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YANG Logical Network Elements

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8530.
Authors Lou Berger , Christian Hopps , Acee Lindem , Dean Bogdanović
Last updated 2017-03-13
Replaces draft-rtgyangdt-rtgwg-lne-model
RFC stream Internet Engineering Task Force (IETF)
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Stream WG state WG Document
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IESG IESG state Became RFC 8530 (Proposed Standard)
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Network Working Group                                          L. Berger
Internet-Draft                                   LabN Consulting, L.L.C.
Intended status: Standards Track                                C. Hopps
Expires: September 14, 2017                             Deutsche Telekom
                                                               A. Lindem
                                                           Cisco Systems
                                                           D. Bogdanovic
                                                          March 13, 2017

                     YANG Logical Network Elements


   This document defines a logical network element module.  This module
   along with the network instance module can be used to manage the
   logical and virtual resource representations that may be present on a
   network device.  Examples of common industry terms for logical
   resource representations are Logical Systems or Logical Routers.
   Examples of of common industry terms for virtual resource
   representations are Virtual Routing and Forwarding (VRF) instances
   and Virtual Switch Instances (VSIs).

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

   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 September 14, 2017.

Copyright Notice

   Copyright (c) 2017 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

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   ( 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 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.  Status of Work and Open Issues  . . . . . . . . . . . . .   3
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Logical Network Elements  . . . . . . . . . . . . . . . . . .   6
     3.1.  LNE Management - Host Network Device View . . . . . . . .   6
     3.2.  LNE Management - LNE View . . . . . . . . . . . . . . . .   8
     3.3.  LNE Instantiation . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Logical Network Element Model . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  12
   Appendix B.  Contributors . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   This document defines a YANG [RFC6020] module to support the creation
   of logical network elements on a network device.  A logical network
   element (LNE) is an independently managed virtual device made up of
   resources allocated to it from the host, or parent, network device.
   (An LNE running on a host network device conceptually parallels a
   virtual machine running on a host system.)  Using host-virtualization
   terminology one could refer to an LNE as a "Guest", and the
   containing network-device as the "Host".  While LNEs may be
   implemented via host-virtualization technologies this is not a

   This document also defines the necessary augmentations for allocating
   host resources to a given LNE.  As the interface management model
   [RFC7223] is the only a module that currently defines host resources,
   this document currently defines only a single augmentation to cover
   the assignment of interfaces to an LNE.

   As each LNE is an independently managed device, each will have its
   own set of YANG modeled data that is independent of the host device

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   and other LNEs.  For example, multiple LNEs may all have their own
   "Tunnel0" interface defined which will not conflict with each other
   and will not exist in the host's interface model.  An LNE will have
   it's own management interfaces possibly including independent
   instances of netconf/restconf/etc servers to support configuration of
   their YANG models.  As an example of this independence, an
   implementation may choose to completely rename assigned interfaces,
   so on the host the assigned interface might be called "Ethernet0/1"
   while within the LNE it might be called "eth1".

   In addition to standard management interfaces, a host device
   implementation may support accessing LNE configuration and
   operational YANG models directly from the host system.  When
   supported, such access is accomplished through a yang-schema-mount
   mount point [I-D.ietf-netmod-schema-mount] under which the root level
   LNE YANG models may be accessed.

   Examples of vendor terminology for an LNE include logical system or
   logical router, and virtual switch, chassis, or fabric.

   This document was motivated by, and derived from,

1.1.  Status of Work and Open Issues

   The top open issues are:

   1.  This document will need to match the evolution and
       standardization of [I-D.openconfig-netmod-opstate] or
       [I-D.ietf-netmod-opstate-reqs] by the Netmod WG.

   It will also make use of emerging YANG functionality supported by
   YANG Schema Mount.

