Network Working Group                                            J. Dong
Internet-Draft                                                    X. Wei
Intended status: Standards Track                     Huawei Technologies
Expires: October 24, 2015                                 April 22, January 7, 2016                                    July 6, 2015

            A YANG Data Model for Layer-2 Network Topologies
              draft-ietf-i2rs-yang-l2-network-topology-00
              draft-ietf-i2rs-yang-l2-network-topology-01

Abstract

   This document defines a YANG data model for layer-2 Layer 2 network
   topologies.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 24, 2015. January 7, 2016.

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   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Layer-2 Topology Model  . . . . . . . . . . . . . . . . . . .   2
   3.  Layer-2 Topology Yang Module  . . . . . . . . . . . . . . . .   5   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13  17
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  13  18
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  18
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     6.2.  18
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  13  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14  19

1.  Introduction

   [I-D.medved-i2rs-topology-im] specifies the generic network topology
   information model, and approaches to extend the generic network
   topology information model to specific type of network topologies.
   It also provides the extensions made for Layer-3 unicast IGP, IS-IS
   and OSPF topologies.

   [I-D.ietf-i2rs-yang-network-topo] defines the Yang [RFC6020]
   [RFC6021] data models for generic of the abstract (generic) network topology, L3
   unicast IGP, IS-IS, OSPF and TED which are derived from the
   information model defined in [I-D.medved-i2rs-topology-im].

   Besides the information collected through "live" layer-3 IGP,
   [I-D.amante-i2rs-topology-use-cases] also specifies the collection of network information which is not visible within the Layer 3 IGP's
   LSDB.
   topology.  Such information models can be links, nodes, or properties of those
   links or nodes in lower layers of the network.  The requirements on
   the topology data model in [I-D.medved-i2rs-topology-requirements]
   also include the physical properties associated with the ports/
   interfaces, and information associated augmented with the network element's
   immediately adjacent neighbors. technology-specific
   details to build more specific topology models.

   This document defines the Yang data model for layer-2 Layer 2 network
   topologies by extending augmenting the generic network and network topology
   data model
   defined in [I-D.ietf-i2rs-yang-network-topo]. models with L2 specific topology attributes.

2.  Layer-2 Topology Model

   In order to represent a layer-2 network topology, the generic

   The Layer 2 network topology model needs is designed to be extended generic and
   applicable to contain layer-2 specific
   information.  Module "l2-topology" Layer 2 networks built with different L2 technologies.

   The Layer 2 topology model applies the generic network and network
   topology model models to layer-2 Layer 2 network topologies, and augments the
   generic network topology models with information specific to layer-2 in Layer 2 networks.  The
   relationship between the l2-topology Layer 2 topology model and the generic
   network and network topology model is shown in the figure below:

                           +---------------------+
                           |   network-topology    ietf-network     |
                          +----------+----------+
                                     ^
                           +----------^----------+
                                      |
                                      |
                           +---------------------+
                           |ietf-network-topology|
                           +----------^----------+
                                      |    l2-topology
                                      |
                           +----------^----------+
                           |   ietf-l2-topology  |
                           +---------------------+
                   Figure 1. L2-topology and generic network-topology

   For layer-2 model structure

   In order to represent a Layer 2 network topology, there are some layer-2 specific
   parameters and capabilities to be added to the generic network
   and topology model, models are augmented with Layer-2 specific information,
   such as properties the identifiers, descriptions, attributes and states of layer-2 links or the
   Layer-2 networks, nodes,
   descriptions, layer-2 addresses, encapsulations, etc.  Part links and termination points.  Some of the
   Information
   information may be collected through LLDP could via Link Layer Discovery Protocl (LLDP)
   or other Layer-2 protocols, and some of them may be included in the layer-2
   network topology. locally
   configured.

