LabN Consulting, L.L.C.

chopps@chopps.org

rtg lsr This document defines a YANG module for managing the reverse metric extension to the Intermediate System to Intermediate System (IS-IS) intra-domain routing information exchange protocol.

Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at .

Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents () in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.

Table of Contents

• .  Introduction
• .  YANG Management
  • .  YANG Tree
  • .  YANG Module
• .  IANA Considerations
  • .  Updates to the IETF XML Registry
  • .  Updates to the YANG Module Names Registry
• .  Security Considerations
• .  Normative References
• .  Informative References
• .  Examples
  • .  Enablement Example Using XML YANG Instance Data
  • .  Usage Example Using XML YANG Instance Data
  • .  Usage Example Using JSON YANG Instance Data
• Author's Address

Introduction This document defines a YANG module for managing the reverse metric extension to IS-IS . Please refer to for the description and definition of the functionality managed by this module. The YANG data model described in this document conforms to the Network Management Datastore Architecture defined in .

YANG Management

YANG Tree The following is the YANG tree diagram for the IS-IS reverse metric extension additions. module: ietf-isis-reverse-metric augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis: +--rw reverse-metric +--rw enable-receive? boolean augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis/isis:interfaces /isis:interface: +--rw reverse-metric +--rw metric? isis:wide-metric +--rw flags | +--rw whole-lan? boolean | +--rw allow-unreachable? boolean +--rw exclude-te-metric? boolean +--rw level-1 | +--rw metric? isis:wide-metric | +--rw flags | | +--rw whole-lan? boolean | | +--rw allow-unreachable? boolean | +--rw exclude-te-metric? boolean +--rw level-2 +--rw metric? isis:wide-metric +--rw flags | +--rw whole-lan? boolean | +--rw allow-unreachable? boolean +--rw exclude-te-metric? boolean augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/isis:isis/isis:interfaces /isis:interface/isis:adjacencies/isis:adjacency: +--ro reverse-metric +--ro metric? isis:wide-metric +--ro flags | +--ro whole-lan? boolean | +--ro allow-unreachable? boolean +--ro te-metric? uint32

YANG Module The following is the YANG module for managing the IS-IS reverse metric functionality defined in . It imports modules from and . This YANG module uses the same per-level hierarchical configuration structure as that defined in the augmented base module. module ietf-isis-reverse-metric { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-isis-reverse-metric"; prefix isis-rmetric; 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"; } organization "IETF LSR Working Group (LSR)"; contact "WG Web: <https://datatracker.ietf.org/wg/lsr/> WG List: <mailto:lsr@ietf.org> Author: Christian Hopps <mailto:chopps@chopps.org>"; description "This module defines the configuration and operational state for managing the IS-IS reverse metric functionality (RFC 8500). Copyright (c) 2022 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 9194; see the RFC itself for full legal notices."; reference "RFC 8500: IS-IS Routing with Reverse Metric"; revision 2022-10-19 { description "Initial revision."; reference "RFC 9194: A YANG Module for IS-IS Reverse Metric"; } grouping reverse-metric-data { description "IS-IS reverse metric data."; leaf metric { type isis:wide-metric; description "The reverse metric value."; reference "RFC 8500: IS-IS Routing with Reverse Metric, Section 2"; } container flags { description "The reverse metric flag values."; leaf whole-lan { type boolean; description "The 'Whole LAN' bit (W bit) (RFC 8500). If true, then a Designated Intermediate System (DIS) processing this reverse metric will add the metric value to all the nodes it advertises in the pseudonode Link State Protocol Data Unit (LSP) for this interface. Otherwise, it will only increment the metric for the advertising node in the pseudonode LSP for this interface."; reference "RFC 8500: IS-IS Routing with Reverse Metric, Section 2"; } leaf allow-unreachable { type boolean; description "The 'Unreachable' bit (U bit) (RFC 8500). If true, it allows the neighbor to increment the overall metric up to 2^24-1 rather than the lesser maximum of 2^24-2. If the metric is then set by the neighbor to 2^24-1, it will cause traffic to stop using, rather than avoid using, the interface."; reference "RFC 8500: IS-IS Routing with Reverse Metric, Section 2"; } } } grouping reverse-metric-if-config-data { description "IS-IS reverse metric config data."; uses reverse-metric-data; leaf exclude-te-metric { type boolean; default "false"; description "If true and there is a TE metric defined for this interface, then do not send the Traffic Engineering Metric sub-TLV in the Reverse Metric TLV."; reference "RFC 8500: IS-IS Routing with Reverse Metric, Section 2"; } } grouping tlv16-reverse-metric { description "IS-IS Reverse Metric TLV data."; uses reverse-metric-data; leaf te-metric { type uint32; description "The TE metric value from the sub-TLV, if present."; reference "RFC 8500: IS-IS Routing with Reverse Metric, Section 2"; } } augment "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/" + "isis:isis" { when "derived-from-or-self(../rt:type, 'isis:isis')" { description "This augment is only valid when the routing protocol instance type is 'isis'."; } description "The reverse metric configuration for an IS-IS instance."; container reverse-metric { description "Global reverse metric configuration."; leaf enable-receive { type boolean; default "false"; description "Enables handling of reverse metric announcements from neighbors. By default, reverse metric handling is disabled and must be explicitly enabled through this configuration."; } } } augment "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/" + "isis:isis/isis:interfaces/isis:interface" { when "derived-from-or-self(../../../rt:type, 'isis:isis')" { description "This augment is only valid when the routing protocol instance type is 'isis'."; } description "The reverse metric configuration for an interface."; container reverse-metric { description "Announces a reverse metric to neighbors. The configuration is hierarchical and follows the same behavior as that defined for per-level values in the augmented base module. Reverse metric operation is enabled by the configuration of a 'reverse-metric' metric value either at the top level or under a level-specific container node. If a 'reverse-metric' metric value is only specified under a level-specific container node, then operation is only enabled at the specified level. As the reverse metric is advertised in IS-IS Hello Protocol Data Units (IIH PDUs), level-specific configuration is only available for broadcast interface types."; uses reverse-metric-if-config-data { refine "flags/whole-lan" { default "false"; } refine "flags/allow-unreachable" { default "false"; } } container level-1 { when '../../isis:interface-type = "broadcast"'; description "Announces a reverse metric to level-1 neighbors."; uses reverse-metric-if-config-data; } container level-2 { when '../../isis:interface-type = "broadcast"'; description "Announces a reverse metric to level-2 neighbors."; uses reverse-metric-if-config-data; } } } augment "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/" + "isis:isis/isis:interfaces/isis:interface/" + "isis:adjacencies/isis:adjacency" { when "derived-from-or-self(../../../../../rt:type, 'isis:isis')" { description "This augment is only valid when the routing protocol instance type is 'isis'."; } description "The reverse metric state advertised by an adjacency."; container reverse-metric { description "IS-IS Reverse Metric TLV data."; uses tlv16-reverse-metric; } } }

