A YANG Data Model for MPLS-TE Topology

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Copyright Notice

Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved.¶

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

1. Introduction

This document defines a YANG data model for representing, retrieving, and manipulating MPLS-TE network topologies. It is based on and augments existing YANG models that describe network and traffic engineering packet network topologies.¶

This document also defines a collection of common YANG data types and groupings specific to MPLS-TE. These common types and groupings are intended to be imported by modules that model MPLS-TE technology-specific configuration and state capabilities, such as the MPLS-TE topology model, defined in this document, and the MPLS-TE tunnel model, defined in [I-D.ietf-teas-yang-te-mpls].¶

MPLS Transport Profile (MPLS-TP) is a profile of the MPLS protocol that is used in packet switched transport networks and operated in a similar manner to other existing transport technologies (e.g., OTN), as described in [RFC5921].¶

The YANG models defined in this document can also be used for MPLS-TP network topologies.¶

The YANG models defined in this document conform to the Network Management Datastore Architecture defined in [RFC8342].¶

2. MPLS-TE Types Overview

The module ietf-mpls-te-types contains the following YANG types and groupings which can be used by other MPLS-TE YANG models:¶

load-balancing-type:¶

• This identity defines the types of load-balancing algorithms used on a bundled MPLS-TE link.¶

te-mpls-label-hop:¶

• This grouping is used for augmentation of the TE label for MPLS-TE paths.¶

3. MPLS-TE Topology Model Overview

The MPLS-TE technology-specific topology model augments the ietf-te- topology-packet YANG module, defined in [I-D.ietf-teas-yang-l3-te-topo], which in turn augments the generic ietf-te-topology YANG module, defined in [RFC8795], as shown in Figure 1.¶

                +------------------+
   TE generic   | ietf-te-topology |
                +---------+--------+
                          ^
                          |
                          | Augments
                          |
             +------------+------------+
   Packet TE | ietf-te-topology-packet |
             +------------+------------+
                          ^
                          |
                          | Augments
                          |
              +-----------+-----------+
   MPLS-TE    | ietf-te-mpls-topology |
              +-----------------------+

Given the guidance for augmentation in [RFC8795], the following technology-specific augmentations need are provided:¶

• A network-type to indicate that the TE topology is an MPLS-TE topology, as follow:¶

      augment /nw:networks/nw:network/nw:network-types
              /tet:te-topology/tet-pkt:packet:
        +--rw mpls-topology!

• TE Label augmentations as described in Section 3.1.¶

Note: TE bandwidth augmentations for paths, LSPs, and links are provided by the ietf-te-topology-packet module, defined in [I-D.ietf-teas-yang-l3-te-topo].¶

    augment /nw:networks/nw:network/nt:link/tet:te:
      +--rw load-balancing-type?   mte-types:load-balancing-type

    augment /nw:networks/nw:network/nw:node/nt:termination-point
            /tet:te:
      +--ro uhp-incapable?   empty

4. YANG model for common MPLS-TE Types

<CODE BEGINS> file "ietf-mpls-te-types@2023-10-13.yang"

module ietf-mpls-te-types {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-mpls-te-types";
  prefix mpls-te-types;

  import ietf-routing-types {
    prefix rt-types;
    reference
      "RFC 8294: Common YANG Data Types for the Routing Area";
  }

  organization
    "Internet Engineering Task Force (IETF) TEAS WG";
  contact
    "WG Web:   <https://datatracker.ietf.org/wg/teas/>
     WG List:  <mailto:teas@ietf.org>

     Editor:   Italo Busi
               <mailto:italo.busi@huawei.com>

     Editor:   Aihua Guo
               <mailto:aihuaguo.ietf@gmail.com>

     Editor:   Xufeng Liu
               <mailto:xufeng.liu.ietf@gmail.com>

     Editor:   Tarek Saad
               <mailto:tsaad.net@gmail.com>

     Editor:   Rakesh Gandhi
               <mailto:rgandhi@cisco.com>";

  description
    "This module defines a collection of common YANG data type
    and grouping definitions specific to MPLS-TE.

    Copyright (c) 2023 IETF Trust and the persons
    identified as authors of the code.  All rights reserved.

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

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

  revision 2023-10-13 {
    description
      "Initial Version";
    reference
      "RFC XXXX: A YANG Data Model for MPLS-TE Topology";
  }
  // RFC Editor: replace XXXX with the actual RFC number assigned
  // to the RFC once this draft
  // becomes an RFC, update date information and remove this note.

