<?xmlversion="1.0" encoding="US-ASCII"?> <!DOCTYPE rfc SYSTEM "rfc2629.dtd"> <?rfc toc="yes"?> <?rfc tocompact="yes"?> <?rfc tocdepth="3"?> <?rfc tocindent="yes"?> <?rfc symrefs="yes"?> <?rfc sortrefs="yes"?> <?rfc comments="yes"?> <?rfc inline="yes"?> <?rfc compact="yes"?> <?rfc subcompact="no"?>version='1.0' encoding='utf-8'?> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" version="3" category="std" consensus="true" docName="draft-ietf-pce-segment-routing-16" indexInclude="true" ipr="trust200902"updates="8408">number="8664" prepTime="2019-12-04T22:27:30" scripts="Common,Latin" sortRefs="true" submissionType="IETF" symRefs="true" tocDepth="3" tocInclude="true" updates="8408" xml:lang="en"> <link href="https://datatracker.ietf.org/doc/draft-ietf-pce-segment-routing-16" rel="prev"/> <link href="https://dx.doi.org/10.17487/rfc8664" rel="alternate"/> <link href="urn:issn:2070-1721" rel="alternate"/> <front> <title abbrev="PCEP Extensions for SegmentRouting"> PCEPRouting">Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing</title> <seriesInfo name="RFC" value="8664" stream="IETF"/> <author fullname="Siva Sivabalan" initials="S." surname="Sivabalan"><organization>Cisco<organization showOnFrontPage="true">Cisco Systems, Inc.</organization> <address> <postal> <street>2000 Innovation Drive</street> <city>Kanata</city> <region>Ontario</region> <code>K2K 3E8</code> <country>Canada</country> </postal> <email>msiva@cisco.com</email> </address> </author> <author fullname="Clarence Filsfils" initials="C." surname="Filsfils"><organization>Cisco<organization showOnFrontPage="true">Cisco Systems, Inc.</organization> <address> <postal> <street>Pegasus Parc</street> <city>De kleetlaan 6a</city><region>DIEGEM</region> <code>BRABANT<region>Diegem</region> <code>Brabant 1831</code><country>BELGIUM</country><country>Belgium</country> </postal> <email>cfilsfil@cisco.com</email> </address> </author> <author fullname="Jeff Tantsura" initials="J." surname="Tantsura"><organization>Apstra,<organization showOnFrontPage="true">Apstra, Inc.</organization> <address> <postal> <street>333 Middlefield Rd #200</street> <city>Menlo Park</city> <region>CA</region> <code>94025</code><country>USA</country><country>United States of America</country> </postal> <email>jefftant.ietf@gmail.com</email> </address> </author> <author fullname="Wim Henderickx" initials="W." surname="Henderickx"><organization>Nokia</organization><organization showOnFrontPage="true">Nokia</organization> <address> <postal> <street>Copernicuslaan50 </street>50</street> <city>Antwerp 2018</city> <region>CA</region> <code>95134</code><country>BELGIUM</country><country>Belgium</country> </postal><email>wim.henderickx@alcatel-lucent.com</email><email>wim.henderickx@nokia.com</email> </address> </author> <author fullname="Jon Hardwick" initials="J." surname="Hardwick"><organization>Metaswitch<organization showOnFrontPage="true">Metaswitch Networks</organization> <address> <postal> <street>100 Church Street</street> <city>Enfield</city> <region>Middlesex</region><country>UK</country><country>United Kingdom</country> </postal> <email>jonathan.hardwick@metaswitch.com</email> </address> </author> <dateday="4" month="March" year="2019" />month="12" year="2019"/> <workgroup>PCE</workgroup><abstract> <t>Segment<keyword>SR</keyword> <keyword>Traffic-Engineering</keyword> <keyword>PCE</keyword> <abstract pn="section-abstract"> <t pn="section-abstract-1">Segment Routing (SR) enables any head-end node to select any path without relying on a hop-by-hop signaling technique (e.g., LDP or RSVP-TE). It depends only on "segments" that are advertised by link-state Interior Gateway Protocols (IGPs).A Segment Routing PathAn SR path can be derived from a variety of mechanisms, including an IGP Shortest Path Tree (SPT), an explicit configuration, or a Path Computation Element (PCE). This document specifies extensions to the Path Computation Element Communication Protocol (PCEP) that allow a stateful PCE to compute and initiateTraffic EngineeringTraffic-Engineering (TE) paths, as well as aPCCPath Computation Client (PCC) to request a path subject to certain constraints and optimization criteria in SRnetworks.networks.</t> <t pn="section-abstract-2"> This document updates RFC 8408. </t> </abstract><note title="Requirements Language"> <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY",<boilerplate> <section anchor="status-of-memo" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.1"> <name slugifiedName="name-status-of-this-memo">Status of This Memo</name> <t pn="section-boilerplate.1-1"> This is an Internet Standards Track document. </t> <t pn="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"OPTIONAL"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. </t> <t pn="section-boilerplate.1-3"> Information about the current status of thisdocument aredocument, any errata, and how to provide feedback on it may beinterpretedobtained at <eref target="https://www.rfc-editor.org/info/rfc8664" brackets="none"/>. </t> </section> <section anchor="copyright" numbered="false" removeInRFC="false" toc="exclude" pn="section-boilerplate.2"> <name slugifiedName="name-copyright-notice">Copyright Notice</name> <t pn="section-boilerplate.2-1"> Copyright (c) 2019 IETF Trust and the persons identified asdescribed inthe document authors. All rights reserved. </t> <t pn="section-boilerplate.2-2"> This document is subject to BCP14 <xref target="RFC2119"/> <xref target="RFC8174"/> when,78 andonly when,the IETF Trust's Legal Provisions Relating to IETF Documents (<eref target="https://trustee.ietf.org/license-info" brackets="none"/>) in effect on the date of publication of this document. Please review these documents carefully, as theyappeardescribe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described inall capitals,Section 4.e of the Trust Legal Provisions and are provided without warranty asshown here.described in the Simplified BSD License. </t></note></section> </boilerplate> <toc> <section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" pn="section-toc.1"> <name slugifiedName="name-table-of-contents">Table of Contents</name> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1"> <li pn="section-toc.1-1.1"> <t keepWithNext="true" pn="section-toc.1-1.1.1"><xref derivedContent="1" format="counter" sectionFormat="of" target="section-1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-introduction">Introduction</xref></t> </li> <li pn="section-toc.1-1.2"> <t keepWithNext="true" pn="section-toc.1-1.2.1"><xref derivedContent="2" format="counter" sectionFormat="of" target="section-2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-terminology">Terminology</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.2.2"> <li pn="section-toc.1-1.2.2.1"> <t keepWithNext="true" pn="section-toc.1-1.2.2.1.1"><xref derivedContent="2.1" format="counter" sectionFormat="of" target="section-2.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-requirements-language">Requirements Language</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.3"> <t keepWithNext="true" pn="section-toc.1-1.3.1"><xref derivedContent="3" format="counter" sectionFormat="of" target="section-3"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-overview-of-pcep-operation-">Overview of PCEP Operation in SR Networks</xref></t> </li> <li pn="section-toc.1-1.4"> <t keepWithNext="true" pn="section-toc.1-1.4.1"><xref derivedContent="4" format="counter" sectionFormat="of" target="section-4"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-object-formats">Object Formats</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.4.2"> <li pn="section-toc.1-1.4.2.1"> <t keepWithNext="true" pn="section-toc.1-1.4.2.1.1"><xref derivedContent="4.1" format="counter" sectionFormat="of" target="section-4.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-the-open-object">The OPEN Object</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.4.2.1.2"> <li pn="section-toc.1-1.4.2.1.2.1"> <t keepWithNext="true" pn="section-toc.1-1.4.2.1.2.1.1"><xref derivedContent="4.1.1" format="counter" sectionFormat="of" target="section-4.1.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-the-path-setup-type-capabil">The Path Setup Type Capability TLV</xref></t> </li> <li pn="section-toc.1-1.4.2.1.2.2"> <t keepWithNext="true" pn="section-toc.1-1.4.2.1.2.2.1"><xref derivedContent="4.1.2" format="counter" sectionFormat="of" target="section-4.1.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-the-sr-pce-capability-sub-t">The SR PCE Capability Sub-TLV</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.4.2.2"> <t keepWithNext="true" pn="section-toc.1-1.4.2.2.1"><xref derivedContent="4.2" format="counter" sectionFormat="of" target="section-4.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-the-rp-srp-object">The RP/SRP Object</xref></t> </li> <li pn="section-toc.1-1.4.2.3"> <t keepWithNext="true" pn="section-toc.1-1.4.2.3.1"><xref derivedContent="4.3" format="counter" sectionFormat="of" target="section-4.3"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-ero">ERO</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.4.2.3.2"> <li pn="section-toc.1-1.4.2.3.2.1"> <t keepWithNext="true" pn="section-toc.1-1.4.2.3.2.1.1"><xref derivedContent="4.3.1" format="counter" sectionFormat="of" target="section-4.3.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-sr-ero-subobject">SR-ERO Subobject</xref></t> </li> <li pn="section-toc.1-1.4.2.3.2.2"> <t keepWithNext="true" pn="section-toc.1-1.4.2.3.2.2.1"><xref derivedContent="4.3.2" format="counter" sectionFormat="of" target="section-4.3.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-nai-associated-with-sid">NAI Associated with SID</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.4.2.4"> <t keepWithNext="true" pn="section-toc.1-1.4.2.4.1"><xref derivedContent="4.4" format="counter" sectionFormat="of" target="section-4.4"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-rro">RRO</xref></t> </li> <li pn="section-toc.1-1.4.2.5"> <t keepWithNext="true" pn="section-toc.1-1.4.2.5.1"><xref derivedContent="4.5" format="counter" sectionFormat="of" target="section-4.5"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-metric-object">METRIC Object</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.5"> <t keepWithNext="true" pn="section-toc.1-1.5.1"><xref derivedContent="5" format="counter" sectionFormat="of" target="section-5"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-procedures">Procedures</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.5.2"> <li pn="section-toc.1-1.5.2.1"> <t keepWithNext="true" pn="section-toc.1-1.5.2.1.1"><xref derivedContent="5.1" format="counter" sectionFormat="of" target="section-5.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-exchanging-the-sr-pce-capab">Exchanging the SR PCE Capability</xref></t> </li> <li pn="section-toc.1-1.5.2.2"> <t keepWithNext="true" pn="section-toc.1-1.5.2.2.1"><xref derivedContent="5.2" format="counter" sectionFormat="of" target="section-5.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-ero-processing">ERO Processing</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.5.2.2.2"> <li pn="section-toc.1-1.5.2.2.2.1"> <t keepWithNext="true" pn="section-toc.1-1.5.2.2.2.1.1"><xref derivedContent="5.2.1" format="counter" sectionFormat="of" target="section-5.2.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-sr-ero-validation">SR-ERO Validation</xref></t> </li> <li pn="section-toc.1-1.5.2.2.2.2"> <t keepWithNext="true" pn="section-toc.1-1.5.2.2.2.2.1"><xref derivedContent="5.2.2" format="counter" sectionFormat="of" target="section-5.2.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-interpreting-the-sr-ero">Interpreting the SR-ERO</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.5.2.3"> <t keepWithNext="true" pn="section-toc.1-1.5.2.3.1"><xref derivedContent="5.3" format="counter" sectionFormat="of" target="section-5.3"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-rro-processing">RRO Processing</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.6"> <t keepWithNext="true" pn="section-toc.1-1.6.1"><xref derivedContent="6" format="counter" sectionFormat="of" target="section-6"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-management-considerations">Management Considerations</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.6.2"> <li pn="section-toc.1-1.6.2.1"> <t keepWithNext="true" pn="section-toc.1-1.6.2.1.1"><xref derivedContent="6.1" format="counter" sectionFormat="of" target="section-6.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-controlling-the-path-setup-">Controlling the Path Setup Type</xref></t> </li> <li pn="section-toc.1-1.6.2.2"> <t keepWithNext="true" pn="section-toc.1-1.6.2.2.1"><xref derivedContent="6.2" format="counter" sectionFormat="of" target="section-6.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-migrating-a-network-to-use-">Migrating a Network to Use PCEP Segment-Routed Paths</xref></t> </li> <li pn="section-toc.1-1.6.2.3"> <t keepWithNext="true" pn="section-toc.1-1.6.2.3.1"><xref derivedContent="6.3" format="counter" sectionFormat="of" target="section-6.3"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-verification-of-network-ope">Verification of Network Operation</xref></t> </li> <li pn="section-toc.1-1.6.2.4"> <t keepWithNext="true" pn="section-toc.1-1.6.2.4.1"><xref derivedContent="6.4" format="counter" sectionFormat="of" target="section-6.4"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-relationship-to-existing-ma">Relationship to Existing Management Models</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.7"> <t keepWithNext="true" pn="section-toc.1-1.7.1"><xref derivedContent="7" format="counter" sectionFormat="of" target="section-7"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-security-considerations">Security Considerations</xref></t> </li> <li pn="section-toc.1-1.8"> <t keepWithNext="true" pn="section-toc.1-1.8.1"><xref derivedContent="8" format="counter" sectionFormat="of" target="section-8"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-iana-considerations">IANA Considerations</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.8.2"> <li pn="section-toc.1-1.8.2.1"> <t keepWithNext="true" pn="section-toc.1-1.8.2.1.1"><xref derivedContent="8.1" format="counter" sectionFormat="of" target="section-8.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-pcep-ero-and-rro-subobjects">PCEP ERO and RRO Subobjects</xref></t> </li> <li pn="section-toc.1-1.8.2.2"> <t keepWithNext="true" pn="section-toc.1-1.8.2.2.1"><xref derivedContent="8.2" format="counter" sectionFormat="of" target="section-8.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-new-nai-type-registry">New NAI Type Registry</xref></t> </li> <li pn="section-toc.1-1.8.2.3"> <t keepWithNext="true" pn="section-toc.1-1.8.2.3.1"><xref derivedContent="8.3" format="counter" sectionFormat="of" target="section-8.3"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-new-sr-ero-flag-registry">New SR-ERO Flag Registry</xref></t> </li> <li pn="section-toc.1-1.8.2.4"> <t keepWithNext="true" pn="section-toc.1-1.8.2.4.1"><xref derivedContent="8.4" format="counter" sectionFormat="of" target="section-8.4"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-pcep-error-object">PCEP-Error Object</xref></t> </li> <li pn="section-toc.1-1.8.2.5"> <t keepWithNext="true" pn="section-toc.1-1.8.2.5.1"><xref derivedContent="8.5" format="counter" sectionFormat="of" target="section-8.5"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-pcep-tlv-type-indicators">PCEP TLV Type Indicators</xref></t> </li> <li pn="section-toc.1-1.8.2.6"> <t keepWithNext="true" pn="section-toc.1-1.8.2.6.1"><xref derivedContent="8.6" format="counter" sectionFormat="of" target="section-8.6"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-path-setup-type-capability-">PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators</xref></t> </li> <li pn="section-toc.1-1.8.2.7"> <t keepWithNext="true" pn="section-toc.1-1.8.2.7.1"><xref derivedContent="8.7" format="counter" sectionFormat="of" target="section-8.7"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-new-path-setup-type">New Path Setup Type</xref></t> </li> <li pn="section-toc.1-1.8.2.8"> <t keepWithNext="true" pn="section-toc.1-1.8.2.8.1"><xref derivedContent="8.8" format="counter" sectionFormat="of" target="section-8.8"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-new-metric-type">New Metric Type</xref></t> </li> <li pn="section-toc.1-1.8.2.9"> <t keepWithNext="true" pn="section-toc.1-1.8.2.9.1"><xref derivedContent="8.9" format="counter" sectionFormat="of" target="section-8.9"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-sr-pce-capability-flags">SR PCE Capability Flags</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.9"> <t keepWithNext="true" pn="section-toc.1-1.9.1"><xref derivedContent="9" format="counter" sectionFormat="of" target="section-9"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-references">References</xref></t> <ul bare="true" empty="true" indent="2" spacing="compact" pn="section-toc.1-1.9.2"> <li pn="section-toc.1-1.9.2.1"> <t keepWithNext="true" pn="section-toc.1-1.9.2.1.1"><xref derivedContent="9.1" format="counter" sectionFormat="of" target="section-9.1"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-normative-references">Normative References</xref></t> </li> <li pn="section-toc.1-1.9.2.2"> <t keepWithNext="true" pn="section-toc.1-1.9.2.2.1"><xref derivedContent="9.2" format="counter" sectionFormat="of" target="section-9.2"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-informative-references">Informative References</xref></t> </li> </ul> </li> <li pn="section-toc.1-1.10"> <t keepWithNext="true" pn="section-toc.1-1.10.1"><xref derivedContent="Appendix A" format="default" sectionFormat="of" target="section-appendix.a"/>. <xref derivedContent="" format="title" sectionFormat="of" target="name-compatibility-with-early-im">Compatibility with Early Implementations</xref></t> </li> <li pn="section-toc.1-1.11"> <t keepWithNext="true" pn="section-toc.1-1.11.