YANG Modules for IPv4-in-IPv6 Address plus Port Softwires
draft-ietf-softwire-yang-07

The information below is for an old version of the document
Document Type Active Internet-Draft (softwire WG)
Last updated 2018-10-22
Replaces draft-sun-softwire-yang
Stream IETF
Intended RFC status Proposed Standard
Formats plain text pdf html bibtex
Stream WG state Submitted to IESG for Publication
Document shepherd Sheng Jiang
Shepherd write-up Show (last changed 2018-08-21)
IESG IESG state Waiting for Writeup
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Responsible AD Terry Manderson
Send notices to Sheng Jiang <jiangsheng@huawei.com>
IANA IANA review state Version Changed - Review Needed
IANA action state None
Softwire Working Group                                            Y. Cui
Internet-Draft                                       Tsinghua University
Intended status: Standards Track                               I. Farrer
Expires: April 25, 2019                              Deutsche Telekom AG
                                                            M. Boucadair
                                                                  Orange
                                                                  Q. Sun
                                                                  L. Sun
                                                     Tsinghua University
                                                              S. Zechlin
                                                     Deutsche Telekom AG
                                                                R. Asati
                                                     Cisco Systems, Inc.
                                                        October 22, 2018

       YANG Modules for IPv4-in-IPv6 Address plus Port Softwires
                      draft-ietf-softwire-yang-07

Abstract

   This document defines YANG modules for the configuration and
   operation of IPv4-in-IPv6 softwire Border Relays and Customer
   Premises Equipment for the Lightweight 4over6, MAP-E, and MAP-T
   softwire mechanisms.

Editorial Note (To be removed by RFC Editor)

   Please update these statements within this document with the RFC
   number to be assigned to this document:

   o  "This version of this YANG module is part of RFC XXXX;"

   o  "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
      Softwires";

   o  "reference: RFC XXXX"

   Please update the "revision" date of the YANG module.

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-

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   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 April 25, 2019.

Copyright Notice

   Copyright (c) 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview of the Modules . . . . . . . . . . . . . . . . . . .   4
     2.1.  Overall Structure . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Additional Components Configuration . . . . . . . . . . .   5
   3.  Softwire CE YANG Tree Diagram . . . . . . . . . . . . . . . .   6
     3.1.  CE Tree Diagram . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Softwire CE Tree Diagram Description  . . . . . . . . . .   8
   4.  Softwire BR YANG Tree Diagram . . . . . . . . . . . . . . . .   9
     4.1.  BR Tree Diagram . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  Softwire BR Tree Diagram Description  . . . . . . . . . .  13
   5.  IANA Tunnel Type YANG Module  . . . . . . . . . . . . . . . .  13
   6.  Tunnel Extension to the Interface YANG Module . . . . . . . .  16
   7.  Softwire CE YANG Module . . . . . . . . . . . . . . . . . . .  18
   8.  BR Softwire YANG Module . . . . . . . . . . . . . . . . . . .  23
   9.  Common Softwire Element Groups YANG Module  . . . . . . . . .  35
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  43
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  43
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  45
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  45
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  46
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  46

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     14.2.  Informative References . . . . . . . . . . . . . . . . .  47
   Appendix A.  Configutation Examples . . . . . . . . . . . . . . .  48
     A.1.  Configuration Example for a lw4o6 BR Binding-Table  . . .  48
     A.2.  Configuration Example for a MAP-E BR  . . . . . . . . . .  49
     A.3.  lw4o6 CE Configuration Example  . . . . . . . . . . . . .  51
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  54

1.  Introduction

   The IETF softwire working group has developed several IPv4-in-IPv6
   softwire mechanisms to address various deployment contexts and
   constraints.  As a companion to the architectural specification
   documents, this document focuses on the provisioning of address plus
   port (A+P) softwire functional elements: Border Routers (BRs) and
   Customer Premises Equipment (CEs, a.k.a., CPE).  The softwire
   mechanisms covered in this document are Lightweight 4 over 6
   [RFC7596], MAP-E [RFC7597], and MAP-T [RFC7599].

   This document focuses on A+P mechanisms; the reader can refer to
   [I-D.ietf-softwire-dslite-yang] for a YANG module for DS-Lite
   [RFC6333].

   This document defines YANG data modules [RFC7950] that can be used to
   configure and manage A+P softwire elements using the NETCONF protocol
   [RFC6241] for:

   o  Configuration

   o  Operational State

   o  Notifications

1.1.  Terminology

   The reader should be familiar with the concepts and terms defined in
   [RFC7596], [RFC7597], [RFC7599], and the YANG data modelling language
   defined in [RFC7950].

   The adopts the Network Management Datastore Architecture (NMDA)
   [RFC8342].  The meaning of the symbols in tree diagrams is defined in
   [RFC8340].

   The document uses BR to refer to MAP BR [RFC7597] or Lightweight
   4over6 BR [RFC7596].

   For simplicity, "algorithm" is used to refer to "mapping algorithm"
   [RFC7597].

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2.  Overview of the Modules

2.1.  Overall Structure

   This document specifies the initial version of an IANA-maintained
   module to identify a collection of tunnel types assigned by IANA
   (Section 5).  Furthermore, the document augments the Interface YANG
   module [RFC8343] with a new parameter which is meant to indicate the
   type of a given tunnel (Section 6).  The tree structure of this
   extension is shown below:

   module: ietf-interface-tunnel
     augment /if:interfaces/if:interface:
       +--rw tunnel-type?   identityref

   Moreover, the document defines the following two YANG data modules
   for the configuration and monitoring of softwire functional elements:

   ietf-softwire-ce      Provides configuration and monitoring for
                         softwire CE element.  This module is defined as
                         augments to the interface YANG module
                         [RFC8343].

   ietf-softwire-br      Provides configuration and monitoring for
                         softwire BR element.

   In addition, the following module is defined:

   ietf-softwire-common  Contains groups of common functions that are
                         imported into the CE and BR modules.

   This approach has been taken so that the various modules can be
   easily extended to support additional softwire mechanisms, if
   required.

   Within the BR and CE modules, the YANG "feature" statement is used to
   distinguish which of the different softwire mechanism(s) is relevant
   for a specific element's configuration.  For each module, a choice
   statement 'ce-type' is included for either 'binding' or 'algorithm'.
   'Binding' is used for configuring Lightweight 4over6, whereas
   'algorithm' is used for configuring MAP-T or MAP-E.

   In the 'algo-instances' container, a choice statement 'data-plane' is
   included to specify MAP-E (encapsulation) or MAP-T (translation).
   Table 1 shows how these choices are used to indicate the desired
   softwire mechanism:

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            +--------------------+-----------+---------------+
            |   S46 Mechanism    |  ce-type? |  data-plane?  |
            +--------------------+-----------+---------------+
            | Lightweight 4over6 |  binding  |      n/a      |
            |       MAP-E        | algorithm | encapsulation |
            |       MAP-T        | algorithm |  translation  |
            +--------------------+-----------+---------------+

         Table 1: Softwire Mechanism Choice Statement Enumeration

   NETCONF notifications are also included.

      Note: Earlier versions of this specification combined the softwire
      mechanisms by their associated technologies rather than their
      function in the architecture.  As the document was revised, it
      became apparent that dividing the modules by their role in the
      architecture (CE or BR) was a better approach as this follows the
      intended function and existing implementation approaches more
      closely.

2.2.  Additional Components Configuration

   The softwire modules only aim to provide configuration relevant for
   softwires.  In order to fully provision a CE element, the following
   may also be necessary:

   o  IPv6 forwarding and routing configuration, to enable CE to obtain
      one or more IPv6 prefixes for softwire usage.  A YANG module for
      routing management is described in [RFC8349].

   o  IPv4 routing configuration, to add one or more IPv4 destination
      prefix(es) reachable via the configured softwire.  A YANG module
      for routing management is described in [RFC8349].

   o  Stateful NAT44/NAPT management, to optionally specify a port set
      (Port Set Identifier (PSID)) along with its length.  A YANG module
      for NAT management is described in [I-D.ietf-opsawg-nat-yang].

   o  Stateless NAT46 management, required by softwire translation based
      mechanisms (i.e., the assignment of a Network-Specific Prefix to
      use for IPv4/IPv6 translation).  A YANG module for NAT management
      is described in [I-D.ietf-opsawg-nat-yang].

