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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 9117: Revised Validation Procedure for BGP Flow Specifications</title>
<meta content="James Uttaro" name="author">
<meta content="Juan Alcaide" name="author">
<meta content="Clarence Filsfils" name="author">
<meta content="David Smith" name="author">
<meta content="Pradosh Mohapatra" name="author">
<meta content="
       
   This document describes a modification to the validation procedure defined
   for the dissemination of BGP Flow Specifications.  The dissemination of BGP
   Flow Specifications as specified in RFC 8955 requires that the originator
   of the Flow Specification match the originator of the best-match unicast
   route for the destination prefix embedded in the Flow Specification. For an
   Internal Border Gateway Protocol (iBGP) received route, the originator is
   typically a border router within the same autonomous system (AS).  The
   objective is to allow only BGP speakers within the data forwarding path to
   originate BGP Flow Specifications.  Sometimes it is desirable to originate
   the BGP Flow Specification from any place within the autonomous system
   itself, for example, from a centralized BGP route controller.  However, the
   validation procedure described in RFC 8955 will fail in this scenario.  The modification
   proposed herein relaxes the validation rule to enable Flow Specifications
   to be originated within the same autonomous system as the BGP speaker
   performing the validation.  Additionally, this document revises the AS_PATH
   validation rules so Flow Specifications received from an External Border
   Gateway Protocol (eBGP) peer can be validated when such a peer is a BGP
   route server.

       
       
  This document updates the validation procedure in RFC 8955.
       
    " name="description">
<meta content="xml2rfc 3.9.1" name="generator">
<meta content="BGP flowspec" name="keyword">
<meta content="9117" name="rfc.number">
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<link href="https://dx.doi.org/10.17487/rfc9117" rel="alternate">
  <link href="urn:issn:2070-1721" rel="alternate">
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<table class="ears">
<thead><tr>
<td class="left">RFC 9117</td>
<td class="center">Revised Flowspec Validation Procedure</td>
<td class="right">August 2021</td>
</tr></thead>
<tfoot><tr>
<td class="left">Uttaro, 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/rfc9117" class="eref">9117</a></dd>
<dt class="label-updates">Updates:</dt>
<dd class="updates">
<a href="https://www.rfc-editor.org/rfc/rfc8955" class="eref">8955</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="2021-08" class="published">August 2021</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">J. Uttaro</div>
<div class="org">AT&amp;T</div>
</div>
<div class="author">
      <div class="author-name">J. Alcaide</div>
<div class="org">Cisco</div>
</div>
<div class="author">
      <div class="author-name">C. Filsfils</div>
<div class="org">Cisco</div>
</div>
<div class="author">
      <div class="author-name">D. Smith</div>
<div class="org">Cisco</div>
</div>
<div class="author">
      <div class="author-name">P. Mohapatra</div>
<div class="org">Sproute Networks</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 9117</h1>
<h1 id="title">Revised Validation Procedure for BGP Flow Specifications</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 modification to the validation procedure defined
   for the dissemination of BGP Flow Specifications.  The dissemination of BGP
   Flow Specifications as specified in RFC 8955 requires that the originator
   of the Flow Specification match the originator of the best-match unicast
   route for the destination prefix embedded in the Flow Specification. For an
   Internal Border Gateway Protocol (iBGP) received route, the originator is
   typically a border router within the same autonomous system (AS).  The
   objective is to allow only BGP speakers within the data forwarding path to
   originate BGP Flow Specifications.  Sometimes it is desirable to originate
   the BGP Flow Specification from any place within the autonomous system
   itself, for example, from a centralized BGP route controller.  However, the
   validation procedure described in RFC 8955 will fail in this scenario.  The modification
   proposed herein relaxes the validation rule to enable Flow Specifications
   to be originated within the same autonomous system as the BGP speaker
   performing the validation.  Additionally, this document revises the AS_PATH
   validation rules so Flow Specifications received from an External Border
   Gateway Protocol (eBGP) peer can be validated when such a peer is a BGP
   route server.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
<p id="section-abstract-2">
  This document updates the validation procedure in RFC 8955.<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/rfc9117">https://www.rfc-editor.org/info/rfc9117</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 ulBare ulEmpty toc">
<li class="compact ulBare 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 ulBare ulEmpty toc" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1" class="keepWithNext"><a href="#section-2" class="xref">2</a>.  <a href="#name-definitions-of-terms-used-i" class="xref">Definitions of Terms Used in This Memo</a></p>
</li>
          <li class="compact ulBare ulEmpty toc" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1" class="keepWithNext"><a href="#section-3" class="xref">3</a>.  <a href="#name-motivation" class="xref">Motivation</a></p>
</li>
          <li class="compact ulBare 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-revised-validation-procedur" class="xref">Revised Validation Procedure</a></p>
<ul class="ulEmpty compact ulBare toc">
<li class="ulEmpty compact ulBare 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-revision-of-route-feasibili" class="xref">Revision of Route Feasibility</a></p>
</li>
