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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 9030: An Architecture for IPv6 over the Time-Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)</title>
<meta content="Pascal Thubert" name="author">
<meta content="
          This document describes a network architecture that provides
   low-latency, low-jitter, and high-reliability packet delivery.  It
   combines a high-speed powered backbone and subnetworks using IEEE
   802.15.4 time-slotted channel hopping (TSCH) to meet the
   requirements of low-power wireless deterministic applications.
       
    " name="description">
<meta content="xml2rfc 3.8.0" name="generator">
<meta content="deterministic wireless" name="keyword">
<meta content="radio" name="keyword">
<meta content="mesh" name="keyword">
<meta content="9030" name="rfc.number">
<!-- Generator version information:
  xml2rfc 3.8.0
    Python 3.6.10
    appdirs 1.4.4
    ConfigArgParse 1.2.3
    google-i18n-address 2.3.5
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    pyflakes 2.1.1
    PyYAML 5.3.1
    requests 2.22.0
    setuptools 40.6.2
    six 1.14.0
    WeasyPrint 51
-->
<link href="rfc9030.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

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

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

*/

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

@viewport {
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}
@-ms-viewport {
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/* general and mobile first */
html {
}
body {
  max-width: 90%;
  margin: 1.5em auto;
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  scroll-behavior: smooth;
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.ears {
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/* headings */
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#title {
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dl {
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/* 
dl.nohang > dt {
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*/
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dl > dd > dl {
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/* links */
a {
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a[href] {
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a[href]:hover {
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figcaption a[href],
a[href].selfRef {
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/* XXX probably not this:
a.selfRef:hover {
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#identifiers .authors .org {
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}
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.docInfo .prepared {
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}

/* table of contents */
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}
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nav.toc li {
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}
/* references */
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.refInstance {
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}

.references .ascii {
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}

/* index */
.index ul {
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}
.index ul ul {
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}
.index li {
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.index a {
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}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
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/* authors */
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address.vcard .nameRole {
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address.vcard .type {
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hr.addr {
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/* temporary notes */
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.rfcEditorRemove {
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.cref {
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.crefSource {
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}
/* alternative layout for smaller screens */
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  h1 {
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  #toc h2::before { /* css hamburger */
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}

/* alternative layout for wide screens */
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    max-width: 724px;
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    padding-left: 1.5em;
    padding-right: 29em;
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  #toc {
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    right: 42px;
    width: 25%;
    margin: 0;
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    font-weight: normal;
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    overflow: auto;
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  img { /* future proofing */
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}

/* pagination */
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  figure, pre {
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    font-size: 10pt;
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}

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

.ears thead .center {
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*/

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}

@page {
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  @top-left {
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}

/* Changes introduced to fix issues found during implementation */
/* Make sure links are clickable even if overlapped by following H* */
a {
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}
/* 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 */
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/* Leave room in document info to show Internet-Draft on one line */
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/* Don't waste quite as much whitespace between label and value in doc info */
#identifiers dd {
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/* Give floating toc a background color (needed when it's a div inside section */
#toc {
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}

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

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

/* Style section numbers with more space between number and title */
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/* prevent monospace from becoming overly large */
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/* Fix the height/width aspect for ascii art*/
pre.sourcecode,
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}


/* Add styling for a link in the ToC that points to the top of the document */
a.toplink {
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}

/* 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 {
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}
table td.text-right,
table th.text-right {
  text-align: right;
}

/* Make the alternative author contact informatio look less like just another
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}
address .non-ascii {
  margin: 0 0 0 2em;
}

/* With it being possible to set tables with alignment
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table {
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}

/* 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 {
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}

/* Limit the width of the author address vcard, so names in right-to-left
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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 {
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}
/* Tweak the bcp14 keyword presentation */
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  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
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}
/* 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 {
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}
/* Styling for the external metadata */
div#external-metadata {
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  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
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<table class="ears">
<thead><tr>
<td class="left">RFC 9030</td>
<td class="center">6TiSCH Architecture</td>
<td class="right">May 2021</td>
</tr></thead>
<tfoot><tr>
<td class="left">Thubert</td>
<td class="center">Informational</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc9030" class="eref">9030</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Informational</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2021-05" class="published">May 2021</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Author:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">P. Thubert, <span class="editor">Ed.</span>
</div>
<div class="org">Cisco Systems</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9030</h1>
<h1 id="title">An Architecture for IPv6 over the Time-Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">   This document describes a network architecture that provides
   low-latency, low-jitter, and high-reliability packet delivery.  It
   combines a high-speed powered backbone and subnetworks using IEEE
   802.15.4 time-slotted channel hopping (TSCH) to meet the
   requirements of low-power wireless deterministic applications.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This document is not an Internet Standards Track specification; it is
            published for informational purposes.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by the
            Internet Engineering Steering Group (IESG).  Not all documents
            approved by the IESG are candidates for any level of Internet
            Standard; see Section 2 of RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc9030">https://www.rfc-editor.org/info/rfc9030</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2021 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-terminology" class="xref">Terminology</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.2.2.1">
                <p id="section-toc.1-1.2.2.1.1" class="keepWithNext"><a href="#section-2.1" class="xref">2.1</a>.  <a href="#name-new-terms" class="xref">New Terms</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.2">
                <p id="section-toc.1-1.2.2.2.1" class="keepWithNext"><a href="#section-2.2" class="xref">2.2</a>.  <a href="#name-abbreviations" class="xref">Abbreviations</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.2.2.3">
                <p id="section-toc.1-1.2.2.3.1"><a href="#section-2.3" class="xref">2.3</a>.  <a href="#name-related-documents" class="xref">Related Documents</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-high-level-architecture" class="xref">High-Level Architecture</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-a-non-broadcast-multi-acces" class="xref">A Non-broadcast Multi-access Radio Mesh Network</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="xref">3.2</a>.  <a href="#name-a-multi-link-subnet-model" class="xref">A Multi-Link Subnet Model</a></p>
</li>
              <li class="compact ulEmpty toc" 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-tsch-a-deterministic-mac-la" class="xref">TSCH: a Deterministic MAC Layer</a></p>
</li>
              <li class="compact ulEmpty toc" 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-scheduling-tsch" class="xref">Scheduling TSCH</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.3.2.5">
                <p id="section-toc.1-1.3.2.5.1"><a href="#section-3.5" class="xref">3.5</a>.  <a href="#name-distributed-vs-centralized-" class="xref">Distributed vs. Centralized Routing</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.3.2.6">
                <p id="section-toc.1-1.3.2.6.1"><a href="#section-3.6" class="xref">3.6</a>.  <a href="#name-forwarding-over-tsch" class="xref">Forwarding over TSCH</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.3.2.7">
                <p id="section-toc.1-1.3.2.7.1"><a href="#section-3.7" class="xref">3.7</a>.  <a href="#name-6tisch-stack" class="xref">6TiSCH Stack</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.3.2.8">
                <p id="section-toc.1-1.3.2.8.1"><a href="#section-3.8" class="xref">3.8</a>.  <a href="#name-communication-paradigms-and" class="xref">Communication Paradigms and Interaction Models</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-architecture-components" class="xref">Architecture Components</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.1">
                <p id="section-toc.1-1.4.2.1.1"><a href="#section-4.1" class="xref">4.1</a>.  <a href="#name-6lowpan-and-rpl" class="xref">6LoWPAN (and RPL)</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.1.2.1">
                    <p id="section-toc.1-1.4.2.1.2.1.1"><a href="#section-4.1.1" class="xref">4.1.1</a>.  <a href="#name-rpl-unaware-leaves-and-6low" class="xref">RPL-Unaware Leaves and 6LoWPAN ND</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.1.2.2">
                    <p id="section-toc.1-1.4.2.1.2.2.1"><a href="#section-4.1.2" class="xref">4.1.2</a>.  <a href="#name-6lbr-and-rpl-root" class="xref">6LBR and RPL Root</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.2">
                <p id="section-toc.1-1.4.2.2.1"><a href="#section-4.2" class="xref">4.2</a>.  <a href="#name-network-access-and-addressi" class="xref">Network Access and Addressing</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.2.2.1">
                    <p id="section-toc.1-1.4.2.2.2.1.1"><a href="#section-4.2.1" class="xref">4.2.1</a>.  <a href="#name-join-process" class="xref">Join Process</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.2.2.2">
                    <p id="section-toc.1-1.4.2.2.2.2.1"><a href="#section-4.2.2" class="xref">4.2.2</a>.  <a href="#name-registration" class="xref">Registration</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3">
                <p id="section-toc.1-1.4.2.3.1"><a href="#section-4.3" class="xref">4.3</a>.  <a href="#name-tsch-and-6top" class="xref">TSCH and 6top</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.1">
                    <p id="section-toc.1-1.4.2.3.2.1.1"><a href="#section-4.3.1" class="xref">4.3.1</a>.  <a href="#name-6top" class="xref">6top</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.2">
                    <p id="section-toc.1-1.4.2.3.2.2.1"><a href="#section-4.3.2" class="xref">4.3.2</a>.  <a href="#name-scheduling-functions-and-th" class="xref">Scheduling Functions and the 6top Protocol</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.3">
                    <p id="section-toc.1-1.4.2.3.2.3.1"><a href="#section-4.3.3" class="xref">4.3.3</a>.  <a href="#name-6top-and-rpl-objective-func" class="xref">6top and RPL Objective Function Operations</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.4">
                    <p id="section-toc.1-1.4.2.3.2.4.1"><a href="#section-4.3.4" class="xref">4.3.4</a>.  <a href="#name-network-synchronization" class="xref">Network Synchronization</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.5">
                    <p id="section-toc.1-1.4.2.3.2.5.1"><a href="#section-4.3.5" class="xref">4.3.5</a>.  <a href="#name-slotframes-and-cdu-matrix" class="xref">Slotframes and CDU Matrix</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.3.2.6">
                    <p id="section-toc.1-1.4.2.3.2.6.1"><a href="#section-4.3.6" class="xref">4.3.6</a>.  <a href="#name-distributing-the-reservatio" class="xref">Distributing the Reservation of Cells</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.4">
                <p id="section-toc.1-1.4.2.4.1"><a href="#section-4.4" class="xref">4.4</a>.  <a href="#name-schedule-management-mechani" class="xref">Schedule Management Mechanisms</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.4.2.1">
                    <p id="section-toc.1-1.4.2.4.2.1.1"><a href="#section-4.4.1" class="xref">4.4.1</a>.  <a href="#name-static-scheduling" class="xref">Static Scheduling</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.4.2.2">
                    <p id="section-toc.1-1.4.2.4.2.2.1"><a href="#section-4.4.2" class="xref">4.4.2</a>.  <a href="#name-neighbor-to-neighbor-schedu" class="xref">Neighbor-to-Neighbor Scheduling</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.4.2.3">
                    <p id="section-toc.1-1.4.2.4.2.3.1"><a href="#section-4.4.3" class="xref">4.4.3</a>.  <a href="#name-remote-monitoring-and-sched" class="xref">Remote Monitoring and Schedule Management</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.4.2.4">
                    <p id="section-toc.1-1.4.2.4.2.4.1"><a href="#section-4.4.4" class="xref">4.4.4</a>.  <a href="#name-hop-by-hop-scheduling" class="xref">Hop-by-Hop Scheduling</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5">
                <p id="section-toc.1-1.4.2.5.1"><a href="#section-4.5" class="xref">4.5</a>.  <a href="#name-on-tracks" class="xref">On Tracks</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5.2.1">
                    <p id="section-toc.1-1.4.2.5.2.1.1"><a href="#section-4.5.1" class="xref">4.5.1</a>.  <a href="#name-general-behavior-of-tracks" class="xref">General Behavior of Tracks</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5.2.2">
                    <p id="section-toc.1-1.4.2.5.2.2.1"><a href="#section-4.5.2" class="xref">4.5.2</a>.  <a href="#name-serial-track" class="xref">Serial Track</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5.2.3">
                    <p id="section-toc.1-1.4.2.5.2.3.1"><a href="#section-4.5.3" class="xref">4.5.3</a>.  <a href="#name-complex-track-with-replicat" class="xref">Complex Track with Replication and Elimination</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5.2.4">
                    <p id="section-toc.1-1.4.2.5.2.4.1"><a href="#section-4.5.4" class="xref">4.5.4</a>.  <a href="#name-detnet-end-to-end-path" class="xref">DetNet End-to-End Path</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.5.2.5">
                    <p id="section-toc.1-1.4.2.5.2.5.1"><a href="#section-4.5.5" class="xref">4.5.5</a>.  <a href="#name-cell-reuse" class="xref">Cell Reuse</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.6">
                <p id="section-toc.1-1.4.2.6.1"><a href="#section-4.6" class="xref">4.6</a>.  <a href="#name-forwarding-models" class="xref">Forwarding Models</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.6.2.1">
                    <p id="section-toc.1-1.4.2.6.2.1.1"><a href="#section-4.6.1" class="xref">4.6.1</a>.  <a href="#name-track-forwarding" class="xref">Track Forwarding</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.6.2.2">
                    <p id="section-toc.1-1.4.2.6.2.2.1"><a href="#section-4.6.2" class="xref">4.6.2</a>.  <a href="#name-ipv6-forwarding" class="xref">IPv6 Forwarding</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.6.2.3">
                    <p id="section-toc.1-1.4.2.6.2.3.1"><a href="#section-4.6.3" class="xref">4.6.3</a>.  <a href="#name-fragment-forwarding" class="xref">Fragment Forwarding</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.7">
                <p id="section-toc.1-1.4.2.7.1"><a href="#section-4.7" class="xref">4.7</a>.  <a href="#name-advanced-6tisch-routing" class="xref">Advanced 6TiSCH Routing</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.4.2.7.2.1">
                    <p id="section-toc.1-1.4.2.7.2.1.1"><a href="#section-4.7.1" class="xref">4.7.1</a>.  <a href="#name-packet-marking-and-handling" class="xref">Packet Marking and Handling</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.4.2.7.2.2">
                    <p id="section-toc.1-1.4.2.7.2.2.1"><a href="#section-4.7.2" class="xref">4.7.2</a>.  <a href="#name-replication-retries-and-eli" class="xref">Replication, Retries, and Elimination</a></p>
</li>
                </ul>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.6.2.1">
                <p id="section-toc.1-1.6.2.1.1"><a href="#section-6.1" class="xref">6.1</a>.  <a href="#name-availability-of-remote-serv" class="xref">Availability of Remote Services</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.2">
                <p id="section-toc.1-1.6.2.2.1"><a href="#section-6.2" class="xref">6.2</a>.  <a href="#name-selective-jamming" class="xref">Selective Jamming</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.3">
                <p id="section-toc.1-1.6.2.3.1"><a href="#section-6.3" class="xref">6.3</a>.  <a href="#name-mac-layer-security" class="xref">MAC-Layer Security</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.4">
                <p id="section-toc.1-1.6.2.4.1"><a href="#section-6.4" class="xref">6.4</a>.  <a href="#name-time-synchronization" class="xref">Time Synchronization</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.5">
                <p id="section-toc.1-1.6.2.5.1"><a href="#section-6.5" class="xref">6.5</a>.  <a href="#name-validating-asn" class="xref">Validating ASN</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.6.2.6">
                <p id="section-toc.1-1.6.2.6.1"><a href="#section-6.6" class="xref">6.6</a>.  <a href="#name-network-keying-and-rekeying" class="xref">Network Keying and Rekeying</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.7.2.1">
                <p id="section-toc.1-1.7.2.1.1"><a href="#section-7.1" class="xref">7.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.7.2.2">
                <p id="section-toc.1-1.7.2.2.1"><a href="#section-7.2" class="xref">7.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-appendix.a" class="xref">Appendix A</a>.  <a href="#name-related-work-in-progress" class="xref">Related Work in Progress</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.8.2.1">
                <p id="section-toc.1-1.8.2.1.1"><a href="#section-a.1" class="xref">A.1</a>.  <a href="#name-unchartered-ietf-work-items" class="xref">Unchartered IETF Work Items</a></p>
<ul class="compact ulEmpty toc">
<li class="compact ulEmpty toc" id="section-toc.1-1.8.2.1.2.1">
                    <p id="section-toc.1-1.8.2.1.2.1.1"><a href="#section-a.1.1" class="xref">A.1.1</a>.  <a href="#name-6tisch-zero-touch-security" class="xref">6TiSCH Zero-Touch Security</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.8.2.1.2.2">
                    <p id="section-toc.1-1.8.2.1.2.2.1"><a href="#section-a.1.2" class="xref">A.1.2</a>.  <a href="#name-6tisch-track-setup" class="xref">6TiSCH Track Setup</a></p>
</li>
                  <li class="compact ulEmpty toc" id="section-toc.1-1.8.2.1.2.3">
                    <p id="section-toc.1-1.8.2.1.2.3.1"><a href="#section-a.1.3" class="xref">A.1.3</a>.  <a href="#name-using-bier-in-a-6tisch-netw" class="xref">Using BIER in a 6TiSCH Network</a></p>
</li>
                </ul>
</li>
              <li class="compact ulEmpty toc" id="section-toc.1-1.8.2.2">
                <p id="section-toc.1-1.8.2.2.1"><a href="#section-a.2" class="xref">A.2</a>.  <a href="#name-external-non-ietf-work-item" class="xref">External (Non-IETF) Work Items</a></p>
</li>
            </ul>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-acknowledgments" class="xref">Acknowledgments</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#section-appendix.c" class="xref"></a><a href="#name-contributors" class="xref">Contributors</a></p>
</li>
          <li class="compact ulEmpty toc" id="section-toc.1-1.11">
            <p id="section-toc.1-1.11.1"><a href="#section-appendix.d" class="xref"></a><a href="#name-authors-address" class="xref">Author's Address</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">
         Wireless networks enable a wide variety of devices of any size
         to get interconnected, often at a very low marginal cost per device,
         at any range, and in circumstances where wiring may be impractical,
         for instance, on fast-moving or rotating devices.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">
         On the other hand, Deterministic Networking maximizes the packet
         delivery ratio within a bounded latency so as to enable
         mission-critical machine-to-machine (M2M) operations.
         Applications that need such networks are presented in
         <span>[<a href="#RFC8578" class="xref">RFC8578</a>]</span>
         and
         <span>[<a href="#I-D.ietf-raw-use-cases" class="xref">RAW-USE-CASES</a>]</span>, which presents a number
         of additional use cases for Reliable and Available Wireless networks (RAW).
         The considered applications include professional media, Industrial
         Automation and Control Systems (IACS), building
         automation, in-vehicle command and control, commercial automation and
         asset tracking with mobile scenarios, as well as gaming, drones and 
         edge robotic control, and home automation applications.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">
         The Time-Slotted Channel Hopping (TSCH) <span>[<a href="#RFC7554" class="xref">RFC7554</a>]</span> mode
         of the IEEE Std 802.15.4 <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> Medium Access
         Control (MAC) was introduced with the IEEE Std 802.15.4e
         <span>[<a href="#IEEE802154e" class="xref">IEEE802154e</a>]</span> amendment and is now retrofitted in the
         main standard.  For all practical purposes, this document
         is expected to be insensitive to the revisions of that standard,
         which is thus referenced without a date.
         TSCH is both a Time-Division Multiplexing (TDM) and a Frequency-Division
         Multiplexing (FDM) technique, whereby a different channel can be used for
         each transmission. TSCH allows the scheduling of transmissions for
         deterministic operations and applies to the slower and most 
         energy-constrained wireless use cases.<a href="#section-1-3" class="pilcrow">¶</a></p>
<p id="section-1-4">
         The scheduled operation provides for a more reliable experience, which
         can be used to monitor and manage resources, e.g., energy and water, in
         a more efficient fashion.<a href="#section-1-4" class="pilcrow">¶</a></p>
<p id="section-1-5">
         Proven deterministic networking standards for use in process control,
         including ISA100.11a <span>[<a href="#ISA100.11a" class="xref">ISA100.11a</a>]</span> and WirelessHART
         <span>[<a href="#WirelessHART" class="xref">WirelessHART</a>]</span>, have demonstrated the capabilities
         of the IEEE Std 802.15.4 TSCH MAC for high reliability against interference,
         low-power consumption on well-known flows, and its applicability for
         Traffic Engineering (TE) from a central controller.<a href="#section-1-5" class="pilcrow">¶</a></p>
<p id="section-1-6">To enable the convergence of information technology (IT) and
         operational technology (OT) in Low-Power and Lossy
         Networks (LLNs), the 6TiSCH architecture supports an IETF suite of
         protocols over the IEEE Std 802.15.4 TSCH MAC to provide
         IP connectivity for energy and otherwise constrained wireless devices.<a href="#section-1-6" class="pilcrow">¶</a></p>
<p id="section-1-7">
         The 6TiSCH architecture relies on IPv6 <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span> and the
         use of routing to provide large scaling capabilities. The addition of a
         high-speed federating backbone adds yet another degree of scalability
         to the design. The backbone is typically a Layer 2 transit link such as
         an Ethernet bridged network, but it can also be a more complex routed
         structure.<a href="#section-1-7" class="pilcrow">¶</a></p>
<p id="section-1-8">
         The 6TiSCH architecture introduces an IPv6 multi-link subnet model that
         is composed of a federating backbone and a number of IEEE Std 802.15.4
         TSCH low-power wireless networks federated and synchronized by Backbone
         Routers. If the backbone is a Layer 2 transit link, then the Backbone
         Routers can operate as an IPv6 Neighbor Discovery (IPv6 ND) proxy
         <span>[<a href="#RFC4861" class="xref">RFC4861</a>]</span>.<a href="#section-1-8" class="pilcrow">¶</a></p>
<p id="section-1-9">

