Softwire Working Group I. Farrer, Ed.
Internet-Draft Deutsche Telekom AG
Intended status: Standards Track M. Boucadair, Ed.
Expires: July 19, 2019 Orange
January 15, 2019

YANG Modules for IPv4-in-IPv6 Address plus Port (A+P) Softwires
draft-ietf-softwire-yang-15

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.

Editorial Note (To be removed by RFC Editor)

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

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

Status of This Memo

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

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

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This Internet-Draft will expire on July 19, 2019.

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

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

2. Terminology

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

The 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 abbrieviation '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:

Softwire Mechanism Choice Statement Enumeration
S46 Mechanism ce-type? data-plane?
Lightweight 4over6 binding n/a
MAP-E algorithm encapsulation
MAP-T algorithm translation

NETCONF notifications are also included.

3.2. Additional Components Configuration

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

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:

Further details relevant to binding softwire elements are:

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

Additional information on the notification node is listed below:

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 which are common with the CE module are provided in Section 4.2. Descriptions for additional elements are provided below:

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

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 [I-D.ietf-softwire-iftunnel].

<CODE BEGINS>file "ietf-softwire-ce@2019-01-11.yang"

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

  import ietf-inet-types {
    prefix inet;
    reference "Section 4 of RFC 6991";
  }
  import ietf-interfaces {
    prefix if;
    reference "RFC 8343: A YANG Data Model for Interface Management";
  }
  import ietf-softwire-common {
    prefix softwire-common;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }
  import iana-tunnel-type {
    prefix iana-tunnel-type;
    reference
      "RFC YYYY: Tunnel Interface Types YANG Module";
  }

  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 XXXX; see
     the RFC itself for full legal notices.";

  revision 2019-01-11 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  /*
   * Features
   */

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

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

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

       This feature indicates that the network element can function as
       one or more binding based softwire instances.";
    reference
      "RFC7596: Lightweight 4over6: An Extension to the Dual-Stack Lite 
                Architecture
       RFC7597: Mapping of Address and Port with Encapsulation (MAP-E) 
       RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-E softwire instances.";
    reference 
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-T softwire instances.";
    reference 
      "RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  // Binding Entry

  grouping binding-entry {
    description
      "The binding BR (Border Relay) maintains an address binding table  
       that contains the binding between the CE's IPv6 address, 
       the allocated IPv4 address and restricted port-set.";
    leaf binding-ipv6info {
      type union {
        type inet:ipv6-address;
        type inet:ipv6-prefix;
      }
      description
        "The IPv6 information for a binding entry.

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

         If the IPv6 address type is used, the CE can use
         any valid /128 address from a prefix assigned to
         the CE.";
      reference "Section 5.1 of RFC7596.";
    }
    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@2019-01-11.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 "Section 4 of RFC 6991";
  }
  import ietf-yang-types {
    prefix yang;
    reference "Section 3 of RFC 6991";
  }
  import ietf-softwire-common {
    prefix softwire-common;
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

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

     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 XXXX; see
     the RFC itself for full legal notices.";

  revision 2019-01-11 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

  /*
   * Groupings
   */

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

       This may be a simple port range, or use the Port Set 
       Identifier (PSID) algorithm to represent a range of transport 
       layer ports which will be used by a NAPT.";
    leaf psid-offset {
      type uint8 {
        range "0..16";
      }
      description
        "The number of offset bits. In Lightweight 4over6,
         the default value is 0 for assigning one contiguous
         port range. In MAP-E/T, the default value is 6,
         which means the system ports (0-1023) are excluded by
         default and the assigned port ranges are distributed across 
         the entire port space, depending on either psid-len or the
         number of contiguous ports.";
    }
    leaf psid-len {
      type uint8 {
        range "0..15";
      }
      mandatory true;
      description
        "The length of PSID, representing the sharing
         ratio for an IPv4 address. This, along with ea-len, can
         be used to calculate the number of contiguous ports per
         port range";
    }
    leaf psid {
      type uint16;
      mandatory true;
      description
        "Port Set Identifier (PSID) value, which
         identifies a set of ports algorithmically.";
    }
  }

