File: rfc9090.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 9090: Concise Binary Object Representation (CBOR) Tags for Object Identifiers</title>
<meta content="Carsten Bormann" name="author">
<meta content="
       The Concise Binary Object Representation (CBOR), defined in RFC 8949, is a data
format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the
need for version negotiation. 
       This document defines CBOR tags for
object identifiers (OIDs) and is
the reference document for the IANA registration of the CBOR tags
so defined. 
    " name="description">
<meta content="xml2rfc 3.9.1" name="generator">
<meta content="binary format" name="keyword">
<meta content="data interchange format" name="keyword">
<meta content="ASN.1" name="keyword">
<meta content="OID" name="keyword">
<meta content="Object Identifier" name="keyword">
<meta content="9090" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.9.1
    Python 3.6.10
    appdirs 1.4.4
    ConfigArgParse 1.2.3
    google-i18n-address 2.3.5
    html5lib 1.0.1
    intervaltree 3.0.2
    Jinja2 2.11.2
    kitchen 1.2.6
    lxml 4.4.2
    pycairo 1.19.0
    pycountry 19.8.18
    pyflakes 2.1.1
    PyYAML 5.3.1
    requests 2.22.0
    setuptools 40.6.2
    six 1.14.0
    WeasyPrint 51
-->
<link href="rfc9090.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;
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