2.  Overview

   In this document, we consider network devices that support protocols
   and functions defined within the IETF Routing Area, e.g, routers,
   firewalls and hosts.  Such devices may be physical or virtual, e.g.,
   a classic router with custom hardware or one residing within a
   server-based virtual machine implementing a virtual network function
   (VNF).  Each device may sub-divide their resources into logical
   network elements (LNEs) each of which provides a managed logical
   device.  Examples of vendor terminology for an LNE include logical
   system or logical router, and virtual switch, chassis, or fabric.
   Each LNE may also support virtual routing and forwarding (VRF) and
   virtual switching instance (VSI) functions, which are referred to

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   below as a network instances (NIs).  This breakdown is represented in
   Figure 1.

              |      Network Device (Physical or Virtual)     |
              | .....................   ..................... |
              | :  Logical Network  :   :  Logical Network  : |
              | :      Element      :   :      Element      : |
              | :+-----+-----+-----+:   :+-----+-----+-----+: |
              | :| Net | Net | Net |:   :| Net | Net | Net |: |
              | :|Inst.|Inst.|Inst.|:   :|Inst.|Inst.|Inst.|: |
              | :+-----+-----+-----+:   :+-----+-----+-----+: |
              | :  | |   | |   | |  :   :  | |   | |   | |  : |
              | :..|.|...|.|...|.|..:   :..|.|...|.|...|.|..: |
              |    | |   | |   | |         | |   | |   | |    |
                   | |   | |   | |         | |   | |   | |
                      Interfaces              Interfaces

   Figure 1: Module Element Relationships

   A model for LNEs is described in Section 3 and the model for network
   instances is covered in [I-D.ietf-rtgwg-ni-model].  For more
   information on how these models may be used within an overall device
   model structure, see [I-D.ietf-rtgwg-device-model].

   The interface management model [RFC7223] is and existing model that
   is impacted by the definition of LNEs and network instances.  This
   document and [I-D.ietf-rtgwg-ni-model] define augmentations to the
   interface module to support LNEs and NIs.  Similar elements, although
   perhaps only for LNEs, may also need to be included as part of the
   definition of the future hardware and QoS modules.

   Interfaces are a crucial part of any network device's configuration
   and operational state.  They generally include a combination of raw
   physical interfaces, link-layer interfaces, addressing configuration,
   and logical interfaces that may not be tied to any physical
   interface.  Several system services, and layer 2 and layer 3
   protocols may also associate configuration or operational state data
   with different types of interfaces (these relationships are not shown
   for simplicity).  The interface management model is defined by

   The logical-network-element and network-instance modules augment the
   existing interface management model in two ways: The first, by the
   logical-network-element module, adds an identifier which is used on
   physical interface types to identify an associated LNE.  The second,

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   by the network-instance module, adds a name which is used on
   interface or sub-interface types to identify an associated network
   instance.  Similarly, this name is also added for IPv4 and IPv6
   types, as defined in [RFC7277].

   The interface related augmentations are as follows:

       module: ietf-logical-network-element
       augment /if:interfaces/if:interface:
          +--rw bind-lne-name?   string

       augment /if:interfaces/if:interface:
          +--rw bind-network-instance-name?   string
       augment /if:interfaces/if:interface/ip:ipv4:
          +--rw bind-network-instance-name?   string
       augment /if:interfaces/if:interface/ip:ipv6:
          +--rw bind-network-instance-name?   string

   The following is an example of envisioned combined usage.  The
   interfaces container includes a number of commonly used components as

             +--rw interfaces
             |  +--rw interface* [name]
             |     +--rw name                       string
             |     +--rw lne:bind-lne-name?         string
             |     +--rw ethernet
             |     |  +--rw ni:bind-network-instance-name? string
             |     |  +--rw aggregates
             |     |  +--rw rstp
             |     |  +--rw lldp
             |     |  +--rw ptp
             |     +--rw vlans
             |     +--rw tunnels
             |     +--rw ipv4
             |     |  +--rw ni:bind-network-instance-name? string
             |     |  +--rw arp
             |     |  +--rw icmp
             |     |  +--rw vrrp
             |     |  +--rw dhcp-client
             |     +--rw ipv6
             |        +--rw ni:bind-network-instance-name? string
             |        +--rw vrrp
             |        +--rw icmpv6
             |        +--rw nd
             |        +--rw dhcpv6-client

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   The [RFC7223] defined interface model is structured to include all
   interfaces in a flat list, without regard to logical or virtual
   instances (e.g., VRFs) supported on the device.  The bind-lne-name
   and bind-network-instance-name leaves provide the association between
   an interface and its associated LNE and NI (e.g., VRF or VSI).