   As YANG modules for the above functions are already defined in other
   documents, their functionality is not duplicated here and they should
   be referred to, as needed.  Appendix A.3 provides XML examples of how
   these modules can be used together.

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   The CE must already have minimal IPv6 configuration in place so it is
   reachable by the NETCONF client to obtain softwire configuration.  If
   additional IPv6 specific configuration is necessary, the YANG modules
   defined in [RFC8344] and [RFC8349] may be used.

3.  Softwire CE YANG Tree Diagram

3.1.  CE Tree Diagram

   The CE module provides configuration and monitoring for all of the
   softwire mechanisms covered in this document (i.e., Lightweight
   4over6, MAP-E, and MAP-T).

   This module augments "ietf-interfaces", defined in [RFC8343] with an
   entry for the softwire.  This entry can be referenced to configure
   IPv4 forwarding features for the element.

   Figure 1 describes the tree structure of the softwire CE YANG module.

     module: ietf-softwire-ce
       augment /if:interfaces/if:interface:
         +--rw softwire-payload-mtu?   uint16
         +--rw softwire-path-mru?      uint16
         +--rw (ce-type)?
            +--:(binding) {binding-mode}?
            |  +--rw binding-ipv6info?       union
            |  +--rw br-ipv6-addr            inet:ipv6-address
            +--:(algo) {map-e or map-t}?
               +--rw algo-instances
                  +--rw algo-instance* [id]
                     +--rw id                  uint32
                     +--rw enable?             boolean
                     +--rw algo-versioning
                     |  +--rw version?   uint64
                     |  +--rw date?      yang:date-and-time
                     +--rw name?               string
                     +--rw (data-plane)?
                     |  +--:(encapsulation) {map-e}?
                     |  |  +--rw br-ipv6-addr        inet:ipv6-address
                     |  +--:(translation) {map-t}?
                     |     +--rw dmr-ipv6-prefix?    inet:ipv6-prefix
                     +--rw ea-len              uint8
                     +--rw rule-ipv6-prefix    inet:ipv6-prefix
                     +--rw rule-ipv4-prefix    inet:ipv4-prefix
                     +--rw forwarding          boolean
       augment /if:interfaces/if:interface/if:statistics:
            +--ro sent-ipv4-packets?
            |       yang:zero-based-counter64

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            +--ro sent-ipv4-bytes?
            |       yang:zero-based-counter64
            +--ro sent-ipv6-packets?
            |       yang:zero-based-counter64
            +--ro sent-ipv6-bytes?
            |       yang:zero-based-counter64
            +--ro rcvd-ipv4-packets?
            |       yang:zero-based-counter64
            +--ro rcvd-ipv4-bytes?
            |       yang:zero-based-counter64
            +--ro rcvd-ipv6-packets?
            |       yang:zero-based-counter64
            +--ro rcvd-ipv6-bytes?
            |       yang:zero-based-counter64
            +--ro dropped-ipv4-packets?
            |       yang:zero-based-counter64
            +--ro dropped-ipv4-bytes?
            |       yang:zero-based-counter64
            +--ro dropped-ipv6-packets?
            |       yang:zero-based-counter64
            +--ro dropped-ipv6-bytes?
            |       yang:zero-based-counter64
            +--ro dropped-ipv4-fragments?
            |       yang:zero-based-counter64
            +--ro dropped-ipv4-fragment-bytes?
            |       yang:zero-based-counter64
            +--ro ipv6-fragments-reassembled?
            |       yang:zero-based-counter64
            +--ro ipv6-fragments-bytes-reassembled?
            |       yang:zero-based-counter64
            +--ro out-icmpv4-error-packets?
            |       yang:zero-based-counter64
            +--ro out-icmpv4-error-bytes?
            |       yang:zero-based-counter64
            +--ro out-icmpv6-error-packets?
            |       yang:zero-based-counter64
            +--ro out-icmpv6-error-bytes?
                    yang:zero-based-counter64

       notifications:
         +---n softwire-ce-event {binding-mode}?
            +--ro ce-binding-ipv6-addr-change    inet:ipv6-address

                  Figure 1: Softwire CE YANG Tree Diagram

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3.2.  Softwire CE Tree Diagram Description

   Additional information related to the operation of a CE element is
   provided below:

   o  softwire-payload-mtu: optionally used to set the IPv4 MTU for the
      softwire.  Needed if the softwire implementation is unable to
      correctly calculate the correct IPv4 Maximum Transit Unit (MTU)
      size automatically.

   o  softwire-path-mru: optionally used to set the maximum IPv6
      softwire packet size that can be received, including the
      encapsulation/translation overhead.  Needed if the softwire
      implementation is unable to correctly calculate the correct IPv4
      Maximum Receive Unit (MRU) size automatically.

   o  ce-type: provides a choice statement allowing the binding or
      algorithmic softwire mechanisms to be selected.

   Further details relevant to binding softwire elements are:

   o  binding-ipv6info: used to set the IPv6 binding prefix type to
      identify which IPv6 address to use as the tunnel source.  It can
      be 'ipv6-prefix' or 'ipv6-address'.

   o  br-ipv6-addr: defines the IPv6 address of the remote BR.

   Additional details relevant to some of the important algorithmic
   elements are provided below:

   o  algo-versioning: optionally used to add an incremental version
      number and/or timestamp to the algorithm.  This can be used for
      logging/data retention purposes.  The version number is
      incremented and a new timestamp value written whenever a change is
      made to the algorithm or a new instance is created.

   o  forwarding: specifies whether the rule can be used as a Forward
      Mapping Rule (FMR).  If not set, this rule is a Basic Mapping Rule
      (BMR) only and must not be used for forwarding.  Refer to
      Section 4.1 of [RFC7598].

   o  ea-len: used to set the length of the Embedded-Address (EA), which
      is defined in the mapping rule for a MAP domain.

   o  data-plane: provides a choice statement for either encapsulation
      (MAP-E) or translation (MAP-T).

   o  br-ipv6-addr: defines the IPv6 address of the BR.  This

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      information is valid for MAP-E.

   o  dmr-ipv6-prefix: defines the Default Mapping Rule (DMR) IPv6
      prefix of the BR.  This information is valid for MAP-T.

   Additional information on the notification node is listed below:

   o  ce-binding-ipv6-addr-change: if the CE's binding IPv6 address
      changes for any reason, the NETCONF client will be notified.

4.  Softwire BR YANG Tree Diagram

4.1.  BR Tree Diagram

   The BR YANG module provides configuration and monitoring for all of
   the softwire mechanisms covered in this document (i.e., Lightweight
   4over6, MAP-E, and MAP-T).

   Figure 2 provides the tree structure of this module.

 module: ietf-softwire-br
     +--rw br-instances
        +--rw (br-type)?
           +--:(binding) {binding-mode}?
           |  +--rw binding
           |     +--rw bind-instances* [id]
           |        +--rw binding-table-versioning
           |        |  +--rw version?   uint64
           |        |  +--rw date?      yang:date-and-time
           |        +--rw id                          uint32
           |        +--rw name?                       string
           |        +--rw softwire-num-max      uint32
           |        +--rw softwire-payload-mtu       uint16
           |        +--rw softwire-path-mru           uint16
           |        +--rw enable-hairpinning?         boolean
           |        +--rw binding-table
           |        |  +--rw binding-entry* [binding-ipv6info]
           |        |     +--rw binding-ipv6info     union
           |        |     +--rw binding-ipv4-addr?
           |        |     |       inet:ipv4-address
           |        |     +--rw port-set
           |        |     |  +--rw psid-offset?   uint8
           |        |     |  +--rw psid-len       uint8
           |        |     |  +--rw psid           uint16
           |        |     +--rw br-ipv6-addr?
           |        |             inet:ipv6-address
           |        +--rw icmp-policy
           |        |  +--rw icmpv4-errors

