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For this RFC, original HTML is available from the RFC-Editor: RFC8676

PROPOSED STANDARD

Internet Engineering Task Force (IETF)                    I. Farrer, Ed.
Request for Comments: 8676                           Deutsche Telekom AG
Category: Standards Track                              M. Boucadair, Ed.
ISSN: 2070-1721                                                   Orange
                                                           November 2019


    YANG Modules for IPv4-in-IPv6 Address plus Port (A+P) Softwires

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, Mapping of Address and
   Port with Encapsulation (MAP-E), and Mapping of Address and Port
   using Translation (MAP-T) softwire mechanisms.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8676.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Terminology
   3.  Overview of the Modules
     3.1.  Overall Structure
     3.2.  Configuration for Additional Components
   4.  Softwire CE YANG Tree Diagram
     4.1.  CE Tree Diagram
     4.2.  Softwire CE Tree Diagram Description
   5.  Softwire BR YANG Tree Diagram
     5.1.  BR Tree Diagram
     5.2.  Softwire BR Tree Diagram Description
   6.  Softwire CE YANG Module
   7.  BR Softwire YANG Module
   8.  Common Softwire Element Groups YANG Module
   9.  Security Considerations
   10. IANA Considerations
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Appendix A.  Configuration Examples
     A.1.  Configuration Example for a lw4o6 BR Binding-Table
     A.2.  Configuration Example for a MAP-E BR
     A.3.  lw4o6 CE Configuration Example
   Acknowledgements
   Contributors
   Authors' Addresses

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 Edge (CE) (called "Customer Premises Equipment (CPE)" in
   [RFC7596]).  The softwire mechanisms covered in this document are
   Lightweight 4over6 (lw4o6) [RFC7596], Mapping of Address and Port
   with Encapsulation (MAP-E) [RFC7597], and Mapping of Address and Port
   using Translation (MAP-T) [RFC7599].

   This document focuses on A+P mechanisms [RFC6346]; the reader can
   refer to [RFC8513] for a YANG module for Dual-Stack Lite (DS-Lite)
   [RFC6333].

   This document defines YANG modules [RFC7950] that can be used to
   configure and manage A+P softwire elements using the NETCONF
   [RFC6241] or RESTCONF [RFC8040] protocols for:

   *  Configuration

   *  Operational State

   *  Notifications

2.  Terminology

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

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

   The document uses the abbreviation 'BR' as a general term for
   softwire tunnel concentrators, including both MAP Border Routers
   [RFC7597] and Lightweight 4over6 lwAFTRs [RFC7596].

   For brevity, "algorithm" is used to refer to the "mapping algorithm"
   defined in [RFC7597].

   A network element may support one or multiple instances of a softwire
   mechanism; each of these instances (i.e., binding instances, MAP-E
   instances, or MAP-T instances) may have its own configuration and
   parameters.  The term 'algo-instance' is used to denote both MAP-E
   and MAP-T instances.

3.  Overview of the Modules

3.1.  Overall Structure

   The document defines the following two YANG 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:

            +--------------------+-----------+---------------+
            |   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.

      |  Earlier draft 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.

3.2.  Configuration for Additional Components

   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:

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

   *  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].

   *  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 [RFC8512].

   *  Stateless NAT46 management, which is 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 [RFC8512].

   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.

   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.

4.  Softwire CE YANG Tree Diagram

4.1.  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.  This entry is added only
   if tunnel type (Section 10) is set to 'aplusp'.

   Figure 1 shows 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* [name]
                   +--rw name                string
                   +--rw enable?             boolean
                   +--rw algo-versioning
                   |  +--rw version?   uint64
                   |  +--rw date?      yang:date-and-time
                   +--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
          +--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

4.2.  Softwire CE Tree Diagram Description

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

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

      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 payload Maximum Receive
         Unit (MRU) size automatically (see Section 3.2 of [RFC4213]).

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

   Further details relevant to binding softwire elements are as follows:

      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'.

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

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

      algo-versioning:
         optionally used to associate a version number and/or timestamp
         to the algorithm.  This can be used for logging/data retention
         purposes [RFC7422].  The version number is selected to uniquely
         identify the algorithm configuration and a new value written
         whenever a change is made to the algorithm or a new algo-
         instance is created.

      forwarding:
         specifies whether the rule can be used as a Forwarding 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].