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="" format="title" sectionFormat="of" target="name-acknowledgements">Acknowledgements</xref></t> </li> <li pn="section-toc.1-1.12"> <t keepWithNext="true" pn="section-toc.1-1.12.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.c"/><xref derivedContent="" format="title" sectionFormat="of" target="name-contributors">Contributors</xref></t> </li> <li pn="section-toc.1-1.13"> <t keepWithNext="true" pn="section-toc.1-1.13.1"><xref derivedContent="" format="none" sectionFormat="of" target="section-appendix.d"/><xref derivedContent="" format="title" sectionFormat="of" target="name-authors-addresses">Authors' Addresses</xref></t> </li> </ul> </section> </toc> </front> <middle> <sectiontitle="Introduction"> <t>Segmentnumbered="true" toc="include" removeInRFC="false" pn="section-1"> <name slugifiedName="name-introduction">Introduction</name> <t pn="section-1-1">Segment Routing (SR) leverages thesource routingsource-routing paradigm. Using SR, a source node steers a packet through a path without relying on hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is specified as an ordered list of instructions called "segments". Each segment is an instruction to route the packet to a specific place in thenetwork,network or to perform a function on the packet. A database of segments can be distributed through the network using a routing protocol (such as IS-IS or OSPF) or by any other means. Several types ofsegmentsegments are defined. A node segment uniquely identifies a specific node in the SR domain. Each router in the SR domain associates a node segment with an ECMP-aware shortest path to the node that it identifies. An adjacency segment represents a unidirectional adjacency. An adjacency segment is local to the nodewhichthat advertises it. Both node segments and adjacency segments can be used for SR.</t><t><xref target="RFC8402"/><t pn="section-1-2"><xref target="RFC8402" format="default" sectionFormat="of" derivedContent="RFC8402"/> describes the SR architecture. The corresponding IS-IS and OSPF extensions are specified in <xreftarget="I-D.ietf-isis-segment-routing-extensions"/>target="RFC8667" format="default" sectionFormat="of" derivedContent="RFC8667"/> and <xreftarget="I-D.ietf-ospf-segment-routing-extensions"/>,target="RFC8665" format="default" sectionFormat="of" derivedContent="RFC8665"/>, respectively.</t><t>The<t pn="section-1-3">The SR architecture can be implemented using either an MPLS forwarding plane <xreftarget="I-D.ietf-spring-segment-routing-mpls"/>target="RFC8660" format="default" sectionFormat="of" derivedContent="RFC8660"/> or an IPv6 forwarding plane <xreftarget="I-D.ietf-6man-segment-routing-header"/>.target="I-D.ietf-6man-segment-routing-header" format="default" sectionFormat="of" derivedContent="IPv6-SRH"/>. The MPLS forwarding plane can be applied to SR without anychange,change; in whichcasecase, an SR path corresponds to an MPLS Label Switching Path (LSP). This document is relevant to the MPLS forwarding plane only. In this document, "Node-SID" and"Adjacency-SID""Adj-SID" denote the Node Segment Identifier and Adjacency SegmentIdentifierIdentifier, respectively.</t><t>A Segment Routing<t pn="section-1-4">An SR path(SR path)can be derived from an IGP Shortest Path Tree (SPT).SR-TESegment Routing Traffic-Engineering (SR-TE) paths may not follow an IGP SPT. Such paths may be chosen by a suitable network planning tool and provisioned on the ingress node of the SR-TE path.</t><t> <xref target="RFC5440"/><t pn="section-1-5"><xref target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/> describes the Path Computation Element Communication Protocol (PCEP) for communication between a Path Computation Client (PCC) and a Path Computation Element (PCE) or between a pair of PCEs. A PCE computes paths for MPLSTraffic EngineeringTraffic-Engineering (MPLS-TE) LSPs(MPLS-TE LSPs)based on various constraints and optimization criteria. <xreftarget="RFC8231"/>target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/> specifies extensions to PCEP that allow a stateful PCE to compute and recommend network paths in compliance with <xreftarget="RFC4657"/> andtarget="RFC4657" format="default" sectionFormat="of" derivedContent="RFC4657"/>. It also defines objects and TLVs for MPLS-TE LSPs. Stateful PCEP extensions provide synchronization of LSP state between a PCC and a PCE or between a pair of PCEs, delegation of LSP control, reporting of LSP state from a PCC to a PCE,controllingand control of the setup and path routing of an LSP from a PCE to a PCC. Stateful PCEP extensions are intended for an operational model in which LSPs are configured on the PCC, and control over them is delegated to the PCE.</t><t>A<t pn="section-1-6">A mechanism to dynamically initiate LSPs on a PCC based on the requests from a stateful PCE or a controller using stateful PCE is specified in <xreftarget="RFC8281"/>.target="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/>. This mechanism is useful inSoftware DefinedSoftware-Defined Networking (SDN) applications, such as on-demandengineering,engineering or bandwidth calendaring <xreftarget="RFC8413"/>.</t> <t>Ittarget="RFC8413" format="default" sectionFormat="of" derivedContent="RFC8413"/>.</t> <t pn="section-1-7">It is possible to use a stateful PCE for computing one or more SR-TEpathspaths, taking into account various constraints and objective functions. Once a path is chosen, the stateful PCE can initiate an SR-TE path on a PCC using the PCEP extensions specified in <xreftarget="RFC8281"/> usingtarget="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/> and theSR specificSR-specific PCEP extensions specified in this document. Additionally, using procedures described in this document, a PCC can request an SR path from either a stateful or a stateless PCE.</t><t>This<t pn="section-1-8">This specification relies on the procedures specified in <xreftarget="RFC8408"/>target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/> to exchange thesegment routingSegment Routing capability and to specify that the path setup type of an LSP issegment routing.Segment Routing. This specification also updates <xreftarget="RFC8408"/>target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/> to clarify the use of sub-TLVs in the PATH-SETUP-TYPE-CAPABILITY TLV. See <xreftarget="pst-cap-tlv"/>target="pst-cap-tlv" format="default" sectionFormat="of" derivedContent="Section 4.1.1"/> for details.</t><t>This<t pn="section-1-9">This specification provides a mechanism for a network controller (acting as a PCE) to instantiate candidate paths for an SR Policy onto a head-end node (acting as a PCC) using PCEP. For more information on the SR Policy Architecture, see <xreftarget="I-D.ietf-spring-segment-routing-policy"/>.</t>target="I-D.ietf-spring-segment-routing-policy" format="default" sectionFormat="of" derivedContent="SR-POLICY"/>.</t> </section><!-- Introduction --><sectiontitle="Terminology"> <t>Thenumbered="true" toc="include" removeInRFC="false" pn="section-2"> <name slugifiedName="name-terminology">Terminology</name> <t pn="section-2-1">The followingterminologies areterminology is used in this document:<list style="hanging"> <t hangText="ERO:"></t> <dl newline="false" spacing="normal" indent="8" pn="section-2-2"> <dt pn="section-2-2.1">ERO:</dt> <dd pn="section-2-2.2"> Explicit RouteObject</t> <t hangText="IGP:">Object</dd> <dt pn="section-2-2.3">IGP:</dt> <dd pn="section-2-2.4"> Interior GatewayProtocol</t> <t hangText="IS-IS:">Protocol</dd> <dt pn="section-2-2.5">IS-IS:</dt> <dd pn="section-2-2.6"> Intermediate System to IntermediateSystem</t> <t hangText="LSR:">System</dd> <dt pn="section-2-2.7">LSR:</dt> <dd pn="section-2-2.8"> Label SwitchingRouter</t> <t hangText="MSD:">Router</dd> <dt pn="section-2-2.9">MSD:</dt> <dd pn="section-2-2.10"> Base MPLS Imposition Maximum SID Depth, as defined in <xreftarget="RFC8491"/></t> <t hangText="NAI:">target="RFC8491" format="default" sectionFormat="of" derivedContent="RFC8491"/></dd> <dt pn="section-2-2.11">NAI:</dt> <dd pn="section-2-2.12"> Node or AdjacencyIdentifier</t> <t hangText="OSPF:">Identifier</dd> <dt pn="section-2-2.13">OSPF:</dt> <dd pn="section-2-2.14"> Open Shortest PathFirst</t> <t hangText="PCC:">First</dd> <dt pn="section-2-2.15">PCC:</dt> <dd pn="section-2-2.16"> Path ComputationClient</t> <t hangText="PCE:">Client</dd> <dt pn="section-2-2.17">PCE:</dt> <dd pn="section-2-2.18"> Path ComputationElement</t> <t hangText="PCEP:">Element</dd> <dt pn="section-2-2.19">PCEP:</dt> <dd pn="section-2-2.20"> Path Computation Element CommunicationProtocol</t> <t hangText="RRO:">Protocol</dd> <dt pn="section-2-2.21">RRO:</dt> <dd pn="section-2-2.22"> Record RouteObject</t> <t hangText="SID:">Object</dd> <dt pn="section-2-2.23">SID:</dt> <dd pn="section-2-2.24"> SegmentIdentifier</t> <t hangText="SR:">Identifier</dd> <dt pn="section-2-2.25">SR:</dt> <dd pn="section-2-2.26"> SegmentRouting</t> <t hangText="SR-DB:">Routing</dd> <dt pn="section-2-2.27">SR-DB:</dt> <dd pn="section-2-2.28"> Segment Routing Database: the collection of SRGBs,SRLBsSRLBs, and SIDs and the objects they map to, advertised by alink state IGP</t> <t hangText="SRGB:">link-state IGP</dd> <dt pn="section-2-2.29">SR-TE:</dt> <dd pn="section-2-2.30"> Segment Routing Traffic Engineering</dd> <dt pn="section-2-2.31">SRGB:</dt> <dd pn="section-2-2.32"> Segment Routing GlobalBlock</t> <t hangText="SRLB:">Block</dd> <dt pn="section-2-2.33">SRLB:</dt> <dd pn="section-2-2.34"> Segment Routing LocalBlock</t>Block</dd> </dl> <section numbered="true" toc="include" removeInRFC="false" pn="section-2.1"> <name slugifiedName="name-requirements-language">Requirements Language</name> <thangText="SR-TE:"> Segment Routing Traffic Engineering</t> </list>pn="section-2.1-1">The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in BCP 14 <xref target="RFC2119" format="default" sectionFormat="of" derivedContent="RFC2119"/> <xref target="RFC8174" format="default" sectionFormat="of" derivedContent="RFC8174"/> when, and only when, they appear in all capitals, as shown here. </t> </section><!-- Terminology --></section> <section anchor="Operation-Overview"title="Overviewnumbered="true" toc="include" removeInRFC="false" pn="section-3"> <name slugifiedName="name-overview-of-pcep-operation-">Overview of PCEP Operation in SRNetworks"> <t>InNetworks</name> <t pn="section-3-1">In an SR network, the ingress node of an SR path prepends an SR header to all outgoing packets. The SR header consists of a list of SIDs (or MPLS labels in the context of this document). The header has all necessary information so that, in combination with the information distributed by the IGP, the packets can be guided from the ingress node to the egress node of the path; hence, there is no need for any signaling protocol. </t><t><t pn="section-3-2"> In PCEP messages, LSP route information is carried in the Explicit Route Object (ERO), which consists of a sequence of subobjects. SR-TE paths computed by a PCE can be represented in an ERO in one of the following forms:<list style="symbols"> <t>An</t> <ul spacing="normal" bare="false" empty="false" pn="section-3-3"> <li pn="section-3-3.1">An ordered set of IP addresses representing networknodes/links.</t> <t>Annodes/links.</li> <li pn="section-3-3.2">An ordered set of SIDs, with or without the corresponding IPaddresses.</t> <t>Anaddresses.</li> <li pn="section-3-3.3">An ordered set of MPLS labels, with or without corresponding IPaddress.</t> </list>addresses.</li> </ul> <t pn="section-3-4"> The PCC converts these into an MPLS label stack and next hop, as described in <xreftarget="SR-ERO-INTERPRET"/>.target="SR-ERO-INTERPRET" format="default" sectionFormat="of" derivedContent="Section 5.2.2"/>. </t><t>This<t pn="section-3-5">This document defines a new ERO subobject denoted by "SR-ERO subobject" that is capable of carrying a SID as well as the identity of the node/adjacency represented by the SID. SR-capable PCEP speakers should be able to generate and/or process such an ERO subobject. An ERO containing SR-ERO subobjects can be included in the PCEP Path Computation Reply (PCRep) message defined in <xreftarget="RFC5440"/>,target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>, thePCEPPath Computation LSP Initiate Requestmessage(PCInitiate) message defined in <xreftarget="RFC8281"/>, as well as intarget="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/>, and thePCEP LSPPath Computation Update Request (PCUpd) andPCEP LSPPath Computation State Report (PCRpt) messages for LSPs defined in <xreftarget="RFC8231"/>.</t> <t>Whentarget="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>.</t> <t pn="section-3-6">When a PCEP session between a PCC and a PCE is established, both PCEP speakers exchange their capabilities to indicate their ability to support SR-specific functionality.</t><t>A<t pn="section-3-7">A PCE can update an LSP that is initially established via RSVP-TE signaling to use an SR-TEpath,path by sending a PCUpd to the PCC that delegated the LSP to it(<xref target="RFC8231"/>).<xref target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>. A PCC can update an undelegated LSP that is initially established via RSVP-TE signaling to use an SR-TE path as follows. First, it requests an SR-TEPathpath from a PCE by sending aPCReqPath Computation Request (PCReq) message. If it receives a suitable path, it establishes the path in the dataplane,plane and then tears down the original RSVP-TE path. If the PCE is stateful, then the PCC sends PCRpt messages indicating that the new path is set up and the old path is torn down, per <xreftarget="RFC8231"/>.</t> <t>Similarly,target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>.</t> <t pn="section-3-8">Similarly, a PCE or PCC can update an LSP initially created with an SR-TE path to use RSVP-TE signaling, if necessary. This capability is useful for rolling back a change when a network is migrated from RSVP-TE to SR-TE technology.</t><t>A<t pn="section-3-9">A PCCMAY<bcp14>MAY</bcp14> includean RROa Record Route Object (RRO) containing the recorded LSP in PCReq and PCRpt messages as specified in <xreftarget="RFC5440"/>target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/> and <xreftarget="RFC8231"/>,target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>, respectively. This document defines a new RRO subobject for SR networks. The methods used by a PCC to record the SR-TE LSP are outside the scope of this document.</t><t>In<t pn="section-3-10">In summary, this document:<list style="symbols"> <t>Defines</t> <ul spacing="normal" bare="false" empty="false" pn="section-3-11"> <li pn="section-3-11.1">Defines a new ERO subobject, a new RROsubobjectsubobject, and new PCEP errorcodes.</t> <t>Specifiescodes.</li> <li pn="section-3-11.2">Specifies how two PCEP speakers can establish a PCEP session that can carry information about SR-TEpaths.</t> <t>Specifiespaths.</li> <li pn="section-3-11.3">Specifies processing rules for the EROsubobject.</t> <t>Definessubobject.</li> <li pn="section-3-11.4">Defines a new path setup type to be used in the PATH-SETUP-TYPE and PATH-SETUP-TYPE-CAPABILITY TLVs(<xref target="RFC8408"/>).</t> <t>Defines<xref target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/>.</li> <li pn="section-3-11.5">Defines a new sub-TLV for the PATH-SETUP-TYPE-CAPABILITYTLV.</t> </list> </t> <t>TheTLV.</li> </ul> <t pn="section-3-12">The extensions specified in this document complement the existing PCEP specifications to support SR-TE paths. As such, the PCEP messages (e.g.,Path Computation Request, Path Computation Reply, Path Computation Report, Path Computation Update, Path Computation Initiate, etc.,)PCReq, PCRep, PCRpt, PCUpd, PCInitiate, etc.) are formatted according to <xreftarget="RFC5440"/>, <xref target="RFC8231"/>, <xref target="RFC8281"/>,target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>, <xref target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>, <xref target="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/>, and any other applicable PCEP specifications.</t> </section><!-- Overview of PCEP Operation in SR Networks --><section anchor="object-formats"title="Object Formats">numbered="true" toc="include" removeInRFC="false" pn="section-4"> <name slugifiedName="name-object-formats">Object Formats</name> <section anchor="open-object-fmt"title="Thenumbered="true" toc="include" removeInRFC="false" pn="section-4.1"> <name slugifiedName="name-the-open-object">The OPENObject">Object</name> <section anchor="pst-cap-tlv"title="Thenumbered="true" toc="include" removeInRFC="false" pn="section-4.1.1"> <name slugifiedName="name-the-path-setup-type-capabil">The Path Setup Type CapabilityTLV"> <t><xref target="RFC8408"/>TLV</name> <t pn="section-4.1.1-1"><xref target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/> defines the PATH-SETUP-TYPE-CAPABILITY TLV for use in the OPEN object. The PATH-SETUP-TYPE-CAPABILITY TLV contains an optional list ofsub-TLVssub-TLVs, which are intended to convey parameters that are associated with the path setup types supported by a PCEP speaker.</t><t>This<t pn="section-4.1.1-2">This specification updates <xreftarget="RFC8408"/>,target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/> as follows. It creates a new registrywhichthat defines the valid type indicators of the sub-TLVs of the PATH-SETUP-TYPE-CAPABILITY TLV (see <xreftarget="IANA-subTLV-Type-Indicators"/>).target="IANA-subTLV-Type-Indicators" format="default" sectionFormat="of" derivedContent="Section 8.6"/>). A PCEP speakerMUST NOT<bcp14>MUST NOT</bcp14> include a sub-TLV in the PATH-SETUP-TYPE-CAPABILITY TLV unless it appears in this registry. If a PCEP speaker receives a sub-TLV whose type indicator does not match one of those from theregistry,registry orelseis notrecognisedrecognized by the speaker, then the speakerMUST<bcp14>MUST</bcp14> ignore the sub-TLV.