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           |        |  |  +--rw allow-incoming-icmpv4?    boolean
           |        |  |  +--rw icmpv4-rate?              uint32
           |        |  |  +--rw generate-icmpv4-errors?   boolean
           |        |  +--rw icmpv6-errors
           |        |     +--rw generate-icmpv6-errors?   boolean
           |        |     +--rw icmpv6-rate?              uint32
           |        +--ro traffic-stat
           |           +--ro discontinuity-time       yang:date-and-time
           |           +--ro sent-ipv4-packets?
           |           |       yang:zero-based-counter64
           |           +--ro sent-ipv4-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro sent-ipv6-packets?
           |           |       yang:zero-based-counter64
           |           +--ro sent-ipv6-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro rcvd-ipv4-packets?
           |           |       yang:zero-based-counter64
           |           +--ro rcvd-ipv4-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro rcvd-ipv6-packets?
           |           |       yang:zero-based-counter64
           |           +--ro rcvd-ipv6-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv4-packets?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv4-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv6-packets?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv6-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv4-fragments?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-ipv4-fragment-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro ipv6-fragments-reassembled?
           |           |       yang:zero-based-counter64
           |           +--ro ipv6-fragments-bytes-reassembled?
           |           |       yang:zero-based-counter64
           |           +--ro out-icmpv4-error-packets?
           |           |       yang:zero-based-counter64
           |           +--ro out-icmpv4-error-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro out-icmpv6-error-packets?
           |           |       yang:zero-based-counter64
           |           +--ro out-icmpv6-error-bytes?
           |           |       yang:zero-based-counter64

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           |           +--ro dropped-icmpv4-packets?
           |           |       yang:zero-based-counter64
           |           +--ro dropped-icmpv4-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro hairpin-ipv4-packets?
           |           |       yang:zero-based-counter64
           |           +--ro hairpin-ipv4-bytes?
           |           |       yang:zero-based-counter64
           |           +--ro active-softwire-num?
           |                   uint32
           +--:(algo) {map-e or map-t}?
              +--rw algorithm
                 +--rw algo-instances* [id]
                    +--rw id                  uint32
                    +--rw enable?             boolean
                    +--rw algo-versioning
                    |  +--rw version?   uint64
                    |  +--rw date?      yang:date-and-time
                    +--rw name?               string
                    +--rw (data-plane)?
                    |  +--:(encapsulation) {map-e}?
                    |  |  +--rw br-ipv6-addr        inet:ipv6-address
                    |  +--:(translation) {map-t}?
                    |     +--rw dmr-ipv6-prefix?    inet:ipv6-prefix
                    +--rw ea-len              uint8
                    +--rw rule-ipv6-prefix    inet:ipv6-prefix
                    +--rw rule-ipv4-prefix    inet:ipv4-prefix
                    +--rw forwarding          boolean
                    +--rw port-set
                    |  +--rw psid-offset?   uint8
                    |  +--rw psid-len       uint8
                    |  +--rw psid           uint16
                    +--ro traffic-stat
                       +--ro discontinuity-time     yang:date-and-time
                       +--ro sent-ipv4-packets?
                       |       yang:zero-based-counter64
                       +--ro sent-ipv4-bytes?
                       |       yang:zero-based-counter64
                       +--ro sent-ipv6-packets?
                       |       yang:zero-based-counter64
                       +--ro sent-ipv6-bytes?
                       |       yang:zero-based-counter64
                       +--ro rcvd-ipv4-packets?
                       |       yang:zero-based-counter64
                       +--ro rcvd-ipv4-bytes?
                       |       yang:zero-based-counter64
                       +--ro rcvd-ipv6-packets?
                       |       yang:zero-based-counter64

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                       +--ro rcvd-ipv6-bytes?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv4-packets?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv4-bytes?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv6-packets?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv6-bytes?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv4-fragments?
                       |       yang:zero-based-counter64
                       +--ro dropped-ipv4-fragment-bytes?
                       |       yang:zero-based-counter64
                       +--ro ipv6-fragments-reassembled?
                       |       yang:zero-based-counter64
                       +--ro ipv6-fragments-bytes-reassembled?
                       |       yang:zero-based-counter64
                       +--ro out-icmpv4-error-packets?
                       |       yang:zero-based-counter64
                       +--ro out-icmpv4-error-bytes?
                       |       yang:zero-based-counter64
                       +--ro out-icmpv6-error-packets?
                       |       yang:zero-based-counter64
                       +--ro out-icmpv6-error-bytes?
                               yang:zero-based-counter64

   notifications:
     +---n softwire-binding-instance-event {binding-mode}?
     |  +--ro bind-id?
     |  |       -> /br-instances/binding/bind-instances/id
     |  +--ro invalid-entry*    leafref
     |  +--ro added-entry*      inet:ipv6-address
     |  +--ro modified-entry*   leafref
     +---n softwire-algorithm-instance-event  {map-e, map-t}?
        +--ro algo-id
        |       -> /br-instances/algorithm/algo-instances/id
        +--ro invalid-entry-id*
        |       -> /br-instances/algorithm/algo-instances/id
        +--ro added-entry*
        |       -> /br-instances/algorithm/algo-instances/id
        +--ro modified-entry*
                -> /br-instances/algorithm/algo-instances/id

                      Figure 2: Softwire BR YANG Tree

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4.2.  Softwire BR Tree Diagram Description

   The descriptions for leaves which are common with the CE module are
   provided in Section 3.2.  Descriptions for additional elements are
   provided below:

   o  binding-table-versioning: optionally used to add an incremental
      version number and/or timestamp to the binding table.  This can be
      used for logging or data retention purposes.  The version number
      is incremented and a new timestamp value written whenever a change
      is made to the contents of the binding table or a new binding
      table list is created.

   o  binding-entry: used to define the binding relationship between
      3-tuples {lwB4's IPv6 address/prefix, the allocated IPv4 address,
      restricted port-set}. For detail information, please refer to
      [RFC7596].

   o  softwire-num-max: used to set the maximum number of softwire
      binding rules that can be created on the lw4o6 element
      simultaneously.

   o  active-softwire-num: holds the number of softwires currently
      provisioned on the element.

   Additional information on some of the important notification nodes is
   listed below:

   o  invalid-entry, added-entry, modified-entry: used to notify the
      NETCONF client that a specific binding entry or MAP rule has
      expired, been invalidated, added, or modified.

5.  IANA Tunnel Type YANG Module

   <CODE BEGINS> file "iana-tunnel-type@2018-10-19.yang"

   module iana-tunnel-type {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:iana-tunnel-type";
     prefix iana-tunnel-type;

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

     organization

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       "IANA";
     contact
       "Internet Assigned Numbers Authority

     Postal: ICANN
             12025 Waterfront Drive, Suite 300
             Los Angeles, CA  90094-2536
             United States of America
     Tel:    +1 310 301 5800
     <mailto:iana@iana.org>";

     description
       "This module contains a collection of YANG data types defined
        by IANA and used for tunnel types.

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

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

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2018-10-19 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                    Softwires";
     }

     identity  other {
       base ift:tunnel;
       description
         "None of the following values.";
     }
     identity direct {
       base ift:tunnel;
       description
         "No intermediate header.";
      }
      identity gre {
        base ift:tunnel;

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        description
          "GRE encapsulation.";
      }
      identity minimal {
        base ift:tunnel;
        description
          "Minimal encapsulation.";
      }
      identity l2tp {
        base ift:tunnel;
        description
          "L2TP encapsulation.";
      }
      identity pptp {
        base ift:tunnel;
        description
          "PPTP encapsulation.";
      }
      identity l2f {
        base ift:tunnel;
        description
          "L2F encapsulation.";
      }
      identity udp {
        base ift:tunnel;
        description
          "UDP encapsulation.";
      }
      identity atmp {
        base ift:tunnel;
        description
         "ATMP encapsulation.";
      }
      identity msdp {
        base ift:tunnel;
        description
          "MSDP encapsulation.";
      }
      identity sixtofour {
        base ift:tunnel;
        description
          "6to4 encapsulation.";
      }
      identity sixoverfour {
        base ift:tunnel;
        description
          "6over4 encapsulation.";
      }

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      identity isatap {
        base ift:tunnel;
        description
          "ISATAP encapsulation.";
      }
      identity teredo {
        base ift:tunnel;
        description
          "Teredo encapsulation.";
      }
      identity iphttps {
        base ift:tunnel;
        description
          "IP over HTTPS.";
      }
      identity softwiremesh {
        base ift:tunnel;
        description
          "softwire mesh tunnel.";
      }
      identity dslite {
        base ift:tunnel;
        description
          "DS-Lite tunnel.";
     }
     // TBD: register this value.
     identity  aplusp {
       base ift:tunnel;
       description
         "A+P encapsulation.";
     }
   }
   <CODE ENDS>

6.  Tunnel Extension to the Interface YANG Module

   The ietf-interface-tunnel module imports the modules defined in
   [RFC7224] and [RFC8343].