  /*
  * Typedefs
  */

  typedef load-balancing-type {
    type enumeration {
      enum per-flow {
        description
          "The load-balancing algorithm ensures that packets
           characterized as the same flow (e.g. based on IP 5-tuple)
           that egress on a LAG or a bundled TE link are forwarded
           on the same component link.

           Packets for different flows within the same LSP can be
           forwarded on different component links.";
      }
      enum per-top-label {
        description
          "The load-balancing algorithm ensures incoming MPLS
           packets with the same top MPLS label and that egress on
           on a LAG or bundled TE link are forwarded on the same
           component link.

           Packets for different flows within the same LSP are
           forwarded on the same component link.";
      }
    }
    description
      "The type of load balancing used on bundled links.";
  }  // typedef load-balancing-type

  /*
  * Groupings
  */

  grouping te-mpls-label-hop {
    description
      "MPLS-TE Label Hop.";

    leaf mpls-label {
      type rt-types:mpls-label;
      description
        "MPLS Label.";
    }
  }  // grouping te-mpls-label-hop
}

<CODE ENDS>

5. YANG Model for MPLS-TE Topology

module: ietf-te-mpls-topology

  augment /nw:networks/nw:network/nw:network-types/tet:te-topology
            /tet-pkt:packet:
    +--rw mpls-topology!
  augment /nw:networks/nw:network/nt:link/tet:te:
    +--rw load-balancing-type?   mpls-te-types:load-balancing-type
  augment /nw:networks/nw:network/nw:node/nt:termination-point
            /tet:te:
    +--ro uhp-incapable?   empty

<CODE BEGINS> file "ietf-te-mpls-topology@2023-10-13.yang"

module ietf-te-mpls-topology {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-te-mpls-topology";
  prefix tet-mpls;

  import ietf-network {
    prefix nw;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }

  import ietf-network-topology {
    prefix nt;
    reference
      "RFC 8345: A YANG Data Model for Network Topologies";
  }

  import ietf-te-topology {
    prefix tet;
    reference
      "RFC 8795: YANG Data Model for Traffic Engineering
       (TE) Topologies";
  }

  import ietf-te-topology-packet {
    prefix tet-pkt;
    reference
      "RFC YYYY: YANG Data Model for Layer 3 TE Topologies";
  }
  // RFC Editor: replace YYYY with the actual RFC number assigned
  // to the RFC once draft-ietf-teas-yang-l3-te-topo
  // becomes an RFC and remove this note.

  import ietf-mpls-te-types {
    prefix mpls-te-types;
    reference
      "RFC XXXX: A YANG Data Model for MPLS-TE Topology";
  }
  // RFC Editor: replace XXXX with the actual RFC number assigned
  // to the RFC once this draft
  // becomes an RFC and remove this note.

  organization
    "Internet Engineering Task Force (IETF) TEAS WG";
  contact
    "WG Web:   <https://datatracker.ietf.org/wg/teas/>
     WG List:  <mailto:teas@ietf.org>

     Editor:   Italo Busi
               <mailto:italo.busi@huawei.com>

     Editor:   Aihua Guo
               <mailto:aihuaguo.ietf@gmail.com>

     Editor:   Xufeng Liu
               <mailto:xufeng.liu.ietf@gmail.com>

     Editor:   Tarek Saad
               <mailto:tsaad.net@gmail.com>

     Editor:   Rakesh Gandhi
               <mailto:rgandhi@cisco.com>";

  description
    "This module defines a YANG data model for representing,
    retrieving, and manipulating MPLS-TE network topologies.

    This module defines MPLS-TE technology-specific augmentations
    to the generic Packet TE topology module
    (ietf-te-topology-packet).

    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.";

  revision 2023-10-13 {
    description
      "Initial Version";
    reference
      "RFC XXXX: A YANG Data Model for MPLS-TE Topology";
  }
  // RFC Editor: replace XXXX with the actual RFC number assigned
  // to the RFC once this draft
  // becomes an RFC, update date information and remove this note.