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

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

      br-ipv6-addr:
         defines the IPv6 address of the BR.  This information is valid
         for MAP-E.

      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:

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

5.  Softwire BR YANG Tree Diagram

5.1.  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-instance* [name]
           |        +--rw name                       string
           |        +--rw binding-table-versioning
           |        |  +--rw version?   uint64
           |        |  +--rw date?      yang:date-and-time
           |        +--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
           |        |  |  +--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
           |           +--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-instance* [name]
                    +--rw name                string
                    +--rw enable?             boolean
                    +--rw algo-versioning
                    |  +--rw version?   uint64
                    |  +--rw date?      yang:date-and-time
                    +--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
                       +--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-name?
       |  |       -> /br-instances/binding/bind-instance/name
       |  +--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-name
          |       -> /br-instances/algorithm/algo-instance/name
          +--ro invalid-entry-id*
          |       -> /br-instances/algorithm/algo-instance/name
          +--ro added-entry*
          |       -> /br-instances/algorithm/algo-instance/name
          +--ro modified-entry*
                  -> /br-instances/algorithm/algo-instance/name

                      Figure 2: Softwire BR YANG Tree

5.2.  Softwire BR Tree Diagram Description

   The descriptions for leaves that are common with the CE module are
   provided in Section 4.2.  Descriptions for additional elements are
   provided below:

      binding-table-versioning:
         optionally used to associate a version number and/or timestamp
         to the binding table.  This can be used for logging or data
         retention purposes [RFC7422].  The version number is selected
         to uniquely identify the binding table configuration 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.

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

      softwire-num-max:
         used to set the maximum number of softwire binding rules that
         can be created on the lw4o6 element simultaneously.  This
         parameter must not be set to zero because this is equivalent to
         disabling the BR instance.

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

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

      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.

6.  Softwire CE YANG Module

   This module imports the modules defined in [RFC6991], [RFC8343], and
   [RFC7224].  It also imports the 'ietf-softwire-common' and 'iana-
   tunnel-type' modules [RFC8675].

   <CODE BEGINS> file "ietf-softwire-ce@2019-11-16.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
         "RFC 6991: Common YANG Data Types, Section 4";
     }
     import ietf-interfaces {
       prefix if;
       reference
         "RFC 8343: A YANG Data Model for Interface Management";
     }
     import ietf-softwire-common {
       prefix softwire-common;
       reference
         "RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port
          Softwires";
     }
     import iana-tunnel-type {
       prefix iana-tunnel-type;
       reference
         "RFC 8675: A YANG Data Model for Tunnel Interface Types";
     }

     organization
       "IETF Softwire Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
        WG List:  <mailto:softwire@ietf.org>

        Author:  Qi Sun
                 <mailto:sunqi.ietf@gmail.com>

        Author:  Linhui Sun
                 <mailto:lh.sunlinh@gmail.com>

        Author:  Yong Cui
                 <mailto:yong@csnet1.cs.tsinghua.edu.cn>

        Editor:  Ian Farrer
                 <mailto:ian.farrer@telekom.de>

        Author:  Sladjana Zoric
                 <mailto:sladjana.zoric@telekom.de>

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

        Author:  Rajiv Asati
                  <mailto:rajiva@cisco.com>";
     description
       "This document defines a YANG 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) 2019 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

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

        This version of this YANG module is part of RFC 8676; see
        the RFC itself for full legal notices.";

     revision 2019-11-16 {
       description
         "Initial revision.";
       reference
         "RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port
          (A+P) Softwires";
     }

     /*
      * Features
      */

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

          Binding-based softwire mechanisms are IPv4-over-IPv6 tunneling
          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 network element can function
          as one or more binding-based softwire instances.";
       reference
         "RFC 7596: Lightweight 4over6: An Extension to the Dual-Stack
          Lite Architecture
          RFC 7597: Mapping of Address and Port with Encapsulation
          (MAP-E)
          RFC 7599: 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 network element can function
          as one or more MAP-E softwire instances.";
       reference
         "RFC 7597: 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 and transport layer port
          mapping algorithm defined for MAP-E.

          This feature indicates that the network element can function
          as one or more MAP-T softwire instances.";
       reference
         "RFC 7599: 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 the
          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 RFC 7596.

