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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 9196: YANG Modules Describing Capabilities for Systems and Datastore Update Notifications</title>
<meta content="Balazs Lengyel" name="author">
<meta content="Alexander Clemm" name="author">
<meta content="Benoit Claise" name="author">
<meta content='
        
        This document defines two YANG modules, "ietf-system-capabilities" and 
        "ietf-notification-capabilities".
       
          
       The module "ietf-system-capabilities" provides a placeholder structure that 
       can be used to discover YANG-related system capabilities for servers. 
       The module can be used to report capability information from the server 
       at runtime or at implementation time by making use of the YANG instance data file format.
       
       
       The module "ietf-notification-capabilities" augments "ietf-system-capabilities"
       to specify capabilities related to "Subscription to YANG Notifications 
       for Datastore Updates" (RFC 8641). 
       
    ' name="description">
<meta content="xml2rfc 3.12.2" name="generator">
<meta content="NMDA" name="keyword">
<meta content="NETCONF" name="keyword">
<meta content="RESTCONF" name="keyword">
<meta content="9196" name="rfc.number">
<!-- Generator version information:
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-->
<link href="rfc9196.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 {
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  width: extend-to-zoom;
}
@-ms-viewport {
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  zoom: 1.0;
}
/* general and mobile first */
html {
}
body {
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  margin: 1.5em auto;
  color: #222;
  background-color: #fff;
  font-size: 14px;
  font-family: 'Noto Sans', Arial, Helvetica, sans-serif;
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  scroll-behavior: smooth;
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.ears {
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}

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
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#title {
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h4 {
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svg {
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/* definition lists */
dl {
}
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/* 
dl.nohang > dt {
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}
*/
dl > dd {
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dl > dd > dl {
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/* links */
a {
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}
a[href] {
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}
a[href]:hover {
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figcaption a[href],
a[href].selfRef {
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/* XXX probably not this:
a.selfRef:hover {
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} */

/* Figures */
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pre {
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figure {
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figure blockquote {
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figcaption {
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@media screen {
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/* aside, blockquote */
aside, blockquote {
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blockquote {
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cite {
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/* tables */
table {
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th {
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/* pilcrow */
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.bcp14 {
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.role {
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}

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#identifiers {
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#identifiers dt {
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}
#identifiers dd {
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  margin-bottom: 0;
}
/* Fix PDF info block run off issue */
@media print {
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}
#identifiers .authors .author {
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#identifiers .authors .org {
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}

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.docInfo .prepared {
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}

/* table of contents */
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}
nav.toc ul {
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}
nav.toc li {
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  padding-left: 1.2em;
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}
/* references */
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}
.references dd {
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.refInstance {
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}

.references .ascii {
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}

/* index */
.index ul {
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  padding: 0;
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}
.index ul ul {
  margin: 0;
}
.index li {
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  text-indent: -2em;
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.indexIndex {
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.index a {
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}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
  .index ul {
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  .index ul ul {
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}

/* authors */
address.vcard {
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}

address.vcard .nameRole {
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address.vcard .label {
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address.vcard .type {
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.alternative-contact {
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}
hr.addr {
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}

/* temporary notes */
.rfcEditorRemove::before {
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  padding: 0.2em;
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  color: #9e2a00; /* Arlen: WCAG 2019 */
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.rfcEditorRemove {
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  background-color: #ffd; /* Arlen: WCAG 2019 */
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.cref {
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}
.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;
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  #toc h2 {
    margin: -1px 0 0 0;
    padding: 4px 0 4px 6px;
    padding-right: 1em;
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    text-align: right;
    background-color: #444;
    color: white;
    cursor: pointer;
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  #toc h2::before { /* css hamburger */
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    height: 1px;
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    box-shadow: 0 4px 0 0 white, 0 8px 0 0 white;
    content: "";
  }
  #toc nav {
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    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;
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  #toc h2 {
    border-top: none;
    border-bottom: 1px solid #ddd;
    font-size: 1em;
    font-weight: normal;
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  #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%;
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  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;
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  table {
    border: 1px solid #ddd;
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  td {
    border-top: 1px solid #ddd;
  }
}

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

.ears thead .center {
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.ears tfoot .left {
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.ears tfoot .center {
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.ears tfoot .right {
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*/

@page :first {
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    border: none;
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    content: normal;
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}

@page {
  size: A4;
  margin-bottom: 45mm;
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     the content depends on the document */
  /*
  @top-left {
    content: 'Internet-Draft';
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
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  @top-left {
    content: string(ears-top-left);
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  @top-right {
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  @bottom-center {
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}

/* 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 {
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}