</t> </section> <section anchor="cap-negotiation"title="Thenumbered="true" toc="include" removeInRFC="false" pn="section-4.1.2"> <name slugifiedName="name-the-sr-pce-capability-sub-t">The SR PCE Capabilitysub-TLV"> <t>ThisSub-TLV</name> <t pn="section-4.1.2-1">This document defines a new Path Setup Type (PST) for SR, as follows:<list style="symbols"> <t>PST = 1: Path</t> <ul spacing="normal" empty="true" bare="false" pn="section-4.1.2-2"> <li pn="section-4.1.2-2.1"> <dl newline="false" spacing="normal" pn="section-4.1.2-2.1.1"> <dt pn="section-4.1.2-2.1.1.1">PST = 1:</dt> <dd pn="section-4.1.2-2.1.1.2">Traffic-engineering path issetupset up using SegmentRouting Traffic Engineering.</t> </list> </t> <t>ARouting.</dd> </dl> </li> </ul> <t pn="section-4.1.2-3">A PCEP speakerSHOULD<bcp14>SHOULD</bcp14> indicate its support of the function described in this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN object with this new PST included in the PST list.</t><t>This<t pn="section-4.1.2-4">This document also defines the SR-PCE-CAPABILITY sub-TLV. PCEP speakers use this sub-TLV to exchange information about their SR capability. If a PCEP speaker includes PST=1 in the PSTListlist of the PATH-SETUP-TYPE-CAPABILITYTLVTLV, then itMUST<bcp14>MUST</bcp14> also include the SR-PCE-CAPABILITY sub-TLV inside the PATH-SETUP-TYPE-CAPABILITY TLV.</t><t>The<t pn="section-4.1.2-5">The format of the SR-PCE-CAPABILITY sub-TLV is shown in the following figure:</t> <figure anchor="Capability-TLV-Fmt"title="SR-PCE-CAPABILITY sub-TLV format">align="left" suppress-title="false" pn="figure-1"> <name slugifiedName="name-sr-pce-capability-sub-tlv-f">SR-PCE-CAPABILITY Sub-TLV Format</name> <artworkalign="center"><![CDATA[align="center" name="" type="" alt="" pn="section-4.1.2-6.1"> 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=TBD11Type=26 | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Flags |N|X| MSD |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure><t>The code point<t pn="section-4.1.2-7">The codepoint for the TLV type isTBD11.26. The TLV length is 4 octets.</t><t>The<t pn="section-4.1.2-8">The 32-bit value is formatted as follows.<list style="hanging"> <t hangText="Reserved:"> MUST</t> <dl newline="false" spacing="normal" pn="section-4.1.2-9"> <dt pn="section-4.1.2-9.1">Reserved:</dt> <dd pn="section-4.1.2-9.2"> <bcp14>MUST</bcp14> be set to zero by the sender andMUST<bcp14>MUST</bcp14> be ignored by thereceiver.</t>receiver.</dd> <dt pn="section-4.1.2-9.3">Flags:</dt> <dd pn="section-4.1.2-9.4"> <thangText="Flags:">pn="section-4.1.2-9.4.1"> This document defines the following flag bits. The other bitsMUST<bcp14>MUST</bcp14> be set to zero by the sender andMUST<bcp14>MUST</bcp14> be ignored by the receiver.<list style="symbols"> <t>N: A</t> <ul spacing="normal" empty="true" bare="false" pn="section-4.1.2-9.4.2"> <li pn="section-4.1.2-9.4.2.1"> <dl indent="5" newline="false" spacing="normal" pn="section-4.1.2-9.4.2.1.1"> <dt pn="section-4.1.2-9.4.2.1.1.1">N:</dt> <dd pn="section-4.1.2-9.4.2.1.1.2">A PCC sets this flag bit to 1 to indicate that it is capable of resolving a Node or Adjacency Identifier (NAI) to aSID.</t> <t>X: ASID.</dd> <dt pn="section-4.1.2-9.4.2.1.1.3">X:</dt> <dd pn="section-4.1.2-9.4.2.1.1.4">A PCC sets this flag bit to 1 to indicate that it does not impose any limit on theMSD.</t> </list> </t> <t hangText="MaximumMSD.</dd> </dl> </li> </ul> </dd> <dt pn="section-4.1.2-9.5">Maximum SID Depth(MSD):">(MSD):</dt> <dd pn="section-4.1.2-9.6"> specifies the maximum number of SIDs (MPLS label stack depth in the context of this document) that a PCC is capable of imposing on a packet. <xreftarget="SR-CAP-PROCESS"/>target="SR-CAP-PROCESS" format="default" sectionFormat="of" derivedContent="Section 5.1"/> explains the relationship between this field and theX flag.</t> </list> </t>X-Flag.</dd> </dl> </section> </section> <section anchor="rp-object-fmt"title="Thenumbered="true" toc="include" removeInRFC="false" pn="section-4.2"> <name slugifiedName="name-the-rp-srp-object">The RP/SRPObject"> <t>ToObject</name> <t pn="section-4.2-1">To set up an SR-TE LSP using SR, theRP (Request Parameters)Request Parameter (RP) orSRP (StatefulStateful PCE RequestParameters)Parameter (SRP) objectMUST<bcp14>MUST</bcp14> include the PATH-SETUP-TYPE TLV, specified in <xreftarget="RFC8408"/>,target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/>, with the PST set to 1(path(and path setup using SR-TE).</t><t>The<t pn="section-4.2-2">The LSP-IDENTIFIERS TLVMAY<bcp14>MAY</bcp14> be present for the above PST type.</t> </section> <section anchor="SR-ERO"title="ERO"> <t>Annumbered="true" toc="include" removeInRFC="false" pn="section-4.3"> <name slugifiedName="name-ero">ERO</name> <t pn="section-4.3-1">An SR-TE path consists of one or more SIDs where each SIDMAY<bcp14>MAY</bcp14> be associated with the identifier that represents the node or adjacency corresponding to the SID. This identifier is referred to as the'Node or Adjacency Identifier' (NAI).NAI. As described later,aan NAI can be represented in various formats (e.g., IPv4 address, IPv6 address, etc). Furthermore,aan NAI is used for troubleshooting purposes and, if necessary, to derive a SID value as described below.</t><t>The<t pn="section-4.3-2">The ERO specified in <xreftarget="RFC5440"/>target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/> is used to carry SR-TE path information. In order to carry a SID and/or NAI, this document defines a new ERO subobject referred to as the "SR-EROsubobject"subobject", whose format is specified in the following section. An ERO carrying an SR-TE path consists of one or more ERO subobjects, andMUSTit <bcp14>MUST</bcp14> carry only SR-ERO subobjects. Note that an SR-ERO subobject does not need to have both the SID and NAI. However, at least one of themMUST<bcp14>MUST</bcp14> be present.</t><t>When<t pn="section-4.3-3">When building the MPLS label stack from ERO, a PCCMUST<bcp14>MUST</bcp14> assume that SR-ERO subobjects are organized as a last-in-first-out stack. The first subobject relative to the beginning of ERO contains the information about the topmost label. The last subobject contains information about the bottommost label.</t> <section anchor="SR-ERO-SUB"title="SR-ERO Subobject"> <t>Annumbered="true" toc="include" removeInRFC="false" pn="section-4.3.1"> <name slugifiedName="name-sr-ero-subobject">SR-ERO Subobject</name> <t pn="section-4.3.1-1">An SR-ERO subobject is formatted as shown in the following diagram.</t> <figure anchor="SR-ERO-SUBOBJECT"title="SR-ERO subobject format"> <artwork><![CDATA[align="left" suppress-title="false" pn="figure-2"> <name slugifiedName="name-sr-ero-subobject-format">SR-ERO Subobject Format</name> <artwork name="" type="" align="left" alt="" pn="section-4.3.1-2.1"> 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type=36 | Length | NT | Flags |F|S|C|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NAI (variable, optional) //+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure><t>The<t pn="section-4.3.1-3">The fields in the SR-EROSubobjectsubobject are as follows:<list style="hanging"> <t hangText="The 'L' Flag:"></t> <dl newline="false" spacing="normal" pn="section-4.3.1-4"> <dt pn="section-4.3.1-4.1">The L-Flag:</dt> <dd pn="section-4.3.1-4.2"> Indicates whether the subobject represents aloose-hoploose hop in the LSP <xreftarget="RFC3209"/>.target="RFC3209" format="default" sectionFormat="of" derivedContent="RFC3209"/>. If this flag is set to zero, a PCCMUST NOT<bcp14>MUST NOT</bcp14> overwrite the SID value present in the SR-ERO subobject. Otherwise, a PCCMAY<bcp14>MAY</bcp14> expand or replace one or more SID values in the received SR-ERO based on its localpolicy.</t> <t hangText="Type:">policy.</dd> <dt pn="section-4.3.1-4.3">Type:</dt> <dd pn="section-4.3.1-4.4"> Set to 36.</t> <t hangText="Length:"></dd> <dt pn="section-4.3.1-4.5">Length:</dt> <dd pn="section-4.3.1-4.6"> Contains the total length of the subobject in octets. The LengthMUST<bcp14>MUST</bcp14> be at least8,8 andMUST<bcp14>MUST</bcp14> be a multiple of 4. An SR-ERO subobjectMUST<bcp14>MUST</bcp14> contain at least oneof aSID oranNAI. The flags described below indicate whether the SID or NAI fields areabsent.</t> <t hangText="NAIabsent.</dd> <dt pn="section-4.3.1-4.7">NAI Type(NT):"> Indicates(NT):</dt> <dd pn="section-4.3.1-4.8"> <t pn="section-4.3.1-4.8.1">Indicates the type and format of the NAI contained in the object body, if any is present. If the F bit is set to zero (seebelow)below), then the NT field has no meaning andMUST<bcp14>MUST</bcp14> be ignored by the receiver. This document describes the following NT values:</t><t><list style="hanging"> <t hangText="NT=0">The<dl newline="false" spacing="normal" pn="section-4.3.1-4.8.2"> <dt pn="section-4.3.1-4.8.2.1">NT=0</dt> <dd pn="section-4.3.1-4.8.2.2">The NAI isabsent.</t> <t hangText="NT=1">Theabsent.</dd> <dt pn="section-4.3.1-4.8.2.3">NT=1</dt> <dd pn="section-4.3.1-4.8.2.4">The NAI is an IPv4 nodeID.</t> <t hangText="NT=2">TheID.</dd> <dt pn="section-4.3.1-4.8.2.5">NT=2</dt> <dd pn="section-4.3.1-4.8.2.6">The NAI is an IPv6 nodeID.</t> <t hangText="NT=3">TheID.</dd> <dt pn="section-4.3.1-4.8.2.7">NT=3</dt> <dd pn="section-4.3.1-4.8.2.8">The NAI is an IPv4adjacency.</t> <t hangText="NT=4">Theadjacency.</dd> <dt pn="section-4.3.1-4.8.2.9">NT=4</dt> <dd pn="section-4.3.1-4.8.2.10">The NAI is an IPv6 adjacency with global IPv6addresses.</t> <t hangText="NT=5">Theaddresses.</dd> <dt pn="section-4.3.1-4.8.2.11">NT=5</dt> <dd pn="section-4.3.1-4.8.2.12">The NAI is an unnumbered adjacency with IPv4 nodeIDs.</t> <t hangText="NT=6">TheIDs.</dd> <dt pn="section-4.3.1-4.8.2.13">NT=6</dt> <dd pn="section-4.3.1-4.8.2.14">The NAI is an IPv6 adjacency with link-local IPv6addresses.</t> </list> </t>addresses.</dd> </dl> </dd> <dt pn="section-4.3.1-4.9">Flags:</dt> <dd pn="section-4.3.1-4.10"> <thangText="Flags:">pn="section-4.3.1-4.10.1"> Used to carry additional information pertaining to the SID. This document defines the following flag bits. The other bitsMUST<bcp14>MUST</bcp14> be set to zero by the sender andMUST<bcp14>MUST</bcp14> be ignored by the receiver.<list style="symbols"> <t>M: If</t> <dl newline="false" spacing="normal" indent="5" pn="section-4.3.1-4.10.2"> <dt pn="section-4.3.1-4.10.2.1">M:</dt> <dd pn="section-4.3.1-4.10.2.2">If this bit is set to 1, the SID value represents an MPLS label stack entry as specified in <xreftarget="RFC3032"/>.target="RFC3032" format="default" sectionFormat="of" derivedContent="RFC3032"/>. Otherwise, the SID value is an administratively configured valuewhichthat represents an index into an MPLS label space (either SRGB or SRLB) per <xreftarget="RFC8402"/>.</t> <t>C: Iftarget="RFC8402" format="default" sectionFormat="of" derivedContent="RFC8402"/>.</dd> <dt pn="section-4.3.1-4.10.2.3">C:</dt> <dd pn="section-4.3.1-4.10.2.4">If the M bit and the C bit are both set to 1, then the TC, S, and TTL fields in the MPLS label stack entry are specified by the PCE. However, a PCCMAY<bcp14>MAY</bcp14> choose to override these values according to its local policy and MPLS forwarding rules. If the M bit is set to 1 but the C bit is set to zero, then the TC, S, and TTL fieldsMUST<bcp14>MUST</bcp14> be ignored by the PCC. The PCCMUST<bcp14>MUST</bcp14> set these fields according to its local policy and MPLS forwarding rules. If the M bit is set tozerozero, then the C bitMUST<bcp14>MUST</bcp14> be set tozero.</t> <t>S: Whenzero.</dd> <dt pn="section-4.3.1-4.10.2.5">S:</dt> <dd pn="section-4.3.1-4.10.2.6">When this bit is set to 1, the SID value in the subobject body is absent. In this case, the PCC is responsible for choosing the SID value, e.g., by looking it up in the SR-DB using the NAIwhich,that, in this case,MUST<bcp14>MUST</bcp14> be present in the subobject. If the S bit is set to11, then the M and C bitsMUST<bcp14>MUST</bcp14> be set tozero.</t> <t>F: Whenzero.</dd> <dt pn="section-4.3.1-4.10.2.7">F:</dt> <dd pn="section-4.3.1-4.10.2.8">When this bit is set to 1, the NAI value in the subobject body is absent. The F bitMUST<bcp14>MUST</bcp14> be set to 1 ifNT=0, and otherwise MUSTNT=0; otherwise, it <bcp14>MUST</bcp14> be set to zero. The S and F bitsMUST NOT<bcp14>MUST NOT</bcp14> both be set to1.</t> </list> </t>1.</dd> </dl> </dd> <dt pn="section-4.3.1-4.11">SID:</dt> <dd pn="section-4.3.1-4.12"> <thangText="SID:">pn="section-4.3.1-4.12.1"> The Segment Identifier. Depending on the M bit, it contains either:<list style="symbols"> <t>A 4 octet</t> <ul spacing="normal" bare="false" empty="false" pn="section-4.3.1-4.12.2"> <li pn="section-4.3.1-4.12.2.1">A 4-octet index defining the offset into an MPLS label space per <xreftarget="RFC8402"/>.</t> <t>A 4 octettarget="RFC8402" format="default" sectionFormat="of" derivedContent="RFC8402"/> or</li> <li pn="section-4.3.1-4.12.2.2">A 4-octet MPLSLabel Stack Entry,label stack entry, where the 20 most significant bits encode the label value per <xreftarget="RFC3032"/>.</t> </list> </t> <t hangText="NAI:">target="RFC3032" format="default" sectionFormat="of" derivedContent="RFC3032"/>.</li> </ul> </dd> <dt pn="section-4.3.1-4.13">NAI:</dt> <dd pn="section-4.3.1-4.14"> The NAI associated with the SID. The NAI's format depends on the value in the NTfield,field and is described in the followingsection.</t> </list>section.</dd> </dl> <t pn="section-4.3.1-5"> At least oneof theSID andtheNAIMUST<bcp14>MUST</bcp14> be included in the SR-ERO subobject, and bothMAY<bcp14>MAY</bcp14> be included. </t> </section> <section anchor="SR-ERO-NODAL-32"title="NAInumbered="true" toc="include" removeInRFC="false" pn="section-4.3.2"> <name slugifiedName="name-nai-associated-with-sid">NAI Associated withSID"> <t>ThisSID</name> <t pn="section-4.3.2-1">This document defines the following NAIs:<list style="hanging"> <t hangText="'IPv4</t> <dl newline="false" spacing="normal" pn="section-4.3.2-2"> <dt pn="section-4.3.2-2.1">IPv4 NodeID'">is specifiedID:</dt> <dd pn="section-4.3.2-2.2">Specified as an IPv4 address. In this case, the NT value is11, and the NAI field length is 4octets.</t> <t hangText="'IPv6octets.</dd> <dt pn="section-4.3.2-2.3">IPv6 NodeID'">is specifiedID:</dt> <dd pn="section-4.3.2-2.4">Specified as an IPv6 address. In this case, the NT value is22, and the NAI field length is 16octets.</t>octets.</dd> <dt pn="section-4.3.2-2.5">IPv4 Adjacency:</dt> <dd pn="section-4.3.2-2.6"> <thangText="'IPv4 Adjacency'">is specifiedpn="section-4.3.2-2.6.1">Specified as a pair of IPv4 addresses. In this case, the NT value is33, and the NAI field length is 8 octets. The format of the NAI is shown in the following figure: </t> <figure anchor="ADJ-SID-ERO-SUBOBJECT-32"title="NAIalign="left" suppress-title="false" pn="figure-3"> <name slugifiedName="name-nai-for-ipv4-adjacency">NAI for IPv4adjacency"> <artwork><![CDATA[Adjacency</name> <artwork name="" type="" align="left" alt="" pn="section-4.3.2-2.6.2.1"> 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local IPv4 address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote IPv4 address |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure></t> <t hangText="'IPv6</dd> <dt pn="section-4.3.2-2.7">IPv6 GlobalAdjacency'">is specifiedAdjacency:</dt> <dd pn="section-4.3.2-2.8"> <t pn="section-4.3.2-2.8.1">Specified as a pair of global IPv6 addresses. It is used to describe an IPv6 adjacency for a link that uses global IPv6 addresses. Each global IPv6 address is configured on a specific router interface, so together they identify an adjacency between a pair of routers. In this case, the NT value is44, and the NAI field length is 32 octets. The format of the NAI is shown in the following figure: </t> <figure anchor="ADJ-SID-ERO-SUBOBJECT-128"title="NAIalign="left" suppress-title="false" pn="figure-4"> <name slugifiedName="name-nai-for-ipv6-global-adjacen">NAI for IPv6global adjacency"> <artwork><![CDATA[Global Adjacency</name> <artwork name="" type="" align="left" alt="" pn="section-4.3.2-2.8.2.1"> 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local IPv6 address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Remote IPv6 address (16 octets) //+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure></t> <t hangText="'Unnumbered</dd> <dt pn="section-4.3.2-2.9">Unnumbered Adjacency with IPv4NodeIDs'">is specifiedNodeIDs:</dt> <dd pn="section-4.3.2-2.10"> <t pn="section-4.3.2-2.10.1">Specified as a pair of (node ID, interface ID) tuples. In this case, the NT value is55, and the NAI field length is 16 octets. The format of the NAI is shown in the following figure: </t> <figure anchor="ADJ-SID-ERO-UNNUM-32"title="NAIalign="left" suppress-title="false" pn="figure-5"> <name slugifiedName="name-nai-for-unnumbered-adjacenc">NAI for UnnumberedadjacencyAdjacency with IPv4 NodeIDs"> <artwork><![CDATA[IDs</name> <artwork name="" type="" align="left" alt="" pn="section-4.3.2-2.10.2.1"> 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LocalNode-IDNode ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RemoteNode-IDNode ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Interface ID |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure></t> <t hangText="'IPv6</dd> <dt pn="section-4.3.2-2.11">IPv6 Link-LocalAdjacency'">is specifiedAdjacency:</dt> <dd pn="section-4.3.2-2.12"> <t pn="section-4.3.2-2.12.1">Specified as a pair of (global IPv6 address, interface ID) tuples. It is used to describe an IPv6 adjacency for a link that uses onlylink locallink-local IPv6 addresses. Each global IPv6 address is configured on a specific router, so together they identify a pair of adjacent routers. The interface IDs identify the link that the adjacency is formed over. In this case, the NT value is66, and the NAI field length is 40 octets. The format of the NAI is shown in the following figure: </t> <figure anchor="ADJ-SID-ERO-LINKLOCAL-40"title="NAIalign="left" suppress-title="false" pn="figure-6"> <name slugifiedName="name-nai-for-ipv6-link-local-adj">NAI for IPv6link-local adjacency"> <artwork><![CDATA[Link-Local Adjacency</name> <artwork name="" type="" align="left" alt="" pn="section-4.3.2-2.12.2.1"> 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local IPv6 address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Remote IPv6 address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Interface ID |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure></t> </list> </t></dd> </dl> </section> </section> <section anchor="SR-RRO"title="RRO"> <t>Anumbered="true" toc="include" removeInRFC="false" pn="section-4.4"> <name slugifiedName="name-rro">RRO</name> <t pn="section-4.4-1">A PCC reports an SR-TE LSP to a PCE by sending a PCRpt message, per <xreftarget="RFC8231"/>.target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>. The RRO on this message represents the SID list that was applied by the PCC, that is, the actual path taken by the LSP. The procedures of <xreftarget="RFC8231"/>target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/> with respect to the RRO apply equally to this specification without change.