            If the IPv6 address type is used, the CE can use
            any valid /128 address from a prefix assigned to
            the CE.";
         reference
           "RFC 7596: Lightweight 4over6: An Extension
            to the Dual-Stack Lite Architecture, Section 5.1";
       }
       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(if: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).";
         reference
           "RFC 4213: Basic Transition Mechanisms for IPv6 Hosts and
            Routers";
       }
       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
               "Collection of MAP-E/MAP-T parameters";
             list algo-instance {
               key "name";
               description
                 "MAP forwarding rule instance for
                  MAP-E/MAP-T";
               leaf name {
                 type string;
                 mandatory true;
                 description
                   "The name is used to uniquely identify an algorithm
                    instance.

                    This name can be automatically assigned
                    or explicitly configured.";
               }
               uses softwire-common:algorithm-instance;
             }
           }
         }
       }
     }
     augment "/if:interfaces/if:interface/if:statistics" {
       when "derived-from(../if: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
           "This notification is generated whenever the CE's binding
            IPv6 address changes for any reason.";
       }
     }
   }
   <CODE ENDS>

7.  BR Softwire YANG Module

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

   <CODE BEGINS> file "ietf-softwire-br@2019-11-16.yang"
   module ietf-softwire-br {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-softwire-br";
     prefix softwire-br;

     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types, Section 4";
     }
     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types, Section 3";
     }
     import ietf-softwire-common {
       prefix softwire-common;
       reference
         "RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port
          (A+P) Softwires";
     }

     organization
       "IETF Softwire Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
        WG List:  <mailto:softwire@ietf.org>

        Author:  Qi Sun
                 <mailto:sunqi.ietf@gmail.com>

        Author:  Linhui Sun
                 <mailto:lh.sunlinh@gmail.com>

        Author:  Yong Cui
                 <mailto:yong@csnet1.cs.tsinghua.edu.cn>

        Editor:  Ian Farrer
                 <mailto:ian.farrer@telekom.de>

        Author:  Sladjana Zoric
                 <mailto:sladjana.zoric@telekom.de>

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

        Author:  Rajiv Asati
                  <mailto:rajiva@cisco.com>";

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

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

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

        This version of this YANG module is part of RFC 8676; see
        the RFC itself for full legal notices.";

     revision 2019-11-16 {
       description
         "Initial revision.";
       reference
         "RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port
          (A+P) 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 that 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;
         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 RFC 7596;
            if the IPv6 address type is used, the CE can use
            any valid /128 address from a prefix assigned to
            the CE.";
         reference
           "RFC 7596: 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 {
         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 tunneling
          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 network element can function
          as one or more binding-based softwire instances.";
       reference
         "RFC 7596: Lightweight 4over6: An Extension to the Dual-Stack
          Lite Architecture
          RFC 7597: Mapping of Address and Port with Encapsulation
          (MAP-E)
          RFC 7599: 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 network element can function
          as one or more MAP-E softwire instances.";
       reference
         "RFC 7597: 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 and transport layer
          port mapping algorithm defined for MAP-E.

          This feature indicates that the network element can function
          as one or more MAP-T softwire instances.";
       reference
         "RFC 7599: Mapping of Address and Port using Translation
          (MAP-T)";
     }

     container br-instances {
       description
         "BR instances enabled in a network element.";
       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-instance {
               key "name";
               description
                 "A set of binding instances to be configured.";
               leaf name {
                 type string;
                 mandatory true;
                 description
                   "The name for the binding BR.  It is used to uniquely
                    distinguish a binding instance by its name.";
               }
               container binding-table-versioning {
                 description
                   "binding table's version";
                 leaf version {
                   type uint64;
                   description
                     "Version number for this binding table.";
                 }
                 leaf date {
                   type yang:date-and-time;
                   description
                     "Timestamp when the binding table was activated.

                      A binding instance may be provided with binding
                      entries that may change in time (e.g., increase
                      the size of the port set).  When a party who is
                      the victim of abuse presents an external IP
                      address/port, the version of the binding table
                      is important because, depending on the version,
                      a distinct customer may be identified.

