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Versions: (RFC 7223) 00 draft-ietf-netmod-rfc7223bis

Network Working Group                                       M. Bjorklund
Internet-Draft                                            Tail-f Systems
Obsoletes: rfc7223 (if approved)                         August 21, 2017
Intended status: Standards Track
Expires: February 22, 2018


               A YANG Data Model for Interface Management
                  draft-bjorklund-netmod-rfc7223bis-00

Abstract

   This document defines a YANG data model for the management of network
   interfaces.  It is expected that interface-type-specific data models
   augment the generic interfaces data model defined in this document.
   The data model includes definitions for configuration and system
   state (status information and counters for the collection of
   statistics).  This document obsoletes RFC 7223.

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 http://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 February 22, 2018.

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
   (http://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 Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Summary of Changes from RFC 7223  . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Interfaces Data Model . . . . . . . . . . . . . . . . . . . .   5
     3.1.  The Interface List  . . . . . . . . . . . . . . . . . . .   6
     3.2.  Interface References  . . . . . . . . . . . . . . . . . .   8
     3.3.  Interface Layering  . . . . . . . . . . . . . . . . . . .   8
   4.  Relationship to the IF-MIB  . . . . . . . . . . . . . . . . .   9
   5.  Interfaces YANG Module  . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  34
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  35
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  35
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  35
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  35
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  36
   Appendix A.  Example: Ethernet Interface Module . . . . . . . . .  36
   Appendix B.  Example: Ethernet Bonding Interface Module . . . . .  38
   Appendix C.  Example: VLAN Interface Module . . . . . . . . . . .  39
   Appendix D.  Example: NETCONF <get-config> Reply  . . . . . . . .  40
   Appendix E.  Example: NETCONF <get-data> Reply  . . . . . . . . .  41
   Appendix F.  Examples: Interface Naming Schemes . . . . . . . . .  43
     F.1.  Router with Restricted Interface Names  . . . . . . . . .  43
     F.2.  Router with Arbitrary Interface Names . . . . . . . . . .  44
     F.3.  Ethernet Switch with Restricted Interface Names . . . . .  45
     F.4.  Generic Host with Restricted Interface Names  . . . . . .  45
     F.5.  Generic Host with Arbitrary Interface Names . . . . . . .  46
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  47

1.  Introduction

   This document defines a YANG [RFC7950] data model for the management
   of network interfaces.  It is expected that interface-type-specific
   data models augment the generic interfaces data model defined in this
   document.

   Network interfaces are central to the management of many Internet
   protocols.  Thus, it is important to establish a common data model
   for how interfaces are identified, configured, and monitored.

   The data model includes configuration data and state data (status
   information and counters for the collection of statistics).



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   This version of the interfaces data model supports the Network
   Management Datastore Architecture (NMDA)
   [I-D.ietf-netmod-revised-datastores].

1.1.  Summary of Changes from RFC 7223

   The "/interfaces-state" subtree with "config false" data nodes is
   deprecated.  All "config false" data nodes are now present in the
   "/interfaces" subtree.

   Servers that do not implement NMDA, or that wish to support clients
   that do not implement NMDA, MAY implement the deprecated
   "/interfaces-state" tree.

1.2.  Terminology

   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].

   The following terms are used within this document:

   o  system-controlled interface: An interface is said to be system-
      controlled if the system creates and deletes the interface
      independently of what has been explicitly configured.  Examples
      are interfaces representing physical hardware that appear and
      disappear when hardware (e.g., a line card or hot-pluggable
      wireless interface) is added or removed.  System-controlled
      interfaces may also appear if a certain functionality is enabled
      (e.g., a loopback interface might appear if the IP protocol stack
      is enabled).

   o  user-controlled interface: An interface is said to be user-
      controlled if the creation of the interface is controlled by
      adding explicit interface configuration to the running
      configuration datastore and the removal of the interface is
      controlled by removing explicit interface configuration from the
      running configuration datastore.  Examples are VLAN interfaces
      configured on a system-controlled Ethernet interface.

   The following terms are defined in
   [I-D.ietf-netmod-revised-datastores] and are not redefined here:

   o  client

   o  server




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   o  configuration

   o  system state

   o  operational state datastore

   o  running configuration datastore

   o  startup configuration datastore

   The following terms are defined in [RFC7950] and are not redefined
   here:

   o  augment

   o  data model

   o  data node

   o  presence container

1.3.  Tree Diagrams

   A simplified graphical representation of the data model is used in
   this document.  The meaning of the symbols in these diagrams is as
   follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Abbreviations before data node names: "rw" means configuration
      (read-write), and "ro" means state data (read-only).

   o  Symbols after data node names: "?" means an optional node, "!"
      means a presence container, and "*" denotes either a list or a
      leaf-list.

   o  Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

   o  Ellipsis ("...") stands for contents of subtrees that are not
      shown.

2.  Objectives

   This section describes some of the design objectives for the model
   presented in Section 5.





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   o  It is recognized that existing implementations will have to map
      the interface data model defined in this memo to their proprietary
      native data model.  To facilitate such mappings, the data model
      should be simple.

   o  The data model should be suitable for new implementations to use
      as is, without requiring a mapping to a different native model.

   o  References to interfaces should be as simple as possible,
      preferably by using a single leafref.

   o  The mapping to ifIndex [RFC2863] used by the Simple Network
      Management Protocol (SNMP) to identify interfaces must be clear.

   o  The model must support interface layering: both (1) simple
      layering, where one interface is layered on top of exactly one
      other interface, and (2) more complex scenarios, where one
      interface results from the aggregation of N other interfaces or
      when N interfaces are multiplexed over one other interface.

   o  The data model should support the pre-provisioning of interface
      configuration, i.e., it should be possible to configure an
      interface whose physical interface hardware is not present on the
      device.  It is recommended that devices that support dynamic
      addition and removal of physical interfaces also support pre-
      provisioning.

   o  The data model should support physical interfaces as well as
      logical interfaces.

   o  The data model should include read-only counters in order to
      gather statistics for sent and received octets and packets,
      received packets with errors, and packets that could not be sent
      due to errors.

