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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 8754: IPv6 Segment Routing Header (SRH)</title> <meta content="Clarence Filsfils" name="author"> <meta content="Darren Dukes" name="author"> <meta content="Stefano Previdi" name="author"> <meta content="John Leddy" name="author"> <meta content="Satoru Matsushima" name="author"> <meta content="Daniel Voyer" name="author"> <meta content=" Segment Routing can be applied to the IPv6 data plane using a new type of Routing Extension Header called the Segment Routing Header (SRH). This document describes the SRH and how it is used by nodes that are Segment Routing (SR) capable. 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Undo that. */ dl.olPercent > dd, dd { margin-left: revert; } /* Avoid narrow tables forcing too narrow table captions, which may render badly */ table { min-width: 20em; } /* ol type a */ ol.type-a { list-style-type: lower-alpha; } ol.type-A { list-style-type: upper-alpha; } ol.type-i { list-style-type: lower-roman; } ol.type-I { list-style-type: lower-roman; } /* Apply the print table and row borders in general, on request from the RPC, and increase the contrast between border and odd row background sligthtly */ table { border: 1px solid #ddd; } td { border-top: 1px solid #ddd; } tr:nth-child(2n+1) > td { background-color: #f8f8f8; } /* Use style rules to govern display of the TOC. */ @media screen and (max-width: 1023px) { #toc nav { display: none; } #toc.active nav { display: block; } } </style> <link href="rfc-local.css" rel="stylesheet" type="text/css"> <link href="https://dx.doi.org/10.17487/rfc8754" rel="alternate"> <link href="urn:issn:2070-1721" rel="alternate"> <link href="https://datatracker.ietf.org/doc/draft-ietf-6man-segment-routing-header-26" rel="prev"> </head> <body> <script src="https://www.rfc-editor.org/js/metadata.min.js"></script> <table class="ears"> <thead><tr> <td class="left">RFC 8754</td> <td class="center">IPv6 Segment Routing Header (SRH)</td> <td class="right">March 2020</td> </tr></thead> <tfoot><tr> <td class="left">Filsfils, 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/rfc8754" class="eref">8754</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="2020-03" class="published">March 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">C. Filsfils, <span class="editor">Ed.</span> </div> <div class="org">Cisco Systems, Inc.</div> </div> <div class="author"> <div class="author-name">D. Dukes, <span class="editor">Ed.</span> </div> <div class="org">Cisco Systems, Inc.</div> </div> <div class="author"> <div class="author-name">S. Previdi</div> <div class="org">Huawei</div> </div> <div class="author"> <div class="author-name">J. Leddy</div> <div class="org">Individual</div> </div> <div class="author"> <div class="author-name">S. Matsushima</div> <div class="org">SoftBank</div> </div> <div class="author"> <div class="author-name">D. Voyer</div> <div class="org">Bell Canada</div> </div> </dd> </dl> </div> <h1 id="rfcnum">RFC 8754</h1> <h1 id="title">IPv6 Segment Routing Header (SRH)</h1> <section id="section-abstract"> <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2> <p id="section-abstract-1">Segment Routing can be applied to the IPv6 data plane using a new type of Routing Extension Header called the Segment Routing Header (SRH). This document describes the SRH and how it is used by nodes that are Segment Routing (SR) capable.<a href="#section-abstract-1" class="pilcrow">¶</a></p> </section> <div id="status-of-memo"> <section id="section-boilerplate.1"> <h2 id="name-status-of-this-memo"> <a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a> </h2> <p id="section-boilerplate.1-1"> This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p> <p id="section-boilerplate.1-2"> This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p> <p id="section-boilerplate.1-3"> Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at <span><a href="https://www.rfc-editor.org/info/rfc8754">https://www.rfc-editor.org/info/rfc8754</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-requirements-language" class="xref">Requirements Language</a><a href="#section-toc.1-1.1.2.2.1" 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-segment-routing-header" class="xref">Segment Routing Header</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-srh-tlvs" class="xref">SRH TLVs</a><a href="#section-toc.1-1.2.2.1.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.2.2.1.2.1"> <p id="section-toc.1-1.2.2.1.2.1.1"><a href="#section-2.1.1" class="xref">2.1.1</a>. <a href="#name-padding-tlvs" class="xref">Padding TLVs</a><a href="#section-toc.1-1.2.2.1.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.2.2.1.2.2"> <p id="section-toc.1-1.2.2.1.2.2.1"><a href="#section-2.1.2" class="xref">2.1.2</a>. <a href="#name-hmac-tlv" class="xref">HMAC TLV</a><a href="#section-toc.1-1.2.2.1.2.2.1" class="pilcrow">¶</a></p> </li> </ul> </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-sr-nodes" class="xref">SR Nodes</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-sr-source-node" class="xref">SR Source Node</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-transit-node" class="xref">Transit Node</a><a href="#section-toc.1-1.3.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.3.2.3"> <p id="section-toc.1-1.3.2.3.1"><a href="#section-3.3" class="xref">3.3</a>. <a href="#name-sr-segment-endpoint-node" class="xref">SR Segment Endpoint Node</a><a href="#section-toc.1-1.3.2.3.1" 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-packet-processing" class="xref">Packet Processing</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" 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-sr-source-node-2" class="xref">SR Source Node</a><a href="#section-toc.1-1.4.2.1.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.4.2.1.2.1"> <p id="section-toc.1-1.4.2.1.2.1.1"><a href="#section-4.1.1" class="xref">4.1.1</a>. <a href="#name-reduced-srh" class="xref">Reduced SRH</a><a href="#section-toc.1-1.4.2.1.2.1.1" class="pilcrow">¶</a></p> </li> </ul> </li> <li class="toc ulEmpty" 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-transit-node-2" class="xref">Transit Node</a><a href="#section-toc.1-1.4.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.4.2.3"> <p id="section-toc.1-1.4.2.3.1"><a href="#section-4.3" class="xref">4.3</a>. <a href="#name-sr-segment-endpoint-node-2" class="xref">SR Segment Endpoint Node</a><a href="#section-toc.1-1.4.2.3.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.4.2.3.2.1"> <p id="section-toc.1-1.4.2.3.2.1.1"><a href="#section-4.3.1" class="xref">4.3.1</a>. <a href="#name-fib-entry-is-a-locally-inst" class="xref">FIB Entry Is a Locally Instantiated SRv6 SID</a><a href="#section-toc.1-1.4.2.3.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.4.2.3.2.2"> <p id="section-toc.1-1.4.2.3.2.2.1"><a href="#section-4.3.2" class="xref">4.3.2</a>. <a href="#name-fib-entry-is-a-local-interf" class="xref">FIB Entry Is a Local Interface</a><a href="#section-toc.1-1.4.2.3.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.4.2.3.2.3"> <p id="section-toc.1-1.4.2.3.2.3.1"><a href="#section-4.3.3" class="xref">4.3.3</a>. <a href="#name-fib-entry-is-a-nonlocal-rou" class="xref">FIB Entry Is a Nonlocal Route</a><a href="#section-toc.1-1.4.2.3.2.3.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.4.2.3.2.4"> <p id="section-toc.1-1.4.2.3.2.4.1"><a href="#section-4.3.4" class="xref">4.3.4</a>. <a href="#name-fib-entry-is-a-no-match" class="xref">FIB Entry Is a No Match</a><a href="#section-toc.1-1.4.2.3.2.4.1" class="pilcrow">¶</a></p> </li> </ul> </li> </ul> </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-intra-sr-domain-deployment-" class="xref">Intra-SR-Domain Deployment Model</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.5.2.1"> <p id="section-toc.1-1.5.2.1.1"><a href="#section-5.1" class="xref">5.1</a>. <a href="#name-securing-the-sr-domain" class="xref">Securing the SR Domain</a><a href="#section-toc.1-1.5.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.5.2.2"> <p id="section-toc.1-1.5.2.2.1"><a href="#section-5.2" class="xref">5.2</a>. <a href="#name-sr-domain-as-a-single-syste" class="xref">SR Domain as a Single System with Delegation among Components</a><a href="#section-toc.1-1.5.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.5.2.3"> <p id="section-toc.1-1.5.2.3.1"><a href="#section-5.3" class="xref">5.3</a>. <a href="#name-mtu-considerations" class="xref">MTU Considerations</a><a href="#section-toc.1-1.5.2.3.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.5.2.4"> <p id="section-toc.1-1.5.2.4.1"><a href="#section-5.4" class="xref">5.4</a>. <a href="#name-icmp-error-processing" class="xref">ICMP Error Processing</a><a href="#section-toc.1-1.5.2.4.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.5.2.5"> <p id="section-toc.1-1.5.2.5.1"><a href="#section-5.5" class="xref">5.5</a>. <a href="#name-load-balancing-and-ecmp" class="xref">Load Balancing and ECMP</a><a href="#section-toc.1-1.5.2.5.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.5.2.6"> <p id="section-toc.1-1.5.2.6.1"><a href="#section-5.6" class="xref">5.6</a>. <a href="#name-other-deployments" class="xref">Other Deployments</a><a href="#section-toc.1-1.5.2.6.1" class="pilcrow">¶</a></p> </li> </ul> </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-illustrations" class="xref">Illustrations</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-abstract-representation-of-" class="xref">Abstract Representation of an SRH</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-example-topology" class="xref">Example Topology</a><a href="#section-toc.1-1.6.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.3"> <p id="section-toc.1-1.6.2.3.1"><a href="#section-6.3" class="xref">6.3</a>. <a href="#name-sr-source-node-3" class="xref">SR Source Node</a><a href="#section-toc.1-1.6.2.3.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.6.2.3.2.1"> <p id="section-toc.1-1.6.2.3.2.1.1"><a href="#section-6.3.1" class="xref">6.3.1</a>. <a href="#name-intra-sr-domain-packet" class="xref">Intra-SR-Domain Packet</a><a href="#section-toc.1-1.6.2.3.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.3.2.2"> <p id="section-toc.1-1.6.2.3.2.2.1"><a href="#section-6.3.2" class="xref">6.3.2</a>. <a href="#name-inter-sr-domain-packet-tran" class="xref">Inter-SR-Domain Packet -- Transit</a><a href="#section-toc.1-1.6.2.3.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.3.2.3"> <p id="section-toc.1-1.6.2.3.2.3.1"><a href="#section-6.3.3" class="xref">6.3.3</a>. <a href="#name-inter-sr-domain-packet-inte" class="xref">Inter-SR-Domain Packet -- Internal to External</a><a href="#section-toc.1-1.6.2.3.2.3.1" class="pilcrow">¶</a></p> </li> </ul> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.4"> <p id="section-toc.1-1.6.2.4.1"><a href="#section-6.4" class="xref">6.4</a>. <a href="#name-transit-node-3" class="xref">Transit Node</a><a href="#section-toc.1-1.6.2.4.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.5"> <p id="section-toc.1-1.6.2.5.1"><a href="#section-6.5" class="xref">6.5</a>. <a href="#name-sr-segment-endpoint-node-3" class="xref">SR Segment Endpoint Node</a><a href="#section-toc.1-1.6.2.5.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.6.2.6"> <p id="section-toc.1-1.6.2.6.1"><a href="#section-6.6" class="xref">6.6</a>. <a href="#name-delegation-of-function-with" class="xref">Delegation of Function with HMAC Verification</a><a href="#section-toc.1-1.6.2.6.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.6.2.6.2.1"> <p id="section-toc.1-1.6.2.6.2.1.1"><a href="#section-6.6.1" class="xref">6.6.1</a>. <a href="#name-sid-list-verification" class="xref">SID List Verification</a><a href="#section-toc.1-1.6.2.6.2.1.1" class="pilcrow">¶</a></p> </li> </ul> </li> </ul> </li> <li class="toc ulEmpty" id="section-toc.1-1.7"> <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>. <a href="#name-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" id="section-toc.1-1.7.2.1"> <p id="section-toc.1-1.7.2.1.1"><a href="#section-7.1" class="xref">7.1</a>. <a href="#name-sr-attacks" class="xref">SR Attacks</a><a href="#section-toc.1-1.7.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.7.2.2"> <p id="section-toc.1-1.7.2.2.1"><a href="#section-7.2" class="xref">7.2</a>. <a href="#name-service-theft" class="xref">Service Theft</a><a href="#section-toc.1-1.7.2.2.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.7.2.3"> <p id="section-toc.1-1.7.2.3.1"><a href="#section-7.3" class="xref">7.3</a>. <a href="#name-topology-disclosure" class="xref">Topology Disclosure</a><a href="#section-toc.1-1.7.2.3.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.7.2.4"> <p id="section-toc.1-1.7.2.4.1"><a href="#section-7.4" class="xref">7.4</a>. <a href="#name-icmp-generation" class="xref">ICMP Generation</a><a href="#section-toc.1-1.7.2.4.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.7.2.5"> <p id="section-toc.1-1.7.2.5.1"><a href="#section-7.5" class="xref">7.5</a>. <a href="#name-applicability-of-ah" class="xref">Applicability of AH</a><a href="#section-toc.1-1.7.2.5.1" class="pilcrow">¶</a></p> </li> </ul> </li> <li class="toc ulEmpty" id="section-toc.1-1.8"> <p id="section-toc.1-1.8.1"><a href="#section-8" class="xref">8</a>. <a href="#name-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc ulEmpty" 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-segment-routing-header-flag" class="xref">Segment Routing Header Flags Registry</a><a href="#section-toc.1-1.8.