Cisco Systems

slitkows.ietf@gmail.com

Futurewei Technologies

yingzhen.ietf@gmail.com

LabN Consulting, L.L.C.

acee.ietf@gmail.com

Red Hat, Inc.

ichen@redhat.com

Nvidia

jefftant.ietf@gmail.com

RTG lsr 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 .

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 () 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

• .  Overview
  • .  Tree Diagrams
• .  Design of the YANG Module for IS-IS MPLS Segment Routing
  • .  Segment Routing Activation
  • .  Advertising Mapping Server Policy
  • .  IP Fast Reroute
• .  IS-IS Segment Routing over MPLS YANG Module
• .  Security Considerations
• .  IANA Considerations
• .  References
  • .  Normative References
  • .  Informative References
• .  A Configuration Example
• .  IS-IS MPLS Segment Routing Module Tree
• Acknowledgements
• Authors' Addresses

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

Tree Diagrams This document uses the graphical representation of a data model as defined in .

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 , which defines the global SR management independent of any specific routing protocol configuration, and support of the IS-IS base model , 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.

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.

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.

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.

IS-IS Segment Routing over MPLS YANG Module , , , , , , , , and are referenced in the YANG module.

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."; } } } } }

Security Considerations This section is modeled after the template described in . 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 and RESTCONF . These YANG-based management protocols (1) have to use a secure transport layer (e.g., SSH , TLS , and QUIC ) and (2) have to use mutual authentication. The Network Configuration Access Control Model (NACM) 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 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.

IANA Considerations The IANA has assigned one new URI in the "IETF XML Registry" :

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 :

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

References Normative References This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] This document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021. YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). The loop-free alternates (LFAs) computed following the current remote-LFA specification guarantees only link protection. The resulting remote-LFA next hops (also called "PQ-nodes") may not guarantee node protection for all destinations being protected by it. This document describes an extension to the remote-loop-free-based IP fast reroute mechanisms that specifies procedures for determining whether or not a given PQ-node provides node protection for a specific destination. The document also shows how the same procedure can be utilized for the collection of complete characteristics for alternate paths. Knowledge about the characteristics of all alternate paths is a precursor to applying the operator-defined policy for eliminating paths not fitting the constraints. This document defines a collection of common data types using the YANG data modeling language. These derived common types are designed to be imported by other modules defined in the routing area. The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model. This document obsoletes RFC 6536. This document specifies three YANG modules and one submodule. Together, they form the core routing data model that serves as a framework for configuring and managing a routing subsystem. It is expected that these modules will be augmented by additional YANG modules defining data models for control-plane protocols, route filters, and other functions. The core routing data model provides common building blocks for such extensions -- routes, Routing Information Bases (RIBs), and control-plane protocols. The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA). This document obsoletes RFC 8022. 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. 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. 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. Segment Routing (SR) allows for a flexible definition of end-to-end paths within IGP topologies by encoding paths as sequences of topological sub-paths, called "segments". These segments are advertised by the link-state routing protocols (IS-IS and OSPF). This document describes the IS-IS extensions that need to be introduced for Segment Routing operating on an MPLS data plane. This document defines three YANG data models. The first is for Segment Routing (SR) configuration and operation, which is to be augmented by different Segment Routing data planes. The next is a YANG data model that defines a collection of generic types and groupings for SR. The third module defines the configuration and operational states for the Segment Routing MPLS data plane. This document defines a YANG data model that can be used to configure and manage the IS-IS protocol on network elements. This document presents Topology Independent Loop-Free Alternate (TI-LFA) Fast Reroute (FRR), which is aimed at providing protection of node and Adjacency segments within the Segment Routing (SR) framework. This FRR behavior builds on proven IP FRR concepts being LFAs, Remote LFAs (RLFAs), and Directed Loop-Free Alternates (DLFAs). It extends these concepts to provide guaranteed coverage in any two-connected networks using a link-state IGP. An important aspect of TI-LFA is the FRR path selection approach establishing protection over the expected post-convergence paths from the Point of Local Repair (PLR), reducing the operational need to control the tie-breaks among various FRR options. Informative References The Secure Shell Protocol (SSH) is a protocol for secure remote login and other secure network services over an insecure network. This document describes the SSH authentication protocol framework and public key, password, and host-based client authentication methods. Additional authentication methods are described in separate documents. The SSH authentication protocol runs on top of the SSH transport layer protocol and provides a single authenticated tunnel for the SSH connection protocol. [STANDARDS-TRACK] The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language. This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. This document defines two strategies for handling long lines in width-bounded text content. One strategy, called the "single backslash" strategy, is based on the historical use of a single backslash ('\') character to indicate where line-folding has occurred, with the continuation occurring with the first character that is not a space character (' ') on the next line. The second strategy, called the "double backslash" strategy, extends the first strategy by adding a second backslash character to identify where the continuation begins and is thereby able to handle cases not supported by the first strategy. Both strategies use a self-describing header enabling automated reconstitution of the original content. This document defines the core of the QUIC transport protocol. QUIC provides applications with flow-controlled streams for structured communication, low-latency connection establishment, and network path migration. QUIC includes security measures that ensure confidentiality, integrity, and availability in a range of deployment circumstances. Accompanying documents describe the integration of TLS for key negotiation, loss detection, and an exemplary congestion control algorithm. YumaWorks Orange Huawei This document provides guidelines for authors and reviewers of specifications containing YANG data models, including IANA-maintained modules. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF Protocol implementations that utilize YANG modules. This document obsoletes RFC 8407. Also, this document updates RFC 8126 by providing additional guidelines for writing the IANA considerations for RFCs that specify IANA-maintained modules. Work in Progress

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 . <?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 } ] } } } ] } } }

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 , , and for their major contributions to the document. Also thanks to , , and for their thorough reviews and helpful comments. The authors wish to thank and for extensive AD reviews for the IESG Telechat. Thanks to and for review comments.

Authors' Addresses Cisco Systems

slitkows.ietf@gmail.com

Futurewei Technologies

yingzhen.ietf@gmail.com

LabN Consulting, L.L.C.

acee.ietf@gmail.com

Red Hat, Inc.

ichen@redhat.com

Nvidia

jefftant.ietf@gmail.com