DHC Working Group                                                 Y. Cui
Internet-Draft                                                    L. Sun
Intended status: Standards Track                     Tsinghua University
Expires: June 26, September 5, 2018                                     I. Farrer
                                                              S. Zechlin
                                                     Deutsche Telekom AG
                                                                   Z. He
                                                     Tsinghua University
                                                       December 23, 2017
                                                           March 4, 2018

                YANG Data Model for DHCPv6 Configuration
                     draft-ietf-dhc-dhcpv6-yang-05
                     draft-ietf-dhc-dhcpv6-yang-06

Abstract

   This document describes a YANG data model [RFC6020] for the
   configuration and management of DHCPv6 servers, relays, and clients.

Requirements Language

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

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   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 June 26, September 5, 2018.

Copyright Notice

   Copyright (c) 2017 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  DHCPv6 Tree Diagram . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  DHCPv6 Server Tree Diagrams . . . . . . . . . . . . . . .   3
     2.2.  DHCPv6 Relay Tree Diagrams  . . . . . . . . . . . . . . .  16
     2.3.  DHCPv6 Client Tree Diagrams . . . . . . . . . . . . . . .  20  19
   3.  DHCPv6 YANG Model . . . . . . . . . . . . . . . . . . . . . .  27
     3.1.  DHCPv6 Server YANG Model  . . . . . . . . . . . . . . . .  27
     3.2.  DHCPv6 Relay YANG Model . . . . . . . . . . . . . . . . .  48  45
     3.3.  DHCPv6 Client YANG Model  . . . . . . . . . . . . . . . .  58  55
     3.4.  DHCPv6 Options YANG Model . . . . . . . . . . . . . . . .  67  62
     3.5.  DHCPv6 Types YANG Model . . . . . . . . . . . . . . . . .  91
   4.  Security Considerations (TBD) . . . . . . . . . . . . . . . .  98  95
   5.  IANA Considerations (TBD) . . . . . . . . . . . . . . . . . .  98  96
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  98  96
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  98  96
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  98  96
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  98  97
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  99  97
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 101  99

1.  Introduction

   DHCPv6 [RFC3315] is widely used for supplying configuration and other
   relevant parameters to clients in IPv6 networks.  This document
   defines a DHCPv6 YANG data model, containing sub-modules for the
   configuration and management of DHCPv6 servers, relays and clients.
   A single YANG model covering all of these elements provides an
   operator with a common interface for the management of the entire
   DHCPv6 deployment in their network.

   Since the publication of the original DHCPv6 specification, there
   have been a large number of addional documents that update the
   protocol's operation, add new functions and define new options.  The
   YANG model described in this document incorporates all relevent
   changes.  A full list of the documents which have been considedered
   in the development of this model is included in Appendix A.

   IF - Commment - Does anyone have this list?

   It is worth noting that as DHCPv6 is itself a device configuration
   protocol, it is not the intention of this document to replace the
   configuration of DHCPv6 options and parameters using the DHCPv6
   protocol with the configuration of DHCPv6 options using NETCONF/YANG.
   The DHCPv6 client model is intended for the configuration of the
   DHCPv6 client function and also for obtaining read-only state data
   from the client which has been learnt via the normal DHCPv6 message
   flow.  This gives an operator a better method for managing DHCPv6
   clients and simplifies troubleshooting.

1.1.  Terminology

   The reader should be familiar with the terms defined in DHCPv6
   [RFC3315] and other relevant documents.

   The DHCPv6 tree diagrams provide a concise representation of a YANG
   module to help the reader understand the module structure.

   A simplified graphical representation of the data model is provided
   in this d cument.  For a description of the symbols in these
   diagrams, please refer to [I-D.ietf-netmod-yang-tree-diagrams].

2.  DHCPv6 Tree Diagram

2.1.  DHCPv6 Server Tree Diagrams

module: ietf-dhcpv6-server
    +--rw server!
       +--rw server-config
       |  +--rw serv-attributes
       |  |  +--rw name?                string
 |  |  +--rw duid
       |  |  |  +--rw type-code?                   uint16
       |  |  |  +--rw (duid-type)?
       |  |  |     +--:(duid-llt)
       |  |  |     |  +--rw duid-llt-hardware-type?      uint16
       |  |  |     |  +--rw duid-llt-time?               yang:timeticks
       |  |  |     |  +--rw duid-llt-link-layer-addr?    yang:mac-address
       |  |  |     +--:(duid-en)
       |  |  |     |  +--rw duid-en-enterprise-number?   uint32
       |  |  |     |  +--rw duid-en-identifier?          string
       |  |  |     +--:(duid-ll)
       |  |  |     |  +--rw duid-ll-hardware-type?       uint16
       |  |  |     |  +--rw duid-ll-link-layer-addr?     yang:mac-address
       |  |  |     +--:(duid-uuid)
       |  |  |     |  +--rw uuid?                        yang:uuid
       |  |  |     +--:(duid-invalid)     +--:(duid-unknown)
       |  |  |        +--rw data?                        binary
       |  |  +--rw ipv6-address*        inet:ipv6-address name?                string
       |  |  +--rw description?         string
       |  |  +--rw pd-function          boolean
 |  |  +--rw stateless-service    boolean
 |  |  +--rw rapid-commit         boolean ipv6-address*        inet:ipv6-address
       |  |  +--rw interfaces-config*   string   if:interface-ref
       |  |  +--rw vendor-info
       |  |     +--rw ent-num    uint32
       |  |     +--rw data*      string
       |  +--rw option-sets
       |  |  +--rw option-set* [id] [option-set-id]
       |  |     +--rw id option-set-id                         uint32
       |  |     +--rw server-unicast-option! {server-unicast-op}?
       |  |     |  +--rw server-address?   inet:ipv6-address
       |  |     +--rw sip-server-domain-name-list-option!
                                    {sip-server-domain-name-list-op}?
       |  |     |  +--rw sip-serv-domain-name    string
       |  |     +--rw sip-server-address-list-option!
                                        {sip-server-address-list-op}?
       |  |     |  +--rw sip-server* [sip-serv-id]
       |  |     |     +--rw sip-serv-id      uint8
       |  |     |     +--rw sip-serv-addr    inet:ipv6-address
       |  |     +--rw dns-config-option! {dns-config-op}? dns-servers-option! {dns-servers-op}?
       |  |     |  +--rw dns-server* [dns-serv-id]
       |  |     |     +--rw dns-serv-id      uint8
       |  |     |     +--rw dns-serv-addr    inet:ipv6-address
       |  |     +--rw domain-searchlist-option! {domain-searchlist-op}?
       |  |     |  +--rw domain-searchlist* [domain-searchlist-id]
       |  |     |     +--rw domain-searchlist-id        uint8
       |  |     |     +--rw domain-search-list-entry    string
       |  |     +--rw nis-config-option! {nis-config-op}?
       |  |     |  +--rw nis-server* [nis-serv-id]
       |  |     |     +--rw nis-serv-id      uint8
       |  |     |     +--rw nis-serv-addr    inet:ipv6-address
       |  |     +--rw nis-plus-config-option! {nis-plus-config-op}?
       |  |     |  +--rw nis-plus-server* [nis-plus-serv-id]
       |  |     |     +--rw nis-plus-serv-id      uint8
       |  |     |     +--rw nis-plus-serv-addr    inet:ipv6-address
       |  |     +--rw nis-domain-name-option! {nis-domain-name-op}?
       |  |     |  +--rw nis-domain-name?   string
       |  |     +--rw nis-plus-domain-name-option!{nis-plus-domain-name-op}? nis-plus-domain-name-option!
                                        {nis-plus-domain-name-op}?
       |  |     |  +--rw nis-plus-domain-name?   string
       |  |     +--rw sntp-server-option! {sntp-server-op}?
       |  |     |  +--rw sntp-server* [sntp-serv-id]
       |  |     |     +--rw sntp-serv-id      uint8
       |  |     |     +--rw sntp-serv-addr    inet:ipv6-address
       |  |     +--rw info-refresh-time-option! {info-refresh-time-op}?
       |  |     |  +--rw info-refresh-time    yang:timeticks
       |  |     +--rw client-fqdn-option! {client-fqdn-op}?
       |  |     |  +--rw server-initiate-update    boolean
       |  |     |  +--rw client-initiate-update    boolean
       |  |     |  +--rw modify-name-from-cli      boolean
       |  |     +--rw posix-timezone-option! {posix-timezone-op}?
       |  |     |  +--rw tz-posix    string
       |  |     +--rw tzdb-timezone-option! {tzdb-timezone-op}?
       |  |     |  +--rw tz-database    string
       |  |     +--rw ntp-server-option! {ntp-server-op}?
       |  |     |  +--rw ntp-server* [ntp-serv-id]
       |  |     |     +--rw ntp-serv-id                    uint8
       |  |     |     +--rw (ntp-time-source-suboption)?
       |  |     |        +--:(server-address)
       |  |     |        |  +--rw ntp-serv-addr-suboption*
                                                      inet:ipv6-address
       |  |     |        +--:(server-multicast-address)
       |  |     |        |  +--rw ntp-serv-mul-addr-suboption*
                                                      inet:ipv6-address
       |  |     |        +--:(server-fqdn)
       |  |     |           +--rw ntp-serv-fqdn-suboption*       string
       |  |     +--rw boot-file-url-option! {boot-file-url-op}?
       |  |     |  +--rw boot-file* [boot-file-id]
       |  |     |     +--rw boot-file-id          uint8
       |  |     |     +--rw suitable-arch-type*   uint16
       |  |     |     +--rw suitable-net-if*      uint32
       |  |     |     +--rw boot-file-url         string
       |  |     +--rw boot-file-param-option! {boot-file-param-op}?
       |  |     |  +--rw boot-file-paras* [para-id]
       |  |     |     +--rw para-id      uint8
       |  |     |     +--rw parameter    string
       |  |     +--rw aftr-name-option! {aftr-name-op}?
       |  |     |  +--rw tunnel-endpoint-name    string
       |  |     +--rw kbr-default-name-option! {kbr-default-name-op}?
       |  |     |  +--rw default-realm-name    string
       |  |     +--rw kbr-kdc-option! {kbr-kdc-op}?
       |  |     |  +--rw kdc-info* [kdc-id]
       |  |     |     +--rw kdc-id            uint8
       |  |     |     +--rw priority          uint16
       |  |     |     +--rw weight            uint16
       |  |     |     +--rw transport-type    uint8
       |  |     |     +--rw port-number       uint16
       |  |     |     +--rw kdc-ipv6-addr     inet:ipv6-address
       |  |     |     +--rw realm-name        string
       |  |     +--rw sol-max-rt-option! {sol-max-rt-op}?
       |  |     |  +--rw sol-max-rt-value    yang:timeticks
       |  |     +--rw inf-max-rt-option! {inf-max-rt-op}?
       |  |     |  +--rw inf-max-rt-value    yang:timeticks
       |  |     +--rw addr-selection-option! {addr-selection-op}?
       |  |     |  +--rw a-bit-set       boolean
       |  |     |  +--rw p-bit-set       boolean
       |  |     |  +--rw policy-table* [policy-id]
       |  |     |     +--rw policy-id     uint8
       |  |     |     +--rw label         uint8
       |  |     |     +--rw precedence    uint8
       |  |     |     +--rw prefix-len    uint8
       |  |     |     +--rw prefix        inet:ipv6-prefix
       |  |     +--rw pcp-server-option! {pcp-server-op}?
       |  |     |  +--rw pcp-server* [pcp-serv-id]
       |  |     |     +--rw pcp-serv-id      uint8
       |  |     |     +--rw pcp-serv-addr    inet:ipv6-address
       |  |     +--rw s46-rule-option! {s46-rule-op}?
       |  |     |  +--rw s46-rule* [rule-id]
       |  |     |     +--rw rule-id           uint8
       |  |     |     +--rw rule-type         enumeration
       |  |     |     +--rw prefix4-len       uint8
       |  |     |     +--rw ipv4-prefix       inet:ipv4-prefix
       |  |     |     +--rw prefix6-len       uint8
       |  |     |     +--rw ipv6-prefix       inet:ipv6-prefix
       |  |     |     +--rw port-parameter
       |  |     |        +--rw offset      uint8
       |  |     |        +--rw psid-len    uint8
       |  |     |        +--rw psid        uint16
       |  |     +--rw s46-br-option! {s46-br-op}?
       |  |     |  +--rw br* [br-id]
       |  |     |     +--rw br-id           uint8
       |  |     |     +--rw br-ipv6-addr    inet:ipv6-address
       |  |     +--rw s46-dmr-option! {s46-dmr-op}?
       |  |     |  +--rw dmr* [dmr-id]
       |  |     |     +--rw dmr-id             uint8
       |  |     |     +--rw dmr-prefix-len     uint8
       |  |     |     +--rw dmr-ipv6-prefix    inet:ipv6-prefix
       |  |     +--rw s46-v4-v6-binding-option! {s46-v4-v6-binding-op}?
       |  |     |  +--rw ce* [ce-id]
       |  |     |     +--rw ce-id               uint8
       |  |     |     +--rw ipv4-addr           inet:ipv4-address
       |  |     |     +--rw bind-prefix6-len    uint8
       |  |     |     +--rw bind-ipv6-prefix    inet:ipv6-prefix
       |  |     |     +--rw port-parameter
       |  |     |        +--rw offset      uint8
       |  |     |        +--rw psid-len    uint8
       |  |     |        +--rw psid        uint16
       |  |     +--rw operator-option-ipv6-address!{operator-op-ipv6-address}? operator-option-ipv6-address!
                                              {operator-op-ipv6-address}?

       |  |     |  +--rw operator-ipv6-addr* [operator-ipv6-addr-id]
       |  |     |     +--rw operator-ipv6-addr-id    uint8
       |  |     |     +--rw operator-ipv6-addr       inet:ipv6-address
       |  |     +--rw operator-option-single-flag!{operator-op-single-flag}? operator-option-single-flag!
                                              {operator-op-single-flag}?
       |  |     |  +--rw flag* [flag-id]
       |  |     |     +--rw flag-id       uint8
       |  |     |     +--rw flag-value    boolean
       |  |     +--rw operator-option-ipv6-prefix!{operator-op-ipv6-prefix}? operator-option-ipv6-prefix!
                                              {operator-op-ipv6-prefix}?
       |  |     |  +--rw operator-ipv6-prefix* [operator-ipv6-prefix-id]
       |  |     |     +--rw operator-ipv6-prefix-id      uint8
       |  |     |     +--rw operator-ipv6-prefix6-len    uint8
       |  |     |     +--rw operator-ipv6-prefix         inet:ipv6-prefix
       |  |     +--rw operator-option-int32! {operator-op-int32}?
       |  |     |  +--rw int32val* [int32val-id]
       |  |     |     +--rw int32val-id    uint8
       |  |     |     +--rw int32val       uint32
       |  |     +--rw operator-option-int16! {operator-op-int16}?
       |  |     |  +--rw int16val* [int16val-id]
       |  |     |     +--rw int16val-id    uint8
       |  |     |     +--rw int16val       uint16
       |  |     +--rw operator-option-int8! {operator-op-int8}?
       |  |     |  +--rw int8val* [int8val-id]
       |  |     |     +--rw int8val-id    uint8
       |  |     |     +--rw int8val       uint8
       |  |     +--rw operator-option-uri! {operator-op-uri}?
       |  |     |  +--rw uri* [uri-id]
       |  |     |     +--rw uri-id    uint8
       |  |     |     +--rw uri       string
       |  |     +--rw operator-option-textstring! {operator-op-textstring}?
       |  |     |  +--rw textstring* [textstring-id]
       |  |     |     +--rw textstring-id    uint8
       |  |     |     +--rw textstring       string
       |  |     +--rw operator-option-var-data! {operator-op-var-data}?
       |  |     |  +--rw int32val* [var-data-id]
       |  |     |     +--rw var-data-id    uint8
       |  |     |     +--rw var-data       binary
       |  |     +--rw operator-option-dns-wire! {operator-op-dns-wire}?
       |  |        +--rw operator-option-dns-wire*
                                          [operator-option-dns-wire-id]
       |  |           +--rw operator-option-dns-wire-id    uint8
       |  |           +--rw operator-option-dns-wire       binary
       |  +--rw network-ranges
       |  |  +--rw option-set-id?
            -> /server/server-config/option-sets/option-set/option-set-id
       |  |  +--rw network-range* [network-range-id]
       |  |     +--rw network-range-id       uint32
       |  |     +--rw network-description    string
       |  |     +--rw network-prefix         inet:ipv6-prefix
       |  |     +--rw inherit-option-set     boolean
 |  |   +--rw option-set-id?
            -> /server/server-config/option-sets/option-set/id /server/server-config/option-sets/option-set/option-set-id
       |  |     +--rw reserved-addresses address-pools
       |  |     |  +--rw static-binding* [cli-id]
 | address-pool* [pool-id]
       |  |     |     +--rw cli-id pool-id               uint32
       |  |     |  |     +--rw duid
 |  | pool-prefix           inet:ipv6-prefix
       |  |     |     +--rw type-code?                   uint16
 |  | start-address         inet:ipv6-address-no-zone
       |  |     |     +--rw (duid-type)?
 |  | end-address           inet:ipv6-address-no-zone
       |  |     |     +--:(duid-llt)     +--rw client-class?         string
       |  |     |     +--rw valid-lifetime        yang:timeticks
       |  |     |     +--rw duid-llt-hardware-type?      uint16 renew-time            yang:timeticks
       |  |     |     +--rw rebind-time           yang:timeticks
       |  |     |     +--rw duid-llt-time? preferred-lifetime    yang:timeticks
       |  |     |     +--rw rapid-commit          boolean
       |  |     |     +--rw duid-llt-link-layer-addr? yang:mac-address max-address-count     threshold
       |  |     |     +--rw option-set-id
              -> /server/server-config/option-sets/option-set/option-set-id
       |  |     +--:(duid-en)     +--rw pd-pools
       |  |     |  +--rw pd-pool* [pool-id]
       |  |     |     +--rw duid-en-enterprise-number? pool-id                    uint32
       |  |     |  |  |     |     +--rw duid-en-identifier?          string
 |  |   |  |  |     +--:(duid-ll)
 |  |   | prefix                     inet:ipv6-prefix
       |  |     |     +--rw duid-ll-hardware-type?       uint16
 |  |   | prefix-length              uint8
       |  |     |     +--rw duid-ll-link-layer-addr? yang:mac-address
 |  |   |  |  |     +--:(duid-uuid) client-class?              string
       |  |     |     +--rw valid-lifetime             yang:timeticks
       |  |     |     +--rw uuid?                        yang:uuid
 | renew-time                 yang:timeticks
       |  |     |     +--rw rebind-time                yang:timeticks
       |     +--:(duid-invalid)  |     |     +--rw preferred-lifetime         yang:timeticks
       |  |     |     +--rw data?                        binary
 | rapid-commit               boolean
       |  |     |     +--rw reserv-addr*   inet:ipv6-address max-pd-space-utlization    threshold
       |  |     |     +--rw other-reserv-addr*   inet:ipv6-address option-set-id
              -> /server/server-config/option-sets/option-set/option-set-id
       |  |     +--rw reserved-prefixes
 | host-reservations
       |  |        +--rw static-binding* host-reservation* [cli-id]
       |  |   |  |           +--rw cli-id                       uint32
       |  |           +--rw (client-identifier)?
       |  |  +--rw duid           |  +--:(duid)
       |  |           |  |  +--rw type-code?                   uint16
       |  |           |  |  |  +--rw (duid-type)?
       |  |           |  |  |     +--:(duid-llt)
       |  |           |  |     |     |  +--rw duid-llt-hardware-type?      uint16
       |  |           |  |     |     |  +--rw duid-llt-time?
                                                              yang:timeticks
       |  |           |  |     |     |  +--rw duid-llt-link-layer-addr?
                                                            yang:mac-address
       |  |           |  |  |     +--:(duid-en)
       |  |           |  |     |     |  +--rw duid-en-enterprise-number?   uint32
       |  |           |  |     |     |  +--rw duid-en-identifier?          string
       |  |           |  |  |     +--:(duid-ll)
       |  |           |  |     |     |  +--rw duid-ll-hardware-type?       uint16
       |  |           |  |     |     |  +--rw duid-ll-link-layer-addr?
                                                            yang:mac-address
       |  |           |  |  |     +--:(duid-uuid)
       |  |           |  |     |     |  +--rw uuid?                        yang:uuid
       |  |           |  |  |     +--:(duid-invalid)
 |     +--:(duid-unknown)
       |  |           |  |        +--rw data?                        binary
       |  |           |  |  +--rw reserv-prefix-len    uint8
 |  +--:(hw-address)
       |  |           |     +--rw reserv-prefix        inet:ipv6-prefix
 | hardware-address?       yang:mac-address
       |  |           +--rw exclude-prefix-len     uint8
 | reserv-addr*                 inet:ipv6-address
       |  |           +--rw exclude-prefix         inet:ipv6-prefix prefix-reservation* [reserv-prefix-id]
       |  |           |  +--rw other-reserv-prefix* [reserv-id] reserv-prefix-id     uint32
       |  |           |  +--rw reserv-id     uint32 reserv-prefix        inet:ipv6-prefix
       |  |           |  +--rw prefix-len reserv-prefix-len    uint8
       |  |   |           +--rw prefix        inet:ipv6-prefix hostname?                    string
       |  |           +--rw address-pools option-set-id?
              -> /server/server-config/option-sets/option-set/option-set-id
       |  +--rw relay-opaque-paras
       |  |  +--rw address-pool* [pool-id]
 | relays* [relay-name]
       |  |     +--rw pool-id                          uint32
 | relay-name        string
       |  |     +--rw pool-prefi            inet:ipv6-prefix interface-info* [if-name]
       |  |     |  +--rw start-address         inet:ipv6-address-no-zone if-name         string
       |  |     |  +--rw end-address           inet:ipv6-address-no-zone
 | interface-id    string
       |  |     +--rw renew-time                       yang:timeticks subscribers* [subscriber]
       |  |     |  +--rw rebind-time                      yang:timeticks subscriber       uint32
       |  |     |  +--rw preferred-lifetime               yang:timeticks
 |  |   |     +--rw valid-lifetime                   yang:timeticks
 |  |   |     +--rw max-address-utilization-ratio    threshold
 |  |   |     +--rw inherit-option-set               boolean
 |  |   |     +--rw option-set-id
                 -> /server/server-config/option-sets/option-set/id
 |  |   +--rw prefix-pools
 | subscriber-id    string
       |  |     +--rw prefix-pool* [pool-id]
 | remote-host* [ent-num]
       |  |        +--rw pool-id ent-num      uint32
       |  |   |        +--rw prefix                          inet:ipv6-prefix
 |  | remote-id    string
       |  +--rw prefix-length                   uint8
 |  | rsoo-enabled-options
       |     +--rw renew-time                      yang:timeticks
 |  | rsoo-enabled-option* [option-code]
       |        +--rw rebind-time                     yang:timeticks
 |  | option-code    uint16
       |        +--rw preferred-lifetime              yang:timeticks description    string
       +--ro server-state
          +--ro network-ranges
          |  +--ro network-range* [network-range-id]
          |     +--ro network-range-id     uint32
          |     +--rw valid-lifetime                  yang:timeticks     +--ro address-pools
          |     |  +--ro address-pool* [pool-id]
          |     +--rw max-prefix-utilization-ratio    threshold     |  |  +--ro pool-id                    uint32
          |     +--rw inherit-option-set              boolean     |  |  +--ro total-address-count        uint64
          |     +--rw option-set-id?
                 -> /server/server-config/option-sets/option-set/id     |  |   +--rw hosts  +--ro allocated-address-conut    uint64
          |     |      +--rw host*  +--ro binding-info* [cli-id]
          |     |         +--rw     +--ro cli-id    uint32
          |     |         +--rw     +--ro duid
          |     |     |  +--rw  +--ro type-code?                   uint16
          |     |     |  +--rw  +--ro (duid-type)?
          |     |     |     +--:(duid-llt)
          |     |     |     |  +--rw  +--ro duid-llt-hardware-type?      uint16
          |     |     |     |  +--rw  +--ro duid-llt-time?         yang:timeticks
          |     |     |     |  +--rw  +--ro duid-llt-link-layer-addr?
                                                          yang:mac-address
          |     |     |     +--:(duid-en)
          |     |     |     |  +--rw  +--ro duid-en-enterprise-number?   uint32
          |     |     |     |  +--rw  +--ro duid-en-identifier?          string
          |     |     |     +--:(duid-ll)
          |     |     |     |  +--rw  +--ro duid-ll-hardware-type?       uint16
          |     |     |     |  +--rw  +--ro duid-ll-link-layer-addr?
                                                         yang:mac-address
          |     |     |     +--:(duid-uuid)
          |     |     |     |  +--rw  +--ro uuid?                    yang:uuid
          |     |     |     +--:(duid-invalid)     +--:(duid-unknown)
          |     |     |        +--rw        +--ro data?                        binary
          |     |         +--rw inherit-option-set      boolean
 |  |         +--rw option-set-id?
                  -> /server/server-config/option-sets/option-set/id
 |  |         +--rw nis-domain-name?        string
 |  |         +--rw nis-plus-domain-name?   string
 |  +--rw relay-opaque-paras
 |  |  +--rw relays* [relay-name]
 |  |     +--rw relay-name        string
 |  |     +--rw interface-info* [if-name]
 |  |     |  +--rw if-name         string
 |  |     |  +--rw interface-id    string
 |  |     +--rw subscribers* [subscriber]
 |  |     |  +--rw subscriber       uint32
 |     +--ro cli-ia* [iaid]
          |     |  +--rw subscriber-id        +--ro ia-type     string
          |     |     +--rw remote-host* [ent-num]
 |  |        +--rw ent-num        +--ro iaid        uint32
          |     |        +--rw remote-id    string
 |  +--rw rsoo-enabled-options
 |     +--rw rsoo-enabled-option* [option-code]
 |        +--rw option-code    uint16
 |        +--rw description    string        +--ro server-state
    +--ro network-ranges cli-addr*   inet:ipv6-address
          |  +--ro network-range* [network-range-id]     |        +--ro network-range-id pool-id     uint32
          |     +--ro address-pools pd-pools
          |     |  +--ro address-pool* prefix-pool* [pool-id]
          |     |  |  +--ro pool-id                 uint32
          |     |  |  +--ro total-ipv6-count             uint64
    |   |  |  +--ro used-ipv6-count              uint64
    |   |  |  +--ro address-utilization-ratio    uint16 pd-space-utilization    threshold
          |     |  +--ro binding-info* [cli-id]
          |     |     +--ro cli-id      uint32
          |     |     +--ro duid
          |     |     |  +--ro type-code?                   uint16
          |     |     |  +--ro (duid-type)?
          |     |     |     +--:(duid-llt)
          |     |     |     |  +--ro duid-llt-hardware-type?      uint16
          |     |     |     |  +--ro duid-llt-time?        yang:timeticks
          |     |     |     |  +--ro duid-llt-link-layer-addr?
                                                        yang:mac-address
          |     |     |     +--:(duid-en)
          |     |     |     |  +--ro duid-en-enterprise-number?   uint32
          |     |     |     |  +--ro duid-en-identifier?          string
          |     |     |     +--:(duid-ll)
          |     |     |     |  +--ro duid-ll-hardware-type?       uint16
          |     |     |     |  +--ro duid-ll-link-layer-addr?
                                                        yang:mac-address
          |     |     |     +--:(duid-uuid)
          |     |     |     |  +--ro uuid?                     yang:uuid
          |     |     |     +--:(duid-invalid)     +--:(duid-unknown)
          |     |     |        +--ro data?                        binary
          |     |     +--ro cli-ia* cli-iapd* [iaid]
          |     |        +--ro ia-type     string
    |   |        +--ro iaid              uint32
          |     |        +--ro cli-addr*   inet:ipv6-address cli-prefix*       inet:ipv6-prefix
          |     |        +--ro pool-id     uint32
    |   +--ro prefix-pools
    |   |  +--ro prefix-pool* [pool-id]
    | cli-prefix-len*   uint8
          |     |        +--ro pool-id           uint32
          |   |  |     +--ro prefix-utilization-ratio    uint16
    | host-reservations
          |        +--ro binding-info* [cli-id]
          |   |           +--ro cli-id      uint32
          |   |           +--ro duid
          |           |     |  +--ro type-code?                   uint16
          |           |     |  +--ro (duid-type)?
          |           |     |     +--:(duid-llt)
          |           |     |     |  +--ro duid-llt-hardware-type?      uint16
          |           |     |     |  +--ro duid-llt-time?        yang:timeticks
          |           |     |     |  +--ro duid-llt-link-layer-addr?
                                                        yang:mac-address
          |           |     |     +--:(duid-en)
          |           |     |     |  +--ro duid-en-enterprise-number?   uint32
          |           |     |     |  +--ro duid-en-identifier?          string
          |           |     |     +--:(duid-ll)
          |           |     |     |  +--ro duid-ll-hardware-type?       uint16
          |           |     |     |  +--ro duid-ll-link-layer-addr?
                                                          yang:mac-address
          |           |     |     +--:(duid-uuid)
          |           |     |     |  +--ro uuid?                     yang:uuid
          |           |     |     +--:(duid-invalid)
    |     +--:(duid-unknown)
          |           |        +--ro data?                        binary
          |   |           +--ro cli-iapd* cli-ia* [iaid]
          |           |  +--ro ia-type     string
          |           |  +--ro iaid        uint32
          |           |  +--ro cli-addr*   inet:ipv6-address
          |           +--ro cli-iapd* [iaid]
          |              +--ro iaid              uint32
          |              +--ro cli-prefix*       inet:ipv6-prefix
          |   |              +--ro cli-prefix-len*   uint8
    |   |
          +--ro pool-id packet-stats
             +--ro solicit-count          uint32
             +--ro request-count          uint32
             +--ro renew-count            uint32
             +--ro rebind-count           uint32
             +--ro decline-count          uint32
             +--ro release-count          uint32
             +--ro info-req-count         uint32
             +--ro advertise-count        uint32
             +--ro confirm-count          uint32
             +--ro reply-count            uint32
             +--ro reconfigure-count      uint32
             +--ro relay-forward-count    uint32
             +--ro relay-reply-count      uint32

