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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 7911: Advertisement of Multiple Paths in BGP</title>
<meta content="Daniel Walton" name="author">
<meta content="Alvaro Retana" name="author">
<meta content="Enke Chen" name="author">
<meta content="John Scudder" name="author">
<meta content="
This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. The essence of the extension is
that each path is identified by a Path Identifier in addition to the
address prefix.
" name="description">
<meta content="xml2rfc 3.18.0" name="generator">
<meta content="7911" name="rfc.number">
<link href="tests/input/rfc7911.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
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<link href="https://dx.doi.org/10.17487/rfc7911" rel="alternate">
<link href="urn:issn:2070-1721" rel="alternate">
<link href="https://datatracker.ietf.org/doc/draft-ietf-idr-add-paths" rel="prev">
</head>
<body class="xml2rfc">
<script src="metadata.min.js"></script>
<table class="ears">
<thead><tr>
<td class="left">RFC 7911</td>
<td class="center">ADD-PATH</td>
<td class="right">July 2016</td>
</tr></thead>
<tfoot><tr>
<td class="left">Walton, et al.</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc7911" class="eref">7911</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="2016-07" class="published">July 2016</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">D. Walton</div>
<div class="org">Cumulus Networks</div>
</div>
<div class="author">
<div class="author-name">A. Retana</div>
<div class="org">Cisco Systems, Inc.</div>
</div>
<div class="author">
<div class="author-name">E. Chen</div>
<div class="org">Cisco Systems, Inc.</div>
</div>
<div class="author">
<div class="author-name">J. Scudder</div>
<div class="org">Juniper Networks</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 7911</h1>
<h1 id="title">Advertisement of Multiple Paths in BGP</h1>
<section id="section-abstract">
<h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. The essence of the extension is
that each path is identified by a Path Identifier in addition to the
address prefix.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
<h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
</h2>
<p id="section-boilerplate.1-1">
This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
<span><a href="http://www.rfc-editor.org/info/rfc7911">http://www.rfc-editor.org/info/rfc7911</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) 2016 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="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a></span>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Revised BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Revised BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
<a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
</h2>
<nav class="toc"><ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1">
<p id="section-toc.1-1.1.1" class="keepWithNext"><a href="#section-1" class="auto internal xref">1</a>. <a href="#name-introduction" class="internal xref">Introduction</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.1.2.1">
<p id="section-toc.1-1.1.2.1.1" class="keepWithNext"><a href="#section-1.1" class="auto internal xref">1.1</a>. <a href="#name-specification-of-requiremen" class="internal xref">Specification of Requirements</a></p>
</li>
</ul>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.2">
<p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="auto internal xref">2</a>. <a href="#name-how-to-identify-a-path" class="internal xref">How to Identify a Path</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.3">
<p id="section-toc.1-1.3.1"><a href="#section-3" class="auto internal xref">3</a>. <a href="#name-extended-nlri-encodings" class="internal xref">Extended NLRI Encodings</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.4">
<p id="section-toc.1-1.4.1"><a href="#section-4" class="auto internal xref">4</a>. <a href="#name-add-path-capability" class="internal xref">ADD-PATH Capability</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.5">
<p id="section-toc.1-1.5.1"><a href="#section-5" class="auto internal xref">5</a>. <a href="#name-operation" class="internal xref">Operation</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.6">
<p id="section-toc.1-1.6.1"><a href="#section-6" class="auto internal xref">6</a>. <a href="#name-deployment-considerations" class="internal xref">Deployment Considerations</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.7">
<p id="section-toc.1-1.7.1"><a href="#section-7" class="auto internal xref">7</a>. <a href="#name-iana-considerations" class="internal xref">IANA Considerations</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.8">
<p id="section-toc.1-1.8.1"><a href="#section-8" class="auto internal xref">8</a>. <a href="#name-security-considerations" class="internal xref">Security Considerations</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9">
<p id="section-toc.1-1.9.1"><a href="#section-9" class="auto internal xref">9</a>. <a href="#name-references" class="internal xref">References</a></p>
<ul class="compact toc ulBare ulEmpty">
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9.2.1">
<p id="section-toc.1-1.9.2.1.1"><a href="#section-9.1" class="auto internal xref">9.1</a>. <a href="#name-normative-references" class="internal xref">Normative References</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.9.2.2">
<p id="section-toc.1-1.9.2.2.1"><a href="#section-9.2" class="auto internal xref">9.2</a>. <a href="#name-informative-references" class="internal xref">Informative References</a></p>
</li>
</ul>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.10">
<p id="section-toc.1-1.10.1"><a href="#appendix-A" class="auto internal xref"></a><a href="#name-acknowledgments" class="internal xref">Acknowledgments</a></p>
</li>
<li class="compact toc ulBare ulEmpty" id="section-toc.1-1.11">
<p id="section-toc.1-1.11.1"><a href="#appendix-B" class="auto internal xref"></a><a href="#name-authors-addresses" class="internal xref">Authors' Addresses</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">The BGP specification <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> defines an Update-Send Process to advertise the
routes chosen by the Decision Process to other BGP speakers. No
provisions are made to allow the advertisement of multiple paths for the
same address prefix or Network Layer Reachability Information (NLRI).
