path: root/doc/rfc/rfc9403.txt

Internet Engineering Task Force (IETF)                         A. Lindem
Request for Comments: 9403                       LabN Consulting, L.L.C.
Category: Standards Track                                          Y. Qu
ISSN: 2070-1721                                   Futurewei Technologies
                                                           November 2023


                  A YANG Data Model for RIB Extensions

Abstract

   A Routing Information Base (RIB) is a list of routes and their
   corresponding administrative data and operational state.

   RFC 8349 defines the basic building blocks for the RIB data model,
   and this model augments it to support multiple next hops (aka paths)
   for each route as well as additional attributes.

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
   https://www.rfc-editor.org/info/rfc9403.

Copyright Notice

   Copyright (c) 2023 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.

Table of Contents

   1.  Introduction
   2.  Terminology and Notation
     2.1.  Tree Diagrams
     2.2.  Prefixes in Data Node Names
   3.  Design of the Model
     3.1.  Tags and Preferences
     3.2.  Repair Path
   4.  RIB Model Tree
   5.  RIB Extension YANG Module
   6.  Security Considerations
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  Combined Tree Diagram
   Appendix B.  ietf-rib-extension.yang example
   Acknowledgments
   Authors' Addresses

1.  Introduction

   This document defines a YANG data model [RFC7950] that extends the
   RIB data model defined in the ietf-routing YANG module [RFC8349] with
   more route attributes.

   A RIB is a collection of routes with attributes controlled and
   manipulated by control plane protocols.  Each RIB contains only
   routes of one address family [RFC8349].  Within a protocol, routes
   are selected based on the metrics in use by that protocol, and the
   protocol installs the routes to the RIB.  The RIB selects the
   preferred or active route by comparing the route preference (aka
   administrative distance) of the candidate routes installed by
   different protocols.

   The module defined in this document extends the RIB to support more
   route attributes, such as multiple next hops, route metrics, and
   administrative tags.

   The YANG modules defined and discussed in this document conform to
   the Network Management Datastore Architecture (NMDA) [RFC8342].

2.  Terminology and Notation

   The following terms are defined in [RFC8342]:

   *  configuration

   *  system state

   *  operational state

   The following terms are defined in [RFC7950]:

   *  action

   *  augment

   *  container

   *  container with presence

   *  data model

   *  data node

   *  leaf

   *  list

   *  mandatory node

   *  module

   *  schema tree

   The following term is defined in [RFC8349], Section 5.2:

   *  RIB

2.1.  Tree Diagrams

   Tree diagrams used in this document follow the notation defined in
   [RFC8340].

2.2.  Prefixes in Data Node Names

   In this document, names of data nodes, actions, and other data model
   objects are often used without a prefix, as long as it is clear from
   the context in which YANG module each name is defined.  Otherwise,
   names are prefixed using the standard prefix associated with the
   corresponding YANG module, as shown in Table 1.

            +========+===========================+===========+
            | Prefix | YANG Module               | Reference |
            +========+===========================+===========+
            | if     | ietf-interfaces           | [RFC8343] |
            +--------+---------------------------+-----------+
            | rt     | ietf-routing              | [RFC8349] |
            +--------+---------------------------+-----------+
            | v4ur   | ietf-ipv4-unicast-routing | [RFC8349] |
            +--------+---------------------------+-----------+
            | v6ur   | ietf-ipv6-unicast-routing | [RFC8349] |
            +--------+---------------------------+-----------+
            | inet   | ietf-inet-types           | [RFC6991] |
            +--------+---------------------------+-----------+
            | ospf   | ietf-ospf                 | [RFC9129] |
            +--------+---------------------------+-----------+
            | isis   | ietf-isis                 | [RFC9130] |
            +--------+---------------------------+-----------+

             Table 1: Prefixes and Corresponding YANG Modules

3.  Design of the Model

   The YANG module defined in this document augments the ietf-routing,
   ietf-ipv4-unicast-routing, and ietf-ipv6-unicast-routing YANG modules
   defined in [RFC8349], which provide a basis for routing system data
   model development.  Together with the ietf-routing YANG module and
   other YANG modules defined in [RFC8349], a generic RIB YANG data
   model is defined herein to implement and monitor a RIB.

   The modules in [RFC8349] also define the basic configuration and
   operational state for both IPv4 and IPv6 static routes.  This
   document provides augmentations for static routes to support multiple
   next hops and more next-hop attributes.

3.1.  Tags and Preferences

   Individual route tags are supported at both the route and next-hop
   level.  A preference per next hop is also supported for selection of
   the most preferred reachable static route.