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" 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-segment-routing-header-tlvs" class="xref">Segment Routing Header TLVs Registry</a><a href="#section-toc.1-1.8.2.2.1" class="pilcrow">¶</a></p> </li> </ul> </li> <li class="toc ulEmpty" id="section-toc.1-1.9"> <p id="section-toc.1-1.9.1"><a href="#section-9" class="xref">9</a>. <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.9.1" class="pilcrow">¶</a></p> <ul class="toc ulEmpty"> <li class="toc 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="xref">9.1</a>. <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.9.2.1.1" class="pilcrow">¶</a></p> </li> <li class="toc 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="xref">9.2</a>. <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.9.2.2.1" class="pilcrow">¶</a></p> </li> </ul> </li> <li class="toc ulEmpty" id="section-toc.1-1.10"> <p id="section-toc.1-1.10.1"><a href="#section-appendix.a" class="xref"></a><a href="#name-acknowledgements" class="xref">Acknowledgements</a><a href="#section-toc.1-1.10.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.11"> <p id="section-toc.1-1.11.1"><a href="#section-appendix.b" class="xref"></a><a href="#name-contributors" class="xref">Contributors</a><a href="#section-toc.1-1.11.1" class="pilcrow">¶</a></p> </li> <li class="toc ulEmpty" id="section-toc.1-1.12"> <p id="section-toc.1-1.12.1"><a href="#section-appendix.c" class="xref"></a><a href="#name-authors-addresses" class="xref">Authors' Addresses</a><a href="#section-toc.1-1.12.1" class="pilcrow">¶</a></p> </li> </ul> </nav> </section> </div> <div id="INTRO"> <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">Segment Routing (SR) can be applied to the IPv6 data plane using a new type of routing header called the Segment Routing Header (SRH). This document describes the SRH and how it is used by nodes that are SR capable.<a href="#section-1-1" class="pilcrow">¶</a></p> <p id="section-1-2">"Segment Routing Architecture" <span>[<a href="#RFC8402" class="xref">RFC8402</a>]</span> describes Segment Routing and its instantiation in two data planes: MPLS and IPv6.<a href="#section-1-2" class="pilcrow">¶</a></p> <p id="section-1-3">The encoding of IPv6 segments in the SRH is defined in this document.<a href="#section-1-3" class="pilcrow">¶</a></p> <div id="TERMS"> <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> <p id="section-1.1-1">This document uses the terms Segment Routing (SR), SR domain, SR over IPv6 (SRv6), Segment Identifier (SID), SRv6 SID, Active Segment, and SR Policy as defined in <span>[<a href="#RFC8402" class="xref">RFC8402</a>]</span>.<a href="#section-1.1-1" class="pilcrow">¶</a></p> </section> </div> <section id="section-1.2"> <h3 id="name-requirements-language"> <a href="#section-1.2" class="section-number selfRef">1.2. </a><a href="#name-requirements-language" class="section-name selfRef">Requirements Language</a> </h3> <p id="section-1.2-1"> The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>", "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>", "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>", "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are to be interpreted as described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span> <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> when, and only when, they appear in all capitals, as shown here.<a href="#section-1.2-1" class="pilcrow">¶</a></p> </section> </section> </div> <div id="SRH"> <section id="section-2"> <h2 id="name-segment-routing-header"> <a href="#section-2" class="section-number selfRef">2. </a><a href="#name-segment-routing-header" class="section-name selfRef">Segment Routing Header</a> </h2> <p id="section-2-1">Routing headers are defined in <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span>. The Segment Routing Header (SRH) has a new Routing Type (4).<a href="#section-2-1" class="pilcrow">¶</a></p> <p id="section-2-2">The SRH is defined as follows:<a href="#section-2-2" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-2-3"> <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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry | Flags | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[0] (128-bit IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | ... | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n] (128-bit IPv6 address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // // Optional Type Length Value objects (variable) // // // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ </pre><a href="#section-2-3" class="pilcrow">¶</a> </div> <p id="section-2-4">where:<a href="#section-2-4" class="pilcrow">¶</a></p> <dl class="dlParallel" id="section-2-5"> <dt id="section-2-5.1">Next Header:</dt> <dd id="section-2-5.2">Defined in <span>[<a href="#RFC8200" class="xref">RFC8200</a>], <a href="https://www.rfc-editor.org/rfc/rfc8200#section-4.4" class="relref">Section 4.4</a></span>.<a href="#section-2-5.2" class="pilcrow">¶</a> </dd> <dt id="section-2-5.3">Hdr Ext Len:</dt> <dd id="section-2-5.4">Defined in <span>[<a href="#RFC8200" class="xref">RFC8200</a>], <a href="https://www.rfc-editor.org/rfc/rfc8200#section-4.4" class="relref">Section 4.4</a></span>.<a href="#section-2-5.4" class="pilcrow">¶</a> </dd> <dt id="section-2-5.5">Routing Type:</dt> <dd id="section-2-5.6">4.<a href="#section-2-5.6" class="pilcrow">¶</a> </dd> <dt id="section-2-5.7">Segments Left:</dt> <dd id="section-2-5.8">Defined in <span>[<a href="#RFC8200" class="xref">RFC8200</a>], <a href="https://www.rfc-editor.org/rfc/rfc8200#section-4.4" class="relref">Section 4.4</a></span>.<a href="#section-2-5.8" class="pilcrow">¶</a> </dd> <dt id="section-2-5.9">Last Entry:</dt> <dd id="section-2-5.10">contains the index (zero based), in the Segment List, of the last element of the Segment List.<a href="#section-2-5.10" class="pilcrow">¶</a> </dd> <dt id="section-2-5.11">Flags:</dt> <dd id="section-2-5.12">8 bits of flags. <a href="#SRHFLAGSREG" class="xref">Section 8.1</a> creates an IANA registry for new flags to be defined. The following flags are defined:<a href="#section-2-5.12" class="pilcrow">¶</a> </dd> </dl> <div class="artwork art-text alignLeft" id="section-2-6"> <pre> 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |U U U U U U U U| +-+-+-+-+-+-+-+-+ </pre><a href="#section-2-6" class="pilcrow">¶</a> </div> <dl class="dlParallel" id="section-2-7"> <dt id="section-2-7.1"></dt> <dd id="section-2-7.2">U: Unused and for future use. <span class="bcp14">MUST</span> be 0 on transmission and ignored on receipt.<a href="#section-2-7.2" class="pilcrow">¶</a> </dd> </dl> <dl class="dlParallel" id="section-2-8"> <dt id="section-2-8.1">Tag:</dt> <dd id="section-2-8.2">Tag a packet as part of a class or group of packets -- e.g., packets sharing the same set of properties. When Tag is not used at the source, it <span class="bcp14">MUST</span> be set to zero on transmission. When Tag is not used during SRH processing, it <span class="bcp14">SHOULD</span> be ignored. Tag is not used when processing the SID defined in <a href="#pktENDSID" class="xref">Section 4.3.1</a>. It may be used when processing other SIDs that are not defined in this document. The allocation and use of tag is outside the scope of this document.<a href="#section-2-8.2" class="pilcrow">¶</a> </dd> <dt id="section-2-8.3">Segment List[0..n]:</dt> <dd id="section-2-8.4">128-bit IPv6 addresses representing the nth segment in the Segment List. The Segment List is encoded starting from the last segment of the SR Policy. That is, the first element of the Segment List (Segment List[0]) contains the last segment of the SR Policy, the second element contains the penultimate segment of the SR Policy, and so on.<a href="#section-2-8.4" class="pilcrow">¶</a> </dd> <dt id="section-2-8.5">TLV:</dt> <dd id="section-2-8.6">Type Length Value (TLV) is described in <a href="#TLVS" class="xref">Section 2.1</a>.<a href="#section-2-8.6" class="pilcrow">¶</a> </dd> </dl> <p id="section-2-9">In the SRH, the Next Header, Hdr Ext Len, Routing Type, and Segments Left fields are defined in <span><a href="https://www.rfc-editor.org/rfc/rfc8200#section-4.4" class="relref">Section 4.4</a> of [<a href="#RFC8200" class="xref">RFC8200</a>]</span>. Based on the constraints in that section, Next Header, Header Ext Len, and Routing Type are not mutable while Segments Left is mutable.<a href="#section-2-9" class="pilcrow">¶</a></p> <p id="section-2-10">The mutability of the TLV value is defined by the most significant bit in the type, as specified in <a href="#TLVS" class="xref">Section 2.1</a>.<a href="#section-2-10" class="pilcrow">¶</a></p> <p id="section-2-11"><a href="#ENDSID" class="xref">Section 4.3</a> defines the mutability of the remaining fields in the SRH (Flags, Tag, Segment List) in the context of the SID defined in this document.<a href="#section-2-11" class="pilcrow">¶</a></p> <p id="section-2-12">New SIDs defined in the future <span class="bcp14">MUST</span> specify the mutability properties of the Flags, Tag, and Segment List and indicate how the Hashed Message Authentication Code (HMAC) TLV (<a href="#HMACTLV" class="xref">Section 2.1.2</a>) verification works. Note that, in effect, these fields are mutable.<a href="#section-2-12" class="pilcrow">¶</a></p> <p id="section-2-13">Consistent with the SR model, the source of the SRH always knows how to set the Segment List, Flags, Tag, and TLVs of the SRH for use within the SR domain. How it achieves this is outside the scope of this document but may be based on topology, available SIDs and their mutability properties, the SRH mutability requirements of the destination, or any other information.<a href="#section-2-13" class="pilcrow">¶</a></p> <div id="TLVS"> <section id="section-2.1"> <h3 id="name-srh-tlvs"> <a href="#section-2.1" class="section-number selfRef">2.1. </a><a href="#name-srh-tlvs" class="section-name selfRef">SRH TLVs</a> </h3> <p id="section-2.1-1">This section defines TLVs of the Segment Routing Header.<a href="#section-2.1-1" class="pilcrow">¶</a></p> <p id="section-2.1-2">A TLV provides metadata for segment processing. The only TLVs defined in this document are the HMAC (<a href="#HMACTLV" class="xref">Section 2.1.2</a>) and padding TLVs (<a href="#PADDINGTLV" class="xref">Section 2.1.1</a>). While processing the SID defined in <a href="#pktENDSID" class="xref">Section 4.3.1</a>, all TLVs are ignored unless local configuration indicates otherwise (<a href="#TLVPROCESS" class="xref">Section 4.3.1.1.1</a>). Thus, TLV and HMAC support is optional for any implementation; however, an implementation adding or parsing TLVs <span class="bcp14">MUST</span> support PAD TLVs. Other documents may define additional TLVs and processing rules for them.<a href="#section-2.1-2" class="pilcrow">¶</a></p> <p id="section-2.1-3">TLVs are present when the Hdr Ext Len is greater than (Last Entry+1)*2.<a href="#section-2.1-3" class="pilcrow">¶</a></p> <p id="section-2.1-4">While processing TLVs at a segment endpoint, TLVs <span class="bcp14">MUST</span> be fully contained within the SRH as determined by the Hdr Ext Len. Detection of TLVs exceeding the boundary of the SRH Hdr Ext Len results in an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Hdr Ext Len field of the SRH, and the packet being discarded.<a href="#section-2.1-4" class="pilcrow">¶</a></p> <p id="section-2.1-5">An implementation <span class="bcp14">MAY</span> limit the number and/or length of TLVs it processes based on local configuration. It <span class="bcp14">MAY</span> limit:<a href="#section-2.1-5" class="pilcrow">¶</a></p> <ul> <li id="section-2.1-6.1">the number of consecutive Pad1 (<a href="#PAD1" class="xref">Section 2.1.1.1</a>) options to 1. If padding of more than one byte is required, then PadN (<a href="#PADN" class="xref">Section 2.1.1.2</a>) should be used.<a href="#section-2.1-6.1" class="pilcrow">¶</a> </li> <li id="section-2.1-6.2">The length in PadN to 5.<a href="#section-2.1-6.2" class="pilcrow">¶</a> </li> <li id="section-2.1-6.3">The maximum number of non-Pad TLVs to be processed.<a href="#section-2.1-6.3" class="pilcrow">¶</a> </li> <li id="section-2.1-6.4">The maximum length of all TLVs to be processed.<a href="#section-2.1-6.4" class="pilcrow">¶</a> </li> </ul> <p id="section-2.1-7"> The implementation <span class="bcp14">MAY</span> stop processing additional TLVs in the SRH when these configured limits are exceeded.<a href="#section-2.1-7" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-2.1-8"> <pre> 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+----------------------- | Type | Length | Variable-length data +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+----------------------- </pre><a href="#section-2.1-8" class="pilcrow">¶</a> </div> <dl class="dlParallel" id="section-2.1-9"> <dt id="section-2.1-9.1">Type:</dt> <dd id="section-2.1-9.2">An 8-bit codepoint from the "Segment Routing Header TLVs" <span>[<a href="#IANA-SRHTLV" class="xref">IANA-SRHTLV</a>]</span>. Unrecognized Types <span class="bcp14">MUST</span> be ignored on receipt.<a href="#section-2.1-9.2" class="pilcrow">¶</a> </dd> <dt id="section-2.1-9.3">Length:</dt> <dd id="section-2.1-9.4">The length of the variable-length data field in bytes.<a href="#section-2.1-9.4" class="pilcrow">¶</a> </dd> <dt id="section-2.1-9.5">Variable-length data:</dt> <dd id="section-2.1-9.6">data that is specific to the Type.