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YANG Data Model for DHCPv6 Configuration
draft-ietf-dhc-dhcpv6-yang-18

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 9243.
Author Ian Farrer
Last updated 2021-02-22
Replaces draft-cui-dhc-dhcpv6-yang
RFC stream Internet Engineering Task Force (IETF)
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Stream WG state WG Document
Revised I-D Needed - Issue raised by WG
Associated WG milestone
Jul 2021
WGLC draft-ietf-dhc-dhcpv6-yang
Document shepherd Timothy Winters
IESG IESG state Became RFC 9243 (Proposed Standard)
Consensus boilerplate Yes
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Responsible AD (None)
Send notices to Timothy Winters <tim@qacafe.com>
draft-ietf-dhc-dhcpv6-yang-18
DHC Working Group                                         I. Farrer, Ed.
Internet-Draft                                       Deutsche Telekom AG
Intended status: Standards Track                        22 February 2021
Expires: 26 August 2021

                YANG Data Model for DHCPv6 Configuration
                     draft-ietf-dhc-dhcpv6-yang-18

Abstract

   This document describes YANG data modules for the configuration and
   management of DHCPv6 (Dynamic Host Configuration Protocol for IPv6)
   servers, relays, and clients.

Requirements Language

   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] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 26 August 2021.

Copyright Notice

   Copyright (c) 2021 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.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Extensibility of the DHCPv6 Server YANG Module  . . . . .   3
       1.2.1.  DHCPv6 Option Definitions . . . . . . . . . . . . . .   4
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  DHCPv6 Tree Diagrams  . . . . . . . . . . . . . . . . . . . .   6
     2.1.  DHCPv6 Server Tree Diagram  . . . . . . . . . . . . . . .   6
     2.2.  DHCPv6 Relay Tree Diagram . . . . . . . . . . . . . . . .  13
     2.3.  DHCPv6 Client Tree Diagram  . . . . . . . . . . . . . . .  15
   3.  DHCPv6 YANG Modules . . . . . . . . . . . . . . . . . . . . .  19
     3.1.  DHCPv6 Server YANG Module . . . . . . . . . . . . . . . .  19
     3.2.  DHCPv6 Relay YANG Module  . . . . . . . . . . . . . . . .  36
     3.3.  DHCPv6 Client YANG Module . . . . . . . . . . . . . . . .  46
     3.4.  DHCPv6 Common YANG Module . . . . . . . . . . . . . . . .  58
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  65
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  67
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  68
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  68
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  68
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  68
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  70
   Appendix A.  Example of Augmenting Additional DHCPv6 Option
           Definitions . . . . . . . . . . . . . . . . . . . . . . .  70
   Appendix B.  Example Vendor Specific Server Configuration
           Module  . . . . . . . . . . . . . . . . . . . . . . . . .  75
   Appendix C.  Example definition of class selector
           configuration . . . . . . . . . . . . . . . . . . . . . .  81
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  89

1.  Introduction

   DHCPv6 [RFC8415] is widely used for supplying configuration and other
   relevant parameters to clients in IPv6 networks.  This document
   defines YANG [RFC7950] modules for the configuration and management
   of DHCPv6 'element' (servers, relays and clients) using the Network
   Configuration Protocol (NETCONF [RFC6241]) or RESTCONF [RFC8040]
   protocols.

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   Separate modules are defined for each element.  Additionally, a
   'common' module contains typedefs and groupings used by all of the
   element modules.

   It is worth noting that as DHCPv6 is itself a client configuration
   protocol, it is not the intention of this document to provide a
   replacement for the allocation of DHCPv6 assigned addressing and
   parameters by using NETCONF/YANG.  The DHCPv6 client module is
   intended for the configuration and monitoring of the DHCPv6 client
   function and does not play a part in the normal DHCPv6 message flow.

   The YANG modules in this document adopt the Network Management
   Datastore Architecture (NMDA) [RFC8342].

1.1.  Scope

   [RFC8415] describes the current version of the DHCPv6 base protocol
   specification.  A large number of additional specifications have also
   been published, extending DHCPv6 element functionality and adding new
   options.  The YANG modules contained in this document do not attempt
   to capture all of these extensions and additions, rather to model the
   DHCPv6 functions and options covered in [RFC8415].  A focus has also
   been given on the extensibility of the modules so that it is easy to
   augment in additional functionality as required by a particular
   implementation or deployment scenario.

1.2.  Extensibility of the DHCPv6 Server YANG Module

   The modules in this document only attempt to model DHCPv6 specific
   behavior and do not cover the configuration and management of
   functionality relevant for specific server implementations.  The
   level of variance between implementations is too great to attempt to
   standardize in a way that is useful without being restrictive.

   However, it is recognized that implementation specific configuration
   and management is also an essential part of DHCP deployment and
   operations.  To resolve this, Appendix B contains an example YANG
   module for the configuration of implementation specific functions,
   illustrating how this functionality can be augmented into the main
   'ietf-dhcpv6-server.yang' module.

   In DHCPv6, the concept of 'class selection' for messages received by
   the server is common.  This is the identification and classification
   of messages based on a number of parameters so that the correct
   provisioning information can be supplied.  For example, allocating a
   prefix from the correct pool, or supplying a set of options relevant
   for a specific vendor's client implementation.  During the
   development of this document, research has been carried out into a

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   number of vendor's class selection implementations and the findings
   were that while this function is common to all, the method for
   configuring and implementing this function differs greatly.
   Therefore, configuration of the class selection function has been
   omitted from the DHCPv6 server module to allow implementors to define
   their own suitable YANG module.  Appendix C provides an example of
   this, to demonstrate how this is can be integrated with the main
   'ietf-dhcpv6-server.yang' module.

1.2.1.  DHCPv6 Option Definitions

   A large number of DHCPv6 options have been created in addition to
   those defined in [RFC8415].  As implementations differ widely as to
   which DHCPv6 options they support, the following approach has been
   taken to defining options: Only the DHCPv6 options defined in
   [RFC8415] are included in this document.

   Of these, only the options that require operator configuration are
   modelled.  E.g.  OPTION_IA_NA (3) is created by the DHCP server when
   requested by the client.  The contents of the fields in the option
   are based on a number of input configuration parameters which the
   server will apply when it receives the request (e.g., the T1/T2
   timers that are relevant for the pool of addresses).  As a result,
   there are no fields that are directly configurable in the option, so
   it is not modelled.

   The following table shows the DHCPv6 options that are modelled, the
   element(s) they are sent by, and the relevant YANG module name:

   +---------------------+------+-----+------+-------------------------+
   | Name                |Server|Relay|Client| Module Name             |
   +=====================+======+=====+======+=========================+
   |OPTION_ORO (6) Option|      |     |  X   | ietf-dhcpv6-client.yang |
   | Request Option      |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   |OPTION_PREFERENCE (7)|  X   |     |      | ietf-dhcpv6-server.yang |
   | Preference Option   |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_AUTH (11)    |  X   |  X  |      | ietf-dhcpv6-common.yang |
   |Authentication Option|      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_UNICAST (12) |  X   |     |      | ietf-dhcpv6-server.yang |
   |Server Unicast Option|      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_STATUS_CODE  |  X   |  X  |  X   | ietf-dhcpv6-common.yang |
   | (13) Status Code    |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+

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   | OPTION_RAPID_COMMIT |  X   |     |  X   | ietf-dhcpv6-common.yang |
   | (14) Rapid Commit   |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_USER_CLASS   |      |     |  X   | ietf-dhcpv6-client.yang |
   | (15) User Class     |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_VENDOR_CLASS |      |     |  X   | ietf-dhcpv6-client.yang |
   | (16) Vendor Class   |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_VENDOR_OPTS  |  X   |     |  X   | ietf-dhcpv6-common.yang |
   |(17) Vendor-specific |      |     |      |                         |
   | Information Option  |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_INTERFACE_ID |      |  X  |      | ietf-dhcpv6-relay.yang  |
   | (18) Interface-Id   |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_RECONF_MSG   |  X   |     |      | ietf-dhcpv6-server.yang |
   | (19) Reconfigure    |      |     |      |                         |
   | Message Option      |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   |OPTION_RECONF_ACCEPT |  X   |     |  X   | ietf-dhcpv6-client.yang |
   | (20) Reconfigure    |      |     |      |                         |
   | Accept Option       |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_INFORMATION  |  X   |     |      | ietf-dhcpv6-server.yang |
   | _REFRESH_TIME (32)  |      |     |      |                         |
   | Information Refresh |      |     |      |                         |
   | Time Option         |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_SOL_MAX_RT   |  X   |     |      | ietf-dhcpv6-server.yang |
   | (82) sol max rt     |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+
   | OPTION_INF_MAX_RT   |  X   |     |      | ietf-dhcpv6-server.yang |
   | (83) inf max rt     |      |     |      |                         |
   | Option              |      |     |      |                         |
   +---------------------+------+-----+------+-------------------------+

                      Table 1: Modelled DHCPv6 Options

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   Further options definitions can be added using additional YANG
   modules via augmentation into the relevant element modules from this
   document.  Appendix A contains an example module showing how the
   DHCPv6 option definitions can be extended in this manner.  Some
   guidance on how to write YANG modules for additional DHCPv6 options
   is also provided.

1.3.  Terminology

   The reader should be familiar with the YANG data modelling language
   defined in [RFC7950].

   The YANG modules in this document adopt the Network Management
   Datastore Architecture (NMDA) [RFC8342].  The meanings of the symbols
   used in tree diagrams are defined in [RFC8340].

   The reader should be familiar with DHCPv6 relevant terminology as
   defined in [RFC8415] and other relevant documents.

2.  DHCPv6 Tree Diagrams

2.1.  DHCPv6 Server Tree Diagram

   The tree diagram in Figure 1 provides an overview of the DHCPv6
   server module.  The tree also includes the common functions module
   Section 3.4.

     module: ietf-dhcpv6-server
       +--rw dhcpv6-server
          +--rw enabled?          boolean
          +--rw server-duid?      dhcpv6-common:duid
          +--rw vendor-config
          +--rw option-sets
          |  +--rw option-set* [option-set-id]
          |     +--rw option-set-id                         uint32
          |     +--rw description?                          string
          |     +--rw preference-option
          |     |  +--rw pref-value?   uint8
          |     +--rw auth-option
          |     |  +--rw protocol?           uint8
          |     |  +--rw algorithm?          uint8
          |     |  +--rw rdm?                uint8
          |     |  +--rw replay-detection?   uint64
          |     |  +--rw auth-information?   string
          |     +--rw server-unicast-option
          |     |  +--rw server-address?   inet:ipv6-address
          |     +--rw status-code-option
          |     |  +--rw status-code?      uint16

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          |     |  +--rw status-message?   string
          |     +--rw rapid-commit-option!
          |     +--rw vendor-specific-information-option
          |     |  +--rw vendor-specific-information-option-instances*
          |     |          [enterprise-number]
          |     |     +--rw enterprise-number     uint32
          |     |     +--rw vendor-option-data* [sub-option-code]
          |     |        +--rw sub-option-code    uint16
          |     |        +--rw sub-option-data?   string
          |     +--rw reconfigure-message-option
          |     |  +--rw msg-type?   uint8
          |     +--rw reconfigure-accept-option!
          |     +--rw info-refresh-time-option
          |     |  +--rw info-refresh-time?
          |     |          dhcpv6-common:timer-seconds32
          |     +--rw sol-max-rt-option
          |     |  +--rw sol-max-rt-value?
          |     |          dhcpv6-common:timer-seconds32
          |     +--rw inf-max-rt-option
          |        +--rw inf-max-rt-value?
          |                dhcpv6-common:timer-seconds32
          +--rw class-selector
          +--rw network-ranges
             +--rw option-set-id*               leafref
             +--rw valid-lifetime?
             |       dhcpv6-common:timer-seconds32
             +--rw renew-time?
             |       dhcpv6-common:timer-seconds32
             +--rw rebind-time?
             |       dhcpv6-common:timer-seconds32
             +--rw preferred-lifetime?
             |       dhcpv6-common:timer-seconds32
             +--rw rapid-commit?                boolean
             +--rw network-range* [id]
             |  +--rw id                    uint32
             |  +--rw description           string
             |  +--rw network-prefix        inet:ipv6-prefix
             |  +--rw option-set-id*        leafref
             |  +--rw valid-lifetime?
             |  |       dhcpv6-common:timer-seconds32
             |  +--rw renew-time?
             |  |       dhcpv6-common:timer-seconds32
             |  +--rw rebind-time?
             |  |       dhcpv6-common:timer-seconds32
             |  +--rw preferred-lifetime?
             |  |       dhcpv6-common:timer-seconds32
             |  +--rw rapid-commit?         boolean
             |  +--rw address-pools