              <li class="ulEmpty compact ulBare 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-revision-of-as_path-validat" class="xref">Revision of AS_PATH Validation</a></p>
</li>
            </ul>
</li>
          <li class="compact ulBare 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-topology-considerations" class="xref">Topology Considerations</a></p>
</li>
          <li class="compact ulBare 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-iana-considerations" class="xref">IANA Considerations</a></p>
</li>
          <li class="compact ulBare 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-security-considerations" class="xref">Security Considerations</a></p>
</li>
          <li class="compact ulBare ulEmpty toc" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-8" class="xref">8</a>.  <a href="#name-references" class="xref">References</a></p>
<ul class="ulEmpty compact ulBare toc">
<li class="ulEmpty compact ulBare toc" id="section-toc.1-1.8.2.1">
                <p id="section-toc.1-1.8.2.1.1"><a href="#section-8.1" class="xref">8.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a></p>
</li>
              <li class="ulEmpty compact ulBare toc" id="section-toc.1-1.8.2.2">
                <p id="section-toc.1-1.8.2.2.1"><a href="#section-8.2" class="xref">8.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a></p>
</li>
            </ul>
</li>
          <li class="compact ulBare ulEmpty toc" id="section-toc.1-1.9">
            <p id="section-toc.1-1.9.1"><a href="#appendix-A" class="xref"></a><a href="#name-acknowledgements" class="xref">Acknowledgements</a></p>
</li>
          <li class="compact ulBare ulEmpty toc" id="section-toc.1-1.10">
            <p id="section-toc.1-1.10.1"><a href="#appendix-B" class="xref"></a><a href="#name-authors-addresses" class="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">
  <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> defines BGP Network Layer
  Reachability Information (NLRI) <span>[<a href="#RFC4760" class="xref">RFC4760</a>]</span> that can be used to distribute traffic Flow
  Specifications amongst BGP speakers in support of traffic
  filtering. The primary intention of <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> is to enable downstream autonomous systems to
  signal traffic filtering policies to upstream autonomous systems.  In
  this way, traffic is filtered closer to the source and the upstream
  autonomous systems avoid carrying the traffic to the downstream
  autonomous systems only to be discarded.  <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> also enables more granular traffic filtering based
  upon upper-layer protocol information (e.g., protocol or port
  numbers) as opposed to coarse IP destination prefix-based filtering.
  Flow Specification NLRIs received from a BGP peer is subject to
  validity checks before being considered feasible and subsequently
  installed within the respective Adj-RIB-In.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">
   The validation procedure defined within <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> requires that the originator of the Flow
   Specification NLRI match the originator of the best-match unicast
   route for the destination prefix embedded in the Flow Specification.
   The aim is to make sure that only speakers on the forwarding path
   can originate the Flow Specification.  Let's consider the particular
   case where the Flow Specification is originated in any location
   within the same Local Domain as the speaker performing the
   validation (for example, by a centralized BGP route controller), and
   the best-match unicast route is originated in another Local Domain.
   In order for the validation to succeed for a Flow Specification
   received from an iBGP peer, it would be necessary to disseminate
   such Flow Specification NLRI directly from the specific border
   router (within the Local Domain) that is advertising the
   corresponding best-match unicast route to the Local Domain.  Those
   border routers would be acting as de facto route controllers.  This
   approach would be, however, operationally cumbersome in a Local
   Domain with numerous border routers having complex BGP policies.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">
    <a href="#fig_1" class="xref">Figure 1</a> illustrates this principle.  R1 (the upstream router) and
    RR (a route reflector) need to validate the Flow Specification
    whose embedded destination prefix has a best-match unicast route
    (dest-route) originated by ASBR2.  ASBR2 could originate the Flow
    Specification, and it would be validated when received by RR and R1
    (from their point of view, the originator of both the Flow
    Specification and the best-match unicast route will be ASBR1).
    Sometimes the Flow Specification needs to be originated within AS1.
    ASBR1 could originate it, and the Flow Specification would still be
    validated.  In both cases, the Flow Specification is originated by
    a router in the same forwarding path as the dest-route.  For the
    case where AS1 has thousands of ASBRs, it becomes impractical to
    originate different Flow Specification rules on each ASBR in AS1
    based on which ASBR each dest-route is learned from.  To make the
    situation more tenable, the objective is to advertise all the Flow
    Specifications from the same route controller.<a href="#section-1-3" class="pilcrow">¶</a></p>
<div id="fig_1">
<figure id="figure-1">
        <div class="artwork art-text alignLeft" id="section-1-4.1">
<pre>
        R1(AS1) --- RR(AS1) --- ASBR1(AS1) --- ASBR2(AS2)
                     |
             route controller(AS1)
</pre>
</div>
<figcaption><a href="#figure-1" class="selfRef">Figure 1</a></figcaption></figure>
</div>
<p id="section-1-5"> This document describes a modification to the validation procedure described in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span>, by allowing Flow Specification
      NLRIs to be originated from a centralized BGP route controller located
      within the Local Domain and not necessarily in the data-forwarding path.
