mean that the endpoint is
unable to match datagrams to connections successfully if these values change,
making the connection effectively unable to survive NAT rebinding or migrate to
a new path.<a href="#section-11-3" class="pilcrow">¶</a></p>
<div id="server-generated-connection-id">
<section id="section-11.1">
        <h3 id="name-server-generated-connection">
<a href="#section-11.1" class="section-number selfRef">11.1. </a><a href="#name-server-generated-connection" class="section-name selfRef">Server-Generated Connection ID</a>
        </h3>
<p id="section-11.1-1">QUIC supports a server-generated connection ID that is transmitted to the client during
connection establishment (see <span><a href="https://www.rfc-editor.org/rfc/rfc9000#section-7.2" class="relref">Section 7.2</a> of [<a href="#RFC9000" class="cite xref">QUIC</a>]</span>). Servers behind load
balancers may need to change the connection ID during the handshake, encoding
the identity of the server or information about its load balancing pool, in
order to support stateless load balancing.<a href="#section-11.1-1" class="pilcrow">¶</a></p>
<p id="section-11.1-2">Server deployments with load balancers and other routing infrastructure need to
ensure that this infrastructure consistently routes packets to the server
instance that has the connection state, even if addresses, ports, or
connection IDs change. This might require coordination between servers and
infrastructure. One method of achieving this involves encoding routing
information into the connection ID. For an example of this technique, see
<span>[<a href="#I-D.ietf-quic-load-balancers" class="cite xref">QUIC-LB</a>]</span>.<a href="#section-11.1-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="mitigating-timing-linkability-with-connection-id-migration">
<section id="section-11.2">
        <h3 id="name-mitigating-timing-linkabili">
<a href="#section-11.2" class="section-number selfRef">11.2. </a><a href="#name-mitigating-timing-linkabili" class="section-name selfRef">Mitigating Timing Linkability with Connection ID Migration</a>
        </h3>
<p id="section-11.2-1">If QUIC endpoints do not issue fresh connection IDs, then clients cannot
reduce the linkability of address migration by using them.
Choosing values that are unlinkable to an outside observer
ensures that activity on different paths cannot be trivially correlated
using the connection ID.<a href="#section-11.2-1" class="pilcrow">¶</a></p>
<p id="section-11.2-2">While sufficiently robust connection ID generation schemes will mitigate
linkability issues, they do not provide full protection.  Analysis of
the lifetimes of 6-tuples (source and destination addresses as well as the
migrated Connection ID) may expose these links anyway.<a href="#section-11.2-2" class="pilcrow">¶</a></p>
<p id="section-11.2-3">In the case where connection migration in a server pool is rare, it is trivial
for an observer to associate two connection IDs. Conversely, 
where every server handles multiple simultaneous migrations, even an
exposed server mapping may be insufficient information.<a href="#section-11.2-3" class="pilcrow">¶</a></p>
<p id="section-11.2-4">The most efficient mitigations for these attacks are through network design
and/or operational practices, by using a load-balancing architecture that
loads more flows onto a single server-side address, by coordinating the
timing of migrations in an attempt to increase the number of simultaneous
migrations at a given time, or by using other means.<a href="#section-11.2-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="using-server-retry-for-redirection">
<section id="section-11.3">
        <h3 id="name-using-server-retry-for-redi">
<a href="#section-11.3" class="section-number selfRef">11.3. </a><a href="#name-using-server-retry-for-redi" class="section-name selfRef">Using Server Retry for Redirection</a>
        </h3>
<p id="section-11.3-1">QUIC provides a Retry packet that can be sent by a server in response to
the client Initial packet. The server may choose a new connection ID in that
packet, and the client will retry by sending another client Initial packet with
the server-selected connection ID. This mechanism can be used to redirect a
connection to a different server, e.g., due to performance reasons or when
servers in a server pool are upgraded gradually and therefore may support
different versions of QUIC.<a href="#section-11.3-1" class="pilcrow">¶</a></p>
<p id="section-11.3-2">In this case, it is assumed that all servers belonging to a certain pool are
served in cooperation with load balancers that forward the traffic based on the
connection ID. A server can choose the connection ID in the Retry packet such
that the load balancer will redirect the next Initial packet to a different
server in that pool.  Alternatively, the load balancer can directly offer a Retry
offload as further described in <span>[<a href="#I-D.ietf-quic-retry-offload" class="cite xref">QUIC-RETRY</a>]</span>.<a href="#section-11.3-2" class="pilcrow">¶</a></p>
<p id="section-11.3-3">The approach described in <span><a href="https://www.rfc-editor.org/rfc/rfc5077#section-4" class="relref">Section 4</a> of [<a href="#RFC5077" class="cite xref">RFC5077</a>]</span> for constructing
TLS resumption tickets provides an example that can be also applied to validation tokens.
