



Network Working Group                                      T. Przygienda
Internet-Draft                                                  S. Hegde
Intended status: Standards Track                                 J. Head
Expires: 23 August 2026                                              HPE
                                                               A. Lindem
                                                             Arrcus, Inc
                                                        19 February 2026


              IGP Flooding Reduction Algorithms Framework
                 draft-ietf-lsr-flood-reduction-arch-01

Abstract

   This document introduces a framework making it possible to deploy
   multiple flood reduction algorithms within the same IGP domain in an
   interoperable fashion.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 23 August 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Flooding Pruner Framework . . . . . . . . . . . . . . . . . .   3
     2.1.  Definitions and Axioms  . . . . . . . . . . . . . . . . .   3
       2.1.1.  Maximum of One Flooding Pruner on a Node  . . . . . .   3
       2.1.2.  Connected Component . . . . . . . . . . . . . . . . .   3
       2.1.3.  Flooding Connected Dominating Sets  . . . . . . . . .   4
       2.1.4.  Rules for Flooding Pruners  . . . . . . . . . . . . .   4
     2.2.  Beneficial Properties of the Flooding Pruner Framework  .   5
     2.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Signaling . . . . . . . . . . . . . . . . . . . . . . . .   8
       2.4.1.  IS-IS - Flood Reduction Algorithm Sub-TLV . . . . . .   8
       2.4.2.  OSPFv2/OSPFv3 - Flood Reduction Algorithm TLV . . . .   8
       2.4.3.  Error Handling  . . . . . . . . . . . . . . . . . . .   9
   3.  YANG Data Model . . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Tree for IS-IS Flooding Reduction Algorithm . . . . . . .  10
     3.2.  Tree for OSPF Flooding Reduction Algorithm  . . . . . . .  10
     3.3.  IANA Module for IGP Flooding Algorithms . . . . . . . . .  11
     3.4.  YANG Module for IS-IS Flooding Reduction Algorithm  . . .  13
     3.5.  YANG Module for OSPF Flooding Reduction Algorithm . . . .  16
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
     4.1.  IANA IGP Flooding Algorithm Registry  . . . . . . . . . .  20
     4.2.  IGP Flooding Reduction Algorithm Capabiity  . . . . . . .  20
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  20
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  20
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Scenarios exist where multiple distributed (or centralized) flood
   reduction algorithms may be deployed simultaneously within an IGP
   domain.  These scenarios necessitate certain agreed on cooperative
   behaviors between the involved algorithms to ensure the correctness
   of the overall solution.  This is true in both permanent and
   transient (i.e., migration) deployment cases.  Fortunately, existing
   graph theory concepts allow to provide guidance toward the design of
   algorithms with the necessary properties to ensure their
   interoperable coexistence.










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   This document presents the necessary requirements for the involved
   algorithms and the details of a framework for their interoperable
   deployment.  Although running multiple algorithms simultaneously may
   not be a preferred operational choice, it is necessary if the
   migration from one algorithm to another with minimal network
   disruption is a priority.  A migration itself may be caused by the
   discovery of defects in the deployed algorithms or the deployment of
   new algorithms that offer improvements.

   Dealing with interoperability or lack thereof between this framework
   and other published frameworks such as e.g.  [RFC9667] is explicitly
   outside the scope of this document.

2.  Flooding Pruner Framework

2.1.  Definitions and Axioms

   This section outlines a framework that allows the operation of
   multiple different flood reduction algorithms (called _flooding
   pruners_ or _pruners_ from here on) in an interoperable fashion.

   An important observation upfront, which will become clear later in
   this section, is that full, non-optimized flooding presents a special
   case of a pruner itself.  Normal flooding includes all adjacencies
   without any pruning, and hence we name it the _non-pruner_ or _zero_
   for short.

