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vishnupavan.ietf@gmail.com

Cisco Systems

tsaad.net@gmail.com

Cisco Systems

rgandhi@cisco.com

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xufeng.liu.ietf@gmail.com

TEAS This document defines a YANG data model for the management of topology filters/filter-sets on network elements and controllers.

Introduction A topology filter is a data construct that is used to filter network topologies . It can be applied on either a native topology or a customized topology to produce a filtered set of topological elements. A topology filter-set is a union of multiple topology filters that can be applied in tandem on a topology. This document defines a YANG data model for the management of topology filters/filter-sets on network elements and controllers. The authors acknowledge that an implementation may maintain network topologies that are learnt via routing protocols in a Routing Information Base (RIB) and use routing policies to filter the entries in the RIB. Such an implementation is not the target of this document.

Use-Cases Specification of topology related constraints for TE Path Computation: A few examples of this are - Compute a path within a specified topology. Compute a path within the topology associated with a specific IGP domain. Compute a path within the topology learnt from a specific TE Information Source. Compute a path within the topology defined by the application of one or more topology filters: Use a topology with elements learnt via ISIS Level-2 and include resource-affinity "RED" Use a topology with elements associated with ISIS Flexible Algorithm 128 and exclude resource-affinity "BLUE" Specification of topology associated with a Network Resource Partition (NRP): A few examples of rules for determining the topology associated with the NRP are: All the elements in the specified topology are part of the NRP topology. All the topological elements associated with a specific IGP domain are part of the NRP topology. All the topological elements that include resource-affinity "RED" and exclude resource-affinity "BLUE" are part of the NRP topology.

Terminology The terminology for describing YANG data models is found in . The reader is expected to be familiar with the topology modeling terminology specified in , and . The module defined in this document uses the common YANG data types defined in .

Tree Structure A simplified graphical representation of the data model is presented in the appendix of this document. The tree format defined in is used for the YANG data model tree representation.

Topology Filter Data Model

Model Structure The high-level model structure defined by this document is as shown below:

The top-level 'networks' container is augmented with a set of topology filters and a set of topology filter-sets.

Topology Filters The 'topology-filters' container carries a list of topology filters. Each topology-filter entry specifies a set of include-any, include- all and exclude filtering rules that can be applied on either the native topology or a user specified topology.

Topology Reference The 'topology-ref' container indicates the topology on which the filtering rules need to be applied. The referenced topology could be a predefined TE topology and/or a specific IGP domain. The absence of the 'topology-ref' indicates that the filtering rules are to be applied on the native topology. The 'igp-domain-identifier' container identifies a specific IGP domain using the following attributes: 'protocol-id': The IGP protocol type: OSPFv2, OSPFv3, or IS-IS. The values are those of the 'te-info-source' type defined in , restricted to 'ospfv2', 'ospfv3', and 'isis'. 'instance-id': The identifier of the IGP protocol instance. Multiple instances of the same IGP protocol can coexist on a network element. 'division-id': The identifier of a division within the IGP instance. The semantics of this field depend on the IGP protocol type: for OSPF, this is the Area ID; for IS-IS, this is the Level. 'algo-number': The algorithm number associated with the topology (e.g., the IGP Flexible Algorithm number). 'mt-id': The Multi-Topology Identifier as defined in for OSPF and for IS-IS. When any of these leaves are absent from the 'igp-domain-identifier' container, they are treated as wildcards and match any value. Similarly, when any of the leaves in the 'te-topology-identifier' container are absent, they are treated as wildcards and match any value.