However, the use of more modern cryptographic algorithms is highly recommended.<a href="#section-11.3-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="quality-of-service-qos-and-dscp">
<section id="section-12">
      <h2 id="name-quality-of-service-qos-and-">
<a href="#section-12" class="section-number selfRef">12. </a><a href="#name-quality-of-service-qos-and-" class="section-name selfRef">Quality of Service (QoS) and Diffserv Code Point (DSCP)</a>
      </h2>
<p id="section-12-1">QUIC, as defined in <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span>, has a single congestion controller and
recovery handler. This design
assumes that all packets of a QUIC connection, or at least with the
same 5-tuple {dest addr, source addr, protocol, dest port, source port},
that have the same Diffserv Code Point (DSCP) <span>[<a href="#RFC2475" class="cite xref">RFC2475</a>]</span> will
receive similar network treatment since feedback about loss or delay
of each packet is used as input to the congestion controller. Therefore,
packets belonging to the same connection should use a single DSCP.
<span><a href="https://www.rfc-editor.org/rfc/rfc7657#section-5.1" class="relref">Section 5.1</a> of [<a href="#RFC7657" class="cite xref">RFC7657</a>]</span> provides a discussion of Diffserv interactions
with datagram transport protocols <span>[<a href="#RFC7657" class="cite xref">RFC7657</a>]</span> (in this respect, the
interactions with QUIC resemble those of Stream Control Transmission Protocol (SCTP)).<a href="#section-12-1" class="pilcrow">¶</a></p>
<p id="section-12-2">When multiplexing multiple flows
over a single QUIC connection, the selected DSCP value should be the one
associated with the highest priority requested for all multiplexed flows.<a href="#section-12-2" class="pilcrow">¶</a></p>
<p id="section-12-3">If differential network treatment is desired,
e.g., by the use of different DSCPs, multiple QUIC
connections to the same server may be used. In general, it is
recommended to minimize the number of QUIC connections to the same server to
avoid increased overhead and, more importantly, competing congestion control.<a href="#section-12-3" class="pilcrow">¶</a></p>
<p id="section-12-4">As in other uses of Diffserv,
when a packet enters a network segment that does not support the DSCP value,
this could result in the connection not receiving the network treatment
it expects. The DSCP value in this packet could also be remarked as the
packet travels along the network path, changing the requested treatment.<a href="#section-12-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="use-of-versions-and-cryptographic-handshake">
<section id="section-13">
      <h2 id="name-use-of-versions-and-cryptog">
<a href="#section-13" class="section-number selfRef">13. </a><a href="#name-use-of-versions-and-cryptog" class="section-name selfRef">Use of Versions and Cryptographic Handshake</a>
      </h2>
<p id="section-13-1">Versioning in QUIC may change the protocol's behavior completely, except
for the meaning of a few header fields that have been declared to be invariant
<span>[<a href="#RFC8999" class="cite xref">QUIC-INVARIANTS</a>]</span>. A version of QUIC
with a higher version number will not necessarily provide a better service
but might simply provide a different feature set. As such, an application needs
to be able to select which versions of QUIC it wants to use.<a href="#section-13-1" class="pilcrow">¶</a></p>
<p id="section-13-2">A new version could use an encryption scheme other than TLS 1.3 or higher.
