



Internet Engineering Task Force (IETF)                      S. Litkowski
Request for Comments: 9902                                 Cisco Systems
Category: Standards Track                                          Y. Qu
ISSN: 2070-1721                                   Futurewei Technologies
                                                               A. Lindem
                                                 LabN Consulting, L.L.C.
                                                                 I. Chen
                                                           Red Hat, Inc.
                                                             J. Tantsura
                                                                  Nvidia
                                                           December 2025


  A YANG Data Model for IS-IS Segment Routing over the MPLS Data Plane

Abstract

   This document defines a YANG data model that can be used to manage
   IS-IS extensions for Segment Routing (SR) over the MPLS data plane.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9902.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Overview
     1.1.  Tree Diagrams
   2.  Design of the YANG Module for IS-IS MPLS Segment Routing
     2.1.  Segment Routing Activation
     2.2.  Advertising Mapping Server Policy
     2.3.  IP Fast Reroute
   3.  IS-IS Segment Routing over MPLS YANG Module
   4.  Security Considerations
   5.  IANA Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Appendix A.  A Configuration Example
   Appendix B.  IS-IS MPLS Segment Routing Module Tree
   Acknowledgements
   Authors' Addresses

1.  Overview

   This document defines a device YANG data model [RFC7950] that can be
   used to manage IS-IS extensions for Segment Routing (SR) [RFC8667]
   over the MPLS data plane.  It is an augmentation to the IS-IS YANG
   data model [RFC9130].

1.1.  Tree Diagrams

   This document uses the graphical representation of a data model as
   defined in [RFC8340].

2.  Design of the YANG Module for IS-IS MPLS Segment Routing

   The IS-IS SR MPLS YANG module requires support for the base SR module
   [RFC9020], which defines the global SR management independent of any
   specific routing protocol configuration, and support of the IS-IS
   base model [RFC9130], which defines the basic IS-IS configuration and
   state.

   The "ietf-isis-sr-mpls" data model defines both the data nodes to
   configure IS-IS SR MPLS extensions and the additions to the IS-IS
   Link State Protocol Data Units (LSPs) necessary to support MPLS SR.

2.1.  Segment Routing Activation

   Activation of IS-IS SR MPLS is done by setting the "enable" leaf to
   true.  This triggers advertisement of SR MPLS extensions based on the
   configuration parameters that have been set up using the base SR
   module.

2.2.  Advertising Mapping Server Policy

   The base SR module defines mapping server policies.  By default, IS-
   IS will not advertise or process any mapping server entry.  The IS-IS
   SR MPLS module allows the advertisement of one or multiple mapping
   server policies through the "bindings/advertise/policies" leaf-list.
   The "bindings/receive" leaf controls the reception and process of
   mapping server entries.

2.3.  IP Fast Reroute

   The IS-IS SR MPLS module augments the Fast Reroute (FRR) container
   under interface.  It brings the ability to activate Topology
   Independent Loop-Free Alternate (TI-LFA) and also enhances Remote LFA
   (RLFA) to use SR tunneling instead of LDP.

3.  IS-IS Segment Routing over MPLS YANG Module

   [RFC6991], [RFC8102], [RFC8294], [RFC8349], [RFC8402], [RFC8667],
   [RFC9020], [RFC9130], and [RFC9855] are referenced in the YANG
   module.

   <CODE BEGINS> file "ietf-isis-sr-mpls@2025-12-09.yang"
   module ietf-isis-sr-mpls {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls";
     prefix isis-sr-mpls;

     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349: A YANG Data Model for Routing
                     Management (NMDA Version)";
     }
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-segment-routing-common {
       prefix sr-cmn;
       reference
         "RFC 9020: YANG Data Model for Segment Routing";
     }
     import ietf-segment-routing-mpls {
       prefix sr-mpls;
       reference
         "RFC 9020: YANG Data Model for Segment Routing";
     }
     import ietf-isis {
       prefix isis;
       reference
         "RFC 9130: YANG Data Model for IS-IS Protocol";
     }
     import iana-routing-types {
       prefix iana-rt-types;
       reference
         "RFC 8294: Common YANG Data Types for the Routing Area";
     }
     import ietf-routing-types {
       prefix rt-types;
       reference
         "RFC 8294: Common YANG Data Types for the Routing Area";
     }

     organization
       "IETF LSR - Link State Routing Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/lsr/>
        WG List:  <mailto:lsr@ietf.org>

        Author:    Stephane Litkowski
                   <mailto:slitkows.ietf@gmail.com>
        Author:    Yingzhen Qu
                   <mailto:yingzhen.ietf@gmail.com>
        Author:    Acee Lindem
                   <mailto:acee.ietf@gmail.com>
        Author:    Ing-Wher Chen
                   <mailto:ichen@redhat.com>
        Author:    Jeff Tantsura
                   <mailto:jefftant.ietf@gmail.com>
       ";
     description
       "This YANG module defines the generic configuration and
        operational state for SR IS-IS extensions for the
        MPLS data plane.