                      The timestamp is used as a key to find the
                      appropriate binding table that was put into effect
                      when an abuse occurred.";
                   reference
                     "RFC 7422: Deterministic Address Mapping to Reduce
                      Logging in Carrier-Grade NAT Deployments";
                 }
               }
               leaf softwire-num-max {
                 type uint32 {
                   range "1..max";
                 }
                 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";
                 reference
                   "RFC 4213: Basic Transition Mechanisms for IPv6 Hosts
                              and Routers";
               }
               leaf enable-hairpinning {
                 type boolean;
                 default "true";
                 description
                   "Enables/disables support for locally forwarding
                    (hairpinning) traffic between two CEs";
                 reference
                   "RFC 7596: Lightweight 4over6: An Extension to
                    the Dual-Stack Lite Architecture, 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.";
                 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
                       "RFC 7596: 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
                       "RFC 7596: Lightweight 4over6:
                        An Extension to the Dual-Stack Lite
                        Architecture, Section 5.2";
                   }
                 }
                 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
                       "RFC 7596: Lightweight 4over6:
                        An Extension to the Dual-Stack Lite
                        Architecture, Section 6.2";
                   }
                   leaf icmpv6-rate {
                     type uint32;
                     description
                       "Rate limit threshold in messages per second
                        for sending ICMPv6 errors messages";
                     reference
                       "RFC 7596: Lightweight 4over6: An Extension
                        to the Dual-Stack Lite Architecture, Section 9";
                   }
                 }
               }
               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.

                      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
               "A set of parameters used for MAP-E/MAP-T";
             list algo-instance {
               key "name";
               description
                 "Instances of algorithm";
               leaf name {
                 type string;
                 mandatory true;
                 description
                   "The name is used to uniquely identify an algorithm
                    instance.

                    This name can be automatically assigned
                    or explicitly configured.";
               }
               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 the binding instance when an entry is
          added, modified, or is not valid anymore.";
       leaf bind-name {
         type leafref {
           path "/br-instances/binding/bind-instance/name";
         }
         description
           "The name of the binding-instance that
            generated the notification.";
       }
       leaf-list invalid-entry {
         type leafref {
           path "/br-instances/binding/"
              + "bind-instance[name=current()/../bind-name]/"
              + "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-instance[name=current()/../bind-name]/"
              + "binding-table/binding-entry/binding-ipv6info";
         }
         description
           "The binding table entry that has been modified.";
       }
     }
     notification softwire-algorithm-instance-event {
       if-feature "map-e or map-t";
       description
         "Notifications for an algorithm instance when an entry is
          added, modified, or is not valid anymore.";
       leaf algo-name {
         type leafref {
           path "/br-instances/algorithm/algo-instance/name";
         }
         mandatory true;
         description
           "Algorithmic instance event.";
       }
       leaf-list invalid-entry {
         type leafref {
           path "/br-instances/algorithm/algo-instance/name";
         }
         description
           "Invalid entry.";
       }
       leaf-list added-entry {
         type leafref {
           path "/br-instances/algorithm/algo-instance/name";
         }
         description
           "Added entry.";
       }
       leaf-list modified-entry {
         type leafref {
           path "/br-instances/algorithm/algo-instance/name";
         }
         description
           "Modified entry.";
       }
     }
   }
   <CODE ENDS>

8.  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@2019-11-16.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
         "RFC 6991: Common YANG Data Types, Section 4";
     }
     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types, Section 3";
     }

     organization
       "IETF Softwire Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/softwire/>
        WG List:  <mailto:softwire@ietf.org>

        Author:  Qi Sun
                 <mailto:sunqi.ietf@gmail.com>

        Author:  Linhui Sun
                 <mailto:lh.sunlinh@gmail.com>

        Author:  Yong Cui
                 <mailto:yong@csnet1.cs.tsinghua.edu.cn>

        Editor:  Ian Farrer
                 <mailto:ian.farrer@telekom.de>

        Author:  Sladjana Zoric
                 <mailto:sladjana.zoric@telekom.de>

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

        Author:  Rajiv Asati
                  <mailto:rajiva@cisco.com>";
     description
       "This document defines a YANG module defining types
        common to all A+P modules.

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

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

        This version of this YANG module is part of RFC 8676; see
        the RFC itself for full legal notices.";

     revision 2019-11-16 {
       description
         "Initial revision.";
       reference
         "RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port
                    (A+P) 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 network element can function
          as one or more MAP-E softwire instances.";
       reference
         "RFC 7597: 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 and transport layer
          port mapping algorithm defined for MAP-E.