3.  Interfaces Data Model

   This document defines the YANG module "ietf-interfaces", which has
   the following structure, excluding the deprecated "/interfaces-state"
   subtree:











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   module: ietf-interfaces
       +--rw interfaces
          +--rw interface* [name]
             +--rw name                        string
             +--rw description?                string
             +--rw type                        identityref
             +--rw enabled?                    boolean
             +--rw link-up-down-trap-enable?   enumeration {if-mib}?
             +--ro admin-status                enumeration {if-mib}?
             +--ro oper-status                 enumeration
             +--ro last-change?                yang:date-and-time
             +--ro if-index                    int32 {if-mib}?
             +--ro phys-address?               yang:phys-address
             +--ro higher-layer-if*            interface-ref
             +--ro lower-layer-if*             interface-ref
             +--ro speed?                      yang:gauge64
             +--ro statistics
                +--ro discontinuity-time    yang:date-and-time
                +--ro in-octets?            yang:counter64
                +--ro in-unicast-pkts?      yang:counter64
                +--ro in-broadcast-pkts?    yang:counter64
                +--ro in-multicast-pkts?    yang:counter64
                +--ro in-discards?          yang:counter32
                +--ro in-errors?            yang:counter32
                +--ro in-unknown-protos?    yang:counter32
                +--ro out-octets?           yang:counter64
                +--ro out-unicast-pkts?     yang:counter64
                +--ro out-broadcast-pkts?   yang:counter64
                +--ro out-multicast-pkts?   yang:counter64
                +--ro out-discards?         yang:counter32
                +--ro out-errors?           yang:counter32

3.1.  The Interface List

   The data model for interfaces presented in this document uses a flat
   list of interfaces ("/interfaces/interface").  Each interface in the
   list is identified by its name.  Furthermore, each interface has a
   mandatory "type" leaf.

   The "iana-if-type" module [RFC7224] defines YANG identities for the
   interface types in the IANA-maintained "ifType definitions" registry.

   It is expected that interface-type-specific data models augment the
   interface list and possibly use the "type" leaf to make the
   augmentation conditional.






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   As an example of such an interface-type-specific augmentation,
   consider this YANG snippet.  For a more complete example, see
   Appendix A.

     import interfaces {
         prefix "if";
     }
     import iana-if-type {
       prefix ianaift;
     }

     augment "/if:interfaces/if:interface" {
         when "if:type = 'ianaift:ethernetCsmacd'";

         container ethernet {
             leaf duplex {
                 ...
             }
         }
     }

   For system-controlled interfaces, the "name" is the device-specific
   name of the interface.

   If the device supports arbitrarily named user-controlled interfaces,
   then the server will advertise the "arbitrary-names" feature.  If the
   server does not advertise this feature, the names of user-controlled
   interfaces MUST match the device's naming scheme.  How a client can
   learn the naming scheme of such devices is outside the scope of this
   document.  See Appendix F.1 and Appendix F.2 for examples.

   When a system-controlled interface is created in the operational
   state datastore by the system, the system tries to apply the
   interface configuration in the intended configuration datastore with
   the same name as the new interface.  If no such interface
   configuration is found, or if the configured type does not match the
   real interface type, the system creates the interface without
   applying explicit configuration.

   When a user-controlled interface is created, the configuration
   determines the name of the interface.

   Depending on the operating system and the physical attachment point
   to which a network interface may be attached or removed, it may be
   impossible for an implementation to provide predictable and
   consistent names for system-controlled interfaces across insertion/
   removal cycles as well as in anticipation of initial insertion.  The




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   ability to provide configurations for such interfaces is therefore
   dependent on the implementation and cannot be assumed in all cases.

3.2.  Interface References

   An interface is identified by its name, which is unique within the
   server.  This property is captured in the "interface-ref" and
   typedef, which other YANG modules SHOULD use when they need to
   reference an interface.

3.3.  Interface Layering

   There is no generic mechanism for how an interface is configured to
   be layered on top of some other interface.  It is expected that
   interface-type-specific models define their own data nodes for
   interface layering by using "interface-ref" types to reference lower
   layers.

   Below is an example of a model with such nodes.  For a more complete
   example, see Appendix B.

     import interfaces {
         prefix "if";
     }
     import iana-if-type {
       prefix ianaift;
     }

     augment "/if:interfaces/if:interface" {
         when "if:type = 'ianaift:ieee8023adLag'";

         leaf-list slave-if {
             type if:interface-ref;
             must "/if:interfaces/if:interface[if:name = current()]"
                + "/if:type = 'ianaift:ethernetCsmacd'" {
                 description
                     "The type of a slave interface must be
                      'ethernetCsmacd'.";
             }
         }
         // other bonding config params, failover times, etc.
     }

   While the interface layering is configured in interface-type-specific
   models, two generic state data leaf-lists, "higher-layer-if" and
   "lower-layer-if", represent a read-only view of the interface
   layering hierarchy.




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4.  Relationship to the IF-MIB

   If the device implements the IF-MIB [RFC2863], each entry in the
   "/interfaces/interface" list in the operational state datastore is
   typically mapped to one ifEntry.  The "if-index" leaf MUST contain
   the value of the corresponding ifEntry's ifIndex.

   In most cases, the "name" of an "/interfaces/interface" entry is
   mapped to ifName.  The IF-MIB allows two different ifEntries to have
   the same ifName.  Devices that support this feature and also support
   the data model defined in this document cannot have a 1-1 mapping
   between the "name" leaf and ifName.

   The configured "description" of an "interface" has traditionally been
   mapped to ifAlias in some implementations.  This document allows this
   mapping, but implementers should be aware of the differences in the
   value space and persistence for these objects.  See the YANG module
   definition of the leaf "description" in Section 5 for details.

   The IF-MIB also defines the writable object ifPromiscuousMode.  Since
   this object typically is not implemented as a configuration object by
   SNMP agents, it is not mapped to the "ietf-interfaces" module.

   The ifMtu object from the IF-MIB is not mapped to the
   "ietf-interfaces" module.  It is expected that interface-type-
   specific YANG modules provide interface-type-specific MTU leafs by
   augmenting the "ietf-interfaces" model.

   There are a number of counters in the IF-MIB that exist in two
   versions: one with 32 bits and one with 64 bits.  The 64-bit versions
   were added to support high-speed interfaces with a data rate greater
   than 20,000,000 bits/second.  Today's implementations generally
   support such high-speed interfaces, and hence only 64-bit counters
   are provided in this data model.  Note that NETCONF and SNMP may
   differ in the time granularity in which they provide access to the
   counters.  For example, it is common that SNMP implementations cache
   counter values for some time.

   The objects ifDescr and ifConnectorPresent from the IF-MIB are not
   mapped to the "ietf-interfaces" module.

   The following tables list the YANG data nodes with corresponding
   objects in the IF-MIB.