Filters The 'include-any', 'include-all' and 'exclude' containers carry a varied set of attributes that can be used as rules to filter the topology. If the topology-filter entry carries no filtering rules and only references a specific topology, then the set of filtered topological elements produced is the same as the one defined by the referenced topology. When a filter attribute (leaf-list or list) is absent or empty in a given container, it is treated as a wildcard and does not constrain the filter results for that attribute type. The filtering semantics are as follows: 'include-any': A topological element matches the 'include-any' container if, for each populated attribute list, it matches at least one attribute in that list (OR within each attribute list, AND across attribute lists). 'include-all': A topological element matches the 'include-all' container if, for each populated attribute list, it matches all attributes in that list (AND within each attribute list, AND across attribute lists). 'exclude': A topological element matches the 'exclude' container if, for each populated attribute list, it matches at least one attribute in that list (OR within each attribute list, AND across attribute lists). A topological element is included in the resulting filtered topology if and only if it satisfies all of the following conditions (AND operation across containers): It matches the 'include-any' container (if populated). It matches the 'include-all' container (if populated). It does not match the 'exclude' container (if populated). If an OR operation across attribute lists is desired for 'include-any', this can be achieved by defining multiple topology filters (each with its own 'include-any' container) and combining them using a topology-filter-set, which produces a union of the individual filter results. The 'link-affinity' attribute carries resource affinity names that have a consistent meaning across the domain in which the filter is applied. How a name maps to the affinity values (e.g., administrative-group bits) of a link is outside the scope of this document.

Topology Filter-Sets The 'topology-filter-sets' container carries a list of topology filter-sets. Each topology-filter-set entry constitutes a list of topology-filter references. This is used when there is a need to create a union of multiple topology filters.

../../../topology-filters/topology-filter/name ]]>

YANG Module

file "ietf-topology-filter@2026-11-01.yang" module ietf-topology-filter { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-topology-filter"; prefix topo-filt; import ietf-inet-types { prefix inet; reference "RFC 9911: Common YANG Data Types"; } import ietf-network { prefix nw; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-te-types { prefix te-types; reference "RFC 8776: Common YANG Data Types for Traffic Engineering"; } import ietf-te-topology { prefix tet; reference "RFC 8795: YANG Data Model for Traffic Engineering Topologies"; } organization "IETF Traffic Engineering Architecture and Signaling (TEAS) Working Group."; contact "WG Web: WG List: Editor: Vishnu Pavan Beeram Editor: Tarek Saad Editor: Rakesh Gandhi Editor: Xufeng Liu "; description "This YANG module defines data definitions for managing topology filters. 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). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2026-11-01 { description "Initial revision."; reference "RFC XXXX: YANG Data Model for Topology Filters."; } /* * G R O U P I N G S */ /* * Grouping - Topology Information Source. */ grouping igp-topology-info-source { description "Grouping for igp topology information source."; leaf protocol-id { type tet:te-info-source { enum ospfv2 { description "OSPFv2."; } enum ospfv3 { description "OSPFv3."; } enum isis { description "IS-IS."; } } description "IGP Protocol Type. Only the 'ospfv2', 'ospfv3', and 'isis' values of 'te-info-source' are applicable."; reference "RFC 8795: YANG Data Model for Traffic Engineering (TE) Topologies"; } leaf instance-id { type uint32; description "The identifier of the IGP protocol instance."; } leaf division-id { type uint32; description "The identifier of a division within the IGP instance. The semantics of this field depend on the IGP protocol type: for OSPF, this is the Area ID; for IS-IS, this is the Level."; } } /* * Grouping - IGP Domain Identifier. */ grouping igp-domain-identifier { description "Grouping for igp domain identifier."; container igp-domain-identifier { description "Container for igp domain identifier."; uses igp-topology-info-source; leaf algo-number { type uint8; description "The algorithm number associated with the topology (e.g., the IGP Flexible Algorithm number)."; } leaf mt-id { type uint16; description "The Multi-Topology Identifier."; reference "RFC 4915: Multi-Topology (MT) Routing in OSPF RFC 5120: M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)"; } } } /* * Grouping - Topology Reference */ grouping topology-reference { description "Grouping for topology reference."; container topology-ref { description "Container for topology reference."; uses igp-domain-identifier; uses te-types:te-topology-identifier; } } /* * Grouping - Topology Information Sources */ grouping topology-info-sources { description "Grouping for topology information sources."; list info-source { key "source-id instance-id division-id"; description "List of information-sources."; leaf source-id { type tet:te-info-source; description "Information Source."; } leaf instance-id { type uint32; description "The identifier of the information source routing protocol instance."; } leaf division-id { type uint32; description "The identifier of a division within the information source instance. For OSPF, this is the Area ID; for IS-IS, this is the Level."; } } } /* * Grouping - Custom Topology Filters */ grouping custom-topology-filters { description "Grouping for custom topology filters."; leaf-list link-affinity { type string; description "List of resource affinity names. The names are consistently defined across the domain in which the filter is applied."; } leaf-list link-name { type string; description "List of link names."; } leaf-list node-prefix { type inet:ip-prefix; description "List of IP prefixes that identify nodes."; } leaf-list as { type inet:as-number; description "List of AS numbers."; } uses topology-info-sources; } /* * Grouping - Topology Filters */ grouping topology-filters { description "Grouping for topology filters."; container topology-filters { presence "Enable Topology Filters."; description "Container for topology filters."; list topology-filter { key "name"; description "List of topology filters."; leaf name { type string; description "A string that uniquely identifies the topology filter."; } uses topology-reference; container include-any { description "A topological element matches this container if, for each populated attribute list, it matches at least one attribute in that list (OR within each list, AND across lists)."; uses custom-topology-filters; } container include-all { description "A topological element matches this container if, for each populated attribute list, it matches all attributes in that list (AND within each list, AND across lists)."; uses custom-topology-filters; } container exclude { description "A topological element matches this container if, for each populated attribute list, it matches at least one attribute in that list (OR within each list, AND across lists). Matched elements are excluded from the filtered topology."; uses custom-topology-filters; } } } } /* * Grouping - Topology Filter Sets */ grouping topology-filter-sets { description "Grouping for topology filter sets."; container topology-filter-sets { presence "Enable Topology Filter-Sets."; description "Container for topology filter sets."; list topology-filter-set { key "name"; description "List of topology filter sets."; leaf name { type string; description "A string that uniquely identifies the topology filter-set."; } leaf-list topology-filter { type leafref { path "../../../topo-filt:topology-filters/" + "topo-filt:topology-filter/topo-filt:name"; } description "Reference to a specific topology filter from the list of topology filters."; } } } } /* * Augment - Topology Filters / Topology Filter-Sets */ augment "/nw:networks" { description "Augment networks with topology-filters and topology-filter-sets."; uses topology-filters; uses topology-filter-sets; } } ]]>