         The 6TiSCH architecture leverages 6LoWPAN <span>[<a href="#RFC4944" class="xref">RFC4944</a>]</span> to adapt IPv6
         to the constrained media and the 
          Routing Protocol for Low-Power and Lossy Networks (RPL) <span>[<a href="#RFC6550" class="xref">RFC6550</a>]</span> for the
         distributed routing operations.<a href="#section-1-9" class="pilcrow">¶</a></p>
<p id="section-1-10">
         Centralized routing refers to a model where routes are computed
         and resources are allocated from a central controller. This is
         particularly helpful to schedule deterministic multihop transmissions.
         In contrast, distributed routing refers to a model that relies on
         concurrent peer-to-peer protocol exchanges for TSCH resource allocation
         and routing operations.<a href="#section-1-10" class="pilcrow">¶</a></p>
<p id="section-1-11">
          The architecture defines mechanisms to establish and maintain routing
         and scheduling in a centralized, distributed, or mixed fashion, for use
         in multiple OT environments. It is applicable in particular to highly
         scalable solutions such as those used in Advanced Metering Infrastructure
         <span>[<a href="#AMI" class="xref">AMI</a>]</span> solutions that leverage distributed routing to
         enable multipath forwarding over large LLN meshes.<a href="#section-1-11" 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>
<div id="sixTTerminology">
<section id="section-2.1">
        <h3 id="name-new-terms">
<a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-new-terms" class="section-name selfRef">New Terms</a>
        </h3>
<p id="section-2.1-1">
            The document does not reuse terms from the <span><a href="#IEEE802154" class="xref">IEEE Std 802.15.4</a> [<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> standard such as "path" or "link", which bear
            a meaning that is quite different from classical IETF parlance.<a href="#section-2.1-1" class="pilcrow">¶</a></p>
<p id="section-2.1-2">This document adds the following terms:<a href="#section-2.1-2" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-2.1-3">
          <dt id="section-2.1-3.1">6TiSCH (IPv6 over the TSCH mode of IEEE 802.15.4):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.2">
                  6TiSCH defines an adaptation sublayer for IPv6 over TSCH called 6top,
                 a set of protocols for setting up a TSCH schedule in distributed
                 approach, and a security solution. 6TiSCH may be extended in the future for other
                 MAC/Physical Layer (PHY) pairs providing a service similar to TSCH.<a href="#section-2.1-3.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.3">6top (6TiSCH Operation Sublayer):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.4">
                 The next higher layer of the IEEE Std 802.15.4 TSCH MAC layer.
                 6top provides the abstraction of an IP link over a TSCH MAC,
                 schedules packets over TSCH cells, and exposes a management
                 interface to schedule TSCH cells.<a href="#section-2.1-3.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.5">6P (6top Protocol):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.6">
                    The protocol defined in <span>[<a href="#RFC8480" class="xref">RFC8480</a>]</span>.
                    6P enables Layer 2 peers to allocate, move, or  de-allocate
                    cells in their respective schedules to communicate.
                    6P operates at the 6top sublayer.<a href="#section-2.1-3.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.7">6P transaction:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.8">
                    A 2-way or 3-way sequence of 6P messages used by Layer 2
                    peers to modify their communication schedule.<a href="#section-2.1-3.8" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.9">ASN (Absolute Slot Number):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.10">
                    Defined in <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span>, the ASN is the total
                    number of timeslots that have elapsed since the Epoch time
                    when the TSCH network started.
                    Incremented by one at each timeslot.
                    It is wide enough to not roll over in practice.<a href="#section-2.1-3.10" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.11">bundle:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.12">
                    A group of equivalent scheduled cells, i.e., cells
                    identified by different slotOffset/channelOffset,
                    which are scheduled for a same purpose, with the same
                    neighbor, with the same flags, and the same slotframe.
                    The size of the bundle refers to the number of cells it
                    contains.
                    For a given slotframe length, the size of the bundle
                    translates directly into bandwidth.
                    A bundle is a local abstraction that represents a
                    half-duplex link for either sending or receiving,
                    with bandwidth that amounts to the sum of the cells in the
                    bundle.<a href="#section-2.1-3.12" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.13">Layer 2 vs. Layer 3 bundle:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.14">
                    Bundles are associated with either Layer 2 (switching) or
                    Layer 3 (routing) forwarding operations. A pair of Layer 3
                    bundles (one for each direction) maps to an IP link with a
                    neighbor, whereas a set of Layer 2 bundles (of an
                    "arbitrary" cardinality and direction) corresponds to the relation 
                    of one or more incoming bundle(s) from the
                    previous-hop neighbor(s) with one or more outgoing bundle(s)
                    to the next-hop neighbor(s) along a Track as part of the
                    switching role, which may include replication and elimination.<a href="#section-2.1-3.14" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.15">CCA (Clear Channel Assessment):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.16">
                    A mechanism defined in <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> whereby
                    nodes listen to the channel before sending to
                    detect ongoing transmissions from other parties.
                    Because the network is synchronized, CCA cannot be used to
                    detect colliding transmissions within the same network, but
                    it can be used to detect other radio networks in the vicinity.<a href="#section-2.1-3.16" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.17">cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.18">
                    A unit of transmission resource in the CDU matrix, a cell is
                    identified by a slotOffset and a channelOffset.
                    A cell can be scheduled or unscheduled.<a href="#section-2.1-3.18" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.19">Channel Distribution/Usage (CDU) matrix:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.20">:
                    A matrix of cells (i,j) representing the spectrum (channel)
                    distribution among the different nodes in the 6TiSCH network.
                    The CDU matrix has width in timeslots equal to the period
                    of the network scheduling operation, and  height equal to
                    the number of available channels.
                    Every cell (i,j) in the CDU, identified by slotOffset/channelOffset, 
                    belongs to a specific chunk.<a href="#section-2.1-3.20" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.21">channelOffset:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.22">
                    Identifies a row in the TSCH schedule. The number of
                    channelOffset values is bounded by the number of available
                    frequencies. The channelOffset translates into a frequency
                    with a function that depends on the absolute time when the
                    communication takes place, resulting in a channel-hopping
                    operation.<a href="#section-2.1-3.22" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.23">chunk:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.24">
                    A well-known list of cells, distributed in time and frequency, within a CDU matrix.
                    A chunk represents a portion of a CDU matrix.
                    The partition of the CDU matrix in chunks is globally known by all the nodes in the network to support the appropriation process, which is a negotiation between nodes within an interference domain.
                    A node that manages to appropriate a chunk gets to decide which transmissions will occur over the cells in the chunk within its interference domain, i.e., a parent node will decide when the cells within the appropriated chunk are used and by which node among its children.<a href="#section-2.1-3.24" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.25">CoJP (Constrained Join Protocol):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.26">
                    The Constrained Join Protocol (CoJP) enables a pledge to
                    securely join a 6TiSCH network and obtain network parameters
                    over a secure channel.
                    "<a href="#RFC9031" class="xref">Constrained Join Protocol (CoJP) for 6TiSCH</a>" <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span> defines
                    the minimal CoJP setup with pre-shared keys defined. In that
                    mode, CoJP can operate with a single round-trip exchange.<a href="#section-2.1-3.26" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.27">dedicated cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.28">
                    A cell that is reserved for a given node to transmit to a specific neighbor.<a href="#section-2.1-3.28" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.29">deterministic network:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.30">
                    The generic concept of a deterministic network is defined 
                    in the <span><a href="#RFC8655" class="xref">"Deterministic Networking Architecture"</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span> document.
                    When applied to 6TiSCH, it refers to the reservation of Tracks, 
                    which guarantees an end-to-end latency and optimizes the 
                    Packet Delivery Ratio (PDR) for well-characterized flows.<a href="#section-2.1-3.30" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.31">distributed cell reservation:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.32">
                    A reservation of a cell  done by one or more in-network entities.<a href="#section-2.1-3.32" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.33">distributed Track reservation:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.34">
                    A reservation of a Track done by one or more in-network entities.<a href="#section-2.1-3.34" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.35">EB (Enhanced Beacon):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.36">
                    A special frame defined in <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span>
                    used by a node, including the Join Proxy (JP), to announce the presence
                    of the network.
                    It contains enough information for a pledge to synchronize to the network.<a href="#section-2.1-3.36" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.37">hard cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.38">
                    A scheduled cell that the 6top sublayer may not relocate.<a href="#section-2.1-3.38" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.39">hopping sequence:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.40">
                    Ordered sequence of frequencies, identified by a Hopping_Sequence_ID, used for channel hopping when translating the channelOffset value into a frequency.<a href="#section-2.1-3.40" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.41">IE (Information Element):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.42">
                    Type-Length-Value containers placed at the end of the MAC header and used to pass data between layers or devices.
                    Some IE identifiers are managed by the IEEE <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span>.
                    Some IE identifiers are managed by the IETF <span>[<a href="#RFC8137" class="xref">RFC8137</a>]</span>. <span>[<a href="#RFC9032" class="xref">RFC9032</a>]</span> 
                    uses one subtype to support the selection of the Join Proxy.<a href="#section-2.1-3.42" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.43">join process:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.44">
                    The overall process that includes the discovery of the network by pledge(s) and the execution of the join protocol.<a href="#section-2.1-3.44" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.45">join protocol:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.46">
                    The protocol that allows the pledge to join the network.
                    The join protocol encompasses authentication, authorization, and parameter distribution.
                    The join protocol is executed between the pledge and the JRC.<a href="#section-2.1-3.46" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.47">joined node:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.48">
                    The new device after having completed the join process, often just called a node.<a href="#section-2.1-3.48" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.49">JP (Join Proxy):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.50">
                    A node already part of the 6TiSCH network that serves as a relay to provide connectivity between the pledge and the JRC.
                    The JP announces the presence of the network by regularly sending EB frames.<a href="#section-2.1-3.50" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.51">JRC (Join Registrar/Coordinator):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.52">
                    Central entity responsible for the authentication, authorization, and configuration of the pledge.<a href="#section-2.1-3.52" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.53">link:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.54">
                    A communication facility or medium over which nodes can communicate 
                    at the link layer, which is the layer immediately below IP. In 6TiSCH, the concept is implemented as a collection
                    of Layer 3 bundles. Note:
                    the IETF parlance for the term "link" is adopted, as opposed to the IEEE Std 802.15.4 terminology.<a href="#section-2.1-3.54" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.55">operational technology:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.56">
                    OT refers to technology used in automation, for instance in
                    industrial control networks. The convergence of IT and OT is
                    the main object of the Industrial Internet of Things (IIOT).<a href="#section-2.1-3.56" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.57">pledge:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.58">
                    A new device that attempts to join a 6TiSCH network.<a href="#section-2.1-3.58" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.59">(to) relocate a cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.60">
                    The action operated by the 6top sublayer of changing the slotOffset and/or channelOffset of a soft cell.<a href="#section-2.1-3.60" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.61">(to) schedule a cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.62">
                    The action of turning an unscheduled cell into a scheduled cell.<a href="#section-2.1-3.62" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.63">scheduled cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.64">
                    A cell that is assigned a neighbor MAC address 
                    (broadcast address is also possible) and one or 
                    more of the following flags: TX, RX, Shared, and Timekeeping.
                    A scheduled cell can be used by the IEEE Std 802.15.4 TSCH implementation to communicate.
                    A scheduled cell can either be a hard or a soft cell.<a href="#section-2.1-3.64" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.65">SF (6top Scheduling Function):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.66">
                    The cell management entity that adds or deletes cells dynamically based on application networking requirements.
                    The cell negotiation with a neighbor is done using 6P.<a href="#section-2.1-3.66" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.67">SFID (6top Scheduling Function Identifier):</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.68">
                    A 4-bit field identifying an SF.<a href="#section-2.1-3.68" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.69">shared cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.70">
                    A cell marked with both the TX and Shared flags.
                    This cell can be used by more than one transmitter node.
                    A back-off algorithm is used to resolve contention.<a href="#section-2.1-3.70" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.71">slotframe:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.72">
                    A collection of timeslots repeating in time, analogous to a superframe in that it defines periods of communication opportunities.
                    It is characterized by a slotframe_ID and a slotframe_size.
                    Multiple slotframes can coexist in a node's schedule, 
                    i.e., a node can have multiple activities scheduled in 
                    different slotframes based on the priority of its packets/traffic flows.
                    The timeslots in the slotframe are indexed by the slotOffset; the first timeslot is at slotOffset 0.<a href="#section-2.1-3.72" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.73">slotOffset:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.74">
                    A column in the TSCH schedule, i.e., the number of timeslots since the beginning of the current iteration of the slotframe.<a href="#section-2.1-3.74" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.75">soft cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.76">
                    A scheduled cell that the 6top sublayer can relocate.<a href="#section-2.1-3.76" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.77">time source neighbor:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.78">
                    A neighbor that a node uses as its time reference, and to which it needs to keep its clock synchronized.<a href="#section-2.1-3.78" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.79">timeslot:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.80">
                    A basic communication unit in TSCH that allows
                        a transmitter node to send a frame to a receiver neighbor and
                        that allows the receiver neighbor to optionally send back an acknowledgment.<a href="#section-2.1-3.80" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.81">Track:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.82">
                    A Track is a Directed Acyclic Graph (DAG) that is used as a
                    complex multihop path to the destination(s) of the path.
                    In the case of unicast traffic, the Track is a Destination-Oriented DAG (DODAG) where the Root of the DODAG is the
                    destination of the unicast traffic.
                    A Track enables replication, elimination, and reordering functions on the way (more on those functions in
                    <span>[<a href="#RFC8655" class="xref">RFC8655</a>]</span>).
                    A Track reservation locks physical resources such as cells and buffers in every node along the DODAG.
                    A Track is associated with an owner, which can be for instance the destination of the Track.<a href="#section-2.1-3.82" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.83">TrackID:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.84">
                    A TrackID is either globally unique or locally unique to the Track owner,
                    in which case the identification of the owner must be provided together with the TrackID
                    to provide a full reference to the Track. Typically, the Track owner is the ingress of the
                    Track, the IPv6 source address of packets along the Track can be used as
                    identification of the owner, and a local InstanceID <span>[<a href="#RFC6550" class="xref">RFC6550</a>]</span>
                    in the namespace of that owner can be used as TrackID.
                    If the Track is reversible, then the owner is found in
                    the IPv6 destination address of a packet coming back along the Track.
                    In that case, a RPL Packet Information <span>[<a href="#RFC6550" class="xref">RFC6550</a>]</span> in an IPv6 packet
                    can unambiguously identify the Track and can be expressed in a compressed form using
                    <span>[<a href="#RFC8138" class="xref">RFC8138</a>]</span>.<a href="#section-2.1-3.84" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.85">TSCH:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.86">
                    A medium access mode of the <span><a href="#IEEE802154" class="xref">IEEE Std 802.15.4</a> [<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> standard that uses
                    time synchronization to achieve ultra-low-power operation and
                    channel hopping to enable high reliability.<a href="#section-2.1-3.86" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.87">TSCH Schedule:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.88">
                    A matrix of cells, with each cell indexed by a slotOffset and a channelOffset.
                    The TSCH schedule contains all the scheduled cells from all 
                    slotframes and is sufficient to qualify the communication in the TSCH network.
                    The number of channelOffset values (the "height" of the matrix) is equal to the number of available frequencies.<a href="#section-2.1-3.88" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.1-3.89">Unscheduled Cell:</dt>
          <dd style="margin-left: 1.5em" id="section-2.1-3.90">
                    A cell that is not used by the IEEE Std 802.15.4 TSCH implementation.<a href="#section-2.1-3.90" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</div>
<div id="acronyms">
<section id="section-2.2">
        <h3 id="name-abbreviations">
<a href="#section-2.2" class="section-number selfRef">2.2. </a><a href="#name-abbreviations" class="section-name selfRef">Abbreviations</a>
        </h3>
<p id="section-2.2-1"> This document uses the following abbreviations:<a href="#section-2.2-1" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-2.2-2">
          <dt id="section-2.2-2.1">6BBR:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.2"> 6LoWPAN Backbone Router (router with a proxy ND function)<a href="#section-2.2-2.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.3">6LBR:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.4"> 6LoWPAN Border Router (authoritative on Duplicate Address Detection (DAD))<a href="#section-2.2-2.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.5">6LN:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.6"> 6LoWPAN Node<a href="#section-2.2-2.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.7">6LR:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.8"> 6LoWPAN Router (relay to the registration process)<a href="#section-2.2-2.8" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.9">6CIO:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.10"> Capability Indication Option<a href="#section-2.2-2.10" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.11">(E)ARO:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.12"> (Extended) Address Registration Option<a href="#section-2.2-2.12" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.13">(E)DAR:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.14"> (Extended) Duplicate Address Request<a href="#section-2.2-2.14" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.15">(E)DAC:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.16"> (Extended) Duplicate Address Confirmation<a href="#section-2.2-2.16" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.17">DAD:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.18"> Duplicate Address Detection<a href="#section-2.2-2.18" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.19">DODAG:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.20"> Destination-Oriented Directed Acyclic Graph<a href="#section-2.2-2.20" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.21">LLN:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.22"> Low-Power and Lossy Network (a typical IoT network)<a href="#section-2.2-2.22" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.23">NA:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.24"> Neighbor Advertisement<a href="#section-2.2-2.24" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.25">NCE:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.26"> Neighbor Cache Entry<a href="#section-2.2-2.26" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.27">ND:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.28"> Neighbor Discovery<a href="#section-2.2-2.28" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.29">NDP:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.30"> Neighbor Discovery Protocol<a href="#section-2.2-2.30" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.31">PCE:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.32"> Path Computation Element<a href="#section-2.2-2.32" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.33">NME:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.34"> Network Management Entity<a href="#section-2.2-2.34" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.35">ROVR:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.36"> Registration Ownership Verifier (pronounced rover)<a href="#section-2.2-2.36" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.37">RPL:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.38"> IPv6 Routing Protocol for LLNs (pronounced ripple)<a href="#section-2.2-2.38" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.39">RA:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.40"> Router Advertisement<a href="#section-2.2-2.40" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.41">RS:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.42"> Router Solicitation<a href="#section-2.2-2.42" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.43">TSCH:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.44"> Time-Slotted Channel Hopping<a href="#section-2.2-2.44" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-2.2-2.45">TID:</dt>
          <dd style="margin-left: 1.5em" id="section-2.2-2.46"> Transaction ID (a sequence counter in the EARO)<a href="#section-2.2-2.46" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
</section>
</div>
<div id="lo">
<section id="section-2.3">
        <h3 id="name-related-documents">
<a href="#section-2.3" class="section-number selfRef">2.3. </a><a href="#name-related-documents" class="section-name selfRef">Related Documents</a>
        </h3>
<p id="section-2.3-1">
         The document conforms to the terms and models described in
         <span>[<a href="#RFC3444" class="xref">RFC3444</a>]</span> and <span>[<a href="#RFC5889" class="xref">RFC5889</a>]</span>, uses the
         vocabulary and the concepts defined in <span>[<a href="#RFC4291" class="xref">RFC4291</a>]</span> for the
         IPv6 architecture, and refers to <span>[<a href="#RFC4080" class="xref">RFC4080</a>]</span> for reservation.<a href="#section-2.3-1" class="pilcrow">¶</a></p>
<p id="section-2.3-2">
         The document uses domain-specific terminology defined or referenced 
         in the following:<a href="#section-2.3-2" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-2.3-3.1">6LoWPAN ND: 
          <span><a href="#RFC6775" class="xref">"Neighbor Discovery Optimization for IPv6 over 
          Low-Power Wireless Personal Area Networks (6LoWPANs)"</a> [<a href="#RFC6775" class="xref">RFC6775</a>]</span> and 
          <span><a href="#RFC8505" class="xref">"Registration Extensions for IPv6 over Low-Power 
          Wireless Personal Area Network (6LoWPAN) Neighbor Discovery"</a> [<a href="#RFC8505" class="xref">RFC8505</a>]</span>,<a href="#section-2.3-3.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.3-3.2">
            <span><a href="#RFC7102" class="xref">"Terms Used in Routing for Low-Power and Lossy Networks"</a> [<a href="#RFC7102" class="xref">RFC7102</a>]</span>, and<a href="#section-2.3-3.2" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.3-3.3">RPL:
          <span><a href="#RFC6552" class="xref">"Objective Function Zero for the
          Routing Protocol for Low-Power and Lossy Networks (RPL)"</a> [<a href="#RFC6552" class="xref">RFC6552</a>]</span> and
          <span><a href="#RFC6550" class="xref">"RPL: IPv6 Routing Protocol for
          Low-Power and Lossy Networks"</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span>.<a href="#section-2.3-3.3" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-2.3-4">
   Other terms in use in LLNs are found in <span><a href="#RFC7228" class="xref">"Terminology for Constrained-Node Networks"</a> [<a href="#RFC7228" class="xref">RFC7228</a>]</span>.<a href="#section-2.3-4" class="pilcrow">¶</a></p>
<p id="section-2.3-5">
    Readers are expected to be familiar with all the terms and concepts
    that are discussed in the following:<a href="#section-2.3-5" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-2.3-6.1">
            <span><a href="#RFC4861" class="xref">"Neighbor Discovery for IP version 6 (IPv6)"</a> [<a href="#RFC4861" class="xref">RFC4861</a>]</span> and<a href="#section-2.3-6.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.3-6.2">
            <span><a href="#RFC4862" class="xref">"IPv6 Stateless Address Autoconfiguration"</a> [<a href="#RFC4862" class="xref">RFC4862</a>]</span>.<a href="#section-2.3-6.2" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-2.3-7">In addition, readers would benefit from reading the following
    prior to this specification for a clear understanding of the art 
    in ND-proxying and binding:<a href="#section-2.3-7" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-2.3-8.1">
            <span><a href="#RFC6606" class="xref">"Problem Statement and Requirements for
    IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing"</a> [<a href="#RFC6606" class="xref">RFC6606</a>]</span>,<a href="#section-2.3-8.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.3-8.2">
            <span><a href="#RFC4903" class="xref">"Multi-Link Subnet Issues"</a> [<a href="#RFC4903" class="xref">RFC4903</a>]</span>, and<a href="#section-2.3-8.2" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-2.3-8.3">
            <span><a href="#RFC4919" class="xref">"IPv6 over Low-Power
       Wireless Personal Area Networks (6LoWPANs): Overview, Assumptions,
       Problem Statement, and Goals"</a> [<a href="#RFC4919" class="xref">RFC4919</a>]</span>.<a href="#section-2.3-8.3" class="pilcrow">¶</a>
</li>
        </ul>
</section>
</div>
</section>
<section id="section-3">
      <h2 id="name-high-level-architecture">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-high-level-architecture" class="section-name selfRef">High-Level Architecture</a>
      </h2>
<section id="section-3.1">
        <h3 id="name-a-non-broadcast-multi-acces">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-a-non-broadcast-multi-acces" class="section-name selfRef">A Non-broadcast Multi-access Radio Mesh Network</a>
        </h3>
<p id="section-3.1-1">
         A 6TiSCH network is an IPv6 <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span> subnet that, in
         its basic configuration illustrated in <a href="#fig1" class="xref">Figure 1</a>, is a
         single Low-Power and Lossy Network (LLN) operating over a synchronized
         TSCH-based mesh.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<span id="name-basic-configuration-of-a-6t"></span><div id="fig1">
<figure id="figure-1">
          <div class="artwork art-text alignLeft" id="section-3.1-2.1">
<pre>
            ---+-------- ............ ------------
               |      External Network       |
               |                          +-----+
            +-----+                       | NME |
            |     | LLN Border            | PCE |
            |     | router (6LBR)         +-----+
            +-----+
          o    o   o
      o     o   o     o    o
     o   o 6LoWPAN + RPL o    o
         o   o   o       o
</pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a>:
<a href="#name-basic-configuration-of-a-6t" class="selfRef">Basic Configuration of a 6TiSCH Network</a>
          </figcaption></figure>
</div>
<p id="section-3.1-3">
         Inside a 6TiSCH LLN, nodes rely on <span><a href="#RFC6282" class="xref">6LoWPAN
         header compression (6LoWPAN HC)</a> [<a href="#RFC6282" class="xref">RFC6282</a>]</span> to encode IPv6 packets.
         From the perspective of the network layer, a single LLN interface
         (typically an IEEE Std 802.15.4-compliant radio) may be seen as a collection
         of links with different capabilities for unicast or multicast services.<a href="#section-3.1-3" class="pilcrow">¶</a></p>
<p id="section-3.1-4">
         6TiSCH nodes join a mesh network by attaching to nodes that are already
         members of the mesh (see <a href="#rflo" class="xref">Section 4.2.1</a>). The security aspects
         of the join process are further detailed in <a href="#sec" class="xref">Section 6</a>.
         In a mesh network, 6TiSCH nodes are not necessarily reachable from one
         another at Layer 2, and an LLN may span over multiple links.<a href="#section-3.1-4" class="pilcrow">¶</a></p>
<p id="section-3.1-5">
         This forms a homogeneous non-broadcast multi-access (NBMA) subnet,
         which is beyond the scope of IPv6 Neighbor Discovery (IPv6 ND)
         <span>[<a href="#RFC4861" class="xref">RFC4861</a>]</span> <span>[<a href="#RFC4862" class="xref">RFC4862</a>]</span>. 6LoWPAN Neighbor
         Discovery (6LoWPAN ND) <span>[<a href="#RFC6775" class="xref">RFC6775</a>]</span> <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>
         specifies extensions to IPv6 ND that enable ND operations in this type
         of subnet that can be protected against address theft and impersonation
         with <span>[<a href="#RFC8928" class="xref">RFC8928</a>]</span>.<a href="#section-3.1-5" class="pilcrow">¶</a></p>
<p id="section-3.1-6">
         Once it has joined the 6TiSCH network, a node acquires IPv6 addresses
         and registers them using 6LoWPAN ND. This guarantees that the addresses
         are unique and protects the address ownership over the subnet, more in
         <a href="#rreg" class="xref">Section 4.2.2</a>.<a href="#section-3.1-6" class="pilcrow">¶</a></p>
<p id="section-3.1-7">
         Within the NBMA subnet, <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span> enables
         routing  in the so-called "route-over" fashion, either in storing
         (stateful) or non-storing (stateless, with routing headers) mode.
         From there, some nodes can act as routers for 6LoWPAN ND and RPL
         operations, as detailed in <a href="#RPLvs6lo" class="xref">Section 4.1</a>.<a href="#section-3.1-7" class="pilcrow">¶</a></p>
<p id="section-3.1-8">
         With TSCH, devices are time synchronized at the MAC level. The use of
         a particular RPL Instance for time synchronization is discussed in
         <a href="#sync" class="xref">Section 4.3.4</a>. With this mechanism, the time synchronization
         starts at the RPL Root and follows the RPL loopless routing topology.<a href="#section-3.1-8" class="pilcrow">¶</a></p>
<p id="section-3.1-9">
         RPL forms Destination-Oriented
         Directed Acyclic Graphs (DODAGs) within Instances of the protocol,
         each Instance being associated with an Objective Function (OF) to
         form a routing topology. A particular 6TiSCH node, the LLN Border Router
         (6LBR), acts as RPL Root, 6LoWPAN HC terminator, and Border Router
         for the LLN  to the outside. The 6LBR is usually powered.
         More on RPL Instances can be found in Section 
         <a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.1" class="relref">3.1</a> of
         <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span>, in particular
         "<a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.1.2" class="relref">3.1.2</a> RPL Identifiers" and
         "<a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.1.3" class="relref">3.1.3</a> Instances, DODAGs, and DODAG Versions". 
         RPL adds artifacts in
         the data packets that are compressed with a 
         <span><a href="#RFC8138" class="xref">6LoWPAN Routing Header (6LoRH)</a> [<a href="#RFC8138" class="xref">RFC8138</a>]</span>.
         In a preexisting network, the compression can be globally turned on in a 
         DODAG once all nodes are migrated to support <span>[<a href="#RFC8138" class="xref">RFC8138</a>]</span> 
         using <span>[<a href="#RFC9035" class="xref">RFC9035</a>]</span>.<a href="#section-3.1-9" class="pilcrow">¶</a></p>
<p id="section-3.1-10">
         Additional routing and scheduling protocols may be deployed to
         establish on-demand, peer-to-peer routes with particular characteristics
         inside the 6TiSCH network.
         This may be achieved in a centralized fashion by a Path Computation
         Element (PCE) <span>[<a href="#PCE" class="xref">PCE</a>]</span> that programs both the routes and
         the schedules inside the 6TiSCH nodes or in a distributed fashion by
         using a reactive routing protocol and a hop-by-hop scheduling protocol.<a href="#section-3.1-10" class="pilcrow">¶</a></p>
<p id="section-3.1-11">
        This architecture expects that a 6LoWPAN node can connect as a
        leaf to a RPL network, where the leaf support is the minimal
        functionality to connect as a host to a RPL network without the need to
        participate in the full routing protocol.
        The architecture also expects that a 6LoWPAN node that is unaware
        of RPL may also connect as described in <span>[<a href="#RFC9010" class="xref">RFC9010</a>]</span>.<a href="#section-3.1-11" class="pilcrow">¶</a></p>
</section>
<section id="section-3.2">
        <h3 id="name-a-multi-link-subnet-model">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-a-multi-link-subnet-model" class="section-name selfRef">A Multi-Link Subnet Model</a>
        </h3>
<p id="section-3.2-1">
    An extended configuration of the subnet comprises multiple LLNs as
    illustrated in <a href="#fig2" class="xref">Figure 2</a>.
    In the extended configuration, a Routing Registrar <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>
    may be connected to the node that acts as the RPL Root and/or 6LoWPAN 6LBR
    and provides connectivity to the larger campus or factory plant network
    over a high-speed backbone or a back-haul link. The Routing Registrar
    may perform IPv6 ND proxy operations; redistribute the registration in
    a routing protocol such as <span><a href="#RFC5340" class="xref">OSPF</a> [<a href="#RFC5340" class="xref">RFC5340</a>]</span> or
    <span><a href="#RFC2545" class="xref">BGP</a> [<a href="#RFC2545" class="xref">RFC2545</a>]</span>; or inject a route in a mobility protocol
    such as <span><a href="#RFC6275" class="xref">Mobile IPv6 (MIPv6)</a> [<a href="#RFC6275" class="xref">RFC6275</a>]</span>, 
    <span><a href="#RFC3963" class="xref">Network Mobility (NEMO)</a> [<a href="#RFC3963" class="xref">RFC3963</a>]</span>, or 
    <span><a href="#RFC6830" class="xref">Locator/ID Separation Protocol (LISP)</a> [<a href="#RFC6830" class="xref">RFC6830</a>]</span>.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<p id="section-3.2-2">
    Multiple LLNs can be interconnected and possibly synchronized over a
    backbone, which can be wired or wireless. The backbone can operate with
    IPv6 ND procedures <span>[<a href="#RFC4861" class="xref">RFC4861</a>]</span> <span>[<a href="#RFC4862" class="xref">RFC4862</a>]</span> or a
    hybrid of IPv6 ND and 6LoWPAN ND
    <span>[<a href="#RFC6775" class="xref">RFC6775</a>]</span> <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> <span>[<a href="#RFC8928" class="xref">RFC8928</a>]</span>.<a href="#section-3.2-2" class="pilcrow">¶</a></p>
<span id="name-extended-configuration-of-a"></span><div id="fig2">
<figure id="figure-2">
          <div class="artwork art-text alignLeft" id="section-3.2-3.1">
<pre>
                |
             +-----+                +-----+         +-----+
   (default) |     |     (Optional) |     |         |     | IPv6
      Router |     |           6LBR |     |         |     | Node
             +-----+                +-----+         +-----+
                |  Backbone side       |               |
    --------+---+--------------------+-+---------------+------+---
            |                        |                        |
      +-----------+            +-----------+            +-----------+
      | Routing   |            | Routing   |            | Routing   |
      | Registrar |            | Registrar |            | Registrar |
      +-----------+            +-----------+            +-----------+
        o     Wireless side       o  o                     o o
    o o   o  o                o o   o  o  o          o  o  o  o o
  o   6TiSCH                o   6TiSCH   o  o          o o  6TiSCH o
  o   o LLN     o o           o o LLN   o               o     LLN   o
  o   o  o  o  o            o  o  o o o            o  o    o        o
</pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a>:
<a href="#name-extended-configuration-of-a" class="selfRef">Extended Configuration of a 6TiSCH Network</a>
          </figcaption></figure>
</div>
<p id="section-3.2-4">
    A Routing Registrar that performs proxy IPv6 ND operations over the
    backbone on behalf of the 6TiSCH nodes is called a Backbone Router (6BBR)
    <span>[<a href="#RFC8929" class="xref">RFC8929</a>]</span>. The 6BBRs are
    placed along the wireless edge of a backbone and federate multiple
    wireless links to form a single multi-link subnet. The 6BBRs synchronize
    with one another over the backbone, so as to ensure that the multiple LLNs
    that form the IPv6 subnet stay tightly synchronized.<a href="#section-3.2-4" class="pilcrow">¶</a></p>
<p id="section-3.2-5">
    The use of multicast can also be reduced on the backbone with a registrar
    that would contribute to Duplicate Address Detection as well as address
    lookup using only unicast request/response exchanges.
    <span>[<a href="#I-D.thubert-6man-unicast-lookup" class="xref">ND-UNICAST-LOOKUP</a>]</span> is a proposed method that
    presents an example of how this could be achieved with an extension of
    <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>, using an optional 6LBR as a subnet-level registrar,
    as illustrated in <a href="#fig2" class="xref">Figure 2</a>.<a href="#section-3.2-5" class="pilcrow">¶</a></p>
<p id="section-3.2-6">
    As detailed in <a href="#RPLvs6lo" class="xref">Section 4.1</a>, the 6LBR that serves the LLN and
    the Root of the RPL network need to share information about the devices
    that are learned through either 6LoWPAN ND or RPL, but not both.
    The preferred way of achieving this is to co-locate or combine them.
    The combined RPL Root and 6LBR may be co-located with the 6BBR, or
    directly attached to the 6BBR. In the latter case, it leverages the
    extended registration process defined in <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> to proxy
    the 6LoWPAN ND registration to the 6BBR on behalf of the LLN nodes, so
    that the 6BBR may in turn perform classical ND operations over the
    backbone as a proxy.<a href="#section-3.2-6" class="pilcrow">¶</a></p>
<p id="section-3.2-7"> The <span><a href="#RFC8655" class="xref">"Deterministic Networking Architecture"</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span> 
    studies Layer 3 aspects of Deterministic Networks and
    covers networks that span multiple Layer 2 domains.
    If the backbone is deterministic (such as defined by the Time-Sensitive
    Networking (TSN) Task Group at IEEE), then the Backbone Router ensures that the
    end-to-end deterministic behavior is maintained between the LLN and the
    backbone.<a href="#section-3.2-7" class="pilcrow">¶</a></p>
</section>
<section id="section-3.3">
        <h3 id="name-tsch-a-deterministic-mac-la">
<a href="#section-3.3" class="section-number selfRef">3.3. </a><a href="#name-tsch-a-deterministic-mac-la" class="section-name selfRef">TSCH: a Deterministic MAC Layer</a>
        </h3>
<p id="section-3.3-1">
         Though at a different time scale (several orders of magnitude),
         both IEEE Std 802.1 TSN and IEEE Std 802.15.4 TSCH
         standards provide deterministic capabilities to the point that a packet
         pertaining to a certain flow may traverse a network from node to node following
         a precise schedule, as a train that enters and then leaves intermediate stations
         at precise times along its path.<a href="#section-3.3-1" class="pilcrow">¶</a></p>
<p id="section-3.3-2">
         With TSCH, time is formatted into
         timeslots, and individual communication cells are allocated to unicast or
         broadcast communication at the MAC level. The time-slotted operation
         reduces collisions, saves energy, and enables more closely engineering
         the network for deterministic properties.
         The channel-hopping aspect is a simple and efficient technique to combat
         multipath fading and co-channel interference.<a href="#section-3.3-2" class="pilcrow">¶</a></p>
<p id="section-3.3-3">
         6TiSCH builds on the IEEE Std 802.15.4 TSCH MAC and inherits its advanced
         capabilities to enable them in multiple environments where they can
         be leveraged to improve automated operations.
         The 6TiSCH architecture also inherits the capability to perform a
         centralized route computation to achieve deterministic properties,
         though it relies on the IETF
         <span><a href="#RFC8655" class="xref">DetNet architecture</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span>
         and IETF components such as the PCE
         <span>[<a href="#PCE" class="xref">PCE</a>]</span> for the protocol aspects.<a href="#section-3.3-3" class="pilcrow">¶</a></p>
<p id="section-3.3-4">On top of this inheritance, 6TiSCH adds capabilities for distributed
         routing and scheduling operations based on RPL
         and capabilities for negotiating schedule adjustments between peers.
         These distributed routing and scheduling operations simplify the
         deployment of TSCH networks and enable wireless solutions in a larger
         variety of use cases from operational technology in general. Examples
         of such use cases in industrial environments include plant setup and
         decommissioning, as well as monitoring a multiplicity of minor 
         notifications such as corrosion measurements, events, and access of 
         local devices by mobile workers.<a href="#section-3.3-4" class="pilcrow">¶</a></p>
</section>
<section id="section-3.4">
        <h3 id="name-scheduling-tsch">
<a href="#section-3.4" class="section-number selfRef">3.4. </a><a href="#name-scheduling-tsch" class="section-name selfRef">Scheduling TSCH</a>
        </h3>
<p id="section-3.4-1">A scheduling operation allocates cells in a TDM/FDM matrix 
         called a CDU either to individual transmissions or as multi-access shared resources.
 