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

  /*
   * Features
   */

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

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

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

       This feature indicates that the network element can function as
       one or more binding based softwire instances.";
    reference
      "RFC7596: Lightweight 4over6: An Extension to the Dual-Stack Lite 
                Architecture
       RFC7597: Mapping of Address and Port with Encapsulation (MAP-E) 
       RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-E softwire instances.";
    reference 
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-T softwire instances.";
    reference 
      "RFC7599: 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
                  "RFC7422: 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
                "RFC4213: 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 "Section 6.2 of RFC7596";
            }
            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
                    "RFC7596: Lightweight 4over6: An Extension to 
                              the Dual-Stack Lite Architecture";
                }
                leaf icmpv4-rate {
                  type uint32;
                  description
                    "Rate limit threshold in messages per-second
                     for processing incoming ICMPv4 errors messages";
                }
                leaf generate-icmpv4-errors {
                  type boolean;
                  default "true";
                  description
                    "Enables the generation of outgoing ICMPv4 error
                     messages on receipt of an inbound IPv4 packet 
                     with no matching binding table entry.";
                  reference "Seciton 5.2 of RFC7596.";
                }
              }
              container icmpv6-errors {
                description
                  "ICMPv6 error processing configuration";
                leaf generate-icmpv6-errors {
                  type boolean;
                  default "true";
                  description
                    "Enables the generation of ICMPv6 error messages if
                     no matching binding table entry is found for a
                     received packet.";
                  reference "Section 6.2 of RFC7596.";
                }
                leaf icmpv6-rate {
                  type uint32;
                  description
                    "Rate limit threshold in messages per-second
                     for sending ICMPv6 errors messages";
                  reference "Section 9 of RFC7596.";
                }
              }
            }
            container traffic-stat {
              config false;
              description
                "Traffic statistics information for the BR.";
              leaf discontinuity-time {
                type yang:date-and-time;
                mandatory true;
                description
                  "The time of the most recent occasion on which the BR 
                   instance suffered a discontinuity.  This must be 
                   initialized when the BR instance is configured 
                   or rebooted.";
              }
              uses softwire-common:traffic-stat;
              leaf dropped-icmpv4-packets {
                type yang:zero-based-counter64;
                description
                  "ICMPv4 packets that are dropped as a result
                   of the ICMP policy. Typically, this can be any
                   incoming ICMPv4 packets if ICMPv4 processing is  
                   disabled or incoming ICMPv4 packets that exceed 
                   the ICMPv4 rate-limit threshold.
                            
                   Discontinuities in the value of this counter can 
                   occur at re-initialization of the management
                   system, and at other times as indicated by
                   the value of 'discontinuity-time'.";
              }
              leaf dropped-icmpv4-bytes {
                type yang:zero-based-counter64;
                description
                  "ICMPv4 messages, in bytes, that are dropped as 
                   a result of the ICMP policy. Typically, it 
                   can be any incoming ICMPv4 packets if ICMPv4
                   processing is disabled or incoming ICMPv4  
                   packets that exceed the ICMPv4 rate-limit 
                   threshold.
                            
                   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 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 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 event.";
    }
    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@2019-01-11.yang"

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

  import ietf-inet-types {
    prefix inet;
    reference "Section 4 of RFC 6991";
  }
  import ietf-yang-types {
    prefix yang;
    reference "Section 3 of RFC 6991";
  }

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

     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 XXXX; see
     the RFC itself for full legal notices.";

  revision 2019-01-11 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Modules for IPv4-in-IPv6 Address plus Port
                 Softwires";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-E softwire instances.";
    reference 
      "RFC7597: Mapping of Address and Port with Encapsulation (MAP-E)";
  }

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

       This feature indicates that the network element can function as
       one or more MAP-T softwire instances.";
    reference 
      "RFC7599: Mapping of Address and Port using Translation (MAP-T)";
  }

  /*
   * Groupings
   */

  grouping algorithm-instance {
    description
      "A collection of parameters that is used fro 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
          "RFC7422: 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 (FMR). If set, this rule is used as an FMR;
         if not set, this rule is a Basic Mapping Rule (BMR) only
         and must not be used for forwarding.";
    }
  }

  grouping traffic-stat {
    description
      "Traffic statistics";
    leaf sent-ipv4-packets {
      type yang:zero-based-counter64;
      description
        "Number of decapsulated and forwarded IPv4 packets.
               
         Discontinuities in the value of this counter can occur
         at re-initialization of the management system, and at
         other times as indicated by the value of
         'discontinuity-time'.";
    }
    leaf sent-ipv4-bytes {
      type yang:zero-based-counter64;
      description
        "Decapsulated/translated IPv4 traffic sent, in bytes
              
         Discontinuities in the value of this counter can occur
         at re-initialization of the management system, and at
         other times as indicated by the value of
         'discontinuity-time'.";
    }
    leaf sent-ipv6-packets {
      type yang:zero-based-counter64;
      description
        "Number of encapsulated IPv6 packets sent.

