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Versions: (draft-wilton-netmod-intf-ext-yang) 00 01 02 03 04 05 06 07 08 09 10

Internet Engineering Task Force                           R. Wilton, Ed.
Internet-Draft                                                   D. Ball
Intended status: Standards Track                                T. Singh
Expires: January 30, 2021                                  Cisco Systems
                                                              S. Sivaraj
                                                        Juniper Networks
                                                           July 29, 2020


              Common Interface Extension YANG Data Models
                   draft-ietf-netmod-intf-ext-yang-10

Abstract

   This document defines two YANG modules that augment the Interfaces
   data model defined in the "YANG Data Model for Interface Management"
   with additional configuration and operational data nodes to support
   common lower layer interface properties, such as interface MTU.

   The YANG modules in this document conform to the Network Management
   Datastore Architecture (NMDA) defined in RFC 8342.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 30, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Interface Extensions Module . . . . . . . . . . . . . . . . .   4
     2.1.  Carrier Delay . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Dampening . . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  Suppress Threshold  . . . . . . . . . . . . . . . . .   7
       2.2.2.  Half-Life Period  . . . . . . . . . . . . . . . . . .   7
       2.2.3.  Reuse Threshold . . . . . . . . . . . . . . . . . . .   7
       2.2.4.  Maximum Suppress Time . . . . . . . . . . . . . . . .   7
     2.3.  Encapsulation . . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Loopback  . . . . . . . . . . . . . . . . . . . . . . . .   8
     2.5.  Maximum frame size  . . . . . . . . . . . . . . . . . . .   8
     2.6.  Sub-interface . . . . . . . . . . . . . . . . . . . . . .   8
     2.7.  Forwarding Mode . . . . . . . . . . . . . . . . . . . . .   9
   3.  Interfaces Ethernet-Like Module . . . . . . . . . . . . . . .   9
   4.  Interface Extensions YANG Module  . . . . . . . . . . . . . .  10
   5.  Interfaces Ethernet-Like YANG Module  . . . . . . . . . . . .  21
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
     6.1.  Carrier delay configuration . . . . . . . . . . . . . . .  25
     6.2.  Dampening configuration . . . . . . . . . . . . . . . . .  26
     6.3.  MAC address configuration . . . . . . . . . . . . . . . .  27
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  29
   8.  ChangeLog . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     8.1.  Version -10 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.2.  Version -09 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.3.  Version -08 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.4.  Version -07 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.5.  Version -06 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.6.  Version -05 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.7.  Version -04 . . . . . . . . . . . . . . . . . . . . . . .  29
     8.8.  Version -03 . . . . . . . . . . . . . . . . . . . . . . .  30
     8.9.  Version -02 . . . . . . . . . . . . . . . . . . . . . . .  30
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  30
     9.1.  YANG Module Registrations . . . . . . . . . . . . . . . .  30
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  31
     10.1.  ietf-if-extensions.yang  . . . . . . . . . . . . . . . .  31
     10.2.  ietf-if-ethernet-like.yang . . . . . . . . . . . . . . .  32
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  32
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  32



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     11.2.  Informative References . . . . . . . . . . . . . . . . .  33
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34

1.  Introduction

   This document defines two NMDA compatible [RFC8342] YANG 1.1
   [RFC7950] modules for the management of network interfaces.  It
   defines various augmentations to the generic interfaces data model
   [RFC8343] to support configuration of lower layer interface
   properties that are common across many types of network interface.

   One of the aims of this document is to provide a standard definition
   for these configuration items regardless of the underlying interface
   type.  For example, a definition for configuring or reading the MAC
   address associated with an interface is provided that can be used for
   any interface type that uses Ethernet framing.

   Several of the augmentations defined here are not backed by any
   formal standard specification.  Instead, they are for features that
   are commonly implemented in equivalent ways by multiple independent
   network equipment vendors.  The aim of this document is to define
   common paths and leaves for the configuration of these equivalent
   features in a uniform way, making it easier for users of the YANG
   model to access these features in a vendor independent way.  Where
   necessary, a description of the expected behavior is also provided
   with the aim of ensuring vendors implementations are consistent with
   the specified behaviour.

   Given that the modules contain a collection of discrete features with
   the common theme that they generically apply to interfaces, it is
   plausible that not all implementors of the YANG module will decide to
   support all features.  Hence separate feature keywords are defined
   for each logically discrete feature to allow implementors the
   flexibility to choose which specific parts of the model they support.

   The augmentations are split into two separate YANG modules that each
   focus on a particular area of functionality.  The two YANG modules
   defined in this document are:

      ietf-if-extensions.yang - Defines extensions to the IETF interface
      data model to support common configuration data nodes.

      ietf-if-ethernet-like.yang - Defines a module for any
      configuration and operational data nodes that are common across
      interfaces that use Ethernet framing.






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1.1.  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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

1.2.  Tree Diagrams

   Tree diagrams used in this document follow the notation defined in
   [RFC8340].

2.  Interface Extensions Module

   The Interfaces Extensions YANG module provides some basic extensions
   to the IETF interfaces YANG module.

   The module provides:

   o  A carrier delay feature used to provide control over short lived
      link state flaps.

   o  An interface link state dampening feature that is used to provide
      control over longer lived link state flaps.

   o  An encapsulation container and extensible choice statement for use
      by any interface types that allow for configurable L2
      encapsulations.

   o  A loopback configuration leaf that is primarily aimed at loopback
      at the physical layer.

   o  MTU configuration leaves applicable to all packet/frame based
      interfaces.

   o  A forwarding mode leaf to indicate the OSI layer at which the
      interface handles traffic.

   o  A generic "sub-interface" identity that an interface identity
      definition can derive from if it defines a sub-interface.

   o  A parent interface leaf useable for all types of sub-interface
      that are children of parent interfaces.