In fact, a route with the same NLRI as a previously advertised route
implicitly replaces the previous advertisement.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. The essence of the extension is
that each path is identified by a Path Identifier in addition to the
address prefix.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">The availability of the additional paths can help reduce or eliminate
persistent route oscillations <span>[<a href="#RFC3345" class="cite xref">RFC3345</a>]</span>. It can also help with optimal routing and routing
convergence in a network by providing potential alternate or backup paths,
respectively.<a href="#section-1-3" class="pilcrow">¶</a></p>
<section id="section-1.1">
<h3 id="name-specification-of-requiremen">
<a href="#section-1.1" class="section-number selfRef">1.1. </a><a href="#name-specification-of-requiremen" class="section-name selfRef">Specification of Requirements</a>
</h3>
<p id="section-1.1-1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <span>[<a href="#RFC2119" class="cite xref">RFC2119</a>]</span>.<a href="#section-1.1-1" class="pilcrow">¶</a></p>
</section>
</section>
<section id="section-2">
<h2 id="name-how-to-identify-a-path">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-how-to-identify-a-path" class="section-name selfRef">How to Identify a Path</a>
</h2>
<p id="section-2-1">As defined in <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span>, a path refers to the information reported in the
Path Attribute field of an UPDATE message. As the procedures specified
in <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> allow only
the advertisement of one path for a particular address prefix, a path
for an address prefix from a BGP peer can be keyed on the address
prefix.<a href="#section-2-1" class="pilcrow">¶</a></p>
<p id="section-2-2">In order for a BGP speaker to advertise multiple paths for the same
address prefix, a new identifier (termed "Path Identifier" hereafter)
needs to be introduced so that a particular path for an address prefix
can be identified by the combination of the address prefix and the Path
Identifier.<a href="#section-2-2" class="pilcrow">¶</a></p>
<p id="section-2-3">The assignment of the Path Identifier for a path by a BGP speaker is
purely a local matter. However, the Path Identifier MUST be assigned in
such a way that the BGP speaker is able to use the (Prefix, Path
Identifier) to uniquely identify a path advertised to a neighbor. A BGP
speaker that re-advertises a route MUST generate its own Path Identifier
to be associated with the re-advertised route. A BGP speaker that
receives a route should not assume that the identifier carries any
particular semantics.<a href="#section-2-3" class="pilcrow">¶</a></p>
</section>
<div id="code">
<section id="section-3">
<h2 id="name-extended-nlri-encodings">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-extended-nlri-encodings" class="section-name selfRef">Extended NLRI Encodings</a>
</h2>
<p id="section-3-1">In order to carry the Path Identifier in an UPDATE message, the NLRI
encoding MUST be extended by prepending the Path Identifier field, which
is of four octets.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">For example, the NLRI encoding specified in <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> is extended as the following:<a href="#section-3-2" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-3-3">
<pre>
+--------------------------------+
| Path Identifier (4 octets) |
+--------------------------------+
| Length (1 octet) |
+--------------------------------+
| Prefix (variable) |
+--------------------------------+</pre><a href="#section-3-3" class="pilcrow">¶</a>
</div>
<p id="section-3-4">The usage of the extended NLRI encodings is specified in <a href="#ops" class="auto internal xref">Section 5</a>.<a href="#section-3-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="capa">
<section id="section-4">
<h2 id="name-add-path-capability">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-add-path-capability" class="section-name selfRef">ADD-PATH Capability</a>
</h2>
<p id="section-4-1">The ADD-PATH Capability is a BGP capability <span>[<a href="#RFC5492" class="cite xref">RFC5492</a>]</span>, with Capability Code
69. The Capability Length field of this capability is
