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OPSAWG                                          O. Gonzalez de Dios, Ed.
Internet-Draft                                                S. Barguil
Intended status: Standards Track                              Telefonica
Expires: October 4, 2020                                           Q. Wu
                                                                  Huawei
                                                            M. Boucadair
                                                                  Orange
                                                           April 2, 2020


        A YANG Model for User-Network Interface (UNI) Topologies
                  draft-ogondio-opsawg-uni-topology-01

Abstract

   This document defines a YANG data model for representing an abstract
   view of the Service Provider network topology containing the points
   from which its services can be attached (e.g., basic connectivity,
   VPN, SDWAN).  The data model augments the 'ietf-network' data model
   by adding the concept of service-attachment-points.  The service-
   attachment-points are an abstraction of the points to which network
   services (such as L3 VPN or L2 VPN) can be attached.

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 October 4, 2020.

Copyright Notice

   Copyright (c) 2020 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



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   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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  UNI Topology Model Usage  . . . . . . . . . . . . . . . . . .   4
   3.  YANG Module Structure Details . . . . . . . . . . . . . . . .   5
   4.  YANG module . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The User-Network Interface (UNI) is an important architectural
   concept in many implementations and deployments of services such as
   VPNs or managed VoIP services.

   This document defines a YANG data model for representing, managing
   and controlling the User Network Interface (UNI) topology.  The data
   model augments the 'ietf-network' module [RFC8345] by adding the
   concept of service attachment points.  The service attachment points
   are abstraction of the points where network services such as L3 VPNs
   or L2 VPNs can be attached.

   This document does not make any assumption about the service provided
   by the network to the users.  VPN service is used for illustration
   purposes.

   In the context of Software-Defined Networking (SDN) [RFC7149]
   [RFC7426], the defined YANG data model in this document can be used
   to exchange information between control elements, so as to support
   VPN service provision and resource management discussed in
   [I-D.ietf-opsawg-l3sm-l3nm].  Through this data model, the service
   orchestration layer can learn the capability and available
   endpoint(s) of interconnection resource of the underlying network.



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   The service orchestration layer can determine which endpoint of
   interconnection to add to L2VPN or L3VPN service.  With the help of
   other data models (e.g., L3SM model [RFC8299] and L3NM model) and
   mechanism, hierarchical control elements could determine the
   feasibility of an end-to-end path and to derive the sequence of
   domains and the points of interconnection to use.

   This document explains the scope and purpose of a uni topology model
   and its relation with the service models and describes how it can be
   used by a network operator.  The document also shows how the topology
   and service models fit together.

   The YANG data model in this document conforms to the Network
   Management Datastore Architecture (NMDA) [RFC8342].

1.1.  Terminology

   This document assumes that the reader is familiar with the contents
   of [RFC6241], [RFC7950] and [RFC8309].  The document uses
   terminologies from those documents.  Tree diagrams used in this
   document follow the notation defined in [RFC8340].

   This document uses the following terms:

   Service Provider (SP):   The organization (usually a commercial
      undertaking) responsible for operating the network that offers a
      service (e.g. a VPN) to customers.

   Customer Edge (CE):   An equipment that is dedicated to a particular
      customer and is directly connected to one or more PE devices via
      attachment circuits.  A CE is usually located at the customer
      premises, and is usually dedicated to a single service (e.g VPN),
      although it may support multiple VPNs if each one has separate
      attachment circuits.  A CE device can be a router, bridge, switch,
      etc.

   Provider Edge (PE):  An equipment owned and managed by the SP that
      can support multiple services (e.g.  VPNs) for different
      customers, and is directly connected to one or more CE devices via
      attachment circuits.  A PE is usually located at an SP point of
      presence (PoP).

   Attachment point(AP):  Describe a service's end point characteristics
      and its reference to a Termination Point (TP) of the Provider Edge
      (PE) Node; used as service access point for VPN service, for
      example.





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1.2.  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.  UNI Topology Model Usage

   Management operations of a service provider network can be automated
   using a variety of means such as interfaces based on YANG modules.
   Considering the architecture depicted in Figure 1, the goal is to be
   able to show via a YANG-based interface an abstracted network view
   from the network controller to the service orchestration layer.