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

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

.refInstance {
  margin-bottom: 1.25em;
}

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

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

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

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

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

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

/* pagination */
@media print {
  body {

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

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

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

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

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

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

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

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

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

}

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


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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
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<table class="ears">
<thead><tr>
<td class="left">RFC 9090</td>
<td class="center">CBOR Tags for OIDs</td>
<td class="right">July 2021</td>
</tr></thead>
<tfoot><tr>
<td class="left">Bormann</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/rfc9090" class="eref">9090</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2021-07" class="published">July 2021</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Author:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">C. Bormann</div>
<div class="org">Universität Bremen TZI</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9090</h1>
<h1 id="title">Concise Binary Object Representation (CBOR) Tags for Object Identifiers</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">The Concise Binary Object Representation (CBOR), defined in RFC 8949, is a data
format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the
need for version negotiation.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
<p id="section-abstract-2">This document defines CBOR tags for
object identifiers (OIDs) and is
the reference document for the IANA registration of the CBOR tags
so defined.<a href="#section-abstract-2" 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/rfc9090">https://www.rfc-editor.org/info/rfc9090</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2021 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="ulBare ulEmpty compact toc">
<li class="ulBare ulEmpty compact toc" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" 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-terminology" class="xref">Terminology</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-object-identifiers" class="xref">Object Identifiers</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" id="section-toc.1-1.2.2.1">
                <p id="section-toc.1-1.2.2.1.1" class="keepWithNext"><a href="#section-2.1" class="xref">2.1</a>.  <a href="#name-requirements-on-the-byte-st" class="xref">Requirements on the Byte String Being Tagged</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" id="section-toc.1-1.2.2.2">
                <p id="section-toc.1-1.2.2.2.1"><a href="#section-2.2" class="xref">2.2</a>.  <a href="#name-preferred-serialization-con" class="xref">Preferred Serialization Considerations</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" id="section-toc.1-1.2.2.3">
                <p id="section-toc.1-1.2.2.3.1"><a href="#section-2.3" class="xref">2.3</a>.  <a href="#name-discussion" class="xref">Discussion</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-basic-examples" class="xref">Basic Examples</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-encoding-of-the-sha-256-oid" class="xref">Encoding of the SHA-256 OID</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="xref">3.2</a>.  <a href="#name-encoding-of-a-mib-relative-" class="xref">Encoding of a MIB Relative OID</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-tag-factoring-with-arrays-a" class="xref">Tag Factoring with Arrays and Maps</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="xref">4.1</a>.  <a href="#name-preferred-serialization-cons" class="xref">Preferred Serialization Considerations</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="xref">4.2</a>.  <a href="#name-tag-factoring-example-x500-" class="xref">Tag Factoring Example: X.500 Distinguished Name</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-cddl-control-operators" class="xref">CDDL Control Operators</a></p>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-cddl-type-names" class="xref">CDDL Type Names</a></p>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" 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-cbor-tags" class="xref">CBOR Tags</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" 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-cddl-control-operators-2" class="xref">CDDL Control Operators</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-8" class="xref">8</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a></p>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-9" class="xref">9</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="ulEmpty ulBare compact toc">
<li class="ulEmpty ulBare compact toc" id="section-toc.1-1.9.2.1">
                <p id="section-toc.1-1.9.2.1.1"><a href="#section-9.1" class="xref">9.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="ulEmpty ulBare compact toc" id="section-toc.1-1.9.2.2">
                <p id="section-toc.1-1.9.2.2.1"><a href="#section-9.2" class="xref">9.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#appendix-A" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a></p>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#appendix-B" class="xref"></a><a href="#name-contributors" class="xref">Contributors</a></p>
</li>
          <li class="ulBare ulEmpty compact toc" id="section-toc.1-1.12">
            <p id="section-toc.1-1.12.1"><a href="#appendix-C" class="xref"></a><a href="#name-authors-address" class="xref">Author's Address</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<div id="intro">
<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">The Concise Binary Object Representation (CBOR) <span>[<a href="#RFC8949" class="xref">RFC8949</a>]</span> provides
for the interchange of structured data without a requirement for a
pre-agreed schema.
<span>[<a href="#RFC8949" class="xref">RFC8949</a>]</span> defines a basic set of data types, as well as a tagging
mechanism that enables extending the set of data types supported via
an IANA registry.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">This document defines CBOR tags for object identifiers
(OIDs) <span>[<a href="#X.660" class="xref">X.660</a>]</span>, which many IETF protocols carry.
The ASN.1 Basic Encoding Rules
(BER) <span>[<a href="#X.690" class="xref">X.690</a>]</span> specify binary encodings of both (absolute) object identifiers
and relative object identifiers.
The contents of these encodings (the "value" part of BER's
type-length-value structure) can be carried in a CBOR byte string.
