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Extensions to OSPF for Advertising Prefix Administrative Tags
draft-ietf-lsr-ospf-admin-tags-07

Document Type Active Internet-Draft (lsr WG)
Authors Acee Lindem , Peter Psenak , Yingzhen Qu
Last updated 2022-11-28
Replaces draft-acee-lsr-ospf-admin-tags, draft-acee-ospf-admin-tags
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Formats
Yang Validation 0 errors, 0 warnings
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd Christian Hopps
IESG IESG state I-D Exists
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Send notices to chopps@chopps.org
draft-ietf-lsr-ospf-admin-tags-07
Network Working Group                                     A. Lindem, Ed.
Internet-Draft                                                 P. Psenak
Intended status: Standards Track                           Cisco Systems
Expires: 1 June 2023                                               Y. Qu
                                                               Futurewei
                                                        28 November 2022

     Extensions to OSPF for Advertising Prefix Administrative Tags
                   draft-ietf-lsr-ospf-admin-tags-07

Abstract

   It is useful for routers in OSPFv2 and OSPFv3 routing domains to be
   able to associate tags with prefixes.  Previously, OSPFv2 and OSPFv3
   were relegated to a single tag and only for AS External and Not-So-
   Stubby-Area (NSSA) prefixes.  With the flexible encodings provided by
   OSPFv2 Prefix/Link Attribute Advertisement and OSPFv3 Extended LSAs,
   multiple administrative tags may be advertised for all types of
   prefixes.  These administrative tags can be used for many
   applications including route redistribution policy, selective prefix
   prioritization, selective IP Fast-ReRoute (IPFRR) prefix protection,
   and many others.

   The ISIS protocol supports a similar mechanism that is described in
   RFC 5130.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 1 June 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . . .   3
   3.  Administrative Tag Applicability  . . . . . . . . . . . . . .   4
   4.  Protocol Operation  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Equal-Cost Multipath Applicability  . . . . . . . . . . .   5
   5.  BGP-LS Advertisement  . . . . . . . . . . . . . . . . . . . .   5
   6.  Management Considerations . . . . . . . . . . . . . . . . . .   6
   7.  YANG Data Model . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  16
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  16
   12. Informative References  . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   It is useful for routers in OSPFv2 [RFC2328] and OSPFv3 [RFC5340]
   routing domains to be able to associate tags with prefixes.
   Previously, OSPFv2 and OSPFv3 were relegated to a single tag and only
   for AS External and Not-So-Stubby-Area (NSSA) prefixes.  With the
   flexible encodings provided by OSPFv2 Prefix/Link Attribute
   Advertisement ([RFC7684]) and OSPFv3 Extended LSA ([RFC8362]),
   multiple administrative tags may be advertised for all types of
   prefixes.  These administrative tags can be used in many applications
   including (but not limited to):

   1.  Controlling which routes are redistributed into other protocols
       for re-advertisement.

   2.  Prioritizing selected prefixes for faster convergence and
       installation in the forwarding plane.

   3.  Identifying selected prefixes for Loop-Free Alternative (LFA)
       protection.

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   Throughout this document, OSPF is used when the text applies to both
   OSPFv2 and OSPFv3.  OSPFv2 or OSPFv3 is used when the text is
   specific to one version of the OSPF protocol.

   The definition of the 64-bit tag was considered but discard given
   that there is no strong requirement or use case.  The specification
   is included here for information.

   The ISIS protocol supports a similar mechanism that is described in
   RFC 5130 [RFC5130].

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  32-Bit Administrative Tag Sub-TLV

   This document creates a new Administrative Tag Sub-TLV for OSPFv2 and
   OSPFv3.  This Sub-TLV specifies one or more 32-bit unsigned integers
   that may be associated with an OSPF advertised prefix.  The precise
   usage of these tags is beyond the scope of this document.

   The format of the 32-bit Administrative Tag TLV is as follows:

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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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             First 32-bit Administrative Tag                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             o                                 |
                                    o
      |                             o                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Last 32-bit Administrative Tag                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type     A 16-bit field set to TBD.