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   The "ietf-if-extensions" YANG module has the following structure:


   module: ietf-if-extensions
     augment /if:interfaces/if:interface:
       +--rw carrier-delay {carrier-delay}?
       |  +--rw down?                  uint32
       |  +--rw up?                    uint32
       |  +--ro carrier-transitions?   yang:counter64
       |  +--ro timer-running?         enumeration
       +--rw dampening! {dampening}?
       |  +--rw half-life?           uint32
       |  +--rw reuse?               uint32
       |  +--rw suppress?            uint32
       |  +--rw max-suppress-time?   uint32
       |  +--ro penalty?             uint32
       |  +--ro suppressed?          boolean
       |  +--ro time-remaining?      uint32
       +--rw encapsulation
       |  +--rw (encaps-type)?
       +--rw loopback?          identityref {loopback}?
       +--rw max-frame-size?    uint32 {max-frame-size}?
       +--ro forwarding-mode?   identityref
     augment /if:interfaces/if:interface:
       +--rw parent-interface    if:interface-ref {sub-interfaces}?
     augment /if:interfaces/if:interface/if:statistics:
       +--ro in-discard-unknown-encaps?   yang:counter64
               {sub-interfaces}?


2.1.  Carrier Delay

   The carrier delay feature augments the IETF interfaces data model
   with configuration for a simple algorithm that is used, generally on
   physical interfaces, to suppress short transient changes in the
   interface link state.  It can be used in conjunction with the
   dampening feature described in Section 2.2 to provide effective
   control of unstable links and unwanted state transitions.

   The principle of the carrier delay feature is to use a short per
   interface timer to ensure that any interface link state transition
   that occurs and reverts back within the specified time interval is
   entirely suppressed without providing any signalling to any upper
   layer protocols that the state transition has occurred.  E.g. in the
   case that the link state transition is suppressed then there is no
   change of the /if:interfaces/if:interface/oper-status or
   /if:interfaces/if:interfaces/last-change leaves for the interface
   that the feature is operating on.  One obvious side effect of using



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   this feature that is that any state transition will always be delayed
   by the specified time interval.

   The configuration allows for separate timer values to be used in the
   suppression of down->up->down link transitions vs up->down->up link
   transitions.

   The carrier delay down timer leaf specifies the amount of time that
   an interface that is currently in link up state must be continuously
   down before the down state change is reported to higher level
   protocols.  Use of this timer can cause traffic to be black holed for
   the configured value and delay reconvergence after link failures,
   therefore its use is normally restricted to cases where it is
   necessary to allow enough time for another protection mechanism (such
   as an optical layer automatic protection system) to take effect.

   The carrier delay up timer leaf specifies the amount of time that an
   interface that is currently in link down state must be continuously
   up before the down->up link state transition is reported to higher
   level protocols.  This timer is generally useful as a debounce
   mechanism to ensure that a link is relatively stable before being
   brought into service.  It can also be used effectively to limit the
   frequency at which link state transition events may occur.  The
   default value for this leaf is determined by the underlying network
   device.

2.2.  Dampening

   The dampening feature introduces a configurable exponential decay
   mechanism to suppress the effects of excessive interface link state
   flapping.  This feature allows the network operator to configure a
   device to automatically identify and selectively dampen a local
   interface which is flapping.  Dampening an interface keeps the
   interface operationally down until the interface stops flapping and
   becomes stable.  Configuring the dampening feature can improve
   convergence times and stability throughout the network by isolating
   failures so that disturbances are not propagated, which reduces the
   utilization of system processing resources by other devices in the
   network and improves overall network stability.

   The basic algorithm uses a counter that is increased by 1000 units
   every time the underlying interface link state changes from up to
   down.  If the counter increases above the suppress threshold then the
   interface is kept down (and out of service) until either the maximum
   suppression time is reached, or the counter has reduced below the
   reuse threshold.  The half-life period determines that rate at which
   the counter is periodically reduced by half.




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2.2.1.  Suppress Threshold

   The suppress threshold is the value of the accumulated penalty that
   triggers the device to dampen a flapping interface.  The flapping
   interface is identified by the device and assigned a penalty for each
   up to down link state change, but the interface is not automatically
   dampened.  The device tracks the penalties that a flapping interface
   accumulates.  When the accumulated penalty reaches or exceeds the
   suppress threshold, the interface is placed in a suppressed state.

2.2.2.  Half-Life Period

   The half-life period determines how fast the accumulated penalties
   can decay exponentially.  The accumulated penalty decays at a rate
   that causes its value to be reduced by half after each half-life
   period.

2.2.3.  Reuse Threshold

   If, after one or more half-life periods, the accumulated penalty
   decreases below the reuse threshold and the underlying interface link
   state is up then the interface is taken out of suppressed state and
   is allowed to go up.

2.2.4.  Maximum Suppress Time

   The maximum suppress time represents the maximum amount of time an
   interface can remain dampened when a new penalty is assigned to an
   interface.  The default of the maximum suppress timer is four times
   the half-life period.  The maximum value of the accumulated penalty
   is calculated using the maximum suppress time, reuse threshold and
   half-life period.

2.3.  Encapsulation

   The encapsulation container holds a choice node that is to be
   augmented with datalink layer specific encapsulations, such as HDLC,
   PPP, or sub-interface 802.1Q tag match encapsulations.  The use of a
   choice statement ensures that an interface can only have a single
   datalink layer protocol configured.