        Copyright (c) 2025 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Revised BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC 9902;
        see the RFC itself for full legal notices.";

     revision 2025-12-09 {
       description
         "Initial revision.";
       reference
         "RFC 9902: A YANG Data Model for IS-IS Segment Routing over
                    the MPLS Data Plane";
     }

     /* Features */

     feature remote-lfa-sr {
       description
         "Enhance RLFA to use SR path.";
       reference
         "RFC 8102: Remote-LFA Node Protection and Manageability";
     }

     feature ti-lfa {
       description
         "Topology Independent Loop-Free Alternate (TI-LFA)
          computation using SR.";
       reference
         "RFC 9855: Topology Independent Fast Reroute Using Segment
          Routing";
     }

     /* Identities */

     identity sr-capability {
       description
         "Base identity for IS-IS SR-Capabilities sub-TLV flags.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing";
     }

     identity mpls-ipv4 {
       base sr-capability;
       description
         "If set, then the router is capable of
          processing SR-MPLS-encapsulated IPv4 packets
          on all interfaces.";
     }

     identity mpls-ipv6 {
       base sr-capability;
       description
         "If set, then the router is capable of
          processing SR-MPLS-encapsulated IPv6 packets
          on all interfaces.";
     }

     identity prefix-sid-flag {
       description
         "Base identity for Prefix Segment Identifier (Prefix-SID)
          sub-TLV flags.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity r-flag {
       base prefix-sid-flag;
       description
         "Re-advertisement Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity n-flag {
       base prefix-sid-flag;
       description
         "Node-SID Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity p-flag {
       base prefix-sid-flag;
       description
         "No-PHP (No Penultimate Hop-Popping) Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity e-flag {
       base prefix-sid-flag;
       description
         "Explicit NULL Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity v-flag {
       base prefix-sid-flag;
       description
         "Value Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity l-flag {
       base prefix-sid-flag;
       description
         "Local Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
     }

     identity adj-sid-flag {
       description
         "Base identity for Adjacency Segment Identifier (Adj-SID)
          sub-TLV flags.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity f-flag {
       base adj-sid-flag;
       description
         "Address-Family Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity b-flag {
       base adj-sid-flag;
       description
         "Backup Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity vi-flag {
       base adj-sid-flag;
       description
         "Value/Index Flag - corresponds to V-Flag in reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity lg-flag {
       base adj-sid-flag;
       description
         "Local/Global Flag - corresponds to L-Flag in reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity s-flag {
       base adj-sid-flag;
       description
         "Set Flag - corresponds to S-Flag in reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity pe-flag {
       base adj-sid-flag;
       description
         "Persistent Flag - corresponds to P-Flag in reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
     }

     identity sid-binding-flag {
       description
         "Base identity for SID Binding TLV flags.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     identity af-flag {
       base sid-binding-flag;
       description
         "Address-Family Flag - corresponds to F-Flag in reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     identity m-flag {
       base sid-binding-flag;
       description
         "Mirror Context Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     identity sf-flag {
       base sid-binding-flag;
       description
         "S-Flag.  If set, the Label Binding TLV should be flooded
          across the entire routing domain - corresponds to S-Flag in
          reference.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     identity d-flag {
       base sid-binding-flag;
       description
         "Leaking Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     identity a-flag {
       base sid-binding-flag;
       description
         "Attached Flag.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.4";
     }

     /* Groupings */

     grouping sid-tlv-encoding {
       description
         "SID TLV Encoding - 20-bit label or 32-bit SID index whose
          interpretation is dependent on the TLV length (3 for an
          MPLS label or 4 for a 32-bit value) or the TLV V-Flag and
          L-Flag settings:

           If the V-Flag is set to 0 and L-Flag is set to 0:
           The SID/Index/Label field is a 4-octet index defining
           the offset in the SID/Label space advertised by this
           router.