   The following tree snapshot shows tag and preference entries that
   augment static IPv4 unicast route and IPv6 unicast route next hops.

     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/rt:static-routes/v4ur:ipv4
             /v4ur:route/v4ur:next-hop/v4ur:next-hop-options
             /v4ur:simple-next-hop:
       +--rw preference?   uint32
       +--rw tag?          uint32
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/rt:static-routes/v4ur:ipv4
             /v4ur:route/v4ur:next-hop/v4ur:next-hop-options
             /v4ur:next-hop-list/v4ur:next-hop-list/v4ur:next-hop:
       +--rw preference?   uint32
       +--rw tag?          uint32
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/rt:static-routes/v6ur:ipv6
             /v6ur:route/v6ur:next-hop/v6ur:next-hop-options
             /v6ur:simple-next-hop:
       +--rw preference?   uint32
       +--rw tag?          uint32
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/rt:static-routes/v6ur:ipv6
             /v6ur:route/v6ur:next-hop/v6ur:next-hop-options
             /v6ur:next-hop-list/v6ur:next-hop-list/v6ur:next-hop:
       +--rw preference?   uint32
       +--rw tag?          uint32
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route:
       +--ro metric?            uint32
       +--ro tag*               uint32
       +--ro application-tag?   uint32

3.2.  Repair Path

   The IP Fast Reroute (IPFRR) calculation by routing protocol
   precomputes repair paths [RFC5714], and the repair paths are
   installed in the RIB.

   Each route next hop in the RIB is augmented with a repair path and is
   shown in the following tree snapshot.

     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route
             /rt:next-hop/rt:next-hop-options/rt:simple-next-hop:
       +--ro repair-path
          +--ro outgoing-interface?   if:interface-state-ref
          +--ro next-hop-address?     inet:ip-address-no-zone
          +--ro metric?               uint32
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route
             /rt:next-hop/rt:next-hop-options/rt:next-hop-list
             /rt:next-hop-list/rt:next-hop:
       +--ro repair-path
          +--ro outgoing-interface?   if:interface-state-ref
          +--ro next-hop-address?     inet:ip-address-no-zone
          +--ro metric?               uint32

4.  RIB Model Tree

   The ietf-routing.yang tree with the augmentations herein is included
   in Appendix A.  The meanings of the symbols can be found in
   [RFC8340].

5.  RIB Extension YANG Module

   This YANG module references [RFC6991], [RFC8343], [RFC8349],
   [RFC9129], [RFC9130], and [RFC5714].

   <CODE BEGINS> file "ietf-rib-extension@2023-11-20.yang"
   module ietf-rib-extension {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-rib-extension";
     prefix rib-ext;

     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-interfaces {
       prefix if;
       reference
         "RFC 8343: A YANG Data Model for Interface
                    Management";
     }
     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349: A YANG Data Model for Routing
                    Management (NMDA Version)";
     }
     import ietf-ipv4-unicast-routing {
       prefix v4ur;
       reference
         "RFC 8349: A YANG Data Model for Routing
                    Management (NMDA Version)";
     }
     import ietf-ipv6-unicast-routing {
       prefix v6ur;
       reference
         "RFC 8349: A YANG Data Model for Routing
                    Management (NMDA Version)";
     }

     import ietf-ospf {
       prefix ospf;
       reference "RFC 9129: YANG Data Model for the OSPF Protocol";
     }

     import ietf-isis {
       prefix isis;
       reference "RFC 9130: YANG Data Model for the IS-IS Protocol";
     }

     organization
       "IETF RTGWG (Routing Area Working Group)";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/rtgwg/>
        WG List:  <mailto:rtgwg@ietf.org>

        Author:   Acee Lindem
                  <mailto:acee.ietf@gmail.com>
        Author:   Yingzhen Qu
                  <mailto:yingzhen.qu@futurewei.com>";
     description
       "This YANG module extends the RIB defined in the ietf-routing
        YANG module with additional route attributes.

        This YANG module conforms to the Network Management
        Datastore Architecture (NMDA) as described in RFC 8342.