         The CDU matrix can be formatted in
         chunks that can be allocated exclusively to particular nodes to enable
         distributed scheduling without collision.
         More in <a href="#slotframes" class="xref">Section 4.3.5</a>.<a href="#section-3.4-1" class="pilcrow">¶</a></p>
<p id="section-3.4-2">
         At the MAC layer, the schedule of a 6TiSCH node 
         is the collection of the timeslots at which it must wake up for
         transmission, and the channels to which it should either send or listen
         at those times. The schedule is expressed as one or more repeating slotframes.
         Slotframes may collide and require a device to
         wake up at a same time, in which case the slotframe with the highest
         priority is actionable.<a href="#section-3.4-2" class="pilcrow">¶</a></p>
<p id="section-3.4-3">
         The 6top sublayer (see <a href="#s6Pprot" class="xref">Section 4.3</a> for more) hides the
         complexity of the schedule from the upper layers. The link abstraction
         that IP traffic utilizes is composed of a pair of Layer 3 cell bundles,
         one to receive and one to transmit. Some of the cells may be shared, in
         which case the 6top sublayer must perform some arbitration.<a href="#section-3.4-3" class="pilcrow">¶</a></p>
<p id="section-3.4-4">
         Scheduling enables multiple simultaneous communications in a same
         interference domain using different channels; but a node equipped with
         a single radio can only either transmit or receive on one channel at
         any point of time.
         Scheduled cells that fulfill the same role, e.g., receive IP packets from
         a peer, are grouped in bundles.<a href="#section-3.4-4" class="pilcrow">¶</a></p>
<p id="section-3.4-5">The 6TiSCH architecture identifies four ways a schedule can be managed
         and CDU cells can be allocated: Static Scheduling, Neighbor-to-Neighbor
         Scheduling, Centralized (or Remote) Monitoring and Schedule Management,
         and Hop-by-Hop Scheduling.<a href="#section-3.4-5" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-3.4-6">
          <dt id="section-3.4-6.1">Static Scheduling:</dt>
          <dd style="margin-left: 1.5em" id="section-3.4-6.2">This refers to the minimal
         6TiSCH operation whereby a static schedule is configured for the whole
         network for use in a Slotted ALOHA <span>[<a href="#S-ALOHA" class="xref">S-ALOHA</a>]</span> fashion.
         The static schedule is
         distributed through the native methods in the TSCH MAC layer
         and does not preclude other scheduling operations coexisting on a same
         6TiSCH network. A static schedule is
         necessary for basic operations such as the join process and
         for interoperability during the network formation, which is specified
         as part of the <span><a href="#RFC8180" class="xref">Minimal 6TiSCH Configuration</a> [<a href="#RFC8180" class="xref">RFC8180</a>]</span>.<a href="#section-3.4-6.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-3.4-6.3">Neighbor-to-Neighbor Scheduling:</dt>
          <dd style="margin-left: 1.5em" id="section-3.4-6.4">This refers to the
         dynamic adaptation of the bandwidth of the links that are used for IPv6
         traffic between adjacent peers. Scheduling Functions such as the
         <span><a href="#RFC9033" class="xref">"6TiSCH Minimal Scheduling Function
         (MSF)"</a> [<a href="#RFC9033" class="xref">RFC9033</a>]</span> influence the operation of the MAC layer to add, update,
         and remove cells in its own and its peer's schedules using 6P
         <span>[<a href="#RFC8480" class="xref">RFC8480</a>]</span>
         for the negotiation of the MAC resources.<a href="#section-3.4-6.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-3.4-6.5">Centralized (or Remote) Monitoring and Schedule Management:</dt>
          <dd style="margin-left: 1.5em" id="section-3.4-6.6">
         This refers to the central computation of a schedule and the capability
         to forward a frame based on the cell of arrival. In that case,
         the related portion of the device schedule as well as other device
         resources are managed by an abstract Network Management Entity (NME),
         which may cooperate with the PCE to minimize the interaction
         with, and the load on, the constrained device.
         This model is the TSCH adaption of the
         <span><a href="#RFC8655" class="xref">DetNet architecture</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span>,
         and it enables Traffic Engineering with deterministic properties.<a href="#section-3.4-6.6" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-3.4-6.7">Hop-by-Hop Scheduling:</dt>
          <dd style="margin-left: 1.5em" id="section-3.4-6.8">This refers to the possibility of
         reserving cells along a path for a particular flow using a distributed
         mechanism.<a href="#section-3.4-6.8" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
<p id="section-3.4-7">
         It is not expected that all use cases will require all those mechanisms.
         Static Scheduling with minimal configuration is the only one that
         is expected in all implementations, since it provides a simple and
         solid basis for convergecast routing and time distribution.<a href="#section-3.4-7" class="pilcrow">¶</a></p>
<p id="section-3.4-8">
         A deeper dive into those mechanisms can be found in <a href="#schd" class="xref">Section 4.4</a>.<a href="#section-3.4-8" class="pilcrow">¶</a></p>
</section>
<div id="rtg3">
<section id="section-3.5">
        <h3 id="name-distributed-vs-centralized-">
<a href="#section-3.5" class="section-number selfRef">3.5. </a><a href="#name-distributed-vs-centralized-" class="section-name selfRef">Distributed vs. Centralized Routing</a>
        </h3>
<p id="section-3.5-1">
      6TiSCH enables a mixed model of centralized routes and distributed routes.
      Centralized routes can, for example, be computed by an entity such as a PCE.
      6TiSCH leverages <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span>
      for interoperable, distributed routing operations.<a href="#section-3.5-1" class="pilcrow">¶</a></p>
<p id="section-3.5-2">
      Both methods may inject routes into the routing tables of the 6TiSCH routers.
      In either case, each route is associated with a 6TiSCH topology that can
      be a RPL Instance topology or a Track. The 6TiSCH topology is
      indexed by a RPLInstanceID, in a format that reuses the RPLInstanceID as
      defined in RPL.<a href="#section-3.5-2" class="pilcrow">¶</a></p>
<p id="section-3.5-3">
        <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span> is applicable to Static Scheduling and
        Neighbor-to-Neighbor Scheduling. The architecture also supports a
        centralized routing model for Remote Monitoring and Schedule Management.
        It is expected that a routing protocol that is more optimized for
        point-to-point routing than <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span>, such as
        the <span><a href="#I-D.ietf-roll-aodv-rpl" class="xref">"Asymmetric AODV-P2P-RPL in Low-Power and Lossy Networks" (AODV-RPL)</a> [<a href="#I-D.ietf-roll-aodv-rpl" class="xref">AODV-RPL</a>]</span>,
        which derives from the <span><a href="#I-D.ietf-manet-aodvv2" class="xref">"Ad Hoc On-demand Distance Vector (AODVv2) Routing"</a> [<a href="#I-D.ietf-manet-aodvv2" class="xref">AODVv2</a>]</span>, will be
        selected for Hop-by-Hop Scheduling.<a href="#section-3.5-3" class="pilcrow">¶</a></p>
<p id="section-3.5-4">
      Both RPL and PCE rely on shared sources such as policies to define global
      and local RPLInstanceIDs that can be used by either method. It is possible
      for centralized and distributed routing to share the same topology.
      Generally they will operate in different slotframes, and centralized
      routes will be used for scheduled traffic and will have precedence over
      distributed routes in case of conflict between the slotframes.<a href="#section-3.5-4" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-3.6">
        <h3 id="name-forwarding-over-tsch">
<a href="#section-3.6" class="section-number selfRef">3.6. </a><a href="#name-forwarding-over-tsch" class="section-name selfRef">Forwarding over TSCH</a>
        </h3>
<p id="section-3.6-1">
         The 6TiSCH architecture supports three different forwarding models.
         One is the classical IPv6 Forwarding, where the node selects a feasible
         successor at Layer 3 on a per-packet basis and based on its routing
         table. The second derives from Generalized MPLS (GMPLS) for so-called
         Track Forwarding, whereby a frame received at a particular timeslot
         can be switched into another timeslot at Layer 2 without regard to the
         upper-layer protocol. The third model is the
         6LoWPAN Fragment Forwarding, which allows the forwarding individual 6LoWPAN
         fragments along a route that is set up by the first fragment.<a href="#section-3.6-1" class="pilcrow">¶</a></p>
<p id="section-3.6-2">In more detail:<a href="#section-3.6-2" class="pilcrow">¶</a></p>
<span class="break"></span><dl class="dlParallel" id="section-3.6-3">
          <dt id="section-3.6-3.1">IPv6 Forwarding:</dt>
          <dd style="margin-left: 1.5em" id="section-3.6-3.2">This is the classical IP forwarding
         model, with a Routing Information Base (RIB) that is installed by 
         RPL and used to select a feasible successor per packet.
         The packet is placed on an outgoing link, which the 6top sublayer maps into
         a (Layer 3) bundle of cells, and scheduled for transmission based on QoS
         parameters. Besides RPL, this model also applies to any routing
         protocol that may be operated in the 6TiSCH network and corresponds
         to all the distributed scheduling models: Static, Neighbor-to-Neighbor,
         and Hop-by-Hop Scheduling.<a href="#section-3.6-3.2" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-3.6-3.3">GMPLS Track Forwarding:</dt>
          <dd style="margin-left: 1.5em" id="section-3.6-3.4">This model corresponds to the
         Remote Monitoring and Schedule Management. In this model, a central
         controller (hosting a PCE) computes and installs the schedules in the
         devices per flow. The incoming (Layer 2) bundle of cells from the
         previous node along the path determines the outgoing (Layer 2) bundle
         towards the next hop for that flow as determined by the PCE. The
         programmed sequence for bundles is called a Track and can assume DAG
         shapes that are more complex than a simple direct sequence of nodes.<a href="#section-3.6-3.4" class="pilcrow">¶</a>
</dd>
          <dd class="break"></dd>
<dt id="section-3.6-3.5">6LoWPAN Fragment Forwarding:</dt>
          <dd style="margin-left: 1.5em" id="section-3.6-3.6">This is a hybrid model
         that derives from IPv6 forwarding for the case where packets must
         be fragmented at the 6LoWPAN sublayer. The first fragment is forwarded
         like any IPv6 packet and leaves a state in the intermediate hops to
         enable forwarding of the next fragments that do not have an IP header
         without the need to recompose the packet at every hop.<a href="#section-3.6-3.6" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
</dl>
<p id="section-3.6-4">A deeper dive into these operations can be found in
    <a href="#fwd" class="xref">Section 4.6</a>.<a href="#section-3.6-4" class="pilcrow">¶</a></p>
<p id="section-3.6-5"> <a href="#RaF" class="xref">Table 1</a> summarizes how the forwarding models
       apply to the various routing and scheduling possibilities:<a href="#section-3.6-5" class="pilcrow">¶</a></p>
<div id="RaF">
<table class="center" id="table-1">
          <caption><a href="#table-1" class="selfRef">Table 1</a></caption>
<thead>
            <tr>
              <th class="text-left" rowspan="1" colspan="1">Forwarding Model</th>
              <th class="text-left" rowspan="1" colspan="1">Routing</th>
              <th class="text-left" rowspan="1" colspan="1">Scheduling</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td class="text-left" rowspan="3" colspan="1">classical IPv6 / 6LoWPAN Fragment</td>
              <td class="text-left" rowspan="2" colspan="1">RPL</td>
              <td class="text-left" rowspan="1" colspan="1">Static (Minimal Configuration)</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">Neighbor-to-Neighbor (SF+6P)</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">Reactive</td>
              <td class="text-left" rowspan="1" colspan="1">Hop-by-Hop (AODV-RPL)</td>
            </tr>
            <tr>
              <td class="text-left" rowspan="1" colspan="1">GMPLS Track Forwarding</td>
              <td class="text-left" rowspan="1" colspan="1">PCE</td>
              <td class="text-left" rowspan="1" colspan="1">Remote Monitoring and Schedule Mgt</td>
            </tr>
          </tbody>
        </table>
</div>
</section>
<div id="fsixstac">
<section id="section-3.7">
        <h3 id="name-6tisch-stack">
<a href="#section-3.7" class="section-number selfRef">3.7. </a><a href="#name-6tisch-stack" class="section-name selfRef">6TiSCH Stack</a>
        </h3>
<p id="section-3.7-1">
      The IETF proposes multiple techniques for implementing functions related
      to routing, transport, or security.<a href="#section-3.7-1" class="pilcrow">¶</a></p>
<p id="section-3.7-2">
      The 6TiSCH architecture limits the possible
      variations of the stack and recommends a number of base elements for LLN
      applications to control the complexity of
      possible deployments and device interactions and to limit the size of
      the resulting object code. In particular, UDP <span>[<a href="#RFC0768" class="xref">RFC0768</a>]</span>,
      IPv6 <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span>, and the <span><a href="#RFC7252" class="xref">Constrained
      Application Protocol (CoAP)</a> [<a href="#RFC7252" class="xref">RFC7252</a>]</span> are used as the transport/binding of
      choice for applications and management as opposed to TCP and HTTP.<a href="#section-3.7-2" class="pilcrow">¶</a></p>
<p id="section-3.7-3">
      The resulting protocol stack is represented in <a href="#fig4" class="xref">Figure 3</a>:<a href="#section-3.7-3" class="pilcrow">¶</a></p>
<span id="name-6tisch-protocol-stack"></span><div id="fig4">
<figure id="figure-3">
          <div class="artwork art-text alignLeft" id="section-3.7-4.1">
<pre>
   +--------+--------+
   | Applis |  CoJP  |
   +--------+--------+--------------+-----+
   | CoAP / OSCORE   |  6LoWPAN ND  | RPL |
   +-----------------+--------------+-----+
   |       UDP       |      ICMPv6        |
   +-----------------+--------------------+
   |                 IPv6                 |
   +--------------------------------------+----------------------+
   |     6LoWPAN HC   /   6LoRH HC        | Scheduling Functions |
   +--------------------------------------+----------------------+
   |               6top inc. 6top Protocol                       |
   +-------------------------------------------------------------+
   |                 IEEE Std 802.15.4 TSCH                      |
   +-------------------------------------------------------------+
</pre>
</div>
<figcaption><a href="#figure-3" class="selfRef">Figure 3</a>:
<a href="#name-6tisch-protocol-stack" class="selfRef">6TiSCH Protocol Stack</a>
          </figcaption></figure>
</div>
<p id="section-3.7-5">
         RPL is the routing protocol of choice for LLNs. So far, there is no
         identified need to define a 6TiSCH-specific Objective Function.
         The <span><a href="#RFC8180" class="xref">Minimal 6TiSCH Configuration</a> [<a href="#RFC8180" class="xref">RFC8180</a>]</span> describes the operation of RPL over a static schedule used in
         a Slotted ALOHA fashion <span>[<a href="#S-ALOHA" class="xref">S-ALOHA</a>]</span>, whereby all active slots
         may be used for emission or reception of both unicast and multicast
         frames.<a href="#section-3.7-5" class="pilcrow">¶</a></p>
<p id="section-3.7-6">
         <span><a href="#RFC6282" class="xref">6LoWPAN header compression</a> [<a href="#RFC6282" class="xref">RFC6282</a>]</span> is used
         to compress the IPv6 and UDP headers, whereas the
         <span><a href="#RFC8138" class="xref">6LoWPAN Routing Header (6LoRH)</a> [<a href="#RFC8138" class="xref">RFC8138</a>]</span> is used
         to compress the RPL artifacts in
         the IPv6 data packets, including the RPL Packet Information (RPI),
         the IP-in-IP encapsulation to/from the RPL Root, and the Source Routing
         Header (SRH) in non-storing mode.
         "<a href="#RFC9008" class="xref">Using RPI Option Type, Routing Header for Source Routes, and IPv6-in-IPv6 Encapsulation in the RPL Data Plane</a>" <span>[<a href="#RFC9008" class="xref">RFC9008</a>]</span>
         provides the details on when headers or encapsulation are needed.<a href="#section-3.7-6" class="pilcrow">¶</a></p>
<p id="section-3.7-7">
         The <span><a href="#RFC8613" class="xref">Object Security for Constrained RESTful Environments (OSCORE)</a> [<a href="#RFC8613" class="xref">RFC8613</a>]</span>
         is leveraged by the Constrained Join Protocol (CoJP) and is expected to
         be the primary protocol for the protection of the application payload
         as well. The application payload may also be protected by
         the <span><a href="#RFC6347" class="xref">Datagram Transport Layer Security (DTLS)</a> [<a href="#RFC6347" class="xref">RFC6347</a>]</span> sitting either under CoAP or over CoAP so it can traverse
         proxies.<a href="#section-3.7-7" class="pilcrow">¶</a></p>
<p id="section-3.7-8">
         The 6TiSCH Operation
         Sublayer (6top) is a sublayer of a Logical Link Control (LLC)
         that provides the abstraction of an IP link over a TSCH MAC and
         schedules packets over TSCH cells, as further discussed in the next
         sections, providing in particular dynamic cell allocation with the
         6top Protocol (6P) <span>[<a href="#RFC8480" class="xref">RFC8480</a>]</span>.<a href="#section-3.7-8" class="pilcrow">¶</a></p>
<p id="section-3.7-9">
      The reference stack presented in this document was implemented
      and interoperability-tested by a combination of open source, IETF, and ETSI efforts.
      One goal is to help other bodies to adopt the stack as a whole, making the
      effort to move to an IPv6-based IoT stack easier.<a href="#section-3.7-9" class="pilcrow">¶</a></p>
<p id="section-3.7-10">
      For a particular
      environment, some of the choices that are available in this architecture may not
      be relevant. For instance, RPL is not required for star topologies and
      mesh-under Layer 2 routed networks, and the 6LoWPAN compression may not be
      sufficient for ultra-constrained cases such as some Low-Power Wide Area
      (LPWA) networks. In such cases, it is perfectly doable to adopt a subset
      of the selection that is presented hereafter and then select alternate
      components to complete the solution wherever needed.<a href="#section-3.7-10" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-3.8">
        <h3 id="name-communication-paradigms-and">
<a href="#section-3.8" class="section-number selfRef">3.8. </a><a href="#name-communication-paradigms-and" class="section-name selfRef">Communication Paradigms and Interaction Models</a>
        </h3>
<p id="section-3.8-1">
         <a href="#sixTTerminology" class="xref">Section 2.1</a> provides the terms
         of Communication Paradigms and Interaction Models in combination with
         <span><a href="#RFC3444" class="xref">"On the Difference between Information Models
         and Data Models"</a> [<a href="#RFC3444" class="xref">RFC3444</a>]</span>.
         A Communication Paradigm is an abstract view of a protocol exchange
         and has an Information Model for the information that is being exchanged.
         In contrast, an Interaction Model is more refined and points to standard operation
         such as a Representational State Transfer (REST) "GET" operation and matches
         a Data Model for the data that is provided over the protocol exchange.<a href="#section-3.8-1" class="pilcrow">¶</a></p>
<p id="section-3.8-2">
         <span><a href="https://tools.ietf.org/html/draft-ietf-roll-rpl-industrial-applicability-02#section-2.1.3" class="relref">Section 2.1.3</a> of [<a href="#I-D.ietf-roll-rpl-industrial-applicability" class="xref">RPL-APPLICABILITY</a>]</span> 
         and its following
         sections discuss application-layer paradigms such as source-sink,
         which is a multipeer-to-multipeer model primarily used for
         alarms and alerts, publish-subscribe, which is typically
         used for sensor data, as well as peer-to-peer and
         peer-to-multipeer communications.<a href="#section-3.8-2" class="pilcrow">¶</a></p>
<p id="section-3.8-3">
         Additional considerations on duocast -- one sender, two receivers for redundancy --
         and its N-cast generalization are also provided.
         Those paradigms are frequently used in industrial automation, which is
         a major use case for IEEE Std 802.15.4 TSCH wireless networks with
         <span>[<a href="#ISA100.11a" class="xref">ISA100.11a</a>]</span> and <span>[<a href="#WirelessHART" class="xref">WirelessHART</a>]</span>, which
         provides a wireless access to <span>[<a href="#HART" class="xref">HART</a>]</span> applications and
         devices.<a href="#section-3.8-3" class="pilcrow">¶</a></p>
<p id="section-3.8-4">
         This document focuses on Communication Paradigms and Interaction
         Models for packet forwarding and TSCH resources (cells) management.
         Management mechanisms for the TSCH schedule at the link layer (one hop),
         network layer (multihop along a Track), and application layer
         (remote control) are discussed in <a href="#schd" class="xref">Section 4.4</a>.
         Link-layer frame forwarding interactions are discussed in <a href="#fwd" class="xref">Section 4.6</a>, and
         network-layer packet routing is addressed in <a href="#rtg" class="xref">Section 4.7</a>.<a href="#section-3.8-4" class="pilcrow">¶</a></p>
</section>
</section>
<div id="dd">
<section id="section-4">
      <h2 id="name-architecture-components">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-architecture-components" class="section-name selfRef">Architecture Components</a>
      </h2>
<div id="RPLvs6lo">
<section id="section-4.1">
        <h3 id="name-6lowpan-and-rpl">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-6lowpan-and-rpl" class="section-name selfRef">6LoWPAN (and RPL)</a>
        </h3>
<p id="section-4.1-1">A RPL DODAG is formed of a Root, a collection of routers, and leaves that
    are hosts. Hosts are nodes that do not forward packets that they did not generate.
    RPL-aware leaves will participate in RPL to advertise their own
    addresses, whereas RPL-unaware leaves depend on a connected RPL router to do
    so. RPL interacts with 6LoWPAN ND at multiple levels, in particular at the
    Root and in the RPL-unaware leaves.<a href="#section-4.1-1" class="pilcrow">¶</a></p>
<div id="leaf">
<section id="section-4.1.1">
          <h4 id="name-rpl-unaware-leaves-and-6low">
<a href="#section-4.1.1" class="section-number selfRef">4.1.1. </a><a href="#name-rpl-unaware-leaves-and-6low" class="section-name selfRef">RPL-Unaware Leaves and 6LoWPAN ND</a>
          </h4>
<p id="section-4.1.1-1">RPL needs a set of information to advertise
   a leaf node through a Destination Advertisement Object (DAO) message and establish reachability.<a href="#section-4.1.1-1" class="pilcrow">¶</a></p>
<p id="section-4.1.1-2"><span><a href="#RFC9010" class="xref">"Routing for RPL Leaves"</a> [<a href="#RFC9010" class="xref">RFC9010</a>]</span>
   details the basic interaction of 6LoWPAN ND and RPL and enables a plain 6LN
   that supports <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> to obtain return
   connectivity via the RPL network as a RPL-unaware leaf.
   The leaf indicates that it requires reachability services for the
   Registered Address from a Routing Registrar by setting an 'R' flag in the
   Extended Address Registration Option <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>, and it
   provides a TID that maps to the "Path Sequence" defined in <span><a href="https://www.rfc-editor.org/rfc/rfc6550#section-6.7.8" class="relref">Section 6.7.8</a> of [<a href="#RFC6550" class="xref">RFC6550</a>]</span>, and its operation is defined in <span><a href="https://www.rfc-editor.org/rfc/rfc6550#section-7.2" class="relref">Section 7.2</a> of [<a href="#RFC6550" class="xref">RFC6550</a>]</span>.<a href="#section-4.1.1-2" class="pilcrow">¶</a></p>
<p id="section-4.1.1-3"><span>[<a href="#RFC9010" class="xref">RFC9010</a>]</span> also enables the leaf to signal
   with the RPLInstanceID that it wants to participate by using the
   Opaque field of the EARO. On the backbone, the RPLInstanceID is
   expected to be mapped to an overlay that matches the RPL Instance, e.g.,
   a Virtual LAN (VLAN) or a virtual routing and forwarding (VRF) instance.<a href="#section-4.1.1-3" class="pilcrow">¶</a></p>
<p id="section-4.1.1-4">
    Though, at the time of this writing, the above specification enables a model
    where the separation is possible, this architecture recommends
    co-locating the functions of 6LBR and RPL Root.<a href="#section-4.1.1-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="rpllbr">
<section id="section-4.1.2">
          <h4 id="name-6lbr-and-rpl-root">
<a href="#section-4.1.2" class="section-number selfRef">4.1.2. </a><a href="#name-6lbr-and-rpl-root" class="section-name selfRef">6LBR and RPL Root</a>
          </h4>
<p id="section-4.1.2-1">
    With the 6LoWPAN ND <span>[<a href="#RFC6775" class="xref">RFC6775</a>]</span>, information on the 6LBR is
    disseminated via an Authoritative Border Router Option (ABRO) in RA messages.
    <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> extends <span>[<a href="#RFC6775" class="xref">RFC6775</a>]</span> to enable a
    registration for routing and proxy ND.
    The capability to support <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>
    is indicated in the 6LoWPAN Capability Indication Option (6CIO).
    The discovery and liveliness of the RPL Root are obtained through RPL
    <span>[<a href="#RFC6550" class="xref">RFC6550</a>]</span> itself.<a href="#section-4.1.2-1" class="pilcrow">¶</a></p>
<p id="section-4.1.2-2">
   When 6LoWPAN ND is coupled with RPL, the 6LBR and RPL Root functionalities
   are co-located in order that the address of the 6LBR is indicated by RPL
   DODAG Information Object (DIO) messages and to associate the ROVR from 
   the Extended Duplicate Address Request/Confirmation (EDAR/EDAC)
   exchange <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> with the state that is maintained by RPL.<a href="#section-4.1.2-2" class="pilcrow">¶</a></p>
<p id="section-4.1.2-3">
   <span><a href="https://www.rfc-editor.org/rfc/rfc9010#section-7" class="relref">Section 7</a> of [<a href="#RFC9010" class="xref">RFC9010</a>]</span> specifies how
   the DAO messages are used to reconfirm the registration, thus eliminating a
   duplication of functionality between DAO and EDAR/EDAC messages, as
   illustrated in  <a href="#figReg2" class="xref">Figure 6</a>.
   <span>[<a href="#RFC9010" class="xref">RFC9010</a>]</span> also provides the protocol
   elements that are needed when the 6LBR and RPL Root functionalities are not
   co-located.<a href="#section-4.1.2-3" class="pilcrow">¶</a></p>
<p id="section-4.1.2-4">
   Even though the Root of the RPL network is integrated with the 6LBR,
   it is logically separated from the Backbone Router (6BBR) that
   is used to connect the 6TiSCH LLN to the backbone. This way,
   the Root has all information from 6LoWPAN ND and RPL about the LLN
   devices attached to it.<a href="#section-4.1.2-4" class="pilcrow">¶</a></p>
<p id="section-4.1.2-5">
   This architecture also expects that the Root of the RPL network
   (proxy-)registers the 6TiSCH nodes on their behalf to the 6BBR,
   for whatever operation the 6BBR performs on the backbone, such
   as ND proxy or redistribution in a routing protocol.
   This relies on an extension of the 6LoWPAN ND registration described in
   <span>[<a href="#RFC8929" class="xref">RFC8929</a>]</span>.<a href="#section-4.1.2-5" class="pilcrow">¶</a></p>
<p id="section-4.1.2-6">
   This model supports the movement of a 6TiSCH device across the multi-link
   subnet and allows the proxy registration of 6TiSCH nodes deep into the
   6TiSCH LLN by the 6LBR / RPL Root.
   This is why in <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> the Registered Address is signaled
   in the Target Address field of the Neighbor Solicitation (NS) message as opposed to the IPv6 Source
   Address, which, in the case of a proxy registration, is that of the 6LBR /
   RPL Root itself.<a href="#section-4.1.2-6" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="join">
<section id="section-4.2">
        <h3 id="name-network-access-and-addressi">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-network-access-and-addressi" class="section-name selfRef">Network Access and Addressing</a>
        </h3>
<div id="rflo">
<section id="section-4.2.1">
          <h4 id="name-join-process">
<a href="#section-4.2.1" class="section-number selfRef">4.2.1. </a><a href="#name-join-process" class="section-name selfRef">Join Process</a>
          </h4>
<p id="section-4.2.1-1">
       A new device, called the pledge, undergoes the join protocol to become a node
       in a 6TiSCH network. This usually occurs only once when the device is
       first powered on.  The pledge communicates with the Join Registrar/Coordinator
       (JRC) of the network through a Join Proxy (JP), a radio neighbor of the pledge.<a href="#section-4.2.1-1" class="pilcrow">¶</a></p>
<p id="section-4.2.1-2">
       The JP is discovered though MAC-layer beacons. When multiple JPs from possibly 
       multiple networks are visible, using trial and error until an acceptable position 
       in the right network is obtained becomes inefficient.
       <span>[<a href="#RFC9032" class="xref">RFC9032</a>]</span> adds a new subtype in the Information Element that 
       was delegated to the IETF <span>[<a href="#RFC8137" class="xref">RFC8137</a>]</span> and provides visibility 
       into the network that can be joined and the willingness of the JP and the Root to be used by the pledge.<a href="#section-4.2.1-2" class="pilcrow">¶</a></p>
<p id="section-4.2.1-3">
       The join protocol provides the following functionality:<a href="#section-4.2.1-3" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4.2.1-4.1"> Mutual authentication<a href="#section-4.2.1-4.1" class="pilcrow">¶</a>
</li>
            <li class="normal" id="section-4.2.1-4.2"> Authorization<a href="#section-4.2.1-4.2" class="pilcrow">¶</a>
</li>
            <li class="normal" id="section-4.2.1-4.3"> Parameter distribution to the pledge over a secure channel<a href="#section-4.2.1-4.3" class="pilcrow">¶</a>
</li>
          </ul>
<p id="section-4.2.1-5">
        The Minimal Security Framework for 6TiSCH <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span>
        defines the minimal mechanisms required for this join process to occur in a secure
        manner. The specification defines the Constrained Join Protocol (CoJP), which is used
        to distribute the parameters to the pledge over a secure session established through
        OSCORE <span>[<a href="#RFC8613" class="xref">RFC8613</a>]</span> and which describes the secure configuration of the network
        stack. In the minimal setting with pre-shared keys (PSKs), CoJP allows the pledge to
        join after a single round-trip exchange with the JRC. The provisioning of the PSK to
        the pledge and the JRC needs to be done out of band, through a 'one-touch'
        bootstrapping process, which effectively enrolls the pledge into the domain managed by
        the JRC.<a href="#section-4.2.1-5" class="pilcrow">¶</a></p>
<p id="section-4.2.1-6">
        In certain use cases, the 'one-touch' bootstrapping is not feasible due to the
        operational constraints, and the enrollment of the pledge into the domain needs to occur
        in-band. This is handled through a 'zero-touch' extension of the Minimal Security Framework
        for 6TiSCH. The zero-touch extension <span>[<a href="#I-D.ietf-6tisch-dtsecurity-zerotouch-join" class="xref">ZEROTOUCH-JOIN</a>]</span> leverages
        the "<a href="#RFC8995" class="xref">Bootstrapping Remote Secure Key Infrastructure (BRSKI)</a>" <span>[<a href="#RFC8995" class="xref">RFC8995</a>]</span> 
        work to establish a shared secret between a pledge and the JRC without necessarily having
        them belong to a common (security) domain at join time. This happens through inter-domain
        communication occurring between the JRC of the network and the domain of the pledge,
        represented by a fourth entity, Manufacturer Authorized Signing Authority (MASA). Once
        the zero-touch exchange completes, the CoJP exchange defined in <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span>
        is carried over the secure session established between the pledge and the JRC.<a href="#section-4.2.1-6" class="pilcrow">¶</a></p>
<p id="section-4.2.1-7">
        <a href="#figJoin" class="xref">Figure 4</a> depicts the join process and where a Link-Local
        Address (LLA) is used, versus a Global Unicast Address (GUA).<a href="#section-4.2.1-7" class="pilcrow">¶</a></p>
<span id="name-join-process-in-a-multi-lin"></span><div id="figJoin">
<figure id="figure-4">
            <div class="artwork art-text alignLeft" id="section-4.2.1-8.1">
<pre>
6LoWPAN Node       6LR           6LBR      Join Registrar     MASA
 (pledge)       (Join Proxy)     (Root)    /Coordinator (JRC)
  |               |               |              |              |
  |  6LoWPAN ND   |6LoWPAN ND+RPL | IPv6 network |IPv6 network  |
  |   LLN link    |Route-Over mesh|(the Internet)|(the Internet)|
  |               |               |              |              |
  |   Layer 2     |               |              |              |
  |Enhanced Beacon|               |              |              |
  |&lt;--------------|               |              |              |
  |               |               |              |              |
  |    NS (EARO)  |               |              |              |
  | (for the LLA) |               |              |              |
  |--------------&gt;|               |              |              |
  |    NA (EARO)  |               |              |              |
  |&lt;--------------|               |              |              |
  |               |               |              |              |
  |  (Zero-touch  |               |              |              |
  |   handshake)  |     (Zero-touch handshake)   | (Zero-touch  |
  |   using LLA   |           using GUA          |  handshake)  |
  |&lt;-------------&gt;|&lt;----------------------------&gt;|&lt;------------&gt;|
  |               |               |              |              |
  | CoJP Join Req |               |              |              | \
  |  using LLA    |               |              |              | |
  |--------------&gt;|               |              |              | |
  |               |       CoJP Join Request      |              | |
  |               |           using GUA          |              | |
  |               |-----------------------------&gt;|              | | C
  |               |               |              |              | | o
  |               |       CoJP Join Response     |              | | J
  |               |           using GUA          |              | | P
  |               |&lt;-----------------------------|              | |
  |CoJP Join Resp |               |              |              | |
  |  using LLA    |               |              |              | |
  |&lt;--------------|               |              |              | /
  |               |               |              |              |
</pre>
</div>
<figcaption><a href="#figure-4" class="selfRef">Figure 4</a>:
<a href="#name-join-process-in-a-multi-lin" class="selfRef">Join Process in a Multi-Link Subnet. Parentheses () denote optional exchanges.</a>
            </figcaption></figure>
</div>
</section>
</div>
<div id="rreg">
<section id="section-4.2.2">
          <h4 id="name-registration">
<a href="#section-4.2.2" class="section-number selfRef">4.2.2. </a><a href="#name-registration" class="section-name selfRef">Registration</a>
          </h4>
<p id="section-4.2.2-1">
         Once the pledge successfully completes the CoJP exchange and becomes
         a network node, it obtains the network prefix from neighboring routers
         and registers its IPv6 addresses.
         As detailed in <a href="#RPLvs6lo" class="xref">Section 4.1</a>, the combined 6LoWPAN ND 6LBR
         and Root of the RPL network learn information such as an identifier (device EUI-64 <span>[<a href="#RFC6775" class="xref">RFC6775</a>]</span> or a ROVR <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span> 
         (from 6LoWPAN ND)) and the updated Sequence Number (from RPL), and
         perform 6LoWPAN ND proxy registration to the 6BBR on behalf of the LLN
         nodes.<a href="#section-4.2.2-1" class="pilcrow">¶</a></p>
<p id="section-4.2.2-2">
         <a href="#figReg" class="xref">Figure 5</a> illustrates the initial IPv6 signaling that
         enables a 6LN to form a global address and register it to a 6LBR
         using 6LoWPAN ND <span>[<a href="#RFC8505" class="xref">RFC8505</a>]</span>. It is then carried
         over RPL to the RPL Root and then to the 6BBR. This flow happens
         just once when the address is created and first registered.<a href="#section-4.2.2-2" class="pilcrow">¶</a></p>
<span id="name-initial-registration-flow-o"></span><div id="figReg">
<figure id="figure-5">
            <div class="artwork art-text alignLeft" id="section-4.2.2-3.1">
<pre>
    6LoWPAN Node        6LR             6LBR            6BBR
     (RPL leaf)       (router)         (Root)
         |               |               |               |
         |  6LoWPAN ND   |6LoWPAN ND+RPL | 6LoWPAN ND    | IPv6 ND
         |   LLN link    |Route-Over mesh|Ethernet/serial| Backbone
         |               |               |               |
         |  RS (mcast)   |               |               |
         |--------------&gt;|               |               |
         |-----------&gt;   |               |               |
         |------------------&gt;            |               |
         |  RA (unicast) |               |               |
         |&lt;--------------|               |               |
         |               |               |               |
         |  NS(EARO)     |               |               |
         |--------------&gt;|               |               |
         | 6LoWPAN ND    | Extended DAR  |               |
         |               |--------------&gt;|               |
         |               |               |  NS(EARO)     |
         |               |               |--------------&gt;|
         |               |               |               | NS-DAD
         |               |               |               |------&gt;
         |               |               |               | (EARO)
         |               |               |               |
         |               |               |  NA(EARO)     |&lt;timeout&gt;
         |               |               |&lt;--------------|
         |               | Extended DAC  |               |
         |               |&lt;--------------|               |
         |  NA(EARO)     |               |               |
         |&lt;--------------|               |               |
         |               |               |               |
</pre>
</div>
<figcaption><a href="#figure-5" class="selfRef">Figure 5</a>:
<a href="#name-initial-registration-flow-o" class="selfRef">Initial Registration Flow over Multi-Link Subnet</a>
            </figcaption></figure>
</div>
<p id="section-4.2.2-4">
         <a href="#figReg2" class="xref">Figure 6</a> illustrates the repeating IPv6 signaling that
         enables a 6LN to keep a global address alive and registered with its 6LBR
         using 6LoWPAN ND to the 6LR, RPL to the RPL Root, and then 6LoWPAN ND
         again
         to the 6BBR, which avoids repeating the Extended DAR/DAC flow across
         the network when RPL can suffice as a keep-alive mechanism.<a href="#section-4.2.2-4" class="pilcrow">¶</a></p>
<span id="name-next-registration-flow-over"></span><div id="figReg2">
<figure id="figure-6">
            <div class="artwork art-text alignLeft" id="section-4.2.2-5.1">
<pre>
 6LoWPAN Node        6LR             6LBR            6BBR
  (RPL leaf)       (router)         (Root)
      |               |               |               |
      |  6LoWPAN ND   |6LoWPAN ND+RPL | 6LoWPAN ND    | IPv6 ND
      |   LLN link    |Route-Over mesh| ant IPv6 link | Backbone
      |               |               |
      |               |               |               |
      |  NS(EARO)     |               |               |
      |--------------&gt;|               |               |
      |  NA(EARO)     |               |               |
      |&lt;--------------|               |               |
      |               | DAO           |               |
      |               |--------------&gt;|               |
      |               | DAO-ACK       |               |
      |               |&lt;--------------|               |
      |               |               |  NS(EARO)     |
      |               |               |--------------&gt;|
      |               |               |  NA(EARO)     |
      |               |               |&lt;--------------|
      |               |               |               |
      |               |               |               |
</pre>
</div>
<figcaption><a href="#figure-6" class="selfRef">Figure 6</a>:
<a href="#name-next-registration-flow-over" class="selfRef">Next Registration Flow over Multi-Link Subnet</a>
            </figcaption></figure>
</div>
<p id="section-4.2.2-6">As the network builds up, a node should start as a
   leaf to join the RPL network and may later turn into both a RPL-capable
   router and a 6LR, so as to accept leaf nodes recursively joining the network.<a href="#section-4.2.2-6" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="s6Pprot">
<section id="section-4.3">
        <h3 id="name-tsch-and-6top">
<a href="#section-4.3" class="section-number selfRef">4.3. </a><a href="#name-tsch-and-6top" class="section-name selfRef">TSCH and 6top</a>
        </h3>
<section id="section-4.3.1">
          <h4 id="name-6top">
<a href="#section-4.3.1" class="section-number selfRef">4.3.1. </a><a href="#name-6top" class="section-name selfRef">6top</a>
          </h4>
<p id="section-4.3.1-1">
            6TiSCH expects a high degree of scalability together with a
            distributed routing functionality based on RPL. To achieve this
            goal, the spectrum must be allocated in a way that allows for
            spatial reuse between zones that will not interfere with one
            another.
            In a large and spatially distributed network, a 6TiSCH node is
            often in a good position to determine usage of the spectrum in its
            vicinity.<a href="#section-4.3.1-1" class="pilcrow">¶</a></p>
<p id="section-4.3.1-2">
            With 6TiSCH, the abstraction of an IPv6 link is implemented as a
            pair of bundles of cells, one in each direction. IP links are only
            enabled between RPL parents and children. The 6TiSCH
            operation is optimal when the size of a bundle minimizes both
            the energy wasted in idle listening and the packet drops due to
            congestion loss, while packets are forwarded within
            an acceptable latency.<a href="#section-4.3.1-2" class="pilcrow">¶</a></p>
<p id="section-4.3.1-3">
            Use cases for distributed routing are often associated with a
            statistical distribution of best-effort traffic with variable needs
            for bandwidth on each individual link. The 6TiSCH operation can
            remain optimal if RPL parents can adjust, dynamically and with enough 
            reactivity to match the variations of best-effort traffic,
            the amount of bandwidth that is used to communicate between themselves 
            and their children, in both directions.
            In turn, the agility to fulfill the needs for additional cells
            improves when the number of interactions with other devices and
            the protocol latencies are minimized.<a href="#section-4.3.1-3" class="pilcrow">¶</a></p>
<p id="section-4.3.1-4">
            6top is a logical link control sitting between the IP layer and the
            TSCH MAC layer, which provides the link abstraction that is required
            for IP operations. The 6top Protocol, 6P, which is specified in
            <span>[<a href="#RFC8480" class="xref">RFC8480</a>]</span>, is one of the services provided by 6top.
            In particular, the 6top services are available over a management
            API that enables an external management entity to schedule cells
            and slotframes, and allows the addition of complementary
            functionality, for instance, a Scheduling Function
            that manages a dynamic schedule based on
            observed resource usage as discussed in <a href="#dynsched" class="xref">Section 4.4.2</a>.
            For this purpose, the 6TiSCH architecture differentiates "soft"
            cells and "hard" cells.<a href="#section-4.3.1-4" class="pilcrow">¶</a></p>
<section id="section-4.3.1.1">
            <h5 id="name-hard-cells">
<a href="#section-4.3.1.1" class="section-number selfRef">4.3.1.1. </a><a href="#name-hard-cells" class="section-name selfRef">Hard Cells</a>
            </h5>
<p id="section-4.3.1.1-1">
            "Hard" cells are cells that
            are owned and managed by a separate scheduling entity (e.g., a PCE)
            that specifies the slotOffset/channelOffset of the cells to be
            added/moved/deleted, in which case 6top can only act as instructed
            and may not move hard cells in the TSCH schedule on its own.<a href="#section-4.3.1.1-1" class="pilcrow">¶</a></p>
</section>
<section id="section-4.3.1.2">
            <h5 id="name-soft-cells">
<a href="#section-4.3.1.2" class="section-number selfRef">4.3.1.2. </a><a href="#name-soft-cells" class="section-name selfRef">Soft Cells</a>
            </h5>
<p id="section-4.3.1.2-1">
            In contrast, "soft" cells are cells that 6top can manage locally.
            6top contains a monitoring process that monitors the performance of
            cells and that can add and remove soft cells in the TSCH schedule to adapt
            to the traffic needs, or move one when it performs poorly.
            To reserve a soft cell, the higher layer does not indicate the exact
            slotOffset/channelOffset of the cell to add, but rather the resulting
            bandwidth and QoS requirements. When the monitoring process triggers
            a cell reallocation, the two neighbor devices communicating over this
            cell negotiate its new position in the TSCH schedule.<a href="#section-4.3.1.2-1" class="pilcrow">¶</a></p>
</section>
</section>
<div id="missf">
<section id="section-4.3.2">
          <h4 id="name-scheduling-functions-and-th">
<a href="#section-4.3.2" class="section-number selfRef">4.3.2. </a><a href="#name-scheduling-functions-and-th" class="section-name selfRef">Scheduling Functions and the 6top Protocol</a>
          </h4>
<p id="section-4.3.2-1">In the case of soft cells, the cell management entity that controls the
   dynamic attribution of cells to adapt to the dynamics of variable rate flows
   is called a Scheduling Function (SF).<a href="#section-4.3.2-1" class="pilcrow">¶</a></p>
<p id="section-4.3.2-2">
   There may be multiple SFs that react more or less aggressively to the
   dynamics of the network.<a href="#section-4.3.2-2" class="pilcrow">¶</a></p>
<p id="section-4.3.2-3">
   An SF may be seen as divided between an upper bandwidth-adaptation logic
   that is unaware of the particular technology used to obtain and
   release bandwidth and an underlying service that maps those needs in the
   actual technology. In the case
   of TSCH using the 6top Protocol as illustrated in <a href="#fig6P" class="xref">Figure 7</a>,
   this means mapping the bandwidth onto cells.<a href="#section-4.3.2-3" class="pilcrow">¶</a></p>
<span id="name-sf-6p-stack-in-6top"></span><div id="fig6P">
<figure id="figure-7">
            <div class="artwork art-text alignLeft" id="section-4.3.2-4.1">
<pre>
 +------------------------+          +------------------------+
 |  Scheduling Function   |          |  Scheduling Function   |
 |  Bandwidth adaptation  |          |  Bandwidth adaptation  |
 +------------------------+          +------------------------+
 |  Scheduling Function   |          |  Scheduling Function   |
 | TSCH mapping to cells  |          | TSCH mapping to cells  |
 +------------------------+          +------------------------+
 | 6top cells negotiation | &lt;- 6P -&gt; | 6top cells negotiation |
 +------------------------+          +------------------------+
         Device A                             Device B
</pre>
</div>
<figcaption><a href="#figure-7" class="selfRef">Figure 7</a>:
<a href="#name-sf-6p-stack-in-6top" class="selfRef">SF/6P Stack in 6top</a>
            </figcaption></figure>
</div>
<p id="section-4.3.2-5">
    The SF relies on 6top services that implement the
    <span><a href="#RFC8480" class="xref">6top Protocol (6P)</a> [<a href="#RFC8480" class="xref">RFC8480</a>]</span>
    to negotiate the precise cells that will be allocated or freed based on the
    schedule of the peer. For instance, it may be that a peer wants to use a
    particular timeslot that is free in its schedule, but that timeslot is
    already in use by the other peer to communicate with a third party on a
    different cell. 6P enables the peers to find an agreement in a
    transactional manner that ensures the final consistency of the nodes' state.<a href="#section-4.3.2-5" class="pilcrow">¶</a></p>
<p id="section-4.3.2-6">
    <span><a href="#RFC9033" class="xref">MSF</a> [<a href="#RFC9033" class="xref">RFC9033</a>]</span> is one of the possible
    Scheduling Functions. MSF uses the rendezvous slot from
    <span>[<a href="#RFC8180" class="xref">RFC8180</a>]</span> for network discovery, neighbor discovery, and any
    other broadcast.<a href="#section-4.3.2-6" class="pilcrow">¶</a></p>
<p id="section-4.3.2-7">
    For basic unicast communication with any neighbor, each node uses a receive
    cell at a well-known slotOffset/channelOffset, which is derived from a hash of their
    own MAC address.
    Nodes can reach any neighbor by installing a transmit (shared) cell with
    slotOffset/channelOffset derived from the neighbor's MAC address.<a href="#section-4.3.2-7" class="pilcrow">¶</a></p>
<p id="section-4.3.2-8">
    For child-parent links, MSF continuously monitors the load between parents
    and children. It then uses 6P to install or remove unicast cells whenever the
    current schedule appears to be under-provisioned or over-provisioned.<a href="#section-4.3.2-8" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-4.3.3">
          <h4 id="name-6top-and-rpl-objective-func">
<a href="#section-4.3.3" class="section-number selfRef">4.3.3. </a><a href="#name-6top-and-rpl-objective-func" class="section-name selfRef">6top and RPL Objective Function Operations</a>
          </h4>
<p id="section-4.3.3-1">
            An implementation of a <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span> Objective Function
            (OF), such as the <span><a href="#RFC6552" class="xref">RPL Objective Function Zero (OF0)</a> [<a href="#RFC6552" class="xref">RFC6552</a>]</span> that is used in the <span><a href="#RFC8180" class="xref">Minimal
            6TiSCH Configuration</a> [<a href="#RFC8180" class="xref">RFC8180</a>]</span> to support RPL over a static schedule, may
            leverage for its internal computation the information maintained by 6top.<a href="#section-4.3.3-1" class="pilcrow">¶</a></p>
<p id="section-4.3.3-2">An OF may require metrics about reachability, such as the Expected
            Transmission Count (ETX) metric <span>[<a href="#RFC6551" class="xref">RFC6551</a>]</span>.
            6top creates and maintains an abstract neighbor table,
            and this state may be leveraged to feed an OF and/or store OF information
            as well. A neighbor table entry may contain a set of statistics with
            respect to that specific neighbor.<a href="#section-4.3.3-2" class="pilcrow">¶</a></p>
<p id="section-4.3.3-3">
            The neighbor information may include the time when the last
            packet has been received from that neighbor, a set of cell quality
            metrics, e.g., received signal strength indication (RSSI) or link
            quality indicator (LQI), the number of packets sent to the
            neighbor, or the number of packets received from it. This
            information can be made available through 6top management APIs
            and used, for instance, to compute a Rank Increment that will
            determine the selection of the preferred parent.<a href="#section-4.3.3-3" class="pilcrow">¶</a></p>
<p id="section-4.3.3-4">
            6top provides statistics about the underlying layer so the OF can be tuned
            to the nature of the TSCH MAC layer. 6top also enables the RPL OF to
            influence the MAC behavior, for instance, by configuring the periodicity of
            IEEE Std 802.15.4 Extended Beacons (EBs). By augmenting the EB periodicity, it is
            possible to change the network dynamics so as to improve the support of
            devices that may change their point of attachment in the 6TiSCH network.<a href="#section-4.3.3-4" class="pilcrow">¶</a></p>
<p id="section-4.3.3-5">
            Some RPL control messages, such as the DODAG Information Object (DIO), are
            ICMPv6 messages that are broadcast to all neighbor nodes.
            With 6TiSCH, the broadcast channel requirement is addressed by 6top
            by configuring TSCH to provide a broadcast channel,
            as opposed to, for instance, piggybacking the DIO messages in
            Layer 2 Enhanced Beacons (EBs), which would produce undue timer
            coupling among layers and packet size issues, and could conflict with
            the policy of production networks where EBs are mostly eliminated
            to conserve energy.<a href="#section-4.3.3-5" class="pilcrow">¶</a></p>
</section>
<div id="sync">
<section id="section-4.3.4">
          <h4 id="name-network-synchronization">
<a href="#section-4.3.4" class="section-number selfRef">4.3.4. </a><a href="#name-network-synchronization" class="section-name selfRef">Network Synchronization</a>
          </h4>
<p id="section-4.3.4-1">
            Nodes in a TSCH network must be time synchronized.
            A node keeps synchronized to its time source neighbor
            through a combination of frame-based and acknowledgment-based synchronization.
            To maximize battery life and network throughput, it is advisable that RPL ICMP discovery
            and maintenance traffic (governed by the Trickle timer) be somehow coordinated with the
            transmission of time synchronization packets (especially with Enhanced Beacons).<a href="#section-4.3.4-1" class="pilcrow">¶</a></p>
<p id="section-4.3.4-2">
            This could be achieved through an interaction of the 6top sublayer and the RPL Objective Function,
            or could be controlled by a management entity.<a href="#section-4.3.4-2" class="pilcrow">¶</a></p>
<p id="section-4.3.4-3">
            Time distribution requires a loop-free structure. Nodes caught in a synchronization loop will rapidly
            desynchronize from the network and become isolated. 6TiSCH uses a RPL DAG with a dedicated global Instance for the purpose of time synchronization.
            That Instance is referred to as the Time Synchronization Global Instance (TSGI).
            The TSGI can be operated in either of the three modes that are detailed
            in Section <a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.1.3" class="relref">3.1.3</a>
             of  <span><a href="#RFC6550" class="xref">RPL</a> [<a href="#RFC6550" class="xref">RFC6550</a>]</span>, "Instances, DODAGs, and DODAG Versions".
            Multiple uncoordinated DODAGs with independent Roots may be used if all the Roots
            share a common time source such as the Global Positioning System (GPS).<a href="#section-4.3.4-3" class="pilcrow">¶</a></p>
<p id="section-4.3.4-4">
            In the absence
            of a common time source, the TSGI should form a single DODAG with a virtual Root.
            A backbone network is then used to synchronize and coordinate RPL operations between
            the Backbone Routers that act as sinks for the LLN.
            Optionally, RPL's periodic operations may be used to
            transport the network synchronization. This may
            mean that 6top would need to trigger (override) the Trickle timer if
            no other traffic has occurred for such a time that nodes may get out
            of synchronization.<a href="#section-4.3.4-4" class="pilcrow">¶</a></p>
<p id="section-4.3.4-5">
            A node that has not joined the TSGI advertises a MAC-level Join Priority
            of 0xFF to notify its neighbors that is not capable of serving as time parent.
            A node that has joined the TSGI advertises a MAC-level Join Priority set to
            its DAGRank() in that Instance, where DAGRank() is the operation specified in
            Section <a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.5.1" class="relref">3.5.1</a>  
            of <span>[<a href="#RFC6550" class="xref">RFC6550</a>]</span>, "Rank Comparison".<a href="#section-4.3.4-5" class="pilcrow">¶</a></p>
<p id="section-4.3.4-6">