   The structure of "L2-topology" "ietf-l2-topology" data model is depicted in the
   following diagram.  Brackets enclose list keys, "rw" means
   configuration data, "ro" means operational state data, "?" designates
   optional nodes, "*" designates nodes that can have multiple
   instances.

   module: ietf-l2-topology
   augment /nt:network/nt:network-types: /nw:network/nw:network-types:
      +--rw l2-network!
   augment /nt:network: /nw:network:
      +--rw l2-network-attributes
         +--rw name?   string
         +--rw flag*   flag-type
   augment /nt:network/nt:node: /nw:network/nw:node:
      +--rw l2-node-attributes
         +--rw name?                 string
         +--rw description?          string
         +--rw chassis-id?           yang:mac-address
         +--rw management-address*   inet:ip-prefix   inet:ip-address
         +--rw management-vid?       vlan {VLAN}?
         +--rw nick-name?            nickname nick-name*            trill-nickname {TRILL}?
         +--rw flag*                 flag-type
   augment /nt:network/ntopo:link: /nw:network/nt:link:
      +--rw l2-link-attributes
         +--rw name?    string
         +--rw flag*    flag-type
         +--rw rate?    decimal64
         +--rw flag*   flag-type delay?   uint32
         +--rw srlg*    uint32
   augment /nt:network/nt:node/ntopo:termination-point: /nw:network/nw:node/nt:termination-point:
      +--rw l2-termination-point-attributes
         +--rw description?          string
         +--rw mac-address?          yang:mac-address maximum-frame-size?   uint32
         +--rw port-vlan-id?         vlan (l2-termination-point-type)?
         |  +--:(ethernet)
         |  |  +--rw mac-address?          yang:mac-address
         |  |  +--rw ppvid eth-encapsulation?    identityref
         |  |  +--rw ppvid? port-vlan-id?         vlan {VLAN}?
         |  |  +--rw ppvid-flags?   bits
         +--rw vlan-name* vlan-id-name* [vlan-id] {VLAN}?
         |  |     +--rw vlan-id      vlan
         |  |     +--rw vlan-name?   string
         |  +--:(legacy)
         |     +--rw encapsulation?        identityref
         +--rw
         +--ro tp-state?             enumeration
   notifications:
      +---n l2-node-event
      |  +--ro event-type?           l2-network-event-type
      |  +--ro network-ref?          leafref
      |  +--ro node-ref?             leafref
      |  +--ro l2-network!
      |  +--ro l2-node-attributes
      |     +--ro name?                 string
      |     +--ro description?          string
      |     +--ro management-address*   inet:ip-prefix
      |     +--ro management-vid?       vlan {VLAN}?
      |     +--ro nick-name*            trill-nickname {TRILL}?
      |     +--ro flag*                 flag-type
      +---n l2-link-event
      |  +--ro event-type?           l2-network-event-type
      |  +--ro network-ref?          leafref
      |  +--ro link-ref?             leafref
      |  +--ro l2-network!
      |  +--ro l2-link-attributes
      |     +--ro name?    string
      |     +--ro flag*    flag-type
      |     +--ro rate?    decimal64
      |     +--ro delay?   uint32
      |     +--ro srlg*    uint32
      +---n l2-termination-point-event
         +--ro event-type?                        l2-network-event-type
         +--ro network-ref?                       leafref
         +--ro node-ref?                          leafref
         +--ro tp-ref?                            leafref
         +--ro l2-network!
         +--ro l2-termination-point-attributes
            +--ro description?          string
            +--ro maximum-frame-size?   uint32
         +--rw link-aggregation
            +--ro (termination-point-type)?
            |  +--rw aggregation-status?   bits  +--:(ethernet)
            |  +--rw aggregated-port-id?  |  +--ro mac-address?          yang:mac-address
            |  |  +--ro eth-encapsulation?    identityref
            |  |  +--ro port-vlan-id?         vlan {VLAN}?
            |  |  +--ro vlan-id-name* [vlan-id] {VLAN}?
            |  |     +--ro vlan-id      vlan
            |  |     +--ro vlan-name?   string
            |  +--:(legacy)
            |     +--ro encapsulation?        identityref
            +--ro tp-state?             enumeration

   The L2-topology module augments the generic ietf-network and ietf-
   network-topology module modules as follows:

   o  A new network type "l2-network-type" is introduced.  This is
      represented by a container object, and is inserted under the
      "network-types" container of the generic network ietf-network module in
      [I-D.ietf-i2rs-yang-network-topo].