        Copyright (c) 2023 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 9403; see the
        RFC itself for full legal notices.";

     revision 2023-11-20 {
       description
         "Initial version.";
       reference
         "RFC 9403: A YANG Data Model for RIB Extensions";
     }

     /* Groupings */

     grouping rib-statistics {
       description
         "Statistics grouping used for RIB augmentation.";
       container statistics {
         config false;
         description
           "Container for RIB statistics.";
         leaf total-routes {
           type uint32;
           description
             "Total number of routes in the RIB.";
         }
         leaf total-active-routes {
           type uint32;
           description
             "Total number of active routes in the RIB.  An active
              route is the route that is preferred over other routes
              to the same destination prefix.";
         }
         leaf total-route-memory {
           type uint64;
           units "bytes";
           description
             "Total memory for all routes in the RIB.";
         }
         list protocol-statistics {
           description
             "RIB statistics for routing protocols installing
              routes in the RIB.";
           leaf protocol {
             type identityref {
               base rt:routing-protocol;
             }
             description
               "Routing protocol installing routes in the RIB.";
           }
           leaf routes {
             type uint32;
             description
               "Total number of routes in the RIB for the routing
                protocol identified by the 'protocol' entry.";
           }
           leaf active-routes {
             type uint32;
             description
               "Total number of active routes in the RIB for the
                routing protocol identified by the 'protocol' entry.
                An active route is preferred over other routes to the
                same destination prefix.";
           }
           leaf route-memory {
             type uint64;
             units "bytes";
             description
               "Total memory for all routes in the RIB for the
                routing protocol identified by the 'protocol'
                entry.";
           }
         }
       }
     }

     grouping repair-path {
       description
         "Grouping for the IP Fast Reroute (IPFRR) repair path.";
       container repair-path {
         description
           "IPFRR next-hop repair path.";
         leaf outgoing-interface {
           type if:interface-state-ref;
           description
             "Name of the outgoing interface.";
         }
         leaf next-hop-address {
           type inet:ip-address-no-zone;
           description
             "IP address of the next hop.";
         }
         leaf metric {
           type uint32;
           description
             "The metric for the repair path.  While the reroute
              repair is local and the metric is not advertised
              externally, the metric for the repair path is useful
              for troubleshooting purposes.";
         }
         reference
           "RFC 5714: IP Fast Reroute Framework";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/rt:static-routes/v4ur:ipv4/"
           + "v4ur:route/v4ur:next-hop/v4ur:next-hop-options/"
           + "v4ur:simple-next-hop" {
       description
         "Augment 'simple-next-hop' case in IPv4 unicast route.";
       leaf preference {
         type uint32;
         default "1";
         description
           "The preference is used to select among multiple static
            routes.  Routes with a lower next-hop preference value
            are preferred, and equal-preference routes result in
            Equal-Cost Multipath (ECMP) static routes.";
       }
       leaf tag {
         type uint32;
         default "0";
         description
           "The tag is a 32-bit opaque value associated with the
            route that can be used for policy decisions such as
            advertisement and filtering of the route.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/rt:static-routes/v4ur:ipv4/"
           + "v4ur:route/v4ur:next-hop/v4ur:next-hop-options/"
           + "v4ur:next-hop-list/v4ur:next-hop-list/v4ur:next-hop" {
       description
         "Augment static route configuration 'next-hop-list'.";
       leaf preference {
         type uint32;
         default "1";
         description
           "The preference is used to select among multiple static
            routes.  Routes with a lower next-hop preference value
            are preferred, and equal-preference routes result in
            ECMP static routes.";
       }
       leaf tag {
         type uint32;
         default "0";
         description
           "The tag is a 32-bit opaque value associated with the
            route that can be used for policy decisions such as
            advertisement and filtering of the route.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/rt:static-routes/v6ur:ipv6/"
           + "v6ur:route/v6ur:next-hop/v6ur:next-hop-options/"
           + "v6ur:simple-next-hop" {
       description
         "Augment 'simple-next-hop' case in IPv6 unicast route.";
       leaf preference {
         type uint32;
         default "1";
         description
           "The preference is used to select among multiple static
            routes.  Routes with a lower next-hop preference value
            are preferred, and equal-preference routes result in
            ECMP static routes.";
       }
       leaf tag {
         type uint32;
         default "0";
         description
           "The tag is a 32-bit opaque value associated with the
            route that can be used for policy decisions such as
            advertisement and filtering of the route.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/rt:static-routes/v6ur:ipv6/"
           + "v6ur:route/v6ur:next-hop/v6ur:next-hop-options/"
           + "v6ur:next-hop-list/v6ur:next-hop-list/v6ur:next-hop" {
       description
         "Augment static route configuration 'next-hop-list'.";
       leaf preference {
         type uint32;
         default "1";
         description
           "The preference is used to select among multiple static
            routes.  Routes with a lower next-hop preference value
            are preferred, and equal-preference routes result in
            ECMP static routes.";
       }
       leaf tag {
         type uint32;
         default "0";
         description
           "The tag is a 32-bit opaque value associated with the
            route that can be used for policy decisions such as
            advertisement and filtering of the route.";
       }
     }