           If the V-Flag is set to 1 and L-Flag is set to 1:
           The SID/Index/Label field is a 3-octet local label where the
           20 rightmost bits are used for encoding the label value.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing,
          Section 2.1.1.1";
       choice sid {
         case sid-label {
           leaf label-value {
             type uint32 {
               range "0 .. 1048575";
             }
             description
               "A 20-bit MPLS label.";
           }
         }
         case sid-index {
           leaf index-value {
             type uint32;
             description
               "Index into a label space advertised by this router.";
           }
         }
         description
           "Choice of either a 20-bit MPLS label or 32-bit index into
            an advertised label space.";
       }
     }

     grouping sr-capability {
       description
         "SR-Capability grouping.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 3.1";
       container sr-capability {
         description
           "SR-Capability flags.";
         leaf-list sr-capability-flag {
           type identityref {
             base sr-capability;
           }
           description
             "SR-Capability sub-TLV flags.";
         }
         container global-blocks {
           description
             "Segment Routing Global Blocks (SRGBs).";
           list global-block {
             description
               "Segment Routing Global Block.";
             leaf range-size {
               type rt-types:uint24;
               description
                 "The SID range.";
             }
             uses sid-tlv-encoding;
           }
         }
       }
     }

     grouping sr-algorithm {
       description
         "SR algorithm grouping.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 3.2";
       container sr-algorithms {
         description
           "All SR algorithms.";
         leaf-list sr-algorithm {
           type identityref {
             base sr-cmn:prefix-sid-algorithm;
           }
           description
             "The SR algorithms that the router is
              currently using.";
         }
       }
     }

     grouping srlb {
       description
         "SR Local Block grouping.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 3.3";
       container local-blocks {
         description
           "List of Segment Routing Local Blocks (SRLBs).";
         list local-block {
           description
             "Segment Routing Local Block.";
           leaf range-size {
             type rt-types:uint24;
             description
               "The SID range.";
           }
           uses sid-tlv-encoding;
         }
       }
     }

     grouping srms-preference {
       description
         "The SR Mapping Server (SRMS) Preference TLV is used to
          advertise a preference associated with the node that acts as
          an SRMS.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 3.4";
       container srms-preference {
         description
           "SRMS Preference TLV.";
         leaf preference {
           type uint8;
           description
             "SRMS Preference TLV, value from 0 to 255 with
              255 being the most preferred.";
         }
       }
     }

     grouping adjacency-state {
       description
         "This grouping extends adjacency state.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
       list adjacency-sid {
         config false;
         description
           "List of Adj-SIDs.";
         leaf value {
           type uint32;
           description
             "Value of the Adj-SID.";
         }
         leaf address-family {
           type iana-rt-types:address-family;
           description
             "Address-family associated with the
              segment ID.";
         }
         leaf weight {
           type uint8;
           description
             "Weight associated with
              the Adj-SID.";
         }
         leaf protection-requested {
           type boolean;
           description
             "Describe if the Adj-SID
              must be protected.";
         }
       }
     }

     grouping prefix-sid-sub-tlv {
       description
         "This grouping defines the SR Prefix Segment
          Identifier (Prefix-SID) sub-TLV.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.1";
       container prefix-sid-sub-tlvs {
         description
           "Prefix-SID sub-TLVs.";
         list prefix-sid-sub-tlv {
           description
             "List of Prefix-SID sub-TLVs.";
           container prefix-sid-flags {
             description
               "Describes flags associated with the
                segment ID.";
             leaf-list flag {
               type identityref {
                 base prefix-sid-flag;
               }
               description
                 "Prefix-SID sub-TLV flags.";
             }
           }
           leaf algorithm {
             type identityref {
               base sr-cmn:prefix-sid-algorithm;
             }
             description
               "Algorithm to be used for path computation.";
           }
           uses sid-tlv-encoding;
         }
       }
     }