2.1.1.  Maximum of One Flooding Pruner on a Node

   This framework permits the use of at most one pruner on each node.
   It allows to change a specific pruner at any time on any subset of
   nodes in the network while limiting the impact to the node itself and
   possibly the re-convergence of a set of nodes within its connected
   component.

2.1.2.  Connected Component

   A _connected component_ (or component for short) is defined as a
   subset of all nodes in the network running the same pruner, e.g. A
   (such nodes are denoted by the set notation of A|) where each of the
   nodes has to be connected to all other nodes by a path that traverses
   only nodes that run A.  Observe that there well may be in the network
   multiple components that are not connected, but that run the same
   pruner algorithm.  We denote in such case a component for pruner A as
   A|, and if two _disjoint_ components running the same algorithm A are
   present in the network, we denote such second set as A|' and by
   extension we use A|'' notation for further such sets.




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   Non-pruners also build components denoted as Z| and its primes.

   Another way to visualize components is to consider a network running
   multiple pruners as "islands running pruning algorithms" that are
   connected to each other by components running non-pruners (i.e. using
   normal flooding).

2.1.3.  Flooding Connected Dominating Sets

   A pruner may choose within its component a subset of links to flood
   while making sure that the component remains connected.  In other
   words, after suppressing flooding on some links within the component
   there must still exist paths consisting of the remaining links that
   connect each pair of nodes in the component.  We use for such
   remaining links the term _flooding connected dominating set_ or CDS
   for short (more precisely, a not necessarily loop-free edge
   dominating set).  Such a CDS is colloquially often called _flooding
   topology_ in context of flood reduction algorithms.  A simple
   spanning tree is an easily visualized special case of a CDS.  We
   denote such a CDS for a component A| as A|*.  A|* is often not unique
   for a component and many different sets of links can be a CDS.  Nor
   is it required that a CDS has to be loop-free since there may be many
   different paths on the CDS between two nodes in a component.
   Therefore, it is possible in a most extreme case that each LSP is
   flooded on a different CDS.

   To summarize the section above in simple terms, a pruner must choose
   at least one set of flooding links that guarantees that all
   information can reach all the nodes in the component.

2.1.4.  Rules for Flooding Pruners

   Any flood reduction algorithm expecting to interoperate with other
   algorithms within this framework but without having to understand
   their behavior MUST adhere to the following rules.  Otherwise, the
   algorithm cannot be expected to accommodate other algorithms in the
   network at the same time or is in other words a ship in the night.

   1.  Each node of a pruner (except the non-pruner) MUST advertise in
       its flooded node information the currently active pruner.  It
       MUST also understand such information as advertised by other
       nodes in the network.  A node running a pruner MUST NOT assume
       implicitly that a node is a _non-pruner_ or supports or runs the
       same algorithm.  However, any pruner can safely assume that any
       node that does not advertise any running pruner in its node
       information MUST be a non-pruner.  Observe that a pruner does not
       need to understand how the algorithm of another pruner operates
       (or even whether it is centralized, centrally signalled or fully



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       distributed).  The only requirement is that every pruner uses the
       same signaling information provided in this framework which
       indicates the pruner currently running.

   2.  A pruner MUST NOT prune links in components other than the one it
       participates in or assume flooding behavior on links in other
       components (except in the case of a _non-pruner_ where the
       flooding is well understood).  In other words, each pruner is
       allowed to prune some links from flooding, but only strictly
       within its own component.

   3.  A flooding pruner A MUST also include in its flooding CDS all
       links to adjacent components running a non _non-pruner_ different
       from A.  A node running pruner P that is different from the _non-
       pruner_ SHOULD include in its flooding CDS all links to non-
       pruners.  It MAY use the known behavior the _non-pruner_ for
       further optimizations.  Nevertheless, such optimizations MUST NOT
       assume that there is just a single Z| in the network.  This is
       sufficient (but strictly speaking, more than necessary) to
       guarantee that the overall set of flooding CDSes within each
       component creates an overall flooding CDS over the whole network.
       In other words, the resulting set of links that still flood
       connects all nodes in the network.