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   +--------------------------------------+----------------------------+
   | YANG data node in                    | IF-MIB object              |
   | /interfaces/interface                |                            |
   +--------------------------------------+----------------------------+
   | name                                 | ifName                     |
   | type                                 | ifType                     |
   | description                          | ifAlias                    |
   | admin-status                         | ifAdminStatus              |
   | oper-status                          | ifOperStatus               |
   | last-change                          | ifLastChange               |
   | if-index                             | ifIndex                    |
   | link-up-down-trap-enable             | ifLinkUpDownTrapEnable     |
   | phys-address                         | ifPhysAddress              |
   | higher-layer-if and lower-layer-if   | ifStackTable               |
   | speed                                | ifSpeed and ifHighSpeed    |
   | discontinuity-time                   | ifCounterDiscontinuityTime |
   | in-octets                            | ifHCInOctets               |
   | in-unicast-pkts                      | ifHCInUcastPkts            |
   | in-broadcast-pkts                    | ifHCInBroadcastPkts        |
   | in-multicast-pkts                    | ifHCInMulticastPkts        |
   | in-discards                          | ifInDiscards               |
   | in-errors                            | ifInErrors                 |
   | in-unknown-protos                    | ifInUnknownProtos          |
   | out-octets                           | ifHCOutOctets              |
   | out-unicast-pkts                     | ifHCOutUcastPkts           |
   | out-broadcast-pkts                   | ifHCOutBroadcastPkts       |
   | out-multicast-pkts                   | ifHCOutMulticastPkts       |
   | out-discards                         | ifOutDiscards              |
   | out-errors                           | ifOutErrors                |
   +--------------------------------------+----------------------------+

                YANG Data Nodes and Related IF-MIB Objects

5.  Interfaces YANG Module

   This YANG module imports typedefs from [RFC6991].

   <CODE BEGINS> file "ietf-interfaces@2017-08-14.yang"

   module ietf-interfaces {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-interfaces";
     prefix if;

     import ietf-yang-types {
       prefix yang;
     }




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     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

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

        Editor:   Martin Bjorklund
                  <mailto:mbj@tail-f.com>";

     description
       "This module contains a collection of YANG definitions for
        managing network interfaces.

        Copyright (c) 2017 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 RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2017-08-17 {
       description
         "Updated to support NMDA.";
       reference
         "RFC XXXX: A YANG Data Model for Interface Management";
     }

     revision 2014-05-08 {
       description
         "Initial revision.";
       reference
         "RFC 7223: A YANG Data Model for Interface Management";
     }

     /*
      * Typedefs
      */

     typedef interface-ref {
       type leafref {
         path "/if:interfaces/if:interface/if:name";



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       }
       description
         "This type is used by data models that need to reference
          interfaces.";
     }

     /*
      * Identities
      */

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

     /*
      * Features
      */

     feature arbitrary-names {
       description
         "This feature indicates that the device allows user-controlled
          interfaces to be named arbitrarily.";
     }
     feature pre-provisioning {
       description
         "This feature indicates that the device supports
          pre-provisioning of interface configuration, i.e., it is
          possible to configure an interface whose physical interface
          hardware is not present on the device.";
     }
     feature if-mib {
       description
         "This feature indicates that the device implements
          the IF-MIB.";
       reference
         "RFC 2863: The Interfaces Group MIB";
     }

     /*
      * Data nodes
      */

     container interfaces {
       description
         "Interface parameters.";




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       list interface {
         key "name";

         description
           "The list of interfaces on the device.

            The operational state of an interface is available in this
            list in the operational state datastore.  If the
            configuration of a system-controlled interface cannot be
            used by the system (e.g., the interface hardware present
            does not match the interface type), then the configuration
            is not applied to the system-controlled interface shown in
            the operational state datastore.  If the configuration of a
            user-controlled interface cannot be used by the system, the
            configured interface is not instantiated in the operational
            state datastore.

            System-controlled interfaces created by the system are
            always present in this list in the operational state
            datastore, whether they are configured or not.";

        leaf name {
           type string;
           description
             "The name of the interface.

              A device MAY restrict the allowed values for this leaf,
              possibly depending on the type of the interface.
              For system-controlled interfaces, this leaf is the
              device-specific name of the interface.

              If a client tries to create configuration for a
              system-controlled interface that is not present in the
              operational state datastore, the server MAY reject
              the request if the implementation does not support
              pre-provisioning of interfaces or if the name refers to
              an interface that can never exist in the system.  A
              NETCONF server MUST reply with an rpc-error with the
              error-tag 'invalid-value' in this case.

              If the device supports pre-provisioning of interface
              configuration, the 'pre-provisioning' feature is
              advertised.

              If the device allows arbitrarily named user-controlled
              interfaces, the 'arbitrary-names' feature is advertised.

              When a configured user-controlled interface is created by



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              the system, it is instantiated with the same name in the
              operational state datastore.

              A server implementation MAY map this leaf to the ifName
              MIB object.  Such an implementation needs to use some
              mechanism to handle the differences in size and characters
              allowed between this leaf and ifName.  The definition of
              such a mechanism is outside the scope of this document.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifName";
         }

         leaf description {
           type string;
           description
             "A textual description of the interface.

              A server implementation MAY map this leaf to the ifAlias
              MIB object.  Such an implementation needs to use some
              mechanism to handle the differences in size and characters
              allowed between this leaf and ifAlias.  The definition of
              such a mechanism is outside the scope of this document.

              Since ifAlias is defined to be stored in non-volatile
              storage, the MIB implementation MUST map ifAlias to the
              value of 'description' in the persistently stored
              datastore.

              Specifically, if the device supports the startup
              configuration datastore, when ifAlias is read the device
              MUST return the value of 'description' in the startup
              configuration datastore, and when it is written, it MUST
              be written to the running and startup configuration
              datastores.  Note that it is up to the implementation to
              decide whether to modify this single leaf in the startup
              configuration datastore or perform an implicit copy from
              the running configuration datastore to the startup
              configuration datastore.

              If the device does not support the startup configuration
              datastore, ifAlias MUST be mapped to the 'description'
              leaf in the running configuration datastore.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifAlias";
         }

         leaf type {
           type identityref {



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             base interface-type;
           }
           mandatory true;
           description
             "The type of the interface.

              When an interface entry is created, a server MAY
              initialize the type leaf with a valid value, e.g., if it
              is possible to derive the type from the name of the
              interface.

              If a client tries to set the type of an interface to a
              value that can never be used by the system, e.g., if the
              type is not supported or if the type does not match the
              name of the interface, the server MUST reject the request.
              A NETCONF server MUST reply with an rpc-error with the
              error-tag 'invalid-value' in this case.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifType";
         }

         leaf enabled {
           type boolean;
           default "true";
           description
             "This leaf contains the configured, desired state of the
              interface.