/* 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,
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<link href="https://dx.doi.org/10.17487/rfc9196" rel="alternate">
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  <link href="https://datatracker.ietf.org/doc/draft-ietf-netconf-notification-capabilities-21" rel="prev">
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<table class="ears">
<thead><tr>
<td class="left">RFC 9196</td>
<td class="center">YANG System &amp; Notification Capabilities</td>
<td class="right">February 2022</td>
</tr></thead>
<tfoot><tr>
<td class="left">Lengyel, 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/rfc9196" class="eref">9196</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="2022-02" class="published">February 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">B. Lengyel</div>
<div class="org">Ericsson</div>
</div>
<div class="author">
      <div class="author-name">A. Clemm</div>
<div class="org">Futurewei</div>
</div>
<div class="author">
      <div class="author-name">B. Claise</div>
<div class="org">Huawei</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9196</h1>
<h1 id="title">YANG Modules Describing Capabilities for Systems and Datastore Update Notifications</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1"> 
        This document defines two YANG modules, "ietf-system-capabilities" and 
        "ietf-notification-capabilities".<a href="#section-abstract-1" class="pilcrow">¶</a></p>
<p id="section-abstract-2">   
       The module "ietf-system-capabilities" provides a placeholder structure that 
       can be used to discover YANG-related system capabilities for servers. 
       The module can be used to report capability information from the server 
       at runtime or at implementation time by making use of the YANG instance data file format.<a href="#section-abstract-2" class="pilcrow">¶</a></p>
<p id="section-abstract-3">
       The module "ietf-notification-capabilities" augments "ietf-system-capabilities"
       to specify capabilities related to "Subscription to YANG Notifications 
       for Datastore Updates" (RFC 8641).<a href="#section-abstract-3" 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/rfc9196">https://www.rfc-editor.org/info/rfc9196</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-terminology" class="xref">Terminology</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-providing-system-capability" class="xref">Providing System Capability Information</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-providing-yang-push-notific" class="xref">Providing YANG-Push Notification Capabilities Information</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-system-capabilities-model" class="xref">System Capabilities Model</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="xref">4.1</a>.  <a href="#name-tree-diagram" class="xref">Tree Diagram</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="xref">4.2</a>.  <a href="#name-yang-module" class="xref">YANG Module</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-notification-capabilities-m" class="xref">Notification Capabilities Model</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5.2.1">
                <p id="section-toc.1-1.5.2.1.1"><a href="#section-5.1" class="xref">5.1</a>.  <a href="#name-tree-diagram-2" class="xref">Tree Diagram</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5.2.2">
                <p id="section-toc.1-1.5.2.2.1"><a href="#section-5.2" class="xref">5.2</a>.  <a href="#name-yang-module-2" class="xref">YANG Module</a></p>
</li>
            </ul>
</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-iana-considerations" class="xref">IANA Considerations</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-the-ietf-xml-registry" class="xref">The IETF XML Registry</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-the-yang-module-names-regis" class="xref">The YANG Module Names Registry</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="#section-8" class="xref">8</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.1-1.8.2.1">
                <p id="section-toc.1-1.8.2.1.1"><a href="#section-8.1" class="xref">8.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8.2.2">
                <p id="section-toc.1-1.8.2.2.1"><a href="#section-8.2" class="xref">8.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#appendix-A" class="xref">Appendix A</a>.  <a href="#name-instance-data-example-1" class="xref">Instance Data Example #1</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#appendix-B" class="xref">Appendix B</a>.  <a href="#name-instance-data-example-2" class="xref">Instance Data Example #2</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#appendix-C" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a></p>
</li>
          <li class="compact toc ulBare ulEmpty" id="section-toc.1-1.12">
            <p id="section-toc.1-1.12.1"><a href="#appendix-D" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</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">
        Servers and/or publishers often have capabilities, which can be represented by values that designate operational behavior, that need to be conveyed to clients. The YANG modules that are defined in this document facilitate this.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">          
        There is a need to publish this capability information as it is part of 
        the API contract between the server and client. Examples include the maximum 
        size of data that can be stored or transferred, information about counters (whether a node supports "on-change" telemetry), etc. Such capabilities are often dependent on a vendor's implementation or the available resources at deployment.
        Many such capabilities are specific to the complete system, 
        individual YANG datastores <span>[<a href="#RFC8342" class="xref">RFC8342</a>]</span>, specific parts of the YANG 
        schema, or even individual data nodes. It is a goal of this document to provide a 
        common way to represent such capabilities in a format that is:<a href="#section-1-2" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1-3.1">vendor independent,<a href="#section-1-3.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-3.2">machine readable, and<a href="#section-1-3.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-3.3">available in an identical format both at implementation time and at runtime.<a href="#section-1-3.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-1-4">
          Implementation-time information is needed by Network Management System 
          (NMS) implementers. 
          An NMS implementation that supports notifications needs information 
   about a system's capability so it can send "on-change" notifications. 
          If the information is not documented 
          in a way that is readily available to the NMS designer, but only as instance data from 
          the network node once it is deployed, 
          the NMS implementation will be delayed because it has to wait for the 
          network node to be ready. In addition, the assumption that all 
          NMS implementers will 
          have a correctly configured network node available from which to retrieve data is an expensive proposition and may not always hold. (An NMS may need 
          to be able to handle many dozens of network node types.) 
          Often, a fully functional NMS is a requirement for introducing a new 
          network node type 
          into a network, so delaying NMS readiness effectively also delays the 
          time at which a new network node type can be introduced into the network.<a href="#section-1-4" class="pilcrow">¶</a></p>
<p id="section-1-5">
          Implementation-time information is needed by system integrators. 
          When introducing a network node type into their network, 
          operators often need to integrate the node type into their own 
          management system. The NMS may have management functions that depend 
          on "on-change" notifications. The network operators need to plan their 
          management practices and NMS implementation before they decide to 
          buy the specific network node type. Moreover, the decision to buy the node 
          type sometimes depends on these management possibilities.<a href="#section-1-5" class="pilcrow">¶</a></p>
<p id="section-1-6">        
          Runtime capability information is needed:<a href="#section-1-6" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-1-7.1">for any "purely model-driven" application, e.g., a NETCONF browser. 
              Such applications depend on reading models and capabilities at runtime 
              to support all the publisher's available functionality.<a href="#section-1-7.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-7.2">in case the capability might change during runtime, 
              e.g., due to licensing, hardware constraints, etc.<a href="#section-1-7.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-1-7.3">to check that that capability information provided earlier, at
              implementation time, is what the publisher has implemented.<a href="#section-1-7.3" class="pilcrow">¶</a>
</li>
      </ul>
<div id="terminology">
<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 terms "YANG-Push", "on-change subscription", and "periodic 
          subscription" are used as defined in <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>.<a href="#section-1.1-2" class="pilcrow">¶</a></p>
<p id="section-1.1-3">The terms "subscriber", "publisher", and "receiver" are used as 
          defined in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>.<a href="#section-1.1-3" class="pilcrow">¶</a></p>
<p id="section-1.1-4">The term "server" is used as defined in <span>[<a href="#RFC8342" class="xref">RFC8342</a>]</span>.<a href="#section-1.1-4" class="pilcrow">¶</a></p>
<p id="section-1.1-5">The terms "YANG instance data file format", "instance data", and
         "instance data set" are used as defined in
          <span>[<a href="#RFC9195" class="xref">RFC9195</a>]</span>.<a href="#section-1.1-5" class="pilcrow">¶</a></p>
<p id="section-1.1-6">In addition, this document defines the following terms:<a href="#section-1.1-6" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-1.1-7">
          <dt id="section-1.1-7.1">Implementation-time information:</dt>
          <dd style="margin-left: 1.5em" id="section-1.1-7.2"> Information about the server's
          behavior that is made available during the implementation of the server, 
          available from a source other than a running server.<a href="#section-1.1-7.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-1.1-7.3">
          Runtime information:</dt>
          <dd style="margin-left: 1.5em" id="section-1.1-7.4"> Information about the server's
          behavior that is available from the running server via management protocols 
          such as NETCONF <span>[<a href="#RFC6241" class="xref">RFC6241</a>]</span> or RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span>.<a href="#section-1.1-7.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</div>
</section>
</div>
<div id="capability-information">
<section id="section-2">
      <h2 id="name-providing-system-capability">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-providing-system-capability" class="section-name selfRef">Providing System Capability Information</a>
      </h2>
<p id="section-2-1">
        Capability information is represented by instance data based on one or 
        more "capability-defining YANG modules". This allows a user to discover 
        capabilities both at implementation time and at runtime.<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">For the implementation-time use case:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.2"> Capabilities <span class="bcp14">SHOULD</span> be provided by the 
          implementer as YANG instance data files complying with 
          <span>[<a href="#RFC9195" class="xref">RFC9195</a>]</span>. 
          When provided, the file <span class="bcp14">MUST</span> already be available at implementation time and retrievable in a way that does not depend
          on a live network node, e.g., downloading from a product website.<a href="#section-2-2.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-2.3">For the runtime use case:</dt>
        <dd style="margin-left: 1.5em" id="section-2-2.4"> Capabilities <span class="bcp14">SHOULD</span> be available via 
          NETCONF <span>[<a href="#RFC6241" class="xref">RFC6241</a>]</span> or 
          RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> from the live server (implementing 
          the publisher) during runtime.
          Implementations that support changing these capabilities at 
          runtime <span class="bcp14">SHOULD</span> support "on-change" notifications about the 
          system-capabilities container.<a href="#section-2-2.4" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-2-3"> 
        The module "ietf-system-capabilities" provides a placeholder structure to be used to specify any YANG-related system capability.<a href="#section-2-3" class="pilcrow">¶</a></p>
<p id="section-2-4">
        The module "ietf-notification-capabilities" is defined to allow a publisher to 
        specify capabilities related to "Subscription to YANG Notifications for Datastore Updates" <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>, also known as YANG-Push, augmenting "ietf-system-capabilities".<a href="#section-2-4" class="pilcrow">¶</a></p>
<p id="section-2-5">
        The YANG data models in this document conform to the Network
        Management Datastore Architecture (NMDA) defined in <span>[<a href="#RFC8342" class="xref">RFC8342</a>]</span>.<a href="#section-2-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="Yang-Push-Capabilities">
<section id="section-3">
      <h2 id="name-providing-yang-push-notific">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-providing-yang-push-notific" class="section-name selfRef">Providing YANG-Push Notification Capabilities Information</a>
      </h2>
<p id="section-3-1">A specific case is the need to specify capabilities in the YANG-Push 
        functionality. As defined in <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>, a publisher may allow
 subscribers to subscribe to updates from a datastore and will subsequently push 
 such update notifications to the receiver. Notifications may be sent 
          periodically or "on change" (more or less immediately after each change).<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">A publisher supporting YANG-Push has a number of capabilities defined in  
          <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>
          that are often determined during the implementation of the publisher. These include:<a href="#section-3-2" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-3-3.1">supported (reporting) periods for "periodic" subscriptions.<a href="#section-3-3.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-3-3.2">the maximum number of objects that can be sent in an update.<a href="#section-3-3.2" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-3-3.3">the set of datastores or data nodes for which "periodic" notification is supported.<a href="#section-3-3.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-3-4">Additional capabilities if the optional "on-change" feature is supported include:<a href="#section-3-4" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-3-5.1">supported dampening periods for "on-change" subscriptions.<a href="#section-3-5.1" class="pilcrow">¶</a>
</li>
        <li class="normal" id="section-3-5.2">the set of datastores or data nodes for which "on-change" notification is supported.<a href="#section-3-5.2" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-3-6">
          Publishers might have some capabilities (or limitations) to document -- for example, how many update notifications and how many datastore node 
          updates they can send out in a certain time period. Other publishers might 
          not support "periodic" subscriptions to all datastores. In some cases, a publisher supporting "on-change" notifications will not
          be able to push updates for some object types "on change". Reasons for
          this might be that the value of the datastore node changes frequently
          (e.g., in-octet counter), that small object changes are
          frequent and irrelevant to the receiver (e.g., a temperature gauge changing 0.1
          degrees within a predetermined and acceptable range), or
          that the implementation is not capable of on-change notification for
          a particular object. In all those cases, it will be important for 
          subscriber applications to have a way to identify the objects for which "on-change" notifications are supported and the objects for which they are not.<a href="#section-3-6" class="pilcrow">¶</a></p>
<p id="section-3-7">
          Support for "on-change" notifications does not 
          mean that such notifications will be sent for any specific data node, as the ability to do so may not be supported for every data node. Therefore, subscriber/management applications cannot rely on the "on-change" 
          functionality unless the subscriber has some means to identify the objects for which "on-change" notifications are in fact supported. YANG data models are meant to be used as an 
   interface contract.
   Without identification of the data nodes actually supporting "on-change" notifications, 
   this contract would be incomplete.<a href="#section-3-7" class="pilcrow">¶</a></p>
<p id="section-3-8">Clients of a server (and subscribers to a publisher, as subscribers are also clients) need a method to gather capability information.<a href="#section-3-8" class="pilcrow">¶</a></p>
</section>
</div>
<div id="system_capabilities_model">
<section id="section-4">
      <h2 id="name-system-capabilities-model">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-system-capabilities-model" class="section-name selfRef">System Capabilities Model</a>
      </h2>
<p id="section-4-1">The module "ietf-system-capabilities" is defined to provide a  
       structure that can be used to discover (as a read-only operational state) any YANG-related system capability.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">This module itself does not contain any capabilities; it provides
        augmentation points for capabilities to be defined in subsequent YANG
        modules. "ietf-system-capabilities" is used by other modules to augment in specific
        capability information.  Every set of such capabilities <span class="bcp14">MUST</span> be
        wrapped in a container under the augment statement to cleanly
        separate different groups of capabilities. These "wrapper containers" <span class="bcp14">SHALL</span> be  
        augmented at /sysc:system-capabilities and /sysc:system-capabilities/sysc:datastore-capabilities/sysc:per-node-capabilities.<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">
        Capability values can be specified at the system level, 
        at the datastore level (by selecting all nodes in the datastore),  
        or for specific data nodes of a specific datastore 
        (and their contained subtrees).