<CODE BEGINS> file "ietf-interface-tunnel@2018-10-19.yang"

module ietf-interface-tunnel {
  yang-version 1.1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-interface-tunnel";
  prefix ietf-interface-tunnel;

  import ietf-interfaces {

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

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

  organization "IETF xxx Working Group";

  contact

    "WG Web:   <https://datatracker.ietf.org/wg/softwires/>
     WG List:  <mailto:softwire@ietf.org>

     Editor:  Mohamed Boucadair
              <mailto:mohamed.boucadair@orange.com>";

   description
      "This module is a YANG module for associating a tunnel type with
      tunnel interfaces.

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

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

      This version of this YANG module is part of RFC XXXX; see
      the RFC itself for full legal notices.";

  revision 2018-10-19 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  augment "/if:interfaces/if:interface" {
    when 'derived-from(if:type, "ift:tunnel")';

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    description
      "Augments Interface module with tunnel-specific parameters.

       IANA interface types are maintained at this registry:
       https://www.iana.org/assignments/ianaiftype-mib/ianaiftype-mib.

       tunnel (131),       -- Encapsulation interface";

    leaf tunnel-type {
      type identityref {
        base ift:tunnel;
      }
      description
        "Indicates the type of the tunnel. It corresponds
         to the IANAtunnelType.

         IANA tunnel types are maintained at this registry:
         https://www.iana.org/assignments/ianaiftype-mib/ianaiftype-mib.";
    }
  }
}
<CODE ENDS>

7.  Softwire CE YANG Module

   This module imports the modules defined in [RFC6991], [RFC8343], and
   [RFC7224].  It also imports the 'ietf-softwire-common' module.

<CODE BEGINS>file "ietf-softwire-ce@2018-10-19.yang"

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

  import ietf-inet-types {
    prefix inet;
    reference
      "Section 4 of RFC 6991";
  }

  /*import ietf-yang-types {
    prefix yang;
    reference
      "Section 3 of RFC 6991";
  }*/

  import ietf-interfaces {

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

  import ietf-softwire-common {
    prefix softwire-common;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  import iana-tunnel-type  {
    prefix iana-tunnel-type;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  import ietf-interface-tunnel  {
    prefix ift;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  organization
    "IETF Softwire Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
     WG List:  <mailto:softwire@ietf.org>

    Qi Sun <sunqi.ietf@gmail.com>
    Linhui Sun <lh.sunlinh@gmail.com>
    Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
    Ian Farrer <ian.farrer@telekom.de>
    Sladjana Zoric <sladjana.zoric@telekom.de>
    Mohamed Boucadair <mohamed.boucadair@orange.com>
    Rajiv <Asati rajiva@cisco.com>
    ";

  description
    "This document defines a YANG data module for the configuration and
    management of A+P Softwire Customer Premises Equipment (CEs). It
    covers Lightweight 4over6, MAP-E, and MAP-T mechanisms.

    Copyright (c) 2018 IETF Trust and the persons identified

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    as authors of the code. All rights reserved.
    This version of this YANG module is part of RFC XXXX; see the RFC
    itself for full legal notices.";

  revision 2018-10-19 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  /*
   * Features
   */

  feature binding-mode {
    description
      "Binding is used for configuring the Lightweight 4over6 mechanism.

      Binding based softwire mechanisms are IPv4-over-IPv6 tunnelling
      transition mechanisms specifically intended for complete
      independence between the IPv6 subnet prefix (and IPv6 address)
      and IPv4 address, with or without IPv4 address sharing.

      This is accomplished by maintaining state for each softwire
      (per-subscriber state) in the central Border Relay (BR) and using
      a hub-and-spoke forwarding architecture. In order to delegate the
      NAPT function and achieve IPv4 address sharing, port-restricted
      IPv4 addresses needs to be allocated to CEs.

      This feature indicates that the instance functions as a binding
      based softwire instance.";

    reference
      "RFC7596: Lightweight 4over6: An Extension to the Dual-Stack Lite
                Architecture
       RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)
       RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  feature map-e {
    description
      "MAP-E is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP encapsulation. MAP-E
      allows for a reduction of the amount of centralized state using
      rules to express IPv4/IPv6 address mappings. This introduces an
      algorithmic relationship between the IPv6 subnet and IPv4 address.

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      This feature indicates that the instance functions as a MAP-E.";

    reference
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";
  }

  feature map-t {
    description
     "MAP-T is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP translation. It leverages
      a double stateless NAT64 based solution as well as the stateless
      algorithmic address & transport layer port mapping algorithm
      defined for MAP-E.

      This feature indicates that the instance functions as a MAP-T instance.";

    reference
       "RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  // Binding Entry
  grouping binding-entry {
    description
      "The binding BR (Border Relay) maintains an address binding table
      that contains the binding between the CE's IPv6 address,
      the allocated IPv4 address and restricted port-set.";

    leaf binding-ipv6info {

      type union {
        type inet:ipv6-address;
        type inet:ipv6-prefix;
      }

      description
        "The IPv6 information for a binding entry.

        When the IPv6 prefix type is used,
        the IPv6 source address of the CE is constructed
        according to the description in RFC7596.

        If the IPv6 address type is used, the CE can use
        any valid /128 address from a prefix assigned to
        the CE.";
      reference
        "Section 5.1 of RFC7596.";
    }

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    leaf br-ipv6-addr {
      type inet:ipv6-address;
      mandatory true;
      description
        "The IPv6 address of the binding BR.";
    }
  }

  // configuration and stateful parameters for softwire CE interface
  augment "/if:interfaces/if:interface" {
    when "derived-from(ift:tunnel-type, 'iana-tunnel-type:aplusp')";
    description "Softwire CE interface configuration";

    leaf softwire-payload-mtu {
      type uint16;
      units bytes;
      description
        "The payload IPv4 MTU for the softwire tunnel.";
    }

    leaf softwire-path-mru {
      type uint16;
      units bytes;
      description
        "The path MRU for the softwire (payload + encapsulation
        overhead).";
    }

    choice ce-type {
      description "Sets the softwire CE mechanism";

      case binding {
        if-feature binding-mode;
        description "CE binding configuration";
        uses binding-entry;
      }

      case algo {
        if-feature "map-e or map-t";
        description "CE algorithm configuration";

        container algo-instances {
          description
            "Indicates that the instances supports the MAP-E and/or MAP-T
            function. The instances advertise the MAP-E/MAP-T
            feature through the capability exchange mechanism
            when a NETCONF session is established.";
          list algo-instances {

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            key "id";
            description
              "MAP forwarding rule instance for
              MAP-E/MAP-T";
            leaf id {
              type uint32;
              mandatory true;
              description "Algorithm Instance ID";
            }
            uses softwire-common:algorithm-instance;
          }
        }
      }
    }
  }

  augment "/if:interfaces/if:interface/if:statistics" {
    when "derived-from(../ift:tunnel-type, 'iana-tunnel-type:aplusp')";
    description "Softwire CE interface statistics.";
      uses softwire-common:traffic-stat;
    }

  /*
   * Notifications
   */

  notification softwire-ce-event {
    if-feature binding-mode;
    description "CE notification";
    leaf ce-binding-ipv6-addr-change {
      type inet:ipv6-address;
      mandatory true;
      description
        "If the CE's binding IPv6 address changes for any reason,
         it should notify the NETCONF client.";
    }
  }
}
<CODE ENDS>

8.  BR Softwire YANG Module

   This module imports typedefs from [RFC6991].  It also imports the
   'ietf-softwire-common' module.