   The different encapsulations themselves are defined in separate YANG
   modules defined in other documents that augument the encapsulation
   choice statement.  For example the Ethernet specific basic 'dot1q-
   vlan' encapsulation is defined in ietf-if-l3-vlan.yang and the
   'flexible' encapsulation is defined in ietf-flexible-
   encapsulation.yang, both modules from
   [I-D.ietf-netmod-sub-intf-vlan-model].



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2.4.  Loopback

   The loopback configuration leaf allows any physical interface to be
   configured to be in one of the possible following physical loopback
   modes, i.e. internal loopback, line loopback, or use of an external
   loopback connector.  The use of YANG identities allows for the model
   to be extended with other modes of loopback if required.

   The following loopback modes are defined:

   o  Internal loopback - All egress traffic on the interface is
      internally looped back within the interface to be received on the
      ingress path.

   o  Line loopback - All ingress traffic received on the interface is
      internally looped back within the interface to the egress path.

   o  Loopback Connector - The interface has a physical loopback
      connector attached that loops all egress traffic back into the
      interface's ingress path, with equivalent semantics to internal
      loopback.

2.5.  Maximum frame size

   A maximum frame size configuration leaf (max-frame-size) is provided
   to specify the maximum size of a layer 2 frame that may be
   transmitted or received on an interface.  The value includes the
   overhead of any layer 2 header, the maximum length of the payload,
   and any frame check sequence (FCS) bytes.  If configured, the max-
   frame-size leaf on an interface also restricts the max-frame-size of
   any child sub-interfaces, and the available MTU for protocols.

2.6.  Sub-interface

   The sub-interface feature specifies the minimal leaves required to
   define a child interface that is parented to another interface.

   A sub-interface is a logical interface that handles a subset of the
   traffic on the parent interface.  Separate configuration leaves are
   used to classify the subset of ingress traffic received on the parent
   interface to be processed in the context of a given sub-interface.
   All egress traffic processed on a sub-interface is given to the
   parent interface for transmission.  Otherwise, a sub-interface is
   like any other interface in /if:interfaces and supports the standard
   interface features and configuration.

   For some vendor specific interface naming conventions the name of the
   child interface is sufficient to determine the parent interface,



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   which implies that the child interface can never be reparented to a
   different parent interface after it has been created without deleting
   the existing sub-interface and recreating a new sub-interface.  Even
   in this case it is useful to have a well defined leaf to cleanly
   identify the parent interface.

   The model also allows for arbitrarily named sub-interfaces by having
   an explicit parent-interface leaf define the child -> parent
   relationship.  In this naming scenario it is also possible for
   implementations to allow for logical interfaces to be reparented to
   new parent interfaces without needing the sub-interface to be
   destroyed and recreated.

2.7.  Forwarding Mode

   The forwarding mode leaf provides additional information as to what
   mode or layer an interface is logically operating and forwarding
   traffic at.  The implication of this leaf is that for traffic
   forwarded at a given layer that any headers for lower layers are
   stripped off before the packet is forwarded at the given layer.
   Conversely, on egress any lower layer headers must be added to the
   packet before it is transmitted out of the interface.

   The following forwarding modes are defined:

   o  Physical - Traffic is being forwarded at the physical layer.  This
      includes DWDM or OTN based switching.

   o  Data-link - Layer 2 based forwarding, such as Ethernet/VLAN based
      switching, or L2VPN services.

   o  Network - Network layer based forwarding, such as IP, MPLS, or
      L3VPNs.

3.  Interfaces Ethernet-Like Module

   The Interfaces Ethernet-Like Module is a small module that contains
   all configuration and operational data that is common across
   interface types that use Ethernet framing as their datalink layer
   encapsulation.

   This module currently contains leaves for the configuration and
   reporting of the operational MAC address and the burnt-in MAC address
   (BIA) associated with any interface using Ethernet framing.







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   The "ietf-if-ethernet-like" YANG module has the following structure:


   module: ietf-if-ethernet-like
     augment /if:interfaces/if:interface:
       +--rw ethernet-like
          +--rw mac-address?       yang:mac-address
          |       {configurable-mac-address}?
          +--ro bia-mac-address?   yang:mac-address
     augment /if:interfaces/if:interface/if:statistics:
       +--ro in-drop-unknown-dest-mac-pkts?   yang:counter64


4.  Interface Extensions YANG Module

   This YANG module augments the interface container defined in
   [RFC8343].  It also contains references to [RFC6991] and [RFC7224].


   <CODE BEGINS> file "ietf-if-extensions@2020-07-29.yang"
   module ietf-if-extensions {
     yang-version 1.1;

     namespace "urn:ietf:params:xml:ns:yang:ietf-if-extensions";

     prefix if-ext;

     import ietf-yang-types {
       prefix yang;
       reference "RFC 6991: Common YANG Data Types";
     }

     import ietf-interfaces {
       prefix if;
       reference
         "RFC 8343: A YANG Data Model For Interface Management";
     }

     import iana-if-type {
       prefix ianaift;
       reference "RFC 7224: IANA Interface Type YANG Module";
     }

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

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



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        WG List:  <mailto:netmod@ietf.org>

        Editor:   Robert Wilton
                  <mailto:rwilton@cisco.com>";

     description
       "This module contains common definitions for extending the IETF
        interface YANG model (RFC 8343) with common configurable layer 2
        properties.