        Capability values specified for a specific datastore or 
        node-set override values specified at the system level.<a href="#section-4-3" class="pilcrow">¶</a></p>
<p style="margin-left: 1.5em" id="section-4-4">
        Note: The solution is usable for both NMDA and non-NMDA systems. 
        For non-NMDA servers, "config false" data is
        considered as if it were part of the running datastore.<a href="#section-4-4" class="pilcrow">¶</a></p>
<section id="section-4.1">
        <h3 id="name-tree-diagram">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-tree-diagram" class="section-name selfRef">Tree Diagram</a>
        </h3>
<p id="section-4.1-1">
          The following tree diagram <span>[<a href="#RFC8340" class="xref">RFC8340</a>]</span>
          provides an overview of the data model.<a href="#section-4.1-1" class="pilcrow">¶</a></p>
<div id="section-4.1-2">
<pre class="lang-yangtree sourcecode">
module: ietf-system-capabilities
  +--ro system-capabilities
     +--ro datastore-capabilities* [datastore]
        +--ro datastore       -&gt; /yanglib:yang-library/datastore/name
        +--ro per-node-capabilities* []
           +--ro (node-selection)?
              +--:(node-selector)
                 +--ro node-selector?   nacm:node-instance-identifier
</pre><a href="#section-4.1-2" class="pilcrow">¶</a>
</div>
</section>
<div id="ietf-system-capabilities.yang">
<section id="section-4.2">
        <h3 id="name-yang-module">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-yang-module" class="section-name selfRef">YANG Module</a>
        </h3>
<p id="section-4.2-1">This YANG module imports typedefs from <span>[<a href="#RFC8341" class="xref">RFC8341</a>]</span> and 
          a reference path from <span>[<a href="#RFC8525" class="xref">RFC8525</a>]</span>.<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<div id="section-4.2-2">
<pre class="lang-yang sourcecode">&lt;CODE BEGINS&gt; file "ietf-system-capabilities@2022-02-17.yang"

module ietf-system-capabilities {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-system-capabilities";
  prefix sysc;

  import ietf-netconf-acm {
    prefix nacm;
    reference
      "RFC 8341: Network Configuration Access Control Model";
  }
  import ietf-yang-library {
    prefix yanglib;
    description
      "This module requires ietf-yang-library to be implemented.
       Revision 2019-01-04 or a revision derived from it
       is REQUIRED.";
    reference
      "RFC8525: YANG Library";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/netconf/&gt;
     WG List:  &lt;mailto:netconf@ietf.org&gt;

     Editor:   Balazs Lengyel
               &lt;mailto:balazs.lengyel@ericsson.com&gt;";
  description
    "This module specifies a structure to specify system
     capabilities for a server or a publisher.  System capabilities
     may include capabilities of a NETCONF or RESTCONF server or a
     notification publisher.

     This module does not contain any specific capabilities; it only
     provides a structure where containers containing the actual
     capabilities are augmented in.

     Capability values can be specified at the system level, at the
     datastore level (by selecting all nodes in the datastore), or
     for specific data nodes of a specific datastore (and their
     contained subtrees).
     Capability values specified for a specific datastore or
     node-set override values specified on the system/publisher
     level.

     The same grouping MUST be used to define hierarchical
     capabilities supported both at the system level and at the
     datastore/data-node level.

     To find a capability value for a specific data node in a
     specific datastore, the user SHALL:

     1) search for a datastore-capabilities list entry for
     the specific datastore.  When stating a specific capability, the
     relative path for any specific capability must be the same
     under the system-capabilities container and under the
     per-node-capabilities list.