<a href="#section-2.1-9.6" class="pilcrow">¶</a> </dd> </dl> <p id="section-2.1-10">Type Length Value (TLV) entries contain <span class="bcp14">OPTIONAL</span> information that may be used by the node identified in the Destination Address (DA) of the packet.<a href="#section-2.1-10" class="pilcrow">¶</a></p> <p id="section-2.1-11">Each TLV has its own length, format, and semantic. The codepoint allocated (by IANA) to each TLV Type defines both the format and the semantic of the information carried in the TLV. Multiple TLVs may be encoded in the same SRH.<a href="#section-2.1-11" class="pilcrow">¶</a></p> <p id="section-2.1-12">The highest-order bit of the TLV type (bit 0) specifies whether or not the TLV data of that type can change en route to the packet's final destination:<a href="#section-2.1-12" class="pilcrow">¶</a></p> <ul class="ulEmpty"> <li class="ulEmpty" id="section-2.1-13.1">0: TLV data does not change en route<a href="#section-2.1-13.1" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-2.1-13.2">1: TLV data does change en route<a href="#section-2.1-13.2" class="pilcrow">¶</a> </li> </ul> <p id="section-2.1-14">All TLVs specify their alignment requirements using an xn+y format. The xn+y format is defined as per <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span>. The SR source nodes use the xn+y alignment requirements of TLVs and Padding TLVs when constructing an SRH.<a href="#section-2.1-14" class="pilcrow">¶</a></p> <p id="section-2.1-15">The Length field of the TLV is used to skip the TLV while inspecting the SRH in case the node doesn't support or recognize the Type. The Length defines the TLV length in octets, not including the Type and Length fields.<a href="#section-2.1-15" class="pilcrow">¶</a></p> <p id="section-2.1-16">The following TLVs are defined in this document:<a href="#section-2.1-16" class="pilcrow">¶</a></p> <ul class="ulEmpty"> <li class="ulEmpty" id="section-2.1-17.1">Padding TLVs<a href="#section-2.1-17.1" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-2.1-17.2">HMAC TLV<a href="#section-2.1-17.2" class="pilcrow">¶</a> </li> </ul> <p id="section-2.1-18">Additional TLVs may be defined in the future.<a href="#section-2.1-18" class="pilcrow">¶</a></p> <div id="PADDINGTLV"> <section id="section-2.1.1"> <h4 id="name-padding-tlvs"> <a href="#section-2.1.1" class="section-number selfRef">2.1.1. </a><a href="#name-padding-tlvs" class="section-name selfRef">Padding TLVs</a> </h4> <p id="section-2.1.1-1">There are two types of Padding TLVs, Pad1 and PadN, and the following applies to both:<a href="#section-2.1.1-1" class="pilcrow">¶</a></p> <ul class="ulEmpty"> <li class="ulEmpty" id="section-2.1.1-2.1">Padding TLVs are used for meeting the alignment requirement of the subsequent TLVs.<a href="#section-2.1.1-2.1" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-2.1.1-2.2">Padding TLVs are used to pad the SRH to a multiple of 8 octets.<a href="#section-2.1.1-2.2" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-2.1.1-2.3">Padding TLVs are ignored by a node processing the SRH TLV.<a href="#section-2.1.1-2.3" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-2.1.1-2.4">Multiple Padding TLVs <span class="bcp14">MAY</span> be used in one SRH.<a href="#section-2.1.1-2.4" class="pilcrow">¶</a> </li> </ul> <div id="PAD1"> <section id="section-2.1.1.1"> <h5 id="name-pad1"> <a href="#section-2.1.1.1" class="section-number selfRef">2.1.1.1. </a><a href="#name-pad1" class="section-name selfRef">Pad1</a> </h5> <p id="section-2.1.1.1-1">Alignment requirement: none<a href="#section-2.1.1.1-1" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-2.1.1.1-2"> <pre> 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ | Type | +-+-+-+-+-+-+-+-+</pre><a href="#section-2.1.1.1-2" class="pilcrow">¶</a> </div> <dl class="dlParallel" id="section-2.1.1.1-3"> <dt id="section-2.1.1.1-3.1">Type:</dt> <dd id="section-2.1.1.1-3.2">0<a href="#section-2.1.1.1-3.2" class="pilcrow">¶</a> </dd> </dl> <p id="section-2.1.1.1-4">A single Pad1 TLV <span class="bcp14">MUST</span> be used when a single byte of padding is required. A Pad1 TLV <span class="bcp14">MUST NOT</span> be used if more than one consecutive byte of padding is required.<a href="#section-2.1.1.1-4" class="pilcrow">¶</a></p> </section> </div> <div id="PADN"> <section id="section-2.1.1.2"> <h5 id="name-padn"> <a href="#section-2.1.1.2" class="section-number selfRef">2.1.1.2. </a><a href="#name-padn" class="section-name selfRef">PadN</a> </h5> <p id="section-2.1.1.2-1">Alignment requirement: none<a href="#section-2.1.1.2-1" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-2.1.1.2-2"> <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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Padding (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Padding (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre><a href="#section-2.1.1.2-2" class="pilcrow">¶</a> </div> <dl class="dlParallel" id="section-2.1.1.2-3"> <dt id="section-2.1.1.2-3.1">Type:</dt> <dd id="section-2.1.1.2-3.2">4<a href="#section-2.1.1.2-3.2" class="pilcrow">¶</a> </dd> <dt id="section-2.1.1.2-3.3">Length:</dt> <dd id="section-2.1.1.2-3.4">0 to 5. The length of the Padding field in bytes.<a href="#section-2.1.1.2-3.4" class="pilcrow">¶</a> </dd> <dt id="section-2.1.1.2-3.5">Padding:</dt> <dd id="section-2.1.1.2-3.6">Padding bits have no semantic. They <span class="bcp14">MUST</span> be set to 0 on transmission and ignored on receipt.<a href="#section-2.1.1.2-3.6" class="pilcrow">¶</a> </dd> </dl> <p id="section-2.1.1.2-4">The PadN TLV <span class="bcp14">MUST</span> be used when more than one byte of padding is required.<a href="#section-2.1.1.2-4" class="pilcrow">¶</a></p> </section> </div> </section> </div> <div id="HMACTLV"> <section id="section-2.1.2"> <h4 id="name-hmac-tlv"> <a href="#section-2.1.2" class="section-number selfRef">2.1.2. </a><a href="#name-hmac-tlv" class="section-name selfRef">HMAC TLV</a> </h4> <p id="section-2.1.2-1">Alignment requirement: 8n<a href="#section-2.1.2-1" class="pilcrow">¶</a></p> <p id="section-2.1.2-2">The keyed Hashed Message Authentication Code (HMAC) TLV is <span class="bcp14">OPTIONAL</span> and has the following format:<a href="#section-2.1.2-2" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-2.1.2-3"> <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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |D| RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | HMAC Key ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | // | HMAC (variable) // | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where:</pre><a href="#section-2.1.2-3" class="pilcrow">¶</a> </div> <dl class="dlParallel" id="section-2.1.2-4"> <dt id="section-2.1.2-4.1">Type:</dt> <dd id="section-2.1.2-4.2">5.<a href="#section-2.1.2-4.2" class="pilcrow">¶</a> </dd> <dt id="section-2.1.2-4.3">Length:</dt> <dd id="section-2.1.2-4.4">The length of the variable-length data in bytes.<a href="#section-2.1.2-4.4" class="pilcrow">¶</a> </dd> <dt id="section-2.1.2-4.5">D:</dt> <dd id="section-2.1.2-4.6">1 bit. 1 indicates that the Destination Address verification is disabled due to use of a reduced Segment List (see <a href="#REDUCED" class="xref">Section 4.1.1</a>).<a href="#section-2.1.2-4.6" class="pilcrow">¶</a> </dd> <dt id="section-2.1.2-4.7">RESERVED:</dt> <dd id="section-2.1.2-4.8">15 bits. <span class="bcp14">MUST</span> be 0 on transmission.<a href="#section-2.1.2-4.8" class="pilcrow">¶</a> </dd> <dt id="section-2.1.2-4.9">HMAC Key ID:</dt> <dd id="section-2.1.2-4.10">A 4-octet opaque number that uniquely identifies the pre-shared key and algorithm used to generate the HMAC.<a href="#section-2.1.2-4.10" class="pilcrow">¶</a> </dd> <dt id="section-2.1.2-4.11">HMAC:</dt> <dd id="section-2.1.2-4.12">Keyed HMAC, in multiples of 8 octets, at most 32 octets.<a href="#section-2.1.2-4.12" class="pilcrow">¶</a> </dd> </dl> <p id="section-2.1.2-5">The HMAC TLV is used to verify that the SRH applied to a packet was selected by an authorized party and to ensure that the segment list is not modified after generation. This also allows for verification that the current segment (by virtue of being in the authorized Segment List) is authorized for use. The SR domain ensures that the source node is permitted to use the source address in the packet via ingress filtering mechanisms as defined in BCP 84 <span>[<a href="#RFC3704" class="xref">RFC3704</a>]</span> or other strategies as appropriate.<a href="#section-2.1.2-5" class="pilcrow">¶</a></p> <section id="section-2.1.2.1"> <h5 id="name-hmac-generation-and-verific"> <a href="#section-2.1.2.1" class="section-number selfRef">2.1.2.1. </a><a href="#name-hmac-generation-and-verific" class="section-name selfRef">HMAC Generation and Verification</a> </h5> <p id="section-2.1.2.1-1">Local configuration determines when to check for an HMAC. This local configuration is outside the scope of this document. It may be based on the active segment at an SR Segment endpoint node, the result of an Access Control List (ACL) that considers incoming interface, HMAC Key ID, or other packet fields.<a href="#section-2.1.2.1-1" class="pilcrow">¶</a></p> <p id="section-2.1.2.1-2">An implementation that supports the generation and verification of the HMAC supports the following default behavior, as defined in the remainder of this section.<a href="#section-2.1.2.1-2" class="pilcrow">¶</a></p> <p id="section-2.1.2.1-3">The HMAC verification begins by checking that the current segment is equal to the destination address of the IPv6 header. The check is successful when either:<a href="#section-2.1.2.1-3" class="pilcrow">¶</a></p> <ul> <li id="section-2.1.2.1-4.1">HMAC D bit is 1 and Segments Left is greater than Last Entry, or<a href="#section-2.1.2.1-4.1" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-4.2">HMAC Segments Left is less than or equal to Last Entry, and the destination address is equal to Segment List[Segments Left].<a href="#section-2.1.2.1-4.2" class="pilcrow">¶</a> </li> </ul> <p id="section-2.1.2.1-5">The HMAC field is the output of the HMAC computation as defined in <span>[<a href="#RFC2104" class="xref">RFC2104</a>]</span>, using:<a href="#section-2.1.2.1-5" class="pilcrow">¶</a></p> <ul> <li id="section-2.1.2.1-6.1">key: The pre-shared key identified by HMAC Key ID<a href="#section-2.1.2.1-6.1" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.2">HMAC algorithm: Identified by the HMAC Key ID<a href="#section-2.1.2.1-6.2" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3"> <p id="section-2.1.2.1-6.3.1">Text: A concatenation of the following fields from the IPv6 header and the SRH, as it would be received at the node verifying the HMAC:<a href="#section-2.1.2.1-6.3.1" class="pilcrow">¶</a></p> <ul> <li id="section-2.1.2.1-6.3.2.1">IPv6 header: Source address (16 octets)<a href="#section-2.1.2.1-6.3.2.1" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3.2.2">SRH: Last Entry (1 octet)<a href="#section-2.1.2.1-6.3.2.2" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3.2.3">SRH: Flags (1 octet)<a href="#section-2.1.2.1-6.3.2.3" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3.2.4">SRH: HMAC 16 bits following Length<a href="#section-2.1.2.1-6.3.2.4" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3.2.5">SRH: HMAC Key ID (4 octets)<a href="#section-2.1.2.1-6.3.2.5" class="pilcrow">¶</a> </li> <li id="section-2.1.2.1-6.3.2.6">SRH: All addresses in the Segment List (variable octets)<a href="#section-2.1.2.1-6.3.2.6" class="pilcrow">¶</a> </li> </ul> </li> </ul> <p id="section-2.1.2.1-7">The HMAC digest is truncated to 32 octets and placed in the HMAC field of the HMAC TLV.<a href="#section-2.1.2.1-7" class="pilcrow">¶</a></p> <p id="section-2.1.2.1-8">For HMAC algorithms producing digests less than 32 octets long, the digest is placed in the lowest-order octets of the HMAC field. Subsequent octets <span class="bcp14">MUST</span> be set to zero such that the HMAC length is a multiple of 8 octets.<a href="#section-2.1.2.1-8" class="pilcrow">¶</a></p> <p id="section-2.1.2.1-9">If HMAC verification is successful, processing proceeds as normal.<a href="#section-2.1.2.1-9" class="pilcrow">¶</a></p> <p id="section-2.1.2.1-10">If HMAC verification fails, an ICMP error message (parameter problem, error code 0, pointing to the HMAC TLV) <span class="bcp14">SHOULD</span> be generated (but rate limited) and logged, and the packet <span class="bcp14">SHOULD</span> be discarded.<a href="#section-2.1.2.1-10" class="pilcrow">¶</a></p> </section> <section id="section-2.1.2.2"> <h5 id="name-hmac-pre-shared-key-algorit"> <a href="#section-2.1.2.2" class="section-number selfRef">2.1.2.2. </a><a href="#name-hmac-pre-shared-key-algorit" class="section-name selfRef">HMAC Pre-shared Key Algorithm</a> </h5> <p id="section-2.1.2.2-1">The HMAC Key ID field allows for the simultaneous existence of several hash algorithms (SHA-256, SHA3-256 ... or future ones) as well as pre-shared keys.<a href="#section-2.1.2.2-1" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-2">The HMAC Key ID field is opaque -- i.e., it has neither syntax nor semantic except as an identifier of the right combination of pre-shared key and hash algorithm.<a href="#section-2.1.2.2-2" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-3">At the HMAC TLV generating and verification nodes, the Key ID uniquely identifies the pre-shared key and HMAC algorithm.<a href="#section-2.1.2.2-3" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-4">At the HMAC TLV generating node, the Text for the HMAC computation is set to the IPv6 header fields and SRH fields as they would appear at the verification node(s), not necessarily the same as the source node sending a packet with the HMAC TLV.