      While the proposed modification cannot be used for inter-domain
      coordination of traffic filtering, it greatly simplifies distribution of
      intra-domain traffic filtering policies within a Local Domain that has
      numerous border routers having complex BGP policies.  By relaxing the
      validation procedure for iBGP, the proposed modification allows Flow
      Specifications to be distributed in a standard and scalable manner
      throughout the Local Domain.<a href="#section-1-5" class="pilcrow">¶</a></p>
<p id="section-1-6">

 Throughout this document, some references are made to
 AS_CONFED_SEQUENCE segments; see Sections <a href="#REV_ROUTE" class="xref">4.1</a> and <a href="#topology" class="xref">5</a>.  If AS_CONFED_SET
 segments are also present in the AS_PATH, the same
 considerations apply to them.  Note, however, that the use of
 AS_CONFED_SET segments is not recommended <span>[<a href="#RFC6472" class="xref">RFC6472</a>]</span>.  Refer to <span>[<a href="#I-D.ietf-idr-deprecate-as-set-confed-set" class="xref">CONFED-SET</a>]</span> as well.<a href="#section-1-6" class="pilcrow">¶</a></p>
</section>
<section id="section-2">
      <h2 id="name-definitions-of-terms-used-i">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-definitions-of-terms-used-i" class="section-name selfRef">Definitions of Terms Used in This Memo</a>
      </h2>
<span class="break"></span><dl class="dlParallel" id="section-2-1">
        <dt id="section-2-1.1">Local Domain:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-1.2">the local AS or the local confederation of ASes <span>[<a href="#RFC5065" class="xref">RFC5065</a>]</span>.<a href="#section-2-1.2" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-1.3">eBGP:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-1.4">BGP peering to a router not within the Local Domain.<a href="#section-2-1.4" class="pilcrow">¶</a>
</dd>
        <dd class="break"></dd>
<dt id="section-2-1.5">iBGP:
</dt>
        <dd style="margin-left: 1.5em" id="section-2-1.6">Both classic iBGP and any form of eBGP peering with a router within the
same confederation (i.e., iBGP peering is a peering that is not eBGP as
defined above).<a href="#section-2-1.6" class="pilcrow">¶</a>
</dd>
      <dd class="break"></dd>
</dl>
<p id="section-2-2">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as
    described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> 
    when, and only when, they appear in all capitals, as shown here.<a href="#section-2-2" class="pilcrow">¶</a></p>
</section>
<section id="section-3">
      <h2 id="name-motivation">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-motivation" class="section-name selfRef">Motivation</a>
      </h2>
<p id="section-3-1">Step (b) of the validation procedure in <span><a href="https://www.rfc-editor.org/rfc/rfc8955#section-6" class="relref">Section 6</a> of [<a href="#RFC8955" class="xref">RFC8955</a>]</span> is defined with the
      underlying assumption that the Flow Specification NLRI traverses the
      same path, in the inter-domain and intra-domain route distribution
      graph, as that of the longest-match unicast route for the destination
      prefix embedded in the Flow Specification.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2">
     In the case of inter-domain traffic filtering, the Flow Specification
     originator at the egress border routers of an AS (e.g., RTR-D and RTR-E
     of AS1 in <a href="#fig_2" class="xref">Figure 2</a>) matches the eBGP neighbor that
     advertised the longest match destination prefix (see RTR-F and RTR-G,
     respectively, in <a href="#fig_2" class="xref">Figure 2</a>).<a href="#section-3-2" class="pilcrow">¶</a></p>
<p id="section-3-3">
  Similarly, at the upstream routers of an AS (see RTR-A and RTR-B of
  AS1 in <a href="#fig_2" class="xref">Figure 2</a>), the Flow Specification originator
  matches the egress iBGP border routers that had advertised the
  unicast route for the best-match destination prefix (see RTR-D and
  RTR-E, respectively, in <a href="#fig_2" class="xref">Figure 2</a>).  This is true even
  when upstream routers select paths from different egress border
  routers as the best route based upon IGP distance.  For example, in <a href="#fig_2" class="xref">Figure 2</a>:<a href="#section-3-3" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-3-4.1">RTR-A chooses RTR-D as the best route<a href="#section-3-4.1" class="pilcrow">¶</a>
</li>
        <li class="normal ulEmpty" id="section-3-4.2">RTR-B chooses RTR-E as the best route<a href="#section-3-4.2" class="pilcrow">¶</a>
</li>
      </ul>
<div id="fig_2">
<figure id="figure-2">
        <div class="artwork art-text alignLeft" id="section-3-5.1">
<pre>
                  / - - - - - - - - - - - - -  -
                  |            AS1              |
                    +-------+        +-------+
                  | |       |        |       |  |
                    | RTR-A |        | RTR-B |
                  | |       |        |       |  |
                    +-------+        +-------+
                  |       \           /         |
                     iBGP  \         / iBGP
                  |         \       /           |
                            +-------+
                  |         |       |           |
                            | RTR-C |
                  |         |  RC   |           |
                            +-------+
                  |           /   \             |
                             /     \
                  |   iBGP  /       \ iBGP      |
                    +-------+        +-------+
                  | | RTR-D |        | RTR-E |  |
                    |       |        |       |
                  | |       |        |       |  |
                    +-------+        +-------+
                  |     |                 |     |
                   - - -|- - - - - - - - -|- - -/
                        | eBGP       eBGP |
                   - - -|- - - - - - - - -|- - -/
                  |     |                 |     |
                    +-------+        +-------+
                  | |       |        |       |  |
                    | RTR-F |        | RTR-G |
                  | |       |        |       |  |
                    +-------+        +-------+
                  |            AS2              |
                  / - - - - - - - - - - - - -  -
</pre>
</div>
<figcaption><a href="#figure-2" class="selfRef">Figure 2</a></figcaption></figure>
</div>
<p id="section-3-6">It is highly desirable that mechanisms exist to protect each AS independently 
   from network security attacks using the BGP Flow Specification NLRI for 
   intra-AS purposes only. Network operators often deploy a dedicated 
   Security Operations Center (SOC) within their AS to monitor and detect such security attacks. 