            The provisioning of a RPL Root is out of scope for both RPL and this 
            architecture, whereas RPL enables the propagation of configuration information 
            down the DODAG. This applies to the TSGI as well; a
            Root is configured, or obtains by unspecified means, the knowledge
            of the RPLInstanceID for the TSGI. The Root advertises its DagRank
            in the TSGI, which must be less than 0xFF, as its Join Priority in
            its IEEE Std 802.15.4 EBs.<a href="#section-4.3.4-6" class="pilcrow">¶</a></p>
<p id="section-4.3.4-7">
            A node that reads a Join Priority of less than 0xFF should join the
            neighbor with the lesser Join Priority and use it as time parent. If
            the node is configured to serve as time parent, then the node should
            join the TSGI, obtain a Rank in that Instance, and start advertising
            its own DagRank in the TSGI as its Join Priority in its EBs.<a href="#section-4.3.4-7" class="pilcrow">¶</a></p>
</section>
</div>
<div id="slotframes">
<section id="section-4.3.5">
          <h4 id="name-slotframes-and-cdu-matrix">
<a href="#section-4.3.5" class="section-number selfRef">4.3.5. </a><a href="#name-slotframes-and-cdu-matrix" class="section-name selfRef">Slotframes and CDU Matrix</a>
          </h4>
<p id="section-4.3.5-1">
         6TiSCH enables IPv6 best-effort (stochastic) transmissions over a MAC
         layer that is also capable of scheduled (deterministic) transmissions.
         A window of time is defined
         around the scheduled transmission where the medium must, as much as
         practically feasible, be free of contending energy to ensure that the
         medium is free of contending packets when the time comes for a scheduled
         transmission.
         One simple way to obtain such a window is to format time and
         frequencies in cells of transmission of equal duration. This is the
         method that is adopted in IEEE Std 802.15.4 TSCH as well as the Long
         Term Evolution (LTE) of cellular networks.<a href="#section-4.3.5-1" class="pilcrow">¶</a></p>
<p id="section-4.3.5-2">
         The 6TiSCH architecture defines a global concept that is called a
         Channel Distribution and Usage (CDU) matrix to describe that formatting
         of time and frequencies.<a href="#section-4.3.5-2" class="pilcrow">¶</a></p>
<p id="section-4.3.5-3">
         A CDU matrix is defined centrally
         as part of the network definition. It is a matrix of cells with a
         height equal to the number of available channels (indexed by
         channelOffsets) and a width (in timeslots) that is the period of the
         network scheduling operation (indexed by slotOffsets) for that CDU
         matrix. There are different models for scheduling the usage of the
         cells, which place the responsibility of avoiding collisions either on
         a central controller or on the devices themselves, at an extra cost in
         terms of energy to scan for free cells (more in <a href="#schd" class="xref">Section 4.4</a>).<a href="#section-4.3.5-3" class="pilcrow">¶</a></p>
<p id="section-4.3.5-4">
         The size of a cell is a timeslot duration, and
         values  of 10 to 15 milliseconds are typical in 802.15.4 TSCH to
         accommodate for the transmission of a frame and an ack, including the
         security validation on the receive side, which may take up to a few
         milliseconds on some device architecture.<a href="#section-4.3.5-4" class="pilcrow">¶</a></p>
<p id="section-4.3.5-5">
         A CDU matrix iterates over a well-known channel rotation
         called the hopping sequence.
         In a given network, there might be multiple CDU matrices that operate
         with different widths, so they have different durations and represent
         different periodic operations.
         It is recommended that all CDU matrices in a 6TiSCH domain operate with
         the same cell duration and are aligned so as to reduce the
         chances of interferences from the Slotted ALOHA operations.
         The knowledge of the CDU matrices is shared
         between all the nodes and used in particular to define slotframes.<a href="#section-4.3.5-5" class="pilcrow">¶</a></p>
<p id="section-4.3.5-6">
          A slotframe is a MAC-level abstraction that is common to all nodes and
          contains a series of timeslots of equal length and precedence.
          It is characterized by a slotframe_ID and a slotframe_size.
          A slotframe aligns to a CDU matrix for its parameters, such as number
          and duration of timeslots.<a href="#section-4.3.5-6" class="pilcrow">¶</a></p>
<p id="section-4.3.5-7">
          Multiple slotframes can coexist in a node schedule, i.e., a node can
          have multiple activities scheduled in different slotframes.
          A slotframe is associated with a priority that may be related to
          the precedence of different 6TiSCH topologies. The slotframes may be
          aligned to different CDU matrices and thus have different widths.
          There is typically one slotframe for scheduled traffic that has the
          highest precedence and one or more slotframe(s) for RPL traffic.
          The timeslots in the slotframe are indexed by the slotOffset;
          the first cell is at slotOffset 0.<a href="#section-4.3.5-7" class="pilcrow">¶</a></p>
<p id="section-4.3.5-8">
          When a packet is received from a higher layer for transmission,
          6top inserts that packet in the outgoing queue
          that matches the packet best (Differentiated Services
          <span>[<a href="#RFC2474" class="xref">RFC2474</a>]</span> can therefore be used).
          At each scheduled transmit slot, 6top looks for the frame
          in all the outgoing queues that best matches the cells.
          If a frame is found, it is given to the TSCH MAC for transmission.<a href="#section-4.3.5-8" class="pilcrow">¶</a></p>
</section>
</div>
<div id="DistRsvTS">
<section id="section-4.3.6">
          <h4 id="name-distributing-the-reservatio">
<a href="#section-4.3.6" class="section-number selfRef">4.3.6. </a><a href="#name-distributing-the-reservatio" class="section-name selfRef">Distributing the Reservation of Cells</a>
          </h4>
<p id="section-4.3.6-1">
            The 6TiSCH architecture introduces the concept of chunks
            (<a href="#sixTTerminology" class="xref">Section 2.1</a>) to distribute the allocation of
            the spectrum for a whole group of cells at a time.
            The CDU matrix is formatted into a set of chunks, possibly as
            illustrated in <a href="#fig10" class="xref">Figure 8</a>, each of the chunks
            identified uniquely by a chunk-ID. The knowledge of this
            formatting is shared between all the nodes in a 6TiSCH network.
            It could be conveyed during the join process, codified into a profile document, 
            or obtained using some other mechanism. This is as opposed
            to Static Scheduling, which refers to the preprogrammed mechanism 
            specified in <span>[<a href="#RFC8180" class="xref">RFC8180</a>]</span> and which existed before the
            distribution of the chunk formatting.<a href="#section-4.3.6-1" class="pilcrow">¶</a></p>
<span id="name-cdu-matrix-partitioning-in-"></span><div id="fig10">
<figure id="figure-8">
            <div class="artwork art-text alignCenter" id="section-4.3.6-2.1">
<pre>
             +-----+-----+-----+-----+-----+-----+-----+     +-----+
chan.Off. 0  |chnkA|chnkP|chnk7|chnkO|chnk2|chnkK|chnk1| ... |chnkZ|
             +-----+-----+-----+-----+-----+-----+-----+     +-----+
chan.Off. 1  |chnkB|chnkQ|chnkA|chnkP|chnk3|chnkL|chnk2| ... |chnk1|
             +-----+-----+-----+-----+-----+-----+-----+     +-----+
               ...
             +-----+-----+-----+-----+-----+-----+-----+     +-----+
chan.Off. 15 |chnkO|chnk6|chnkN|chnk1|chnkJ|chnkZ|chnkI| ... |chnkG|
             +-----+-----+-----+-----+-----+-----+-----+     +-----+
                0     1     2     3     4     5     6          M
</pre>
</div>
<figcaption><a href="#figure-8" class="selfRef">Figure 8</a>:
<a href="#name-cdu-matrix-partitioning-in-" class="selfRef">CDU Matrix Partitioning in Chunks</a>
            </figcaption></figure>
</div>
<p id="section-4.3.6-3">
            The 6TiSCH architecture envisions a protocol that enables chunk
            ownership appropriation whereby a RPL parent
            discovers a chunk that is not used in its interference domain,
            claims the chunk, and then defends it in case another RPL
            parent would attempt to appropriate it while it is in use.
            The chunk is the basic unit of ownership that is used in that process.<a href="#section-4.3.6-3" class="pilcrow">¶</a></p>
<p id="section-4.3.6-4">
            As a result of the process of chunk ownership appropriation, the RPL
            parent has exclusive authority to decide which cell in the
            appropriated chunk can be used by which node in its interference
            domain. In other words, it is implicitly delegated the right to
            manage the portion of the CDU matrix that is represented by the
            chunk.<a href="#section-4.3.6-4" class="pilcrow">¶</a></p>
<p id="section-4.3.6-5">
            Initially, those cells are added to the heap of free cells, then
            dynamically placed into existing bundles, into new bundles, or
            allocated opportunistically for one transmission.<a href="#section-4.3.6-5" class="pilcrow">¶</a></p>
<p id="section-4.3.6-6">
            Note that a PCE is expected to have precedence in the
            allocation, so that a RPL parent would only be able to obtain
            portions that are not in use by the PCE.<a href="#section-4.3.6-6" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="schd">
<section id="section-4.4">
        <h3 id="name-schedule-management-mechani">
<a href="#section-4.4" class="section-number selfRef">4.4. </a><a href="#name-schedule-management-mechani" class="section-name selfRef">Schedule Management Mechanisms</a>
        </h3>
<p id="section-4.4-1">
         6TiSCH uses four paradigms to manage the TSCH schedule of the LLN nodes: Static Scheduling,
         Neighbor-to-Neighbor Scheduling, Remote Monitoring and Scheduling Management, and Hop-by-Hop Scheduling.
         Multiple mechanisms are defined that implement the associated Interaction Models,
         and they can be combined and used in the same LLN.
         Which mechanism(s) to use depends on application requirements.<a href="#section-4.4-1" class="pilcrow">¶</a></p>
<div id="mini">
<section id="section-4.4.1">
          <h4 id="name-static-scheduling">
<a href="#section-4.4.1" class="section-number selfRef">4.4.1. </a><a href="#name-static-scheduling" class="section-name selfRef">Static Scheduling</a>
          </h4>
<p id="section-4.4.1-1">
            In the simplest instantiation of a 6TiSCH network, a common fixed
            schedule may be shared by all nodes in the network. Cells are shared,
            and nodes contend for slot access in a Slotted ALOHA manner.<a href="#section-4.4.1-1" class="pilcrow">¶</a></p>
<p id="section-4.4.1-2">
            A static TSCH schedule can be used to bootstrap a network, as an
            initial phase during implementation or as a fall-back mechanism in
            case of network malfunction.
            This schedule is preestablished, for instance, decided by a network
            administrator based on operational needs. It can be preconfigured
            into the nodes, or, more commonly, learned by a node when joining
            the network using standard IEEE Std 802.15.4 Information Elements (IE).
            Regardless, the schedule remains unchanged
            after the node has joined a network.
            RPL is used on the resulting network. This "minimal" scheduling
            mechanism that implements this paradigm is detailed in
            <span>[<a href="#RFC8180" class="xref">RFC8180</a>]</span>.<a href="#section-4.4.1-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="dynsched">
<section id="section-4.4.2">
          <h4 id="name-neighbor-to-neighbor-schedu">
<a href="#section-4.4.2" class="section-number selfRef">4.4.2. </a><a href="#name-neighbor-to-neighbor-schedu" class="section-name selfRef">Neighbor-to-Neighbor Scheduling</a>
          </h4>
<p id="section-4.4.2-1">
            In the simplest instantiation of a 6TiSCH network described in
            <a href="#mini" class="xref">Section 4.4.1</a>, nodes may expect a packet at any cell in
            the schedule and will waste energy idle listening. In a more
            complex instantiation of a 6TiSCH network, a matching portion of the
            schedule is established between peers to reflect the observed amount
            of transmissions between those nodes. The aggregation of the cells
            between a node and a peer forms a bundle that the 6top sublayer uses to
            implement the abstraction of a link for IP. The bandwidth on that
            link is proportional to the number of cells in the bundle.<a href="#section-4.4.2-1" class="pilcrow">¶</a></p>
<p id="section-4.4.2-2">
            If the size of a bundle is configured to fit an average amount of
            bandwidth, peak traffic is dropped. If the size is
            configured to allow for peak emissions, energy is wasted
            idle listening.<a href="#section-4.4.2-2" class="pilcrow">¶</a></p>
<p id="section-4.4.2-3">
            As discussed in more detail in <a href="#s6Pprot" class="xref">Section 4.3</a>, the
            <span><a href="#RFC8480" class="xref">6top Protocol</a> [<a href="#RFC8480" class="xref">RFC8480</a>]</span>
            specifies the exchanges between neighbor nodes to reserve soft cells
            to transmit to one another, possibly under the control of a
            Scheduling Function (SF). Because this reservation is done without
            global knowledge of the schedule of the other nodes in the LLN, scheduling
            collisions are possible.<a href="#section-4.4.2-3" class="pilcrow">¶</a></p>
<p id="section-4.4.2-4">
            And as discussed in <a href="#missf" class="xref">Section 4.3.2</a>,
            an optional SF is used to
            monitor bandwidth usage and to perform requests for dynamic allocation
            by the 6top sublayer.
            The SF component is not part of the 6top sublayer. It may be
            co-located on the same device or may be partially or fully offloaded
            to an external system. The <span><a href="#RFC9033" class="xref">"6TiSCH Minimal Scheduling Function (MSF)"</a> [<a href="#RFC9033" class="xref">RFC9033</a>]</span> provides a simple
            SF that can be used by default by devices that
            support dynamic scheduling of soft cells.<a href="#section-4.4.2-4" class="pilcrow">¶</a></p>
<p id="section-4.4.2-5">
            Monitoring and relocation is done in the 6top sublayer. For the upper
            layer, the connection between two neighbor nodes appears as a number
            of cells.
            Depending on traffic requirements, the upper layer can request 6top
            to add or delete a number of cells scheduled to a particular
            neighbor, without being responsible for choosing the exact
            slotOffset/channelOffset of those cells.<a href="#section-4.4.2-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="topint">
<section id="section-4.4.3">
          <h4 id="name-remote-monitoring-and-sched">
<a href="#section-4.4.3" class="section-number selfRef">4.4.3. </a><a href="#name-remote-monitoring-and-sched" class="section-name selfRef">Remote Monitoring and Schedule Management</a>
          </h4>
<p id="section-4.4.3-1">
          Remote Monitoring and Schedule Management refers to a DetNet/SDN model
          whereby an NME and a scheduling entity, associated with a PCE, reside
          in a central controller and interact with the 6top sublayer to control
          IPv6 links and Tracks (<a href="#ontrk" class="xref">Section 4.5</a>) in a 6TiSCH network.
          The composite centralized controller can assign physical resources
          (e.g., buffers and hard cells) to a particular Track to optimize the
          reliability within a bounded latency for a well-specified flow.<a href="#section-4.4.3-1" class="pilcrow">¶</a></p>
<p id="section-4.4.3-2">
         The work in the 6TiSCH Working Group focused on nondeterministic traffic and
         did not provide the generic data model necessary for the
         controller to  monitor and manage resources of the 6top sublayer.
         This is deferred to future work, see <a href="#unchartered-tracks" class="xref">Appendix A.1.2</a>.<a href="#section-4.4.3-2" class="pilcrow">¶</a></p>
<p id="section-4.4.3-3">
         With respect to centralized routing and scheduling, it is envisioned
         that the related component of the 6TiSCH architecture would be an
         extension of the <span><a href="#RFC8655" class="xref">DetNet architecture</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span>,
         which studies Layer 3 aspects of Deterministic Networks and covers
         networks that span multiple Layer 2 domains.<a href="#section-4.4.3-3" class="pilcrow">¶</a></p>
<p id="section-4.4.3-4">
         The DetNet architecture is a form of Software-Defined Networking (SDN)
         architecture and is composed of three planes: a (User) Application
         Plane, a Controller Plane (where the PCE operates), and a Network Plane,
         which can represent a 6TiSCH LLN.<a href="#section-4.4.3-4" class="pilcrow">¶</a></p>
<p id="section-4.4.3-5">
         <span><a href="#RFC7426" class="xref">"Software-Defined Networking (SDN):
         Layers and Architecture Terminology"</a> [<a href="#RFC7426" class="xref">RFC7426</a>]</span> proposes a generic
         representation of the SDN architecture that is reproduced in
         <a href="#RFC7426archi" class="xref">Figure 9</a>.<a href="#section-4.4.3-5" class="pilcrow">¶</a></p>
<span id="name-sdn-layers-and-architecture"></span><div id="RFC7426archi">
<figure id="figure-9">
            <div class="artwork art-text alignLeft" id="section-4.4.3-6.1">
<pre>
                  o--------------------------------o
                  |                                |
                  | +-------------+   +----------+ |
                  | | Application |   |  Service | |
                  | +-------------+   +----------+ |
                  |       Application Plane        |
                  o---------------Y----------------o
                                  |
    *-----------------------------Y---------------------------------*
    |           Network Services Abstraction Layer (NSAL)           |
    *------Y------------------------------------------------Y-------*
           |                                                |
           |               Service Interface                |
           |                                                |
    o------Y------------------o       o---------------------Y------o
    |      |    Control Plane |       | Management Plane    |      |
    | +----Y----+   +-----+   |       |  +-----+       +----Y----+ |
    | | Service |   | App |   |       |  | App |       | Service | |
    | +----Y----+   +--Y--+   |       |  +--Y--+       +----Y----+ |
    |      |           |      |       |     |               |      |
    | *----Y-----------Y----* |       | *---Y---------------Y----* |
    | | Control Abstraction | |       | | Management Abstraction | |
    | |     Layer (CAL)     | |       | |      Layer (MAL)       | |
    | *----------Y----------* |       | *----------Y-------------* |
    |            |            |       |            |               |
    o------------|------------o       o------------|---------------o
                 |                                 |
                 | CP                              | MP
                 | Southbound                      | Southbound
                 | Interface                       | Interface
                 |                                 |
    *------------Y---------------------------------Y----------------*
    |         Device and resource Abstraction Layer (DAL)           |
    *------------Y---------------------------------Y----------------*
    |            |                                 |                |
    |    o-------Y----------o   +-----+   o--------Y----------o     |
    |    | Forwarding Plane |   | App |   | Operational Plane |     |
    |    o------------------o   +-----+   o-------------------o     |
    |                       Network Device                          |
    +---------------------------------------------------------------+
</pre>
</div>
<figcaption><a href="#figure-9" class="selfRef">Figure 9</a>:
<a href="#name-sdn-layers-and-architecture" class="selfRef">SDN Layers and Architecture Terminology per RFC 7426</a>
            </figcaption></figure>
</div>
<p id="section-4.4.3-7">The PCE establishes end-to-end Tracks of hard cells, which are described
      in more detail in <a href="#trkfwd" class="xref">Section 4.6.1</a>.<a href="#section-4.4.3-7" class="pilcrow">¶</a></p>
<p id="section-4.4.3-8">
      The DetNet work is expected to enable end-to-end deterministic paths
         across heterogeneous networks. This can be, for instance, a 6TiSCH LLN
         and an Ethernet backbone.<a href="#section-4.4.3-8" class="pilcrow">¶</a></p>
<p id="section-4.4.3-9">This model fits the 6TiSCH extended configuration, whereby a
         6BBR federates
         multiple 6TiSCH LLNs in a single subnet over a backbone that can be,
         for instance, Ethernet or Wi-Fi. In that model,
         6TiSCH 6BBRs synchronize with one another over the backbone, so as
         to ensure that the multiple LLNs that form the IPv6 subnet stay
         tightly synchronized.<a href="#section-4.4.3-9" class="pilcrow">¶</a></p>
<p id="section-4.4.3-10">
         If the backbone is deterministic, then the
         Backbone Router ensures that the end-to-end deterministic
         behavior is maintained between the LLN and the backbone.
         It is the responsibility of the PCE to compute a
         deterministic path end to end across the TSCH network and an IEEE Std 802.1
         TSN Ethernet backbone, and it is the responsibility of DetNet to enable end-to-end deterministic
         forwarding.<a href="#section-4.4.3-10" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-4.4.4">
          <h4 id="name-hop-by-hop-scheduling">
<a href="#section-4.4.4" class="section-number selfRef">4.4.4. </a><a href="#name-hop-by-hop-scheduling" class="section-name selfRef">Hop-by-Hop Scheduling</a>
          </h4>
<p id="section-4.4.4-1">
    A node can reserve a <span><a href="#ontrk" class="xref">Track</a> (<a href="#ontrk" class="xref">Section 4.5</a>)</span> to one or more
    destination(s) that are multiple hops away by installing soft cells at each
    intermediate node.
    This forms a Track of soft cells. A Track SF above the 6top
    sublayer of each node on the Track is needed to monitor these soft cells and
    trigger relocation when needed.<a href="#section-4.4.4-1" class="pilcrow">¶</a></p>
<p id="section-4.4.4-2">
    This hop-by-hop reservation mechanism is expected to be similar in essence
    to <span>[<a href="#RFC3209" class="xref">RFC3209</a>]</span> and/or <span>[<a href="#RFC4080" class="xref">RFC4080</a>]</span> and <span>[<a href="#RFC5974" class="xref">RFC5974</a>]</span>.
    The protocol for a node to trigger hop-by-hop scheduling is not yet defined.<a href="#section-4.4.4-2" class="pilcrow">¶</a></p>
</section>
</section>
</div>
<div id="ontrk">
<section id="section-4.5">
        <h3 id="name-on-tracks">
<a href="#section-4.5" class="section-number selfRef">4.5. </a><a href="#name-on-tracks" class="section-name selfRef">On Tracks</a>
        </h3>
<p id="section-4.5-1">
    The architecture introduces the concept of a Track, which is a directed path
    from a source 6TiSCH node to one or more destination 6TiSCH node(s)
    across a 6TiSCH LLN.<a href="#section-4.5-1" class="pilcrow">¶</a></p>
<p id="section-4.5-2">
    A Track is the 6TiSCH instantiation of the concept of a deterministic path
    as described in <span>[<a href="#RFC8655" class="xref">RFC8655</a>]</span>.
    Constrained resources such as memory buffers are reserved for that Track in
    intermediate 6TiSCH nodes to avoid loss related to limited capacity.
    A 6TiSCH node along a Track not only knows which bundles of cells it should
    use to receive packets from a previous hop but also knows which bundle(s)
    it should use to send packets to its next hop along the Track.<a href="#section-4.5-2" class="pilcrow">¶</a></p>
<section id="section-4.5.1">
          <h4 id="name-general-behavior-of-tracks">
<a href="#section-4.5.1" class="section-number selfRef">4.5.1. </a><a href="#name-general-behavior-of-tracks" class="section-name selfRef">General Behavior of Tracks</a>
          </h4>
<p id="section-4.5.1-1">
    A Track is associated with Layer 2 bundles of cells with related schedules
    and logical relationships that ensure that a packet that is injected in
    a Track will progress in due time all the way to destination.<a href="#section-4.5.1-1" class="pilcrow">¶</a></p>
<p id="section-4.5.1-2">
    Multiple cells may be scheduled in a Track for the transmission of a single
    packet, in which case the normal operation of IEEE Std 802.15.4 Automatic
    Repeat-reQuest (ARQ) can take place; the acknowledgment may be omitted in
    some cases, for instance, if there is no scheduled cell for a possible retry.<a href="#section-4.5.1-2" class="pilcrow">¶</a></p>
<p id="section-4.5.1-3">
    There are several benefits for using a Track to forward a packet from a
    source node to the destination node:<a href="#section-4.5.1-3" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-4.5.1-4">
       <li id="section-4.5.1-4.1">
       Track Forwarding, as further described in  <a href="#trkfwd" class="xref">Section 4.6.1</a>, is a
       Layer 2 forwarding scheme, which introduces less process delay and
       overhead than a Layer 3 forwarding scheme.  Therefore, LLN devices can save
       more energy and resources, which is critical for resource-constrained devices.<a href="#section-4.5.1-4.1" class="pilcrow">¶</a>
</li>
            <li id="section-4.5.1-4.2">
       Since channel resources, i.e., bundles of cells, have been reserved for
       communications between 6TiSCH nodes of each hop on the Track, the
       throughput and the maximum latency of the traffic along a Track are
       guaranteed, and the jitter is minimized.<a href="#section-4.5.1-4.2" class="pilcrow">¶</a>
</li>
            <li id="section-4.5.1-4.3">
       By knowing the scheduled timeslots of incoming bundle(s) and outgoing
       bundle(s), 6TiSCH nodes on a Track could save more energy by staying in
       sleep state during inactive slots.<a href="#section-4.5.1-4.3" class="pilcrow">¶</a>
</li>
            <li id="section-4.5.1-4.4">
       Tracks are protected from interfering with one another if a cell is 
       scheduled to belong to at most one Track, and congestion loss is avoided if at most one
       packet can be presented to the MAC to use that cell.
       Tracks enhance the reliability of transmissions and thus further improve
       the energy consumption in LLN devices by reducing the chances of
       retransmission.<a href="#section-4.5.1-4.4" class="pilcrow">¶</a>
</li>
          </ol>
</section>
<section id="section-4.5.2">
          <h4 id="name-serial-track">
<a href="#section-4.5.2" class="section-number selfRef">4.5.2. </a><a href="#name-serial-track" class="section-name selfRef">Serial Track</a>
          </h4>
<p id="section-4.5.2-1">
    A Serial (or simple) Track is the 6TiSCH version of a circuit: a bundle of
    cells that are programmed to receive (RX-cells) is uniquely paired with a
    bundle of cells that are set to transmit (TX-cells), representing a Layer 2
    forwarding state that can be used regardless of the network-layer protocol.
    A Serial Track is thus formed end-to-end as a succession of
    paired bundles: a receive bundle from the previous hop and a transmit bundle
    to the next hop along the Track.<a href="#section-4.5.2-1" class="pilcrow">¶</a></p>
<p id="section-4.5.2-2">
    For a given iteration of the device schedule, the effective channel of the
    cell is obtained by looping through a well-known hopping sequence 
    beginning at Epoch time and starting at the cell's channelOffset, which results
    in a rotation of the frequency that is used for transmission.