   This document does not consider other approaches that guarantee a
   pruner property on e.g. a clique, i.e. a subgraph where every vertex
   is neighbored to all other vertices in the clique.  It assumes that
   such "ship in the night components" can be considered non-pruners due
   to their implicit guarantee of correct flooding to nodes that are
   part of their component where connected to other components.

2.2.  Beneficial Properties of the Flooding Pruner Framework

   Nodes are free to use any kind of pruner to calculate optimized
   flooding.  Any mode of computation, distributed or centralized, will
   work fine as long as it adheres to Section 2.1.4.  Per Section 2.1.2
   a node will become part of one and exactly one component after
   choosing a pruner.

   The framework allows but does not assume any centralized instance or
   election in a component.  Computation and communication within each
   component is completely independent of other components.

   A node is free to choose a different pruner or a _non-pruner_ at any
   point in time independent of all other nodes.  It may end up in
   another component or become a _non-pruner_ with the maximum impact
   consisting of re-computation within two components that see such node
   leave or join.  For a distributed algorithm, it is likely that only



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   the adjoining nodes have to adjust their pruning decisions.  That is
   to say, the framework allows for node-by-node deployment or migration
   of pruners without networkwide recomputation of optimized flooding.
   This is obviously critical to the stability of large networks that
   may not converge within reasonable time if the whole network were to
   revert to non-pruning due to networkwide impact.  However, such
   behavior cannot be excluded, for example, in case of election
   problems due to misconfiguration or topological separation of nodes
   if the whole network runs a single pruner relying on centralized
   election.  The network itself cannot ensure correctness of a pruner
   or prevent a pruner having a blast radius of the whole component
   depending upon the algorithm and further signaling used.

   Although the framework provides extreme operational flexibility when
   deploying pruners, the most likely scenarios are a node-by-node
   deployment of a single pruner in addition to a non-pruner or, if the
   necessity arises, a node-by-node migration to another pruner.

2.3.  Example
































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        +==================+         +==================+
        | A|'   +--+       |         | B|    +--+       |
        |    +--|  |---+   |         |    +--|  |---+   |
        |    |  +--+   |   |         |    |  +--+   |   |
        |  +--+       +--+ |         |  +--+       +--+ |
        |  |  |---X---|  |==============|  |---X---|  | ========#
        |  +--+       +--+ |         |  +--+       +--+ |       #
        +====#==========#==+         +====#==========#==+       #
             ########   #                 #       # =#          #
           +========#===#=====+   +=======#====+  #   +=========#===+
           | Z|'   +--+ #     |   | Z|'' +--+  |  #   | Z|''' +--+  |
           |       |  |##     |   |      |  |  |  #   |       |  |  |
           |       +--+       |   |      +--+  |  #   |       +--+  |
           |  +--+  |    +--+ |   |       #    |  #   |         #   |
           |  |  |--+----|  | |   +=======#====+  #   +=========#===+
           |  +--+       +--+ |           #       #             #
           +====#=============+    #======#       #             #
                #                  #              #             #
                #         +========#=========+    #             #
                #         | A|''  +--+       |    #             #
                #         |    +--|  |---+   |    #             #
                #         |    |  +--+   |   |    #             #
                #         |  +--+       +--+======#             #
                #============|  |---X---|  |====================#
                          |  +--+       +--+ |
                          +==================+

           X : removed link due to reduction
           # : link included on component boundary
           = : link included on component boundary

                     Figure 1: Network of Mixed Pruners

   Figure 1 illustrates a network with three pruners running.  Two
   components run pruner A and are denoted as A|' and A|'' and one
   component runs pruner B.  Remaining three components run the _non-
   pruner_ algorithm (annotated as Z|', Z|'', and Z|''').  CDSes within
   components are shown by indicating the links that were pruned from
   flooding as crossed out.  Additionally, the links that are included
   to connect the CDS of the component following the rules listed in
   Section 2.1.4 have been made thicker.  Despite multiple algorithms
   and components being present in the network, the complete graph is
   obviously still covered by the involved CDSes.

