Internet-Draft OSPF Administrative Tags March 2024
Lindem, et al. Expires 2 September 2024 [Page]
Workgroup:
Network Working Group
Published:
Intended Status:
Standards Track
Expires:
Authors:
A. Lindem, Ed.
LabN Consulting, L.L.C.
P. Psenak
Cisco Systems
Y. Qu
Futurewei

Extensions to OSPF for Advertising Prefix Administrative Tags

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 2 September 2024.

Table of Contents

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.

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:


    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. If the length is 0 or not a multiple of 4 octets, the Sub-TLV should be ignored and the reception SHOULD be logged for further analysis (subject to rate-limiting).

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

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 semantics of the tag order are implementation-dependent. That is, there is no implied meaning to the ordering of the tags that indicates a certain operation or set of operations need be performed based on the order of the tags. Each tag SHOULD be treated as an autonomous identifier that MAY be used in policy to perform a policy action. Whether or not tag A precedes or succeeds tag B SHOULD not change the meaning of the tag set. The number of tags supported MAY limit the number of tags that are propagated. When propagating multiple tags between areas as previously described, the order of the the tags SHOULD be preserved so that implementations supporting fewer tags will have a consistent view across areas.

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 from multiple contributing LSAs up to the maximum number of tags supported. It is RECOMMENDED that tags from LSAs are added to the path in ascending order of LSA originator Router-ID.

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.

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 [RFC9129] 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
      +--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
 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-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@2024-03-01.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 9129: 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>
     Author:   Acee Lindem
               <mailto:acee.ietf@gmail.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 2024-03-01 {
    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 {
      config false;
      description
        "Prefix admin tag sub-TLV.";
      list admin-tag-sub-tlv {
        description
          "Prefix admin tag sub-TLV.";
        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.";
    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
       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/"
        + "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
      "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: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-nssa/"
        + "ospfv3-e-lsa:e-external-tlvs/"
        + "ospfv3-e-lsa:external-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 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].

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.

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:

9. IANA Considerations

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

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

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 [RFC5130] are acknowledged since this document draws upon both the ISIS specification and deployment experience. The text in Section 4 is adopted from RFC 5130.

Thanks to Donnie Savage for his comments and questions.

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

Thanks to Tony Przygienda and Les Ginsberg for discussions on tag selection.

11. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC2328]
Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, , <https://www.rfc-editor.org/info/rfc2328>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <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, , <https://www.rfc-editor.org/info/rfc5340>.
[RFC6020]
Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, , <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, , <https://www.rfc-editor.org/info/rfc6241>.
[RFC6242]
Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, , <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, , <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, , <https://www.rfc-editor.org/info/rfc7752>.
[RFC7950]
Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, , <https://www.rfc-editor.org/info/rfc7950>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc8362>.
[RFC8446]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, , <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, , <https://www.rfc-editor.org/info/rfc9129>.
[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-23, , <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ospfv3-extended-lsa-yang-23>.

12. Informative References

[RFC3101]
Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", RFC 3101, DOI 10.17487/RFC3101, , <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, , <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, , <https://www.rfc-editor.org/info/rfc5130>.

Authors' Addresses

Acee Lindem (editor)
LabN Consulting, L.L.C.
301 Midenhall Way
Cary, NC 27513
United States of America
Peter Psenak
Cisco Systems
Apollo Business Center
Mlynske nivy 43
Bratislava 821 09
Slovakia
Yingzhen Qu
Futurewei
2330 Central Expressway
Santa Clara, CA 95050
United States of America