File: rfc9149.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 9149: TLS Ticket Requests</title>
<meta content="Tommy Pauly" name="author">
<meta content="David Schinazi" name="author">
<meta content="Christopher A. Wood" name="author">
<meta content="
       
   TLS session tickets enable stateless connection resumption for
   clients without server-side, per-client state.  Servers vend an
   arbitrary number of session tickets to clients, at their discretion,
   upon connection establishment.  Clients store and use tickets when
   resuming future connections.  This document describes a mechanism by
   which clients can specify the desired number of tickets needed for
   future connections.  This extension aims to provide a means for
   servers to determine the number of tickets to generate in order to
   reduce ticket waste while simultaneously priming clients for future
   connection attempts. 
    " name="description">
<meta content="xml2rfc 3.12.2" name="generator">
<meta content="TLS" name="keyword">
<meta content="Tickets" name="keyword">
<meta content="9149" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.12.2
    Python 3.6.15
    appdirs 1.4.4
    ConfigArgParse 1.4.1
    google-i18n-address 2.4.0
    html5lib 1.0.1
    intervaltree 3.0.2
    Jinja2 2.11.3
    kitchen 1.2.6
    lxml 4.4.2
    pycairo 1.15.1
    pycountry 19.8.18
    pyflakes 2.1.1
    PyYAML 5.4.1
    requests 2.24.0
    setuptools 40.5.0
    six 1.14.0
    WeasyPrint 52.5
-->
<link href="rfc9149.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

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

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

*/

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

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

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
  margin: 1em 0 0.5em;
  font-weight: bold;
  line-height: 1.3;
}
#title {
  clear: both;
  border-bottom: 1px solid #ddd;
  margin: 0 0 0.5em 0;
  padding: 1em 0 0.5em;
}
.author {
  padding-bottom: 4px;
}
h1 {
  font-size: 26px;
  margin: 1em 0;
}
h2 {
  font-size: 22px;
  margin-top: -20px;  /* provide offset for in-page anchors */
  padding-top: 33px;
}
h3 {
  font-size: 18px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h4 {
  font-size: 16px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h5, h6 {
  font-size: 14px;
}
#n-copyright-notice {
  border-bottom: 1px solid #ddd;
  padding-bottom: 1em;
  margin-bottom: 1em;
}
/* general structure */
p {
  padding: 0;
  margin: 0 0 1em 0;
  text-align: left;
}
div, span {
  position: relative;
}
div {
  margin: 0;
}
.alignRight.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
  padding: 0;
}
.alignRight {
  margin: 1em 0;
}
.alignRight > *:first-child {
  border: none;
  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
  clear: both;
  display: block;
  border: none;
}
svg {
  display: block;
}
.alignCenter.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignCenter.art-text pre {
  padding: 0;
}
.alignCenter {
  margin: 1em 0;
}
.alignCenter > *:first-child {
  border: none;
  /* this isn't optimal, but it's an existence proof.  PrinceXML doesn't
     support flexbox yet.