   To mitigate attacks within an AS, operators require 
   the ability to originate intra-AS Flow Specification NLRIs from a 
   central BGP route controller that is not within the data forwarding plane. 
   In this way, operators can direct border routers within their AS with 
   specific attack-mitigation actions (drop the traffic, forward to a pipe-cleaning location, etc.).<a href="#section-3-6" class="pilcrow">¶</a></p>
<p id="section-3-7">
   In addition, an operator may extend the requirements above for a group of
   ASes via policy.  This is described in <a href="#REV_ROUTE" class="xref">Section 4.1</a> (<a href="#b.2.3" class="xref">b.2.3</a>) of the validation procedure.<a href="#section-3-7" class="pilcrow">¶</a></p>
<p id="section-3-8">
   A central BGP route controller that originates Flow Specification
   NLRI should be able to avoid the complexity of having to determine
   the egress border router whose path was chosen as the best for each
   of its neighbors.

   When a central BGP route controller originates Flow Specification NLRI, the rest of the speakers
   within the AS will see the BGP route controller as the originator of the Flow Specification in terms
   of the validation procedure rules. Thus, it is necessary to modify step (b) of the validation procedure described in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> 
   such that an iBGP peer that is not within the data forwarding plane
   may originate Flow Specification NLRIs.<a href="#section-3-8" class="pilcrow">¶</a></p>
</section>
<section id="section-4">
      <h2 id="name-revised-validation-procedur">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-revised-validation-procedur" class="section-name selfRef">Revised Validation Procedure</a>
      </h2>
<div id="REV_ROUTE">
<section id="section-4.1">
        <h3 id="name-revision-of-route-feasibili">
<a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-revision-of-route-feasibili" class="section-name selfRef">Revision of Route Feasibility</a>
        </h3>
<p id="section-4.1-1">Step (b) of the validation procedure specified in <span><a href="https://www.rfc-editor.org/rfc/rfc8955#section-6" class="relref">Section 6</a> of [<a href="#RFC8955" class="xref">RFC8955</a>]</span> is
        redefined as follows:<a href="#section-4.1-1" class="pilcrow">¶</a></p>
<blockquote id="section-4.1-2">
          <span class="break"></span><dl class="dlParallel" id="section-4.1-2.1">
            <dt id="section-4.1-2.1.1">b)</dt>
            <dd style="margin-left: 1.5em" id="section-4.1-2.1.2">
              <p id="section-4.1-2.1.2.1">One of the following conditions <span class="bcp14">MUST</span> hold true:<a href="#section-4.1-2.1.2.1" class="pilcrow">¶</a></p>
<div id="step_b">
<ol start="1" type="1" class="normal type-1" id="section-4.1-2.1.2.2">
       <li id="section-4.1-2.1.2.2.1">
<div id="b.1">The originator of the Flow Specification matches the
       originator of the best-match unicast route for the destination
       prefix embedded in the Flow Specification (this is the unicast
       route with the longest possible prefix length covering the
       destination prefix embedded in the Flow Specification).<a href="#b.1" class="pilcrow">¶</a>
</div>
                </li>
<li id="section-4.1-2.1.2.2.2">
<div id="b.2">
                  <p id="section-4.1-2.1.2.2.2.1">The AS_PATH attribute of the Flow Specification is empty or
                contains only an AS_CONFED_SEQUENCE segment <span>[<a href="#RFC5065" class="xref">RFC5065</a>]</span>.<a href="#section-4.1-2.1.2.2.2.1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-4.1-2.1.2.2.2.2">
   <li id="section-4.1-2.1.2.2.2.2.1">
<div id="b.1.1">This condition <span class="bcp14">SHOULD</span> be
   enabled by default.<a href="#b.1.1" class="pilcrow">¶</a>
</div>
                    </li>
<li id="section-4.1-2.1.2.2.2.2.2">
<div id="b.2.2">This condition <span class="bcp14">MAY</span> be disabled by
                  explicit configuration on a BGP speaker.<a href="#b.2.2" class="pilcrow">¶</a>
</div>
                    </li>
<li id="section-4.1-2.1.2.2.2.2.3">
<div id="b.2.3">As an extension to this rule, a given non-empty AS_PATH
                  (besides AS_CONFED_SEQUENCE segments) <span class="bcp14">MAY</span> be
                  permitted by policy.<a href="#b.2.3" class="pilcrow">¶</a>
</div>
                  </li>
</ol>
</div>
              </li>
</ol>
</div>
</dd>
          <dd class="break"></dd>
</dl>
</blockquote>
<p id="section-4.1-3">Explanation:<a href="#section-4.1-3" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-4.1-4.1">
Receiving either an empty AS_PATH or one
with only an AS_CONFED_SEQUENCE segment indicates that the Flow Specification was
originated inside the Local Domain.<a href="#section-4.1-4.1" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.1-4.2">
With the above modification to the <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> validation procedure, a BGP peer within the Local Domain
that is not within the data-forwarding path can originate a Flow Specification.<a href="#section-4.1-4.2" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.1-4.3">
Disabling the new condition above (see <a href="#b.2.2" class="xref">step
b.2.2</a> in <a href="#REV_ROUTE" class="xref">Section 4.1</a>) could be a good practice if the
