Internet Y. Qu Internet-Draft Futurewei Technologies Intended status: Standards Track A. Lindem Expires: 7 January 2026 M. Joshi Arrcus, Inc. 6 July 2025 YANG Model for IS-IS Application-Specific Link Attributes and Flexible Algorithm draft-ietf-lsr-isis-flex-algo-yang-00 Abstract This document defines a YANG data model to support IS-IS Application- Specific Link Attributes and Flexible Algorithm. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 7 January 2026. 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. Qu, et al. Expires 7 January 2026 [Page 1] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. YANG Module for IS-IS Application-Specific Link Attributes . 2 3. YANG Module for IS-IS Flexible Algorithm . . . . . . . . . . 13 4. Security Considerations . . . . . . . . . . . . . . . . . . . 25 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 7. Normative References . . . . . . . . . . . . . . . . . . . . 26 Appendix A. Example IS-IS Flex-Algo Configuration . . . . . . . 28 Appendix B. Example IS-IS Flex-Algo Configuration (JSON) . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 1. Overview This document defines two YANG [RFC7950] data modules. The first module is to provide support for configuration and operational state for IS-IS Application-Specific Link Attributes as defined in [RFC9479], and the second module is to support IS-IS Flexible Algorithm as defined in [RFC9350]. Both modules are augmenting the IETF IS-IS YANG model [RFC9130]. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. 2. YANG Module for IS-IS Application-Specific Link Attributes This document defined a YANG module for IS-IS Application-Specific Link Attributes as defined in [RFC9479]. module: ietf-isis-link-attr augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis: +--rw isis-link-attr-op +--rw (link-attr-op-mode) +--:(legacy) | +--rw legacy? empty +--:(transition) | +--rw transition? empty +--:(app-specific) +--rw app-specific? empty augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis/isis:interfaces /isis:interface: Qu, et al. Expires 7 January 2026 [Page 2] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 +--rw isis-asla +--rw interface-asla* [app-id] +--rw app-id uint16 +--rw unidirectional-link-delay? uint32 +--rw metric-type? uint8 +--rw metric? uint32 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 asla-sub-tlvs +--ro asla-sub-tlv* [] +--ro l-flag? boolean +--ro sabm-length? uint8 +--ro r-flag? boolean +--ro udabm-length? uint8 +--ro sabm | +--ro sabm-bits* identityref +--ro udabm +--ro unknown-tlvs +--ro unknown-tlv* [] +--ro type? uint16 +--ro length? uint16 +--ro value? yang:hex-string 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 asla-sub-tlvs +--ro asla-sub-tlv* [] +--ro l-flag? boolean +--ro sabm-length? uint8 +--ro r-flag? boolean +--ro udabm-length? uint8 +--ro sabm | +--ro sabm-bits* identityref +--ro udabm +--ro unknown-tlvs +--ro unknown-tlv* [] +--ro type? uint16 +--ro length? uint16 +--ro value? yang:hex-string augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis/isis:database /isis:levels/isis:lsp: +--ro application-specific-srlg-tlv +--ro as-srlg-tlv* [] +--ro neighbor-system-id? isis:system-id Qu, et al. Expires 7 January 2026 [Page 3] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 +--ro pseudo-node-id? uint8 +--ro l-flag? boolean +--ro sabm-length? uint8 +--ro r-flag? boolean +--ro udabm-length? uint8 +--ro sabm | +--ro sabm-bits* identityref +--ro udabm +--ro length-of-sub-tlvs? uint8 +--ro link-id-sub-tlvs | +--ro link-local-remote-ids | | +--ro link-local-id? union | | +--ro link-remote-id? union | +--ro ipv4-interface-addr | | +--ro ipv4-int-addr? inet:ipv4-address | +--ro ipv4-neighbor-addr | | +--ro ipv4-neighbor-addr? inet:ipv4-address | +--ro ipv6-interface-addr | | +--ro ipv6-int-addr? inet:ipv6-address | +--ro ipv6-neighbor-addr | +--ro ipv6-neighbor-addr? inet:ipv6-address +--ro srlgs +--ro srlg* uint32 file "ietf-isis-link-attr@2025-07-06.yang" module ietf-isis-link-attr { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-isis-link-attr"; prefix isis-link-attr; import ietf-inet-types { prefix inet; reference "RFC 6991 - Common YANG Data Types"; } import ietf-routing { prefix rt; reference "RFC 8349: A YANG Data Model for Routing Management (NMDA Version)"; } import ietf-isis { prefix isis; reference "RFC 9130: YANG Data Model for the IS-IS Protocol"; Qu, et al. Expires 7 January 2026 [Page 4] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 } organization "IETF LSR - Link State Routing Working Group"; contact "WG Web: WG List: Author: Yingzhen Qu Author: Acee Lindem Author: Stephane Litkowski Author: Madhavi Joshi "; description "This YANG module defines the configuration and operational state for IS-IS application specific link attributes feature as defined in RFC 9479. This YANG model conforms to the Network Management Datastore Architecture (NMDA) as described in RFC 8342. 