                            +---------------+
                            |   Customer    |
                            +---------------+
            Customer Service Models |
                                    |
                            +-----------------+
                            |    Service      |
                            |  Orchestration  |
                            +-----------------+
            Service Network Models | | UNI Topology Model
                                   | |
                            +-----------------+
                            |     Network     |
                            |   Controller    |
                            +-------|----------+
                                    |
            +------------------------------------------------+
                                  Network

                                 Figure 1

   The service orchestration layer does not need to know about the
   internals of the network.  Hence, the abstraction's need is to be
   able to get the set of nodes, and the attachment points associated
   with the nodes from which network services can be grafted
   (delivered).  Let us consider the example of a typical Service
   Provider network (Figure 2), with PE and P nodes.  The Service
   orchestration layer would see a set of PEs, and a set of client-
   facing ports to which CEs can be connected (or are actually
   connected).  Service orchestration layer will have also access to a
   set of Customer Service Model, e.g., a L3SM or L2SM data model in the
   customer-facing interface and a set of Network models, e.g., L3NM and



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   Network topology data models.  In this use case, it is assumed that
   the network controller is unaware of what happens beyond the PEs
   towards the CEs; it is only responsible for the management and
   control of the network between PEs.

                      *---|-|---*         *---|-|---*
                     -|   PE    |        -|   PE    |-
                      *----|----*         *----|----*
                                 \       /
                                *----|----*
                                |    P    |
                                *----|----*
                                 /        \
                      *----|----*         *----|----*
                     -|   PE    |         |   PE    |-
                      *---|-|---*         *-|-|-|-|-*

                                 Figure 2

   How the abstracted view of the network controller can look like is
   depicted in Figure 3.

                      +---|-|---+         +---|-|---+
                     -|   PE    |---------|   PE    |-
                      +----|----+         +----|----+
                           |                   |
                      +----|----+         +----|----+
                     -|   PE    |---------|   PE    |-
                      +---|-|---+         +-|-|-|-|-+

                                 Figure 3

3.  YANG Module Structure Details

   The abstract (base) network data model is defined in the 'ietf-
   network' module of [RFC8345].

   The UNI-topology builds on the network data model defined in the
   'ietf-network' module [RFC8345], augmenting the nodes with service-
   attachment points, which anchor the links and are contained in nodes.
   The structure of the 'ietf-uni-topology' module is shown in Figure 4.










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   module: ietf-uni-topology
     augment /nw:networks/nw:network/nw:node:
       +--rw service-attachment-point* [attachment-id]
          +--rw attachment-id         nt:tp-id
          +--rw type?                 identityref
          +--rw admin-status?         boolean
          +--rw oper-status?          boolean
          +--rw encapsulation-type?   string

                                 Figure 4

4.  YANG module

   This module imports types from [RFC8343] and [RFC8345].

   <CODE BEGINS>  file "ietf-uni-topology@2020-04-02.yang"
   module ietf-uni-topology {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-uni-topology";
     prefix uni;

     import ietf-interfaces {
       prefix if;
       reference
         "RFC 8343: A YANG Data Model for Interface Management";
     }
     import ietf-network-topology {
       prefix nt;
       reference
         "Section 6.2 of RFC 8345: A YANG Data Model for Network
           Topologies";
     }
     import ietf-network {
       prefix nw;
       reference
         "Section 6.1 of RFC 8345: A YANG Data Model for Network
             Topologies";
     }

     organization
       "IETF OPSA (Operations and Management Area) Working Group ";
     contact
      "   Editor:    Oscar Gonzalez de Dios
                    <mailto:oscar.gonzalezdedios@telefonica.com>
          Editor:   Samier Barguil
                    <mailto:alejandro.aguado_martin@nokia.com>
          Editor:    Qin Wu
                    <mailto:victor.lopezalvarez@telefonica.com>



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          Editor:   Mohamed Boucadair
                    <mailto:daniel.voyer@bell.ca>
      ";
     description
       "This YANG module defines a model for representing, managing
        and controlling the User Network Interface (UNI) topology.
        Copyright (c) 2020 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 Simplified 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
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.";

     revision 2020-04-02 {
       description
         "Initial version";
       reference
         "RFC XXXX: A YANG Model for User-Network Interface (UNI)
                    Topologies";
     }

     grouping uni-information-group {
       description
         "User-Network Interface Information";
       list service-attachment-point {
         key "attachment-id";
         description
           "The service attachment points are abstraction of
            the points where network services such as L3 VPNs
            or L2 VPNs can be attached.";
         leaf attachment-id {
           type nt:tp-id;
           description
             "Name of the interface";
         }
         leaf type {
           type identityref {
             base if:interface-type;
           }
           config false;
           description