This document defines two CBOR tags that cover the two kinds of
ASN.1 object identifiers encoded in this way and a third one to enable a
common optimization.
The tags can also be applied to arrays and maps to efficiently tag all
elements of an array or all keys of a map.
This document is the reference document for the IANA registration of
the tags so defined.<a href="#section-1-2" class="pilcrow">¶</a></p>
<div id="terms">
<section id="section-1.1">
        <h3 id="name-terminology">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-terminology" class="section-name selfRef">Terminology</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>
<p id="section-1.1-2">The terminology of <span>[<a href="#RFC8949" class="xref">RFC8949</a>]</span> applies; in particular,
the term "byte" is used in its now-customary sense as a synonym for
"octet".
The verb "to tag (something)" is used to express the construction of a
CBOR tag, with the object (something) as the tag content and a tag
number indicated elsewhere in the sentence (for instance, in a "with"
clause or by the shorthand "an NNN tag" for "a tag with tag number NNN"). The term "SDNV" (Self-Delimiting Numeric Value) is used as defined in
<span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span>, with the additional restriction detailed in <a href="#reqts" class="xref">Section 2.1</a> (no
leading zeros).<a href="#section-1.1-2" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="oids">
<section id="section-2">
      <h2 id="name-object-identifiers">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-object-identifiers" class="section-name selfRef">Object Identifiers</a>
      </h2>
<p id="section-2-1">The International Object Identifier tree <span>[<a href="#X.660" class="xref">X.660</a>]</span> is
a hierarchically managed space of
identifiers, each of which is uniquely represented as a sequence of
unsigned integer values
<span>[<a href="#X.680" class="xref">X.680</a>]</span>.
(These integer values are called "primary integer values" in <span>[<a href="#X.660" class="xref">X.660</a>]</span> because they can be accompanied by (not necessarily unambiguous)
secondary identifiers.  We ignore the latter and simply use the term
"integer values" here, occasionally calling out their unsignedness.
We also use the term "arc" when the focus is on the edge of the tree
labeled by such an integer value, as well as in the sense of a "long
arc", i.e., a (sub)sequence of such integer values.)<a href="#section-2-1" class="pilcrow">¶</a></p>
<p id="section-2-2">While these sequences can easily be represented in CBOR arrays of
unsigned integers, a more compact representation can often be achieved
by adopting the widely used representation of object identifiers
defined in BER; this representation may also be more amenable to
processing by other software that makes use of object identifiers.<a href="#section-2-2" class="pilcrow">¶</a></p>
<p id="section-2-3">BER represents the sequence of unsigned integers by concatenating
self-delimiting representations <span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span> of each of the integer values in sequence.<a href="#section-2-3" class="pilcrow">¶</a></p>
<p id="section-2-4">ASN.1 distinguishes absolute object identifiers (ASN.1 type <code>OBJECT IDENTIFIER</code>),
which begin at a root arc (<span>[<a href="#X.660" class="xref">X.660</a>]</span>, Clause 3.5.21), from relative object
identifiers (ASN.1 type <code>RELATIVE-OID</code>), which begin
relative to some object identifier known from context (<span>[<a href="#X.680" class="xref">X.680</a>]</span>,
Clause 3.8.63).
As a special optimization,
BER combines the first two integers in an absolute object identifier
into one numeric identifier by making use of the property of the
hierarchy that the first arc has only three integer values (0, 1, and 2)
and the second arcs under 0 and 1 are limited to the integer values between
0 and 39.  (The root arc <code>joint-iso-itu-t(2)</code> has
no such limitations on its second arc.)
If X and Y are the first two integer values,
the single integer value actually encoded is computed as:<a href="#section-2-4" class="pilcrow">¶</a></p>
<p style="margin-left: 1.5em" id="section-2-5">X * 40 + Y<a href="#section-2-5" class="pilcrow">¶</a></p>
<p id="section-2-6">The inverse transformation (again making use of the known ranges of X
and Y) is applied when decoding the object identifier.<a href="#section-2-6" class="pilcrow">¶</a></p>
<p id="section-2-7">Since the semantics of absolute and relative object identifiers
differ and since it is very common for companies to use self-assigned numbers
under the arc <code>1.3.6.1.4.1</code> (IANA Private Enterprise Number OID
<span>[<a href="#IANA.enterprise-numbers" class="xref">IANA.enterprise-numbers</a>]</span>) that adds 5 fixed bytes to an encoded OID value,
this specification defines three tags, collectively called the
"OID tags" here:<a href="#section-2-7" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-2-8">
        <dt id="section-2-8.1">Tag number 111:</dt>
        <dd style="margin-left: 1.5em" id="section-2-8.2">Used to tag a byte string as the BER encoding <span>[<a href="#X.690" class="xref">X.690</a>]</span> of an
absolute object identifier (simply "object identifier" or "OID").<a href="#section-2-8.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-8.3">Tag number 110:</dt>
        <dd style="margin-left: 1.5em" id="section-2-8.4">Used to tag a byte string as the BER encoding <span>[<a href="#X.690" class="xref">X.690</a>]</span> of a relative
object identifier (also called "relative OID").  Since the encoding of each
number is the same as for Self-Delimiting Numeric Values
(SDNVs) <span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span>, this tag can also be used for tagging a byte string that
contains a sequence of zero or more SDNVs (or a more
application-specific tag can be created for such an application).<a href="#section-2-8.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-8.5">Tag number 112:</dt>
        <dd style="margin-left: 1.5em" id="section-2-8.6">Structurally like tag 110 but understood to be relative to
<code>1.3.6.1.4.1</code> (IANA Private Enterprise Number OID <span>[<a href="#IANA.enterprise-numbers" class="xref">IANA.enterprise-numbers</a>]</span>).  Hence, the
semantics of the result are that of an absolute object identifier.<a href="#section-2-8.6" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<div id="reqts">
<section id="section-2.1">
        <h3 id="name-requirements-on-the-byte-st">
<a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-requirements-on-the-byte-st" class="section-name selfRef">Requirements on the Byte String Being Tagged</a>
        </h3>
<p id="section-2.1-1">To form a valid tag, a byte string tagged with 111, 110, or 112
<span class="bcp14">MUST</span> be syntactically valid contents (the value part) for a BER
representation of an object identifier (see <a href="#oid-x.690" class="xref">Table 1</a>):<a href="#section-2.1-1" class="pilcrow">¶</a></p>
<span id="name-tag-number-and-section-of-x"></span><div id="oid-x.690">
<table class="center" id="table-1">
          <caption>
<a href="#table-1" class="selfRef">Table 1</a>:
<a href="#name-tag-number-and-section-of-x" class="selfRef">Tag Number and Section of X.690 Governing Tag Content</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Tag number</th>
              <th class="text-left" rowspan="1" colspan="1">Section of <span>[<a href="#X.690" class="xref">X.690</a>]</span>
</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">111</td>
              <td class="text-left" rowspan="1" colspan="1">8.19</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">110</td>
              <td class="text-left" rowspan="1" colspan="1">8.20</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">112</td>
              <td class="text-left" rowspan="1" colspan="1">8.20</td>
            </tr>
          </tbody>
        </table>
</div>
<p id="section-2.1-3">This is a concatenation of zero or
more SDNV values, where each SDNV value is a sequence of one or more bytes that
all have their most significant bit set, except for the last byte,
where it is unset.
Also, the first byte of each SDNV cannot be a
leading zero in SDNV's base-128 arithmetic, so it cannot take the
value 0x80 (bullet (c) in Section 8.1.2.4.2 of <span>[<a href="#X.690" class="xref">X.690</a>]</span>).<a href="#section-2.1-3" class="pilcrow">¶</a></p>
<p id="section-2.1-4">In other words:<a href="#section-2.1-4" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-2.1-5.1">The byte string's first byte, and any byte that follows a byte that has the most significant
bit unset, <span class="bcp14">MUST NOT</span> be 0x80 (this requirement requires expressing the
integer values in their shortest form, with no leading zeroes).<a href="#section-2.1-5.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.1-5.2">The byte string's last byte <span class="bcp14">MUST NOT</span> have the most significant bit set (this
requirement excludes an incomplete final integer value).<a href="#section-2.1-5.2" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-2.1-6">If either of these invalid conditions are encountered, the tag is
invalid.<a href="#section-2.1-6" class="pilcrow">¶</a></p>
<p id="section-2.1-7"><span>[<a href="#X.680" class="xref">X.680</a>]</span> restricts RELATIVE-OID values to having at least
one arc, i.e., their encoding would have at least one SDNV.
This specification permits
empty relative object identifiers; they may
still be excluded by application semantics.<a href="#section-2.1-7" class="pilcrow">¶</a></p>
<p id="section-2.1-8">To facilitate the search for specific object ID values, it is <span class="bcp14">RECOMMENDED</span>
that definite length encoding (see <span><a href="https://www.rfc-editor.org/rfc/rfc8949#section-3.2.3" class="relref">Section 3.2.3</a> of [<a href="#RFC8949" class="xref">RFC8949</a>]</span>) be used
for the byte strings that are used as tag content for these tags.<a href="#section-2.1-8" class="pilcrow">¶</a></p>
<p id="section-2.1-9">The valid set of byte strings can also be expressed using regular
expressions on bytes, using no specific notation but resembling Perl Compatible Regular Expressions
<span>[<a href="#PCRE" class="xref">PCRE</a>]</span>.  Unlike typical regular expressions that operate on
character sequences, the following regular expressions take bytes as
their domain, so they can be applied directly to CBOR byte strings.<a href="#section-2.1-9" class="pilcrow">¶</a></p>
<p id="section-2.1-10">For byte strings with tag 111:<a href="#section-2.1-10" class="pilcrow">¶</a></p>
<p style="margin-left: 1.5em" id="section-2.1-11">
            <code>/^(([\x81-\xFF][\x80-\xFF]*)?[\x00-\x7F])+$/</code><a href="#section-2.1-11" class="pilcrow">¶</a></p>
<p id="section-2.1-12">For byte strings with tags 110 or 112:<a href="#section-2.1-12" class="pilcrow">¶</a></p>
<p style="margin-left: 1.5em" id="section-2.1-13">
            <code>/^(([\x81-\xFF][\x80-\xFF]*)?[\x00-\x7F])*$/</code><a href="#section-2.1-13" class="pilcrow">¶</a></p>
<p id="section-2.1-14">A tag with tagged content that does not conform to the applicable
regular expression is invalid.<a href="#section-2.1-14" class="pilcrow">¶</a></p>
</section>
</div>
<div id="prefser">
<section id="section-2.2">
        <h3 id="name-preferred-serialization-con">
<a href="#section-2.2" class="section-number selfRef">2.2. </a><a href="#name-preferred-serialization-con" class="section-name selfRef">Preferred Serialization Considerations</a>
        </h3>
<p id="section-2.2-1">For an absolute OID with a prefix of <code>1.3.6.1.4.1</code>, representations
with both the 111 and 112 tags are applicable, where the
representation with 112 will be five bytes shorter (by leaving out
the prefix h'2b06010401' from the enclosed byte string).
This specification makes that shorter representation the preferred
serialization (see Sections <a href="https://www.rfc-editor.org/rfc/rfc8949#section-3.4" class="relref">3.4</a> and <a href="https://www.rfc-editor.org/rfc/rfc8949#section-4.1" class="relref">4.1</a> of <span>[<a href="#RFC8949" class="xref">RFC8949</a>]</span>).
Note that this also implies that the Core Deterministic Encoding
Requirements (<span><a href="https://www.rfc-editor.org/rfc/rfc8949#section-4.2.1" class="relref">Section 4.2.1</a> of [<a href="#RFC8949" class="xref">RFC8949</a>]</span>) require the use of 112
tags instead of 111 tags wherever that is possible.<a href="#section-2.2-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="discussion">
<section id="section-2.3">
        <h3 id="name-discussion">
<a href="#section-2.3" class="section-number selfRef">2.3. </a><a href="#name-discussion" class="section-name selfRef">Discussion</a>
        </h3>
<p id="section-2.3-1">Staying close to the way object identifiers are encoded in ASN.1
BER makes back-and-forth translation easy; otherwise, we would choose a
more efficient encoding.  Object
identifiers in IETF protocols
are serialized in dotted decimal form or BER form, so
there is an advantage in not inventing a third form.  Also,
expectations of the cost of encoding object identifiers are
based on BER; using a different encoding might not be aligned with
these expectations. If additional information about an OID is desired,
lookup services such as
the <span><a href="#X.672" class="xref">OID Resolution Service (ORS)</a> [<a href="#X.672" class="xref">X.672</a>]</span>
and the <span><a href="#OID-INFO" class="xref">OID Repository</a> [<a href="#OID-INFO" class="xref">OID-INFO</a>]</span> are available.<a href="#section-2.3-1" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="examples">
<section id="section-3">
      <h2 id="name-basic-examples">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-basic-examples" class="section-name selfRef">Basic Examples</a>
      </h2>
<p id="section-3-1">This section gives simple examples of an absolute and a relative
object identifier, represented via tag numbers 111 and 110,
respectively.<a href="#section-3-1" class="pilcrow">¶</a></p>
<div id="encoding-of-the-sha-256-oid">
<section id="section-3.1">
        <h3 id="name-encoding-of-the-sha-256-oid">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-encoding-of-the-sha-256-oid" class="section-name selfRef">Encoding of the SHA-256 OID</a>
        </h3>
<span class="break"></span><dl class="dlParallel" id="section-3.1-1">
          <dt id="section-3.1-1.1">ASN.1 Value Notation:</dt>
          <dd style="margin-left: 1.5em" id="section-3.1-1.2">
            <div id="section-3.1-1.2.1">