<span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span> specifies requirements for the cryptographic handshake as currently
realized by TLS 1.3 and described in a separate specification
<span>[<a href="#RFC9001" class="cite xref">QUIC-TLS</a>]</span>. This split is performed to enable
lightweight versioning with different cryptographic handshakes.<a href="#section-13-2" class="pilcrow">¶</a></p>
<p id="section-13-3">The "QUIC Versions" registry established in <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span> allows for
provisional registrations for experimentation. Registration, also of
experimental versions, is important to avoid collision. Experimental
versions should not be used long-term or registered as permanent to minimize
the risk of fingerprinting based on the version number.<a href="#section-13-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="enabling-deployment-of-new-versions">
<section id="section-14">
      <h2 id="name-enabling-deployment-of-new-">
<a href="#section-14" class="section-number selfRef">14. </a><a href="#name-enabling-deployment-of-new-" class="section-name selfRef">Enabling Deployment of New Versions</a>
      </h2>
<p id="section-14-1">QUIC version 1 does not specify a version negotiation mechanism in the base
specification, but <span>[<a href="#I-D.ietf-quic-version-negotiation" class="cite xref">QUIC-VERSION-NEGOTIATION</a>]</span> proposes an
extension that provides compatible version negotiation.<a href="#section-14-1" class="pilcrow">¶</a></p>
<p id="section-14-2">This approach uses a three-stage deployment mechanism, enabling
progressive rollout and experimentation with multiple versions across
a large server deployment. In this approach, all servers in the deployment
must accept connections using a new version (stage 1) before any server
advertises it (stage 2), and authentication of the new version (stage 3)
only proceeds after advertising of that version is completely deployed.<a href="#section-14-2" class="pilcrow">¶</a></p>
<p id="section-14-3">See <span><a href="https://datatracker.ietf.org/doc/html/draft-ietf-quic-version-negotiation-10#section-5" class="relref">Section 5</a> of [<a href="#I-D.ietf-quic-version-negotiation" class="cite xref">QUIC-VERSION-NEGOTIATION</a>]</span> for details.<a href="#section-14-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="unreliable-datagram-service-over-quic">
<section id="section-15">
      <h2 id="name-unreliable-datagram-service">
<a href="#section-15" class="section-number selfRef">15. </a><a href="#name-unreliable-datagram-service" class="section-name selfRef">Unreliable Datagram Service over QUIC</a>
      </h2>
<p id="section-15-1"><span>[<a href="#RFC9221" class="cite xref">RFC9221</a>]</span> specifies a QUIC extension to enable sending
and receiving unreliable datagrams over QUIC. Unlike operating directly over
UDP, applications that use the QUIC datagram service do not need to implement
their own congestion control, per <span>[<a href="#RFC8085" class="cite xref">RFC8085</a>]</span>, as QUIC datagrams are
congestion controlled.<a href="#section-15-1" class="pilcrow">¶</a></p>
<p id="section-15-2">QUIC datagrams are not flow controlled, and as such data chunks may be dropped
if the receiver is overloaded. While the reliable transmission service of QUIC
provides a stream-based interface to send and receive data in order over
multiple QUIC streams, the datagram service has an unordered message-based
interface. If needed, an application-layer framing can be used on top to
allow separate flows of unreliable datagrams to be multiplexed on one QUIC
connection.<a href="#section-15-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="iana-considerations">
<section id="section-16">
      <h2 id="name-iana-considerations">
<a href="#section-16" class="section-number selfRef">16. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-16-1">This document has no actions for IANA; however, note that <a href="#ports" class="auto internal xref">Section 8</a>
recommends that an application that has already registered a TCP port 
but wants to specify QUIC as a transport should register 
a UDP port analogous to their existing TCP registration.<a href="#section-16-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="security-considerations">
<section id="section-17">
      <h2 id="name-security-considerations">
<a href="#section-17" class="section-number selfRef">17. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-17-1">See the security considerations in <span>[<a href="#RFC9000" class="cite xref">QUIC</a>]</span> and <span>[<a href="#RFC9001" class="cite xref">QUIC-TLS</a>]</span>; the security
considerations for the underlying transport protocol are relevant for
applications using QUIC. Considerations on linkability, replay attacks,
and randomness discussed in <span>[<a href="#RFC9001" class="cite xref">QUIC-TLS</a>]</span> should be taken into account when
deploying and using QUIC.<a href="#section-17-1" class="pilcrow">¶</a></p>
<p id="section-17-2">Further, migration to a new address exposes
a linkage between client addresses to the server and may expose this linkage
also to the path if the connection ID cannot be changed or flows can
otherwise be correlated. When migration is supported, this needs to be
considered with respective to user privacy.<a href="#section-17-2" class="pilcrow">¶</a></p>
<p id="section-17-3">Application developers should note that any fallback they use when QUIC cannot
be used due to network blocking of UDP should guarantee the same security
properties as QUIC. If this is not possible, the connection should fail to
allow the application to explicitly handle fallback to a less-secure
alternative. See <a href="#fallback" class="auto internal xref">Section 2</a>.<a href="#section-17-3" class="pilcrow">¶</a></p>
<p id="section-17-4">Further, <span>[<a href="#RFC9114" class="cite xref">QUIC-HTTP</a>]</span> provides security considerations specific to HTTP.
