| Internet-Draft | IS-IS ASLA and Flex-Algo YANG | June 2026 |
| Qu, et al. | Expires 27 December 2026 | [Page] |
This document defines a YANG data model to support IS-IS Application-Specific Link Attributes and Flexible Algorithm.¶
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 27 December 2026.¶
Copyright (c) 2026 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.¶
This document defines a YANG [RFC7950] data model, which is composed of two YANG modules. The first module provides support for configuration and operational state for IS-IS Application-Specific Link Attributes as defined in [RFC9479], and the second module supports IS-IS Flexible Algorithm as defined in [RFC9350]. Both modules augment the IETF IS-IS YANG data model [RFC9130].¶
The first YANG module, ietf-isis-link-attr, augments the IS-IS YANG data model [RFC9130] to support configuration and operational state for IS-IS Application-Specific Link Attributes (ASLA) as specified in [RFC9479]. This module is related to the IS-IS TE extensions defined in [RFC5305] and reuses identity definitions from the IANA-maintained IGP link-attribute application registry.¶
The second YANG module, ietf-isis-flex-algo, augments the IS-IS YANG data model [RFC9130] to support IS-IS Flexible Algorithm as specified in [RFC9350]. It uses identity definitions from the IANA-maintained IGP Algorithm Types and IGP Metric Type registries, and references the TE YANG data types [RFC8776] for admin-group and SRLG feature support.¶
The meanings of the symbols in the YANG tree diagrams are defined in [RFC8340].¶
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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
This document defines a YANG module for IS-IS Application-Specific Link Attributes as defined in [RFC9479]. This YANG module references [RFC9479], [RFC9911], [RFC8349], [RFC9130], [RFC5305], and [IANA-Link-Attr-Apps].¶
module: ietf-isis-link-attr
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/isis:isis:
+--rw isis-link-attr
+--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:
+--rw isis-asla
+--rw interface-asla* [link-attr-app]
+--rw link-attr-app identityref
+--rw te-metric? te-types:te-metric
+--rw admin-group? te-types:admin-group
+--rw srlgs
+--rw srlg* te-types:srlg
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
| +--ro sabm-bit* identityref
+--ro udabm
+--ro te-metric?
| te-types:te-metric
+--ro admin-group?
| te-types:admin-group
+--ro max-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro max-reservable-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro unreserved-bandwidths
| +--ro unreserved-bandwidth* []
| +--ro priority? uint8
| +--ro unreserved-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-delay
| +--ro flags
| | +--ro unidirectional-link-delay-subtlv-flags*
| | identityref
| +--ro value? uint32
+--ro min-max-unidirectional-link-delay
| +--ro flags
| | +--ro min-max-unidirectional-link-delay-subtlv-flags*
| | identityref
| +--ro min-value? uint32
| +--ro max-value? uint32
+--ro unidirectional-link-delay-variation
| +--ro value? uint32
+--ro unidirectional-link-loss
| +--ro flags
| | +--ro unidirectional-link-loss-subtlv-flags*
| | identityref
| +--ro value? uint32
+--ro unidirectional-link-residual-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-available-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-utilized-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--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
| +--ro sabm-bit* identityref
+--ro udabm
+--ro te-metric?
| te-types:te-metric
+--ro admin-group?
| te-types:admin-group
+--ro max-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro max-reservable-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro unreserved-bandwidths
| +--ro unreserved-bandwidth* []
| +--ro priority? uint8
| +--ro unreserved-bandwidth?
| rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-delay
| +--ro flags
| | +--ro unidirectional-link-delay-subtlv-flags*
| | identityref
| +--ro value? uint32
+--ro min-max-unidirectional-link-delay
| +--ro flags
| | +--ro min-max-unidirectional-link-delay-subtlv-flags*
| | identityref
| +--ro min-value? uint32
| +--ro max-value? uint32
+--ro unidirectional-link-delay-variation
| +--ro value? uint32
+--ro unidirectional-link-loss
| +--ro flags
| | +--ro unidirectional-link-loss-subtlv-flags*
| | identityref
| +--ro value? uint32
+--ro unidirectional-link-residual-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-available-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--ro unidirectional-link-utilized-bandwidth
| +--ro value? rt-types:bandwidth-ieee-float32
+--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
+--ro pseudo-node-id? uint8
+--ro l-flag? boolean
+--ro sabm
| +--ro sabm-bit* identityref
+--ro udabm
+--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* te-types:srlg
¶
<CODE BEGINS> file "ietf-isis-link-attr@2026-06-25.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 9911: 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";
}
import ietf-routing-types {
prefix rt-types;
reference
"RFC 8294: Common YANG Data Types for the
Routing Area";
}
import ietf-te-types {
prefix te-types;
reference
"RFC 8776: Common YANG Data Types for Traffic Engineering";
}
import iana-igp-link-attr-apps {
prefix iana-link-attr-apps;
reference
"IANA IGP Link-Attribute Application Identifiers registry,
<https://www.iana.org/assignments/igp-parameters>.";
}
organization
"IETF LSR - Link State Routing Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/lsr>
WG List: <mailto:lsr@ietf.org>
Author: Yingzhen Qu
<mailto:yingzhen.ietf@gmail.com>
Author: Acee Lindem
<mailto:acee.ietf@gmail.com>
Author: Madhavi Joshi
<madhavi@arrcus.com>
";
description
"This YANG module defines the configuration and operational
state for IS-IS application specific link attributes feature as
defined in RFC 9479.
Copyright (c) 2026 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).
All revisions of IETF and IANA published modules can be found
at the YANG Parameters registry group
(https://www.iana.org/assignments/yang-parameters).
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.";
revision 2026-06-25 {
description
"Initial version";
reference
"RFC XXXX: A YANG Data Model for IS-IS Application-Specific
Link Attributes and Flexible Algorithm";
}
grouping isis-te-link-attrs {
description
"IS-IS Application-Specific Link Attributes (ASLA)
inherited from the base IS-IS TE attributes";
leaf te-metric {
type te-types:te-metric;
description
"TE default metric.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering,
Section 3.7";
}
leaf admin-group {
type te-types:admin-group;
description
"Administrative Group / Resource Class/Color.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering,
Section 3.1";
}
leaf max-bandwidth {
type rt-types:bandwidth-ieee-float32;
units "bytes per second";
description
"Maximum bandwidth.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering,
Section 3.4";
}
leaf max-reservable-bandwidth {
type rt-types:bandwidth-ieee-float32;
units "bytes per second";
description
"Maximum reservable bandwidth.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering,
Section 3.5";
}
container unreserved-bandwidths {
description
"All unreserved bandwidths.";
list unreserved-bandwidth {
leaf priority {
type uint8 {
range "0..7";
}
description
"Priority from 0 to 7.";
}
leaf unreserved-bandwidth {
type rt-types:bandwidth-ieee-float32;
units "bytes per second";
description
"Unreserved bandwidth.";
}
description
"List of unreserved bandwidths for different
priorities.";
}
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering,
Section 3.6";
}
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering";
}
grouping application-identifier-bit-mask {
description
"Identification of the set of applications associated with
link attribute advertisements";
leaf l-flag {
type boolean;
description
"Legacy Flag. When the SABM Length or UDABM Length is
non-zero and the L-flag is not set, all applications
specified in the bit mask use the link
attribute advertisements in the sub-TLV.";
reference
"RFC 9479: IS-IS Application-Specific Link Attributes,
Section 3";
}
container sabm {
leaf-list sabm-bit {
type identityref {
base iana-link-attr-apps:igp-link-attr-app;
}
description
"Standard Application Identifier Bit Mask bits. This
leaf-list contains identities for the bits which are
set to 1 in the SABM field.";
}
description
"Standard Application Identifier Bit Mask.";
}
container udabm {
description
"User Defined Application Identifier Bit Mask (UDABM).
