File: rfc8703.html

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<!DOCTYPE html>
<html lang="en" class="RFC">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 8703: Dynamic Link Exchange Protocol (DLEP) Link Identifier Extension</title>
<meta content="Rick Taylor" name="author">
<meta content="Stan Ratliff" name="author">
<meta content="
       The Dynamic Link Exchange Protocol (DLEP) is a protocol for modems to
      advertise the status of wireless links between reachable destinations to
      attached routers. The core specification of the protocol (RFC 8175)
      assumes that every modem in the radio network has an attached DLEP
      router and requires that the Media Access Control (MAC) address of the
      DLEP interface on the attached router be used to identify the
      destination in the network, for purposes of reporting the state and
      quality of the link to that destination.   
       This document describes a DLEP extension that allows modems that do not
      meet the strict requirement above to use DLEP to describe link
      availability and quality to one or more destinations reachable beyond a
      device on the Layer 2 domain.   
    " name="description">
<meta content="xml2rfc 2.39.0" name="generator">
<meta content="DLEP" name="keyword">
<meta content="MANET" name="keyword">
<meta content="Link-Aware" name="keyword">
<meta content="Radio-Aware" name="keyword">
<meta content="8703" name="rfc.number">
<link href="rfc8703.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

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

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

*/

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

.refInstance {
  margin-bottom: 1.25em;
}

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

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

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

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

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

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

/* pagination */
@media print {
  body {

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

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

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

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

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

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

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

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

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

}

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


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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