        Copyright (c) 2020 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     revision 2020-07-29 {
       description
         "Initial revision.";

       reference
         "RFC XXXX, Common Interface Extension YANG Data Models";
     }

     feature carrier-delay {
       description
         "This feature indicates that configurable interface carrier
          delay is supported, which is a feature is used to limit the
          propagation of very short interface link state flaps.";
       reference "RFC XXXX, Section 2.1 Carrier Delay";
     }

     feature dampening {
       description



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         "This feature indicates that the device supports interface
          dampening, which is a feature that is used to limit the
          propagation of interface link state flaps over longer
          periods.";
       reference "RFC XXXX, Section 2.2 Dampening";
     }

     feature loopback {
       description
         "This feature indicates that configurable interface loopback is
          supported.";
       reference "RFC XXXX, Section 2.4 Loopback";
     }

     feature max-frame-size {
       description
         "This feature indicates that the device supports configuring or
          reporting the maximum frame size on interfaces.";
       reference "RFC XXXX, Section 2.5 Maximum Frame Size";
     }

     feature sub-interfaces {
       description
         "This feature indicates that the device supports the
          instantiation of sub-interfaces.  Sub-interfaces are defined
          as logical child interfaces that allow features and forwarding
          decisions to be applied to a subset of the traffic processed
          on the specified parent interface.";
       reference "RFC XXXX, Section 2.6 Sub-interface";
     }

     /*
      * Define common identities to help allow interface types to be
      * assigned properties.
      */
     identity sub-interface {
       description
         "Base type for generic sub-interfaces.

          New or custom interface types can derive from this type to
          inherit generic sub-interface configuration.";
       reference "RFC XXXX, Section 2.6 Sub-interface";
     }

     identity ethSubInterface{
       base ianaift:l2vlan;
       base sub-interface;




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       description
         "This identity represents the child sub-interface of any
          interface types that uses Ethernet framing (with or without
          802.1Q tagging).";
     }

     identity loopback {
       description "Base identity for interface loopback options";
       reference "RFC XXXX, Section 2.4";
     }
     identity internal {
       base loopback;
       description
         "All egress traffic on the interface is internally looped back
          within the interface to be received on the ingress path.";
       reference "RFC XXXX, Section 2.4";
     }
     identity line {
       base loopback;
       description
         "All ingress traffic received on the interface is internally
          looped back within the interface to the egress path.";
       reference "RFC XXXX, Section 2.4";
     }
     identity connector {
       base loopback;
       description
         "The interface has a physical loopback connector attached that
          loops all egress traffic back into the interface's ingress
          path, with equivalent semantics to loopback internal.";
       reference "RFC XXXX, Section 2.4";
     }


     identity forwarding-mode {
       description "Base identity for forwarding-mode options.";
       reference "RFC XXXX, Section 2.7";
     }
     identity physical {
       base forwarding-mode;
       description
         "Physical layer forwarding.  This includes DWDM or OTN based
          optical switching.";
       reference "RFC XXXX, Section 2.7";
     }
     identity data-link {
       base forwarding-mode;
       description



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         "Layer 2 based forwarding, such as Ethernet/VLAN based
          switching, or L2VPN services.";
       reference "RFC XXXX, Section 2.7";
     }
     identity network {
       base forwarding-mode;
       description
         "Network layer based forwarding, such as IP, MPLS, or L3VPNs.";
       reference "RFC XXXX, Section 2.7";
     }


     /*
      * Augments the IETF interfaces model with leaves to configure
      * and monitor carrier-delay on an interface.
      */
     augment "/if:interfaces/if:interface" {
       description
         "Augments the IETF interface model with optional common
          interface level commands that are not formally covered by any
          specific standard.";

       /*
        * Defines standard YANG for the Carrier Delay feature.
        */
       container carrier-delay {
         if-feature "carrier-delay";
         description
           "Holds carrier delay related feature configuration.";
         leaf down {
           type uint32;
           units milliseconds;
           description
             "Delays the propagation of a 'loss of carrier signal' event
              that would cause the interface state to go down, i.e. the
              command allows short link flaps to be suppressed. The
              configured value indicates the minimum time interval (in
              milliseconds) that the carrier signal must be continuously
              down before the interface state is brought down. If not
              configured, the behaviour on loss of carrier signal is
              vendor/interface specific, but with the general
              expectation that there should be little or no delay.";
         }
         leaf up {
           type uint32;
           units milliseconds;
           description
             "Defines the minimum time interval (in milliseconds) that



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              the carrier signal must be continuously present and error
              free before the interface state is allowed to transition
              from down to up.  If not configured, the behaviour is
              vendor/interface specific, but with the general
              expectation that sufficient default delay should be used
              to ensure that the interface is stable when enabled before
              being reported as being up.  Configured values that are
              too low for the hardware capabilties may be rejected.";
         }
         leaf carrier-transitions {
           type yang:counter64;
           units transitions;
           config false;
           description
             "Defines the number of times the underlying carrier state
              has changed to, or from, state up.  This counter should be
              incremented even if the high layer interface state changes
              are being suppressed by a running carrier-delay timer.";
         }
         leaf timer-running {
           type enumeration {
             enum none {
               description
                 "No carrier delay timer is running.";
             }
             enum up {
               description
                 "Carrier-delay up timer is running.  The underlying
                  carrier state is up, but interface state is not
                  reported as up.";
             }
             enum down {
               description
                 "Carrier-delay down timer is running.  Interface state
                  is reported as up, but the underlying carrier state is
                  actually down.";
             }
           }
           config false;
           description
             "Reports whether a carrier delay timer is actively running,
              in which case the interface state does not match the
              underlying carrier state.";
         }

         reference "RFC XXXX, Section 2.1 Carrier Delay";
       }




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       /*
        * Augments the IETF interfaces model with a container to hold
        * generic interface dampening
        */
       container dampening {
         if-feature "dampening";
         presence
           "Enable interface link flap dampening with default settings
            (that are vendor/device specific).";
         description
           "Interface dampening limits the propagation of interface link
            state flaps over longer periods.";
         reference "RFC XXXX, Section 2.2 Dampening";