  notifications:
    +---n notifications
       +--ro dhcpv6-server-event
          +--ro address-pool-running-out
          |  +--ro address-prefix-assign-param* [cli-id] total-address-count        uint64
          |  +--ro cli-id                      uint32 max-address-count          uint64
          |  +--ro source-ipv6-addr?           inet:ipv6-address allocated-address-conut    uint64
          |  +--ro duid
          |  |  +--ro type-code?                   uint16
          |  |  +--ro (duid-type)?
          |  |     +--:(duid-llt)
          |  |     |  +--ro duid-llt-hardware-type?      uint16
          |  |     |  +--ro duid-llt-time?               yang:timeticks
          |  |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
          |  |     +--:(duid-en)
          |  |     |  +--ro duid-en-enterprise-number?   uint32
          |  |     |  +--ro duid-en-identifier?          string
          |  |     +--:(duid-ll)
          |  |     |  +--ro duid-ll-hardware-type?       uint16
          |  |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
          |  |     +--:(duid-uuid)
          |  |     |  +--ro uuid?                        yang:uuid
          |  |     +--:(duid-invalid)     +--:(duid-unknown)
          |  |        +--ro data?                        binary
          |  +--ro iaid*                       uint32
    |      +--ro preferred-addr*             inet:ipv6-address
    |      +--ro preferred-prefix-len*       uint8
    |      +--ro client-fqdn? serv-name?                 string
          |  +--ro client-link-layer-addr?     uint16
    |      +--ro client-enterprise-number?   uint32
    |      +--ro client-sys-archi-type*      uint16
    +--ro packet-stats
       +--ro solicit-count          uint32
       +--ro request-count          uint32
       +--ro renew-count            uint32
       +--ro rebind-count           uint32
       +--ro decline-count          uint32
       +--ro release-count          uint32
       +--ro info-req-count         uint32
       +--ro advertise-count        uint32
       +--ro confirm-count          uint32
       +--ro reply-count            uint32
       +--ro reconfigure-count      uint32
       +--ro relay-forward-count    uint32
       +--ro relay-reply-count      uint32

notifications:
+---n notifications
   +--ro dhcpv6-server-event
      +--ro pool-running-out
      |  +--ro max-address-utilization-ratio    uint16
      | pool-name                  string
          +--ro address-utilization-ratio        uint16 pd-pool-running-out
          |  +--ro max-prefix-utilization-ratio     uint16 max-pd-space-utilization    threshold
          |  +--ro prefix-utilization-ratio         uint16 pd-space-utilization        threshold
          |  +--ro duid
          |  |  +--ro type-code?                   uint16
          |  |  +--ro (duid-type)?
          |  |     +--:(duid-llt)
          |  |     |  +--ro duid-llt-hardware-type?      uint16
          |  |     |  +--ro duid-llt-time?               yang:timeticks
          |  |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
          |  |     +--:(duid-en)
          |  |     |  +--ro duid-en-enterprise-number?   uint32
          |  |     |  +--ro duid-en-identifier?          string
          |  |     +--:(duid-ll)
          |  |     |  +--ro duid-ll-hardware-type?       uint16
          |  |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
          |  |     +--:(duid-uuid)
          |  |     |  +--ro uuid?                        yang:uuid
          |  |     +--:(duid-invalid)     +--:(duid-unknown)
          |  |        +--ro data?                        binary
          |  +--ro serv-name?                  string
          |  +--ro pool-name                   string
          +--ro invalid-client-detected
             +--ro duid
             |  +--ro type-code?                   uint16
             |  +--ro (duid-type)?
             |     +--:(duid-llt)
             |     |  +--ro duid-llt-hardware-type?      uint16
             |     |  +--ro duid-llt-time?               yang:timeticks
             |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
             |     +--:(duid-en)
             |     |  +--ro duid-en-enterprise-number?   uint32
             |     |  +--ro duid-en-identifier?          string
             |     +--:(duid-ll)
             |     |  +--ro duid-ll-hardware-type?       uint16
             |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
             |     +--:(duid-uuid)
             |     |  +--ro uuid?                        yang:uuid
             |     +--:(duid-invalid)     +--:(duid-unknown)
             |        +--ro data?                        binary
             +--ro description?   string

                   Figure 1: DHCPv6 Data Model Structure

   Introduction of important nodes:

   o  server-config: This container contains the configuration data of a
      server.

   o  serv-attributes: This container contains basic attributes of a
      DHCPv6 server such as DUID, server name and so on.  Some optional
      functions that can be provided by the server is also included.

   o  duid: Each server and client has only one DUID (DHCP Unique
      Identifier).  The DUID here identifies a unique DHCPv6 server for
      clients.  DUID consists of a two-octet type field and an arbitrary
      length (no more than 128 bytes) content field.  Currently there
      are four defined types of DUIDs in [RFC3315] and [RFC6355] - DUID-
      LLT, DUID-EN, DUID-LL and DUID-UUID.  DUID-INVALID  DUID-Unknown represents
      those unconventional DUIDs.

   o  pd-function: Whether the server can act as a delegating router to
      perform prefix delegation [RFC3633].

   o  operator-option-ipv6-address, operator-option-single-flag,
      operator-option-ipv6-prefix, operator-option-int32, operator-
      option-int16, operator-option-int8, operator-option-uri, operator-
      option-textstring, operator-option-var-data, operator-option-dns-
      wire: are generic option formats described in [RFC7227].

   o  stateless-service: A boolean value specifies whether the server
      support client-server exchanges involving two messages defined in
      [RFC3315].

   o  rapid-commit: Setting the value to '1' represents the server
      support the Solicit-Reply message exchange. '0' means the server
      will simply ignore the Rapid Commit option in Solicit message.

   o  interfaces-config: A leaf list to denote which one or more
      interfaces the server should listen on.  The default value is to
      listen on all the interfaces.  This node is also used to set a
      unicast address for the server to listen with a specific
      interface.  For example, if the server is being configured to
      listen on a unicast address assigned to a specific interface, the
      format "eth1/2001:db8::1" can be used.

   o  option-sets: DHCPv6 employs various options to carry additional
      information and parameters in DHCP messages.  This container
      defines all the possible options that need to be configured at the
      server side.  The relevant RFCs that define those options include:
      [RFC3315], [RFC3319], [RFC3646], [RFC3898], [RFC4242], [RFC4704],
      [RFC4833], [RFC5908], [RFC5970], [RFC4075], [RFC6334], [RFC6784],
      [RFC7078], [RFC7083], [RFC7291], [RFC7598].

   o  option-set: A server may allow different option sets to be
      configured for different conditions (i.e. different networks,
      clients and etc).  This "option-set" list enables various sets of
      options being defined and configured in a single server.
      Different sets are distinguished by the key called "option-set-
      id".  All the possible options discussed above are defined in the
      list and each option is corresponding to a container.  Since all
      the options in the list are optional, each container in this list
      has a 'presence' statement to indicate whether this option
      (container) will be included in the current option set or not.  In
      addition, each container also has a 'if-feature' statement to
      indicate whether the server supports this option (container).

   o  network-ranges: This model supports a hierarchy to achieve dynamic
      configuration.  That is to say we could configure the server at
      different levels through this model.  The top level is a global
      level which is defined as the container "network-ranges".  The
      following levels are defined as sub-containers under it.  The
      "network-ranges" contains the parameters (e.g. option-sets) that
      would be allocated to all the clients served by this server

   o  network-range: Under the "network-ranges" container, a "network-
      range" list is defined to configure the server at a network level
      which is also considered as the second level.  Different network
      are identified by the key "network-range-id".  This is because a
      server may have different configuration parameters (e.g. option
      sets) for different networks.

   o  address-pools: Under the "network-range" list, a container
      describes the DHCPv6 server's address pools for a specific network
      is defined.  This container supports the server to be configured
      at a pool level.

   o  address-pool: A DHCPv6 server can be configured with several
      address pools for a specific network.  This list defines such
      address pools which are distinguish by the key called "pool-id".

   o  max-address-utilization-ratio: The threshold of address pool
      utiliztion,  rapid-commit: Setting the value of which is settable.

   o  binding-info: A list records a binding information for each DHCPv6
      client to '1' represents the adress/
      prefix pool support the Solicit-Reply message exchange. '0' means
      the server will simply ignore the Rapid Commit option in Solicit
      message.

   o  client-class: If this is instantiated, the address/pd pool will
      only serve the clients belonging to this class.

   o  max-address-count: Maximum count of addresses that has already been can be
      allocated IPv6 addresses. in this pool.  This value may be less than count of
      total addresses in this pool.

   o  prefix-pools: If a server supports prefix delegation function,
      this container under the "network-range" list will be valid to
      define the delegating router's prefix pools for a specific
      network.  This container also supports the server to be configured
      at a pool level.

   o  prefix-pool: Similar to server's address pools, a delegating
      router can also be configured with multiple prefix pools specified
      by a list called "prefix-pool".

   o  max-prefix-utilization-ratio: The threshold  max-pd-space-utlization: Maximum utilization of prefix pd space in this
      pool
      utiliztion, the value of which is settable.

   o  binding-info: A list records a binding information for each DHCPv6
      requesting router that has already been configured IPv6 prefixes.

   o  hosts: A  host-reservations: This container allows the server may also desire to be configured make
      reservations at a host level
      under some circumstances. level.

   o  host-reservation: This container include a list called
      "host" to allow allows the server carrying different parameters (e.g.
      option sets) to reserve
      addresses, prefixes, hostname and options for different hosts. clients.
      A server may reserve multiple addresses and prefixes for a single
      client.

   o  relay-opaque-paras: This container contains some opaque values in
      Relay Agent options that need to be configured on the server side
      only for value match.  Such Relay Agent options include Interface-
      Id option, Remote-Id option and Subscriber-Id option.

   o  rsoo-enabled-options: [RFC6422] requires that the server SHOULD
      have an administrator-configurable list of RSOO-enabled options.
      This container include a list called "rsoo-enabled-option" to
      allow new RSOO-enabled options to be defined at the server side.

   o  server-state: This container includes the state data of a server.

   o  address-prefix-assign-param: This  binding-info: A list includes some parameters/
      identifiers that the server obtains from records a static binding information for each
      DHCPv6 options client that has already been assigned IPv6 addresses/
      prefixes that are dynamically allocated and reserved in this
      network-range.  The server may take these parameters/identifiers
      into account when assigning a(n) address/prefix. advance.

   o  packet-stats: A container presents the packet statistics related
      to the DHCPv6 server.

   Information about notifications:

   o  pool-running-out:  address/pd-pool-running-out: raised when the address/prefix pool
      is going to run out.  A threshold for utilization ratio of the
      pool (max-address-count/max-pd-space utilization) has been defined
      in the server feature so that it will notify the administrator
      when the utilization ratio reaches the threshold, and such
      threshold is a settable parameter.

   o  invalid-client-detected: raised when the server has found a client
      which can be regarded as a potential attacker.  Some description
      could also be included.

2.2.  DHCPv6 Relay Tree Diagrams

module: ietf-dhcpv6-relay
    +--rw relay!
       +--rw relay-config
       |  +--rw relay-attributes
       |  |  +--rw name?          string
       |  |  +--rw description?   string
       |  |  +--rw dest-addrs*    inet:ipv6-address
       |  |  +--rw subscribers* [subscriber]
       |  |  |  +--rw subscriber       uint8
       |  |  |  +--rw subscriber-id    string
       |  |  +--rw remote-host* [ent-num]
       |  |  |  +--rw ent-num      uint32
       |  |  |  +--rw remote-id    string
       |  |  +--rw vendor-info
       |  |     +--rw ent-num    uint32
       |  |     +--rw data*      string
       |  +--rw rsoo-option-sets
       |  |  +--rw option-set* [id] [option-set-id]
       |  |     +--rw id option-set-id                   uint32
       |  |     +--rw erp-local-domain-name-option!
                                  {erp-local-domain-name-op}?
       |  |        +--rw erp-for-client* [cli-id]
       |  |           +--rw cli-id      uint32
       |  |           +--rw duid
       |  |           |  +--rw type-code?                   uint16
       |  |           |  +--rw (duid-type)?
       |  |           |     +--:(duid-llt)
       |  |           |     |  +--rw duid-llt-hardware-type?      uint16
       |  |           |     |  +--rw duid-llt-time?        yang:timeticks
       |  |           |     |  +--rw duid-llt-link-layer-addr?
                                                        yang:mac-address
       |  |           |     +--:(duid-en)
       |  |           |     |  +--rw duid-en-enterprise-number?   uint32
       |  |           |     |  +--rw duid-en-identifier?          string
       |  |           |     +--:(duid-ll)
       |  |           |     |  +--rw duid-ll-hardware-type?       uint16
       |  |           |     |  +--rw duid-ll-link-layer-addr?
                                                        yang:mac-address
       |  |           |     +--:(duid-uuid)
       |  |           |     |  +--rw uuid?                     yang:uuid
       |  |           |     +--:(duid-invalid)     +--:(duid-unknown)
       |  |           |        +--rw data?                        binary
       |  |           +--rw erp-name    string
       |  +--rw relay-if* [if-name]
       |     +--rw if-name               string               if:interface-ref
       |     +--rw enable                boolean interface-id?         string
       |     +--rw ipv6-address?         inet:ipv6-address
       |     +--rw interface-id?         string
       |     +--rw rsoo-option-set-id?
        -> /relay/relay-config/rsoo-option-sets/option-set/id /relay/relay-config/rsoo-option-sets/option-set/option-set-id
       |     +--rw next-entity* [dest-addr]
       |        +--rw dest-addr    inet:ipv6-address
       |        +--rw available    boolean
       |        +--rw multicast    boolean
       |        +--rw server       boolean
       +--ro relay-state
          +--ro relay-if* [if-name]
          |  +--ro if-name        string
          |  +--ro pd-route* [pd-route-id]
          |  |  +--ro pd-route-id             uint8
          |  |  +--ro requesting-router-id    uint32
          |  |  +--ro delegating-router-id    uint32
          |  |  +--ro next-router             inet:ipv6-address
          |  |  +--ro last-router             inet:ipv6-address
          |  +--ro next-entity* [dest-addr]
          |     +--ro dest-addr       inet:ipv6-address
          |     +--ro packet-stats
          |        +--ro solicit-rvd-count       uint32
          |        +--ro request-rvd-count       uint32
          |        +--ro renew-rvd-count         uint32
          |        +--ro rebind-rvd-count        uint32
          |        +--ro decline-rvd-count       uint32
          |        +--ro release-rvd-count       uint32
          |        +--ro info-req-rvd-count      uint32
          |        +--ro relay-for-rvd-count     uint32
          |        +--ro relay-rep-rvd-count     uint32
          |        +--ro packet-to-cli-count     uint32
          |        +--ro adver-sent-count        uint32
          |        +--ro confirm-sent-count      uint32
          |        +--ro reply-sent-count        uint32
          |        +--ro reconfig-sent-count     uint32
          |        +--ro relay-for-sent-count    uint32
          |        +--ro relay-rep-sent-count    uint32
          +--ro relay-stats
             +--ro cli-packet-rvd-count      uint32
             +--ro relay-for-rvd-count       uint32
             +--ro relay-rep-rvd-count       uint32
             +--ro packet-to-cli-count       uint32
             +--ro relay-for-sent-count      uint32
             +--ro relay-rep-sent-count      uint32
             +--ro discarded-packet-count    uint32

  notifications:
    +---n notifications
       +--ro dhcpv6-relay-event
          +--ro topo-changed
             +--ro relay-if-name       string
             +--ro first-hop           boolean
             +--ro last-entity-addr    inet:ipv6-address

   Introduction of important nodes:

   o  relay-config: This container contains the configuration data of
      the relay.

   o  relay-attributes: A container describes some basic attributes of
      the relay agent including some relay agent specific options data
      that need to be configured previously.  Such options include
      Remote-Id option and Subscriber-Id option.

   o  dest-addrs: Each DHCPv6 relay agent may be configured with a list
      of destination addresses.  This node defines such a list of IPv6
      addresses that may include unicast addresses, multicast addresses
      or other addresses.

   o  rsoo-options-sets: DHCPv6 relay agent could provide some
      information that would be useful to DHCPv6 client.  Since relay
      agent cannot provide options directly to the client, [RFC6422]
      defines RSOO-enabled options to propose options for the server to
      send to the client.  This container models such RSOO-enabled
      options.

   o  option-set: This list under the "rsoo-option-sets" container is
      similar to the that defined in server module.  It allows the relay
      to implement several sets of RSOO-enabled options for different
      interfaces.  The list only include the EAP Re-authentication
      Protocol (ERP) Local Domain Name DHCPv6 Option defined in
      [RFC6440], since it is the only one RSOO-enabled options accepted
      by IANA so far.

   o  relay-if: A relay agent may have several interfaces, we should
      provide a way to configure and manage parameters on the interface-
      level.  A list that describes specific interfaces and their
      corresponding parameters is employed to fulfil the configfuration.
      Here we use a string called "if-name" as the key of list.

   o  relay-state: This container contains the configuration data of the
      relay.

   o  pd-route: A sub-container of "relay-if" which describes the route
      for delegated prefixes into the provider edge router.

   o  next-entity: This node defines a list that is used to describe the
      next hop entity of this relay agent.  Different entities are
      distinguished by their addresses.

   o  packet-stats: A container shows packet state information of a
      specific data communication.

   o  relay-stats: The "relay-stats" container records and presents the
      overall packet statistics of the relay agent.

   Information about notifications:

   o  topo-changed: raised when the topology of the relay agent is
      changed.