     2) If the datastore entry is found within that entry, process
     all per-node-capabilities entries in the order they appear in
     the list.  The first entry that specifies the specific
     capability and has a node-selector selecting the specific data
     node defines the capability value.

     3) If the capability value is not found above and the specific
     capability is specified under the system-capabilities container
     (outside the datastore-capabilities list), this value shall be
     used.

     4) If no values are found in the previous steps, the
     system/publisher is not capable of providing a value.  Possible
     reasons are that it is unknown, the capability is changing for
     some reason, there is no specified limit, etc.  In this case,
     the system's behavior is unspecified.

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
     'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
     'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
     are to be interpreted as described in BCP 14 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.

     Copyright (c) 2022 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC 9196
     (https://www.rfc-editor.org/info/rfc9196); see the RFC itself
     for full legal notices.";

  revision 2022-02-17 {
    description
      "Initial version";
    reference
      "RFC 9196: YANG Modules Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  container system-capabilities {
    config false;
    description
      "System capabilities.
       Capability values specified here at the system level
       are valid for all datastores and are used when the
       capability is not specified at the datastore level
       or for specific data nodes.";
    /*
     * "Augmentation point for system-level capabilities."
     */
    list datastore-capabilities {
      key "datastore";
      description
        "Capabilities values per datastore.

         For non-NMDA servers/publishers, 'config false' data is
         considered as if it were part of the running datastore.";
      leaf datastore {
        type leafref {
          path
            "/yanglib:yang-library/yanglib:datastore/yanglib:name";
        }
        description
          "The datastore for which capabilities are defined.
           Only one specific datastore can be specified,
           e.g., ds:conventional must not be used, as it
           represents a set of configuration datastores.";
      }
      list per-node-capabilities {
        description
          "Each list entry specifies capabilities for the selected
           data nodes.  The same capabilities apply to the data nodes
           in the subtree below the selected nodes.

           The system SHALL order the entries according to their
           precedence. The order of the entries MUST NOT change
           unless the underlying capabilities also change.

           Note that the longest patch matching can be achieved
           by ordering more specific matches before less
           specific ones.";
        choice node-selection {
          description
            "A method to select some or all nodes within a
             datastore.";
          leaf node-selector {
            type nacm:node-instance-identifier;
            description
              "Selects the data nodes for which capabilities are
               specified. The special value '/' denotes all data
               nodes in the datastore, consistent with the path
               leaf node on page 41 of [RFC8341].";
            reference
              "RFC 8341: Network Configuration Access Control Model";
          }
        }
        /*
         * "Augmentation point for datastore- or data-node-level
         * capabilities."
         */
      }
    }
  }
}


&lt;CODE ENDS&gt;</pre><a href="#section-4.2-2" class="pilcrow">¶</a>
</div>
</section>
</div>
</section>
</div>
<div id="notification-capabilities_model">
<section id="section-5">
      <h2 id="name-notification-capabilities-m">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-notification-capabilities-m" class="section-name selfRef">Notification Capabilities Model</a>
      </h2>
<p id="section-5-1">
        The YANG module "ietf-notification-capabilities" provides information related to the YANG-Push capability.<a href="#section-5-1" class="pilcrow">¶</a></p>
<section id="section-5.1">
        <h3 id="name-tree-diagram-2">
<a href="#section-5.1" class="section-number selfRef">5.1. </a><a href="#name-tree-diagram-2" class="section-name selfRef">Tree Diagram</a>
        </h3>
<p id="section-5.1-1">
          The following tree diagram <span>[<a href="#RFC8340" class="xref">RFC8340</a>]</span>
          provides an overview of the data model.<a href="#section-5.1-1" class="pilcrow">¶</a></p>
<div id="section-5.1-2">
<pre class="lang-yangtree sourcecode">
module: ietf-notification-capabilities
  augment /sysc:system-capabilities:
    +--ro subscription-capabilities
       +--ro max-nodes-per-update?               uint32
       +--ro periodic-notifications-supported?   notification-support
       +--ro (update-period)?
       |  +--:(minimum-update-period)
       |  |  +--ro minimum-update-period?        uint32
       |  +--:(supported-update-period)
       |     +--ro supported-update-period*      uint32
       +--ro on-change-supported?                notification-support
       |       {yp:on-change}?
       +--ro minimum-dampening-period?           uint32
       |       {yp:on-change}?
       +--ro supported-excluded-change-type*     union
               {yp:on-change}?
  augment /sysc:system-capabilities/sysc:datastore-capabilities
            /sysc:per-node-capabilities:
    +--ro subscription-capabilities
       +--ro max-nodes-per-update?               uint32
       +--ro periodic-notifications-supported?   notification-support
       +--ro (update-period)?
       |  +--:(minimum-update-period)
       |  |  +--ro minimum-update-period?        uint32
       |  +--:(supported-update-period)
       |     +--ro supported-update-period*      uint32
       +--ro on-change-supported?                notification-support
       |       {yp:on-change}?
       +--ro minimum-dampening-period?           uint32
       |       {yp:on-change}?
       +--ro supported-excluded-change-type*     union
               {yp:on-change}?
</pre><a href="#section-5.1-2" class="pilcrow">¶</a>
</div>
</section>
<div id="ietf-notification-capabilities.yang">
<section id="section-5.2">
        <h3 id="name-yang-module-2">
<a href="#section-5.2" class="section-number selfRef">5.2. </a><a href="#name-yang-module-2" class="section-name selfRef">YANG Module</a>
        </h3>
<p id="section-5.2-1">This YANG module imports a feature and typedefs from <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>
        and also imports the "ietf-system-capabilities" specified in this document.<a href="#section-5.2-1" class="pilcrow">¶</a></p>
<div id="section-5.2-2">
<pre class="lang-yang sourcecode">&lt;CODE BEGINS&gt; file "ietf-notification-capabilities@2022-02-17.yang"

module ietf-notification-capabilities {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
  prefix notc;

  import ietf-yang-push {
    prefix yp;
    description
      "This module requires ietf-yang-push to be implemented.";
    reference
      "RFC 8641: Subscription to YANG Notifications for
       Datastore Updates";
  }
  import ietf-system-capabilities {
    prefix sysc;
    description
      "This module requires ietf-system-capabilities to be
       implemented.";
    reference
      "RFC 9196: YANG Modules Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   &lt;https://datatracker.ietf.org/wg/netconf/&gt;
     WG List:  &lt;mailto:netconf@ietf.org&gt;

     Editor:   Balazs Lengyel
               &lt;mailto:balazs.lengyel@ericsson.com&gt;";
  description
    "This module specifies publisher capabilities related to
     YANG-Push (RFC 8641).

     The module contains:

     - a specification of the data nodes that support 'on-change' or
     'periodic' notifications.

     - capabilities related to the throughput of notification data
     that the publisher can support.  (Note that for a specific
     subscription, the publisher MAY allow only longer periods
     or smaller updates depending on, e.g., actual load conditions.)

     Capability values can be specified at the system/publisher
     level, at the datastore level, or for specific data nodes of
     a specific datastore (and their contained subtrees), as defined
     in the ietf-system-capabilities module.

     If different data nodes covered by a single subscription
     have different values for a specific capability, then using
     values that are only acceptable for some of these data nodes,
     but not for others, may result in the rejection of the
     subscription.

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
     'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
     'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
     are to be interpreted as described in BCP 14 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.