   o  Additional network attributes are introduced in a grouping "l2-
      network-attributes", which augments the "network" list of the
      network module in [I-D.ietf-i2rs-yang-network-topo].
      ietf-network module.  The attributes include an Layer-2 network name
      and a set of flags.  Each type of flag is represented by a
      separate identity.

   o  Additional data objects for Layer-2 nodes are introduced by
      augmenting the "node" list of the generic network ietf-network module.
      New objects include a
      series of layer-2 Layer-2 node parameters, as well as identifier, description,
      management address, and a set of flags.

   o  Additional data objects for Layer-2 termination points are
      introduced by augmenting the "termination-point" list of the generic network-
      topology module. ietf-
      network-topology module defined in
      [I-D.ietf-i2rs-yang-network-topo].  New objects include a series of port properties Layer-2
      termination point descriptions, Layer-2 termination point type
      specific attributes and parameters. Layer-2 termination point states.

   o  Links in the ietf-network-topology module are augmented as well
      with a set of Layer-2 parameters, allowing to associate a link
      with an L2 a name, the link rate and another a set of Layer-2 link attributes and flags.

   o  The optional L2 technology specific attributes are introduced in
      this module as Layer-2 features.

3.  Layer-2 Topology Yang Module

   <CODE BEGINS>
   file "ietf-l2-topology@2015-04-22.yang" "ietf-l2-topology@2015-06-23.yang"
   module ietf-l2-topology {
       yang-version 1;
       namespace "urn:ietf:params:xml:ns:yang:ietf-l2-topology";
       prefix "l2t";

       import network ietf-network {
         prefix "nt"; "nw";
       }

       import network-topology ietf-network-topology {
         prefix "ntopo"; "nt";
       }

       import ietf-inet-types {
         prefix "inet";
       }

       import ietf-yang-types {
         prefix "yang";
       }

       organization "TBD";
       contact "I-D Editor: jie.dong@huawei.com";

       description
         "This module defines a basic model for
          the layer-2 topology of a network";

       revision "2015-04-22" "2015-06-23" {
         description "Initial revision";
         reference "draft-ietf-i2rs-yang-l2-network-topology-00"; "draft-ietf-i2rs-l2-network-topology-01";
       }

      /*
       * Typedefs
       */

       typedef vlan {
        description "VLAN ID";
         type uint16 {
           range "0..4095";
         }
         description "VLAN ID";
       }
       typedef nickname trill-nickname {
         type uint16;
         description "TRILL Nickname";
        type uint16;
       }

       typedef flag-type {
         type identityref {
           base "flag-identity";
         }
    }

    /*
    * Features
    */

    feature QinQ {
         description
          "Indicates that the system supports the qinq functions"; "Base type for flags";
       }

    feature PBB

       typedef l2-network-event-type {
         type enumeration {
           enum "add" {
             value 0;
             description
         "Indicates "An L2 node or link or termination-point
             has been added";
           }
           enum "remove" {
             value 1;
             description "An L2 node or link or termination-point
             has been removed";
           }
           enum "update" {
             value 2;
             description "An L2 node or link or termination-point
             has been updated";
           }
         }
         description "l2 network event type for notifications";
       } // l2-topology-event-type

       /*
       * Features
       */

       feature VLAN {
         description
           "Indicates that the system supports the
            vlan functions";
       }

       feature QinQ {
         description
           "Indicates that the system supports the
            qinq functions";
       }

       feature PBB {
         description
          "Indicates that the device supports the
           provider-backbone-bridging functions";
       }

       feature VPLS {
         description
           "Indicates that the device supports the
            VPLS functions";
         reference "RFC 4761, RFC 4762";
       }

       feature TRILL {
         description
           "Indicates that the device supports the
            TRILL functions";
         reference "RFC 6325";
       }

       feature VXLAN {
         description
           "Indicates that the device supports the
            VXLAN functions";
         reference "RFC 7348";
       }