variable. The Capability Value field consists of one or more of the
following tuples:<a href="#section-4-1" class="pilcrow">¶</a></p>
<div class="alignLeft art-text artwork" id="section-4-2">
<pre>
+------------------------------------------------+
| Address Family Identifier (2 octets) |
+------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
+------------------------------------------------+
| Send/Receive (1 octet) |
+------------------------------------------------+</pre><a href="#section-4-2" class="pilcrow">¶</a>
</div>
<p id="section-4-3">The meaning and use of the fields are as follows:<a href="#section-4-3" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-4-4.1">
<p id="section-4-4.1.1">Address Family Identifier (AFI):<a href="#section-4-4.1.1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4-4.1.2.1">
<p id="section-4-4.1.2.1.1">This field is the same as the one used in <span>[<a href="#RFC4760" class="cite xref">RFC4760</a>]</span>.<a href="#section-4-4.1.2.1.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="normal ulEmpty" id="section-4-4.2">
<p id="section-4-4.2.1">Subsequent Address Family Identifier (SAFI):<a href="#section-4-4.2.1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4-4.2.2.1">
<p id="section-4-4.2.2.1.1">This field is the same as the one used in <span>[<a href="#RFC4760" class="cite xref">RFC4760</a>]</span>.<a href="#section-4-4.2.2.1.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="normal ulEmpty" id="section-4-4.3">
<p id="section-4-4.3.1">Send/Receive:<a href="#section-4-4.3.1" class="pilcrow">¶</a></p>
<ul class="normal">
<li class="normal" id="section-4-4.3.2.1">
<p id="section-4-4.3.2.1.1">This field indicates whether the sender is (a) able to
receive multiple paths from its peer (value 1), (b) able to send
multiple paths to its peer (value 2), or (c) both (value 3) for
the <AFI, SAFI>.<a href="#section-4-4.3.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="normal" id="section-4-4.3.2.2">
<p id="section-4-4.3.2.2.1">If any other value is received, then the capability SHOULD be
treated as not understood and ignored <span>[<a href="#RFC5492" class="cite xref">RFC5492</a>]</span>.<a href="#section-4-4.3.2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
</ul>
<p id="section-4-5">A BGP speaker that wishes to indicate support for multiple
AFI/SAFIs MUST do so by including the information in a single instance of
the ADD-PATH Capability.<a href="#section-4-5" class="pilcrow">¶</a></p>
</section>
</div>
<div id="ops">
<section id="section-5">
<h2 id="name-operation">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-operation" class="section-name selfRef">Operation</a>
</h2>
<p id="section-5-1">The Path Identifier specified in <a href="#code" class="auto internal xref">Section 3</a> can be used to
advertise multiple paths for the same address prefix without subsequent
advertisements replacing the previous ones. Apart from the fact that
this is now possible, the route advertisement rules of <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> are not changed. In
particular, a new advertisement for a given address prefix and a given
Path Identifier replaces a previous advertisement for the same address
prefix and Path Identifier. If a BGP speaker receives a message to
withdraw a prefix with a Path Identifier not seen before, it SHOULD
silently ignore it.<a href="#section-5-1" class="pilcrow">¶</a></p>
<p id="section-5-2">For a BGP speaker to be able to send multiple paths to its peer, that
BGP speaker MUST advertise the ADD-PATH Capability with the Send/Receive
field set to either 2 or 3, and MUST receive from its peer the ADD-PATH
Capability with the Send/Receive field set to either 1 or 3, for the
corresponding <AFI, SAFI>.<a href="#section-5-2" class="pilcrow">¶</a></p>
<p id="section-5-3">A BGP speaker MUST follow the procedures defined in <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> when generating an
UPDATE message for a particular <AFI, SAFI> to a peer unless the
BGP speaker advertises the ADD-PATH Capability to the peer indicating
its ability to send multiple paths for the <AFI, SAFI>, and also
receives the ADD-PATH Capability from the peer indicating its ability to
receive multiple paths for the <AFI, SAFI>, in which case the