<a href="#section-2.1.2.2-4" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-5">Pre-Shared key rollover is supported by having two key IDs in use while the HMAC TLV generating node and verifying node converge to a new key.<a href="#section-2.1.2.2-5" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-6">The HMAC TLV generating node may need to revoke an SRH for which it previously generated an HMAC. Revocation is achieved by allocating a new key and key ID, then rolling over the key ID associated with the SRH to be revoked. The HMAC TLV verifying node drops packets with the revoked SRH.<a href="#section-2.1.2.2-6" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-7">An implementation supporting HMAC can support multiple hash functions. An implementation supporting HMAC <span class="bcp14">MUST</span> implement SHA-2 <span>[<a href="#FIPS180-4" class="xref">FIPS180-4</a>]</span> in its SHA-256 variant.<a href="#section-2.1.2.2-7" class="pilcrow">¶</a></p> <p id="section-2.1.2.2-8">The selection of pre-shared key and algorithm and their distribution is outside the scope of this document. Some options may include:<a href="#section-2.1.2.2-8" class="pilcrow">¶</a></p> <ul> <li id="section-2.1.2.2-9.1">setting these items in the configuration of the HMAC generating or verifying nodes, either by static configuration or any SDN-oriented approach<a href="#section-2.1.2.2-9.1" class="pilcrow">¶</a> </li> <li id="section-2.1.2.2-9.2">dynamically using a trusted key distribution protocol such as <span>[<a href="#RFC6407" class="xref">RFC6407</a>]</span><a href="#section-2.1.2.2-9.2" class="pilcrow">¶</a> </li> </ul> <p id="section-2.1.2.2-10">While key management is outside the scope of this document, the recommendations of BCP 107 <span>[<a href="#RFC4107" class="xref">RFC4107</a>]</span> should be considered when choosing the key management system.<a href="#section-2.1.2.2-10" class="pilcrow">¶</a></p> </section> </section> </div> </section> </div> </section> </div> <div id="SRNODES"> <section id="section-3"> <h2 id="name-sr-nodes"> <a href="#section-3" class="section-number selfRef">3. </a><a href="#name-sr-nodes" class="section-name selfRef">SR Nodes</a> </h2> <p id="section-3-1">There are different types of nodes that may be involved in segment routing networks: SR source nodes that originate packets with a segment in the destination address of the IPv6 header, transit nodes that forward packets destined to a remote segment, and SR segment endpoint nodes that process a local segment in the destination address of an IPv6 header.<a href="#section-3-1" class="pilcrow">¶</a></p> <div id="SOURCE"> <section id="section-3.1"> <h3 id="name-sr-source-node"> <a href="#section-3.1" class="section-number selfRef">3.1. </a><a href="#name-sr-source-node" class="section-name selfRef">SR Source Node</a> </h3> <p id="section-3.1-1">A SR source node is any node that originates an IPv6 packet with a segment (i.e., SRv6 SID) in the destination address of the IPv6 header. The packet leaving the SR source node may or may not contain an SRH. This includes either:<a href="#section-3.1-1" class="pilcrow">¶</a></p> <ul> <li id="section-3.1-2.1">A host originating an IPv6 packet, or<a href="#section-3.1-2.1" class="pilcrow">¶</a> </li> <li id="section-3.1-2.2">An SR domain ingress router encapsulating a received packet in an outer IPv6 header, followed by an optional SRH.<a href="#section-3.1-2.2" class="pilcrow">¶</a> </li> </ul> <p id="section-3.1-3">It is out of the scope of this document to describe the mechanism through which a segment in the destination address of the IPv6 header and the Segment List in the SRH are derived.<a href="#section-3.1-3" class="pilcrow">¶</a></p> </section> </div> <div id="TRANSIT"> <section id="section-3.2"> <h3 id="name-transit-node"> <a href="#section-3.2" class="section-number selfRef">3.2. </a><a href="#name-transit-node" class="section-name selfRef">Transit Node</a> </h3> <p id="section-3.2-1">A transit node is any node forwarding an IPv6 packet where the destination address of that packet is not locally configured as a segment or a local interface. A transit node is not required to be capable of processing a segment or SRH.<a href="#section-3.2-1" class="pilcrow">¶</a></p> </section> </div> <section id="section-3.3"> <h3 id="name-sr-segment-endpoint-node"> <a href="#section-3.3" class="section-number selfRef">3.3. </a><a href="#name-sr-segment-endpoint-node" class="section-name selfRef">SR Segment Endpoint Node</a> </h3> <p id="section-3.3-1">An SR segment endpoint node is any node receiving an IPv6 packet where the destination address of that packet is locally configured as a segment or local interface.<a href="#section-3.3-1" class="pilcrow">¶</a></p> </section> </section> </div> <div id="PacketProcessing"> <section id="section-4"> <h2 id="name-packet-processing"> <a href="#section-4" class="section-number selfRef">4. </a><a href="#name-packet-processing" class="section-name selfRef">Packet Processing</a> </h2> <p id="section-4-1">This section describes SRv6 packet processing at the SR source, Transit, and SR segment endpoint nodes.<a href="#section-4-1" class="pilcrow">¶</a></p> <div id="pktSourceNode"> <section id="section-4.1"> <h3 id="name-sr-source-node-2"> <a href="#section-4.1" class="section-number selfRef">4.1. </a><a href="#name-sr-source-node-2" class="section-name selfRef">SR Source Node</a> </h3> <p id="section-4.1-1">A source node steers a packet into an SR Policy. If the SR Policy results in a Segment List containing a single segment, and there is no need to add information to the SRH flag or add TLV; the DA is set to the single Segment List entry, and the SRH <span class="bcp14">MAY</span> be omitted.<a href="#section-4.1-1" class="pilcrow">¶</a></p> <p id="section-4.1-2">When needed, the SRH is created as follows:<a href="#section-4.1-2" class="pilcrow">¶</a></p> <dl class="dlParallel" id="section-4.1-3"> <dt id="section-4.1-3.1"></dt> <dd id="section-4.1-3.2">The Next Header and Hdr Ext Len fields are set as specified in <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span>.<a href="#section-4.1-3.2" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.3"></dt> <dd id="section-4.1-3.4">The Routing Type field is set to 4.<a href="#section-4.1-3.4" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.5"></dt> <dd id="section-4.1-3.6">The DA of the packet is set with the value of the first segment.<a href="#section-4.1-3.6" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.7"></dt> <dd id="section-4.1-3.8">The first element of the SRH Segment List is the ultimate segment. The second element is the penultimate segment, and so on.<a href="#section-4.1-3.8" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.9"></dt> <dd id="section-4.1-3.10">The Segments Left field is set to n-1, where n is the number of elements in the SR Policy.<a href="#section-4.1-3.10" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.11"></dt> <dd id="section-4.1-3.12">The Last Entry field is set to n-1, where n is the number of elements in the SR Policy.<a href="#section-4.1-3.12" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.13"></dt> <dd id="section-4.1-3.14">TLVs (including HMAC) may be set according to their specification.<a href="#section-4.1-3.14" class="pilcrow">¶</a> </dd> <dt id="section-4.1-3.15"></dt> <dd id="section-4.1-3.16">The packet is forwarded toward the packet's Destination Address (the first segment).<a href="#section-4.1-3.16" class="pilcrow">¶</a> </dd> </dl> <div id="REDUCED"> <section id="section-4.1.1"> <h4 id="name-reduced-srh"> <a href="#section-4.1.1" class="section-number selfRef">4.1.1. </a><a href="#name-reduced-srh" class="section-name selfRef">Reduced SRH</a> </h4> <p id="section-4.1.1-1">When a source does not require the entire SID list to be preserved in the SRH, a reduced SRH may be used.<a href="#section-4.1.1-1" class="pilcrow">¶</a></p> <p id="section-4.1.1-2">A reduced SRH does not contain the first segment of the related SR Policy (the first segment is the one already in the DA of the IPv6 header), and the Last Entry field is set to n-2, where n is the number of elements in the SR Policy.<a href="#section-4.1.1-2" class="pilcrow">¶</a></p> </section> </div> </section> </div> <section id="section-4.2"> <h3 id="name-transit-node-2"> <a href="#section-4.2" class="section-number selfRef">4.2. </a><a href="#name-transit-node-2" class="section-name selfRef">Transit Node</a> </h3> <p id="section-4.2-1">As specified in <span>[<a href="#RFC8200" class="xref">RFC8200</a>]</span>, the only node allowed to inspect the Routing Extension Header (and therefore the SRH) is the node corresponding to the DA of the packet. Any other transit node <span class="bcp14">MUST NOT</span> inspect the underneath routing header and <span class="bcp14">MUST</span> forward the packet toward the DA according to its IPv6 routing table.<a href="#section-4.2-1" class="pilcrow">¶</a></p> <p id="section-4.2-2">When a SID is in the destination address of an IPv6 header of a packet, it's routed through an IPv6 network as an IPv6 address. SIDs, or the prefix(es) covering SIDs, and their reachability may be distributed by means outside the scope of this document. For example, <span>[<a href="#RFC5308" class="xref">RFC5308</a>]</span> or <span>[<a href="#RFC5340" class="xref">RFC5340</a>]</span> may be used to advertise a prefix covering the SIDs on a node.<a href="#section-4.2-2" class="pilcrow">¶</a></p> </section> <div id="ENDSID"> <section id="section-4.3"> <h3 id="name-sr-segment-endpoint-node-2"> <a href="#section-4.3" class="section-number selfRef">4.3. </a><a href="#name-sr-segment-endpoint-node-2" class="section-name selfRef">SR Segment Endpoint Node</a> </h3> <p id="section-4.3-1">Without constraining the details of an implementation, the SR segment endpoint node creates Forwarding Information Base (FIB) entries for its local SIDs.<a href="#section-4.3-1" class="pilcrow">¶</a></p> <p id="section-4.3-2">When an SRv6-capable node receives an IPv6 packet, it performs a longest-prefix-match lookup on the packet's destination address. This lookup can return any of the following:<a href="#section-4.3-2" class="pilcrow">¶</a></p> <ul> <li id="section-4.3-3.1">A FIB entry that represents a locally instantiated SRv6 SID<a href="#section-4.3-3.1" class="pilcrow">¶</a> </li> <li id="section-4.3-3.2">A FIB entry that represents a local interface, not locally instantiated as an SRv6 SID<a href="#section-4.3-3.2" class="pilcrow">¶</a> </li> <li id="section-4.3-3.3">A FIB entry that represents a nonlocal route<a href="#section-4.3-3.3" class="pilcrow">¶</a> </li> <li id="section-4.3-3.4">No Match<a href="#section-4.3-3.4" class="pilcrow">¶</a> </li> </ul> <div id="pktENDSID"> <section id="section-4.3.1"> <h4 id="name-fib-entry-is-a-locally-inst"> <a href="#section-4.3.1" class="section-number selfRef">4.3.1. </a><a href="#name-fib-entry-is-a-locally-inst" class="section-name selfRef">FIB Entry Is a Locally Instantiated SRv6 SID</a> </h4> <p id="section-4.3.1-1">This document and section define a single SRv6 SID. Future documents may define additional SRv6 SIDs. In such a case, the entire content of this section will be defined in that document.<a href="#section-4.3.1-1" class="pilcrow">¶</a></p> <p id="section-4.3.1-2">If the FIB entry represents a locally instantiated SRv6 SID, process the next header chain of the IPv6 header as defined in <span><a href="https://www.rfc-editor.org/rfc/rfc8200#section-4" class="relref">Section 4</a> of [<a href="#RFC8200" class="xref">RFC8200</a>]</span>. <a href="#SRHPROC" class="xref">Section 4.3.1.1</a> describes how to process an SRH; <a href="#UPPERHEADER" class="xref">Section 4.3.1.2</a> describes how to process an upper-layer header or the absence of a Next Header.<a href="#section-4.3.1-2" class="pilcrow">¶</a></p> <p id="section-4.3.1-3">Processing this SID modifies the Segments Left and, if configured to process TLVs, it may modify the "variable-length data" of TLV types that change en route. Therefore, Segments Left is mutable, and TLVs that change en route are mutable. The remainder of the SRH (Flags, Tag, Segment List, and TLVs that do not change en route) are immutable while processing this SID.<a href="#section-4.3.1-3" class="pilcrow">¶</a></p> <div id="SRHPROC"> <section id="section-4.3.1.1"> <h5 id="name-srh-processing"> <a href="#section-4.3.1.1" class="section-number selfRef">4.3.1.1. </a><a href="#name-srh-processing" class="section-name selfRef">SRH Processing</a> </h5> <div class="artwork art-text alignLeft" id="section-4.3.1.1-1"> <pre> S01. When an SRH is processed { S02. If Segments Left is equal to zero { S03. Proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. Else { S06. If local configuration requires TLV processing { S07. Perform TLV processing (see TLV Processing) S08. } S09. max_last_entry = ( Hdr Ext Len / 2 ) - 1 S10. If ((Last Entry > max_last_entry) or S11. (Segments Left is greater than (Last Entry+1)) { S12. Send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Segments Left field, and discard the packet. S13. } S14. Else { S15. Decrement Segments Left by 1. S16. Copy Segment List[Segments Left] from the SRH to the destination address of the IPv6 header. S17. If the IPv6 Hop Limit is less than or equal to 1 { S18. Send an ICMP Time Exceeded -- Hop Limit Exceeded in Transit message to the Source Address and discard the packet. S19. } S20. Else { S21. Decrement the Hop Limit by 1 S22. Resubmit the packet to the IPv6 module for transmission to the new destination. S23. } S24. } S25. } S26. } </pre><a href="#section-4.3.1.1-1" class="pilcrow">¶</a> </div> <div id="TLVPROCESS"> <section id="section-4.3.1.1.1"> <h6 id="name-tlv-processing"> <a href="#section-4.3.1.1.1" class="section-number selfRef">4.3.1.1.1. </a><a href="#name-tlv-processing" class="section-name selfRef">TLV Processing</a> </h6> <p id="section-4.3.1.1.1-1">Local configuration determines how TLVs are to be processed when the Active Segment is a local SID defined in this document. The definition of local configuration is outside the scope of this document.