  */
  display: table;
  margin: 0 auto;
}

/* lists */
ol, ul {
  padding: 0;
  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
  margin-left: 1em;
}
li {
  margin: 0 0 0.25em 0;
}
.ulCompact li {
  margin: 0;
}
ul.empty, .ulEmpty {
  list-style-type: none;
}
ul.empty li, .ulEmpty li {
  margin-top: 0.5em;
}
ul.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;
  }
  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 {
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<table class="ears">
<thead><tr>
<td class="left">RFC 9149</td>
<td class="center">TLS Ticket Requests</td>
<td class="right">April 2022</td>
</tr></thead>
<tfoot><tr>
<td class="left">Pauly, et al.</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc9149" class="eref">9149</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2022-04" class="published">April 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">T. Pauly</div>
<div class="org">Apple Inc.</div>
</div>
<div class="author">
      <div class="author-name">D. Schinazi</div>
<div class="org">Google LLC</div>
</div>
<div class="author">
      <div class="author-name">C.A. Wood</div>
<div class="org">Cloudflare</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9149</h1>
<h1 id="title">TLS Ticket Requests</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">
   TLS session tickets enable stateless connection resumption for
   clients without server-side, per-client state.  Servers vend an
   arbitrary number of session tickets to clients, at their discretion,
   upon connection establishment.  Clients store and use tickets when
   resuming future connections.  This document describes a mechanism by
   which clients can specify the desired number of tickets needed for
   future connections.  This extension aims to provide a means for
   servers to determine the number of tickets to generate in order to
   reduce ticket waste while simultaneously priming clients for future
   connection attempts.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc9149">https://www.rfc-editor.org/info/rfc9149</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2022 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Revised BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Revised BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.1">
                <p id="section-toc.1-1.1.2.1.1" class="keepWithNext"><a href="#section-1.1" class="xref">1.1</a>.  <a href="#name-requirements-language" class="xref">Requirements Language</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="xref">2</a>.  <a href="#name-use-cases" class="xref">Use Cases</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-ticket-requests" class="xref">Ticket Requests</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-performance-considerations" class="xref">Performance Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7.2.1">
                <p id="section-toc.1-1.7.2.1.1"><a href="#section-7.1" class="xref">7.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7.2.2">
                <p id="section-toc.1-1.7.2.2.1"><a href="#section-7.2" class="xref">7.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#appendix-A" class="xref"></a><a href="#name-acknowledgements" class="xref">Acknowledgements</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#appendix-B" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<div id="sect-1">
<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">
   As described in <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span>, TLS servers
   vend clients an arbitrary number of session tickets at their own discretion
   in NewSessionTicket messages.  There are at least three limitations with
   this design.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">
   First, servers vend some (often hard-coded) number of tickets per
   connection.  Some server implementations return a different default number
   of tickets for session resumption than for the initial connection that
   created the session.  No static choice, whether fixed or dependent upon
   resumption, is ideal for all situations.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">
   Second, clients do not have a way of expressing their desired number of
   tickets, which can impact future connection establishment.  For example,
   clients can open parallel TLS connections to the same server for HTTP, or
   they can race TLS connections across different network interfaces.  The
   latter is especially useful in transport systems that implement Happy
   Eyeballs <span>[<a href="#RFC8305" class="xref">RFC8305</a>]</span>.  Since clients control
   connection concurrency and resumption, a standard mechanism for requesting
   more than one ticket is desirable for avoiding ticket reuse.  See <span><a href="https://www.rfc-editor.org/rfc/rfc8446#appendix-C.4" class="relref">Appendix C.4</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span> for
   discussion of ticket reuse risks.<a href="#section-1-3" class="pilcrow">¶</a></p>
<p id="section-1-4">
   Third, all tickets in the client's possession ultimately derive from
   some initial connection.  Especially when the client was initially
   authenticated with a client certificate, that session may need to be
   refreshed from time to time.  Consequently, a server may periodically
   force a new connection even when the client presents a valid ticket.
   When that happens, it is possible that any other tickets derived from
   the same original session are equally invalid.  A client avoids a
   full handshake on subsequent connections if it replaces all stored
   tickets with new ones obtained from the just-performed full
   handshake.  The number of tickets the server should vend for a new
   connection may therefore need to be larger than the number for
   routine resumption.<a href="#section-1-4" class="pilcrow">¶</a></p>
<p id="section-1-5">
   This document specifies a new TLS extension, "ticket_request", that
   clients can use to express their desired number of session tickets.