              Systems that implement the IF-MIB use the value of this
              leaf in the running configuration datastore to set
              IF-MIB.ifAdminStatus to 'up' or 'down' after an ifEntry
              has been initialized, as described in RFC 2863.

              Changes in this leaf in the running configuration
              datastore are reflected in ifAdminStatus, but if
              ifAdminStatus is changed over SNMP, this leaf is not
              affected.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifAdminStatus";
         }

         leaf link-up-down-trap-enable {
           if-feature if-mib;
           type enumeration {
             enum enabled {
               value 1;
               description
                 "The device will generate linkUp/linkDown SNMP



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                  notifications for this interface.";
             }
             enum disabled {
               value 2;
               description
                 "The device will not generate linkUp/linkDown SNMP
                  notifications for this interface.";
             }
           }
           description
             "Controls whether linkUp/linkDown SNMP notifications
              should be generated for this interface.

              If this node is not configured, the value 'enabled' is
              operationally used by the server for interfaces that do
              not operate on top of any other interface (i.e., there are
              no 'lower-layer-if' entries), and 'disabled' otherwise.";
           reference
             "RFC 2863: The Interfaces Group MIB -
                        ifLinkUpDownTrapEnable";
         }

         leaf admin-status {
           if-feature if-mib;
           type enumeration {
             enum up {
               value 1;
               description
                 "Ready to pass packets.";
             }
             enum down {
               value 2;
               description
                 "Not ready to pass packets and not in some test mode.";
             }
             enum testing {
               value 3;
               description
                 "In some test mode.";
             }
           }
           config false;
           mandatory true;
           description
             "The desired state of the interface.

              This leaf has the same read semantics as ifAdminStatus.";
           reference



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             "RFC 2863: The Interfaces Group MIB - ifAdminStatus";
         }

         leaf oper-status {
           type enumeration {
             enum up {
               value 1;
               description
                 "Ready to pass packets.";
             }
             enum down {
               value 2;
               description
                 "The interface does not pass any packets.";
             }
             enum testing {
               value 3;
               description
                 "In some test mode.  No operational packets can
                  be passed.";
             }
             enum unknown {
               value 4;
               description
                 "Status cannot be determined for some reason.";
             }
             enum dormant {
               value 5;
               description
                 "Waiting for some external event.";
             }
             enum not-present {
               value 6;
               description
                 "Some component (typically hardware) is missing.";
             }
             enum lower-layer-down {
               value 7;
               description
                 "Down due to state of lower-layer interface(s).";
             }
           }
           config false;
           mandatory true;
           description
             "The current operational state of the interface.

              This leaf has the same semantics as ifOperStatus.";



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           reference
             "RFC 2863: The Interfaces Group MIB - ifOperStatus";
         }

         leaf last-change {
           type yang:date-and-time;
           config false;
           description
             "The time the interface entered its current operational
              state.  If the current state was entered prior to the
              last re-initialization of the local network management
              subsystem, then this node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifLastChange";
         }

         leaf if-index {
           if-feature if-mib;
           type int32 {
             range "1..2147483647";
           }
           config false;
           mandatory true;
           description
             "The ifIndex value for the ifEntry represented by this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifIndex";
         }

         leaf phys-address {
           type yang:phys-address;
           config false;
           description
             "The interface's address at its protocol sub-layer.  For
              example, for an 802.x interface, this object normally
              contains a Media Access Control (MAC) address.  The
              interface's media-specific modules must define the bit
              and byte ordering and the format of the value of this
              object.  For interfaces that do not have such an address
              (e.g., a serial line), this node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifPhysAddress";
         }

         leaf-list higher-layer-if {
           type interface-ref;
           config false;



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           description
             "A list of references to interfaces layered on top of this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifStackTable";
         }

         leaf-list lower-layer-if {
           type interface-ref;
           config false;
           description
             "A list of references to interfaces layered underneath this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifStackTable";
         }

         leaf speed {
           type yang:gauge64;
           units "bits/second";
           config false;
           description
               "An estimate of the interface's current bandwidth in bits
                per second.  For interfaces that do not vary in
                bandwidth or for those where no accurate estimation can
                be made, this node should contain the nominal bandwidth.
                For interfaces that have no concept of bandwidth, this
                node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB -
                        ifSpeed, ifHighSpeed";
         }

         container statistics {
           config false;
           description
             "A collection of interface-related statistics objects.";

           leaf discontinuity-time {
             type yang:date-and-time;
             mandatory true;
             description
               "The time on the most recent occasion at which any one or
                more of this interface's counters suffered a
                discontinuity.  If no such discontinuities have occurred
                since the last re-initialization of the local management
                subsystem, then this node contains the time the local
                management subsystem re-initialized itself.";



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           }

           leaf in-octets {
             type yang:counter64;
             description
               "The total number of octets received on the interface,
                including framing characters.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCInOctets";
           }

           leaf in-unicast-pkts {
             type yang:counter64;
             description
               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were not addressed to a
                multicast or broadcast address at this sub-layer.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCInUcastPkts";
           }

           leaf in-broadcast-pkts {
             type yang:counter64;
             description
               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were addressed to a broadcast
                address at this sub-layer.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCInBroadcastPkts";
           }

           leaf in-multicast-pkts {



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             type yang:counter64;
             description
               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were addressed to a multicast
                address at this sub-layer.  For a MAC-layer protocol,
                this includes both Group and Functional addresses.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCInMulticastPkts";
           }

           leaf in-discards {
             type yang:counter32;
             description
               "The number of inbound packets that were chosen to be
                discarded even though no errors had been detected to
                prevent their being deliverable to a higher-layer
                protocol.  One possible reason for discarding such a
                packet could be to free up buffer space.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifInDiscards";
           }

           leaf in-errors {
             type yang:counter32;
             description
               "For packet-oriented interfaces, the number of inbound
                packets that contained errors preventing them from being
                deliverable to a higher-layer protocol.  For character-
                oriented or fixed-length interfaces, the number of
                inbound transmission units that contained errors
                preventing them from being deliverable to a higher-layer
                protocol.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";



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             reference
               "RFC 2863: The Interfaces Group MIB - ifInErrors";
           }

           leaf in-unknown-protos {
             type yang:counter32;
             description
               "For packet-oriented interfaces, the number of packets
                received via the interface that were discarded because
                of an unknown or unsupported protocol.  For
                character-oriented or fixed-length interfaces that
                support protocol multiplexing, the number of
                transmission units received via the interface that were
                discarded because of an unknown or unsupported protocol.
                For any interface that does not support protocol
                multiplexing, this counter is not present.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifInUnknownProtos";
           }


           leaf out-octets {
             type yang:counter64;
             description
               "The total number of octets transmitted out of the
                interface, including framing characters.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCOutOctets";
           }

           leaf out-unicast-pkts {
             type yang:counter64;
             description
               "The total number of packets that higher-level protocols
                requested be transmitted, and that were not addressed
                to a multicast or broadcast address at this sub-layer,
                including those that were discarded or not sent.