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 (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; reference "RFC XXXX"; Qu, et al. Expires 7 January 2026 [Page 5] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 revision 2025-07-06 { description "Initial version"; reference "RFC XXXX: A YANG Data Model for IS-IS Application-Specific Link Attributes."; } identity sabm-bit { description "Base identity for sabm bits."; reference "RFC 8919: IS-IS Application-Specific Link Attributes"; } identity rsvp-te-bit { base sabm-bit; description "R bit, RSVP-TE."; } identity sr-policy-bit { base sabm-bit; description "S bit, Segment Routing Policy."; } identity lfa-bit { base sabm-bit; description "F bit, Loop Free Alternate (LFA). Includes all LFA types."; } identity flex-algo-bit { base sabm-bit; description "X bit, flexible algorithm."; reference "RFC 9350: IGP Flexible Algorithm, Section 12."; } grouping application-identifier-bit-mask { description "Identification of the set of applications associated with link attribute advertisements"; leaf l-flag { type boolean; Qu, et al. Expires 7 January 2026 [Page 6] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 description "Legacy Flag. When set, all of the applications specified in the bit mask MUST use the legacy advertisements."; } leaf sabm-length { type uint8; description "Standard Application Identifier Bit Mask Length in octets."; } leaf r-flag { type boolean; default false; description "Reserved."; } leaf udabm-length { type uint8; description "User Defined Application Identifier Bit Mask Length in octets."; } container sabm { leaf-list sabm-bits { type identityref { base sabm-bit; } description "SABM bits list. This list will contain identities for the bits which are set in the SABA bits."; } description "Standard Application Identifier Bit Mask."; } container udabm { description "User Defined Application Identifier Bit Mask. This container is to be augmented by user defined applications."; } } grouping application-specific-link-attributes-sub-tlv { description "Grouping for specification of the applications and application-specific attribute values."; Qu, et al. Expires 7 January 2026 [Page 7] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 container asla-sub-tlvs { list asla-sub-tlv { uses application-identifier-bit-mask; uses isis:unknown-tlvs; description "List of application specific link attributes sub-tlvs."; } description "Application specific link attributes sub-tlv."; } } grouping application-specific-srlg-tlv { description "Grouping of a TLV to advertise application-specific SRLGs for a given link."; container application-specific-srlg-tlv { list as-srlg-tlv { leaf neighbor-system-id { type isis:system-id; description "Neighbor System-ID."; } leaf pseudo-node-id { type uint8; description "Pseudo-node ID."; } uses application-identifier-bit-mask; leaf length-of-sub-tlvs { type uint8; description "Length of sub-tlvs."; } container link-id-sub-tlvs { description "Link Identifier sub-TLVs."; container link-local-remote-ids { description "Link local/remote identifier sub-tlv."; leaf link-local-id { type union { type inet:ipv4-address; type uint32; } description "Local identifier of the link. Qu, et al. Expires 7 January 2026 [Page 8] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 It could be an IPv4 address or a local identifier."; } leaf link-remote-id { type union { type inet:ipv4-address; type uint32; } description "Remote identifier of the link. It could be an IPv4 address or a remotely learned identifier."; } } container ipv4-interface-addr { leaf ipv4-int-addr { type inet:ipv4-address; description "IPv4 address for the interface."; } description "IPv4 interface address sub-tlv."; } container ipv4-neighbor-addr { leaf ipv4-neighbor-addr { type inet:ipv4-address; description "IPv4 address for a neighboring router on this link."; } description "IPv4 neighbor address sub-tlv."; } container ipv6-interface-addr { leaf ipv6-int-addr { type inet:ipv6-address; description "IPv6 address for the interface."; } description "IPv6 interface address sub-tlv."; } container ipv6-neighbor-addr { leaf ipv6-neighbor-addr { type inet:ipv6-address; description "IPv6 address for a neighboring router on this link."; } Qu, et al. Expires 7 January 2026 [Page 9] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 description "IPv6 neighbor address sub-tlv."; } } container srlgs { description "List of