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             |  |  +--rw address-pool* [pool-id]
             |  |     +--rw pool-id               uint32
             |  |     +--rw pool-prefix           inet:ipv6-prefix
             |  |     +--rw start-address
             |  |     |       inet:ipv6-address-no-zone
             |  |     +--rw end-address
             |  |     |       inet:ipv6-address-no-zone
             |  |     +--rw max-address-count
             |  |     |       dhcpv6-common:threshold
             |  |     +--rw option-set-id*        leafref
             |  |     +--rw valid-lifetime?
             |  |     |       dhcpv6-common:timer-seconds32
             |  |     +--rw renew-time?
             |  |     |       dhcpv6-common:timer-seconds32
             |  |     +--rw rebind-time?
             |  |     |       dhcpv6-common:timer-seconds32
             |  |     +--rw preferred-lifetime?
             |  |     |       dhcpv6-common:timer-seconds32
             |  |     +--rw rapid-commit?         boolean
             |  |     +--rw host-reservations
             |  |     |  +--rw host-reservation* [reserved-addr]
             |  |     |     +--rw client-duid?
             |  |     |     |       dhcpv6-common:duid
             |  |     |     +--rw reserved-addr
             |  |     |     |       inet:ipv6-address
             |  |     |     +--rw option-set-id*        leafref
             |  |     |     +--rw valid-lifetime?
             |  |     |     |       dhcpv6-common:timer-seconds32
             |  |     |     +--rw renew-time?
             |  |     |     |       dhcpv6-common:timer-seconds32
             |  |     |     +--rw rebind-time?
             |  |     |     |       dhcpv6-common:timer-seconds32
             |  |     |     +--rw preferred-lifetime?
             |  |     |     |       dhcpv6-common:timer-seconds32
             |  |     |     +--rw rapid-commit?         boolean
             |  |     +--ro active-leases
             |  |        +--ro total-count        uint64
             |  |        +--ro allocated-count    uint64
             |  |        +--ro active-lease* [leased-address]
             |  |           +--ro leased-address
             |  |           |       inet:ipv6-address
             |  |           +--ro client-duid?
             |  |           |       dhcpv6-common:duid
             |  |           +--ro iaid                  uint32
             |  |           +--ro allocation-time?
             |  |           |       yang:date-and-time
             |  |           +--ro last-renew-rebind?
             |  |           |       yang:date-and-time

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             |  |           +--ro preferred-lifetime?
             |  |           |       dhcpv6-common:timer-seconds32
             |  |           +--ro valid-lifetime?
             |  |           |       dhcpv6-common:timer-seconds32
             |  |           +--ro lease-t1?
             |  |           |       dhcpv6-common:timer-seconds32
             |  |           +--ro lease-t2?
             |  |                   dhcpv6-common:timer-seconds32
             |  +--rw prefix-pools {prefix-delegation}?
             |     +--rw prefix-pool* [pool-id]
             |        +--rw pool-id                     uint32
             |        +--rw pool-prefix
             |        |       inet:ipv6-prefix
             |        +--rw client-prefix-length        uint8
             |        +--rw max-pd-space-utilization
             |        |       dhcpv6-common:threshold
             |        +--rw option-set-id*              leafref
             |        +--rw valid-lifetime?
             |        |       dhcpv6-common:timer-seconds32
             |        +--rw renew-time?
             |        |       dhcpv6-common:timer-seconds32
             |        +--rw rebind-time?
             |        |       dhcpv6-common:timer-seconds32
             |        +--rw preferred-lifetime?
             |        |       dhcpv6-common:timer-seconds32
             |        +--rw rapid-commit?               boolean
             |        +--rw host-reservations
             |        |  +--rw prefix-reservation* [reserved-prefix]
             |        |  |  +--rw client-duid?
             |        |  |  |       dhcpv6-common:duid
             |        |  |  +--rw reserved-prefix
             |        |  |  |       inet:ipv6-prefix
             |        |  |  +--rw reserved-prefix-len?   uint8
             |        |  +--rw option-set-id*        leafref
             |        |  +--rw valid-lifetime?
             |        |  |       dhcpv6-common:timer-seconds32
             |        |  +--rw renew-time?
             |        |  |       dhcpv6-common:timer-seconds32
             |        |  +--rw rebind-time?
             |        |  |       dhcpv6-common:timer-seconds32
             |        |  +--rw preferred-lifetime?
             |        |  |       dhcpv6-common:timer-seconds32
             |        |  +--rw rapid-commit?         boolean
             |        +--ro active-leases
             |           +--ro total-count        uint64
             |           +--ro allocated-count    uint64
             |           +--ro active-lease* [leased-prefix]
             |              +--ro leased-prefix

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             |              |       inet:ipv6-prefix
             |              +--ro client-duid?
             |              |       dhcpv6-common:duid
             |              +--ro iaid                  uint32
             |              +--ro allocation-time?
             |              |       yang:date-and-time
             |              +--ro last-renew-rebind?
             |              |       yang:date-and-time
             |              +--ro preferred-lifetime?
             |              |       dhcpv6-common:timer-seconds32
             |              +--ro valid-lifetime?
             |              |       dhcpv6-common:timer-seconds32
             |              +--ro lease-t1?
             |              |       dhcpv6-common:timer-seconds32
             |              +--ro lease-t2?
             |                      dhcpv6-common:timer-seconds32
             +--ro solicit-count?               uint32
             +--ro advertise-count?             uint32
             +--ro request-count?               uint32
             +--ro confirm-count?               uint32
             +--ro renew-count?                 uint32
             +--ro rebind-count?                uint32
             +--ro reply-count?                 uint32
             +--ro release-count?               uint32
             +--ro decline-count?               uint32
             +--ro reconfigure-count?           uint32
             +--ro information-request-count?   uint32

       rpcs:
         +---x delete-address-lease
         |  +---w input
         |  |  +---w lease-address-to-delete    inet:ipv6-address
         |  +--ro output
         |     +--ro return-message?   string
         +---x delete-prefix-lease
            +---w input
            |  +---w lease-prefix-to-delete    inet:ipv6-prefix
            +--ro output
               +--ro return-message?   string

       notifications:
         +---n address-pool-utilization-threshold-exceeded
         |  +--ro pool-id?                   leafref
         |  +--ro total-address-count        uint64
         |  +--ro max-address-count          uint64
         |  +--ro allocated-address-count    uint64
         +---n prefix-pool-utilization-threshold-exceeded
         |       {prefix-delegation}?

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         |  +--ro pool-id                     leafref
         |  +--ro max-pd-space-utilization    leafref
         |  +--ro pd-space-utilization?       uint64
         +---n invalid-client-detected
         |  +--ro duid?          dhcpv6-common:duid
         |  +--ro description?   string
         +---n decline-received
         |  +--ro duid?                 dhcpv6-common:duid
         |  +--ro declined-resources* []
         |     +--ro (resource-type)?
         |        +--:(declined-address)
         |        |  +--ro address?   inet:ipv6-address
         |        +--:(declined-prefix)
         |           +--ro prefix?    inet:ipv6-prefix
         +---n non-success-code-sent
            +--ro status-code    uint16
            +--ro duid?          dhcpv6-common:duid

               Figure 1: DHCPv6 Server Data Module Structure

   Descriptions of important nodes:

   *  enabled: Enables/disables the function of the DHCPv6 server.

   *  dhcpv6-server: This container holds the server's DHCPv6 specific
      configuration.

   *  server-duid: Each server must have a DUID (DHCP Unique Identifier)
      to identify itself to clients.  A DUID consists of a two-octet
      type field and an arbitrary length (of no more than 128-bytes)
      content field.  Currently there are four defined types of DUIDs in
      [RFC8415] and [RFC6355].  The DUID may be configured using the
      format for one of these types, or using the 'unstructured' format.
      The DUID type definitions are imported from the 'ietf-
      dhcpv6-common.yang' module.  [IANA-HARDWARE-TYPES] and [IANA-PEN]
      are referenced for the relevant DUID types.

   *  vendor-config: This container is provided as a location for
      additional implementation specific YANG nodes for the
      configuration of the device to be augmented.  See Appendix B for
      an example of such a module.

   *  option-sets: The server can be configured with multiple option-
      sets.  These are groups of DHCPv6 options with common parameters
      which will be supplied to clients on request.  The 'option-set-id'
      field is used to reference an option-set elsewhere in the server's
      configuration.

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   *  option-set: Holds configuration parameters for DHCPv6 options.
      The initial set of applicable option definitions are defined here
      and additional options that are also relevant to the relay and/or
      client are imported from the 'ietf-dhcpv6-common' module.  Where
      needed, other DHCPv6 option modules can be augmented as they are
      defined.

   *  class-selector: This is provided as a location for additional
      implementation specific YANG nodes for vendor specific class
      selector nodes to be augmented.  See Appendix C for an example of
      this.

   *  network-ranges: A hierarchical model is used for the allocation of
      addresses and prefixes.  At the top level 'network-ranges' holds
      global configuration parameters.  Under this, a list of 'network-
      ranges' can be defined.  Inside 'network-rages', 'address-pools'
      (for IA_NA and IA_TA allocations), and 'prefix-pools' (for IA_PD
      allocation) are defined.  Finally within the pools, specific host-
      reservations are held.

   *  prefix-pools: Defines pools to be used for prefix delegation to
      clients.  As prefix delegation is not supported by all DHCPv6
      server implementations, it is enabled by a feature statement.

   Information about notifications:

   *  address/prefix-pool-utilization-threshold-exceeded: Raised when
      number of leased addresses or prefixes exceeds the configured
      usage threshold.

   *  invalid-client-detected: Raised when the server detects an invalid
      client.  A description of the error that has generated the
      notification can be included.

   *  decline-received: Raised when a DHCPv6 Decline message is received
      from a client.

   *  non-success-code-sent: Raised when a status message is raised for
      an error.

   Information about RPCs

   *  delete-address-lease: Allows the deletion of a lease for an
      individual IPv6 address from the server's lease database.

   *  delete-prefix-lease: Allows the deletion of a lease for an
      individual IPv6 prefix from the server's lease database.

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2.2.  DHCPv6 Relay Tree Diagram

   The tree diagram in Figure 2 provides an overview of the DHCPv6 relay
   module.  The tree also includes the common functions module
   Section 3.4.

       module: ietf-dhcpv6-relay
         +--rw dhcpv6-relay
            +--rw enabled?                                boolean
            +--rw relay-if* [if-name]
            |  +--rw if-name
            |  |       if:interface-ref
            |  +--rw enabled?                              boolean
            |  +--rw destination-addresses*
            |  |       inet:ipv6-address
            |  +--rw link-address?                         binary
            |  +--rw relay-options
            |  |  +--rw auth-option
            |  |  |  +--rw protocol?           uint8
            |  |  |  +--rw algorithm?          uint8
            |  |  |  +--rw rdm?                uint8
            |  |  |  +--rw replay-detection?   uint64
            |  |  |  +--rw auth-information?   string
            |  |  +--rw status-code-option
            |  |  |  +--rw status-code?      uint16
            |  |  |  +--rw status-message?   string
            |  |  +--rw interface-id-option
            |  |     +--rw interface-id?   string
            |  +--ro solicit-received-count?               uint32
            |  +--ro advertise-sent-count?                 uint32
            |  +--ro request-received-count?               uint32
            |  +--ro confirm-received-count?               uint32
            |  +--ro renew-received-count?                 uint32
            |  +--ro rebind-received-count?                uint32
            |  +--ro reply-sent-count?                     uint32
            |  +--ro release-received-count?               uint32
            |  +--ro decline-received-count?               uint32
            |  +--ro reconfigure-sent-count?               uint32
            |  +--ro information-request-received-count?   uint32
            |  +--ro unknown-message-received-count?       uint32
            |  +--ro unknown-message-sent-count?           uint32
            |  +--ro discarded-message-count?              uint32
            |  +--rw prefix-delegation! {prefix-delegation}?
            |     +--ro pd-leases* [ia-pd-prefix]
            |        +--ro ia-pd-prefix           inet:ipv6-prefix
            |        +--ro last-renew?            yang:date-and-time
            |        +--ro client-peer-address?   inet:ipv6-address
            |        +--ro client-duid?           dhcpv6-common:duid

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            |        +--ro server-duid?           dhcpv6-common:duid
            +--ro relay-forward-sent-count?               uint32
            +--ro relay-forward-received-count?           uint32
            +--ro relay-reply-received-count?             uint32
            +--ro relay-forward-unknown-sent-count?       uint32
            +--ro relay-forward-unknown-received-count?   uint32
            +--ro discarded-message-count?                uint32

         rpcs:
           +---x clear-prefix-entry
           |  +---w input
           |  |  +---w lease-prefix    inet:ipv6-prefix
           |  +--ro output
           |     +--ro return-message?   string
           +---x clear-client-prefixes
           |  +---w input
           |  |  +---w client-duid    dhcpv6-common:duid
           |  +--ro output
           |     +--ro return-message?   string
           +---x clear-interface-prefixes
              +---w input
              |  +---w interface    if:interface-ref
              +--ro output
                 +--ro return-message?   string

         notifications:
           +---n relay-event
              +--ro topology-change
                 +--ro relay-if-name?
                 |       -> /dhcpv6-relay/relay-if/if-name
                 +--ro last-ipv6-addr?   inet:ipv6-address

                Figure 2: DHCPv6 Relay Data Module Structure

   Descriptions of important nodes:

   *  enabled: Globally enables/disables all DHCPv6 relay functions.

   *  dhcpv6-relay: This container holds the relay's DHCPv6 specific
      configuration.

   *  relay-if: As a relay may have multiple client-facing interfaces,
      they are configured in a list.  The if-name leaf is the key and is
      an interface-ref to the applicable interface defined by the 'ietf-
      interfaces' YANG module.

   *  enabled: Enables/disables all DHCPv6 relay function for the
      specific interface.