<a href="#section-4.3.1.1.1-1" class="pilcrow">¶</a></p> <p id="section-4.3.1.1.1-2">For illustration purposes only, two example local configurations that may be associated with a SID are provided below.<a href="#section-4.3.1.1.1-2" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-4.3.1.1.1-3"> <pre> Example 1: For any packet received from interface I2 Skip TLV processing Example 2: For any packet received from interface I1 If first TLV is HMAC { Process the HMAC TLV } Else { Discard the packet }</pre><a href="#section-4.3.1.1.1-3" class="pilcrow">¶</a> </div> </section> </div> </section> </div> <div id="UPPERHEADER"> <section id="section-4.3.1.2"> <h5 id="name-upper-layer-header-or-no-ne"> <a href="#section-4.3.1.2" class="section-number selfRef">4.3.1.2. </a><a href="#name-upper-layer-header-or-no-ne" class="section-name selfRef">Upper-Layer Header or No Next Header</a> </h5> <p id="section-4.3.1.2-1">When processing the upper-layer header of a packet matching a FIB entry locally instantiated as an SRv6 SID defined in this document:<a href="#section-4.3.1.2-1" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-4.3.1.2-2"> <pre> IF (Upper-layer Header is IPv4 or IPv6) and local configuration permits { Perform IPv6 decapsulation Resubmit the decapsulated packet to the IPv4 or IPv6 module } ELSE { Send an ICMP parameter problem message to the Source Address and discard the packet. Error code (4) "SR Upper-layer Header Error", pointer set to the offset of the upper-layer header. } </pre><a href="#section-4.3.1.2-2" class="pilcrow">¶</a> </div> <p id="section-4.3.1.2-3">A unique error code allows an SR source node to recognize an error in SID processing at an endpoint.<a href="#section-4.3.1.2-3" class="pilcrow">¶</a></p> </section> </div> </section> </div> <section id="section-4.3.2"> <h4 id="name-fib-entry-is-a-local-interf"> <a href="#section-4.3.2" class="section-number selfRef">4.3.2. </a><a href="#name-fib-entry-is-a-local-interf" class="section-name selfRef">FIB Entry Is a Local Interface</a> </h4> <p id="section-4.3.2-1">If the FIB entry represents a local interface and is not locally instantiated as an SRv6 SID, the SRH is processed as follows:<a href="#section-4.3.2-1" class="pilcrow">¶</a></p> <ul class="ulEmpty"> <li class="ulEmpty" id="section-4.3.2-2.1">If Segments Left is zero, the node must ignore the routing header and proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header.<a href="#section-4.3.2-2.1" class="pilcrow">¶</a> </li> <li class="ulEmpty" id="section-4.3.2-2.2">If Segments Left is non-zero, the node must discard the packet and send an ICMP Parameter Problem, Code 0, message to the packet's Source Address, pointing to the unrecognized Routing Type.<a href="#section-4.3.2-2.2" class="pilcrow">¶</a> </li> </ul> </section> <section id="section-4.3.3"> <h4 id="name-fib-entry-is-a-nonlocal-rou"> <a href="#section-4.3.3" class="section-number selfRef">4.3.3. </a><a href="#name-fib-entry-is-a-nonlocal-rou" class="section-name selfRef">FIB Entry Is a Nonlocal Route</a> </h4> <p id="section-4.3.3-1">Processing is not changed by this document.<a href="#section-4.3.3-1" class="pilcrow">¶</a></p> </section> <section id="section-4.3.4"> <h4 id="name-fib-entry-is-a-no-match"> <a href="#section-4.3.4" class="section-number selfRef">4.3.4. </a><a href="#name-fib-entry-is-a-no-match" class="section-name selfRef">FIB Entry Is a No Match</a> </h4> <p id="section-4.3.4-1">Processing is not changed by this document.<a href="#section-4.3.4-1" class="pilcrow">¶</a></p> </section> </section> </div> </section> </div> <div id="DEP"> <section id="section-5"> <h2 id="name-intra-sr-domain-deployment-"> <a href="#section-5" class="section-number selfRef">5. </a><a href="#name-intra-sr-domain-deployment-" class="section-name selfRef">Intra-SR-Domain Deployment Model</a> </h2> <p id="section-5-1">The use of the SIDs exclusively within the SR domain and solely for packets of the SR domain is an important deployment model.<a href="#section-5-1" class="pilcrow">¶</a></p> <p id="section-5-2">This enables the SR domain to act as a single routing system.<a href="#section-5-2" class="pilcrow">¶</a></p> <p id="section-5-3">This section covers:<a href="#section-5-3" class="pilcrow">¶</a></p> <ul> <li id="section-5-4.1">securing the SR domain from external attempts to use its SIDs<a href="#section-5-4.1" class="pilcrow">¶</a> </li> <li id="section-5-4.2">using the SR domain as a single system with delegation between components<a href="#section-5-4.2" class="pilcrow">¶</a> </li> <li id="section-5-4.3">handling packets of the SR domain<a href="#section-5-4.3" class="pilcrow">¶</a> </li> </ul> <div id="SECSRDOMAIN"> <section id="section-5.1"> <h3 id="name-securing-the-sr-domain"> <a href="#section-5.1" class="section-number selfRef">5.1. </a><a href="#name-securing-the-sr-domain" class="section-name selfRef">Securing the SR Domain</a> </h3> <p id="section-5.1-1">Nodes outside the SR domain are not trusted: they cannot directly use the SIDs of the domain. This is enforced by two levels of access control lists:<a href="#section-5.1-1" class="pilcrow">¶</a></p> <ol start="1" type="1" class="normal type-1" id="section-5.1-2"> <li id="section-5.1-2.1"> <p id="section-5.1-2.1.1">Any packet entering the SR domain and destined to a SID within the SR domain is dropped. This may be realized with the following logic. Other methods with equivalent outcome are considered compliant:<a href="#section-5.1-2.1.1" class="pilcrow">¶</a></p> <ul> <li id="section-5.1-2.1.2.1">Allocate all the SIDs from a block S/s<a href="#section-5.1-2.1.2.1" class="pilcrow">¶</a> </li> <li id="section-5.1-2.1.2.2">Configure each external interface of each edge node of the domain with an inbound infrastructure access list (IACL) that drops any incoming packet with a destination address in S/s<a href="#section-5.1-2.1.2.2" class="pilcrow">¶</a> </li> <li id="section-5.1-2.1.2.3">Failure to implement this method of ingress filtering exposes the SR domain to source-routing attacks, as described and referenced in <span>[<a href="#RFC5095" class="xref">RFC5095</a>]</span><a href="#section-5.1-2.1.2.3" class="pilcrow">¶</a> </li> </ul> </li> <li id="section-5.1-2.2"> <p id="section-5.1-2.2.1">The distributed protection in #1 is complemented with per-node protection, dropping packets to SIDs from source addresses outside the SR domain. This may be realized with the following logic. Other methods with equivalent outcome are considered compliant:<a href="#section-5.1-2.2.1" class="pilcrow">¶</a></p> <ul> <li id="section-5.1-2.2.2.1">Assign all interface addresses from prefix A/a<a href="#section-5.1-2.2.2.1" class="pilcrow">¶</a> </li> <li id="section-5.1-2.2.2.2">At node k, all SIDs local to k are assigned from prefix Sk/sk<a href="#section-5.1-2.2.2.2" class="pilcrow">¶</a> </li> <li id="section-5.1-2.2.2.3">Configure each internal interface of each SR node k in the SR domain with an inbound IACL that drops any incoming packet with a destination address in Sk/sk if the source address is not in A/a.<a href="#section-5.1-2.2.2.3" class="pilcrow">¶</a> </li> </ul> </li> </ol> </section> </div> <div id="SINGLESYS"> <section id="section-5.2"> <h3 id="name-sr-domain-as-a-single-syste"> <a href="#section-5.2" class="section-number selfRef">5.2. </a><a href="#name-sr-domain-as-a-single-syste" class="section-name selfRef">SR Domain as a Single System with Delegation among Components</a> </h3> <p id="section-5.2-1">All intra-SR-domain packets are of the SR domain. The IPv6 header is originated by a node of the SR domain and is destined to a node of the SR domain.<a href="#section-5.2-1" class="pilcrow">¶</a></p> <p id="section-5.2-2">All interdomain packets are encapsulated for the part of the packet journey that is within the SR domain. The outer IPv6 header is originated by a node of the SR domain and is destined to a node of the SR domain.<a href="#section-5.2-2" class="pilcrow">¶</a></p> <p id="section-5.2-3">As a consequence, any packet within the SR domain is of the SR domain.<a href="#section-5.2-3" class="pilcrow">¶</a></p> <p id="section-5.2-4">The SR domain is a system in which the operator may want to distribute or delegate different operations of the outermost header to different nodes within the system.<a href="#section-5.2-4" class="pilcrow">¶</a></p> <p id="section-5.2-5">An operator of an SR domain may choose to delegate SRH addition to a host node within the SR domain and delegate validation of the contents of any SRH to a more trusted router or switch attached to the host. Consider a top-of-rack switch T connected to host H via interface I. H receives an SRH (SRH1) with a computed HMAC via some SDN method outside the scope of this document. H classifies traffic it sources and adds SRH1 to traffic requiring a specific Service Level Agreement (SLA). T is configured with an IACL on I requiring verification of the SRH for any packet destined to the SID block of the SR domain (S/s). T checks and verifies that SRH1 is valid and contains an HMAC TLV; T then verifies the HMAC.<a href="#section-5.2-5" class="pilcrow">¶</a></p> <p id="section-5.2-6">An operator of the SR domain may choose to have all segments in the SR domain verify the HMAC. This mechanism would verify that the SRH Segment List is not modified while traversing the SR domain.<a href="#section-5.2-6" class="pilcrow">¶</a></p> </section> </div> <div id="MTU"> <section id="section-5.3"> <h3 id="name-mtu-considerations"> <a href="#section-5.3" class="section-number selfRef">5.3. </a><a href="#name-mtu-considerations" class="section-name selfRef">MTU Considerations</a> </h3> <p id="section-5.3-1">An SR domain ingress edge node encapsulates packets traversing the SR domain and needs to consider the MTU of the SR domain. Within the SR domain, well-known mitigation techniques are <span class="bcp14">RECOMMENDED</span>, such as deploying a greater MTU value within the SR domain than at the ingress edges.<a href="#section-5.3-1" class="pilcrow">¶</a></p> <p id="section-5.3-2">Encapsulation with an outer IPv6 header and SRH shares the same MTU and fragmentation considerations as IPv6 tunnels described in <span>[<a href="#RFC2473" class="xref">RFC2473</a>]</span>. Further investigation on the limitation of various tunneling methods (including IPv6 tunnels) is discussed in <span>[<a href="#I-D.ietf-intarea-tunnels" class="xref">INTAREA-TUNNELS</a>]</span> and <span class="bcp14">SHOULD</span> be considered by operators when considering MTU within the SR domain.<a href="#section-5.3-2" class="pilcrow">¶</a></p> </section> </div> <div id="ICMP"> <section id="section-5.4"> <h3 id="name-icmp-error-processing"> <a href="#section-5.4" class="section-number selfRef">5.4. </a><a href="#name-icmp-error-processing" class="section-name selfRef">ICMP Error Processing</a> </h3> <p id="section-5.4-1">ICMP error packets generated within the SR domain are sent to source nodes within the SR domain. The invoking packet in the ICMP error message may contain an SRH. Since the destination address of a packet with an SRH changes as each segment is processed, it may not be the destination used by the socket or application that generated the invoking packet.<a href="#section-5.4-1" class="pilcrow">¶</a></p> <p id="section-5.4-2">For the source of an invoking packet to process the ICMP error message, the ultimate destination address of the IPv6 header may be required. The following logic is used to determine the destination address for use by protocol-error handlers.<a href="#section-5.4-2" class="pilcrow">¶</a></p> <ul> <li id="section-5.4-3.1"> <p id="section-5.4-3.1.1">Walk all extension headers of the invoking IPv6 packet to the routing extension header preceding the upper-layer header.<a href="#section-5.4-3.1.1" class="pilcrow">¶</a></p> <ul> <li id="section-5.4-3.1.2.1"> <p id="section-5.4-3.1.2.1.1">If routing header is type 4 Segment Routing Header (SRH)<a href="#section-5.4-3.1.2.1.1" class="pilcrow">¶</a></p> <ul> <li id="section-5.4-3.1.2.1.2.1">The SID at Segment List[0] may be used as the destination address of the invoking packet.<a href="#section-5.4-3.1.2.1.2.1" class="pilcrow">¶</a> </li> </ul> </li> </ul> </li> </ul> <p id="section-5.4-4">ICMP errors are then processed by upper-layer transports as defined in <span>[<a href="#RFC4443" class="xref">RFC4443</a>]</span>.<a href="#section-5.4-4" class="pilcrow">¶</a></p> <p id="section-5.4-5">For IP packets encapsulated in an outer IPv6 header, ICMP error handling is as defined in <span>[<a href="#RFC2473" class="xref">RFC2473</a>]</span>.<a href="#section-5.4-5" class="pilcrow">¶</a></p> </section> </div> <div id="LBECMP"> <section id="section-5.5"> <h3 id="name-load-balancing-and-ecmp"> <a href="#section-5.5" class="section-number selfRef">5.5. </a><a href="#name-load-balancing-and-ecmp" class="section-name selfRef">Load Balancing and ECMP</a> </h3> <p id="section-5.5-1">For any interdomain packet, the SR source node <span class="bcp14">MUST</span> impose a flow label computed based on the inner packet. The computation of the flow label is as recommended in <span>[<a href="#RFC6438" class="xref">RFC6438</a>]</span> for the sending Tunnel End Point.