RFC 8676: YANG Modules for IPv4-in-IPv6 Address plus Port (A+P) Softwires

RFC 8676	YANG Modules for A+P Softwires	November 2019
Farrer & Boucadair	Standards Track	[Page]

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.¶

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:¶

Table 1: 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. 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 "[email protected]"

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:[email protected]>

     Author:  Qi Sun 
              <mailto:[email protected]>

     Author:  Linhui Sun 
              <mailto:[email protected]>

     Author:  Yong Cui 
              <mailto:[email protected]>

     Editor:  Ian Farrer 
              <mailto:[email protected]>

     Author:  Sladjana Zoric 
              <mailto:[email protected]>

     Editor:  Mohamed Boucadair 
              <mailto:[email protected]>

     Author:  Rajiv Asati  
               <mailto:[email protected]>";
  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 "[email protected]"

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:[email protected]>

     Author:  Qi Sun 
              <mailto:[email protected]>

     Author:  Linhui Sun 
              <mailto:[email protected]>

     Author:  Yong Cui 
              <mailto:[email protected]>

     Editor:  Ian Farrer 
              <mailto:[email protected]>

     Author:  Sladjana Zoric 
              <mailto:[email protected]>

     Editor:  Mohamed Boucadair 
              <mailto:[email protected]>

     Author:  Rajiv Asati 
               <mailto:[email protected]>";

  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 "[email protected]"

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:[email protected]>

     Author:  Qi Sun 
              <mailto:[email protected]>

     Author:  Linhui Sun 
              <mailto:[email protected]>

     Author:  Yong Cui 
              <mailto:[email protected]>

     Editor:  Ian Farrer 
              <mailto:[email protected]>

     Author:  Sladjana Zoric 
              <mailto:[email protected]>

     Editor:  Mohamed Boucadair 
              <mailto:[email protected]>

     Author:  Rajiv Asati 
               <mailto:[email protected]>";
  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.¶

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

RFC 8676

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