   Figure 1 also illustrates why the overall CDS can easily be more than
   just a spanning tree of the overall network.  A node seeing its
   neighbor running another algorithm cannot always decide based on
   local knowledge whether the link should be included in flooding or



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   not.  Such a decision could be based on the overall view of the
   network using some global tie-breaking algorithm.  However, due to
   the potential long flooding paths and one-link minimal cuts, such an
   algorithm is not considered here but could be proposed in the future.

2.4.  Signaling

   Nodes are REQUIRED to signal when they are actively running any
   pruner (except a non-pruner).  The absence of such an advertisement
   indicates that a node is either running a non-pruner or some other
   algorithm where within its component it behaves in an equivalent
   fashion while also guaranteeing flooding on links connected to other
   components.

2.4.1.  IS-IS - Flood Reduction Algorithm Sub-TLV

   The Flood Reduction Algorithm Sub-TLV is advertised as a sub-TLV
   within a Router Capability TLV (242) defined in [RFC7981].  It uses
   the following format:

              0                   1                   2
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |     Type      |     Length    |   Algorithm   |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 2

   *  *Type:*TBD1

   *  *Length:*1

   *  *Algorithm:*An 8-bit numerical identifier allocated from the "IGP
      Algorithm Type For Computing Flooding Topology" registry.

   This sub-TLV MUST only contain the currently active running pruner
   (other than a non-pruner).  It MUST be flooded within a Router
   Capability TLV that is strictly area-scoped and MUST NOT be leaked
   between levels.

2.4.2.  OSPFv2/OSPFv3 - Flood Reduction Algorithm TLV

   The Flood Reduction Algorithm TLV is advertised within a OSPFv2
   Router Information (RI) Opaque LSA or OSPFv3 Router Information LSA
   as defined in [RFC7770].  It uses the following format:






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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Type             |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Algorithm   |
     +-+-+-+-+-+-+-+-+

                                  Figure 3

   *  *Type:*TBD1

   *  *Length:*1

   *  *Algorithm:*An 8-bit numerical identifier allocated from the "IGP
      Algorithm Type For Computing Flooding Topology" registry.

   Nodes MUST advertise this TLV when they actively run any pruner
   (other than a non-pruner).

   Pruner signaling MUST be flooded in a way that is strictly area-
   scoped that will not leak between areas.  For OSPFv2, the TLV MUST be
   flooded within a Router Information (RI) Opaque LSA as Type-10.  For
   OSPFv3, the TLV MUST be flooded within a Router Information (RI) LSA
   with the S2-bit set to 1.

2.4.3.  Error Handling

   This section defines error handling regardless of the deployed IGP or
   active algorithm.

   If a node receives an advertisement with more than one algorithm, it
   SHOULD be logged at least once.

   If a node receives an advertisement with an unrecognized/invalid
   algorithm, it SHOULD be logged at least once.

   If a node receives an advertisement with a mismatched algorithm, it
   SHOULD be logged at least once.

3.  YANG Data Model

   YANG [RFC7950] is a data definition language used to define the
   contents of a conceptual data store that allows networked devices to
   be managed using NETCONF [RFC6241] or RESTCONF [RFC8040].






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   This section defines three YANG modules.  Module iana-igp-flooding-
   topo-algo defines the identities the 'IGP AlgorithmType for Computing
   Flooding Topology' in the 'Interior Gateway Protocol (IGP)
   Parameters' registry group.  Section 4.1.  Module ietf-isis-flooding-
   reduction-algo, which augments the IS-IS YANG data model [RFC9130]
   and the YANG Data Model for Routing Management [RFC8349], can be used
   to configure and manage a flooding reduction algorithm in an IS-IS
   level 1 or level 2 area.  Module ietf-ospf-flooding-reduction-algo,
   which augments the OSPF YANG data model [RFC9129] and the YANG Data
   Model for Routing Management [RFC8349], can be used to configure and
   manage a flooding reduction algorithm in an OSPF area.