}
/* Avoid wrapping of URLs in references */
@media screen {
  .references a {
    white-space: nowrap;
  }
}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
}
div#internal-metadata {
  padding: 0.5em;                       /* to match the external-metadata padding */
}
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<table class="ears">
<thead><tr>
<td class="left">RFC 8703</td>
<td class="center">DLEP Link Identifier Extension</td>
<td class="right">February 2020</td>
</tr></thead>
<tfoot><tr>
<td class="left">Taylor &amp; Ratliff</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc8703" class="eref">8703</a></dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2020-02" class="published">February 2020</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Authors:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">R. Taylor</div>
<div class="org">Airbus Defence &amp; Space</div>
</div>
<div class="author">
  <div class="author-name">S. Ratliff</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8703</h1>
<h1 id="title">Dynamic Link Exchange Protocol (DLEP) Link Identifier Extension</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">The Dynamic Link Exchange Protocol (DLEP) is a protocol for modems to
      advertise the status of wireless links between reachable destinations to
      attached routers. The core specification of the protocol (RFC 8175)
      assumes that every modem in the radio network has an attached DLEP
      router and requires that the Media Access Control (MAC) address of the
      DLEP interface on the attached router be used to identify the
      destination in the network, for purposes of reporting the state and
      quality of the link to that destination.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
<p id="section-abstract-2">This document describes a DLEP extension that allows modems that do not
      meet the strict requirement above to use DLEP to describe link
      availability and quality to one or more destinations reachable beyond a
      device on the Layer 2 domain.<a href="#section-abstract-2" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc8703">https://www.rfc-editor.org/info/rfc8703</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) 2020 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.1.2.1">
                <p id="section-toc.1-1.1.2.1.1"><a href="#section-1.1" class="xref">1.1</a>.  <a href="#name-terminology" class="xref">Terminology</a><a href="#section-toc.1-1.1.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.1.2.2">
                <p id="section-toc.1-1.1.2.2.1"><a href="#section-1.2" class="xref">1.2</a>.  <a href="#name-applicability" class="xref">Applicability</a><a href="#section-toc.1-1.1.2.2.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.1.2.3">
                <p id="section-toc.1-1.1.2.3.1"><a href="#section-1.3" class="xref">1.3</a>.  <a href="#name-requirements-language" class="xref">Requirements Language</a><a href="#section-toc.1-1.1.2.3.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-operation" class="xref">Operation</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.2.2.1">
                <p id="section-toc.1-1.2.2.1.1"><a href="#section-2.1" class="xref">2.1</a>.  <a href="#name-identifier-restrictions" class="xref">Identifier Restrictions</a><a href="#section-toc.1-1.2.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.2.2.2">
                <p id="section-toc.1-1.2.2.2.1"><a href="#section-2.2" class="xref">2.2</a>.  <a href="#name-negotiation" class="xref">Negotiation</a><a href="#section-toc.1-1.2.2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-new-data-items" class="xref">New Data Items</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.3.2.1">
                <p id="section-toc.1-1.3.2.1.1"><a href="#section-3.1" class="xref">3.1</a>.  <a href="#name-link-identifier-length-data" class="xref">Link Identifier Length Data Item</a><a href="#section-toc.1-1.3.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.3.2.2">
                <p id="section-toc.1-1.3.2.2.1"><a href="#section-3.2" class="xref">3.2</a>.  <a href="#name-link-identifier-data-item" class="xref">Link Identifier Data Item</a><a href="#section-toc.1-1.3.2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" 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-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.6.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" 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-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.6.2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-appendix.a" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
</li>
</ul>
</nav>
</section>
</div>
<div id="introduction">
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">The Dynamic Link Exchange Protocol (DLEP) is a
      protocol for modems to advertise the status of wireless links between
      reachable destinations to attached routers. The core specification of
      the protocol <span>[<a href="#RFC8175" class="xref">RFC8175</a>]</span> assumes that every modem in the radio network has an
      attached DLEP router and requires that the MAC address of the DLEP
      interface on the attached router be used to identify the destination in
      the network, for purposes of reporting the state and quality of the link
      to that destination.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">This document describes a DLEP extension that allows modems that do not