         leaf half-life {
           type uint32;
           units seconds;
           description
             "The time (in seconds) after which a penalty would be half
              its original value.  Once the interface has been assigned
              a penalty, the penalty is decreased at a decay rate
              equivalent to the half-life.  For some devices, the
              allowed values may be restricted to particular multiples
              of seconds.  The default value is vendor/device
              specific.";
           reference "RFC XXXX, Section 2.3.2 Half-Life Period";
         }

         leaf reuse {
           type uint32;
           description
             "Penalty value below which a stable interface is
              unsuppressed (i.e. brought up) (no units).  The default
              value is vendor/device specific.  The penalty value for a
              link up->down state change is 1000 units.";
           reference "RFC XXXX, Section 2.2.3 Reuse Threshold";
         }

         leaf suppress {
           type uint32;
           description
             "Limit at which an interface is suppressed (i.e. held down)
              when its penalty exceeds that limit (no units).  The value
              must be greater than the reuse threshold.  The default
              value is vendor/device specific.  The penalty value for a
              link up->down state change is 1000 units.";
           reference "RFC XXXX, Section 2.2.1 Suppress Threshold";
         }



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         leaf max-suppress-time {
           type uint32;
           units seconds;
           description
             "Maximum time (in seconds) that an interface can be
              suppressed before being unsuppressed if no further link
              up->down state change penalties have been applied.  This
              value effectively acts as a ceiling that the penalty value
              cannot exceed.  The default value is vendor/device
              specific.";
           reference "RFC XXXX, Section 2.2.4 Maximum Suppress Time";
         }

         leaf penalty {
           type uint32;
           config false;
           description
             "The current penalty value for this interface.  When the
              penalty value exceeds the 'suppress' leaf then the
              interface is suppressed (i.e. held down).";
           reference "RFC XXXX, Section 2.2 Dampening";
         }

         leaf suppressed {
           type boolean;
           config false;
           description
             "Represents whether the interface is suppressed (i.e. held
              down) because the 'penalty' leaf value exceeds the
              'suppress' leaf.";
           reference "RFC XXXX, Section 2.2 Dampening";
         }

         leaf time-remaining {
           when '../suppressed = "true"' {
             description
               "Only suppressed interfaces have a time remaining.";
           }
           type uint32;
           units seconds;
           config false;
           description
             "For a suppressed interface, this leaf represents how long
              (in seconds) that the interface will remain suppressed
              before it is allowed to go back up again.";
           reference "RFC XXXX, Section 2.2 Dampening";
         }
       }



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       /*
        * Various types of interfaces support a configurable layer 2
        * encapsulation, any that are supported by YANG should be
        * listed here.
        *
        * Different encapsulations can hook into the common encaps-type
        * choice statement.
        */
       container encapsulation {
         when
           "derived-from-or-self(../if:type,
                                 'ianaift:ethernetCsmacd') or
            derived-from-or-self(../if:type,
                                 'ianaift:ieee8023adLag') or
            derived-from-or-self(../if:type, 'ianaift:pos') or
            derived-from-or-self(../if:type,
                                 'ianaift:atmSubInterface') or
            derived-from-or-self(../if:type, 'ianaift:l2vlan') or
            derived-from-or-self(../if:type, 'ethSubInterface')" {

           description
             "All interface types that can have a configurable L2
              encapsulation.";
         }

         description
           "Holds the OSI layer 2 encapsulation associated with an
            interface.";
         choice encaps-type {
           description
             "Extensible choice of layer 2 encapsulations";
           reference "RFC XXXX, Section 2.3 Encapsulation";
         }
       }

        /*
         * Various types of interfaces support loopback configuration,
         * any that are supported by YANG should be listed here.
         */
       leaf loopback {
         when "derived-from-or-self(../if:type,
                                    'ianaift:ethernetCsmacd') or
               derived-from-or-self(../if:type, 'ianaift:sonet') or
               derived-from-or-self(../if:type, 'ianaift:atm') or
               derived-from-or-self(../if:type, 'ianaift:otnOtu')" {
           description
             "All interface types that support loopback configuration.";
         }



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         if-feature "loopback";
         type identityref {
           base loopback;
         }
         description "Enables traffic loopback.";
         reference "RFC XXXX, Section 2.4 Loopback";
       }

       /*
        * Allows the maximum frame size to be configured or reported.
        */
       leaf max-frame-size {
         if-feature "max-frame-size";
         type uint32 {
           range "64 .. max";
         }
         description
           "The maximum size of layer 2 frames that may be transmitted
            or received on the interface (including any frame header,
            maximum frame payload size, and frame checksum sequence).

            If configured, the max-frame-size also limits the maximum
            frame size of any child sub-interfaces.  The MTU available
            to higher layer protocols is restricted to the maximum frame
            payload size, and MAY be further restricted by explicit
            layer 3 or protocol specific MTU configuration.";

         reference "RFC XXXX, Section 2.5 Maximum Frame Size";
       }

       /*
        * Augments the IETF interfaces model with a leaf that indicates
        * which mode, or layer, is being used to forward the traffic.
        */
       leaf forwarding-mode {
         type identityref {
           base forwarding-mode;
         }
         config false;

         description
           "The forwarding mode that the interface is operating in.";
         reference "RFC XXXX, Section 2.7 Forwarding Mode";
       }
     }

     /*
      * Add generic support for sub-interfaces.