    The bundles may be computed so as to accommodate both variable rates and
    retransmissions, so they might not be fully used in the iteration of the
    schedule.<a href="#section-4.5.2-2" class="pilcrow">¶</a></p>
</section>
<section id="section-4.5.3">
          <h4 id="name-complex-track-with-replicat">
<a href="#section-4.5.3" class="section-number selfRef">4.5.3. </a><a href="#name-complex-track-with-replicat" class="section-name selfRef">Complex Track with Replication and Elimination</a>
          </h4>
<p id="section-4.5.3-1">
    The art of Deterministic Networks already includes packet replication and
    elimination techniques. Example
    standards include the Parallel Redundancy Protocol (PRP) and the
    High-availability Seamless Redundancy (HSR) <span>[<a href="#IEC62439" class="xref">IEC62439</a>]</span>.
    Similarly, and as opposed to a Serial Track that is a sequence of nodes
    and links, a Complex Track is shaped as a directed acyclic graph towards one
    or more destination(s) to support multipath forwarding and route around
    failures.<a href="#section-4.5.3-1" class="pilcrow">¶</a></p>
<p id="section-4.5.3-2">
    A Complex Track may branch off over noncongruent branches for the purpose
    of multicasting and/or redundancy, in which case, it reconverges later down
    the path.
    This enables the Packet Replication, Elimination, and Ordering Functions (PREOF)
    defined by DetNet. Packet ARQ, Replication, Elimination, and Overhearing (PAREO)
    adds radio-specific capabilities of Layer 2 ARQ and promiscuous listening to
    redundant transmissions to compensate for the lossiness of the medium and meet
    industrial expectations of a RAW network.
    Combining PAREO and PREOF, a Track may extend beyond the 6TiSCH network into 
    a larger DetNet network.<a href="#section-4.5.3-2" class="pilcrow">¶</a></p>
<p id="section-4.5.3-3">
    In the art of TSCH, a path does not necessarily support PRE, but it is almost
    systematically multipath. This means that a Track is scheduled so as to
    ensure that each hop has at least two forwarding solutions, and the
    forwarding decision is to try the preferred one and use the other in
    case of Layer 2 transmission failure as detected by ARQ. Similarly,
    at each 6TiSCH hop along the Track, the PCE may schedule more than one
    timeslot for a packet, so as to support Layer 2 retries (ARQ). It is also
    possible that the field device only uses the second branch if sending over
    the first branch fails.<a href="#section-4.5.3-3" class="pilcrow">¶</a></p>
</section>
<section id="section-4.5.4">
          <h4 id="name-detnet-end-to-end-path">
<a href="#section-4.5.4" class="section-number selfRef">4.5.4. </a><a href="#name-detnet-end-to-end-path" class="section-name selfRef">DetNet End-to-End Path</a>
          </h4>
<p id="section-4.5.4-1">
    Ultimately, DetNet should
    enable extending a Track beyond the 6TiSCH LLN as illustrated in
    <a href="#elifig" class="xref">Figure 10</a>. In that example, a Track is laid out from a
    field device in a 6TiSCH network to an IoT gateway that is located on an
    802.1 Time-Sensitive Networking (TSN) backbone.
    A 6TiSCH-aware DetNet service layer handles the Packet Replication,
    Elimination, and Ordering Functions over the DODAG that forms a Track.<a href="#section-4.5.4-1" class="pilcrow">¶</a></p>
<p id="section-4.5.4-2">
    The Replication function in the 6TiSCH Node sends a copy of each packet over
    two different branches, and the PCE schedules each hop of both branches so
    that the two copies arrive in due time at the gateway. In case of a loss on
    one branch, hopefully the other copy of the packet still makes it in due
    time. If two copies make it to the IoT gateway, the Elimination function
    in the gateway ignores the extra packet and presents only one copy to upper
    layers.<a href="#section-4.5.4-2" class="pilcrow">¶</a></p>
<span id="name-example-end-to-end-detnet-t"></span><div id="elifig">
<figure id="figure-10">
            <div class="artwork art-text alignLeft" id="section-4.5.4-3.1">
<pre>
                  +-=-=-+
                  | IoT |
                  | G/W |
                  +-=-=-+
                     ^  &lt;=== Elimination
     Track branch   | |
            +-=-=-=-+ +-=-=-=-=+ Subnet backbone
            |                  |
         +-=|-=+            +-=|-=+
         |  |  | Backbone   |  |  | Backbone
    o    |  |  | Router     |  |  | Router
         +-=/-=+            +-=|-=+
    o     /    o     o-=-o-=-=/       o
        o    o-=-o-=/   o      o   o  o   o
   o     \  /     o               o   LLN    o
      o   v  &lt;=== Replication
          o
</pre>
</div>
<figcaption><a href="#figure-10" class="selfRef">Figure 10</a>:
<a href="#name-example-end-to-end-detnet-t" class="selfRef">Example End-to-End DetNet Track</a>
            </figcaption></figure>
</div>
</section>
<section id="section-4.5.5">
          <h4 id="name-cell-reuse">
<a href="#section-4.5.5" class="section-number selfRef">4.5.5. </a><a href="#name-cell-reuse" class="section-name selfRef">Cell Reuse</a>
          </h4>
<p id="section-4.5.5-1">
    The 6TiSCH architecture provides the means to avoid waste of cells as
    well as overflows in the transmit bundle of a Track, as follows:<a href="#section-4.5.5-1" class="pilcrow">¶</a></p>
<p id="section-4.5.5-2">
        A TX-cell that is not needed for the current iteration may
        be reused opportunistically on a per-hop basis for routed packets.
        When all of the frames that were received for a given Track are
        effectively transmitted, any available TX-cell for that Track can be
        reused for upper-layer traffic for which the next-hop router matches the
        next hop along the Track.
        In that case, the cell that is being used is effectively a TX-cell from
        the Track, but the short address for the destination is that of the
        next-hop router.<a href="#section-4.5.5-2" class="pilcrow">¶</a></p>
<p id="section-4.5.5-3">
        It results in a frame that is received in an RX-cell of a Track with a
        destination MAC address set to this node, as opposed to the broadcast MAC
        address that must be extracted from the Track and delivered to the upper layer.
        Note that a frame with an unrecognized destination MAC address is dropped
        at the lower MAC layer and thus is not received at the 6top sublayer.<a href="#section-4.5.5-3" class="pilcrow">¶</a></p>
<p id="section-4.5.5-4">
        On the other hand, it might happen that there are not enough TX-cells
        in the transmit bundle to accommodate the Track traffic, for instance, if
        more retransmissions are needed than provisioned.
        In that case, and if the frame transports an IPv6 packet, then it can be
        placed for transmission in the bundle that is used for Layer 3 traffic
        towards the next hop along the Track.
        The MAC address should be set to the next-hop MAC address to avoid
        confusion.<a href="#section-4.5.5-4" class="pilcrow">¶</a></p>
<p id="section-4.5.5-5">
        It results in a frame that is received over a Layer 3 bundle that may be in
        fact associated with a Track. In a classical IP link such as an Ethernet,
        off-Track traffic is typically in excess over reservation to be routed
        along the non-reserved path based on its QoS setting.
        But with 6TiSCH, since the use of the Layer 3 bundle may be due to
        transmission failures, it makes sense for the receiver to recognize a
        frame that should be re-Tracked and to place it back on the appropriate
        bundle if possible.
        A frame is re-Tracked by scheduling it for transmission over the
        transmit bundle associated with the Track, with the destination MAC
        address set to broadcast.<a href="#section-4.5.5-5" class="pilcrow">¶</a></p>
</section>
</section>
</div>
<div id="fwd">
<section id="section-4.6">
        <h3 id="name-forwarding-models">
<a href="#section-4.6" class="section-number selfRef">4.6. </a><a href="#name-forwarding-models" class="section-name selfRef">Forwarding Models</a>
        </h3>
<p id="section-4.6-1">
         By forwarding, this document means the per-packet operation that
         allows delivery of a packet to a next hop or an upper layer in this node.
         Forwarding is based on preexisting state that was installed as a
         result of a routing computation, see <a href="#rtg" class="xref">Section 4.7</a>.
         6TiSCH supports three different forwarding models: (GMPLS) Track
         Forwarding, (classical) IPv6 Forwarding, and (6LoWPAN) Fragment Forwarding.<a href="#section-4.6-1" class="pilcrow">¶</a></p>
<div id="trkfwd">
<section id="section-4.6.1">
          <h4 id="name-track-forwarding">
<a href="#section-4.6.1" class="section-number selfRef">4.6.1. </a><a href="#name-track-forwarding" class="section-name selfRef">Track Forwarding</a>
          </h4>
<p id="section-4.6.1-1">
            Forwarding along a Track can be seen as a Generalized Multiprotocol
            Label Switching (GMPLS) operation in that the information used to
            switch a frame is not an explicit label but is rather related to other
            properties of the way the packet was received, a particular cell in
            the case of 6TiSCH.
            As a result, as long as the TSCH MAC (and Layer 2 security) accepts
            a frame, that frame can be switched regardless of the protocol,
            whether this is an IPv6 packet, a 6LoWPAN fragment, or a frame from
            an alternate protocol such as WirelessHART or ISA100.11a.<a href="#section-4.6.1-1" class="pilcrow">¶</a></p>
<p id="section-4.6.1-2">
            A data frame that is forwarded along a Track normally has a
            destination MAC address that is set to broadcast or a multicast
            address depending on MAC support.
            This way, the MAC layer in the intermediate nodes accepts the
            incoming frame and 6top switches it without incurring a change in
            the MAC header.
            In the case of IEEE Std 802.15.4, this means effectively to
            broadcast, so that along the Track the short address for the
            destination of the frame is set to 0xFFFF.<a href="#section-4.6.1-2" class="pilcrow">¶</a></p>
<p id="section-4.6.1-3">
            There are two modes for a Track: an IPv6 native mode and a 
            protocol-independent tunnel mode.<a href="#section-4.6.1-3" class="pilcrow">¶</a></p>
<section id="section-4.6.1.1">
            <h5 id="name-native-mode">
<a href="#section-4.6.1.1" class="section-number selfRef">4.6.1.1. </a><a href="#name-native-mode" class="section-name selfRef">Native Mode</a>
            </h5>
<p id="section-4.6.1.1-1">
               In native mode, the Protocol Data Unit (PDU) is associated
               with flow-dependent metadata that refers uniquely to the Track,
               so the 6top sublayer can place the frame in the appropriate cell
               without ambiguity. In the case of IPv6 traffic, this flow
               may be identified using a 6-tuple as discussed in
               <span>[<a href="#RFC8939" class="xref">RFC8939</a>]</span>. In particular,
               implementations of this document should support identification of
               DetNet flows based on the IPv6 Flow Label field.<a href="#section-4.6.1.1-1" class="pilcrow">¶</a></p>
<p id="section-4.6.1.1-2">
   The flow follows a Track that is identified using a RPL
   Instance (see <span><a href="https://www.rfc-editor.org/rfc/rfc6550#section-3.1.3" class="relref">Section 3.1.3</a> of [<a href="#RFC6550" class="xref">RFC6550</a>]</span>), 
   signaled in a RPL Packet Information (more in 
   <span><a href="https://www.rfc-editor.org/rfc/rfc6550#section-11.2.2.1" class="relref">Section 11.2.2.1</a> of [<a href="#RFC6550" class="xref">RFC6550</a>]</span>) 
   and the source address of a packet going down the DODAG formed by a local instance.  One or more
   flows may be placed in a same Track and the Track identification
   (TrackID plus owner) may be placed in an IP-in-IP encapsulation.  The forwarding
   operation is based on the Track and does not depend on the flow
   therein.<a href="#section-4.6.1.1-2" class="pilcrow">¶</a></p>
<p id="section-4.6.1.1-3">
   The Track identification is validated at egress before restoring the
   destination MAC address (DMAC) and punting to the upper layer.<a href="#section-4.6.1.1-3" class="pilcrow">¶</a></p>
<p id="section-4.6.1.1-4"><a href="#fig6t" class="xref">Figure 11</a> illustrates the Track Forwarding operation
            that happens at the 6top sublayer, below IP.<a href="#section-4.6.1.1-4" class="pilcrow">¶</a></p>
<span id="name-track-forwarding-native-mod"></span><div id="fig6t">
<figure id="figure-11">
              <div class="artwork art-text alignLeft" id="section-4.6.1.1-5.1">
<pre>
                       | Packet flowing across the network  ^
   +--------------+    |                                    |
   |     IPv6     |    |                                    |
   +--------------+    |                                    |
   |  6LoWPAN HC  |    |                                    |
   +--------------+  ingress                              egress
   |     6top     |   sets     +----+          +----+    restores
   +--------------+  DMAC to   |    |          |    |    DMAC to
   |   TSCH MAC   |   brdcst   |    |          |    |     dest
   +--------------+    |       |    |          |    |       |
   |   LLN PHY    |    +-------+    +--...-----+    +-------+
   +--------------+
                     Ingress   Relay            Relay     Egress
      Stack Layer     Node     Node             Node       Node
</pre>
</div>
<figcaption><a href="#figure-11" class="selfRef">Figure 11</a>:
<a href="#name-track-forwarding-native-mod" class="selfRef">Track Forwarding, Native Mode</a>
              </figcaption></figure>
</div>
</section>
<section id="section-4.6.1.2">
            <h5 id="name-tunnel-mode">
<a href="#section-4.6.1.2" class="section-number selfRef">4.6.1.2. </a><a href="#name-tunnel-mode" class="section-name selfRef">Tunnel Mode</a>
            </h5>
<p id="section-4.6.1.2-1">
               In tunnel mode, the frames originate from an arbitrary protocol over a compatible MAC
               that may or may not be synchronized with the 6TiSCH network. An example of
               this would be a router with a dual radio that is capable of receiving and sending WirelessHART
               or ISA100.11a frames with the second radio by presenting itself as an access
               point or a Backbone Router, respectively.
               In that mode, some entity (e.g., PCE) can coordinate with a
               WirelessHART Network Manager or an ISA100.11a System Manager to
               specify the flows that are transported.<a href="#section-4.6.1.2-1" class="pilcrow">¶</a></p>
<span id="name-track-forwarding-tunnel-mod"></span><div id="fig6">
<figure id="figure-12">
              <div class="artwork art-text alignLeft" id="section-4.6.1.2-2.1">
<pre>
   +--------------+
   |     IPv6     |
   +--------------+
   |  6LoWPAN HC  |
   +--------------+             set            restore
   |     6top     |            +DMAC+          +DMAC+
   +--------------+          to|brdcst       to|nexthop
   |   TSCH MAC   |            |    |          |    |
   +--------------+            |    |          |    |
   |   LLN PHY    |    +-------+    +--...-----+    +-------+
   +--------------+    |   ingress                 egress   |
                       |                                    |
   +--------------+    |                                    |
   |   LLN PHY    |    |                                    |
   +--------------+    |  Packet flowing across the network |
   |   TSCH MAC   |    |                                    |
   +--------------+    | DMAC =                             | DMAC =
   |ISA100/WiHART |    | nexthop                            v nexthop
   +--------------+
                     Source   Ingress          Egress   Destination
      Stack Layer     Node     Node             Node       Node
</pre>
</div>
<figcaption><a href="#figure-12" class="selfRef">Figure 12</a>:
<a href="#name-track-forwarding-tunnel-mod" class="selfRef">Track Forwarding, Tunnel Mode</a>
              </figcaption></figure>
</div>
<p id="section-4.6.1.2-3">
               In that case, the TrackID that identifies the Track at
               the ingress 6TiSCH router is derived from the RX-cell.
               The DMAC
               is set to this node, but the TrackID indicates that the
               frame must be tunneled over a particular Track, so the frame is
               not passed to the upper layer. Instead, the DMAC is forced to
               broadcast, and the frame is passed to the 6top sublayer for
               switching.<a href="#section-4.6.1.2-3" class="pilcrow">¶</a></p>
<p id="section-4.6.1.2-4">
               At the egress 6TiSCH router, the reverse operation occurs. Based
               on tunneling information of the Track, which may for instance
               indicate that the tunneled datagram is an IP packet,
               the datagram is passed to the appropriate link-layer with the
               destination MAC restored.<a href="#section-4.6.1.2-4" class="pilcrow">¶</a></p>
</section>
<section id="section-4.6.1.3">
            <h5 id="name-tunneling-information">
<a href="#section-4.6.1.3" class="section-number selfRef">4.6.1.3. </a><a href="#name-tunneling-information" class="section-name selfRef">Tunneling Information</a>
            </h5>
<p id="section-4.6.1.3-1">
               Tunneling information coming with the Track configuration
               provides the destination MAC address
               of the egress endpoint as well as the tunnel mode and specific
               data depending on the mode,
               for instance, a service access point for frame delivery at egress.<a href="#section-4.6.1.3-1" class="pilcrow">¶</a></p>
<p id="section-4.6.1.3-2">
               If the tunnel egress point does not have a MAC address that
               matches the configuration, the Track installation fails.<a href="#section-4.6.1.3-2" class="pilcrow">¶</a></p>
<p id="section-4.6.1.3-3">
               If the Layer 3 destination address belongs to
               the tunnel termination, then it is possible that the IPv6 address
               of the destination is compressed at the 6LoWPAN sublayer based on
               the MAC address. Restoring the wrong MAC address at the egress
               would then also result in the wrong IP address in the packet
               after decompression.
               For that reason, a packet can be injected in a Track only if
               the destination MAC address is effectively that of the tunnel
               egress point.
               It is thus mandatory for the ingress router to validate that the
               MAC address used at the 6LoWPAN
               sublayer for compression matches that of the tunnel egress point
               before it overwrites it to broadcast.