However, discussions such as on cross-protocol attacks, traffic analysis
and padding, or migration might be relevant for other applications using QUIC
as well.<a href="#section-17-4" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-18">
      <h2 id="name-references">
<a href="#section-18" class="section-number selfRef">18. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-18.1">
        <h3 id="name-normative-references">
<a href="#section-18.1" class="section-number selfRef">18.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC9000">[QUIC]</dt>
        <dd>
<span class="refAuthor">Iyengar, J., Ed.</span> and <span class="refAuthor">M. Thomson, Ed.</span>, <span class="refTitle">"QUIC: A UDP-Based Multiplexed and Secure Transport"</span>, <span class="seriesInfo">RFC 9000</span>, <span class="seriesInfo">DOI 10.17487/RFC9000</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9000">https://www.rfc-editor.org/info/rfc9000</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8999">[QUIC-INVARIANTS]</dt>
        <dd>
<span class="refAuthor">Thomson, M.</span>, <span class="refTitle">"Version-Independent Properties of QUIC"</span>, <span class="seriesInfo">RFC 8999</span>, <span class="seriesInfo">DOI 10.17487/RFC8999</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8999">https://www.rfc-editor.org/info/rfc8999</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9001">[QUIC-TLS]</dt>
      <dd>
<span class="refAuthor">Thomson, M., Ed.</span> and <span class="refAuthor">S. Turner, Ed.</span>, <span class="refTitle">"Using TLS to Secure QUIC"</span>, <span class="seriesInfo">RFC 9001</span>, <span class="seriesInfo">DOI 10.17487/RFC9001</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9001">https://www.rfc-editor.org/info/rfc9001</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-18.2">
        <h3 id="name-informative-references">
<a href="#section-18.2" class="section-number selfRef">18.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="Edeline16">[Edeline16]</dt>
        <dd>
<span class="refAuthor">Edeline, K.</span>, <span class="refAuthor">Kühlewind, M.</span>, <span class="refAuthor">Trammell, B.</span>, <span class="refAuthor">Aben, E.</span>, and <span class="refAuthor">B. Donnet</span>, <span class="refTitle">"Using UDP for Internet Transport Evolution"</span>, <span class="seriesInfo">DOI 10.48550/arXiv.1612.07816</span>, <time datetime="2016-12-22" class="refDate">22 December 2016</time>, <span>&lt;<a href="https://arxiv.org/abs/1612.07816">https://arxiv.org/abs/1612.07816</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="Hatonen10">[Hatonen10]</dt>
        <dd>
<span class="refAuthor">Hätönen, S.</span>, <span class="refAuthor">Nyrhinen, A.</span>, <span class="refAuthor">Eggert, L.</span>, <span class="refAuthor">Strowes, S.</span>, <span class="refAuthor">Sarolahti, P.</span>, and <span class="refAuthor">M. Kojo</span>, <span class="refTitle">"An Experimental Study of Home Gateway Characteristics"</span>, <span class="refContent">Proc. ACM IMC 2010</span>, <time datetime="2010-11" class="refDate">November 2010</time>, <span>&lt;<a href="https://conferences.sigcomm.org/imc/2010/papers/p260.pdf">https://conferences.sigcomm.org/imc/2010/papers/p260.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8470">[HTTP-REPLAY]</dt>
        <dd>
<span class="refAuthor">Thomson, M.</span>, <span class="refAuthor">Nottingham, M.</span>, and <span class="refAuthor">W. Tarreau</span>, <span class="refTitle">"Using Early Data in HTTP"</span>, <span class="seriesInfo">RFC 8470</span>, <span class="seriesInfo">DOI 10.17487/RFC8470</span>, <time datetime="2018-09" class="refDate">September 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8470">https://www.rfc-editor.org/info/rfc8470</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="PaaschNanog">[PaaschNanog]</dt>
        <dd>
<span class="refAuthor">Paasch, C.</span>, <span class="refTitle">"Network support for TCP Fast Open"</span>, <span class="refContent">NANOG 67 Presentation</span>, <time datetime="2016-06-13" class="refDate">13 June 2016</time>, <span>&lt;<a href="https://www.nanog.org/sites/default/files/Paasch_Network_Support.pdf">https://www.nanog.org/sites/default/files/Paasch_Network_Support.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-quic-ack-frequency">[QUIC-ACK-FREQUENCY]</dt>