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             "The type of the interface.";
           reference
             "RFC 8343: A YANG Data Model for Interface Management";
         }
         leaf admin-status {
           type boolean;
           description
             "Administrative Status UP/DOWN";
         }
         leaf oper-status {
           type boolean;
           description
             "Operational Status UP/DOWN";
         }
         leaf encapsulation-type {
           type string;
           description
             "Encapsulation type.  By default, the
              encapsulation type is set to 'untagged'.";
         }
       }
     }

     augment "/nw:networks/nw:network/nw:network-types" {
       description
         "Introduces new network type for UNI Unicast topology";
       container uni-topology {
         presence "indicates UNI Unicast topology";
         description
           "The presence of the container node indicates UNI
            topology";
       }
     }

     augment "/nw:networks/nw:network/nw:node" {
       description
         "Parameters for the service edge point level.";
       uses uni-information-group;
     }
   }
   <CODE ENDS>

                                 Figure 5








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5.  IANA Considerations

   This document registers the following namespace URI in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

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

   This document registers the following YANG module in the YANG Module
   Names registry [RFC6020] within the "YANG Parameters" registry:

    --------------------------------------------------------------------
    name:         ietf-uni-topology
    namespace:    urn:ietf:params:xml:ns:yang:ietf-uni-topology
    maintained by IANA: N
    prefix:       uni
    reference:    RFC XXXX
    --------------------------------------------------------------------

6.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The Configuration Access Control Model (NACM) [RFC8341] provides the
   means to restrict access for particular NETCONF or RESTCONF users to
   a preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   o  /nw:networks/nw:network/nw:node/uni:service-attachment-point/
      uni:attachment-id




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      This subtree specifies the configurations of the nodes in a UNI
      network topology.  Unexpected changes to this subtree could lead
      to service disruption and/or network misbehavior.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   o  /nw:networks/nw:network/nw:node/uni:service-attachment-point

      Unauthorized access to this subtree can disclose the operational
      state information of the nodes in a UNI topology.

7.  Implementation Status

   This section will be used to track the status of the implementations
   of the model.  It is aimed at being removed if the document becomes
   RFC.

8.  Acknowledgements

   Thanks to Adrian Farrell and Daniel King for the suggestions on the
   names.

9.  References

9.1.  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>.

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

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

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.



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   [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>.

   [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>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

   [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>.

9.2.  Informative References

   [I-D.ietf-opsawg-l3sm-l3nm]
              Barguil, S., Dios, O., Boucadair, M., Munoz, L., and A.
              Aguado, "A Layer 3 VPN Network YANG Model", draft-ietf-
              opsawg-l3sm-l3nm-02 (work in progress), March 2020.

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
              <https://www.rfc-editor.org/info/rfc7149>.

   [RFC7426]  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
              Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
              Defined Networking (SDN): Layers and Architecture
              Terminology", RFC 7426, DOI 10.17487/RFC7426, January
              2015, <https://www.rfc-editor.org/info/rfc7426>.




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   [RFC8299]  Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki,
              "YANG Data Model for L3VPN Service Delivery", RFC 8299,
              DOI 10.17487/RFC8299, January 2018,
              <https://www.rfc-editor.org/info/rfc8299>.

   [RFC8309]  Wu, Q., Liu, W., and A. Farrel, "Service Models
              Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
              <https://www.rfc-editor.org/info/rfc8309>.

   [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>.

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

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

Authors' Addresses

   Oscar Gonzalez de Dios (editor)
   Telefonica
   Madrid
   ES

   Email: oscar.gonzalezdedios@telefonica.com


   Samier Barguil
   Telefonica
   Madrid
   ES

   Email: samier.barguilgiraldo.ext@telefonica.com


   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com




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   Mohamed Boucadair
   Orange
   Caen
   France

   Email: mohamed.boucadair@orange.com













































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