     Copyright (c) 2022 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC 9196
     (https://www.rfc-editor.org/info/rfc9196); see the RFC itself
     for full legal notices.";

  revision 2022-02-17 {
    description
      "Initial version";
    reference
      "RFC 9196: YANG Modules Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  grouping subscription-capabilities {
    description
      "Capabilities related to YANG-Push subscriptions
       and notifications";
    container subscription-capabilities {
      description
        "Capabilities related to YANG-Push subscriptions
         and notifications";
      typedef notification-support {
        type bits {
          bit config-changes {
            description
              "The publisher is capable of sending
               notifications for 'config true' nodes for the
               relevant scope and subscription type.";
          }
          bit state-changes {
            description
              "The publisher is capable of sending
               notifications for 'config false' nodes for the
               relevant scope and subscription type.";
          }
        }
        description
          "Type for defining whether 'on-change' or
           'periodic' notifications are supported for all data nodes,
           'config false' data nodes, 'config true' data nodes, or
           no data nodes.

           The bits config-changes or state-changes have no effect
           when they are set for a datastore or for a set of nodes
           that does not contain nodes with the indicated config
           value.  In those cases, the effect is the same as if no
           support was declared.  One example of this is indicating
           support for state-changes for a candidate datastore that
           has no effect.";
      }

      leaf max-nodes-per-update {
        type uint32 {
          range "1..max";
        }
        description
          "Maximum number of data nodes that can be sent
           in an update. The publisher MAY support more data nodes
           but SHOULD support at least this number.

           May be used to avoid the 'update-too-big' error
           during subscription.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, the 'update-too-big' error/identity";
      }
      leaf periodic-notifications-supported {
        type notification-support;
        description
          "Specifies whether the publisher is capable of
           sending 'periodic' notifications for the selected
           data nodes, including any subtrees that may exist
           below them.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, 'periodic' subscription concept";
      }
      choice update-period {
        description
          "Supported update period value or values for
           'periodic' subscriptions.";
        leaf minimum-update-period {
          type uint32;
          units "centiseconds";
          description
            "Indicates the minimal update period that is
             supported for a 'periodic' subscription.

             A subscription request to the selected data nodes with
             a smaller period than what this leaf specifies is
             likely to result in a 'period-unsupported' error.";
          reference
            "RFC 8641: Subscription to YANG Notifications for
             Datastore Updates, the period leaf in the ietf-yang-push
             YANG module";
        }
        leaf-list supported-update-period {
          type uint32;
          units "centiseconds";
          description
            "Supported update period values for a 'periodic'
             subscription.

             A subscription request to the selected data nodes with a
             period not included in the leaf-list will result in a
             'period-unsupported' error.";
          reference
            "RFC 8641: Subscription to YANG Notifications for
             Datastore Updates, the period leaf in the ietf-yang-push
             YANG module";
        }
      }
      leaf on-change-supported {
        if-feature "yp:on-change";
        type notification-support;
        description
          "Specifies whether the publisher is capable of
           sending 'on-change' notifications for the selected
           data nodes and the subtree below them.";
        reference
          "RFC 8641: Subscription to YANG Notifications for Datastore
           Updates, on-change concept";
      }
      leaf minimum-dampening-period {
        if-feature "yp:on-change";
        type uint32;
        units "centiseconds";
        description
          "The minimum dampening period supported for 'on-change'
           subscriptions for the selected data nodes.

           If this value is present and greater than zero,
           that implies dampening is mandatory.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, the dampening-period leaf in the
           ietf-yang-push YANG module";
      }
      leaf-list supported-excluded-change-type {
        if-feature "yp:on-change";
        type union {
          type enumeration {
            enum none {
              value -2;
              description
                "None of the change types can be excluded.";
            }
            enum all {
              value -1;
              description
                "Any combination of change types can be excluded.";
            }
          }
          type yp:change-type;
        }
        description
          "The change types that can be excluded in
           YANG-Push subscriptions for the selected data nodes.";
        reference
          "RFC 8641: Subscription to YANG Notifications for Datastore
           Updates, the change-type typedef in the ietf-yang-push
           YANG module";
      }
    }
  }

  augment "/sysc:system-capabilities" {
    description
      "Add system level capabilities";
    uses subscription-capabilities {
      refine
        "subscription-capabilities/supported-excluded-change-type" {
        default "none";
      }
    }
  }

  augment "/sysc:system-capabilities/sysc:datastore-capabilities"
        + "/sysc:per-node-capabilities" {
    description
      "Add datastore and node-level capabilities";
    uses subscription-capabilities {
      refine
        "subscription-capabilities/supported-excluded-change-type" {
        default "none";
      }
    }
  }
}

&lt;CODE ENDS&gt;</pre><a href="#section-5.2-2" class="pilcrow">¶</a>
</div>
<p id="section-5.2-3">&lt;CODE ENDS&gt;<a href="#section-5.2-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="security">
<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"> 
         The YANG modules specified in this document define a schema for data 
         that is designed to be accessed via network management protocols such 
         as NETCONF <span>[<a href="#RFC6241" class="xref">RFC6241</a>]</span> or RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span>
         or as YANG instance data.  
  The lowest NETCONF layer is the secure transport layer, and the 
  mandatory-to-implement secure transport is Secure Shell (SSH) 
  <span>[<a href="#RFC6242" class="xref">RFC6242</a>]</span>. The lowest RESTCONF layer is HTTPS, and 
  the mandatory-to-implement secure transport is TLS <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span>.<a href="#section-6-1" class="pilcrow">¶</a></p>
<p id="section-6-2">
         The Network Configuration Access Control Model (NACM) <span>[<a href="#RFC8341" class="xref">RFC8341</a>]</span> 
         provides the means to restrict access for particular NETCONF or 
         RESTCONF users to a preconfigured subset of all available NETCONF or 
         RESTCONF protocol operations and content.<a href="#section-6-2" class="pilcrow">¶</a></p>
<p id="section-6-3">
         This document outlines a framework for conveying system capability 
  information that is inherently flexible and extensible.  While the full 
  set of use cases is not known now, they may range as wide as conveying 
  the minimum update period for periodic subscription updates and what 
  protocols might be used for such notifications.  Knowledge of this type 
  of value might, for example, allow an attacker to gain insight into how 
  long unauthorized configuration changes might be active prior to detection 
  and what communications channels might be disrupted to extend the period 
  of non-detection.  Documents adding additional capabilities via augmenting 
  this module are encouraged to document the security considerations of the