  /*
   * Augmentations
   */

  augment "/nw:networks/nw:network/nw:network-types/"
        + "tet:te-topology/tet-pkt:packet" {
    description
      "Augment network types to include MPLS-TE Topology Type";
    container mpls-topology {
      presence
        "Indicates an MPLS-TE Topology Type.";
      description
        "Its presence indicates an MPLS-TE Topology";
    }
  }

  augment "/nw:networks/nw:network/nt:link/tet:te" {
    when "../../nw:network-types/tet:te-topology/"
       + "tet-pkt:packet/tet-mpls:mpls-topology"  {
      description
        "Augment MPLS-TE Topology.";
    }
    description
      "Augment TE Link.";

    leaf load-balancing-type {
      type mpls-te-types:load-balancing-type;
      default 'per-flow';
      description
        "Indicates the type of load-balancing (per-flow or per-LSP)
         performed by the bundled TE Link.

         This leaf is not present when the TE Link is not bundled.";
    }  // leaf load-balancing-type
  }

  augment "/nw:networks/nw:network/nw:node/nt:termination-point/"
        + "tet:te" {
    when "../../../nw:network-types/tet:te-topology/"
       + "tet-pkt:packet/tet-mpls:mpls-topology" {
      description "Augment MPLS-TE Topology.";
    }
    description "Augment LTP.";

    leaf uhp-incapable {
      type empty;
      config false;
      description
        "When present, indicates that the LTP is not capable to
         support Ultimate Hop Popping (UHP).";
    }   // leaf uhp-incapable
  }
}

<CODE ENDS>

6. Security Considerations

The configuration, state, and action data defined in this document are designed to be accessed via a management protocol with a secure transport layer, 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 [RFC8341] provides the means to restrict access for particular NETCONF users to a preconfigured subset of all available NETCONF protocol operations and content.¶

The ietf-mpls-te-types model presented in this document defines common types intended to be used as imports by other YANG models. Those other models are responsible for considering the security of the objects they define using those imports. Writers of those other models should consider the vulnerabilities created by exposing information about link characteristics and behaviors (such as how packets may be steered onto parallel links), and should be aware of the risks of enabling configuration of which labels are used on hops within an LSP.¶

The ietf-te-mpls-topology model presented in this document defines technology-specific objects to describe an MPLS-TE topology. It is intended as an aumentation of the te-topology model [RFC8795] and so the core security considerations for that model also apply. In addition, this model defines objects that could expose information about the network behavior or which, if modified by an attacker could disrupt the delivery of services in the network.¶

The leaf objects defined in ietf-te-mpls-topology are read-only so the risk is from unauthorized access to the information, or from misrepresenting the information reported from the network elements. The objects are:¶

"tet:te-topology/tet-pkt:packet": Unauthorized read access to this simply indicates that the network topology is MPLS-TE packet-capable: that information is not very valuable to an attacker. Modification of this information might cause a path computation element to incorrectly presume that a network is capable or incapable of supporting MPLS-TE services.¶

"tet-pkt:packet/tet-mpls:mpls-topology/load-balancing-type": Unauthorized read access to this indicates the mechanism used by a nework node to share traffic across members of a LAG or bundled MPLS-TE link. Such knowledge might help an attacker predict which component link is carrying specific traffic making a physical attack slightly easier. Modification of this information might cause a path computation element to incorrectly presume that a link is suitable or unsuitable for use to provide an MPLS-TP service.¶

"tet-pkt:packet/tet-mpls:mpls-topology/uhp-incapable": Unauthorized read access to this will give an attacker knowledge about whether PHP is being applied on the final hop of all LSPs to a particular node on the associated link: that information is of little use to an attacker except it may help them to parse an inflight packet. Modification of this information would cause a path computation element to incorrectly consider the associated link as suitable or unsuitable for inclusion in the path of an MPLS-TP service.¶

7. IANA Considerations

This document requests IANA to register the following URIs in the "ns" subregistry within the "IETF XML Registry" [RFC3688]. Following the format in [RFC3688], the following registrations are requested.¶

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

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

This document requests IANA to register the following YANG modules in the "IANA Module Names" [RFC6020]. Following the format in [RFC6020], the following registrations are requested:¶

      name:      ietf-mpls-te-types
      namespace: urn:ietf:params:xml:ns:yang:ietf-mpls-te-types
      prefix:    mpls-te-types
      reference: RFC XXXX

      name:      ietf-te-mpls-topology
      namespace: urn:ietf:params:xml:ns:yang:ietf-te-mpls-topology
      prefix:    tet-mpls
      reference: RFC XXXX

RFC Editor: Please replace XXXX with the RFC number assigned to this document.¶

Acknowledgments

We thank Loa Andersson for providing useful suggestions for this draft.¶

This document was prepared using kramdown.¶

Previous versions of this document was prepared using 2-Word-v2.0.template.dot.¶

Contributors

Authors' Addresses