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

         Discontinuities in the value of this counter can occur
         at re-initialization of the management system, and at
         other times as indicated by the value of
         'discontinuity-time'.";
    }
    leaf rcvd-ipv4-packets {
      type yang:zero-based-counter64;
      description
        "Number of 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 is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].

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

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

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

This document requests IANA to assign a new tunnel type under the "tunnelType" sub-registry of the "ifType definitions" registry maintained at [TUNNELTYPE-IANA-REGISTRY] and use the following data for the new entry:

       Decimal:           TDB1
       Name:              aplusp
       Description:       A+P encapsulation
       Reference:         [RFC6346]
         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.          

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

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

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

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

This document requests that IANA registers the following YANG modules in the "YANG Module Names" subregistry [RFC7950] within the "YANG Parameters" registry.

11. 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.

12. Contributors

   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R. China
   Phone: +86-10-6260-3059
   Email: cuiyong@tsinghua.edu.cn

   Qi Sun
   Tsinghua University
   Beijing  100084
   P.R. China
   Phone: +86-10-6278-5822
   Email: sunqi.ietf@gmail.com

   Linhui Sun
   Tsinghua University
   Beijing  100084
   P.R. China
   Phone: +86-10-6278-5822
   Email: lh.sunlinh@gmail.com

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

   Rajiv Asati
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   RTP, NC  27709
   USA
   Email: Rajiva@cisco.com

The following individuals are co-authors:

13. Contributors

The following individual contributed to this document:

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

14. References

14.1. Normative References

[I-D.ietf-softwire-iftunnel] Boucadair, M. and I. Farrer, "Tunnel Interface Types YANG Module"
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.
[RFC7224] Bjorklund, M., "IANA Interface Type YANG Module", RFC 7224, DOI 10.17487/RFC7224, May 2014.
[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.
[RFC7597] Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S., Murakami, T. and T. Taylor, "Mapping of Address and Port with Encapsulation (MAP-E)", RFC 7597, DOI 10.17487/RFC7597, July 2015.
[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.
[RFC7599] Li, X., Bao, C., Dec, W., Troan, O., Matsushima, S. and T. Murakami, "Mapping of Address and Port using Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July 2015.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.
[TUNNELTYPE-IANA-REGISTRY] Internet Assigned Numbers Authority, "tunnelType Definitions"

14.2. Informative References

[I-D.ietf-opsawg-nat-yang] Boucadair, M., Sivakumar, S., Jacquenet, C., Vinapamula, S. and Q. Wu, "A YANG Module for Network Address Translation (NAT) and Network Prefix Translation (NPT)", Internet-Draft draft-ietf-opsawg-nat-yang-17, September 2018.
[I-D.ietf-softwire-dslite-yang] Boucadair, M., Jacquenet, C. and S. Sivakumar, "A YANG Data Model for Dual-Stack Lite (DS-Lite)", Internet-Draft draft-ietf-softwire-dslite-yang-17, May 2018.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for IPv6 Hosts and Routers", RFC 4213, DOI 10.17487/RFC4213, October 2005.
[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.
[RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the IPv4 Address Shortage", RFC 6346, DOI 10.17487/RFC6346, August 2011.
[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.
[RFC8340] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018.
[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.
[RFC8344] Bjorklund, M., "A YANG Data Model for IP Management", RFC 8344, DOI 10.17487/RFC8344, March 2018.
[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.

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 which contains the following 3-tuples:

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

Consider an example for the following lw4o6 binding table entry:

lwB4 Binding IPv6 Address:
2001:db8::1
lwB4 Binding IPv4 Address:
192.0.2.1
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:

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 convienience.

Consider an example for the following lw4o6 CE configuration:

lwB4 Binding IPv6 Address:
2001:db8::1
lwB4 Binding IPv4 Address:
192.0.2.1
lwB4 PSID:
0x34
lwB4 PSID Length
8
BR IPv6 Address:
2001:db8:1::2
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
    <interface>
      <name>lw4o6-wan</name>
      <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-unicast-routing">
            <route>
              <destination-prefix>0.0.0.0/0</destination-prefix>
              <next-hop>
                <outgoing-interface>lw4o6-wan</outgoing-interface>
              </next-hop>
            </route>
          </ipv4>
        </static-routes>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>
    

Figure 6: lw4o6 CE Routing Configuration XML

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

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

Authors' Addresses

Ian Farrer (editor) Deutsche Telekom AG CTO-ATI, Landgrabenweg 151 Bonn, NRW 53227 Germany EMail: ian.farrer@telekom.de
Mohamed Boucadair (editor) Orange Rennes, 35000 France EMail: mohamed.boucadair@orange.com