   This document uses the graphical representation of data model per
   [RFC8340].

3.1.  Tree for IS-IS Flooding Reduction Algorithm

   The following shows the tree diagram of the module for an IS-IS
   Flooding Reduction Algorithm:

     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol/isis:isis:
       +--rw level-1
       |  +--rw flooding-reduction-algo
       |     +--rw flooding-reduction-algo?   identityref
       +--rw level-2
          +--rw flooding-reduction-algo
             +--rw flooding-reduction-algo?   identityref
     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol/isis:isis/isis:database
               /isis:levels/isis:lsp/isis:router-capabilities:
       +--ro flooding-reduction-algo-tlv
          +--ro flooding-reduction-algo?   identityref

3.2.  Tree for OSPF Flooding Reduction Algorithm

   The following shows the tree diagram of the module for an OSPF
   Flooding Reduction Algorithm:













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     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol/ospf:ospf/ospf:areas
               /ospf:area:
       +--rw flooding-reduction-algo
          +--rw flooding-reduction-algo?   identityref
     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol/ospf:ospf/ospf:areas
               /ospf:area/ospf:database/ospf:area-scope-lsa-type
               /ospf:area-scope-lsas/ospf:area-scope-lsa/ospf:version
               /ospf:ospfv2/ospf:ospfv2/ospf:body/ospf:opaque
               /ospf:ri-opaque:
       +--ro flooding-reduction-algo-tlv
          +--ro flooding-reduction-algo?   identityref
     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol/ospf:ospf/ospf:areas
               /ospf:area/ospf:database/ospf:area-scope-lsa-type
               /ospf:area-scope-lsas/ospf:area-scope-lsa/ospf:version
               /ospf:ospfv3/ospf:ospfv3/ospf:body
               /ospf:router-information:
       +--ro flooding-reduction-algo-tlv
          +--ro flooding-reduction-algo?   identityref

3.3.  IANA Module for IGP Flooding Algorithms

   IANA has created a registry titled 'IGP Algorithm Type for Computing
   Flooding Topology' in the 'Interior Gateway Protocol (IGP)
   Parameters' registry group."; Module iana-igp-flooding-topo-algo is
   an IANA-maintained module, which defines the identities for the IGP
   algorithms for computing flooding topologies as in the IANA "IGP
   Algorithm Type for Computing Flooding Topology" registry.

   This module is maintained by IANA and will be updated if and when
   there is any change to the registry.

   This document defines the initial version of the IANA-maintained YANG
   module for the "IGP Algorithm Type for Computing Flooding Topology"
   registry.  registry Section 4.1.

   <CODE BEGINS> file "iana-igp-flooding-topo-algo@2026-02-10.yang"
   module iana-igp-flooding-topo-algo {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:"
             + "iana-igp-flooding-topo-algo";
     prefix iana-igp-flood-algo;

     organization
       "Internet Assigned Numbers Authority (IANA)";
     contact



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       "Internet Assigned Numbers Authority

        ICANN
        12025 Waterfront Drive, Suite 300
        Los Angeles, CA 90094-2536
        United States of America

        Tel:    +1 310 301 5800
        <mailto:iana@iana.org>";
     description
       "This YANG module defines the identities for IGP Algorithms
        for Computing Flooding Topologies.

        This YANG module is maintained by IANA and reflects the
        'IGP Flooding Reduction Algorithm' registry.

        Copyright (c) 2026 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This initial version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.