        <dd>
<span class="refAuthor">Iyengar, J.</span> and <span class="refAuthor">I. Swett</span>, <span class="refTitle">"QUIC Acknowledgement Frequency"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-quic-ack-frequency-02</span>, <time datetime="2022-07-11" class="refDate">11 July 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-quic-ack-frequency-02">https://datatracker.ietf.org/doc/html/draft-ietf-quic-ack-frequency-02</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9114">[QUIC-HTTP]</dt>
        <dd>
<span class="refAuthor">Bishop, M., Ed.</span>, <span class="refTitle">"HTTP/3"</span>, <span class="seriesInfo">RFC 9114</span>, <span class="seriesInfo">DOI 10.17487/RFC9114</span>, <time datetime="2022-06" class="refDate">June 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9114">https://www.rfc-editor.org/info/rfc9114</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-quic-load-balancers">[QUIC-LB]</dt>
        <dd>
<span class="refAuthor">Duke, M.</span>, <span class="refAuthor">Banks, N.</span>, and <span class="refAuthor">C. Huitema</span>, <span class="refTitle">"QUIC-LB: Generating Routable QUIC Connection IDs"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-quic-load-balancers-14</span>, <time datetime="2022-07-11" class="refDate">11 July 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-quic-load-balancers-14">https://datatracker.ietf.org/doc/html/draft-ietf-quic-load-balancers-14</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9312">[QUIC-MANAGEABILITY]</dt>
        <dd>
<span class="refAuthor">Kühlewind, M.</span> and <span class="refAuthor">B. Trammell</span>, <span class="refTitle">"Manageability of the QUIC Transport Protocol"</span>, <span class="seriesInfo">RFC 9312</span>, <span class="seriesInfo">DOI 10.17487/RFC9312</span>, <time datetime="2022-09" class="refDate">September 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9312">https://www.rfc-editor.org/info/rfc9312</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-quic-retry-offload">[QUIC-RETRY]</dt>
        <dd>
<span class="refAuthor">Duke, M.</span> and <span class="refAuthor">N. Banks</span>, <span class="refTitle">"QUIC Retry Offload"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-quic-retry-offload-00</span>, <time datetime="2022-05-25" class="refDate">25 May 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-quic-retry-offload-00">https://datatracker.ietf.org/doc/html/draft-ietf-quic-retry-offload-00</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-quic-version-negotiation">[QUIC-VERSION-NEGOTIATION]</dt>
        <dd>
<span class="refAuthor">Schinazi, D.</span> and <span class="refAuthor">E. Rescorla</span>, <span class="refTitle">"Compatible Version Negotiation for QUIC"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-quic-version-negotiation-10</span>, <time datetime="2022-09-27" class="refDate">27 September 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-quic-version-negotiation-10">https://datatracker.ietf.org/doc/html/draft-ietf-quic-version-negotiation-10</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC1034">[RFC1034]</dt>
        <dd>
<span class="refAuthor">Mockapetris, P.</span>, <span class="refTitle">"Domain names - concepts and facilities"</span>, <span class="seriesInfo">STD 13</span>, <span class="seriesInfo">RFC 1034</span>, <span class="seriesInfo">DOI 10.17487/RFC1034</span>, <time datetime="1987-11" class="refDate">November 1987</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc1034">https://www.rfc-editor.org/info/rfc1034</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC2475">[RFC2475]</dt>
        <dd>
<span class="refAuthor">Blake, S.</span>, <span class="refAuthor">Black, D.</span>, <span class="refAuthor">Carlson, M.</span>, <span class="refAuthor">Davies, E.</span>, <span class="refAuthor">Wang, Z.</span>, and <span class="refAuthor">W. Weiss</span>, <span class="refTitle">"An Architecture for Differentiated Services"</span>, <span class="seriesInfo">RFC 2475</span>, <span class="seriesInfo">DOI 10.17487/RFC2475</span>, <time datetime="1998-12" class="refDate">December 1998</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2475">https://www.rfc-editor.org/info/rfc2475</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5077">[RFC5077]</dt>
        <dd>
