File: rfc8650.html

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<!DOCTYPE html>
<html lang="en" class="RFC">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 8650: Dynamic Subscription to YANG Events and Datastores over RESTCONF</title>
<meta content="Eric Voit" name="author">
<meta content="Reshad Rahman" name="author">
<meta content="Einar Nilsen-Nygaard" name="author">
<meta content="Alexander Clemm" name="author">
<meta content="Andy Bierman" name="author">
<meta content="
       This document provides a RESTCONF binding to the dynamic subscription
      capability of both subscribed notifications and YANG-Push. 
    " name="description">
<meta content="xml2rfc 2.35.0" name="generator">
<meta content="YANG-Push" name="keyword">
<meta content="8650" name="rfc.number">
<link href="rfc8650.xml" type="application/rfc+xml" rel="alternate">
<link href="#copyright" rel="license">
<style type="text/css">/*

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

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

*/

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

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

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

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

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

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

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

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

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

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

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

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

/* info block */
#identifiers {
  margin: 0;
  font-size: 0.9em;
}
#identifiers dt {
  width: 3em;
  clear: left;
}
#identifiers dd {
  float: left;
  margin-bottom: 0;
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

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

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

.refInstance {
  margin-bottom: 1.25em;
}

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

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

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

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

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

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

/* pagination */
@media print {
  body {

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

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

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

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

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

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

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

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

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

}

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


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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