</t><t>An<t pn="section-4.4-2">An RRO contains one or more subobjects called "SR-RROsubobjects"subobjects", whose format is shown below:</t> <figure anchor="SR-RRO-SUBOBJECT"title="SR-RROalign="left" suppress-title="false" pn="figure-7"> <name slugifiedName="name-sr-rro-subobject-format">SR-RRO Subobjectformat"> <artwork><![CDATA[Format</name> <artwork name="" type="" align="left" alt="" pn="section-4.4-3.1"> 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=36 | Length | NT | Flags |F|S|C|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NAI (variable) //+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork> </figure><t>The<t pn="section-4.4-4">The format of the SR-RRO subobject is the same as that of the SR-ERO subobject, but without theL flag.</t> <t>AL-Flag.</t> <t pn="section-4.4-5">A PCCMUST<bcp14>MUST</bcp14> order the SR-RRO subobjects such that the first subobject relative to the beginning of the RRO identifies the first segment visited by the SR-TE LSP, and the last subobject identifies the final segment of the SR-TE LSP, that is, its endpoint.</t> </section><!-- SR-RRO --><section anchor="SR-METRIC"title="METRIC Object"> <t>Anumbered="true" toc="include" removeInRFC="false" pn="section-4.5"> <name slugifiedName="name-metric-object">METRIC Object</name> <t pn="section-4.5-1">A PCCMAY<bcp14>MAY</bcp14> request that PCE optimizes an individual path computation request to minimize the SID depth of the computed path by using the METRIC object defined in <xreftarget="RFC5440"/>.target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>. This document defines a new type for the METRIC object to be used for this purpose, as follows:<list style="symbols"> <t>T = 11: Maximum</t> <ul spacing="normal" empty="true" bare="false" pn="section-4.5-2"> <li pn="section-4.5-2.1"> <dl newline="false" spacing="normal" pn="section-4.5-2.1.1"> <dt pn="section-4.5-2.1.1.1">T = 11:</dt> <dd pn="section-4.5-2.1.1.2">Maximum SID Depth of the requestedpath.</t> </list> </t> <t>Ifpath.</dd> </dl> </li> </ul> <t pn="section-4.5-3">If the PCC includes a METRIC object of this type on a path computation request, then the PCE minimizes the SID depth of the computed path. If the B (bound) bit is set toto1 in the METRIC object, then the PCEMUST NOT<bcp14>MUST NOT</bcp14> return a path whose SID depth exceeds the givenmetric-value.metric value. If the PCC did not set theX flagX-Flag in its SR-PCE-CAPABILITY TLV, then itMUST<bcp14>MUST</bcp14> set the B bit to 1. If the PCC set theX flagX-Flag in its SR-PCE-CAPABILITY TLV, then itMAY<bcp14>MAY</bcp14> set the B bit to 1 or zero.</t><t>If<t pn="section-4.5-4">If a PCEP session is established with a non-zero default MSD value, then the PCCMUST NOT<bcp14>MUST NOT</bcp14> send an MSD METRIC object with an MSD greater than the session's default MSD. If the PCE receives a path computation request with an MSD METRIC object on such a session that is greater than the session's default MSD, then itMUST<bcp14>MUST</bcp14> consider the request invalid and send aPCErrPCEP Error (PCErr) with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 9 ("MSD exceeds the default for the PCEP session"). </t> </section><!-- SR-METRIC --> </section> <!-- object-formats --></section> <section anchor="procedures"title="Procedures">numbered="true" toc="include" removeInRFC="false" pn="section-5"> <name slugifiedName="name-procedures">Procedures</name> <section anchor="SR-CAP-PROCESS"title="Exchangingnumbered="true" toc="include" removeInRFC="false" pn="section-5.1"> <name slugifiedName="name-exchanging-the-sr-pce-capab">Exchanging the SR PCECapability"> <t>ACapability</name> <t pn="section-5.1-1">A PCC indicates that it is capable of supporting the head-end functions for SR-TE LSP by including the SR-PCE-CAPABILITY sub-TLV in the Open message that it sends to a PCE. A PCE indicates that it is capable of computing SR-TE paths by including the SR-PCE-CAPABILITY sub-TLV in the Open message that it sends to a PCC.</t><t>If<t pn="section-5.1-2">If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV with a PST list containing PST=1, and supports that path setup type, then it checks for the presence of the SR-PCE-CAPABILITY sub-TLV. If that sub-TLV is absent, then the PCEP speakerMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10(Reception("Reception of an invalidobject)object") andError-Value TBD1 (MissingError-value = 12 ("Missing PCE-SR-CAPABILITYsub-TLV)sub-TLV") andMUST<bcp14>MUST</bcp14> then close the PCEP session. If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV with a SR-PCE-CAPABILITY sub-TLV, but the PST list does not contain PST=1, then the PCEP speakerMUST<bcp14>MUST</bcp14> ignore the SR-PCE-CAPABILITY sub-TLV.</t><t>If<t pn="section-5.1-3">If a PCC sets theN flagN-Flag to 1, then the PCEMAY<bcp14>MAY</bcp14> send an SR-ERO subobject containing an NAI and no SID (see <xreftarget="SR-ERO-PROCESS"/>).target="SR-ERO-PROCESS" format="default" sectionFormat="of" derivedContent="Section 5.2"/>). Otherwise, the PCEMUST NOT<bcp14>MUST NOT</bcp14> send an SR-ERO subobject containing an NAI and no SID.</t><t>The<t pn="section-5.1-4">The number of SIDs that can be imposed on a packet depends on the PCC'sdata plane'sdata-plane capability. If a PCC sets theX flagX-Flag to11, then the MSD is not used andMUST<bcp14>MUST</bcp14> be set to zero. If a PCE receives an SR-PCE-CAPABILITY sub-TLV with theX flagX-Flag set to11, then itMUST<bcp14>MUST</bcp14> ignore the MSD field andassumesassume that the sender can impose a SID stack of any depth. If a PCC sets theX flagX-Flag to zero, then it sets the MSD field to the maximum number of SIDs that it can impose on a packet. In this case, the PCCMUST<bcp14>MUST</bcp14> set the MSD to a number greater than zero. If a PCE receives an SR-PCE-CAPABILITY sub-TLV with theX flagX-Flag and MSD both set tozerozero, then itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10(Reception("Reception of an invalidobject)object") andError-Value TBD10 (MaximumError-value = 21 ("Maximum SID depth must benonzero)non-zero") andMUST<bcp14>MUST</bcp14> then close the PCEP session.</t><t>Note<t pn="section-5.1-5">Note that the MSD value exchanged via the SR-PCE-CAPABILITY sub-TLV indicates the SID/label imposition limit for the PCC node. It is anticipated that, in many deployments, the PCCs will have network interfaces that are homogeneous with respect to MSD (that is, each interface has the same MSD). In such cases, having a per-node MSD on the PCEP session is sufficient; the PCESHOULD<bcp14>SHOULD</bcp14> interpret this to mean that all network interfaces on the PCC have the given MSD. However, the PCEMAY<bcp14>MAY</bcp14> also learn a per-node MSD and a per-interface MSD from the routing protocols, as specifiedin: <xref target="RFC8491"/>;in <xreftarget="RFC8476"/>;target="RFC8491" format="default" sectionFormat="of" derivedContent="RFC8491"/>, <xref target="RFC8476" format="default" sectionFormat="of" derivedContent="RFC8476"/>, and <xreftarget="I-D.ietf-idr-bgp-ls-segment-routing-msd"/>.target="I-D.ietf-idr-bgp-ls-segment-routing-msd" format="default" sectionFormat="of" derivedContent="MSD-BGP"/>. If the PCE learns the per-node MSD of a PCC from a routing protocol, then itMUST<bcp14>MUST</bcp14> ignore the per-node MSD value in the SR-PCE-CAPABILITY sub-TLV and use the per-node MSD learned from the routing protocol instead. If the PCE learns the MSD of a network interface on a PCC from a routing protocol, then itMUST<bcp14>MUST</bcp14> use the per-interface MSD instead of the MSD value in the SR-PCE-CAPABILITY sub-TLV when it computes a path that uses that interface.</t><t>Once<t pn="section-5.1-6">Once an SR-capable PCEP session is established with a non-zero MSD value, the corresponding PCEMUST NOT<bcp14>MUST NOT</bcp14> send SR-TE paths with a number of SIDs exceeding that MSD value. If a PCC needs to modify the MSD value, itMUST<bcp14>MUST</bcp14> close the PCEP session and re-establish it with the new MSD value. If a PCEP session is established with a non-zero MSD value, and the PCC receives an SR-TE path containing more SIDs than specified in the MSD value, the PCCMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10(Reception("Reception of an invalidobject)object") andError-ValueError-value = 3(Unsupported("Unsupported number ofSegment ERO subobjects).SR-ERO subobjects"). If a PCEP session is established with an MSD value of zero, then the PCCMAY<bcp14>MAY</bcp14> specify an MSD for each path computation request that it sends to the PCE, by including a "maximum SID depth"metricMETRIC object on the request, as defined in <xreftarget="SR-METRIC"/>.</t> <t>The N flag, X flagtarget="SR-METRIC" format="default" sectionFormat="of" derivedContent="Section 4.5"/>.</t> <t pn="section-5.1-7">The N-Flag, X-Flag, and MSD value inside the SR-PCE-CAPABILITY sub-TLV are meaningful only in the Open message sent from a PCC to a PCE. As such, a PCEMUST<bcp14>MUST</bcp14> set theN flagN-Flag to zero,the X flagX-Flag to11, and MSD value to zero in an outbound message to a PCC. Similarly, a PCCMUST<bcp14>MUST</bcp14> ignore any MSD value received from a PCE. If a PCE receives multiple SR-PCE-CAPABILITY sub-TLVs in an Open message, it processes only the first sub-TLV received.</t> </section> <section anchor="SR-ERO-PROCESS"title="ERO Processing">numbered="true" toc="include" removeInRFC="false" pn="section-5.2"> <name slugifiedName="name-ero-processing">ERO Processing</name> <section anchor="SR-ERO-VALIDATION"title="SR-ERO Validation"> <t>Ifnumbered="true" toc="include" removeInRFC="false" pn="section-5.2.1"> <name slugifiedName="name-sr-ero-validation">SR-ERO Validation</name> <t pn="section-5.2.1-1">If a PCC does not support the SR PCE Capability and thus cannot recognize the SR-ERO or SR-RRO subobjects, it will respond according to the rules for a malformed object per <xreftarget="RFC5440"/>.</t> <t>Ontarget="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>.</t> <t pn="section-5.2.1-2">On receiving an SR-ERO, a PCCMUST<bcp14>MUST</bcp14> validate that the Length field,theS bit,theFbitbit, andtheNT field are consistent, as follows.<list style="symbols"> <t>If</t> <ul spacing="normal" bare="false" empty="false" pn="section-5.2.1-3"> <li pn="section-5.2.1-3.1">If NT=0, the F bitMUST<bcp14>MUST</bcp14> be 1, the S bitMUST<bcp14>MUST</bcp14> bezerozero, and the LengthMUST<bcp14>MUST</bcp14> be8.</t> <t>If8.</li> <li pn="section-5.2.1-3.2">If NT=1, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be8, otherwise8; otherwise, the LengthMUST<bcp14>MUST</bcp14> be12.</t> <t>If12.</li> <li pn="section-5.2.1-3.3">If NT=2, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be20, otherwise20; otherwise, the LengthMUST<bcp14>MUST</bcp14> be24.</t> <t>If24.</li> <li pn="section-5.2.1-3.4">If NT=3, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be12, otherwise12; otherwise, the LengthMUST<bcp14>MUST</bcp14> be16.</t> <t>If16.</li> <li pn="section-5.2.1-3.5">If NT=4, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be36, otherwise36; otherwise, the LengthMUST<bcp14>MUST</bcp14> be40.</t> <t>If40.</li> <li pn="section-5.2.1-3.6">If NT=5, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be20, otherwise20; otherwise, the LengthMUST<bcp14>MUST</bcp14> be24.</t> <t>If24.</li> <li pn="section-5.2.1-3.7">If NT=6, the F bitMUST<bcp14>MUST</bcp14> be zero. If the S bit is 1, the LengthMUST<bcp14>MUST</bcp14> be44, otherwise44; otherwise, the LengthMUST<bcp14>MUST</bcp14> be48.</t> </list></t> <t>If48.</li> </ul> <t pn="section-5.2.1-4">If a PCC finds that the NT field, Length field, Sbitbit, and F bit are not consistent, itMUST<bcp14>MUST</bcp14> consider the entire ERO invalid andMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 11 ("Malformed object").</t><t>If<t pn="section-5.2.1-5">If a PCC does notrecogniserecognize or support the value in the NT field, itMUST<bcp14>MUST</bcp14> consider the entire ERO invalid andMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD213 ("Unsupported NAI Type inSegment EROthe SR-ERO/SR-RRO subobject").</t><t>If<t pn="section-5.2.1-6">If a PCC receives an SR-ERO subobject in which the S and F bits are both set to 1 (that is, both the SID and NAI are absent), itMUST<bcp14>MUST</bcp14> consider the entire ERO invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 6 ("Both SID and NAI are absent in the SR-ERO subobject").</t><t>If<t pn="section-5.2.1-7">If a PCC receives an SR-ERO subobject in which the S bit is set to 1 and the F bit is set to zero (that is, the SID is absent and the NAI is present), but the PCC does not support NAI resolution, itMUST<bcp14>MUST</bcp14> consider the entire ERO invalid and send a PCErr message with Error-Type = 4 ("Not supported object") andError-ValueError-value = 4 ("Unsupported parameter").</t><t>If<t pn="section-5.2.1-8">If a PCC receives an SR-ERO subobject in which the S bit is set to 1 and eitheror both of(or both) the M bit or the Cbitsbit is set to 1, itMUST<bcp14>MUST</bcp14> consider the entire ERO invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 11 ("Malformed object").</t><t>If<t pn="section-5.2.1-9">If a PCC receives an SR-ERO subobject in which the S bit is set to zero and the M bit is set to 1, then the subobject contains an MPLS label. The PCCMAY<bcp14>MAY</bcp14> choose not to accept a label provided by the PCE, based onitits local policy. The PCCMUST NOT<bcp14>MUST NOT</bcp14> accept MPLS label value 3 (Implicit NULL), but itMAY<bcp14>MAY</bcp14> accept otherspecial purposespecial-purpose MPLS label values. If the PCC decides not to accept an MPLS label value, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError ValueError-value = 2 ("Bad label value").</t><t>If<t pn="section-5.2.1-10">If both the M and C bits of an SR-ERO subobject are set to 1, and if a PCC finds an erroneous setting in one or more of the TC, S, and TTL fields, itMAY<bcp14>MAY</bcp14> overwrite those fields with values chosen according to its own policy. If the PCC does not overwrite them, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 4 ("Bad label format").</t><t>If<t pn="section-5.2.1-11">If the M bit of an SR-ERO subobject is set to zero but the C bit is set to 1, then the PCCMUST<bcp14>MUST</bcp14> consider the entire ERO invalid andMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 11 ("Malformed object").</t><t>If<t pn="section-5.2.1-12">If a PCC receives an SR-ERO subobject in which the S bit is set to zero and the M bit is set to zero, then the subobject contains a SID index value. If the SID is anAdjacency-SIDAdj-SID, then theL flag MUST NOTL-Flag <bcp14>MUST NOT</bcp14> be set. If theL flagL-Flag is set for anAdjacency-SIDAdj-SID, then the PCCMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 11 ("Malformed object").</t><t>If<t pn="section-5.2.1-13">If a PCC detects that the subobjects of an ERO are a mixture of SR-ERO subobjects and subobjects of other types, then itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 5 ("ERO mixes SR-ERO subobjects with other subobject types").</t><t>The<t pn="section-5.2.1-14">The SR-ERO subobjects can be classified according to whether they contain a SID representing an MPLS labelvalue, a SID representingvalue or an index value, or no SID. If a PCC detects that the SR-ERO subobjects are a mixture of more than one of these types, then itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD920 ("Inconsistent SIDs inSR-ERO / SR-RROSR-ERO/SR-RRO subobjects").</t><t>If<t pn="section-5.2.1-15">If an ERO specifies a new SR-TE path for an existing LSP and the PCC determines that the ERO contains SR-ERO subobjects that are not valid, then the PCCMUST NOT<bcp14>MUST NOT</bcp14> update the LSP.</t> </section> <section anchor="SR-ERO-INTERPRET"title="Interpretingnumbered="true" toc="include" removeInRFC="false" pn="section-5.2.2"> <name slugifiedName="name-interpreting-the-sr-ero">Interpreting theSR-ERO"> <t>SR-ERO</name> <t pn="section-5.2.2-1"> The SR-ERO contains a sequence of subobjects. Each SR-ERO subobject in the sequence identifies a segment that the traffic will be directed to, in the order given. That is, the first subobject identifies the first segment the traffic will be directed to, the second subobject represents the second segment, and so on. </t><t><t pn="section-5.2.2-2"> The PCC interprets the SR-ERO by converting it to an MPLS label stack plus a next hop. The PCC sends packets along thesegment routedsegment-routed path by prepending the MPLS label stack onto the packets and sending the resulting, modified packet to the next hop. </t><t><t pn="section-5.2.2-3"> The PCC uses a different procedure to do this conversion, depending on the information that the PCE has provided in the subobjects.