<pre class="sourcecode lang-asn.1">
{ joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101)
  csor(3) nistalgorithm(4) hashalgs(2) sha256(1) }
</pre><a href="#section-3.1-1.2.1" class="pilcrow">¶</a>
</div>
</dd>
          <dd class="break"></dd>
<dt id="section-3.1-1.3">
Dotted Decimal Notation:  </dt>
          <dd style="margin-left: 1.5em" id="section-3.1-1.4">
            <p id="section-3.1-1.4.1">2.16.840.1.101.3.4.2.1<a href="#section-3.1-1.4.1" class="pilcrow">¶</a></p>
</dd>
        <dd class="break"></dd>
</dl>
<span id="name-sha-256-oid-in-ber"></span><div id="fig-sha-ber">
<figure id="figure-1">
          <div id="section-3.1-2.1">
<pre class="sourcecode">
06                                # UNIVERSAL TAG 6
   09                             # 9 bytes, primitive
      60 86 48 01 65 03 04 02 01  # X.690 Clause 8.19
#      |   840  1  |  3  4  2  1    show component encoding
#   2.16         101
</pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a>:
<a href="#name-sha-256-oid-in-ber" class="selfRef">SHA-256 OID in BER</a>
          </figcaption></figure>
</div>
<span id="name-sha-256-oid-in-cbor"></span><div id="fig-sha-cbor">
<figure id="figure-2">
          <div id="section-3.1-3.1">
<pre class="sourcecode lang-cbor-pretty">
D8 6F                             # tag(111)
   49                             # 0b010_01001: mt 2, 9 bytes
      60 86 48 01 65 03 04 02 01  # X.690 Clause 8.19
</pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a>:
<a href="#name-sha-256-oid-in-cbor" class="selfRef">SHA-256 OID in CBOR</a>
          </figcaption></figure>
</div>
</section>
</div>
<div id="encoding-of-a-mib-relative-oid">
<section id="section-3.2">
        <h3 id="name-encoding-of-a-mib-relative-">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-encoding-of-a-mib-relative-" class="section-name selfRef">Encoding of a MIB Relative OID</a>
        </h3>
<p id="section-3.2-1">Given some OID (e.g., <code>lowpanMib</code>, assumed to be <code>1.3.6.1.2.1.226</code> <span>[<a href="#RFC7388" class="xref">RFC7388</a>]</span>),
to which the following is added:<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-3.2-2">
          <dt id="section-3.2-2.1">ASN.1 Value Notation:</dt>
          <dd style="margin-left: 1.5em" id="section-3.2-2.2">
            <div id="section-3.2-2.2.1">
<pre class="sourcecode lang-asn.1">
{ lowpanObjects(1) lowpanStats(1) lowpanOutTransmits(29) }
</pre><a href="#section-3.2-2.2.1" class="pilcrow">¶</a>
</div>
</dd>
          <dd class="break"></dd>
<dt id="section-3.2-2.3">
Dotted Decimal Notation:  </dt>
          <dd style="margin-left: 1.5em" id="section-3.2-2.4">
            <p id="section-3.2-2.4.1">.1.1.29<a href="#section-3.2-2.4.1" class="pilcrow">¶</a></p>
</dd>
        <dd class="break"></dd>
</dl>
<span id="name-mib-relative-object-identif"></span><div id="fig-mib-ber">
<figure id="figure-3">
          <div id="section-3.2-3.1">
<pre class="sourcecode">
0D                                # UNIVERSAL TAG 13
   03                             # 3 bytes, primitive
      01 01 1D                    # X.690 Clause 8.20
#      1  1 29                      show component encoding
</pre>
</div>
<figcaption><a href="#figure-3" class="selfRef">Figure 3</a>:
<a href="#name-mib-relative-object-identif" class="selfRef">MIB Relative Object Identifier in BER</a>
          </figcaption></figure>
</div>
<span id="name-mib-relative-object-identifi"></span><div id="fig-mib-cbor">
<figure id="figure-4">
          <div id="section-3.2-4.1">
<pre class="sourcecode lang-cbor-pretty">
D8 6E                             # tag(110)
   43                             # 0b010_00011: mt 2 (bstr), 3 bytes
      01 01 1D                    # X.690 Clause 8.20
</pre>
</div>
<figcaption><a href="#figure-4" class="selfRef">Figure 4</a>:
<a href="#name-mib-relative-object-identifi" class="selfRef">MIB Relative Object Identifier in CBOR</a>
          </figcaption></figure>
</div>
<p id="section-3.2-5">This relative OID saves seven bytes compared to the full OID encoding.<a href="#section-3.2-5" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="tfs">
<section id="section-4">
      <h2 id="name-tag-factoring-with-arrays-a">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-tag-factoring-with-arrays-a" class="section-name selfRef">Tag Factoring with Arrays and Maps</a>
      </h2>
<p id="section-4-1">The tag content of OID tags can be byte strings (as discussed above) but also CBOR arrays and maps.
The idea in the latter case is that
the tag construct is factored out from each individual item in the container;
the tag is placed on the array or map instead.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">When the tag content of an OID tag is an array, this means
that the respective tag is imputed to all elements of the array that are
byte strings, arrays, or maps.  (There is no effect on other elements,
including text strings or tags.)
For example, when the tag content of a 111 tag is an array,
every array element that is a byte string
is an OID, and every element that is an array or map is, in turn,
treated as discussed here.<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">When the tag content of an OID tag is a map, this means that a tag
with the same tag number is imputed to all keys in the map that are byte
strings, arrays, or maps; again, there is no effect on keys of other major types.
Note that there is also no effect on the values in the map.<a href="#section-4-3" class="pilcrow">¶</a></p>
<p id="section-4-4">As a result of these rules, tag factoring in nested arrays and maps is supported.
For example,
a 3-dimensional array of OIDs can be composed by using
a single 111 tag containing an array of arrays of arrays
of byte strings. All such byte strings are then considered OIDs.<a href="#section-4-4" class="pilcrow">¶</a></p>
<div id="preferred-serialization-considerations">
<section id="section-4.1">
        <h3 id="name-preferred-serialization-cons">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-preferred-serialization-cons" class="section-name selfRef">Preferred Serialization Considerations</a>
        </h3>
<p id="section-4.1-1">Where tag factoring with tag number 111 is used, some OIDs enclosed in the
tag may be encoded in a shorter way by using tag number 112 instead of
encoding an unadorned byte string.
This remains the preferred serialization (see also <a href="#prefser" class="xref">Section 2.2</a>).
However, this specification does not make the presence or absence of
tag factoring a preferred serialization; application protocols can
define where tag factoring is to be used or not (and will need to do
so if they have deterministic encoding requirements).<a href="#section-4.1-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="tag-factoring-example-x500-distinguished-name">
<section id="section-4.2">
        <h3 id="name-tag-factoring-example-x500-">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-tag-factoring-example-x500-" class="section-name selfRef">Tag Factoring Example: X.500 Distinguished Name</a>
        </h3>
<p id="section-4.2-1">Consider the X.500 distinguished name:<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<span id="name-example-x500-distinguished-"></span><div id="tab-dn-data">
<table class="center" id="table-2">