}
/* Avoid wrapping of URLs in references */
@media screen {
  .references a {
    white-space: nowrap;
  }
}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
}
div#internal-metadata {
  padding: 0.5em;                       /* to match the external-metadata padding */
}
/* Styling for title RFC Number */
h1#rfcnum {
  clear: both;
  margin: 0 0 -1em;
  padding: 1em 0 0 0;
}
/* Make .olPercent look the same as <ol><li> */
dl.olPercent > dd {
  margin: 0 0 0.25em 0;
  min-height: initial;
}
/* Give aside some styling to set it apart */
aside {
  border-left: 1px solid #ddd;
  margin: 1em 0 1em 2em;
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<table class="ears">
<thead><tr>
<td class="left">RFC 8650</td>
<td class="center">RESTCONF Transport for Event Notifications</td>
<td class="right">November 2019</td>
</tr></thead>
<tfoot><tr>
<td class="left">Voit, 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/rfc8650" class="eref">8650</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="2019-11" class="published">November 2019</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">E. Voit</div>
<div class="org">Cisco Systems</div>
</div>
<div class="author">
      <div class="author-name">R. Rahman</div>
<div class="org">Cisco Systems</div>
</div>
<div class="author">
      <div class="author-name">E. Nilsen-Nygaard</div>
<div class="org">Cisco Systems</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">A. Bierman</div>
<div class="org">YumaWorks</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8650</h1>
<h1 id="title">Dynamic Subscription to YANG Events and Datastores over RESTCONF</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document provides a RESTCONF binding to the dynamic subscription
      capability of both subscribed notifications and YANG-Push.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc8650">https://www.rfc-editor.org/info/rfc8650</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) 2019 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-terminology" class="xref">Terminology</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc 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-dynamic-subscriptions" class="xref">Dynamic Subscriptions</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-transport-connectivity" class="xref">Transport Connectivity</a><a href="#section-toc.1-1.3.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="xref">3.2</a>.  <a href="#name-discovery" class="xref">Discovery</a><a href="#section-toc.1-1.3.2.2.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.3.2.3">
                <p id="section-toc.1-1.3.2.3.1"><a href="#section-3.3" class="xref">3.3</a>.  <a href="#name-restconf-rpcs-and-http-stat" class="xref">RESTCONF RPCs and HTTP Status Codes</a><a href="#section-toc.1-1.3.2.3.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.3.2.4">
                <p id="section-toc.1-1.3.2.4.1"><a href="#section-3.4" class="xref">3.4</a>.  <a href="#name-call-flow-for-server-sent-e" class="xref">Call Flow for Server-Sent Events</a><a href="#section-toc.1-1.3.2.4.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc 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-qos-treatment" class="xref">QoS Treatment</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc 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-messages" class="xref">Notification Messages</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc 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-yang-tree" class="xref">YANG Tree</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc 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-yang-module" class="xref">YANG Module</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc 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-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-9" class="xref">9</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.9.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#section-10" class="xref">10</a>. <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.10.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.10.2.1">
                <p id="section-toc.1-1.10.2.1.1"><a href="#section-10.1" class="xref">10.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.10.2.1.1" class="pilcrow">¶</a></p>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.10.2.2">
                <p id="section-toc.1-1.10.2.2.1"><a href="#section-10.2" class="xref">10.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.10.2.2.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#section-appendix.a" class="xref">Appendix A</a>.  <a href="#name-examples" class="xref">Examples</a><a href="#section-toc.1-1.11.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.11.2.1">
                <p id="section-toc.1-1.11.2.1.1"><a href="#section-a.1" class="xref">A.1</a>.  <a href="#name-dynamic-subscriptions-2" class="xref">Dynamic Subscriptions</a><a href="#section-toc.1-1.11.2.1.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.11.2.1.2.1">
                    <p id="section-toc.1-1.11.2.1.2.1.1"><a href="#section-a.1.1" class="xref">A.1.1</a>.  <a href="#name-establishing-dynamic-subscr" class="xref">Establishing Dynamic Subscriptions</a><a href="#section-toc.1-1.11.2.1.2.1.1" class="pilcrow">¶</a></p>
</li>
                  <li class="toc ulEmpty" id="section-toc.1-1.11.2.1.2.2">
                    <p id="section-toc.1-1.11.2.1.2.2.1"><a href="#section-a.1.2" class="xref">A.1.2</a>.  <a href="#name-modifying-dynamic-subscript" class="xref">Modifying Dynamic Subscriptions</a><a href="#section-toc.1-1.11.2.1.2.2.1" class="pilcrow">¶</a></p>
</li>
                  <li class="toc ulEmpty" id="section-toc.1-1.11.2.1.2.3">
                    <p id="section-toc.1-1.11.2.1.2.3.1"><a href="#section-a.1.3" class="xref">A.1.3</a>.  <a href="#name-deleting-dynamic-subscripti" class="xref">Deleting Dynamic Subscriptions</a><a href="#section-toc.1-1.11.2.1.2.3.1" class="pilcrow">¶</a></p>
</li>
                </ul>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.11.2.2">
                <p id="section-toc.1-1.11.2.2.1"><a href="#section-a.2" class="xref">A.2</a>.  <a href="#name-subscription-state-notifica" class="xref">Subscription State Notifications</a><a href="#section-toc.1-1.11.2.2.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.11.2.2.2.1">
                    <p id="section-toc.1-1.11.2.2.2.1.1"><a href="#section-a.2.1" class="xref">A.2.1</a>.  <a href="#name-subscription-modified" class="xref">"subscription-modified"</a><a href="#section-toc.1-1.11.2.2.2.1.1" class="pilcrow">¶</a></p>
</li>
                  <li class="toc ulEmpty" id="section-toc.1-1.11.2.2.2.2">
                    <p id="section-toc.1-1.11.2.2.2.2.1"><a href="#section-a.2.2" class="xref">A.2.2</a>.  <a href="#name-subscription-completed-subs" class="xref">"subscription-completed", "subscription-resumed", and "replay-completed"</a><a href="#section-toc.1-1.11.2.2.2.2.1" class="pilcrow">¶</a></p>
</li>
                  <li class="toc ulEmpty" id="section-toc.1-1.11.2.2.2.3">
                    <p id="section-toc.1-1.11.2.2.2.3.1"><a href="#section-a.2.3" class="xref">A.2.3</a>.  <a href="#name-subscription-terminated-and" class="xref">"subscription-terminated" and "subscription-suspended"</a><a href="#section-toc.1-1.11.2.2.2.3.1" class="pilcrow">¶</a></p>
</li>
                </ul>
</li>
              <li class="toc ulEmpty" id="section-toc.1-1.11.2.3">
                <p id="section-toc.1-1.11.2.3.1"><a href="#section-a.3" class="xref">A.3</a>.  <a href="#name-filter-example" class="xref">Filter Example</a><a href="#section-toc.1-1.11.2.3.1" class="pilcrow">¶</a></p>
</li>
            </ul>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.12">
            <p id="section-toc.1-1.12.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a><a href="#section-toc.1-1.12.1" class="pilcrow">¶</a></p>
</li>
          <li class="toc ulEmpty" id="section-toc.1-1.13">
            <p id="section-toc.1-1.13.1"><a href="#section-appendix.c" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a><a href="#section-toc.1-1.13.1" class="pilcrow">¶</a></p>
</li>
        </ul>
</nav>
</section>
</div>
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">Mechanisms to support event subscription and YANG-Push are defined in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>. Enhancements to <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span> that enable YANG datastore subscription and YANG-Push are defined in <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>. 
This document provides a transport specification for dynamic subscriptions over RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span>.  Requirements for these mechanisms are captured in <span>[<a href="#RFC7923" class="xref">RFC7923</a>]</span>.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">The streaming of notifications that encapsulate the resulting information push is done via the mechanism described in <span><a href="https://www.rfc-editor.org/rfc/rfc8040#section-6.3" class="relref">Section 6.3</a> of [<a href="#RFC8040" class="xref">RFC8040</a>]</span>.<a href="#section-1-2" class="pilcrow">¶</a></p>
</section>
<section id="section-2">
      <h2 id="name-terminology">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-terminology" class="section-name selfRef">Terminology</a>
      </h2>
<p id="section-2-1">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> 
    when, and only when, they appear in all capitals, as shown here.<a href="#section-2-1" class="pilcrow">¶</a></p>
<p id="section-2-2">The following terms use the definitions from <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>: dynamic subscription, event stream, notification message, publisher, receiver, subscriber, and subscription.<a href="#section-2-2" class="pilcrow">¶</a></p>
<p id="section-2-3">Other terms reused include datastore, which is defined in <span>[<a href="#RFC8342" class="xref">RFC8342</a>]</span>, and HTTP/2 stream, which maps to the definition of "stream" within <span>[<a href="#RFC7540" class="xref">RFC7540</a>], <a href="https://www.rfc-editor.org/rfc/rfc7540#section-2" class="relref">Section 2</a></span>.<a href="#section-2-3" class="pilcrow">¶</a></p>
</section>
<div id="dyn-subs">
<section id="section-3">
      <h2 id="name-dynamic-subscriptions">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-dynamic-subscriptions" class="section-name selfRef">Dynamic Subscriptions</a>
      </h2>
<p id="section-3-1">This section provides specifics on how to establish and maintain dynamic subscriptions over RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span>. Subscribing to event streams is accomplished in this way via RPCs defined within <span>[<a href="#RFC8639" class="xref">RFC8639</a>], <a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.4" class="relref">Section 2.4</a></span>. The RPCs are done via RESTCONF POSTs. YANG datastore subscription is accomplished via augmentations to <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span> as described within <span>[<a href="#RFC8641" class="xref">RFC8641</a>], <a href="https://www.rfc-editor.org/rfc/rfc8641#section-4.4" class="relref">Section 4.4</a></span>.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">As described in <span><a href="https://www.rfc-editor.org/rfc/rfc8040#section-6.3" class="relref">Section 6.3</a> of [<a href="#RFC8040" class="xref">RFC8040</a>]</span>, a GET needs to be performed on a
      specific URI on the publisher. Subscribers cannot predetermine the URI
      against which a subscription might exist on a publisher, as the URI will
      only exist after the "establish-subscription" RPC has been
      accepted. Therefore, the POST for the "establish-subscription" RPC
      replaces the GET request for the "location" leaf that is used in <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> to obtain the URI. The subscription
      URI will be determined and sent as part of the response to the
      "establish-subscription" RPC, and a subsequent GET to this URI will be
      done in order to start the flow of notification messages back to the
      subscriber.  As specified in <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.4.1" class="relref">Section 2.4.1</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span>, a subscription does not move to the active state
      until the GET is received.<a href="#section-3-2" class="pilcrow">¶</a></p>
<section id="section-3.1">
        <h3 id="name-transport-connectivity">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-transport-connectivity" class="section-name selfRef">Transport Connectivity</a>
        </h3>