2.3.  DHCPv6 Client Tree Diagrams

module: ietf-dhcpv6-client
    +--rw client!
       +--rw client-config
       |  +--rw duid
       |  |  +--rw type-code?                   uint16
       |  |  +--rw (duid-type)?
       |  |     +--:(duid-llt)
       |  |     |  +--rw duid-llt-hardware-type?      uint16
       |  |     |  +--rw duid-llt-time?               yang:timeticks
       |  |     |  +--rw duid-llt-link-layer-addr?    yang:mac-address
       |  |     +--:(duid-en)
       |  |     |  +--rw duid-en-enterprise-number?   uint32
       |  |     |  +--rw duid-en-identifier?          string
       |  |     +--:(duid-ll)
       |  |     |  +--rw duid-ll-hardware-type?       uint16
       |  |     |  +--rw duid-ll-link-layer-addr?     yang:mac-address
       |  |     +--:(duid-uuid)
       |  |     |  +--rw uuid?                        yang:uuid
       |  |     +--:(duid-invalid)     +--:(duid-unknown)
       |  |        +--rw data?                        binary
       |  +--rw client-if* [if-name]
       |     +--rw if-name                      string                      if:interface-ref
       |     +--rw cli-id                       uint32
       |     +--rw description?                 string
       |     +--rw pd-function                  boolean
       |     +--rw rapid-commit                 boolean
       |     +--rw mo-tab
       |     |  +--rw m-tab    boolean
       |     |  +--rw o-tab    boolean
       |     +--rw client-configured-options
       |        +--rw new-or-standard-cli-option* [option-code]
       |        |  +--rw option-code           uint16
       |        |  +--rw option-name           string
       |        |  +--rw option-description    string
       |        |  +--rw option-reference?     string
       |        |  +--rw option-value          string
       |        +--rw option-request-option! {option-request-op}?
       |        |  +--rw oro-option* [option-code]
       |        |     +--rw option-code    uint16
       |        |     +--rw description    string
       |        +--rw user-class-option! {user-class-op}?
       |        |  +--rw user-class* [user-class-id]
       |        |     +--rw user-class-id      uint8
       |        |     +--rw user-class-data    string
       |        +--rw vendor-class-option! {vendor-class-op}?
       |        |  +--rw enterprise-number    uint32
       |        |  +--rw vendor-class* [vendor-class-id]
       |        |     +--rw vendor-class-id      uint8
       |        |     +--rw vendor-class-data    string
       |        +--rw client-fqdn-option! {client-fqdn-op}?
       |        |  +--rw fqdn                      string
       |        |  +--rw server-initiate-update    boolean
       |        |  +--rw client-initiate-update    boolean
       |        +--rw client-arch-type-option! {client-arch-type-op}?
       |        |  +--rw architecture-types* [type-id]
       |        |     +--rw type-id           uint16
       |        |     +--rw most-preferred    boolean
       |        +--rw client-network-interface-identifier-option!
                            {client-network-interface-identifier-op}?
       |        |  +--rw type     uint8
       |        |  +--rw major    uint8
       |        |  +--rw minor    uint8
       |        +--rw kbr-principal-name-option! {kbr-principal-name-op}?
       |        |  +--rw principle-name* [principle-name-id]
       |        |     +--rw principle-name-id    uint8
       |        |     +--rw name-type            int32
       |        |     +--rw name-string          string
       |        +--rw kbr-realm-name-option! {kbr-realm-name-op}?
       |        |  +--rw realm-name    string
       |        +--rw client-link-layer-addr-option!
                                            {client-link-layer-addr-op}?
       |           +--rw link-layer-type    uint16
       |           +--rw link-layer-addr    string
       +--ro client-state
          +--ro if-other-paras
          |  +--ro server-unicast-option! {server-unicast-op}?
          |  |  +--ro server-address?   inet:ipv6-address
          |  +--ro sip-server-domain-name-list-option!
                                        {sip-server-domain-name-list-op}?
          |  |  +--ro sip-serv-domain-name    string
          |  +--ro sip-server-address-list-option!
                                            {sip-server-address-list-op}?
          |  |  +--ro sip-server* [sip-serv-id]
          |  |     +--ro sip-serv-id      uint8
          |  |     +--ro sip-serv-addr    inet:ipv6-address
          |  +--ro dns-config-option! {dns-config-op}? dns-servers-option! {dns-servers-op}?
          |  |  +--ro dns-server* [dns-serv-id]
          |  |     +--ro dns-serv-id      uint8
          |  |     +--ro dns-serv-addr    inet:ipv6-address
          |  +--ro domain-searchlist-option! {domain-searchlist-op}?
          |  |  +--ro domain-searchlist* [domain-searchlist-id]
          |  |     +--ro domain-searchlist-id        uint8
          |  |     +--ro domain-search-list-entry    string
          |  +--ro nis-config-option! {nis-config-op}?
          |  |  +--ro nis-server* [nis-serv-id]
          |  |     +--ro nis-serv-id      uint8
          |  |     +--ro nis-serv-addr    inet:ipv6-address
          |  +--ro nis-plus-config-option! {nis-plus-config-op}?
          |  |  +--ro nis-plus-server* [nis-plus-serv-id]
          |  |     +--ro nis-plus-serv-id      uint8
          |  |     +--ro nis-plus-serv-addr    inet:ipv6-address
          |  +--ro nis-domain-name-option! {nis-domain-name-op}?
          |  |  +--ro nis-domain-name?   string
          |  +--ro nis-plus-domain-name-option! {nis-plus-domain-name-op}?
          |  |  +--ro nis-plus-domain-name?   string
          |  +--ro sntp-server-option! {sntp-server-op}?
          |  |  +--ro sntp-server* [sntp-serv-id]
          |  |     +--ro sntp-serv-id      uint8
          |  |     +--ro sntp-serv-addr    inet:ipv6-address
          |  +--ro info-refresh-time-option! {info-refresh-time-op}?
          |  |  +--ro info-refresh-time    yang:timeticks
          |  +--ro client-fqdn-option! {client-fqdn-op}?
          |  |  +--ro server-initiate-update    boolean
          |  |  +--ro client-initiate-update    boolean
          |  |  +--ro modify-name-from-cli      boolean
          |  +--ro posix-timezone-option! {posix-timezone-op}?
          |  |  +--ro tz-posix    string
          |  +--ro tzdb-timezone-option! {tzdb-timezone-op}?
          |  |  +--ro tz-database    string
          |  +--ro ntp-server-option! {ntp-server-op}?
          |  |  +--ro ntp-server* [ntp-serv-id]
          |  |     +--ro ntp-serv-id                    uint8
          |  |     +--ro (ntp-time-source-suboption)?
          |  |        +--:(server-address)
          |  |        |  +--ro ntp-serv-addr-suboption*  inet:ipv6-address
          |  |        +--:(server-multicast-address)
          |  |        |  +--ro ntp-serv-mul-addr-suboption*
                                                        inet:ipv6-address
          |  |        +--:(server-fqdn)
          |  |           +--ro ntp-serv-fqdn-suboption*       string
          |  +--ro boot-file-url-option! {boot-file-url-op}?
          |  |  +--ro boot-file* [boot-file-id]
          |  |     +--ro boot-file-id          uint8
          |  |     +--ro suitable-arch-type*   uint16
          |  |     +--ro suitable-net-if*      uint32
          |  |     +--ro boot-file-url         string
          |  +--ro boot-file-param-option! {boot-file-param-op}?
          |  |  +--ro boot-file-paras* [para-id]
          |  |     +--ro para-id      uint8
          |  |     +--ro parameter    string
          |  +--ro aftr-name-option! {aftr-name-op}?
          |  |  +--ro tunnel-endpoint-name    string
          |  +--ro kbr-default-name-option! {kbr-default-name-op}?
          |  |  +--ro default-realm-name    string
          |  +--ro kbr-kdc-option! {kbr-kdc-op}?
          |  |  +--ro kdc-info* [kdc-id]
          |  |     +--ro kdc-id            uint8
          |  |     +--ro priority          uint16
          |  |     +--ro weight            uint16
          |  |     +--ro transport-type    uint8
          |  |     +--ro port-number       uint16
          |  |     +--ro kdc-ipv6-addr     inet:ipv6-address
          |  |     +--ro realm-name        string
          |  +--ro sol-max-rt-option! {sol-max-rt-op}?
          |  |  +--ro sol-max-rt-value    yang:timeticks
          |  +--ro inf-max-rt-option! {inf-max-rt-op}?
          |  |  +--ro inf-max-rt-value    yang:timeticks
          |  +--ro addr-selection-option! {addr-selection-op}?
          |  |  +--ro a-bit-set       boolean
          |  |  +--ro p-bit-set       boolean
          |  |  +--ro policy-table* [policy-id]
          |  |     +--ro policy-id     uint8
          |  |     +--ro label         uint8
          |  |     +--ro precedence    uint8
          |  |     +--ro prefix-len    uint8
          |  |     +--ro prefix        inet:ipv6-prefix
          |  +--ro pcp-server-option! {pcp-server-op}?
          |  |  +--ro pcp-server* [pcp-serv-id]
          |  |     +--ro pcp-serv-id      uint8
          |  |     +--ro pcp-serv-addr    inet:ipv6-address
          |  +--ro s46-rule-option! {s46-rule-op}?
          |  |  +--ro s46-rule* [rule-id]
          |  |     +--ro rule-id           uint8
          |  |     +--ro rule-type         enumeration
          |  |     +--ro prefix4-len       uint8
          |  |     +--ro ipv4-prefix       inet:ipv4-prefix
          |  |     +--ro prefix6-len       uint8
          |  |     +--ro ipv6-prefix       inet:ipv6-prefix
          |  |     +--ro port-parameter
          |  |        +--ro offset      uint8
          |  |        +--ro psid-len    uint8
          |  |        +--ro psid        uint16
          |  +--ro s46-br-option! {s46-br-op}?
          |  |  +--ro br* [br-id]
          |  |     +--ro br-id           uint8
          |  |     +--ro br-ipv6-addr    inet:ipv6-address
          |  +--ro s46-dmr-option! {s46-dmr-op}?
          |  |  +--ro dmr* [dmr-id]
          |  |     +--ro dmr-id             uint8
          |  |     +--ro dmr-prefix-len     uint8
          |  |     +--ro dmr-ipv6-prefix    inet:ipv6-prefix
          |  +--ro s46-v4-v6-binding-option! {s46-v4-v6-binding-op}?
          |     +--ro ce* [ce-id]
          |        +--ro ce-id               uint8
          |        +--ro ipv4-addr           inet:ipv4-address
          |        +--ro bind-prefix6-len    uint8
          |        +--ro bind-ipv6-prefix    inet:ipv6-prefix
          |        +--ro port-parameter
          |           +--ro offset      uint8
          |           +--ro psid-len    uint8
          |           +--ro psid        uint16
          +--ro packet-stats
             +--ro solicit-count        uint32
             +--ro request-count        uint32
             +--ro renew-count          uint32
             +--ro rebind-count         uint32
             +--ro decline-count        uint32
             +--ro release-count        uint32
             +--ro info-req-count       uint32
             +--ro advertise-count      uint32
             +--ro confirm-count        uint32
             +--ro reply-count          uint32
             +--ro reconfigure-count    uint32

  notifications:
    +---n notifications
       +--ro dhcpv6-client-event
          +--ro ia-lease-event
          |  +--ro event-type     enumeration
          |  +--ro duid
          |  |  +--ro type-code?                   uint16
          |  |  +--ro (duid-type)?
          |  |     +--:(duid-llt)
          |  |     |  +--ro duid-llt-hardware-type?      uint16
          |  |     |  +--ro duid-llt-time?               yang:timeticks
          |  |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
          |  |     +--:(duid-en)
          |  |     |  +--ro duid-en-enterprise-number?   uint32
          |  |     |  +--ro duid-en-identifier?          string
          |  |     +--:(duid-ll)
          |  |     |  +--ro duid-ll-hardware-type?       uint16
          |  |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
          |  |     +--:(duid-uuid)
          |  |     |  +--ro uuid?                        yang:uuid
          |  |     +--:(duid-invalid)     +--:(duid-unknown)
          |  |        +--ro data?                        binary
          |  +--ro iaid           uint32
          |  +--ro serv-name?     string
          |  +--ro description?   string
          +--ro invalid-ia-detected
          |  +--ro duid
          |  |  +--ro type-code?                   uint16
          |  |  +--ro (duid-type)?
          |  |     +--:(duid-llt)
          |  |     |  +--ro duid-llt-hardware-type?      uint16
          |  |     |  +--ro duid-llt-time?               yang:timeticks
          |  |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
          |  |     +--:(duid-en)
          |  |     |  +--ro duid-en-enterprise-number?   uint32
          |  |     |  +--ro duid-en-identifier?          string
          |  |     +--:(duid-ll)
          |  |     |  +--ro duid-ll-hardware-type?       uint16
          |  |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
          |  |     +--:(duid-uuid)
          |  |     |  +--ro uuid?                        yang:uuid
          |  |     +--:(duid-invalid)     +--:(duid-unknown)
          |  |        +--ro data?                        binary
          |  +--ro cli-duid       uint32
          |  +--ro iaid           uint32
          |  +--ro serv-name?     string
          |  +--ro description?   string
          +--ro retransmission-failed
          |  +--ro duid
          |  |  +--ro type-code?                   uint16
          |  |  +--ro (duid-type)?
          |  |     +--:(duid-llt)
          |  |     |  +--ro duid-llt-hardware-type?      uint16
          |  |     |  +--ro duid-llt-time?               yang:timeticks
          |  |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
          |  |     +--:(duid-en)
          |  |     |  +--ro duid-en-enterprise-number?   uint32
          |  |     |  +--ro duid-en-identifier?          string
          |  |     +--:(duid-ll)
          |  |     |  +--ro duid-ll-hardware-type?       uint16
          |  |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
          |  |     +--:(duid-uuid)
          |  |     |  +--ro uuid?                        yang:uuid
          |  |     +--:(duid-invalid)     +--:(duid-unknown)
          |  |        +--ro data?                        binary
          |  +--ro description    enumeration
          +--ro failed-status-turn-up
             +--ro duid
             |  +--ro type-code?                   uint16
             |  +--ro (duid-type)?
             |     +--:(duid-llt)
             |     |  +--ro duid-llt-hardware-type?      uint16
             |     |  +--ro duid-llt-time?               yang:timeticks
             |     |  +--ro duid-llt-link-layer-addr?    yang:mac-address
             |     +--:(duid-en)
             |     |  +--ro duid-en-enterprise-number?   uint32
             |     |  +--ro duid-en-identifier?          string
             |     +--:(duid-ll)
             |     |  +--ro duid-ll-hardware-type?       uint16
             |     |  +--ro duid-ll-link-layer-addr?     yang:mac-address
             |     +--:(duid-uuid)
             |     |  +--ro uuid?                        yang:uuid
             |     +--:(duid-invalid)     +--:(duid-unknown)
             |        +--ro data?                        binary
             +--ro status-code    enumeration

   Introduction of important nodes:

   o  client-config: This container includes the configuration data of
      the client.

   o  duid: Each server and client has only one DUID (DHCP Unique
      Identifier).  The DUID here will be carried in the Client ID
      option to identify a specific DHCPv6 client.  This leaf are same
      as the "duid" leaf in "dhcpv6-server" feature.

   o  client-if: A client may have several interfaces, it is more
      reasonable to configure and manage parameters on the interface-
      level.  The list defines a specific client interface and its data.
      Different interfaces are distinguished by the "ifName" key which
      is a configurable string value.

   o  duid: Each server and client has only one DUID (DHCP Unique
      Identifier).  The DUID here will be carried in the Client ID
      option to identify a specific DHCPv6 client.  This leaf are same
      as the "duid" leaf in "dhcpv6-server" feature.

   o  pd-function: Whether the client can act as a requesting router to
      request prefixes using prefix delegation ([RFC3633]).

   o  rapid-commit: '1' indicates a client can initiate a Solicit-Reply
      message exchange by adding a Rapid Commit option in Solicit
      message.  '0' means the client is not allowed to add a Rapid
      Commit option to request addresses in a two-message exchange
      pattern.

   o  mo-tab: The management tab label indicates the operation mode of  client-configured-options: Similar to the DHCPv6 client. 'm'=1 and 'o'=1 indicate server, the client will use
      DHCPv6 also
      need to obtain configure some options to fulfil some desired functions.
      This container include all the configuration data. 'm'=1 and 'o'=0 are a
      meaningless combination. 'm'=0 and 'o'=1 indicate the client will
      use stateless DHCPv6 to obtain configuration data apart from
      addresses/prefixes data. 'm'=0 and 'o'=0 represent the client will
      not use DHCPv6 but use SLAAC to achieve configuration.

   o  client-configured-options: Similar to the server, the client also
      need to configure some options to fulfil some desired functions.
      This container include all the potential options that need to be
      configured at potential options that need to be
      configured at the client side.  The relevant RFCs that define
      those options include: [RFC3315], [RFC4704], [RFC5970], [RFC6784],
      [RFC6939].

   o  option-request-option: This container provide a way to configure
      the list of options that the client will request in its ORO
      option.

   o  client-state: This container includes the state data of the
      client.

   o  if-other-paras: A client can obtain extra configuration data other
      than address and prefix information through DHCPv6 options.  This
      container describes such data the client was configured through
      DHCPv6.  The potential configuration data may include DNS server
      parameters, SIP server parameters and etc.

   o  packet-stats: A container records all the packet status
      information of a specific interface.

   Information about notifications:

   o  ia-lease-event: raised when the client was allocated a new IA from
      the server or it renew/rebind/release its current IA.

   o  invalid-ia-detected: raised when the identity association of the
      client can be proved to be invalid.  Possible condition includes
      duplicated address, illegal address, etc.

   o  retransmission-failed: raised when the retransmission mechanism
      defined in [RFC3315] is failed.

   o  failed-status-turn-up: raised when the client receives a message
      includes an unsuccessful Status Code option.

3.  DHCPv6 YANG Model

3.1.  DHCPv6 Server YANG Model

   This module imports typedefs from [RFC6991]. [RFC6991], [RFC7223].

<CODE BEGINS> file "ietf-dhcpv6-server@2017-12-22.yang" "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;
    revision-date "2013-07-15";
  }
  import ietf-yang-types {
    prefix yang;
    revision-date "2013-07-15";
  }
  import ietf-dhcpv6-options {
    prefix dhcpv6-options;
    revision-date "2017-12-22";
  }
  import ietf-dhcpv6-types {
    prefix dhcpv6-types;
  }
  import ietf-interfaces {
    prefix if;
  }

  organization "DHC WG";
  contact "yong@csnet1.cs.tsinghua.edu.cn
    "cuiyong@tsinghua.edu.cn
     lh.sunlinh@gmail.com
     ian.farrer@telekom.de
     sladjana.zechlin@telekom.de
     hezihao9512@gmail.com";

  description "This model defines a YANG data model that can be
      used to configure and manage a DHCPv6 server.";

  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";
  }

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

  /*
  * Grouping Data Nodes
  */

  grouping vendor-infor
  container server {
    presence "Enables the server";
    description "Vendor information."; "DHCPv6 server portion";

    /*
     * Configuration data
     */
    container vendor-info server-config {
      description "";
     leaf ent-num "This container contains the configuration data
            of a server.";
      container serv-attributes {
       type uint32;
       mandatory true;
        description "enterprise number";
         "This container contains basic attributes of a DHCPv6 server
         such as IPv6 address, server name  and so on. Some optional
         functions that can be provided  by the server is also included.";
        container duid {
          description "Sets the DUID of server";
          uses dhcpv6-types:duid;
        }
     leaf-list data
        leaf name {
          type string;
          description "specific vendor info";
     }
   } "server's name";
        }

  grouping duid {
      description "DHCP Unique Identifier";
      reference "RFC3315: Section 9 and RFC6355: Section 4";
        leaf type-code description {
          type uint16;
        default 65535; string;
          description "Type code "description of this DUID"; the server.";
        }
      choice duid-type
        leaf-list ipv6-address {
      default duid-invalid;
          type inet:ipv6-address;
          description "Selects the format for the DUID.";
        case duid-llt "server's IPv6 address.";
        }
        leaf-list interfaces-config {
          description "DUID Based on Link-layer Address Plus Time (Type 1
          // Note - DUID-LLT)";
          reference "RFC3315 Section 9.2";
          leaf duid-llt-hardware-type { this should probably be references to
          // entries in the ietf-interfaces model
          type uint16; if:interface-ref;
          description "Hardware type as assigned by IANA (RFC826).";
          } "A leaf duid-llt-time {
            type yang:timeticks;
            description "The time list to denote which one or more interfaces
            the server should listen on. The default value is to listen
            on all the time that the DUID interfaces. This node is generated
              represented in seconds since midnight (UTC), January 1, 2000,
              modulo 2^32.";
          }
          leaf duid-llt-link-layer-addr {
            type yang:mac-address;
            description "Link-layer also used to set a unicast
            address as described in RFC2464";
          }
        }
        case duid-en {
          description "DUID Assigned by Vendor Based on Enterprise Number (Type 2 - DUID-EN)";
          reference "RFC3315 Section 9.3";
          leaf duid-en-enterprise-number {
            type uint32;
            description "Vendor's registered Private Enterprise Number as
              maintained by IANA";
          }
          leaf duid-en-identifier {
            type string;
            description "Indentifier, unique for the server to listen with a specific interface.
            For example, if people want the device that is using it";
          }
        }
        case duid-ll {
          description "DUID Based server to listen on Link-layer Address (Type 3 - DUID-LL)";
          reference "RFC3315 Section 9.4";
          leaf duid-ll-hardware-type {
            type uint16;
            description "Hardware type as assigned by IANA (RFC826).";
          }
          leaf duid-ll-link-layer-addr {
              type yang:mac-address;
              description "Link-layer a unicast
            address as described in RFC2464";
        }
        }
        case duid-uuid {
          description "DUID Based on Universally Unique Identifier (Type 4 - DUID-UUID)";
          reference "RFC6335 Defination of the UUID-Based Unique Identifier";
          leaf uuid {
            type yang:uuid;
            description "A Universally Unique IDentifier in with a specific interface, he can use the string representation
                defined in RFC 4122.  The canonical representation uses
                lowercase characters"; format like
            'eth1/2001:db8::1'.";
        }
        uses dhcpv6-types:vendor-infor;
      }
        case duid-invalid {
          description "DUID based on free raw bytes";
          leaf data

      container option-sets {
            type binary;
            description "The bits to be used as the identifier";
          }
        }
      }
    }

  /*
   * Data Nodes
   */

  container server {
    presence "Enables the server";
        description "DHCPv6 server portion";
    /*
     * Configuration data
     */
    container server-config {
      description "configuration tree of server";
         container serv-attributes {
            description "This container contains basic attributes
              of a DHCPv6 server such as IPv6 address, server name
              and so on. Some optional functions that can be provided
              by 0the server is also included.";
            leaf name {
              type string;
              description "server's name";
            }
            container duid {
              description "Sets the DUID";
              uses duid;
            }
            leaf-list ipv6-address {
              type inet:ipv6-address;
              description "Server's IPv6 address.";
            }
            leaf description {
              type string;
              description "Description of the server.";
            }
            leaf pd-function {
              type boolean;
              mandatory true;
              description "Whether the server can act as a
                delegating router to perform prefix delegation
                ([RFC3633]).";
            }
            leaf stateless-service {
              type boolean;
              mandatory true;
              description "A boolean value specifies whether
                the server support client-server exchanges
                involving two messages defined in ([RFC3315]).";
            }
            leaf rapid-commit {
              type boolean;
              mandatory true;
              description "A boolean value specifies whether
                the server support client-server exchanges
                involving two messages defined in ([RFC3315]).";
            }
            leaf-list interfaces-config {
              // Note - this should probably be references to
              // entries in the ietf-interfaces model
              type string;
              description "A leaf list to denote which one or
                more interfaces the server should listen on. The
                default value is to listen on all the interfaces.
                This node is also used to set a unicast address
                for the server to listen with a specific interface.
                  For example, if people want the server to listen
                    on a unicast address with a specific interface, he
                    can use the format like 'eth1/2001:db8::1'.";
            }
            uses vendor-infor;
          }

          container option-sets {
            description "DHCPv6 employs various options employs various options to carry additional
          information and parameters in DHCP messages. This container defines
                  all the possible options that need to be configured at the server
                  side. ";
              list option-set {
                  key id;
                description "A server may allow different option sets to be
                    configured for different conditions (i.e. different networks,
                    clients and etc). This 'option-set' list enables various sets of
                    options being defined and configured in a single server. Different
                    sets are distinguished by the key called 'option-set-id'. All the
                    possible options discussed above are defined in the list and each
                    option is corresponding to a container. Since all the options in
                    the list are optional, each container in this list has a 'presence'
                    statement to indicate whether this option (container) will be
                    included in the current option set or not. In addition, each container
                    also has a 'if-feature' statement to indicate whether the server
                    supports this option (container).";
                  leaf id {
                    type uint32;
                    description "option set id";
                  }
                uses dhcpv6-options:server-option-definitions;
                uses dhcpv6-options:custom-option-definitions;
              }
            }

            container network-ranges {
              description "This model supports a hierarchy
                to achieve dynamic configuration. That is to
                say we could configure the server at different
                levels through this model. The top level is a
                global level which is defined as the container
                'network-ranges'. The following levels are
                defined as sub-containers under it. The
                'network-ranges' contains the parameters
                (e.g. option-sets) that would be allocated to
                all the clients served by this server.";
              list network-range {
                key network-range-id;
                description "Under the 'network-ranges'
                  container, a 'network-range' list is
                  defined to configure the server at a
                  network level which is also considered
                  as the second level. Different network
                  are identified by the key 'network-range-id'.
                  This is because a server may have different
                  configuration parameters (e.g. option sets)
                  for different networks.";
                leaf network-range-id {
                  type uint32;
                  mandatory true;
                  description "equivalent to subnet id";
                }
                leaf network-description {
                  type string;
                  mandatory true;
                  description "description of the subnet";
                }
                leaf network-prefix {
                  type inet:ipv6-prefix;
                  mandatory true;
                  description "subnet prefix";
                }
                leaf inherit-option-set {
                  type boolean;
                  mandatory true;
                  description "indicate whether to inherit
                    the configuration from higher level";
                }
                leaf option-set-id {
                  type leafref {
                    path "/server/server-config/option-sets/option-set/id";