speaker MUST generate a route update for the <AFI, SAFI> based on
the combination of the address prefix and the Path Identifier, and use
the extended NLRI encodings specified in this document. The peer SHALL
act accordingly in processing an UPDATE message related to a particular
<AFI, SAFI>.<a href="#section-5-3" class="pilcrow">¶</a></p>
<p id="section-5-4">A BGP speaker SHOULD include the best route <span>[<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> when more than one path is
advertised to a neighbor, unless it is a path received from
that neighbor.<a href="#section-5-4" class="pilcrow">¶</a></p>
<p id="section-5-5">As the Path Identifiers are locally assigned, and may or may not be
persistent across a control plane restart of a BGP speaker, an
implementation SHOULD take special care so that the underlying
forwarding plane of a "Receiving Speaker" as described in <span>[<a href="#RFC4724" class="cite xref">RFC4724</a>]</span> is not affected
during the graceful restart of a BGP session.<a href="#section-5-5" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-6">
<h2 id="name-deployment-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-deployment-considerations" class="section-name selfRef">Deployment Considerations</a>
</h2>
<p id="section-6-1">The extension proposed in this document provides a mechanism for a
BGP speaker to advertise multiple paths over a BGP session. Care needs
to be taken in its deployment to ensure consistent routing and
forwarding in a network <span>[<a href="#ADDPATH" class="cite xref">ADDPATH</a>]</span>.<a href="#section-6-1" class="pilcrow">¶</a></p>
<p id="section-6-2">The only explicit indication that the encoding described in <a href="#code" class="auto internal xref">Section 3</a>
is in use in a particular BGP session is the exchange of Capabilities
described in <a href="#capa" class="auto internal xref">Section 4</a>. If the exchange is successful <span>[<a href="#RFC5492" class="cite xref">RFC5492</a>]</span>, then the BGP speakers
will be able to process all BGP UPDATES properly, as described in <a href="#ops" class="auto internal xref">Section 5</a>.
However, if, for example, a packet analyzer is used on the wire to examine
an active BGP session, it may not be able to properly decode the BGP UPDATES
because it lacks prior knowledge of the exchanged Capabilities.<a href="#section-6-2" class="pilcrow">¶</a></p>
<p id="section-6-3">When deployed as a provider edge router or a peering router that
interacts with external neighbors, a BGP speaker usually advertises at
most one path to the internal neighbors in a network. In the case where the
speaker is configured to advertise multiple paths to the internal
neighbors, and additional information is needed for the application, the
speaker could use attributes such as the Edge_Discriminator attribute
<span>[<a href="#FAST" class="cite xref">FAST</a>]</span>. The use of that type of
additional information is outside the scope of this document.<a href="#section-6-3" class="pilcrow">¶</a></p>
</section>
<section id="section-7">
<h2 id="name-iana-considerations">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
</h2>
<p id="section-7-1">IANA has assigned the value 69 for the ADD-PATH Capability
described in this document. This registration is in the "Capability
Codes" registry.<a href="#section-7-1" class="pilcrow">¶</a></p>
</section>
<section id="section-8">
<h2 id="name-security-considerations">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
</h2>
<p id="section-8-1">This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. As a result, multiple paths for
a large number of prefixes may be received by a BGP speaker, potentially
depleting memory resources or even causing network-wide instability, which
can be considered a denial-of-service attack. Note that this is not a new
vulnerability, but one that is present in the base BGP specification <span>[<a href="#RFC4272" class="cite xref">RFC4272</a>]</span>.<a href="#section-8-1" class="pilcrow">¶</a></p>
<p id="section-8-2">
The use of the ADD-PATH Capability is intended to address specific
needs related to, for example, <span><a href="#STOP-OSC" class="internal xref">eliminating route oscillations that
were induced by the MULTI_EXIT_DISC (MED) attribute</a> [<a href="#STOP-OSC" class="cite xref">STOP-OSC</a>]</span>.