<CODE BEGINS>file "ietf-softwire-br@2018-10-19.yang"

module ietf-softwire-br {

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  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-softwire-br";
  prefix "softwire-br";

  import ietf-inet-types {
    prefix inet;
    reference
      "Section 4 of RFC 6991";
  }

  import ietf-yang-types {
    prefix yang;
    reference
      "Section 3 of RFC 6991";
  }

  import ietf-softwire-common {
    prefix softwire-common;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  organization
    "IETF Softwire Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
     WG List:  <mailto:softwire@ietf.org>

    Qi Sun <sunqi.ietf@gmail.com>
    Linhui Sun <lh.sunlinh@gmail.com>
    Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
    Ian Farrer <ian.farrer@telekom.de>
    Sladjana Zoric <sladjana.zoric@telekom.de>
    Mohamed Boucadair <mohamed.boucadair@orange.com>
    Rajiv <Asati rajiva@cisco.com>
    ";

  description
    "This document defines a YANG data module for the configuration and
    management of A+P Softwire Border Routers. It covers Lightweight
    4over6, MAP-E, and MAP-T mechanisms.

    Copyright (c) 2018 IETF Trust and the persons identified
    as authors of the code. All rights reserved.
    This version of this YANG module is part of RFC XXXX; see the RFC
    itself for full legal notices.";

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  revision 2018-10-19 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  /*
   * Groupings
   */

  grouping port-set {
    description
      "Describes a set of layer 4 port numbers.

      This may be a simple port range, or use the Port Set
      Identifier (PSID) algorithm to represent a range of transport
      layer ports which will be used by a NAPT.";

    leaf psid-offset {
      type uint8 {
        range 0..16;
      }
      description
        "The number of offset bits. In Lightweight 4over6,
        the default value is 0 for assigning one contiguous
        port range. In MAP-E/T, the default value is 6,
        which means the system ports (0-1023) are excluded by
        default and the assigned port ranges are distributed across the
        entire port space, depending on either psid-len or the
        number of contiguous ports.";
    }

    leaf psid-len {
      type uint8 {
        range 0..15;
      }
      mandatory true;
      description
        "The length of PSID, representing the sharing
        ratio for an IPv4 address. This, along with ea-len, can
        be used to calculate the number of contiguous ports per
        port range";
    }

    leaf psid {
      type uint16;

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      mandatory true;
      description
        "Port Set Identifier (PSID) value, which
        identifies a set of ports algorithmically.";
    }
  }

  grouping binding-entry {
    description
      "The binding BR maintains an address binding table that
      contains the binding between the CE's IPv6 address,
      the allocated IPv4 address and restricted port-set.";
    leaf binding-ipv6info {
      type union {
        type inet:ipv6-address;
        type inet:ipv6-prefix;
      }
      description
        "The IPv6 information for a CE binding entry.
        When the IPv6 prefix type is used,
        the IPv6 source address of the CE is constructed
        according to the description in RFC7596;
        if the IPv6 address type is used, the CE can use
        any valid /128 address from a prefix assigned to
        the CE.";
      reference
        "RFC7596: Lightweight 4over6: An Extension to the Dual-Stack
                  Lite Architecture";
    }
    leaf binding-ipv4-addr {
      type inet:ipv4-address;
      description
        "The IPv4 address assigned to the binding CE,
        which is used as the IPv4 external address
        for binding CE local NAPT44.";
    }
    container port-set {
      description
        "For Lightweight 4over6, the default value
        for offset should be 0, to configure one contiguous
        port range.";
      uses port-set {
        refine "psid-offset" {
          default "0";
        }
      }
    }
    leaf br-ipv6-addr {

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      type inet:ipv6-address;
      description
        "The IPv6 address for binding BR.";
    }
  }

  /*
   * Features
   */

  feature binding-mode {
    description
      "Binding is used for configuring the Lightweight 4over6 mechanism.

      Binding based softwire mechanisms are IPv4-over-IPv6 tunnelling
      transition mechanisms specifically intended for complete
      independence between the IPv6 subnet prefix (and IPv6 address) and
      IPv4 address, with or without IPv4 address sharing.

      This is accomplished by maintaining state for each softwire
      (per-subscriber state) in the central Border Relay (BR) and using
      a hub-and-spoke forwarding architecture. In order to delegate the
      NAPT function and achieve IPv4 address sharing, port-restricted
      IPv4 addresses needs to be allocated to CEs.

      This feature indicates that the instance functions as a binding
      based softwire instance.";

    reference
      "RFC7596: Lightweight 4over6: An Extension to the Dual-Stack Lite
                Architecture
       RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)
       RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  feature map-e {
    description
      "MAP-E is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP encapsulation. MAP-E
      allows for a reduction of the amount of centralized state using
      rules to express IPv4/IPv6 address mappings. This introduces an
      algorithmic relationship between the IPv6 subnet and IPv4 address.

      This feature indicates that the instance functions as a MAP-E.";

    reference
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";
  }

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  feature map-t {
    description
     "MAP-T is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP translation. It leverages
      a double stateless NAT64 based solution as well as the stateless
      algorithmic address & transport layer port mapping algorithm
      defined for MAP-E.

      This feature indicates that the instance functions as a MAP-T instance.";

    reference
       "RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  container br-instances {
    description
      "BR Instances";

    choice br-type {
      description
        "Select binding or algorithmic BR functionality.";
      case binding {
        if-feature binding-mode;
        container binding {
          description
            "binding mechanism (binding table) configuration.";
          list bind-instances {
            key "id";
            description
              "A set of binding BRs to be configured.";
            container binding-table-versioning {
              description "binding table's version";
              leaf version{
                type uint64;
                description "Incremental version number of the binding
                  table";
              }
              leaf date {
                type yang:date-and-time;
                description "Timestamp of the binding
                  table";
              }
            }
            leaf id {
              type uint32;
              mandatory true;
              description "An instance identifier.";
            }

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            leaf name {
              type string;
              description "The name for the binding BR.";
            }
            leaf softwire-num-max {
              type uint32;
              mandatory true;
              description
                "The maximum number of softwires that can be created on
                the binding BR.";
            }
            leaf softwire-payload-mtu {
              type uint16;
              units bytes;
              mandatory true;
              description
                "The payload IPv4 MTU for binding softwire.";
            }
            leaf softwire-path-mru {
              type uint16;
              units bytes;
              mandatory true;
              description
                "The path MRU for binding softwire.";
            }
            leaf enable-hairpinning {
              type boolean;
              default true;
              description
                "Enables/disables support for locally forwarding
                (hairpinning) traffic between two CEs.";
              reference
                "RFC7596 Section 6.2";
            }
            container binding-table {
              description "binding table";
              list binding-entry {
                key "binding-ipv6info";
                description "binding entry";
                uses binding-entry;
              }
            }
            container icmp-policy {
              description
                "The binding BR can be configured to process or drop
                incoming ICMP messages, and to generate outgoing ICMP
                error messages.";

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              container icmpv4-errors {
                description
                  "ICMPv4 error processing configuration";
                leaf allow-incoming-icmpv4 {
                  type boolean;
                  default true;
                  description
                    "Enables the processing of incoming ICMPv4
                    packets.";
                  reference
                    "RFC7596: Lightweight 4over6: An Extension to the
                              Dual-Stack Lite Architecture";
                }
                leaf icmpv4-rate {
                  type uint32;
                  description
                    "Rate limit threshold in messages per-second
                    for processing incoming ICMPv4 errors messages";
                }
                leaf generate-icmpv4-errors {
                  type boolean;
                  default true;
                  description
                    "Enables the generation of outgoing ICMPv4 error
                    messages on receipt of an inbound IPv4 packet with
                    no matching binding table entry.";
                  reference
                    "Seciton 5.2 of RFC7596.";
                }
              }

              container icmpv6-errors {
                description
                  "ICMPv6 error processing configuration";
                leaf generate-icmpv6-errors {
                  type boolean;
                  default true;
                  description
                    "Enables the generation of ICMPv6 error messages if
                    no matching binding table entry is found for a
                    received packet.";
                  reference
                    "Section 6.2 of RFC7596.";
                }
                leaf icmpv6-rate {
                  type uint32;
                  description
                    "Rate limit threshold in messages per-second

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                    for sending ICMPv6 errors messages";
                  reference
                    "Section 9 of RFC7596.";
                }
              }
            }

            container traffic-stat {
              config false;
              description
                "Traffic statistics information for the BR.";

              leaf discontinuity-time {
                type yang:date-and-time;
                mandatory true;
                description
                  "The time of the most recent occasion on which the BR
                   instance suffered a discontinuity.  This must be
                   initialized when the BR instance is configured
                   or rebooted.";
              }

              uses softwire-common:traffic-stat;

              leaf dropped-icmpv4-packets {
                type yang:zero-based-counter64;
                description
                  "ICMPv4 packets that are dropped as a result
                   of the ICMP policy. Typically, this can be any
                   incoming ICMPv4 packets if ICMPv4 processing is
                   disabled or incoming ICMPv4 packets that exceed
                   the ICMPv4 rate-limit threshold.