This container is intended to be augmented by documents
defining user-defined application identifiers. Each
such augmentation SHOULD add a leaf-list of identityref
type whose base identity represents the user-defined
application, following the same pattern as the
'sabm-bit' leaf-list. Refer to RFC 9479, Section 3
for the on-wire encoding of the UDABM field.";
reference
"RFC 9479: IS-IS Application-Specific Link Attributes,
Section 3";
}
}
grouping application-specific-link-attributes-sub-tlv {
description
"Grouping for specification of the applications and
application-specific attribute values.";
container asla-sub-tlvs {
list asla-sub-tlv {
uses application-identifier-bit-mask;
uses isis-te-link-attrs;
uses isis:neighbor-extended-te-extensions;
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;
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.
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.";
}
description
"IPv6 neighbor address sub-tlv.";
}
}
container srlgs {
description
"List of SRLGs.";
leaf-list srlg {
type te-types:srlg;
description
"SRLG value of the link.";
}
}
description
"List of application specific SRLG tlvs.";
}
description
"Application specific SRLG tlv.";
}
}
/* Management */
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 IS-IS routing protocol when used";
}
description
"This augments IS-IS protocol management
with application specific link attributes.";
container isis-link-attr {
choice link-attr-op-mode {
default "legacy";
leaf legacy {
type empty;
description
"Only send legacy advertisements.";
}
leaf transition {
type empty;
description
"Send both application-specific and legacy
advertisements.";
}
leaf app-specific {
type empty;
description
"Only send application-specific advertisements.";
}
description
"Link attributes mode. Default to legacy mode for
backward compatibility.";
}
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 IS-IS routing protocol when used.";
}
description
"This augments IS-IS interface management
with application specific link attributes.";
container isis-asla {
list interface-asla {
key "link-attr-app";
leaf link-attr-app {
type identityref {
base iana-link-attr-apps:igp-link-attr-app;
}
description
"Application-specific attributes. Note that
when encoded, applications with identical
attributes may be included in the same sub-TLV.";
}
leaf te-metric {
type te-types:te-metric;
description
"TE metric.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering";
}
leaf admin-group {
type te-types:admin-group;
description
"Administrative Group / Resource Class/Color.";
reference
"RFC 5305: IS-IS Extensions for Traffic Engineering";
}
container srlgs {
description
"List of SRLGs.";
leaf-list srlg {
type te-types:srlg;
description
"SRLG value of the link.";
}
}
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 IS-IS routing protocol when used";
}
description
"This augments IS-IS 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" {
when "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:type = 'isis:isis'" {
description
"This augment IS-IS routing protocol when used";
}
description
"This augments IS-IS 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 IS-IS routing protocol when used";
}
description
"This augments IS-IS protocol LSDB.";
uses application-specific-srlg-tlv;
}
}
<CODE ENDS>¶
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]. This YANG module references [RFC7308], [RFC8349], [RFC8776], [RFC9130], [I-D.ietf-teas-yang-te], [IANA-IGP-Algo-Types], and [IANA-IGP-Metric-Types].¶
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
+--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 algo-number? uint8
+--ro metric-type? identityref
+--ro calc-type? identityref
+--ro priority? uint8
+--ro fa-ex-ag-sub-tlv
| +--ro extended-admin-group*
| te-types:extended-admin-group
+--ro fa-in-any-ag-sub-tlv
| +--ro extended-admin-group* uint64
+--ro fa-in-all-ag-sub-tlv
| +--ro extended-admin-group* 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 algo-number? 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 algo-number? uint8
+--ro metric? 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 fapm-sub-tlvs
+--ro fapm-sub-tlv* []
+--ro algo-number? 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 algo-number? uint8
+--ro metric? uint32
notifications:
+---n flex-algo-not-supported
+--ro routing-protocol-name? leafref
+--ro isis-level? level
+--ro algo-number? uint8
¶
<CODE BEGINS> file "ietf-isis-flex-algo@2026-06-25.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 {
prefix te;
reference
"RFC XXXX: A YANG Data Model for Traffic Engineering
Tunnels, Label Switched Paths, and Interfaces";
}
import iana-igp-algo-types {
prefix iana-algo-types;
reference
"IANA IGP Algorithm Types registry,
<https://www.iana.org/assignments/igp-parameters>.";
}
import iana-igp-metric-types {
prefix iana-metric-type;
reference
"IANA IGP Metric-Type registry,
<https://www.iana.org/assignments/igp-parameters>.";
}
organization
"IETF LSR - Link State Routing Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/lsr>
WG List: <mailto:lsr@ietf.org>
Author: Yingzhen Qu
<mailto:yingzhen.ietf@gmail.com>
Author: Acee Lindem
<mailto:acee.ietf@gmail.com>
Author: Madhavi Joshi
<madhavi@arrcus.com>
";
description
"The YANG module defines the configuration and operational
state for IS-IS Flexible Algorithm as defined in RFC 9350.