      meet the strict requirement above to use DLEP to describe link
      availability and quality to one or more destinations reachable beyond a
      device on the Layer 2 domain.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">As with core DLEP <span>[<a href="#RFC8175" class="xref">RFC8175</a>]</span>, a router can use this
      knowledge to influence any routing or flow-control decisions regarding
      traffic to this destination, understanding that such traffic flows via
      Layer 3.<a href="#section-1-3" class="pilcrow">¶</a></p>
<div id="terminology">
<section id="section-1.1">
        <h3 id="name-terminology">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-terminology" class="section-name selfRef">Terminology</a>
        </h3>
<dl class="dlParallel" id="section-1.1-1">
          <dt id="section-1.1-1.1">Local Layer 2 domain:</dt>
<dd id="section-1.1-1.2">The Layer 2 domain that links the router and modem participants
   of the current DLEP session.<a href="#section-1.1-1.2" class="pilcrow">¶</a>
</dd>
<dt id="section-1.1-1.3">Layer 3 DLEP Destination:</dt>
<dd id="section-1.1-1.4">A DLEP Destination that is not directly addressable within the
   local Layer 2 domain but is reachable via a node addressable within
   the local Layer 2 domain.<a href="#section-1.1-1.4" class="pilcrow">¶</a>
</dd>
<dt id="section-1.1-1.5">Gateway Node:</dt>
<dd id="section-1.1-1.6">The last device with a MAC address reachable in the local Layer
   2 domain on the path from the DLEP router participant towards the
   Layer 3 DLEP Destination. This device is commonly the DLEP peer
   modem but could be another DLEP Destination in the Layer 2 domain.<a href="#section-1.1-1.6" class="pilcrow">¶</a>
</dd>
</dl>
</section>
</div>
<div id="applicability">
<section id="section-1.2">
        <h3 id="name-applicability">
<a href="#section-1.2" class="section-number selfRef">1.2. </a><a href="#name-applicability" class="section-name selfRef">Applicability</a>
        </h3>
<p id="section-1.2-1">This extension was designed primarily to address the following use
 cases:<a href="#section-1.2-1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal" id="section-1.2-2">
          <li id="section-1.2-2.1">A radio system that does not operate in Layer 2 bridge mode but
   instead provides Layer 3 connectivity between destinations, often
   using its own embedded Layer 3 routing function.<a href="#section-1.2-2.1" class="pilcrow">¶</a>
</li>
<li id="section-1.2-2.2">A point-to-multipoint tunnel system, such as a software-defined
   wide-area network (SD-WAN)
   deployment, where the tunnel provider acts as a modem that has
   knowledge of the characteristics of the underlay network and
   provides that information as availability and metrics between
   tunnel endpoints in the overlay network.<a href="#section-1.2-2.2" class="pilcrow">¶</a>
</li>
<li id="section-1.2-2.3">A modem that provides connectivity to a remote wide-area network
   via a wireless link, but the concept of a Layer 2 reachable remote
   router does not apply. An example of such a modem would be an LTE
   device or 802.11 station that provides variable connectivity to the
   Internet.<a href="#section-1.2-2.3" class="pilcrow">¶</a>
</li>
</ol>
<p id="section-1.2-3">This list of use cases is not exhaustive, and this extension may
 well be applicable to future, currently unforeseen, use cases.<a href="#section-1.2-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="requirements">
<section id="section-1.3">
        <h3 id="name-requirements-language">
<a href="#section-1.3" class="section-number selfRef">1.3. </a><a href="#name-requirements-language" class="section-name selfRef">Requirements Language</a>
        </h3>
<p id="section-1.3-1">                                                        
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>",
    "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>",
    "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>", 
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are
    to be interpreted as 
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span>
    when, and only when, they appear in all capitals, as shown here.<a href="#section-1.3-1" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="operation">
<section id="section-2">
      <h2 id="name-operation">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-operation" class="section-name selfRef">Operation</a>
      </h2>
<p id="section-2-1">To refer to a Layer 3 DLEP Destination, the DLEP session participant
      adds a Link Identifier Data Item (<a href="#lid_di" class="xref">Section 3.2</a>) to the relevant
      Destination Message and (as usual) includes
      a MAC Address Data Item. When paired with a Link Identifier Data Item,
      the MAC Address Data Item <span class="bcp14">MUST</span> contain the MAC address of the Gateway
      Node.<a href="#section-2-1" class="pilcrow">¶</a></p>
<p id="section-2-2">As only modems are initially aware of Layer 3 DLEP Destinations, Link
      Identifier Data Items referring to a new link <span class="bcp14">MUST</span> first appear in a
      DLEP Destination Up Message from the modem to the router. Once a link
      has been identified in this way, Link Identifier Data Items may be used
      by either DLEP participant during the lifetime of a DLEP
      session. Because of this, a router <span class="bcp14">MUST NOT</span> send a DLEP Destination