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   *  destination-addresses: Defines a list of IPv6 addresses that
      client messages will be relayed to.  May include unicast or
      multicast addresses.

   *  link-address: Configures the value that the relay will put into
      the link-address field of Relay-Forward messages.

   *  prefix-delegation: As prefix delegation is not supported by all
      DHCPv6 relay implementations, it is enabled by this feature
      statement where required.

   *  pd-leases: Contains read-only nodes for holding information about
      active delegated prefix leases.

   *  relay-options: Holds configuration parameters for DHCPv6 options
      which can be sent by the relay.  The initial set of applicable
      option definitions are defined here and additional options that
      are also relevant to the server and/or client are imported from
      the 'ietf-dhcpv6-common' module.  Where needed, other DHCPv6
      option modules can be augmented as they are defined.

   Information about notifications:

   *  topology-changed: Raised when the topology of the relay agent is
      changed, e.g. a client facing interface is reconfigured.

   Information about RPCs

   *  clear-prefix-lease: Allows the removal of a delegated lease entry
      from the relay.

   *  clear-client-prefixes: Allows the removal of all of the delegated
      lease entries for a single client (referenced by client DUID) from
      the relay.

   *  clear-interface-prefixes: Allows the removal of all of the
      delegated lease entries from an interface on the relay.

2.3.  DHCPv6 Client Tree Diagram

   The tree diagram in Figure 3 provides an overview of the DHCPv6
   client module.  The tree also includes the common functions module
   Section 3.4.

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     module: ietf-dhcpv6-client
       +--rw dhcpv6-client
          +--rw enabled?     boolean
          +--rw client-if* [if-name]
             +--rw if-name                      if:interface-ref
             +--rw enabled?                     boolean
             +--rw duid?                        dhcpv6-common:duid
             +--rw client-configured-options
             |  +--rw option-request-option
             |  |  +--rw oro-option*   uint16
             |  +--rw status-code-option
             |  |  +--rw status-code?      uint16
             |  |  +--rw status-message?   string
             |  +--rw rapid-commit-option!
             |  +--rw user-class-option!
             |  |  +--rw user-class-data* [user-class-datum-id]
             |  |     +--rw user-class-datum-id    uint8
             |  |     +--rw user-class-datum?      string
             |  +--rw vendor-class-option
             |  |  +--rw vendor-class-option-instances*
             |  |          [enterprise-number]
             |  |     +--rw enterprise-number    uint32
             |  |     +--rw vendor-class* [vendor-class-datum-id]
             |  |        +--rw vendor-class-datum-id    uint8
             |  |        +--rw vendor-class-datum?      string
             |  +--rw vendor-specific-information-option
             |  |  +--rw vendor-specific-information-option-instances*
             |  |          [enterprise-number]
             |  |     +--rw enterprise-number     uint32
             |  |     +--rw vendor-option-data* [sub-option-code]
             |  |        +--rw sub-option-code    uint16
             |  |        +--rw sub-option-data?   string
             |  +--rw reconfigure-accept-option!
             +--rw ia-na* [iaid]
             |  +--rw iaid             uint32
             |  +--rw ia-na-options
             |  +--ro lease-state
             |     +--ro ia-na-address?        inet:ipv6-address
             |     +--ro preferred-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro valid-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro lease-t1?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro lease-t2?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro allocation-time?      yang:date-and-time
             |     +--ro last-renew-rebind?    yang:date-and-time

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             |     +--ro server-duid?          dhcpv6-common:duid
             +--rw ia-ta* [iaid]
             |  +--rw iaid             uint32
             |  +--rw ia-ta-options
             |  +--ro lease-state
             |     +--ro ia-ta-address?        inet:ipv6-address
             |     +--ro preferred-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro valid-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro allocation-time?      yang:date-and-time
             |     +--ro last-renew-rebind?    yang:date-and-time
             |     +--ro server-duid?          dhcpv6-common:duid
             +--rw ia-pd* [iaid]
             |  +--rw iaid             uint32
             |  +--rw ia-pd-options
             |  +--ro lease-state
             |     +--ro ia-pd-prefix?         inet:ipv6-prefix
             |     +--ro preferred-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro valid-lifetime?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro lease-t1?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro lease-t2?
             |     |       dhcpv6-common:timer-seconds32
             |     +--ro allocation-time?      yang:date-and-time
             |     +--ro last-renew-rebind?    yang:date-and-time
             |     +--ro server-duid?          dhcpv6-common:duid
             +--ro solicit-count?               uint32
             +--ro advertise-count?             uint32
             +--ro request-count?               uint32
             +--ro confirm-count?               uint32
             +--ro renew-count?                 uint32
             +--ro rebind-count?                uint32
             +--ro reply-count?                 uint32
             +--ro release-count?               uint32
             +--ro decline-count?               uint32
             +--ro reconfigure-count?           uint32
             +--ro information-request-count?   uint32

       notifications:
         +---n invalid-ia-detected
         |  +--ro iaid           uint32
         |  +--ro description?   string
         +---n retransmission-failed
         |  +--ro failure-type    enumeration
         +---n unsuccessful-status-code

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         |  +--ro status-code    uint16
         |  +--ro server-duid    dhcpv6-common:duid
         +---n server-duid-changed
            +--ro new-server-duid         dhcpv6-common:duid
            +--ro previous-server-duid    dhcpv6-common:duid
            +--ro lease-ia-na?
            |       -> /dhcpv6-client/client-if/ia-na/iaid
            +--ro lease-ia-ta?
            |       -> /dhcpv6-client/client-if/ia-ta/iaid
            +--ro lease-ia-pd?
                    -> /dhcpv6-client/client-if/ia-pd/iaid

               Figure 3: DHCPv6 Client Data Module Structure

   Descriptions of important nodes:

   *  enabled: Globally enables/disables all DHCPv6 client functions.

   *  dhcpv6-client: This container holds the client's DHCPv6 specific
      configuration.

   *  client-if: As a client may have multiple interfaces requesting
      configuration over DHCP, they are configured in a list.  The if-
      name leaf is the key and is an interface-ref to the applicable
      interface defined by the 'ietf-interfaces' YANG module.

   *  enabled: Enables/disables all DHCPv6 client function for the
      specific interface.

   *  client-duid: Each client must have a DUID (DHCP Unique Identifier)
      to identify itself to servers and relays.  A DUID consists of a
      two-octet type field and an arbitrary length (of no more than
      128-bytes) content field.  Currently there are four defined types
      of DUIDs in [RFC8415] and [RFC6355].  The DUID may be configured
      using the format for one of these types, or using the
      'unstructured' format.  The DUID type definitions are imported
      from the 'ietf-dhcpv6-common.yang' module.  [IANA-HARDWARE-TYPES]
      and [IANA-PEN] are referenced for the relevant DUID types.

   *  client-configured-options: Holds configuration parameters for
      DHCPv6 options which can be sent by the client.  The initial set
      of applicable option definitions are defined here and additional
      options that are also relevant to the relay and/or server are
      imported from the 'ietf-dhcpv6-common' module.  Where needed,
      other DHCPv6 option modules can be augmented as they are defined.

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   *  ia-na, ia-ta, ia-pd: Contains configuration nodes relevant for
      requesting one or more of each of the lease types.  Read-only
      nodes related to the active lease are also located here.

   Information about notifications:

   *  invalid-ia-detected: Raised when the identity association of the
      client can be proved to be invalid.  Possible conditions include:
      duplicated address, illegal address, etc.

   *  retransmission-failed: Raised when the retransmission mechanism
      defined in [RFC8415] has failed.

3.  DHCPv6 YANG Modules

3.1.  DHCPv6 Server YANG Module

   This module imports typedefs from [RFC6991], [RFC8343].

   <CODE BEGINS> file "ietf-dhcpv6-server.yang"

   module ietf-dhcpv6-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-server";
     prefix "dhcpv6-server";

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

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

     import ietf-dhcpv6-common {
       prefix dhcpv6-common;
       reference
         "RFC XXXX: To be updated on publication";
     }

     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";

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     }

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description "This YANG module defines components for the
       configuration and management of DHCPv6 servers.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";

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       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-12-02 {
       description "Major reworking of the module.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-10";
     }

     revision 2018-09-04 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2018-03-04 {
       description "Resolved most issues on the DHC official
         github";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-12-22 {
       description "Resolve most issues on Ian's github.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-11-24 {
       description "First version of the separated server specific
         YANG model.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Features

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      */

     feature prefix-delegation {
       description "Denotes that the server implements DHCPv6 prefix
         delegation.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 6.2";
     }

     /*
      * Groupings
      */

     grouping resource-config {
       description "Nodes that are reused at multiple levels in the
         DHCPv6 server's addressing hierarchy.";
       leaf-list option-set-id {
         type leafref {
           path "/dhcpv6-server/option-sets/option-set/option-set-id";
         }
         description "The ID field of relevant set of DHCPv6 options
           (option-set) to be provisioned to clients of this
           network-range.";
       }
       leaf valid-lifetime {
         type dhcpv6-common:timer-seconds32;
         description "Valid lifetime for the Identity Association
           (IA).";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 6";
       }
       leaf renew-time {
         type dhcpv6-common:timer-seconds32;
         description "Renew (T1) time.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 4.2";
       }
       leaf rebind-time {
         type dhcpv6-common:timer-seconds32;
         description "Rebind (T2) time.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 4.2";
       }
       leaf preferred-lifetime {
         type dhcpv6-common:timer-seconds32;
         description "Preferred lifetime for the Identity Association
           (IA).";
         reference "RFC 8415: Dynamic Host Configuration Protocol for

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           IPv6 (DHCPv6), Section 6";
       }
       leaf rapid-commit {
         type boolean;
         description "When set to 'true', Specifies that the pool
           supports client-server exchanges involving two messages.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 5.2";
       }
     }

     grouping lease-information {
       description "Binding information for each client that has
         been allocated an IPv6 address or prefix.";
       leaf client-duid {
         type dhcpv6-common:duid;
         description "Client DUID.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 11";
       }
       leaf iaid {
         type uint32;
         mandatory true;
         description "Client's IAID";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 12";
       }
       leaf allocation-time {
         type yang:date-and-time;
         description "Time and date that the lease was made.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 18";
       }
       leaf last-renew-rebind {
         type yang:date-and-time;
         description "Time of the last successful renew or
           rebind.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 18";
       }
       leaf preferred-lifetime {
         type dhcpv6-common:timer-seconds32;
         description "The preferred lifetime expressed in
           seconds.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 6";
       }
       leaf valid-lifetime {

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         type dhcpv6-common:timer-seconds32;
         description "The valid lifetime for the leased prefix
           expressed in seconds.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 6";
       }
       leaf lease-t1 {
         type dhcpv6-common:timer-seconds32;
         description "The time interval after which the client
           should contact the server from which the addresses
           in the IA_NA were obtained to extend the lifetimes
           of the addresses assigned to the IA_PD.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 4.2";
       }
       leaf lease-t2 {
         type dhcpv6-common:timer-seconds32;
         description "The time interval after which the client
           should contact any available server to extend
           the lifetimes of the addresses assigned to the
           IA_PD.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 4.2";
       }
     }

     grouping message-stats {
       description "Counters for DHCPv6 messages.";
       leaf solicit-count {
         type uint32;
         config "false";
         description "Number of Solicit (1) messages received.";
       }
       leaf advertise-count {
         type uint32;
         config "false";
         description "Number of Advertise (2) messages sent.";
       }
       leaf request-count {
         type uint32;
         config "false";
         description "Number of Request (3) messages received.";
       }
       leaf confirm-count {
         type uint32;
         config "false";
         description "Number of Confirm (4) messages received.";
       }

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       leaf renew-count {
         type uint32;
         config "false";
         description "Number of Renew (5) messages received.";
       }
       leaf rebind-count {
         type uint32;
         config "false";
         description "Number of Rebind (6) messages received.";
       }
       leaf reply-count {
         type uint32;
         config "false";
         description "Number of Reply (7) messages sent.";
       }
       leaf release-count {
         type uint32;
         config "false";
         description "Number of Release (8) messages received.";
       }
       leaf decline-count {
         type uint32;
         config "false";
         description "Number of Decline (9) messages received.";
       }
       leaf reconfigure-count {
         type uint32;
         config "false";
         description "Number of Reconfigure (10) messages sent.";
       }
       leaf information-request-count {
         type uint32;
         config "false";
         description "Number of Information-request (11) messages
           received.";
       }
     }

     grouping preference-option-group {
       description "OPTION_PREFERENCE (7) Preference Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.8";
      container preference-option {
        description "OPTION_PREFERENCE (7) Preference Option
          container.";
        leaf pref-value {
           type uint8;
           description "The preference value for the server in this