        The latest version of this YANG module is available at
        https://www.iana.org/assignments/yang-parameters.";

     revision 2026-02-10 {
       description
         "Initial version";
       reference
         "RFC 9667: Dynamic Flooding on Dense Graphs";
     }

     identity igp-flooding-topo-algo {
       description
         "Base identity for IGP algorithms for computing flooding
          topologies. Algorithms are defined in the 'IGP Algorithm



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          Type for Computing Flooding Topology' in the 'Interior
          Gateway Protocol (IGP) Parameters' registry group.";
     }
   }
   <CODE ENDS>

3.4.  YANG Module for IS-IS Flooding Reduction Algorithm

   The following is the YANG module for IS-IS Flooding Reduction
   Algorithm:

   <CODE BEGINS> file "ietf-isis-flooding-reduction-algo@2026-02-10.yang"
   module ietf-isis-flooding-reduction-algo {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:"
             + "ietf-isis-flooding-reduction-algo";
     prefix isis-flood-reduce-algo;

     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349: A YANG Data Model for Routing Management
                    (NMDA Version)";
     }
     import ietf-isis {
       prefix isis;
       reference
         "RFC 9130: YANG Data Model for the IS-IS Protocol";
     }
     import iana-igp-flooding-topo-algo {
       prefix iana-igp-flood-algo;
       reference
         "RFC 9667: Dynamic Flooding on Dense Graphs";
     }

     organization
       "IETF Link State Routing (LSR) Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/lsr/>
        WG List:  <mailto:lsr@ietf.org>

        Author:   Acee Lindem
                  <mailto:acee.ietf@gmail.com>";
     description
       "This YANG module defines the operational state for
        the flooding reduction algorithm in IS-IS as defined
        in RFC XXXX.




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        Copyright (c) 2026 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.
        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2026-02-10 {
       description
         "Initial version";
       reference
         "RFC XXXX: IGP Flooding Reduction Algorithms Framework";
     }

     /*
      * IS-IS Flooding Reduction Algorithm configuration
      */

     grouping flooding-reduction-algo-config {
       description
         "Grouping for IS-IS flooding algorithm router
          configuration.";
       container flooding-reduction-algo {
         description
           "IS-IS Level-1 flooding algorithm routing configuration.
            This containers includes configuration related to the
            active flooding reduction algorithm.";
         leaf flooding-reduction-algo {
           type identityref {
             base iana-igp-flood-algo:igp-flooding-topo-algo;
           }
           description
             "Specifies the active flooding reduction algorithm
              in for IS-IS Level 1.
              RFC XXXX: IGP Flooding Reduction Algorithms Framework";
         }
       }
     }




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     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis" {
       when "/rt:routing/rt:control-plane-protocols/"
          + "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
           "This augment IS-IS routing protocol when used";
       }
       description
         "This augments IS-IS with flooding reduction algorithm
          configuration.";
       container level-1 {
         uses flooding-reduction-algo-config;
         description
           "IS-IS Level-1 Flooding Reduction Algorithm
            configuration.";
       }
       container level-2 {
         uses flooding-reduction-algo-config;
         description
           "IS-IS Level-2 Flooding Reduction Algorithm
            configuration.";
       }
     }

     /*
      * IS-IS Flooding Reduction Algorithm Router Capabilities
      */

     grouping flooding-reduction-algorithm-tlv {
       description
         "Grouping for IS-IS flooding reduction algorithm
          TLV types.";
       reference
         "RFC 7981: IS-IS Extensions for Advertising Router
                    Information
          RFC XXXX: Flooding Reduction Algorithms Framework";
       container flooding-reduction-algo-tlv {
         description
           "IS-IS Router Flooding Algorithm TLV.";
         leaf flooding-reduction-algo {
           type identityref {
             base iana-igp-flood-algo:igp-flooding-topo-algo;
           }
           description
             "Flooding reduction algorithm active in the
              IS-IS routing domain";
           reference