      Announce Message containing a Link Identifier Data Item referring to a
      link that has not been mentioned in a prior DLEP Destination Up
      Message. If a modem receives such a message, it <span class="bcp14">MUST</span> terminate the
      session by issuing a Session Termination Message containing a Status
      Data Item with status code set to 131 ('Invalid Destination') and
      transition to the Session Termination state. If a router receives a
      Destination Up Message specifying a Link Identifier that has already
      been used, the router <span class="bcp14">MUST</span> respond with a Destination Up Response
      Message containing a Status Data Item with status code set to 130
      ('Invalid Data') and transition to the Session Termination state.<a href="#section-2-2" class="pilcrow">¶</a></p>
<p id="section-2-3">Because the MAC address associated with any DLEP Destination Message
      containing a Link Identifier Data Item is not the Layer 2 address of the
      final destination, all DLEP Destination Up Messages containing a Link
      Identifier Data Item <span class="bcp14">MUST</span> contain Layer 3 information. 
      In the case of
      modems that provide Layer 3 wide area network connectivity between
      devices, this means one or more IPv4 or IPv6 Address Data Items
      providing the Layer 3 address of the final destination. 
      When referring to
      some upstream backbone network infrastructures, this means one or more
      IPv4 or IPv6 Attached Subnet Data Items, for example: '0.0.0.0/0' or
      '::/0'. This mechanism allows the DLEP peer router to understand the properties of
      the link to those routes. The address or addresses in the IPv4 or IPv6
      Address Data Items <span class="bcp14">MUST</span> be the addresses in use on the public side of
      any Network Address Translation.<a href="#section-2-3" class="pilcrow">¶</a></p>
<p id="section-2-4">When the DLEP peer router wishes to route packets to the Layer 3 DLEP
      Destination, the MAC address associated with the Gateway Node <span class="bcp14">MUST</span> be
      used as the Layer 2 destination of the packet if it wishes to use the
      modem network to forward the packet.<a href="#section-2-4" class="pilcrow">¶</a></p>
<p id="section-2-5">As routers populate their Routing Information Base with the IP
      address of the next-hop router towards a destination, implementations
      supporting this extension <span class="bcp14">SHOULD</span> announce at least one valid IPv4 or
      IPv6 addresses of the Gateway Node; this removes the need for the router
      to use an additional IP address resolution protocol before adding the
      route to its Routing Information Base.<a href="#section-2-5" class="pilcrow">¶</a></p>
<div id="identifier-restrictions">
<section id="section-2.1">
        <h3 id="name-identifier-restrictions">
<a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-identifier-restrictions" class="section-name selfRef">Identifier Restrictions</a>
        </h3>
<p id="section-2.1-1">A Link Identifier is, by default, 4 octets in length. If a modem
 wishes to use a Link Identifier of a different length, it <span class="bcp14">MUST</span> be
 announced using the Link
 Identifier Length Data Item (<a href="#lid_len_di" class="xref">Section 3.1</a>) contained in the DLEP Session
 Initialization Response Message sent by the modem to the router.<a href="#section-2.1-1" class="pilcrow">¶</a></p>
<p id="section-2.1-2">During the lifetime of a DLEP session, the length of Link
 Identifiers <span class="bcp14">MUST</span> remain constant, i.e., the Length field of the Link
 Identifier Data Item <span class="bcp14">MUST NOT</span> differ between destinations.<a href="#section-2.1-2" class="pilcrow">¶</a></p>
<p id="section-2.1-3">The method for generating Link Identifiers is a modem
 implementation matter and out of scope of this document. Routers must
 not make any assumptions about the meaning of Link Identifiers or how
 Link Identifiers are generated.<a href="#section-2.1-3" class="pilcrow">¶</a></p>
<p id="section-2.1-4">Within a single DLEP session, all Link Identifiers <span class="bcp14">MUST</span> be unique
 per MAC address. This means that a Layer 3 DLEP Destination is
 uniquely identified by the pair: {MAC Address,Link Identifier}.<a href="#section-2.1-4" class="pilcrow">¶</a></p>
<p id="section-2.1-5">Link Identifiers <span class="bcp14">MUST NOT</span> be reused, i.e., a {MAC Address,Link
 Identifier} pair that has been used to refer to one Layer 3 DLEP
 Destination <span class="bcp14">MUST NOT</span> be used again within the lifetime of a single
 DLEP peer-to-peer session.<a href="#section-2.1-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="negotiation">
<section id="section-2.2">
        <h3 id="name-negotiation">
<a href="#section-2.2" class="section-number selfRef">2.2. </a><a href="#name-negotiation" class="section-name selfRef">Negotiation</a>
        </h3>
<p id="section-2.2-1">To use this extension, as with all DLEP extensions, the extension
 <span class="bcp14">MUST</span> be announced during DLEP session initialization. A router
 advertises support by including the value 3 ('Link Identifiers') (<a href="#tbd" class="xref">Section 5</a>), in the Extension Data Item
 within the Session Initialization Message. A modem advertises support
 by including the value 3 ('Link Identifiers') in the Extension Data Item