     grouping adjacency-segment-id {
       description
         "This grouping defines SR extensions
          for adjacencies.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing, Section 2.2";
       container adj-sid-sub-tlvs {
         description
           "Adj-SID optional sub-TLVs.";
         list adj-sid-sub-tlv {
           description
             "List of segments.";
           container adj-sid-flags {
             description
               "Adj-SID sub-TLV flags.";
             leaf-list flag {
               type identityref {
                 base adj-sid-flag;
               }
               description
                 "Adj-SID sub-TLV flags list.";
             }
           }
           leaf weight {
             type uint8;
             description
               "The value represents the weight of the Adj-SID
                for the purpose of load balancing.";
           }
           leaf neighbor-id {
             type isis:system-id;
             description
               "Describes the system ID of the neighbor
                associated with the SID value.  This is only
                used on LAN adjacencies.";
           }
           uses sid-tlv-encoding;
         }
       }
     }

     grouping sid-binding-tlv {
       description
         "SID/Label Binding TLV, type 149.";
       reference
         "RFC 8667: IS-IS Extensions for Segment Routing,
          Section 2.4";
       leaf prefix {
         type inet:ip-prefix;
         description
           "The prefix represents the Forwarding Equivalence
            Class (FEC) at the tail end of the advertised path.";
       }
       leaf range {
         type uint16;
         description
           "Provides the ability to specify a range of addresses
            and their associated Prefix-SIDs.";
       }
       container sid-binding-flags {
         description
           "Binding TLV flags.";
         leaf-list flag {
           type identityref {
             base sid-binding-flag;
           }
           description
             "SID Binding TLV flags.";
         }
       }
       list prefix-sid-sub-tlvs {
         description
           "List of Prefix-SID sub-TLVs.";
         reference
           "RFC 8667: IS-IS Extensions for Segment Routing,
            Section 2.4.4";
         uses prefix-sid-sub-tlv;
       }
       list sid-sub-tlv {
         description
           "List of Prefix-SID sub-TLVs.";
         reference
           "RFC 8667: IS-IS Extensions for Segment Routing,
            Section 2.4.5";
         uses sid-tlv-encoding;
       }
       uses isis:unknown-tlvs;
     }

     /* Configuration */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis" {
       when "derived-from-or-self(../rt:type, 'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol configuration
          with SR for the MPLS data plane.";
       uses sr-mpls:sr-control-plane;
       container protocol-srgb {
         if-feature "sr-mpls:protocol-srgb";
         description
           "Per-protocol SRGB.";
         reference
           "RFC 8402: Segment Routing Architecture, Section 2";
         uses sr-cmn:srgb;
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface" {
       when "derived-from-or-self(../../../rt:type, 'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol configuration
          with SR.";
       uses sr-mpls:igp-interface {
         augment "segment-routing/adjacency-sid/adj-sids" {
           when "../../../isis:interface-type = 'broadcast'" {
             description
               "This augments the broadcast interface.";
           }
           description
             "This augments the LAN interface adj-sid with system-id.";
           leaf neighbor-system-id {
             type isis:system-id;
             mandatory true;
             description
               "Neighbor system ID.";
           }
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa" {
       when "derived-from-or-self(../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS interface IP Fast Reroute (IP-FRR)
          with TI-LFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         description
           "Topology Independent Loop-Free Alternate
            (TI-LFA) support.";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
         container selection-tie-breakers {
           description
             "Configure path selection tie-breakers and their
              respective priorities for the TI-LFA computation.";
           container node-protection {
             presence "Presence of container enables the node
                       protection tie-breaker.";
             description
               "Enable node protection as a TI-LFA path
                selection tie-breaker.  A path providing node
                protection will be selected over one that
                doesn't provide node protection.";
             leaf priority {
               type uint8;
               default "128";
               description
                 "Priority for node protection tie-breaker with
                  a lower priority being more preferred.";
             }
           }
           container srlg-disjoint {
             presence "Presence of container enables the SRLG
                       disjoint tie-breaker.";
             description
               "Enable Shared Risk Link Group (SRLG)
                disjoint as a TI-LFA path selection tie-breaker.
                A path providing a node with a disjoint path for SRLG
                links from the primary path will be selected over
                a path that doesn't provide an SRLG disjoint path.";
             leaf priority {
               type uint8;
               default "128";
               description
                 "Priority for SRLG disjoint tie-breaker with
                  a lower priority being more preferred.";
             }
           }
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa/isis:level-1" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS interface level-1 IP FRR with
          TI-LFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         description
           "TI-LFA configuration.";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa/isis:level-2" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS interface level-2 IP FRR with
          TI-LFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         description
           "TI-LFA configuration.";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa/isis:remote-lfa" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS RLFA configuration with
          use of the SR path.";
       leaf use-segment-routing-path {
         if-feature "remote-lfa-sr";
         type boolean;
         default "false";
         description
           "Force RLFA to use the SR path instead of
            LDP path.  The value of this leaf is in effect only when
            remote-lfa is enabled.";
       }
     }