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             "RFC 7981: IS-IS Extensions for Advertising Router
                        Information
              RFC XXXX: Flooding Reduction Algorithms Framework";
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp"
           + "/isis:router-capabilities" {
       when "/rt:routing/rt:control-plane-protocols/"
          + "rt:control-plane-protocol/"
          + "rt:type = 'isis:isis'" {
         description
           "This augment IS-IS routing protocol when used";
       }
       description
         "This augments IS-IS protocol LSDB router capability.";
       uses flooding-reduction-algorithm-tlv;
     }
   }
   <CODE ENDS>

3.5.  YANG Module for OSPF Flooding Reduction Algorithm

   The following is the YANG module for OSPF Flooding Reduction
   Algorithm:

   <CODE BEGINS> file "ietf-ospf-flooding-reduction-algo@2026-02-10.yang"
   module ietf-ospf-flooding-reduction-algo {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:"
             + "ietf-ospf-flooding-reduction-algo";
     prefix ospf-fc;

     import ietf-routing {
       prefix rt;
       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 iana-igp-flooding-topo-algo {



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       prefix iana-igp-flood-algo;
       reference
         "RFC 9667: Dynamic Flooding on Dense Graphs";
     }

     organization
       "IETF Link State Routing (LSR) Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/lsr/>
        WG List:  <mailto:lsr@ietf.org>

        Author:   Acee Lindem
                  <mailto:acee.ietf@gmail.com>";
     description
       "This YANG module defines the configuration and operational
        state for the flooding reduction algorithms in OSPF as
        defined in RFC XXXX.

        Copyright (c) 2026 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.
        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2026-02-10 {
       description
         "Initial version";
       reference
         "RFC XXXX: IGP Flooding Reduction Algorithms Framework";
     }

     grouping flooding-reduction-algorithm-tlv {
       description
         "Grouping for OSPF flooding algorithm capabilities
          TLV types.";
       reference
         "RFC 7770: Extensions to OSPF for Advertising Optional
                    Router Capabilities



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          RFC XXXX: IGP Flooding Reduction Algorithms Framework";
       container flooding-reduction-algo-tlv {
         description
           "OSPF Flooding Reduction Algorithm TLV.";
         leaf flooding-reduction-algo {
           type identityref {
             base iana-igp-flood-algo:igp-flooding-topo-algo;
           }
           description
             "Flooding reduction algorithm active in the
              OSPF routing domain area
              RFC XXXX: Flooding Reduction Algorithms Framework";
         }
       }
     }

     /*
      * OSPF Flooding Reduciton Algorithm Configuration
      */

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/ospf:ospf/"
           + "ospf:areas/ospf:area" {
       when "derived-from-or-self(/rt:routing/"
          + "rt:control-plane-protocols/"
          + "rt:control-plane-protocol/rt:type, 'ospf:ospf')" {
         description
           "This augmentation is only valid for both
            OSPFv2 and OSPFv3";
       }
       container flooding-reduction-algo {
         description
           "OSPF area-level flooding reduction algorithm routing
            configuration. This container includes configuration related
            to the active flooding reduction algorithm.";
         leaf flooding-reduction-algo {
           type identityref {
             base iana-igp-flood-algo:igp-flooding-topo-algo;
           }
           description
             "Specifies the active flooding reduction algorithm
              in the OSPF area.
              RFC XXXX: IGP Flooding Reduction Algorithms Framework";
         }
       }
       description
         "This augments the OSPF protocol area configuration with
          flood reduction algorithm specification.";



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     }

     /*
      * OSPFv2 Router-Information Opaque LSA Flooding Reduction TLV
      */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol/"
           + "ospf:ospf/ospf:areas/"
           + "ospf:area/ospf:database/"
           + "ospf:area-scope-lsa-type/ospf:area-scope-lsas/"
           + "ospf:area-scope-lsa/ospf:version/ospf:ospfv2/"
           + "ospf:ospfv2/ospf:body/ospf:opaque/"
           + "ospf:ri-opaque" {
       when "derived-from-or-self(/rt:routing/"
          + "rt:control-plane-protocols/"
          + "rt:control-plane-protocol/rt:type, 'ospf:ospfv2')" {
         description
           "This augmentation is only valid for OSPFv2.";
       }
       description
         "OSPFv2 Opaque Area-Scoped Router-Information LSA Router
          Functional capabilities.";
       uses flooding-reduction-algorithm-tlv;
       reference
         "RFC 7770: Extensions to OSPF for Advertising Optional
                    Router Capabilities
          RFC XXXX: IGP Flooding Reduction Algorithms Framework";
     }