<list style="symbols"> <t></t> <ul spacing="normal" bare="false" empty="false" pn="section-5.2.2-4"> <li pn="section-5.2.2-4.1"> If the subobjects contain SID index values, then the PCC converts them into the corresponding MPLS labels by following the procedure defined in <xreftarget="I-D.ietf-spring-segment-routing-mpls"/>. </t> <t>target="RFC8660" format="default" sectionFormat="of" derivedContent="RFC8660"/>. </li> <li pn="section-5.2.2-4.2"> If the subobjects containNAINAIs only, the PCC first converts each NAI into a SID index value and then proceeds as above. To convert an NAI to a SID index, the PCC looks for afully-specifiedfully specified prefix or adjacency matching the fields in the NAI. If the PCC finds a matching prefix/adjacency, and the matching prefix/adjacency has a SID associated with it, then the PCC uses that SID. If the PCC cannot find a matching prefix/adjacency, or if the matching prefix/adjacency has no SID associated with it, the PCC behaves as specified in <xreftarget="SR-ERO-INTERPRET-ERROR"/>. </t> <t>target="SR-ERO-INTERPRET-ERROR" format="default" sectionFormat="of" derivedContent="Section 5.2.2.1"/>. </li> <li pn="section-5.2.2-4.3"> If the subobjects contain MPLS labels, then the PCC looks up the offset of the first subobject's label in its SRGB or SRLB. This gives the first SID. The PCC pushes the labels in any remaining subobjects onto the packet (with the final subobject specifying the bottom-of-stack label).</t> </list></li> </ul> <t pn="section-5.2.2-5"> For all cases above, after the PCC has imposed the label stack on the packet, it sends the packet to the segment identified by the first SID. </t> <section anchor="SR-ERO-INTERPRET-ERROR"title="Handlingnumbered="true" toc="exclude" removeInRFC="false" pn="section-5.2.2.1"> <name slugifiedName="name-handling-errors-during-sr-e">Handling Errors During SR-EROConversion"> <t>ThereConversion</name> <t pn="section-5.2.2.1-1">There are several errors that can occur during the process of converting an SR-ERO sequence to an MPLS label stack and a next hop. The PCC deals with them as follows.<list style="symbols"> <t>If</t> <ul spacing="normal" bare="false" empty="false" pn="section-5.2.2.1-2"> <li pn="section-5.2.2.1-2.1">If the PCC cannot find a SID index in the SR-DB, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD314 ("UnknownSID").</t> <t>IfSID").</li> <li pn="section-5.2.2.1-2.2">If the PCC cannot find an NAI in the SR-DB, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD415 ("NAI cannot be resolved to aSID").</t> <t>IfSID").</li> <li pn="section-5.2.2.1-2.3">If the PCC needs to convert a SID into an MPLS label value but cannot find the corresponding router's SRGB in the SR-DB, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD516 ("Could not findSRGB").</t> <t>IfSRGB").</li> <li pn="section-5.2.2.1-2.4">If the PCC finds that a router's SRGB is not large enough for a SID index value, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD617 ("SID index exceeds SRGBsize").</t> <t>Ifsize").</li> <li pn="section-5.2.2.1-2.5">If the PCC needs to convert a SID into an MPLS label value but cannot find the corresponding router's SRLB in the SR-DB, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD718 ("Could not findSRLB").</t> <t>IfSRLB").</li> <li pn="section-5.2.2.1-2.6">If the PCC finds that a router's SRLB is not large enough for a SID index value, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD819 ("SID index exceeds SRLBsize").</t> <t>Ifsize").</li> <li pn="section-5.2.2.1-2.7">If the number of labels in the computed label stack exceeds the maximum number of SIDs that the PCC can impose on the packet, itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 3 ("Unsupported number ofSegment ERO subobjects").</t> </list></t> <t>IfSR-ERO subobjects").</li> </ul> <t pn="section-5.2.2.1-3">If an ERO specifies a new SR-TE path for an existing LSP and the PCC encounters an error while processing the ERO, then the PCCMUST NOT<bcp14>MUST NOT</bcp14> update the LSP.</t> </section> </section> </section> <section anchor="SR-RRO-PROCESS"title="RRO Processing"> <t>The syntax checkingnumbered="true" toc="include" removeInRFC="false" pn="section-5.3"> <name slugifiedName="name-rro-processing">RRO Processing</name> <t pn="section-5.3-1">The syntax-checking rules that apply to the SR-RRO subobject are identical to those of the SR-ERO subobject, except as noted below.</t><t>If<t pn="section-5.3-2">If a PCEP speaker receives an SR-RRO subobject in which both SID and NAI are absent, itMUST<bcp14>MUST</bcp14> consider the entire RRO invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 7 ("Both SID and NAI are absent in the SR-RRO subobject").</t><t>If<t pn="section-5.3-3">If a PCE detects that the subobjects of an RRO are a mixture of SR-RRO subobjects and subobjects of other types, then itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value = 10 ("RRO mixes SR-RRO subobjects with other subobject types").</t><t>The<t pn="section-5.3-4">The SR-RRO subobjects can be classified according to whether they contain a SID representing an MPLS label value ora SID representingan index value, or no SID. If a PCE detects that the SR-RRO subobjects are a mixture of more than one of these types, then itMUST<bcp14>MUST</bcp14> send a PCErr message with Error-Type = 10 ("Reception of an invalid object") andError-ValueError-value =TBD920 ("Inconsistent SIDs in SR-ERO / SR-RRO subobjects").</t> </section> </section><!-- Procedures --><section anchor="Management"title="Management Considerations"> <t>Thisnumbered="true" toc="include" removeInRFC="false" pn="section-6"> <name slugifiedName="name-management-considerations">Management Considerations</name> <t pn="section-6-1">This document adds a new path setup type to PCEP to allow LSPs to be set up usingsegment routingSegment Routing techniques. This path setup type may be used with PCEP alongside other path setup types, such as RSVP-TE, or it may be used exclusively.</t> <section anchor="control"title="Controllingnumbered="true" toc="include" removeInRFC="false" pn="section-6.1"> <name slugifiedName="name-controlling-the-path-setup-">Controlling the Path SetupType"> <t>TheType</name> <t pn="section-6.1-1">The following factors control which path setup type is used for a given LSP.<list style="symbols"> <t></t> <ul spacing="normal" bare="false" empty="false" pn="section-6.1-2"> <li pn="section-6.1-2.1"> The available path setup types are constrained to those that are supported by, or enabled on, the PCEP speakers. The PATH-SETUP-TYPE-CAPABILITY TLV indicates which path setup types a PCEP speaker supports. To usesegment routingSegment Routing as a path setup type, it is a prerequisite that the PCC and PCE both include PST=1 in the list of supported path setup types in thisTLV,TLV and also include the SR-PCE-CAPABILITYsub-TLV.</t> <t>sub-TLV.</li> <li pn="section-6.1-2.2"> When a PCE initiates an LSP, it proposes which path setup type to use by including it in the PATH-SETUP-TYPE TLV in the SRP object of the PCInitiate message. The PCE chooses the path setup type based on the capabilities of the network nodes on the path and on its local policy. The PCCMAY<bcp14>MAY</bcp14> choose to accept the proposed path setuptype,type or to reject the PCInitiate request, based on its localpolicy.</t> <t>policy.</li> <li pn="section-6.1-2.3"> When a PCC requests a path for an LSP, it can nominate a preferred path setup type by including it in the PATH-SETUP-TYPE TLV in the RP object of the PCReq message. The PCEMAY<bcp14>MAY</bcp14> choose to reply with a path of the requested type,or toreply with a path of a different type, ortoreject the request, based on the capabilities of the network nodes on the path and on its localpolicy.</t> </list> </t> <t>Thepolicy.</li> </ul> <t pn="section-6.1-3">The operator can influence the path setup type as follows.<list style="symbols"> <t></t> <ul spacing="normal" bare="false" empty="false" pn="section-6.1-4"> <li pn="section-6.1-4.1"> ImplementationsMUST<bcp14>MUST</bcp14> allow the operator to enable and disable thesegment routingSegment Routing path setup type on a PCEP-speaking device. ImplementationsMAY<bcp14>MAY</bcp14> also allow the operator to enable and disable the RSVP-TE path setuptype.</t> <t>type.</li> <li pn="section-6.1-4.2"> PCE implementationsMUST<bcp14>MUST</bcp14> allow the operator to specify that an LSP should be instantiated usingsegment routingSegment Routing or RSVP-TE as the proposed path setup type.</t> <t></li> <li pn="section-6.1-4.3"> PCE implementationsMAY<bcp14>MAY</bcp14> allow the operator to configure a preference for the PCE to propose paths usingsegment routingSegment Routing or RSVP-TE in the absence of a specified path setuptype.</t> <t>type.</li> <li pn="section-6.1-4.4"> PCC implementationsMUST<bcp14>MUST</bcp14> allow the operator to specify that a path requested for an LSP nominatessegment routingSegment Routing or RSVP-TE as the path setuptype.</t> <t>type.</li> <li pn="section-6.1-4.5"> PCC implementationsMAY<bcp14>MAY</bcp14> allow the operator to configure a preference for the PCC to nominatesegment routingSegment Routing or RSVP-TE as the path setup type if none is specified for anLSP.</t> <t>LSP.</li> <li pn="section-6.1-4.6"> PCC implementationsSHOULD<bcp14>SHOULD</bcp14> allow the operator to configure a PCC to refuse to set up an LSP using an undesired path setuptype.</t> </list> </t>type.</li> </ul> </section> <section anchor="migrating"title="Migratingnumbered="true" toc="include" removeInRFC="false" pn="section-6.2"> <name slugifiedName="name-migrating-a-network-to-use-">Migrating a Network to Use PCEPSegment Routed Paths"> <t>Segment-Routed Paths</name> <t pn="section-6.2-1"> This section discusses the steps that the operator takes when migrating a network to enable PCEP to set up paths usingsegment routingSegment Routing as the path setup type.<list style="symbols"> <t></t> <ul spacing="normal" bare="false" empty="false" pn="section-6.2-2"> <li pn="section-6.2-2.1"> The operator enables thesegment routingSegment Routing PST on the PCEservers.</t> <t>servers.</li> <li pn="section-6.2-2.2"> The operator enables thesegment routingSegment Routing PST on thePCCs.</t> <t>PCCs.</li> <li pn="section-6.2-2.3"> The operator resets each PCEP session. The PCEP sessions come back up withsegment routing enabled.</t> <t>Segment Routing enabled.</li> <li pn="section-6.2-2.4"> If the operator detects a problem, they can roll the network back to its initial state by disabling thesegment routingSegment Routing PST on the PCEP speakers and resetting the PCEPsessions.</t> </list> </t> <t>Notesessions.</li> </ul> <t pn="section-6.2-3">Note that the data plane is unaffected if a PCEP session is reset. Any LSPs that were set up before the session reset will remain in place and will still be present after the session comes back up.</t><t>An<t pn="section-6.2-4">An implementationSHOULD<bcp14>SHOULD</bcp14> allow the operator to manually trigger a PCEP session to be reset.</t><t>An<t pn="section-6.2-5">An implementationMAY<bcp14>MAY</bcp14> automatically reset a PCEP session when an operator reconfigures the PCEP speaker's capabilities. However, note that if the capabilities at both ends of the PCEP session are not reconfigured simultaneously, then the session could be reset twice, which could lead to unnecessary network traffic. Therefore, such implementationsSHOULD<bcp14>SHOULD</bcp14> allow the operator to override thisbehaviourbehavior and wait instead for a manual reset.</t><t>Once segment routing<t pn="section-6.2-6">Once Segment Routing is enabled on a PCEP session, it can be used as the path setup type for future LSPs.</t><t>User<t pn="section-6.2-7">User traffic is not automatically migrated from existing LSPs ontosegment routedsegment-routed LSPs just by enabling thesegment routingSegment Routing PST in PCEP. The migration of user traffic from existing LSPs ontosegment routingSegment Routing LSPs is beyond the scope of this document.</t> </section> <section anchor="verification"title="Verificationnumbered="true" toc="include" removeInRFC="false" pn="section-6.3"> <name slugifiedName="name-verification-of-network-ope">Verification of NetworkOperation"> <t>TheOperation</name> <t pn="section-6.3-1">The operator needs the following information to verify that PCEP is operating correctly with respect to thesegment routingSegment Routing path setup type.<list style="symbols"> <t></t> <ul spacing="normal" bare="false" empty="false" pn="section-6.3-2"> <li pn="section-6.3-2.1"> An implementationSHOULD<bcp14>SHOULD</bcp14> allow the operator to view whether the PCEP speaker sent thesegment routingSegment Routing PST capability to its peer. If the PCEP speaker is a PCC, then the implementationSHOULD<bcp14>SHOULD</bcp14> also allow the operator to view the values of theLL-Flag andN flagsN-Flag that weresent,sent and the value of the MSD field that wassent.</t> <t>sent.</li> <li pn="section-6.3-2.2"> An implementationSHOULD<bcp14>SHOULD</bcp14> allow the operator to view whether the peer sent thesegment routingSegment Routing PST capability. If the peer is a PCC, then the implementationSHOULD<bcp14>SHOULD</bcp14> also allow the operator to view the values of theLL-Flag andN flagsN-Flag and MSD fields that the peersent.</t> <t>sent.</li> <li pn="section-6.3-2.3"> An implementationSHOULD<bcp14>SHOULD</bcp14> allow the operator to view whether thesegment routingSegment Routing PST is enabled on the PCEPsession.</t> <t>session.</li> <li pn="section-6.3-2.4"> If one PCEP speaker advertises thesegment routingSegment Routing PST capability, but the other does not, then the implementationSHOULD<bcp14>SHOULD</bcp14> create a log to inform the operator of the capabilitymismatch.</t> <t>mismatch.</li> <li pn="section-6.3-2.5"> An implementationSHOULD<bcp14>SHOULD</bcp14> allow the operator to view the PST that was proposed, or requested, for anLSP,LSP and the PST that was actuallyused.</t> <t>used.</li> <li pn="section-6.3-2.6"> If a PCEP speaker decides to use a different PST to the one that was proposed, or requested, for an LSP, then the implementationSHOULD<bcp14>SHOULD</bcp14> create a log to inform the operator that the expected PST has not been used. The logSHOULD<bcp14>SHOULD</bcp14> give the reason for this choice (local policy, equipmentcapability etc.)</t> <t>capability, etc.).</li> <li pn="section-6.3-2.7"> If a PCEP speaker rejects asegment routingSegment Routing path, then itSHOULD<bcp14>SHOULD</bcp14> create a log to inform the operator, giving the reason for the decision (local policy, MSDexceeded etc.)</t> </list> </t>exceeded, etc.).</li> </ul> </section> <section anchor="models"title="Relationshipnumbered="true" toc="include" removeInRFC="false" pn="section-6.4"> <name slugifiedName="name-relationship-to-existing-ma">Relationship to Existing ManagementModels"> <t>TheModels</name> <t pn="section-6.4-1">The PCEP YANG module is defined in <xreftarget="I-D.ietf-pce-pcep-yang"/>.target="I-D.ietf-pce-pcep-yang" format="default" sectionFormat="of" derivedContent="PCE-PCEP-YANG"/>. In the future, this YANG module should be extended or augmented to provide the following additional information relating tosegment routing: <list style="symbols"> <t>Segment Routing: </t> <ul spacing="normal" bare="false" empty="false" pn="section-6.4-2"> <li pn="section-6.4-2.1"> The advertised PST capabilities and MSD per PCEPsession.</t> <t>session.</li> <li pn="section-6.4-2.2"> The PST configured for, and used by, eachLSP.</t> </list> </t> <t>TheLSP.</li> </ul> <t pn="section-6.4-3">The PCEP MIB <xreftarget="RFC7420"/>target="RFC7420" format="default" sectionFormat="of" derivedContent="RFC7420"/> could also be updated to include this information.</t> </section> </section> <section anchor="Security"title="Security Considerations"> <t>Thenumbered="true" toc="include" removeInRFC="false" pn="section-7"> <name slugifiedName="name-security-considerations">Security Considerations</name> <t pn="section-7-1">The security considerations described in <xreftarget="RFC5440"/>, <xref target="RFC8231"/>, <xref target="RFC8281"/> and <xref target="RFC8408"/>target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>, <xref target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>, <xref target="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/>, and <xref target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/> are applicable to this specification. No additional securitymeasure ismeasures are required.</t><t>Note<t pn="section-7-2">Note that this specification enables a network controller to instantiate a path in the network without the use of a hop-by-hop signaling protocol (such as RSVP-TE). This creates an additional vulnerability if the security mechanisms of <xreftarget="RFC5440"/>, <xref target="RFC8231"/>target="RFC5440" format="default" sectionFormat="of" derivedContent="RFC5440"/>, <xref target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/>, and <xreftarget="RFC8281"/>target="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/> are not used. If there is no integrity protection on the session, then an attacker could create a pathwhichthat is not subjected to the further verification checks that would be performed by the signaling protocol.</t><t>Note<t pn="section-7-3">Note that this specification adds the MSD field to theOPENOpen message (see <xreftarget="cap-negotiation"/>)target="cap-negotiation" format="default" sectionFormat="of" derivedContent="Section 4.1.2"/>), which discloses how many MPLS labels the sender can push onto packets that it forwards into the network. If the security mechanisms of <xreftarget="RFC8231"/>target="RFC8231" format="default" sectionFormat="of" derivedContent="RFC8231"/> and <xreftarget="RFC8281"/>target="RFC8281" format="default" sectionFormat="of" derivedContent="RFC8281"/> are not used with strong encryption, then an attacker could use this new field to gain intelligence about the capabilities of the edge devices in the network.