      Length   A 16-bit field that indicates the length of the value
               portion in octets and MUST be a multiple of 4 octets
               dependent on the number of administrative tags
               advertised. At least one administrative tag must be
               advertised.

      Value    A variable length list of one or more administrative
               tags.

                Figure 1: 32-bit Administrative Tag Sub-TLV

   This sub-TLV will carry one or more 32-bit unsigned integer values
   that will be used as administrative tags.

3.  Administrative Tag Applicability

   The administrative tag TLV specified herein will be valid as a sub-
   TLV of the following TLVs specified in [RFC7684]:

   1.  Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA

   The administrative tag TLV specified herein will be valid as a sub-
   TLV of the following TLVs specified in [RFC8362]:

   1.  Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA

   2.  Intra-Area-Prefix TLV advertised in the E-Intra-Area-Prefix-LSA.

   3.  External-Prefix TLV advertised in the E-AS-External-LSA and the
       E-NSSA-LSA

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4.  Protocol Operation

   An OSPF router supporting this specification MUST be able to
   advertise and interpret at least one 32-bit tag for all type of
   prefixes.  An OSPF router supporting this specification MAY be able
   to advertise and propagate multiple 32-bit tags.  The maximum tags
   that an implementation supports is a local matter depending upon
   supported applications using prefix tags.

   When tags are advertised for AS External or NSSA LSA prefixes, the
   existing tag in the OSPFv2 and OSPFv3 AS-External-LSA and NSSA-LSA
   encodings SHOULD be utilized for the first tag.  This will facilitate
   backward compatibility with implementations that do not support this
   specification.

   An OSPF router supporting this specification SHOULD propagate
   administrative tags when acting as an Area Border Router and
   originating summary advertisements into other areas (unless inhibited
   by local policy Section 6).  Similarly, an OSPF router supporting
   this specification and acting as an ABR for a Not-So-Stubby Area
   (NSSA) SHOULD propagate tags when translating NSSA routes to AS
   External advertisements [RFC3101] (also subject to local policy
   Section 6).  The number of tags supported MAY limit the number of
   tags that are propagated.  When propagating multiple tags, the order
   of the the tags SHOULD be preserved.

   For configured area ranges, NSSA ranges, and configured summarization
   of redistributed routes, tags from component routes SHOULD NOT be
   propagated to the summary.  Implementations SHOULD provide a
   mechanism to configure multiple tags for area ranges, NSSA ranges,
   and redistributed route summaries.

4.1.  Equal-Cost Multipath Applicability

   When multiple LSAs contribute to an OSPF route, it is possible that
   these LSAs will all have different tags.  In this situation, the OSPF
   router MUST associate the tags from one of the LSAs contributing a
   path and, if the implementation supports multiple tags, MAY associate
   tags for multiple contributing LSAs up to the maximum number of tags
   supported.

5.  BGP-LS Advertisement

   BGP-LS [RFC7752] introduced the support for advertising
   administrative tags associated with prefixes using the BGP-LS IGP
   Route Tag TLV (TLV 1153) that is used to carry the OSPF
   Administrative Tags specified in this document.

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6.  Management Considerations

   Implementations MAY include configuration of policies to inhibit the
   advertisement of tags on and redistributed prefixes.  Implementations
   MAY also include configuration of policies to filter the propagation
   of admin-tags between areas (both E-Inter-Area-Prefix-LSAs and
   translated E-AS-External-LSAs).  However, the default behavior SHOULD
   be to advertise or propagate the lesser of all the tags associated
   with the prefix or the maximum number of tags supported by the
   implementation.

7.  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].

   This section defines a YANG data model that can be used to configure
   and manage the prefix administrative tags defined in this document,
   which augments the OSPF YANG data model [I-D.ietf-ospf-yang] and the
   OSPFv3 Extended LSA YANG data model
   [I-D.ietf-lsr-ospfv3-extended-lsa-yang].