3.  Logical Network Elements

   Logical network elements represent the capability of some devices to
   partition resources into independent logical routers and/or switches.
   Device support for multiple logical network elements is
   implementation specific.  Systems without such capabilities need not
   include support for the logical-network-element module.  In physical
   devices, some hardware features are shared across partitions, but
   control plane (e.g., routing) protocol instances, tables, and
   configuration are managed separately.  For example, in virtual
   routers or VNFs, this may correspond to establishing multiple logical
   instances using a single software installation.  The model supports
   configuration of multiple instances on a single device by creating a
   list of logical network elements, each with their own configuration
   and operational state related to routing and switching protocols, as
   shown below:

       module: ietf-logical-network-element
          +--rw logical-network-inventory
             +--rw logical-network-element* [name]
                +--rw name?   string
                +--rw description? string
                +--rw managed?     boolean
                +--rw root?        yang-schema-mount
       augment /if:interfaces/if:interface:
          +--rw bind-lne-name?     string

   `name` identifies the logical network element.  `managed` indicates
   if the host network device is able to manage the LNE via the `root`

3.1.  LNE Management - Host Network Device View

   There are multiple implementation approaches possible to enable a
   network device to support the logical-network-element module and
   multiple LNEs.  Some approaches will allow the management functions
   operating at network device level to access LNE configuration and
   operation information, while others will not.  Similarly, even when
   LNE management from the network device is supported by the
   implementation, it may be prohibited by user policy.

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   The `managed` boolean mentioned above is used to indicate when LNE
   management from the network device context is possible.  When the
   `managed` boolean is `false`, the LNE cannot be managed by the host
   system and can only be managed from within the context of the LNE as
   described in the next section, Section 3.2.

   When the `managed` boolean is `true`, the LNE can be managed from
   both the context of the LNE and the host network device.  In this
   case, the same information that is available from within the LNE
   context is made available via the `root` element, with paths modified
   as described in [I-D.ietf-netmod-schema-mount].

   As an example, consider the case where an LNE with a `name` of "one"
   is defined on a network device.  In this case the following structure
   might be made available:

                                                  (network-device state)

 +--rw yanglib:modules-state        [RFC7895]
 +--rw lne:logical-network-elements [This document]
     +--rw logical-network-element* [name]
         +--rw name="one"           string
         +--rw manged=true          boolean
         +--rw root                 yang-schema-mount
            |                        (exposed LNE state if managed=true)
            +--rw yanglib:modules-state  [RFC7895]
            +--rw if:intefaces           [RFC7223]
            +--rw hardware
            +--rw qos
            +--rw system-management
            +--rw network-services
            +--rw oam-protocols
            +--rw rt:routing             [I-D.ietf-netmod-routing-cfg]
            +--rw mpls
            +--rw ieee-dot1Q
            +--rw ni:network-instances   [I-D.ietf-rtgwg-ni-model]

   As an LNE is a network device itself, all modules that may be present
   at the top level network device may also be present for the LNE, be
   made available under `root`, and be accessible via paths modified per
   [I-D.ietf-netmod-schema-mount].  The list of available modules is
   expected to be implementation dependent.  As is the method used by an
   implementation to support LNEs.

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   Resources assigned to the LNE will be represented in that LNE's
   resource modules. e.g., an LNE's interfaces module will contain the
   interfaces assigned to that LNE from the containing network-device.

3.2.  LNE Management - LNE View

   Management functions operating with the context of an LNE are
   accessed through standard LNE's management interfaces, e.g., NETCONF
   and SNMP.  When accessing an LNE via an LNE's management interface, a
   network-device representation will be presented, but its scope will
   be limited to the specific LNE.  Normal YANG/NETCONF mechanisms,
   together with yang library [RFC7895], can be used to identify the
   available modules.  Each supported module will be presented as a top
   level module.  Only LNE associated resources will be reflected in
   resource related modules, e.g., interfaces, hardware and perhaps QoS.
   From the management perspective, there will be no difference between
   the available LNE view (information) and an a physical network

   Multiple implementation approaches are possible to provide LNE views,
   and these are outside the scope of this document.

3.3.  LNE Instantiation

   Logical network elements may be controlled by clients using existing
   list operations.  When list entries are created, a new LNE is
   instantiated.  The models mounted under an LNE root is expected to be
   dependent on the server implementation.  When a list entry is
   deleted, an existing LNE is destroyed.  For more information see
   [RFC7950] Section 7.8.6.