  new YANG nodes, according to the guidance in BCP 216 <span>[<a href="#RFC8407" class="xref">RFC8407</a>]</span>.<a href="#section-6-3" class="pilcrow">¶</a></p>
<p id="section-6-4"> All protocol-accessible data nodes in augmented modules are read-only 
     and cannot be modified. Access control may be configured to avoid exposing any read-only data that is defined by the augmenting module
  documentation as being security sensitive.<a href="#section-6-4" class="pilcrow">¶</a></p>
<p id="section-6-5">When that data is in file format, the data should be protected against 
      modification or unauthorized access using normal file-handling mechanisms.
 The data in file format also inherits all the security considerations of 
 <span>[<a href="#RFC9195" class="xref">RFC9195</a>]</span>, which includes additional 
 considerations about read protections and distinguishes between data at 
 rest and in motion.<a href="#section-6-5" class="pilcrow">¶</a></p>
</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>
<section id="section-7.1">
        <h3 id="name-the-ietf-xml-registry">
<a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-the-ietf-xml-registry" class="section-name selfRef">The IETF XML Registry</a>
        </h3>
<p id="section-7.1-1">This document registers the following URIs in the "IETF XML 
          Registry" <span>[<a href="#RFC3688" class="xref">RFC3688</a>]</span>:<a href="#section-7.1-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlCompact dlParallel" id="section-7.1-2">
          <dt id="section-7.1-2.1">URI:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-2.2"> urn:ietf:params:xml:ns:yang:ietf-system-capabilities<a href="#section-7.1-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.1-2.3">Registrant Contact:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-2.4">The IESG.<a href="#section-7.1-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.1-2.5">XML:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-2.6"> N/A, the requested URI is an XML namespace.<a href="#section-7.1-2.6" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
<span class="break"></span><dl class="dlCompact dlParallel" id="section-7.1-3">
          <dt id="section-7.1-3.1">URI:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-3.2"> urn:ietf:params:xml:ns:yang:ietf-notification-capabilities<a href="#section-7.1-3.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.1-3.3">Registrant Contact:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-3.4">The IESG.<a href="#section-7.1-3.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.1-3.5">XML:</dt>
          <dd style="margin-left: 1.5em" id="section-7.1-3.6"> N/A, the requested URI is an XML namespace.<a href="#section-7.1-3.6" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
<section id="section-7.2">
        <h3 id="name-the-yang-module-names-regis">
<a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-the-yang-module-names-regis" class="section-name selfRef">The YANG Module Names Registry</a>
        </h3>
<p id="section-7.2-1">This document registers the following YANG modules in the
          "YANG Module Names" registry <span>[<a href="#RFC6020" class="xref">RFC6020</a>]</span>:<a href="#section-7.2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlCompact dlParallel" id="section-7.2-2">
          <dt id="section-7.2-2.1">name:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-2.2">       ietf-system-capabilities<a href="#section-7.2-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-2.3">namespace:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-2.4">  urn:ietf:params:xml:ns:yang:ietf-system-capabilities<a href="#section-7.2-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-2.5">prefix:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-2.6">     sysc<a href="#section-7.2-2.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-2.7">reference:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-2.8">  RFC 9196<a href="#section-7.2-2.8" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
<span class="break"></span><dl class="dlCompact dlParallel" id="section-7.2-3">
          <dt id="section-7.2-3.1">name:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-3.2">       ietf-notification-capabilities<a href="#section-7.2-3.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-3.3">namespace:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-3.4">  
        urn:ietf:params:xml:ns:yang:ietf-notification-capabilities<a href="#section-7.2-3.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-3.5">prefix:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-3.6">     notc<a href="#section-7.2-3.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-7.2-3.7">reference:</dt>
          <dd style="margin-left: 1.5em" id="section-7.2-3.8">  RFC 9196<a href="#section-7.2-3.8" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</section>
</div>
<section id="section-8">
      <h2 id="name-references">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-8.1">
        <h3 id="name-normative-references">
<a href="#section-8.1" class="section-number selfRef">8.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="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="RFC3688">[RFC3688]</dt>
        <dd>
<span class="refAuthor">Mealling, M.</span>, <span class="refTitle">"The IETF XML Registry"</span>, <span class="seriesInfo">BCP 81</span>, <span class="seriesInfo">RFC 3688</span>, <span class="seriesInfo">DOI 10.17487/RFC3688</span>, <time datetime="2004-01" class="refDate">January 2004</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3688">https://www.rfc-editor.org/info/rfc3688</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6020">[RFC6020]</dt>
        <dd>
<span class="refAuthor">Bjorklund, M., Ed.</span>, <span class="refTitle">"YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)"</span>, <span class="seriesInfo">RFC 6020</span>, <span class="seriesInfo">DOI 10.17487/RFC6020</span>, <time datetime="2010-10" class="refDate">October 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6020">https://www.rfc-editor.org/info/rfc6020</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6241">[RFC6241]</dt>
        <dd>
<span class="refAuthor">Enns, R., Ed.</span>, <span class="refAuthor">Bjorklund, M., Ed.</span>, <span class="refAuthor">Schoenwaelder, J., Ed.</span>, and <span class="refAuthor">A. Bierman, Ed.</span>, <span class="refTitle">"Network Configuration Protocol (NETCONF)"</span>, <span class="seriesInfo">RFC 6241</span>, <span class="seriesInfo">DOI 10.17487/RFC6241</span>, <time datetime="2011-06" class="refDate">June 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6241">https://www.rfc-editor.org/info/rfc6241</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6242">[RFC6242]</dt>
        <dd>
<span class="refAuthor">Wasserman, M.</span>, <span class="refTitle">"Using the NETCONF Protocol over Secure Shell (SSH)"</span>, <span class="seriesInfo">RFC 6242</span>, <span class="seriesInfo">DOI 10.17487/RFC6242</span>, <time datetime="2011-06" class="refDate">June 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6242">https://www.rfc-editor.org/info/rfc6242</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8040">[RFC8040]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span>, <span class="refAuthor">Bjorklund, M.</span>, and <span class="refAuthor">K. Watsen</span>, <span class="refTitle">"RESTCONF Protocol"</span>, <span class="seriesInfo">RFC 8040</span>, <span class="seriesInfo">DOI 10.17487/RFC8040</span>, <time datetime="2017-01" class="refDate">January 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8040">https://www.rfc-editor.org/info/rfc8040</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="RFC8341">[RFC8341]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span> and <span class="refAuthor">M. Bjorklund</span>, <span class="refTitle">"Network Configuration Access Control Model"</span>, <span class="seriesInfo">STD 91</span>, <span class="seriesInfo">RFC 8341</span>, <span class="seriesInfo">DOI 10.17487/RFC8341</span>, <time datetime="2018-03" class="refDate">March 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8341">https://www.rfc-editor.org/info/rfc8341</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8342">[RFC8342]</dt>
        <dd>
<span class="refAuthor">Bjorklund, M.</span>, <span class="refAuthor">Schoenwaelder, J.</span>, <span class="refAuthor">Shafer, P.</span>, <span class="refAuthor">Watsen, K.</span>, and <span class="refAuthor">R. Wilton</span>, <span class="refTitle">"Network Management Datastore Architecture (NMDA)"</span>, <span class="seriesInfo">RFC 8342</span>, <span class="seriesInfo">DOI 10.17487/RFC8342</span>, <time datetime="2018-03" class="refDate">March 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8342">https://www.rfc-editor.org/info/rfc8342</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="RFC8525">[RFC8525]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span>, <span class="refAuthor">Bjorklund, M.</span>, <span class="refAuthor">Schoenwaelder, J.</span>, <span class="refAuthor">Watsen, K.</span>, and <span class="refAuthor">R. Wilton</span>, <span class="refTitle">"YANG Library"</span>, <span class="seriesInfo">RFC 8525</span>, <span class="seriesInfo">DOI 10.17487/RFC8525</span>, <time datetime="2019-03" class="refDate">March 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8525">https://www.rfc-editor.org/info/rfc8525</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8639">[RFC8639]</dt>
        <dd>
<span class="refAuthor">Voit, E.</span>, <span class="refAuthor">Clemm, A.</span>, <span class="refAuthor">Gonzalez Prieto, A.</span>, <span class="refAuthor">Nilsen-Nygaard, E.</span>, and <span class="refAuthor">A. Tripathy</span>, <span class="refTitle">"Subscription to YANG Notifications"</span>, <span class="seriesInfo">RFC 8639</span>, <span class="seriesInfo">DOI 10.17487/RFC8639</span>, <time datetime="2019-09" class="refDate">September 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8639">https://www.rfc-editor.org/info/rfc8639</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8641">[RFC8641]</dt>
        <dd>
<span class="refAuthor">Clemm, A.</span> and <span class="refAuthor">E. Voit</span>, <span class="refTitle">"Subscription to YANG Notifications for Datastore Updates"</span>, <span class="seriesInfo">RFC 8641</span>, <span class="seriesInfo">DOI 10.17487/RFC8641</span>, <time datetime="2019-09" class="refDate">September 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8641">https://www.rfc-editor.org/info/rfc8641</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9195">[RFC9195]</dt>
      <dd>
<span class="refAuthor">Lengyel, B.</span> and <span class="refAuthor">B. Claise</span>, <span class="refTitle">"A File Format for YANG Instance Data"</span>, <span class="seriesInfo">RFC 9195</span>, <span class="seriesInfo">DOI 10.17487/RFC9195</span>, <time datetime="2022-02" class="refDate">February 2022</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9195">https://www.rfc-editor.org/info/rfc9195</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-8.2">
        <h3 id="name-informative-references">
<a href="#section-8.2" class="section-number selfRef">8.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC8340">[RFC8340]</dt>
        <dd>
<span class="refAuthor">Bjorklund, M.</span> and <span class="refAuthor">L. Berger, Ed.</span>, <span class="refTitle">"YANG Tree Diagrams"</span>, <span class="seriesInfo">BCP 215</span>, <span class="seriesInfo">RFC 8340</span>, <span class="seriesInfo">DOI 10.17487/RFC8340</span>, <time datetime="2018-03" class="refDate">March 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8340">https://www.rfc-editor.org/info/rfc8340</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8407">[RFC8407]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span>, <span class="refTitle">"Guidelines for Authors and Reviewers of Documents Containing YANG Data Models"</span>, <span class="seriesInfo">BCP 216</span>, <span class="seriesInfo">RFC 8407</span>, <span class="seriesInfo">DOI 10.17487/RFC8407</span>, <time datetime="2018-10" class="refDate">October 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8407">https://www.rfc-editor.org/info/rfc8407</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8792">[RFC8792]</dt>
      <dd>
<span class="refAuthor">Watsen, K.</span>, <span class="refAuthor">Auerswald, E.</span>, <span class="refAuthor">Farrel, A.</span>, and <span class="refAuthor">Q. Wu</span>, <span class="refTitle">"Handling Long Lines in Content of Internet-Drafts and RFCs"</span>, <span class="seriesInfo">RFC 8792</span>, <span class="seriesInfo">DOI 10.17487/RFC8792</span>, <time datetime="2020-06" class="refDate">June 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8792">https://www.rfc-editor.org/info/rfc8792</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<section id="appendix-A">
      <h2 id="name-instance-data-example-1">
<a href="#appendix-A" class="section-number selfRef">Appendix A. </a><a href="#name-instance-data-example-1" class="section-name selfRef">Instance Data Example #1</a>
      </h2>
<p id="appendix-A-1">The following examples use artwork folding 
           <span>[<a href="#RFC8792" class="xref">RFC8792</a>]</span> for better formatting.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
<p id="appendix-A-2">
        The following instance data example describes the notification 
        capabilities of a hypothetical "acme-router". The router implements 
        the running and operational datastores.
        Every change can be reported "on-change" from the running datastore, 
        but only "config false" nodes and some "config false" data can be reported on-change from the 
        operational datastore.
        Interface statistics are not reported "on-change"; only two important counters are.
        Datastore subscription capabilities are not reported "on-change", as they 
        never change on the acme-router during runtime.<a href="#appendix-A-2" class="pilcrow">¶</a></p>
<span id="name-notification-capabilities-w"></span><div id="acme-router-notification-capabilities">
<figure id="figure-1">
        <div id="appendix-A-3.1">
<pre class="lang-xml sourcecode">
========== NOTE: '\' line wrapping per RFC 8792) ===========