<span class="refAuthor">Salowey, J.</span>, <span class="refAuthor">Zhou, H.</span>, <span class="refAuthor">Eronen, P.</span>, and <span class="refAuthor">H. Tschofenig</span>, <span class="refTitle">"Transport Layer Security (TLS) Session Resumption without Server-Side State"</span>, <span class="seriesInfo">RFC 5077</span>, <span class="seriesInfo">DOI 10.17487/RFC5077</span>, <time datetime="2008-01" class="refDate">January 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5077">https://www.rfc-editor.org/info/rfc5077</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5382">[RFC5382]</dt>
        <dd>
<span class="refAuthor">Guha, S., Ed.</span>, <span class="refAuthor">Biswas, K.</span>, <span class="refAuthor">Ford, B.</span>, <span class="refAuthor">Sivakumar, S.</span>, and <span class="refAuthor">P. Srisuresh</span>, <span class="refTitle">"NAT Behavioral Requirements for TCP"</span>, <span class="seriesInfo">BCP 142</span>, <span class="seriesInfo">RFC 5382</span>, <span class="seriesInfo">DOI 10.17487/RFC5382</span>, <time datetime="2008-10" class="refDate">October 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5382">https://www.rfc-editor.org/info/rfc5382</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5905">[RFC5905]</dt>
        <dd>
<span class="refAuthor">Mills, D.</span>, <span class="refAuthor">Martin, J., Ed.</span>, <span class="refAuthor">Burbank, J.</span>, and <span class="refAuthor">W. Kasch</span>, <span class="refTitle">"Network Time Protocol Version 4: Protocol and Algorithms Specification"</span>, <span class="seriesInfo">RFC 5905</span>, <span class="seriesInfo">DOI 10.17487/RFC5905</span>, <time datetime="2010-06" class="refDate">June 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5905">https://www.rfc-editor.org/info/rfc5905</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6335">[RFC6335]</dt>
        <dd>
<span class="refAuthor">Cotton, M.</span>, <span class="refAuthor">Eggert, L.</span>, <span class="refAuthor">Touch, J.</span>, <span class="refAuthor">Westerlund, M.</span>, and <span class="refAuthor">S. Cheshire</span>, <span class="refTitle">"Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry"</span>, <span class="seriesInfo">BCP 165</span>, <span class="seriesInfo">RFC 6335</span>, <span class="seriesInfo">DOI 10.17487/RFC6335</span>, <time datetime="2011-08" class="refDate">August 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6335">https://www.rfc-editor.org/info/rfc6335</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6762">[RFC6762]</dt>
        <dd>
<span class="refAuthor">Cheshire, S.</span> and <span class="refAuthor">M. Krochmal</span>, <span class="refTitle">"Multicast DNS"</span>, <span class="seriesInfo">RFC 6762</span>, <span class="seriesInfo">DOI 10.17487/RFC6762</span>, <time datetime="2013-02" class="refDate">February 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6762">https://www.rfc-editor.org/info/rfc6762</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7301">[RFC7301]</dt>
        <dd>
<span class="refAuthor">Friedl, S.</span>, <span class="refAuthor">Popov, A.</span>, <span class="refAuthor">Langley, A.</span>, and <span class="refAuthor">E. Stephan</span>, <span class="refTitle">"Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension"</span>, <span class="seriesInfo">RFC 7301</span>, <span class="seriesInfo">DOI 10.17487/RFC7301</span>, <time datetime="2014-07" class="refDate">July 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7301">https://www.rfc-editor.org/info/rfc7301</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7413">[RFC7413]</dt>
        <dd>
<span class="refAuthor">Cheng, Y.</span>, <span class="refAuthor">Chu, J.</span>, <span class="refAuthor">Radhakrishnan, S.</span>, and <span class="refAuthor">A. Jain</span>, <span class="refTitle">"TCP Fast Open"</span>, <span class="seriesInfo">RFC 7413</span>, <span class="seriesInfo">DOI 10.17487/RFC7413</span>, <time datetime="2014-12" class="refDate">December 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7413">https://www.rfc-editor.org/info/rfc7413</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7657">[RFC7657]</dt>
        <dd>