          <caption>
<a href="#table-2" class="selfRef">Table 2</a>:
<a href="#name-example-x500-distinguished-" class="selfRef">Example X.500 Distinguished Name</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Attribute Types</th>
              <th class="text-left" rowspan="1" colspan="1">Attribute Values</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">c (2.5.4.6)</td>
              <td class="text-left" rowspan="1" colspan="1">US</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">l (2.5.4.7)<br>s (2.5.4.8)<br>postalCode (2.5.4.17)</td>
              <td class="text-left" rowspan="1" colspan="1">Los Angeles<br>CA<br>90013</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">street (2.5.4.9)</td>
              <td class="text-left" rowspan="1" colspan="1">532 S Olive St</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">businessCategory (2.5.4.15)<br>buildingName (0.9.2342.19200300.100.1.48)</td>
              <td class="text-left" rowspan="1" colspan="1">Public Park<br>Pershing Square</td>
            </tr>
          </tbody>
        </table>
</div>
<p id="section-4.2-3"><a href="#tab-dn-data" class="xref">Table 2</a> has four "relative distinguished names" (RDNs). The
country (first) and street (third) RDNs are single valued.
The second and fourth RDNs are multivalued.<a href="#section-4.2-3" class="pilcrow">¶</a></p>
<p id="section-4.2-4">The equivalent representations in CBOR diagnostic notation (<span><a href="https://www.rfc-editor.org/rfc/rfc8949#section-8" class="relref">Section 8</a> of [<a href="#RFC8949" class="xref">RFC8949</a>]</span>) and CBOR are:<a href="#section-4.2-4" class="pilcrow">¶</a></p>
<span id="name-distinguished-name-in-cbor-"></span><div id="fig-dn-cbor-diag">
<figure id="figure-5">
          <div id="section-4.2-5.1">
<pre class="sourcecode lang-cbor-diag">
111([{ h'550406': "US" },
     { h'550407': "Los Angeles",
       h'550408': "CA",
       h'550411': "90013" },
     { h'550409': "532 S Olive St" },
     { h'55040f': "Public Park",
       h'0992268993f22c640130': "Pershing Square" }])
</pre>
</div>
<figcaption><a href="#figure-5" class="selfRef">Figure 5</a>:
<a href="#name-distinguished-name-in-cbor-" class="selfRef">Distinguished Name in CBOR Diagnostic Notation</a>
          </figcaption></figure>
</div>
<span id="name-distinguished-name-in-cbor-1"></span><div id="fig-dn-cbor">
<figure id="figure-6">
          <div id="section-4.2-6.1">
<pre class="sourcecode lang-cbor-pretty">
d8 6f                                      # tag(111)
   84                                      # array(4)
      a1                                   # map(1)
         43 550406                         # 2.5.4.6 (4)
         62                                # text(2)
            5553                           # "US"
      a3                                   # map(3)
         43 550407                         # 2.5.4.7 (4)
         6b                                # text(11)
            4c6f7320416e67656c6573         # "Los Angeles"
         43 550408                         # 2.5.4.8 (4)
         62                                # text(2)
            4341                           # "CA"
         43 550411                         # 2.5.4.17 (4)
         65                                # text(5)
            3930303133                     # "90013"
      a1                                   # map(1)
         43 550409                         # 2.5.4.9 (4)
         6e                                # text(14)
            3533322053204f6c697665205374   # "532 S Olive St"
      a2                                   # map(2)
         43 55040f                         # 2.5.4.15 (4)
         6b                                # text(11)
            5075626c6963205061726b         # "Public Park"
         4a 0992268993f22c640130    # 0.9.2342.19200300.100.1.48 (11)
         6f                                # text(15)
            5065727368696e6720537175617265 # "Pershing Square"
</pre>
</div>
<figcaption><a href="#figure-6" class="selfRef">Figure 6</a>:
<a href="#name-distinguished-name-in-cbor-1" class="selfRef">Distinguished Name in CBOR (109 Bytes)</a>
          </figcaption></figure>
</div>
<p id="section-4.2-7">(This example encoding assumes that all attribute values are UTF-8 strings or can be represented as UTF-8 strings with no loss of information.)<a href="#section-4.2-7" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="control">
<section id="section-5">
      <h2 id="name-cddl-control-operators">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-cddl-control-operators" class="section-name selfRef">CDDL Control Operators</a>
      </h2>
<p id="section-5-1">Concise Data Definition Language (CDDL) specifications <span>[<a href="#RFC8610" class="xref">RFC8610</a>]</span> may
want to specify the use of SDNVs or SDNV
sequences (as defined for the tag content for tag 110).  This document
introduces two new control operators that can be applied to a target
value that is a byte string:<a href="#section-5-1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-5-2.1">
          <code>.sdnv</code>, with a control type that contains unsigned integers.  The
byte string is specified to be encoded as an SDNV (BER
encoding) <span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span> for the matching values of the control type.<a href="#section-5-2.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-5-2.2">
          <code>.sdnvseq</code>, with a control type that contains arrays of unsigned
integers.  The byte string is specified to be encoded as a sequence
of SDNVs (BER encoding) <span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span> that decodes to an array of
unsigned integers matching the control type.<a href="#section-5-2.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-5-2.3">
          <code>.oid</code>, like <code>.sdnvseq</code>, except that the X*40+Y translation for
absolute OIDs is included (see <a href="#fig-dn-cddl-oid" class="xref">Figure 8</a>).<a href="#section-5-2.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-5-3"><a href="#fig-dn-cddl" class="xref">Figure 7</a> shows an example for the use of <code>.sdnvseq</code> for a part
of a structure using OIDs that could be used in <a href="#fig-dn-cbor" class="xref">Figure 6</a>;
<a href="#fig-dn-cddl-oid" class="xref">Figure 8</a> shows the same with the <code>.oid</code> operator.<a href="#section-5-3" class="pilcrow">¶</a></p>
<span id="name-using-sdnvseq"></span><div id="fig-dn-cddl">
<figure id="figure-7">
        <div id="section-5-4.1">
<pre class="sourcecode lang-cddl">
country-rdn = {country-oid =&gt; country-value}
country-oid = bytes .sdnvseq [85, 4, 6]
country-value = text .size 2
</pre>
</div>
<figcaption><a href="#figure-7" class="selfRef">Figure 7</a>:
<a href="#name-using-sdnvseq" class="selfRef">Using .sdnvseq</a>
        </figcaption></figure>
</div>
<span id="name-using-oid"></span><div id="fig-dn-cddl-oid">
<figure id="figure-8">
        <div id="section-5-5.1">
<pre class="sourcecode lang-cddl">
country-rdn = {country-oid =&gt; country-value}
country-oid = bytes .oid [2, 5, 4, 6]
country-value = text .size 2
</pre>
</div>
<figcaption><a href="#figure-8" class="selfRef">Figure 8</a>:
<a href="#name-using-oid" class="selfRef">Using .oid</a>