operator knew with certainty that a Flow Specification would not be originated
inside the Local Domain. An additional case would be if it was known for a
fact that only the right egress border routers (i.e., those that were also
egress border routers for the best routes) were originating Flow Specification
NLRI.<a href="#section-4.1-4.3" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.1-4.4">
Also, policy may be useful to permit a specific set of non-empty AS_PATHs (see
<a href="#b.2.3" class="xref">step b.2.3</a> in <a href="#REV_ROUTE" class="xref">Section 4.1</a>). For example, it could validate a Flow Specification
whose AS_PATH contained only an AS_SEQUENCE segment with ASes that were all
known to belong to the same administrative domain.<a href="#section-4.1-4.4" class="pilcrow">¶</a>
</li>
        </ul>
</section>
</div>
<div id="AS_PATH">
<section id="section-4.2">
        <h3 id="name-revision-of-as_path-validat">
<a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-revision-of-as_path-validat" class="section-name selfRef">Revision of AS_PATH Validation</a>
        </h3>
<p id="section-4.2-1">
<span><a href="https://www.rfc-editor.org/rfc/rfc8955#section-6" class="relref">Section 6</a> of [<a href="#RFC8955" class="xref">RFC8955</a>]</span>
states:<a href="#section-4.2-1" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-4.2-2.1">
            <blockquote id="section-4.2-2.1.1">
BGP implementations <span class="bcp14">MUST</span> also enforce that the
AS_PATH attribute of a route received via the External Border Gateway Protocol (eBGP) 
contains the neighboring AS in the left-most position of the AS_PATH attribute. While this rule is optional in the BGP specification, it
   becomes necessary to enforce it here for security reasons.<a href="#section-4.2-2.1.1" class="pilcrow">¶</a>
</blockquote>
</li>
        </ul>
<p id="section-4.2-3">
This rule prevents the exchange of BGP Flow Specification NLRIs at Internet
exchanges with BGP route servers, which by design don't insert their own AS
number into the AS_PATH (<span><a href="https://www.rfc-editor.org/rfc/rfc7947#section-2.2.2.1" class="relref">Section 2.2.2.1</a> of [<a href="#RFC7947" class="xref">RFC7947</a>]</span>).  Therefore, this document also
redefines the <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> AS_PATH validation
procedure referenced above as follows:<a href="#section-4.2-3" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-4.2-4.1">
            <blockquote id="section-4.2-4.1.1">
BGP Flow Specification implementations <span class="bcp14">MUST</span> enforce that the AS in the left-most position of the AS_PATH attribute of a Flow Specification route
received via the External Border Gateway Protocol (eBGP) matches the AS in the left-most position of the AS_PATH attribute of the best-match unicast route for the destination prefix 
embedded in the Flow Specification NLRI.<a href="#section-4.2-4.1.1" class="pilcrow">¶</a>
</blockquote>
</li>
        </ul>
<p id="section-4.2-5">
Explanation:<a href="#section-4.2-5" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-4.2-6.1">For clarity, the AS in the left-most position of the AS_PATH means the AS that was last added to an AS_SEQUENCE.<a href="#section-4.2-6.1" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.2">This proposed modification enables the exchange of 
BGP Flow Specification NLRIs at Internet exchanges with 
BGP route servers while at the same time, for security reasons, 
prevents an eBGP peer from advertising an inter-domain 
Flow Specification for a destination prefix that it does 
not provide reachability information for.<a href="#section-4.2-6.2" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.3">
Comparing only the left-most AS in the AS-PATH for eBGP-learned Flow Specification NLRIs is 
roughly equivalent to checking the neighboring AS. 
If the peer is a route server, security is necessarily weakened for the Flow Specification NLRI, as it is for any unicast route advertised from a route server. An example is discussed in the <a href="#Security" class="xref">Security Considerations</a> section.<a href="#section-4.2-6.3" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.4">
Redefinition of this AS_PATH validation rule for a Flow Specification does not
mean that the original rule in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span>
cannot be enforced as well.  Its enforcement remains optional per <span><a href="https://www.rfc-editor.org/rfc/rfc4271#section-6.3" class="relref">Section 6.3</a> of [<a href="#RFC4271" class="xref">RFC4271</a>]</span>.  That
is, a BGP speaker can enforce the first AS in the AS_PATH to be the same as
the neighbor AS for a route belonging to any Address Family (including Flow
Specification Address Family).  If the BGP speaker peer is not a route server,
when enforcing this optional rule, the security characteristics are exactly
equivalent to those specified in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span>.<a href="#section-4.2-6.4" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.5">
Alternatively, enforcing this optional rule for unicast routes (even if not enforced on Flow Specification NLRIs) achieves exactly the same security characteristics.