<a href="#section-5.5-1" class="pilcrow">¶</a></p> <p id="section-5.5-2">For any intradomain packet, the SR source node <span class="bcp14">SHOULD</span> impose a flow label computed as described in <span>[<a href="#RFC6437" class="xref">RFC6437</a>]</span> to assist ECMP load balancing at transit nodes incapable of computing a 5-tuple beyond the SRH.<a href="#section-5.5-2" class="pilcrow">¶</a></p> <p id="section-5.5-3">At any transit node within an SR domain, the flow label <span class="bcp14">MUST</span> be used as defined in <span>[<a href="#RFC6438" class="xref">RFC6438</a>]</span> to calculate the ECMP hash toward the destination address. If a flow label is not used, the transit node would likely hash all packets between a pair of SR Edge nodes to the same link.<a href="#section-5.5-3" class="pilcrow">¶</a></p> <p id="section-5.5-4">At an SR segment endpoint node, the flow label <span class="bcp14">MUST</span> be used as defined in <span>[<a href="#RFC6438" class="xref">RFC6438</a>]</span> to calculate any ECMP hash used to forward the processed packet to the next segment.<a href="#section-5.5-4" class="pilcrow">¶</a></p> </section> </div> <div id="other"> <section id="section-5.6"> <h3 id="name-other-deployments"> <a href="#section-5.6" class="section-number selfRef">5.6. </a><a href="#name-other-deployments" class="section-name selfRef">Other Deployments</a> </h3> <p id="section-5.6-1">Other deployment models and their implications on security, MTU, HMAC, ICMP error processing, and interaction with other extension headers are outside the scope of this document.<a href="#section-5.6-1" class="pilcrow">¶</a></p> </section> </div> </section> </div> <div id="ILL"> <section id="section-6"> <h2 id="name-illustrations"> <a href="#section-6" class="section-number selfRef">6. </a><a href="#name-illustrations" class="section-name selfRef">Illustrations</a> </h2> <p id="section-6-1">This section provides illustrations of SRv6 packet processing at SR source, transit, and SR segment endpoint nodes.<a href="#section-6-1" class="pilcrow">¶</a></p> <section id="section-6.1"> <h3 id="name-abstract-representation-of-"> <a href="#section-6.1" class="section-number selfRef">6.1. </a><a href="#name-abstract-representation-of-" class="section-name selfRef">Abstract Representation of an SRH</a> </h3> <p id="section-6.1-1">For a node k, its IPv6 address is represented as Ak, and its SRv6 SID is represented as Sk.<a href="#section-6.1-1" class="pilcrow">¶</a></p> <p id="section-6.1-2">IPv6 headers are represented as the tuple of (source,destination). For example, a packet with source address A1 and destination address A2 is represented as (A1,A2). The payload of the packet is omitted.<a href="#section-6.1-2" class="pilcrow">¶</a></p> <p id="section-6.1-3">An SR Policy is a list of segments. A list of segments is represented as <S1,S2,S3> where S1 is the first SID to visit, S2 is the second SID to visit, and S3 is the last SID to visit.<a href="#section-6.1-3" class="pilcrow">¶</a></p> <p id="section-6.1-4">(SA,DA) (S3,S2,S1; SL) represents an IPv6 packet with:<a href="#section-6.1-4" class="pilcrow">¶</a></p> <ul> <li id="section-6.1-5.1">Source Address SA, Destination Addresses DA, and next header SRH.<a href="#section-6.1-5.1" class="pilcrow">¶</a> </li> <li id="section-6.1-5.2">SRH with SID list <S1,S2,S3> with SegmentsLeft = SL.<a href="#section-6.1-5.2" class="pilcrow">¶</a> </li> <li id="section-6.1-5.3">Note the difference between the <> and () symbols. <S1,S2,S3> represents a SID list where the leftmost segment is the first segment. In contrast, (S3,S2,S1; SL) represents the same SID list but encoded in the SRH Segment List format where the leftmost segment is the last segment. When referring to an SR Policy in a high-level use case, it is simpler to use the <S1,S2,S3> notation. When referring to an illustration of detailed behavior, the (S3,S2,S1; SL) notation is more convenient.<a href="#section-6.1-5.3" class="pilcrow">¶</a> </li> </ul> <p id="section-6.1-6">At its SR Policy headend, the Segment List <S1,S2,S3> results in SRH (S3,S2,S1; SL=2) represented fully as:<a href="#section-6.1-6" class="pilcrow">¶</a></p> <div class="artwork art-text alignLeft" id="section-6.1-7"> <pre> Segments Left=2 Last Entry=2 Flags=0 Tag=0 Segment List[0]=S3 Segment List[1]=S2 Segment List[2]=S1</pre><a href="#section-6.1-7" class="pilcrow">¶</a> </div> </section> <section id="section-6.2"> <h3 id="name-example-topology"> <a href="#section-6.2" class="section-number selfRef">6.2. </a><a href="#name-example-topology" class="section-name selfRef">Example Topology</a> </h3> <p id="section-6.2-1">The following topology is used in examples below:<a href="#section-6.2-1" class="pilcrow">¶</a></p> <div id="TOPO1"> <figure id="figure-1"> <div class="artwork art-text alignLeft" id="section-6.2-2.1"> <pre> + * * * * * * * * * * * * * * * * * * * * + * [8] [9] * | | * | | * [1]----[3]--------[5]----------------[6]---------[4]---[2] * | | * | | * | | * +--------[7]-------+ * * + * * * * * * * SR domain * * * * * * * +</pre> </div> <figcaption><a href="#figure-1" class="selfRef">Figure 1</a></figcaption></figure> </div> <ul> <li id="section-6.2-3.1">3 and 4 are SR domain edge routers<a href="#section-6.2-3.1" class="pilcrow">¶</a> </li> <li id="section-6.2-3.2">5, 6, and 7 are all SR domain routers<a href="#section-6.2-3.2" class="pilcrow">¶</a> </li> <li id="section-6.2-3.3">8 and 9 are hosts within the SR domain<a href="#section-6.2-3.3" class="pilcrow">¶</a> </li> <li id="section-6.2-3.4">1 and 2 are hosts outside the SR domain<a href="#section-6.2-3.4" class="pilcrow">¶</a> </li> <li id="section-6.2-3.5">The SR domain implements ingress filtering as per <a href="#SECSRDOMAIN" class="xref">Section 5.1</a> and no external packet can enter the domain with a destination address equal to a segment of the domain.<a href="#section-6.2-3.5" class="pilcrow">¶</a> </li> </ul> </section> <section id="section-6.3"> <h3 id="name-sr-source-node-3"> <a href="#section-6.3" class="section-number selfRef">6.3. </a><a href="#name-sr-source-node-3" class="section-name selfRef">SR Source Node</a> </h3> <section id="section-6.3.1"> <h4 id="name-intra-sr-domain-packet"> <a href="#section-6.3.1" class="section-number selfRef">6.3.1. </a><a href="#name-intra-sr-domain-packet" class="section-name selfRef">Intra-SR-Domain Packet</a> </h4> <p id="section-6.3.1-1">When host 8 sends a packet to host 9 via an SR Policy <S7,A9> the packet is<a href="#section-6.3.1-1" class="pilcrow">¶</a></p> <p id="section-6.3.1-2">P1: (A8,S7)(A9,S7; SL=1)<a href="#section-6.3.1-2" class="pilcrow">¶</a></p> <section id="section-6.3.1.1"> <h5 id="name-reduced-variant"> <a href="#section-6.3.1.1" class="section-number selfRef">6.3.1.1. </a><a href="#name-reduced-variant" class="section-name selfRef">Reduced Variant</a> </h5> <p id="section-6.3.1.1-1">When host 8 sends a packet to host 9 via an SR Policy <S7,A9> and it wants to use a reduced SRH, the packet is<a href="#section-6.3.1.1-1" class="pilcrow">¶</a></p> <p id="section-6.3.1.1-2">P2: (A8,S7)(A9; SL=1)<a href="#section-6.3.1.1-2" class="pilcrow">¶</a></p> </section> </section> <section id="section-6.3.2"> <h4 id="name-inter-sr-domain-packet-tran"> <a href="#section-6.3.2" class="section-number selfRef">6.3.2. </a><a href="#name-inter-sr-domain-packet-tran" class="section-name selfRef">Inter-SR-Domain Packet -- Transit</a> </h4> <p id="section-6.3.2-1">When host 1 sends a packet to host 2, the packet is<a href="#section-6.3.2-1" class="pilcrow">¶</a></p> <p id="section-6.3.2-2">P3: (A1,A2)<a href="#section-6.3.2-2" class="pilcrow">¶</a></p> <p id="section-6.3.2-3">The SR domain ingress router 3 receives P3 and steers it to SR domain egress router 4 via an SR Policy <S7,S4>. Router 3 encapsulates the received packet P3 in an outer header with an SRH. The packet is<a href="#section-6.3.2-3" class="pilcrow">¶</a></p> <p id="section-6.3.2-4">P4: (A3,S7)(S4,S7; SL=1)(A1,A2)<a href="#section-6.3.2-4" class="pilcrow">¶</a></p> <p id="section-6.3.2-5">If the SR Policy contains only one segment (the egress router 4), the ingress router 3 encapsulates P3 into an outer header (A3,S4) without SRH. The packet is<a href="#section-6.3.2-5" class="pilcrow">¶</a></p> <p id="section-6.3.2-6">P5: (A3,S4)(A1,A2)<a href="#section-6.3.2-6" class="pilcrow">¶</a></p> <section id="section-6.3.2.1"> <h5 id="name-reduced-variant-2"> <a href="#section-6.3.2.1" class="section-number selfRef">6.3.2.1. </a><a href="#name-reduced-variant-2" class="section-name selfRef">Reduced Variant</a> </h5> <p id="section-6.3.2.1-1">The SR domain ingress router 3 receives P3 and steers it to SR domain egress router 4 via an SR Policy <S7,S4>. If router 3 wants to use a reduced SRH, it encapsulates the received packet P3 in an outer header with a reduced SRH. The packet is<a href="#section-6.3.2.1-1" class="pilcrow">¶</a></p> <p id="section-6.3.2.1-2">P6: (A3,S7)(S4; SL=1)(A1,A2)<a href="#section-6.3.2.1-2" class="pilcrow">¶</a></p> </section> </section> <section id="section-6.3.3"> <h4 id="name-inter-sr-domain-packet-inte"> <a href="#section-6.3.3" class="section-number selfRef">6.3.3. </a><a href="#name-inter-sr-domain-packet-inte" class="section-name selfRef">Inter-SR-Domain Packet -- Internal to External</a> </h4> <p id="section-6.3.3-1">When host 8 sends a packet to host 1, the packet is encapsulated for the portion of its journey within the SR domain. From 8 to 3 the packet is<a href="#section-6.3.3-1" class="pilcrow">¶</a></p> <p id="section-6.3.3-2">P7: (A8,S3)(A8,A1)<a href="#section-6.3.3-2" class="pilcrow">¶</a></p> <p id="section-6.3.3-3">In the opposite direction, the packet generated from 1 to 8 is<a href="#section-6.3.3-3" class="pilcrow">¶</a></p> <p id="section-6.3.3-4">P8: (A1,A8)<a href="#section-6.3.3-4" class="pilcrow">¶</a></p> <p id="section-6.3.3-5">At node 3, P8 is encapsulated for the portion of its journey within the SR domain, with the outer header destined to segment S8. This results in<a href="#section-6.3.3-5" class="pilcrow">¶</a></p> <p id="section-6.3.3-6">P9: (A3,S8)(A1,A8)<a href="#section-6.3.3-6" class="pilcrow">¶</a></p> <p id="section-6.3.3-7">At node 8, the outer IPv6 header is removed by S8 processing, then processed again when received by A8.<a href="#section-6.3.3-7" class="pilcrow">¶</a></p> </section> </section> <section id="section-6.4"> <h3 id="name-transit-node-3"> <a href="#section-6.4" class="section-number selfRef">6.4. </a><a href="#name-transit-node-3" class="section-name selfRef">Transit Node</a> </h3> <p id="section-6.4-1">Node 5 acts as transit node for packet P1 and sends packet<a href="#section-6.4-1" class="pilcrow">¶</a></p> <p id="section-6.4-2">P1: (A8,S7)(A9,S7;SL=1)<a href="#section-6.4-2" class="pilcrow">¶</a></p> <p id="section-6.4-3">on the interface toward node 7.<a href="#section-6.4-3" class="pilcrow">¶</a></p> </section> <section id="section-6.5"> <h3 id="name-sr-segment-endpoint-node-3"> <a href="#section-6.5" class="section-number selfRef">6.5. </a><a href="#name-sr-segment-endpoint-node-3" class="section-name selfRef">SR Segment Endpoint Node</a> </h3> <p id="section-6.5-1">Node 7 receives packet P1 and, using the logic in <a href="#pktENDSID" class="xref">Section 4.3.1</a>, sends packet<a href="#section-6.5-1" class="pilcrow">¶</a></p> <p id="section-6.5-2">P7: (A8,A9)(A9,S7; SL=0)<a href="#section-6.5-2" class="pilcrow">¶</a></p> <p id="section-6.5-3">on the interface toward router 6.<a href="#section-6.5-3" class="pilcrow">¶</a></p> </section> <section id="section-6.6"> <h3 id="name-delegation-of-function-with"> <a href="#section-6.6" class="section-number selfRef">6.6. </a><a href="#name-delegation-of-function-with" class="section-name selfRef">Delegation of Function with HMAC Verification</a> </h3> <p id="section-6.6-1">This section describes how a function may be delegated within the SR domain. In the following sections, consider a host 8 connected to a top of rack 5.<a href="#section-6.6-1" class="pilcrow">¶</a></p> <section id="section-6.6.1"> <h4 id="name-sid-list-verification"> <a href="#section-6.6.1" class="section-number selfRef">6.6.1. </a><a href="#name-sid-list-verification" class="section-name selfRef">SID List Verification</a> </h4> <p id="section-6.6.1-1">An operator may prefer to apply the SRH at source 8, while 5 verifies that the SID list is valid.<a href="#section-6.6.1-1" class="pilcrow">¶</a></p> <p id="section-6.6.1-2">For illustration purposes, an SDN controller provides 8 an SRH terminating at node 9, with Segment List <S5,S7,S6,A9>, and HMAC TLV computed for the SRH. The HMAC key ID and key associated with the HMAC TLV is shared with 5. Node 8 does not know the key. Node 5 is configured with an IACL applied to the interface connected to 8, requiring HMAC verification for any packet destined to S/s.<a href="#section-6.6.1-2" class="pilcrow">¶</a></p> <p id="section-6.6.1-3">Node 8 originates packets with the received SRH, including HMAC TLV.