While describing the applications for the
ADD-PATH Capability is outside the scope of this document, users
are encouraged to examine their behavior and potential impact by
studying the best practices described in <span>[<a href="#ADDPATH" class="cite xref">ADDPATH</a>]</span>.<a href="#section-8-2" class="pilcrow">¶</a></p>
<p id="section-8-3">Security concerns in the base operation of <span><a href="#RFC4271" class="internal xref">BGP</a> [<a href="#RFC4271" class="cite xref">RFC4271</a>]</span> also apply.<a href="#section-8-3" class="pilcrow">¶</a></p>
</section>
<section id="section-9">
<h2 id="name-references">
<a href="#section-9" class="section-number selfRef">9. </a><a href="#name-references" class="section-name selfRef">References</a>
</h2>
<section id="section-9.1">
<h3 id="name-normative-references">
<a href="#section-9.1" class="section-number selfRef">9.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
</h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
<dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span><<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC4271">[RFC4271]</dt>
<dd>
<span class="refAuthor">Rekhter, Y., Ed.</span>, <span class="refAuthor">Li, T., Ed.</span>, and <span class="refAuthor">S. Hares, Ed.</span>, <span class="refTitle">"A Border Gateway Protocol 4 (BGP-4)"</span>, <span class="seriesInfo">RFC 4271</span>, <span class="seriesInfo">DOI 10.17487/RFC4271</span>, <time datetime="2006-01" class="refDate">January 2006</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4271">https://www.rfc-editor.org/info/rfc4271</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC4760">[RFC4760]</dt>
<dd>
<span class="refAuthor">Bates, T.</span>, <span class="refAuthor">Chandra, R.</span>, <span class="refAuthor">Katz, D.</span>, and <span class="refAuthor">Y. Rekhter</span>, <span class="refTitle">"Multiprotocol Extensions for BGP-4"</span>, <span class="seriesInfo">RFC 4760</span>, <span class="seriesInfo">DOI 10.17487/RFC4760</span>, <time datetime="2007-01" class="refDate">January 2007</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4760">https://www.rfc-editor.org/info/rfc4760</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC5492">[RFC5492]</dt>
<dd>
<span class="refAuthor">Scudder, J.</span> and <span class="refAuthor">R. Chandra</span>, <span class="refTitle">"Capabilities Advertisement with BGP-4"</span>, <span class="seriesInfo">RFC 5492</span>, <span class="seriesInfo">DOI 10.17487/RFC5492</span>, <time datetime="2009-02" class="refDate">February 2009</time>, <span><<a href="https://www.rfc-editor.org/info/rfc5492">https://www.rfc-editor.org/info/rfc5492</a>></span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-9.2">
<h3 id="name-informative-references">
<a href="#section-9.2" class="section-number selfRef">9.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
</h3>
<dl class="references">
<dt id="ADDPATH">[ADDPATH]</dt>
<dd>
<span class="refAuthor">Uttaro, J.</span>, <span class="refAuthor">Francois, P.</span>, <span class="refAuthor">Patel, K.</span>, <span class="refAuthor">Haas, J.</span>, <span class="refAuthor">Simpson, A.</span>, and <span class="refAuthor">R. Fragassi</span>, <span class="refTitle">"Best Practices for Advertisement of Multiple Paths in IBGP"</span>, <span class="seriesInfo">Work in Progress, draft-ietf-idr-add-paths-guidelines-08</span>, <time datetime="2016-04-25" class="refDate">April 25, 2016</time>. </dd>
<dd class="break"></dd>
<dt id="FAST">[FAST]</dt>
<dd>
<span class="refAuthor">Mohapatra, P.</span>, <span class="refAuthor">Fernando, R.</span>, <span class="refAuthor">Filsfils, C.</span>, and <span class="refAuthor">R. Raszuk</span>, <span class="refTitle">"Fast Connectivity Restoration Using BGP Add-path"</span>, <span class="seriesInfo">Work in Progress, draft-pmohapat-idr-fast-conn-restore-03</span>, <time datetime="2013-01-22" class="refDate">January 22, 2013</time>. </dd>
<dd class="break"></dd>
<dt id="RFC3345">[RFC3345]</dt>
<dd>
<span class="refAuthor">McPherson, D.</span>, <span class="refAuthor">Gill, V.</span>, <span class="refAuthor">Walton, D.</span>, and <span class="refAuthor">A. Retana</span>, <span class="refTitle">"Border Gateway Protocol (BGP) Persistent Route Oscillation Condition"</span>, <span class="seriesInfo">RFC 3345</span>, <span class="seriesInfo">DOI 10.17487/RFC3345</span>, <time datetime="2002-08" class="refDate">August 2002</time>, <span><<a href="https://www.rfc-editor.org/info/rfc3345">https://www.rfc-editor.org/info/rfc3345</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC4272">[RFC4272]</dt>