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                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCOutUcastPkts";
           }

           leaf out-broadcast-pkts {
             type yang:counter64;
             description
               "The total number of packets that higher-level protocols
                requested be transmitted, and that were addressed to a
                broadcast address at this sub-layer, including those
                that were discarded or not sent.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCOutBroadcastPkts";
           }

           leaf out-multicast-pkts {
             type yang:counter64;
             description
               "The total number of packets that higher-level protocols
                requested be transmitted, and that were addressed to a
                multicast address at this sub-layer, including those
                that were discarded or not sent.  For a MAC-layer
                protocol, this includes both Group and Functional
                addresses.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCOutMulticastPkts";
           }

           leaf out-discards {
             type yang:counter32;
             description
               "The number of outbound packets that were chosen to be



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                discarded even though no errors had been detected to
                prevent their being transmitted.  One possible reason
                for discarding such a packet could be to free up buffer
                space.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifOutDiscards";
           }

           leaf out-errors {
             type yang:counter32;
             description
               "For packet-oriented interfaces, the number of outbound
                packets that could not be transmitted because of errors.
                For character-oriented or fixed-length interfaces, the
                number of outbound transmission units that could not be
                transmitted because of errors.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifOutErrors";
           }
         }

       }
     }

     /*
      * Legacy typedefs
      */

     typedef interface-state-ref {
       type leafref {
         path "/if:interfaces-state/if:interface/if:name";
       }
       status deprecated;
       description
         "This type is used by data models that need to reference
          the operationally present interfaces.";
     }




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     /*
      * Legacy operational state data nodes
      */

     container interfaces-state {
       config false;
       status deprecated;
       description
         "Data nodes for the operational state of interfaces.";

       list interface {
         key "name";
         status deprecated;

         description
           "The list of interfaces on the device.

            System-controlled interfaces created by the system are
            always present in this list, whether they are configured or
            not.";

         leaf name {
           type string;
           status deprecated;
           description
             "The name of the interface.

              A server implementation MAY map this leaf to the ifName
              MIB object.  Such an implementation needs to use some
              mechanism to handle the differences in size and characters
              allowed between this leaf and ifName.  The definition of
              such a mechanism is outside the scope of this document.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifName";
         }

         leaf type {
           type identityref {
             base interface-type;
           }
           mandatory true;
           status deprecated;
           description
             "The type of the interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifType";
         }




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         leaf admin-status {
           if-feature if-mib;
           type enumeration {
             enum up {
               value 1;
               description
                 "Ready to pass packets.";
             }
             enum down {
               value 2;
               description
                 "Not ready to pass packets and not in some test mode.";
             }
             enum testing {
               value 3;
               description
                 "In some test mode.";
             }
           }
           mandatory true;
           status deprecated;
           description
             "The desired state of the interface.

              This leaf has the same read semantics as ifAdminStatus.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifAdminStatus";
         }

         leaf oper-status {
           type enumeration {
             enum up {
               value 1;
               description
                 "Ready to pass packets.";
             }
             enum down {
               value 2;
               description
                 "The interface does not pass any packets.";
             }
             enum testing {
               value 3;
               description
                 "In some test mode.  No operational packets can
                  be passed.";
             }
             enum unknown {



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               value 4;
               description
                 "Status cannot be determined for some reason.";
             }
             enum dormant {
               value 5;
               description
                 "Waiting for some external event.";
             }
             enum not-present {
               value 6;
               description
                 "Some component (typically hardware) is missing.";
             }
             enum lower-layer-down {
               value 7;
               description
                 "Down due to state of lower-layer interface(s).";
             }
           }
           mandatory true;
           status deprecated;
           description
             "The current operational state of the interface.

              This leaf has the same semantics as ifOperStatus.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifOperStatus";
         }

         leaf last-change {
           type yang:date-and-time;
           status deprecated;
           description
             "The time the interface entered its current operational
              state.  If the current state was entered prior to the
              last re-initialization of the local network management
              subsystem, then this node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifLastChange";
         }

         leaf if-index {
           if-feature if-mib;
           type int32 {
             range "1..2147483647";
           }
           mandatory true;



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           status deprecated;
           description
             "The ifIndex value for the ifEntry represented by this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifIndex";
         }

         leaf phys-address {
           type yang:phys-address;
           status deprecated;
           description
             "The interface's address at its protocol sub-layer.  For
              example, for an 802.x interface, this object normally
              contains a Media Access Control (MAC) address.  The
              interface's media-specific modules must define the bit
              and byte ordering and the format of the value of this
              object.  For interfaces that do not have such an address
              (e.g., a serial line), this node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifPhysAddress";
         }

         leaf-list higher-layer-if {
           type interface-state-ref;
           status deprecated;
           description
             "A list of references to interfaces layered on top of this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifStackTable";
         }

         leaf-list lower-layer-if {
           type interface-state-ref;
           status deprecated;
           description
             "A list of references to interfaces layered underneath this
              interface.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifStackTable";
         }

         leaf speed {
           type yang:gauge64;
           units "bits/second";
           status deprecated;
           description



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               "An estimate of the interface's current bandwidth in bits
                per second.  For interfaces that do not vary in
                bandwidth or for those where no accurate estimation can
                be made, this node should contain the nominal bandwidth.
                For interfaces that have no concept of bandwidth, this
                node is not present.";
           reference
             "RFC 2863: The Interfaces Group MIB -
                        ifSpeed, ifHighSpeed";
         }

         container statistics {
           status deprecated;
           description
             "A collection of interface-related statistics objects.";

           leaf discontinuity-time {
             type yang:date-and-time;
             mandatory true;
             status deprecated;
             description
               "The time on the most recent occasion at which any one or
                more of this interface's counters suffered a
                discontinuity.  If no such discontinuities have occurred
                since the last re-initialization of the local management
                subsystem, then this node contains the time the local
                management subsystem re-initialized itself.";
           }

           leaf in-octets {
             type yang:counter64;
             status deprecated;
             description
               "The total number of octets received on the interface,
                including framing characters.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCInOctets";
           }

           leaf in-unicast-pkts {
             type yang:counter64;
             status deprecated;
             description