<span class="refAuthor">Black, D., Ed.</span> and <span class="refAuthor">P. Jones</span>, <span class="refTitle">"Differentiated Services (Diffserv) and Real-Time Communication"</span>, <span class="seriesInfo">RFC 7657</span>, <span class="seriesInfo">DOI 10.17487/RFC7657</span>, <time datetime="2015-11" class="refDate">November 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7657">https://www.rfc-editor.org/info/rfc7657</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7838">[RFC7838]</dt>
        <dd>
<span class="refAuthor">Nottingham, M.</span>, <span class="refAuthor">McManus, P.</span>, and <span class="refAuthor">J. Reschke</span>, <span class="refTitle">"HTTP Alternative Services"</span>, <span class="seriesInfo">RFC 7838</span>, <span class="seriesInfo">DOI 10.17487/RFC7838</span>, <time datetime="2016-04" class="refDate">April 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7838">https://www.rfc-editor.org/info/rfc7838</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8085">[RFC8085]</dt>
        <dd>
<span class="refAuthor">Eggert, L.</span>, <span class="refAuthor">Fairhurst, G.</span>, and <span class="refAuthor">G. Shepherd</span>, <span class="refTitle">"UDP Usage Guidelines"</span>, <span class="seriesInfo">BCP 145</span>, <span class="seriesInfo">RFC 8085</span>, <span class="seriesInfo">DOI 10.17487/RFC8085</span>, <time datetime="2017-03" class="refDate">March 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8085">https://www.rfc-editor.org/info/rfc8085</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8981">[RFC8981]</dt>
        <dd>
<span class="refAuthor">Gont, F.</span>, <span class="refAuthor">Krishnan, S.</span>, <span class="refAuthor">Narten, T.</span>, and <span class="refAuthor">R. Draves</span>, <span class="refTitle">"Temporary Address Extensions for Stateless Address Autoconfiguration in IPv6"</span>, <span class="seriesInfo">RFC 8981</span>, <span class="seriesInfo">DOI 10.17487/RFC8981</span>, <time datetime="2021-02" class="refDate">February 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8981">https://www.rfc-editor.org/info/rfc8981</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9218">[RFC9218]</dt>
        <dd>
<span class="refAuthor">Oku, K.</span> and <span class="refAuthor">L. Pardue</span>, <span class="refTitle">"Extensible Prioritization Scheme for HTTP"</span>, <span class="seriesInfo">RFC 9218</span>, <span class="seriesInfo">DOI 10.17487/RFC9218</span>, <time datetime="2022-06" class="refDate">June 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9218">https://www.rfc-editor.org/info/rfc9218</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9221">[RFC9221]</dt>
        <dd>
<span class="refAuthor">Pauly, T.</span>, <span class="refAuthor">Kinnear, E.</span>, and <span class="refAuthor">D. Schinazi</span>, <span class="refTitle">"An Unreliable Datagram Extension to QUIC"</span>, <span class="seriesInfo">RFC 9221</span>, <span class="seriesInfo">DOI 10.17487/RFC9221</span>, <time datetime="2022-03" class="refDate">March 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9221">https://www.rfc-editor.org/info/rfc9221</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="SSDP">[SSDP]</dt>
        <dd>
<span class="refAuthor">Donoho, A.</span>, <span class="refAuthor">Roe, B.</span>, <span class="refAuthor">Bodlaender, M.</span>, <span class="refAuthor">Gildred, J.</span>, <span class="refAuthor">Messer, A.</span>, <span class="refAuthor">Kim, Y.</span>, <span class="refAuthor">Fairman, B.</span>, and <span class="refAuthor">J. Tourzan</span>, <span class="refTitle">"UPnP Device Architecture 2.0"</span>, <time datetime="2020-04-17" class="refDate">17 April 2020</time>, <span>&lt;<a href="https://openconnectivity.org/upnp-specs/UPnP-arch-DeviceArchitecture-v2.0-20200417.pdf">https://openconnectivity.org/upnp-specs/UPnP-arch-DeviceArchitecture-v2.0-20200417.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="Swett16">[Swett16]</dt>
        <dd>
<span class="refAuthor">Swett, I.</span>, <span class="refTitle">"QUIC Deployment Experience @Google"</span>, <span class="refContent">IETF96 QUIC BoF Presentation</span>, <time datetime="2016-07-20" class="refDate">20 July 2016</time>, <span>&lt;<a href="https://www.ietf.org/proceedings/96/slides/slides-96-quic-3.pdf">https://www.ietf.org/proceedings/96/slides/slides-96-quic-3.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-taps-arch">[TAPS-ARCH]</dt>
        <dd>