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             message. A 1-octet unsigned integer.";
         }
       }
     }

     grouping server-unicast-option-group {
       description "OPTION_UNICAST (12) Server Unicast Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.12";
       container server-unicast-option {
         description "OPTION_UNICAST (12) Server Unicast Option
           container.";
         leaf server-address {
           type inet:ipv6-address;
           description "The 128-bit address to which the client
             should send messages delivered using unicast.";
         }
       }
     }

     grouping reconfigure-message-option-group {
       description "OPTION_RECONF_MSG (19) Reconfigure Message
         Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.19";
       container reconfigure-message-option {
         description "OPTION_RECONF_MSG (19) Reconfigure Message
           Option.";
         leaf msg-type {
           type uint8;
           description "5 for Renew message, 6 for Rebind message,
             11 for Information-request message.";
         }
       }
     }

     grouping info-refresh-time-option-group {
       description "OPTION_INFORMATION_REFRESH_TIME (32)
         Information Refresh Time Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.23";
       container info-refresh-time-option {
         description "OPTION_INFORMATION_REFRESH_TIME (32)
           Information Refresh Time option container.";
         leaf info-refresh-time {
           type dhcpv6-common:timer-seconds32;
           description "Time duration relative to the current time,
             expressed in units of seconds.";

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         }
       }
     }

     grouping sol-max-rt-option-group {
       description "OPTION_SOL_MAX_RT (82) sol max rt Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.24";
      container sol-max-rt-option {
         description "OPTION_SOL_MAX_RT (82) sol max rt option
           container.";
         leaf sol-max-rt-value {
           type dhcpv6-common:timer-seconds32;
           description "sol max rt value";
         }
       }
     }

     grouping inf-max-rt-option-group {
       description "OPTION_INF_MAX_RT (83) inf max rt Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.25";
       container inf-max-rt-option {
         description "OPTION_INF_MAX_RT (83) inf max rt option
           container.";
         leaf inf-max-rt-value {
           type dhcpv6-common:timer-seconds32;
           description "inf max rt value";
         }
       }
     }

     /*
      * Data Nodes
      */

     container dhcpv6-server {
       description "Configuration nodes for the DHCPv6 server.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 18.3";
       leaf enabled {
         type boolean;
         default true;
         description "Enables the DHCP server function.";
       }
       leaf server-duid {
         type dhcpv6-common:duid;
         description "DUID of the server.";

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         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 11";
       }
       container vendor-config {
         description "This container provides a location for
           augmenting vendor or implementation specific
           configuration nodes.";
       }
       container option-sets {
         description "A server may allow different option sets
           to be configured for clients matching specific parameters
           such as topological location or client type. The
           'option-set' list is a set of options and their
           contents that will be returned to clients.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 21";
         list option-set {
           key option-set-id;
           description "YANG definitions for DHCPv6 options are
             contained in separate YANG modules and augmented to this
             container as required.";
           leaf option-set-id {
             type uint32;
             description "Option set identifier.";
           }
           leaf description {
             type string;
             description "An optional field for storing additional
               information relevant to the option set.";
           }
           uses preference-option-group;
           uses dhcpv6-common:auth-option-group;
           uses server-unicast-option-group;
           uses dhcpv6-common:status-code-option-group;
           uses dhcpv6-common:rapid-commit-option-group;
           uses dhcpv6-common:vendor-specific-information-option-group;
           uses reconfigure-message-option-group;
           uses dhcpv6-common:reconfigure-accept-option-group;
           uses info-refresh-time-option-group;
           uses sol-max-rt-option-group;
           uses inf-max-rt-option-group;
         }
       }

       container class-selector {
         description "DHCPv6 servers use a 'class-selector' function
           in order to identify and classify incoming client messages
           so that they can be given the correct configuration.

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           The mechanisms used for implementing this function vary
           greatly between different implementations such that they
           are not possible to include in this module. This container
           provides a location for server implementors to augment
           their own class-selector YANG.";
       }

       container network-ranges {
         description "This model is based on an address and parameter
           allocation hierarchy.  The top level is 'global' - which
           is defined as the container for all network-ranges. Under
           this are the individual network-ranges.";
         uses resource-config;
         list network-range {
           key id;
           description "Network-ranges are identified by the
             'id' key.";
           leaf id {
             type uint32;
             mandatory true;
             description "Equivalent to subnet ID.";
           }
           leaf description {
             type string;
             mandatory true;
             description "Description for the network range.";
           }
           leaf network-prefix {
             type inet:ipv6-prefix;
             mandatory true;
             description "Network prefix.";
           }
           uses resource-config;
           container address-pools {
             description "Configuration for the DHCPv6 server's
               address pools.";
             list address-pool {
               key pool-id;
               description "List of address pools for allocation to
                 clients, distinguished by 'pool-id'.";
               leaf pool-id {
                 type uint32;
                 mandatory true;
                 description "Unique identifier for the pool.";
               }
               leaf pool-prefix {
                 type inet:ipv6-prefix;
                 mandatory true;

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                 description "IPv6 prefix for the pool.";
               }
               leaf start-address {
                 type inet:ipv6-address-no-zone;
                 mandatory true;
                 description "Start IPv6 address for the pool.";
               }
               leaf end-address {
                 type inet:ipv6-address-no-zone;
                 mandatory true;
                 description "End IPv6 address for the pool.";
               }
               leaf max-address-count {
                 type dhcpv6-common:threshold;
                 mandatory true;
                 description "Maximum number of addresses that can
                   be simultaneously allocated from this pool.";
               }
               uses resource-config;
               container host-reservations {
                 description "Configuration for host reservations from
                   the address pool.";
                 list host-reservation {
                   key reserved-addr;
                   description "List of host reservations.";
                   leaf client-duid {
                     type dhcpv6-common:duid;
                     description "Client DUID for the reservation.";
                   }
                   leaf reserved-addr {
                     type inet:ipv6-address;
                     description "Reserved IPv6 address.";
                   }
                   uses resource-config;
                 }
               }
               container active-leases {
                 config false;
                 description "Holds state related to active client
                   leases.";
                 leaf total-count {
                   type uint64;
                   mandatory true;
                   description "The total number of addresses in the
                     pool.";
                 }
                 leaf allocated-count {
                   type uint64;

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                   mandatory true;
                   description "The number of addresses or prefixes
                     in the pool that are currently allocated.";
                 }
                 list active-lease {
                   key leased-address;
                   description "List of active address leases.";
                   leaf leased-address {
                     type inet:ipv6-address;
                     description "Active address lease entry.";
                   }
                   uses lease-information;
                 }
               }
             }
           }
           container prefix-pools {
             if-feature prefix-delegation;
             description "Configuration for the DHCPv6 server's
               prefix pools.";
             list prefix-pool {
               key pool-id;
               description "List of prefix pools for allocation to
                 clients, distinguished by 'pool-id'.";
               leaf pool-id {
                 type uint32;
                 mandatory true;
                 description "Unique identifier for the pool.";
               }
               leaf pool-prefix {
                 type inet:ipv6-prefix;
                 mandatory true;
                 description "IPv6 prefix for the pool.";
               }
               leaf client-prefix-length {
                 type uint8;
                 mandatory true;
                 description "Length of the prefixes that will be
                   delegated to clients.";
               }
               leaf max-pd-space-utilization {
                 type dhcpv6-common:threshold;
                 mandatory true;
                 description "Maximum percentage utilization of the
                   prefix pool in this pool.";
               }
               uses resource-config;
               container host-reservations {

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                 description "Configuration for host reservations
                   from the prefix pool.";
                 list prefix-reservation {
                   key reserved-prefix;
                   description "reserved prefix reservation";
                   leaf client-duid {
                     type dhcpv6-common:duid;
                     description "Client DUID for the reservation.";
                   }
                   leaf reserved-prefix {
                     type inet:ipv6-prefix;
                     description "Reserved IPv6 prefix";
                   }
                   leaf reserved-prefix-len {
                     type uint8;
                     description "Reserved IPv6 prefix length.";
                   }
                 }
                 uses resource-config;
               }
               container active-leases {
                 config false;
                 description "Holds state related to for active client
                   prefix leases.";
                 leaf total-count {
                   type uint64;
                   mandatory true;
                   description "The total number of prefixes in
                     the pool.";
                 }
                 leaf allocated-count {
                   type uint64;
                   mandatory true;
                   description "The number of prefixes in the pool
                     that are currently allocated.";
                 }
                 list active-lease {
                   key leased-prefix;
                   description "List of active prefix leases.";
                   leaf leased-prefix {
                     type inet:ipv6-prefix;
                     description "Active leased prefix entry.";
                   }
                   uses lease-information;
                 }
               }
             }
           }

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         }
         uses message-stats;
       }
     }

     /*
      * Notifications
      */

     notification address-pool-utilization-threshold-exceeded {
       description "Notification sent when the address pool
         utilization exceeds the configured threshold.";
       leaf pool-id {
         type leafref {
           path "/dhcpv6-server/network-ranges/network-range/" +
             "address-pools/address-pool/pool-id";
         }
         description "Leafref to the address pool which the notification
           is being generated for.";
       }
       leaf total-address-count {
         type uint64;
         mandatory true;
         description "Count of the total addresses in the pool.";
       }
       leaf max-address-count {
         type uint64;
         mandatory true;
         description "Maximum count of addresses that can be allocated
           in the pool. This value may be less than count of total
           addresses.";
       }
       leaf allocated-address-count {
         type uint64;
         mandatory true;
         description "Count of allocated addresses in the pool.";
       }
     }

     notification prefix-pool-utilization-threshold-exceeded {
       if-feature prefix-delegation;
       description "Notification sent when the prefix pool
         utilization exceeds the configured threshold.";
       leaf pool-id {
         type leafref {
           path "/dhcpv6-server/network-ranges/network-range/" +
             "prefix-pools/prefix-pool/pool-id";
         }

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         mandatory true;
         description "Unique identifier for the pool.";
       }
       leaf max-pd-space-utilization {
         type leafref {
           path "/dhcpv6-server/network-ranges/network-range/" +
             "prefix-pools/prefix-pool/max-pd-space-utilization";
         }
         mandatory true;
         description "PD space utilization threshold.";
       }
       leaf pd-space-utilization {
         type uint64;
         description "Current PD space utilization";
       }
     }

     notification invalid-client-detected {
       description "Notification sent when the server detects an
         invalid client.";
       leaf duid {
         type dhcpv6-common:duid;
         description "Client DUID.";
       }
       leaf description {
         type string;
         description "Description of the event (e.g. and error code or
           log message).";
       }
     }

     notification decline-received {
       description "Notification sent when the server has received a
         Decline (9) message from a client.";
       leaf duid {
         type dhcpv6-common:duid;
         description "Client DUID.";
       }
       list declined-resources {
         description "List of declined addresses and/or prefixes.";
         choice resource-type {
           description "Type of resource that has been declined.";
           case declined-address {
             leaf address {
               type inet:ipv6-address;
               description "Address that has been declined.";
             }
           }

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           case declined-prefix {
             leaf prefix {
               type inet:ipv6-prefix;
               description "Prefix that has been declined.";
             }
           }
         }
       }
     }

     notification non-success-code-sent {
       description "Notification sent when the server responded
         to a client with non-success status code.";
       leaf status-code {
         type uint16;
         mandatory true;
         description "Status code returned to the client.";
       }
       leaf duid {
         type dhcpv6-common:duid;
         description "Client DUID.";
       }
     }

     /*
      * RPCs
      */

     rpc delete-address-lease {
       nacm:default-deny-all;
       description "Deletes a client's active address lease from the
         server's lease database. Note, this will not cause the address
         to be revoked from the client, and the lease may be refreshed
         or renewed by the client.";
       input {
         leaf lease-address-to-delete {
           type inet:ipv6-address;
             mandatory true;
           description "IPv6 address of an active lease that will be
             deleted from the server.";
         }
       }
       output {
         leaf return-message {
           type string;
           description "Response message from the server.";
         }
       }

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     }
     rpc delete-prefix-lease {
       nacm:default-deny-all;
       description "Deletes a client's active prefix lease from the
         server's lease database. Note, this will not cause the prefix
         to be revoked from the client, and the lease may be refreshed
         or renewed by the client.";
       input {
         leaf lease-prefix-to-delete {
           type inet:ipv6-prefix;
             mandatory true;
           description "IPv6 prefix of an active lease that will be
             deleted from the server.";
         }
       }
       output {
         leaf return-message {
           type string;
           description "Response message from the server.";
         }
       }
     }
   }
   <CODE ENDS>

3.2.  DHCPv6 Relay YANG Module

   This module imports typedefs from [RFC6991], [RFC8343].

   <CODE BEGINS> file "ietf-dhcpv6-relay.yang"

   module ietf-dhcpv6-relay {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-relay";
     prefix "dhcpv6-relay";

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

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

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     import ietf-dhcpv6-common {
       prefix dhcpv6-common;
       reference
         "RFC XXXX: To be updated on publication";
     }

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

     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";
     }

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description
       "This YANG module defines components necessary for the
       configuration and management of DHCPv6 relays.