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      *
      * This should be extended to cover all interface types that are
      * child interfaces of other interfaces.
      */
     augment "/if:interfaces/if:interface" {
       when "derived-from(if:type, 'sub-interface') or
             derived-from-or-self(if:type, 'ianaift:l2vlan') or
             derived-from-or-self(if:type, 'ianaift:atmSubInterface') or
             derived-from-or-self(if:type, 'ianaift:frameRelay')"  {
         description
           "Any ianaift:types that explicitly represent sub-interfaces
            or any types that derive from the sub-interface identity.";
       }
       if-feature "sub-interfaces";

       description
         "Adds a parent interface field to interfaces that model
          sub-interfaces.";
       leaf parent-interface {

         type if:interface-ref;

         mandatory true;
         description
           "This is the reference to the parent interface of this
            sub-interface.";
         reference "RFC XXXX, Section 2.6 Sub-interface";
       }
     }

     /*
      * Add discard counter for unknown sub-interface encapsulation
      */
     augment "/if:interfaces/if:interface/if:statistics" {
       when "derived-from-or-self(../if:type,
                                  'ianaift:ethernetCsmacd') or
             derived-from-or-self(../if:type,
                                  'ianaift:ieee8023adLag') or
             derived-from-or-self(../if:type, 'ianaift:ifPwType')" {
         description
           "Applies to interfaces that can demultiplex ingress frames to
            sub-interfaces.";
       }
       if-feature "sub-interfaces";

       description
         "Augment the interface model statistics with a sub-interface
          demux discard counter.";



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       leaf in-discard-unknown-encaps {
         type yang:counter64;
         units frames;
         description
           "A count of the number of frames that were well formed, but
            otherwise discarded because their encapsulation does not
            classify the frame to the interface or any child
            sub-interface.  E.g., a frame might be discarded because the
            it has an unknown VLAN Id, or does not have a VLAN Id when
            one is expected.

            For consistency, frames counted against this counter are
            also counted against the IETF interfaces statistics.  In
            particular, they are included in in-octets and in-discards,
            but are not included in in-unicast-pkts, in-multicast-pkts
            or in-broadcast-pkts, because they are not delivered to a
            higher layer.

            Discontinuities in the values of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of the 'discontinuity-time'
            leaf defined in the ietf-interfaces YANG module
            (RFC 8343).";
       }
     }
   }
   <CODE ENDS>


5.  Interfaces Ethernet-Like YANG Module

   This YANG module augments the interface container defined in RFC 8343
   [RFC8343] for Ethernet-like interfaces.  This includes Ethernet
   interfaces, 802.3 LAG (802.1AX) interfaces, Switch Virtual
   interfaces, and Pseudo-Wire Head-End interfaces.  It also contains
   references to [RFC6991], [RFC7224], and [IEEE802.3.2-2019].


   <CODE BEGINS> file "ietf-if-ethernet-like@2019-11-04.yang"
   module ietf-if-ethernet-like {
     yang-version 1.1;

     namespace
       "urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like";

     prefix ethlike;

     import ietf-interfaces {



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       prefix if;
       reference
         "RFC 8343: A YANG Data Model For Interface Management";
     }

     import ietf-yang-types {
       prefix yang;
       reference "RFC 6991: Common YANG Data Types";
     }

     import iana-if-type {
       prefix ianaift;
       reference "RFC 7224: IANA Interface Type YANG Module";
     }

     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:   Robert Wilton
                  <mailto:rwilton@cisco.com>";

     description
       "This module contains YANG definitions for configuration for
        'Ethernet-like' interfaces.  It is applicable to all interface
        types that use Ethernet framing and expose an Ethernet MAC
        layer, and includes such interfaces as physical Ethernet
        interfaces, Ethernet LAG interfaces and VLAN sub-interfaces.

        Additional interface configuration and counters for physical
        Ethernet interfaces are defined in
        ieee802-ethernet-interface.yang, as part of IEEE Std
        802.3.2-2019.

        Copyright (c) 2019 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX



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        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.";

     revision 2019-11-04 {
       description "Initial revision.";

       reference
         "RFC XXXX, Common Interface Extension YANG Data Models";
     }

     feature configurable-mac-address {
       description
         "This feature indicates that MAC addresses on Ethernet-like
          interfaces can be configured.";
       reference
         "RFC XXXX, Section 3, Interfaces Ethernet-Like Module";
     }


     /*
      * Configuration parameters for Ethernet-like interfaces.
      */
     augment "/if:interfaces/if:interface" {
       when "derived-from-or-self(if:type, 'ianaift:ethernetCsmacd') or
             derived-from-or-self(if:type, 'ianaift:ieee8023adLag') or
             derived-from-or-self(if:type, 'ianaift:ifPwType')" {
         description "Applies to all Ethernet-like interfaces";
       }
       description
         "Augment the interface model with parameters for all
          Ethernet-like interfaces.";

       container ethernet-like {
         description
           "Contains parameters for interfaces that use Ethernet framing
            and expose an Ethernet MAC layer.";

         leaf mac-address {
           if-feature "configurable-mac-address";
           type yang:mac-address;
           description
             "The MAC address of the interface.  The operational value
              matches the /if:interfaces/if:interface/if:phys-address
              leaf defined in ietf-interface.yang.";
         }

         leaf bia-mac-address {
           type yang:mac-address;



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           config false;
           description
             "The 'burnt-in' MAC address.  I.e the default MAC address
              assigned to the interface if no MAC address has been
              explicitly configured on it.";
         }
       }
     }


     /*
      * Configuration parameters for Ethernet-like interfaces.
      */
     augment "/if:interfaces/if:interface/if:statistics" {
       when "derived-from-or-self(../if:type,
                                  'ianaift:ethernetCsmacd') or
             derived-from-or-self(../if:type,
                                  'ianaift:ieee8023adLag') or
             derived-from-or-self(../if:type, 'ianaift:ifPwType')" {
         description "Applies to all Ethernet-like interfaces";
       }
       description
         "Augment the interface model statistics with additional
          counters related to Ethernet-like interfaces.";

       leaf in-discard-unknown-dest-mac-pkts {
         type yang:counter64;
         units frames;
         description
           "A count of the number of frames that were well formed, but
            otherwise discarded because the destination MAC address did
            not pass any ingress destination MAC address filter.