          This feature indicates that the network element can function
          as one or more MAP-T softwire instances.";
       reference
         "RFC 7599: Mapping of Address and Port using Translation
          (MAP-T)";
     }

     /*
      * Groupings
      */

     grouping algorithm-instance {
       description
         "A collection of parameters that is used for MAP-E/MAP-T.";
       leaf enable {
         type boolean;
         description
           "Enable/disable an individual MAP-E or MAP-T rule.";
       }
       container algo-versioning {
         description
           "Version number for this algorithm instance";
         leaf version {
           type uint64;
           description
             "A version number for the mapping algorithm
              rules provided to the algorithm instance";
         }
         leaf date {
           type yang:date-and-time;
           description
             "Timestamp when the algorithm instance was activated.

              An algorithm instance may be provided with mapping
              rules that may change in time (for example, increase
              the size of the port set).  When a party who is the victim
              of abuse presents an external IP address/port, the version
              of the algorithm is important because depending on
              the version, a distinct customer may be identified.

              The timestamp is used as a key to find the appropriate
              algorithm that was put into effect when an abuse
              occurred.";
           reference
             "RFC 7422: Deterministic Address Mapping to Reduce
                        Logging in Carrier-Grade NAT Deployments";
         }
       }
       choice data-plane {
         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
           "This parameter specifies whether the rule may be used for
            forwarding; if set, this rule is used as a Forwarding
            Mapping Rule (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 IPv4 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-ipv4-bytes {
         type yang:zero-based-counter64;
         description
           "IPv4 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 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.

            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
            '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'.";
       }
     }
   }
   <CODE ENDS>

9.  Security Considerations

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

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

   All data nodes defined in the YANG modules which can be created,
   modified, and deleted (i.e., config true, which is the default) are
   considered sensitive.  Write operations (e.g., edit-config) to these
   data nodes without proper protection can have a negative effect on
   network operations.  An attacker who is able to access the BR can
   undertake various attacks, such as:

   *  Setting the value of 'br-ipv6-addr' on the CE to point to an
      illegitimate BR so that it can intercept all the traffic sent by a
      CE.  Illegitimately intercepting users' traffic is an attack with
      severe implications on privacy.

   *  Setting the MTU to a low value, which may increase the number of
      fragments ('softwire-payload-mtu').

   *  Disabling hairpinning (i.e., setting 'enable-hairpinning' to
      'false') to prevent communications between CEs.

   *  Setting 'softwire-num-max' to an arbitrary high value, which may
      be exploited by a misbehaving user to perform a DoS on the binding
      BR by mounting a massive number of softwires.

   *  Setting 'icmpv4-rate' or 'icmpv6-rate' to a low value, which may
      lead to the deactivation of ICMP messages handling.

   *  Instructing the BR to install entries, which, in turn, will induce
      a DDoS attack by means of the notifications generated by the BR.
      This DDoS can be softened by defining a notification interval, but
      given that this interval parameter can be disabled or set to a low
      value by the misbehaving entity, the same problem will be
      observed.

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

   *  the binding Table (/br-instances/binding/bind-instance/binding-
      table)

   *  the algorithm configuration (/br-instances/algorithm/algo-
      instance/)

   Security considerations related to lw4o6, MAP-T, and MAP-E are
   discussed in [RFC7596], [RFC7597], and [RFC7599] respectively.

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

10.  IANA Considerations

   IANA has assigned the following new tunnel type under the tunnelType
   subregistry of the "ifType Definitions" registry maintained in the
   SMI Numbers registry [TUNNELTYPE-IANA-REGISTRY]:

      Decimal:      18
      Name:         aplusp
      Description:  A+P encapsulation
      Reference:    [RFC6346]

   IANA has registered the following in the "ns" subregistry within the
   "IETF XML Registry" [RFC3688]:

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

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

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

   IANA has registered the following YANG modules in the "YANG Module
   Names" subregistry [RFC6020] within the "YANG Parameters" registry.

      name:  ietf-softwire-ce
      namespace:  urn:ietf:params:xml:ns:yang:ietf-softwire-ce
      prefix:  softwire-ce
      reference:  RFC 8676

      name:  ietf-softwire-br
      namespace:  urn:ietf:params:xml:ns:yang:ietf-softwire-br
      prefix:  softwire-br
      reference:  RFC 8676

      name:  ietf-softwire-common
      namespace:  urn:ietf:params:xml:ns:yang:ietf-softwire-common
      prefix:  softwire-common
      reference:  RFC 8676

11.  References

11.1.  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>.