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               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were not addressed to a
                multicast or broadcast address at this sub-layer.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCInUcastPkts";
           }

           leaf in-broadcast-pkts {
             type yang:counter64;
             status deprecated;
             description
               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were addressed to a broadcast
                address at this sub-layer.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCInBroadcastPkts";
           }

           leaf in-multicast-pkts {
             type yang:counter64;
             status deprecated;
             description
               "The number of packets, delivered by this sub-layer to a
                higher (sub-)layer, that were addressed to a multicast
                address at this sub-layer.  For a MAC-layer protocol,
                this includes both Group and Functional addresses.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCInMulticastPkts";
           }

           leaf in-discards {



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             type yang:counter32;
             status deprecated;
             description
               "The number of inbound packets that were chosen to be
                discarded even though no errors had been detected to
                prevent their being deliverable to a higher-layer
                protocol.  One possible reason for discarding such a
                packet could be to free up buffer space.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifInDiscards";
           }

           leaf in-errors {
             type yang:counter32;
             status deprecated;
             description
               "For packet-oriented interfaces, the number of inbound
                packets that contained errors preventing them from being
                deliverable to a higher-layer protocol.  For character-
                oriented or fixed-length interfaces, the number of
                inbound transmission units that contained errors
                preventing them from being deliverable to a higher-layer
                protocol.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifInErrors";
           }

           leaf in-unknown-protos {
             type yang:counter32;
             status deprecated;
             description
               "For packet-oriented interfaces, the number of packets
                received via the interface that were discarded because
                of an unknown or unsupported protocol.  For
                character-oriented or fixed-length interfaces that
                support protocol multiplexing, the number of
                transmission units received via the interface that were
                discarded because of an unknown or unsupported protocol.



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                For any interface that does not support protocol
                multiplexing, this counter is not present.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifInUnknownProtos";
           }


           leaf out-octets {
             type yang:counter64;
             status deprecated;
             description
               "The total number of octets transmitted out of the
                interface, including framing characters.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCOutOctets";
           }

           leaf out-unicast-pkts {
             type yang:counter64;
             status deprecated;
             description
               "The total number of packets that higher-level protocols
                requested be transmitted, and that were not addressed
                to a multicast or broadcast address at this sub-layer,
                including those that were discarded or not sent.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifHCOutUcastPkts";
           }

           leaf out-broadcast-pkts {
             type yang:counter64;
             status deprecated;
             description



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               "The total number of packets that higher-level protocols
                requested be transmitted, and that were addressed to a
                broadcast address at this sub-layer, including those
                that were discarded or not sent.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCOutBroadcastPkts";
           }

           leaf out-multicast-pkts {
             type yang:counter64;
             status deprecated;
             description
               "The total number of packets that higher-level protocols
                requested be transmitted, and that were addressed to a
                multicast address at this sub-layer, including those
                that were discarded or not sent.  For a MAC-layer
                protocol, this includes both Group and Functional
                addresses.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB -
                          ifHCOutMulticastPkts";
           }

           leaf out-discards {
             type yang:counter32;
             status deprecated;
             description
               "The number of outbound packets that were chosen to be
                discarded even though no errors had been detected to
                prevent their being transmitted.  One possible reason
                for discarding such a packet could be to free up buffer
                space.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";



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             reference
               "RFC 2863: The Interfaces Group MIB - ifOutDiscards";
           }

           leaf out-errors {
             type yang:counter32;
             status deprecated;
             description
               "For packet-oriented interfaces, the number of outbound
                packets that could not be transmitted because of errors.
                For character-oriented or fixed-length interfaces, the
                number of outbound transmission units that could not be
                transmitted because of errors.

                Discontinuities in the value of this counter can occur
                at re-initialization of the management system, and at
                other times as indicated by the value of
                'discontinuity-time'.";
             reference
               "RFC 2863: The Interfaces Group MIB - ifOutErrors";
           }
         }
       }
     }
   }

   <CODE ENDS>

6.  IANA Considerations

   This document registers a URI in the "IETF XML Registry" [RFC3688].
   Following the format in RFC 3688, the following registration has been
   made.

     URI: urn:ietf:params:xml:ns:yang:ietf-interfaces

     Registrant Contact: The IESG.

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

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

     name:         ietf-interfaces
     namespace:    urn:ietf:params:xml:ns:yang:ietf-interfaces
     prefix:       if
     reference:    RFC XXXX




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7.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241].  The lowest NETCONF layer is the
   secure transport layer and the mandatory-to-implement secure
   transport is SSH [RFC6242].  The NETCONF access control model
   [RFC6536] provides the means to restrict access for particular
   NETCONF users to a pre-configured subset of all available NETCONF
   protocol operations and content.

   There are a number of data nodes defined in the YANG module which 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:

   /interfaces/interface:  This list specifies the configured interfaces
      on a device.  Unauthorized access to this list could cause the
      device to ignore packets it should receive and process.

   /interfaces/interface/enabled:  This leaf controls whether an
      interface is enabled or not.  Unauthorized access to this leaf
      could cause the device to ignore packets it should receive and
      process.

8.  Acknowledgments

   The author wishes to thank Alexander Clemm, Per Hedeland, Ladislav
   Lhotka, and Juergen Schoenwaelder for their helpful comments.

9.  References

9.1.  Normative References

   [I-D.ietf-netmod-revised-datastores]
              Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore
              Architecture", draft-ietf-netmod-revised-datastores-03
              (work in progress), July 2017.

   [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>.





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   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
              MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
              <https://www.rfc-editor.org/info/rfc2863>.

   [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>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [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>.

9.2.  Informative References

   [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>.

   [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>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012, <https://www.rfc-
              editor.org/info/rfc6536>.

   [RFC7224]  Bjorklund, M., "IANA Interface Type YANG Module",
              RFC 7224, DOI 10.17487/RFC7224, May 2014,
              <https://www.rfc-editor.org/info/rfc7224>.