The reason is that, after all validations, the neighboring AS will be the same as the left-most AS in the AS-PATH for the unicast route, and the left-most AS in the AS_PATH for the unicast route 
will be the same as the left-most AS in the AS_PATH for the Flow Specification NLRI. Therefore, the neighboring AS will be the same as the left-most AS in the AS_PATH for the Flow Specification NLRI (as the original
AS_PATH validation rule in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> states).<a href="#section-4.2-6.5" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.6">
Note, however, that not checking the full AS_PATH allows any rogue or
misconfigured AS the ability to originate undesired Flow Specifications. This
is a BGP security threat, already present in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span>, but out of the scope of this document.<a href="#section-4.2-6.6" class="pilcrow">¶</a>
</li>
          <li class="normal ulEmpty" id="section-4.2-6.7">
Using the new rule to validate a Flow Specification route received from a peer belonging to the same Local Domain 
is out of the scope of this document. Note that although it's possible, its utility is dubious. 
Although it is conceivable that a router in the same Local Domain could send a rogue update, only eBGP risk is considered within this document
(in the same spirit as the aforementioned AS_PATH validation in <span>[<a href="#RFC4271" class="xref">RFC4271</a>]</span>).<a href="#section-4.2-6.7" class="pilcrow">¶</a>
</li>
        </ul>
</section>
</div>
</section>
<div id="topology">
<section id="section-5">
      <h2 id="name-topology-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-topology-considerations" class="section-name selfRef">Topology Considerations</a>
      </h2>
<p id="section-5-1">
<span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> indicates that the originator may
refer to the originator path attribute (ORIGINATOR_ID) or (if the attribute is
not present) the transport address of the peer from which the BGP speaker
received the update.  If the latter applies, a network should be designed so
it has a congruent topology amongst unicast routes and Flow Specification
routes.  By congruent topology, it is understood that the two routes (i.e.,
the Flow Specification route and its best-match unicast route) are learned
from the same peer across the AS.  That would likely not be true, for
instance, if some peers only negotiated one Address Family or if each Address
Family peering had a different set of policies. Failing to have a congruent
topology would result in step (<a href="#b.1" class="xref">b.1</a>) of the
validation procedure to fail.<a href="#section-5-1" class="pilcrow">¶</a></p>
<p id="section-5-2">
With the additional second condition (<a href="#b.2" class="xref">b.2</a>) in the validation procedure, non-congruent topologies are supported within the Local Domain if the Flow Specification
is originated within the Local Domain.<a href="#section-5-2" class="pilcrow">¶</a></p>
<p id="section-5-3">
Explanation:<a href="#section-5-3" class="pilcrow">¶</a></p>
<ul class="normal ulEmpty">
<li class="normal ulEmpty" id="section-5-4.1">
          <p id="section-5-4.1.1">Consider the following scenarios of a non-congruent topology without the second condition (<a href="#b.2" class="xref">b.2</a>) being added to the validation procedure:<a href="#section-5-4.1.1" class="pilcrow">¶</a></p>
<ol start="1" type="1" class="normal type-1" id="section-5-4.1.2">
<li id="section-5-4.1.2.1">Consider a topology with two BGP
          speakers with two iBGP peering sessions between them, one for
          unicast and one for Flow Specification. This is a non-congruent
          topology. Let's assume that the ORIGINATOR_ID attribute was not
          received (e.g., a route reflector receiving routes from its
          clients). In this case, the Flow Specification validation procedure
          will fail because of the first condition (<a href="#b.1" class="xref">b.1</a>).<a href="#section-5-4.1.2.1" class="pilcrow">¶</a>
</li>
            <li id="section-5-4.1.2.2">Consider a confederation of ASes with local AS X and local AS Y (both belonging to the same Local Domain), and a given BGP speaker X1 inside local AS X. 
The ORIGINATOR_ID attribute is not advertised when propagating routes across local ASes.
Let's assume the Flow Specification route is received from peer Y1 and the best-match unicast route
is received from peer Y2. Both peers belong to local AS Y.