   The following show the tree diagram of the module:

   module: ietf-ospf-admin-tags

    augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area
            /ospf:ranges/ospf:range:
      +--rw admin-tags
         +--rw tags*   uint32
    augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area
            /ospf:interfaces/ospf:interface:
      +--rw admin-tags
         +--rw tags* [tag]
            +--rw tag                   uint32
            +--rw advertise-prefixes* [prefix]
               +--rw prefix    inet:ip-prefix
    augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area
            /ospf:interfaces/ospf:interface/ospf:database
            /ospf:link-scope-lsa-type/ospf:link-scope-lsas
            /ospf:link-scope-lsa/ospf:version/ospf:ospfv2/ospf:ospfv2
            /ospf:body/ospf:opaque/ospf:extended-prefix-opaque
            /ospf:extended-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs

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         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32
    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:extended-prefix-opaque
            /ospf:extended-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32
   vv augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:database
            /ospf:as-scope-lsa-type/ospf:as-scope-lsas/ospf:as-scope-lsa
            /ospf:version/ospf:ospfv2/ospf:ospfv2/ospf:body/ospf:opaque
            /ospf:extended-prefix-opaque/ospf:extended-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32
    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/ospfv3-e-lsa:e-inter-area-prefix
            /ospfv3-e-lsa:e-inter-prefix-tlvs
            /ospfv3-e-lsa:inter-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32
    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/ospfv3-e-lsa:e-intra-area-prefix
            /ospfv3-e-lsa:e-intra-prefix-tlvs
            /ospfv3-e-lsa:intra-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32
    augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:database
            /ospf:as-scope-lsa-type/ospf:as-scope-lsas/ospf:as-scope-lsa
            /ospf:version/ospf:ospfv3/ospf:ospfv3/ospf:body
            /ospfv3-e-lsa:e-as-external/ospfv3-e-lsa:e-external-tlvs
            /ospfv3-e-lsa:external-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32

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    augment /rt:routing/rt:control-plane-protocols
            /rt:control-plane-protocol/ospf:ospf/ospf:database
            /ospf:as-scope-lsa-type/ospf:as-scope-lsas/ospf:as-scope-lsa
            /ospf:version/ospf:ospfv3/ospf:ospfv3/ospf:body
            /ospfv3-e-lsa:e-nssa/ospfv3-e-lsa:e-external-tlvs
            /ospfv3-e-lsa:external-prefix-tlv:
      +--ro perfix-admin-tag-sub-tlvs
         +--ro admin-tag-sub-tlv* []
            +--ro admin-tags*   uint32

   The following is the YANG module:

   <CODE BEGINS> file "ietf-ospf-admin-tags@2022-10-11.yang"
   module ietf-ospf-admin-tags {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-ospf-admin-tags";
     prefix ospf-admin-tags;

     import ietf-routing {
       prefix "rt";
       reference "RFC 8349: A YANG Data Model for Routing
                  Management (NMDA Version)";
     }

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

     import ietf-inet-types {
       prefix "inet";
       reference "RFC 6991: Common YANG Data Types";
     }

     import ietf-ospfv3-extended-lsa {
       prefix "ospfv3-e-lsa";
       reference "RFC xxxx: YANG Model for OSPFv3 Extended LSAs.";
     }

     organization
       "IETF LSR - Link State Routing Working Group";

     contact
        "WG Web:   <https://datatracker.ietf.org/wg/lsr/>
         WG List:  <mailto:lsr@ietf.org>

         Author:   Yingzhen Qu
                   <mailto:yingzhen.qu@futurewei.com>

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         Author:   Acee Lindem
                   <mailto:acee@cisco.com>
         Author:   Peter Psenak
                   <mailto:ppsenak@cisco.com>";

     description
       "This YANG module defines the configuration
        and operational state for OSPF administrative tags.