<span class="refAuthor">Pauly, T.</span>, <span class="refAuthor">Trammell, B.</span>, <span class="refAuthor">Brunstrom, A.</span>, <span class="refAuthor">Fairhurst, G.</span>, and <span class="refAuthor">C. Perkins</span>, <span class="refTitle">"An Architecture for Transport Services"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-taps-arch-14</span>, <time datetime="2022-09-27" class="refDate">27 September 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-taps-arch-14">https://datatracker.ietf.org/doc/html/draft-ietf-taps-arch-14</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8446">[TLS13]</dt>
        <dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refTitle">"The Transport Layer Security (TLS) Protocol Version 1.3"</span>, <span class="seriesInfo">RFC 8446</span>, <span class="seriesInfo">DOI 10.17487/RFC8446</span>, <time datetime="2018-08" class="refDate">August 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8446">https://www.rfc-editor.org/info/rfc8446</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="Trammell16">[Trammell16]</dt>
      <dd>
<span class="refAuthor">Trammell, B.</span> and <span class="refAuthor">M. Kühlewind</span>, <span class="refTitle">"Internet Path Transparency Measurements using RIPE Atlas"</span>, <span class="refContent">RIPE 72 MAT Presentation</span>, <time datetime="2016-05-25" class="refDate">25 May 2016</time>, <span>&lt;<a href="https://ripe72.ripe.net/wp-content/uploads/presentations/86-atlas-udpdiff.pdf">https://ripe72.ripe.net/wp-content/uploads/presentations/86-atlas-udpdiff.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="acknowledgments">
<section id="appendix-A">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<p id="appendix-A-1">Special thanks to Last Call reviewers <span class="contact-name">Chris Lonvick</span> and <span class="contact-name">Ines Robles</span>.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
<p id="appendix-A-2">This work was partially supported by the European Commission under Horizon 2020
grant agreement no. 688421 Measurement and Architecture for a Middleboxed
Internet (MAMI) and by the Swiss State Secretariat for Education, Research, and
Innovation under contract no. 15.0268. This support does not imply endorsement.<a href="#appendix-A-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="contributors">
<section id="appendix-B">
      <h2 id="name-contributors">
<a href="#name-contributors" class="section-name selfRef">Contributors</a>
      </h2>
<p id="appendix-B-1">The following people have contributed significant text to or feedback
on this document:<a href="#appendix-B-1" class="pilcrow">¶</a></p>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Gorry Fairhurst</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Ian Swett</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Igor Lubashev</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Lucas Pardue</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Mike Bishop</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Mark Nottingham</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Martin Duke</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Martin Thomson</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Sean Turner</span></div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Tommy Pauly</span></div>
</address>
</section>
</div>
<div id="authors-addresses">
<section id="appendix-C">
      <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">Mirja Kühlewind</span></div>
<div dir="auto" class="left"><span class="org">Ericsson</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:mirja.kuehlewind@ericsson.com" class="email">mirja.kuehlewind@ericsson.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Brian Trammell</span></div>
<div dir="auto" class="left"><span class="org">Google Switzerland GmbH</span></div>
<div dir="auto" class="left"><span class="street-address">Gustav-Gull-Platz 1</span></div>
<div dir="auto" class="left">CH-<span class="postal-code">8004</span> <span class="locality">Zurich</span>
</div>
<div dir="auto" class="left"><span class="country-name">Switzerland</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:ietf@trammell.ch" class="email">ietf@trammell.ch</a>
</div>
</address>
</section>
</div>
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