                  }
                  description "The ID field of relevant option-set to be
                    provisioned to clients of this network-range.";
                }

                container reserved-addresses {
                  description "reserved addresses";
                  list static-binding {
                    key cli-id;
                    description "static binding of
                      reserved addresses";
                    leaf cli-id {
                      type uint32;
                      mandatory true;
                      description "client id";
                    }
                    container duid {
                      description "Sets the DUID";
                      uses duid;
                    }
                    leaf-list reserv-addr {
                      type inet:ipv6-address;
                      description "reserved addr";
                    }
                  }
                  leaf-list other-reserv-addr {
                    type inet:ipv6-address;
                    description "other reserved
                      addr";
                  }
                }

                container reserved-prefixes {
                  description "reserved prefixes";
                  list static-binding {
                    key cli-id;
                    description "static binding";
                    leaf cli-id {
                      type uint32;
                      mandatory true;
                      description "client id";
                    }
                    container duid {
                      description "Sets the DUID";
                      uses duid;
                    }
                    leaf reserv-prefix-len {
                      type uint8;
                      mandatory true;
                      description "reserved
                        prefix length";
                    }
                    leaf reserv-prefix {
                      type inet:ipv6-prefix;
                      mandatory true;
                      description
                        "reserved prefix";
                    }
                  }
                  leaf exclude-prefix-len {
                    type uint8;
                    mandatory true;
                    description "exclude prefix
                      length";
                  }
                  leaf exclude-prefix {
                    type inet:ipv6-prefix;
                    mandatory true;
                    description "exclude prefix";
                  }
                  list other-reserv-prefix {
                    key reserv-id;
                    description
                      "other reserved prefix";
                    leaf reserv-id {
                      type uint32;
                      mandatory true;
                      description
                        "reserved prefix id";
                    }
                    leaf prefix-len {
                      type uint8;
                      mandatory true;
                      description "prefix length";
                    }
                    leaf prefix {
                      type inet:ipv6-prefix;
                      mandatory true;
                      description
                        "reserved prefix";
                    }
                  }
                }

                container address-pools {
                  description "A container that describes
                    the DHCPv6 server's address pools.";
                  list address-pool {
                    key pool-id;
                    description "A DHCPv6 server can
                      be configured with several address
                      pools. This list defines such
                      address pools which are distinguished
                      by the key called 'pool-name'.";
                    leaf pool-id {
                      type uint32;
                      mandatory true;
                      description "pool id";
                    }
                    leaf pool-prefix {
                      type inet:ipv6-prefix;
                      mandatory true;
                      description "pool prefix";
                    }
                    leaf start-address {
                      type inet:ipv6-address-no-zone;
                      mandatory true;
                      description "start address";
                    }
                    leaf end-address {
                      type inet:ipv6-address-no-zone;
                      mandatory true;
                      description "end address";
                    }
                    leaf renew-time {
                      type yang:timeticks;
                      mandatory true;
                      description "renew time";
                    }
                    leaf rebind-time {
                      type yang:timeticks;
                      mandatory true;
                      description "rebind time";
                    }
                    leaf preferred-lifetime {
                      type yang:timeticks;
                      mandatory true;
                      description "preferred lifetime
                        for IA";
                    }
                    leaf valid-lifetime {
                      type yang:timeticks;
                      mandatory true;
                      description "valid liftime for IA";
                    }
                    leaf max-address-utilization-ratio {
                      type threshold;
                      mandatory true;
                      description "address pool utilization ratio threshold";
                    }
                    leaf inherit-option-set {
                      type boolean;
                      mandatory true;
                      description "indicate whether to
                        inherit the configuration from
                        higher level";
                    }
                    leaf option-set-id {
                      type leafref {
                        path "/server/server-config/option-sets/option-set/id";
                      }
                      mandatory true;
                      description "The ID field of relevant option-set to be
                        provisioned to clients of this address-pool.";
                    }
                }
              }

                container prefix-pools {
                    description "If a server supports prefix
                      delegation function, this container will
                      be used to define the delegating router's
                      refix pools.";
                    list prefix-pool {
                      key pool-id;
                      description "Similar to server's
                        address pools, a delegating router
                        can also be configured with multiple
                        prefix pools specified by a list
                        called 'prefix-pool'.";
                      leaf pool-id {
                        type uint32;
                        mandatory true;
                        description "pool id";
                      }
                      leaf prefix {
                        type inet:ipv6-prefix;
                        mandatory true;
                        description "ipv6 prefix";
                      }
                      leaf prefix-length {
                        type uint8;
                        mandatory true;
                        description "prefix length";
                      }
                      leaf renew-time {
                        type yang:timeticks;
                        mandatory true;
                        description "renew time";
                      }
                      leaf rebind-time {
                        type yang:timeticks;
                        mandatory true;
                        description "rebind time";
                      }
                      leaf preferred-lifetime {
                        type yang:timeticks;
                        mandatory true;
                        description "preferred lifetime for
                          IA";
                      }
                      leaf valid-lifetime {
                        type yang:timeticks;
                        mandatory true;
                        description "valid lifetime for IA";
                      }
                      leaf max-prefix-utilization-ratio {
                        type threshold;
                        mandatory true;
                        description "prefix pool utilization ratio threshold";
                      }
                      leaf inherit-option-set {
                        type boolean;
                        mandatory true;
                        description "whether to inherit
                          configuration from higher level";
                      }
                      leaf option-set-id {
                        type leafref {
                          path "/server/server-config/option-sets/option-set/id";
                        }
                        description "The ID field of relevant option-set to be
                          provisioned to clients of this prefix-pool.";
                      }
                    }
                  }
                  container hosts {
                    description "hosts level";
                    list host {
                      key cli-id;
                      description "specific host";
                      leaf cli-id {
                        type uint32;
                        mandatory true;
                        description "client id";
                      }
                      container duid {
                        description "Sets the DUID";
                        uses duid;
                      }
                      leaf inherit-option-set {
                        type boolean;
                        mandatory true;
                        description "whether to inherit
                          configuration
                          from higher level";
                      }
                      leaf option-set-id {
                        type leafref {
                          path "/server/server-config/option-sets/option-set/id";
                        }
                        description "The ID field of relevant option-set to be
                          provisioned to clients of this prefix-pool.";
                      }
                      leaf nis-domain-name {
                        type string;
                        description "nis domain name";
                      }
                      leaf nis-plus-domain-name {
                        type string;
                        description "nisp domain name";
                      }
                    }
                  }
              }

            }
            container relay-opaque-paras {
              description "This container contains some
                opaque values parameters in Relay Agent DHCP messages. This container defines
          all the possible options that need to be configured on at the server side
                only for value match. Such Relay Agent
                options include Interface-Id option,
                Remote-Id option and Subscriber-Id option.";
          side. ";
        list relays option-set {
            key relay-name;
                description "relay agents";
                leaf relay-name {
                  type string;
                  mandatory true; option-set-id;
            description "relay agent name";
                } "A server may allow different option sets to be
              configured for different conditions (i.e. different networks,
              clients and etc). This 'option-set' list interface-info { enables various sets of
              options being defined and configured in a single server. Different
              sets are distinguished by the key if-name;
                  description "interface info";
                  leaf if-name {
                    type string;
                    mandatory true;
                    description "interface name";
                  }
                  leaf interface-id {
                    type string;
                    mandatory true;
                    description "interface id";
                  }
                } called 'option-set-id'. All the
              possible options discussed above are defined in the list subscribers {
                  key subscriber;
                  description "subscribers";
                  leaf subscriber {
                    type uint32;
                    mandatory true;
                    description "subscriber";
                  }
                  leaf subscriber-id {
                    type string;
                    mandatory true;
                    description "subscriber id";
                  }
                } and each
              option is corresponding to a container. Since all the options in
              the list remote-host {
                  key ent-num;
                  description "remote host";
                  leaf ent-num {
                    type uint32;
                    mandatory true;
                    description "enterprise number";
                  }
                  leaf remote-id {
                    type string;
                    mandatory true;
                    description "remote id";
                  }
                }
              }
            } are optional, each container rsoo-enabled-options {
              description "rsoo enabled options"; in this list rsoo-enabled-option{
                key option-code;
                description "rsoo enabled option"; has a 'presence'
              statement to indicate whether this option (container) will be
              included in the current option set or not. In addition, each container
              also has a 'if-feature' statement to indicate whether the server
              supports this option (container).";
            leaf option-code option-set-id {
              type uint16;
                  mandatory true; uint32;
              description "option code";
                }
                leaf description {
                  type string;
                  mandatory true;
                  description "description of the option";
                } set id";
            }
          uses dhcpv6-options:server-option-definitions;
          uses dhcpv6-options:custom-option-definitions;
        }
      }

    /*
     * State data
     */
    container server-state{
      config "false";
      description "states of server";

      container network-ranges{ network-ranges {
        description "This model supports a hierarchy
          to achieve dynamic configuration. That is to say we could configure the
          server at different levels through this model. The top level is a global
          level which is defined as the container 'network-ranges'. The following
          levels are defined as sub-containers under it. The 'network-ranges'
          contains the parameters (e.g. option-sets) that would be allocated to
          all the clients served by this server.";
        list network-range{
          key network-range-id;

        leaf option-set-id {
          type leafref {
            path "/server/server-config/option-sets/option-set/option-set-id";
          }
          description
            "The ID field of relevant global option-set to be provisioned to clients of this network-range.";
            clients.";
        }
        list network-range {
          key network-range-id;
          description
          "Under the 'network-ranges' container, a 'network-range' list
           is defined to configure the server at a network level which is also
           considered as the second level. Different network are identified by the
           key 'network-range-id'. This is because a server may have different
           configuration parameters (e.g. option sets) for different networks.";
          leaf network-range-id {
            type uint32;
            mandatory true;
            description "equivalent to subnet id";
          }
          leaf network-description {
            type string;
            mandatory true;
            description "description of the subnet";
          }
          leaf network-prefix {
            type inet:ipv6-prefix;
            mandatory true;
            description "subnet prefix";
          }
          leaf option-set-id {
            type leafref {
              path "/server/server-config/option-sets/option-set/option-set-id";
            }
            description "The ID field of relevant option-set to be provisioned to
            clients of this network-range.";
          }

          container address-pools{ address-pools {
            description
            "A container that describes the DHCPv6 server's
             address pools"; pools.";
            list address-pool{ address-pool {
              key pool-id;
              description "A DHCPv6 server can be configured with
              several address pools. This list defines such address pools
              which are distinguished by the key called 'pool-id'.";
              leaf pool-id {
                type uint32;
                mandatory true;
                description "pool id";
              }
                description "...";
              leaf total-ipv6-count pool-prefix {
                type uint64; inet:ipv6-prefix;
                mandatory true;
                description "how many ipv6 addresses
                    are in the pool"; "pool prefix";
              }
              leaf used-ipv6-count start-address {
                type uint64; inet:ipv6-address-no-zone;
                mandatory true;
                description "how many are allocated"; "start address";
              }
              leaf address-utilization-ratio end-address {
                type uint16; inet:ipv6-address-no-zone;
                mandatory true;
                description "current address pool utilization ratio";
                } "end address";
              }
              list binding-info
              leaf valid-lifetime {
                key cli-id;
                type yang:timeticks;
                mandatory true;
                description "A list that records a binding
                  information "valid liftime for each DHCPv6 client
                  that has already been allocated
                  IPv6 addresses."; IA";
              }
              leaf cli-id renew-time {
                type uint32; yang:timeticks;
                mandatory true;
                description "client id"; "renew time";
              }
                container duid
              leaf rebind-time {
                type yang:timeticks;
                mandatory true;
                description "Read the DUID";
                  uses duid; "rebind time";
              }
                list cli-ia{
                  key iaid;
                  description "client IA";
              leaf ia-type preferred-lifetime {
                type string; yang:timeticks;
                mandatory true;
                description "IA type"; "preferred lifetime for IA";
              }
              leaf iaid rapid-commit {
                type uint32; boolean;
                mandatory true;
                description "IAID"; "A boolean value specifies whether the pool
                supports client-server exchanges involving two messages.";
              }
                  leaf-list cli-addr
              leaf client-class {
                type inet:ipv6-address; string;
                description "client addr";
                "If this leaf is specified, this pool will only serve
                the clients belonging to this class.";
              }
              leaf pool-id max-address-count {
                type uint32; threshold;
                mandatory true;
                description "pool id"; "maximum count of addresses that can
                  be allocated in this pool. This value may be
                  less than count of total addresses.";
              }
              leaf option-set-id {
                type leafref {
                  path "/server/server-config/option-sets/option-set/option-set-id";
                }
                mandatory true;
                description "The ID field of relevant option-set to be
                    provisioned to clients of this address-pool.";
              }
            }
          }
          container prefix-pools{ pd-pools {
            description "If a server supports prefix delegation function, this
              container will be used to define  the delegating router's prefix
              pools.";
            list prefix-pool pd-pool {
              key pool-id;
              description "Similar to server's address pools, a delegating
                router can also be configured with multiple prefix pools
                specified by a list called 'prefix-pool'.";
              leaf pool-id {
                type uint32;
                mandatory true;
                description "pool id";
              }
                leaf prefix-utilization-ratio {
                  type uint16;
                  mandatory true;
                  description "current prefix pool utilization ratio";
              leaf prefix {
                  type inet:ipv6-prefix;
                  mandatory true;
                  description "ipv6 prefix";
              }
              leaf prefix-length {
                  type uint8;
                  mandatory true;
                  description "prefix length";
              }
              leaf valid-lifetime {
                type yang:timeticks;
                mandatory true;
                description "valid lifetime for IA";
              }
              leaf renew-time {
                type yang:timeticks;
                mandatory true;
                description "renew time";
              }
              leaf rebind-time {
                type yang:timeticks;
                mandatory true;
                description "rebind time";
              }
              leaf preferred-lifetime {
                type yang:timeticks;
                mandatory true;
                description "preferred lifetime for IA";
              }
              leaf rapid-commit {
                type boolean;
                mandatory true;
                description "A boolean value specifies whether the server
                support client-server exchanges involving two messages defined.";
              }
              leaf client-class {
                type string;
                description "client class";
              }
              leaf max-pd-space-utlization {
                type threshold;
                mandatory true;
                description "Maximum utilization of pd space in this pool";
              }
              leaf option-set-id {
                type leafref {
                    path "/server/server-config/option-sets/option-set/option-set-id";
                  }
                  mandatory true;
                  description "The ID field of relevant option-set to be
                    provisioned to clients of this prefix-pool.";
              }
            }
          }

          container host-reservations {
            description
              "This container allows the server to make reservations at host level.";
            list binding-info host-reservation {
              key cli-id;
              description "A "This list records a binding information allows the server to reserve addresses,
              prefixes, hostname and options for each DHCPv6 client that has already been
                alloated IPv6 addresses."; different clients.";
              leaf cli-id {
                type uint32;
                mandatory true;
                description "client id";
              }
                container duid

              choice client-identifier {
                description "Reads "When making reservations, the DUID"; server needs to choose a
                identifier to identify the server. Currently 'DUID' and 'hardware
                address' are supported.";
                case duid {
                  description "DUID";
                  uses duid; dhcpv6-types:duid;
                }
                list cli-iapd
                case hw-address {
                  key iaid;
                  description "client IAPD"; "hardware address";
                  leaf iaid hardware-address {
                  type uint32;
                    mandatory true; yang:mac-address;
                  description "IAID"; "MAC address of client";
                  }
                }
              }

              leaf-list cli-prefix reserv-addr {
                type inet:ipv6-prefix; inet:ipv6-address;
                description "client ipv6 prefix"; "reserved addr";
              }
                  leaf-list cli-prefix-len

              list prefix-reservation {
                    type uint8;
                key reserv-prefix-id;
                description "client "reserved prefix length";
                  } reservation";
                leaf pool-id reserv-prefix-id {
                  type uint32;
                  mandatory true;
                  description "pool "reserved prefix id";
                }

                }
              }
            }

            list address-prefix-assign-param
                leaf reserv-prefix {
              // Zihao - This probably needs further updated.
              // But is it a way to represent the address/prefix assignment
              // logic?
              key cli-id;
                  type inet:ipv6-prefix;
                  mandatory true;
                  description "This list includes some parameters/identifiers
                that the server obtains from DHCPv6 options in this network-range.
                These identifiers may be helpful for the server to assign
                addresses/prefixes.";
              reference "Section 3.12 of RFC7824"; "reserved prefix";
                }
                leaf cli-id reserv-prefix-len {
                  type uint32; uint8;
                  mandatory true;
                  description "client id"; "reserved prefix length";
                }
              }

              leaf source-ipv6-addr hostname {
                type inet:ipv6-address; string;
                description "reserved hostname";
              }

              leaf option-set-id {
                type leafref {
                  path "/server/server-config/option-sets/option-set/option-set-id";
                }
                description "The adrress ID field of the link relevant option-set to which be provisioned
                  in the client
                  is attached."; host reservation.";
              }
            }
          }

        }
      }

      container duid relay-opaque-paras {
        description "The DUID supplied by "This container contains some opaque values in Relay Agent
          options that need to be configured on the client.";
                  uses duid;
              }
              leaf-list iaid {
                type uint32; server side only for value
          match. Such Relay Agent options include Interface-Id option,
          Remote-Id option and Subscriber-Id option.";
        list relays {
          key relay-name;
          description "IAID";
              }
              leaf-list preferred-addr "relay agents";
          leaf relay-name {
            type inet:ipv6-address; string;
            mandatory true;
            description "The IPv6 address preferred by the client."; "relay agent name";
          }
              leaf-list preferred-prefix-len
          list interface-info {
                type uint8;
            key if-name;
            description "The prefix length preferred by the client.";
              } "interface info";
            leaf client-fqdn if-name {
              type string;
              mandatory true;
              description "Fully Qualified Domain Name supplied by the client."; "interface name";
            }
            leaf client-link-layer-addr interface-id {
              type uint16; string;
              mandatory true;
              description "Link-layer address supplied by the client."; "interface id";
            }
          }
          list subscribers {
            key subscriber;
            description "subscribers";
            leaf client-enterprise-number subscriber {
              type uint32;
              mandatory true;
              description "Enterprise number supplied by the client."; "subscriber";
            }
              leaf-list client-sys-archi-type
            leaf subscriber-id {
              type uint16; string;
              mandatory true;
              description "Supported system architecture type supplied by
                  the client";
              }
            } "subscriber id";
            }
          }

        container packet-stats
          list remote-host {
            key ent-num;
            description "A container presents
              the packet statistics related to
              the DHCPv6 server."; "remote host";
            leaf solicit-count ent-num {
              type uint32;
              mandatory true;
              description "solicit counter"; "enterprise number";
            }
            leaf request-count remote-id {
              type uint32; string;
              mandatory true;
              description "request counter"; "remote id";
            }
          }
        }
      }

      container rsoo-enabled-options {
        description "rsoo enabled options";
        list rsoo-enabled-option {
          key option-code;
          description "rsoo enabled option";
          leaf renew-count option-code {
            type uint32; uint16;
            mandatory true;
            description "renew counter"; "option code";
          }
          leaf rebind-count description {
            type uint32; string;
            mandatory true;
            description "rebind counter"; "description of the option";
          }
            leaf decline-count
        }
      }

    }

    /*
     * State data
     */
    container server-state {
      config "false";
      description "states of server";
      container network-ranges {
        description "This model supports a hierarchy to achieve dynamic configuration.
          That is to say we could configure the server  at different levels through
          this model. The top level is a global level which is defined as the container
          'network-ranges'. The following levels are defined as sub-containers under it.
          The 'network-ranges' contains the parameters (e.g. option-sets) that  would be
          allocated to all the clients served by this server.";
        list network-range {
              type uint32;
              mandatory true;
          key network-range-id;
          description "decline count";
            } "The ID field of relevant option-set to be provisioned
            to clients of this network-range.";
          leaf release-count network-range-id {
            type uint32;
            mandatory true;
            description "release counter"; "equivalent to subnet id";
          }
            leaf info-req-count
          container address-pools {
              type uint32;
              mandatory true;
            description "information request
                counter";
            }
            leaf advertise-count "A container that describes the DHCPv6 server's address pools";
              list address-pool {
              type uint32;
              mandatory true;
                key pool-id;
                description "advertise counter";
            } "A DHCPv6 server can be configured with
                several address pools. This list defines such address pools
                which are distinguished by the key called 'pool-id'.";
                leaf confirm-count pool-id {
                  type uint32;
                  mandatory true;
                  description "confirm counter"; "pool id";
                }
                leaf reply-count total-address-count {
                  type uint32; uint64;
                  mandatory true;
                  description "reply counter"; "count of total addresses in the pool";
                }
                leaf reconfigure-count allocated-address-conut {
                  type uint32; uint64;
                  mandatory true;
                  description "reconfigure counter"; "count of allocated addresses in the pool";
                }
            leaf relay-forward-count
              }
              list binding-info {
              type uint32;
              mandatory true;
                key cli-id;
                description "relay forward counter";
            } "A list that records a binding information for each DHCPv6
                  client that has already been allocated IPv6 addresses.";
                leaf relay-reply-count cli-id {
                  type uint32;
                  mandatory true;
                  description "relay reply counter";
            }
          }
        } "client id";
                }

  /*
   * Notifications
   */

  notification notifications {
    description "dhcpv6 server notification module";
    container dhcpv6-server-event {
      description "dhcpv6 server event";
                container pool-running-out duid {
                  description "raised when the address/prefix pool is going to
          run out.  A threshold for utilization ratio of the pool has
          been defined in the server feature so that it will notify the
          administrator when the utilization ratio reaches "Read the
          threshold, and such threshold is a settable parameter";
      leaf max-address-utilization-ratio {
        type uint16;
        mandatory true;
        description "address pool utilization ratio threshold"; DUID";
                  uses dhcpv6-types:duid;
                }
      leaf address-utilization-ratio
                list cli-ia {
        type uint16;
        mandatory true;
                  key iaid;
                  description "current address pool utilization ratio";
      } "client IA";
                  leaf max-prefix-utilization-ratio ia-type {
                    type uint16; string;
                    mandatory true;
                    description "prefix pool utilization ratio threshold"; "IA type";
                  }
                  leaf prefix-utilization-ratio iaid {
                    type uint16; uint32;
                    mandatory true;
                    description "current prefix pool utilization ratio";
      }
      container duid {
        description "Sets the DUID";
        uses duid; "IAID";
                  }
      leaf serv-name
                  leaf-list cli-addr {
                    type string; inet:ipv6-address;
                    description "server name"; "client addr";
                  }
                  leaf pool-name pool-id {
                    type string; uint32;
                    mandatory true;
                    description "pool name"; id";
                  }
                }
              }
            }
            container invalid-client-detected pd-pools {
              description "raised when the server has found "If a client which
        can server supports prefix delegation function,
                this container will be regarded as a potential attacker. Some used to define the delegating
                router's prefix pools.";
              list prefix-pool {
                key pool-id;
                description
        could "Similar to server's address pools, a delegating
                  router can also be included.";
      container duid configured with multiple prefix pools
                  specified by a list called 'prefix-pool'.";
                leaf pool-id {
                  type uint32;
                  mandatory true;
                  description "Sets the DUID";
        uses duid; "pool id";
                }
                leaf description pd-space-utilization {
                  type string; threshold;
                  mandatory true;
                  description "description of the event";
      }
    }
  }
  } "current PD space utilization";
                }

<CODE ENDS>

3.2.  DHCPv6 Relay YANG Model

   This module imports typedefs from [RFC6991].