<p id="section-3.1-1">For a dynamic subscription, when a RESTCONF session doesn't already exist, a new RESTCONF session is initiated from the subscriber.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<p id="section-3.1-2">As stated in <span><a href="https://www.rfc-editor.org/rfc/rfc8040#section-2.1" class="relref">Section 2.1</a> of [<a href="#RFC8040" class="xref">RFC8040</a>]</span>, a subscriber <span class="bcp14">MUST</span> establish the HTTP session over TLS <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span> in order to secure the content in transit.<a href="#section-3.1-2" class="pilcrow">¶</a></p>
<p id="section-3.1-3">Without the involvement of additional protocols, HTTP sessions by
   themselves do not support quick recognition of the loss of the
   communication path to the publisher. Where quick recognition of the loss of a publisher is required, a subscriber <span class="bcp14">SHOULD</span> use a TLS heartbeat <span>[<a href="#RFC6520" class="xref">RFC6520</a>]</span>, just from subscriber to publisher, to track HTTP session continuity.<a href="#section-3.1-3" class="pilcrow">¶</a></p>
<p id="section-3.1-4">Loss of the heartbeat <span class="bcp14">MUST</span> result in the teardown
of any subscription-related TCP sessions between those endpoints.  
A subscriber can then attempt to re-establish the dynamic subscription by using the procedure described in <a href="#SSE" class="xref">Section 3.4</a>.<a href="#section-3.1-4" class="pilcrow">¶</a></p>
</section>
<section id="section-3.2">
        <h3 id="name-discovery">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-discovery" class="section-name selfRef">Discovery</a>
        </h3>
<p id="section-3.2-1">Subscribers can learn which event streams a RESTCONF server supports by querying the "streams" container of ietf-subscribed-notifications.yang in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>. Support for the "streams" container of ietf-restconf-monitoring.yang in <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> is not required. In the case when the RESTCONF binding specified by this document is used to convey the "streams" container from ietf-restconf-monitoring.yang (i.e., that feature is supported), any event streams contained therein are also expected to be present in the "streams" container of ietf-restconf-monitoring.yang.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<p id="section-3.2-2">Subscribers can learn which datastores a RESTCONF server supports by following <span><a href="https://www.rfc-editor.org/rfc/rfc8527#section-2" class="relref">Section 2</a> of [<a href="#RFC8527" class="xref">RFC8527</a>]</span>.<a href="#section-3.2-2" class="pilcrow">¶</a></p>
</section>
<section id="section-3.3">
        <h3 id="name-restconf-rpcs-and-http-stat">
<a href="#section-3.3" class="section-number selfRef">3.3. </a><a href="#name-restconf-rpcs-and-http-stat" class="section-name selfRef">RESTCONF RPCs and HTTP Status Codes</a>
        </h3>
<p id="section-3.3-1">Specific HTTP response codes as defined in <span><a href="https://www.rfc-editor.org/rfc/rfc7231#section-6" class="relref">Section 6</a> of [<a href="#RFC7231" class="xref">RFC7231</a>]</span> will indicate the result of RESTCONF RPC requests with the publisher.  An HTTP status code of 200 is the proper response to any successful RPC defined within <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span> or <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>.<a href="#section-3.3-1" class="pilcrow">¶</a></p>
<p id="section-3.3-2">If a publisher fails to serve the RPC request for one of the reasons indicated in <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.4.6" class="relref">Section 2.4.6</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span> or <span><a href="https://www.rfc-editor.org/rfc/rfc8641#appendix-A" class="relref">Appendix A</a> of [<a href="#RFC8641" class="xref">RFC8641</a>]</span>, this will be indicated by an appropriate error code, as shown below, transported in the HTTP response.<a href="#section-3.3-2" class="pilcrow">¶</a></p>
<p id="section-3.3-3">When an HTTP error code is returned, the RPC reply <span class="bcp14">MUST</span> include 
an &lt;rpc-error&gt; element per <span><a href="https://www.rfc-editor.org/rfc/rfc8040#section-7.1" class="relref">Section 7.1</a> of [<a href="#RFC8040" class="xref">RFC8040</a>]</span> 
with the following parameter values:<a href="#section-3.3-3" class="pilcrow">¶</a></p>
<ul>
<li id="section-3.3-4.1">an "error-type" node of "application".<a href="#section-3.3-4.1" class="pilcrow">¶</a>
</li>
          <li id="section-3.3-4.2">an "error-tag" node whose value is a string that corresponds 
           to an identity associated with the error.  This "error-tag" will
           come from one of two places and will correspond to the error 
           identities either within 
           <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.4.6" class="relref">Section 2.4.6</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span> 
           for general subscription errors (<a href="#gen-sub-errors" class="xref">Table 1</a>) 
           or within <span><a href="https://www.rfc-editor.org/rfc/rfc8641#appendix-A.1" class="relref">Appendix A.1</a> of [<a href="#RFC8641" class="xref">RFC8641</a>]</span>
           for subscription errors specific to YANG datastores (<a href="#datastore-specific-errors" class="xref">Table 2</a>).<a href="#section-3.3-4.2" class="pilcrow">¶</a>
</li>
          <li id="section-3.3-4.3">an "error-app-tag" node whose value is a string that corresponds to an 
          identity associated with the error, as defined in 
           <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.4.6" class="relref">Section 2.4.6</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span> 
           for general subscriptions or 
           <span><a href="https://www.rfc-editor.org/rfc/rfc8641#appendix-A.1" class="relref">Appendix A.1</a> of [<a href="#RFC8641" class="xref">RFC8641</a>]</span> 
           for subscription errors specific to YANG datastores. The tag to use depends on the RPC for which the 
           error occurred.  Viable errors for different RPCs are found in <a href="#rpc-errors" class="xref">Table 3</a>.<a href="#section-3.3-4.3" class="pilcrow">¶</a>
</li>
        </ul>
<span id="name-general-subscription-error-"></span><div id="gen-sub-errors">
<table class="center" id="table-1">
          <caption>
<a href="#table-1" class="selfRef">Table 1</a>:
<a href="#name-general-subscription-error-" class="selfRef">General Subscription Error Identities and Associated "error-tag" Use</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Error identity</th>
              <th class="text-left" rowspan="1" colspan="1">Uses "error-tag"</th>
              <th class="text-left" rowspan="1" colspan="1">HTTP code</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">dscp-unavailable</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">encoding-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">filter-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">insufficient-resources</td>
              <td class="text-left" rowspan="1" colspan="1">resource-denied</td>
              <td class="text-left" rowspan="1" colspan="1">409</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">no-such-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">404</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">replay-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">operation-not-supported</td>
              <td class="text-left" rowspan="1" colspan="1">501</td>
            </tr>
          </tbody>
        </table>
</div>
<span id="name-datastore-specific-error-id"></span><div id="datastore-specific-errors">
<table class="center" id="table-2">
          <caption>
<a href="#table-2" class="selfRef">Table 2</a>:
<a href="#name-datastore-specific-error-id" class="selfRef">Datastore-Specific Error Identities and Associated "error-tag" Use</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Error identity</th>
              <th class="text-left" rowspan="1" colspan="1">Uses "error-tag"</th>
              <th class="text-left" rowspan="1" colspan="1">HTTP code</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">cant-include</td>
              <td class="text-left" rowspan="1" colspan="1">operation-not-supported</td>
              <td class="text-left" rowspan="1" colspan="1">501</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">datastore-not-subscribable</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">no-such-subscription-resync</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">404</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">on-change-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">operation-not-supported</td>
              <td class="text-left" rowspan="1" colspan="1">501</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">on-change-sync-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">operation-not-supported</td>
              <td class="text-left" rowspan="1" colspan="1">501</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">period-unsupported</td>
              <td class="text-left" rowspan="1" colspan="1">invalid-value</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">update-too-big</td>
              <td class="text-left" rowspan="1" colspan="1">too-big</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">sync-too-big</td>
              <td class="text-left" rowspan="1" colspan="1">too-big</td>
              <td class="text-left" rowspan="1" colspan="1">400</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">unchanging-selection</td>
              <td class="text-left" rowspan="1" colspan="1">operation-failed</td>
              <td class="text-left" rowspan="1" colspan="1">500</td>
            </tr>
          </tbody>
        </table>
</div>
<span id="name-rpc-errors-and-associated-e"></span><div id="rpc-errors">
<table class="center" id="table-3">
          <caption>
<a href="#table-3" class="selfRef">Table 3</a>:
<a href="#name-rpc-errors-and-associated-e" class="selfRef">RPC Errors and Associated Error Identities</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">RPC</th>
              <th class="text-left" rowspan="1" colspan="1">Select an identity with a base</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">establish-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">establish-subscription-error</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">modify-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">modify-subscription-error</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">delete-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">delete-subscription-error</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">kill-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">delete-subscription-error</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">resync-subscription</td>
              <td class="text-left" rowspan="1" colspan="1">resync-subscription-error</td>
            </tr>
          </tbody>
        </table>
</div>
<p id="section-3.3-8">Each error identity will be inserted as the "error-app-tag" using JSON encoding following the form &lt;modulename&gt;:&lt;identityname&gt;.  An example of such a valid encoding would be "ietf-subscribed-notifications:no-such-subscription".<a href="#section-3.3-8" class="pilcrow">¶</a></p>
<p id="section-3.3-9">In the case of error responses to an "establish-subscription" or
 "modify-subscription" request, there is the option to include an
 "error-info" node.  This node may contain hints for parameter settings
 that might lead to successful RPC requests in the future. Tables <a href="#error-info-estab-sub" class="xref">4</a> and <a href="#error-info-mod-sub" class="xref">5</a> show the yang-data structures that may be returned.<a href="#section-3.3-9" class="pilcrow">¶</a></p>
<span id="name-optional-error-info-node-hi"></span><div id="error-info-estab-sub">
<table class="center" id="table-4">
          <caption>
<a href="#table-4" class="selfRef">Table 4</a>:
<a href="#name-optional-error-info-node-hi" class="selfRef">Optional "error-info" Node Hints for an "establish-subscription" Request</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Target:</th>
              <th class="text-left" rowspan="1" colspan="1">Return hints in yang-data structure</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">event stream</td>
              <td class="text-left" rowspan="1" colspan="1">establish-subscription-stream-error-info</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">datastore</td>
              <td class="text-left" rowspan="1" colspan="1">establish-subscription-datastore-error-info</td>
            </tr>
          </tbody>
        </table>
</div>
<span id="name-optional-error-info-node-hin"></span><div id="error-info-mod-sub">
<table class="center" id="table-5">
          <caption>