 within the Session Initialization Response Message. If both DLEP peers
 advertise support for this extension, then Link Identifier Data Items
 can be included in DLEP Messages.<a href="#section-2.2-1" class="pilcrow">¶</a></p>
<p id="section-2.2-2">If a modem requires support for this extension in order to describe
 destinations and the router does not advertise support, then the
 modem <span class="bcp14">MUST NOT</span> include a Link Identifier Data Item in any DLEP
 Message. However, the modem <span class="bcp14">SHOULD NOT</span> immediately terminate the DLEP
 session; rather, it <span class="bcp14">SHOULD</span> use a combination of DLEP Session Messages
 and DLEP Attached Subnet Data Items to provide general information.<a href="#section-2.2-2" class="pilcrow">¶</a></p>
</section>
</div>
</section>
</div>
<div id="new-data-items">
<section id="section-3">
      <h2 id="name-new-data-items">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-new-data-items" class="section-name selfRef">New Data Items</a>
      </h2>
<p id="section-3-1">This extension introduces two new DLEP Data Items: 1) the Link
      Identifier Length Data Item (<a href="#lid_len_di" class="xref">Section 3.1</a>) used to announce the length of Link
      Identifiers at session initialization and 2) the Link
      Identifier Data Item (<a href="#lid_di" class="xref">Section 3.2</a>)
      used to identify a Layer 3 link at or beyond a destination.<a href="#section-3-1" class="pilcrow">¶</a></p>
<div id="lid_len_di">
<section id="section-3.1">
        <h3 id="name-link-identifier-length-data">
<a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-link-identifier-length-data" class="section-name selfRef">Link Identifier Length Data Item</a>
        </h3>
<p id="section-3.1-1">The Link Identifier Length Data Item is used by a DLEP modem
 implementation to specify the length of Link Identifier Data Items. If
 the router advertised support by including the value 3 ('Link
 Identifiers') in the Extension Data Item inside the Session
 Initialization Message, this Data Item <span class="bcp14">MAY</span> be used in the Session
 Initialization Response Message if the specified length is not the
 default value of 4 octets. If the router did not specify support by
 including the value 3 ('Link Identifiers') in the Extension Data Item,
 this Data Item <span class="bcp14">MUST NOT</span> be sent.<a href="#section-3.1-1" class="pilcrow">¶</a></p>
<div class="artwork art-text alignLeft" id="section-3.1-2">
<pre>
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type                | Length                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Identifier Length        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</pre><a href="#section-3.1-2" class="pilcrow">¶</a>
</div>
<dl class="dlParallel" id="section-3.1-3">
          <dt id="section-3.1-3.1">Data Item Type:</dt>
<dd id="section-3.1-3.2">
          26 (see <a href="#tbd" class="xref">Section 5</a>)<a href="#section-3.1-3.2" class="pilcrow">¶</a>
</dd>
<dt id="section-3.1-3.3">Length:</dt>
<dd id="section-3.1-3.4">2<a href="#section-3.1-3.4" class="pilcrow">¶</a>
</dd>
<dt id="section-3.1-3.5">Link Identifier Length:</dt>
<dd id="section-3.1-3.6">The length, in octets, of Link Identifiers used by the DLEP
   modem for this session.<a href="#section-3.1-3.6" class="pilcrow">¶</a>
</dd>
</dl>
<p id="section-3.1-4">A Link Identifier Length Data Item that specifies a Link Identifier
 Length of 4 octets (the default) is valid, even if it has no effect.<a href="#section-3.1-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="lid_di">
<section id="section-3.2">
        <h3 id="name-link-identifier-data-item">
<a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-link-identifier-data-item" class="section-name selfRef">Link Identifier Data Item</a>
        </h3>
<p id="section-3.2-1">The Link Identifier Data Item <span class="bcp14">MAY</span> be used wherever a MAC Address
 Data Item is defined as usable in core DLEP <span>[<a href="#RFC8175" class="xref">RFC8175</a>]</span>.<a href="#section-3.2-1" class="pilcrow">¶</a></p>
<div class="artwork art-text alignLeft" id="section-3.2-2">
<pre>
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type                | Length                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                   Link Identifier...                          :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</pre><a href="#section-3.2-2" class="pilcrow">¶</a>
</div>
<dl class="dlParallel" id="section-3.2-3">
          <dt id="section-3.2-3.1">Data Item Type:</dt>
<dd id="section-3.2-3.2">
            27 (see <a href="#tbd" class="xref">Section 5</a>)<a href="#section-3.2-3.2" class="pilcrow">¶</a>
</dd>
<dt id="section-3.2-3.3">Length:</dt>
<dd id="section-3.2-3.4">The length of the Data Item, by default 4, but may be different
   if a Link Identifier Length Data Item (<a href="#lid_len_di" class="xref">Section 3.1</a>) has been announced during session 
   initialization.<a href="#section-3.2-3.4" class="pilcrow">¶</a>
</dd>
<dt id="section-3.2-3.5">Link Identifier:</dt>
<dd id="section-3.2-3.6">The unique identifier of the Layer 3 DLEP Destination. This Link
   Identifier has no implicit meaning and is only used to discriminate
   between multiple links.<a href="#section-3.2-3.6" class="pilcrow">¶</a>
</dd>
</dl>
</section>
</div>
</section>
</div>
<div id="security-considerations">