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;instance-data-set xmlns=\
    "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data"&gt;
  &lt;name&gt;acme-router-notification-capabilities&lt;/name&gt;
  &lt;content-schema&gt;
    &lt;module&gt;ietf-system-capabilities@2022-02-17&lt;/module&gt;
    &lt;module&gt;ietf-notification-capabilities@2022-02-17&lt;/module&gt;
  &lt;/content-schema&gt;
  &lt;description&gt;Defines the notification capabilities of an
    acme-router. The router only has running and operational
    datastores. Every change can be reported on-change from the
    running datastore, but only "config false" nodes and some
    "config false" data can be reported on-change from the
    operational datastore. Statistics
    are not reported on-change except for two important counters,
    where a small dampening period is mandated.
  &lt;/description&gt;
  &lt;content-data&gt;
    &lt;system-capabilities \
     xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
     xmlns:notc=\
       "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
     xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"&gt;
     &lt;notc:subscription-capabilities&gt;
      &lt;notc:minimum-update-period&gt;500&lt;/notc:minimum-update-period&gt;
      &lt;notc:max-nodes-per-update&gt;2000&lt;/notc:max-nodes-per-update&gt;
      &lt;notc:minimum-dampening-period&gt;\
         100\
      &lt;/notc:minimum-dampening-period&gt;
      &lt;notc:periodic-notifications-supported&gt;\
         config-changes state-changes\
      &lt;/notc:periodic-notifications-supported&gt;
      &lt;notc:on-change-supported&gt;\
         config-changes state-changes\
      &lt;/notc:on-change-supported&gt;
      &lt;notc:supported-excluded-change-type&gt;\
         all\
      &lt;/notc:supported-excluded-change-type&gt;
     &lt;/notc:subscription-capabilities&gt;
      &lt;datastore-capabilities&gt;
        &lt;datastore&gt;ds:operational&lt;/datastore&gt;
        &lt;per-node-capabilities&gt;
          &lt;node-selector&gt;\
              /if:interfaces/if:interface[if:name='lo']\
          &lt;/node-selector&gt;
          &lt;notc:subscription-capabilities&gt;
            &lt;notc:on-change-supported/&gt;
            &lt;notc:periodic-notifications-supported/&gt;
          &lt;/notc:subscription-capabilities&gt;
        &lt;/per-node-capabilities&gt;
        &lt;per-node-capabilities&gt;
          &lt;node-selector&gt;\
              /if:interfaces/if:interface/if:statistics/if:in-octets\
          &lt;/node-selector&gt;
          &lt;notc:subscription-capabilities&gt;
            &lt;notc:minimum-dampening-period&gt;10
              &lt;/notc:minimum-dampening-period&gt;
            &lt;notc:on-change-supported&gt;\
              state-changes\
            &lt;/notc:on-change-supported&gt;
          &lt;/notc:subscription-capabilities&gt;
        &lt;/per-node-capabilities&gt;
        &lt;per-node-capabilities&gt;
          &lt;node-selector&gt;\
          /if:interfaces/if:interface/if:statistics/if:out-octets\
          &lt;/node-selector&gt;
          &lt;notc:subscription-capabilities&gt;
            &lt;notc:minimum-dampening-period&gt;10
              &lt;/notc:minimum-dampening-period&gt;
            &lt;notc:on-change-supported&gt;\
              state-changes\
            &lt;/notc:on-change-supported&gt;
          &lt;/notc:subscription-capabilities&gt;
        &lt;/per-node-capabilities&gt;
        &lt;per-node-capabilities&gt;
          &lt;node-selector&gt;\
              /if:interfaces/if:interface/if:statistics\
          &lt;/node-selector&gt;
          &lt;notc:subscription-capabilities&gt;
            &lt;notc:on-change-supported/&gt;
          &lt;/notc:subscription-capabilities&gt;
        &lt;/per-node-capabilities&gt;
      &lt;/datastore-capabilities&gt;
    &lt;/system-capabilities&gt;
  &lt;/content-data&gt;
&lt;/instance-data-set&gt;
</pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a>:
<a href="#name-notification-capabilities-w" class="selfRef">Notification Capabilities with Settings Specific to the Data Node</a>
        </figcaption></figure>
</div>
</section>
<section id="appendix-B">
      <h2 id="name-instance-data-example-2">
<a href="#appendix-B" class="section-number selfRef">Appendix B. </a><a href="#name-instance-data-example-2" class="section-name selfRef">Instance Data Example #2</a>
      </h2>
<p id="appendix-B-1">The following examples use artwork folding 
        <span>[<a href="#RFC8792" class="xref">RFC8792</a>]</span> for better formatting.<a href="#appendix-B-1" class="pilcrow">¶</a></p>
<p id="appendix-B-2">
        The following instance data example describes the notification 
        capabilities of a hypothetical "acme-switch". The switch implements 
        the running, candidate, and operational 
        datastores.
 