   Servers can use this extension as a hint for the number of NewSessionTicket
   messages to vend.  This extension is only applicable to TLS 1.3 <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span>, DTLS 1.3 <span>[<a href="#RFC9147" class="xref">RFC9147</a>]</span>, and
   future versions of (D)TLS.<a href="#section-1-5" class="pilcrow">¶</a></p>
<div id="sect-1.1">
<section id="section-1.1">
        <h3 id="name-requirements-language">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-requirements-language" class="section-name selfRef">Requirements Language</a>
        </h3>
<p id="section-1.1-1">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> 
    when, and only when, they appear in all capitals, as shown here.<a href="#section-1.1-1" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="sect-2">
<section id="section-2">
      <h2 id="name-use-cases">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-use-cases" class="section-name selfRef">Use Cases</a>
      </h2>
<p id="section-2-1">
   The ability to request one or more tickets is useful for a variety of
   purposes:<a href="#section-2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-2-2">
        <dt id="section-2-2.1">Parallel HTTP connections:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.2">To improve performance, a client may open parallel connections. To avoid
ticket reuse, the client may use distinct tickets on each connection. Clients
must therefore bound the number of parallel connections they initiate by the
number of tickets in their possession or risk ticket reuse.<a href="#section-2-2.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.3">Connection racing:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.4">Happy Eyeballs V2 <span>[<a href="#RFC8305" class="xref">RFC8305</a>]</span> describes
techniques for performing connection racing.  The Transport Services
Implementation document <span>[<a href="#I-D.ietf-taps-impl" class="xref">TAPS</a>]</span>
also describes how connections can race across interfaces and address
families.  In such cases, clients may use more than one ticket while racing
connection attempts in order to establish one successful connection.  Having
multiple tickets equips clients with enough tickets to initiate connection
racing while avoiding ticket reuse and ensuring that their cache of tickets
does not empty during such races.  Moreover, as some servers may implement
single-use tickets, distinct tickets prevent premature ticket invalidation by
racing.<a href="#section-2-2.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.5">Less ticket waste:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.6">Currently, TLS servers use application-specific, and often
implementation-specific, logic to determine how many tickets to issue.  By
moving the burden of ticket count to clients, servers do not generate wasteful
tickets.  As an example, clients might only request one ticket during
resumption.  Moreover, as ticket generation might involve expensive
computation, e.g., public key cryptographic operations, avoiding waste is
desirable.<a href="#section-2-2.6" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.7">Decline resumption:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.8">Clients can indicate they do not intend to resume a connection by sending
a ticket request with count of zero.<a href="#section-2-2.8" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
</section>
</div>
<div id="sect-3">
<section id="section-3">
      <h2 id="name-ticket-requests">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-ticket-requests" class="section-name selfRef">Ticket Requests</a>
      </h2>
<p id="section-3-1">
   As discussed in <a href="#sect-1" class="xref">Section 1</a>, clients may want different numbers of
   tickets for new or resumed connections.  Clients may indicate to
   servers their desired number of tickets to receive on a single
   connection, in the case of a new or resumed connection, via the
   following "ticket_request" extension:<a href="#section-3-1" class="pilcrow">¶</a></p>
<div id="section-3-2">
<pre class="lang-tls-presentation sourcecode">
enum {
    ticket_request(58), (65535)
} ExtensionType;
</pre><a href="#section-3-2" class="pilcrow">¶</a>
</div>
<p id="section-3-3">
   Clients <span class="bcp14">MAY</span> send this extension in ClientHello.  It contains the
   following structure:<a href="#section-3-3" class="pilcrow">¶</a></p>
<div id="section-3-4">
<pre class="lang-tls-presentation sourcecode">
struct {
    uint8 new_session_count;
    uint8 resumption_count;
} ClientTicketRequest;
</pre><a href="#section-3-4" class="pilcrow">¶</a>
</div>
<span class="break"></span><dl class="dlParallel" id="section-3-5">
        <dt id="section-3-5.1">new_session_count:</dt>
        <dd style="margin-left: 1.5em" id="section-3-5.2">
 The number of tickets desired by the client if the server chooses to
 negotiate a new connection.<a href="#section-3-5.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-3-5.3">resumption_count:</dt>
        <dd style="margin-left: 1.5em" id="section-3-5.4">
 The number of tickets desired by the client if the server is willing
 to resume using a ticket presented in this ClientHello.<a href="#section-3-5.4" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-3-6">
   A client starting a new connection <span class="bcp14">SHOULD</span> set new_session_count to
   the desired number of session tickets and resumption_count to 0.