<CODE BEGINS> file "ietf-dhcpv6-relay@2017-12-22.yang"
module ietf-dhcpv6-relay {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-relay";
  prefix "dhcpv6-client";

  import ietf-inet-types {
    prefix inet;
    revision-date "2013-07-15";
              }

  import ietf-dhcpv6-options
              list binding-info {
    prefix dhcpv6-options;
    revision-date "2017-12-22";
  }

  organization "DHC WG";
  contact "yong@csnet1.cs.tsinghua.edu.cn
    lh.sunlinh@gmail.com
    ian.farrer@telekom.de
    sladjana.zechlin@telekom.de
    hezihao9512@gmail.com";
                key cli-id;
                description "This model defines a YANG data model that can be
    used to configure and manage "A list records a binding information for each DHCPv6 relay.";

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

  revision 2017-11-24
                  client that has already been alloated IPv6 prefixes.";
                leaf cli-id {
                  type uint32;
                  mandatory true;
                  description "First version of the separated relay specific
      YANG model.";

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

  /*
   * Grouping
   */

  grouping vendor-infor "client id";
                }
                container duid {
                  description "Vendor information.";
   container vendor-info "Reads the DUID";
                  uses dhcpv6-types:duid;

                }
                list cli-iapd {
                  key iaid;
                  description ""; "client IAPD";
                  leaf ent-num iaid {
                    type uint32;
                    mandatory true;
                    description "enterprise number"; "IAID";
                  }
                  leaf-list data cli-prefix {
                    type string; inet:ipv6-prefix;
                    description "specific vendor info";
     } "client ipv6 prefix";
                  }
                  leaf-list cli-prefix-len {
                    type uint8;
                    description "client prefix length";
                  }
  /*
   * Data Nodes
   */

container relay
                  leaf pool-id {
    presence "Enables the relay";
                    type uint32;
                    mandatory true;
                    description "dhcpv6 relay portion"; "pool id";
                  }
                }
              }
            }

          container relay-config{ host-reservations {
            description "configuration tree of relay"; "This container relay-attributes provides host reservations in the host level.";
            list binding-info {
              key cli-id;
              description
                "A list records a binding information for each DHCPv6
                client that has already been alloated IPv6 addresses or prefixes
                by host reservations.";
              leaf cli-id {
                type uint32;
                mandatory true;
                description "client id";
              }
              container describes
              some basic attributes of duid {
                description "Reads the relay
              agent including some relay agent
              specific options data that need to
              be configured previously. Such options
              include Remote-Id option and
              Subscriber-Id option."; DUID";
                uses dhcpv6-types:duid;
              }
              list cli-ia {
                key iaid;
                description "client IA";
                leaf name ia-type {
                  type string;
                  mandatory true;
                  description "relay agent name"; "IA type, IA_NA or IA_TA";
                }
                leaf description iaid {
                  type string; uint32;
                  mandatory true;
                  description "description of the relay agent"; "IAID";
                }
                leaf-list dest-addrs cli-addr {
                  type inet:ipv6-address;
                  description "Each DHCPv6 relay agent may
                be configured with a list of destination
                addresses. This node defines such a "client addr";
                }
              }

              list
                of IPv6 addresses that may include
                unicast addresses, multicast addresses
                or other addresses."; cli-iapd {
                key iaid;
                description "client IAPD";
                leaf iaid {
                  type uint32;
                  mandatory true;
                  description "IAID";
                }
                leaf-list cli-prefix {
                  type inet:ipv6-prefix;
                  description "client ipv6 prefix";
                }
                leaf-list cli-prefix-len {
                  type uint8;
                  description "client prefix length";
                }
              }
            }
          }
            list subscribers

          }
        }

        container packet-stats {
              key subscriber;
          description "subscribers"; "A container presents the packet statistics related to
            the DHCPv6 server.";
          leaf subscriber solicit-count {
            type uint8; uint32;
            mandatory true;
            description "subscriber"; "solicit counter";
          }
          leaf subscriber-id request-count {
            type string; uint32;
            mandatory true;
            description "subscriber id";
              } "request counter";
          }
            list remote-host {
              key ent-num;
              description "remote host";
          leaf ent-num renew-count {
            type uint32;
            mandatory true;
            description "enterprise number"; "renew counter";
          }
          leaf remote-id rebind-count {
            type string; uint32;
            mandatory true;
            description "remote id";
              }
            }
            uses vendor-infor; "rebind counter";
          }

          container rsoo-option-sets {
          description "DHCPv6 relay agent could provide
                some information that would be useful to DHCPv6 client.
            Since relay agent cannot provide options directly to
            the client, RSOO-enabled options are defined to
            propose options for the server to send to the client.
            This container models such RSOO-enabled options.";
          reference "RFC6422";
            list option-set {
              key id;
              description "This list under the 'rsoo-option-sets' container
              is similar to the that defined in server module. It allows
              the relay to implement several sets of RSOO-enabled options
              for different interfaces. The list only include the EAP
              Re-authentication Protocol (ERP) Local Domain Name DHCPv6 Option
              defined in RFC6440, since it is the only one
              RSOO-enabled options accepted by IANA so far.";
          leaf id decline-count {
            type uint32;
            mandatory true;
            description "option sed id";
                }
              uses dhcpv6-options:relay-supplied-option-definitions;
            } "decline count";
          }

          list relay-if
          leaf release-count {
            // if - This should reference an entry in ietf-interfaces
            key if-name;
            description "A relay agent may have several
              interfaces, we should provide a way to configure
              and manage parameters on the interface-level. A
              list that describes specific interfaces and
              their corresponding parameters is employed to
              fulfil the configfuration. Here we use a string
              called 'if-name; as the key of list.";
            type uint32;
            mandatory true;
            description "release counter";
          }
          leaf if-name info-req-count {
            type string; uint32;
            mandatory true;
            description "interface name"; "information request counter";
          }
          leaf enable advertise-count {
            type boolean; uint32;
            mandatory true;
            description
                "whether this interface is enabled"; "advertise counter";
          }
          leaf ipv6-address confirm-count {
            type inet:ipv6-address; uint32;
            mandatory true;
            description
                "ipv6 address for this interface"; "confirm counter";
          }
          leaf interface-id reply-count {
            type string; uint32;
            mandatory true;
            description "interface id"; "reply counter";
          }
          leaf rsoo-option-set-id reconfigure-count {
            type leafref {
                path "/relay/relay-config/rsoo-option-sets/option-set/id";
              } uint32;
            mandatory true;
            description "Configured Relay Supplied Option set"; "reconfigure counter";
          }
            list next-entity
          leaf relay-forward-count {
              key dest-addr;
            type uint32;
            mandatory true;
            description "This node defines
                a list that is used to describe
                the next hop entity of this
                relay distinguished by their
                addresses."; "relay forward counter";
          }
          leaf dest-addr relay-reply-count {
            type inet:ipv6-address; uint32;
            mandatory true;
            description "destination addr"; "relay reply counter";
          }
        }
      }
    }

  /*
  * Notifications
  */

  notification notifications {
    description "dhcpv6 server notification module";
    container dhcpv6-server-event {
      description "dhcpv6 server event";
      container address-pool-running-out {
        description "raised when the address pool is going to
          run out.  A threshold for utilization ratio of the pool has
          been defined in the server feature so that it will notify the
          administrator when the utilization ratio reaches the
          threshold, and such threshold is a settable parameter";
        leaf available total-address-count {
          type boolean; uint64;
          mandatory true;
          description "whether "count of total addresses in the next entity
                  is available or not"; pool";
        }
        leaf multicast max-address-count {
          type boolean; uint64;
          mandatory true;
          description "whether "maximum count of addresses that can be allocated
            in the address is
                  multicast or not"; pool. This value may be less than count of total
            addresses";
        }
        leaf server allocated-address-conut {
          type boolean; uint64;
          mandatory true;
          description "whether "count of allocated addresses in the next entity
                  is a server";
              }
            }
          } pool";
        }
        container relay-state{
    config "false"; duid {
          description "state tree of relay";
    list relay-if{
      key if-name; "server duid";
          uses dhcpv6-types:duid;
        }
        leaf serv-name {
          type string;
          description "..."; "server name";
        }
        leaf if-name{ pool-name {
          type string;
          mandatory true;
          description "interface "pool name";
        }
            list pd-route
      }
      container pd-pool-running-out {
                // if - need to look at if/how we model these. If they are
                //
        description "raised when the address/prefix pool is going to be modelled, then they should be ro state
                // entries (we're not trying to configure routes here)
                key pd-route-id;
                description "pd route";
          run out.  A threshold for utilization ratio of the pool has
          been defined in the server feature so that it will notify the
          administrator when the utilization ratio reaches the
          threshold, and such threshold is a settable parameter";
        leaf pd-route-id max-pd-space-utilization {
          type uint8; threshold;
          mandatory true;
          description "pd route id"; "maximum pd space utilization";
        }
        leaf requesting-router-id pd-space-utilization {
          type uint32; threshold;
          mandatory true;
          description "requesting router id"; "current pd space utilization";
        }
                leaf delegating-router-id
        container duid {
                  type uint32;
                  mandatory true;
          description "delegating router id"; "Sets the DUID";
          uses dhcpv6-types:duid;
        }
        leaf next-router serv-name {
          type inet:ipv6-address;
                  mandatory true; string;
          description "next router"; "server name";
        }
        leaf last-router pool-name {
          type inet:ipv6-address; string;
          mandatory true;
          description "previous router"; "pool name";
        }
      }
      list next-entity{
        key dest-addr;
      container invalid-client-detected {
        description "This node defines "raised when the server has found a list that is used to
          describe client which
          can be regarded as a potential attacker. Some description
          could also be included.";
        container duid {
          description "Sets the next hop entity of this relay agent.
          Different entities are distinguished by their
          addresses."; DUID";
          uses dhcpv6-types:duid;
        }
        leaf dest-addr{ description {
          type inet:ipv6-address;
          mandatory true; string;
          description "destination addr"; "description of the event";
        }
        container packet-stats
      }
    }
  }
}
<CODE ENDS>

3.2.  DHCPv6 Relay YANG Model

   This module imports typedefs from [RFC6991], [RFC7223].

<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;
  }
  import ietf-dhcpv6-options {
    prefix dhcpv6-options;
  }
  import ietf-dhcpv6-types {
    prefix dhcpv6-types;
  }
  import ietf-interfaces {
    prefix if;
  }

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

  contact
    "cuiyong@tsinghua.edu.cn
     lh.sunlinh@gmail.com
     ian.farrer@telekom.de
     sladjana.zechlin@telekom.de
     hezihao9512@gmail.com";

  description "packet statistics";
          leaf solicit-rvd-count
    "This model defines a YANG data model that can be
     used to configure and manage a DHCPv6 relay.";

  revision 2018-03-04 {
                      type uint32;
                      mandatory true;
    description
                        "solicit received counter"; "Resolved most issues on the DHC official
    github";
    reference "I-D: draft-ietf-dhc-dhcpv6-yang";
  }
                  leaf request-rvd-count

  revision 2017-12-22 {
                    type uint32;
                    mandatory true;
    description
                      "request received counter";
      "Resolve most issues on Ian's github.";
    reference
      "I-D: draft-ietf-dhc-dhcpv6-yang";
  }
                  leaf renew-rvd-count

  revision 2017-11-24 {
                    type uint32;
                    mandatory true;
    description
                      "renew received counter";
      "First version of the separated relay specific
       YANG model.";
    reference
      "I-D: draft-ietf-dhc-dhcpv6-yang";
  }
                  leaf rebind-rvd-count

  /*
   * Data Nodes
   */

  container relay {
                    type uint32;
                    mandatory true;
    presence
      "Enables the relay";
    description
                      "rebind recevied counter";
                  }
                  leaf decline-rvd-count
      "DHCPv6 relay portion";

    container relay-config {
                    type uint32;
                    mandatory true;
      description
                      "decline received counter";
                  }
                  leaf release-rvd-count
        "This container contains the configuration data
        of the relay.";
      container relay-attributes {
                    type uint32;
                    mandatory true;
        description
                      "release received counter";
                  }
          "A container describes some basic attributes of the relay
           agent including some relay agent specific options data that
           need to be configured previously.
           Such options include Remote-Id option and Subscriber-Id
           option.";
        leaf info-req-rvd-count name {
          type uint32;
                    mandatory true; string;
          description
                      "information request counter";
            "Relay agent name";
        }
        leaf relay-for-rvd-count description {
          type uint32;
                    mandatory true; string;
          description
                      "relay forward received counter";
            "Textual description of the relay agent";
        }
                  leaf relay-rep-rvd-count
        leaf-list dest-addrs {
          type uint32;
                    mandatory true; inet:ipv6-address;
          description
                      "relay reply received counter";
            "Each DHCPv6 relay agent may be configured with a list
             of destination addresses.
             This node defines such a list of IPv6 addresses that
             may include unicast addresses, multicast addresses or
             other addresses.";
        }
                  leaf packet-to-cli-count
        list subscribers {
                    type uint32;
                    mandatory true;
          key subscriber;
          description
                      "packet to client counter";
                  }
            "Subscribers";
          leaf adver-sent-count subscriber {
            type uint32; uint8;
            mandatory true;
            description
                      "advertisement sent counter";
              "Subscriber";
          }
          leaf confirm-sent-count subscriber-id {
            type uint32; string;
            mandatory true;
            description
                      "confirm sent counter";
              "Subscriber id";
          }
        }
        list remote-host {
          key ent-num;
          description
            "Remote host";
          leaf reply-sent-count ent-num {
            type uint32;
            mandatory true;
            description
                      "reply sent counter";
              "Enterprise number";
          }
          leaf reconfig-sent-count remote-id {
            type uint32; string;
            mandatory true;
            description
                      "reconfigure sent counter";
              "Remote id";
          }
        }
        uses dhcpv6-types:vendor-infor;
      }
      container rsoo-option-sets {
        description
         "DHCPv6 relay agent could provide some information that would
          be useful to DHCPv6 client.
          Since relay agent cannot provide options directly to the
          client, RSOO-enabled options are defined to propose options
          for the server to send to the client.
          This container models such RSOO-enabled options.";
        reference
          "RFC6422";
        list option-set {
          key option-set-id;
          description
            "This list under the 'rsoo-option-sets' container is similar
             to the that defined in server module.
             It allows the relay to implement several sets of RSOO-enabled
             options for different interfaces.
             The list only includes the EAP Re-authentication Protocol
             (ERP) Local Domain Name DHCPv6 Option defined in RFC6440,
             since it is the only one RSOO-enabled options accepted by
             IANA so far.";
          leaf relay-for-sent-count option-set-id {
            type uint32;
                    mandatory true;
            description
                      "relay forward sent counter"; "Option sed id";
          }
          uses dhcpv6-options:relay-supplied-option-definitions;
        }
      }

      list relay-if {
        // if - This should reference an entry in ietf-interfaces
        key if-name;
        description
        "A relay agent may have several interfaces, we should provide
         a way to configure and manage parameters on the interface-level.
         A list that describes specific interfaces and their corresponding
         parameters is employed to fulfil the configfuration. Here we use
         a string called 'if-name' as the key of list.";
        leaf relay-rep-sent-count if-name {
          type uint32; if:interface-ref;
          mandatory true;
          description
                      "relay reply sent counter";
                  }
        }

      }
            "Interface name";
        }

      container relay-stats
        leaf interface-id {
          config "false";
          type string;
          description "relay statistics";
            "Interface id";

        }

        /*
        leaf cli-packet-rvd-count enable {
          type uint32; boolean;
          mandatory true;
          description "client packet received counter"; "whether this interface is enabled";
        }
        */

        leaf relay-for-rvd-count ipv6-address {
          type uint32;
            mandatory true; inet:ipv6-address;
          description "relay forward received counter";
            "IPv6 address for this interface";
        }

        leaf relay-rep-rvd-count rsoo-option-set-id {
          type uint32;
            mandatory true; leafref {
            path "/relay/relay-config/rsoo-option-sets/option-set/option-set-id";
          }
          description "relay reply recevied counter"; "Configured Relay Supplied Option set";
        }

        list next-entity {
          key dest-addr;
          description
            "This node defines a list that is used to describe the
             next hop entity of this relay distinguished by their
             addresses.";
          leaf packet-to-cli-count dest-addr {
            type uint32; inet:ipv6-address;
            mandatory true;
            description "packet to client counter";
              "Destination addr";
          }
          leaf relay-for-sent-count available {
            type uint32; boolean;
            mandatory true;
            description "relay forward sent counter";
              "Whether the next entity is available or not";
          }
          leaf relay-rep-sent-count multicast {
            type uint32; boolean;
            mandatory true;
            description "relay reply sent counter";
              "Whether the address is multicast or not";
          }
          leaf discarded-packet-count server {
            type uint32; boolean;
            mandatory true;
            description "discarded packet counter";
              "Whether the next entity is a server";
          }
        }
      }
    }

  /*
   * Notifications
   */

  notification notifications {
    description "dhcpv6 relay notification module";

    container dhcpv6-relay-event relay-state {
      config "false";
      description "dhcpv6 relay event";
      container topo-changed
        "State data of relay";
      list relay-if {
        key if-name;
        description "raised when the topology
          of the
        "A relay agent may have several interfaces, we should provide
         a way to configure and manage parameters on the interface-level.
         A list that describes specific interfaces and their corresponding
         parameters is changed."; employed to fulfil the configfuration. Here we use
         a string called 'if-name' as the key of list.";
        leaf if-name{
          type string;
          mandatory true;
          description
            "Interface name";
        }
        list pd-route {
          // if - need to look at if/how we model these. If they are
          // going to be modelled, then they should be ro state
          // entries (we're not trying to configure routes here)
          key pd-route-id;
          description "pd route";
          leaf relay-if-name pd-route-id {
            type string; uint8;
            mandatory true;
            description "relay interface name";
              "PD route id";
          }
          leaf first-hop requesting-router-id {
            type boolean; uint32;
            mandatory true;
            description "first hop";
              "Requesting router id";
          }
          leaf last-entity-addr delegating-router-id {
            type inet:ipv6-address; uint32;
            mandatory true;
            description "last entity address";
        }
      }
    }
  }
              "Delegating router id";
          }

<CODE ENDS>

3.3.  DHCPv6 Client YANG Model

   This module imports typedefs from [RFC6991].

<CODE BEGINS> file "ietf-dhcpv6-client@2017-12-22.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
          leaf next-router {
    prefix inet;
    revision-date "2013-07-15";
            type inet:ipv6-address;
            mandatory true;
            description
              "Next router";
          }
  import ietf-yang-types
          leaf last-router {
    prefix yang;
    revision-date "2013-07-15";
            type inet:ipv6-address;
            mandatory true;
            description
              "Previous router";
          }
  import ietf-dhcpv6-options {
    prefix dhcpv6-options;
    revision-date "2017-12-22";
        }

  organization "DHC WG";
  contact "yong@csnet1.cs.tsinghua.edu.cn
    wangh13@mails.tsinghua.edu.cn
    lh.sunlinh@gmail.com
    ian.farrer@telekom.de
    sladjana.zechlin@telekom.de
    hezihao9512@gmail.com  ";
        list next-entity {
          key dest-addr;
          description "This model node defines a YANG data model list that can be is used to configure and manage a DHCPv6 client.";

  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
            describe the separated client specific
        YANG model.";
      reference "I-D: draft-ietf-dhc-dhcpv6-yang";
  }

  /*
   * Grouping
   */

  grouping vendor-infor next hop entity of this relay agent.
            Different entities are distinguished by their
            addresses.";
          leaf dest-addr {
            type inet:ipv6-address;
            mandatory true;
            description "Vendor information."; "destination addr";
          }
          container vendor-info packet-stats {
            description ""; "packet statistics";
            leaf ent-num solicit-rvd-count {
              type uint32;
              mandatory true;
              description "enterprise number"; "solicit received counter";
            }
     leaf-list data
            leaf request-rvd-count {
              type string; uint32;
              mandatory true;
              description "specific vendor info";
     }
   } "request received counter";
            }

  grouping duid {
      description "DHCP Unique Identifier";
      reference "RFC3315: Section 9";
            leaf type-code renew-rvd-count {
              type uint16;
          default 65535;
          description "Type code of this DUID";
        }
      choice duid-type {
      default duid-invalid;
        description "Selects the format for the DUID.";
        case duid-llt { uint32;
              mandatory true;
              description "DUID Based on Link-layer Address Plus Time (Type 1 - DUID-LLT)";
          reference "RFC3315 Section 9.2"; "renew received counter";
            }
            leaf duid-llt-hardware-type rebind-rvd-count {
              type uint16; uint32;
              mandatory true;
              description "Hardware type as assigned by IANA (RFC826)."; "rebind recevied counter";
            }
            leaf duid-llt-time decline-rvd-count {
              type yang:timeticks; uint32;
              mandatory true;
              description "The time value is the time that the DUID is generated
              represented in seconds since midnight (UTC), January 1, 2000,
                          modulo 2^32."; "decline received counter";
            }
            leaf duid-llt-link-layer-addr release-rvd-count {
              type yang:mac-address; uint32;
              mandatory true;
              description "Link-layer address as described in RFC2464"; "release received counter";
            }
            leaf info-req-rvd-count {
              type uint32;
              mandatory true;
              description "information request counter";
            }
        case duid-en
            leaf relay-for-rvd-count {
              type uint32;
              mandatory true;
              description "DUID Assigned by Vendor Based on Enterprise Number (Type 2 - DUID-EN)";
          reference "RFC3315 Section 9.3"; "relay forward received counter";
            }
            leaf duid-en-enterprise-number relay-rep-rvd-count {
              type uint32;
              mandatory true;
              description "Vendor's registered Private Enterprise Number as
              maintained by IANA"; "relay reply received counter";
            }
            leaf duid-en-identifier packet-to-cli-count {
              type string; uint32;
              mandatory true;
              description "Indentifier, unique "packet to the device that is using it";
          } client counter";
            }
        case duid-ll
            leaf adver-sent-count {
              type uint32;
              mandatory true;
              description "DUID Based on Link-layer Address (Type 3 - DUID-LL)";
          reference "RFC3315 Section 9.4"; "advertisement sent counter";
            }
            leaf duid-ll-hardware-type confirm-sent-count {
              type uint16; uint32;
              mandatory true;
              description "Hardware type as assigned by IANA (RFC826)."; "confirm sent counter";
            }
            leaf duid-ll-link-layer-addr reply-sent-count {
              type yang:mac-address; uint32;
              mandatory true;
              description "Link-layer address as described in RFC2464";
        } "reply sent counter";
            }
        case duid-uuid
            leaf reconfig-sent-count {
              type uint32;
              mandatory true;
              description "DUID Based on Universally Unique Identifier (Type 4 - DUID-UUID)";
          reference "RFC6335 Defination of the UUID-Based Unique Identifier"; "reconfigure sent counter";
            }
            leaf uuid relay-for-sent-count {
              type yang:uuid; uint32;
              mandatory true;
              description "A Universally Unique IDentifier in the string representation
                defined in RFC 4122.  The canonical representation uses
                lowercase characters";

          } "relay forward sent counter";
            }
        case duid-invalid {
          description "DUID based on free raw bytes";
            leaf data relay-rep-sent-count {
              type binary; uint32;
              mandatory true;
              description "The bits to be used as the identifier"; "relay reply sent counter";
            }
          }
        }
      }
  grouping portset-para {
    description "portset parameters";
      container port-parameter relay-stats {
        config "false";
        description "port parameter";
          "Relay statistics";
        leaf offset cli-packet-rvd-count {
          type uint8; uint32;
          mandatory true;
          description "offset in a port set";
            "Client packet received counter";
        }
        leaf psid-len relay-for-rvd-count {
          type uint8; uint32;
          mandatory true;
          description "length of a psid";
            "Relay forward received counter";
        }
        leaf psid relay-rep-rvd-count {
          type uint16; uint32;
          mandatory true;
          description "psid value";
      }
    }
            "Relay reply recevied counter";
        }

  grouping iaid
        leaf packet-to-cli-count {
          type uint32;
          mandatory true;
          description "IA is a construct through which a server and a
            "Packet to client can identify, group, and manage a set of related IPv6
        addresses. The key of the list is a 4-byte number IAID defined
        in [RFC3315].";
      list identity-association counter";
        }
        leaf relay-for-sent-count {
        config "false";
        key iaid;
          type uint32;
          mandatory true;
          description "IA";
            "Relay forward sent counter";
        }
        leaf iaid relay-rep-sent-count {
          type uint32;
          mandatory true;
          description "IAID";
            "Relay reply sent counter";
        }
        leaf ia-type discarded-packet-count {
          type string; uint32;
          mandatory true;
          description "IA type";
            "Discarded packet counter";
        }
        leaf-list ipv6-addr
      }
    }
  }

  /*
   * Notifications
   */

  notification notifications {
    description "DHCPv6 relay notification module";
    container dhcpv6-relay-event {
      description
        "DHCPv6 relay event";
      container topo-changed {
        description
        "Raised when the topology of the relay agent is changed.";
        leaf relay-if-name {
          type inet:ipv6-address; string;
          mandatory true;
          description "ipv6 address";
            "Relay interface name";
        }
        leaf-list ipv6-prefix
        leaf first-hop {
          type inet:ipv6-prefix; boolean;
          mandatory true;
          description "ipv6 prefix";
            "First hop";
        }
        leaf-list prefix-length
        leaf last-entity-addr {
          type uint8; inet:ipv6-address;
          mandatory true;
          description "ipv6
            "Last entity address";

        }
      }
    }
  }
}
<CODE ENDS>

3.3.  DHCPv6 Client YANG Model

   This module imports typedefs from [RFC6991], [RFC7223].