     /* Operational states */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:adjacencies/isis:adjacency" {
       when "derived-from-or-self(../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol configuration
          with SR.";
       uses adjacency-state;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:router-capabilities/isis:router-capability" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol Link State Database (LSDB)
          router capability.";
       uses sr-capability;
       uses sr-algorithm;
       uses srlb;
       uses srms-preference;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:extended-is-neighbor/isis:neighbor/isis:instances"
           + "/isis:instance" {
       when "derived-from-or-self(../../../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB neighbor.";
       uses adjacency-segment-id;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:mt-is-neighbor/isis:neighbor/isis:instances"
           + "/isis:instance" {
       when "derived-from-or-self(../../../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB neighbor.";
       uses adjacency-segment-id;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:extended-ipv4-reachability/isis:prefixes" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:mt-extended-ipv4-reachability/isis:prefixes" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:ipv6-reachability/isis:prefixes" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:mt-ipv6-reachability/isis:prefixes" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp" {
       when "derived-from-or-self(../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments the IS-IS routing protocol when used.";
       }
       description
         "This augments the IS-IS protocol LSDB.";
       container sid-binding-tlvs {
         description
           "List of SID/Label Binding TLVs.";
         list sid-binding-tlv {
           key "prefix";
           description
             "SID/Label Binding TLV, type 149.";
           uses sid-binding-tlv;
         }
       }
       container mt-sid-binding-tlvs {
         description
           "List of Multi-Topology SID/Label Binding TLVs.";
         list mt-sid-binding-tlv {
           key "prefix mt-id";
           description
             "Multi-Topology SID/Label Binding TLV, type 150.";
           reference
             "RFC 8667: IS-IS Extensions for Segment Routing,
              Section 2.5";
           uses sid-binding-tlv;
           leaf mt-id {
             type uint16;
             description
               "A 12-bit field containing the non-zero ID
                of the topology.";
           }
         }
       }
     }
   }
   <CODE ENDS>

                                  Figure 1

4.  Security Considerations

   This section is modeled after the template described in Section 3.7
   of [YANG-GUIDE].

   The "ietf-isis-sr-mpls" YANG module defines a data model that is
   designed to be accessed via YANG-based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  These YANG-based
   management protocols (1) have to use a secure transport layer (e.g.,
   SSH [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and (2) have to use
   mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., "config true", which is the
   default).  All writable data nodes are likely to be sensitive or
   vulnerable in some network environments.  Write operations (e.g.,
   edit-config) and delete operations to these data nodes without proper
   protection or authentication can have a negative effect on network
   operations.  The following subtrees and data nodes have particular
   sensitivities/vulnerabilities:

   *  /isis:isis/segment-routing

   *  /isis:isis/protocol-srgb

   *  /isis:isis/isis:interfaces/isis:interface/segment-routing

   *  /isis:isis/isis:interfaces/isis:interface/isis:fast-reroute/ti-lfa

   The ability to disable or enable IS-IS SR support and/or change SR
   configurations can result in a Denial-of-Service (DoS) attack, as
   this may cause traffic to be dropped or misrouted.  Please refer to
   Section 5 of [RFC8667] for more information on SR extensions.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  Specifically, the following
   subtrees and data nodes have particular sensitivities/
   vulnerabilities:

   *  /isis:router-capabilities/sr-capability

   *  /isis:router-capabilities/sr-algorithms

   *  /isis:router-capabilities/local-blocks

   *  /isis:router-capabilities/srms-preference

   *  and the augmentations to the IS-IS LSDB.

   Unauthorized access to any data node of these subtrees can disclose
   the operational state information of the IS-IS protocol on a device.

   There are no particularly sensitive RPC or action operations.

5.  IANA Considerations

   The IANA has assigned one new URI in the "IETF XML Registry"
   [RFC3688]:

   URI:  urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace

   This document also registers one new YANG module name in the "YANG
   Module Names" registry [RFC6020]:

   Name:  ietf-isis-sr-mpls
   Maintained by IANA?  N
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls
   Prefix:  isis-sr-mpls
   Reference:  RFC 9902

6.  References

6.1.  Normative References

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8102]  Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and
              S. Litkowski, "Remote-LFA Node Protection and
              Manageability", RFC 8102, DOI 10.17487/RFC8102, March
              2017, <https://www.rfc-editor.org/info/rfc8102>.