</t> </section> <section anchor="IANA"title="IANA Considerations">numbered="true" toc="include" removeInRFC="false" pn="section-8"> <name slugifiedName="name-iana-considerations">IANA Considerations</name> <section anchor="PCEP-Object-Codepoints"title="PCEPnumbered="true" toc="include" removeInRFC="false" pn="section-8.1"> <name slugifiedName="name-pcep-ero-and-rro-subobjects">PCEP ERO and RROsubobjects"> <t>ThisSubobjects</name> <t pn="section-8.1-1">This document defines a new subobject type for the PCEPexplicit route object (ERO),ERO and a new subobject type for the PCEPrecord route object (RRO).RRO. Thecode pointscodepoints for subobject types of these objectsisare maintained in theRSVP parameters"Resource Reservation Protocol (RSVP) Parameters" registry, under the EXPLICIT_ROUTE and ROUTE_RECORDobjects. IANA is requested to confirm the early allocation of the following code points in the RSVP Parameters registry for each of the new subobject types defined in this document.</t> <texttableobjects, respectively.</t> <table anchor="IANA-Subobject-Type"style="none" suppress-title="true"> <ttcol align="left" width='40%'>Object</ttcol> <ttcol align="left" width='40%'>Subobject</ttcol> <ttcol align="left" width='60%'>Subobject Type</ttcol> <c>---------------------</c><c>--------------------------</c><c>------------------</c> <c>EXPLICIT_ROUTE</c><c>SR-ERO (PCEP-specific)</c><c>36</c> <c>ROUTE_RECORD</c><c>SR-RRO (PCEP-specific)</c><c>36</c> </texttable>align="center" pn="table-1"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Object</th> <th align="left" colspan="1" rowspan="1">Subobject</th> <th align="left" colspan="1" rowspan="1">Subobject Type</th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">EXPLICIT_ROUTE</td> <td align="left" colspan="1" rowspan="1">SR-ERO (PCEP specific)</td> <td align="left" colspan="1" rowspan="1">36</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">ROUTE_RECORD</td> <td align="left" colspan="1" rowspan="1">SR-RRO (PCEP specific)</td> <td align="left" colspan="1" rowspan="1">36</td> </tr> </tbody> </table> </section> <section anchor="NAI-Type-Registry"title="Newnumbered="true" toc="include" removeInRFC="false" pn="section-8.2"> <name slugifiedName="name-new-nai-type-registry">New NAI TypeRegistry"> <t>IANA is requested to createRegistry</name> <t pn="section-8.2-1">IANA has created a new sub-registry within the "Path Computation Element Protocol (PCEP) Numbers" registry called "PCEP SR-ERO NAI Types". The allocation policy for this new registryshould beis by IETFReview.Review <xref target="RFC8126" format="default" sectionFormat="of" derivedContent="RFC8126"/>. The new registryshould containcontains the following values: </t><texttable<table anchor="New-PCEP-SR-ERO-NAI-value"style="none" suppress-title="true"> <ttcol align="left" width='40%'>Value</ttcol> <ttcol align="left" width='75%'>Description </ttcol> <ttcol align="left" width='55%'>Reference </ttcol> <c></c><c> </c><c></c> <c>0</c><c>NAI is absent.</c><c>This document</c> <c>1</c><c>NAIalign="center" pn="table-2"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Value</th> <th align="left" colspan="1" rowspan="1">Description </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">0</td> <td align="left" colspan="1" rowspan="1">NAI is absent.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">1</td> <td align="left" colspan="1" rowspan="1">NAI is an IPv4 nodeID.</c><c>This document</c> <c>2</c><c>NAIID.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">2</td> <td align="left" colspan="1" rowspan="1">NAI is an IPv6 nodeID.</c><c>This document</c> <c>3</c><c>NAIID.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">3</td> <td align="left" colspan="1" rowspan="1">NAI is an IPv4adjacency.</c><c>This document</c> <c>4</c><c>NAIadjacency.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">4</td> <td align="left" colspan="1" rowspan="1">NAI is an IPv6 adjacency with global IPv6addresses.</c><c>This document</c> <c>5</c><c>NAIaddresses.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">5</td> <td align="left" colspan="1" rowspan="1">NAI is an unnumbered adjacency with IPv4 nodeIDs.</c><c>This document</c> <c>6</c><c>NAIIDs.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">6</td> <td align="left" colspan="1" rowspan="1">NAI is an IPv6 adjacency with link-local IPv6addresses.</c><c>This document</c> </texttable>addresses.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">7-15</td> <td align="left" colspan="1" rowspan="1">Unassigned</td> <td align="left" colspan="1" rowspan="1"/> </tr> </tbody> </table> </section> <section anchor="IANA-SR-ERO-FLAG"title="Newnumbered="true" toc="include" removeInRFC="false" pn="section-8.3"> <name slugifiedName="name-new-sr-ero-flag-registry">New SR-ERO FlagRegistry"> <t>IANA is requested to createRegistry</name> <t pn="section-8.3-1">IANA has created a new sub-registry, named "SR-ERO Flag Field", within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the Flag field of the SR-ERO subobject. New values are to be assigned by Standards Action <xreftarget="RFC8126"/>.target="RFC8126" format="default" sectionFormat="of" derivedContent="RFC8126"/>. Each bit should be tracked with the following qualities:<list style="symbols"> <t>Bit</t> <ul spacing="normal" bare="false" empty="false" pn="section-8.3-2"> <li pn="section-8.3-2.1">Bit number (counting from bit 0 as the most significantbit)</t> <t>Capability description</t> <t>Defining RFC</t> </list> </t> <t>Thebit)</li> <li pn="section-8.3-2.2">Capability description</li> <li pn="section-8.3-2.3">Defining RFC</li> </ul> <t pn="section-8.3-3">The following values are defined in this document:</t><texttable<table anchor="SR-ERO-Flags"style="none" suppress-title="true"> <ttcolalign="center"width='15%'>Bit</ttcol> <ttcolpn="table-3"> <thead> <tr> <th align="center" colspan="1" rowspan="1">Bit</th> <th align="left" colspan="1" rowspan="1">Description </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="center" colspan="1" rowspan="1">0-7</td> <td align="left" colspan="1" rowspan="1">Unassigned</td> <td align="left" colspan="1" rowspan="1"/> </tr> <tr> <td align="center" colspan="1" rowspan="1">8</td> <td align="left"width='30%'>Description </ttcol> <ttcol align="left" width='55%'>Reference </ttcol> <c></c><c> </c><c></c> <c>0-7</c><c>Unassigned</c><c></c> <c>8</c><c>NAIcolspan="1" rowspan="1">NAI is absent(F)</c><c>This document</c> <c>9</c><c>SID(F)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="center" colspan="1" rowspan="1">9</td> <td align="left" colspan="1" rowspan="1">SID is absent(S)</c><c>This document</c> <c>10</c><c>SID(S)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="center" colspan="1" rowspan="1">10</td> <td align="left" colspan="1" rowspan="1">SID specifies TC,SS, and TTL in addition to an MPLS label(C)</c><c>This document</c> <c>11</c><c>SID(C)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="center" colspan="1" rowspan="1">11</td> <td align="left" colspan="1" rowspan="1">SID specifies an MPLS label(M)</c><c>This document</c> </texttable>(M)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section><!-- SR-ERO Flags --><section anchor="IANA-Error-Object"title="PCEP-Error Object"> <t>IANA is requested to confirm the early allocation ofnumbered="true" toc="include" removeInRFC="false" pn="section-8.4"> <name slugifiedName="name-pcep-error-object">PCEP-Error Object</name> <t pn="section-8.4-1">IANA has allocated thecode-pointsfollowing codepoints in thePCEP-ERROR"PCEP-ERROR Object Error Types andValuesValues" registry for the following newerror-values: <vspace blankLines="1" /> <?rfc subcompact="yes"?> <list style="hanging" hangIndent="13"> <t hangText="Error-Type">Meaning</t> <t hangText="---------- -------"></t> <t hangText="10">ReceptionError-values:</t> <table anchor="PCEP-Error-table" align="center" pn="table-4"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Error-Type</th> <th align="left" colspan="1" rowspan="1">Meaning</th> <th align="left" colspan="1" rowspan="1">Error-value</th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">10</td> <td align="left" colspan="1" rowspan="1">Reception of an invalidobject. <list style="hanging" hangIndent="37"> <t hangText=" Error-value = 2:">Badobject</td> <td align="left" colspan="1" rowspan="1"/> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">2: Bad labelvalue</t> <t hangText=" Error-value = 3:">Unsupportedvalue</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">3: Unsupported number of SR-EROsubobjects</t> <t hangText=" Error-value = 4:">Badsubobjects</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">4: Bad labelformat</t> <t hangText=" Error-value = 5:">EROformat</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">5: ERO mixes SR-ERO subobjects with other subobjecttypes</t> <t hangText=" Error-value = 6:">Bothtypes</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">6: Both SID and NAI are absent in the SR-EROsubobject</t> <t hangText=" Error-value = 7:">Bothsubobject</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">7: Both SID and NAI are absent in the SR-RROsubobject</t> <t hangText=" Error-value = 9:">MSDsubobject</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">9: MSD exceeds the default for the PCEPsession</t> <t hangText=" Error-value = 10:">RROsession</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">10: RRO mixes SR-RRO subobjects with other subobjecttypes</t> <t hangText=" Error-value = TBD1:">Missingtypes</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">12: Missing PCE-SR-CAPABILITYsub-TLV</t> <t hangText=" Error-value = TBD2:">Unsupportedsub-TLV</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">13: Unsupported NAI Type inSR-ERO subobject</t> <t hangText=" Error-value = TBD3:">Unknown SID</t> <t hangText=" Error-value = TBD4:">NAIthe SR-ERO/SR-RRO subobject</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">14: Unknown SID</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">15: NAI cannot be resolved to aSID</t> <t hangText=" Error-value = TBD5:">CouldSID</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">16: Could not findSRGB</t> <t hangText=" Error-value = TBD6:">SIDSRGB</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">17: SID index exceeds SRGBsize</t> <t hangText=" Error-value = TBD7:">Couldsize</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">18: Could not findSRLB</t> <t hangText=" Error-value = TBD8:">SIDSRLB</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">19: SID index exceeds SRLBsize</t> <t hangText=" Error-value = TBD9:">Inconsistentsize</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">20: Inconsistent SIDs in SR-ERO / SR-RROsubobjects</t> <t hangText=" Error-value = TBD10:">MSDsubobjects</td> </tr> <tr> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1"/> <td align="left" colspan="1" rowspan="1">21: MSD must benonzero</t> </list> </t> </list> </t> <t>Note to IANA: this draft originally had an early allocation for Error-value=11 (Malformed object) innon-zero</td> </tr> </tbody> </table> </section> <section anchor="IANA-TLV-Type-Indicators" numbered="true" toc="include" removeInRFC="false" pn="section-8.5"> <name slugifiedName="name-pcep-tlv-type-indicators">PCEP TLV Type Indicators</name> <t pn="section-8.5-1">IANA has allocated theabove list. However, we have since movedfollowing codepoint in thedefinition of"PCEP TLV Type Indicators" registry. Note thatcode point to RFC8408.</t> <t>Note to IANA: some Error-values in the above list were defined after the early allocation took place, and so do not currently have a code point assigned. Please assign code points from the indicated registry and replace each instance of "TBD1", "TBD2" etc. in this document with the respective code points.</t> <t>Note to IANA: some of the Error-value descriptive strings above have changed since the early allocation. Please refresh the registry.</t> </section> <section anchor="IANA-TLV-Type-Indicators" title="PCEP TLV Type Indicators"> <t>IANA is requested to confirm the early allocation of the following code point in the PCEP TLV Type Indicators registry. Note that this TLV type indicator is deprecated but retainedthis TLV type indicator is deprecated but retained in the registry to ensure compatibility with early implementations of this specification. See <xreftarget="Early"/>target="Early" format="default" sectionFormat="of" derivedContent="Appendix A"/> for details.</t><texttable<table anchor="PCEP-New-TLV-CP"style="none" suppress-title="true"> <ttcol align="left" width='65%'>Value</ttcol> <ttcol align="left" width='40%'>Meaning </ttcol> <ttcol align="left" width='35%'>Reference </ttcol> <c>-------------------------</c><c>----------------------------</c><c>--------------</c> <c>26</c><c>SR-PCE-CAPABILITY (deprecated)</c><c>This document</c> </texttable>align="center" pn="table-5"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Value</th> <th align="left" colspan="1" rowspan="1">Meaning </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">26</td> <td align="left" colspan="1" rowspan="1">SR-PCE-CAPABILITY (deprecated)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section> <section anchor="IANA-subTLV-Type-Indicators"title="PATH-SETUP-TYPE-CAPABILITYnumbered="true" toc="include" removeInRFC="false" pn="section-8.6"> <name slugifiedName="name-path-setup-type-capability-">PATH-SETUP-TYPE-CAPABILITY Sub-TLV TypeIndicators"> <t>IANA is requested to createIndicators</name> <t pn="section-8.6-1">IANA has created a new sub-registry, named "PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators", within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the type indicator space for sub-TLVs of the PATH-SETUP-TYPE-CAPABILITY TLV. New values are to be assigned by Standards Action <xreftarget="RFC8126"/>.target="RFC8126" format="default" sectionFormat="of" derivedContent="RFC8126"/>. The valid range of values in the registry is 0-65535. IANAis requested to initializehas initialized the registry with the following values. All other values in the registry should be marked as "Unassigned".</t><texttable<table anchor="PCEP-New-subTLV-CP"style="none" suppress-title="true"> <ttcol align="left" width='65%'>Value</ttcol> <ttcol align="left" width='40%'>Meaning </ttcol> <ttcol align="left" width='35%'>Reference </ttcol> <c>-------------------------</c><c>----------------------------</c><c>--------------</c> <c>0</c><c>Reserved</c><c>This document</c> <c>TBD11 (recommended 26)</c><c>SR-PCE-CAPABILITY</c><c>This document</c> </texttable> <t>Note to IANA: Please replace each instance of "TBD11" in this document with the allocated code point. We have recommended that value 26 be used for consistency with the deprecated value in the PCEP TLV Type Indicators registry.</t>align="center" pn="table-6"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Value</th> <th align="left" colspan="1" rowspan="1">Meaning </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">0</td> <td align="left" colspan="1" rowspan="1">Reserved</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="left" colspan="1" rowspan="1">26</td> <td align="left" colspan="1" rowspan="1">SR-PCE-CAPABILITY</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section> <section anchor="IANA-PATH-SETUP-TYPE"title="Newnumbered="true" toc="include" removeInRFC="false" pn="section-8.7"> <name slugifiedName="name-new-path-setup-type">New Path SetupType"> <t><xref target="RFC8408"/> created aType</name> <t pn="section-8.7-1">A sub-registry within the "Path Computation Element Protocol (PCEP) Numbers" registry called "PCEP Path SetupTypes".Types" was created in <xref target="RFC8408" format="default" sectionFormat="of" derivedContent="RFC8408"/>. IANAis requested to allocatehas allocated a newcode pointcodepoint within this registry, as follows:</t><texttable<table anchor="PATH-SETUP-TLV-value"style="none" suppress-title="true"> <ttcol align="left" width='50%'>Value</ttcol> <ttcol align="left" width='50%'>Description </ttcol> <ttcol align="left" width='35%'>Reference </ttcol> <c>-------------------------</c><c>----------------------------</c><c>--------------</c> <c>1</c><c>Traffic engineeringalign="center" pn="table-7"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Value</th> <th align="left" colspan="1" rowspan="1">Description </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">1</td> <td align="left" colspan="1" rowspan="1">Traffic-engineering path issetupset up using SegmentRouting.</c><c>This document</c> </texttable>Routing.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section> <section anchor="IANA-METRIC-TYPE"title="Newnumbered="true" toc="include" removeInRFC="false" pn="section-8.8"> <name slugifiedName="name-new-metric-type">New MetricType"> <t>IANA is requested to confirm the early allocation ofType</name> <t pn="section-8.8-1">IANA has allocated the followingcode pointcodepoint in the PCEPMETRIC object"METRIC Object TfieldField" registry:</t><texttable<table anchor="METRIC-type"style="none" suppress-title="true"> <ttcol align="left" width='50%'>Value</ttcol> <ttcol align="left" width='50%'>Description </ttcol> <ttcol align="left" width='35%'>Reference </ttcol> <c>-------------------------</c><c>----------------------------</c><c>--------------</c> <c>11</c><c>Segment-IDalign="center" pn="table-8"> <thead> <tr> <th align="left" colspan="1" rowspan="1">Value</th> <th align="left" colspan="1" rowspan="1">Description </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="left" colspan="1" rowspan="1">11</td> <td align="left" colspan="1" rowspan="1">Segment-ID (SID)Depth.</c><c>This document</c> </texttable>Depth.