SRLGs."; leaf-list srlg { type uint32; description "SRLG value of the link."; } } description "List of application specific SRLG tlvs."; } description "Application specific SRLG tlv."; } } /* Configuration */ augment "/rt:routing/" + "rt:control-plane-protocols/rt:control-plane-protocol"+ "/isis:isis" { when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol configuration with application specific link attributes."; container isis-link-attr-op { choice link-attr-op-mode { mandatory "true"; leaf legacy { type empty; description "Only send legacy advertisements."; } leaf transition { type empty; description "Send both application-specific and legacy advertisements."; Qu, et al. Expires 7 January 2026 [Page 10] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 } leaf app-specific{ type empty; description "Only send application-specific advertisements."; } description "Link attributes mode"; } description "Link attributes operation mode."; } } augment "/rt:routing/" + "rt:control-plane-protocols/rt:control-plane-protocol"+ "/isis:isis/isis:interfaces/isis:interface" { when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used."; } description "This augments ISIS interface configuration with application specific link attributes."; container isis-asla { list interface-asla { key app-id; leaf app-id { type uint16 { range "0 .. 1023"; } description "Application ID. 0 - RSVP TE. 1 - Segment Routing Policy. 2 - Loop-Free Alternate."; } leaf unidirectional-link-delay { type uint32 { range "0 .. 16777215"; } description "This 24-bit field carries the average link delay in Qu, et al. Expires 7 January 2026 [Page 11] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 microseconds."; } leaf metric-type { type uint8; description "IGP metric type."; } leaf metric { type uint32 { range "1 .. 16777215"; } description "metric value."; } description "ASLA interface configuration."; } description "Application specific link attributes configuration."; } } /* TLV 22 */ 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 "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB TLV22."; uses application-specific-link-attributes-sub-tlv; } /* TLV 223 */ 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" { Qu, et al. Expires 7 January 2026 [Page 12] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB TLV223."; uses application-specific-link-attributes-sub-tlv; } /* application-specific SRLG TLV 238 */ augment "/rt:routing/" + "rt:control-plane-protocols/rt:control-plane-protocol"+ "/isis:isis/isis:database/isis:levels/isis:lsp" { when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB."; uses application-specific-srlg-tlv; } } 3. YANG Module for IS-IS Flexible Algorithm This section defines the YANG module for IS-IS Flexible Algorithm. The module uses the identities defined in the IANA-maintained YANG modules for IGP Algorithm Types [IANA-IGP-ALGO-Types] and IGP Metric Type [IANA-IGP-Metric-Types] in [I-D.ietf-lsr-ospf-flex-algo-yang]. module: ietf-isis-flex-algo augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis: +--rw isis-flex-algo +--rw flex-algo* [algo-number] +--rw algo-number uint8 +--rw advertise-definition? boolean +--rw admin-groups | {te-types:extended-admin-groups, | te-types:named-extended-admin-groups}? | +--rw exclude-admin-groups* leafref | +--rw include-any-admin-groups* leafref | +--rw include-all-admin-groups* leafref Qu, et al. Expires 7 January 2026 [Page 13] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 +--rw exclude-srlgs* | -> /te:te/globals/named-srlgs/named-srlg/name | {te-types:named-srlg-groups}? +--rw metric-type? identityref +--rw calc-type? identityref +--rw prefix-metric! +--rw priority? uint8 augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis/isis:database /isis:levels/isis:lsp/isis:router-capabilities: +--ro fad-tlvs +--ro fad-tlv* [] +--ro flex-algo? uint8 +--ro metric-type? identityref +--ro calc-type? identityref +--ro priority? uint8 +--ro fa-ex-ag-sub-tlv | +--ro extended-admin-groups* uint64 +--ro fa-in-any-ag-sub-tlv | +--ro extended-admin-groups* uint64 +--ro fa-in-all-ag-sub-tlv | +--ro extended-admin-groups* uint64 +--ro fad-flags-sub-tlv | +--ro fad-flags* identityref +--ro fa-ex-srlg-sub-tlv | +--ro srlgs* uint32 +--ro unknown-tlvs +--ro unknown-tlv* [] +--ro type? uint16 +--ro length? uint16 +--ro value? yang:hex-string 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 fapm-sub-tlvs +--ro fapm-sub-tlv* [] +--ro flex-algo? uint8 +--ro metric? 