   Once a client's ticket cache is primed, a resumption_count of 1 is a
   good choice that allows the server to replace each ticket with a new
   ticket without over-provisioning the client with excess tickets.
   However, clients that race multiple connections and place a separate
   ticket in each will ultimately end up with just the tickets from a
   single resumed session.  In that case, clients can send a
   resumption_count equal to the number of connections they are
   attempting in parallel.  (Clients that send a resumption_count less
   than the number of parallel connection attempts might end up with
   zero tickets.)<a href="#section-3-6" class="pilcrow">¶</a></p>
<p id="section-3-7">
   When a client presenting a previously obtained ticket finds that the
   server nevertheless negotiates a new connection, the client <span class="bcp14">SHOULD</span>
   assume that any other tickets associated with the same session as the
   presented ticket are also no longer valid for resumption.  This
   includes tickets obtained during the initial (new) connection and all
   tickets subsequently obtained as part of subsequent resumptions.
   Requesting more than one ticket when servers complete a new
   connection helps keep the session cache primed.<a href="#section-3-7" class="pilcrow">¶</a></p>
<p id="section-3-8">
   Servers <span class="bcp14">SHOULD NOT</span> send more tickets than requested for the
   connection type selected by the server (new or resumed connection).
   Moreover, servers <span class="bcp14">SHOULD</span> place a limit on the number of tickets they
   are willing to send, whether for new or resumed connections, to save
   resources.  Therefore, the number of NewSessionTicket messages sent
   will typically be the minimum of the server's self-imposed limit and
   the number requested.  Servers <span class="bcp14">MAY</span> send additional tickets, typically
   using the same limit, if the tickets that are originally sent are
   somehow invalidated.<a href="#section-3-8" class="pilcrow">¶</a></p>
<p id="section-3-9">
   A server that supports and uses a client "ticket_request" extension
   <span class="bcp14">MUST</span> also send the "ticket_request" extension in the
   EncryptedExtensions message.  It contains the following structure:<a href="#section-3-9" class="pilcrow">¶</a></p>
<div id="section-3-10">
<pre class="lang-tls-presentation sourcecode">
struct {
    uint8 expected_count;
} ServerTicketRequestHint;
</pre><a href="#section-3-10" class="pilcrow">¶</a>
</div>
<span class="break"></span><dl class="dlParallel" id="section-3-11">
        <dt id="section-3-11.1">expected_count:</dt>
        <dd style="margin-left: 1.5em" id="section-3-11.2">
 The number of tickets the server expects to send in this connection.<a href="#section-3-11.2" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-3-12">
   Servers <span class="bcp14">MUST NOT</span> send the "ticket_request" extension in any handshake
   message, including ServerHello or HelloRetryRequest messages.  A
   client <span class="bcp14">MUST</span> abort the connection with an "illegal_parameter" alert if
   the "ticket_request" extension is present in any server handshake
   message.<a href="#section-3-12" class="pilcrow">¶</a></p>
<p id="section-3-13">
   If a client receives a HelloRetryRequest, the presence (or absence)
   of the "ticket_request" extension <span class="bcp14">MUST</span> be maintained in the second
   ClientHello message.  Moreover, if this extension is present, a
   client <span class="bcp14">MUST NOT</span> change the value of ClientTicketRequest in the second
   ClientHello message.<a href="#section-3-13" class="pilcrow">¶</a></p>
</section>
</div>
<div id="sect-4">
<section id="section-4">
      <h2 id="name-iana-considerations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-4-1">
   IANA has added the following entry to the "TLS ExtensionType Values"
   registry <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span> <span>[<a href="#RFC8447" class="xref">RFC8447</a>]</span>:<a href="#section-4-1" class="pilcrow">¶</a></p>
<span id="name-addition-to-tls-extensionty"></span><div id="iana_table">
<table class="center" id="table-1">
        <caption>
<a href="#table-1" class="selfRef">Table 1</a>:
<a href="#name-addition-to-tls-extensionty" class="selfRef">Addition to TLS ExtensionType Values Registry</a>
        </caption>
<thead>
          <tr>
            <th class="text-left" rowspan="1" colspan="1">Value</th>