     augment "/rt:routing/rt:ribs/rt:rib" {
       description
         "Augment a RIB with statistics.";
       uses rib-statistics;
     }

     augment "/rt:routing/rt:ribs/rt:rib/"
           + "rt:routes/rt:route" {
       description
         "Augment a route in the RIB with common attributes.";
       leaf metric {
         when "not(derived-from("
           + "../rt:source-protocol, 'ospf:ospf')) "
           + "and not(derived-from( "
           + "../rt:source-protocol, 'isis:isis'))" {
           description
             "This augmentation is only valid for routes that don't
              have OSPF or IS-IS as the source protocol.  The YANG
              data models for OSPF and IS-IS already include a
              'metric' augmentation for routes.";
         }
         type uint32;
         description
           "The metric is a numeric value indicating the cost
            of the route from the perspective of the routing
            protocol installing the route.  In general, routes with
            a lower metric installed by the same routing protocol
            are lower cost to reach and are preferable to routes
            with a higher metric.  However, metrics from different
            routing protocols are not comparable.";
       }
       leaf-list tag {
         when "not(derived-from("
           + "../rt:source-protocol, 'ospf:ospf')) "
           + "and not(derived-from( "
           + "../rt:source-protocol, 'isis:isis'))" {
           description
             "This augmentation is only valid for routes that don't
              have OSPF or IS-IS as the source protocol.  The YANG
              data models for OSPF and IS-IS already include a 'tag'
              augmentation for routes.";
         }
         type uint32;
         description
           "A tag is a 32-bit opaque value associated with the
            route that can be used for policy decisions such as
            advertisement and filtering of the route.";
       }
       leaf application-tag {
         type uint32;
         description
           "The application-specific tag is an additional tag that
            can be used by applications that require semantics and/or
            policy different from that of the tag.  For example,
            the tag is usually automatically advertised in OSPF
            AS-External Link State Advertisements (LSAs) while this
            application-specific tag is not advertised implicitly.";
       }
     }

     augment "/rt:routing/rt:ribs/rt:rib/"
           + "rt:routes/rt:route/rt:next-hop/rt:next-hop-options/"
           + "rt:simple-next-hop" {
       description
         "Augment 'simple-next-hop' with 'repair-path'.";
       uses repair-path;
     }

     augment "/rt:routing/rt:ribs/rt:rib/"
           + "rt:routes/rt:route/rt:next-hop/rt:next-hop-options/"
           + "rt:next-hop-list/rt:next-hop-list/rt:next-hop" {
       description
         "Augment the next hop with a repair path.";
       uses repair-path;
     }
   }
   <CODE ENDS>

6.  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 [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
   [RFC8446].

   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 the ietf-rib-
   extension.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 are the subtrees and data nodes and their sensitivity/
   vulnerability:

   *  /v4ur:next-hop-options/v4ur:simple-next-hop/rib-ext:preference

   *  /v4ur:next-hop-options/v4ur:simple-next-hop/rib-ext:tag

   *  /v4ur:next-hop-options/v4ur:next-hop-list/v4ur:next-hop-list
      /v4ur:next-hop/rib-ext:preference

   *  /v4ur:next-hop-options/v4ur:next-hop-list/v4ur:next-hop-list
      /v4ur:next-hop/rib-ext:tag

   *  /v6ur:next-hop-options/v6ur:simple-next-hop/rib-ext:preference

   *  /v6ur:next-hop-options/v6ur:simple-next-hop/rib-ext:tag

   *  /v6ur:next-hop-options/v6ur:next-hop-list/v6ur:next-hop-list
      /v6ur:next-hop/rib-ext:preference

   *  /v6ur:next-hop-options/v6ur:next-hop-list/v6ur:next-hop-list
      /v6ur:next-hop/rib-ext:tag

      For these augmentations to ietf-routing.yang, the ability to
      delete, add, and modify IPv4 and IPv6 static route preferences and
      tags would allow traffic to be misrouted.

   Some of the readable data nodes in the ietf-rib-extension.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:

   *  /rt:routing/rt:ribs/rt:rib/rib-ext:statistics

   *  /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rib-ext:metric

   *  /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rib-ext:tag

   *  /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rib-ext:application-
      tag

   *  /rt:route/rt:next-hop/rt:next-hop-options/rt:simple-next-hop/rib-
      ext:repair-path

   *  /rt:routes/rt:route/rt:next-hop/rt:next-hop-options/rt:next-hop-
      list/rt:next-hop-list/rt:next-hop/rib-ext:repair-path

      Exposing the RIB will expose the routing topology of the network.
      This may be undesirable due to the fact that such exposure may
      facilitate other attacks.  Additionally, network operators may
      consider their topologies to be sensitive confidential data.