<a href="#table-5" class="selfRef">Table 5</a>:
<a href="#name-optional-error-info-node-hin" class="selfRef">Optional "error-info" Node Hints for an "modify-subscription" Request</a>
          </caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Target:</th>
              <th class="text-left" rowspan="1" colspan="1">Returns hints in yang-data structure</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">event stream</td>
              <td class="text-left" rowspan="1" colspan="1">modify-subscription-stream-error-info</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">datastore</td>
              <td class="text-left" rowspan="1" colspan="1">modify-subscription-datastore-error-info</td>
            </tr>
          </tbody>
        </table>
</div>
<p id="section-3.3-12">The yang-data included within "error-info" <span class="bcp14">SHOULD NOT</span> include the
      optional leaf "reason", as such a leaf would be redundant
      with information that is already placed within the
      "error-app-tag".<a href="#section-3.3-12" class="pilcrow">¶</a></p>
<p id="section-3.3-13">In case of an &lt;rpc-error&gt; as a result of a "delete-subscription", a
      "kill-subscription", or a "resync-subscription" request, no
      "error-info" needs to be included, as the "subscription-id" is
      the only RPC input parameter, and no hints regarding this RPC input
      parameters need to be provided.<a href="#section-3.3-13" class="pilcrow">¶</a></p>
<p id="section-3.3-14">Note that "error-path" <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> does not need to be included with the &lt;rpc-error&gt; element, as subscription errors are generally associated with the choice of RPC input parameters.<a href="#section-3.3-14" class="pilcrow">¶</a></p>
</section>
<div id="SSE">
<section id="section-3.4">
        <h3 id="name-call-flow-for-server-sent-e">
<a href="#section-3.4" class="section-number selfRef">3.4. </a><a href="#name-call-flow-for-server-sent-e" class="section-name selfRef">Call Flow for Server-Sent Events</a>
        </h3>
<p id="section-3.4-1">The call flow for Server-Sent Events (SSE) is defined in <a href="#dyn-sse" class="xref">Figure 1</a>.  The logical connections denoted
 by (a) and (b) can be a TCP connection or an HTTP/2 stream (if HTTP/2
 is used, multiple HTTP/2 streams can be carried in one TCP
 connection). Requests to RPCs as defined in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span> or <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span> are
 sent on a connection indicated by (a).  A successful
 "establish-subscription" will result in an RPC response returned with
 both a subscription identifier that uniquely identifies a
 subscription, as well as a URI that uniquely identifies the location
 of subscription on the publisher (b). This URI is defined via the
 "uri" leaf in the data model in <a href="#YANG-module" class="xref">Section 7</a>.<a href="#section-3.4-1" class="pilcrow">¶</a></p>
<p id="section-3.4-2">An HTTP GET is then sent on a separate logical connection (b) to the URI on the publisher.  This signals the publisher to initiate the flow of notification messages that are sent in SSE <span>[<a href="#W3C-20150203" class="xref">W3C-20150203</a>]</span> as a response to the GET. There cannot be two or more simultaneous GET requests on a subscription URI: any GET request received while there is a current GET request on the same URI <span class="bcp14">MUST</span> be rejected with HTTP error code 409.<a href="#section-3.4-2" class="pilcrow">¶</a></p>
<p id="section-3.4-3">As described in <span><a href="https://www.rfc-editor.org/rfc/rfc8040#section-6.4" class="relref">Section 6.4</a> of [<a href="#RFC8040" class="xref">RFC8040</a>]</span>, RESTCONF servers <span class="bcp14">SHOULD NOT</span> send the "event" or "id" fields in the SSE event notifications.<a href="#section-3.4-3" class="pilcrow">¶</a></p>
<span id="name-dynamic-subscriptions-with-"></span><div id="dyn-sse">
<figure id="figure-1">
          <div class="artwork art-text alignLeft" id="section-3.4-4.1">
<pre>
+--------------+                             +--------------+
|  Subscriber  |                             |   Publisher  |
|              |                             |              |
|    Logical   |                             |     Logical  |
|  Connection  |                             |   Connection |
|  (a)  (b)    |                             |    (a)  (b)  |
+--------------+                             +--------------+
    | RESTCONF POST (RPC:establish-subscription)   |
    |---------------------------------------------&gt;|
    |                          HTTP 200 OK (ID,URI)|
    |&lt;---------------------------------------------|
    |    |HTTP GET (URI)                                |
    |    |---------------------------------------------&gt;|
    |    |                                   HTTP 200 OK|
    |    |&lt;---------------------------------------------|
    |    |                           SSE (notif-message)|
    |    |&lt;---------------------------------------------|
    | RESTCONF POST (RPC:modify-subscription)      |    |
    |---------------------------------------------&gt;|    |
    |    |                              HTTP 200 OK|    |
    |&lt;---------------------------------------------|    |
    |    |                   SSE (subscription-modified)|
    |    |&lt;------------------------------------------(c)|
    |    |                           SSE (notif-message)|
    |    |&lt;---------------------------------------------|
    | RESTCONF POST (RPC:delete-subscription)      |    |
    |---------------------------------------------&gt;|    |
    |    |                              HTTP 200 OK|    |
    |&lt;---------------------------------------------|    |
    |    |                                         |    |
    |    |                                         |    |
    (a) (b)                                       (a)  (b) </pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a>:
<a href="#name-dynamic-subscriptions-with-" class="selfRef">Dynamic Subscriptions with Server-Sent Events</a>
          </figcaption></figure>
</div>
<p id="section-3.4-5">Additional requirements for dynamic subscriptions over SSE include:<a href="#section-3.4-5" class="pilcrow">¶</a></p>
<ul>
<li id="section-3.4-6.1">
   A publisher <span class="bcp14">MUST</span> return all subscription state notifications
   in a separate SSE message used by the subscription to 
   which the state change refers.<a href="#section-3.4-6.1" class="pilcrow">¶</a>
</li>
          <li id="section-3.4-6.2">Subscription RPCs <span class="bcp14">MUST NOT</span> use the connection currently providing notification messages for that subscription.<a href="#section-3.4-6.2" class="pilcrow">¶</a>
</li>
          <li id="section-3.4-6.3">In addition to an RPC response for a "modify-subscription" RPC traveling over (a), a "subscription-modified" state change notification <span class="bcp14">MUST</span> be sent within (b).  This allows the receiver to know exactly when, within the stream of events, the new terms of the subscription have been applied to the notification messages.  See arrow (c).<a href="#section-3.4-6.3" class="pilcrow">¶</a>
</li>
          <li id="section-3.4-6.4">In addition to any required access permissions (e.g., Network Configuration Access Control Model (NACM)), the RPCs "modify-subscription", "resync-subscription", and
"delete-subscription" <span class="bcp14">SHOULD</span> only be allowed by the same RESTCONF username <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> that invoked "establish-subscription". Such a restriction generally serves to preserve users' privacy, but exceptions might be made for administrators that may need to modify or delete other users' subscriptions.<a href="#section-3.4-6.4" class="pilcrow">¶</a>
</li>
          <li id="section-3.4-6.5">The "kill-subscription" RPC can be invoked by any RESTCONF username with the required administrative permissions.<a href="#section-3.4-6.5" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-3.4-7">A publisher <span class="bcp14">MUST</span> terminate a subscription in the following cases:<a href="#section-3.4-7" class="pilcrow">¶</a></p>
<ul>
<li id="section-3.4-8.1">Receipt of a "delete-subscription" or a "kill-subscription" RPC for that subscription<a href="#section-3.4-8.1" class="pilcrow">¶</a>
</li>
          <li id="section-3.4-8.2">Loss of TLS heartbeat<a href="#section-3.4-8.2" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-3.4-9">A publisher <span class="bcp14">MAY</span> terminate a subscription at any time as stated in <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-1.3" class="relref">Section 1.3</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span>.<a href="#section-3.4-9" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<section id="section-4">
      <h2 id="name-qos-treatment">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-qos-treatment" class="section-name selfRef">QoS Treatment</a>
      </h2>
<p id="section-4-1">Qos treatment for event streams is described in <span><a href="https://www.rfc-editor.org/rfc/rfc8639#section-2.3" class="relref">Section 2.3</a> of [<a href="#RFC8639" class="xref">RFC8639</a>]</span>. In addition, if HTTP/2 is used, the publisher <span class="bcp14">MUST</span>:<a href="#section-4-1" class="pilcrow">¶</a></p>
<ul>
<li id="section-4-2.1">Take the "weighting" leaf node in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span> and copy it into the HTTP/2 stream weight, <span><a href="https://www.rfc-editor.org/rfc/rfc7540#section-5.3" class="relref">Section 5.3</a> of [<a href="#RFC7540" class="xref">RFC7540</a>]</span>, and<a href="#section-4-2.1" class="pilcrow">¶</a>
</li>
        <li id="section-4-2.2">Take any existing subscription "dependency", as specified by the
 "dependency" leaf node in <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>,
 and use the HTTP/2 stream for the parent subscription as the HTTP/2
 stream dependency (as described in <span><a href="https://www.rfc-editor.org/rfc/rfc7540#section-5.3.1" class="relref">Section 5.3.1</a> of [<a href="#RFC7540" class="xref">RFC7540</a>]</span>) of the dependent
 subscription.<a href="#section-4-2.2" class="pilcrow">¶</a>
</li>
        <li id="section-4-2.3">Set the exclusive flag (<span><a href="https://www.rfc-editor.org/rfc/rfc7540#section-5.3.1" class="relref">Section 5.3.1</a> of [<a href="#RFC7540" class="xref">RFC7540</a>]</span>) to 0.<a href="#section-4-2.3" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-4-3">For dynamic subscriptions with the same Differentiated Services Code Point (DSCP) value to a specific publisher, it is recommended that the subscriber sends all URI GET requests on a common HTTP/2 session (if HTTP/2 is used). Conversely, a subscriber cannot use a common HTTP/2 session for subscriptions with different DSCP values.<a href="#section-4-3" class="pilcrow">¶</a></p>
</section>
<section id="section-5">
      <h2 id="name-notification-messages">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-notification-messages" class="section-name selfRef">Notification Messages</a>
      </h2>
<p id="section-5-1">Notification messages transported over RESTCONF will be encoded according to <span>[<a href="#RFC8040" class="xref">RFC8040</a>], <a href="https://www.rfc-editor.org/rfc/rfc8040#section-6.4" class="relref">Section 6.4</a></span>.<a href="#section-5-1" class="pilcrow">¶</a></p>
</section>
<div id="YANG-tree">
<section id="section-6">
      <h2 id="name-yang-tree">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-yang-tree" class="section-name selfRef">YANG Tree</a>
      </h2>
<p id="section-6-1"> The YANG module defined in <a href="#YANG-module" class="xref">Section 7</a> has one leaf that augments three nodes of <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>.<a href="#section-6-1" class="pilcrow">¶</a></p>
<div id="section-6-2">
<pre class="sourcecode lang-yangtree">
module: ietf-restconf-subscribed-notifications
  augment /sn:establish-subscription/sn:output:
    +--ro uri?   inet:uri
  augment /sn:subscriptions/sn:subscription:
    +--ro uri?   inet:uri
  augment /sn:subscription-modified:
    +--ro uri?   inet:uri </pre><a href="#section-6-2" class="pilcrow">¶</a>
</div>
</section>
</div>
<div id="YANG-module">
<section id="section-7">
      <h2 id="name-yang-module">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-yang-module" class="section-name selfRef">YANG Module</a>
      </h2>
<p id="section-7-1">This module references <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>.<a href="#section-7-1" class="pilcrow">¶</a></p>
<div id="section-7-2">
<pre class="sourcecode lang-yang">&lt;CODE BEGINS&gt; file "ietf-restconf-subscribed-notifications@2019-11-17.yang"