</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section> <section anchor="IANA-SR-PCE-CAP-FLAG"title="SRnumbered="true" toc="include" removeInRFC="false" pn="section-8.9"> <name slugifiedName="name-sr-pce-capability-flags">SR PCE CapabilityFlags"> <t>IANA is requested to createFlags</name> <t pn="section-8.9-1">IANA has created a new sub-registry, named "SR Capability Flag Field", within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the Flag field of the SR-PCE-CAPABILITY TLV. New values are to be assigned by Standards Action <xreftarget="RFC8126"/>.target="RFC8126" format="default" sectionFormat="of" derivedContent="RFC8126"/>. Each bit should be tracked with the following qualities:<list style="symbols"> <t>Bit</t> <ul spacing="normal" bare="false" empty="false" pn="section-8.9-2"> <li pn="section-8.9-2.1">Bit number (counting from bit 0 as the most significantbit)</t> <t>Capability description</t> <t>Defining RFC</t> </list> </t> <t>Thebit)</li> <li pn="section-8.9-2.2">Capability description</li> <li pn="section-8.9-2.3">Defining RFC</li> </ul> <t pn="section-8.9-3">The following values are defined in this document:</t><texttable<table anchor="SR-PCE-CAP-Flags"style="none" suppress-title="true"> <ttcolalign="center"width='15%'>Bit</ttcol> <ttcolpn="table-9"> <thead> <tr> <th align="center" colspan="1" rowspan="1">Bit</th> <th align="left" colspan="1" rowspan="1">Description </th> <th align="left" colspan="1" rowspan="1">Reference </th> </tr> </thead> <tbody> <tr> <td align="center" colspan="1" rowspan="1">0-5</td> <td align="left"width='30%'>Description </ttcol> <ttcol align="left" width='55%'>Reference </ttcol> <c></c><c> </c><c></c> <c>0-5</c><c>Unassigned</c><c></c> <c>6</c><c>Nodecolspan="1" rowspan="1">Unassigned</td> <td align="left" colspan="1" rowspan="1"/> </tr> <tr> <td align="center" colspan="1" rowspan="1">6</td> <td align="left" colspan="1" rowspan="1">Node or Adjacency Identifier (NAI) is supported(N)</c><c>This document</c> <c>7</c><c>Unlimited Maximum SID Depth (X)</c><c>This document</c> </texttable> <t>Note to IANA: The name of bit 7 has changed from "Unlimited Maximum SID Depth (L)" to "Unlimited(N)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> <tr> <td align="center" colspan="1" rowspan="1">7</td> <td align="left" colspan="1" rowspan="1">Unlimited Maximum SID Depth(X)".</t> </section> <!-- SR PCE Capability Flags --> </section> <section anchor="Contributors" title="Contributors"> <?rfc subcompact="yes"?> <t>The following people contributed to this document: <list style="empty"> <t>- Lakshmi Sharma</t> <t>- Jan Medved</t> <t>- Edward Crabbe</t> <t>- Robert Raszuk</t> <t>- Victor Lopez</t> </list> </t> <?rfc subcompact="no"?>(X)</td> <td align="left" colspan="1" rowspan="1">This document</td> </tr> </tbody> </table> </section><section anchor="Acknowledgement" title="Acknowledgements"> <t>We thank Ina Minei, George Swallow, Marek Zavodsky, Dhruv Dhody, Ing-Wher Chen and Tomas Janciga for the valuable comments.</t></section> </middle> <back> <displayreference target="I-D.ietf-6man-segment-routing-header" to="IPv6-SRH"/> <displayreference target="I-D.ietf-spring-segment-routing-policy" to="SR-POLICY"/> <displayreference target="I-D.ietf-idr-bgp-ls-segment-routing-msd" to="MSD-BGP"/> <displayreference target="I-D.ietf-pce-pcep-yang" to="PCE-PCEP-YANG"/> <referencestitle="Normative References"> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.3032.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.5440.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8174.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8231.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8281.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8402.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8408.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8491.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-spring-segment-routing-mpls-18.xml"?> </references>pn="section-9"> <name slugifiedName="name-references">References</name> <referencestitle="Informative References"> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.3209.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4657.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.7420.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8126.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8413.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.8476.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-6man-segment-routing-header-16.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-spring-segment-routing-policy-02.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-isis-segment-routing-extensions-22.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-ospf-segment-routing-extensions-27.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-idr-bgp-ls-segment-routing-msd-02.xml"?> <?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-pce-pcep-yang-09.xml"?> </references> <section anchor="Early" title="Compatibility with Early Implementations"> <t> An early implementation of this specification will send the SR-CAPABILITY-TLV as a top-level TLVpn="section-9.1"> <name slugifiedName="name-normative-references">Normative References</name> <reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2119" quoteTitle="true" derivedAnchor="RFC2119"> <front> <title>Key words for use in RFCs to Indicate Requirement Levels</title> <author initials="S." surname="Bradner" fullname="S. Bradner"> <organization showOnFrontPage="true"/> </author> <date year="1997" month="March"/> <abstract> <t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="2119"/> <seriesInfo name="DOI" value="10.17487/RFC2119"/> </reference> <reference anchor="RFC3032" target="https://www.rfc-editor.org/info/rfc3032" quoteTitle="true" derivedAnchor="RFC3032"> <front> <title>MPLS Label Stack Encoding</title> <author initials="E." surname="Rosen" fullname="E. Rosen"> <organization showOnFrontPage="true"/> </author> <author initials="D." surname="Tappan" fullname="D. Tappan"> <organization showOnFrontPage="true"/> </author> <author initials="G." surname="Fedorkow" fullname="G. Fedorkow"> <organization showOnFrontPage="true"/> </author> <author initials="Y." surname="Rekhter" fullname="Y. Rekhter"> <organization showOnFrontPage="true"/> </author> <author initials="D." surname="Farinacci" fullname="D. Farinacci"> <organization showOnFrontPage="true"/> </author> <author initials="T." surname="Li" fullname="T. Li"> <organization showOnFrontPage="true"/> </author> <author initials="A." surname="Conta" fullname="A. Conta"> <organization showOnFrontPage="true"/> </author> <date year="2001" month="January"/> <abstract> <t>This document specifies the encoding to be used by an LSR in order to transmit labeled packets on Point-to-Point Protocol (PPP) data links, on LAN data links, and possibly on other data links as well. This document also specifies rules and procedures for processing the various fields of the label stack encoding. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="3032"/> <seriesInfo name="DOI" value="10.17487/RFC3032"/> </reference> <reference anchor="RFC5440" target="https://www.rfc-editor.org/info/rfc5440" quoteTitle="true" derivedAnchor="RFC5440"> <front> <title>Path Computation Element (PCE) Communication Protocol (PCEP)</title> <author initials="JP." surname="Vasseur" fullname="JP. Vasseur" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="JL." surname="Le Roux" fullname="JL. Le Roux" role="editor"> <organization showOnFrontPage="true"/> </author> <date year="2009" month="March"/> <abstract> <t>This document specifies the Path Computation Element (PCE) Communication Protocol (PCEP) for communications between a Path Computation Client (PCC) and a PCE, or between two PCEs. Such interactions include path computation requests and path computation replies as well as notifications of specific states related to the use of a PCE in the context of Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering. PCEP is designed to be flexible and extensible so as to easily allow for the addition of further messages and objects, should further requirements be expressed in the future. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5440"/> <seriesInfo name="DOI" value="10.17487/RFC5440"/> </reference> <reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8174" quoteTitle="true" derivedAnchor="RFC8174"> <front> <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title> <author initials="B." surname="Leiba" fullname="B. Leiba"> <organization showOnFrontPage="true"/> </author> <date year="2017" month="May"/> <abstract> <t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="8174"/> <seriesInfo name="DOI" value="10.17487/RFC8174"/> </reference> <reference anchor="RFC8231" target="https://www.rfc-editor.org/info/rfc8231" quoteTitle="true" derivedAnchor="RFC8231"> <front> <title>Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE</title> <author initials="E." surname="Crabbe" fullname="E. Crabbe"> <organization showOnFrontPage="true"/> </author> <author initials="I." surname="Minei" fullname="I. Minei"> <organization showOnFrontPage="true"/> </author> <author initials="J." surname="Medved" fullname="J. Medved"> <organization showOnFrontPage="true"/> </author> <author initials="R." surname="Varga" fullname="R. Varga"> <organization showOnFrontPage="true"/> </author> <date year="2017" month="September"/> <abstract> <t>The Path Computation Element Communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform path computations in response to Path Computation Client (PCC) requests.</t> <t>Although PCEP explicitly makes no assumptions regarding the information available to the PCE, it also makes no provisions for PCE control of timing and sequence of path computations within and across PCEP sessions. This document describes a set of extensions to PCEP to enable stateful control of MPLS-TE and GMPLS Label Switched Paths (LSPs) via PCEP.</t> </abstract> </front> <seriesInfo name="RFC" value="8231"/> <seriesInfo name="DOI" value="10.17487/RFC8231"/> </reference> <reference anchor="RFC8281" target="https://www.rfc-editor.org/info/rfc8281" quoteTitle="true" derivedAnchor="RFC8281"> <front> <title>Path Computation Element Communication Protocol (PCEP) Extensions for PCE-Initiated LSP Setup in a Stateful PCE Model</title> <author initials="E." surname="Crabbe" fullname="E. Crabbe"> <organization showOnFrontPage="true"/> </author> <author initials="I." surname="Minei" fullname="I. Minei"> <organization showOnFrontPage="true"/> </author> <author initials="S." surname="Sivabalan" fullname="S. Sivabalan"> <organization showOnFrontPage="true"/> </author> <author initials="R." surname="Varga" fullname="R. Varga"> <organization showOnFrontPage="true"/> </author> <date year="2017" month="December"/> <abstract> <t>The Path Computation Element Communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform path computations in response to Path Computation Client (PCC) requests.</t> <t>The extensions for stateful PCE provide active control of Multiprotocol Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE LSPs) via PCEP, for a model where the PCC delegates control over one or more locally configured LSPs to the PCE. This document describes the creation and deletion of PCE-initiated LSPs under the stateful PCE model.</t> </abstract> </front> <seriesInfo name="RFC" value="8281"/> <seriesInfo name="DOI" value="10.17487/RFC8281"/> </reference> <reference anchor="RFC8402" target="https://www.rfc-editor.org/info/rfc8402" quoteTitle="true" derivedAnchor="RFC8402"> <front> <title>Segment Routing Architecture</title> <author initials="C." surname="Filsfils" fullname="C. Filsfils" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="S." surname="Previdi" fullname="S. Previdi" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="L." surname="Ginsberg" fullname="L. Ginsberg"> <organization showOnFrontPage="true"/> </author> <author initials="B." surname="Decraene" fullname="B. Decraene"> <organization showOnFrontPage="true"/> </author> <author initials="S." surname="Litkowski" fullname="S. Litkowski"> <organization showOnFrontPage="true"/> </author> <author initials="R." surname="Shakir" fullname="R. Shakir"> <organization showOnFrontPage="true"/> </author> <date year="2018" month="July"/> <abstract> <t>Segment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". A segment can represent any instruction, topological or service based. A segment can have a semantic local to an SR node or global within an SR domain. SR provides a mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain.</t> <t>SR can be directly applied to the MPLS architecture with no change to the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. Upon completion of a segment, the related label is popped from the stack.</t> <t>SR can be applied to the IPv6 architecture, with a new type of routing header. A segment is encoded as an IPv6 address. An ordered list of segments is encoded as an ordered list of IPv6 addresses in the routing header. The active segment is indicated by the Destination Address (DA) of the packet. The next active segment is indicated by a pointer in the new routing header.</t> </abstract> </front> <seriesInfo name="RFC" value="8402"/> <seriesInfo name="DOI" value="10.17487/RFC8402"/> </reference> <reference anchor="RFC8408" target="https://www.rfc-editor.org/info/rfc8408" quoteTitle="true" derivedAnchor="RFC8408"> <front> <title>Conveying Path Setup Type in PCE Communication Protocol (PCEP) Messages</title> <author initials="S." surname="Sivabalan" fullname="S. Sivabalan"> <organization showOnFrontPage="true"/> </author> <author initials="J." surname="Tantsura" fullname="J. Tantsura"> <organization showOnFrontPage="true"/> </author> <author initials="I." surname="Minei" fullname="I. Minei"> <organization showOnFrontPage="true"/> </author> <author initials="R." surname="Varga" fullname="R. Varga"> <organization showOnFrontPage="true"/> </author> <author initials="J." surname="Hardwick" fullname="J. Hardwick"> <organization showOnFrontPage="true"/> </author> <date year="2018" month="July"/> <abstract> <t>A Path Computation Element (PCE) can compute Traffic Engineering (TE) paths through a network; these paths are subject to various constraints. Currently, TE paths are Label Switched Paths (LSPs) that are set up using the RSVP-TE signaling protocol. However, other TE path setup methods are possible within the PCE architecture. This document proposes an extension to the PCE Communication Protocol (PCEP) to allow support for different path setup methods over a given PCEP session.</t> </abstract> </front> <seriesInfo name="RFC" value="8408"/> <seriesInfo name="DOI" value="10.17487/RFC8408"/> </reference> <reference anchor="RFC8491" target="https://www.rfc-editor.org/info/rfc8491" quoteTitle="true" derivedAnchor="RFC8491"> <front> <title>Signaling Maximum SID Depth (MSD) Using IS-IS</title> <author initials="J." surname="Tantsura" fullname="J. Tantsura"> <organization showOnFrontPage="true"/> </author> <author initials="U." surname="Chunduri" fullname="U. Chunduri"> <organization showOnFrontPage="true"/> </author> <author initials="S." surname="Aldrin" fullname="S. Aldrin"> <organization showOnFrontPage="true"/> </author> <author initials="L." surname="Ginsberg" fullname="L. Ginsberg"> <organization showOnFrontPage="true"/> </author> <date year="2018" month="November"/> <abstract> <t>This document defines a way for an Intermediate System to Intermediate System (IS-IS) router to advertise multiple types of supported Maximum SID Depths (MSDs) at node and/or link granularity. Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular Segment ID (SID) stack can be supported in a given network. This document only defines one type of MSD: Base MPLS Imposition. However, it defines an encoding that can support other MSD types. This document focuses on MSD use in a network that is Segment Routing (SR) enabled, but MSD may also be useful when SR is not enabled.</t> </abstract> </front> <seriesInfo name="RFC" value="8491"/> <seriesInfo name="DOI" value="10.17487/RFC8491"/> </reference> <reference anchor="RFC8660" target="https://www.rfc-editor.org/info/rfc8660" quoteTitle="true" derivedAnchor="RFC8660"> <front> <title>Segment Routing with the MPLS Data Plane</title> <author initials="A" surname="Bashandy" fullname="Ahmed Bashandy" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="C" surname="Filsfils" fullname="Clarence Filsfils" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Previdi" fullname="Stefano Previdi"> <organization showOnFrontPage="true"/> </author> <author initials="B" surname="Decraene" fullname="Bruno Decraene"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Litkowski" fullname="Stephane Litkowski"> <organization showOnFrontPage="true"/> </author> <author initials="R" surname="Shakir" fullname="Rob Shakir"> <organization showOnFrontPage="true"/> </author> <date month="December" year="2019"/> </front> <seriesInfo name="RFC" value="8660"/> <seriesInfo name="DOI" value="10.17487/RFC8660"/> </reference> </references> <references pn="section-9.2"> <name slugifiedName="name-informative-references">Informative References</name> <reference anchor="I-D.ietf-6man-segment-routing-header" quoteTitle="true" target="https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26" derivedAnchor="IPv6-SRH"> <front> <title>IPv6 Segment Routing Header (SRH)</title> <author initials="C" surname="Filsfils" fullname="Clarence Filsfils"> <organization showOnFrontPage="true"/> </author> <author initials="D" surname="Dukes" fullname="Darren Dukes"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Previdi" fullname="Stefano Previdi"> <organization showOnFrontPage="true"/> </author> <author initials="J" surname="Leddy" fullname="John Leddy"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Matsushima" fullname="Satoru Matsushima"> <organization showOnFrontPage="true"/> </author> <author initials="D" surname="Voyer" fullname="Daniel Voyer"> <organization showOnFrontPage="true"/> </author> <date month="October" day="22" year="2019"/> <abstract> <t>Segment Routing can be applied to the IPv6 data plane using a new type of Routing Extension Header called the Segment Routing Header. This document describes the Segment Routing Header and how it is used by Segment Routing capable nodes.