<dd>
<span class="refAuthor">Murphy, S.</span>, <span class="refTitle">"BGP Security Vulnerabilities Analysis"</span>, <span class="seriesInfo">RFC 4272</span>, <span class="seriesInfo">DOI 10.17487/RFC4272</span>, <time datetime="2006-01" class="refDate">January 2006</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4272">https://www.rfc-editor.org/info/rfc4272</a>></span>. </dd>
<dd class="break"></dd>
<dt id="RFC4724">[RFC4724]</dt>
<dd>
<span class="refAuthor">Sangli, S.</span>, <span class="refAuthor">Chen, E.</span>, <span class="refAuthor">Fernando, R.</span>, <span class="refAuthor">Scudder, J.</span>, and <span class="refAuthor">Y. Rekhter</span>, <span class="refTitle">"Graceful Restart Mechanism for BGP"</span>, <span class="seriesInfo">RFC 4724</span>, <span class="seriesInfo">DOI 10.17487/RFC4724</span>, <time datetime="2007-01" class="refDate">January 2007</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4724">https://www.rfc-editor.org/info/rfc4724</a>></span>. </dd>
<dd class="break"></dd>
<dt id="STOP-OSC">[STOP-OSC]</dt>
<dd>
<span class="refAuthor">Walton, D.</span>, <span class="refAuthor">Retana, A.</span>, <span class="refAuthor">Chen, E.</span>, and <span class="refAuthor">J. Scudder</span>, <span class="refTitle">"BGP Persistent Route Oscillation Solutions"</span>, <span class="seriesInfo">Work in Progress, draft-ietf-idr-route-oscillation-stop-03</span>, <time datetime="2016-04-30" class="refDate">April 30, 2016</time>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<section id="appendix-A">
<h2 id="name-acknowledgments">
<a href="#name-acknowledgments" class="section-name selfRef">Acknowledgments</a>
</h2>
<p id="appendix-A-1">We would like to thank David Cook and Naiming Shen for their
contributions to the design and development of the extension.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
<p id="appendix-A-2">Many people have made valuable comments and suggestions, including
Rex Fernando, Eugene Kim, Danny McPherson, Dave Meyer, Pradosh
Mohapatra, Keyur Patel, Robert Raszuk, Eric Rosen, Srihari Sangli, Dan
Tappan, Mark Turner, Jeff Haas, Jay Borkenhagen, Mach Chen, Denis Ovsienko,
Carlos Pignataro, Meral Shirazipour, and Kathleen Moriarty.<a href="#appendix-A-2" class="pilcrow">¶</a></p>
</section>
<div id="authors-addresses">
<section id="appendix-B">
<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">Daniel Walton</span></div>
<div dir="auto" class="left"><span class="org">Cumulus Networks</span></div>
<div dir="auto" class="left"><span class="street-address">185 E. Dana Street</span></div>
<div dir="auto" class="left">
<span class="locality">Mountain View</span>, <span class="region">CA</span> <span class="postal-code">94041</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:dwalton@cumulusnetworks.com" class="email">dwalton@cumulusnetworks.com</a>
</div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Alvaro Retana</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems, Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">Kit Creek Rd.</span></div>
<div dir="auto" class="left">
<span class="locality">Research Triangle Park</span>, <span class="region">NC</span> <span class="postal-code">27709</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:aretana@cisco.com" class="email">aretana@cisco.com</a>
</div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">Enke Chen</span></div>
<div dir="auto" class="left"><span class="org">Cisco Systems, Inc.</span></div>
<div dir="auto" class="left"><span class="street-address">170 W. Tasman Dr.</span></div>
<div dir="auto" class="left">
<span class="locality">San Jose</span>, <span class="region">CA</span> <span class="postal-code">95134</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:enkechen@cisco.com" class="email">enkechen@cisco.com</a>
</div>
</address>
<address class="vcard">
<div dir="auto" class="left"><span class="fn nameRole">John Scudder</span></div>
<div dir="auto" class="left"><span class="org">Juniper Networks</span></div>
<div dir="auto" class="left"><span class="street-address">1194 N. Mathilda Ave</span></div>
<div dir="auto" class="left">
<span class="locality">Sunnyvale</span>, <span class="region">CA</span> <span class="postal-code">94089</span>
</div>
<div dir="auto" class="left"><span class="country-name">United States of America</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:jgs@juniper.net" class="email">jgs@juniper.net</a>
</div>
</address>
</section>
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