The Flow Specification validation procedure will also fail because of the first condition (<a href="#b.1" class="xref">b.1</a>).<a href="#section-5-4.1.2.2" class="pilcrow">¶</a>
</li>
          </ol>
</li>
        <li class="normal ulEmpty" id="section-5-4.2">
Consider now that the second condition (<a href="#b.2" class="xref">b.2</a>) is
added to the validation procedure. In the scenarios above, if Flow
Specifications are originated in the same Local Domain, the AS_PATH will be
empty or contain only an AS_CONFED_SEQUENCE segment.  Condition (<a href="#b.2" class="xref">b.2</a>) will evaluate to true. Therefore, using the second
condition (<a href="#b.2" class="xref">b.2</a>), as defined by this document,
guarantees that the overall validation procedure will pass.  Thus,
non-congruent topologies are supported if the Flow Specification is originated
in the same Local Domain.<a href="#section-5-4.2" class="pilcrow">¶</a>
</li>
        <li class="normal ulEmpty" id="section-5-4.3">
Flow Specifications originated in a different Local Domain sill need a
congruent topology. The reason is that in a non-congruent topology, the second
condition (<a href="#b.2" class="xref">b.2</a>) evaluates to false and
only the first condition (<a href="#b.1" class="xref">b.1</a>) is
evaluated.<a href="#section-5-4.3" class="pilcrow">¶</a>
</li>
      </ul>
</section>
</div>
<div id="IANA">
<section id="section-6">
      <h2 id="name-iana-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-6-1">This document has no IANA actions.<a href="#section-6-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="Security">
<section id="section-7">
      <h2 id="name-security-considerations">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-7-1">
    This document updates the route feasibility validation procedures for Flow
    Specifications learned from iBGP peers and through route servers.  This
    change is in line with the procedures described in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> and, thus, security characteristics remain essentially
    equivalent to the existing security properties of BGP unicast routing,
    except as detailed below.<a href="#section-7-1" class="pilcrow">¶</a></p>
<p id="section-7-2">
    The security considerations discussed in <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span> apply to this
    specification as well.<a href="#section-7-2" class="pilcrow">¶</a></p>
<p id="section-7-3">
   This document makes the original AS_PATH validation rule (<span><a href="https://www.rfc-editor.org/rfc/rfc4271#section-6.3" class="relref">Section 6.3</a> of [<a href="#RFC4271" class="xref">RFC4271</a>]</span>) again
   <span class="bcp14">OPTIONAL</span> (<a href="#AS_PATH" class="xref">Section 4.2</a>) for Flow Specification Address Family (the rule is no longer
   mandatory as had been specified by <span>[<a href="#RFC8955" class="xref">RFC8955</a>]</span>).  If that original rule is
   not enforced for Flow Specification, it may introduce some new security
   risks.  A speaker in AS X peering with a route server could advertise a
   rogue Flow Specification route whose first AS in AS_PATH was Y. Assume Y is
   the first AS in the AS_PATH of the best-match unicast route.  When the
   route server advertises the Flow Specification to a speaker in AS Z, it
   will be validated by that speaker.  This risk is impossible to prevent if
   the Flow Specification route is received from a route server peer.  If
   configuration (or other means beyond the scope of this document) indicates
   that the peer is not a route server, that optional rule
   <span class="bcp14">SHOULD</span> be enforced for unicast and/or for Flow
   Specification routes (as discussed in the <a href="#AS_PATH" class="xref">Revision of AS_PATH Validation</a> section, just
   enforcing it in one of those Address Families is enough).  If the indication
   is that the peer is not a route server or there is no conclusive
   indication, that optional rule <span class="bcp14">SHOULD NOT</span> be enforced.<a href="#section-7-3" class="pilcrow">¶</a></p>
<p id="section-7-4">
   A route server itself may be in a good position to enforce the AS_PATH validation rule described
   in the previous paragraph. If it is known that a route server is not peering with any other route server,
   it can enforce the AS_PATH validation rule across all its peers.<a href="#section-7-4" class="pilcrow">¶</a></p>
<p id="section-7-5">
 BGP updates learned from iBGP peers are considered 
    trusted, so the Traffic Flow Specifications contained in BGP updates
    are also considered trusted.  Therefore, it is not required to
    validate that the originator of an intra-domain Traffic Flow
    Specification matches the originator of the best-match unicast route
 for the destination prefix embedded in that Flow Specification.  Note that this trustworthiness consideration is not
    absolute and the new possibility that an iBGP speaker could send a rogue Flow Specification is introduced.<a href="#section-7-5" class="pilcrow">¶</a></p>
<p id="section-7-6">
  The changes in <a href="#REV_ROUTE" class="xref">Section 4.1</a> don't affect the validation
  procedures for eBGP-learned routes.<a href="#section-7-6" class="pilcrow">¶</a></p>
<p id="section-7-7">
 It's worth mentioning that allowing (or making operationally feasible)
 Flow Specifications to originate within the Local Domain makes
 the network overall more secure. Flow Specifications can be originated
 more readily during attacks and improve the stability and security of
 the network.<a href="#section-7-7" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-8">
      <h2 id="name-references">
<a href="#section-8" class="section-number selfRef">8. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-8.1">
        <h3 id="name-normative-references">
<a href="#section-8.1" class="section-number selfRef">8.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
        <dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03" class="refDate">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="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>&lt;<a href="https://www.rfc-editor.org/info/rfc4271">https://www.rfc-editor.org/info/rfc4271</a>&gt;</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>&lt;<a href="https://www.rfc-editor.org/info/rfc4760">https://www.rfc-editor.org/info/rfc4760</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC5065">[RFC5065]</dt>