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

        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 XXXX;
        see the RFC itself for full legal notices.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     reference "RFC XXXX";

     revision 2022-10-11 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for OSPFv2 Administrative Tags.";
     }

     grouping prefix-admin-tag-sub-tlvs {
       description "Prefix Administrative Tag sub-TLVs.";

       container perfix-admin-tag-sub-tlvs{
         description "Prefix admin tag sub-TLV.";
         list admin-tag-sub-tlv {
           description "Prefix admin tag sub-TLV.";

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           leaf-list admin-tags {
             type uint32;
             description "32-bit administrative tag.";
           }
         }
       }
     }

     /* Configuration */
     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/ospf:ospf/"
           + "ospf:areas/ospf:area/ospf:ranges/ospf:range" {
           when "derived-from-or-self(../../../../../"
              + "rt:type, 'ospf:ospf')" {
         description
           "This augments the OSPF routing protocol area range
            configuration.";
       }
       description
         "This augments the OSPF protocol area range configuration
          with Administrative Tags. The configured tags will be
          advertised with summary prefix when it is active.";

       container admin-tags {
         when "../ospf:advertise = 'true'";
         leaf-list tags {
           type uint32;
           description
             "32-bit administrative tags.";
         }
         description
           "OSPF prefix administrative tags.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/ospf:ospf/"
           + "ospf:areas/ospf:area/ospf:interfaces/ospf:interface" {
           when "derived-from-or-self(../../../../../"
              + "rt:type, 'ospf:ospf')" {
         description
           "This augments the OSPF routing protocol interface
            configuration.";
       }
       description
         "This augments the OSPF protocol interface configuration
          with Administrative Tags. The configured tags will be
          advertised with local prefixes configured for the interface.";

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       container admin-tags {
         list tags {
           key "tag";
           leaf tag {
             type uint32;
             description
               "32-bit administrative tag.";
           }
           list advertise-prefixes {
              key "prefix";
              leaf prefix {
                type inet:ip-prefix;
                description
                   "IPv4 or IPv6 prefix";
              }
              description
                "By default, the tag advertised will be advertised
                 for all prefixes associated with the interface.
                 If advertise-prefixes is specified, the tag is
                 only applied to interfaces prefixes in the list";
           }
           description
             "List of administrative tags that are to be advertised
              with prefixes associated with the interfaces. Optionally,
              tag advertisement may be restricted to specific
              prefixes.";
         }
         description
           "OSPF prefix administrative tags.";
       }
     }

     /* Database */
     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol/"
           + "ospf:ospf/ospf:areas/ospf:area/"
           + "ospf:interfaces/ospf:interface/ospf:database/"
           + "ospf:link-scope-lsa-type/ospf:link-scope-lsas/"
           + "ospf:link-scope-lsa/ospf:version/ospf:ospfv2/"
           + "ospf:ospfv2/ospf:body/ospf:opaque/"
           + "ospf:extended-prefix-opaque/ospf:extended-prefix-tlv" {
       when "derived-from-or-self(../../../../../../../../../../"
          + "../../../../rt:type, 'ospf:ospfv2')" {
         description
           "This augmentation is only valid for OSPFv2.";
       }
       description
         "Prefix Administrative Tag Sub-TLVs for OSPFv2 extended prefix

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          TLV in type 9 opaque LSA.";
       uses prefix-admin-tag-sub-tlvs;
     }