   All the security considerations for writable and readable data nodes
   defined in [RFC8349] apply to the augmentations described herein.

7.  IANA Considerations

   This document registers the following URI in the "IETF XML Registry"
   [RFC3688].

   URI:  urn:ietf:params:xml:ns:yang:ietf-rib-extension
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   IANA has registered the following YANG module in the "YANG Module
   Names" registry [RFC6020].

   Name:  ietf-rib-extension
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-rib-extension
   Prefix:  rib-ext
   Reference:  RFC 9403

8.  References

8.1.  Normative References

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [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,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [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,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC9129]  Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem,
              "YANG Data Model for the OSPF Protocol", RFC 9129,
              DOI 10.17487/RFC9129, October 2022,
              <https://www.rfc-editor.org/info/rfc9129>.

   [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,
              <https://www.rfc-editor.org/info/rfc9130>.

   [W3C.REC-xml-20081126]
              Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <https://www.w3.org/TR/2008/REC-xml-20081126>.

8.2.  Informative References

   [RFC5714]  Shand, M. and S. Bryant, "IP Fast Reroute Framework",
              RFC 5714, DOI 10.17487/RFC5714, January 2010,
              <https://www.rfc-editor.org/info/rfc5714>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [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,
              <https://www.rfc-editor.org/info/rfc8792>.

Appendix A.  Combined Tree Diagram

   This appendix provides the combined ietf-routing.yang, ietf-ipv4-
   unicast-routing.yang, ietf-ipv6-unicast-routing.yang, and ietf-rib-
   extension.yang tree diagram.