module ietf-restconf-subscribed-notifications {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:"
          + "ietf-restconf-subscribed-notifications";
  prefix rsn;

  import ietf-subscribed-notifications {
    prefix sn;
  }
  import ietf-inet-types {
    prefix inet;
  }

  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:   Eric Voit
               &lt;mailto:evoit@cisco.com&gt;

     Editor:   Alexander Clemm
               &lt;mailto:ludwig@clemm.org&gt;

     Editor:   Reshad Rahman
               &lt;mailto:rrahman@cisco.com&gt;";
  description
    "Defines RESTCONF as a supported transport for subscribed
     event notifications.

     Copyright (c) 2019 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 Simplified 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 8650; see the
     RFC itself for full legal notices.";

  revision 2019-11-17 {
    description
      "Initial version";
    reference
      "RFC 8650: Dynamic Subscription to YANG Events and Datastores
       over RESTCONF";
  }

  grouping uri {
    description
      "Provides a reusable description of a URI.";
    leaf uri {
      type inet:uri;
      config false;
      description
        "Location of a subscription-specific URI on the publisher.";
    }
  }

  augment "/sn:establish-subscription/sn:output" {
    description
      "This augmentation allows RESTCONF-specific parameters for a
       response to a publisher's subscription request.";
    uses uri;
  }

  augment "/sn:subscriptions/sn:subscription" {
    description
      "This augmentation allows RESTCONF-specific parameters to be
       exposed for a subscription.";
    uses uri;
  }

  augment "/sn:subscription-modified" {
    description
      "This augmentation allows RESTCONF-specific parameters to be
       included as part of the notification that a subscription has
       been modified.";
    uses uri;
  }
}

&lt;CODE ENDS&gt;</pre><a href="#section-7-2" class="pilcrow">¶</a>
</div>
</section>
</div>
<section id="section-8">
      <h2 id="name-iana-considerations">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-8-1">
      This document registers the following namespace URI in the "ns"
      subregistry of the "IETF XML Registry" <span>[<a href="#RFC3688" class="xref">RFC3688</a>]</span>:<a href="#section-8-1" class="pilcrow">¶</a></p>
<dl class="dlParallel" id="section-8-2">
        <dt id="section-8-2.1">URI:</dt>
        <dd id="section-8-2.2">urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-notifications<a href="#section-8-2.2" class="pilcrow">¶</a>
</dd>
<dt id="section-8-2.3">Registrant Contact:</dt>
        <dd id="section-8-2.4">The IESG.<a href="#section-8-2.4" class="pilcrow">¶</a>
</dd>
<dt id="section-8-2.5">XML:</dt>
        <dd id="section-8-2.6">N/A; the requested URI is an XML namespace.<a href="#section-8-2.6" class="pilcrow">¶</a>
</dd>
</dl>
<p id="section-8-3">
      This document registers the following YANG module in the "YANG Module
      Names" registry <span>[<a href="#RFC6020" class="xref">RFC6020</a>]</span>:<a href="#section-8-3" class="pilcrow">¶</a></p>
<dl class="dlParallel" id="section-8-4">
        <dt id="section-8-4.1">Name:</dt>
        <dd id="section-8-4.2">ietf-restconf-subscribed-notifications<a href="#section-8-4.2" class="pilcrow">¶</a>
</dd>
<dt id="section-8-4.3">Namespace:</dt>
        <dd id="section-8-4.4">urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-notifications<a href="#section-8-4.4" class="pilcrow">¶</a>
</dd>
<dt id="section-8-4.5">Prefix:</dt>
        <dd id="section-8-4.6">rsn<a href="#section-8-4.6" class="pilcrow">¶</a>
</dd>
<dt id="section-8-4.7">Reference:</dt>
        <dd id="section-8-4.8">RFC 8650<a href="#section-8-4.8" class="pilcrow">¶</a>
</dd>
</dl>
</section>
<div id="security">
<section id="section-9">
      <h2 id="name-security-considerations">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-9-1">The YANG module specified in this document defines a schema for data that is designed to be accessed via network management transports such as NETCONF <span>[<a href="#RFC6241" class="xref">RFC6241</a>]</span> or RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span>.  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-9-1" class="pilcrow">¶</a></p>
<p id="section-9-2">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-9-2" class="pilcrow">¶</a></p>
<p id="section-9-3">The one new data node introduced in this YANG module may be considered sensitive or vulnerable in some network environments.  It is thus important to control read access (e.g., via get, get-config, or notification) to this data node.  These are the subtrees and data nodes and their sensitivity/vulnerability:<a href="#section-9-3" class="pilcrow">¶</a></p>
<p id="section-9-4">Container: "/subscriptions"<a href="#section-9-4" class="pilcrow">¶</a></p>
<ul>
<li id="section-9-5.1">"uri": leaf will show where subscribed resources might be located on a publisher.  Access control must be set so that only someone with proper access permissions, i.e., the same RESTCONF <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> user credentials that invoked the corresponding "establish-subscription", has the ability to access this resource.<a href="#section-9-5.1" class="pilcrow">¶</a>
</li>
      </ul>
<p id="section-9-6">The subscription URI is implementation specific and is encrypted via the use of TLS. Therefore, even if an attacker succeeds in guessing the subscription URI, a RESTCONF username <span>[<a href="#RFC8040" class="xref">RFC8040</a>]</span> with the required administrative permissions must be used to be able to access or modify that subscription. It is recommended that the subscription URI values not be easily predictable.<a href="#section-9-6" class="pilcrow">¶</a></p>
<p id="section-9-7">The access permission considerations for the RPCs "modify-subscription", "resync-subscription", "delete-subscription", and "kill-subscription" are described in <a href="#SSE" class="xref">Section 3.4</a>.<a href="#section-9-7" class="pilcrow">¶</a></p>
<p id="section-9-8">If a buggy or compromised RESTCONF subscriber sends a number of "establish-subscription" requests, then these subscriptions accumulate and may
    use up system resources.  In such a situation, the publisher <span class="bcp14">MAY</span> also suspend or terminate a subset of the active
    subscriptions from that RESTCONF subscriber in order to reclaim resources and preserve normal operation for the other subscriptions.<a href="#section-9-8" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-10">
      <h2 id="name-references">
<a href="#section-10" class="section-number selfRef">10. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-10.1">
        <h3 id="name-normative-references">
<a href="#section-10.1" class="section-number selfRef">10.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03">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>
<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">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>
<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">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>
<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><span class="refAuthor">, and 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">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>
<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">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>
<dt id="RFC6520">[RFC6520]</dt>
        <dd>
<span class="refAuthor">Seggelmann, R.</span><span class="refAuthor">, Tuexen, M.</span><span class="refAuthor">, and M. Williams</span>, <span class="refTitle">"Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"</span>, <span class="seriesInfo">RFC 6520</span>, <span class="seriesInfo">DOI 10.17487/RFC6520</span>, <time datetime="2012-02">February 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6520">https://www.rfc-editor.org/info/rfc6520</a>&gt;</span>. </dd>
<dt id="RFC7540">[RFC7540]</dt>
        <dd>
<span class="refAuthor">Belshe, M.</span><span class="refAuthor">, Peon, R.</span><span class="refAuthor">, and M. Thomson, Ed.</span>, <span class="refTitle">"Hypertext Transfer Protocol Version 2 (HTTP/2)"</span>, <span class="seriesInfo">RFC 7540</span>, <span class="seriesInfo">DOI 10.17487/RFC7540</span>, <time datetime="2015-05">May 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7540">https://www.rfc-editor.org/info/rfc7540</a>&gt;</span>. </dd>
<dt id="RFC8040">[RFC8040]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span><span class="refAuthor">, Bjorklund, M.</span><span class="refAuthor">, and 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">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>
<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">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>
<dt id="RFC8341">[RFC8341]</dt>
        <dd>
<span class="refAuthor">Bierman, A.</span><span class="refAuthor"> and 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">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>
<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><span class="refAuthor">, and 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">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>
<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">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>
<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><span class="refAuthor">, and 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">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>
<dt id="RFC8641">[RFC8641]</dt>
        <dd>
<span class="refAuthor">Clemm, A.</span><span class="refAuthor"> and 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">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>
<dt id="W3C-20150203">[W3C-20150203]</dt>
      <dd>
<span class="refAuthor">Hickson, I.</span>, <span class="refTitle">"Server-Sent Events"</span>, <span class="seriesInfo">W3C Recommendation</span>, <time datetime="2015-02-03">3 February 2015</time>, <span>&lt;<a href="https://www.w3.org/TR/2015/REC-eventsource-20150203/">https://www.w3.org/TR/2015/REC-eventsource-20150203/</a>&gt;</span>. <span class="annotation">Latest version available at &lt;<span><a href="https://www.w3.org/TR/eventsource/">https://www.w3.org/TR/eventsource/</a></span>&gt;.</span>
        </dd>
</dl>
</section>
<section id="section-10.2">
        <h3 id="name-informative-references">
<a href="#section-10.2" class="section-number selfRef">10.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC7231">[RFC7231]</dt>
        <dd>
<span class="refAuthor">Fielding, R., Ed.</span><span class="refAuthor"> and J. Reschke, Ed.</span>, <span class="refTitle">"Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content"</span>, <span class="seriesInfo">RFC 7231</span>, <span class="seriesInfo">DOI 10.17487/RFC7231</span>, <time datetime="2014-06">June 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7231">https://www.rfc-editor.org/info/rfc7231</a>&gt;</span>. </dd>
<dt id="RFC7923">[RFC7923]</dt>
        <dd>
<span class="refAuthor">Voit, E.</span><span class="refAuthor">, Clemm, A.</span><span class="refAuthor">, and A. Gonzalez Prieto</span>, <span class="refTitle">"Requirements for Subscription to YANG Datastores"</span>, <span class="seriesInfo">RFC 7923</span>, <span class="seriesInfo">DOI 10.17487/RFC7923</span>, <time datetime="2016-06">June 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7923">https://www.rfc-editor.org/info/rfc7923</a>&gt;</span>. </dd>
<dt id="RFC7951">[RFC7951]</dt>
        <dd>
<span class="refAuthor">Lhotka, L.</span>, <span class="refTitle">"JSON Encoding of Data Modeled with YANG"</span>, <span class="seriesInfo">RFC 7951</span>, <span class="seriesInfo">DOI 10.17487/RFC7951</span>, <time datetime="2016-08">August 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7951">https://www.rfc-editor.org/info/rfc7951</a>&gt;</span>. </dd>
<dt id="RFC8347">[RFC8347]</dt>
        <dd>
<span class="refAuthor">Liu, X., Ed.</span><span class="refAuthor">, Kyparlis, A.</span><span class="refAuthor">, Parikh, R.</span><span class="refAuthor">, Lindem, A.</span><span class="refAuthor">, and M. Zhang</span>, <span class="refTitle">"A YANG Data Model for the Virtual Router Redundancy Protocol (VRRP)"</span>, <span class="seriesInfo">RFC 8347</span>, <span class="seriesInfo">DOI 10.17487/RFC8347</span>, <time datetime="2018-03">March 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8347">https://www.rfc-editor.org/info/rfc8347</a>&gt;</span>. </dd>
<dt id="RFC8527">[RFC8527]</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><span class="refAuthor">, and R. Wilton</span>, <span class="refTitle">"RESTCONF Extensions to Support the Network Management Datastore Architecture"</span>, <span class="seriesInfo">RFC 8527</span>, <span class="seriesInfo">DOI 10.17487/RFC8527</span>, <time datetime="2019-03">March 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8527">https://www.rfc-editor.org/info/rfc8527</a>&gt;</span>. </dd>
<dt id="RFC8640">[RFC8640]</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><span class="refAuthor">, and A. Tripathy</span>, <span class="refTitle">"Dynamic Subscription to YANG Events and Datastores over NETCONF"</span>, <span class="seriesInfo">RFC 8640</span>, <span class="seriesInfo">DOI 10.17487/RFC8640</span>, <time datetime="2019-09">September 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8640">https://www.rfc-editor.org/info/rfc8640</a>&gt;</span>. </dd>
<dt id="XPATH">[XPATH]</dt>
      <dd>
<span class="refAuthor">Clark, J.</span><span class="refAuthor"> and S. DeRose</span>, <span class="refTitle">"XML Path Language (XPath) Version 1.0"</span>, <span class="seriesInfo">W3C Recommendation</span>, <time datetime="1999-11-16">16 November 1999</time>, <span>&lt;<a href="http://www.w3.org/TR/1999/REC-xpath-19991116">http://www.w3.org/TR/1999/REC-xpath-19991116</a>&gt;</span>. <span class="annotation">Latest version available at &lt;<span><a href="https://www.w3.org/TR/xpath/">https://www.w3.org/TR/xpath/</a></span>&gt;.</span>
        </dd>
</dl>
</section>
</section>
<section id="section-appendix.a">
      <h2 id="name-examples">
<a href="#section-appendix.a" class="section-number selfRef">Appendix A. </a><a href="#name-examples" class="section-name selfRef">Examples</a>
      </h2>
<p id="section-appendix.a-1">This section is non-normative.  To allow easy comparison, this section mirrors the functional examples shown with NETCONF over XML within <span>[<a href="#RFC8640" class="xref">RFC8640</a>]</span>.  In addition, HTTP/2 vs HTTP/1.1 headers are not shown as the contents of the JSON encoded objects are identical within.<a href="#section-appendix.a-1" class="pilcrow">¶</a></p>
<p id="section-appendix.a-2">The subscription URI values used in the examples in this section are purely illustrative, and are not indicative of the expected usage that is described in <a href="#security" class="xref">Section 9</a>.<a href="#section-appendix.a-2" class="pilcrow">¶</a></p>
<p id="section-appendix.a-3">The DSCP values are only for example purposes and are all indicated in decimal since the encoding is JSON <span>[<a href="#RFC7951" class="xref">RFC7951</a>]</span>.<a href="#section-appendix.a-3" class="pilcrow">¶</a></p>
<section id="section-a.1">
        <h2 id="name-dynamic-subscriptions-2">
<a href="#section-a.1" class="section-number selfRef">A.1. </a><a href="#name-dynamic-subscriptions-2" class="section-name selfRef">Dynamic Subscriptions</a>
        </h2>
<section id="section-a.1.1">
          <h3 id="name-establishing-dynamic-subscr">
<a href="#section-a.1.1" class="section-number selfRef">A.1.1. </a><a href="#name-establishing-dynamic-subscr" class="section-name selfRef">Establishing Dynamic Subscriptions</a>
          </h3>
<p id="section-a.1.1-1">The following figure shows two successful
   "establish-subscription" RPC requests as per <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>.  The first request is given a subscription
   identifier of 22, and the second, an identifier of 23.<a href="#section-a.1.1-1" class="pilcrow">¶</a></p>
<span id="name-multiple-subscriptions-over"></span><div id="mess-flow-establishment">
<figure id="figure-2">
            <div class="artwork art-text alignLeft" id="section-a.1.1-2.1">
<pre>
   +------------+                  +-----------+
   | Subscriber |                  | Publisher |
   +------------+                  +-----------+
         |                               |
         |establish-subscription         |
         |------------------------------&gt;|  (a)
         |     HTTP 200 OK, id#22, URI#1 |
         |&lt;------------------------------|  (b)
         |GET (URI#1)                    |
         |------------------------------&gt;|  (c)
         | HTTP 200 OK,notif-mesg (id#22)|
         |&lt;------------------------------|
         |                               |
         |                               |
         |establish-subscription         |
         |------------------------------&gt;|
         |      HTTP 200 OK, id#23, URI#2|
         |&lt;------------------------------|
         |GET (URI#2)                    |
         |------------------------------&gt;|
         |                               |
         |                               |
         |             notif-mesg (id#22)|
         |&lt;------------------------------|
         | HTTP 200 OK,notif-mesg (id#23)|
         |&lt;------------------------------|
         |                               | </pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a>:
<a href="#name-multiple-subscriptions-over" class="selfRef">Multiple Subscriptions over RESTCONF/HTTP</a>
            </figcaption></figure>
</div>
<p id="section-a.1.1-3">To provide examples of the information being transported, example messages for interactions in  <a href="#mess-flow-establishment" class="xref">Figure 2</a> are detailed below:<a href="#section-a.1.1-3" class="pilcrow">¶</a></p>
<span id="name-establish-subscription-requ"></span><div id="establish-subs">
<figure id="figure-3">
            <div class="artwork art-text alignLeft" id="section-a.1.1-4.1">
<pre>
POST /restconf/operations
     /ietf-subscribed-notifications:establish-subscription