                   Discontinuities in the value of this counter can
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
              leaf dropped-icmpv4-bytes {
                type yang:zero-based-counter64;
                description
                  "ICMPv4 messages, in bytes, that are dropped as
                   a result of the ICMP policy. Typically, it
                   can be any incoming ICMPv4 packets if ICMPv4
                   processing is disabled or incoming ICMPv4
                   packets that exceed the ICMPv4 rate-limit
                   threshold.

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                   Discontinuities in the value of this counter can
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
              leaf hairpin-ipv4-packets {
                type yang:zero-based-counter64;
                description
                  "IPv4 packets locally routed between two CEs
                   (hairpinned).

                   Discontinuities in the value of this counter can
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
              leaf hairpin-ipv4-bytes {
                type yang:zero-based-counter64;
                description
                  "IPv4 bytes locally routed between two CEs
                   (hairpinned).

                   Discontinuities in the value of this counter can
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
              leaf active-softwire-num {
                type uint32;
                config false;
                description
                  "The number of currently active softwires on the
                   binding instance.

                   Discontinuities in the value of this counter can
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
            }
          }
        }
      }
      case algo {
        if-feature "map-e or map-t";
        container algorithm {
          description
            "Indicate that the instance supports the MAP-E and/or MAP-T

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            function. The instances advertise the MAP-E/MAP-T feature
            through the capability exchange mechanism when a NETCONF
            session is established.";
          list algo-instances {
            key "id";
            description "Instances of algorithm";
            leaf id {
              type uint32;
              mandatory true;
              description "Identifier of the algorithm instance.";
            }
            uses softwire-common:algorithm-instance;
            container port-set {
              description "Indicates a set of ports.";
              uses port-set;
            }
            container traffic-stat {
              config false;
              description
                "Traffic statistics information for the BR.";
              leaf discontinuity-time {
                type yang:date-and-time;
                mandatory true;
                description
                  "The time of the most recent occasion on which the BR
                   instance suffered a discontinuity.  This must be reset
                   to the current date-and-time when the BR instance
                   is configured or rebooted.";
              }
              uses softwire-common:traffic-stat;
            }
          }
        }
      }
    }
  }

  /*
   * Notifications
   */

  notification softwire-binding-instance-event {
    if-feature binding-mode;
    description "Notifications for binding instance.";
    leaf bind-id {
      type leafref {
        path
          "/br-instances/binding/"

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          + "bind-instances/id";
      }
      description "The ID of the binding-instance that
        generated the notification.";
    }
    leaf-list invalid-entry {
      type leafref {
        path
          "/br-instances/binding/"
          + "bind-instances[id=current()/../bind-id]/"
          + "binding-table/binding-entry/binding-ipv6info";
      }
      description
        "Notify the client that a specific binding entry has
        expired or is invalid. The binding-ipv6info identifies an entry.";
    }
    leaf-list added-entry {
      type inet:ipv6-address;
      description
        "Notify the client that a binding entry has been added.
        The ipv6 address of that entry is the index. The client
        gets other information from the binding BR about the entry
        indexed by that ipv6 address.
        ";
    }
    leaf-list modified-entry {
      type leafref {
        path
          "/br-instances/binding/"
          + "bind-instances[id=current()/../bind-id]/"
          + "binding-table/binding-entry/binding-ipv6info";
      }
      description "The ID of the the binding-table entry that
        has been modified.";
    }
  }

  notification softwire-algorithm-instance-event {
    if-feature "map-e or map-t";
    description "Notifications for algorithmic instance.";
    leaf algo-id {
      type leafref {
        path
          "/br-instances/algorithm/algo-instances/id";
      }
      mandatory true;
      description "algorithmic instance event.";
    }

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    leaf-list invalid-entry-id {
      type leafref {
        path
          "/br-instances/algorithm/algo-instances/id";
      }
      description "Invalid entry event.";
    }
    leaf-list added-entry {
      type leafref {
        path
          "/br-instances/algorithm/algo-instances/id";
      }
      description "Added entry.";
    }
    leaf-list modified-entry {
      type leafref {
        path
          "/br-instances/algorithm/algo-instances/id";
      }
      description "Modified entry.";
    }
  }
}
<CODE ENDS>

9.  Common Softwire Element Groups YANG Module

   This module imports typedefs from [RFC6991].

   The following YANG module contains definitions that are used by both
   the softwire CE and softwire BR YANG modules.

<CODE BEGINS>file "ietf-softwire-common@2018-10-19.yang"

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

  import ietf-inet-types {
    prefix inet;
    reference
      "Section 4 of RFC 6991";
  }

  import ietf-yang-types {
    prefix yang;
    reference

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      "Section 3 of RFC 6991";
  }

  organization
    "IETF Softwire Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
     WG List:  <mailto:softwire@ietf.org>

    Qi Sun <sunqi.ietf@gmail.com>
    Linhui Sun <lh.sunlinh@gmail.com>
    Yong Cui <yong@csnet1.cs.tsinghua.edu.cn>
    Ian Farrer <ian.farrer@telekom.de>
    Sladjana Zoric <sladjana.zoric@telekom.de>
    Mohamed Boucadair <mohamed.boucadair@orange.com>
    Rajiv <Asati rajiva@cisco.com>
    ";

  description
    "This document defines a YANG data module defining types
     common to all A+P modules.

    Copyright (c) 2018 IETF Trust and the persons identified
    as authors of the code. All rights reserved.
    This version of this YANG module is part of RFC XXXX; see the RFC
    itself for full legal notices.";

  revision 2018-10-19 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  feature map-e {
    description
      "MAP-E is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP encapsulation. MAP-E
      allows for a reduction of the amount of centralized state using
      rules to express IPv4/IPv6 address mappings. This introduces an
      algorithmic relationship between the IPv6 subnet and IPv4 address.

      This feature indicates that the instance functions as a MAP-E.";

    reference
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";

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  }

  feature map-t {
    description
     "MAP-T is an IPv6 transition mechanism for transporting IPv4
      packets across an IPv6 network using IP translation. It leverages
      a double stateless NAT64 based solution as well as the stateless
      algorithmic address & transport layer port mapping algorithm
      defined for MAP-E.

      This feature indicates that the instance functions as a MAP-T instance.";

    reference
       "RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  /*
   * Groupings
   */

  grouping algorithm-instance {
    description
      "Indicates that the instance supports the MAP-E and/or MAP-T
      function. The instance advertises the MAP-E/MAP-T feature
      through the capability exchange mechanism when a NETCONF
      session is established.";

    leaf enable {
      type boolean;
      description
        "Enable/disable an individual MAP-E or MAP-T rule.";
    }
    container algo-versioning {
      description "algorithm's version";
      leaf version {
        type uint64;
        description "Incremental version number for the algorithm";
      }
      leaf date {
        type yang:date-and-time;
        description "Timestamp when the algorithm instance was activated.";
      }
    }
    leaf name {
      type string;
      description "The name for the instance.";
    }
    choice data-plane {

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      description "Selects MAP-E (encapsulation) or MAP-T
      (translation)";
      case encapsulation {
        if-feature map-e;
        description "encapsulation for MAP-E";
        leaf br-ipv6-addr {
          type inet:ipv6-address;
          mandatory true;
          description
            "The IPv6 address of the MAP-E BR.";
        }
      }
      case translation {
        if-feature map-t;
        description "translation for MAP-T";
        leaf dmr-ipv6-prefix {
          type inet:ipv6-prefix;
          description
            "The IPv6 prefix of the MAP-T BR.";
        }
      }
    }
    leaf ea-len {
      type uint8;
      mandatory true;
      description
        "Embedded Address (EA) bits are the IPv4 EA-bits in the IPv6
        address identifying an IPv4 prefix/address (or part thereof) or
        a shared IPv4 address (or part thereof) and a port-set
        identifier. The length of the EA-bits is defined as part of
        a MAP rule for a MAP domain.";
    }
    leaf rule-ipv6-prefix {
      type inet:ipv6-prefix;
      mandatory true;
      description
        "The Rule IPv6 prefix defined in the mapping rule.";
    }
    leaf rule-ipv4-prefix {
      type inet:ipv4-prefix;
      mandatory true;
      description
        "The Rule IPv4 prefix defined in the mapping rule.";
    }
    leaf forwarding {
      type boolean;
      mandatory true;
      description