<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-dhcpv6-options {
    prefix dhcpv6-options;
  }
  import ietf-dhcpv6-types {
    prefix length"; dhcpv6-types;
  }
        leaf t1-time
  import ietf-interfaces {
          type yang:timeticks;
          mandatory true;
          description "t1 time";
    prefix if;
  }
        leaf t2-time

  organization "DHC WG";
  contact
   "cuiyong@tsinghua.edu.cn
    wangh13@mails.tsinghua.edu.cn
    lh.sunlinh@gmail.com
    ian.farrer@telekom.de
    sladjana.zechlin@telekom.de
    hezihao9512@gmail.com  ";

  description "This model defines a YANG data model that can be
    used to configure and manage a DHCPv6 client.";

  revision 2018-03-04 {
          type yang:timeticks;
          mandatory true;
    description "t2 time"; "Resolved most issues on the DHC official
    github";
    reference "I-D: draft-ietf-dhc-dhcpv6-yang";
  }
        leaf preferred-lifetime

  revision 2017-12-22 {
          type yang:timeticks;
          mandatory true;
    description "preferred lifetime"; "Resolve most issues on Ian's github.";
    reference "I-D: draft-ietf-dhc-dhcpv6-yang";

  }
        leaf valid-lifetime

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

  /*
   * Data Nodes
   */

  container client {
    presence "Enables the client";
    description "dhcpv6 client portion";

    container client-config{ client-config {
      description "configuration tree of client";
      container duid {
        description "Sets the DUID";
        uses duid; dhcpv6-types:duid;
      }
      list client-if {
        key if-name;
        description "A client may have several interfaces, it is more reasonable to
          configure and manage parameters on the interface-level. The list defines
          specific client interfaces and their data. Different interfaces are
          distinguished by the key which is a configurable string value.";
        leaf if-name {
          type string; if:interface-ref;
          mandatory true;
          description "interface name";
        }

        leaf cli-id {
          type uint32;
          mandatory true;
          description "client id";
        }

        /*
        leaf description {
          type string;
          description "description of the client interface";
        }
        */

        leaf pd-function {
          type boolean;
          mandatory true;
          description "Whether the client can act as a requesting router
            to request prefixes using prefix delegation ([RFC3633]).";
        }
        leaf rapid-commit {
          type boolean;
          mandatory true;
          description "'1' indicates a client can initiate a Solicit-Reply message
            exchange by adding a Rapid Commit option in Solicit message. '0' means
            the client is not allowed to add a Rapid Commit option to request
            addresses in a two-message exchange pattern.";
        }

        /*
        container mo-tab {
          description "The management tab label indicates the operation mode of the
            DHCPv6 client.
            'm'=1 and 'o'=1 indicate the client will use DHCPv6 to  obtain all the configuration
            data.
            'm'=1 and 'o'=0 are a meaningless combination.
            'm'=0 and 'o'=1 indicate the client will use stateless DHCPv6 to obtain configuration
            data apart from addresses/prefixes data.
            'm'=0 and 'o'=0 represent the client will not use DHCPv6 but use SLAAC to
            achieve configuration.";

            // if - not sure about the intended use here as it seems
            // to be redfining what will be received in the PIO. Is
            // the intention to be whether they PIO options will be
            // obeyed as received or overridden?
          leaf m-tab {
            type boolean;
            mandatory true;
            description "m tab";
          }
          leaf o-tab {
            type boolean;
            mandatory true;
            description "o tab";
          }
        }
        */

        container client-configured-options {
          description "client configured options";
          uses dhcpv6-options:client-option-definitions;
        }
      }

    }

    container client-state{ client-state {
      config "false";
      description "state tree of client";
      container if-other-paras {
        description "A client can obtain extra configuration
          data other than address and prefix information through
          DHCPv6. This container describes such data the client
          was configured. The potential configuration data may
          include DNS server addresses, SIP server domain names, etc.";
        uses dhcpv6-options:server-option-definitions;
      }
     container packet-stats {
        config "false";
        description "A container records
          all the packet status information
          of a specific interface.";
        leaf solicit-count {
          type uint32;
          mandatory true;
          description "solicit counter";
        }
        leaf request-count {
          type uint32;
          mandatory true;
          description "request counter";
        }
        leaf renew-count {
          type uint32;
          mandatory true;
          description "renew counter";
        }
        leaf rebind-count {
          type uint32;
          mandatory true;
          description "rebind counter";
        }
        leaf decline-count {
          type uint32;
          mandatory true;
          description "decline counter";
        }
        leaf release-count {
          type uint32;
          mandatory true;
          description "release counter";
        }
        leaf info-req-count {
          type uint32;
          mandatory true;
          description "information request counter";
        }
        leaf advertise-count {
          type uint32;
          mandatory true;
          description "advertise counter";
        }
        leaf confirm-count {
          type uint32;
          mandatory true;
          description "confirm counter";
        }
        leaf reply-count {
          type uint32;
          mandatory true;
          description "reply counter";
        }
        leaf reconfigure-count {
          type uint32;
          mandatory true;
          description "recofigure counter";
        }
      }
    }

  }

  /*
   * Notifications
   */

  notification notifications {
    description "dhcpv6 client notification module";
    container dhcpv6-client-event {
      description "dhcpv6 client event";

      container ia-lease-event {
        description "raised when the client was allocated
          a new IA from the server or it renew/rebind/release
          its current IA";
        leaf event-type {
          type enumeration{ enumeration {
            enum "allocation" {
              description "allocate";
            }
            enum "rebind" {
              description "rebind";
            }
            enum "renew" {
              description "renew";
            }
            enum "release" {
              description "release";
            }
          }
          mandatory true;
          description "event type";
        }
        container duid {
          description "Sets the DUID";
          uses duid; dhcpv6-types:duid;
        }
        leaf iaid {
          type uint32;
          mandatory true;
          description "IAID";
        }
        leaf serv-name {
          type string;
          description "server name";
        }
        leaf description {
          type string;
          description "description of event";
        }
      }

      container invalid-ia-detected {
        description "raised when the identity association of the
          client can be proved to be invalid.  Possible condition
          includes duplicated address, illegal address, etc.";
        container duid {
          description "Sets the DUID";
          uses duid; dhcpv6-types:duid;
        }
        leaf cli-duid {
          type uint32;
          mandatory true;
          description "duid of client";
        }
        leaf iaid {
          type uint32;
          mandatory true;
          description "IAID";
        }
        leaf serv-name {
          type string;
          description "server name";
        }
        leaf description {
          type string;
          description "description of the event";
        }
      }

      container retransmission-failed {
        description "raised when the retransmission mechanism defined
          in [RFC3315] is failed.";
        container duid {
          description "Sets the DUID";
          uses duid; dhcpv6-types:duid;
        }
        leaf description {
          type enumeration {
            enum "MRC failed" {
              description "MRC failed";
            }
            enum "MRD failed" {
              description "MRD failed";
            }
          }
          mandatory true;
          description "description of failure";
        }
      }

      container failed-status-turn-up {
        description "raised when the client receives a message includes
          an unsuccessful Status Code option.";
        container duid {
          description "Sets the DUID";
          uses duid; dhcpv6-types:duid;
        }
        leaf status-code {
          type enumeration {
            enum "1" {
              description "UnspecFail";
            }
            enum "2" {
              description "NoAddrAvail";
            }
            enum "3" {
              description "NoBinding";
            }
            enum "4" {
              description "NotOnLink";
            }
            enum "5" {
              description "UseMulticast";
            }
          }
          mandatory true;
          description "employed status code";
        }
      }

    }
  }
}
<CODE ENDS>

3.4.  DHCPv6 Options YANG Model

   This module imports typedefs from [RFC6991]. [RFC6991], [RFC7223].

<CODE BEGINS> file "ietf-dhcpv6-options@2017-12-22.yang" "ietf-dhcpv6-options.yang"
module ietf-dhcpv6-options {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-options";
  prefix "dhcpv6-options";

  import ietf-inet-types {
    prefix inet;
    revision-date "2013-07-15";
  }
  import ietf-yang-types {
    prefix yang;
    revision-date "2013-07-15";
  }
  import ietf-dhcpv6-types {
    prefix dhcpv6-types;
  }

  organization "DHC WG";
  contact "yong@csnet1.cs.tsinghua.edu.cn
   "cuiyong@tsinghua.edu.cn
    wangh13@mails.tsinghua.edu.cn
    lh.sunlinh@gmail.com
    ian.farrer@telekom.de
    sladjana.zechlin@telekom.de
    hezihao9512@gmail.com";

  description "This model defines a YANG data model that can be
    used to configure and manage a DHCPv6 server."; options.";

  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 DHCPv6 options
      YANG model.";
    reference "I-D:draft-ietf-dhc-dhcpv6-yang";
  }

  /*
   * Features
   */

  //  features for server options
  feature server-unicast-op {
    description "Support for Server Unicast option";
  }
  feature sip-server-domain-name-list-op {
    description "Support for SIP Server Domain Name List option";
  }
  feature sip-server-address-list-op {
    description "Support for SIP Server Address List option";
  }
  feature dns-config-op dns-servers-op {
    description "Support for DNS Recursive Name Server option"; Servers Option";
  }
  feature domain-searchlist-op {
    description "Support for Domain Search List Option";
  }
  feature nis-config-op {
    description "Support for Network Information Service (NIS)
      Servers option";
  }
  feature nis-plus-config-op {
    description "Support for Network Information Service V2 (NIS+)
      Servers option";
  }
  feature nis-domain-name-op {
    description "Support for Network Information Service (NIS)
      Domain Name option";
  }
  feature nis-plus-domain-name-op {
    description "Support for Network Information Service V2 (NIS+)
      Server option";
  }
  feature sntp-server-op {
    description "Support for Simple Network Protocol Configuration
      (SNTP) Servers option";
  }
  feature info-refresh-time-op {
    description "Support for Information Refresh Time option";
  }
  feature client-fqdn-op {
    description "Support for Client FQDN option";
  }
  feature posix-timezone-op {
    description "Support for New POIX Timezone option";
  }
  feature tzdb-timezone-op {
    description "Support for New TZDB Timezone option";
  }
  feature ntp-server-op {
    description "Support for Network Time Protocol (NTP)
      Server option";
  }
  feature boot-file-url-op {
    description "Support for Boot File URL option";
  }
  feature boot-file-param-op {
    description "Support for Boot File Parameters option";
  }
  feature aftr-name-op {
    description "Support for Address Family Transition
      Router (AFTR) option";
  }
  feature kbr-default-name-op {
    description "Support for Kerberos Default Name
      Option";
  }
  feature kbr-kdc-op {
    description "Support for Kerberos KDC option";
  }
  feature sol-max-rt-op {
    description "Support for SOL_MAX_RT option";
  }
  feature inf-max-rt-op {
    description "Support for INF_MAX_RT option";
  }
  feature addr-selection-op {
    description "Support for Address Selection opiton";
  }
  feature pcp-server-op {
    description "Support for Port Control Protocol (PCP)
      option";
  }
  feature s46-rule-op {
    description "Support for S46 Rule option";
  }
  feature s46-br-op {
    description "Support for S46 Border Relay (BR) option";
  }
  feature s46-dmr-op {
    description "Support for S46 Default Mapping Rule
      (DMR) option";
  }
  feature s46-v4-v6-binding-op {
    description "Support for S46 IPv4/IPv6 Address
      Bind option";
  }

  // features for relay-supplied options
  feature erp-local-domain-name-op {
    description "Support for ERP Local Domain
      Name option";
  }

  // features for client options
  feature option-request-op {
    description "Support for Option Request option";
  }
  feature rapid-commit-op {
    description "Support for Rapid Commit option";
  }
  feature user-class-op {
    description "Support for User Class option";
  }
  feature vendor-class-op {
    description "Support for Vendor Class option";
  }
  feature client-arch-type-op {
    description "Support for Client System Architecture
      Type option";
  }
  feature client-network-interface-identifier-op {
    description "Support for Client Network Interface
      Identifier option";
  }
  feature kbr-principal-name-op {
    description "Support for Kerberos Principal
      Name option";
  }
  feature kbr-realm-name-op {
    description "Support Kerberos Realm Name option";
  }
  feature client-link-layer-addr-op {
    description "Support for Client Link-Layer Address
      Option";
  }

  // features for custom options
  feature operator-op-ipv6-address {
    description "Support for Option with IPv6 Addresses";
  }
  feature operator-op-single-flag {
    description "Support for Option with Single Flag";
  }
  feature operator-op-ipv6-prefix {
    description "Support for Option with IPv6 Prefix";
  }
  feature operator-op-int32 {
    description "Support for Opion with 32-bit
      Integer Value";
  }
  feature operator-op-int16 {
    description "Support for Opion with 16-bit
      Integer Value";
  }
  feature operator-op-int8 {
    description "Support for Opion with 8-bit
      Integer Value";
  }
  feature operator-op-uri {
    description "Support for Opion with URI";
  }
  feature operator-op-textstring {
    description "Support for Opion with Text
      String"; S46 Default Mapping Rule
      (DMR) option";
  }
  feature operator-op-var-data s46-v4-v6-binding-op {
    description "Support for Opion with
      Variable-Length Data"; S46 IPv4/IPv6 Address
      Bind option";
  }

  // features for relay-supplied options
  feature operator-op-dns-wire erp-local-domain-name-op {
    description "Support for Opion with DNS Wire
      Format ERP Local Domain Name List";
  }

  /*
   * Groupings
   */

  grouping portset-para {
   description "portset parameters";
   container port-parameter {
     description "port parameter";
     leaf offset {
       type uint8;
       mandatory true;
       description "offset in a port set";
     }
     leaf psid-len {
       type uint8;
       mandatory true;
       description "length of a psid"; option";
  }
     leaf psid

  // features for client options
  feature option-request-op {
       type uint16;
       mandatory true;
    description "psid value";
     }
   } "Support for Option Request option";
  }

  grouping duid {
      description "DHCP Unique Identifier";
      reference "RFC3315: Section 9";
      leaf type-code
  feature rapid-commit-op {
          type uint16;
          default 65535;
    description "Type code of this DUID"; "Support for Rapid Commit option";
  }
      choice duid-type
  feature user-class-op {
      default duid-invalid;
    description "Selects the format "Support for the DUID.";
        case duid-llt {
          description "DUID Based on Link-layer Address Plus Time (Type 1 - DUID-LLT)";
          reference "RFC3315 Section 9.2";

          leaf duid-llt-hardware-type {
            type uint16;
            description "Hardware type as assigned by IANA (RFC826)."; User Class option";
  }
          leaf duid-llt-time
  feature vendor-class-op {
            type yang:timeticks;
    description "The time value is the time that the DUID is generated
              represented in seconds since midnight (UTC), January 1, 2000,
                          modulo 2^32."; "Support for Vendor Class option";
  }
          leaf duid-llt-link-layer-addr
  feature client-arch-type-op {
            type yang:mac-address;
    description "Link-layer address as described in RFC2464";
          } "Support for Client System Architecture
      Type option";
  }
        case duid-en {
          description "DUID Assigned by Vendor Based on Enterprise Number (Type 2 - DUID-EN)";
          reference "RFC3315 Section 9.3";
          leaf duid-en-enterprise-number {
            type uint32;
  feature client-network-interface-identifier-op {
    description "Vendor's registered Private Enterprise Number as
              maintained by IANA"; "Support for Client Network Interface
      Identifier option";
  }
          leaf duid-en-identifier
  feature kbr-principal-name-op {
            type string;
    description "Indentifier, unique to the device that is using it"; "Support for Kerberos Principal
      Name option";
  }
  feature kbr-realm-name-op {
    description "Support Kerberos Realm Name option";
  }
        case duid-ll
  feature client-link-layer-addr-op {
    description "DUID Based on Link-layer "Support for Client Link-Layer Address (Type 3 - DUID-LL)";
          reference "RFC3315 Section 9.4";
          leaf duid-ll-hardware-type
      Option";
  }

  // features for custom options
  feature operator-op-ipv6-address {
            type uint16;
    description "Hardware type as assigned by IANA (RFC826)."; "Support for Option with IPv6 Addresses";
  }
          leaf duid-ll-link-layer-addr
  feature operator-op-single-flag {
              type yang:mac-address;
    description "Link-layer address as described in RFC2464";
        } "Support for Option with Single Flag";
  }
        case duid-uuid
  feature operator-op-ipv6-prefix {
    description "DUID Based on Universally Unique Identifier (Type 4 - DUID-UUID)";
          reference "RFC6335 Defination of the UUID-Based Unique Identifier";
          leaf uuid "Support for Option with IPv6 Prefix";
  }
  feature operator-op-int32 {
            type yang:uuid;
    description "A Universally Unique IDentifier in the string representation
                defined in RFC 4122.  The canonical representation uses
                lowercase characters"; "Support for Opion with 32-bit
      Integer Value";
  }
  feature operator-op-int16 {
    description "Support for Opion with 16-bit Integer Value";
  }
        case duid-invalid
  feature operator-op-int8 {
    description "DUID based on free raw bytes";
          leaf data "Support for Opion with 8-bit Integer Value";
  }
  feature operator-op-uri {
            type binary;
    description "The bits to be used as the identifier"; "Support for Opion with URI";
  }
  feature operator-op-textstring {
    description "Support for Opion with Text String";
  }
  feature operator-op-var-data {
    description "Support for Opion with Variable-Length Data";
  }
  feature operator-op-dns-wire {
    description "Support for Opion with DNS Wire
      Format Domain Name List";
  }
  /*
   * Groupings
   */

  grouping server-option-definitions {
    description "Contains definitions for options configured on the
      DHCPv6 server which will be supplied to clients.";

    container server-unicast-option {
      if-feature server-unicast-op;
      presence "Enable this option";
      description "OPTION_UNICAST (12) Server Unicast Option";
      reference "RFC3315: Dynamic Host Configuration Protocol for
        IPv6 (DHCPv6)";
      leaf server-address {
        type inet:ipv6-address;
        description "server ipv6 address";
      }
    }

    container sip-server-domain-name-list-option {
      if-feature sip-server-domain-name-list-op;
      presence "Enable this option";
      description "OPTION_SIP_SERVER_D (21) SIP Servers Domain Name List";
      reference "RFC3319: Dynamic Host Configuration Protocol
        (DHCPv6) Options for Session Initiation Protocol (SIP) Servers";
      leaf sip-serv-domain-name {
        type string;
        mandatory true;
        description "sip server domain name";
      }
    }

    container sip-server-address-list-option {
      if-feature sip-server-address-list-op;
      presence "Enable this option";
      description "OPTION_SIP_SERVER_A (22) SIP Servers IPv6 Address List";
      reference "RFC3319: Dynamic Host Configuration Protocol (DHCPv6)
        Options for Session Initiation Protocol (SIP) Servers";
      list sip-server {
        key sip-serv-id;
        description "sip server info";
        leaf sip-serv-id {
          type uint8;
          mandatory true;
          description "sip server id";
        }
        leaf sip-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "sip server addr";
        }
      }
    }

    container dns-config-option dns-servers-option {
      if-feature dns-config-op; dns-servers-op;
      presence "Enable this option";
      description "OPTION_DNS_SERVERS (23) DNS recursive Name Server option";
      reference "RFC3646: DNS Configuration options for Dynamic Host Configuration
        Protocol for IPv6 (DHCPv6)";
      list dns-server {
        key dns-serv-id;
        description "dns server info";
        leaf dns-serv-id {
          type uint8;
          mandatory true;
          description "DNS server list entry ID.";
        }
        leaf dns-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "DNS server address.";
        }
      }
    }

    container domain-searchlist-option {
      if-feature domain-searchlist-op;
      presence "Enable this option";
      description "OPTION_DOMAIN_LIST (24) Domain Search List Option";
      reference "RFC3646: DNS Configuration options for Dynamic
        Host Configuration Protocol for IPv6 (DHCPv6)";
      list domain-searchlist {
        key domain-searchlist-id;
        description "dns server info";
        leaf domain-searchlist-id {
          type uint8;
          mandatory true;
          description "Domain seachlist entry ID.";
        }
        leaf domain-search-list-entry {
          type string;
          mandatory true;
          description "Domain search list entry.";
        }

      }
    }

    container nis-config-option {
      if-feature nis-config-op;
      presence "Enable this option";
      description "OPTION_NIS_SERVERS (27) Network Information Service (NIS)
        Servers Option.";
      reference "RFC3898: Network Information Service (NIS) Configuration
        Options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)";
      list nis-server {
        key nis-serv-id;
        description "nis server info";
        leaf nis-serv-id {
          type uint8;
          mandatory true;
          description "nis server id";
        }
        leaf nis-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "nis server addr";
        }
      }
    }

    container nis-plus-config-option {
      if-feature nis-plus-config-op;
      presence "Enable this option";
      description "OPTION_NISP_SERVERS (28): Network Information Service V2
        (NIS+) Servers Option.";
      reference "RFC3989: Network Information Service (NIS) Configuration
        Options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)";
      list nis-plus-server {
        key nis-plus-serv-id;
        description "NIS+ server information.";
        leaf nis-plus-serv-id {
          type uint8;
          mandatory true;
          description "nisp server id";
        }
        leaf nis-plus-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "nisp server addr";
        }
      }
    }
    container nis-domain-name-option {
      if-feature nis-domain-name-op;
      presence "Enable this option";
      description "OPTION_NIS_DOMAIN_NAME (29) Network Information
        Service (NIS) Domain Name Option";
      reference "RFC3989: Network Information Service (NIS)
        Configuration Options for Dynamic Host Configuration Protocol
        for IPv6 (DHCPv6)";
      leaf nis-domain-name {
        type string;
        description "The Network Information Service (NIS) Domain Name
          option is used by the server to convey client's NIS Domain Name
          info to the client.";
      }
    }

    container nis-plus-domain-name-option nis-plus-domain-name-option {
      if-feature nis-plus-domain-name-op;
      presence "Enable this option";
      description "OPTION_NISP_DOMAIN_NAME (30) Network Information
        Service V2 (NIS+) Domain Name Option";
      reference "RFC3989: Network Information Service (NIS)
        Configuration Options for Dynamic Host Configuration Protocol
        for IPv6 (DHCPv6)";
      leaf nis-plus-domain-name {
        type string;
        description "The Network Information Service V2 (NIS+) Domain Name
        option is used by the server to convey client's NIS+ Domain Name
        info to the client.";
      }
    }

    container sntp-server-option {
      if-feature sntp-server-op;
      presence "Enable this option";
      description "OPTION_SNTP_SERVERS (31) Simple Network Time Protocol
        (SNTP) Servers Option";
      reference "RFC4075: Simple Network Time Protocol (SNTP) Configuration
        Option for DHCPv6";
      list sntp-server {
        key sntp-serv-id;
        description "sntp server info";
        leaf sntp-serv-id {
          type uint8;
          mandatory true;
          description "sntp server id";
        }
        leaf sntp-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "sntp server addr";
        }
      }
    }

    container info-refresh-time-option {
      if-feature info-refresh-time-op;
      presence "Enable this option";
      description "OPTION_INFORMATION_REFRESH_TIME (32) Information Refresh
        Time option.";
      reference "RFC4242: Information Refresh Time Option for Dynamic Host
        Configuration Protocol for IPv6 (DHCPv6";
      leaf info-refresh-time {
        type yang:timeticks;
        mandatory true;
        description "The refresh time.";
      }
    }

    container client-fqdn-option {
      if-feature client-fqdn-op;
      presence "Enable this option";
      description "OPTION_CLIENT_FQDN (39) DHCPv6 Client FQDN Option";
      reference "RFC4704: The Dynamic Host Configuration Protocol for IPv6
        (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option";
      leaf server-initiate-update {
        type boolean;
        mandatory true;
        description "server initiate";
      }
      leaf client-initiate-update {
        type boolean;
        mandatory true;
        description "client initiate";
      }
      leaf modify-name-from-cli {
        type boolean;
        mandatory true;
        description "modify by client";
      }
    }

    container posix-timezone-option {
      if-feature posix-timezone-op;
      presence "Enable this option";
      description "OPTION_NEW_POSIX_TIMEZONE (41) Posix Timezone option";
      reference "RFC4833: Timezone Options for DHCP";
      leaf tz-posix {
        type string;
        mandatory true;
        description "TZ Posix IEEE 1003.1 String";
      }
    }

    container tzdb-timezone-option {
      if-feature nis-plus-domain-name-op; tzdb-timezone-op;
      presence "Enable this option";
      description "OPTION_NISP_DOMAIN_NAME (30) Network Information
          Service V2 (NIS+) Domain Name Option"; "OPTION_NEW_TZDB_TIMEZONE (42) Timezone Database option";
      reference "RFC3989: Network Information Service (NIS)
          Configuration "RFC4822: Timezone Options for Dynamic Host Configuration Protocol
          for IPv6 (DHCPv6)"; DHCP";
      leaf nis-plus-domain-name tz-database {
        type string;
        mandatory true;
        description "The Network Information Service V2 (NIS+) Domain Name
          option is used by the server to convey client's NIS+ Domain Name
          info "Reference to the client."; TZ Database";
      }
    }

    container sntp-server-option ntp-server-option {
      //This option looks like it needs work to correctly model the
      //option as defined in the RFC.