      /*
       * Identities
       */

       identity flag-identity {
         description "Base type for flags";
       }

       identity encapsulation-type {
         description
           "Base identity from which specific encapsulation
            types are derived.";
       }

       identity ethernet eth-encapsulation-type {
         base encapsulation-type;
         description
           "Base identity from which specific ethernet
            encapsulation types are derived.";

       }

       identity ethernet {
         base eth-encapsulation-type;
         description
           "native ethernet encapsulation";
       }

       identity vlan {
         base encapsulation-type; eth-encapsulation-type;
         description
           "vlan encapsulation";
       }

       identity qinq {
         base encapsulation-type; eth-encapsulation-type;
         description
           "qinq encapsulation";
       }

       identity pbb {
         base encapsulation-type; eth-encapsulation-type;
         description
           "pbb encapsulation";
       }

       identity trill {
         base encapsulation-type; eth-encapsulation-type;
         description
           "trill encapsulation";
       }

       identity vpls {
         base encapsulation-type; eth-encapsulation-type;
         description
           "vpls encapsulation";
       }

       identity vxlan {
         base encapsulation-type; eth-encapsulation-type;
         description
           "vxlan encapsulation";
       }

       identity frame-relay {
         base encapsulation-type;
         description
           "Frame Relay encapsulation";
       }

       identity ppp {
         base encapsulation-type;
         description
           "PPP encapsulation";
       }

       identity hdlc {
         base encapsulation-type;
         description
           "HDLC encapsulation";
       }

       identity atm {
         base encapsulation-type;
         description
           "Base identity from which specific ATM
            encapsulation types are derived.";

       }

       identity pwe3 {
         base encapsulation-type;
         description
           "Base identity from which specific pw
            encapsulation types are derived.";
       }

      /*
       * Groupings
       */

       grouping l2-network-type {
         description "Identify the topology type to be L2.";
         container l2-network {
           presence "indicates L2 Network";
           description
           "The presence of the container node indicates
            L2 Topology";
         }
       }
       grouping l2-network-attributes {
         description "L2 Topology scope attributes";
         container l2-network-attributes {
           description "Containing L2 network attributes";
           leaf name {
             type string;
             description "Name of the L2 network";
                type string;
           }

           leaf-list flag {
             type flag-type;
             description "L2 network flags";
                type flag-type;
           }
         }
       }

       grouping l2-node-attributes {
         description "L2 node attributes";
         container l2-node-attributes {
           description "Containing L2 node attributes";
           leaf name {
             type string;
             description "Node name";
                type string;
           }
           leaf description {
                description "Node description";
             type string;
            }
            leaf chassis-id {
             description "System MAC address";
                type yang:mac-address; "Node description";
           }
           leaf-list management-address {
             type inet:ip-address;
             description "System management address";
                type inet:ip-prefix;
           }
           leaf management-vid {
             if-feature VLAN;
             type vlan;
             description "System management VID";
                type vlan;
           }

            leaf
           leaf-list nick-name {
             if-feature TRILL;
             type trill-nickname;
             description "Nickname of the RBridge";
                type nickname;
           }
           leaf-list flag {
             type flag-type;
             description "Node operational flags";
                type flag-type;
           }
         }
       }  // grouping l2-node-attributes
       grouping l2-link-attributes {
         description "L2 link attributes";
         container l2-link-attributes {
           description "Containing L2 link attributes";
           leaf name {
             type string;
             description "Link name";
           }
           leaf-list flag {
             type string; flag-type;
             description "Link flags";
           }
           leaf rate {
                description "Link rate";
             type decimal64 {
               fraction-digits 2;
             }
             description "Link rate";