IANA Considerations

Updates to the IETF XML Registry This document registers a URI in the "IETF XML Registry" . Following the format in , the following registration has been made:

URI:

urn:ietf:params:xml:ns:yang:ietf-isis-reverse-metric

Registrant Contact:

The IESG.

XML:

N/A; the requested URI is an XML namespace.

Updates to the YANG Module Names Registry This document registers one YANG module in the "YANG Module Names" registry . Following the format in , the following registration has been made:

Name:

ietf-isis-reverse-metric

Maintained by IANA?

N

Namespace:

urn:ietf:params:xml:ns:yang:ietf-isis-reverse-metric

Prefix:

isis-rmetric

Reference:

RFC 9194

Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . 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. The YANG module defined in this document can enable, disable, and modify the behavior of metrics used by routing. For the security implications regarding these types of changes, consult -- which defines the functionality -- as well as . 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). 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. These YANG nodes correspond directly to the functionality provided in RFC 8500, and the security considerations of the functionality are described in RFC 8500. These are the subtrees and data nodes: Under "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/isis:isis" - /isis-rmetric:reverse-metric/isis-rmetric:enable-receive Under "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/isis:isis/" + "isis:interfaces/isis:interface/" + "isis-rmetric:reverse-metric" - /isis-rmetric:metric - /isis-rmetric:flags/isis-rmetric:whole-lan - /isis-rmetric:flags/isis-rmetric:allow-unreachable - /isis-rmetric:exclude-te-metric Under "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/isis:isis/" + "isis:interfaces/isis:interface/" + "isis-rmetric:reverse-metric/" + "isis-rmetric:level-1/" - /isis-rmetric:metric - /isis-rmetric:flags/isis-rmetric:whole-lan - /isis-rmetric:flags/isis-rmetric:allow-unreachable - /isis-rmetric:exclude-te-metric Under "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/isis:isis/" + "isis:interfaces/isis:interface/" + "isis-rmetric:reverse-metric/" + "isis-rmetric:level-2/" - /isis-rmetric:metric - /isis-rmetric:flags/isis-rmetric:whole-lan - /isis-rmetric:flags/isis-rmetric:allow-unreachable - /isis-rmetric:exclude-te-metric Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These YANG nodes correspond directly to the functionality provided in RFC 8500, and the security considerations of the functionality are described in RFC 8500. These are the subtrees and data nodes: Under "/rt:routing/rt:control-plane-protocols/" + "rt:control-plane-protocol/isis:isis/" + "isis:interfaces/isis:interface/" + "isis:adjacencies/isis:adjacency/" + "isis-rmetric:reverse-metric" - /isis-rmetric:metric - /isis-rmetric:flags/isis-rmetric:whole-lan - /isis-rmetric:flags/isis-rmetric:allow-unreachable - /isis-rmetric:te-metric