      // Zihao - Re-modelled so it only contains one time source suboption

      if-feature sntp-server-op; ntp-server-op;
      presence "Enable this option";
      description "OPTION_SNTP_SERVERS (31) Simple Network Time Protocol
        (SNTP) Servers Option"; "OPTION_NTP_SERVER (56) NTP Server Option for DHCPv6";
      reference "RFC4075: Simple "RFC5908: Network Time Protocol (SNTP) Configuration (NTP) Server Option for
        DHCPv6";
      list sntp-server ntp-server {
        key sntp-serv-id; ntp-serv-id;
        description "sntp "ntp server info";
        leaf sntp-serv-id ntp-serv-id {
          type uint8;
          mandatory true;
          description "sntp "NTP server id";
        }
        leaf sntp-serv-addr
        choice ntp-time-source-suboption {
          description "Select a NTP time source suboption.";
          case server-address {
            leaf-list ntp-serv-addr-suboption {
                type inet:ipv6-address;
          mandatory true;
                description "sntp "NTP server addr";
            }
          }
          case server-multicast-address {
            leaf-list ntp-serv-mul-addr-suboption {
              type inet:ipv6-address;
              description "NTP server multicast addr";
            }
          }
          case server-fqdn {
            leaf-list ntp-serv-fqdn-suboption {
              type string;
              description "NTP server fqdn";
            }
          }
        }
      }
    }

    container info-refresh-time-option boot-file-url-option {
      if-feature info-refresh-time-op; boot-file-url-op;
      presence "Enable this option";
      description "OPTION_INFORMATION_REFRESH_TIME (32) Information Refresh
        Time option."; "OPT_BOOTFILE_URL (59) Boot File URL option";
      reference "RFC4242: Information Refresh Time Option for Dynamic Host
        Configuration Protocol "RFC5970: DHCPv6 Options for IPv6 (DHCPv6"; Network Boot";
      list boot-file {
        key boot-file-id;
        description "boot file info";
        leaf boot-file-id {
          type uint8;
          mandatory true;
          description "boot file id";
        }
        leaf-list suitable-arch-type {
          type uint16;
          description "architecture type";
        }
        leaf-list suitable-net-if {
          type uint32;
          description "network interface";
        }
        leaf info-refresh-time boot-file-url {
          type yang:timeticks; string;
          mandatory true;
          description "The refresh time."; "url for boot file";
        }
      }
    }

    container client-fqdn-option boot-file-param-option {
      if-feature client-fqdn-op; boot-file-param-op;
      presence "Enable this option";
      description "OPTION_CLIENT_FQDN (39) DHCPv6 Client FQDN "OPT_BOOTFiLE_PARAM (60) Boot File Parameters Option";
      reference "RFC4704: The Dynamic Host Configuration Protocol "RFC5970: DHCPv6 Options for IPv6
        (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option";
      leaf server-initiate-update Network Boot";
      list boot-file-paras {
        type boolean;
        mandatory true;
        key para-id;
        description "server initiate";
      } "boot file parameters";
        leaf client-initiate-update para-id {
          type boolean; uint8;
          mandatory true;
          description "client initiate"; "parameter id";
        }
        leaf modify-name-from-cli parameter {
          type boolean; string;
          mandatory true;
          description "modify by client"; "parameter value";
        }
      }
    }

    container posix-timezone-option aftr-name-option {
      if-feature posix-timezone-op; aftr-name-op;
      presence "Enable this option";
      description "OPTION_NEW_POSIX_TIMEZONE (41) Posix Timezone option"; "OPTION_AFTR_NAME (64) AFTR-Name DHCPv6 Option";
      reference "RFC4833: Timezone Options "RFC6334: Dynamic Host Configuration Protocol for DHCP"; IPv6
        (DHCPv6) Option for Dual-Stack Lite";
      leaf tz-posix tunnel-endpoint-name {
        type string;
        mandatory true;
        description "TZ Posix IEEE 1003.1 String"; "aftr name";
      }
    }

    container tzdb-timezone-option kbr-default-name-option {
      if-feature tzdb-timezone-op; kbr-default-name-op;
      presence "Enable this option";
      description "OPTION_NEW_TZDB_TIMEZONE (42) Timezone Database option"; "OPTION_KRB_DEFAULT_REALM_NAME (77) Kerberos Default Realm Name Option";
      reference "RFC4822: Timezone "RFC6784: Kerberos Options for DHCP"; DHCPv6";
      leaf tz-database default-realm-name {
        type string;
        mandatory true;
        description "Reference to the TZ Database"; "default realm name";
      }
    }

    container ntp-server-option kbr-kdc-option {
      //This option looks like it needs work to correctly model the
      //option as defined in the RFC.

      // Zihao - Re-modelled so it only contains one
      // time source suboption
      if-feature ntp-server-op; kbr-kdc-op;
      presence "Enable this option";
      description "OPTION_NTP_SERVER (56) NTP Server Option for DHCPv6"; "OPTION_KRB_KDC (78) Kerberos KDB Option";
      reference "RFC5908: Network Time Protocol (NTP) Server Option "RFC6784: Kerberos Options for DHCPv6";
      list ntp-server kdc-info {
        key ntp-serv-id; kdc-id;
        description "ntp server "kdc info";
        leaf ntp-serv-id kdc-id {
          type uint8;
          mandatory true;
          description "ntp server "kdc id";
        }
        choice ntp-time-source-suboption
        leaf priority {
          type uint16;
          mandatory true;
          description "Select a NTP time source suboption.";
          case server-address {
        leaf-list ntp-serv-addr-suboption "priority";
        }
        leaf weight {
          type inet:ipv6-address; uint16;
          mandatory true;
          description "ntp server addr"; "weight";
        }
        leaf transport-type {
          type uint8;
          mandatory true;
          description "transport type";
        }
          case server-multicast-address
        leaf port-number {
            leaf-list ntp-serv-mul-addr-suboption
          type uint16;
          mandatory true;
          description "port number";
        }
        leaf kdc-ipv6-addr {
          type inet:ipv6-address;
          mandatory true;
          description "ntp server multicast "kdc ipv6 addr";
        }
          }
          case server-fqdn {
            leaf-list ntp-serv-fqdn-suboption
        leaf realm-name {
          type string;
          mandatory true;
          description "ntp server fqdn";
                  }
          } "realm name";
        }
      }
    }

    container boot-file-url-option sol-max-rt-option {
      if-feature boot-file-url-op; sol-max-rt-op;
      presence "Enable this option";
      description "OPT_BOOTFILE_URL (59) Boot File URL "OPTION_SOL_MAX_RT (82) sol max rt option";
      reference "RFC5970: DHCPv6 Options for Network Boot";
      list boot-file {
        key boot-file-id;
        description "boot file info"; "RFC7083: Modification to Default Values of
        SOL_MAX_RT and INF_MAX_RT";
        leaf boot-file-id sol-max-rt-value {
          type uint8; yang:timeticks;
          mandatory true;
          description "boot file id"; "sol max rt value";
        }
            leaf-list suitable-arch-type {
                type uint16;
                description "architecture type";
    }
              leaf-list suitable-net-if

    container inf-max-rt-option {
                type uint32;
      if-feature inf-max-rt-op;
      presence "Enable this option";
      description "network interface";
              } "OPTION_INF_MAX_RT (83) inf max rt option";
      reference "RFC7083: Modification to Default Values of
        SOL_MAX_RT and INF_MAX_RT";
      leaf boot-file-url inf-max-rt-value {
        type string; yang:timeticks;
        mandatory true;
        description "url for boot file";
        } "inf max rt value";
      }
    }

    container boot-file-param-option addr-selection-option {
      if-feature boot-file-param-op; addr-selection-op;
      presence "Enable this option";
      description "OPT_BOOTFiLE_PARAM (60) Boot File Parameters Option"; "OPTION_ADDRSEL (84) and OPTION_ADDRSEL_TABLE (85)";
      reference "RFC5970: DHCPv6 Options for Network Boot"; "RFC7078: Distributing Address Selection Policy Using
        DHCPv6";
      // if - Needs checking to see if this matches the RFC - there
      // are two options here.
      // Zihao - I think this matches RFC7078
      leaf a-bit-set {
        type boolean;
        mandatory true;
        description "a bit";
      }
      leaf p-bit-set {
        type boolean;
        mandatory true;
        description "p bit";
      }
      list boot-file-paras policy-table {
        key para-id; policy-id;
        description "boot file parameters"; "policy table";
        leaf policy-id {
          type uint8;
          mandatory true;
          description "policy id";
        }
        leaf para-id label {
          type uint8;
          mandatory true;
          description "parameter id"; "label";
        }
        leaf parameter precedence {
          type string; uint8;
          mandatory true;
          description "parameter
                  value";
              }

            } "precedence";
        }
    container aftr-name-option
        leaf prefix-len {
      if-feature aftr-name-op;
      presence "Enable this option";
          type uint8;
          mandatory true;
          description "OPTION_AFTR_NAME (64) AFTR-Name DHCPv6 Option";
      reference "RFC6334: Dynamic Host Configuration Protocol for IPv6
      (DHCPv6) Option for Dual-Stack Lite"; "prefix length";
        }
        leaf tunnel-endpoint-name prefix {
          type string; inet:ipv6-prefix;
          mandatory true;
          description "aftr name"; "prefix";
        }
      }
    }

    container kbr-default-name-option pcp-server-option {
      if-feature kbr-default-name-op; pcp-server-op;
      presence "Enable this option";
      description "OPTION_KRB_DEFAULT_REALM_NAME (77) Kerberos Default Realm Name Option"; "OPTION_V6_PCP_SERVER (86) pcp server option";
      reference "RFC6784: Kerberos "RFC7291: DHCP Options for DHCPv6"; the Port Control
        Protocol (PCP)";
      list pcp-server {
        key pcp-serv-id;
        description "pcp server info";
        leaf default-realm-name pcp-serv-id {
          type string; uint8;
          mandatory true;
          description "default realm name"; "pcp server id";
        }
        leaf pcp-serv-addr {
          type inet:ipv6-address;
          mandatory true;
          description "pcp server addr";
        }
      }
    }

    container kbr-kdc-option s46-rule-option {
      if-feature kbr-kdc-op; s46-rule-op;
      presence "Enable this option";
      description "OPTION_KRB_KDC (78) Kerberos KDB Option"; "OPTION_S46_RULE (89) S46 rule option";
      reference "RFC6784: Kerberos "RFC7598: DHCPv6 Options for DHCPv6"; Configuration of
        Softwire Address and Port-Mapped Clients";
      list kdc-info s46-rule {
        key kdc-id; rule-id;
        description "kdc info"; "s46 rule";
        leaf kdc-id rule-id {
          type uint8;
          mandatory true;
          description "kdc "rule id";
        }
        leaf priority rule-type {
          type uint16;
              mandatory true; enumeration {
            enum "BMR" {
              description "priority"; "BMR";
            }
            leaf weight
            enum "FMR" {
              type uint16;
              description "FMR";
            }
          }
          mandatory true;
          description "weight"; "rule type";
        }
        leaf transport-type prefix4-len {
          type uint8;
          mandatory true;
          description "transport type"; "ipv4 prefix length";
        }
        leaf port-number ipv4-prefix {
          type uint16; inet:ipv4-prefix;
          mandatory true;
          description "port number"; "ipv4 prefix";
        }
        leaf kdc-ipv6-addr prefix6-len {
          type inet:ipv6-address; uint8;
          mandatory true;
          description "kdc ipv6 addr"; "ipv6 prefix length";
        }
        leaf realm-name ipv6-prefix {
          type string; inet:ipv6-prefix;
          mandatory true;
          description "realm name"; "ipv6 prefix";
        }
        uses dhcpv6-types:portset-para;
      }
    }

    container sol-max-rt-option s46-br-option {
      if-feature sol-max-rt-op; s46-br-op;
      presence "Enable this option";
      description "OPTION_SOL_MAX_RT (82) sol max rt option"; "OPTION_S46_BR (90) S46 BR Option";
      reference "RFC7083: Modification to Default Values "RFC7598: DHCPv6 Options for Configuration of
        SOL_MAX_RT
        Softwire Address and INF_MAX_RT"; Port-Mapped Clients";
      list br {
        key br-id;
        description "br info";
        leaf sol-max-rt-value br-id {
          type yang:timeticks; uint8;
          mandatory true;
          description "sol max rt value";
        } "br id";
        }
    container inf-max-rt-option {
      if-feature inf-max-rt-op;
      presence "Enable this option";
      description "OPTION_INF_MAX_RT (83) inf max rt option";
      reference "RFC7083: Modification to Default Values of
        SOL_MAX_RT and INF_MAX_RT";
        leaf inf-max-rt-value br-ipv6-addr {
          type yang:timeticks; inet:ipv6-address;
          mandatory true;
          description "inf max rt value"; "br ipv6 addr";
        }
      }
    }

    container addr-selection-option s46-dmr-option {
      if-feature addr-selection-op; s46-dmr-op;
      presence "Enable this option";
      description "OPTION_ADDRSEL (84) and OPTION_ADDRSEL_TABLE (85)"; "OPTION_S46_DMR (91) S46 DMR Option";
      reference "RFC7078: Distributing "RFC7598: DHCPv6 Options for Configuration of
        Softwire Address Selection Policy Using
      DHCPv6";
      // if - Needs checking to see if this matches the RFC - there
      // are two options here.
      // Zihao - I think this matches RFC7078 and Port-Mapped Clients";
      list dmr {
        key dmr-id;
        description "dmr info";
        leaf a-bit-set dmr-id {
          type boolean; uint8;
          mandatory true;
          description "a bit"; "dmr id";
        }
        leaf p-bit-set dmr-prefix-len {
          type boolean; uint8;
          mandatory true;
          description "p bit"; "dmr prefix length";
        }
      list policy-table {
        key policy-id;
        description "policy table";
        leaf policy-id dmr-ipv6-prefix {
          type uint8; inet:ipv6-prefix;
          mandatory true;
          description "policy id"; "dmr ipv6 prefix";
        }
      }
    }

    container s46-v4-v6-binding-option {
      if-feature s46-v4-v6-binding-op;
      presence "Enable this option";
      description "OPTION_S46_V4V6BIND (92) S46 IPv4/IPv6 Address
        Binding option";
      reference "RFC7598: DHCPv6 Options for Configuration of
        Softwire Address and Port-Mapped Clients";
      list ce {
        key ce-id;
        description "ce info";
        leaf label ce-id {
          type uint8;
          mandatory true;
          description "label"; "ce id";
        }
        leaf precedence ipv4-addr {
          type uint8; inet:ipv4-address;
          mandatory true;
          description "precedence"; "ce ipv4 addr";
        }
        leaf prefix-len bind-prefix6-len {
          type uint8;
          mandatory true;
          description "prefix "bind ipv6 prefix
            length";
        }
        leaf prefix bind-ipv6-prefix {
          type inet:ipv6-prefix;
          mandatory true;
          description "prefix"; "bind ipv6 prefix";
        }
        uses dhcpv6-types:portset-para;
      }
    }

  }
  //if - NB - The list of options needs to be updated.

  grouping relay-supplied-option-definitions {
    // if - The structure here needs to be checked and probably reworked.
    description "OPTION_RSOO (66) Relay-Supplied Options option";
    reference "RFC6422: Relay-Supplied DHCP Options";
    container pcp-server-option erp-local-domain-name-option {
      if-feature pcp-server-op; erp-local-domain-name-op;
      presence "Enable this option";
      description "OPTION_V6_PCP_SERVER (86)
        pcp server option"; "OPTION_ERP_LOCAL_DOMAIN_NAME (65) DHCPv6 ERP Local
        Domain Name Option";
      reference "RFC7291: DHCP Options for the Port Control "RFC6440: The EAP Re-authentication Protocol (PCP)"; (ERP)
        Local Domain Name DHCPv6 Option";

      list pcp-server erp-for-client {
        key pcp-serv-id; cli-id;
        description "pcp server info"; "erp for client";
        leaf pcp-serv-id cli-id {
          type uint8; uint32;
          mandatory true;
          description "pcp server "client id";
        }
        container duid {
          description "Sets the DUID";
          // uses duid;
          // if - Maybe DUID definition needs to be moved to this module.
          uses dhcpv6-types:duid;
        }
        leaf pcp-serv-addr erp-name {
          type inet:ipv6-address; string;
          mandatory true;
          description "pcp server addr"; "erp name";
        }
      }
    }
    container s46-rule-option
  }

  grouping client-option-definitions {
      if-feature s46-rule-op;
      presence "Enable this option";
    description "OPTION_S46_RULE (89) S46 rule option";
      reference "RFC7598: DHCPv6 Options "Contains definitions for Configuration of
        Softwire Address and Port-Mapped Clients"; options configured on the
      DHCPv6 client which will be sent to the server.";

    list s46-rule new-or-standard-cli-option {
      key rule-id; option-code;
      description "s46 rule"; "new or standard client option";
      leaf rule-id option-code {
        type uint8; uint16;
        mandatory true;
        description "rule id"; "option code";
      }
      leaf rule-type option-name {
        type enumeration {
            enum "BMR" { string;
        mandatory true;
        description "BMR"; "option name";
      }
          enum "FMR"
      leaf option-description {
            description "FMR";
          }
        }
        type string;
        mandatory true;
        description "rule type"; "description of client
          option";
      }
      leaf prefix4-len option-reference {
        type uint8;
        mandatory true; string;
        description "ipv4 prefix length"; "the reference of option";
      }
      leaf ipv4-prefix option-value {
        type inet:ipv4-prefix; string;
        mandatory true;
        description "ipv4 prefix"; "the option value";
      }
    }

    container option-request-option {
      if-feature option-request-op;
      presence "Enable this option";
      description "OPTION_ORO (6) Option Request Option";
      reference "RFC3315: Dynamic Host Configuration Protocol for
      IPv6 (DHCPv6)";
      list oro-option {
        key option-code;
        description "oro option";
        leaf prefix6-len option-code {
          type uint8; uint16;
          mandatory true;
          description "ipv6 prefix length"; "option code";
        }
        leaf ipv6-prefix description {
          type inet:ipv6-prefix; string;
          mandatory true;
          description "ipv6 prefix"; "description of oro
            options";
        }
        uses portset-para;
      }
    }

    container s46-br-option user-class-option {
      if-feature s46-br-op; user-class-op;
      presence "Enable this option";
      description "OPTION_S46_BR (90) S46 BR "OPTION_USER_CLASS (15) User Class Option";
      reference "RFC7598: DHCPv6 Options for "RFC3315: Dynamic Host Configuration of
        Softwire Address and Port-Mapped Clients"; Protocol
        for IPv6 (DHCPv6)";
      list br user-class {
        key br-id; user-class-id;
        description "br info"; "user class";
        leaf br-id user-class-id {
          type uint8;
          mandatory true;
          description "br "user class id";
        }
        leaf br-ipv6-addr user-class-data {
          type inet:ipv6-address; string;
          mandatory true;
          description "br ipv6 addr"; "The information contained in the data area
            of this option is contained in one or more opaque
            fields that represent the user class or classes of
            which the client is a member. ";
        }
      }
    }

    container s46-dmr-option vendor-class-option {
      if-feature s46-dmr-op; vendor-class-op;
      presence "Enable this option";
      description "OPTION_S46_DMR (91) S46 DMR "OPTION_VENDOR_CLASS (16) Vendor Class Option";
      reference "RFC7598: DHCPv6 Options for "RFC3315: Dynamic Host Configuration of
        Softwire Address and Port-Mapped Clients";
      list dmr {
        key dmr-id;
        description "dmr info"; Protocol
        for IPv6 (DHCPv6)";
      leaf dmr-id enterprise-number {
        type uint8; uint32;
        mandatory true;
        description "dmr id"; "enterprise number";
      }
      list vendor-class {
        key vendor-class-id;
        description "vendor class";
        leaf dmr-prefix-len vendor-class-id {
          type uint8;
          mandatory true;
          description "dmr prefix length"; "vendor class id";
        }
        leaf dmr-ipv6-prefix vendor-class-data {
          type inet:ipv6-prefix; string;
          mandatory true;
          description "dmr ipv6 prefix"; "The vendor-class-data is composed of a series of
            separate items, each of which describes some characteristic
            of the client's hardware configuration. Examples of
            vendor-class-data instances might include the version of the
            operating system the client is running or the amount of memory
            installed on the client.";
        }
      }
    }

    container s46-v4-v6-binding-option client-fqdn-option {
      if-feature s46-v4-v6-binding-op; client-fqdn-op;
      presence "Enable this option";
      description "OPTION_S46_V4V6BIND (92) S46 IPv4/IPv6 Address
        Binding option";
      reference "RFC7598: DHCPv6 Options "OPTION_CLIENT_FQDN (39) The Dynamic Host
        Configuration Protocol for IPv6 (DHCPv6) Client Fully
        Qualified Domain Name (FQDN) Option";
      reference "RFC4704: The Dynamic Host Configuration of
        Softwire Address and Port-Mapped Clients";
      list ce Protocol
        for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
        Option";
      leaf fqdn {
        key ce-id;
        type string;
        mandatory true;
        description "ce info"; "fqdn";
      }
      leaf ce-id server-initiate-update {
        type uint8; boolean;
        mandatory true;
        description "ce id"; "whether server initiate";
      }
      leaf ipv4-addr client-initiate-update {
        type inet:ipv4-address; boolean;
        mandatory true;
        description "ce ipv4 addr"; "whether client initiate";
      }
    }

    container client-arch-type-option {
      if-feature client-arch-type-op;
      presence "Enable this option";
      description "OPTION_CLIENT_ARCH_TYPE (61) Client System
        Architecture Type Option";
      reference "RFC5970: DHCPv6 Options for Network Boot";
      list architecture-types {
        key type-id;
        description "architecture types";
        leaf bind-prefix6-len type-id {
          type uint8; uint16;
          mandatory true;
          description "bind ipv6 prefix
            length"; "type id";
        }
        leaf bind-ipv6-prefix most-preferred {
          type inet:ipv6-prefix; boolean;
          mandatory true;
          description "bind ipv6 prefix";
        }
        uses portset-para; "most preferred flag";
        }
      }
    }
  //if - NB - The list of options needs to be updated.

  grouping relay-supplied-option-definitions {
    // if - The structure here needs to be checked and probably reworked.
    description "OPTION_RSOO (66) Relay-Supplied Options option";
    reference "RFC6422: Relay-Supplied DHCP Options";

    container erp-local-domain-name-option client-network-interface-identifier-option {
      if-feature erp-local-domain-name-op; client-network-interface-identifier-op;
      presence "Enable this option";
      description "OPTION_ERP_LOCAL_DOMAIN_NAME (65) DHCPv6 ERP Local
        Domain Name "OPTION_NII (62) Client Network Interface
        Identifier Option";
      reference "RFC6440: The EAP Re-authentication Protocol (ERP)
        Local Domain Name "RFC5970: DHCPv6 Option";
      list erp-for-client {
        key cli-id;
        description "erp Options for client"; Network Boot";
      leaf cli-id type {
        type uint32; uint8;
        mandatory true;
        description "client id"; "type";
      }
        container duid
      leaf major {
        type uint8;
        mandatory true;
        description "Sets the DUID";
          // uses duid;
          // if - Maybe DUID definition needs to be moved to this module.
          uses duid; "major";
      }
      leaf erp-name minor {
        type string; uint8;
        mandatory true;
        description "erp name";
        }
      } "minor";
      }
    }

  grouping client-option-definitions

    container kbr-principal-name-option {
      if-feature kbr-principal-name-op;
      presence "Enable this option";
      description "Contains definitions "OPTION_KRB_PRINCIPAL_NAME (75) Kerberos
        Principal Name Option";
      reference "RFC6784: Kerberos Options for options configured on the
      DHCPv6 client which will be sent to the server."; DHCPv6";
      list new-or-standard-cli-option principle-name {
        key option-code; principle-name-id;
        description "new or standard client option"; "principle name";
        leaf option-code principle-name-id {
          type uint16; uint8;
          mandatory true;
          description "option code"; "principle name id";
        }
        leaf option-name name-type {
          type string; int32;
          mandatory true;
          description "option name"; "This field specifies the type of name that follows.";
        }
        leaf option-description name-string {
          type string;
          mandatory true;
          description "description "This field encodes a sequence of client
          option"; components that form
            a name, each component encoded as a KerberoString";
        }
      leaf option-reference
      }
    }

    container kbr-realm-name-option {
        type string;
      if-feature kbr-realm-name-op;
      presence "Enable this option";
      description "the "OPTION_KRB_REALM_NAME (76) Kerberos Realm Name Option";
      reference of option";
      } "RFC6784: Kerberos Options for DHCPv6";
      leaf option-value realm-name {
        type string;
        mandatory true;
        description "the option value"; "realm name";
      }
    }

    container option-request-option client-link-layer-addr-option {
      if-feature option-request-op; client-link-layer-addr-op;
      presence "Enable this option";
      description "OPTION_ORO (6) Option Request "OPTION_CLIENT_LINKLAYER_ADDR (79) DHCPv6 Client
        Link-Layer Address Option";
      reference "RFC3315: Dynamic Host Configuration Protocol
      for IPv6 (DHCPv6)";
      list oro-option {
        key option-code;
        description "oro option"; "RFC6939: Client Link-Layer Address Option in
        DHCPv6";
      leaf option-code link-layer-type {
        type uint16;
        mandatory true;
        description "option code"; "Client link-layer address type. The link-layer
          type MUST be a valid hardware type assigned by the IANA,
          as described in [RFC0826]";
      }
      leaf description link-layer-addr {
        type string;
        mandatory true;
        description "description of oro
            options"; "Client link-layer address";
      }
    }