{
   "ietf-subscribed-notifications:input": {
      "stream-xpath-filter": "/example-module:foo/",
      "stream": "NETCONF",
      "dscp": 10
   }
} </pre>
</div>
<figcaption><a href="#figure-3" class="selfRef">Figure 3</a>:
<a href="#name-establish-subscription-requ" class="selfRef">"establish-subscription" Request (a)</a>
            </figcaption></figure>
</div>
<p id="section-a.1.1-5">As the publisher was able to fully satisfy the request, the publisher sends the subscription identifier of the accepted subscription and the URI:<a href="#section-a.1.1-5" class="pilcrow">¶</a></p>
<span id="name-establish-subscription-succ"></span><div id="positive-establish-subs">
<figure id="figure-4">
            <div class="artwork art-text alignLeft" id="section-a.1.1-6.1">
<pre>
HTTP status code - 200

{
   "id": 22,
   "uri": "https://example.com/restconf/subscriptions/22"
} </pre>
</div>
<figcaption><a href="#figure-4" class="selfRef">Figure 4</a>:
<a href="#name-establish-subscription-succ" class="selfRef">"establish-subscription" Success (b)</a>
            </figcaption></figure>
</div>
<p id="section-a.1.1-7">Upon receipt of the successful response, the subscriber does a
   GET to the provided URI to start the flow of notification messages.
   When the publisher receives this, the subscription is moved to the
   active state (c).<a href="#section-a.1.1-7" class="pilcrow">¶</a></p>
<span id="name-establish-subscription-subs"></span><div id="positive-establish-post">
<figure id="figure-5">
            <div class="artwork art-text alignLeft" id="section-a.1.1-8.1">
<pre>
GET /restconf/subscriptions/22 </pre>
</div>
<figcaption><a href="#figure-5" class="selfRef">Figure 5</a>:
<a href="#name-establish-subscription-subs" class="selfRef">"establish-subscription" Subsequent POST</a>
            </figcaption></figure>
</div>
<p id="section-a.1.1-9">While not shown in <a href="#mess-flow-establishment" class="xref">Figure 2</a>, if the publisher had not been able to fully satisfy the request, or the subscriber has no authorization to establish the subscription, the publisher would have sent an RPC error response. For instance, if the "dscp" value of 10 asserted by the subscriber in <a href="#establish-subs" class="xref">Figure 3</a> proved unacceptable, the publisher may have returned:<a href="#section-a.1.1-9" class="pilcrow">¶</a></p>
<span id="name-an-unsuccessful-establish-s"></span><div id="negative-establish-subs">
<figure id="figure-6">
            <div class="artwork art-text alignLeft" id="section-a.1.1-10.1">
<pre>
HTTP status code - 400