       Copyright (c) 2021 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.";

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     revision 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-09-20 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-10";
     }

     revision 2018-03-04 {
       description "Resolved most issues on the DHC official
         github";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-12-22 {

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       description
         "Resolve most issues on Ians Github.";
       reference
         "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-11-24 {
       description
         "First version of the separated relay specific
         YANG model.";
       reference
         "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Features
      */

     feature prefix-delegation {
       description "Enable if the relay functions as a delegating router
         for DHCPv6 prefix delegation.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 6.2";
     }

     /*
      * Groupings
      */

     grouping pd-lease-state {
       description "State data for the relay.";
       list pd-leases {
         key ia-pd-prefix;
         config false;
         description "Information about an active IA_PD prefix
           delegation.";
        leaf ia-pd-prefix {
           type inet:ipv6-prefix;
           description "Prefix that is delegated.";
         }
         leaf last-renew {
           type yang:date-and-time;
           description "Time of the last successful refresh or renew
             of the delegated prefix.";
         }
         leaf client-peer-address {
           type inet:ipv6-address;
           description "Peer-address of the client.";

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         }
         leaf client-duid {
           type dhcpv6-common:duid;
           description "DUID of the leasing client.";
         }
         leaf server-duid {
           type dhcpv6-common:duid;
           description "DUID of the delegating server.";
         }
       }
     }

     grouping message-statistics {
       description "Contains counters for the different DHCPv6
         message types.";
       leaf solicit-received-count {
         type uint32;
         config "false";
         description "Number of Solicit (1) messages received.";
       }
       leaf advertise-sent-count {
         type uint32;
         config "false";
         description "Number of Advertise (2) messages sent.";
       }
       leaf request-received-count {
         type uint32;
         config "false";
         description "Number of Request (3) messages received.";
       }
       leaf confirm-received-count {
         type uint32;
         config "false";
         description "Number of Confirm (4) messages received.";
       }
       leaf renew-received-count {
         type uint32;
         config "false";
         description "Number of Renew (5) messages received.";
       }
       leaf rebind-received-count {
         type uint32;
         config "false";
         description "Number of Rebind (6) messages received.";
       }
       leaf reply-sent-count {
         type uint32;
         config "false";

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         description "Number of Reply (7) messages received.";
       }
       leaf release-received-count {
         type uint32;
         config "false";
         description "Number of Release (8) messages sent.";
       }
       leaf decline-received-count {
         type uint32;
         config "false";
         description "Number of Decline (9) messages sent.";
       }
       leaf reconfigure-sent-count {
         type uint32;
         config "false";
         description "Number of Reconfigure (10) messages sent.";
       }
       leaf information-request-received-count {
         type uint32;
         config "false";
         description "Number of Information-request (11) messages
           received.";
       }
       leaf unknown-message-received-count {
         type uint32;
         config "false";
         description
           "Number of messages of unknown type that have been
              received.";
       }
       leaf unknown-message-sent-count {
         type uint32;
         config "false";
         description
           "Number of messages of unknown type that have been sent.";
       }
       leaf discarded-message-count {
         type uint32;
         config "false";
         description
           "Number of messages that have been discarded for any
              reason.";
       }
     }

     grouping global-statistics {
       description "Global statistics for the device.";
       leaf relay-forward-sent-count {

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         type uint32;
         config "false";
         description "Number of Relay-forward (12) messages sent.";
       }
       leaf relay-forward-received-count {
         type uint32;
         config "false";
         description "Number of Relay-forward (12) messages received.";
       }
       leaf relay-reply-received-count {
         type uint32;
         config "false";
         description "Number of Relay-reply (13) messages received.";
       }
       leaf relay-forward-unknown-sent-count {
         type uint32;
         config "false";
         description "Number of Relay-forward (12) messages containing
           a message of unknown type sent.";
       }
       leaf relay-forward-unknown-received-count {
         type uint32;
         config "false";
         description "Number of Relay-forward (12) messages containing
           a message of unknown type received.";
       }
       leaf discarded-message-count {
         type uint32;
         config "false";
         description "Number of messages that have been discarded
           for any reason.";
       }
     }

     grouping interface-id-option-group {
       description "OPTION_INTERFACE_ID (18) Interface-Id Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 21.18";
       container interface-id-option {
        description "OPTION_INTERFACE_ID (18) Interface-Id Option
          container.";
        leaf interface-id {
           type string;
           description "An opaque value of arbitrary length generated
             by the relay agent to identify one of the relay agent's
             interfaces.";
         }
       }

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     }

     /*
      * Data Nodes
      */

     container dhcpv6-relay {
       description
         "This container contains the configuration data nodes for
         the relay.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
           IPv6 (DHCPv6), Section 19";
      leaf enabled {
         type boolean;
         default true;
         description "Globally enables the DHCP relay function.";
       }
       list relay-if {
         key if-name;
         description "List of interfaces configured for DHCPv6
           relaying.";
         leaf if-name {
           type if:interface-ref;
           description "interface-ref to the relay interface.";
         }
         leaf enabled {
           type boolean;
           default true;
           description "Enables the DHCP relay function for this
             interface.";
         }
         leaf-list destination-addresses {
           type inet:ipv6-address;
           description "Each DHCPv6 relay agent may be configured with
             a list of destination addresses for relayed messages.
             The list may include unicast addresses, multicast addresses
             or other valid addresses.";
         }
         leaf link-address {
           type binary {
             length "0..16";
           }
           description "An address that may be used by the server
             to identify the link on which the client is located.";
        }
         container relay-options {
           description "Definitions for DHCPv6 options that can be sent
             by the relay are augmented to this location from other YANG

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             modules as required.";
           uses dhcpv6-common:auth-option-group;
           uses dhcpv6-common:status-code-option-group;
           uses interface-id-option-group;
         }
         uses message-statistics;
         container prefix-delegation {
           if-feature prefix-delegation;
           presence "Enables prefix delegation for this interface.";
           description "Controls and holds state information for prefix
             delegation.";
           uses pd-lease-state;
         }
       }
       uses global-statistics;
     }

     /*
      * Notifications
      */

     notification relay-event {
       description
         "DHCPv6 relay event notifications.";
       container topology-change {
         description "Raised if the entry for an interface with DHCPv6
           related configuration or state is removed from
           if:interface-refs.";
         leaf relay-if-name {
           type leafref {
             path "/dhcpv6-relay/relay-if/if-name";
           }
           description "Name of the interface that has been removed.";
         }
         leaf last-ipv6-addr {
           type inet:ipv6-address;
           description "Last IPv6 address configured on the interface.";
         }
       }
     }

     /*
      * RPCs
      */

     rpc clear-prefix-entry {
       nacm:default-deny-all;
       description "Clears an entry for an active delegated prefix

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         from the relay.";
       reference "draft-ietf-dhc-dhcpv6-pd-relay-requirements: DHCPv6
         Prefix Delegating Relay Requirements, Section 4.4";
       input {
         leaf lease-prefix {
           type inet:ipv6-prefix;
           mandatory true;
           description "IPv6 prefix of an active lease entry that will
             be deleted from the relay.";
         }
       }
       output {
         leaf return-message {
           type string;
           description "Response message from the relay.";
         }
       }
     }
     rpc clear-client-prefixes {
       nacm:default-deny-all;
       description "Clears all active prefix entries for a single
         client.";
       reference "draft-ietf-dhc-dhcpv6-pd-relay-requirements: DHCPv6
         Prefix Delegating Relay Requirements, Section 4.4";
      input {
         leaf client-duid {
           type dhcpv6-common:duid;
           mandatory true;
           description "DUID of the client .";
         }
       }
       output {
         leaf return-message {
           type string;
           description "Response message from the relay.";
         }
       }
     }
     rpc clear-interface-prefixes {
       nacm:default-deny-all;
       description "Clears all delegated prefix bindings from an
         interface on the relay.";
       reference "draft-ietf-dhc-dhcpv6-pd-relay-requirements: DHCPv6
         Prefix Delegating Relay Requirements, Section 4.4";
      input {
         leaf interface {
           type if:interface-ref;
           mandatory true;

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           description "Reference to the relay interface that will have
             all active prefix delegation bindings deleted.";
         }
       }
       output {
         leaf return-message {
           type string;
           description "Response message from the relay.";
         }
       }
     }
   }
   <CODE ENDS>

3.3.  DHCPv6 Client YANG Module

   This module imports typedefs from [RFC6991], [RFC8343].

   <CODE BEGINS> file "ietf-dhcpv6-client.yang"

   module ietf-dhcpv6-client {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-client";
     prefix "dhcpv6-client";

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

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

     import ietf-dhcpv6-common {
       prefix dhcpv6-common;
       reference
         "RFC XXXX: To be updated on publication";
     }

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

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     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description
       "This YANG module defines components necessary for the
       configuration and management of DHCPv6 clients.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";

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     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-09-20 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-10";
     }

     revision 2018-09-04 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2018-03-04 {
       description "Resolved most issues on the DHC official github";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-12-22 {
       description "Resolve most issues on Ian's Github.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2017-11-24 {
       description "First version of the separated client specific
         YANG model.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Groupings
      */

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     grouping message-statistics {
       description "Counters for DHCPv6 messages.";
       leaf solicit-count {
         type uint32;
         config "false";
         description "Number of Solicit (1) messages sent.";
       }
       leaf advertise-count {
         type uint32;
         config "false";
         description "Number of Advertise (2) messages received.";
       }
       leaf request-count {
         type uint32;
         config "false";
         description "Number of Request (3) messages sent.";
       }
       leaf confirm-count {
         type uint32;
         config "false";
         description "Number of Confirm (4) messages sent.";
       }
       leaf renew-count {
         type uint32;
         config "false";
         description "Number of Renew (5) messages sent.";
       }
       leaf rebind-count {
         type uint32;
         config "false";
         description "Number of Rebind (6) messages sent.";
       }
       leaf reply-count {
         type uint32;
         config "false";
         description "Number of Reply (7) messages received.";
       }
       leaf release-count {
         type uint32;
         config "false";
         description "Number of Release (8) messages sent.";
       }
       leaf decline-count {
         type uint32;
         config "false";
         description "Number of Decline (9) messages sent.";
       }
       leaf reconfigure-count {

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         type uint32;
         config "false";
         description "Number of Reconfigure (10) messages received.";
       }
       leaf information-request-count {
         type uint32;
         config "false";
         description "Number of Information-request (11) messages
           sent.";
       }
     }

     grouping option-request-option-group {
       description "OPTION_ORO (6) Option Request Option. A client
         MUST include an Option Request option in a Solicit, Request,
         Renew, Rebind, or Information-request message to inform
         the server about options the client wants the server to send
         to the client.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.7";
       container option-request-option {
         description "OPTION_ORO (6) Option Request Option container.";
         leaf-list oro-option {
           type uint16;
          description "List of options that the client is requesting,
            identified by option code";
         }
       }
     }

     grouping user-class-option-group {
       description "OPTION_USER_CLASS (15) User Class Option";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.15";
       container user-class-option {
         presence "Configures the option";
         description "OPTION_USER_CLASS (15) User Class Option
           container.";
         list user-class-data {
           key user-class-datum-id;
           min-elements 1;
           description "The user classes of which the client
             is a member.";
           leaf user-class-datum-id {
             type uint8;
             description "User class datum ID";
           }
           leaf user-class-datum {

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             type string;
             description "Opaque field representing a User Class
               of which the client is a member.";
           }
         }
       }
     }

     grouping vendor-class-option-group {
       description "OPTION_VENDOR_CLASS (16) Vendor Class Option";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.16";
       container vendor-class-option {
         description "OPTION_VENDOR_CLASS (16) Vendor Class Option
           container.";
         list vendor-class-option-instances {
           key enterprise-number;
           description "The vendor class option allows for multiple
             instances in a single message. Each list entry defines
             the contents of an instance of the option.";
           leaf enterprise-number {
             type uint32;
             description "The vendor's registered Enterprise Number
               as maintained by IANA.";
           }
           list vendor-class {
             key vendor-class-datum-id;
             description "The vendor classes of which the client is
               a member.";
             leaf vendor-class-datum-id {
               type uint8;
               description "Vendor class datum ID";
             }
             leaf vendor-class-datum {
               type string;
               description "Opaque field representing a vendor class
                 of which the client is a member.";
             }
           }
         }
       }
     }

     /*
      * Data Nodes
      */

     container dhcpv6-client {

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       description "DHCPv6 client configuration and state.";
       leaf enabled {
         type boolean;
         default true;
         description "Globally enables the DHCP client function.";
       }
       list client-if {
         key if-name;
         description "The list of interfaces that the client will be
           requesting DHCPv6 configuration for.";
         leaf if-name {
           type if:interface-ref;
           mandatory true;
           description "Reference to the interface entry that
             the requested configuration is relevant to.";
         }
         leaf enabled {
           type boolean;
           default true;
           description "Enables the DHCP client function for this
             interface.";
         }
         leaf duid {
           type dhcpv6-common:duid;
           description "Client DUID.";
           reference "RFC 8415: Dynamic Host Configuration Protocol for
             IPv6 (DHCPv6), Section 11";
         }
         container client-configured-options {
           description " Definitions for DHCPv6 options that can be be
             sent by the client. Additional option definitions can be
             augmented to this location from other YANG modules as
             required.";
           uses option-request-option-group;
           uses dhcpv6-common:status-code-option-group;
           uses dhcpv6-common:rapid-commit-option-group;
           uses user-class-option-group;
           uses vendor-class-option-group;
           uses dhcpv6-common:vendor-specific-information-option-group;
           uses dhcpv6-common:reconfigure-accept-option-group;
         }
         list ia-na {
           key iaid;
           description "Configuration relevant for an IA_NA.";
           reference "RFC 8415: Dynamic Host Configuration Protocol
             for IPv6 (DHCPv6), Section 13.1";
           leaf iaid {
             type uint32;