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 fapm-sub-tlvs +--ro fapm-sub-tlv* [] +--ro flex-algo? uint8 +--ro metric? uint32 augment /rt:routing/rt:control-plane-protocols Qu, et al. Expires 7 January 2026 [Page 14] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 /rt:control-plane-protocol/isis:isis/isis:database /isis:levels/isis:lsp/isis:ipv6-reachability /isis:prefixes: +--ro fapm-sub-tlvs +--ro fapm-sub-tlv* [] +--ro flex-algo? uint8 +--ro metric? 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 fapm-sub-tlvs +--ro fapm-sub-tlv* [] +--ro flex-algo? uint8 +--ro metric? uint32 notifications: +---n flex-algo-not-supported +--ro routing-protocol-name? leafref +--ro isis-level? level +--ro flex-algo-number? uint8 file "ietf-isis-flex-algo@2025-07-06.yang" module ietf-isis-flex-algo { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-isis-flex-algo"; prefix isis-flex-algo; import ietf-routing { prefix rt; reference "RFC 8349: A YANG Data Model for Routing Management (NMDA Version)"; } import ietf-te-types { prefix te-types; reference "RFC8776: Common YANG Data Types for Traffic Engineering."; } import ietf-isis { prefix isis; reference "RFC 9130: YANG Data Model for the IS-IS Protocol"; } import ietf-te { Qu, et al. Expires 7 January 2026 [Page 15] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 prefix te; } import iana-igp-algo-types { prefix iana-algo-types; } import iana-igp-metric-types { prefix iana-metric-type; } organization "IETF LSR - Link State Routing Working Group"; contact "WG Web: WG List: Author: Yingzhen Qu Author: Acee Lindem Author: Stephane Litkowski Author: Madhavi Joshi "; description "The YANG module defines the configuration and operational state for ISIS Flexible Algorithm as defined in RFC 9350. This YANG model conforms to the Network Management Datastore Architecture (NMDA) as described in RFC 8342. 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 XXXX; see the RFC itself for full legal notices. Qu, et al. Expires 7 January 2026 [Page 16] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; reference "RFC XXXX: YANG Data Model for ISIS Flexible Algorithm."; revision 2025-07-06 { description "Initial Version"; reference "RFC XXXX: YANG Data Model for ISIS Flexible Algorithm."; } /* Identities */ identity fad-flags { description "Base identity for ISIS FAD flags."; } identity m-bit { base fad-flags; description "M bit, when set, the flex-algo specific prefix and ASBR metric MUST be used for inter-area and external prefix calculation."; } /* Groupings */ grouping fa-ex-ag-sub-tlv { container fa-ex-ag-sub-tlv { leaf-list extended-admin-groups { type uint64; description "Extended administrative group as defined in RFC 7308."; } description "The flex-algo exclude admin group sub-tlv."; } description "The flex-algo exclude admin group sub-tlv."; } grouping fa-in-any-ag-sub-tlv { Qu, et al. Expires 7 January 2026 [Page 17] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 container fa-in-any-ag-sub-tlv { leaf-list extended-admin-groups { type uint64; description "Extended administrative group as defined in RFC 7308."; } description "The flex-algo include-any admin group sub-tlv."; } description "The flex-algo include-any admin group sub-tlv."; } grouping fa-in-all-ag-sub-tlv { container fa-in-all-ag-sub-tlv { leaf-list extended-admin-groups { type uint64; description "Extended administrative group as defined in RFC 7308."; } description "The flex-algo include-all admin group sub-tlv."; } description "The flex-algo include-all admin group sub-tlv."; } grouping fad-flags-sub-tlv { container fad-flags-sub-tlv { leaf-list fad-flags { type identityref { base fad-flags; } description "Flex-algo definition flags list."; } description "ISIS flex-algo definition flags."; } description "The flex-algo definition flags sub-tlv."; } grouping fa-ex-srlg-sub-tlv { container fa-ex-srlg-sub-tlv { leaf-list srlgs { type uint32; description Qu, et al. Expires 7 January 2026 [Page 18] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 "SRLG value as defined in RFC 4203."; } description "The flex-algo exclude SRLG sub-tlv."; } description "The flex-algo exclude SRLG sub-tlv."; } grouping fad-tlvs { container fad-tlvs { list fad-tlv { leaf flex-algo { type uint8; description "Flex-algo number, value between 128 and 255 inclusive."; } leaf metric-type { type identityref { base iana-metric-type:metric-type; } description "Type of metric to be used during the calculation."; } leaf calc-type { type identityref { base iana-algo-types:algo-type; } description "IGP algorithm types, value from 0 to 127 as defined under 'Interior Gateway Protocol (IGP) Parameter' by IANA."; } leaf priority { type uint8; description "Priority of the advertisement."; } uses fa-ex-ag-sub-tlv; uses fa-in-any-ag-sub-tlv; uses fa-in-all-ag-sub-tlv; uses fad-flags-sub-tlv; uses fa-ex-srlg-sub-tlv; uses