               The 6top sublayer at the tunnel egress point reverts that
               operation to the MAC address obtained from the tunnel
               information.<a href="#section-4.6.1.3-3" class="pilcrow">¶</a></p>
</section>
</section>
</div>
<section id="section-4.6.2">
          <h4 id="name-ipv6-forwarding">
<a href="#section-4.6.2" class="section-number selfRef">4.6.2. </a><a href="#name-ipv6-forwarding" class="section-name selfRef">IPv6 Forwarding</a>
          </h4>
<p id="section-4.6.2-1">
            As the packets are routed at Layer 3, traditional QoS and Active
            Queue Management (AQM) operations are expected to prioritize flows.<a href="#section-4.6.2-1" class="pilcrow">¶</a></p>
<span id="name-ip-forwarding"></span><div id="fig9">
<figure id="figure-13">
            <div class="artwork art-text alignLeft" id="section-4.6.2-2.1">
<pre>
                       | Packet flowing across the network  ^
   +--------------+    |                                    |
   |     IPv6     |    |       +-QoS+          +-QoS+       |
   +--------------+    |       |    |          |    |       |
   |  6LoWPAN HC  |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |     6top     |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   TSCH MAC   |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   LLN PHY    |    +-------+    +--...-----+    +-------+
   +--------------+
                     Source   Ingress          Egress   Destination
      Stack Layer     Node    Router           Router      Node
</pre>
</div>
<figcaption><a href="#figure-13" class="selfRef">Figure 13</a>:
<a href="#name-ip-forwarding" class="selfRef">IP Forwarding</a>
            </figcaption></figure>
</div>
</section>
<section id="section-4.6.3">
          <h4 id="name-fragment-forwarding">
<a href="#section-4.6.3" class="section-number selfRef">4.6.3. </a><a href="#name-fragment-forwarding" class="section-name selfRef">Fragment Forwarding</a>
          </h4>
<p id="section-4.6.3-1">
            Considering that, per <span><a href="https://www.rfc-editor.org/rfc/rfc4944#section-4" class="relref">Section 4</a> of [<a href="#RFC4944" class="xref">RFC4944</a>]</span>, 6LoWPAN
            packets can be as large as 1280 bytes (the IPv6 minimum MTU)
            and that the non-storing mode of RPL implies source routing, which requires space for routing
            headers, and that an IEEE Std 802.15.4 frame with security may carry in the order of 80 bytes of
            effective payload, an IPv6 packet might be fragmented into more than 16 fragments at the
            6LoWPAN sublayer.<a href="#section-4.6.3-1" class="pilcrow">¶</a></p>
<p id="section-4.6.3-2">
            This level of fragmentation is much higher than that traditionally experienced over the Internet
            with IPv4 fragments, where fragmentation is already known as harmful.<a href="#section-4.6.3-2" class="pilcrow">¶</a></p>
<p id="section-4.6.3-3">
            In the case of a multihop route within a 6TiSCH network, hop-by-hop recomposition occurs at each
            hop to reform the packet and route it. This creates additional latency and forces intermediate
            nodes to store a portion of a packet for an undetermined time, thus impacting critical resources such
            as memory and battery.<a href="#section-4.6.3-3" class="pilcrow">¶</a></p>
<p id="section-4.6.3-4">
            <span>[<a href="#RFC8930" class="xref">RFC8930</a>]</span> describes a framework for forwarding fragments end-to-end 
            across a 6TiSCH route-over mesh.  Within that framework, 
            <span>[<a href="#I-D.ietf-lwig-6lowpan-virtual-reassembly" class="xref">VIRTUAL-REASSEMBLY</a>]</span> details a virtual reassembly 
            buffer mechanism whereby the datagram tag in the 6LoWPAN fragment is used as a label 
            for switching at the 6LoWPAN sublayer.<a href="#section-4.6.3-4" class="pilcrow">¶</a></p>
<p id="section-4.6.3-5">
            Building on this technique, <span>[<a href="#RFC8931" class="xref">RFC8931</a>]</span> introduces a new format for 
            6LoWPAN fragments that enables the selective recovery of individual fragments 
            and allows for a degree of flow control based on an Explicit Congestion Notification (ECN).<a href="#section-4.6.3-5" class="pilcrow">¶</a></p>
<span id="name-forwarding-first-fragment"></span><div id="fig7">
<figure id="figure-14">
            <div class="artwork art-text alignLeft" id="section-4.6.3-6.1">
<pre>
                       | Packet flowing across the network  ^
   +--------------+    |                                    |
   |     IPv6     |    |       +----+          +----+       |
   +--------------+    |       |    |          |    |       |
   |  6LoWPAN HC  |    |       learn           learn        |
   +--------------+    |       |    |          |    |       |
   |     6top     |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   TSCH MAC   |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   LLN PHY    |    +-------+    +--...-----+    +-------+
   +--------------+
                     Source   Ingress          Egress   Destination
      Stack Layer     Node    Router           Router      Node
</pre>
</div>
<figcaption><a href="#figure-14" class="selfRef">Figure 14</a>:
<a href="#name-forwarding-first-fragment" class="selfRef">Forwarding First Fragment</a>
            </figcaption></figure>
</div>
<p id="section-4.6.3-7">
            In that model, the first fragment is routed based on the IPv6 header that is present in that fragment.
            The 6LoWPAN sublayer learns the next-hop selection, generates a new datagram tag for transmission to
            the next hop, and stores that information indexed by the incoming MAC address and datagram tag. The next
            fragments are then switched based on that stored state.<a href="#section-4.6.3-7" class="pilcrow">¶</a></p>
<span id="name-forwarding-next-fragment"></span><div id="fig8">
<figure id="figure-15">
            <div class="artwork art-text alignLeft" id="section-4.6.3-8.1">
<pre>
                       | Packet flowing across the network  ^
   +--------------+    |                                    |
   |     IPv6     |    |                                    |
   +--------------+    |                                    |
   |  6LoWPAN HC  |    |       replay          replay       |
   +--------------+    |       |    |          |    |       |
   |     6top     |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   TSCH MAC   |    |       |    |          |    |       |
   +--------------+    |       |    |          |    |       |
   |   LLN PHY    |    +-------+    +--...-----+    +-------+
   +--------------+
                     Source   Ingress          Egress   Destination
      Stack Layer     Node    Router           Router      Node
</pre>
</div>
<figcaption><a href="#figure-15" class="selfRef">Figure 15</a>:
<a href="#name-forwarding-next-fragment" class="selfRef">Forwarding Next Fragment</a>
            </figcaption></figure>
</div>
<p id="section-4.6.3-9">
            A bitmap and an ECN echo in the end-to-end acknowledgment enable the source to resend the missing
            fragments selectively. The first fragment may be resent to carve a new path in case of a path failure.
            The ECN echo set indicates that the number of outstanding fragments should be reduced.<a href="#section-4.6.3-9" class="pilcrow">¶</a></p>
</section>
</section>
</div>
<div id="rtg">
<section id="section-4.7">
        <h3 id="name-advanced-6tisch-routing">
<a href="#section-4.7" class="section-number selfRef">4.7. </a><a href="#name-advanced-6tisch-routing" class="section-name selfRef">Advanced 6TiSCH Routing</a>
        </h3>
<div id="pmh">
<section id="section-4.7.1">
          <h4 id="name-packet-marking-and-handling">
<a href="#section-4.7.1" class="section-number selfRef">4.7.1. </a><a href="#name-packet-marking-and-handling" class="section-name selfRef">Packet Marking and Handling</a>
          </h4>
<p id="section-4.7.1-1">
   All packets inside a 6TiSCH domain must carry the RPLInstanceID that
   identifies the 6TiSCH topology (e.g., a Track) that is to be used for
   routing and forwarding that packet.  The location of that information
   must be the same for all packets forwarded inside the domain.<a href="#section-4.7.1-1" class="pilcrow">¶</a></p>
<p id="section-4.7.1-2">
   For packets that are routed by a PCE along a Track, the tuple formed
   by 1) (typically) the IPv6 source or (possibly) destination address
   in the IPv6 header and 2) a local RPLInstanceID in the RPI that 
   serves as TrackID, identify uniquely the Track and
   associated transmit bundle.<a href="#section-4.7.1-2" class="pilcrow">¶</a></p>
<p id="section-4.7.1-3">
   For packets that are routed by RPL, that information is the RPLInstanceID
   that is carried in the RPL Packet Information (RPI), as discussed in
   <span><a href="https://www.rfc-editor.org/rfc/rfc6550#section-11.2" class="relref">Section 11.2</a> of [<a href="#RFC6550" class="xref">RFC6550</a>]</span>, "Loop Avoidance and Detection".
   The RPI is transported by a RPL Option in the IPv6 Hop-By-Hop Options header
   <span>[<a href="#RFC6553" class="xref">RFC6553</a>]</span>.<a href="#section-4.7.1-3" class="pilcrow">¶</a></p>
<p id="section-4.7.1-4">
   A compression mechanism for the RPL packet artifacts that integrates the
   compression of IP-in-IP encapsulation and the Routing Header type 3
   <span>[<a href="#RFC6554" class="xref">RFC6554</a>]</span>
   with that of the RPI in a 6LoWPAN dispatch/header type is specified in
   <span>[<a href="#RFC8025" class="xref">RFC8025</a>]</span> and <span>[<a href="#RFC8138" class="xref">RFC8138</a>]</span>.<a href="#section-4.7.1-4" class="pilcrow">¶</a></p>
<p id="section-4.7.1-5">
   Either way, the method and format used for encoding the RPLInstanceID
   is generalized to all 6TiSCH topological Instances, which include
   both RPL Instances and Tracks.<a href="#section-4.7.1-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="pmhrre">
<section id="section-4.7.2">
          <h4 id="name-replication-retries-and-eli">
<a href="#section-4.7.2" class="section-number selfRef">4.7.2. </a><a href="#name-replication-retries-and-eli" class="section-name selfRef">Replication, Retries, and Elimination</a>
          </h4>
<p id="section-4.7.2-1">
   6TiSCH supports the PREOF operations of elimination and reordering of packets
   along a complex Track, but has no requirement about tagging a sequence number
   in the packet for that purpose.
   With 6TiSCH, the schedule can tell when multiple receive timeslots correspond
   to copies of a same packet, in which case the receiver may avoid listening to
   the extra copies once it has received one instance of the packet.<a href="#section-4.7.2-1" class="pilcrow">¶</a></p>
<p id="section-4.7.2-2">
   The semantics of the configuration enable correlated timeslots to be
   grouped for transmit (and receive, respectively) with 'OR' relations,
   and then an 'AND' relation can be configurable between groups.
   The semantics are such that if the transmit (and receive, respectively) operation
   succeeded in one timeslot in an 'OR' group, then all the other timeslots in
   the group are ignored.
   Now, if there are at least two groups, the 'AND' relation between the groups
   indicates that one operation must succeed in each of the groups.<a href="#section-4.7.2-2" class="pilcrow">¶</a></p>
<p id="section-4.7.2-3">
   On the transmit side, timeslots provisioned for retries along a same branch
   of a Track are placed in the same 'OR' group. The 'OR' relation indicates that if
   a transmission is acknowledged, then retransmissions of that packet should
   not be attempted for the remaining timeslots in that group. There are as many
   'OR' groups as there are branches of the Track departing from this node.
   Different 'OR' groups are programmed for the purpose of replication, each
   group corresponding to one branch of the Track. The 'AND' relation between the
   groups indicates that transmission over any of branches must be attempted
   regardless of whether a transmission succeeded in another branch. It is also
   possible to place cells to different next-hop routers in the same 'OR' group.
   This allows routing along multipath Tracks, trying one next hop and then
   another only if sending to the first fails.<a href="#section-4.7.2-3" class="pilcrow">¶</a></p>
<p id="section-4.7.2-4">
   On the receive side, all timeslots are programmed in the same 'OR' group.
   Retries of the same copy as well as converging branches for elimination
   are converged, meaning that the first successful reception is enough and that
   all the other timeslots can be ignored. An 'AND' group denotes different
   packets that must all be received and transmitted over the associated
   transmit groups within their respected 'AND' or 'OR' rules.<a href="#section-4.7.2-4" class="pilcrow">¶</a></p>
<p id="section-4.7.2-5">
   As an example, say that we have a simple network as represented in
   <a href="#figANDORref" class="xref">Figure 16</a>, and we want to enable PREOF between an ingress
   node I and an egress node E.<a href="#section-4.7.2-5" class="pilcrow">¶</a></p>
<span id="name-scheduling-preof-on-a-simpl"></span><div id="figANDORref">
<figure id="figure-16">
            <div class="artwork art-text alignCenter" id="section-4.7.2-6.1">
<pre>
            +-+         +-+
         -- |A|  ------ |C| --
       /    +-+         +-+    \
     /                           \
+-+                                +-+
|I|                                |E|
+-+                                +-+
     \                           /
       \    +-+         +-+    /
         -- |B| ------- |D| --
            +-+         +-+
</pre>
</div>
<figcaption><a href="#figure-16" class="selfRef">Figure 16</a>:
<a href="#name-scheduling-preof-on-a-simpl" class="selfRef">Scheduling PREOF on a Simple Network</a>
            </figcaption></figure>
</div>
<p id="section-4.7.2-7">
   The assumption for this particular problem is
   that a 6TiSCH node has a single radio, so it cannot perform two receive and/or
   transmit operations at the same time, even on two different channels.<a href="#section-4.7.2-7" class="pilcrow">¶</a></p>
<p id="section-4.7.2-8">
   Say we have six possible channels, and at least ten timeslots per slotframe.
   <a href="#figsc" class="xref">Figure 17</a> shows a possible schedule whereby each transmission
   is retried two or three times, and redundant copies are forwarded in parallel via
   A and C on the one hand, and B and D on the other, providing time diversity,
   spatial diversity though different physical paths, and frequency diversity.<a href="#section-4.7.2-8" class="pilcrow">¶</a></p>
<span id="name-example-global-schedule"></span><div id="figsc">
<figure id="figure-17">
            <div class="artwork art-text alignCenter" id="section-4.7.2-9.1">
<pre>
   slotOffset      0    1    2    3    4    5    6    7    9
                +----+----+----+----+----+----+----+----+----+
channelOffset 0 |    |    |    |    |    |    |B-&gt;D|    |    | ...
                +----+----+----+----+----+----+----+----+----+
channelOffset 1 |    |I-&gt;A|    |A-&gt;C|B-&gt;D|    |    |    |    | ...
                +----+----+----+----+----+----+----+----+----+
channelOffset 2 |I-&gt;A|    |    |I-&gt;B|    |C-&gt;E|    |D-&gt;E|    | ...
                +----+----+----+----+----+----+----+----+----+
channelOffset 3 |    |    |    |    |A-&gt;C|    |    |    |    | ...
                +----+----+----+----+----+----+----+----+----+
channelOffset 4 |    |    |I-&gt;B|    |    |B-&gt;D|    |    |D-&gt;E| ...
                +----+----+----+----+----+----+----+----+----+
channelOffset 5 |    |    |A-&gt;C|    |    |    |C-&gt;E|    |    | ...
                +----+----+----+----+----+----+----+----+----+
</pre>
</div>
<figcaption><a href="#figure-17" class="selfRef">Figure 17</a>:
<a href="#name-example-global-schedule" class="selfRef">Example Global Schedule</a>
            </figcaption></figure>
</div>
<p id="section-4.7.2-10">
   This translates into a different slotframe that provides the
   waking and sleeping times for every node, and the channelOffset to be used when awake.
   <a href="#figsfA" class="xref">Figure 18</a> shows the corresponding slotframe for node A.<a href="#section-4.7.2-10" class="pilcrow">¶</a></p>
<span id="name-example-slotframe-for-node-"></span><div id="figsfA">
<figure id="figure-18">
            <div class="artwork art-text alignCenter" id="section-4.7.2-11.1">
<pre>
   slotOffset      0    1    2    3    4    5    6    7    9
                +----+----+----+----+----+----+----+----+----+
operation       |rcv |rcv |xmit|xmit|xmit|none|none|none|none| ...
                +----+----+----+----+----+----+----+----+----+
channelOffset   |  2 |  1 |  5 |  1 |  3 |N/A |N/A |N/A |N/A | ...
                +----+----+----+----+----+----+----+----+----+
</pre>
</div>
<figcaption><a href="#figure-18" class="selfRef">Figure 18</a>:
<a href="#name-example-slotframe-for-node-" class="selfRef">Example Slotframe for Node A</a>
            </figcaption></figure>
</div>
<p id="section-4.7.2-12">
   The logical relationship between the timeslots is given
   by <a href="#figslog" class="xref">Table 2</a>:<a href="#section-4.7.2-12" class="pilcrow">¶</a></p>
<div id="figslog">
<table class="center" id="table-2">
            <caption><a href="#table-2" class="selfRef">Table 2</a></caption>
<thead>
              <tr>
                <th class="text-center" rowspan="1" colspan="1">Node</th>
                <th class="text-center" rowspan="1" colspan="1">rcv slotOffset</th>
                <th class="text-center" rowspan="1" colspan="1">xmit slotOffset</th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">I</td>
                <td class="text-center" rowspan="1" colspan="1">N/A</td>
                <td class="text-center" rowspan="1" colspan="1">(0 OR 1) AND (2 OR 3)</td>
              </tr>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">A</td>
                <td class="text-center" rowspan="1" colspan="1">(0 OR 1)</td>
                <td class="text-center" rowspan="1" colspan="1">(2 OR 3 OR 4)</td>
              </tr>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">B</td>
                <td class="text-center" rowspan="1" colspan="1">(2 OR 3)</td>
                <td class="text-center" rowspan="1" colspan="1">(4 OR 5 OR 6)</td>
              </tr>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">C</td>
                <td class="text-center" rowspan="1" colspan="1">(2 OR 3 OR 4)</td>
                <td class="text-center" rowspan="1" colspan="1">(5 OR 6)</td>
              </tr>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">D</td>
                <td class="text-center" rowspan="1" colspan="1">(4 OR 5 OR 6)</td>
                <td class="text-center" rowspan="1" colspan="1">(7 OR 8)</td>
              </tr>
              <tr>
                <td class="text-center" rowspan="1" colspan="1">E</td>
                <td class="text-center" rowspan="1" colspan="1">(5 OR 6 OR 7 OR 8)</td>
                <td class="text-center" rowspan="1" colspan="1">N/A</td>
              </tr>
            </tbody>
          </table>
</div>
</section>
</div>
</section>
</div>
</section>
</div>
<section id="section-5">
      <h2 id="name-iana-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-5-1">
      This document has no IANA actions.<a href="#section-5-1" class="pilcrow">¶</a></p>
</section>
<div id="sec">
<section id="section-6">
      <h2 id="name-security-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-6-1">
   The <span><a href="#RFC9031" class="xref">"Minimal Security
   Framework for 6TiSCH"</a> [<a href="#RFC9031" class="xref">RFC9031</a>]</span> was optimized for Low-Power and TSCH operations.
   The reader is encouraged to review the Security Considerations section of
   that document (Section <a href="https://www.rfc-editor.org/rfc/rfc9031#section-9" class="relref">9</a>), 
   which discusses 6TiSCH security issues in more details.<a href="#section-6-1" class="pilcrow">¶</a></p>
<div id="det">
<section id="section-6.1">
        <h3 id="name-availability-of-remote-serv">
<a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-availability-of-remote-serv" class="section-name selfRef">Availability of Remote Services</a>
        </h3>
<p id="section-6.1-1">
    The operation of 6TiSCH Tracks inherits its high-level operation from DetNet
    and is subject to the observations in
    <span><a href="https://www.rfc-editor.org/rfc/rfc8655#section-5" class="relref">Section 5</a> of [<a href="#RFC8655" class="xref">RFC8655</a>]</span>.  The installation and the
    maintenance of the 6TiSCH Tracks depend on the availability of a controller
    with a PCE to compute and push them in the network. When that connectivity
    is lost, existing Tracks may continue to operate until the end of their
    lifetime, but cannot be removed or updated, and new Tracks cannot be
    installed.<a href="#section-6.1-1" class="pilcrow">¶</a></p>
<p id="section-6.1-2">
    In an LLN, the communication with a remote PCE may be slow and unreactive to
    rapid changes in the condition of the wireless communication. An attacker
    may introduce extra delay by selectively jamming some packets or some flows.
    The expectation is that the 6TiSCH Tracks enable enough redundancy to
    maintain the critical traffic in operation while new routes are calculated
    and programmed into the network.<a href="#section-6.1-2" class="pilcrow">¶</a></p>
<p id="section-6.1-3">
    As with DetNet in general, the communication with the PCE must be secured
    and should be protected against DoS attacks, including delay injection and
    blackholing attacks, and secured as discussed in the security considerations
    defined for Abstraction and Control of Traffic Engineered Networks (ACTN) in
    <span><a href="https://www.rfc-editor.org/rfc/rfc8453#section-9" class="relref">Section 9</a> of [<a href="#RFC8453" class="xref">RFC8453</a>]</span>, which applies equally to DetNet and
    6TiSCH. In a similar manner, the communication with the JRC must
    be secured and should be protected against DoS attacks when possible.<a href="#section-6.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="phy">
<section id="section-6.2">
        <h3 id="name-selective-jamming">
<a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-selective-jamming" class="section-name selfRef">Selective Jamming</a>
        </h3>
<p id="section-6.2-1">
    The hopping sequence of a TSCH network is well known, meaning that if a
    rogue manages to identify a cell of a particular flow, then it may
    selectively jam that cell without impacting any other traffic.
    This attack can be performed at the PHY layer without any knowledge of the
    Layer 2 keys, and it is very hard to detect and diagnose because only one flow
    is impacted.<a href="#section-6.2-1" class="pilcrow">¶</a></p>
<p id="section-6.2-2">
    <span>[<a href="#I-D.tiloca-6tisch-robust-scheduling" class="xref">ROBUST-SCHEDULING</a>]</span> proposes
    a method to obfuscate the hopping sequence and make it harder to perpetrate
    that particular attack.<a href="#section-6.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="iee">
<section id="section-6.3">
        <h3 id="name-mac-layer-security">
<a href="#section-6.3" class="section-number selfRef">6.3. </a><a href="#name-mac-layer-security" class="section-name selfRef">MAC-Layer Security</a>
        </h3>
<p id="section-6.3-1">
    This architecture operates on IEEE Std 802.15.4 and expects the link-layer
    security to be enabled at all times between connected devices, except for
    the very first step of the device join process, where a joining device may
    need some initial, unsecured exchanges so as to obtain its initial key
    material. In a typical deployment, all joined nodes use the same keys, and
    rekeying needs to be global.<a href="#section-6.3-1" class="pilcrow">¶</a></p>
<p id="section-6.3-2">
    The 6TISCH architecture relies on the join process to deny authorization of
    invalid nodes and to preserve the integrity of the network keys. A rogue that
    managed to access the network can perform a large variety of attacks from
    DoS to injecting forged packets and routing information.
    "Zero-trust" properties would be highly desirable but are mostly not
    available at the time of this writing. <span>[<a href="#RFC8928" class="xref">RFC8928</a>]</span>
    is a notable exception that protects the ownership of IPv6 addresses and
    prevents a rogue node with L2 access from stealing and injecting traffic
    on behalf of a legitimate node.<a href="#section-6.3-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="ts">
<section id="section-6.4">
        <h3 id="name-time-synchronization">
<a href="#section-6.4" class="section-number selfRef">6.4. </a><a href="#name-time-synchronization" class="section-name selfRef">Time Synchronization</a>
        </h3>
<p id="section-6.4-1">
    Time synchronization in TSCH induces another event horizon whereby a node
    will only communicate with another node if they are synchronized within a
    guard time. The pledge discovers the synchronization of the network based
    on the time of reception of the beacon. If an attacker synchronizes a pledge
    outside of the guard time of the legitimate nodes, then the pledge will never
    see a legitimate beacon and may not discover the attack.<a href="#section-6.4-1" class="pilcrow">¶</a></p>
<p id="section-6.4-2">As discussed in <span>[<a href="#RFC8655" class="xref">RFC8655</a>]</span>, measures
    must be taken to protect the time synchronization, and for 6TiSCH this
    includes ensuring that the Absolute Slot Number (ASN), which is the node's
    sense of time, is not compromised. Once installed and as long as the node is
    synchronized to the network, ASN is implicit in the transmissions.<a href="#section-6.4-2" class="pilcrow">¶</a></p>
<p id="section-6.4-3">
    <span><a href="#IEEE802154" class="xref">IEEE Std 802.15.4</a> [<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> specifies that in a TSCH
    network, the nonce that is used for the computation of the Message Integrity
    Code (MIC) to secure link-layer frames is composed of the address
    of the source of the frame and of the ASN. The standard assumes that the ASN
    is distributed securely by other means. The ASN is not passed explicitly in
    the data frames and does not constitute a complete anti-replay protection.
    As a result, upper-layer protocols must provide a way to detect
    duplicates and cope with them.<a href="#section-6.4-3" class="pilcrow">¶</a></p>
<p id="section-6.4-4">
    If the receiver and the sender have a different sense of ASN, the MIC will
    not validate and the frame will be dropped. In that sense, TSCH induces an
    event horizon whereby only nodes that have a common sense of ASN can talk to
    one another in an authenticated manner. With 6TiSCH, the pledge discovers a
    tentative ASN in beacons from nodes that have already joined the network.
    But even if the beacon can be authenticated, the ASN cannot be trusted as it
    could be a replay by an attacker, announcing an ASN that
    represents a time in the  past. If the pledge uses an ASN that is learned
    from a replayed beacon for an encrypted transmission, a nonce-reuse attack
    becomes possible, and the network keys may be compromised.<a href="#section-6.4-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="asv">
<section id="section-6.5">
        <h3 id="name-validating-asn">
<a href="#section-6.5" class="section-number selfRef">6.5. </a><a href="#name-validating-asn" class="section-name selfRef">Validating ASN</a>
        </h3>
<p id="section-6.5-1">
    After obtaining the tentative ASN, a pledge that wishes to join the
    6TiSCH network must use a join protocol to obtain its security keys.
    The join protocol used in 6TiSCH is the Constrained Join Protocol (CoJP).
    In the minimal setting defined in
    <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span>, the authentication
    requires a pre-shared key, based on which a secure session is derived.
    The CoJP exchange may also be preceded by a zero-touch handshake
    <span>[<a href="#I-D.ietf-6tisch-dtsecurity-zerotouch-join" class="xref">ZEROTOUCH-JOIN</a>]</span> in order
    to enable pledge joining based on certificates and/or inter-domain
    communication.<a href="#section-6.5-1" class="pilcrow">¶</a></p>
<p id="section-6.5-2">
    As detailed in <a href="#rflo" class="xref">Section 4.2.1</a>,
    a Join Proxy (JP) helps the pledge with the join procedure by relaying the
    link-scope Join Request over the IP network to a Join Registrar/Coordinator
    (JRC) that can authenticate the pledge and validate that it is attached to
    the appropriate network. As a result of the CoJP exchange, the pledge is in
    possession of link-layer material including keys and a short address, and
    if the ASN is known to be correct, all traffic can now be secured using CCM*
    <span>[<a href="#CCMstar" class="xref">CCMstar</a>]</span> at the link layer.<a href="#section-6.5-2" class="pilcrow">¶</a></p>
<p id="section-6.5-3">
    The authentication steps must be such that they cannot be replayed by an
    attacker, and they must not depend on the tentative ASN being valid.
    During the authentication, the keying material that the pledge obtains from
    the JRC does not provide protection against spoofed ASN. Once the pledge has
    obtained the keys to use in the network, it may still need to verify the ASN.
    If the nonce used in the Layer 2 security derives from the extended (MAC-64)
    address, then replaying the ASN alone cannot enable a nonce-reuse attack
    unless the same node has lost its state with a previous ASN. But
    if the nonce derives from the short address (e.g., assigned by the JRC), then
    the JRC must ensure that it never assigns short addresses that were already
    given to this or other nodes with the same keys. In other words, the network
    must be rekeyed before the JRC runs out of short addresses.<a href="#section-6.5-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="keying">
<section id="section-6.6">
        <h3 id="name-network-keying-and-rekeying">
<a href="#section-6.6" class="section-number selfRef">6.6. </a><a href="#name-network-keying-and-rekeying" class="section-name selfRef">Network Keying and Rekeying</a>
        </h3>
<p id="section-6.6-1">
      <a href="#rflo" class="xref">Section 4.2.1</a> provides an overview of the CoJP process described in
      <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span> by which an LLN
      can be assembled in the field, having been provisioned in a lab.
      <span>[<a href="#I-D.ietf-6tisch-dtsecurity-zerotouch-join" class="xref">ZEROTOUCH-JOIN</a>]</span> is future
      work that precedes and then leverages CoJP using the
      <span>[<a href="#I-D.ietf-anima-constrained-voucher" class="xref">CONSTRAINED-VOUCHER</a>]</span> constrained profile
      of <span>[<a href="#RFC8995" class="xref">RFC8995</a>]</span>.
      This later work requires a yet-to-be standardized Lightweight Authenticated
      Key Exchange protocol.<a href="#section-6.6-1" class="pilcrow">¶</a></p>
<p id="section-6.6-2">
      CoJP results in distribution of a network-wide key that
      is to be used with <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> security. The details of use are
      described in <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span>, Sections <a href="https://www.rfc-editor.org/rfc/rfc9031#section-9.2" class="relref">9.2</a>
      and <a href="https://www.rfc-editor.org/rfc/rfc9031#section-9.3.2" class="relref">9.3.2</a>.<a href="#section-6.6-2" class="pilcrow">¶</a></p>
<p id="section-6.6-3">
      The BRSKI mechanism may lead to the use of CoJP, in which case
      it also results in distribution of a network-wide key.  Alternatively
      the BRSKI mechanism may be followed by use of <span>[<a href="#I-D.ietf-ace-coap-est" class="xref">EST-COAPS</a>]</span>
      to enroll certificates for each device.  In that case, the certificates
      may be used with an <span>[<a href="#IEEE802154" class="xref">IEEE802154</a>]</span> key agreement protocol.  The
      description of this mechanism, while conceptually straightforward, still
      has significant standardization hurdles to pass.<a href="#section-6.6-3" class="pilcrow">¶</a></p>
<p id="section-6.6-4">