<a href="#section-6.6.1-3" class="pilcrow">¶</a></p> <p id="section-6.6.1-4">P15: (A8,S5)(A9,S6,S7,S5;SL=3;HMAC)<a href="#section-6.6.1-4" class="pilcrow">¶</a></p> <p id="section-6.6.1-5">Node 5 receives and verifies the HMAC for the SRH, then forwards the packet to the next segment<a href="#section-6.6.1-5" class="pilcrow">¶</a></p> <p id="section-6.6.1-6">P16: (A8,S7)(A9,S6,S7,S5;SL=2;HMAC)<a href="#section-6.6.1-6" class="pilcrow">¶</a></p> <p id="section-6.6.1-7">Node 6 receives<a href="#section-6.6.1-7" class="pilcrow">¶</a></p> <p id="section-6.6.1-8">P17: (A8,S6)(A9,S6,S7,S5;SL=1;HMAC)<a href="#section-6.6.1-8" class="pilcrow">¶</a></p> <p id="section-6.6.1-9">Node 9 receives<a href="#section-6.6.1-9" class="pilcrow">¶</a></p> <p id="section-6.6.1-10">P18: (A8,A9)(A9,S6,S7,S5;SL=0;HMAC)<a href="#section-6.6.1-10" class="pilcrow">¶</a></p> <p id="section-6.6.1-11">This use of an HMAC is particularly valuable within an enterprise-based SR domain <span>[<a href="#SRN" class="xref">SRN</a>]</span>.<a href="#section-6.6.1-11" class="pilcrow">¶</a></p> </section> </section> </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 section reviews security considerations related to the SRH, given the SRH processing and deployment models discussed in this document.<a href="#section-7-1" class="pilcrow">¶</a></p> <p id="section-7-2">As described in <a href="#DEP" class="xref">Section 5</a>, it is necessary to filter packets' ingress to the SR domain, destined to SIDs within the SR domain (i.e., bearing a SID in the destination address). This ingress filtering is via an IACL at SR domain ingress border nodes. Additional protection is applied via an IACL at each SR Segment Endpoint node, filtering packets not from within the SR domain, destined to SIDs in the SR domain. ACLs are easily supported for small numbers of seldom changing prefixes, making summarization important.<a href="#section-7-2" class="pilcrow">¶</a></p> <p id="section-7-3">Additionally, ingress filtering of IPv6 source addresses as recommended in BCP 38 <span>[<a href="#RFC2827" class="xref">RFC2827</a>]</span> <span class="bcp14">SHOULD</span> be used.<a href="#section-7-3" class="pilcrow">¶</a></p> <section id="section-7.1"> <h3 id="name-sr-attacks"> <a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-sr-attacks" class="section-name selfRef">SR Attacks</a> </h3> <p id="section-7.1-1">An SR domain implements distributed and per-node protection as described in <a href="#SECSRDOMAIN" class="xref">Section 5.1</a>. Additionally, domains deny traffic with spoofed addresses by implementing the recommendations in BCP 84 <span>[<a href="#RFC3704" class="xref">RFC3704</a>]</span>.<a href="#section-7.1-1" class="pilcrow">¶</a></p> <p id="section-7.1-2">Full implementation of the recommended protection blocks the attacks documented in <span>[<a href="#RFC5095" class="xref">RFC5095</a>]</span> from outside the SR domain, including bypassing filtering devices, reaching otherwise-unreachable Internet systems, network topology discovery, bandwidth exhaustion, and defeating anycast.<a href="#section-7.1-2" class="pilcrow">¶</a></p> <p id="section-7.1-3">Failure to implement distributed and per-node protection allows attackers to bypass filtering devices and exposes the SR domain to these attacks.<a href="#section-7.1-3" class="pilcrow">¶</a></p> <p id="section-7.1-4">Compromised nodes within the SR domain may mount the attacks listed above along with other known attacks on IP networks (e.g., DoS/DDoS, topology discovery, man-in-the-middle, traffic interception/siphoning).<a href="#section-7.1-4" class="pilcrow">¶</a></p> </section> <section id="section-7.2"> <h3 id="name-service-theft"> <a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-service-theft" class="section-name selfRef">Service Theft</a> </h3> <p id="section-7.2-1">Service theft is defined as the use of a service offered by the SR domain by a node not authorized to use the service.<a href="#section-7.2-1" class="pilcrow">¶</a></p> <p id="section-7.2-2">Service theft is not a concern within the SR domain, as all SR source nodes and SR segment endpoint nodes within the domain are able to utilize the services of the domain. If a node outside the SR domain learns of segments or a topological service within the SR domain, IACL filtering denies access to those segments.<a href="#section-7.2-2" class="pilcrow">¶</a></p> </section> <section id="section-7.3"> <h3 id="name-topology-disclosure"> <a href="#section-7.3" class="section-number selfRef">7.3. </a><a href="#name-topology-disclosure" class="section-name selfRef">Topology Disclosure</a> </h3> <p id="section-7.3-1">The SRH is unencrypted and may contain SIDs of some intermediate SR nodes in the path towards the destination within the SR domain. If packets can be snooped within the SR domain, the SRH may reveal topology, traffic flows, and service usage.<a href="#section-7.3-1" class="pilcrow">¶</a></p> <p id="section-7.3-2">This is applicable within an SR domain, but the disclosure is less relevant as an attacker has other means of learning topology, flows, and service usage.<a href="#section-7.3-2" class="pilcrow">¶</a></p> </section> <section id="section-7.4"> <h3 id="name-icmp-generation"> <a href="#section-7.4" class="section-number selfRef">7.4. </a><a href="#name-icmp-generation" class="section-name selfRef">ICMP Generation</a> </h3> <p id="section-7.4-1">The generation of ICMPv6 error messages may be used to attempt denial-of-service attacks by sending an error-causing destination address or SRH in back-to-back packets. An implementation that correctly follows <span><a href="https://www.rfc-editor.org/rfc/rfc4443#section-2.4" class="relref">Section 2.4</a> of [<a href="#RFC4443" class="xref">RFC4443</a>]</span> would be protected by the ICMPv6 rate-limiting mechanism.<a href="#section-7.4-1" class="pilcrow">¶</a></p> </section> <section id="section-7.5"> <h3 id="name-applicability-of-ah"> <a href="#section-7.5" class="section-number selfRef">7.5. </a><a href="#name-applicability-of-ah" class="section-name selfRef">Applicability of AH</a> </h3> <p id="section-7.5-1">The SR domain is a trusted domain, as defined in <span>[<a href="#RFC8402" class="xref">RFC8402</a>]</span>, Sections <a href="https://www.rfc-editor.org/rfc/rfc8402#section-2" class="relref">2</a> and <a href="https://www.rfc-editor.org/rfc/rfc8402#section-8.2" class="relref">8.2</a>. The SR source is trusted to add an SRH (optionally verified as having been generated by a trusted source via the HMAC TLV in this document), and segments advertised within the domain are trusted to be accurate and advertised by trusted sources via a secure control plane. As such, the SR domain does not rely on the Authentication Header (AH) as defined in <span>[<a href="#RFC4302" class="xref">RFC4302</a>]</span> to secure the SRH.<a href="#section-7.5-1" class="pilcrow">¶</a></p> <p id="section-7.5-2">The use of SRH with AH by an SR source node and its processing at an SR segment endpoint node are not defined in this document. Future documents may define use of SRH with AH and its processing.<a href="#section-7.5-2" class="pilcrow">¶</a></p> </section> </section> </div> <div id="IANA"> <section id="section-8"> <h2 id="name-iana-considerations"> <a href="#section-8" class="section-number selfRef">8. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a> </h2> <p id="section-8-1">This document makes the following registrations in the "Internet Protocol Version 6 (IPv6) Parameters" "Routing Types" subregistry maintained by IANA:<a href="#section-8-1" class="pilcrow">¶</a></p> <span id="name-srh-registration"></span><div id="SRH-REG"> <table class="center" id="table-1"> <caption> <a href="#table-1" class="selfRef">Table 1</a>: <a href="#name-srh-registration" class="selfRef">SRH Registration</a> </caption> <thead> <tr> <th class="text-left" rowspan="1" colspan="1">Value</th> <th class="text-left" rowspan="1" colspan="1">Description</th> <th class="text-left" rowspan="1" colspan="1">Reference</th> </tr> </thead> <tbody> <tr> <td class="text-left" rowspan="1" colspan="1">4</td> <td class="text-left" rowspan="1" colspan="1">Segment Routing Header (SRH)</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> </tbody> </table> </div> <p id="section-8-3">This document makes the following registrations in the "Type 4 - Parameter Problem" message of the "Internet Control Message Protocol version 6 (ICMPv6) Parameters" registry maintained by IANA:<a href="#section-8-3" class="pilcrow">¶</a></p> <span id="name-sr-upper-layer-header-error"></span><div id="UPPER-LAYER"> <table class="center" id="table-2"> <caption> <a href="#table-2" class="selfRef">Table 2</a>: <a href="#name-sr-upper-layer-header-error" class="selfRef">SR Upper-layer Header Error Registration</a> </caption> <thead> <tr> <th class="text-left" rowspan="1" colspan="1">Code</th> <th class="text-left" rowspan="1" colspan="1">Name</th> </tr> </thead> <tbody> <tr> <td class="text-left" rowspan="1" colspan="1">4</td> <td class="text-left" rowspan="1" colspan="1">SR Upper-layer Header Error</td> </tr> </tbody> </table> </div> <div id="SRHFLAGSREG"> <section id="section-8.1"> <h3 id="name-segment-routing-header-flag"> <a href="#section-8.1" class="section-number selfRef">8.1. </a><a href="#name-segment-routing-header-flag" class="section-name selfRef">Segment Routing Header Flags Registry</a> </h3> <p id="section-8.1-1">This document describes a new IANA-managed registry to identify SRH Flags Bits. The registration procedure is "IETF Review" <span>[<a href="#RFC8126" class="xref">RFC8126</a>]</span>. The registry name is "Segment Routing Header Flags". Flags are 8 bits.<a href="#section-8.1-1" class="pilcrow">¶</a></p> </section> </div> <div id="SRHTLVREG"> <section id="section-8.2"> <h3 id="name-segment-routing-header-tlvs"> <a href="#section-8.2" class="section-number selfRef">8.2. </a><a href="#name-segment-routing-header-tlvs" class="section-name selfRef">Segment Routing Header TLVs Registry</a> </h3> <p id="section-8.2-1">This document describes a new IANA-managed registry to identify SRH TLVs. The registration procedure is "IETF Review". The registry name is "Segment Routing Header TLVs". A TLV is identified through an unsigned 8-bit codepoint value, with assigned values 0-127 for TLVs that do not change en route and 128-255 for TLVs that may change en route. The following codepoints are defined in this document:<a href="#section-8.2-1" class="pilcrow">¶</a></p> <span id="name-segment-routing-header-tlvs-"></span><div id="TLV-REG"> <table class="center" id="table-3"> <caption> <a href="#table-3" class="selfRef">Table 3</a>: <a href="#name-segment-routing-header-tlvs-" class="selfRef">Segment Routing Header TLVs Registry</a> </caption> <thead> <tr> <th class="text-left" rowspan="1" colspan="1">Value</th> <th class="text-left" rowspan="1" colspan="1">Description</th> <th class="text-left" rowspan="1" colspan="1">Reference</th> </tr> </thead> <tbody> <tr> <td class="text-left" rowspan="1" colspan="1">0</td> <td class="text-left" rowspan="1" colspan="1">Pad1 TLV</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">1</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">2</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">3</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">4</td> <td class="text-left" rowspan="1" colspan="1">PadN TLV</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">5</td> <td class="text-left" rowspan="1" colspan="1">HMAC TLV</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">6</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">124-126</td> <td class="text-left" rowspan="1" colspan="1">Experimentation and Test</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">127</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">252-254</td> <td class="text-left" rowspan="1" colspan="1">Experimentation and Test</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> <tr> <td class="text-left" rowspan="1" colspan="1">255</td> <td class="text-left" rowspan="1" colspan="1">Reserved</td> <td class="text-left" rowspan="1" colspan="1">This document</td> </tr> </tbody> </table> </div> <p id="section-8.2-3">Values 1, 2, 3, and 6 were defined in draft versions of this specification and are Reserved for backwards compatibility with early implementations and should not be reassigned. Values 127 and 255 are Reserved to allow for expansion of the Type field in future specifications, if needed.<a href="#section-8.2-3" class="pilcrow">¶</a></p> </section> </div> </section> </div> <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="FIPS180-4">[FIPS180-4]</dt> <dd> <span class="refAuthor">National Institute of Standards and Technology (NIST)</span>, <span class="refTitle">"Secure Hash Standard (SHS)"</span>, <span class="refContent">FIPS PUB 180-4</span>, <span class="refContent">DOI 10.6028/NIST.FIPS.180-4</span>, <time datetime="2015-08">August 2015</time>, <span><<a href="http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf">http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf</a>></span>. </dd> <dt id="IANA-SRHTLV">[IANA-SRHTLV]</dt> <dd> <span class="refAuthor">IANA</span>, <span class="refTitle">"Segment Routing Header TLVs"</span>, <span><<a href="https://www.iana.org/assignments/ipv6-parameters/">https://www.iana.org/assignments/ipv6-parameters/</a>></span>. </dd> <dt id="RFC2104">[RFC2104]</dt> <dd> <span class="refAuthor">Krawczyk, H.</span><span class="refAuthor">, Bellare, M.</span><span class="refAuthor">, and R. Canetti</span>, <span class="refTitle">"HMAC: Keyed-Hashing for Message Authentication"</span>, <span class="seriesInfo">RFC 2104</span>, <span class="seriesInfo">DOI 10.17487/RFC2104</span>, <time datetime="1997-02">February 1997</time>, <span><<a href="https://www.rfc-editor.org/info/rfc2104">https://www.rfc-editor.org/info/rfc2104</a>></span>. </dd> <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><<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>></span>. </dd> <dt id="RFC2473">[RFC2473]</dt> <dd> <span class="refAuthor">Conta, A.