     /*
      * OSPFv3 Router-Information LSA Flooding Reduction TLV
      */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol/"
           + "ospf:ospf/ospf:areas/"
           + "ospf:area/ospf:database/"
           + "ospf:area-scope-lsa-type/ospf:area-scope-lsas/"
           + "ospf:area-scope-lsa/ospf:version/ospf:ospfv3/"
           + "ospf:ospfv3/ospf:body/ospf:router-information" {
       when "derived-from-or-self(/rt:routing/"
          + "rt:control-plane-protocols/"
          + "rt:control-plane-protocol/rt:type, 'ospf:ospfv3')" {
         description
           "This augmentation is only valid for OSPFv3.";
       }
       description



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         "OSPFv3 Area-Scoped Router-Information LSA Router
          Functional capabilities.";
       uses flooding-reduction-algorithm-tlv;
       reference
         "RFC 7770: Extensions to OSPF for Advertising Optional
                    Router Capabilities
          RFC XXXX: IGP Flooding Reduction Algorithms Framework";
     }
   }
   <CODE ENDS>

4.  IANA Considerations

4.1.  IANA IGP Flooding Algorithm Registry

   The existing IANA registry "IGP Algorithm Type for Computing Flooding
   Topology" in the "Interior Gateway Protocol (IGP) Parameters"
   registry group [RFC9667] is reused for algorithm definitions in this
   document.  No further IANA action is required.

4.2.  IGP Flooding Reduction Algorithm Capabiity

   This section requests that IANA reserve a single value from each of
   the following registries.  Both should be named: "Flood Reduction
   Algorithm".

   *  IS-IS Sub-TLVs for IS-IS Router CAPABILITY TLV Registry (from
      within the 1-32767 range)

   *  OSPF Router Information (RI) TLVs Registry

5.  Security Considerations

   This document outlines a framework for extensions to an IGP protocol
   for operation on high-density network topologies.  Implementations
   SHOULD implement cryptographic authentication compliant to e.g.
   [RFC5304], and should enable other security measures in accordance
   with the best common practices for the relevant IGP protocol.

6.  Contributors

   The following people have contributed to this draft and are mentioned
   without any particular order: Raj Chetan, Les Ginsberg, Peter Psenak
   and Tony Li.

7.  Normative References





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   [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>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/info/rfc7770>.

   [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>.

   [RFC7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/info/rfc7981>.

   [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>.

   [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>.

   [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>.

   [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>.

8.  Informative References

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.




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   [RFC9667]  Li, T., Ed., Psenak, P., Ed., Chen, H., Jalil, L., and S.
              Dontula, "Dynamic Flooding on Dense Graphs", RFC 9667,
              DOI 10.17487/RFC9667, October 2024,
              <https://www.rfc-editor.org/info/rfc9667>.

Authors' Addresses

   Tony Przygienda
   HPE
   1701 East Mossy Oaks Road
   Spring, TX 77389
   United States of America
   Email: antoni.przygienda@hpe.com


   Shraddha Hegde
   HPE
   1701 East Mossy Oaks Road
   Spring, TX 77389
   United States of America
   Email: shraddha.hegde@hpe.com


   Jordan Head
   HPE
   1701 East Mossy Oaks Road
   Spring, TX 77389
   United States of America
   Email: jordan.head@hpe.com


   Acee Lindem
   Arrcus, Inc
   301 Midenhall Way
   Cary, NC 27513
   United States of America
   Email: acee.ietf@gmail.com














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