            <th class="text-left" rowspan="1" colspan="1">Extension Name</th>
            <th class="text-left" rowspan="1" colspan="1">TLS 1.3</th>
            <th class="text-left" rowspan="1" colspan="1">DTLS-Only</th>
            <th class="text-left" rowspan="1" colspan="1">Recommended</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">58</td>
            <td class="text-left" rowspan="1" colspan="1">ticket_request</td>
            <td class="text-left" rowspan="1" colspan="1">CH, EE</td>
            <td class="text-left" rowspan="1" colspan="1">N</td>
            <td class="text-left" rowspan="1" colspan="1">Y</td>
          </tr>
        </tbody>
      </table>
</div>
</section>
</div>
<div id="sect-5">
<section id="section-5">
      <h2 id="name-performance-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-performance-considerations" class="section-name selfRef">Performance Considerations</a>
      </h2>
<p id="section-5-1">
   Servers can send tickets in NewSessionTicket messages any time after
   the server Finished message (see <span><a href="https://www.rfc-editor.org/rfc/rfc8446#section-4.6.1" class="relref">Section 4.6.1</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>).  A server
   that chooses to send a large number of tickets to a client can
   potentially harm application performance if the tickets are sent
   before application data.  For example, if the transport connection
   has a constrained congestion window, ticket messages could delay
   sending application data.  To avoid this, servers should prioritize
   sending application data over tickets when possible.<a href="#section-5-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="sect-6">
<section id="section-6">
      <h2 id="name-security-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-6-1">
   Ticket reuse is a security and privacy concern.  Moreover, clients must
   take care when pooling tickets as a means of avoiding or amortizing
   handshake costs.  If servers do not rotate session ticket encryption keys
   frequently, clients may be encouraged to obtain and use tickets beyond
   common lifetime windows of, e.g., 24 hours.  Despite ticket lifetime hints
   provided by servers, clients <span class="bcp14">SHOULD</span> dispose of cached
   tickets after some reasonable amount of time that mimics the session ticket
   encryption key rotation period.  Specifically, as specified in <span><a href="https://www.rfc-editor.org/rfc/rfc8446#section-4.6.1" class="relref">Section 4.6.1</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>,
   clients <span class="bcp14">MUST NOT</span> cache tickets for longer than 7 days.<a href="#section-6-1" class="pilcrow">¶</a></p>
<p id="section-6-2">
   In some cases, a server may send NewSessionTicket messages immediately upon
   sending the server Finished message rather than waiting for the client
   Finished message.  If the server has not verified the client's ownership of its IP
   address, e.g., with the TLS cookie extension (see <span><a href="https://www.rfc-editor.org/rfc/rfc8446#section-4.2.2" class="relref">Section 4.2.2</a> of [<a href="#RFC8446" class="xref">RFC8446</a>]</span>), an attacker may
   take advantage of this behavior to create an amplification attack
   proportional to the count value toward a target by performing a (DTLS) key
   exchange over UDP with spoofed packets.  Servers <span class="bcp14">SHOULD</span>
   limit the number of NewSessionTicket messages they send until they have
   verified the client's ownership of its IP address.<a href="#section-6-2" class="pilcrow">¶</a></p>
<p id="section-6-3">
   Servers that do not enforce a limit on the number of NewSessionTicket
   messages sent in response to a "ticket_request" extension could leave
   themselves open to DoS attacks, especially if ticket creation is
   expensive.<a href="#section-6-3" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-7">
      <h2 id="name-references">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-7.1">
        <h3 id="name-normative-references">
<a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8174">[RFC8174]</dt>
        <dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8446">[RFC8446]</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="RFC8447">[RFC8447]</dt>
        <dd>