</span><span class="refAuthor"> and S. Deering</span>, <span class="refTitle">"Generic Packet Tunneling in IPv6 Specification"</span>, <span class="seriesInfo">RFC 2473</span>, <span class="seriesInfo">DOI 10.17487/RFC2473</span>, <time datetime="1998-12">December 1998</time>, <span><<a href="https://www.rfc-editor.org/info/rfc2473">https://www.rfc-editor.org/info/rfc2473</a>></span>. </dd> <dt id="RFC2827">[RFC2827]</dt> <dd> <span class="refAuthor">Ferguson, P.</span><span class="refAuthor"> and D. Senie</span>, <span class="refTitle">"Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing"</span>, <span class="seriesInfo">BCP 38</span>, <span class="seriesInfo">RFC 2827</span>, <span class="seriesInfo">DOI 10.17487/RFC2827</span>, <time datetime="2000-05">May 2000</time>, <span><<a href="https://www.rfc-editor.org/info/rfc2827">https://www.rfc-editor.org/info/rfc2827</a>></span>. </dd> <dt id="RFC3704">[RFC3704]</dt> <dd> <span class="refAuthor">Baker, F.</span><span class="refAuthor"> and P. Savola</span>, <span class="refTitle">"Ingress Filtering for Multihomed Networks"</span>, <span class="seriesInfo">BCP 84</span>, <span class="seriesInfo">RFC 3704</span>, <span class="seriesInfo">DOI 10.17487/RFC3704</span>, <time datetime="2004-03">March 2004</time>, <span><<a href="https://www.rfc-editor.org/info/rfc3704">https://www.rfc-editor.org/info/rfc3704</a>></span>. </dd> <dt id="RFC4107">[RFC4107]</dt> <dd> <span class="refAuthor">Bellovin, S.</span><span class="refAuthor"> and R. Housley</span>, <span class="refTitle">"Guidelines for Cryptographic Key Management"</span>, <span class="seriesInfo">BCP 107</span>, <span class="seriesInfo">RFC 4107</span>, <span class="seriesInfo">DOI 10.17487/RFC4107</span>, <time datetime="2005-06">June 2005</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4107">https://www.rfc-editor.org/info/rfc4107</a>></span>. </dd> <dt id="RFC4302">[RFC4302]</dt> <dd> <span class="refAuthor">Kent, S.</span>, <span class="refTitle">"IP Authentication Header"</span>, <span class="seriesInfo">RFC 4302</span>, <span class="seriesInfo">DOI 10.17487/RFC4302</span>, <time datetime="2005-12">December 2005</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4302">https://www.rfc-editor.org/info/rfc4302</a>></span>. </dd> <dt id="RFC5095">[RFC5095]</dt> <dd> <span class="refAuthor">Abley, J.</span><span class="refAuthor">, Savola, P.</span><span class="refAuthor">, and G. Neville-Neil</span>, <span class="refTitle">"Deprecation of Type 0 Routing Headers in IPv6"</span>, <span class="seriesInfo">RFC 5095</span>, <span class="seriesInfo">DOI 10.17487/RFC5095</span>, <time datetime="2007-12">December 2007</time>, <span><<a href="https://www.rfc-editor.org/info/rfc5095">https://www.rfc-editor.org/info/rfc5095</a>></span>. </dd> <dt id="RFC6407">[RFC6407]</dt> <dd> <span class="refAuthor">Weis, B.</span><span class="refAuthor">, Rowles, S.</span><span class="refAuthor">, and T. Hardjono</span>, <span class="refTitle">"The Group Domain of Interpretation"</span>, <span class="seriesInfo">RFC 6407</span>, <span class="seriesInfo">DOI 10.17487/RFC6407</span>, <time datetime="2011-10">October 2011</time>, <span><<a href="https://www.rfc-editor.org/info/rfc6407">https://www.rfc-editor.org/info/rfc6407</a>></span>. </dd> <dt id="RFC6437">[RFC6437]</dt> <dd> <span class="refAuthor">Amante, S.</span><span class="refAuthor">, Carpenter, B.</span><span class="refAuthor">, Jiang, S.</span><span class="refAuthor">, and J. Rajahalme</span>, <span class="refTitle">"IPv6 Flow Label Specification"</span>, <span class="seriesInfo">RFC 6437</span>, <span class="seriesInfo">DOI 10.17487/RFC6437</span>, <time datetime="2011-11">November 2011</time>, <span><<a href="https://www.rfc-editor.org/info/rfc6437">https://www.rfc-editor.org/info/rfc6437</a>></span>. </dd> <dt id="RFC6438">[RFC6438]</dt> <dd> <span class="refAuthor">Carpenter, B.</span><span class="refAuthor"> and S. Amante</span>, <span class="refTitle">"Using the IPv6 Flow Label for Equal Cost Multipath Routing and Link Aggregation in Tunnels"</span>, <span class="seriesInfo">RFC 6438</span>, <span class="seriesInfo">DOI 10.17487/RFC6438</span>, <time datetime="2011-11">November 2011</time>, <span><<a href="https://www.rfc-editor.org/info/rfc6438">https://www.rfc-editor.org/info/rfc6438</a>></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><<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>></span>. </dd> <dt id="RFC8200">[RFC8200]</dt> <dd> <span class="refAuthor">Deering, S.</span><span class="refAuthor"> and R. Hinden</span>, <span class="refTitle">"Internet Protocol, Version 6 (IPv6) Specification"</span>, <span class="seriesInfo">STD 86</span>, <span class="seriesInfo">RFC 8200</span>, <span class="seriesInfo">DOI 10.17487/RFC8200</span>, <time datetime="2017-07">July 2017</time>, <span><<a href="https://www.rfc-editor.org/info/rfc8200">https://www.rfc-editor.org/info/rfc8200</a>></span>. </dd> <dt id="RFC8402">[RFC8402]</dt> <dd> <span class="refAuthor">Filsfils, C., Ed.</span><span class="refAuthor">, Previdi, S., Ed.</span><span class="refAuthor">, Ginsberg, L.</span><span class="refAuthor">, Decraene, B.</span><span class="refAuthor">, Litkowski, S.</span><span class="refAuthor">, and R. Shakir</span>, <span class="refTitle">"Segment Routing Architecture"</span>, <span class="seriesInfo">RFC 8402</span>, <span class="seriesInfo">DOI 10.17487/RFC8402</span>, <time datetime="2018-07">July 2018</time>, <span><<a href="https://www.rfc-editor.org/info/rfc8402">https://www.rfc-editor.org/info/rfc8402</a>></span>. </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="I-D.ietf-intarea-tunnels">[INTAREA-TUNNELS]</dt> <dd> <span class="refAuthor">Touch, J.</span><span class="refAuthor"> and M. Townsley</span>, <span class="refTitle">"IP Tunnels in the Internet Architecture"</span>, <span class="refContent">Work in Progress</span>, <span class="seriesInfo">Internet-Draft, draft-ietf-intarea-tunnels-10</span>, <time datetime="2019-09-12">12 September 2019</time>, <span><<a href="https://tools.ietf.org/html/draft-ietf-intarea-tunnels-10">https://tools.ietf.org/html/draft-ietf-intarea-tunnels-10</a>></span>. </dd> <dt id="RFC4443">[RFC4443]</dt> <dd> <span class="refAuthor">Conta, A.</span><span class="refAuthor">, Deering, S.</span><span class="refAuthor">, and M. Gupta, Ed.</span>, <span class="refTitle">"Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"</span>, <span class="seriesInfo">STD 89</span>, <span class="seriesInfo">RFC 4443</span>, <span class="seriesInfo">DOI 10.17487/RFC4443</span>, <time datetime="2006-03">March 2006</time>, <span><<a href="https://www.rfc-editor.org/info/rfc4443">https://www.rfc-editor.org/info/rfc4443</a>></span>. </dd> <dt id="RFC5308">[RFC5308]</dt> <dd> <span class="refAuthor">Hopps, C.</span>, <span class="refTitle">"Routing IPv6 with IS-IS"</span>, <span class="seriesInfo">RFC 5308</span>, <span class="seriesInfo">DOI 10.17487/RFC5308</span>, <time datetime="2008-10">October 2008</time>, <span><<a href="https://www.rfc-editor.org/info/rfc5308">https://www.rfc-editor.org/info/rfc5308</a>></span>. </dd> <dt id="RFC5340">[RFC5340]</dt> <dd> <span class="refAuthor">Coltun, R.</span><span class="refAuthor">, Ferguson, D.</span><span class="refAuthor">, Moy, J.</span><span class="refAuthor">, and A. Lindem</span>, <span class="refTitle">"OSPF for IPv6"</span>, <span class="seriesInfo">RFC 5340</span>, <span class="seriesInfo">DOI 10.17487/RFC5340</span>, <time datetime="2008-07">July 2008</time>, <span><<a href="https://www.rfc-editor.org/info/rfc5340">https://www.rfc-editor.org/info/rfc5340</a>></span>. </dd> <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><<a href="https://www.rfc-editor.org/info/rfc8126">https://www.rfc-editor.org/info/rfc8126</a>></span>. </dd> <dt id="SRN">[SRN]</dt> <dd> <span class="refAuthor">Lebrun, D.</span><span class="refAuthor">, Jadin, M.</span><span class="refAuthor">, Clad, F.</span><span class="refAuthor">, Filsfils, C.</span><span class="refAuthor">, and O. Bonaventure</span>, <span class="refTitle">"Software Resolved Networks: Rethinking Enterprise Networks with IPv6 Segment Routing"</span>, <time datetime="2018">2018</time>, <span><<a href="https://inl.info.ucl.ac.be/system/files/sosr18-final15-embedfonts.pdf">https://inl.info.ucl.ac.be/system/files/sosr18-final15-embedfonts.pdf</a>></span>. </dd> </dl> </section> </section> <div id="Acknowledgements"> <section id="section-appendix.a"> <h2 id="name-acknowledgements"> <a href="#name-acknowledgements" class="section-name selfRef">Acknowledgements</a> </h2> <p id="section-appendix.a-1">The authors would like to thank <span class="contact-name">Ole Troan</span>, <span class="contact-name">Bob Hinden</span>, <span class="contact-name">Ron Bonica</span>, <span class="contact-name">Fred Baker</span>, <span class="contact-name">Brian Carpenter</span>, <span class="contact-name">Alexandru Petrescu</span>, <span class="contact-name">Punit Kumar Jaiswal</span>, <span class="contact-name">David Lebrun</span>, <span class="contact-name">Benjamin Kaduk</span>, <span class="contact-name">Frank Xialiang</span>, <span class="contact-name">Mirja Kühlewind</span>, <span class="contact-name">Roman Danyliw</span>, <span class="contact-name">Joe Touch</span>, and <span class="contact-name">Magnus Westerlund</span> for their comments to this document.<a href="#section-appendix.a-1" class="pilcrow">¶</a></p> </section> </div> <div id="Contributors"> <section id="section-appendix.b"> <h2 id="name-contributors"> <a href="#name-contributors" class="section-name selfRef">Contributors</a> </h2> <p id="section-appendix.b-1"><span class="contact-name">Kamran Raza</span>, <span class="contact-name">Zafar Ali</span>, <span class="contact-name">Brian Field</span>, <span class="contact-name">Daniel Bernier</span>, <span class="contact-name">Ida Leung</span>, <span class="contact-name">Jen Linkova</span>, <span class="contact-name">Ebben Aries</span>, <span class="contact-name">Tomoya Kosugi</span>, <span class="contact-name">Éric Vyncke</span>, <span class="contact-name">David Lebrun</span>, <span class="contact-name">Dirk Steinberg</span>, <span class="contact-name">Robert Raszuk</span>, <span class="contact-name">Dave Barach</span>, <span class="contact-name">John Brzozowski</span>, <span class="contact-name">Pierre Francois</span>, <span class="contact-name">Nagendra Kumar</span>, <span class="contact-name">Mark Townsley</span>, <span class="contact-name">Christian Martin</span>, <span class="contact-name">Roberta Maglione</span>, <span class="contact-name">James Connolly</span>, and <span class="contact-name">Aloys Augustin</span> contributed to the content of this document.<a href="#section-appendix.b-1" class="pilcrow">¶</a></p> </section> </div> <div id="authors-addresses"> <section id="section-appendix.c"> <h2 id="name-authors-addresses"> <a href="#name-authors-addresses" class="section-name selfRef">Authors' Addresses</a> </h2> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">Clarence Filsfils (<span class="role">editor</span>)</span></div> <div dir="auto" class="left"><span class="org">Cisco Systems, Inc.</span></div> <div dir="auto" class="left"><span class="locality">Brussels</span></div> <div dir="auto" class="left"><span class="country-name">Belgium</span></div> <div class="email"> <span>Email:</span> <a href="mailto:cfilsfil@cisco.com" class="email">cfilsfil@cisco.com</a> </div> </address> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">Darren Dukes (<span class="role">editor</span>)</span></div> <div dir="auto" class="left"><span class="org">Cisco Systems, Inc.</span></div> <div dir="auto" class="left"> <span class="locality">Ottawa</span> </div> <div dir="auto" class="left"><span class="country-name">Canada</span></div> <div class="email"> <span>Email:</span> <a href="mailto:ddukes@cisco.com" class="email">ddukes@cisco.com</a> </div> </address> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">Stefano Previdi</span></div> <div dir="auto" class="left"><span class="org">Huawei</span></div> <div dir="auto" class="left"><span class="country-name">Italy</span></div> <div class="email"> <span>Email:</span> <a href="mailto:stefano@previdi.net" class="email">stefano@previdi.net</a> </div> </address> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">John Leddy</span></div> <div dir="auto" class="left"><span class="org">Individual</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:john@leddy.net" class="email">john@leddy.net</a> </div> </address> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">Satoru Matsushima</span></div> <div dir="auto" class="left"><span class="org">SoftBank</span></div> <div class="email"> <span>Email:</span> <a href="mailto:satoru.matsushima@g.softbank.co.jp" class="email">satoru.matsushima@g.softbank.co.jp</a> </div> </address> <address class="vcard"> <div dir="auto" class="left"><span class="fn nameRole">Daniel Voyer</span></div> <div dir="auto" class="left"><span class="org">Bell Canada</span></div> <div class="email"> <span>Email:</span> <a href="mailto:daniel.voyer@bell.ca" class="email">daniel.voyer@bell.ca</a> </div> </address> </section> </div> <script>const toc = document.getElementById("toc"); toc.querySelector("h2").addEventListener("click", e => { toc.classList.toggle("active"); }); toc.querySelector("nav").addEventListener("click", e => { toc.classList.remove("active"); }); </script> </body> </html>