Acknowledgements The authors would like to thank Sudharsana Venkatraman for her input from discussions.

IANA Considerations IANA is requested to register the following URI in the "ns" registry within the "IETF XML Registry" group :

IANA is requested to register the following YANG module in the "YANG Module Names" registry within the "YANG Parameters" registry group.

Security Considerations This section is modeled after the template described in Section 3.7.1 of . The "ietf-topology-filter" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as the Network Configuration Protocol (NETCONF) and RESTCONF . These YANG-based management protocols (1) have to use a secure transport layer (e.g., Secure Shell (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: "/networks/topology-filters/": This subtree specifies the configurations for topology filters. By manipulating these data nodes, a malicious attacker may cause unauthorized and improper behavior to any service that is making use of the filtered set of topological elements produced by the application of the compromised topology filter. "/networks/topology-filter-sets": This subtree specifies the configurations for topology filter-sets. By manipulating these data nodes, a malicious attacker may cause unauthorized and improper behavior to any service that is making use of the filtered set of topological elements produced by the application of the compromised topology filter-set. 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. These are the subtrees and data nodes and their sensitivity/vulnerability: "/networks/topology-filters": Unauthorized access to this subtree can disclose the topology filters used in the network. "/networks/topology-filter-sets": Unauthorized access to this subtree can disclose the topology filter-sets used in the network.