4.  Security Considerations


5.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688].
   Following the format in RFC 3688, the following registration is
   requested to be made.

        URI: urn:ietf:params:xml:ns:yang:ietf-logical-network-element

        Registrant Contact: The IESG.

        XML: N/A, the requested URI is an XML namespace.

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   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

   name:        ietf-logical-network-element
   namespace:   urn:ietf:params:xml:ns:yang:ietf-logical-network-element
   prefix:      lne
   reference:   RFC XXXX

6.  Logical Network Element Model

   The structure of the model defined in this document is described by
   the YANG module below.

 <CODE BEGINS> file "ietf-logical-network-element@2017-03-13.yang"
 module ietf-logical-network-element {

   yang-version 1.1;

   // namespace
   namespace "urn:ietf:params:xml:ns:yang:ietf-logical-network-element";

   prefix lne;

   // import some basic types
   import ietf-interfaces {
     prefix if;

   import ietf-yang-schema-mount {
     prefix yangmnt;

   // meta
   organization "IETF Routing Area Working Group (rtgwg)";

       "Routing Area Working Group - <>";

     "This module is used to support multiple logical network
      elements on a single physical or virtual system.";

   revision "2017-03-13" {
       "Initial revision.";
     reference "RFC TBD";

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   // feature statements
   feature bind-lne-name {
       "Logical network element to which an interface is bound";

   // top level device definition statements
   container logical-network-elements {
     description "Allows a network device to support multiple logical
                  network element (device) instances";
     list logical-network-element {
       key name;
       description "List of logical network elements";
       leaf name {
         type string;
           "Device-wide unique identifier for the
            logical network element";
       leaf managed {
         type boolean;
           "True if the host can manage the LNE using the root mount
       leaf description {
         type string;
           "Description of the logical network element";
       yangmnt:mount-point root {
             "Root for models supported per logical
              network element.  This mount point will
              typically be of type inline.  It shall
              always contain a yang library instance.";

   // augment statements
   augment "/if:interfaces/if:interface" {
         "Add a node for the identification of the logical network
         element associated with an interface. Applies to interfaces
         that can be assigned on a per logical network element basis.
         A <TBD> error is returned when the interface type cannot be

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     leaf bind-lne-name {
       type string;
         "Logical network element ID to which interface is bound";

   // rpc statements

   // notification statements


7.  References

7.1.  Normative References

              Bjorklund, M. and L. Lhotka, "YANG Schema Mount", draft-
              ietf-netmod-schema-mount-04 (work in progress), March

              Berger, L., Hopps, C., Lindem, A., and D. Bogdanovic,
              "YANG Network Instances", draft-ietf-rtgwg-ni-model-01
              (work in progress), October 2016.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,

   [RFC7277]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 7277, DOI 10.17487/RFC7277, June 2014,

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7.2.  Informative References

              Watsen, K. and T. Nadeau, "Terminology and Requirements
              for Enhanced Handling of Operational State", draft-ietf-
              netmod-opstate-reqs-04 (work in progress), January 2016.

              Lhotka, L. and A. Lindem, "A YANG Data Model for Routing
              Management", draft-ietf-netmod-routing-cfg-25 (work in
              progress), November 2016.

              Lindem, A., Berger, L., Bogdanovic, D., and C. Hopps,
              "Network Device YANG Organizational Models", draft-ietf-
              rtgwg-device-model-01 (work in progress), October 2016.

              Shakir, R., Shaikh, A., and M. Hines, "Consistent Modeling
              of Operational State Data in YANG", draft-openconfig-
              netmod-opstate-01 (work in progress), July 2015.

   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,

Appendix A.  Acknowledgments

   The Routing Area Yang Architecture design team members included Acee
   Lindem, Anees Shaikh, Christian Hopps, Dean Bogdanovic, Lou Berger,
   Qin Wu, Rob Shakir, Stephane Litkowski, and Yan Gang.

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

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Appendix B.  Contributors

   Contributors' Addresses


Authors' Addresses

   Lou Berger
   LabN Consulting, L.L.C.


   Christan Hopps
   Deutsche Telekom


   Acee Lindem
   Cisco Systems
   301 Midenhall Way
   Cary, NC  27513


   Dean Bogdanovic


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