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        "This parameter specifies whether the rule may be used for
        forwarding (FMR). If set, this rule is used as an FMR;
        if not set, this rule is a Basic Mapping Rule (BMR) only
        and must not be used for forwarding.";
    }
  }

  grouping traffic-stat {
    description "Traffic statistics";
    leaf sent-ipv4-packets {
      type yang:zero-based-counter64;
      description "Number of decapsulated and forwarded IPv4 packets.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf sent-ipv4-bytes {
      type yang:zero-based-counter64;
      description "Decapsulated/translated IPv4 traffic sent, in bytes

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf sent-ipv6-packets {
      type yang:zero-based-counter64;
      description "Number of encapsulated IPv6 packets sent.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf sent-ipv6-bytes {
      type yang:zero-based-counter64;
      description "Encapsulated IPv6 traffic sent, in bytes

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf rcvd-ipv4-packets {
      type yang:zero-based-counter64;
      description "Number of incoming IPv4 packets at the

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      Internet-facing interface.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf rcvd-ipv4-bytes {
      type yang:zero-based-counter64;
      description "IPv4 traffic received for processing, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf rcvd-ipv6-packets {
      type yang:zero-based-counter64;
      description "Number of IPv4-in-IPv6 packets received.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf rcvd-ipv6-bytes {
      type yang:zero-based-counter64;
      description "IPv4-in-IPv6 traffic received, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv4-packets {
      type yang:zero-based-counter64;
      description "Number of IPv4 packets dropped at the
      Internet-facing interface.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv4-bytes {
      type yang:zero-based-counter64;
      description "IPv4 traffic dropped at the Internet-facing
      interface, in bytes.

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      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv6-packets {
      type yang:zero-based-counter64;
      description "Number of IPv4-in-IPv6 packets dropped.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv6-bytes {
      type yang:zero-based-counter64;
      description "IPv4-in-IPv6 traffic dropped, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv4-fragments {
      type yang:zero-based-counter64;
      description "Number of fragmented IPv4 packets dropped.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf dropped-ipv4-fragment-bytes {
      type yang:zero-based-counter64;
      description "Fragmented IPv4 traffic dropped, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf ipv6-fragments-reassembled {
      type yang:zero-based-counter64;
      description "Number of IPv6 fragments successfully reassembled.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of

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      'discontinuity-time'.";
    }
    leaf ipv6-fragments-bytes-reassembled {
      type yang:zero-based-counter64;
      description "IPv6 fragments successfully reassembled, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf out-icmpv4-error-packets {
      type yang:zero-based-counter64;
      description "Internally generated ICMPv4 error packets.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf out-icmpv4-error-bytes {
      type yang:zero-based-counter64;
      description "Internally generated ICMPv4 error messages, in bytes.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf out-icmpv6-error-packets {
      type yang:zero-based-counter64;
      description "Internally generated ICMPv6 error packets.

      Discontinuities in the value of this counter can occur
      at re-initialization of the management system, and at
      other times as indicated by the value of
      'discontinuity-time'.";
    }
    leaf out-icmpv6-error-bytes {
      type yang:zero-based-counter64;
      description "Internally generated ICMPv6 error messages, in bytes.

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

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}
<CODE ENDS>

10.  Security Considerations

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

   The NETCONF access control model [RFC8341] provides the means to
   restrict access for particular NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

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

11.  IANA Considerations

   This document requests IANA to assign a new tunnel type under
   "tunnelType" sub-registry (under "ifType definitions" registry):

   o  aplusp: A+P Encapsulation [RFC XXXX].

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

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

            URI: urn:ietf:params:xml:ns:yang:iana-tunnel-type
            Registrant Contact: IANA.
            XML: N/A; the requested URI is an XML namespace.

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

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

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

   This document requests that IANA registers the following YANG modules
   in the "YANG Module Names" registry [RFC6020]:

            name: ietf-interface-tunnel
            namespace: urn:ietf:params:xml:ns:yang:ietf-interface-tunnel
            prefix: ietf-interface-tunnel
            reference: RFC XXXX

            name: iana-tunnel-type
            namespace: urn:ietf:params:xml:ns:yang:iana-tunnel-type
            prefix: iana-tunnel-type
            reference: RFC XXXX

            name: ietf-softwire-ce
            namespace: urn:ietf:params:xml:ns:yang:softwire-ce
            prefix: softwire-ce
            reference: RFC XXXX

            name: ietf-softwire-br
            namespace: urn:ietf:params:xml:ns:yang:softwire-br
            prefix: softwire-br
            reference: RFC XXXX

            name: ietf-softwire-common
            namespace: urn:ietf:params:xml:ns:yang:softwire-common
            prefix: softwire-common
            reference: RFC XXXX

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   This document defines the initial version of the IANA-maintained
   iana-tunnel-type YANG module.  IANA is requested to add this note:

      Tunnel type values must not be directly added to the iana-tunnel-
      type YANG module.  They must instead be respectively added to the
      "tunnelType" sub-registry (under "ifType definitions" registry).

   When an tunnel type is added to the "tunnelType" registry, a new
   "identity" statement must be added to the iana-tunnel-type YANG
   module.  The name of the "identity" is the same as the corresponding
   enumeration in the IANAifType-MIB.  The following substatements to
   the "identity" statement should be defined:

   "base":        Contains the value of the tunnel type in lowercase.

   "description": Replicate the description from the registry.

   "reference":   Replicate the reference from the registry and add the
                  title of the document.

   Unassigned or reserved values are not present in the module.

   When the iana-tunnel-type YANG module is updated, a new "revision"
   statement must be added in front of the existing revision statements.

   IANA is requested to add this note to "tunnelType" registry:

      When this registry is modified, the YANG module iana-tunnel-type
      must be updated as defined in [RFCXXXX].

12.  Acknowledgements

   The authors would like to thank Lishan Li, Bert Wijnen, Giles Heron,
   Ole Troan, Andy Wingo and Leo Tietz for their contributions to this
   work.

   Thanks to Sheng Jiang for the review.

   Special thanks to Tom Petch for the detailed review and suggestions.

13.  Contributors

   The following individuals contributed to this document:

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     Hao Wang
     Tsinghua University
     Beijing 100084
     P.R.China
     Phone: +86-10-6278-5822
     Email: wangh13@mails.tsinghua.edu.cn

14.  References

14.1.  Normative References

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

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

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

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

   [RFC7596]  Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
              Farrer, "Lightweight 4over6: An Extension to the Dual-
              Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
              July 2015, <https://www.rfc-editor.org/info/rfc7596>.

   [RFC7597]  Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
              Murakami, T., and T. Taylor, Ed., "Mapping of Address and
              Port with Encapsulation (MAP-E)", RFC 7597,
              DOI 10.17487/RFC7597, July 2015,
              <https://www.rfc-editor.org/info/rfc7597>.

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   [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>.

   [RFC7599]  Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
              and T. Murakami, "Mapping of Address and Port using
              Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July
              2015, <https://www.rfc-editor.org/info/rfc7599>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

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

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

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

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

14.2.  Informative References

   [I-D.ietf-opsawg-nat-yang]
              Boucadair, M., Sivakumar, S., Jacquenet, C., Vinapamula,
              S., and Q. Wu, "A YANG Module for Network Address
              Translation (NAT) and Network Prefix Translation (NPT)",
              draft-ietf-opsawg-nat-yang-17 (work in progress),
              September 2018.

   [I-D.ietf-softwire-dslite-yang]
              Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG
              Data Model for Dual-Stack Lite (DS-Lite)", draft-ietf-
              softwire-dslite-yang-17 (work in progress), May 2018.

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   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
              <https://www.rfc-editor.org/info/rfc6333>.

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

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

   [RFC8344]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 8344, DOI 10.17487/RFC8344, March 2018,
              <https://www.rfc-editor.org/info/rfc8344>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

Appendix A.  Configutation Examples

   The following sections provide examples of how the softwire YANG
   modules can be used for configuring softwire elements.