{ "ietf-restconf:errors" : {
    "error" : [
      {
        "error-type": "application",
        "error-tag": "invalid-value",
        "error-severity": "error",
        "error-app-tag":
            "ietf-subscribed-notifications:dscp-unavailable"
      }
    ]
  }
} </pre>
</div>
<figcaption><a href="#figure-6" class="selfRef">Figure 6</a>:
<a href="#name-an-unsuccessful-establish-s" class="selfRef">An Unsuccessful "establish-subscription"</a>
            </figcaption></figure>
</div>
<p id="section-a.1.1-11">The subscriber can use this information in future attempts to establish a subscription.<a href="#section-a.1.1-11" class="pilcrow">¶</a></p>
</section>
<section id="section-a.1.2">
          <h3 id="name-modifying-dynamic-subscript">
<a href="#section-a.1.2" class="section-number selfRef">A.1.2. </a><a href="#name-modifying-dynamic-subscript" class="section-name selfRef">Modifying Dynamic Subscriptions</a>
          </h3>
<p id="section-a.1.2-1">An existing subscription may be modified.  The following exchange shows a negotiation of such a modification via several exchanges between a subscriber and a publisher.  This negotiation consists of a failed RPC modification request/response followed by a successful one.<a href="#section-a.1.2-1" class="pilcrow">¶</a></p>
<span id="name-interaction-model-for-succe"></span><div id="mess-flow-subs-modification">
<figure id="figure-7">
            <div class="artwork art-text alignLeft" id="section-a.1.2-2.1">
<pre>
   +------------+                 +-----------+
   | Subscriber |                 | Publisher |
   +------------+                 +-----------+
         |                              |
         |  notification message (id#23)|
         |&lt;-----------------------------|
         |                              |
         |modify-subscription (id#23)   |
         |-----------------------------&gt;|  (d)
         |    HTTP 400 error (with hint)|
         |&lt;-----------------------------|  (e)
         |                              |
         |modify-subscription (id#23)   |
         |-----------------------------&gt;|
         |                  HTTP 200 OK |
         |&lt;-----------------------------|
         |                              |
         |            notif-mesg (id#23)|
         |&lt;-----------------------------|
         |                              | </pre>
</div>
<figcaption><a href="#figure-7" class="selfRef">Figure 7</a>:
<a href="#name-interaction-model-for-succe" class="selfRef">Interaction Model for Successful Subscription Modification</a>
            </figcaption></figure>
</div>
<p id="section-a.1.2-3">If the subscription being modified in <a href="#mess-flow-subs-modification" class="xref">Figure 7</a> is a datastore subscription as per <span>[<a href="#RFC8641" class="xref">RFC8641</a>]</span>, the modification request made in (d) may look like that shown in <a href="#simple-modify-subs" class="xref">Figure 8</a>.  As can be seen, the modifications being attempted are the application of a new XML Path Language (XPath) filter as well as the setting of a new periodic time interval.<a href="#section-a.1.2-3" class="pilcrow">¶</a></p>
<span id="name-subscription-modification-r"></span><div id="simple-modify-subs">
<figure id="figure-8">
            <div class="artwork art-text alignLeft" id="section-a.1.2-4.1">
<pre>
POST /restconf/operations
     /ietf-subscribed-notifications:modify-subscription

{
 "ietf-subscribed-notifications:input": {
    "id": 23,
    "ietf-yang-push:datastore-xpath-filter": 
       "/example-module:foo/example-module:bar",
    "ietf-yang-push:periodic": {
       "ietf-yang-push:period": 500
    }
  }
} </pre>
</div>
<figcaption><a href="#figure-8" class="selfRef">Figure 8</a>:
<a href="#name-subscription-modification-r" class="selfRef">Subscription Modification Request (c)</a>
            </figcaption></figure>
</div>
<p id="section-a.1.2-5">If the publisher can satisfy both changes, the publisher sends a positive result for the RPC. If the publisher cannot satisfy either of the proposed changes, the publisher sends an RPC error response (e).  The following is an example RPC error response for (e) that includes a hint. This hint is an alternative time period value that might have resulted in a successful modification:<a href="#section-a.1.2-5" class="pilcrow">¶</a></p>
<span id="name-modify-subscription-failure"></span><div id="negative-modify-subs">
<figure id="figure-9">
            <div class="artwork art-text alignLeft" id="section-a.1.2-6.1">
<pre>
HTTP status code - 400

{ "ietf-restconf:errors" : {
    "error" : [
      "error-type": "application",
      "error-tag": "invalid-value",
      "error-severity": "error",
      "error-app-tag": "ietf-yang-push:period-unsupported",
      "error-info": {
        "ietf-yang-push":
        "modify-subscription-datastore-error-info": {
           "period-hint": 3000
        }
      }
    ]
  }
} </pre>
</div>
<figcaption><a href="#figure-9" class="selfRef">Figure 9</a>:
<a href="#name-modify-subscription-failure" class="selfRef">"modify-subscription" Failure with Hint (e)</a>
            </figcaption></figure>
</div>
</section>
<section id="section-a.1.3">
          <h3 id="name-deleting-dynamic-subscripti">
<a href="#section-a.1.3" class="section-number selfRef">A.1.3. </a><a href="#name-deleting-dynamic-subscripti" class="section-name selfRef">Deleting Dynamic Subscriptions</a>
          </h3>
<p id="section-a.1.3-1">The following demonstrates deleting a subscription.  This subscription may have been to either a stream or a datastore.<a href="#section-a.1.3-1" class="pilcrow">¶</a></p>
<span id="name-delete-subscription-request"></span><div id="simple-delete-subs">
<figure id="figure-10">
            <div class="artwork art-text alignLeft" id="section-a.1.3-2.1">
<pre>
POST /restconf/operations
     /ietf-subscribed-notifications:delete-subscription

{
 "delete-subscription": {
    "id": "22"
 }
} </pre>
</div>
<figcaption><a href="#figure-10" class="selfRef">Figure 10</a>:
<a href="#name-delete-subscription-request" class="selfRef">"delete-subscription" Request</a>
            </figcaption></figure>
</div>
<p id="section-a.1.3-3">If the publisher can satisfy the request, the publisher replies with success to the RPC request.<a href="#section-a.1.3-3" class="pilcrow">¶</a></p>
<p id="section-a.1.3-4">If the publisher cannot satisfy the request, the publisher sends
   an &lt;rpc-error&gt; element indicating the modification didn't work. <a href="#negative-delete-subs" class="xref">Figure 11</a> shows a valid
   response for an existing valid subscription identifier, but that subscription identifier was created on a different transport session:<a href="#section-a.1.3-4" class="pilcrow">¶</a></p>
<span id="name-unsuccessful-delete-subscri"></span><div id="negative-delete-subs">
<figure id="figure-11">
            <div class="artwork art-text alignLeft" id="section-a.1.3-5.1">
<pre>
HTTP status code - 404