   [RFC8294]  Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
              "Common YANG Data Types for the Routing Area", RFC 8294,
              DOI 10.17487/RFC8294, December 2017,
              <https://www.rfc-editor.org/info/rfc8294>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

   [RFC9020]  Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J.
              Tantsura, "YANG Data Model for Segment Routing", RFC 9020,
              DOI 10.17487/RFC9020, May 2021,
              <https://www.rfc-editor.org/info/rfc9020>.

   [RFC9130]  Litkowski, S., Ed., Yeung, D., Lindem, A., Zhang, J., and
              L. Lhotka, "YANG Data Model for the IS-IS Protocol",
              RFC 9130, DOI 10.17487/RFC9130, October 2022,
              <https://www.rfc-editor.org/info/rfc9130>.

   [RFC9855]  Bashandy, A., Litkowski, S., Filsfils, C., Francois, P.,
              Decraene, B., and D. Voyer, "Topology Independent Fast
              Reroute Using Segment Routing", RFC 9855,
              DOI 10.17487/RFC9855, October 2025,
              <https://www.rfc-editor.org/info/rfc9855>.

6.2.  Informative References

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/info/rfc4252>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [YANG-GUIDE]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-28, 5 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-28>.

Appendix A.  A Configuration Example

   The following is an XML example using the IS-IS SR MPLS YANG module
   defined in this document.

   Note: '\' line wrapping per [RFC8792].

   <?xml version='1.0' encoding='UTF-8'?>
   <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
     <interface>
       <name>eth0</name>
       <admin-status>up</admin-status>
       <oper-status>up</oper-status>
       <if-index>1</if-index>
       <statistics>
         <discontinuity-time>2024-10-27T14:30:00Z</discontinuity-time>
       </statistics>
     </interface>
   </interfaces>
   <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <router-id>1.1.1.1</router-id>
    <control-plane-protocols>
      <control-plane-protocol>
        <type xmlns:isis="urn:ietf:params:xml:ns:yang:ietf-isis">\
          isis:isis</type>
        <name>isis</name>
        <isis xmlns="urn:ietf:params:xml:ns:yang:ietf-isis">
          <system-id>1111.2222.3333</system-id>
          <area-address>49.0001.0000.0000.0001</area-address>
          <interfaces>
            <interface>
              <name>eth0</name>
              <segment-routing xmlns="urn:ietf:params:xml:ns:yang:\
                ietf-isis-sr-mpls">
                <adjacency-sid>
                  <adj-sids>
                    <value>38888</value>
                    <neighbor-system-id>4444.5555.6666\
                    </neighbor-system-id>
                  </adj-sids>
                </adjacency-sid>
              </segment-routing>
            </interface>
          </interfaces>
          <segment-routing xmlns="urn:ietf:params:xml:ns:yang:\
            ietf-isis-sr-mpls">
            <enabled>true</enabled>
          </segment-routing>
          <protocol-srgb xmlns="urn:ietf:params:xml:ns:yang:\
            ietf-isis-sr-mpls">
            <srgb>
              <lower-bound>4000</lower-bound>
              <upper-bound>5000</upper-bound>
            </srgb>
          </protocol-srgb>
          </isis>
       </control-plane-protocol>
    </control-plane-protocols>
   </routing>

   The following is the same example using JSON format.

   {
     "ietf-interfaces:interfaces": {
       "interface": [
         {
           "name": "eth0",
           "admin-status": "up",
           "oper-status": "up",
           "if-index": 1,
           "statistics": {
             "discontinuity-time": "2024-10-27T07:30:00-07:00"
           }
         }
       ]
     },
     "ietf-routing:routing": {
       "router-id": "1.1.1.1",
       "control-plane-protocols": {
         "control-plane-protocol": [
           {
             "type": "ietf-isis:isis",
             "name": "isis",
             "ietf-isis:isis": {
               "system-id": "1111.2222.3333",
               "area-address": [
                 "49.0001.0000.0000.0001"
               ],
               "interfaces": {
                 "interface": [
                   {
                     "name": "eth0",
                     "ietf-isis-sr-mpls:segment-routing": {
                       "adjacency-sid": {
                         "adj-sids": [
                           {
                             "value": 38888,
                             "neighbor-system-id": "4444.5555.6666"
                           }
                         ]
                       }
                     }
                   }
                 ]
               },
               "ietf-isis-sr-mpls:segment-routing": {
                 "enabled": true
               },
               "ietf-isis-sr-mpls:protocol-srgb": {
                 "srgb": [
                   {
                     "lower-bound": 4000,
                     "upper-bound": 5000
                   }
                 ]
               }
             }
           }
         ]
       }
     }
   }