Appendix A.  Example: Ethernet Interface Module

   This section gives a simple example of how an Ethernet interface
   module could be defined.  It demonstrates how media-specific
   configuration parameters can be conditionally augmented to the
   generic interface list.  It also shows how operational state
   parameters can be conditionally augmented to the operational



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   interface list.  The example is not intended as a complete module for
   Ethernet configuration.

   module ex-ethernet {
     namespace "http://example.com/ethernet";
     prefix "eth";

     import ietf-interfaces {
       prefix if;
     }
     import iana-if-type {
       prefix ianaift;
     }

     // configuration and state parameters for Ethernet interfaces
     augment "/if:interfaces/if:interface" {
       when "if:type = 'ianaift:ethernetCsmacd'";

       container ethernet {
         choice transmission-params {
           case auto {
             leaf auto-negotiate {
               type empty;
             }
           }
           case manual {
             leaf duplex {
               type enumeration {
                 enum "half";
                 enum "full";
               }
             }

             leaf speed {
               type enumeration {
                 enum "10Mb";
                 enum "100Mb";
                 enum "1Gb";
                 enum "10Gb";
               }
             }
           }
         }
         leaf duplexx {
           type enumeration {
             enum "half";
             enum "full";
           }



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           config false;
         }
         // other Ethernet-specific params...
       }
     }
   }

Appendix B.  Example: Ethernet Bonding Interface Module

   This section gives an example of how interface layering can be
   defined.  An Ethernet bonding interface that bonds several Ethernet
   interfaces into one logical interface is defined.

   module ex-ethernet-bonding {
     namespace "http://example.com/ethernet-bonding";
     prefix "bond";

     import ietf-interfaces {
       prefix if;
     }
     import iana-if-type {
       prefix ianaift;
     }



     augment "/if:interfaces/if:interface" {
       when "if:type = 'ianaift:ieee8023adLag'";

       leaf-list slave-if {
         type if:interface-ref;
         must "/if:interfaces/if:interface[if:name = current()]"
            + "/if:type = 'ianaift:ethernetCsmacd'" {
           description
             "The type of a slave interface must be 'ethernetCsmacd'.";
         }
       }
       leaf bonding-mode {
         type enumeration {
           enum round-robin;
           enum active-backup;
           enum broadcast;
         }
       }
       // other bonding config params, failover times, etc.
     }
   }




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Appendix C.  Example: VLAN Interface Module

   This section gives an example of how a VLAN interface module can be
   defined.

   module ex-vlan {
     namespace "http://example.com/vlan";
     prefix "vlan";

     import ietf-interfaces {
       prefix if;
     }
     import iana-if-type {
       prefix ianaift;
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'ianaift:ethernetCsmacd' or
             if:type = 'ianaift:ieee8023adLag'";
       leaf vlan-tagging {
         type boolean;
         default false;
       }
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'ianaift:l2vlan'";

       leaf base-interface {
         type if:interface-ref;
         must "/if:interfaces/if:interface[if:name = current()]"
            + "/vlan:vlan-tagging = 'true'" {
           description
             "The base interface must have VLAN tagging enabled.";
         }
       }
       leaf vlan-id {
         type uint16 {
           range "1..4094";
         }
         must "../base-interface" {
           description
             "If a vlan-id is defined, a base-interface must
              be specified.";
         }
       }
     }
   }



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Appendix D.  Example: NETCONF <get-config> Reply

   This section gives an example of a reply to the NETCONF <get-config>
   request for <running> for a device that implements the example data
   models above.

   <rpc-reply
       xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
       message-id="101">
     <data>
       <interfaces
           xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
           xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"
           xmlns:vlan="http://example.com/vlan">

         <interface>
           <name>eth0</name>
           <type>ianaift:ethernetCsmacd</type>
           <enabled>false</enabled>
         </interface>

         <interface>
           <name>eth1</name>
           <type>ianaift:ethernetCsmacd</type>
           <enabled>true</enabled>
           <vlan:vlan-tagging>true</vlan:vlan-tagging>
         </interface>

         <interface>
           <name>eth1.10</name>
           <type>ianaift:l2vlan</type>
           <enabled>true</enabled>
           <vlan:base-interface>eth1</vlan:base-interface>
           <vlan:vlan-id>10</vlan:vlan-id>
         </interface>

         <interface>
           <name>lo1</name>
           <type>ianaift:softwareLoopback</type>
           <enabled>true</enabled>
         </interface>

       </interfaces>
     </data>
   </rpc-reply>






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Appendix E.  Example: NETCONF <get-data> Reply

   This section gives an example of a reply to the NETCONF <get-data>
   request for <operational> for a device that implements the example
   data models above.

   <rpc-reply
       xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
       message-id="101">
     <data>
       <interfaces
           xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
           xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"
           xmlns:vlan="http://example.com/vlan"
           xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin">

         <interface or:origin="or:intended">
           <name>eth0</name>
           <type>ianaift:ethernetCsmacd</type>
           <enabled>false</enabled>
           <admin-status>down</admin-status>
           <oper-status>down</oper-status>
           <if-index>2</if-index>
           <phys-address>00:01:02:03:04:05</phys-address>
           <statistics>
             <discontinuity-time>
               2013-04-01T03:00:00+00:00
             </discontinuity-time>
             <!-- counters now shown here -->
           </statistics>
         </interface>

         <interface or:origin="or:intended">
           <name>eth1</name>
           <type>ianaift:ethernetCsmacd</type>
           <enabled>true</enabled>
           <admin-status>up</admin-status>
           <oper-status>up</oper-status>
           <if-index>7</if-index>
           <phys-address>00:01:02:03:04:06</phys-address>
           <higher-layer-if>eth1.10</higher-layer-if>
           <statistics>
             <discontinuity-time>
               2013-04-01T03:00:00+00:00
             </discontinuity-time>
             <!-- counters now shown here -->
           </statistics>
           <vlan:vlan-tagging>true</vlan:vlan-tagging>



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         </interface>

         <interface or:origin="or:intended">
           <name>eth1.10</name>
           <type>ianaift:l2vlan</type>
           <enabled>true</enabled>
           <admin-status>up</admin-status>
           <oper-status>up</oper-status>
           <if-index>9</if-index>
           <lower-layer-if>eth1</lower-layer-if>
           <statistics>
             <discontinuity-time>
               2013-04-01T03:00:00+00:00
             </discontinuity-time>
             <!-- counters now shown here -->
           </statistics>
           <vlan:base-interface>eth1</vlan:base-interface>
           <vlan:vlan-id>10</vlan:vlan-id>
         </interface>

         <!-- This interface is not configured -->
         <interface or:origin="or:system">
           <name>eth2</name>
           <type>ianaift:ethernetCsmacd</type>
           <admin-status>down</admin-status>
           <oper-status>down</oper-status>
           <if-index>8</if-index>
           <phys-address>00:01:02:03:04:07</phys-address>
           <statistics>
             <discontinuity-time>
               2013-04-01T03:00:00+00:00
             </discontinuity-time>
             <!-- counters now shown here -->
           </statistics>
         </interface>

         <interface or:origin="or:intended">
           <name>lo1</name>
           <type>ianaift:softwareLoopback</type>
           <enabled>true</enabled>
           <admin-status>up</admin-status>
           <oper-status>up</oper-status>
           <if-index>1</if-index>
           <statistics>
             <discontinuity-time>
               2013-04-01T03:00:00+00:00
             </discontinuity-time>
             <!-- counters now shown here -->



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           </statistics>
         </interface>

       </interfaces>
     </data>
   </rpc-reply>

Appendix F.  Examples: Interface Naming Schemes

   This section gives examples of some implementation strategies.