        </figcaption></figure>
</div>
<p id="section-5-6">Note that the control type need not be a literal; for example, <code>bytes .oid
[2, 5, 4, *uint]</code> matches all OIDs inside OID arc <code>2.5.4</code>,
<code>attributeType</code>.<a href="#section-5-6" class="pilcrow">¶</a></p>
</section>
</div>
<div id="cddl-typenames">
<section id="section-6">
      <h2 id="name-cddl-type-names">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-cddl-type-names" class="section-name selfRef">CDDL Type Names</a>
      </h2>
<p id="section-6-1">For the use with CDDL, the
type names defined in <a href="#tag-cddl" class="xref">Figure 9</a> are recommended:<a href="#section-6-1" class="pilcrow">¶</a></p>
<span id="name-recommended-type-names-for-"></span><div id="tag-cddl">
<figure id="figure-9">
        <div id="section-6-2.1">
<pre class="sourcecode lang-cddl">
oid = #6.111(bstr)
roid = #6.110(bstr)
pen = #6.112(bstr)
</pre>
</div>
<figcaption><a href="#figure-9" class="selfRef">Figure 9</a>:
<a href="#name-recommended-type-names-for-" class="selfRef">Recommended Type Names for CDDL</a>
        </figcaption></figure>
</div>
</section>
</div>
<div id="iana">
<section id="section-7">
      <h2 id="name-iana-considerations">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<div id="cbor-tags">
<section id="section-7.1">
        <h3 id="name-cbor-tags">
<a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-cbor-tags" class="section-name selfRef">CBOR Tags</a>
        </h3>
<p id="section-7.1-1">IANA has assigned the CBOR tag numbers in <a href="#tab-tag-values-new" class="xref">Table 3</a> 
in the 1+1 byte space (24..255) of the "CBOR Tags" registry
<span>[<a href="#IANA.cbor-tags" class="xref">IANA.cbor-tags</a>]</span>, with this document as the specification reference.<a href="#section-7.1-1" class="pilcrow">¶</a></p>
<span id="name-new-tag-numbers"></span><div id="tab-tag-values-new">
<table class="center" id="table-3">
          <caption>
<a href="#table-3" class="selfRef">Table 3</a>:
<a href="#name-new-tag-numbers" class="selfRef">New Tag Numbers</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Tag</th>
              <th class="text-left" rowspan="1" colspan="1">Data Item</th>
              <th class="text-left" rowspan="1" colspan="1">Semantics</th>
              <th class="text-left" rowspan="1" colspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">111</td>
              <td class="text-left" rowspan="1" colspan="1">byte string, array, or map</td>
              <td class="text-left" rowspan="1" colspan="1">object identifier (BER encoding)</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">110</td>
              <td class="text-left" rowspan="1" colspan="1">byte string, array, or map</td>
              <td class="text-left" rowspan="1" colspan="1">relative object identifier (BER encoding); SDNV <span>[<a href="#RFC6256" class="xref">RFC6256</a>]</span> sequence</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">112</td>
              <td class="text-left" rowspan="1" colspan="1">byte string, array, or map</td>
              <td class="text-left" rowspan="1" colspan="1">object identifier (BER encoding), relative to 1.3.6.1.4.1</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
          </tbody>
        </table>
</div>
</section>
</div>
<div id="cddl-control-operators">
<section id="section-7.2">
        <h3 id="name-cddl-control-operators-2">
<a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-cddl-control-operators-2" class="section-name selfRef">CDDL Control Operators</a>
        </h3>
<p id="section-7.2-1">IANA has assigned the CDDL control operators in
<a href="#tab-operators-new" class="xref">Table 4</a> in the "CDDL Control Operators" registry
<span>[<a href="#IANA.cddl" class="xref">IANA.cddl</a>]</span>, with this document as the specification
reference.<a href="#section-7.2-1" class="pilcrow">¶</a></p>
<span id="name-new-cddl-control-operators"></span><div id="tab-operators-new">
<table class="center" id="table-4">
          <caption>
<a href="#table-4" class="selfRef">Table 4</a>:
<a href="#name-new-cddl-control-operators" class="selfRef">New CDDL Control Operators</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Name</th>
              <th class="text-left" rowspan="1" colspan="1">Reference</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">.sdnv</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">.sdnvseq</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">.oid</td>
              <td class="text-left" rowspan="1" colspan="1">RFC 9090</td>
            </tr>
          </tbody>
        </table>
</div>
</section>
</div>
</section>
</div>
<div id="security-considerations">
<section id="section-8">
      <h2 id="name-security-considerations">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-8-1">The security considerations of <span>[<a href="#RFC8949" class="xref">RFC8949</a>]</span> apply.<a href="#section-8-1" class="pilcrow">¶</a></p>
<p id="section-8-2">The encodings in Clauses 8.19 and 8.20 of <span>[<a href="#X.690" class="xref">X.690</a>]</span> are quite compact and unambiguous
but <span class="bcp14">MUST</span> be followed precisely to avoid security pitfalls.
In particular, the requirements set out in <a href="#reqts" class="xref">Section 2.1</a> of this document need to be
followed; otherwise, an attacker may be able to subvert a checking
process by submitting alternative representations that are later taken
as the original (or even something else entirely) by another decoder
that is intended to be protected by the checking process.<a href="#section-8-2" class="pilcrow">¶</a></p>
<p id="section-8-3">OIDs and relative OIDs can always be treated as opaque byte strings.
Actually understanding the structure that was used for generating them
is not necessary, and, except for checking the structure requirements,
it is strongly <span class="bcp14">NOT RECOMMENDED</span> to perform any
processing of this kind (e.g., converting into dotted notation and
back) unless absolutely necessary.
If the OIDs are translated into other representations, the usual
security considerations for non-trivial representation conversions
apply; the integer values are unlimited in range.<a href="#section-8-3" class="pilcrow">¶</a></p>
<p id="section-8-4">An attacker might trick an application into using a byte string inside
a tag-factored data item, where the byte string is not actually
intended to fall under one of the tags defined here.  This may cause
the application to emit data with semantics different from what was
intended.  Applications therefore need to be restrictive with respect
to what data items they apply tag factoring to.<a href="#section-8-4" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-9">
      <h2 id="name-references">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-9.1">
        <h3 id="name-normative-references">
<a href="#section-9.1" class="section-number selfRef">9.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="IANA.cbor-tags">[IANA.cbor-tags]</dt>
        <dd>
<span class="refAuthor">IANA</span>, <span class="refTitle">"Concise Binary Object Representation (CBOR) Tags"</span>, <span>&lt;<a href="https://www.iana.org/assignments/cbor-tags">https://www.iana.org/assignments/cbor-tags</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="IANA.cddl">[IANA.cddl]</dt>