      <span><a href="https://www.rfc-editor.org/rfc/rfc9031#section-8.2" class="relref">Section 8.2</a> of [<a href="#RFC9031" class="xref">RFC9031</a>]</span> describes
      a mechanism to change (rekey) the network.
      There are a number of reasons to initiate a network rekey: to remove
      unwanted (corrupt/malicious) nodes, to recover unused 2-byte short
      addresses, or due to limits in encryption algorithms.
      For all of the mechanisms that distribute a network-wide key, rekeying
      is also needed on a periodic basis. In more detail:<a href="#section-6.6-4" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-6.6-5.1">
      The mechanism described in
      <span><a href="https://www.rfc-editor.org/rfc/rfc9031#section-8.2" class="relref">Section 8.2</a> of [<a href="#RFC9031" class="xref">RFC9031</a>]</span> requires
      advance communication between the JRC and every one of the nodes before
      the key change.  Given that many nodes may be sleepy, this operation
      may take a significant amount of time and may consume a significant
      portion of the available bandwidth.  As such, network-wide rekeys
      to exclude nodes that have become malicious will not be
      particularly quick.  If a rekey is already in progress, but the
      unwanted node has not yet been updated, then it is possible to just
      continue the operation.  If the unwanted node has already received the
      update, then the rekey operation will need to be restarted.<a href="#section-6.6-5.1" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-6.6-5.2">
      The cryptographic mechanisms used by IEEE Std 802.15.4 include the 2-byte
      short address in the calculation of the context.
      A nonce-reuse attack may become feasible if a short address is reassigned
      to another node while the  same network-wide keys are in operation.
      A network that gains and loses nodes on a regular
      basis is likely to reach the 65536 limit of the 2-byte (16-bit) short
      addresses, even if the network has only a few thousand nodes. Network
      planners should consider the need to rekey the network on a periodic
      basis in order to recover 2-byte addresses.  The rekey can update the
      short addresses for active nodes if desired, but there is actually no
      need to do this as long as the key has been changed.<a href="#section-6.6-5.2" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-6.6-5.3">
      With TSCH as it stands at the time of this writing, the ASN will wrap
      after 2^40 timeslot durations, meaning around 350 years with the default values. 
     Wrapping ASN is not expected to happen within the lifetime of
      most LLNs. Yet, should the ASN wrap, the network must be rekeyed to avoid
      a nonce-reuse attack.<a href="#section-6.6-5.3" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-6.6-5.4">
      Many cipher algorithms have some suggested limits on how many bytes
      should be encrypted with that algorithm before a new key is used.
      These numbers are typically in the many to hundreds of gigabytes of
      data.  On very fast backbone networks, this becomes an important
      concern. On LLNs with typical data rates in the kilobits/second,
      this concern is significantly less. With IEEE Std 802.15.4 as it stands
      at the time of this writing, the ASN will wrap before the limits of the
      current L2 crypto (AES-CCM-128) are reached, so the problem should never
      occur.<a href="#section-6.6-5.4" class="pilcrow">¶</a>
</li>
          <li class="normal" id="section-6.6-5.5">
      In any fashion, if the LLN is expected to operate continuously for decades,
      then the operators are advised to plan for the need to rekey.<a href="#section-6.6-5.5" class="pilcrow">¶</a>
</li>
        </ul>
<p id="section-6.6-6">
      Except for urgent rekeys caused by malicious nodes, the rekey operation
      described in <span>[<a href="#RFC9031" class="xref">RFC9031</a>]</span>
      can be done as a background task and can be done incrementally.  It
      is a make-before-break mechanism.  The switch over to the new key is
      not signaled by time, but rather by observation that the new key is in
      use.  As such, the update can take as long as needed, or occur in as
      short a time as practical.<a href="#section-6.6-6" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<section id="section-7">
      <h2 id="name-references">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-7.1">
        <h3 id="name-normative-references">
<a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC0768">[RFC0768]</dt>
        <dd>
<span class="refAuthor">Postel, J.</span>, <span class="refTitle">"User Datagram Protocol"</span>, <span class="seriesInfo">STD 6</span>, <span class="seriesInfo">RFC 768</span>, <span class="seriesInfo">DOI 10.17487/RFC0768</span>, <time datetime="1980-08" class="refDate">August 1980</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc768">https://www.rfc-editor.org/info/rfc768</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4861">[RFC4861]</dt>
        <dd>
<span class="refAuthor">Narten, T.</span>, <span class="refAuthor">Nordmark, E.</span>, <span class="refAuthor">Simpson, W.</span>, and <span class="refAuthor">H. Soliman</span>, <span class="refTitle">"Neighbor Discovery for IP version 6 (IPv6)"</span>, <span class="seriesInfo">RFC 4861</span>, <span class="seriesInfo">DOI 10.17487/RFC4861</span>, <time datetime="2007-09" class="refDate">September 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4861">https://www.rfc-editor.org/info/rfc4861</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4862">[RFC4862]</dt>
        <dd>
<span class="refAuthor">Thomson, S.</span>, <span class="refAuthor">Narten, T.</span>, and <span class="refAuthor">T. Jinmei</span>, <span class="refTitle">"IPv6 Stateless Address Autoconfiguration"</span>, <span class="seriesInfo">RFC 4862</span>, <span class="seriesInfo">DOI 10.17487/RFC4862</span>, <time datetime="2007-09" class="refDate">September 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4862">https://www.rfc-editor.org/info/rfc4862</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4944">[RFC4944]</dt>
        <dd>
<span class="refAuthor">Montenegro, G.</span>, <span class="refAuthor">Kushalnagar, N.</span>, <span class="refAuthor">Hui, J.</span>, and <span class="refAuthor">D. Culler</span>, <span class="refTitle">"Transmission of IPv6 Packets over IEEE 802.15.4 Networks"</span>, <span class="seriesInfo">RFC 4944</span>, <span class="seriesInfo">DOI 10.17487/RFC4944</span>, <time datetime="2007-09" class="refDate">September 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4944">https://www.rfc-editor.org/info/rfc4944</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5889">[RFC5889]</dt>
        <dd>
<span class="refAuthor">Baccelli, E., Ed.</span> and <span class="refAuthor">M. Townsley, Ed.</span>, <span class="refTitle">"IP Addressing Model in Ad Hoc Networks"</span>, <span class="seriesInfo">RFC 5889</span>, <span class="seriesInfo">DOI 10.17487/RFC5889</span>, <time datetime="2010-09" class="refDate">September 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5889">https://www.rfc-editor.org/info/rfc5889</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6282">[RFC6282]</dt>
        <dd>
<span class="refAuthor">Hui, J., Ed.</span> and <span class="refAuthor">P. Thubert</span>, <span class="refTitle">"Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks"</span>, <span class="seriesInfo">RFC 6282</span>, <span class="seriesInfo">DOI 10.17487/RFC6282</span>, <time datetime="2011-09" class="refDate">September 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6282">https://www.rfc-editor.org/info/rfc6282</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6550">[RFC6550]</dt>
        <dd>
<span class="refAuthor">Winter, T., Ed.</span>, <span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Brandt, A.</span>, <span class="refAuthor">Hui, J.</span>, <span class="refAuthor">Kelsey, R.</span>, <span class="refAuthor">Levis, P.</span>, <span class="refAuthor">Pister, K.</span>, <span class="refAuthor">Struik, R.</span>, <span class="refAuthor">Vasseur, JP.</span>, and <span class="refAuthor">R. Alexander</span>, <span class="refTitle">"RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks"</span>, <span class="seriesInfo">RFC 6550</span>, <span class="seriesInfo">DOI 10.17487/RFC6550</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6550">https://www.rfc-editor.org/info/rfc6550</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6551">[RFC6551]</dt>
        <dd>
<span class="refAuthor">Vasseur, JP., Ed.</span>, <span class="refAuthor">Kim, M., Ed.</span>, <span class="refAuthor">Pister, K.</span>, <span class="refAuthor">Dejean, N.</span>, and <span class="refAuthor">D. Barthel</span>, <span class="refTitle">"Routing Metrics Used for Path Calculation in Low-Power and Lossy Networks"</span>, <span class="seriesInfo">RFC 6551</span>, <span class="seriesInfo">DOI 10.17487/RFC6551</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6551">https://www.rfc-editor.org/info/rfc6551</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6552">[RFC6552]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refTitle">"Objective Function Zero for the Routing Protocol for Low-Power and Lossy Networks (RPL)"</span>, <span class="seriesInfo">RFC 6552</span>, <span class="seriesInfo">DOI 10.17487/RFC6552</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6552">https://www.rfc-editor.org/info/rfc6552</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6553">[RFC6553]</dt>
        <dd>
<span class="refAuthor">Hui, J.</span> and <span class="refAuthor">JP. Vasseur</span>, <span class="refTitle">"The Routing Protocol for Low-Power and Lossy Networks (RPL) Option for Carrying RPL Information in Data-Plane Datagrams"</span>, <span class="seriesInfo">RFC 6553</span>, <span class="seriesInfo">DOI 10.17487/RFC6553</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6553">https://www.rfc-editor.org/info/rfc6553</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6554">[RFC6554]</dt>
        <dd>
<span class="refAuthor">Hui, J.</span>, <span class="refAuthor">Vasseur, JP.</span>, <span class="refAuthor">Culler, D.</span>, and <span class="refAuthor">V. Manral</span>, <span class="refTitle">"An IPv6 Routing Header for Source Routes with the Routing Protocol for Low-Power and Lossy Networks (RPL)"</span>, <span class="seriesInfo">RFC 6554</span>, <span class="seriesInfo">DOI 10.17487/RFC6554</span>, <time datetime="2012-03" class="refDate">March 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6554">https://www.rfc-editor.org/info/rfc6554</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6775">[RFC6775]</dt>
        <dd>
<span class="refAuthor">Shelby, Z., Ed.</span>, <span class="refAuthor">Chakrabarti, S.</span>, <span class="refAuthor">Nordmark, E.</span>, and <span class="refAuthor">C. Bormann</span>, <span class="refTitle">"Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)"</span>, <span class="seriesInfo">RFC 6775</span>, <span class="seriesInfo">DOI 10.17487/RFC6775</span>, <time datetime="2012-11" class="refDate">November 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6775">https://www.rfc-editor.org/info/rfc6775</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7102">[RFC7102]</dt>
        <dd>
<span class="refAuthor">Vasseur, JP.</span>, <span class="refTitle">"Terms Used in Routing for Low-Power and Lossy Networks"</span>, <span class="seriesInfo">RFC 7102</span>, <span class="seriesInfo">DOI 10.17487/RFC7102</span>, <time datetime="2014-01" class="refDate">January 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7102">https://www.rfc-editor.org/info/rfc7102</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7228">[RFC7228]</dt>
        <dd>
<span class="refAuthor">Bormann, C.</span>, <span class="refAuthor">Ersue, M.</span>, and <span class="refAuthor">A. Keranen</span>, <span class="refTitle">"Terminology for Constrained-Node Networks"</span>, <span class="seriesInfo">RFC 7228</span>, <span class="seriesInfo">DOI 10.17487/RFC7228</span>, <time datetime="2014-05" class="refDate">May 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7228">https://www.rfc-editor.org/info/rfc7228</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7252">[RFC7252]</dt>
        <dd>
<span class="refAuthor">Shelby, Z.</span>, <span class="refAuthor">Hartke, K.</span>, and <span class="refAuthor">C. Bormann</span>, <span class="refTitle">"The Constrained Application Protocol (CoAP)"</span>, <span class="seriesInfo">RFC 7252</span>, <span class="seriesInfo">DOI 10.17487/RFC7252</span>, <time datetime="2014-06" class="refDate">June 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7252">https://www.rfc-editor.org/info/rfc7252</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7554">[RFC7554]</dt>
        <dd>
<span class="refAuthor">Watteyne, T., Ed.</span>, <span class="refAuthor">Palattella, M.</span>, and <span class="refAuthor">L. Grieco</span>, <span class="refTitle">"Using IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the Internet of Things (IoT): Problem Statement"</span>, <span class="seriesInfo">RFC 7554</span>, <span class="seriesInfo">DOI 10.17487/RFC7554</span>, <time datetime="2015-05" class="refDate">May 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7554">https://www.rfc-editor.org/info/rfc7554</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8025">[RFC8025]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span> and <span class="refAuthor">R. Cragie</span>, <span class="refTitle">"IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Paging Dispatch"</span>, <span class="seriesInfo">RFC 8025</span>, <span class="seriesInfo">DOI 10.17487/RFC8025</span>, <time datetime="2016-11" class="refDate">November 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8025">https://www.rfc-editor.org/info/rfc8025</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8137">[RFC8137]</dt>
        <dd>
<span class="refAuthor">Kivinen, T.</span> and <span class="refAuthor">P. Kinney</span>, <span class="refTitle">"IEEE 802.15.4 Information Element for the IETF"</span>, <span class="seriesInfo">RFC 8137</span>, <span class="seriesInfo">DOI 10.17487/RFC8137</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8137">https://www.rfc-editor.org/info/rfc8137</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8138">[RFC8138]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Bormann, C.</span>, <span class="refAuthor">Toutain, L.</span>, and <span class="refAuthor">R. Cragie</span>, <span class="refTitle">"IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing Header"</span>, <span class="seriesInfo">RFC 8138</span>, <span class="seriesInfo">DOI 10.17487/RFC8138</span>, <time datetime="2017-04" class="refDate">April 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8138">https://www.rfc-editor.org/info/rfc8138</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8180">[RFC8180]</dt>
        <dd>
<span class="refAuthor">Vilajosana, X., Ed.</span>, <span class="refAuthor">Pister, K.</span>, and <span class="refAuthor">T. Watteyne</span>, <span class="refTitle">"Minimal IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) Configuration"</span>, <span class="seriesInfo">BCP 210</span>, <span class="seriesInfo">RFC 8180</span>, <span class="seriesInfo">DOI 10.17487/RFC8180</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8180">https://www.rfc-editor.org/info/rfc8180</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8200">[RFC8200]</dt>
        <dd>
<span class="refAuthor">Deering, S.</span> and <span class="refAuthor">R. Hinden</span>, <span class="refTitle">"Internet Protocol, Version 6 (IPv6) Specification"</span>, <span class="seriesInfo">STD 86</span>, <span class="seriesInfo">RFC 8200</span>, <span class="seriesInfo">DOI 10.17487/RFC8200</span>, <time datetime="2017-07" class="refDate">July 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8200">https://www.rfc-editor.org/info/rfc8200</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8453">[RFC8453]</dt>
        <dd>
<span class="refAuthor">Ceccarelli, D., Ed.</span> and <span class="refAuthor">Y. Lee, Ed.</span>, <span class="refTitle">"Framework for Abstraction and Control of TE Networks (ACTN)"</span>, <span class="seriesInfo">RFC 8453</span>, <span class="seriesInfo">DOI 10.17487/RFC8453</span>, <time datetime="2018-08" class="refDate">August 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8453">https://www.rfc-editor.org/info/rfc8453</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8480">[RFC8480]</dt>
        <dd>
<span class="refAuthor">Wang, Q., Ed.</span>, <span class="refAuthor">Vilajosana, X.</span>, and <span class="refAuthor">T. Watteyne</span>, <span class="refTitle">"6TiSCH Operation Sublayer (6top) Protocol (6P)"</span>, <span class="seriesInfo">RFC 8480</span>, <span class="seriesInfo">DOI 10.17487/RFC8480</span>, <time datetime="2018-11" class="refDate">November 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8480">https://www.rfc-editor.org/info/rfc8480</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8505">[RFC8505]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Nordmark, E.</span>, <span class="refAuthor">Chakrabarti, S.</span>, and <span class="refAuthor">C. Perkins</span>, <span class="refTitle">"Registration Extensions for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery"</span>, <span class="seriesInfo">RFC 8505</span>, <span class="seriesInfo">DOI 10.17487/RFC8505</span>, <time datetime="2018-11" class="refDate">November 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8505">https://www.rfc-editor.org/info/rfc8505</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8655">[RFC8655]</dt>
        <dd>
<span class="refAuthor">Finn, N.</span>, <span class="refAuthor">Thubert, P.</span>, <span class="refAuthor">Varga, B.</span>, and <span class="refAuthor">J. Farkas</span>, <span class="refTitle">"Deterministic Networking Architecture"</span>, <span class="seriesInfo">RFC 8655</span>, <span class="seriesInfo">DOI 10.17487/RFC8655</span>, <time datetime="2019-10" class="refDate">October 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8655">https://www.rfc-editor.org/info/rfc8655</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8928">[RFC8928]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Sarikaya, B.</span>, <span class="refAuthor">Sethi, M.</span>, and <span class="refAuthor">R. Struik</span>, <span class="refTitle">"Address-Protected Neighbor Discovery for Low-Power and Lossy Networks"</span>, <span class="seriesInfo">RFC 8928</span>, <span class="seriesInfo">DOI 10.17487/RFC8928</span>, <time datetime="2020-11" class="refDate">November 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8928">https://www.rfc-editor.org/info/rfc8928</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8929">[RFC8929]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Perkins, C.E.</span>, and <span class="refAuthor">E. Levy-Abegnoli</span>, <span class="refTitle">"IPv6 Backbone Router"</span>, <span class="seriesInfo">RFC 8929</span>, <span class="seriesInfo">DOI 10.17487/RFC8929</span>, <time datetime="2020-11" class="refDate">November 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8929">https://www.rfc-editor.org/info/rfc8929</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8930">[RFC8930]</dt>
        <dd>
<span class="refAuthor">Watteyne, T., Ed.</span>, <span class="refAuthor">Thubert, P., Ed.</span>, and <span class="refAuthor">C. Bormann</span>, <span class="refTitle">"On Forwarding 6LoWPAN Fragments over a Multi-Hop IPv6 Network"</span>, <span class="seriesInfo">RFC 8930</span>, <span class="seriesInfo">DOI 10.17487/RFC8930</span>, <time datetime="2020-11" class="refDate">November 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8930">https://www.rfc-editor.org/info/rfc8930</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8931">[RFC8931]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refTitle">"IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Selective Fragment Recovery"</span>, <span class="seriesInfo">RFC 8931</span>, <span class="seriesInfo">DOI 10.17487/RFC8931</span>, <time datetime="2020-11" class="refDate">November 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8931">https://www.rfc-editor.org/info/rfc8931</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9008">[RFC9008]</dt>
        <dd>
<span class="refAuthor">Robles, M.I.</span>, <span class="refAuthor">Richardson, M.</span>, and <span class="refAuthor">P. Thubert</span>, <span class="refTitle">"Using RPI Option Type, Routing Header for Source Routes, and IPv6-in-IPv6 Encapsulation in the RPL Data Plane"</span>, <span class="seriesInfo">RFC 9008</span>, <span class="seriesInfo">DOI 10.17487/RFC9008</span>, <time datetime="2021-04" class="refDate">April 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9008">https://www.rfc-editor.org/info/rfc9008</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9010">[RFC9010]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span> and <span class="refAuthor">M. Richardson</span>, <span class="refTitle">"Routing for RPL (Routing Protocol for Low-Power and Lossy Networks) Leaves"</span>, <span class="seriesInfo">RFC 9010</span>, <span class="seriesInfo">DOI 10.17487/RFC9010</span>, <time datetime="2021-04" class="refDate">April 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9010">https://www.rfc-editor.org/info/rfc9010</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9031">[RFC9031]</dt>
        <dd>
<span class="refAuthor">Vučinić, M., Ed.</span>, <span class="refAuthor">Simon, J.</span>, <span class="refAuthor">Pister, K.</span>, and <span class="refAuthor">M. Richardson</span>, <span class="refTitle">"Constrained Join Protocol (CoJP) for 6TiSCH"</span>, <span class="seriesInfo">RFC 9031</span>, <span class="seriesInfo">DOI 10.17487/RFC9031</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9031">https://www.rfc-editor.org/info/rfc9031</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9032">[RFC9032]</dt>
        <dd>
<span class="refAuthor">Dujovne, D., Ed.</span> and <span class="refAuthor">M. Richardson</span>, <span class="refTitle">"Encapsulation of 6TiSCH Join and Enrollment Information Elements"</span>, <span class="seriesInfo">RFC 9032</span>, <span class="seriesInfo">DOI 10.17487/RFC9032</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9032">https://www.rfc-editor.org/info/rfc9032</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9033">[RFC9033]</dt>
      <dd>
<span class="refAuthor">Chang, T., Ed.</span>, <span class="refAuthor">Vučinić, M.</span>, <span class="refAuthor">Vilajosana, X.</span>, <span class="refAuthor">Duquennoy, S.</span>, and <span class="refAuthor">D. Dujovne</span>, <span class="refTitle">"6TiSCH Minimal Scheduling Function (MSF)"</span>, <span class="seriesInfo">RFC 9033</span>, <span class="seriesInfo">DOI 10.17487/RFC9033</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9033">https://www.rfc-editor.org/info/rfc9033</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-7.2">
        <h3 id="name-informative-references">
<a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="AMI">[AMI]</dt>
        <dd>
<span class="refAuthor">U.S. Department of Energy</span>, <span class="refTitle">"Advanced Metering Infrastructure and Customer Systems"</span>, <time datetime="2006" class="refDate">2006</time>, <span>&lt;<a href="https://www.energy.gov/sites/prod/files/2016/12/f34/AMI%20Summary%20Report_09-26-16.pdf">https://www.energy.gov/sites/prod/files/2016/12/f34/AMI%20Summary%20Report_09-26-16.pdf</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="ANIMA">[ANIMA]</dt>
        <dd>
<span class="refAuthor">IETF</span>, <span class="refTitle">"Autonomic Networking Integrated Model and Approach (anima)"</span>, <span>&lt;<a href="https://datatracker.ietf.org/doc/charter-ietf-anima/">https://datatracker.ietf.org/doc/charter-ietf-anima/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-roll-aodv-rpl">[AODV-RPL]</dt>
        <dd>
<span class="refAuthor">Anamalamudi, S.</span>, <span class="refAuthor">Zhang, M.</span>, <span class="refAuthor">Perkins, C. E.</span>, <span class="refAuthor">Anand, S.</span>, and <span class="refAuthor">B. Liu</span>, <span class="refTitle">"Supporting Asymmetric Links in Low Power Networks: AODV-RPL"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-roll-aodv-rpl-10</span>, <time datetime="2021-04-04" class="refDate">4 April 2021</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-roll-aodv-rpl-10">https://tools.ietf.org/html/draft-ietf-roll-aodv-rpl-10</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-manet-aodvv2">[AODVv2]</dt>
        <dd>
<span class="refAuthor">Perkins, C. E.</span>, <span class="refAuthor">Ratliff, S.</span>, <span class="refAuthor">Dowdell, J.</span>, <span class="refAuthor">Steenbrink, L.</span>, and <span class="refAuthor">V. Mercieca</span>, <span class="refTitle">"Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-manet-aodvv2-16</span>, <time datetime="2016-05-04" class="refDate">4 May 2016</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-manet-aodvv2-16">https://tools.ietf.org/html/draft-ietf-manet-aodvv2-16</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.thubert-6lo-bier-dispatch">[BITSTRINGS-6LORH]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Brodard, Z.</span>, <span class="refAuthor">Jiang, H.</span>, and <span class="refAuthor">G. Texier</span>, <span class="refTitle">"A 6loRH for BitStrings"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-thubert-6lo-bier-dispatch-06</span>, <time datetime="2019-01-28" class="refDate">28 January 2019</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-thubert-6lo-bier-dispatch-06">https://tools.ietf.org/html/draft-thubert-6lo-bier-dispatch-06</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="CCAMP">[CCAMP]</dt>
        <dd>
<span class="refAuthor">IETF</span>, <span class="refTitle">"Common Control and Measurement Plane (ccamp)"</span>, <span>&lt;<a href="https://datatracker.ietf.org/doc/charter-ietf-ccamp/">https://datatracker.ietf.org/doc/charter-ietf-ccamp/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="CCMstar">[CCMstar]</dt>
        <dd>
<span class="refAuthor">Struik, R.</span>, <span class="refTitle">"Formal Specification of the CCM* Mode of Operation"</span>, <time datetime="2004-09" class="refDate">September 2004</time>, <span>&lt;<a href="http://www.ieee802.org/15/pub/2004/15-04-0537-00-004b-formal-specification-ccm-star-mode-operation.doc">http://www.ieee802.org/15/pub/2004/15-04-0537-00-004b-formal-specification-ccm-star-mode-operation.doc</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-anima-constrained-voucher">[CONSTRAINED-VOUCHER]</dt>
        <dd>
<span class="refAuthor">Richardson, M.</span>, <span class="refAuthor">van der Stok, P.</span>, and <span class="refAuthor">P. Kampanakis</span>, <span class="refTitle">"Constrained Voucher Artifacts for Bootstrapping Protocols"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-anima-constrained-voucher-10</span>, <time datetime="2021-02-21" class="refDate">21 February 2021</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-anima-constrained-voucher-10">https://tools.ietf.org/html/draft-ietf-anima-constrained-voucher-10</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-roll-dao-projection">[DAO-PROJECTION]</dt>
        <dd>
<span class="refAuthor">Thubert, P.</span>, <span class="refAuthor">Jadhav, R. A.</span>, and <span class="refAuthor">M. Gillmore</span>, <span class="refTitle">"Root initiated routing state in RPL"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-roll-dao-projection-16</span>, <time datetime="2021-01-15" class="refDate">15 January 2021</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-roll-dao-projection-16">https://tools.ietf.org/html/draft-ietf-roll-dao-projection-16</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.selander-ace-cose-ecdhe">[EDHOC]</dt>
        <dd>
<span class="refAuthor">Selander, G.</span>, <span class="refAuthor">Mattsson, J.</span>, and <span class="refAuthor">F. Palombini</span>, <span class="refTitle">"Ephemeral Diffie-Hellman Over COSE (EDHOC)"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-selander-ace-cose-ecdhe-14</span>, <time datetime="2019-09-11" class="refDate">11 September 2019</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-selander-ace-cose-ecdhe-14">https://tools.ietf.org/html/draft-selander-ace-cose-ecdhe-14</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-ace-coap-est">[EST-COAPS]</dt>
        <dd>
<span class="refAuthor">van der Stok, P.</span>, <span class="refAuthor">Kampanakis, P.</span>, <span class="refAuthor">Richardson, M.</span>, and <span class="refAuthor">S. Raza</span>, <span class="refTitle">"EST over secure CoAP (EST-coaps)"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-ace-coap-est-18</span>, <time datetime="2020-01-06" class="refDate">6 January 2020</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-ace-coap-est-18">https://tools.ietf.org/html/draft-ietf-ace-coap-est-18</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="HART">[HART]</dt>
        <dd>
<span class="refAuthor">FieldComm Group</span>, <span class="refTitle">"HART"</span>, <span>&lt;<a href="https://fieldcommgroup.org/technologies/hart">https://fieldcommgroup.org/technologies/hart</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="IEC62439">[IEC62439]</dt>
        <dd>
<span class="refAuthor">IEC</span>, <span class="refTitle">"Industrial communication networks - High availability automation networks - Part 3: Parallel Redundancy Protocol (PRP) and High-availability Seamless Redundancy (HSR)"</span>, <span class="seriesInfo">IEC 62439-3:2016</span>, <time datetime="2016" class="refDate">2016</time>, <span>&lt;<a href="https://webstore.iec.ch/publication/24438">https://webstore.iec.ch/publication/24438</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="IEEE802154">[IEEE802154]</dt>
        <dd>
<span class="refAuthor">IEEE</span>, <span class="refTitle">"IEEE Standard for Low-Rate Wireless Networks"</span>, <span class="seriesInfo">IEEE Standard 802.15.4-2015</span>, <span class="seriesInfo">DOI 10.1109/IEEESTD.2016.7460875</span>, <time datetime="2016-04" class="refDate">April 2016</time>, <span>&lt;<a href="https://ieeexplore.ieee.org/document/7460875">https://ieeexplore.ieee.org/document/7460875</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="IEEE802154e">[IEEE802154e]</dt>
        <dd>
<span class="refAuthor">IEEE</span>, <span class="refTitle">"IEEE Standard for Local and metropolitan area networks -- Part. 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs) Amendment 1: MAC sublayer"</span>, <span class="seriesInfo">IEEE Standard 802.15.4e-2012</span>, <span class="seriesInfo">DOI 10.1109/IEEESTD.2012.6185525</span>, <time datetime="2012-04" class="refDate">April 2012</time>, <span>&lt;<a href="https://ieeexplore.ieee.org/document/6185525">https://ieeexplore.ieee.org/document/6185525</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="ISA100">[ISA100]</dt>
        <dd>
<span class="refAuthor">ISA/ANSI</span>, <span class="refTitle">"ISA100, Wireless Systems for Automation"</span>, <span>&lt;<a href="https://www.isa.org/isa100/">https://www.isa.org/isa100/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="ISA100.11a">[ISA100.11a]</dt>
        <dd>
<span class="refAuthor">ISA/ANSI</span>, <span class="refTitle">"Wireless Systems for Industrial Automation: Process Control and Related Applications - ISA100.11a-2011"</span>, <span class="seriesInfo">IEC 62734:2014</span>, <time datetime="2011" class="refDate">2011</time>, <span>&lt;<a href="https://webstore.iec.ch/publication/65581">https://webstore.iec.ch/publication/65581</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.thubert-6man-unicast-lookup">[ND-UNICAST-LOOKUP]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span> and <span class="refAuthor">E. Levy-Abegnoli</span>, <span class="refTitle">"IPv6 Neighbor Discovery Unicast Lookup"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-thubert-6man-unicast-lookup-00</span>, <time datetime="2019-07-29" class="refDate">29 July 2019</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-thubert-6man-unicast-lookup-00">https://tools.ietf.org/html/draft-thubert-6man-unicast-lookup-00</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="PCE">[PCE]</dt>
        <dd>
<span class="refAuthor">IETF</span>, <span class="refTitle">"Path Computation Element (pce)"</span>, <span>&lt;<a href="https://datatracker.ietf.org/doc/charter-ietf-pce/">https://datatracker.ietf.org/doc/charter-ietf-pce/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.pthubert-raw-architecture">[RAW-ARCHITECTURE]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span> and <span class="refAuthor">G. Z. Papadopoulos</span>, <span class="refTitle">"Reliable and Available Wireless Problem Statement"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-pthubert-raw-architecture-05</span>, <time datetime="2020-11-15" class="refDate">15 November 2020</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-pthubert-raw-architecture-05">https://tools.ietf.org/html/draft-pthubert-raw-architecture-05</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-raw-use-cases">[RAW-USE-CASES]</dt>
        <dd>
<span class="refAuthor">Papadopoulos, G. Z.</span>, <span class="refAuthor">Thubert, P.</span>, <span class="refAuthor">Theoleyre, F.</span>, and <span class="refAuthor">C. J. Bernardos</span>, <span class="refTitle">"RAW use cases"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-raw-use-cases-01</span>, <time datetime="2021-02-21" class="refDate">21 February 2021</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-raw-use-cases-01">https://tools.ietf.org/html/draft-ietf-raw-use-cases-01</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC2474">[RFC2474]</dt>
        <dd>
<span class="refAuthor">Nichols, K.</span>, <span class="refAuthor">Blake, S.</span>, <span class="refAuthor">Baker, F.</span>, and <span class="refAuthor">D. Black</span>, <span class="refTitle">"Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers"</span>, <span class="seriesInfo">RFC 2474</span>, <span class="seriesInfo">DOI 10.17487/RFC2474</span>, <time datetime="1998-12" class="refDate">December 1998</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2474">https://www.rfc-editor.org/info/rfc2474</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC2545">[RFC2545]</dt>
        <dd>
<span class="refAuthor">Marques, P.</span> and <span class="refAuthor">F. Dupont</span>, <span class="refTitle">"Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing"</span>, <span class="seriesInfo">RFC 2545</span>, <span class="seriesInfo">DOI 10.17487/RFC2545</span>, <time datetime="1999-03" class="refDate">March 1999</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2545">https://www.rfc-editor.org/info/rfc2545</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3209">[RFC3209]</dt>
        <dd>
<span class="refAuthor">Awduche, D.</span>, <span class="refAuthor">Berger, L.</span>, <span class="refAuthor">Gan, D.</span>, <span class="refAuthor">Li, T.</span>, <span class="refAuthor">Srinivasan, V.</span>, and <span class="refAuthor">G. Swallow</span>, <span class="refTitle">"RSVP-TE: Extensions to RSVP for LSP Tunnels"</span>, <span class="seriesInfo">RFC 3209</span>, <span class="seriesInfo">DOI 10.17487/RFC3209</span>, <time datetime="2001-12" class="refDate">December 2001</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3209">https://www.rfc-editor.org/info/rfc3209</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3444">[RFC3444]</dt>
        <dd>
<span class="refAuthor">Pras, A.</span> and <span class="refAuthor">J. Schoenwaelder</span>, <span class="refTitle">"On the Difference between Information Models and Data Models"</span>, <span class="seriesInfo">RFC 3444</span>, <span class="seriesInfo">DOI 10.17487/RFC3444</span>, <time datetime="2003-01" class="refDate">January 2003</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3444">https://www.rfc-editor.org/info/rfc3444</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC3963">[RFC3963]</dt>
        <dd>
<span class="refAuthor">Devarapalli, V.</span>, <span class="refAuthor">Wakikawa, R.</span>, <span class="refAuthor">Petrescu, A.</span>, and <span class="refAuthor">P. Thubert</span>, <span class="refTitle">"Network Mobility (NEMO) Basic Support Protocol"</span>, <span class="seriesInfo">RFC 3963</span>, <span class="seriesInfo">DOI 10.17487/RFC3963</span>, <time datetime="2005-01" class="refDate">January 2005</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc3963">https://www.rfc-editor.org/info/rfc3963</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4080">[RFC4080]</dt>
        <dd>
<span class="refAuthor">Hancock, R.</span>, <span class="refAuthor">Karagiannis, G.</span>, <span class="refAuthor">Loughney, J.</span>, and <span class="refAuthor">S. Van den Bosch</span>, <span class="refTitle">"Next Steps in Signaling (NSIS): Framework"</span>, <span class="seriesInfo">RFC 4080</span>, <span class="seriesInfo">DOI 10.17487/RFC4080</span>, <time datetime="2005-06" class="refDate">June 2005</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4080">https://www.rfc-editor.org/info/rfc4080</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4291">[RFC4291]</dt>
        <dd>
<span class="refAuthor">Hinden, R.</span> and <span class="refAuthor">S. Deering</span>, <span class="refTitle">"IP Version 6 Addressing Architecture"</span>, <span class="seriesInfo">RFC 4291</span>, <span class="seriesInfo">DOI 10.17487/RFC4291</span>, <time datetime="2006-02" class="refDate">February 2006</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4291">https://www.rfc-editor.org/info/rfc4291</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4903">[RFC4903]</dt>
        <dd>
<span class="refAuthor">Thaler, D.</span>, <span class="refTitle">"Multi-Link Subnet Issues"</span>, <span class="seriesInfo">RFC 4903</span>, <span class="seriesInfo">DOI 10.17487/RFC4903</span>, <time datetime="2007-06" class="refDate">June 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4903">https://www.rfc-editor.org/info/rfc4903</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC4919">[RFC4919]</dt>
        <dd>
<span class="refAuthor">Kushalnagar, N.</span>, <span class="refAuthor">Montenegro, G.</span>, and <span class="refAuthor">C. Schumacher</span>, <span class="refTitle">"IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): Overview, Assumptions, Problem Statement, and Goals"</span>, <span class="seriesInfo">RFC 4919</span>, <span class="seriesInfo">DOI 10.17487/RFC4919</span>, <time datetime="2007-08" class="refDate">August 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc4919">https://www.rfc-editor.org/info/rfc4919</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5340">[RFC5340]</dt>
        <dd>
<span class="refAuthor">Coltun, R.</span>, <span class="refAuthor">Ferguson, D.</span>, <span class="refAuthor">Moy, J.</span>, and <span class="refAuthor">A. Lindem</span>, <span class="refTitle">"OSPF for IPv6"</span>, <span class="seriesInfo">RFC 5340</span>, <span class="seriesInfo">DOI 10.17487/RFC5340</span>, <time datetime="2008-07" class="refDate">July 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5340">https://www.rfc-editor.org/info/rfc5340</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5974">[RFC5974]</dt>
        <dd>
<span class="refAuthor">Manner, J.</span>, <span class="refAuthor">Karagiannis, G.</span>, and <span class="refAuthor">A. McDonald</span>, <span class="refTitle">"NSIS Signaling Layer Protocol (NSLP) for Quality-of-Service Signaling"</span>, <span class="seriesInfo">RFC 5974</span>, <span class="seriesInfo">DOI 10.17487/RFC5974</span>, <time datetime="2010-10" class="refDate">October 2010</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5974">https://www.rfc-editor.org/info/rfc5974</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6275">[RFC6275]</dt>
        <dd>
<span class="refAuthor">Perkins, C., Ed.</span>, <span class="refAuthor">Johnson, D.</span>, and <span class="refAuthor">J. Arkko</span>, <span class="refTitle">"Mobility Support in IPv6"</span>, <span class="seriesInfo">RFC 6275</span>, <span class="seriesInfo">DOI 10.17487/RFC6275</span>, <time datetime="2011-07" class="refDate">July 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6275">https://www.rfc-editor.org/info/rfc6275</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6347">[RFC6347]</dt>
        <dd>
<span class="refAuthor">Rescorla, E.</span> and <span class="refAuthor">N. Modadugu</span>, <span class="refTitle">"Datagram Transport Layer Security Version 1.2"</span>, <span class="seriesInfo">RFC 6347</span>, <span class="seriesInfo">DOI 10.17487/RFC6347</span>, <time datetime="2012-01" class="refDate">January 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6347">https://www.rfc-editor.org/info/rfc6347</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6606">[RFC6606]</dt>
        <dd>
<span class="refAuthor">Kim, E.</span>, <span class="refAuthor">Kaspar, D.</span>, <span class="refAuthor">Gomez, C.</span>, and <span class="refAuthor">C. Bormann</span>, <span class="refTitle">"Problem Statement and Requirements for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing"</span>, <span class="seriesInfo">RFC 6606</span>, <span class="seriesInfo">DOI 10.17487/RFC6606</span>, <time datetime="2012-05" class="refDate">May 2012</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6606">https://www.rfc-editor.org/info/rfc6606</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6830">[RFC6830]</dt>
        <dd>
<span class="refAuthor">Farinacci, D.</span>, <span class="refAuthor">Fuller, V.</span>, <span class="refAuthor">Meyer, D.</span>, and <span class="refAuthor">D. Lewis</span>, <span class="refTitle">"The Locator/ID Separation Protocol (LISP)"</span>, <span class="seriesInfo">RFC 6830</span>, <span class="seriesInfo">DOI 10.17487/RFC6830</span>, <time datetime="2013-01" class="refDate">January 2013</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6830">https://www.rfc-editor.org/info/rfc6830</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7426">[RFC7426]</dt>
        <dd>
<span class="refAuthor">Haleplidis, E., Ed.</span>, <span class="refAuthor">Pentikousis, K., Ed.</span>, <span class="refAuthor">Denazis, S.</span>, <span class="refAuthor">Hadi Salim, J.</span>, <span class="refAuthor">Meyer, D.</span>, and <span class="refAuthor">O. Koufopavlou</span>, <span class="refTitle">"Software-Defined Networking (SDN): Layers and Architecture Terminology"</span>, <span class="seriesInfo">RFC 7426</span>, <span class="seriesInfo">DOI 10.17487/RFC7426</span>, <time datetime="2015-01" class="refDate">January 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7426">https://www.rfc-editor.org/info/rfc7426</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8578">[RFC8578]</dt>
        <dd>
<span class="refAuthor">Grossman, E., Ed.</span>, <span class="refTitle">"Deterministic Networking Use Cases"</span>, <span class="seriesInfo">RFC 8578</span>, <span class="seriesInfo">DOI 10.17487/RFC8578</span>, <time datetime="2019-05" class="refDate">May 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8578">https://www.rfc-editor.org/info/rfc8578</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8613">[RFC8613]</dt>
        <dd>
<span class="refAuthor">Selander, G.</span>, <span class="refAuthor">Mattsson, J.</span>, <span class="refAuthor">Palombini, F.</span>, and <span class="refAuthor">L. Seitz</span>, <span class="refTitle">"Object Security for Constrained RESTful Environments (OSCORE)"</span>, <span class="seriesInfo">RFC 8613</span>, <span class="seriesInfo">DOI 10.17487/RFC8613</span>, <time datetime="2019-07" class="refDate">July 2019</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8613">https://www.rfc-editor.org/info/rfc8613</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8939">[RFC8939]</dt>
        <dd>
<span class="refAuthor">Varga, B., Ed.</span>, <span class="refAuthor">Farkas, J.</span>, <span class="refAuthor">Berger, L.</span>, <span class="refAuthor">Fedyk, D.</span>, and <span class="refAuthor">S. Bryant</span>, <span class="refTitle">"Deterministic Networking (DetNet) Data Plane: IP"</span>, <span class="seriesInfo">RFC 8939</span>, <span class="seriesInfo">DOI 10.17487/RFC8939</span>, <time datetime="2020-11" class="refDate">November 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8939">https://www.rfc-editor.org/info/rfc8939</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8995">[RFC8995]</dt>
        <dd>
<span class="refAuthor">Pritikin, M.</span>, <span class="refAuthor">Richardson, M.</span>, <span class="refAuthor">Eckert, T.</span>, <span class="refAuthor">Behringer, M.</span>, and <span class="refAuthor">K. Watsen</span>, <span class="refTitle">"Bootstrapping Remote Secure Key Infrastructure (BRSKI)"</span>, <span class="seriesInfo">RFC 8995</span>, <span class="seriesInfo">DOI 10.17487/RFC8995</span>, <time datetime="2021-05" class="refDate">May 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8995">https://www.rfc-editor.org/info/rfc8995</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC9035">[RFC9035]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span> and <span class="refAuthor">L. Zhao</span>, <span class="refTitle">"A Routing Protocol for Low-Power and Lossy Networks (RPL) Destination-Oriented Directed Acyclic Graph (DODAG) Configuration Option for the 6LoWPAN Routing Header"</span>, <span class="seriesInfo">RFC 9035</span>, <span class="seriesInfo">DOI 10.17487/RFC9035</span>, <time datetime="2021-04" class="refDate">April 2021</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc9035">https://www.rfc-editor.org/info/rfc9035</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.tiloca-6tisch-robust-scheduling">[ROBUST-SCHEDULING]</dt>
        <dd>
<span class="refAuthor">Tiloca, M.</span>, <span class="refAuthor">Duquennoy, S.</span>, and <span class="refAuthor">G. Dini</span>, <span class="refTitle">"Robust Scheduling against Selective Jamming in 6TiSCH Networks"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-tiloca-6tisch-robust-scheduling-02</span>, <time datetime="2019-06-10" class="refDate">10 June 2019</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-tiloca-6tisch-robust-scheduling-02">https://tools.ietf.org/html/draft-tiloca-6tisch-robust-scheduling-02</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-roll-rpl-industrial-applicability">[RPL-APPLICABILITY]</dt>
        <dd>
<span class="refAuthor">Phinney, T., Ed.</span>, <span class="refAuthor">Thubert, P.</span>, and <span class="refAuthor">R. Assimiti</span>, <span class="refTitle">"RPL applicability in industrial networks"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-roll-rpl-industrial-applicability-02</span>, <time datetime="2013-10-21" class="refDate">21 October 2013</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-roll-rpl-industrial-applicability-02">https://tools.ietf.org/html/draft-ietf-roll-rpl-industrial-applicability-02</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.thubert-roll-bier">[RPL-BIER]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refTitle">"RPL-BIER"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-thubert-roll-bier-02</span>, <time datetime="2018-07-24" class="refDate">24 July 2018</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-thubert-roll-bier-02">https://tools.ietf.org/html/draft-thubert-roll-bier-02</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-roll-capabilities">[RPL-MOP]</dt>
        <dd>
<span class="refAuthor">Jadhav, R., Ed.</span>, <span class="refAuthor">Thubert, P.</span>, <span class="refAuthor">Richardson, M.</span>, and <span class="refAuthor">R. Sahoo</span>, <span class="refTitle">"RPL Capabilities"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-roll-capabilities-08</span>, <time datetime="2021-03-17" class="refDate">17 March 2021</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-roll-capabilities-08">https://tools.ietf.org/html/draft-ietf-roll-capabilities-08</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="S-ALOHA">[S-ALOHA]</dt>
        <dd>
<span class="refAuthor">Roberts, L. G.</span>, <span class="refTitle">"ALOHA packet system with and without slots and capture"</span>, <span class="refContent">ACM SIGCOMM Computer Communication Review</span>, <span class="seriesInfo">DOI 10.1145/1024916.1024920</span>, <time datetime="1975-04" class="refDate">April 1975</time>, <span>&lt;<a href="https://dl.acm.org/citation.cfm?id=1024920">https://dl.acm.org/citation.cfm?id=1024920</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.thubert-bier-replication-elimination">[TE-PREF]</dt>
        <dd>
<span class="refAuthor">Thubert, P., Ed.</span>, <span class="refAuthor">Eckert, T.</span>, <span class="refAuthor">Brodard, Z.</span>, and <span class="refAuthor">H. Jiang</span>, <span class="refTitle">"BIER-TE extensions for Packet Replication and Elimination Function (PREF) and OAM"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-thubert-bier-replication-elimination-03</span>, <time datetime="2018-03-03" class="refDate">3 March 2018</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-thubert-bier-replication-elimination-03">https://tools.ietf.org/html/draft-thubert-bier-replication-elimination-03</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="TEAS">[TEAS]</dt>
        <dd>
<span class="refAuthor">IETF</span>, <span class="refTitle">"Traffic Engineering Architecture and Signaling (teas)"</span>, <span>&lt;<a href="https://datatracker.ietf.org/doc/charter-ietf-teas/">https://datatracker.ietf.org/doc/charter-ietf-teas/</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-lwig-6lowpan-virtual-reassembly">[VIRTUAL-REASSEMBLY]</dt>
        <dd>
<span class="refAuthor">Bormann, C.</span> and <span class="refAuthor">T. Watteyne</span>, <span class="refTitle">"Virtual reassembly buffers in 6LoWPAN"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-lwig-6lowpan-virtual-reassembly-02</span>, <time datetime="2020-03-09" class="refDate">9 March 2020</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-lwig-6lowpan-virtual-reassembly-02">https://tools.ietf.org/html/draft-ietf-lwig-6lowpan-virtual-reassembly-02</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="WirelessHART">[WirelessHART]</dt>
        <dd>
<span class="refAuthor">International Electrotechnical Commission</span>, <span class="refTitle">"Industrial networks - Wireless communication network and communication profiles - WirelessHART(TM)"</span>, <span class="seriesInfo">IEC 62591:2016</span>, <time datetime="2016-03" class="refDate">March 2016</time>, <span>&lt;<a href="https://webstore.iec.ch/publication/24433">https://webstore.iec.ch/publication/24433</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="I-D.ietf-6tisch-dtsecurity-zerotouch-join">[ZEROTOUCH-JOIN]</dt>
      <dd>
<span class="refAuthor">Richardson, M.</span>, <span class="refTitle">"6tisch Zero-Touch Secure Join protocol"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-6tisch-dtsecurity-zerotouch-join-04</span>, <time datetime="2019-07-08" class="refDate">8 July 2019</time>, <span>&lt;<a href="https://tools.ietf.org/html/draft-ietf-6tisch-dtsecurity-zerotouch-join-04">https://tools.ietf.org/html/draft-ietf-6tisch-dtsecurity-zerotouch-join-04</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<section id="section-appendix.a">
      <h2 id="name-related-work-in-progress">
<a href="#section-appendix.a" class="section-number selfRef">Appendix A. </a><a href="#name-related-work-in-progress" class="section-name selfRef">Related Work in Progress</a>
      </h2>
<p id="section-appendix.a-1">This document has been incremented as the work progressed following the
      evolution of the WG charter and the availability of dependent work.
      The intent was to publish when the WG concluded on the covered items.
      At the time of publishing, the following specifications are still in progress
      and may affect the evolution of the stack in a 6TiSCH-aware node.<a href="#section-appendix.a-1" class="pilcrow">¶</a></p>
<div id="unchartered">
<section id="section-a.1">
        <h2 id="name-unchartered-ietf-work-items">
<a href="#section-a.1" class="section-number selfRef">A.1. </a><a href="#name-unchartered-ietf-work-items" class="section-name selfRef">Unchartered IETF Work Items</a>
        </h2>
<div id="unchartered-sec">
<section id="section-a.1.1">
          <h3 id="name-6tisch-zero-touch-security">
<a href="#section-a.1.1" class="section-number selfRef">A.1.1. </a><a href="#name-6tisch-zero-touch-security" class="section-name selfRef">6TiSCH Zero-Touch Security</a>
          </h3>
<p id="section-a.1.1-1">
      The security model and in particular the zero-touch join process
      <span>[<a href="#I-D.ietf-6tisch-dtsecurity-zerotouch-join" class="xref">ZEROTOUCH-JOIN</a>]</span> depend on
      the ANIMA (Autonomic Networking Integrated Model and Approach) <span>[<a href="#ANIMA" class="xref">ANIMA</a>]</span>
      "<a href="#RFC8995" class="xref">Bootstrapping Remote Secure Key Infrastructure (BRSKI)</a>" <span>[<a href="#RFC8995" class="xref">RFC8995</a>]</span>
      to enable zero-touch security provisioning; for highly
      constrained nodes, a minimal model based on pre-shared keys (PSK)
      is also available. As currently written, it also depends on
      a number of documents in progress in the CORE (Constrained RESTful Environments) WG and on
      <span><a href="#I-D.selander-ace-cose-ecdhe" class="xref">"Ephemeral Diffie-Hellman Over
      COSE (EDHOC)"</a> [<a href="#I-D.selander-ace-cose-ecdhe" class="xref">EDHOC</a>]</span>, which is being considered for adoption by the LAKE 
      (Lightweight Authenticated Key Exchange) WG.<a href="#section-a.1.1-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="unchartered-tracks">
<section id="section-a.1.2">
          <h3 id="name-6tisch-track-setup">
<a href="#section-a.1.2" class="section-number selfRef">A.1.2. </a><a href="#name-6tisch-track-setup" class="section-name selfRef">6TiSCH Track Setup</a>
          </h3>
<p id="section-a.1.2-1">
      ROLL (Routing Over Low power and Lossy networks) is now standardizing a reactive routing protocol based on RPL
      <span>[<a href="#I-D.ietf-roll-aodv-rpl" class="xref">AODV-RPL</a>]</span>.
      The need of a reactive routing protocol to establish on-demand,
      constraint-optimized routes and a reservation protocol to establish
      Layer 3 Tracks is being discussed in 6TiSCH but not yet chartered.<a href="#section-a.1.2-1" class="pilcrow">¶</a></p>
<p id="section-a.1.2-2">