   module: ietf-routing
     +--rw routing
     +--rw router-id?                 yang:dotted-quad {router-id}?
     +--ro interfaces
     |  +--ro interface*   if:interface-ref
     +--rw control-plane-protocols
     |  +--rw control-plane-protocol* [type name]
     |     +--rw type             identityref
     |     +--rw name             string
     |     +--rw description?     string
     |     +--rw static-routes
     |        +--rw v4ur:ipv4
     |        |  +--rw v4ur:route* [destination-prefix]
     |        |     +--rw v4ur:destination-prefix    inet:ipv4-prefix
     |        |     +--rw v4ur:description?          string
     |        |     +--rw v4ur:next-hop
     |        |        +--rw (v4ur:next-hop-options)
     |        |           +--:(v4ur:simple-next-hop)
     |        |           |  +--rw v4ur:outgoing-interface?
     |        |           |  |   if:interface-ref
     |        |           |  +--rw v4ur:next-hop-address?
     |        |           |  |   inet:ipv4-address
     |        |           |  +--rw rib-ext:preference?      uint32
     |        |           |  +--rw rib-ext:tag?             uint32
     |        |           +--:(v4ur:special-next-hop)
     |        |           |  +--rw v4ur:special-next-hop?   enumeration
     |        |           +--:(v4ur:next-hop-list)
     |        |              +--rw v4ur:next-hop-list
     |        |                 +--rw v4ur:next-hop* [index]
     |        |                    +--rw v4ur:index            string
     |        |                    +--rw v4ur:outgoing-interface?
     |        |                    |   if:interface-ref
     |        |                    +--rw v4ur:next-hop-address?
     |        |                    |   inet:ipv4-address
     |        |                    +--rw rib-ext:preference?   uint32
     |        |                    +--rw rib-ext:tag?          uint32
     |        +--rw v6ur:ipv6
     |           +--rw v6ur:route* [destination-prefix]
     |              +--rw v6ur:destination-prefix    inet:ipv6-prefix
     |              +--rw v6ur:description?          string
     |              +--rw v6ur:next-hop
     |                 +--rw (v6ur:next-hop-options)
     |                    +--:(v6ur:simple-next-hop)
     |                    |  +--rw v6ur:outgoing-interface?
     |                    |  |   if:interface-ref
     |                    |  +--rw v6ur:next-hop-address?
     |                    |  |   inet:ipv6-address
     |                    |  +--rw rib-ext:preference?      uint32
     |                    |  +--rw rib-ext:tag?             uint32
     |                    +--:(v6ur:special-next-hop)
     |                    |  +--rw v6ur:special-next-hop?   enumeration
     |                    +--:(v6ur:next-hop-list)
     |                       +--rw v6ur:next-hop-list
     |                          +--rw v6ur:next-hop* [index]
     |                             +--rw v6ur:index              string
     |                             +--rw v6ur:outgoing-interface?
     |                             |   if:interface-ref
     |                             +--rw v6ur:next-hop-address?
     |                             |   inet:ipv6-address
     |                             +--rw rib-ext:preference?     uint32
     |                             +--rw rib-ext:tag?            uint32
     +--rw ribs
        +--rw rib* [name]
           +--rw name                          string
           +--rw address-family                identityref
           +--ro default-rib?                  boolean {multiple-ribs}?
           +--ro routes
           |  +--ro route* []
           |     +--ro route-preference?       route-preference
           |     +--ro next-hop
           |     |  +--ro (next-hop-options)
           |     |     +--:(simple-next-hop)
           |     |     |  +--ro outgoing-interface?
           |     |     |  |   if:interface-ref
           |     |     |  +--ro v4ur:next-hop-address?
           |     |     |  |   inet:ipv4-address
           |     |     |  +--ro v6ur:next-hop-address?
           |     |     |  |   inet:ipv6-address
           |     |     |  +--ro rib-ext:repair-path
           |     |     |     +--ro rib-ext:outgoing-interface?
           |     |     |     |   if:interface-state-ref
           |     |     |     +--ro rib-ext:next-hop-address?
           |     |     |     |   inet:ip-address-no-zone
           |     |     |     +--ro rib-ext:metric?               uint32
           |     |     +--:(special-next-hop)
           |     |     |  +--ro special-next-hop?        enumeration
           |     |     +--:(next-hop-list)
           |     |        +--ro next-hop-list
           |     |           +--ro next-hop* []
           |     |              +--ro outgoing-interface?
           |     |              |   if:interface-ref
           |     |              +--ro v4ur:address?
           |     |              |   inet:ipv4-address
           |     |              +--ro v6ur:address?
           |     |              |   inet:ipv6-address
           |     |              +--ro rib-ext:repair-path
           |     |                 +--ro rib-ext:outgoing-interface?
           |     |                 |   if:interface-state-ref
           |     |                 +--ro rib-ext:next-hop-address?
           |     |                 |   inet:ip-address-no-zone
           |     |                 +--ro rib-ext:metric?         uint32
           |     +--ro source-protocol            identityref
           |     +--ro active?                    empty
           |     +--ro last-updated?              yang:date-and-time
           |     +--ro v4ur:destination-prefix?   inet:ipv4-prefix
           |     +--ro v6ur:destination-prefix?   inet:ipv6-prefix
           |     +--ro rib-ext:metric?            uint32
           |     +--ro rib-ext:tag*               uint32
           |     +--ro rib-ext:application-tag?   uint32
           +---x active-route
           |  +---w input
           |  |  +---w v4ur:destination-address?   inet:ipv4-address
           |  |  +---w v6ur:destination-address?   inet:ipv6-address
           |  +--ro output
           |     +--ro route
           |        +--ro next-hop
           |        |  +--ro (next-hop-options)
           |        |     +--:(simple-next-hop)
           |        |     |  +--ro outgoing-interface?
           |        |     |  |   if:interface-ref
           |        |     |  +--ro v4ur:next-hop-address?
           |        |     |  |   inet:ipv4-address
           |        |     |  +--ro v6ur:next-hop-address?
           |        |     |  |   inet:ipv6-address
           |        |     +--:(special-next-hop)
           |        |     |  +--ro special-next-hop?        enumeration
           |        |     +--:(next-hop-list)
           |        |        +--ro next-hop-list
           |        |           +--ro next-hop* []
           |        |              +--ro outgoing-interface?
           |        |              |   if:interface-ref
           |        |              +--ro v4ur:next-hop-address?
           |        |              |   inet:ipv4-address
           |        |              +--ro v6ur:next-hop-address?
           |        |              |   inet:ipv6-address
           |        +--ro source-protocol            identityref
           |        +--ro active?                    empty
           |        +--ro last-updated?              yang:date-and-time
           |        +--ro v4ur:destination-prefix?   inet:ipv4-prefix
           |        +--ro v6ur:destination-prefix?   inet:ipv6-prefix
           +--rw description?                        string
           +--ro rib-ext:statistics
              +--ro rib-ext:total-routes?              uint32
              +--ro rib-ext:total-active-routes?       uint32
              +--ro rib-ext:total-route-memory?        uint64
              +--ro rib-ext:protocol-statistics* []
                 +--ro rib-ext:protocol?             identityref
                 +--ro rib-ext:routes?    uint32
                 +--ro rib-ext:active-routes?   uint32
                 +--ro rib-ext:route-memory?    uint64

Appendix B.  ietf-rib-extension.yang example

   The following is an XML example [W3C.REC-xml-20081126] using the RIB
   extension module and RFC 8349.

      |  Note: '\' line wrapping per [RFC8792].