  }

  grouping custom-option-definitions {
    description "operator customized options";

    container user-class-option operator-option-ipv6-address {
      if-feature user-class-op; operator-op-ipv6-address;
      presence "Enable this option";
      description "OPTION_USER_CLASS (15) User Class Option"; "operator ipv6 address option";
      reference "RFC3315: Dynamic Host Configuration Protocol "RFC7227: Guidelines for IPv6 (DHCPv6)"; Creating New DHCPv6 Options";
      list user-class operator-ipv6-addr {
        key user-class-id; operator-ipv6-addr-id;
        description "user class"; "operator ipv6 address info";
        leaf user-class-id operator-ipv6-addr-id {
          type uint8;
          mandatory true;
          description "user class "operator ipv6 address id";
        }
        leaf user-class-data operator-ipv6-addr {
          type string; inet:ipv6-address;
          mandatory true;
          description "The information contained in the data area
            of "operator ipv6 address id";
        }
      }
    }

    container operator-option-single-flag {
      if-feature operator-op-single-flag;
      presence "Enable this option is contained in one or more opaque
            fields that represent the user class or classes of
            which the client is a member. "; option";
      description "operator single flag";
      reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list flag {
        key flag-id;
        description "operator single flag info";
        leaf flag-id {
          type uint8;
          mandatory true;
          description "operator single flag id";
        }
        leaf flag-value{
          type boolean;
          mandatory true;
          description "operator single flag value";
        }
      }
    }

    container vendor-class-option operator-option-ipv6-prefix {
      if-feature vendor-class-op; operator-op-ipv6-prefix;
      presence "Enable this option";
      description "OPTION_VENDOR_CLASS (16) Vendor Class Option"; "operator ipv6 prefix option";
      reference "RFC3315: Dynamic Host Configuration Protocol "RFC7227: Guidelines for IPv6 (DHCPv6)"; Creating New DHCPv6
        Options";
      list operator-ipv6-prefix {
        key operator-ipv6-prefix-id;
        description "operator ipv6 prefix info";
        leaf enterprise-number operator-ipv6-prefix-id {
          type uint32; uint8;
          mandatory true;
          description "enterprise number"; "operator ipv6 prefix id";
        }
      list vendor-class {
        key vendor-class-id;
        description "vendor class";
        leaf vendor-class-id operator-ipv6-prefix6-len {
          type uint8;
          mandatory true;
          description "vendor class id"; "operator ipv6 prefix length";

        }
        leaf vendor-class-data operator-ipv6-prefix {
          type string; inet:ipv6-prefix;
          mandatory true;
          description "The vendor-class-data is composed of a series
                  of separate items, each of which describes some
                  characteristic of the client's hardware configuration.
                  Examples of vendor-class-data instances might include the
                  version of the operating system the client is running or
                  the amount of memory installed on the client."; "operator ipv6 prefix";
        }
      }
    }

    container client-fqdn-option operator-option-int32 {
      if-feature client-fqdn-op; operator-op-int32;
      presence "Enable this option";
      description "OPTION_CLIENT_FQDN (39) The Dynamic Host
        Configuration Protocol for IPv6 (DHCPv6) Client Fully
        Qualified Domain Name (FQDN) Option"; "operator integer 32 option";
      reference "RFC4704: The Dynamic Host Configuration Protocol "RFC7227: Guidelines for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
        Option";
      leaf fqdn Creating New DHCPv6
        Options";
      list int32val {
        type string;
        mandatory true;
        key int32val-id;
        description "fqdn";
      } "operator integer 32 info";
        leaf server-initiate-update int32val-id {
          type boolean; uint8;
          mandatory true;
          description "whether server initiate"; "operator integer 32 id";
        }
        leaf client-initiate-update int32val {
          type boolean; uint32;
          mandatory true;
          description "whether client initiate"; "operator integer 32 value";
        }
      }
    }

    container client-arch-type-option operator-option-int16 {
      if-feature client-arch-type-op; operator-op-int16;
      presence "Enable this option";
      description "OPTION_CLIENT_ARCH_TYPE (61) Client System
        Architecture Type Option"; "operator integer 16 option";
      reference "RFC5970: DHCPv6 Options "RFC7227: Guidelines for Network Boot"; Creating New DHCPv6
        Options";
      list architecture-types int16val {
        key type-id; int16val-id;
        description "architecture types"; "operator integer 16 info";
        leaf type-id int16val-id {
          type uint16; uint8;
          mandatory true;
          description "type "operator integer 16 id";
        }
        leaf most-preferred int16val {
          type boolean; uint16;
          mandatory true;
          description "most preferred flag"; "operator integer 16 value";
        }
      }
    }

    container client-network-interface-identifier-option operator-option-int8 {
      if-feature client-network-interface-identifier-op; operator-op-int8;
      presence "Enable this option";
      description "OPTION_NII (62) Client Network Interface
        Identifier Option"; "operator integer 8 option";
      reference "RFC5970: DHCPv6 Options "RFC7227: Guidelines for Network Boot";
      leaf type Creating New DHCPv6
        Options";
      list int8val {
        type uint8;
        mandatory true;
        key int8val-id;
        description "type";
      } "operator integer 8 info";
        leaf major int8val-id {
          type uint8;
          mandatory true;
          description "major"; "operator integer 8 id";
        }
        leaf minor int8val {
          type uint8;
          mandatory true;
          description "minor"; "operator integer 8 value";
        }
      }
    }

    container kbr-principal-name-option operator-option-uri {
      if-feature kbr-principal-name-op; operator-op-uri;
      presence "Enable this option";
      description "OPTION_KRB_PRINCIPAL_NAME (75) Kerberos
        Principal Name Option"; "operator uri option";
      reference "RFC6784: Kerberos Options "RFC7227: Guidelines for DHCPv6"; Creating New DHCPv6 Options";
      list principle-name { uri{
        key principle-name-id; uri-id;
        description "principle name"; "operator uri info";
        leaf principle-name-id uri-id {
          type uint8;
          mandatory true;
          description "principle name "operator uri id";
        }
        leaf name-type {
          type int32;
          mandatory true;
          description "This field specifies the type of name that follows.";
        }
        leaf name-string uri {
          type string;
          mandatory true;
          description "This field encodes a sequence of components that form
            a name, each component encoded as a KerberoString"; "operator uri value";
        }
      }
    }
    container kbr-realm-name-option operator-option-textstring {
      if-feature kbr-realm-name-op; operator-op-textstring;
      presence "Enable this option";
      description "OPTION_KRB_REALM_NAME (76) Kerberos Realm Name Option"; "operator itext string option";
      reference "RFC6784: Kerberos Options "RFC7227: Guidelines for DHCPv6"; Creating New DHCPv6 Options";
      list textstring{
        key textstring-id;
        description "operator text string info";
        leaf realm-name textstring-id {
          type uint8;
          mandatory true;
          description "operator text string id";
        }
        leaf textstring {
          type string;
          mandatory true;
          description "realm name"; "operator text string value";
        }
      }
    }

    container client-link-layer-addr-option operator-option-var-data {
      if-feature client-link-layer-addr-op; operator-op-var-data;
      presence "Enable this option";
      description "OPTION_CLIENT_LINKLAYER_ADDR (79) DHCPv6 Client
        Link-Layer Address Option"; "operator variable length data option";
      reference "RFC6939: Client Link-Layer Address Option in
        DHCPv6"; "RFC7227: Guidelines for Creating New DHCPv6 Options";
      list int32val {
        key var-data-id;
        description "operator ivariable length data info";
        leaf link-layer-type var-data-id {
          type uint16; uint8;
          mandatory true;
          description "Client link-layer address type. The link-layer
          type MUST be a valid hardware type assigned by the IANA,
          as described in [RFC0826]"; "operator variable length id";
        }
        leaf link-layer-addr var-data {
          type string; binary;
          mandatory true;
          description "Client link-layer address"; "operator variable length value";
        }
      }
    }

  grouping custom-option-definitions {
  description "operator customized options";

    container operator-option-ipv6-address operator-option-dns-wire {
      if-feature operator-op-ipv6-address; operator-op-dns-wire;
      presence "Enable this option";
      description "operator ipv6 address dns wire format domain name list option";
      reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";

      list operator-ipv6-addr operator-option-dns-wire {
        key operator-ipv6-addr-id; operator-option-dns-wire-id;
        description "operator ipv6 address dns wire format info";
        leaf operator-ipv6-addr-id operator-option-dns-wire-id {
          type uint8;
          mandatory true;
          description "operator ipv6 address dns wire format id";
        }
        leaf operator-ipv6-addr operator-option-dns-wire{
          type binary;
          mandatory true;
          description "operator dns wire format value";
        }
      }
    }
  }
}
<CODE ENDS>

3.5.  DHCPv6 Types YANG Model

   This module imports typedefs from [RFC6991].

<CODE BEGINS> file "ietf-dhcpv6-types.yang"
module ietf-dhcpv6-types {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv6-types";
  prefix "dhcpv6-types";

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

  organization "DHC WG";
  contact
   "cuiyong@tsinghua.edu.cn
    lh.sunlinh@gmail.com
    ian.farrer@telekom.de
    sladjana.zechlin@telekom.de
    hezihao9512@gmail.com";

  description "This model defines a YANG data model that can be
    used to define some commonly used DHCPv6 types";

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

  /*
  * Grouping
  */
  grouping vendor-infor {
    description "Vendor information.";
    container vendor-info {
      description "";
      leaf ent-num {
        type uint32;
        mandatory true;
        description "enterprise number";
      }
      leaf-list data {
        type string;
        description "specific vendor info";
      }
    }
  }

  grouping duid {
    description
      "Each server and client has only one DUID (DHCP Unique Identifier).
      The DUID here identifies a unique DHCPv6 server for clients. DUID
      consists of a two-octet type field and an arbitrary length (no more
      than 128 bytes) content field. Currently there are four defined types
      of DUIDs in RFC3315 and RFC6355 - DUID-LLT, DUID-EN, DUID-LL and
      DUID-UUID. DUID-Uknown represents those unconventional DUIDs.";
    reference "RFC3315: Section 9 and RFC6355: Section 4";
    leaf type-code {
      type inet:ipv6-address;
          mandatory true; uint16;
      default 65535;
      description "operator ipv6 address id";
        }
      } "Type code of this DUID";
    }
    container operator-option-single-flag
    choice duid-type {
      if-feature operator-op-single-flag;
      presence "Enable this option";
    default duid-unknown;
      description "operator single flag";
      reference "RFC7227: Guidelines "Selects the format for Creating New DHCPv6
        Options";

      list flag the DUID.";
      case duid-llt {
        key flag-id;
        description "operator single flag info"; "DUID Based on Link-layer Address Plus Time
          (Type 1 - DUID-LLT)";
        reference "RFC3315 Section 9.2";
        leaf flag-id duid-llt-hardware-type {
          type uint8;
          mandatory true; uint16;
          description "operator single flag id";
        }
        leaf flag-value{ "Hardware type boolean;
          mandatory true;
          description "operator single flag value";
        }
      } as assigned by IANA (RFC826).";
        }
    container operator-option-ipv6-prefix {
      if-feature operator-op-ipv6-prefix;
      presence "Enable this option";
      description "operator ipv6 prefix option";
      reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list operator-ipv6-prefix{
        key operator-ipv6-prefix-id;
        description "operator ipv6 prefix info";
        leaf operator-ipv6-prefix-id duid-llt-time {
          type uint8;
          mandatory true;
          description "operator ipv6 prefix id";
        }
        leaf operator-ipv6-prefix6-len{
          type uint8;
          mandatory true; yang:timeticks;
          description "operator ipv6 prefix length"; "The time value is the time that the DUID is
          generated represented in seconds since midnight (UTC),
          January 1, 2000, modulo 2^32.";
        }
        leaf operator-ipv6-prefix duid-llt-link-layer-addr {
          type inet:ipv6-prefix;
          mandatory true; yang:mac-address;
          description "operator ipv6 prefix";
        } "Link-layer address as described in RFC2464";
        }
      }
    container operator-option-int32
      case duid-en {
      if-feature operator-op-int32;
      presence "Enable this option";
        description "operator integer 32 option"; "DUID Assigned by Vendor Based on Enterprise Number
          (Type 2 - DUID-EN)";
        reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list int32val{
        key int32val-id;
        description "operator integer 32 info"; "RFC3315 Section 9.3";
        leaf int32val-id duid-en-enterprise-number {
          type uint8;
          mandatory true; uint32;
          description "operator integer 32 id"; "Vendor's registered Private Enterprise Number as
            maintained by IANA";
        }
        leaf int32val{ duid-en-identifier {
          type uint32;
          mandatory true; string;
          description "operator integer 32 value";
        } "Indentifier, unique to the device that is
          using it";
        }
      }
    container operator-option-int16
      case duid-ll {
      if-feature operator-op-int16;
      presence "Enable this option";
          description "operator integer 16 option"; "DUID Based on Link-layer Address (Type 3 - DUID-LL)";
          reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list int16val{
        key int16val-id;
        description "operator integer 16 info"; "RFC3315 Section 9.4";
          leaf int16val-id duid-ll-hardware-type {
            type uint8;
          mandatory true; uint16;
            description "operator integer 16 id"; "Hardware type as assigned by IANA (RFC826).";
          }
          leaf int16val{ duid-ll-link-layer-addr {
            type uint16;
          mandatory true; yang:mac-address;
            description "operator integer 16 value";
        } "Link-layer address as described in RFC2464";
        }
      }
    container operator-option-int8
      case duid-uuid {
      if-feature operator-op-int8;
      presence "Enable this option";
        description "operator integer 8 option"; "DUID Based on Universally Unique Identifier
          (Type 4 - DUID-UUID)";
        reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list int8val{
        key int8val-id;
        description "operator integer 8 info"; "RFC6335 Defination of the UUID-Based Unique Identifier";
        leaf int8val-id uuid {
          type uint8;
          mandatory true; yang:uuid;
          description "operator integer 8 id"; "A Universally Unique IDentifier in the string
            representation defined in RFC 4122. The canonical
            representation uses lowercase characters";
        }

      }
      case duid-unknown {
        description "DUID based on free raw bytes";
        leaf int8val{ data {
          type uint8;
          mandatory true; binary;
          description "operator integer 8 value"; "The bits to be used as the identifier";
        }
      }
    }
  }

  grouping portset-para {
    description "portset parameters";
    container operator-option-uri port-parameter {
      if-feature operator-op-uri;
      presence "Enable this option";
      description "operator uri option";
      reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list uri{
        key uri-id; "port parameter";
      leaf offset {
        type uint8;
        mandatory true;
        description "operator uri info"; "offset in a port set";
      }
      leaf uri-id psid-len {
        type uint8;
        mandatory true;
        description "operator uri id"; "length of a psid";
      }
      leaf uri{ psid {
        type string; uint16;
        mandatory true;
        description "operator uri "psid value";
      }
    }
  }
    container operator-option-textstring

  grouping iaid {
      if-feature operator-op-textstring;
      presence "Enable this option";
    description "operator itext string option";
      reference "RFC7227: Guidelines for Creating New DHCPv6 Options";
      list textstring{ "IA is a construct through which a server and a
        client can identify, group, and manage a set of related IPv6
        addresses. The key textstring-id; of the list is a 4-byte number IAID defined
        in [RFC3315].";
    list identity-association {
      config "false";
      description "operator text string info"; "IA";
      leaf textstring-id iaid {
        type uint8; uint32;
        mandatory true;
        description "operator text string id"; "IAID";
      }
      leaf textstring{ ia-type {
        type string;
        mandatory true;
        description "operator text string value";
        } "IA type";
      }
      leaf-list ipv6-addr {
        type inet:ipv6-address;
        description "ipv6 address";
      }
    container operator-option-var-data
      leaf-list ipv6-prefix {
      if-feature operator-op-var-data;
      presence "Enable this option";
        type inet:ipv6-prefix;
        description "operator variable length data option";
      reference "RFC7227: Guidelines for Creating New DHCPv6 Options";
      list int32val{
        key var-data-id; "ipv6 prefix";
      }
      leaf-list prefix-length {
        type uint8;
        description "operator ivariable length data info"; "ipv6 prefix length";
      }
      leaf var-data-id t1-time {
        type uint8; yang:timeticks;
        mandatory true;
        description "operator variable length id"; "t1 time";
      }
      leaf var-data{ t2-time {
        type binary; yang:timeticks;
        mandatory true;
        description "operator variable length value";
        }
      } "t2 time";
      }
    container operator-option-dns-wire {
      if-feature operator-op-dns-wire;
      presence "Enable this option";
      description "operator dns wire format domain name list option";
      reference "RFC7227: Guidelines for Creating New DHCPv6
        Options";
      list operator-option-dns-wire{
        key operator-option-dns-wire-id;
        description "operator dns wire format info";
      leaf operator-option-dns-wire-id preferred-lifetime {
        type uint8; yang:timeticks;
        mandatory true;
        description "operator dns wire format id"; "preferred lifetime";
      }
      leaf operator-option-dns-wire{ valid-lifetime {
        type binary; yang:timeticks;
        mandatory true;
        description "operator dns wire format value";
        } "valid lifetime";
      }
    }
  }
}
<CODE ENDS>

4.  Security Considerations (TBD)

   TBD

5.  IANA Considerations (TBD)

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

   name:           ietf-dhcpv6
   namespace:      urn:ietf:params:xml:ns:yang:ietf-dhcpv6
   prefix:         dhcpv6
   reference:      TBD

6.  Acknowledgements

   The authors would like to thank Qi Sun, Lishan Li, Sladjana Zoric,
   Tomek Mrugalski, Marcin Siodelski, Bernie Volz and Bing Liu for their
   valuable comments and contributions to this work.

7.  Contributors

   The following individuals contributed to this effort:
     Hao Wang
     Tsinghua University
     Beijing 100084
     P.R.China
     Phone: +86-10-6278-5822
     Email: wangh13@mails.tsinghua.edu.cn

     Ted Lemon
     Nomium, Inc
     950 Charter St.
     Redwood City, CA 94043
     USA
     Email: Ted.Lemon@nomium.com

     Bernie Volz
     Cisco Systems, Inc.
     1414 Massachusetts Ave
     Boxborough, MA 01719
     USA
     Email: volz@cisco.com

8.  References
8.1.  Normative References

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

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <https://www.rfc-editor.org/info/rfc3315>.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              DOI 10.17487/RFC3633, December 2003,
              <https://www.rfc-editor.org/info/rfc3633>.

   [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>.

   [RFC6087]  Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", RFC 6087, DOI 10.17487/RFC6087,
              January 2011, <https://www.rfc-editor.org/info/rfc6087>.

   [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>.

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

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
              <https://www.rfc-editor.org/info/rfc7223>.

8.2.  Informative References

   [I-D.ietf-netmod-yang-tree-diagrams]
              Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
              ietf-netmod-yang-tree-diagrams-04
              ietf-netmod-yang-tree-diagrams-06 (work in progress),
              December 2017.
              February 2018.

   [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>.

   [RFC3646]  Droms, R., Ed., "DNS Configuration options for Dynamic
              Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              DOI 10.17487/RFC3646, December 2003,
              <https://www.rfc-editor.org/info/rfc3646>.

   [RFC3898]  Kalusivalingam, V., "Network Information Service (NIS)
              Configuration Options for Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6)", RFC 3898,
              DOI 10.17487/RFC3898, October 2004,
              <https://www.rfc-editor.org/info/rfc3898>.

   [RFC4075]  Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
              Configuration Option for DHCPv6", RFC 4075,
              DOI 10.17487/RFC4075, May 2005,
              <https://www.rfc-editor.org/info/rfc4075>.

   [RFC4242]  Venaas, S., Chown, T., and B. Volz, "Information Refresh
              Time Option for Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 4242, DOI 10.17487/RFC4242, November
              2005, <https://www.rfc-editor.org/info/rfc4242>.

   [RFC4704]  Volz, B., "The Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
              Option", RFC 4704, DOI 10.17487/RFC4704, October 2006,
              <https://www.rfc-editor.org/info/rfc4704>.

   [RFC4833]  Lear, E. and P. Eggert, "Timezone Options for DHCP",
              RFC 4833, DOI 10.17487/RFC4833, April 2007,
              <https://www.rfc-editor.org/info/rfc4833>.

   [RFC5908]  Gayraud, R. and B. Lourdelet, "Network Time Protocol (NTP)
              Server Option for DHCPv6", RFC 5908, DOI 10.17487/RFC5908,
              June 2010, <https://www.rfc-editor.org/info/rfc5908>.

   [RFC5970]  Huth, T., Freimann, J., Zimmer, V., and D. Thaler, "DHCPv6
              Options for Network Boot", RFC 5970, DOI 10.17487/RFC5970,
              September 2010, <https://www.rfc-editor.org/info/rfc5970>.

   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, DOI 10.17487/RFC6334, August 2011,
              <https://www.rfc-editor.org/info/rfc6334>.

   [RFC6422]  Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options",
              RFC 6422, DOI 10.17487/RFC6422, December 2011,
              <https://www.rfc-editor.org/info/rfc6422>.

   [RFC6440]  Zorn, G., Wu, Q., and Y. Wang, "The EAP Re-authentication
              Protocol (ERP) Local Domain Name DHCPv6 Option", RFC 6440,
              DOI 10.17487/RFC6440, December 2011,
              <https://www.rfc-editor.org/info/rfc6440>.

   [RFC6784]  Sakane, S. and M. Ishiyama, "Kerberos Options for DHCPv6",
              RFC 6784, DOI 10.17487/RFC6784, November 2012,
              <https://www.rfc-editor.org/info/rfc6784>.

   [RFC6939]  Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
              Address Option in DHCPv6", RFC 6939, DOI 10.17487/RFC6939,
              May 2013, <https://www.rfc-editor.org/info/rfc6939>.

   [RFC7078]  Matsumoto, A., Fujisaki, T., and T. Chown, "Distributing
              Address Selection Policy Using DHCPv6", RFC 7078,
              DOI 10.17487/RFC7078, January 2014,
              <https://www.rfc-editor.org/info/rfc7078>.

   [RFC7083]  Droms, R., "Modification to Default Values of SOL_MAX_RT
              and INF_MAX_RT", RFC 7083, DOI 10.17487/RFC7083, November
              2013, <https://www.rfc-editor.org/info/rfc7083>.

   [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
              <https://www.rfc-editor.org/info/rfc7227>.

   [RFC7291]  Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
              the Port Control Protocol (PCP)", RFC 7291,
              DOI 10.17487/RFC7291, July 2014,
              <https://www.rfc-editor.org/info/rfc7291>.

   [RFC7598]  Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
              W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
              Configuration of Softwire Address and Port-Mapped
              Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
              <https://www.rfc-editor.org/info/rfc7598>.

Authors' Addresses
   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn cuiyong@tsinghua.edu.cn

   Linhui Sun
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5822
   Email: lh.sunlinh@gmail.com

   Ian Farrer
   Deutsche Telekom AG
   CTO-ATI, Landgrabenweg 151
   Bonn, NRW  53227
   Germany

   Email: ian.farrer@telekom.de

   Sladjana Zechlin
   Deutsche Telekom AG
   CTO-IPT, Landgrabenweg 151
   Bonn, NRW  53227
   Germany

   Email: sladjana.zechlin@telekom.de

   Zihao He
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5822
   Email: hezihao9512@gmail.com