<span class="refAuthor">Salowey, J.</span> and <span class="refAuthor">S. Turner</span>, <span class="refTitle">"IANA Registry Updates for TLS and DTLS"</span>, <span class="seriesInfo">RFC 8447</span>, <span class="seriesInfo">DOI 10.17487/RFC8447</span>, <time datetime="2018-08" class="refDate">August 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8447">https://www.rfc-editor.org/info/rfc8447</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9147">[RFC9147]</dt>
      <dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refAuthor">Tschofenig, H.</span>, and <span class="refAuthor">N. Modadugu</span>, <span class="refTitle">"The Datagram Transport Layer Security (DTLS) Protocol Version 1.3"</span>, <span class="seriesInfo">RFC 9147</span>, <span class="seriesInfo">DOI 10.17487/RFC9147</span>, <time datetime="2022-04" class="refDate">April 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9147">https://www.rfc-editor.org/info/rfc9147</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-7.2">
        <h3 id="name-informative-references">
<a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC8305">[RFC8305]</dt>
        <dd>
<span class="refAuthor">Schinazi, D.</span> and <span class="refAuthor">T. Pauly</span>, <span class="refTitle">"Happy Eyeballs Version 2: Better Connectivity Using Concurrency"</span>, <span class="seriesInfo">RFC 8305</span>, <span class="seriesInfo">DOI 10.17487/RFC8305</span>, <time datetime="2017-12" class="refDate">December 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8305">https://www.rfc-editor.org/info/rfc8305</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-taps-impl">[TAPS]</dt>
      <dd>
<span class="refAuthor">Brunstrom, A., Ed.</span>, <span class="refAuthor">Pauly, T., Ed.</span>, <span class="refAuthor">Enghardt, T.</span>, <span class="refAuthor">Tiesel, P.</span>, and <span class="refAuthor">M. Welzl</span>, <span class="refTitle">"Implementing Interfaces to Transport Services"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-taps-impl-12</span>, <time datetime="2022-03-07" class="refDate">7 March 2022</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-taps-impl-12">https://datatracker.ietf.org/doc/html/draft-ietf-taps-impl-12</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="sect-7">
<section id="appendix-A">
      <h2 id="name-acknowledgements">
<a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a>
      </h2>
<p id="appendix-A-1">
   The authors would like to thank <span class="contact-name">David Benjamin</span>,
   <span class="contact-name">Eric Rescorla</span>, <span class="contact-name">Nick Sullivan</span>,
   <span class="contact-name">Martin Thomson</span>, <span class="contact-name">Hubert Kario</span>,
   and other members of the TLS Working Group for discussions on earlier draft
   versions of this document.  <span class="contact-name">Viktor Dukhovni</span>
   contributed text allowing clients to send multiple counts in a ticket
   request.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="authors-addresses">
<section id="appendix-B">
      <h2 id="name-authors-addresses">
<a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Tommy Pauly</span></div>
<div dir="auto" class="left"><span class="org">Apple Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">One Apple Park Way</span></div>
<div dir="auto" class="left">
<span class="locality">Cupertino</span>, <span class="region">CA</span> <span class="postal-code">95014</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:tpauly@apple.com" class="email">tpauly@apple.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">David Schinazi</span></div>
<div dir="auto" class="left"><span class="org">Google LLC</span></div>
<div dir="auto" class="left"><span class="street-address">1600 Amphitheatre Parkway</span></div>
<div dir="auto" class="left">
<span class="locality">Mountain View</span>, <span class="region">CA</span> <span class="postal-code">94043</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:dschinazi.ietf@gmail.com" class="email">dschinazi.ietf@gmail.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Christopher A. Wood</span></div>
<div dir="auto" class="left"><span class="org">Cloudflare</span></div>
<div dir="auto" class="left"><span class="street-address">101 Townsend St</span></div>
<div dir="auto" class="left">
<span class="locality">San Francisco</span>, <span class="region">CA</span> <span class="postal-code">94107</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:caw@heapingbits.net" class="email">caw@heapingbits.net</a>
</div>
</address>
</section>
</div>
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