   <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
     <control-plane-protocols>
       <control-plane-protocol>
         <type>static</type>
         <name>static-routing-protocol</name>
         <static-routes>
           <ipv4 xmlns="urn:ietf:params:xml:ns:yang:\
             ietf-ipv4-unicast-routing">
             <route>
               <destination-prefix>0.0.0.0/0</destination-prefix>
               <next-hop>
                 <next-hop-address>192.0.2.2</next-hop-address>
                 <preference xmlns="urn:ietf:params:xml:ns:yang:\
                   ietf-rib-extension">30</preference>
                 <tag xmlns="urn:ietf:params:xml:ns:yang:\
                   ietf-rib-extension">99</tag>
               </next-hop>
             </route>
           </ipv4>
           <ipv6 xmlns="urn:ietf:params:xml:ns:yang:\
             ietf-ipv6-unicast-routing">
             <route>
               <destination-prefix>::/0</destination-prefix>
               <next-hop>
                <next-hop-address>2001:db8:aaaa::1111</next-hop-address>
                <preference xmlns="urn:ietf:params:xml:ns:yang:\
                  ietf-rib-extension">30</preference>
                <tag xmlns="urn:ietf:params:xml:ns:yang:\
                  ietf-rib-extension">66</tag>
               </next-hop>
             </route>
           </ipv6>
         </static-routes>
       </control-plane-protocol>
     </control-plane-protocols>
     <ribs>
       <rib>
         <name>ipv4-primary</name>
         <address-family xmlns:v4ur="urn:ietf:params:xml:ns:yang:\
           ietf-ipv4-unicast-routing">v4ur:ipv4-unicast</address-family>
         <default-rib>true</default-rib>
         <routes>
           <route>
             <destination-prefix xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-ipv4-unicast-routing">0.0.0.0/0</destination-prefix>
             <next-hop>
               <next-hop-address xmlns="urn:ietf:params:xml:ns:yang:\
                 ietf-ipv4-unicast-routing">192.0.2.2</next-hop-address>
             </next-hop>
             <route-preference>5</route-preference>
             <source-protocol>static</source-protocol>
             <last-updated>2015-10-24T18:02:45+02:00</last-updated>
           </route>
           <route>
             <destination-prefix xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-ipv4-unicast-routing">198.51.100.0/24\
             </destination-prefix>
             <next-hop>
               <next-hop-address xmlns="urn:ietf:params:xml:ns:yang:\
                 ietf-ipv4-unicast-routing">192.0.2.2</next-hop-address>
               <repair-path xmlns="urn:ietf:params:xml:ns:yang:\
                 ietf-rib-extension">
                 <next-hop-address>203.0.113.1</next-hop-address>
                 <metric>200</metric>
               </repair-path>
             </next-hop>
             <route-preference>120</route-preference>
             <source-protocol xmlns:rip="urn:ietf:params:xml:ns:yang:\
               ietf-rip">rip:rip</source-protocol>
             <last-updated>2015-10-24T18:02:45+02:00</last-updated>
           </route>
         </routes>
       </rib>
       <rib>
         <name>ipv6-primary</name>
         <address-family xmlns:v6ur="urn:ietf:params:xml:ns:yang:\
           ietf-ipv6-unicast-routing">v6ur:ipv6-unicast</address-family>
         <default-rib>true</default-rib>
         <routes>
           <route>
             <destination-prefix xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-ipv6-unicast-routing">0::/0</destination-prefix>
             <next-hop>
               <next-hop-address xmlns="urn:ietf:params:xml:ns:yang:\
                 ietf-ipv6-unicast-routing">2001:db8:aaaa::1111\
               </next-hop-address>
             </next-hop>
             <route-preference>5</route-preference>
             <source-protocol>static</source-protocol>
             <last-updated>2015-10-24T18:02:45+02:00</last-updated>
           </route>
           <route>
             <destination-prefix xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-ipv6-unicast-routing">2001:db8:bbbb::/64\
             </destination-prefix>
             <next-hop>
               <next-hop-address xmlns="urn:ietf:params:xml:ns:yang:\
                 ietf-ipv6-unicast-routing">2001:db8:aaaa::1111\
               </next-hop-address>
               <repair-path xmlns="urn:ietf:params:xml:ns:yang:\
                ietf-rib-extension">
                <next-hop-address>2001:db8:cccc::2222</next-hop-address>
                <metric>200</metric>
               </repair-path>
             </next-hop>
             <route-preference>120</route-preference>
             <source-protocol xmlns:rip="urn:ietf:params:xml:ns:yang:\
               ietf-rip">rip:rip</source-protocol>
             <last-updated>2015-10-24T18:02:45+02:00</last-updated>
           </route>
         </routes>
       </rib>
     </ribs>
   </routing>

   The following is the same example using JSON format [RFC7951].