{
  "ietf-restconf:errors" : {
    "error" : [
      "error-type": "application",
      "error-tag": "invalid-value",
      "error-severity": "error",
      "error-app-tag":
         "ietf-subscribed-notifications:no-such-subscription"
    ]
  }
} </pre>
</div>
<figcaption><a href="#figure-11" class="selfRef">Figure 11</a>:
<a href="#name-unsuccessful-delete-subscri" class="selfRef">Unsuccessful "delete-subscription"</a>
            </figcaption></figure>
</div>
</section>
</section>
<section id="section-a.2">
        <h2 id="name-subscription-state-notifica">
<a href="#section-a.2" class="section-number selfRef">A.2. </a><a href="#name-subscription-state-notifica" class="section-name selfRef">Subscription State Notifications</a>
        </h2>
<p id="section-a.2-1">A publisher will send subscription state notifications according to the definitions within <span>[<a href="#RFC8639" class="xref">RFC8639</a>]</span>.<a href="#section-a.2-1" class="pilcrow">¶</a></p>
<section id="section-a.2.1">
          <h3 id="name-subscription-modified">
<a href="#section-a.2.1" class="section-number selfRef">A.2.1. </a><a href="#name-subscription-modified" class="section-name selfRef">"subscription-modified"</a>
          </h3>
<p id="section-a.2.1-1">A "subscription-modified" encoded in JSON would look like:<a href="#section-a.2.1-1" class="pilcrow">¶</a></p>
<span id="name-subscription-modified-subsc"></span><div id="subscription-modified-ctrl-plane-notif">
<figure id="figure-12">
            <div id="section-a.2.1-2.1">
<pre class="sourcecode lang-json">
{
  "ietf-restconf:notification" : {
    "eventTime": "2007-09-01T10:00:00Z",
    "ietf-subscribed-notifications:subscription-modified": {
      "id": 39,
      "uri": "https://example.com/restconf/subscriptions/22"
      "stream-xpath-filter": "/example-module:foo",
      "stream": {
         "ietf-netconf-subscribed-notifications" : "NETCONF"
      }
    }
  }
} </pre><a href="#section-a.2.1-2.1" class="pilcrow">¶</a>
</div>
<figcaption><a href="#figure-12" class="selfRef">Figure 12</a>:
<a href="#name-subscription-modified-subsc" class="selfRef">"subscription-modified" Subscription State Notification</a>
            </figcaption></figure>
</div>
</section>
<section id="section-a.2.2">
          <h3 id="name-subscription-completed-subs">
<a href="#section-a.2.2" class="section-number selfRef">A.2.2. </a><a href="#name-subscription-completed-subs" class="section-name selfRef">"subscription-completed", "subscription-resumed", and "replay-completed"</a>
          </h3>
<p id="section-a.2.2-1">A "subscription-completed" notification would look like:<a href="#section-a.2.2-1" class="pilcrow">¶</a></p>
<span id="name-subscription-completed-noti"></span><div id="subscription-completed">
<figure id="figure-13">
            <div id="section-a.2.2-2.1">
<pre class="sourcecode lang-json">
{
  "ietf-restconf:notification" : {
    "eventTime": "2007-09-01T10:00:00Z",
    "ietf-subscribed-notifications:subscription-completed": {
      "id": 39,
    }
  }
} </pre><a href="#section-a.2.2-2.1" class="pilcrow">¶</a>
</div>
<figcaption><a href="#figure-13" class="selfRef">Figure 13</a>:
<a href="#name-subscription-completed-noti" class="selfRef">"subscription-completed" Notification in JSON</a>
            </figcaption></figure>
</div>
<p id="section-a.2.2-3">The "subscription-resumed" and "replay-complete" are virtually identical, with "subscription-completed" simply being replaced by "subscription-resumed" and "replay-complete".<a href="#section-a.2.2-3" class="pilcrow">¶</a></p>
</section>
<section id="section-a.2.3">
          <h3 id="name-subscription-terminated-and">
<a href="#section-a.2.3" class="section-number selfRef">A.2.3. </a><a href="#name-subscription-terminated-and" class="section-name selfRef">"subscription-terminated" and "subscription-suspended"</a>
          </h3>
<p id="section-a.2.3-1">A "subscription-terminated" would look like:<a href="#section-a.2.3-1" class="pilcrow">¶</a></p>
<span id="name-subscription-terminated-sub"></span><div id="subscription-terminated">
<figure id="figure-14">
            <div id="section-a.2.3-2.1">
<pre class="sourcecode lang-json">
{
  "ietf-restconf:notification" : {
    "eventTime": "2007-09-01T10:00:00Z",
    "ietf-subscribed-notifications:subscription-terminated": {
      "id": 39,
      "error-id": "suspension-timeout"
    }
  }
} </pre><a href="#section-a.2.3-2.1" class="pilcrow">¶</a>
</div>
<figcaption><a href="#figure-14" class="selfRef">Figure 14</a>:
<a href="#name-subscription-terminated-sub" class="selfRef">"subscription-terminated" Subscription State Notification</a>
            </figcaption></figure>
</div>
<p id="section-a.2.3-3">The "subscription-suspended" is virtually identical, with "subscription-terminated" simply being replaced by "subscription-suspended".<a href="#section-a.2.3-3" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-a.3">
        <h2 id="name-filter-example">
<a href="#section-a.3" class="section-number selfRef">A.3. </a><a href="#name-filter-example" class="section-name selfRef">Filter Example</a>
        </h2>
<p id="section-a.3-1">This section provides an example that illustrates the method of filtering event record contents.  The example is based on the YANG notification "vrrp-protocol-error-event" as defined per the ietf-vrrp.yang module within <span>[<a href="#RFC8347" class="xref">RFC8347</a>]</span>.  Event records based on this specification that are generated by the publisher might appear as:<a href="#section-a.3-1" class="pilcrow">¶</a></p>
<span id="name-rfc-8347-vrrp-example-notif"></span><div id="VRRP-notification">
<figure id="figure-15">
          <div class="artwork art-text alignLeft" id="section-a.3-2.1">
<pre>
data: {
data:   "ietf-restconf:notification" : {
data:     "eventTime" : "2018-09-14T08:22:33.44Z",
data:     "ietf-vrrp:vrrp-protocol-error-event" : {
data:       "protocol-error-reason" : "checksum-error"
data:     }
data:   }
data: } </pre>
</div>
<figcaption><a href="#figure-15" class="selfRef">Figure 15</a>:
<a href="#name-rfc-8347-vrrp-example-notif" class="selfRef">RFC 8347 (VRRP) - Example Notification</a>
          </figcaption></figure>
</div>
<p id="section-a.3-3">Suppose a subscriber wanted to establish a subscription that only passes instances of event records where there is a "checksum-error" as part of a Virtual Router Redundancy Protocol (VRRP) protocol event.  Also assume the publisher places such event records into the NETCONF stream.  To get a continuous series of matching event records, the subscriber might request the application of an XPath filter against the NETCONF stream.  An "establish-subscription" RPC to meet this objective might be:<a href="#section-a.3-3" class="pilcrow">¶</a></p>
<span id="name-establishing-a-subscription"></span><div id="VRRP-XPATH">
<figure id="figure-16">
          <div class="artwork art-text alignLeft" id="section-a.3-4.1">
<pre>
POST /restconf/operations
     /ietf-subscribed-notifications:establish-subscription
{
   "ietf-subscribed-notifications:input": {
      "stream": "NETCONF",
      "stream-xpath-filter": 
        "/ietf-vrrp:vrrp-protocol-error-event[
          protocol-error-reason='checksum-error']/",
   }
} </pre>
</div>
<figcaption><a href="#figure-16" class="selfRef">Figure 16</a>:
<a href="#name-establishing-a-subscription" class="selfRef">Establishing a Subscription Error Reason via XPath</a>
          </figcaption></figure>
</div>
<p id="section-a.3-5">For more examples of XPath filters, see <span>[<a href="#XPATH" class="xref">XPATH</a>]</span>.<a href="#section-a.3-5" class="pilcrow">¶</a></p>
<p id="section-a.3-6">Suppose the "establish-subscription" in <a href="#VRRP-XPATH" class="xref">Figure 16</a> was accepted. And suppose later a subscriber decided they wanted to broaden this subscription cover to all VRRP protocol events (i.e., not just those with a "checksum error").  The subscriber might attempt to modify the subscription in a way that replaces the XPath filter with a subtree filter that sends all VRRP protocol events to a subscriber. Such a "modify-subscription" RPC might look like:<a href="#section-a.3-6" class="pilcrow">¶</a></p>
<span id="name-example-modify-subscription"></span><div id="VRRP-Subtree">
<figure id="figure-17">
          <div class="artwork art-text alignLeft" id="section-a.3-7.1">
<pre>
POST /restconf/operations
     /ietf-subscribed-notifications:modify-subscription
{
   "ietf-subscribed-notifications:input": {
      "stream": "NETCONF",
      "stream-subtree-filter": {
        "/ietf-vrrp:vrrp-protocol-error-event" : {}
      }
   }
} </pre>
</div>
<figcaption><a href="#figure-17" class="selfRef">Figure 17</a>:
<a href="#name-example-modify-subscription" class="selfRef">Example "modify-subscription" RPC</a>
          </figcaption></figure>
</div>
<p id="section-a.3-8">For more examples of subtree filters, see <span>[<a href="#RFC6241" class="xref">RFC6241</a>], <a href="https://www.rfc-editor.org/rfc/rfc6241#section-6.4" class="relref">Section 6.4</a></span>.<a href="#section-a.3-8" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-appendix.b">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<p id="section-appendix.b-1">We wish to acknowledge the helpful contributions, comments, and suggestions that were received from Ambika Prasad Tripathy, Alberto Gonzalez Prieto, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent Watsen, Michael Scharf, Guangying Zheng, Martin Bjorklund, Qin Wu, and Robert Wilton.<a href="#section-appendix.b-1" class="pilcrow">¶</a></p>
</section>
<div id="authors-addresses">
<section id="section-appendix.c">
      <h2 id="name-authors-addresses">
<a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Eric Voit</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:evoit@cisco.com" class="email">evoit@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Reshad Rahman</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:rrahman@cisco.com" class="email">rrahman@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Einar Nilsen-Nygaard</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:einarnn@cisco.com" class="email">einarnn@cisco.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 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">Andy Bierman</span></div>
<div dir="auto" class="left"><span class="org">YumaWorks</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:andy@yumaworks.com" class="email">andy@yumaworks.com</a>
</div>
</address>
</section>
</div>
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