   The examples make use of the example data model "ex-vlan" (see
   Appendix C) to show how user-controlled interfaces can be configured.

F.1.  Router with Restricted Interface Names

   In this example, a router has support for 4 line cards, each with 8
   ports.  The slots for the cards are physically numbered from 0 to 3,
   and the ports on each card from 0 to 7.  Each card has Fast Ethernet
   or Gigabit Ethernet ports.

   The device-specific names for these physical interfaces are
   "fastethernet-N/M" or "gigabitethernet-N/M".

   The name of a VLAN interface is restricted to the form
   "<physical-interface-name>.<subinterface-number>".

   It is assumed that the operator is aware of this naming scheme.  The
   implementation auto-initializes the value for "type" based on the
   interface name.

   The NETCONF server does not advertise the "arbitrary-names" feature
   in the <hello> message.

   An operator can configure a physical interface by sending an
   <edit-config> containing:

     <interface nc:operation="create">
       <name>fastethernet-1/0</name>
     </interface>

   When the server processes this request, it will set the leaf "type"
   to "ianaift:ethernetCsmacd".  Thus, if the client performs a
   <get-config> right after the <edit-config> above, it will get:







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     <interface>
       <name>fastethernet-1/0</name>
       <type>ianaift:ethernetCsmacd</type>
     </interface>

   The client can configure a VLAN interface by sending an <edit-config>
   containing:

     <interface nc:operation="create">
       <name>fastethernet-1/0.10005</name>
       <type>ianaift:l2vlan</type>
       <vlan:base-interface>fastethernet-1/0</vlan:base-interface>
       <vlan:vlan-id>5</vlan:vlan-id>
     </interface>

   If the client tries to change the type of the physical interface with
   an <edit-config> containing:

     <interface nc:operation="merge">
       <name>fastethernet-1/0</name>
       <type>ianaift:tunnel</type>
     </interface>

   then the server will reply with an "invalid-value" error, since the
   new type does not match the name.

F.2.  Router with Arbitrary Interface Names

   In this example, a router has support for 4 line cards, each with 8
   ports.  The slots for the cards are physically numbered from 0 to 3,
   and the ports on each card from 0 to 7.  Each card has Fast Ethernet
   or Gigabit Ethernet ports.

   The device-specific names for these physical interfaces are
   "fastethernet-N/M" or "gigabitethernet-N/M".

   The implementation does not restrict the user-controlled interface
   names.  This allows an operator to more easily apply the interface
   configuration to a different interface.  However, the additional
   level of indirection also makes it a bit more complex to map
   interface names found in other protocols to configuration entries.

   The NETCONF server advertises the "arbitrary-names" feature in the
   <hello> message.

   Physical interfaces are configured as in Appendix F.1.





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   An operator can configure a VLAN interface by sending an
   <edit-config> containing:

     <interface nc:operation="create">
       <name>acme-interface</name>
       <type>ianaift:l2vlan</type>
       <vlan:base-interface>fastethernet-1/0</vlan:base-interface>
       <vlan:vlan-id>5</vlan:vlan-id>
     </interface>

   If necessary, the operator can move the configuration named
   "acme-interface" over to a different physical interface with an
   <edit-config> containing:

     <interface nc:operation="merge">
       <name>acme-interface</name>
       <vlan:base-interface>fastethernet-1/1</vlan:base-interface>
     </interface>

F.3.  Ethernet Switch with Restricted Interface Names

   In this example, an Ethernet switch has a number of ports, each
   identified by a simple port number.

   The device-specific names for the physical interfaces are numbers
   that match the physical port number.

   An operator can configure a physical interface by sending an
   <edit-config> containing:

     <interface nc:operation="create">
       <name>6</name>
     </interface>

   When the server processes this request, it will set the leaf "type"
   to "ianaift:ethernetCsmacd".  Thus, if the client performs a
   <get-config> right after the <edit-config> above, it will get:

     <interface>
       <name>6</name>
       <type>ianaift:ethernetCsmacd</type>
     </interface>

F.4.  Generic Host with Restricted Interface Names

   In this example, a generic host has interfaces named by the kernel.
   The system identifies the physical interface by the name assigned by
   the operating system to the interface.



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   The name of a VLAN interface is restricted to the form
   "<physical-interface-name>:<vlan-number>".

   The NETCONF server does not advertise the "arbitrary-names" feature
   in the <hello> message.

   An operator can configure an interface by sending an <edit-config>
   containing:

     <interface nc:operation="create">
       <name>eth8</name>
     </interface>

   When the server processes this request, it will set the leaf "type"
   to "ianaift:ethernetCsmacd".  Thus, if the client performs a
   <get-config> right after the <edit-config> above, it will get:

     <interface>
       <name>eth8</name>
       <type>ianaift:ethernetCsmacd</type>
     </interface>

   The client can configure a VLAN interface by sending an <edit-config>
   containing:

     <interface nc:operation="create">
       <name>eth8:5</name>
       <type>ianaift:l2vlan</type>
       <vlan:base-interface>eth8</vlan:base-interface>
       <vlan:vlan-id>5</vlan:vlan-id>
     </interface>

F.5.  Generic Host with Arbitrary Interface Names

   In this example, a generic host has interfaces named by the kernel.
   The system identifies the physical interface by the name assigned by
   the operating system to the interface.

   The implementation does not restrict the user-controlled interface
   names.  This allows an operator to more easily apply the interface
   configuration to a different interface.  However, the additional
   level of indirection also makes it a bit more complex to map
   interface names found in other protocols to configuration entries.

   The NETCONF server advertises the "arbitrary-names" feature in the
   <hello> message.

   Physical interfaces are configured as in Appendix F.4.



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   An operator can configure a VLAN interface by sending an
   <edit-config> containing:

     <interface nc:operation="create">
       <name>acme-interface</name>
       <type>ianaift:l2vlan</type>
       <vlan:base-interface>eth8</vlan:base-interface>
       <vlan:vlan-id>5</vlan:vlan-id>
     </interface>

   If necessary, the operator can move the configuration named
   "acme-interface" over to a different physical interface with an
   <edit-config> containing:

     <interface nc:operation="merge">
       <name>acme-interface</name>
       <vlan:base-interface>eth3</vlan:base-interface>
     </interface>

Author's Address

   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com


























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