   [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>.

   [RFC8675]  Boucadair, M., Farrer, I., and R. Asati, "A YANG Data
              Model for Tunnel Interface Types", RFC 8675,
              DOI 10.17487/RFC8675, November 2019,
              <https://www.rfc-editor.org/info/rfc8675>.

   [TUNNELTYPE-IANA-REGISTRY]
              IANA, "Structure of Management Information (SMI) Numbers
              (MIB Module Registrations)",
              <https://www.iana.org/assignments/smi-numbers>.

11.2.  Informative References

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213,
              DOI 10.17487/RFC4213, October 2005,
              <https://www.rfc-editor.org/info/rfc4213>.

   [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>.

   [RFC6346]  Bush, R., Ed., "The Address plus Port (A+P) Approach to
              the IPv4 Address Shortage", RFC 6346,
              DOI 10.17487/RFC6346, August 2011,
              <https://www.rfc-editor.org/info/rfc6346>.

   [RFC7422]  Donley, C., Grundemann, C., Sarawat, V., Sundaresan, K.,
              and O. Vautrin, "Deterministic Address Mapping to Reduce
              Logging in Carrier-Grade NAT Deployments", RFC 7422,
              DOI 10.17487/RFC7422, December 2014,
              <https://www.rfc-editor.org/info/rfc7422>.

   [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>.

   [RFC8512]  Boucadair, M., Ed., Sivakumar, S., Jacquenet, C.,
              Vinapamula, S., and Q. Wu, "A YANG Module for Network
              Address Translation (NAT) and Network Prefix Translation
              (NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019,
              <https://www.rfc-editor.org/info/rfc8512>.

   [RFC8513]  Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG
              Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513,
              DOI 10.17487/RFC8513, January 2019,
              <https://www.rfc-editor.org/info/rfc8513>.

Appendix A.  Configuration 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 that contains the
   following 3-tuples:

   *  IPv6 Address for a single lwB4

   *  Public IPv4 Address

   *  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 decapsulation.

   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

   lwB4 PSID:                  0x34

   lwB4 PSID Length            8

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

       <br-instances>
         <binding>
             <bind-instance>
               <name>mybinding-instance</name>
               <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>

              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:

   *  Rule IPv6 Prefix

   *  Rule IPv4 Prefix

   *  Rule EA-bit bit length

   *  IPv6 Address of MAP-BR

   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.

       <br-instances>
         <algorithm>
           <algo-instance>
             <name>myalgo-instance</name>
             <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-instance>
         </algorithm>
       </br-instances>

                   Figure 4: MAP-E FMR Configuration XML

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 convenience.

   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>
         <type>iana-tunnel-type:aplusp</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].

   <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-unicas\
             t-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 [RFC8512].

   <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>
             <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

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 and Martin Bjorklund for the detailed
   review and suggestions.

Contributors

   The following individuals are co-authors:

      Yong Cui
      Tsinghua University
      China
      Phone: +86-10-6260-3059
      Email: cuiyong@tsinghua.edu.cn

      Qi Sun
      Tsinghua University
      China
      Phone: +86-10-6278-5822
      Email: sunqi.ietf@gmail.com

      Linhui Sun
      Tsinghua University
      China
      Phone: +86-10-6278-5822
      Email: lh.sunlinh@gmail.com

      Sladjana Zechlin
      Deutsche Telekom AG
      Germany
      Email: sladjana.zechlin@telekom.de

      Rajiv Asati
      Cisco Systems, Inc.
      United States of America
      Email: Rajiva@cisco.com

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

Authors' Addresses

   Ian Farrer (editor)
   Deutsche Telekom AG
   CTO-ATI, Landgrabenweg 151
   53227 Bonn
   Germany

   Email: ian.farrer@telekom.de


   Mohamed Boucadair (editor)
   Orange
   35000 Rennes
   France

   Email: mohamed.boucadair@orange.com


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