      At the time of this writing, there is new work planned in the IETF to provide
      limited deterministic networking capabilities for wireless networks with a
      focus on forwarding behaviors to react quickly and locally to the changes
      as described in <span>[<a href="#I-D.pthubert-raw-architecture" class="xref">RAW-ARCHITECTURE</a>]</span>.<a href="#section-a.1.2-2" class="pilcrow">¶</a></p>
<p id="section-a.1.2-3">
      ROLL is also standardizing an extension to RPL to set up centrally computed
      routes <span>[<a href="#I-D.ietf-roll-dao-projection" class="xref">DAO-PROJECTION</a>]</span>.<a href="#section-a.1.2-3" class="pilcrow">¶</a></p>
<p id="section-a.1.2-4">
      The 6TiSCH architecture should thus inherit from the
      <span><a href="#RFC8655" class="xref">DetNet architecture</a> [<a href="#RFC8655" class="xref">RFC8655</a>]</span> and
      thus depends on it. The PCE should be a
      core component of that architecture.
      An extension to RPL or to TEAS (Traffic Engineering Architecture and Signaling) <span>[<a href="#TEAS" class="xref">TEAS</a>]</span> will be required to
      expose the 6TiSCH node capabilities and the network peers to the PCE,
      possibly in combination with <span>[<a href="#I-D.ietf-roll-capabilities" class="xref">RPL-MOP</a>]</span>.
      A protocol such as a lightweight Path Computation Element Communication Protocol (PCEP) or an adaptation of 
      Common Control and Measurement Plane (CCAMP)
      <span>[<a href="#CCAMP" class="xref">CCAMP</a>]</span> GMPLS formats and procedures could be used in
      combination to <span>[<a href="#I-D.ietf-roll-dao-projection" class="xref">DAO-PROJECTION</a>]</span> to install
      the Tracks, as computed by the PCE, to the 6TiSCH nodes.<a href="#section-a.1.2-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="unchartered-bier">
<section id="section-a.1.3">
          <h3 id="name-using-bier-in-a-6tisch-netw">
<a href="#section-a.1.3" class="section-number selfRef">A.1.3. </a><a href="#name-using-bier-in-a-6tisch-netw" class="section-name selfRef">Using BIER in a 6TiSCH Network</a>
          </h3>
<p id="section-a.1.3-1"> ROLL is actively working on Bit Index
    Explicit Replication (BIER) as a method to compress both the
    data-plane packets and the routing tables in storing mode
    <span>[<a href="#I-D.thubert-roll-bier" class="xref">RPL-BIER</a>]</span>.<a href="#section-a.1.3-1" class="pilcrow">¶</a></p>
<p id="section-a.1.3-2">
    BIER could also be used in the context of the DetNet service layer.
    <span><a href="#I-D.thubert-bier-replication-elimination" class="xref">"BIER-TE extensions for Packet Replication and Elimination Function
                             (PREF) and OAM"</a> [<a href="#I-D.thubert-bier-replication-elimination" class="xref">TE-PREF</a>]</span> leverages BIER
    Traffic Engineering (TE) to control the
    DetNet Replication and Elimination activities in the data plane, and to provide traceability
    on links where replication and loss happen, in a manner that is abstract to
    the forwarding information.<a href="#section-a.1.3-2" class="pilcrow">¶</a></p>
<p id="section-a.1.3-3">
    <span><a href="#I-D.thubert-6lo-bier-dispatch" class="xref">"A 6loRH for BitStrings"</a> [<a href="#I-D.thubert-6lo-bier-dispatch" class="xref">BITSTRINGS-6LORH</a>]</span>
    proposes a 6LoWPAN compression for the BIER BitString based on
    <span><a href="#RFC8138" class="xref">6LoWPAN Routing Header</a> [<a href="#RFC8138" class="xref">RFC8138</a>]</span>.<a href="#section-a.1.3-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="external">
<section id="section-a.2">
        <h2 id="name-external-non-ietf-work-item">
<a href="#section-a.2" class="section-number selfRef">A.2. </a><a href="#name-external-non-ietf-work-item" class="section-name selfRef">External (Non-IETF) Work Items</a>
        </h2>
<p id="section-a.2-1">
      The current charter positions 6TiSCH on IEEE Std 802.15.4 only.
      Though most of the design should be portable to other link types,
      6TiSCH has a strong dependency on IEEE Std 802.15.4 and its evolution.
      The impact of changes to TSCH on this architecture should be minimal to
      nonexistent, but deeper work such as 6top and security may be impacted.
      A 6TiSCH Interest Group at the IEEE maintains the synchronization
      and helps foster work at the IEEE should 6TiSCH demand it.<a href="#section-a.2-1" class="pilcrow">¶</a></p>
<p id="section-a.2-2">
      Work is being proposed at IEEE (802.15.12 PAR) for an LLC that would
      logically include the 6top sublayer. The interaction with the 6top sublayer
      and the Scheduling Functions described in this document are yet to be
      defined.<a href="#section-a.2-2" class="pilcrow">¶</a></p>
<p id="section-a.2-3">
      ISA100 <span>[<a href="#ISA100" class="xref">ISA100</a>]</span> Common Network Management (CNM) is another
      external work of interest for 6TiSCH. The group, referred to as ISA100.20,
      defines a Common Network Management framework that should enable the
      management of resources that are controlled by heterogeneous protocols
      such as ISA100.11a <span>[<a href="#ISA100.11a" class="xref">ISA100.11a</a>]</span>, WirelessHART
      <span>[<a href="#WirelessHART" class="xref">WirelessHART</a>]</span>, and 6TiSCH. Interestingly, the
      establishment of 6TiSCH deterministic paths, called Tracks,
      are also in scope, and ISA100.20 is working on requirements for DetNet.<a href="#section-a.2-3" class="pilcrow">¶</a></p>
</section>
</div>
</section>
<section id="section-appendix.b">
      <h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
      </h2>
<section id="section-b.1">
        <h2 id="name-special-thanks">
<a href="#name-special-thanks" class="section-name selfRef">Special Thanks</a>
        </h2>
<p id="section-b.1-1">
      Special thanks to <span class="contact-name">Jonathan Simon</span>, 
      <span class="contact-name">Giuseppe Piro</span>, <span class="contact-name">Subir Das</span>, and 
      <span class="contact-name">Yoshihiro Ohba</span> for their deep contributions to the initial security
      work, to <span class="contact-name">Yasuyuki Tanaka</span> for his work on implementation and simulation
      that tremendously helped build a robust system, to <span class="contact-name">Diego Dujovne</span> for
      starting and leading the SF0 effort, and to <span class="contact-name">Tengfei Chang</span> for evolving it
      in the MSF.<a href="#section-b.1-1" class="pilcrow">¶</a></p>
<p id="section-b.1-2">
      Special thanks also to <span class="contact-name">Pat Kinney</span>, 
      <span class="contact-name">Charlie Perkins</span>, and <span class="contact-name">Bob Heile</span> for their
      support in maintaining the connection active and the design in line with
      work happening at IEEE 802.15.<a href="#section-b.1-2" class="pilcrow">¶</a></p>
<p id="section-b.1-3">
      Special thanks to <span class="contact-name">Ted Lemon</span>, who was the INT Area Director while this
      document was initiated, for his great support and help throughout,
      and to <span class="contact-name">Suresh Krishnan</span>, who took over with that kind efficiency of his till
      publication.<a href="#section-b.1-3" class="pilcrow">¶</a></p>
<p id="section-b.1-4">
      Also special thanks to <span class="contact-name">Ralph Droms</span>, who performed the first INT Area
      Directorate review, which was very deep and thorough and radically changed
      the orientations of this document, and then to <span class="contact-name">Eliot Lear</span> 
      and <span class="contact-name">Carlos Pignataro</span>, who helped finalize this 
      document in preparation for the IESG reviews, 
      and to <span class="contact-name">Gorry Fairhurst</span>, 
<span class="contact-name">David Mandelberg</span>, <span class="contact-name">Qin Wu</span>, 
<span class="contact-name">Francis Dupont</span>, <span class="contact-name">Éric Vyncke</span>, 
<span class="contact-name">Mirja Kühlewind</span>, <span class="contact-name">Roman Danyliw</span>, 
<span class="contact-name">Benjamin Kaduk</span>, and <span class="contact-name">Andrew Malis</span>, 
who contributed to the final shaping of this document
      through the IESG review procedure.<a href="#section-b.1-4" class="pilcrow">¶</a></p>
</section>
<section id="section-b.2">
        <h2 id="name-and-do-not-forget">
<a href="#name-and-do-not-forget" class="section-name selfRef">And Do Not Forget</a>
        </h2>
<p id="section-b.2-1">This document is the result of multiple interactions, in
      particular during the 6TiSCH (bi)Weekly Interim call, relayed through
      the 6TiSCH mailing list at the IETF, over the course of more than 5 years.<a href="#section-b.2-1" class="pilcrow">¶</a></p>
<p id="section-b.2-2">
      The authors wish to thank in arbitrary order:
<span class="contact-name">Alaeddine Weslati</span>, <span class="contact-name">Chonggang Wang</span>, 
<span class="contact-name">Georgios Exarchakos</span>, <span class="contact-name">Zhuo Chen</span>,
<span class="contact-name">Georgios Papadopoulos</span>, <span class="contact-name">Eric Levy-Abegnoli</span>,
<span class="contact-name">Alfredo Grieco</span>, <span class="contact-name">Bert Greevenbosch</span>, 
<span class="contact-name">Cedric Adjih</span>, <span class="contact-name">Deji Chen</span>, 
<span class="contact-name">Martin Turon</span>, <span class="contact-name">Dominique Barthel</span>, 
<span class="contact-name">Elvis Vogli</span>, <span class="contact-name">Geraldine Texier</span>, 
<span class="contact-name">Guillaume Gaillard</span>, <span class="contact-name">Herman Storey</span>, 
<span class="contact-name">Kazushi Muraoka</span>, <span class="contact-name">Ken Bannister</span>,
<span class="contact-name">Kuor Hsin Chang</span>, <span class="contact-name">Laurent Toutain</span>, 
<span class="contact-name">Maik Seewald</span>, <span class="contact-name">Michael Behringer</span>, 
<span class="contact-name">Nancy Cam Winget</span>, <span class="contact-name">Nicola Accettura</span>, 
<span class="contact-name">Nicolas Montavont</span>, <span class="contact-name">Oleg Hahm</span>, 
<span class="contact-name">Patrick Wetterwald</span>, <span class="contact-name">Paul Duffy</span>, 
<span class="contact-name">Peter van der Stok</span>, <span class="contact-name">Rahul Sen</span>,
<span class="contact-name">Pieter de Mil</span>, <span class="contact-name">Pouria Zand</span>, 
<span class="contact-name">Rouhollah Nabati</span>, <span class="contact-name">Rafa Marin-Lopez</span>,
<span class="contact-name">Raghuram Sudhaakar</span>, <span class="contact-name">Sedat Gormus</span>, 
<span class="contact-name">Shitanshu Shah</span>, <span class="contact-name">Steve Simlo</span>,
<span class="contact-name">Tina Tsou</span>, <span class="contact-name">Tom Phinney</span>, 
<span class="contact-name">Xavier Lagrange</span>, <span class="contact-name">Ines Robles</span>, and
<span class="contact-name">Samita Chakrabarti</span> for their participation and various contributions.<a href="#section-b.2-2" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-appendix.c">
      <h2 id="name-contributors">
<a href="#name-contributors" class="section-name selfRef">Contributors</a>
      </h2>
<p id="section-appendix.c-1">The co-authors of this document are listed below:<a href="#section-appendix.c-1" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-appendix.c-2.1">
          <p id="section-appendix.c-2.1.1"><span class="contact-name">Thomas Watteyne</span>
          for his contributions to the whole design, in particular on TSCH and security,
          and to the open source community that he created with openWSN;<a href="#section-appendix.c-2.1.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.2">
          <p id="section-appendix.c-2.2.1"><span class="contact-name">Xavier Vilajosana</span>,
          who led the design of the minimal support with RPL and contributed
          deeply to the 6top design and the GMPLS operation of Track switching;<a href="#section-appendix.c-2.2.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.3">
          <p id="section-appendix.c-2.3.1"><span class="contact-name">Kris Pister</span>
         for creating TSCH and his continuing guidance through the elaboration
         of this design;<a href="#section-appendix.c-2.3.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.4">
          <p id="section-appendix.c-2.4.1"><span class="contact-name">Mališa Vučinić</span>
         for the work on the one-touch join process and his contribution to the
         Security Design Team;<a href="#section-appendix.c-2.4.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.5">
          <p id="section-appendix.c-2.5.1"><span class="contact-name">Michael Richardson</span>
         for his leadership role in the Security Design Team and his
         contribution throughout this document;<a href="#section-appendix.c-2.5.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.6">
          <p id="section-appendix.c-2.6.1"><span class="contact-name">Tero Kivinen</span>
          for his contribution to the security work in general and the security
          section in particular;<a href="#section-appendix.c-2.6.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.7">
          <p id="section-appendix.c-2.7.1"><span class="contact-name">Maria Rita Palattella</span>
         for managing the Terminology document that was merged into this document through the work of 6TiSCH;<a href="#section-appendix.c-2.7.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.8">
          <p id="section-appendix.c-2.8.1"><span class="contact-name">Simon Duquennoy</span>
          for his contribution to the open source community with the 6TiSCH
          implementation of contiki, and for his contribution to MSF and
          autonomous unicast cells;<a href="#section-appendix.c-2.8.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.9">
          <p id="section-appendix.c-2.9.1"><span class="contact-name">Qin Wang</span>,
          who led the design of the 6top sublayer and contributed related text
          that was moved and/or adapted into this document;<a href="#section-appendix.c-2.9.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.10">
          <p id="section-appendix.c-2.10.1"><span class="contact-name">Rene Struik</span>
         for the security section and his contribution to the Security Design
         Team;<a href="#section-appendix.c-2.10.1" class="pilcrow">¶</a></p>
</li>
        <li class="normal ulEmpty" id="section-appendix.c-2.11">
          <p id="section-appendix.c-2.11.1"><span class="contact-name">Robert Assimiti</span>
          for his breakthrough work on RPL over TSCH and initial text and
          guidance.<a href="#section-appendix.c-2.11.1" class="pilcrow">¶</a></p>
</li>
      </ul>
</section>
<div id="authors-addresses">
<section id="section-appendix.d">
      <h2 id="name-authors-address">
<a href="#name-authors-address" class="section-name selfRef">Author's Address</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Pascal Thubert (<span class="role">editor</span>)</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems, Inc</span></div>
<div dir="auto" class="left"><span class="extended-address">Building D</span></div>
<div dir="auto" class="left"><span class="street-address">45 Allee des Ormes - BP1200</span></div>
<div dir="auto" class="left">
<span class="postal-code">06254</span> <span class="locality">Mougins - Sophia Antipolis</span>
</div>
<div dir="auto" class="left"><span class="country-name">France</span></div>
<div class="tel">
<span>Phone:</span>
<a href="tel:+33%20497%2023%2026%2034" class="tel">+33 497 23 26 34</a>
</div>
<div class="email">
<span>Email:</span>
<a href="mailto:pthubert@cisco.com" class="email">pthubert@cisco.com</a>
</div>
</address>
</section>
</div>
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