   module ietf-network {
     yang-version 1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-network";
     prefix nd;

     organization
       "IETF I2RS (Interface to the Routing System) Working Group";

     contact
       "WG Web:    <http://tools.ietf.org/wg/i2rs/>
        WG List:   <mailto:i2rs@ietf.org>

        WG Chair:  Susan Hares
                   <mailto:shares@ndzh.com>

        WG Chair:  Jeffrey Haas
                   <mailto:jhaas@pfrc.org>

        Editor:    Alexander Clemm
                   <mailto:alex@cisco.com>

        Editor:    Jan Medved
                   <mailto:jmedved@cisco.com>

        Editor:    Robert Varga
                   <mailto:rovarga@cisco.com>

        Editor:    Tony Tkacik
                   <mailto:ttkacik@cisco.com>

        Editor:    Nitin Bahadur
                   <mailto:nitin_bahadur@yahoo.com>

        Editor:    Hariharan Ananthakrishnan
                   <mailto:hari@packetdesign.com>";

     description
       "This module defines a common base model for a collection
        of nodes in a network. Node definitions are further used
        in network topologies and inventories.

        Copyright (c) 2015 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
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of
        draft-ietf-i2rs-yang-network-topo-02;
        see the RFC itself for full legal notices.

        NOTE TO RFC EDITOR: Please replace above reference to
        draft-ietf-i2rs-yang-network-topo-02 with RFC
        number when published (i.e. RFC xxxx).";

     revision 2015-12-08 {
       description
         "Initial revision.
          NOTE TO RFC EDITOR: Please replace the following reference
          to draft-ietf-i2rs-yang-network-topo-02 with
          RFC number when published (i.e. RFC xxxx).";
       reference
         "draft-ietf-i2rs-yang-network-topo-02";
     }

     typedef node-id {
       type string;
       description
         "Identifier for a node.";
     }

     typedef network-id {
       type string;
       description
         "Identifier for a network.";
     }
     grouping network-ref {
       description
         "Contains the information necessary to reference a network,
          for example an underlay network.";
       leaf network-ref {
         type leafref {
           path "/nd:networks/nd:network/nd:network-id";
         require-instance false;
         }
         description
           "Used to reference a network, for example an underlay
            network.";
       }
     }

     grouping node-ref {
       description
         "Contains the information necessary to reference a node.";
       leaf node-ref {
         type leafref {
           path "/nd:networks/nd:network[nd:network-id=current()/../"+
             "network-ref]/nd:node/nd:node-id";
           require-instance false;
         }
         description
           "Used to reference a node.
            Nodes are identified relative to the network they are
            contained in.";
       }
       uses network-ref;
     }

     container networks {
       description
         "Serves as top-level container for a list of networks.";
       list network {
         key "network-id";
         description
           "Describes a network.
            A network typically contains an inventory of nodes,
            topological information (augmented through
            network-topology model), as well as layering
            information.";
         container network-types {
           description
             "Serves as an augmentation target.
              The network type is indicated through corresponding
              presence containers augmented into this container.";
         }
         leaf network-id {
           type network-id;
           description
             "Identifies a network.";
         }
         list supporting-network {
           key "network-ref";
           description
             "An underlay network, used to represent layered network
              topologies.";
           leaf network-ref {
             type leafref {
               path "/networks/network/network-id";
             require-instance false;
             }
             description
               "References the underlay network.";
           }
         }
         list node {
           key "node-id";
           description
             "The inventory of nodes of this network.";
           leaf node-id {
             type node-id;
             description
               "Identifies a node uniquely within the containing
                network.";
           }
           list supporting-node {
             key "network-ref node-ref";
             description
               "Represents another node, in an underlay network, that
                this node is supported by.  Used to represent layering
                structure.";
             leaf network-ref {
               type leafref {
                 path "../../../supporting-network/network-ref";
               require-instance false;
               }
               description
                 "References the underlay network that the
                  underlay node is part of.";
             }
             leaf node-ref {
               type leafref {
                 path "/networks/network/node/node-id";
               require-instance false;
               }
               description
                 "References the underlay node itself.";
             }
           }
         }
       }
     }
     container networks-state {
       config false;
       description
         "Serves as top-level container for a list of state information
          for networks";
       list network {
         key "network-ref";
         description
           "Data nodes representing operational data and state of
            networks.
            An instance is automatically created for every network
            in the corresponding list under the networks container.";
         uses network-ref;
         leaf server-provided {
           type boolean;
           description
             "Indicates whether the information concerning this
              particular network is populated by the server
              (server-provided true, the general case for network
              information discovered from the server),
              or whether it is configured by a client
              (server-provided true, possible e.g. for
              service overlays managed through a controller).";
         }
       }
     }
   }