Normative References ISO International Standard 10589: 2002, Second Edition This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language. 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. Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950. This document specifies three YANG modules and one submodule. Together, they form the core routing data model that serves as a framework for configuring and managing a routing subsystem. It is expected that these modules will be augmented by additional YANG modules defining data models for control-plane protocols, route filters, and other functions. The core routing data model provides common building blocks for such extensions -- routes, Routing Information Bases (RIBs), and control-plane protocols. The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA). This document obsoletes RFC 8022. This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. This document describes a mechanism to allow IS-IS routing to quickly and accurately shift traffic away from either a point-to-point or multi-access LAN interface during network maintenance or other operational events. This is accomplished by signaling adjacent IS-IS neighbors with a higher reverse metric, i.e., the metric towards the signaling IS-IS router. World Wide Web Consortium Recommendation REC-xml-20081126 Informative References This document defines encoding rules for representing configuration data, state data, parameters of Remote Procedure Call (RPC) operations or actions, and notifications defined using YANG as JavaScript Object Notation (JSON) text.

Examples

Enablement Example Using XML YANG Instance Data Below is an example of XML YANG instance data to enable reverse metric processing.

Example XML Data to Enable Reverse Metric Processing <rt:routing xmlns:rt="urn:ietf:params:xml:ns:yang:ietf-routing" xmlns:isis="urn:ietf:params:xml:ns:yang:ietf-isis" xmlns:isis-rmetric= "urn:ietf:params:xml:ns:yang:ietf-isis-reverse-metric"> <rt:control-plane-protocols> <rt:control-plane-protocol> <rt:type>isis:isis</rt:type> <rt:name>default</rt:name> <isis:isis> <isis:area-address>00</isis:area-address> <isis-rmetric:reverse-metric> <isis-rmetric:enable-receive>true</isis-rmetric:enable-receive> </isis-rmetric:reverse-metric> </isis:isis> </rt:control-plane-protocol> </rt:control-plane-protocols> </rt:routing>

Usage Example Using XML YANG Instance Data Below is an example of XML YANG instance data for the "ietf-isis-reverse-metric" module.

Example XML Data for the "ietf-isis-reverse-metric" Module <if:interfaces xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces" xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"> <if:interface> <if:name>eth0</if:name> <if:type>ianaift:ethernetCsmacd</if:type> </if:interface> </if:interfaces> <rt:routing xmlns:rt="urn:ietf:params:xml:ns:yang:ietf-routing" xmlns:isis="urn:ietf:params:xml:ns:yang:ietf-isis" xmlns:isis-rmetric= "urn:ietf:params:xml:ns:yang:ietf-isis-reverse-metric"> <rt:control-plane-protocols> <rt:control-plane-protocol> <rt:type>isis:isis</rt:type> <rt:name>default</rt:name> <isis:isis> <isis:area-address>00</isis:area-address> <isis:interfaces> <isis:interface> <isis:name>eth0</isis:name> <isis-rmetric:reverse-metric> <isis-rmetric:metric> 65535 </isis-rmetric:metric> </isis-rmetric:reverse-metric> </isis:interface> </isis:interfaces> </isis:isis> </rt:control-plane-protocol> </rt:control-plane-protocols> </rt:routing>

Usage Example Using JSON YANG Instance Data Below is an example of JSON YANG instance data for the "ietf-isis-reverse-metric" module.

Example JSON Data for the Level-1-Only Reverse Metric { "ietf-interfaces:interfaces": { "interface": [ { "name": "eth0", "type": "iana-if-type:ethernetCsmacd" } ] }, "ietf-routing:routing": { "control-plane-protocols": { "control-plane-protocol": [ { "type": "ietf-isis:isis", "name": "default", "ietf-isis:isis": { "area-address": [ "00" ], "interfaces": { "interface": [ { "name": "eth0", "ietf-isis-reverse-metric:reverse-metric": { "level-1": { "metric": 65535, "exclude-te-metric": true } } } ] } } } ] } } }

Author's Address LabN Consulting, L.L.C.

chopps@chopps.org