Appendix B.  IS-IS MPLS Segment Routing Module Tree

   The figure below describes the overall structure of the "ietf-isis-
   sr-mpls" YANG module:

   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis:
     +--rw segment-routing
     |  +--rw enabled?    boolean
     |  +--rw bindings {mapping-server}?
     |     +--rw advertise
     |     |  +--rw policies*   leafref
     |     +--rw receive?     boolean
     +--rw protocol-srgb {sr-mpls:protocol-srgb}?
        +--rw srgb* [lower-bound upper-bound]
           +--rw lower-bound    uint32
           +--rw upper-bound    uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface:
     +--rw segment-routing
        +--rw adjacency-sid
           +--rw adj-sids* [value]
           |  +--rw value-type?           enumeration
           |  +--rw value                 uint32
           |  +--rw protected?            boolean
           |  +--rw weight?               uint8
           |  +--rw neighbor-system-id    isis:system-id
           +--rw advertise-adj-group-sid* [group-id]
           |  +--rw group-id    uint32
           +--rw advertise-protection?      enumeration
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa:
     +--rw ti-lfa {ti-lfa}?
        +--rw enabled?                  boolean
        +--rw selection-tie-breakers
           +--rw node-protection!
           |  +--rw priority?   uint8
           +--rw srlg-disjoint!
              +--rw priority?   uint8
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa/isis:level-1:
     +--rw ti-lfa {ti-lfa}?
        +--rw enabled?   boolean
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa/isis:level-2:
     +--rw ti-lfa {ti-lfa}?
        +--rw enabled?   boolean
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa
             /isis:remote-lfa:
     +--rw use-segment-routing-path?   boolean {remote-lfa-sr}?
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:adjacencies/isis:adjacency:
     +--ro adjacency-sid* []
        +--ro value?                  uint32
        +--ro address-family?         iana-rt-types:address-family
        +--ro weight?                 uint8
        +--ro protection-requested?   boolean
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:router-capabilities
             /isis:router-capability:
     +--ro sr-capability
     |  +--ro sr-capability-flag*   identityref
     |  +--ro global-blocks
     |     +--ro global-block* []
     |        +--ro range-size?          rt-types:uint24
     |        +--ro (sid)?
     |           +--:(sid-label)
     |           |  +--ro label-value?   uint32
     |           +--:(sid-index)
     |              +--ro index-value?   uint32
     +--ro sr-algorithms
     |  +--ro sr-algorithm*   identityref
     +--ro local-blocks
     |  +--ro local-block* []
     |     +--ro range-size?          rt-types:uint24
     |     +--ro (sid)?
     |        +--:(sid-label)
     |        |  +--ro label-value?   uint32
     |        +--:(sid-index)
     |           +--ro index-value?   uint32
     +--ro srms-preference
        +--ro preference?   uint8
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:extended-is-neighbor
             /isis:neighbor/isis:instances/isis:instance:
     +--ro adj-sid-sub-tlvs
        +--ro adj-sid-sub-tlv* []
           +--ro adj-sid-flags
           |  +--ro flag*   identityref
           +--ro weight?              uint8
           +--ro neighbor-id?         isis:system-id
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:mt-is-neighbor/isis:neighbor
             /isis:instances/isis:instance:
     +--ro adj-sid-sub-tlvs
        +--ro adj-sid-sub-tlv* []
           +--ro adj-sid-flags
           |  +--ro flag*   identityref
           +--ro weight?              uint8
           +--ro neighbor-id?         isis:system-id
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:extended-ipv4-reachability
             /isis:prefixes:
     +--ro prefix-sid-sub-tlvs
        +--ro prefix-sid-sub-tlv* []
           +--ro prefix-sid-flags
           |  +--ro flag*   identityref
           +--ro algorithm?           identityref
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:mt-extended-ipv4-reachability
             /isis:prefixes:
     +--ro prefix-sid-sub-tlvs
        +--ro prefix-sid-sub-tlv* []
           +--ro prefix-sid-flags
           |  +--ro flag*   identityref
           +--ro algorithm?           identityref
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:ipv6-reachability
             /isis:prefixes:
     +--ro prefix-sid-sub-tlvs
        +--ro prefix-sid-sub-tlv* []
           +--ro prefix-sid-flags
           |  +--ro flag*   identityref
           +--ro algorithm?           identityref
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:mt-ipv6-reachability
             /isis:prefixes:
     +--ro prefix-sid-sub-tlvs
        +--ro prefix-sid-sub-tlv* []
           +--ro prefix-sid-flags
           |  +--ro flag*   identityref
           +--ro algorithm?           identityref
           +--ro (sid)?
              +--:(sid-label)
              |  +--ro label-value?   uint32
              +--:(sid-index)
                 +--ro index-value?   uint32
   augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp:
     +--ro sid-binding-tlvs
     |  +--ro sid-binding-tlv* [prefix]
     |     +--ro prefix                 inet:ip-prefix
     |     +--ro range?                 uint16
     |     +--ro sid-binding-flags
     |     |  +--ro flag*   identityref
     |     +--ro prefix-sid-sub-tlvs* []
     |     |  +--ro prefix-sid-sub-tlvs
     |     |     +--ro prefix-sid-sub-tlv* []
     |     |        +--ro prefix-sid-flags
     |     |        |  +--ro flag*   identityref
     |     |        +--ro algorithm?           identityref
     |     |        +--ro (sid)?
     |     |           +--:(sid-label)
     |     |           |  +--ro label-value?   uint32
     |     |           +--:(sid-index)
     |     |              +--ro index-value?   uint32
     |     +--ro sid-sub-tlv* []
     |     |  +--ro (sid)?
     |     |     +--:(sid-label)
     |     |     |  +--ro label-value?   uint32
     |     |     +--:(sid-index)
     |     |        +--ro index-value?   uint32
     |     +--ro unknown-tlvs
     |        +--ro unknown-tlv* []
     |           +--ro type?     uint16
     |           +--ro length?   uint16
     |           +--ro value?    yang:hex-string
     +--ro mt-sid-binding-tlvs
        +--ro mt-sid-binding-tlv* [prefix mt-id]
           +--ro prefix                 inet:ip-prefix
           +--ro range?                 uint16
           +--ro sid-binding-flags
           |  +--ro flag*   identityref
           +--ro prefix-sid-sub-tlvs* []
           |  +--ro prefix-sid-sub-tlvs
           |     +--ro prefix-sid-sub-tlv* []
           |        +--ro prefix-sid-flags
           |        |  +--ro flag*   identityref
           |        +--ro algorithm?           identityref
           |        +--ro (sid)?
           |           +--:(sid-label)
           |           |  +--ro label-value?   uint32
           |           +--:(sid-index)
           |              +--ro index-value?   uint32
           +--ro sid-sub-tlv* []
           |  +--ro (sid)?
           |     +--:(sid-label)
           |     |  +--ro label-value?   uint32
           |     +--:(sid-index)
           |        +--ro index-value?   uint32
           +--ro unknown-tlvs
           |  +--ro unknown-tlv* []
           |     +--ro type?     uint16
           |     +--ro length?   uint16
           |     +--ro value?    yang:hex-string
           +--ro mt-id                  uint16

Acknowledgements

   The authors would like to thank Pushpasis Sarkar, Derek Yeung, and Yi
   Yang for their major contributions to the document.  Also thanks to
   Reshad Rahman, Tom Petch, and Renato Westphal for their thorough
   reviews and helpful comments.

   The authors wish to thank Mohamed Boucadair and Ketan Talaulikar for
   extensive AD reviews for the IESG Telechat.  Thanks to Éric Vyncke
   and Mahesh Jethanandani for review comments.

Authors' Addresses

   Stephane Litkowski
   Cisco Systems
   Email: slitkows.ietf@gmail.com


   Yingzhen Qu
   Futurewei Technologies
   Email: yingzhen.ietf@gmail.com


   Acee Lindem
   LabN Consulting, L.L.C.
   Email: acee.ietf@gmail.com


   Ing-Wher Chen
   Red Hat, Inc.
   Email: ichen@redhat.com


   Jeff Tantsura
   Nvidia
   Email: jefftant.ietf@gmail.com