     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:extended-prefix-opaque/ospf:extended-prefix-tlv" {
       when "derived-from-or-self(../../../../../../../../../../"
          + "../../rt:type, 'ospf:ospfv2')" {
         description
           "This augmentation is only valid for OSPFv2.";
       }
       description
         "Prefix Administrative Tag Sub-TLVs for OSPFv2 extended prefix
          TLV in type 10 opaque LSA.";
       uses prefix-admin-tag-sub-tlvs;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol/"
           + "ospf:ospf/ospf:database/"
           + "ospf:as-scope-lsa-type/ospf:as-scope-lsas/"
           + "ospf:as-scope-lsa/ospf:version/ospf:ospfv2/"
           + "ospf:ospfv2/ospf:body/ospf:opaque/"
           + "ospf:extended-prefix-opaque/ospf:extended-prefix-tlv" {
       when "derived-from-or-self(../../../../../../../../"
          + "../../rt:type, 'ospf:ospfv2')" {
         description
           "This augmentation is only valid for OSPFv2.";
       }
       description
         "Prefix Administrative Tag Sub-TLVs for OSPFv2 extended prefix
          TLV in type 11 opaque LSA.";
       uses prefix-admin-tag-sub-tlvs;
     }

     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/ospfv3-e-lsa:e-inter-area-prefix/"

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       + "ospfv3-e-lsa:e-inter-prefix-tlvs/"
       + "ospfv3-e-lsa:inter-prefix-tlv" {
       when "derived-from-or-self(../../../../../../../../../../"
          + "../../rt:type, 'ospf:ospfv3')" {
         description
           "This augmentation is only valid for OSPFv3.";
       }
       description
         "Augment OSPFv3 Inter-Area-Prefix TLV in the
          E-Inter-Area-Prefix LSA.";

       uses prefix-admin-tag-sub-tlvs;
     }

     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/ospfv3-e-lsa:e-intra-area-prefix/"
       + "ospfv3-e-lsa:e-intra-prefix-tlvs/"
       + "ospfv3-e-lsa:intra-prefix-tlv" {
       when "/rt:routing/rt:control-plane-protocols"
          + "/rt:control-plane-protocol/rt:type = 'ospf:ospfv3'" {
         description
           "This augmentation is only valid for OSPFv3.";
       }
       description
         "Augment OSPFv3 Intra-Area-Prefix TLV in the
          E-Intra-Area-Prefix LSA.";

       uses prefix-admin-tag-sub-tlvs;
     }

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

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         "Augment OSPFv3 External-Prefix TLV in the E-AS-External-LSA.";

       uses prefix-admin-tag-sub-tlvs;
     }

     augment "/rt:routing/"
       + "rt:control-plane-protocols/rt:control-plane-protocol/"
       + "ospf:ospf/ospf:database/"
       + "ospf:as-scope-lsa-type/ospf:as-scope-lsas/"
       + "ospf:as-scope-lsa/ospf:version/ospf:ospfv3/"
       + "ospf:ospfv3/ospf:body/ospfv3-e-lsa:e-nssa/"
       + "ospfv3-e-lsa:e-external-tlvs/"
       + "ospfv3-e-lsa:external-prefix-tlv" {
       when "derived-from-or-self(../../../../../../../../"
          + "../../rt:type, 'ospf:ospfv3')" {
         description
           "This augmentation is only valid for OSPFv3.";
       }
       description
         "Augment OSPFv3 External-Prefix TLV in the E-NSSA-LSA.";

       uses prefix-admin-tag-sub-tlvs;
     }
   }
   <CODE ENDS>

8.  Security Considerations

   This document describes a generic mechanism for advertising
   administrative tags for OSPF prefixes.  The administrative tags are
   generally less critical than the topology information currently
   advertised by the base OSPF protocol.  The security considerations
   for the generic mechanism are dependent on their application.  One
   such application is to control leaking of OSPF routes to other
   protocols (e.g., BGP [RFC4271]).  If an attacker were able to modify
   the admin tags associated with OSPF routes and they were being used
   for this application, such routes could be prevented from being
   advertised in routing domains where they are required (subtle denial
   or service) or they could be advertised into routing domains where
   they shouldn't be advertised (routing vulnerability).  Security
   considerations for the base OSPF protocol are covered in [RFC2328]
   and [RFC5340].

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   The YANG modules specified in this document define 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 NETCONF Access Control Model (NACM) [RFC8341] provides the means
   to restrict access for particular NETCONF or RESTCONF users to a pre-
   configured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   The following data nodes defined in the YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  The modifications to these data nodes without proper
   protection can have a negative effect on network operations.