</t> </abstract> </front> <seriesInfo name="Internet-Draft" value="draft-ietf-6man-segment-routing-header-26"/> <format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-6man-segment-routing-header-26.txt"/> <refcontent>Work in Progress</refcontent> </reference> <reference anchor="I-D.ietf-idr-bgp-ls-segment-routing-msd" quoteTitle="true" target="https://tools.ietf.org/html/draft-ietf-idr-bgp-ls-segment-routing-msd-09" derivedAnchor="MSD-BGP"> <front> <title>Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link-State</title> <author initials="J" surname="Tantsura" fullname="Jeff Tantsura"> <organization showOnFrontPage="true"/> </author> <author initials="U" surname="Chunduri" fullname="Uma Chunduri"> <organization showOnFrontPage="true"/> </author> <author initials="K" surname="Talaulikar" fullname="Ketan Talaulikar"> <organization showOnFrontPage="true"/> </author> <author initials="G" surname="Mirsky" fullname="Gregory Mirsky"> <organization showOnFrontPage="true"/> </author> <author initials="N" surname="Triantafillis" fullname="Nikos Triantafillis"> <organization showOnFrontPage="true"/> </author> <date month="October" day="15" year="2019"/> <abstract> <t>This document defines a way for a Border Gateway Protocol Link-State (BGP-LS) speaker to advertise multiple types of supported Maximum SID Depths (MSDs) at node and/or link granularity. Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular Segment Identifier (SID) stack can be supported in a given network.</t> </abstract> </front> <seriesInfo name="Internet-Draft" value="draft-ietf-idr-bgp-ls-segment-routing-msd-09"/> <format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-idr-bgp-ls-segment-routing-msd-09.txt"/> <refcontent>Work in Progress</refcontent> </reference> <reference anchor="I-D.ietf-pce-pcep-yang" quoteTitle="true" target="https://tools.ietf.org/html/draft-ietf-pce-pcep-yang-13" derivedAnchor="PCE-PCEP-YANG"> <front> <title>A YANG Data Model for Path Computation Element Communications Protocol (PCEP)</title> <author initials="D" surname="Dhody" fullname="Dhruv Dhody"> <organization showOnFrontPage="true"/> </author> <author initials="J" surname="Hardwick" fullname="Jonathan Hardwick"> <organization showOnFrontPage="true"/> </author> <author initials="V" surname="Beeram" fullname="Vishnu Beeram"> <organization showOnFrontPage="true"/> </author> <author initials="J" surname="Tantsura" fullname="Jeff Tantsura"> <organization showOnFrontPage="true"/> </author> <date month="October" day="31" year="2019"/> <abstract> <t>This document defines a YANG data model for the management of Path Computation Element communications Protocol (PCEP) for communications between a Path Computation Client (PCC) and a Path Computation Element (PCE), or between two PCEs. The data model includes configuration and state data.</t> </abstract> </front> <seriesInfo name="Internet-Draft" value="draft-ietf-pce-pcep-yang-13"/> <format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-pce-pcep-yang-13.txt"/> <refcontent>Work in Progress</refcontent> </reference> <reference anchor="RFC3209" target="https://www.rfc-editor.org/info/rfc3209" quoteTitle="true" derivedAnchor="RFC3209"> <front> <title>RSVP-TE: Extensions to RSVP for LSP Tunnels</title> <author initials="D." surname="Awduche" fullname="D. Awduche"> <organization showOnFrontPage="true"/> </author> <author initials="L." surname="Berger" fullname="L. Berger"> <organization showOnFrontPage="true"/> </author> <author initials="D." surname="Gan" fullname="D. Gan"> <organization showOnFrontPage="true"/> </author> <author initials="T." surname="Li" fullname="T. Li"> <organization showOnFrontPage="true"/> </author> <author initials="V." surname="Srinivasan" fullname="V. Srinivasan"> <organization showOnFrontPage="true"/> </author> <author initials="G." surname="Swallow" fullname="G. Swallow"> <organization showOnFrontPage="true"/> </author> <date year="2001" month="December"/> <abstract> <t>This document describes the use of RSVP (Resource Reservation Protocol), including all the necessary extensions, to establish label-switched paths (LSPs) in MPLS (Multi-Protocol Label Switching). Since the flow along an LSP is completely identified by the label applied at the ingress node of the path, these paths may be treated as tunnels. A key application of LSP tunnels is traffic engineering with MPLS as specified in RFC 2702. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="3209"/> <seriesInfo name="DOI" value="10.17487/RFC3209"/> </reference> <reference anchor="RFC4657" target="https://www.rfc-editor.org/info/rfc4657" quoteTitle="true" derivedAnchor="RFC4657"> <front> <title>Path Computation Element (PCE) Communication Protocol Generic Requirements</title> <author initials="J." surname="Ash" fullname="J. Ash" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="J.L." surname="Le Roux" fullname="J.L. Le Roux" role="editor"> <organization showOnFrontPage="true"/> </author> <date year="2006" month="September"/> <abstract> <t>The PCE model is described in the "PCE Architecture" document and facilitates path computation requests from Path Computation Clients (PCCs) to Path Computation Elements (PCEs). This document specifies generic requirements for a communication protocol between PCCs and PCEs, and also between PCEs where cooperation between PCEs is desirable. Subsequent documents will specify application-specific requirements for the PCE communication protocol. This memo provides information for the Internet community.</t> </abstract> </front> <seriesInfo name="RFC" value="4657"/> <seriesInfo name="DOI" value="10.17487/RFC4657"/> </reference> <reference anchor="RFC7420" target="https://www.rfc-editor.org/info/rfc7420" quoteTitle="true" derivedAnchor="RFC7420"> <front> <title>Path Computation Element Communication Protocol (PCEP) Management Information Base (MIB) Module</title> <author initials="A." surname="Koushik" fullname="A. Koushik"> <organization showOnFrontPage="true"/> </author> <author initials="E." surname="Stephan" fullname="E. Stephan"> <organization showOnFrontPage="true"/> </author> <author initials="Q." surname="Zhao" fullname="Q. Zhao"> <organization showOnFrontPage="true"/> </author> <author initials="D." surname="King" fullname="D. King"> <organization showOnFrontPage="true"/> </author> <author initials="J." surname="Hardwick" fullname="J. Hardwick"> <organization showOnFrontPage="true"/> </author> <date year="2014" month="December"/> <abstract> <t>This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes managed objects for modeling of the Path Computation Element Communication Protocol (PCEP) for communications between a Path Computation Client (PCC) and a Path Computation Element (PCE), or between two PCEs.</t> </abstract> </front> <seriesInfo name="RFC" value="7420"/> <seriesInfo name="DOI" value="10.17487/RFC7420"/> </reference> <reference anchor="RFC8126" target="https://www.rfc-editor.org/info/rfc8126" quoteTitle="true" derivedAnchor="RFC8126"> <front> <title>Guidelines for Writing an IANA Considerations Section in RFCs</title> <author initials="M." surname="Cotton" fullname="M. Cotton"> <organization showOnFrontPage="true"/> </author> <author initials="B." surname="Leiba" fullname="B. Leiba"> <organization showOnFrontPage="true"/> </author> <author initials="T." surname="Narten" fullname="T. Narten"> <organization showOnFrontPage="true"/> </author> <date year="2017" month="June"/> <abstract> <t>Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).</t> <t>To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.</t> <t>This is the third edition of this document; it obsoletes RFC 5226.</t> </abstract> </front> <seriesInfo name="BCP" value="26"/> <seriesInfo name="RFC" value="8126"/> <seriesInfo name="DOI" value="10.17487/RFC8126"/> </reference> <reference anchor="RFC8413" target="https://www.rfc-editor.org/info/rfc8413" quoteTitle="true" derivedAnchor="RFC8413"> <front> <title>Framework for Scheduled Use of Resources</title> <author initials="Y." surname="Zhuang" fullname="Y. Zhuang"> <organization showOnFrontPage="true"/> </author> <author initials="Q." surname="Wu" fullname="Q. Wu"> <organization showOnFrontPage="true"/> </author> <author initials="H." surname="Chen" fullname="H. Chen"> <organization showOnFrontPage="true"/> </author> <author initials="A." surname="Farrel" fullname="A. Farrel"> <organization showOnFrontPage="true"/> </author> <date year="2018" month="July"/> <abstract> <t>Time-Scheduled (TS) reservation of Traffic Engineering (TE) resources can be used to provide resource booking for TE Label Switched Paths so as to better guarantee services for customers and to improve the efficiency of network resource usage at any moment in time, including network usage that is planned for the future. This document provides a framework that describes and discusses the architecture for supporting scheduled reservation of TE resources. This document does not describe specific protocols or protocol extensions needed to realize this service.</t> </abstract> </front> <seriesInfo name="RFC" value="8413"/> <seriesInfo name="DOI" value="10.17487/RFC8413"/> </reference> <reference anchor="RFC8476" target="https://www.rfc-editor.org/info/rfc8476" quoteTitle="true" derivedAnchor="RFC8476"> <front> <title>Signaling Maximum SID Depth (MSD) Using OSPF</title> <author initials="J." surname="Tantsura" fullname="J. Tantsura"> <organization showOnFrontPage="true"/> </author> <author initials="U." surname="Chunduri" fullname="U. Chunduri"> <organization showOnFrontPage="true"/> </author> <author initials="S." surname="Aldrin" fullname="S. Aldrin"> <organization showOnFrontPage="true"/> </author> <author initials="P." surname="Psenak" fullname="P. Psenak"> <organization showOnFrontPage="true"/> </author> <date year="2018" month="December"/> <abstract> <t>This document defines a way for an Open Shortest Path First (OSPF) router to advertise multiple types of supported Maximum SID Depths (MSDs) at node and/or link granularity. Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular Segment Identifier (SID) stack can be supported in a given network. This document only refers to the Signaling MSD as defined in RFC 8491, but it defines an encoding that can support other MSD types. Here, the term "OSPF" means both OSPFv2 and OSPFv3.</t> </abstract> </front> <seriesInfo name="RFC" value="8476"/> <seriesInfo name="DOI" value="10.17487/RFC8476"/> </reference> <reference anchor="RFC8665" target="https://www.rfc-editor.org/info/rfc8665" quoteTitle="true" derivedAnchor="RFC8665"> <front> <title>OSPF Extensions for Segment Routing</title> <author initials="P" surname="Psenak" fullname="Peter Psenak" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Previdi" fullname="Stefano Previdi" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="C" surname="Filsfils" fullname="Clarence Filsfils"> <organization showOnFrontPage="true"/> </author> <author initials="H" surname="Gredler" fullname="Hannes Gredler"> <organization showOnFrontPage="true"/> </author> <author initials="R" surname="Shakir" fullname="Rob Shakir"> <organization showOnFrontPage="true"/> </author> <author initials="W" surname="Henderickx" fullname="Wim Henderickx"> <organization showOnFrontPage="true"/> </author> <author initials="J" surname="Tantsura" fullname="Jeff Tantsura"> <organization showOnFrontPage="true"/> </author> <date month="December" year="2019"/> </front> <seriesInfo name="RFC" value="8665"/> <seriesInfo name="DOI" value="10.17487/RFC8665"/> </reference> <reference anchor="RFC8667" target="https://www.rfc-editor.org/info/rfc8667" quoteTitle="true" derivedAnchor="RFC8667"> <front> <title>IS-IS Extensions for Segment Routing</title> <author initials="S" surname="Previdi" fullname="Stefano Previdi" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="L" surname="Ginsberg" fullname="Les Ginsberg" role="editor"> <organization showOnFrontPage="true"/> </author> <author initials="C" surname="Filsfils" fullname="Clarence Filsfils"> <organization showOnFrontPage="true"/> </author> <author initials="A" surname="Bashandy" fullname="Ahmed Bashandy"> <organization showOnFrontPage="true"/> </author> <author initials="H" surname="Gredler" fullname="Hannes Gredler"> <organization showOnFrontPage="true"/> </author> <author initials="B" surname="Decraene" fullname="Bruno Decraene"> <organization showOnFrontPage="true"/> </author> <date month="December" year="2019"/> </front> <seriesInfo name="RFC" value="8667"/> <seriesInfo name="DOI" value="10.17487/RFC8667"/> </reference> <reference anchor="I-D.ietf-spring-segment-routing-policy" quoteTitle="true" target="https://tools.ietf.org/html/draft-ietf-spring-segment-routing-policy-05" derivedAnchor="SR-POLICY"> <front> <title>Segment Routing Policy Architecture</title> <author initials="C" surname="Filsfils" fullname="Clarence Filsfils"> <organization showOnFrontPage="true"/> </author> <author initials="S" surname="Sivabalan" fullname="Siva Sivabalan"> <organization showOnFrontPage="true"/> </author> <author initials="D" surname="Voyer" fullname="Daniel Voyer"> <organization showOnFrontPage="true"/> </author> <author initials="A" surname="Bogdanov" fullname="Alex Bogdanov"> <organization showOnFrontPage="true"/> </author> <author initials="P" surname="Mattes" fullname="Paul Mattes"> <organization showOnFrontPage="true"/> </author> <date month="November" day="17" year="2019"/> <abstract> <t>Segment Routing (SR) allows a headend node to steer a packet flow along any path. Intermediate per-flow states are eliminated thanks to source routing. The headend node steers a flow into an SR Policy. The header of a packet steered in an SR Policy is augmented with an ordered list of segments associated with that SR Policy. This document details the concepts of SR Policy and steering into an SR Policy.</t> </abstract> </front> <seriesInfo name="Internet-Draft" value="draft-ietf-spring-segment-routing-policy-05"/> <format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-spring-segment-routing-policy-05.txt"/> <refcontent>Work in Progress</refcontent> </reference> </references> </references> <section anchor="Early" numbered="true" toc="include" removeInRFC="false" pn="section-appendix.a"> <name slugifiedName="name-compatibility-with-early-im">Compatibility with Early Implementations</name> <t pn="section-appendix.a-1"> An early implementation of this specification will send the SR-CAPABILITY-TLV as a top-level TLV in the OPEN object instead of sending the PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN object. Implementations that wish to interoperate with such early implementations should also send the SR-CAPABILITY-TLV as a top-level TLV in their OPEN object and should interpret receiving this top-level TLV as though the sender had sent a PATH-SETUP-TYPE-CAPABILITY TLV with a PST list of (0, 1) (that is, both RSVP-TE and SR-TE PSTs are supported) with the SR-CAPABILITY-TLV as a sub-TLV. If a PCEP speaker receives an OPEN object in which both the SR-CAPABILITY-TLV and PATH-SETUP-TYPE-CAPABILITY TLV appear as top-level TLVs, then it should ignore the top-level SR-CAPABILITY-TLV and process only the PATH-SETUP-TYPE-CAPABILITY TLV. </t> </section> <section anchor="Acknowledgement" numbered="false" toc="include" removeInRFC="false" pn="section-appendix.b"> <name slugifiedName="name-acknowledgements">Acknowledgements</name> <t pn="section-appendix.b-1">We thank Ina Minei, George Swallow, Marek Zavodsky, Dhruv Dhody, Ing-Wher Chen, and Tomas Janciga for the valuable comments.</t> </section> <section anchor="Contributors" numbered="false" toc="include" removeInRFC="false" pn="section-appendix.c"> <name slugifiedName="name-contributors">Contributors</name> <t pn="section-appendix.c-1">The following people contributed to this document: </t> <ul spacing="compact" bare="false" empty="false" pn="section-appendix.c-2"> <li pn="section-appendix.c-2.1">Lakshmi Sharma</li> <li pn="section-appendix.c-2.2">Jan Medved</li> <li pn="section-appendix.c-2.3">Edward Crabbe</li> <li pn="section-appendix.c-2.4">Robert Raszuk</li> <li pn="section-appendix.c-2.5">Victor Lopez</li> </ul> </section> <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc="include" pn="section-appendix.d"> <name slugifiedName="name-authors-addresses">Authors' Addresses</name> <author fullname="Siva Sivabalan" initials="S." surname="Sivabalan"> <organization showOnFrontPage="true">Cisco Systems, Inc.</organization> <address> <postal> <street>2000 Innovation Drive</street> <city>Kanata</city> <region>Ontario</region> <code>K2K 3E8</code> <country>Canada</country> </postal> <email>msiva@cisco.com</email> </address> </author> <author fullname="Clarence Filsfils" initials="C." surname="Filsfils"> <organization showOnFrontPage="true">Cisco Systems, Inc.</organization> <address> <postal> <street>Pegasus Parc</street> <city>De kleetlaan 6a</city> <region>Diegem</region> <code>Brabant 1831</code> <country>Belgium</country> </postal> <email>cfilsfil@cisco.com</email> </address> </author> <author fullname="Jeff Tantsura" initials="J." surname="Tantsura"> <organization showOnFrontPage="true">Apstra, Inc.</organization> <address> <postal> <street>333 Middlefield Rd #200</street> <city>Menlo Park</city> <region>CA</region> <code>94025</code> <country>United States of America</country> </postal> <email>jefftant.ietf@gmail.com</email> </address> </author> <author fullname="Wim Henderickx" initials="W." surname="Henderickx"> <organization showOnFrontPage="true">Nokia</organization> <address> <postal> <street>Copernicuslaan 50</street> <city>Antwerp 2018</city> <region>CA</region> <code>95134</code> <country>Belgium</country> </postal> <email>wim.henderickx@nokia.com</email> </address> </author> <author fullname="Jon Hardwick" initials="J." surname="Hardwick"> <organization showOnFrontPage="true">Metaswitch Networks</organization> <address> <postal> <street>100 Church Street</street> <city>Enfield</city> <region>Middlesex</region> <country>United Kingdom</country> </postal> <email>jonathan.hardwick@metaswitch.com</email> </address> </author> </section> </back> </rfc>