A.1.  Configuration Example for a lw4o6 BR Binding-Table

   The lwAFTR maintains an address binding table which contains the
   following 3-tuples:

   o  IPv6 Address for a single lwB4

   o  Public IPv4 Address

   o  Restricted port-set

   The entry has two functions: the IPv6 encapsulation of inbound IPv4
   packets destined to the lwB4 and the validation of outbound IPv4-in-
   IPv6 packets received from the lwB4 for de-capsulation.

   Consider an example for the following lw4o6 binding table entry:

   lwB4 Binding IPv6 Address:  2001:db8::1

   lwB4 Binding IPv4 Address:  192.0.2.1

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   lwB4 PSID:                  0x34

   lwB4 PSID Length            8

   BR IPv6 Address:            2001:db8:1::2

<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <softwire-config xmlns="urn:ietf:params:xml:ns:yang:ietf-softwire-br">
    <br-instances>
      <binding>
          <bind-instance>
            <id>1</id>
            <binding-table>
              <binding-entry>
                <binding-ipv6info>2001:db8::1</binding-ipv6info>
                <binding-ipv4-addr>192.0.2.1</binding-ipv4-addr>
                <port-set>
                  <psid>52</psid>
                  <psid-len>8</psid-len>
                </port-set>
                <br-ipv6-addr>2001:db8:1::2</br-ipv6-addr>
              </binding-entry>
            </binding-table>
            <softwire-num-max>1024</softwire-num-max>
            <softwire-path-mru>1540</softwire-path-mru>
            <softwire-payload-mtu>1500</softwire-payload-mtu>
          </bind-instance>
      </binding>
    </br-instances>
  </softwire-config>
</config>

              Figure 3: lw4o6 Binding-Table Configuration XML

A.2.  Configuration Example for a MAP-E BR

   A MAP-E BR is configured with forward mapping rules for the CEs it is
   serving.  In this example (taken from [RFC7597], Appendix A, Example
   2), the following parameters are required:

   o  Rule IPv6 Prefix

   o  Rule IPv4 Prefix

   o  Rule EA-bit bit length

   o  IPv6 Address of MAP-BR

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   The mapping rule has two functions: identifying the destination CE
   IPv6 address for encapsulating inbound IPv4 packets and the
   validation of outbound IPv4-in-IPv6 packets received from the CE for
   de-capsulation.

   The transport type for the data plane also needs to be configured for
   encapsulation to enable MAP-E and forwarding needs to be enabled.

   Consider an example for the following MAP-E Forwarding Mapping Rule:

   Data plane:         encapsulation

   Rule IPv6 Prefix:   2001:db8::/40

   Rule IPv4 Prefix:   192.0.2.0/24

   Rule EA-bit Length: 16

   BR IPv6 Address:    2001:db8:ffff::1

   Figure 4 provides the example MAP-E BR configuration xml.

<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <softwire-config xmlns="urn:ietf:params:xml:ns:yang:ietf-softwire-br">
    <br-instances>
      <algorithm>
        <algo-instances>
          <id>1234</id>
          <encapsulation>
            <br-ipv6-addr>2001:db8:ffff::1</br-ipv6-addr>
          </encapsulation>
          <ea-len>16</ea-len>
          <rule-ipv4-prefix>192.0.2.0/24</rule-ipv4-prefix>
          <rule-ipv6-prefix>2001:db8::/40</rule-ipv6-prefix>
          <forwarding>true</forwarding>
          <port-set>
            <psid-offset>6</psid-offset>
            <psid-len>8</psid-len>
          </port-set>
        </algo-instances>
      </algorithm>
    </br-instances>
  </softwire-config>
</config>

                   Figure 4: MAP-E FMR Configuration XML

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A.3.  lw4o6 CE Configuration Example

   This section provides XML examples for configuring a lw4o6 CE.
   Examples for routing and NAT44 are also provided for convienience.

   Consider an example for the following lw4o6 CE configuration:

   lwB4 Binding IPv6 Address:  2001:db8::1

   lwB4 Binding IPv4 Address:  192.0.2.1

   lwB4 PSID:                  0x34

   lwB4 PSID Length            8

   BR IPv6 Address:            2001:db8:1::2

   <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
       <interface>
         <name>lw4o6-wan</name>
         <tunnel-type
           xmlns:iana="urn:ietf:params:xml:ns:yang:iana-tunnel-type">
           iana-tunnel-type:aplusp
         </tunnel-type>
         <br-ipv6-addr
           xmlns="urn:ietf:params:xml:ns:yang:ietf-softwire-ce">
           2001:db8:1::2
         </br-ipv6-addr>
         <binding-ipv6info
           xmlns="urn:ietf:params:xml:ns:yang:ietf-softwire-ce">
           2001:db8::1
         </binding-ipv6info>
       </interface>
     </interfaces>
   </config>

                   Figure 5: lw4o6 CE Configuration XML

   In the example depicted in Figure 5, the interface name is defined
   for the softwire tunnel.  This name is then referenced by the routing
   configuration for the IPv4 route.  Figure 6 provides an example
   configuration for the CE's IPv4 routing, using the YANG module
   described in [RFC8349].

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<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <control-plane-protocols>
      <control-plane-protocol>
        <type>static</type>
        <name>v4</name>
        <static-routes>
          <ipv4
          xmlns="urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing">
            <route>
              <destination-prefix>0.0.0.0/0</destination-prefix>
              <next-hop>
                <outgoing-interface>lw4o6-wan</outgoing-interface>
              </next-hop>
            </route>
          </ipv4>
        </static-routes>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>

               Figure 6: lw4o6 CE Routing Configuration XML

   Figure 7 provides an example configuration for the CE's NAPT44
   function, using the YANG module described in
   [I-D.ietf-opsawg-nat-yang].

 <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <nat xmlns="urn:ietf:params:xml:ns:yang:ietf-nat">
    <instances>
      <instance>
        <id>1</id>
        <policy>
         <policy-id>1</policy-id>
         <external-ip-address-pool>
           <pool-id>1</pool-id>
           <external-ip-pool>192.0.2.1</external-ip-pool>
         </external-ip-address-pool>
         <port-set-restrict>
           <port-set-algo>
             <psid-offset>6</psid-offset>
             <psid-len>8</psid-len>
             <psid>52</psid>
           </port-set-algo>
         </port-set-restrict>
         <notify-pool-usage>
           <pool-id>1</pool-id>

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           <high-threshold>80</high-threshold>
         </notify-pool-usage>
         </policy>
         <mapping-limits>
          <limit-per-protocol>
           <protocol-id>1</protocol-id>
           <limit>8</limit>
          </limit-per-protocol>
          <limit-per-protocol>
           <protocol-id>6</protocol-id>
           <limit>32</limit>
          </limit-per-protocol>
          <limit-per-protocol>
           <protocol-id>17</protocol-id>
           <limit>16</limit>
          </limit-per-protocol>
         </mapping-limits>
         <mapping-table>
           <mapping-entry>
             <index>1</index>
             <external-src-address>192.0.2.1/32</external-src-address>
             <internal-src-address>192.168.1.0/24</internal-src-address>
             <transport-protocol>6</transport-protocol>
           </mapping-entry>
           <mapping-entry>
             <index>2</index>
             <external-src-address>192.0.2.1/32</external-src-address>
             <internal-src-address>192.168.1.0/24</internal-src-address>
             <transport-protocol>17</transport-protocol>
           </mapping-entry>
           <mapping-entry>
             <index>3</index>
             <external-src-address>192.0.2.1/32</external-src-address>
             <internal-src-address>192.168.1.0/24</internal-src-address>
             <transport-protocol>1</transport-protocol>
           </mapping-entry>
         </mapping-table>
       </instance>
     </instances>
   </nat>
 </config>

                   Figure 7: lw4o6 NAT Configuration XML

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Authors' Addresses

   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R. China

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

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

   Email: ian.farrer@telekom.de

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com

   Qi Sun
   Tsinghua University
   Beijing  100084
   P.R. China

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

   Linhui Sun
   Tsinghua University
   Beijing  100084
   P.R. China

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

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

   Email: sladjana.zechlin@telekom.de

   Rajiv Asati
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   RTP, NC  27709
   USA

   Email: Rajiva@cisco.com

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