   {
    "ietf-routing:routing": {
      "control-plane-protocols": {
        "control-plane-protocol": [
          {
            "type": "static",
            "name": "static-routing-protocol",
            "static-routes": {
              "ietf-ipv4-unicast-routing:ipv4": {
                "route": [
                  {
                    "destination-prefix": "0.0.0.0/0",
                    "next-hop": {
                      "next-hop-address": "192.0.2.2",
                      "ietf-rib-extension:preference": 30,
                      "ietf-rib-extension:tag": 99
                    }
                  }
                ]
              },
              "ietf-ipv6-unicast-routing:ipv6": {
                "route": [
                  {
                    "destination-prefix": "::/0",
                    "next-hop": {
                      "next-hop-address": "2001:db8:aaaa::1111",
                      "ietf-rib-extension:preference": 30,
                      "ietf-rib-extension:tag": 66
                    }
                  }
                ]
              }
            }
          }
        ]
      },
      "ribs": {
        "rib": [
          {
            "name": "ipv4-primary",
            "address-family": "ietf-ipv4-unicast-routing:ipv4-unicast",
            "default-rib": true,
            "routes": {
              "route": [
                {
                  "next-hop": {
                    "ietf-ipv4-unicast-routing:next-hop-address": \
                    "192.0.2.2"
                  },
                  "route-preference": 5,
                  "source-protocol": "static",
                  "last-updated": "2015-10-24T18:02:45+02:00",
                  "ietf-ipv4-unicast-routing:destination-prefix": \
                  "0.0.0.0/0"
                },
                {
                  "next-hop": {
                    "ietf-rib-extension:repair-path": {
                      "next-hop-address": "203.0.113.1",
                      "metric": 200
                    },
                    "ietf-ipv4-unicast-routing:next-hop-address": \
                    "192.0.2.2"
                  },
                  "route-preference": 120,
                  "source-protocol": "ietf-rip:rip",
                  "last-updated": "2015-10-24T18:02:45+02:00",
                  "ietf-ipv4-unicast-routing:destination-prefix": \
                  "198.51.100.0/24"
                }
              ]
            }
          },
          {
            "name": "ipv6-primary",
            "address-family": "ietf-ipv6-unicast-routing:ipv6-unicast",
            "default-rib": true,
            "routes": {
              "route": [
                {
                  "next-hop": {
                    "ietf-ipv6-unicast-routing:next-hop-address": \
                    "2001:db8:aaaa::1111"
                  },
                  "route-preference": 5,
                  "source-protocol": "static",
                  "last-updated": "2015-10-24T18:02:45+02:00",
                  "ietf-ipv6-unicast-routing:destination-prefix": "::/0"
                },
                {
                  "next-hop": {
                    "ietf-rib-extension:repair-path": {
                      "next-hop-address": "2001:db8:cccc::2222",
                      "metric": 200
                    },
                    "ietf-ipv6-unicast-routing:next-hop-address": \
                    "2001:db8:aaaa::1111"
                  },
                  "route-preference": 120,
                  "source-protocol": "ietf-rip:rip",
                  "last-updated": "2015-10-24T18:02:45+02:00",
                  "ietf-ipv6-unicast-routing:destination-prefix": \
                  "2001:db8:bbbb::/64"
                }
              ]
            }
          }
        ]
      }
    }
   }

Acknowledgments

   The authors wish to thank Les Ginsberg, Krishna Deevi, and Suyoung
   Yoon for their helpful comments and suggestions.

   The authors wish to thank Tom Petch, Rob Wilton, Chris Hopps, Martin
   Björklund, Jeffrey Zhang, Éric Vyncke, Lars Eggert, and Bo Wu for
   their reviews and comments.

Authors' Addresses

   Acee Lindem
   LabN Consulting, L.L.C.
   301 Midenhall Way
   Cary, NC 27513
   United States of America
   Email: acee.ietf@gmail.com


   Yingzhen Qu
   Futurewei Technologies
   2330 Central Expressway
   Santa Clara, CA 95050
   United States of America
   Email: yingzhen.qu@futurewei.com