isis:unknown-tlvs; description "List of flex-algo definition TLVs."; Qu, et al. Expires 7 January 2026 [Page 19] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 } description "ISIS Flexible Algorithm Definition TLV."; } description "ISIS Flexible Algorithm Definition (FAD) TLV."; } grouping fapm-sub-tlvs { container fapm-sub-tlvs { list fapm-sub-tlv { leaf flex-algo { type uint8; description "Flex-algo number, value between 128 and 255 inclusive."; } leaf metric { type uint32; description "Prefix metric."; } description "List of flex-algo prefix sub-tlvs."; } description "Flex-algo prefix metric sub-tlvs."; } description "Flexible Algorithm Prefix Metric (FAPM) sub TLVs."; } /* Configurations */ augment "/rt:routing/" + "rt:control-plane-protocols/rt:control-plane-protocol"+ "/isis:isis" { when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol configuration with flexible algorithm."; container isis-flex-algo { Qu, et al. Expires 7 January 2026 [Page 20] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 list flex-algo { key "algo-number"; leaf algo-number { type uint8 { range "128..255"; } description "An identifier in the range 128-255 that's associated with the Flexible Algorithm Definition."; } leaf advertise-definition { type boolean; default true; description "Enable to advertise the flex-algo definition."; } container admin-groups { if-feature "te-types:extended-admin-groups"; if-feature "te-types:named-extended-admin-groups"; leaf-list exclude-admin-groups { type leafref { path "/te:te/te:globals/te:named-admin-groups/" + "te:named-admin-group/te:name"; } description "Exclude rule used during the flex-algo path computation."; } leaf-list include-any-admin-groups { type leafref { path "/te:te/te:globals/te:named-admin-groups/" + "te:named-admin-group/te:name"; } description "Include-any rule used during the flex-algo path computation."; } leaf-list include-all-admin-groups { type leafref { path "/te:te/te:globals/te:named-admin-groups/" + "te:named-admin-group/te:name"; } description "Include-all rule used during the flex-algo path computation."; Qu, et al. Expires 7 January 2026 [Page 21] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 } description "Specify links for the flex-algo path computation."; } leaf-list exclude-srlgs { if-feature "te-types:named-srlg-groups"; type leafref { path "/te:te/te:globals/te:named-srlgs/te:named-srlg/" + "te:name"; } description "Shared Risk Link Groups (SRLGs) to be excluded during the flex-algo path computation."; } leaf metric-type { type identityref { base iana-metric-type:metric-type; } description "Type of metric to be used during the calculation."; } leaf calc-type { type identityref { base iana-algo-types:algo-type; } default iana-algo-types:algo-spf; description "Calcuation-type. Value from 0-127 inclusive from the IANA 'IGP Algorithm Types' registry defined under the 'Interior Gateway Protocol (IGP) Parameters' registry."; } container prefix-metric { presence "Use flex-algo specific prefix metric."; description "Use flex-algo prefix metric."; } leaf priority { type uint8; description "Priority of the advertisement."; } Qu, et al. Expires 7 January 2026 [Page 22] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 description "List of flex-algo configurations."; } description "Flexible Algorithm configuration."; } } /* Database */ augment "/rt:routing/" + "rt:control-plane-protocols/rt:control-plane-protocol"+ "/isis:isis/isis:database/isis:levels/isis:lsp"+ "/isis:router-capabilities" { when "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB router capability."; uses fad-tlvs; } 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 "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB prefix."; uses fapm-sub-tlvs; } 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 "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ Qu, et al. Expires 7 January 2026 [Page 23] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB prefix."; uses fapm-sub-tlvs; } 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 "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB prefix."; uses fapm-sub-tlvs; } 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 "/rt:routing/rt:control-plane-protocols/"+ "rt:control-plane-protocol/"+ "rt:type = 'isis:isis'" { description "This augment ISIS routing protocol when used"; } description "This augments ISIS protocol LSDB prefix."; uses fapm-sub-tlvs; } /* notification */ notification flex-algo-not-supported { uses isis:notification-instance-hdr; leaf flex-algo-number { type uint8 { range "128..255"; } description Qu, et al. Expires 7 January 2026 [Page 24] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 "Flex-algo