      /ospf:ospf/ospf:areas/ospf:area/ospf:interfaces/ospf:interface/
      admin-tags

      /ospf:ospf/ospf:areas/ospf:area/ospf:ranges/ospf:range/admin-tags

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  Exposure of
   the OSPF link state database may be useful in mounting a Denial-of-
   Service (DoS) attacks.  These are the readable data nodes:

      /ospf:ospf/ospf:areas/ospf:area/ospf:interfaces/ospf:interface/
      admin-tags

      /ospf:ospf/ospf:areas/ospf:area/ospf:ranges/ospf:range/admin-tags

      /prefix-admin-tag-sub-tlvs

9.  IANA Considerations

   The following values should be allocated from the OSPF Extended
   Prefix TLV Sub-TLV Registry [RFC7684]:

   *  TBD - 32-bit Administrative Tag TLV

   The following values should be allocated from the OSPFv3 Extended-LSA
   Sub-TLV Registry [RFC8362]:

   *  TBD - 32-bit Administrative Tag TLV

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   The IANA is requested to assign one new URI from the IETF XML
   registry ([RFC3688]).  Authors are suggesting the following URI:

               URI: urn:ietf:params:xml:ns:yang:ietf-ospf-admin-tags
               Registrant Contact: The IESG.
               XML: N/A, the requested URI is an XML namespace

   This document also requests one new YANG module name in the YANG
   Module Names registry ([RFC6020]) with the following suggestion :

            name: ietf-ospf-admin-tags
            namespace: urn:ietf:params:xml:ns:yang:ietf-ospf-admin-tags
            prefix: ospf-admin-tags
            reference: RFC XXXX

10.  Acknowledgments

   The authors of RFC 5130 are acknowledged since this document draws
   upon both the ISIS specification and deployment experience.

   Thanks to Donnie Savage for his comments and questions.

   Thanks to Ketan Talaulikar for his comments and providing the BGP-LS
   text.

   The RFC text was produced using Marshall Rose's xml2rfc tool.

11.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.

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

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

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   [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>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

   [RFC8362]  Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
              F. Baker, "OSPFv3 Link State Advertisement (LSA)
              Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
              2018, <https://www.rfc-editor.org/info/rfc8362>.

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   [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>.

   [I-D.ietf-ospf-yang]
              Yeung, D. M., Qu, Y., Zhang, Z. J., Chen, I., and A.
              Lindem, "YANG Data Model for the OSPF Protocol", Work in
              Progress, Internet-Draft, draft-ietf-ospf-yang-29, 17
              October 2019, <https://www.ietf.org/archive/id/draft-ietf-
              ospf-yang-29.txt>.

   [I-D.ietf-lsr-ospfv3-extended-lsa-yang]
              Lindem, A., Palani, S., and Y. Qu, "YANG Model for OSPFv3
              Extended LSAs", Work in Progress, Internet-Draft, draft-
              ietf-lsr-ospfv3-extended-lsa-yang-12, 30 August 2022,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-ospfv3-
              extended-lsa-yang-12.txt>.

12.  Informative References

   [RFC3101]  Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
              RFC 3101, DOI 10.17487/RFC3101, January 2003,
              <https://www.rfc-editor.org/info/rfc3101>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC5130]  Previdi, S., Shand, M., Ed., and C. Martin, "A Policy
              Control Mechanism in IS-IS Using Administrative Tags",
              RFC 5130, DOI 10.17487/RFC5130, February 2008,
              <https://www.rfc-editor.org/info/rfc5130>.

Authors' Addresses

   Acee Lindem (editor)
   Cisco Systems
   301 Midenhall Way
   Cary, NC 27513
   United States of America
   Email: acee@cisco.com

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   Peter Psenak
   Cisco Systems
   Apollo Business Center
   Mlynske nivy 43
   Bratislava 821 09
   Slovakia
   Email: ppsenak@cisco.com

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

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