            For consistency, frames counted against this counter are
            also counted against the IETF interfaces statistics.  In
            particular, they are included in in-octets and in-discards,
            but are not included in in-unicast-pkts, in-multicast-pkts
            or in-broadcast-pkts, because they are not delivered to a
            higher layer.

            Discontinuities in the values of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of the 'discontinuity-time'
            leaf defined in the ietf-interfaces YANG module
            (RFC 8343).";
       }
     }
   }



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   <CODE ENDS>


6.  Examples

   The following sections give some examples of how different parts of
   the YANG modules could be used.  Examples are not given for the more
   trivial configuration, or for sub-interfaces, for which examples are
   contained in [I-D.ietf-netmod-sub-intf-vlan-model].

6.1.  Carrier delay configuration

   The following example shows how the operational state datastore could
   look like for an Ethernet interface without any carrier delay
   configuration.  The down leaf value of 0 indicates that link down
   events as always propagated to high layers immediately, but an up
   leaf value of 50 indicates that the interface must be up and stable
   for at least 50 msecs before the interface is reported as being up to
   the high layers.


   <?xml version="1.0" encoding="utf-8"?>
   <interfaces
    xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
    xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"
   xmlns:if-ext="urn:ietf:params:xml:ns:yang:ietf-if-extensions">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <if-ext:carrier-delay>
         <if-ext:down>0</if-ext:down>
         <if-ext:up>50</if-ext:up>
       </if-ext:carrier-delay>
     </interface>
   </interfaces>


   The following example shows explicit carrier delay up and down values
   have been configured.  A 50 msec down leaf value has been used to
   potentially allow optical protection to recover the link before the
   higher layer protocol state is flapped.  A 1 second (1000
   milliseconds) up leaf value has been used to ensure that the link is
   always reasonably stable before allowing traffic to be carried over
   it.  This also has the benefit of greatly reducing the rate at which
   higher layer protocol state flaps could occur.






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   <?xml version="1.0" encoding="utf-8"?>
   <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <interfaces
       xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
       xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type"
       xmlns:if-ext="urn:ietf:params:xml:ns:yang:ietf-if-extensions">
       <interface>
         <name>eth0</name>
         <type>ianaift:ethernetCsmacd</type>
         <if-ext:carrier-delay>
           <if-ext:down>50</if-ext:down>
           <if-ext:up>1000</if-ext:up>
         </if-ext:carrier-delay>
       </interface>
     </interfaces>
   </config>


6.2.  Dampening configuration

   The following example shows what the operational state datastore may
   look like for an interface configured with interface dampening.  The
   'suppressed' leaf indicates that the interface is currently
   suppressed (i.e. down) because the 'penalty' is greater than the
   'suppress' leaf threshold.  The 'time-remaining' leaf indicates that
   the interface will remain suppressed for another 103 seconds before
   the 'penalty' is below the 'reuse' leaf value and the interface is
   allowed to go back up again.























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   <?xml version="1.0" encoding="utf-8"?>
   <interfaces
    xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
    xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <oper-status>down</oper-status>
       <dampening
        xmlns="urn:ietf:params:xml:ns:yang:ietf-if-extensions">
         <half-life>60</half-life>
         <reuse>750</reuse>
         <suppress>2000</suppress>
         <max-suppress-time>240</max-suppress-time>
         <penalty>2480</penalty>
         <suppressed>true</suppressed>
         <time-remaining>103</time-remaining>
       </dampening>
     </interface>
   </interfaces>


6.3.  MAC address configuration

   The following example shows how the operational state datastore could
   look like for an Ethernet interface without an explicit MAC address
   configured.  The mac-address leaf always reports the actual
   operational MAC address that is in use.  The bia-mac-address leaf
   always reports the default MAC address assigned to the hardware.


   <?xml version="1.0" encoding="utf-8"?>
     <interfaces
       xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
       xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
       <interface>
         <name>eth0</name>
         <type>ianaift:ethernetCsmacd</type>
         <phys-address>00:00:5E:00:53:30</phys-address>
         <ethernet-like
           xmlns="urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like">
           <mac-address>00:00:5E:00:53:30</mac-address>
           <bia-mac-address>00:00:5E:00:53:30</bia-mac-address>
         </ethernet-like>
       </interface>
     </interfaces>





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   The following example shows the intended configuration for interface
   eth0 with an explicit MAC address configured.


   <?xml version="1.0" encoding="utf-8"?>
   <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <interfaces
       xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
       xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
       <interface>
         <name>eth0</name>
         <type>ianaift:ethernetCsmacd</type>
         <ethernet-like
           xmlns="urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like">
           <mac-address>00:00:5E:00:53:35</mac-address>
         </ethernet-like>
       </interface>
     </interfaces>
   </config>


   After the MAC address configuration has been successfully applied,
   the operational state datastore reporting the interface MAC address
   properties would contain the following, with the mac-address leaf
   updated to match the configured value, but the bia-mac-address leaf
   retaining the same value - which should never change.