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             description "A unique identifier for this IA_NA.";
             reference "RFC 8415: Dynamic Host Configuration Protocol
               for IPv6 (DHCPv6), Section 12";
           }
           container ia-na-options {
             description "An augmentation point for additional options
               that the client will send in the IA_NA-options field
               of OPTION_IA_NA.";
           }
           container lease-state {
             config "false";
             description "Information about the active IA_NA lease.";
             leaf ia-na-address {
               type inet:ipv6-address;
               description "Address that is currently leased.";
             }
             leaf preferred-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The preferred lifetime for the leased
                 address expressed in units of seconds.";
             }
             leaf valid-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The valid lifetime for the leased address
                 expressed in units of seconds.";
             }
             leaf lease-t1 {
               type dhcpv6-common:timer-seconds32;
               description "The time interval after which the client
                 should contact the server from which the addresses
                 in the IA_NA were obtained to extend the lifetimes
                 of the addresses assigned to the IA_NA.";
             }
             leaf lease-t2 {
               type dhcpv6-common:timer-seconds32;
               description "The time interval after which the client
                 should contact any available server to extend
                 the lifetimes of the addresses assigned to the IA_NA.";
             }
             leaf allocation-time {
               type yang:date-and-time;
               description "Time and date that the address was first
                 leased.";
             }
             leaf last-renew-rebind {
               type yang:date-and-time;
               description "Time of the last successful renew or rebind
                 of the leased address.";

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             }
             leaf server-duid {
               type dhcpv6-common:duid;
               description "DUID of the leasing server.";
             }
           }
         }
         list ia-ta {
           key iaid;
           description "Configuration relevant for an IA_TA.";
           reference "RFC 8415: Dynamic Host Configuration Protocol for
             IPv6 (DHCPv6), Section 13.2";
             leaf iaid {
               type uint32;
               description "The unique identifier for this IA_TA.";
               reference "RFC 8415: Dynamic Host Configuration Protocol
                 for IPv6 (DHCPv6), Section 12";
             }
           container ia-ta-options {
             description "An augmentation point for additional options
               that the client will send in the IA_TA-options field
               of OPTION_IA_TA.";
           }
           container lease-state {
             config "false";
             description "Information about an active IA_TA lease.";
             leaf ia-ta-address {
               type inet:ipv6-address;
               description "Address that is currently leased.";
             }
             leaf preferred-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The preferred lifetime for the leased
                 address expressed in units of seconds.";
             }
             leaf valid-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The valid lifetime for the leased address
                 expressed in units of seconds.";
             }
             leaf allocation-time {
               type yang:date-and-time;
               description "Time and date that the address was first
                 leased.";
             }
             leaf last-renew-rebind {
               type yang:date-and-time;
               description "Time of the last successful renew or rebind

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                 of the address.";
             }
             leaf server-duid {
               type dhcpv6-common:duid;
               description "DUID of the leasing server.";
             }
           }
         }
         list ia-pd {
           key iaid;
           description "Configuration relevant for an IA_PD.";
           reference "RFC 8415: Dynamic Host Configuration Protocol for
             IPv6 (DHCPv6), Section 13.3";
           leaf iaid {
             type uint32;
             description "The unique identifier for this IA_PD.";
             reference "RFC 8415: Dynamic Host Configuration Protocol
               for IPv6 (DHCPv6), Section 12";
           }
           container ia-pd-options {
             description "An augmentation point for additional options
               that the client will send in the IA_PD-options field
               of OPTION_IA_TA.";
           }
           container lease-state {
             config "false";
             description "Information about an active IA_PD delegated
               prefix.";
             leaf ia-pd-prefix {
               type inet:ipv6-prefix;
               description "Delegated prefix that is currently leased.";
             }
             leaf preferred-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The preferred lifetime for the leased prefix
                 expressed in units of seconds.";
             }
             leaf valid-lifetime {
               type dhcpv6-common:timer-seconds32;
               description "The valid lifetime for the leased prefix
                 expressed in units of seconds.";
             }
             leaf lease-t1 {
               type dhcpv6-common:timer-seconds32;
               description "The time interval after which the client
                 should contact the server from which the addresses
                 in the IA_NA were obtained to extend the lifetimes
                 of the addresses assigned to the IA_PD.";

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             }
             leaf lease-t2 {
               type dhcpv6-common:timer-seconds32;
               description "The time interval after which the client
                 should contact any available server to extend
                 the lifetimes of the addresses assigned to the IA_PD.";
             }
             leaf allocation-time {
               type yang:date-and-time;
               description "Time and date that the prefix was first
                 leased.";
             }
             leaf last-renew-rebind {
               type yang:date-and-time;
               description "Time of the last successful renew or rebind
                 of the delegated prefix.";
             }
             leaf server-duid {
               type dhcpv6-common:duid;
               description "DUID of the delegating server.";
             }
           }
         }
         uses message-statistics;
       }
     }

     /*
      * Notifications
      */

     notification invalid-ia-detected {
       description "Notification sent when the identity association
         of the client can be proved to be invalid. Possible conditions
         include a duplicate or otherwise illegal address.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 18.2.10.1";
       leaf iaid {
         type uint32;
         mandatory true;
         description "IAID";
       }
       leaf description {
         type string;
         description "Description of the event.";
       }
     }

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     notification retransmission-failed {
       description "Notification sent when the retransmission mechanism
         defined in RFC 8415 is unsuccessful.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 7.6";
       leaf failure-type {
         type enumeration {
           enum "MRC-exceeded" {
             description "Maximum retransmission count exceeded.";
           }
           enum "MRD-exceeded" {
             description "Maximum retransmission duration exceeded.";
           }
         }
         mandatory true;
         description "Description of the failure.";
       }
     }

     notification unsuccessful-status-code {
       description "Notification sent when the client receives a message
         that includes an unsuccessful Status Code option.";
         reference "RFC 8415: Dynamic Host Configuration Protocol for
             IPv6 (DHCPv6), Section 21.13";
       leaf status-code {
         type uint16;
         mandatory true;
         description "Unsuccessful status code received by a client.";
       }
       leaf server-duid {
         type dhcpv6-common:duid;
         mandatory true;
         description "DUID of the server sending the unsuccessful
           error code.";
       }
     }

     notification server-duid-changed {
       description "Notification sent when the client receives a lease
         from a server with different DUID to the one currently stored
         by the client.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 18.2.10.1";
       leaf new-server-duid {
         type dhcpv6-common:duid;
         mandatory true;
         description "DUID of the new server.";
       }

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       leaf previous-server-duid {
         type dhcpv6-common:duid;
         mandatory true;
         description "DUID of the previous server.";
       }
       leaf lease-ia-na {
         type leafref {
           path "/dhcpv6-client/client-if/ia-na/iaid";
         }
         description "Reference to the IA_NA lease.";
       }
       leaf lease-ia-ta {
         type leafref {
           path "/dhcpv6-client/client-if/ia-ta/iaid";
         }
         description "Reference to the IA_TA lease.";
       }
       leaf lease-ia-pd {
         type leafref {
           path "/dhcpv6-client/client-if/ia-pd/iaid";
         }
         description "Reference to the IA_PD lease.";
       }
     }
   }
   <CODE ENDS>

3.4.  DHCPv6 Common YANG Module

   This module imports typedefs from [RFC6991].

   <CODE BEGINS> file "ietf-dhcpv6-common.yang"

   module ietf-dhcpv6-common {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-common";
     prefix "dhcpv6-common";

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

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>

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        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description "This YANG module defines common components
       used for the configuration and management of DHCPv6.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

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     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2018-09-04 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     revision 2018-01-30 {
       description "Initial revision";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     typedef threshold {
       type union {
         type uint16 {
           range 0..100;
         }
         type enumeration {
           enum "disabled" {
             description "No threshold.";
           }
         }
       }
       description "Threshold value in percent.";
     }

     typedef timer-seconds32 {
       type uint32;
       units "seconds";
       description
         "Timer value type, in seconds (32-bit range).";
     }

     typedef duid-base {
       type string {
         length '6..260';
       }
       description "Each DHCP server and client has a DUID (DHCP
         Unique Identifier). The DUID consists of a two-octet

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         type field and an arbitrary length (between 1 and 128 bytes)
         content field.  Currently, there are four defined types of
         DUIDs in RFC 8415 and RFC 6355 - DUID-LLT, DUID-EN, DUID-LL
         and DUID-UUID.  DUID-unstructured represents DUIDs which
         do not follow any of the defined formats.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11
         RFC 6355: Definition of the UUID-Based DHCPv6 Unique
         Identifier (DUID-UUID), Section 4";
     }

     typedef duid-llt {
       type duid-base {
         pattern '^0001'
           + '[0-9a-fA-F]{12,}';
       }
       description "DUID type 1, based on Link-Layer Address Plus Time
         (DUID-LLT). Constructed with a 2-byte hardware type assigned
         by IANA,  4-bytes containing the time the DUID is generated
         (represented in seconds since midnight (UTC), January 1, 2000,
         modulo 2^32), and a link-layer address. The address is encoded
         without separator characters.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11.2
         IANA 'Hardware Types' registry.
           <https://www.iana.org/assignments/arp-parameters>";
     }

     typedef duid-en {
       type duid-base {
         pattern '^0002'
           + '[0-9a-fA-F]{4,}';
       }
       description "DUID type 2, assigned by vendor based on Enterprise
         Number (DUID-EN). This DUID consists of the 4-octet vendor's
         registered Private Enterprise Number as maintained by IANA
         followed by a unique identifier assigned by the vendor.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11.3
         IANA 'Private Enterprise Numbers' registry.
           <https://www.iana.org/assignments/enterprise-numbers>";
     }

     typedef duid-ll {
       type duid-base {
         pattern '^0003'
           + '([0-9a-fA-F]){4,}';
       }

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       description "DUID type 3, based on Link-Layer Address (DUID-LL).
         Constructed with a 2-byte hardware type assigned
         by IANA, and a link-layer address. The address is encoded
         without separator characters.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11.4
         IANA 'Hardware Types' registry.
           <https://www.iana.org/assignments/arp-parameters>";
     }

     typedef duid-uuid {
       type duid-base {
         pattern '^0004'
           + '[0-9a-fA-F]{32}';
       }
       description "DUID type 4, based on Universally Unique Identifier
         (DUID-UUID).  This type of DUID consists of 16 octets
         containing a 128-bit UUID.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11.5
         RFC 6355: Definition of the UUID-Based DHCPv6 Unique Identifier

         (DUID-UUID)";
     }

     typedef duid-unstructured {
       type duid-base {
         pattern '^[0-9a-fA-F]{3}'
           + '[05-9a-fA-F]'
           + '([0-1a-fA-F])*';
       }
       description "Used for DUIDs following any other formats than
         DUID types 1-4.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 11";
     }

     typedef duid {
       type union {
         type duid-llt;
         type duid-en;
         type duid-ll;
         type duid-uuid;
         type duid-unstructured;
       }
       description "Represents the DUID and is neutral to the DUID's
        construction format.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for

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         IPv6 (DHCPv6), Section 11";
     }

     /*
      * Groupings
      */

     grouping auth-option-group {
       description "OPTION_AUTH (11) Authentication Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.11";
       container auth-option {
         description "OPTION_AUTH (11) Authentication Option
           container.";
         leaf protocol {
           type uint8;
           description "The authentication protocol used by this
             Authentication option.";
         }
         leaf algorithm {
           type uint8;
           description "The algorithm used in the authentication
             protocol.";
         }
         leaf rdm {
           type uint8;
           description "The Replay Detection Method (RDM) used
             in this Authentication option.";
         }
         leaf replay-detection {
           type uint64;
           description "The replay detection information for the RDM.";
         }
         leaf auth-information {
           type string;
           description "The authentication information, as specified
             by the protocol and algorithm used in this Authentication
             option.";
         }
       }
     }

     grouping status-code-option-group {
       description "OPTION_STATUS_CODE (13) Status Code Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.13";
       container status-code-option {
         description "OPTION_STATUS_CODE (13) Status Code Option

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           container.";
         leaf status-code {
           type uint16;
           description "The numeric code for the status encoded
             in this option. See the Status Codes registry at
             <https://www.iana.org/assignments/dhcpv6-parameters>
             for the current list of status codes.";
         }
         leaf status-message {
           type string;
           description "A UTF-8 encoded text string suitable for
             display to an end user. MUST NOT be null-terminated.";
         }
       }
     }

     grouping rapid-commit-option-group {
       description "OPTION_RAPID_COMMIT (14) Rapid Commit Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol for
         IPv6 (DHCPv6), Section 21.14";
       container rapid-commit-option {
         presence "Enable sending of this option";
         description "OPTION_RAPID_COMMIT (14) Rapid Commit Option
           container.";
       }
     }

     grouping vendor-specific-information-option-group {
       description "OPTION_VENDOR_OPTS (17) Vendor-specific
         Information Option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.17";
       container vendor-specific-information-option {
         description "OPTION_VENDOR_OPTS (17) Vendor-specific
           Information Option container.";
         list vendor-specific-information-option-instances {
           key enterprise-number;
           description "The vendor specific information option allows
             for multiple instances in a single message. Each list entry
             defines the contents of an instance of the option.";
           leaf enterprise-number {
             type uint32;
             description "The vendor's registered Enterprise Number,
               as maintained by IANA.";
             reference "IANA 'Private Enterprise Numbers' registry.
               <https://www.iana.org/assignments/enterprise-numbers>";
           }
           list vendor-option-data {

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             key sub-option-code;
             description "Vendor options, interpreted by vendor-specific
               client/server functions.";
             leaf sub-option-code {
               type uint16;
               description "The code for the sub-option.";
             }
             leaf sub-option-data {
               type string;
               description "The data area for the sub-option.";
             }
           }
         }
       }
     }

     grouping reconfigure-accept-option-group {
       description "OPTION_RECONF_ACCEPT (20) Reconfigure Accept
         Option.
         A client uses the Reconfigure Accept option to announce to
         the server whether the client is willing to accept Reconfigure
         messages, and a server uses this option to tell the client
         whether or not to accept Reconfigure messages.  In the absence
         of this option, the default behavior is that the client is
         unwilling to accept Reconfigure messages.  The presence node
         is used to enable the option.";
       reference "RFC 8415: Dynamic Host Configuration Protocol
         for IPv6 (DHCPv6), Section 21.20";
       container reconfigure-accept-option {
         presence "Enable sending of this option";
         description "OPTION_RECONF_ACCEPT (20)  Reconfigure Accept
           Option container.";
       }
     }
   }
   <CODE ENDS>

4.  Security Considerations

   The YANG modules defined in this document are designed to be accessed
   via network management protocols such as NETCONF [RFC6241] or
   RESTCONF [RFC8040].  The lowest NETCONF layer is the secure transport
   layer, and the mandatory-to-implement secure transport is Secure
   Shell (SSH) [RFC6242].  The lowest RESTCONF layer is HTTPS, and the
   mandatory-to-implement secure transport is TLS [RFC8446].