           }
            leaf-list flag
           leaf delay {
             type uint32;
             description "Link flags"; delay in microseconds";
           }
           leaf-list srlg {
             type flag-type; uint32;
             description
               "List of Shared Risk Link Groups
                this link belongs to.";
           }
         }
       } // grouping l2-link-attributes

       grouping l2-termination-point-attributes {
        container l2-termination-point-attributes {
         description "L2 termination point attributes";
         container l2-termination-point-attributes {
           description "Containing L2 TP attributes";
           leaf description {
             type string;
             description "Port description";
           }

           leaf maximum-frame-size {
             type string; uint32;
             description "Maximum frame size";
           }

           choice l2-termination-point-type {
             description
               "Indicates termination-point type
                specific attributes";
             case ethernet {
               leaf mac-address {
                 type yang:mac-address;
                 description "Interface MAC address";
                 type yang:mac-address;
               }

               leaf port-vlan-id eth-encapsulation {
                 description "Port VLAN ID";
                 type vlan;
             }

             container ppvid identityref {
                   base eth-encapsulation-type;
                 }
                 description "Port and protocol VLAN ID";
                 leaf ppvid {
                   "Encapsulation type vlan; of this
                    ternimation point.";
               }

               leaf ppvid-flags port-vlan-id {
                 if-feature VLAN;
                 type bits {
                         bit port-protocol-vlan-supported {
                             position 1;
                         }
                         bit port-protocol-vlan-enabled {
                             position 2;
                         }
                     }
                 } vlan;
                 description "Port VLAN ID";
               }

               list vlan-name vlan-id-name {
                 if-feature VLAN;
                 key "vlan-id";
                 description "Interface configured VLANs";
                 leaf vlan-id {
                   type vlan;
                   description "VLAN ID";
                 }
                 leaf vlan-name {
                   type string;
                   description "VLAN Name";
                 }
               }
             } //case ethernet

             case legacy {
               leaf encapsulation {
                 description "encapsulation type of this termination point.";
                 type identityref {
                   base encapsulation-type;
                 }
             }

             leaf maximum-frame-size {
                 description "interface maximum frame size";
                   "Encapsulation type uint32;
             }

             container link-aggregation {
                 leaf aggregation-status {
                     description "Link aggregation capabilities and status";
                     type bits {
                         bit aggregation-capability {
                             position 0;
                         }
                         bit aggregation-status {
                             position 1;
                         }
                     } of this termination point.";
               }
                 leaf aggregated-port-id {
                     type string;
             } //case legacy

           } //choice termination-point-type

           leaf tp-state {
                 config false;
             type enumeration {
               enum "forwarding" in-use {
                 value 0;
                 description
                   "the termination point is in forwarding state";
               }
               enum "blocking" blocking {
                 value 1;
                 description
                   "the termination point is in blocking state";
               }
               enum "others" down {
                 value 2;
                 description
                   "the termination point is in down state";
               }
               enum others {
                 value 3;
                 description
                   "the termination point is in other state";
               }
             }
             config false;
             description "State of the termination point";
           }
         }
       } // grouping l2-termination-point-attributes

   /*** grouping of network/node/link/tp leaf-refs ***/

     grouping network-ref {
       description
         "Grouping for an absolute reference to a network topology
         instance.";
       leaf network-ref {
         type leafref {
           path "/nw:network/nw:network-id";
         }
         description
           "An absolute reference to a network topology instance.";
       }
     }

     grouping link-ref {
       description
         "Grouping for an absolute reference to a link instance.";
         uses network-ref;
         leaf link-ref {
           type leafref {
             path "/nw:network"
               +"[nw:network-id = current()/../network-ref]"
               +"/nt:link/nt:link-id";
           }
         description
           "An absolute reference to a link instance.";
       }
     }

     grouping node-ref {
       description
         "Grouping for an absolute reference to a node instance.";
       uses network-ref;
       leaf node-ref {
         type leafref {
           path "/nw:network"
             +"[nw:network-id = current()/../network-ref]"
             +"/nw:node/nw:node-id";
         }
         description
           "An absolute reference to a node instance.";
       }
     }

     grouping tp-ref {
       description
         "Grouping for an absolute reference to a termination point.";
       uses node-ref;
       leaf tp-ref {
         type leafref {
           path "/nw:network"
             +"[nw:network-id = current()/../network-ref]"
             +"/nw:node[nw:node-id = current()/../node-ref]"
             +"/nt:termination-point/nt:tp-id";
         }
         description
           "Grouping for an absolute reference to a TP.";
       }
     }