identifier which is not supported by the IS-IS instance."; } description "This notification is sent when an IS-IS instance does not support this flex-algo."; } } 4. Security Considerations The YANG modules specified in this document define a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246]. The NETCONF access control model [RFC6536] provides the means to restrict access for particular NETCONF or RESTCONF users to a pre- configured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in the modules that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. Some of the readable data nodes in the modules 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. The exposure of the Link State Database (LSDB) will expose the detailed topology of the network. This may be undesirable since both due to the fact that exposure may facilitate other attacks. Additionally, network operators may consider their topologies to be sensitive confidential data. 5. IANA Considerations This document registers a URI in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested: Qu, et al. Expires 7 January 2026 [Page 25] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 URI: urn:ietf:params:xml:ns:yang:ietf-isis-link-attr Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-isis-flex-algo Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. This document registers the YANG module in the YANG Module Names registry [RFC6020]. name: ietf-isis-link-attr Maintained by IANA? N namespace: urn:ietf:params:xml:ns:yang:ietf-isis-link-attr prefix: isis-link-attr reference: RFC XXXX name: ietf-isis-flex-algo Maintained by IANA? N namespace: urn:ietf:params:xml:ns:yang:ietf-isis-flex-algo prefix: isis-flex-algo reference: RFC XXXX 6. Acknowledgements This document was produced using Marshall Rose's xml2rfc tool. The YANG model was developed using the suite of YANG tools written and maintained by numerous authors. 7. Normative References [I-D.ietf-lsr-ospf-flex-algo-yang] Qu, Y. and A. Lindem, "YANG Data Model for OSPF Application-Specific Link Attributes and Flexible Algorithm", Work in Progress, Internet-Draft, draft-ietf- lsr-ospf-flex-algo-yang-00, 6 July 2025, . [IANA-IGP-ALGO-Types] IANA, "IGP Algorithm Types", . [IANA-IGP-Metric-Types] IANA, "IGP Metric-Type", . Qu, et al. Expires 7 January 2026 [Page 26] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 [IANA-YANG-Parameters] IANA, "YANG Module Names", . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . Qu, et al. Expires 7 January 2026 [Page 27] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 [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, . [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, . [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, . [RFC9350] Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", RFC 9350, DOI 10.17487/RFC9350, February 2023, . [RFC9479] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and J. Drake, "IS-IS Application-Specific Link Attributes", RFC 9479, DOI 10.17487/RFC9479, October 2023, . Appendix A. Example IS-IS Flex-Algo Configuration The following is an example configuration for IS-IS Flexible Algorithm using the YANG model defined in this document. Note: '\' line wrapping per [RFC8792]. Qu, et al. Expires 7 January 2026 [Page 28] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 isis:isis default 128 true red blue green SRLG1 iana-metric-type:igp-metric iana-algo-types:algo-spf 10 Appendix B. Example IS-IS Flex-Algo Configuration (JSON) The following is an example configuration for IS-IS Flexible Algorithm in JSON format using the YANG model defined in this document. Qu, et al. Expires 7 January 2026 [Page 29] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 { "ietf-routing:routing": { "control-plane-protocols": { "control-plane-protocol": [ { "type": "ietf-isis:isis", "name": "default", "ietf-isis:isis": { "ietf-isis-flex-algo:isis-flex-algo": { "flex-algo": [ { "algo-number": 128, "advertise-definition": true, "admin-groups": { "exclude-admin-groups": ["red"], "include-any-admin-groups": ["blue"], "include-all-admin-groups": ["green"] }, "exclude-srlgs": ["SRLG1"], "metric-type": "iana-metric-type:igp-metric", "calc-type": "iana-algo-types:algo-spf", "prefix-metric": {}, "priority": 10 } ] } } } ] } } } Authors' Addresses Yingzhen Qu Futurewei Technologies United States of America Email: yingzhen.ietf@gmail.com Acee Lindem Arrcus, Inc. United States of America Email: acee.ietf@gmail.com Qu, et al. Expires 7 January 2026 [Page 30] Internet-Draft IS-IS ASLA and Flex-Algo YANG July 2025 Madhavi Joshi Arrcus, Inc. United States of America Email: madhavi@arrcus.com Qu, et al. Expires 7 January 2026 [Page 31]