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. This document describes an extension to Open Shortest Path First (OSPF) in order to define independent IP topologies called Multi- Topologies (MTs). The Multi-Topologies extension can be used for computing different paths for unicast traffic, multicast traffic, different classes of service based on flexible criteria, or an in- band network management topology. An optional extension to exclude selected links from the default topology is also described. [STANDARDS-TRACK] This document describes an optional mechanism within Intermediate System to Intermediate Systems (IS-ISs) used today by many ISPs for IGP routing within their clouds. This document describes how to run, within a single IS-IS domain, a set of independent IP topologies that we call Multi-Topologies (MTs). This MT extension can be used for a variety of purposes, such as an in-band management network "on top" of the original IGP topology, maintaining separate IGP routing domains for isolated multicast or IPv6 islands within the backbone, or forcing a subset of an address space to follow a different topology. [STANDARDS-TRACK] 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] 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] 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). 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). 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 defines an abstract (generic, or base) YANG data model for network/service topologies and inventories. The data model serves as a base model that is augmented with technology-specific details in other, more specific topology and inventory data models. This document defines a collection of common data types and groupings in YANG data modeling language. These derived common types and groupings are intended to be imported by modules that model Traffic Engineering (TE) configuration and state capabilities. This document defines a YANG data model for representing, retrieving, and manipulating Traffic Engineering (TE) Topologies. The model serves as a base model that other technology-specific TE topology models can augment. 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 obsoletes RFC 8446, which specified TLS 1.3. This document obsoletes RFC 5246 (specifying TLS 1.2) and RFCs 5077, 6961, 7627, and 8422, all of which pertain to TLS 1.2 or earlier, and updates RFCs 5705 and 6066. This document also specifies new requirements for TLS 1.2 implementations. This document defines a collection of common data types to be used with the YANG data modeling language. It includes several new type definitions and obsoletes RFC 6991. 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] 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 defines a YANG data model for the Routing Information Base (RIB) that aligns with the Interface to the Routing System (I2RS) RIB information model. 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. This document defines a YANG data model for configuring and managing routing policies in a vendor-neutral way. The model provides a generic routing policy framework that can be extended for specific routing protocols using the YANG 'augment' mechanism. This document describes network slicing in the context of networks built from IETF technologies. It defines the term "IETF Network Slice" to describe this type of network slice and establishes the general principles of network slicing in the IETF context. The document discusses the general framework for requesting and operating IETF Network Slices, the characteristics of an IETF Network Slice, the necessary system components and interfaces, and the mapping of abstract requests to more specific technologies. The document also discusses related considerations with monitoring and security. This document also provides definitions of related terms to enable consistent usage in other IETF documents that describe or use aspects of IETF Network Slices. This document provides guidelines for authors and reviewers of specifications containing YANG data models, including IANA-maintained YANG 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; it also updates RFC 8126 by providing additional guidelines for writing the IANA considerations for RFCs that specify IANA-maintained YANG modules.

Usage Examples This appendix provides JSON encoding examples of the topology filter configuration as defined in this document. The examples use JSON encoding per and .

Example 1: ISIS Level-2 Filter with Include-Any This example creates a topology filter named "isis-level2-red" that operates on the IS-IS Level-2 topology and includes topological elements that have link-affinity "RED". Since only one attribute list is populated in 'include-any', an element is included if it matches at least one value in that list. This corresponds to the use-case: "Use a topology with elements learnt via ISIS Level-2 and include resource-affinity RED".

Example 2: ISIS Flex-Algo Filter with Exclude This example creates a topology filter named "isis-flexalgo128-no-blue" that operates on the IS-IS topology associated with Flexible Algorithm 128 and excludes topological elements with link-affinity "BLUE". This corresponds to the use-case: "Use a topology with elements associated with ISIS Flexible Algorithm 128 and exclude resource-affinity BLUE".

Example 3: NRP Filter with Include-All and Exclude This example creates a topology filter named "nrp-filter" for defining a Network Resource Partition (NRP) topology. It uses 'include-all' to require that topological elements match all values in each populated attribute list (AND within each list) and satisfy all populated attribute lists (AND across lists). In this case, elements must have link-affinity "RED" AND belong to AS 64496. It also excludes any element with link-affinity "BLUE". Additionally, a topology-filter-set named "nrp-filter-set" is created that references both "isis-level2-red" (from Example 1) and "nrp-filter" to form a union of the two filters.

Complete Model Tree Structure

../../../topology-filters/topology-filter/name ]]>

Contributors HPE

jonathan.barth@hpe.com

HPE

srihari.sangli@hpe.com

HPE

chandrasekar.ramachandran@hpe.com