 Every change can be reported "on-change" from the
         running datastore, nothing can be reported on-change from the candidate datastore, and all 
         "config false" data can be reported on-change from the operational datastore.
        "Periodic" subscriptions are supported for running and 
        operational but not for candidate datastores.<a href="#appendix-B-2" class="pilcrow">¶</a></p>
<span id="name-notification-capabilities-wi"></span><div id="acme-switch-notification-capabilities">
<figure id="figure-2">
        <div id="appendix-B-3.1">
<pre class="lang-xml sourcecode">
========== NOTE: '\' line wrapping per RFC 8792) ===========

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;instance-data-set xmlns=\
    "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data"&gt;
  &lt;name&gt;acme-switch-notification-capabilities&lt;/name&gt;
  &lt;content-schema&gt;
    &lt;module&gt;ietf-system-capabilities@2022-02-17&lt;/module&gt;
    &lt;module&gt;ietf-notification-capabilities@2022-02-17&lt;/module&gt;
  &lt;/content-schema&gt;
  &lt;description&gt;Notification capabilities of acme-switch.
    Acme-switch implements the running, candidate, and operational
    datastores. Every change can be reported on-change from the
    running datastore, nothing from the candidate datastore and
    all "config false" data from the operational datastore. Periodic
    subscriptions are supported for running and operational, but not
    for candidate datastore.
  &lt;/description&gt;
  &lt;content-data&gt;
    &lt;system-capabilities \
     xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
     xmlns:notc=\
       "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
     xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"&gt;
     &lt;notc:subscription-capabilities&gt;
      &lt;notc:minimum-update-period&gt;500&lt;/notc:minimum-update-period&gt;
      &lt;notc:max-nodes-per-update&gt;2000&lt;/notc:max-nodes-per-update&gt;
      &lt;notc:minimum-dampening-period&gt;\
        100\
      &lt;/notc:minimum-dampening-period&gt;
      &lt;notc:periodic-notifications-supported&gt;\
        config-changes state-changes\
      &lt;/notc:periodic-notifications-supported&gt;
     &lt;/notc:subscription-capabilities&gt;
     &lt;datastore-capabilities&gt;
       &lt;datastore&gt;ds:operational&lt;/datastore&gt;
       &lt;per-node-capabilities&gt;
         &lt;node-selector&gt;/&lt;/node-selector&gt;
         &lt;notc:subscription-capabilities&gt;
           &lt;notc:on-change-supported&gt;\
             state-changes\
           &lt;/notc:on-change-supported&gt;
         &lt;/notc:subscription-capabilities&gt;
       &lt;/per-node-capabilities&gt;
     &lt;/datastore-capabilities&gt;
     &lt;datastore-capabilities&gt;
       &lt;datastore&gt;ds:candidate&lt;/datastore&gt;
       &lt;per-node-capabilities&gt;
         &lt;node-selector&gt;/&lt;/node-selector&gt;
         &lt;notc:subscription-capabilities&gt;
           &lt;notc:on-change-supported/&gt;
           &lt;notc:periodic-notifications-supported/&gt;
         &lt;/notc:subscription-capabilities&gt;
       &lt;/per-node-capabilities&gt;
     &lt;/datastore-capabilities&gt;
     &lt;datastore-capabilities&gt;
      &lt;datastore&gt;ds:running&lt;/datastore&gt;
       &lt;per-node-capabilities&gt;
         &lt;node-selector&gt;/&lt;/node-selector&gt;
         &lt;notc:subscription-capabilities&gt;
           &lt;notc:on-change-supported&gt;\
             config-changes\
           &lt;/notc:on-change-supported&gt;
         &lt;/notc:subscription-capabilities&gt;
       &lt;/per-node-capabilities&gt;
     &lt;/datastore-capabilities&gt;
    &lt;/system-capabilities&gt;
  &lt;/content-data&gt;
&lt;/instance-data-set&gt;
</pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a>:
<a href="#name-notification-capabilities-wi" class="selfRef">Notification Capabilities with Datastore-Level Settings</a>
        </figcaption></figure>
</div>
</section>
<section id="appendix-C">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<p id="appendix-C-1">For their valuable comments, discussions, and feedback, we wish to 
        acknowledge <span class="contact-name">Andy Bierman</span>, <span class="contact-name">Juergen Schoenwaelder</span>, <span class="contact-name">Rob Wilton</span>, <span class="contact-name">Kent Watsen</span>, 
        <span class="contact-name">Eric Voit</span>, <span class="contact-name">Joe Clarke</span>, <span class="contact-name">Martin Bjorklund</span>, <span class="contact-name">Ladislav Lhotka</span>, <span class="contact-name">Qin Wu</span>, 
        <span class="contact-name">Mahesh Jethanandani</span>, <span class="contact-name">Ran Tao</span>, <span class="contact-name">Reshad Rahman</span>, and other members of the Netmod Working Group.<a href="#appendix-C-1" class="pilcrow">¶</a></p>
</section>
<div id="authors-addresses">
<section id="appendix-D">
      <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">Balazs Lengyel</span></div>
<div dir="auto" class="left"><span class="org">Ericsson</span></div>
<div dir="auto" class="left"><span class="locality">Budapest</span></div>
<div dir="auto" class="left"><span class="street-address">Magyar Tudosok korutja 11</span></div>
<div dir="auto" class="left"><span class="postal-code">1117</span></div>
<div dir="auto" class="left"><span class="country-name">Hungary</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:balazs.lengyel@ericsson.com" class="email">balazs.lengyel@ericsson.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Alexander Clemm</span></div>
<div dir="auto" class="left"><span class="org">Futurewei</span></div>
<div dir="auto" class="left"><span class="street-address">2330 Central Expressway</span></div>
<div dir="auto" class="left">
<span class="locality">Santa Clara</span>, <span class="region">CA</span> <span class="postal-code">95050</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:ludwig@clemm.org" class="email">ludwig@clemm.org</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Benoit Claise</span></div>
<div dir="auto" class="left"><span class="org">Huawei</span></div>
<div dir="auto" class="left"><span class="street-address">George's Court Townsend Street</span></div>
<div dir="auto" class="left"><span class="locality">Dublin 2</span></div>
<div dir="auto" class="left"><span class="country-name">Ireland</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:benoit.claise@huawei.com" class="email">benoit.claise@huawei.com</a>
</div>
</address>
</section>
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