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   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   All data nodes defined in the YANG modules which can be created,
   modified, and deleted (i.e., config true, which is the default) are
   considered sensitive.  Write operations (e.g., edit-config) to these
   data nodes without proper protection can have a negative effect on
   network operations.

   As the RPCs for deleting/clearing active address and prefix entries
   in the server and relay modules are particularly sensitive, these use
   'nacm:default-deny-all'.

   An attacker who is able to access the DHCPv6 server can undertake
   various attacks, such as:

   *  Denial of service attacks, based on re-configuring messages to a
      rogue DHCPv6 server.

   *  Various attacks based on re-configuring the contents of DHCPv6
      options.  E.g., changing the address of a the DNS server supplied
      in a DHCP option to point to a rogue server.

   An attacker who is able to access the DHCPv6 relay can undertake
   various attacks, such as:

   *  Re-configuring the relay's destination address to send messages to
      a rogue DHCPv6 server.

   *  Deleting information about a client's delegated prefix, causing a
      denial of service attack as traffic will no longer be routed to
      the client.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  Therefore, it
   is important to control read access (e.g., only permitting get, get-
   config, or notifications) to these data nodes.  These subtrees and
   data nodes can be misused to track the activity of a host:

   *  Information the server holds about clients with active leases:
      (dhcpv6-server/network-ranges/network-range/ address-pools/
      address-pool/active-leases)

   *  Information the relay holds about clients with active leases:
      (dhcpv6-relay/relay-if/prefix-delegation/)

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   Security considerations related to DHCPv6 are discussed in [RFC8415].

   Security considerations given in [RFC7950] are also applicable here.

5.  IANA Considerations

   This document requests IANA to register the following URIs in the
   "IETF XML Registry" [RFC3688]:

   URI:  urn:ietf:params:xml:ns:yang:ietf-dhcpv6-server
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-dhcpv6-relay
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-dhcpv6-client
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-dhcpv6-common
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   This document registers the following YANG modules in the "YANG
   Module Names" registry [RFC6020].

   name:           ietf-dhcpv6-server
   namespace:      urn:ietf:params:xml:ns:yang:ietf-dhcpv6-server
   prefix:         dhcpv6-server
   reference:      RFC XXXX YANG Data Model for DHCPv6 Configuration

   name:           ietf-dhcpv6-relay
   namespace:      urn:ietf:params:xml:ns:yang:ietf-dhcpv6-relay
   prefix:         dhcpv6-client
   reference:      RFC XXXX YANG Data Model for DHCPv6 Configuration

   name:           ietf-dhcpv6-client
   namespace:      urn:ietf:params:xml:ns:yang:ietf-dhcpv6-client
   prefix:         dhcpv6-relay
   reference:      RFC XXXX YANG Data Model for DHCPv6 Configuration

   name:           ietf-dhcpv6-common
   namespace:      urn:ietf:params:xml:ns:yang:ietf-dhcpv6-common
   prefix:         dhcpv6-common
   reference:      RFC XXXX YANG Data Model for DHCPv6 Configuration

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6.  Acknowledgments

   The authors would like to thank Qi Sun, Lishan Li, Hao Wang, Tomek
   Mrugalski, Marcin Siodelski, Bernie Volz, Ted Lemon, Bing Liu, and
   Tom Petch for their valuable comments and contributions to this work.

7.  Contributors

   The following individuals are co-authors of this document:

           Yong Cui
           Tsinghua University
           Beijing, 100084
           P.R. China
           Email: cuiyong@tsinghua.edu.cn

           Linhui Sun
           Tsinghua University
           Beijing, 100084
           P.R. China
           Email: lh.sunlinh@gmail.com

           Sladjana Zechlin
           Deutsche Telekom AG
           CTO-IPT, Landgrabenweg 151
           53227, Bonn
           Germany
           Email: sladjana.zechlin@telekom.de

           Zihao He
           Tsinghua University
           Beijing, 100084
           P.R. China
           Email: hezihao9512@gmail.com

           Michal Nowikowski
           Internet Systems Consortium
           Gdansk
           Poland
           Email: godfryd@isc.org

8.  References

8.1.  Normative References

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   [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>.

   [RFC6355]  Narten, T. and J. Johnson, "Definition of the UUID-Based
              DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355,
              DOI 10.17487/RFC6355, August 2011,
              <https://www.rfc-editor.org/info/rfc6355>.

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [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>.

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   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [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>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

   [IANA-HARDWARE-TYPES]
              Internet Assigned Numbers Authority, "Hardware Types",
              <https://www.iana.org/assignments/arp-parameters>.

   [IANA-PEN] Internet Assigned Numbers Authority, "Private Enterprise
              Numbers",
              <https://www.iana.org/assignments/enterprise-numbers>.

8.2.  Informative References

   [RFC3319]  Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
              Protocol (DHCPv6) Options for Session Initiation Protocol
              (SIP) Servers", RFC 3319, DOI 10.17487/RFC3319, July 2003,
              <https://www.rfc-editor.org/info/rfc3319>.

Appendix A.  Example of Augmenting Additional DHCPv6 Option Definitions

   The following section provides a example of how the DHCPv6 option
   definitions can be extended to include additional options.  It is
   expected that additional specification documents will be published
   for this in the future.

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   The example defines YANG models for OPTION_SIP_SERVER_D (21) and
   OPTION_SIP_SERVER_D (22) defined in [RFC3319].  The module is
   constructed as follows:

   *  The module is named using a meaningful, shortened version of the
      document name in which the DHCP option format is specified.

   *  A separate grouping is used to define each option.

   *  The name of the option is taken from the registered IANA name for
      the option, with an '-option' suffix added.

   *  The description field is taken from the relevant option code name
      and number.

   *  The reference section is the number and name of the RFC in which
      the DHCPv6 option is defined.

   *  The remaining fields match the fields in the DHCP option.  They
      are in the same order as defined in the DHCP option.  Where-ever
      possible, the format that is defined for the DHCP field should be
      matched by the relevant YANG type.

   *  Fields which can have multiple entries or instances are defined
      using list or leaf-list nodes.

   Below the groupings for option definitions, augment statements are
   used to add the option definitions for use in the relevant DHCP
   element's module (server, relay and/or client).

   <CODE BEGINS> file "ietf-example-dhcpv6-options-sip-server.yang"

   module ietf-example-dhcpv6-options-sip-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:" +
       "ietf-example-dhcpv6-options-sip-server";
     prefix "sip-srv";

     import ietf-inet-types {
       prefix inet;
     }

     import ietf-dhcpv6-server {
       prefix dhcpv6-server;
     }

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

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     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description "This YANG module contains DHCPv6 options defined
       in RFC 3319 that can be used by DHCPv6 servers.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";

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       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-10-18 {
       description "Initial version.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Groupings
      */

     grouping sip-server-domain-name-list-option-group {
       description "OPTION_SIP_SERVER_D (21) SIP Servers Domain Name
         List";
       reference "RFC 3319: Dynamic Host Configuration Protocol
         (DHCPv6) Options for Session Initiation Protocol (SIP)
         Servers";
       container sip-server-domain-name-list-option {
        description "OPTION_SIP_SERVER_D (21) SIP Servers Domain Name
          List container.";
        list sip-server {
           key sip-serv-id;
           description "SIP server information.";
           leaf sip-serv-id {
             type uint8;
             description "SIP server list identifier identifier.";
           }
           leaf sip-serv-domain-name {
             type inet:domain-name;
             description "SIP server domain name.";
           }
         }
       }
     }

     grouping sip-server-address-list-option-group {

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       description "OPTION_SIP_SERVER_A (22) SIP Servers IPv6 Address
         List";
       reference "RFC 3319: Dynamic Host Configuration Protocol
         (DHCPv6) Options for Session Initiation Protocol (SIP)
         Servers";
       container sip-server-address-list-option {
         description "OPTION_SIP_SERVER_A (22) SIP Servers IPv6 Address
           List container.";
        list sip-server {
           key sip-serv-id;
           description "SIP server information.";
           leaf sip-serv-id {
             type uint8;
             description "SIP server list entry identifier.";
           }
           leaf sip-serv-addr {
             type inet:ipv6-address;
             description "SIP server IPv6 address.";
           }
         }
       }
     }

     /*
      * Augmentations
      */

     augment "/dhcpv6-server:dhcpv6-server/dhcpv6-server:option-sets/" +

       "dhcpv6-server:option-set" {
       description "Augment the option definition groupings to the
         server module.";
       uses sip-server-domain-name-list-option-group;
       uses sip-server-address-list-option-group;
     }
   }
   <CODE ENDS>

   The correct location to augment the new option definition(s) will
   vary according to the specific rules defined for the use of that
   specific option.  E.g. for options which will be augmented into the
   ietf-dhcpv6-server module, in many cases, these will be augmented to:

   '/dhcpv6-server:dhcpv6-server/dhcpv6-server:option-sets/\ dhcpv6-
   server:option-set'

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   so that they can be defined within option sets.  However, there are
   some options which are only applicable for specific deployment
   scenarios and in these cases it may be more logical to augment the
   option group to a location relevant for the option.

   One example for this could be OPTION_PD_EXCLUDE (67).  This option is
   only relevant in combination with a delegated prefix which contains a
   specific prefix.  In this case, the following location for the
   augmentation may be more suitable:

   '/dhcpv6-server:dhcpv6-server/dhcpv6-server:network-ranges/\ dhcpv6-
   server:network-range/dhcpv6-server:prefix-pools/\ dhcpv6-
   server:prefix-pool"

Appendix B.  Example Vendor Specific Server Configuration Module

   This section shows how to extend the server YANG module defined in
   this document with vendor specific configuration nodes, e.g.,
   configuring access to a lease storage database.

   The example module defines additional server attributes such as name
   and description.  Storage for leases is configured using a lease-
   storage container.  It allows storing leases in one of three options:
   memory (memfile), MySQL and PosgreSQL.  For each case, the necessary
   configuration parameters are provided.

   At the end there is an augment statement which adds the vendor
   specific configuration defined in "dhcpv6-server-config:config" under
   the "/dhcpv6-server:config/dhcpv6-server:vendor-config" mount point.