        <dd>
<span class="refAuthor">IANA</span>, <span class="refTitle">"Concise Data Definition Language (CDDL)"</span>, <span>&lt;<a href="https://www.iana.org/assignments/cddl">https://www.iana.org/assignments/cddl</a>&gt;</span>. </dd>
<dd class="break"></dd>
<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="RFC6256">[RFC6256]</dt>
        <dd>
<span class="refAuthor">Eddy, W.</span> and <span class="refAuthor">E. Davies</span>, <span class="refTitle">"Using Self-Delimiting Numeric Values in Protocols"</span>, <span class="seriesInfo">RFC 6256</span>, <span class="seriesInfo">DOI 10.17487/RFC6256</span>, <time datetime="2011-05" class="refDate">May 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6256">https://www.rfc-editor.org/info/rfc6256</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="RFC8610">[RFC8610]</dt>
        <dd>
<span class="refAuthor">Birkholz, H.</span>, <span class="refAuthor">Vigano, C.</span>, and <span class="refAuthor">C. Bormann</span>, <span class="refTitle">"Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures"</span>, <span class="seriesInfo">RFC 8610</span>, <span class="seriesInfo">DOI 10.17487/RFC8610</span>, <time datetime="2019-06" class="refDate">June 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8610">https://www.rfc-editor.org/info/rfc8610</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8949">[RFC8949]</dt>
        <dd>
<span class="refAuthor">Bormann, C.</span> and <span class="refAuthor">P. Hoffman</span>, <span class="refTitle">"Concise Binary Object Representation (CBOR)"</span>, <span class="seriesInfo">STD 94</span>, <span class="seriesInfo">RFC 8949</span>, <span class="seriesInfo">DOI 10.17487/RFC8949</span>, <time datetime="2020-12" class="refDate">December 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8949">https://www.rfc-editor.org/info/rfc8949</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="X.660">[X.660]</dt>
        <dd>
<span class="refAuthor">ITU-T</span>, <span class="refTitle">"Information technology - Procedures for the operation of object identifier registration authorities: General procedures and top arcs of the international object identifier tree"</span>, <span class="seriesInfo">ITU-T Recommendation X.660</span>, <time datetime="2011-07" class="refDate">July 2011</time>, <span>&lt;<a href="https://www.itu.int/rec/T-REC-X.660">https://www.itu.int/rec/T-REC-X.660</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="X.680">[X.680]</dt>
        <dd>
<span class="refAuthor">ITU-T</span>, <span class="refTitle">"Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation"</span>, <span class="seriesInfo">ITU-T Recommendation X.680</span>, <time datetime="2015-08" class="refDate">August 2015</time>, <span>&lt;<a href="https://www.itu.int/rec/T-REC-X.680">https://www.itu.int/rec/T-REC-X.680</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="X.690">[X.690]</dt>
      <dd>
<span class="refAuthor">ITU-T</span>, <span class="refTitle">"Information technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)"</span>, <span class="seriesInfo">ITU-T Recommendation X.690</span>, <time datetime="2015-08" class="refDate">August 2015</time>, <span>&lt;<a href="https://www.itu.int/rec/T-REC-X.690">https://www.itu.int/rec/T-REC-X.690</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-9.2">
        <h3 id="name-informative-references">
<a href="#section-9.2" class="section-number selfRef">9.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="IANA.enterprise-numbers">[IANA.enterprise-numbers]</dt>
        <dd>
<span class="refAuthor">IANA</span>, <span class="refTitle">"Private Enterprise Numbers"</span>, <span>&lt;<a href="https://www.iana.org/assignments/enterprise-numbers">https://www.iana.org/assignments/enterprise-numbers</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="OID-INFO">[OID-INFO]</dt>
        <dd>
<span class="refAuthor">Orange SA</span>, <span class="refTitle">"Object Identifier (OID) Repository"</span>, <span>&lt;<a href="http://www.oid-info.com/">http://www.oid-info.com/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="PCRE">[PCRE]</dt>
        <dd>
<span class="refTitle">"PCRE - Perl Compatible Regular Expressions"</span>, <span>&lt;<a href="http://www.pcre.org/">http://www.pcre.org/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7388">[RFC7388]</dt>
        <dd>
<span class="refAuthor">Schoenwaelder, J.</span>, <span class="refAuthor">Sehgal, A.</span>, <span class="refAuthor">Tsou, T.</span>, and <span class="refAuthor">C. Zhou</span>, <span class="refTitle">"Definition of Managed Objects for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)"</span>, <span class="seriesInfo">RFC 7388</span>, <span class="seriesInfo">DOI 10.17487/RFC7388</span>, <time datetime="2014-10" class="refDate">October 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7388">https://www.rfc-editor.org/info/rfc7388</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="X.672">[X.672]</dt>
      <dd>
<span class="refAuthor">ITU-T</span>, <span class="refTitle">"Information technology - Open systems interconnection - Object identifier resolution system (ORS)"</span>, <span class="seriesInfo">ITU-T Recommendation X.672</span>, <time datetime="2010-08" class="refDate">August 2010</time>, <span>&lt;<a href="https://www.itu.int/rec/T-REC-X.672">https://www.itu.int/rec/T-REC-X.672</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"><span class="contact-name">Sean Leonard</span> started the work on this document in 2014 with an
elaborate proposal.
<span class="contact-name">Jim Schaad</span> provided a significant review of this document.
<span class="contact-name">Rob Wilton</span>'s IESG review prompted us to provide preferred
serialization considerations.<a href="#appendix-A-1" 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>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Sean Leonard</span></div>
<div dir="auto" class="left"><span class="org">Penango, Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">5900 Wilshire Boulevard<br>21st Floor</span></div>
<div dir="auto" class="left">
<span class="locality">Los Angeles</span>, <span class="region">CA</span> <span class="postal-code">90036</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:dev+ietf@seantek.com" class="email">dev+ietf@seantek.com</a>
</div>
</address>
</section>
</div>
<div id="authors-addresses">
<section id="appendix-C">
      <h2 id="name-authors-address">
<a href="#name-authors-address" class="section-name selfRef">Author's Address</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Carsten Bormann</span></div>
<div dir="auto" class="left"><span class="org">Universität Bremen TZI</span></div>
<div dir="auto" class="left"><span class="street-address">Postfach 330440</span></div>
<div dir="auto" class="left">
<span class="postal-code">D-28359</span> <span class="locality">Bremen</span>
</div>
<div dir="auto" class="left"><span class="country-name">Germany</span></div>
<div class="tel">
<span>Phone:</span>
<a href="tel:+49-421-218-63921" class="tel">+49-421-218-63921</a>
</div>
<div class="email">
<span>Email:</span>
<a href="mailto:cabo@tzi.org" class="email">cabo@tzi.org</a>
</div>
</address>
</section>
</div>
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