<section id="section-4">
      <h2 id="name-security-considerations">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-4-1">As an extension to core DLEP <span>[<a href="#RFC8175" class="xref">RFC8175</a>]</span>, the security
      considerations of that protocol apply to this extension. This extension
      adds no additional security mechanisms or features.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">None of the features introduced by this extension require extra
      security considerations by an implementation.<a href="#section-4-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="tbd">
<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">IANA has assigned the following value to the "Extension Type Values" registry
      within the "Dynamic Link Exchange Protocol (DLEP) Parameters"
      registry. This new value is
      in the range with the "Specification Required" <span>[<a href="#RFC8126" class="xref">RFC8126</a>]</span>
      policy.<a href="#section-5-1" class="pilcrow">¶</a></p>
<span id="name-addition-to-the-extension-t"></span><div id="iana1">
<table class="left" id="table-1">
        <caption>
<a href="#table-1" class="selfRef">Table 1</a>:
<a href="#name-addition-to-the-extension-t" class="selfRef">Addition to the Extension Type Values Registry</a>
        </caption>
<thead>
          <tr>
            <th class="text-left" rowspan="1" colspan="1">Code</th>
            <th class="text-left" rowspan="1" colspan="1">Description</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">3</td>
            <td class="text-left" rowspan="1" colspan="1">Link Identifiers</td>
          </tr>
        </tbody>
      </table>
</div>
<p id="section-5-3">IANA has assigned two new values to the "Data Item Type Values" registry
within the "Dynamic Link Exchange Protocol (DLEP) Parameters" registry. These
new values are in the range with the "Specification Required" <span>[<a href="#RFC8126" class="xref">RFC8126</a>]</span> policy.<a href="#section-5-3" class="pilcrow">¶</a></p>
<span id="name-additions-to-the-data-item-"></span><div id="iana2">
<table class="left" id="table-2">
        <caption>
<a href="#table-2" class="selfRef">Table 2</a>:
<a href="#name-additions-to-the-data-item-" class="selfRef">Additions to the Data Item Type Values Registry</a>
        </caption>
<thead>
          <tr>
            <th class="text-left" rowspan="1" colspan="1">Type Code</th>
            <th class="text-left" rowspan="1" colspan="1">Description</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">26</td>
            <td class="text-left" rowspan="1" colspan="1">Link Identifier Length</td>
          </tr>
          <tr>
            <td class="text-left" rowspan="1" colspan="1">27</td>
            <td class="text-left" rowspan="1" colspan="1">Link Identifier</td>
          </tr>
        </tbody>
      </table>
</div>
</section>
</div>
<section id="section-6">
      <h2 id="name-references">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-6.1">
        <h3 id="name-normative-references">
<a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
<dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dt id="RFC8174">[RFC8174]</dt>
<dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dt id="RFC8175">[RFC8175]</dt>
<dd>
<span class="refAuthor">Ratliff, S.</span><span class="refAuthor">, Jury, S.</span><span class="refAuthor">, Satterwhite, D.</span><span class="refAuthor">, Taylor, R.</span><span class="refAuthor">, and B. Berry</span>, <span class="refTitle">"Dynamic Link Exchange Protocol (DLEP)"</span>, <span class="seriesInfo">RFC 8175</span>, <span class="seriesInfo">DOI 10.17487/RFC8175</span>, <time datetime="2017-06">June 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8175">https://www.rfc-editor.org/info/rfc8175</a>&gt;</span>. </dd>
</dl>
</section>
<section id="section-6.2">
        <h3 id="name-informative-references">
<a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC8126">[RFC8126]</dt>
<dd>
<span class="refAuthor">Cotton, M.</span><span class="refAuthor">, Leiba, B.</span><span class="refAuthor">, and T. Narten</span>, <span class="refTitle">"Guidelines for Writing an IANA Considerations Section in RFCs"</span>, <span class="seriesInfo">BCP 26</span>, <span class="seriesInfo">RFC 8126</span>, <span class="seriesInfo">DOI 10.17487/RFC8126</span>, <time datetime="2017-06">June 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8126">https://www.rfc-editor.org/info/rfc8126</a>&gt;</span>. </dd>
</dl>
</section>
</section>
<div id="authors-addresses">
<section id="section-appendix.a">
      <h2 id="name-authors-addresses">
<a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Rick Taylor</span></div>
<div dir="auto" class="left"><span class="org">Airbus Defence &amp; Space</span></div>
<div dir="auto" class="left"><span class="extended-address">Quadrant House<br>Celtic Springs<br>Coedkernew</span></div>
<div dir="auto" class="left"><span class="locality">Newport</span></div>
<div dir="auto" class="left"><span class="postal-code">NP10 8FZ</span></div>
<div dir="auto" class="left"><span class="country-name">United Kingdom</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:rick.taylor@airbus.com" class="email">rick.taylor@airbus.com</a>
</div>
</address>
<address class="vcard">
  <div dir="auto" class="left"><span class="fn nameRole">Stan Ratliff</span></div>
</address>
</section>
</div>
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