Copyright (c) 2026 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).
All revisions of IETF and IANA published modules can be found
at the YANG Parameters registry group
(https://www.iana.org/assignments/yang-parameters).
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.";
revision 2026-06-25 {
description
"Initial Version";
reference
"RFC XXXX: A YANG Data Model for IS-IS Application-Specific
Link Attributes and Flexible Algorithm";
}
/* Identities */
identity fad-flags {
description
"Base identity for IS-IS FAD flags.";
}
identity m-flag {
base fad-flags;
description
"M-flag in the Flex-Algorithm Definition (FAD) flags sub-TLV.
When this flag is present in the fad-flags leaf-list, the
Flex-Algorithm-specific prefix metric is used for inter-area
and external prefix calculation. Note that this flag is not
applicable to prefixes advertised as SRv6 locators.";
reference
"RFC 9350: IGP Flexible Algorithm, Section 9.1";
}
/* Groupings */
grouping fa-ex-ag-sub-tlv {
container fa-ex-ag-sub-tlv {
leaf-list extended-admin-group {
type te-types:extended-admin-group;
description
"Extended administrative group value.";
reference
"RFC 7308: Extended Administrative Groups in MPLS-TE";
}
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 {
container fa-in-any-ag-sub-tlv {
leaf-list extended-admin-group {
type uint64;
description
"Extended administrative group value.";
reference
"RFC 7308: Extended Administrative Groups in MPLS-TE";
}
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-group {
type uint64;
description
"Extended administrative group value.";
reference
"RFC 7308: Extended Administrative Groups in MPLS-TE";
}
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
"IS-IS 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
"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 algo-number {
type uint8;
description
"Flex-algo number - A value not in the inclusive range
of 128-255 is an invalid FAD TLV specification. Valid
Flex-Algorithm numbers are in the inclusive range
128-255 as specified in RFC 9350.";
reference
"RFC 9350: IGP Flexible Algorithm, Section 5";
}
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.";
}
description
"IS-IS Flexible Algorithm Definition TLV.";
}
description
"IS-IS Flexible Algorithm Definition (FAD) TLV.";
}
grouping fapm-sub-tlvs {
container fapm-sub-tlvs {
list fapm-sub-tlv {
leaf algo-number {
type uint8;
description
"Flex-algo number - A value not in the inclusive range
of 128-255 is an invalid FAPM sub-TLV specification.";
}
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.";
}
/* Management */
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 IS-IS routing protocol when used";
}
description
"This augments IS-IS protocol management
with flexible algorithm.";
container isis-flex-algo {
list flex-algo {
key "algo-number";
leaf algo-number {
type uint8 {
range "128..255";
}
description
"Flex-algo number - must be in the inclusive range
of 128-255.";
}
leaf advertise-definition {
type boolean;
default "true";
description
"When set to true, enables advertisement of the
Flexible Algorithm Definition (FAD) TLV for this
flex-algo instance.";
}
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.";
}
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
"Calculation-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.";
}
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 IS-IS routing protocol when used";
}
description
"This augments IS-IS 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 IS-IS routing protocol when used";
}
description
"This augments IS-IS 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/"
+ "rt:type = 'isis:isis'" {
description
"This augment IS-IS routing protocol when used";
}
description
"This augments IS-IS 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 IS-IS routing protocol when used";
}
description
"This augments IS-IS 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 IS-IS routing protocol when used";
}
description
"This augments IS-IS protocol LSDB prefix.";
uses fapm-sub-tlvs;
}
/* Notification */
notification flex-algo-not-supported {
uses isis:notification-instance-hdr;
leaf algo-number {
type uint8;
description
"Flex-algo identifier which is not supported by the IS-IS
instance. Valid Flex-Algorithm numbers are in the
inclusive range 128-255 as specified in RFC 9350.