        <dd>
<span class="refAuthor">Traina, P.</span>, <span class="refAuthor">McPherson, D.</span>, and <span class="refAuthor">J. Scudder</span>, <span class="refTitle">"Autonomous System Confederations for BGP"</span>, <span class="seriesInfo">RFC 5065</span>, <span class="seriesInfo">DOI 10.17487/RFC5065</span>, <time datetime="2007-08" class="refDate">August 2007</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5065">https://www.rfc-editor.org/info/rfc5065</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC7947">[RFC7947]</dt>
        <dd>
<span class="refAuthor">Jasinska, E.</span>, <span class="refAuthor">Hilliard, N.</span>, <span class="refAuthor">Raszuk, R.</span>, and <span class="refAuthor">N. Bakker</span>, <span class="refTitle">"Internet Exchange BGP Route Server"</span>, <span class="seriesInfo">RFC 7947</span>, <span class="seriesInfo">DOI 10.17487/RFC7947</span>, <time datetime="2016-09" class="refDate">September 2016</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7947">https://www.rfc-editor.org/info/rfc7947</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8174">[RFC8174]</dt>
        <dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05" class="refDate">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC8955">[RFC8955]</dt>
      <dd>
<span class="refAuthor">Loibl, C.</span>, <span class="refAuthor">Hares, S.</span>, <span class="refAuthor">Raszuk, R.</span>, <span class="refAuthor">McPherson, D.</span>, and <span class="refAuthor">M. Bacher</span>, <span class="refTitle">"Dissemination of Flow Specification Rules"</span>, <span class="seriesInfo">RFC 8955</span>, <span class="seriesInfo">DOI 10.17487/RFC8955</span>, <time datetime="2020-12" class="refDate">December 2020</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8955">https://www.rfc-editor.org/info/rfc8955</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
<section id="section-8.2">
        <h3 id="name-informative-references">
<a href="#section-8.2" class="section-number selfRef">8.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="I-D.ietf-idr-deprecate-as-set-confed-set">[CONFED-SET]</dt>
        <dd>
<span class="refAuthor">Kumari, W.</span>, <span class="refAuthor">Sriram, K.</span>, <span class="refAuthor">Hannachi, L.</span>, and <span class="refAuthor">J. Haas</span>, <span class="refTitle">"Deprecation of AS_SET and AS_CONFED_SET in BGP"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-idr-deprecate-as-set-confed-set-05</span>, <time datetime="2021-03-12" class="refDate">12 March 2021</time>, <span>&lt;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-idr-deprecate-as-set-confed-set-05">https://datatracker.ietf.org/doc/html/draft-ietf-idr-deprecate-as-set-confed-set-05</a>&gt;</span>. </dd>
<dd class="break"></dd>
<dt id="RFC6472">[RFC6472]</dt>
      <dd>
<span class="refAuthor">Kumari, W.</span> and <span class="refAuthor">K. Sriram</span>, <span class="refTitle">"Recommendation for Not Using AS_SET and AS_CONFED_SET in BGP"</span>, <span class="seriesInfo">BCP 172</span>, <span class="seriesInfo">RFC 6472</span>, <span class="seriesInfo">DOI 10.17487/RFC6472</span>, <time datetime="2011-12" class="refDate">December 2011</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc6472">https://www.rfc-editor.org/info/rfc6472</a>&gt;</span>. </dd>
<dd class="break"></dd>
</dl>
</section>
</section>
<div id="Acknowledgements">
<section id="appendix-A">
      <h2 id="name-acknowledgements">
<a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a>
      </h2>
<p id="appendix-A-1">The authors would like to thank <span class="contact-name">Han Nguyen</span> for
      his direction on this work as well as <span class="contact-name">Waqas Alam</span>,
      <span class="contact-name">Keyur Patel</span>, <span class="contact-name">Robert Raszuk</span>,
      <span class="contact-name">Eric Rosen</span>, <span class="contact-name">Shyam Sethuram</span>,
      <span class="contact-name">Susan Hares</span>, <span class="contact-name">Alvaro Retana</span>,
      and <span class="contact-name">John Scudder</span> for their review and comments.<a href="#appendix-A-1" class="pilcrow">¶</a></p>
</section>
</div>
<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">James Uttaro</span></div>
<div dir="auto" class="left"><span class="org">AT&amp;T</span></div>
<div dir="auto" class="left"><span class="street-address">200 S. Laurel Ave</span></div>
<div dir="auto" class="left">
<span class="locality">Middletown</span>, <span class="region">NJ</span> <span class="postal-code">07748</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:ju1738@att.com" class="email">ju1738@att.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Juan Alcaide</span></div>
<div dir="auto" class="left"><span class="org">Cisco</span></div>
<div dir="auto" class="left"><span class="extended-address">Research Triangle Park</span></div>
<div dir="auto" class="left"><span class="street-address">7100 Kit Creek Road</span></div>
<div dir="auto" class="left">
<span class="locality">Morrisville</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:jalcaide@cisco.com" class="email">jalcaide@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Clarence Filsfils</span></div>
<div dir="auto" class="left"><span class="org">Cisco</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:cf@cisco.com" class="email">cf@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">David Smith</span></div>
<div dir="auto" class="left"><span class="org">Cisco</span></div>
<div dir="auto" class="left"><span class="street-address">111 Wood Ave South</span></div>
<div dir="auto" class="left">
<span class="locality">Iselin</span>, <span class="region">NJ</span> <span class="postal-code">08830</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:djsmith@cisco.com" class="email">djsmith@cisco.com</a>
</div>
</address>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">Pradosh Mohapatra</span></div>
<div dir="auto" class="left"><span class="org">Sproute Networks</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:mpradosh@yahoo.com" class="email">mpradosh@yahoo.com</a>
</div>
</address>
</section>
</div>
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