      /*
       * Data nodes
       */
       augment "/nt:network/nt:network-types" "/nw:network/nw:network-types" {
         description
           "Introduce new network type for L2 topology";
         uses l2-network-type;
       }

       augment "/nt:network" "/nw:network" {
         when "nt:network-types/l2-network"; "nw:network-types/l2-network" {
           description
             "Augmentation parameters apply only for networks
              with L2 topology";
         }
         description
           "Configuration parameters for the L2 network
            as a whole";
         uses l2-network-attributes;
       }

       augment "/nt:network/nt:node" "/nw:network/nw:node" {
         when "../nt:network-types/l2-network"; "../nw:network-types/l2-network" {
           description
             "Augmentation parameters apply only for networks
              with L2 topology";
         }
         description
           "Configuration parameters for L2 at the node
            level";
         uses l2-node-attributes;
       }

       augment "/nt:network/ntopo:link" "/nw:network/nt:link" {
         when "/nt:network/nt:network-types/l2-network"; "/nw:network/nw:network-types/l2-network" {
           description
             "Augmentation parameters apply only for networks
              with L2 topology";
         }
         description "Augment L2 topology link information";
         uses l2-link-attributes;
       }

       augment "/nt:network/nt:node/ntopo:termination-point" "/nw:network/nw:node/nt:termination-point" {
         when "/nt:network/nt:network-types/l2-network"; "/nw:network/nw:network-types/l2-network" {
           description
             "Augmentation parameters apply only for networks
              with L2 topology";
         }
         description
           "Augment L2 topology termination point configuration";

         uses l2-termination-point-attributes;
       }

      /*
       * Notifications: to be added Notifications
       */

       notification l2-node-event {
         description "Notification event for L2 node";
         leaf event-type {
           type l2-network-event-type;
           description "Event type";
         }
         uses node-ref;
         uses l2-network-type;
         uses l2-node-attributes;
       }

       notification l2-link-event {
         description "Notification event for L2 link";
         leaf event-type {
           type l2-network-event-type;
           description "Event type";
         }
         uses link-ref;
         uses l2-network-type;
         uses l2-link-attributes;
       }

       notification l2-termination-point-event {
         description "Notification event for L2 termination point";
         leaf event-type {
           type l2-network-event-type;
           description "Event type";
         }
         uses tp-ref;
         uses l2-network-type;
         uses l2-termination-point-attributes;
       }

   }  // module l2-topology
   <CODE ENDS>

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

   TBD

5.  Security Considerations

   The transport protocol used for sending the topology data MUST
   support authentication and SHOULD support encryption.  The data-model
   by itself does not create any security implications.

6.  Acknowledgements

   The authors would like to acknowledge the comments and suggestions
   received from Susan Hares, Alia Atlas, Juergen Schoenwaelder, Mach
   Chen, Alexander Clemm and Sriganesh Kini.

7.  References

6.1.

7.1.  Normative References

   [I-D.ietf-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Varga, R., Tkacik, T., Bahadur, N.,
              and H. Ananthakrishnan, "A Data Model for Network
              Topologies", draft-ietf-i2rs-yang-network-topo-00 draft-ietf-i2rs-yang-network-topo-01 (work in
              progress), April June 2015.

   [I-D.medved-i2rs-topology-im]
              Medved, J., Bahadur, N., Clemm, A., and H.
              Ananthakrishnan, "An Information Model for Network
              Topologies", draft-medved-i2rs-topology-im-01 (work in
              progress), October 2013.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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

   [RFC6021]  Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
              October 2010.

6.2.

7.2.  Informative References

   [I-D.amante-i2rs-topology-use-cases]
              Medved, J., Previdi, S., Lopez, V., and S. Amante,
              "Topology API Use Cases", draft-amante-i2rs-topology-use-
              cases-01 (work in progress), October 2013.

   [I-D.medved-i2rs-topology-requirements]
              Medved, J., Previdi, S., Gredler, H., Nadeau, T., and S.
              Amante, "Topology API Requirements", draft-medved-i2rs-
              topology-requirements-00 (work in progress), February
              2013.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: jie.dong@huawei.com

   Xiugang Wei
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: weixiugang@huawei.com