A value outside this range in a received FAD TLV
is invalid.";
reference
"RFC 9350: IGP Flexible Algorithm, Section 5";
}
description
"This notification is sent when an IS-IS instance does not
support this flex-algo.";
}
}
<CODE ENDS>¶
The YANG modules defined in this document are designed to be accessed via YANG-based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to use a secure transport layer (e.g., SSH [RFC4252], TLS [I-D.ietf-tls-rfc8446bis], and QUIC [RFC9000]) and 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 reasonably 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:¶
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 exposure may facilitate other attacks. Additionally, network operators may consider their topologies to be sensitive confidential data.¶
The flex-algo-not-supported notification defined in this document may reveal information about the local IS-IS instance's algorithm capabilities. Access to this notification SHOULD be restricted using NACM [RFC8341] to authorized management stations.¶
This document registers two URIs in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested:¶
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 modules in the YANG Module Names registry [RFC7950].¶
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¶
Thanks to Michal Vasko for his YANG doctors review.¶
Thanks to Adrian Farrel for his OPS directorate review.¶
Thanks to Renato Westphal for review and comments.¶
Thanks to Med Boucadair for extensive review and comments.¶
The following is an example configuration for IS-IS Flexible Algorithm using the YANG model defined in this document.¶
Note: '\' line wrapping per [RFC8792].¶
<?xml version='1.0' encoding='UTF-8'?>
<te xmlns="urn:ietf:params:xml:ns:yang:ietf-te">
<enable>true</enable>
<globals>
<named-admin-groups>
<named-admin-group>
<name>blue</name>
</named-admin-group>
</named-admin-groups>
</globals>
</te>
<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>
<isis-flex-algo xmlns="urn:ietf:params:xml:ns:yang:\
ietf-isis-flex-algo">
<flex-algo>
<algo-number>200</algo-number>
<admin-groups>
<exclude-admin-groups>blue</exclude-admin-groups>
</admin-groups>
<metric-type xmlns:iana-metric-types=\
"urn:ietf:params:xml:ns:yang:iana-igp-metric-types">\
iana-metric-types:igp-metric</metric-type>
<calc-type xmlns:iana-algo-types=\
"urn:ietf:params:xml:ns:yang:iana-igp-algo-types">\
iana-algo-types:algo-spf</calc-type>
<prefix-metric/>
<priority>100</priority>
</flex-algo>
</isis-flex-algo>
</isis>
</control-plane-protocol>
</control-plane-protocols>
</routing>
¶
The following is an example configuration for IS-IS Flexible Algorithm in JSON format using the YANG module defined in this document.¶
{
"ietf-te:te": {
"enable": true,
"globals": {
"named-admin-groups": {
"named-admin-group": [
{
"name": "blue"
}
]
}
}
},
"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",
"ietf-isis-flex-algo:isis-flex-algo": {
"flex-algo": [
{
"algo-number": 200,
"admin-groups": {
"exclude-admin-groups": ["blue"]
},
"metric-type": "iana-igp-metric-types:igp-metric",
"calc-type": "iana-igp-algo-types:algo-spf",
"prefix-metric": [null],
"priority": 100
}
]
}
}
}
]
}
}
}
¶