   <?xml version="1.0" encoding="utf-8"?>
   <interfaces
    xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
    xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
         <phys-address>00:00:5E:00:53:35</phys-address>
       <ethernet-like
         xmlns="urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like">
         <mac-address>00:00:5E:00:53:35</mac-address>
         <bia-mac-address>00:00:5E:00:53:30</bia-mac-address>
       </ethernet-like>
     </interface>
   </interfaces>








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7.  Acknowledgements

   The authors wish to thank Eric Gray, Ing-Wher Chen, Jon Culver,
   Juergen Schoenwaelder, Ladislav Lhotka, Lou Berger, Mahesh
   Jethanandani, Martin Bjorklund, Michael Zitao, Neil Ketley, Qin Wu,
   William Lupton, Xufeng Liu, Andy Bierman, and Vladimir Vassilev for
   their helpful comments contributing to this document.

8.  ChangeLog

   XXX, RFC Editor, please delete this change log before publication.

8.1.  Version -10

   o  Update modules from github and tree diagram.

8.2.  Version -09

   o  Fixed IANA section.

8.3.  Version -08

   o  Initial updates after WG LC comments.

8.4.  Version -07

   o  Minor editorial updates

8.5.  Version -06

   o  Remove reservable-bandwidth, based on Acee's suggestion

   o  Add examples

   o  Add additional state parameters for carrier-delay and dampening

8.6.  Version -05

   o  Incorporate feedback from Andy Bierman

8.7.  Version -04

   o  Incorporate feedback from Lada, some comments left as open issues.








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8.8.  Version -03

   o  Fixed incorrect module name references, and updated tree output

8.9.  Version -02

   o  Minor changes only: Fix errors in when statements, use derived-
      from-or-self() for future proofing.

9.  IANA Considerations

9.1.  YANG Module Registrations

   The following YANG modules are requested to be registred in the IANA
   "YANG Module Names" [RFC6020] registry:

   The ietf-if-extensions module:

      Name: ietf-if-extensions

      XML Namespace: urn:ietf:params:xml:ns:yang:ietf-if-extensions

      Prefix: if-ext

      Reference: [RFCXXXX]

   The ietf-if-ethernet-like module:

      Name: ietf-if-ethernet-like

      XML Namespace: urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like

      Prefix: ethlike

      Reference: [RFCXXXX]

   This document registers two URIs in the "IETF XML Registry"
   [RFC3688].  Following the format in RFC 3688, the following
   registrations have been made.

      URI: urn:ietf:params:xml:ns:yang:ietf-if-extensions

      Registrant Contact: The IESG.

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

      URI: urn:ietf:params:xml:ns:yang:ietf-if-ethernet-like




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      Registrant Contact: The IESG.

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

10.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol RFC 6241 [RFC6241].  The lowest NETCONF layer is
   the secure transport layer and the mandatory to implement secure
   transport is SSH RFC 6242 [RFC6242].  The NETCONF access control
   model RFC 6536 [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 this 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:

10.1.  ietf-if-extensions.yang

   The ietf-if-extensions YANG module contains various configuration
   leaves that affect the behavior of interfaces.  Modifying these
   leaves can cause an interface to go down, or become unreliable, or to
   drop traffic forwarded over it.  More specific details of the
   possible failure modes are given below.

   The following leaf could cause the interface to go down and stop
   processing any ingress or egress traffic on the interface.  It could
   also cause broadcast traffic storms.

   o  /if:interfaces/if:interface/loopback

   The following leaves could cause instabilities at the interface link
   layer, and cause unwanted higher layer routing path changes if the
   leaves are modified, although they would generally only affect a
   device that had some underlying link stability issues:

   o  /if:interfaces/if:interface/carrier-delay/down

   o  /if:interfaces/if:interface/carrier-delay/up

   o  /if:interfaces/if:interface/dampening/half-life

   o  /if:interfaces/if:interface/dampening/reuse



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   o  /if:interfaces/if:interface/dampening/suppress

   o  /if:interfaces/if:interface/dampening/max-suppress-time

   The following leaves could cause traffic loss on the interface
   because the received or transmitted frames do not comply with the
   frame matching criteria on the interface and hence would be dropped:

   o  /if:interfaces/if:interface/encapsulation

   o  /if:interfaces/if:interface/max-frame-size

   o  /if:interfaces/if:interface/forwarding-mode

   Changing the parent-interface leaf could cause all traffic on the
   affected interface to be dropped.  The affected leaf is:

   o  /if:interfaces/if:interface/parent-interface

10.2.  ietf-if-ethernet-like.yang

   Generally, the configuration nodes in the ietf-if-ethernet-like YANG
   module are concerned with configuration that is common across all
   types of Ethernet-like interfaces.  The module currently only
   contains a node for configuring the operational MAC address to use on
   an interface.  Adding/modifying/deleting this leaf has the potential
   risk of causing protocol instability, excessive protocol traffic, and
   general traffic loss, particularly if the configuration change caused
   a duplicate MAC address to be present on the local network .  The
   following leaf is affected:

   o  interfaces/interface/ethernet-like/mac-address

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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






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   [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>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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

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

11.2.  Informative References

   [I-D.ietf-netmod-sub-intf-vlan-model]
              Wilton, R., Ball, D., tapsingh@cisco.com, t., and S.
              Sivaraj, "Sub-interface VLAN YANG Data Models", draft-
              ietf-netmod-sub-intf-vlan-model-07 (work in progress),
              July 2020.

   [IEEE802.3.2-2019]
              IEEE WG802.3 - Ethernet Working Group, "IEEE
              802.3.2-2019", 2019.

   [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>.




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

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

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

Authors' Addresses

   Robert Wilton (editor)
   Cisco Systems

   Email: rwilton@cisco.com


   David Ball
   Cisco Systems

   Email: daviball@cisco.com


   Tapraj Singh
   Cisco Systems

   Email: tapsingh@cisco.com


   Selvakumar Sivaraj
   Juniper Networks

   Email: ssivaraj@juniper.net















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