   <CODE BEGINS> file "ietf-example-dhcpv6-server-config.yang"

   module ietf-example-dhcpv6-server-config {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:" +
       "ietf-example-dhcpv6-server-config";
     prefix "dhcpv6-server-config";

     import ietf-inet-types {
       prefix inet;
     }

     import ietf-interfaces {
       prefix if;
     }

     import ietf-dhcpv6-server {
       prefix dhcpv6-server;

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     }

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description "This YANG module defines components for the
       configuration and management of vendor/implementation specific
       DHCPv6 server functionality. As this functionality varies
       greatly between different implementations, the module
       provided as an example only.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

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     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-06-04 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Groupings
      */

     grouping config {
       description "Parameters necessary for the configuration of a
         DHCPv6 server";
       container serv-attributes {
         description "Contains basic attributes necessary for running a
           DHCPv6 server.";
         leaf name {
           type string;
           description "Name of the DHCPv6 server.";
         }
         leaf description {
           type string;
           description "Description of the DHCPv6 server.";
         }
         leaf ipv6-listen-port {
           type uint16;
           default 547;
           description "UDP port that the server will listen on.";

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         }
         choice listening-interfaces {
           default all-interfaces;
           description "Configures which interface or addresses the
             server will listen for incoming messages on.";
           case all-interfaces {
             container all-interfaces {
             presence true;
             description "Configures the server to listen for
               incoming messages on all IPv6 addresses (unicast and
               multicast) on all of its network interfaces.";
             }
           }
           case interface-list {
             leaf-list interfaces {
               type if:interface-ref;
               description "List of interfaces that the server will
                 listen for incoming messages on. Messages addressed
                 to any valid IPv6 address (unicast and multicast) will
                 be received.";
             }
           }
           case address-list {
             leaf-list address-list {
               type inet:ipv6-address;
               description "List of IPv6 address(es) that the server
                 will listen for incoming messages on.";
             }
           }
         }
         leaf-list interfaces-config {
           type if:interface-ref;
           default "if:interfaces/if:interface/if:name";
           description "A leaf list to denote which one or more
             interfaces the server should listen on.";
         }
         container lease-storage {
           description "Configures how the server will stores leases.";
           choice storage-type {
             description "The type storage that will be used for lease
               information.";
             case memfile {
               description "Configuration for storing leases information
                 in a CSV file.";
               leaf memfile-name {
                 type string;
                 description "Specifies the absolute location
                   of the lease file. The format of the string follow

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                   the semantics of the relevant operating system.";
               }
               leaf memfile-lfc-interval {
                 type uint64;
                 description "Specifies the interval in seconds,
                   at which the server will perform a lease file cleanup
                   (LFC).";
               }
             }
             case mysql {
               leaf mysql-name {
                 type string;
                 description "Name of the database.";
               }
               choice mysql-host {
                 description "Define host or address for MySQL server.";
                 case mysql-server-hostname {
                   leaf mysql-hostname {
                     type inet:domain-name;
                     default "localhost";
                     description "If the database is located on a
                       different system to the DHCPv6 server, the
                         domain name can be specified.";
                   }
                 }
                 case mysql-server-address {
                   leaf mysql-address {
                     type inet:ip-address;
                     default "::";
                     description "Configure the location of the
                       database using an IP (v6 or v6) literal
                       address";
                   }
                 }
               }
               leaf mysql-username {
                 type string;
                 description "User name of the account under which the
                   server will access the database.";
               }
               leaf mysql-password {
                 type string;
                 description "Password of the account under which
                   the server will access the database.";
               }
               leaf mysql-port {
                 type inet:port-number;
                 default 5432;

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                 description "If the database is located on a different
                   system, the port number may be specified.";
               }
               leaf mysql-lfc-interval {
                 type uint64;
                 description "Specifies the interval in seconds,
                   at which the server will perform a lease file cleanup
                   (LFC).";
               }
               leaf mysql-connect-timeout {
                 type uint64;
                 description "Defines the timeout interval for
                   connecting to the database. A longer interval can
                   be specified if the database is remote.";
               }
             }
             case postgresql {
               choice postgresql-host {
                 description "Define host or address for postgresql
                   server.";
                 case postgresql-server-hostname {
                   leaf postgresql-hostname {
                     type inet:domain-name;
                     default "localhost";
                     description "If the database is located on a
                       different system to the DHCPv6 server, the
                       domain name can be specified.";
                   }
                 }
                 case postgresql-server-address {
                   leaf postgresql-address {
                     type inet:ip-address;
                     default "::";
                     description "Configure the location of the database
                       using an IP (v6 or v6) literal address";
                   }
                 }
               }
               leaf postgresql-username {
                 type string;
                 description "User name of the account under which
                   the server will access the database";
               }
               leaf postgresql-password {
                 type string;
                 description "Password of the account under which
                   the server will access the database";
               }

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               leaf postgresql-port {
                 type inet:port-number;
                 default 5432;
                 description "If the database is located on a different
                   system, the port number may be specified";
               }
               leaf postgresql-lfc-interval {
                 type uint64;
                 description "Specifies the interval in seconds,
                   at which the server will perform a lease file cleanup
                   (LFC)";
               }
               leaf postgresql-connect-timeout {
                 type uint64;
                 description "Defines the timeout interval for
                   connecting to the database. A longer interval can
                   be specified if the database is remote.";
               }
             }
           }
         }
       }
     }

     /*
      * Augmentations
      */

     augment "/dhcpv6-server:dhcpv6-server/dhcpv6-server:vendor-config"
   {
       description "Augment the server specific YANG to the
         ietf-dhcpv6-server module.";
       uses dhcpv6-server-config:config;
     }
   }
   <CODE ENDS>

Appendix C.  Example definition of class selector configuration

   The module "ietf-example-dhcpv6-class-selector" provides an example
   of how vendor specific class selection configuration can be modelled
   and integrated with the "ietf-dhcpv6-server" module defined in this
   document.

   The example module defines "client-class-names" with associated
   matching rules.  A client can be classified based on "client-id",
   "interface-id" (ingress interface of the client's messages), packets
   source or destination address, relay link address, relay link

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   interface-id and more.  Actually, there are endless methods for
   classifying clients.  So this standard does not try to provide full
   specification for class selection, it only shows an example how it
   can be defined.

   At the end of the example augment statements are used to add the
   defined class selector rules into the overall DHCPv6 addressing
   hierarchy.  This is done in two main parts:

   *  The augmented class-selector configuration in the main DHCPv6
      Server configuration.

   *  client-class leafrefs augmented to "network-range", "address-pool"
      and "pd-pool", pointing to the "client-class-name" that is
      required.

   The mechanism is as follows: class is associated to client based on
   rules and then client is allowed to get address(es)/prefix(es) from
   given network-range/pool if the class name matches.

   <CODE BEGINS> file "ietf-example-dhcpv6-class-selector.yang"

   module ietf-example-dhcpv6-class-selector {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:" +
       "ietf-example-dhcpv6-class-selector";
     prefix "dhcpv6-class-selector";

     import ietf-inet-types {
       prefix inet;
     }

     import ietf-interfaces {
       prefix if;
     }

     import ietf-dhcpv6-common {
       prefix dhcpv6-common;
     }

     import ietf-dhcpv6-server {
       prefix dhcpv6-server;
     }

     organization
       "IETF DHC (Dynamic Host Configuration) Working Group";

     contact

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       "WG Web:   <http://datatracker.ietf.org/wg/dhc/>
        WG List:  <mailto:dhcwg@ietf.org>
        Author:   Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
        Author:   Linhui Sun <lh.sunlinh@gmail.com>
        Editor:   Ian Farrer <ian.farrer@telekom.de>
        Author:   Sladjana Zeichlin <sladjana.zechlin@telekom.de>
        Author:   Zihao He <hezihao9512@gmail.com>
        Author:   Michal Nowikowski <godfryd@isc.org>";

     description "This YANG module defines components for the definition
       and configuration of the client class selector function for a
       DHCPv6 server.  As this functionality varies greatly between
       different implementations, the module provided as an example
       only.

       Copyright (c) 2021 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 2021-02-22 {
       description "Version update for draft -18 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-18";
     }

     revision 2021-01-29 {
       description "Version update for draft -17 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-17";
     }

     revision 2021-01-06 {
       description "Version update for draft -16 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-16";
     }

     revision 2020-12-22 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-15";
     }

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     revision 2020-12-10 {
       description "Version update for draft -13 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-13";
     }

     revision 2020-12-01 {
       description "Version update for draft -12 publication.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-12";
     }

     revision 2020-05-26 {
       description "Version update for draft -11 publication and
         to align revisions across the different modules.";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang-11";
     }

     revision 2019-06-13 {
       description "";
       reference "I-D: draft-ietf-dhc-dhcpv6-yang";
     }

     /*
      * Groupings
      */

     grouping client-class-id {
       description "Definitions of client message classification for
         authorization and assignment purposes.";
       leaf client-class-name {
         type string;
         description "Unique Identifier for client class identification
           list entries.";
       }
       choice id-type {
         mandatory true;
         description "Definitions for different client identifier
           types.";
         case client-id-id {
           leaf client-id {
             type string;
             mandatory true;
             description "String literal client identifier.";
           }
           description "Client class selection based on a string literal
             client identifier.";
         }
         case received-interface-id {
           description "Client class selection based on the incoming

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             interface of the DHCPv6 message.";
           leaf received-interface {
             type if:interface-ref;
             description "Reference to the interface entry
               for the incoming DHCPv6 message.";
           }
         }
         case packet-source-address-id {
           description "Client class selection based on the source
             address of the DHCPv6 message.";
           leaf packet-source-address {
             type inet:ipv6-address;
             mandatory true;
             description "Source address of the DHCPv6 message.";
           }
         }
         case packet-destination-address-id {
           description "Client class selection based on the destination
             address of the DHCPv6 message.";
           leaf packet-destination-address {
             type inet:ipv6-address;
             mandatory true;
             description "Destination address of the DHCPv6 message.";
           }
         }
         case relay-link-address-id {
           description "Client class selection based on the prefix
             of the link-address field in the relay agent message
             header.";
           leaf relay-link-address {
             type inet:ipv6-prefix;
             mandatory true;
             description "Prefix of the link-address field in the relay
               agent message header.";
           }
         }
         case relay-peer-address-id {
           description "Client class selection based on the value of the
             peer-address field in the relay agent message header.";
           leaf relay-peer-address {
             type inet:ipv6-prefix;
             mandatory true;
             description "Prefix of the peer-address field
               in the relay agent message header.";
           }
         }
         case relay-interface-id {
           description "Client class selection based on the incoming

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             interface-id option.";
           leaf relay-interface {
             type string;
             description "Reference to the interface entry
               for the incoming DHCPv6 message.";
           }
         }
         case user-class-option-id {
           description "Client class selection based on the value of the
             OPTION_USER_CLASS(15) and its user-class-data field.";
           leaf user-class-data {
             type string;
             mandatory true;
             description "Value of the enterprise-number field.";
           }
         }
         case vendor-class-present-id {
           description "Client class selection based on the presence of
             OPTION_VENDOR_CLASS(16) in the received message.";
           leaf vendor-class-present {
             type boolean;
             mandatory true;
             description "Presence of OPTION_VENDOR_CLASS(16)
               in the received message.";
           }
         }
         case vendor-class-option-enterprise-number-id {
           description "Client class selection based on the value of the
             enterprise-number field in OPTION_VENDOR_CLASS(16).";
           leaf vendor-class-option-enterprise-number {
             type uint32;
             mandatory true;
             description "Value of the enterprise-number field.";
           }
         }
         case vendor-class-option-data-id {
           description "Client class selection based on the value
             of a data field within a vendor-class-data entry
             for a matching enterprise-number field
               in OPTION_VENDOR_CLASS(16).";
           container vendor-class-option-data {
             description "Vendor class option data container.";
             leaf vendor-class-option-enterprise-number {
               type uint32;
               mandatory true;
               description "Value of the enterprise-number field
                 for matching the data contents.";
             }

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             leaf vendor-class-data {
               type string;
               mandatory true;
               description "Vendor class data to match.";
             }
           }
         }
         case remote-id {
           description "Client class selection based on the value
             of Remote-ID .";
           container remote-id {
             description "Remote-id client class selector container.";
             leaf vendor-class-option-enterprise-number {
               type uint32;
               mandatory true;
               description "Value of the enterprise-number field
                 for matching the data contents.";
             }
             leaf remote-id {
               type string;
               mandatory true;
               description "Remote-ID data to match.";
             }
           }
         }
         case client-duid-id {
           description "Client class selection based on the value
             of the received client DUID.";
           leaf duid {
             type dhcpv6-common:duid;
             description "Client DUID.";
           }
         }
       }
     }

     /*
      * Augmentations
      */

     augment "/dhcpv6-server:dhcpv6-server/dhcpv6-server:class-selector"
    {
       description "Augment class selector functions to the DHCPv6
         server module.";
       container client-classes {
         description "Client classes to augment.";
         list class {
           key client-class-name;

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           description "List of the client class identifiers applicable
             to clients served by this address pool";
           uses dhcpv6-class-selector:client-class-id;
         }
       }
     }

     augment "/dhcpv6-server:dhcpv6-server/" +
       "dhcpv6-server:network-ranges/dhcpv6-server:network-range" {
       description "Augment class selector functions to the DHCPv6
         server network-ranges.";
       leaf-list client-class {
         type leafref {
           path "/dhcpv6-server:dhcpv6-server/dhcpv6-server:" +
             "class-selector/client-classes/class/client-class-name";
         }
         description "Leafrefs to client classes.";
       }
     }

     augment "/dhcpv6-server:dhcpv6-server/dhcpv6-server:" +
       "network-ranges/dhcpv6-server:network-range/dhcpv6-server:" +
       "address-pools/dhcpv6-server:address-pool" {
       description "Augment class selector functions to the DHCPv6
         server address-pools.";
       leaf-list client-class {
         type leafref {
           path "/dhcpv6-server:dhcpv6-server/dhcpv6-server:" +
             "class-selector/client-classes/class/client-class-name";
         }
         description "Leafrefs to client classes.";
       }
     }

     augment "/dhcpv6-server:dhcpv6-server/dhcpv6-server:" +
       "network-ranges/dhcpv6-server:network-range/dhcpv6-server:" +
       "prefix-pools/dhcpv6-server:prefix-pool" {
       description "Augment class selector functions to the DHCPv6
         server prefix-pools.";
       leaf-list client-class {
         type leafref {
           path "/dhcpv6-server:dhcpv6-server/dhcpv6-server:" +
             "class-selector/client-classes/class/client-class-name";
         }
         description "Leafrefs to client classes.";
       }
     }
   }

Farrer                   Expires 26 August 2021                [Page 88]
Internet-Draft              DHCPv6 YANG Model              February 2021

   <CODE ENDS>

Author's Address

   Ian Farrer (editor)
   Deutsche Telekom AG
   TAI, Landgrabenweg 151
   53227 Bonn
   Germany

   Email: ian.farrer@telekom.de

Farrer                   Expires 26 August 2021                [Page 89]